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Abstract

The general method of optimization kinematic synthesis by example of the 8-link planar lever mechanism is considered. The mechanism is intended for reproduction of the set movement of a target link and trajectory of the specified point. Synthesis is carried out on the basis of structural properties of the mechanism.

Keywords: the planar lever mechanism, mechanism's structure, optimization kinematic synthesis.

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The optimal design of human lower limb prostheses, in particular of knee devices, is fundamental in order to restore the lost functionality and aesthetic aspect of the amputee's locomotion. Among all knee devices, the four-bar linkage is still the most widespread mechanism, since, despite its simplicity, it allows the prosthesis to be sufficiently stable and, at the same time, to replicate the natural motion of the joint with a sufficient accuracy. This paper presents an optimization procedure for the synthesis of a four-bar linkage for knee prosthesis. Starting from an experimental reference motion and given some patient-specific requirements related to his capacity to control and to stabilize the prosthesis, the procedure identifies the four-bar linkage that best-fits the experimental motion, at the same time respecting the given specifications. During optimization procedure a set of four bar knee configurations are evaluated to allow a more normal gait to be achieved. Geometry of these new designs increases stability while allowing swing flexion, thereby rendering a locking feature unnecessary. Simulation shows that increase in instant center will be apple advantage for the user and also minimize the energy consumption. Extra toe clearance as compared to single axis knee is also providing a more natural gait.

Keywords: Gait Cycle, Optimization, four-bar synthesis, knee prosthesis, four-bar centrode

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Abstract

This paper presents an optimization scheme based on the principle of harmony-search for path synthesis of Grashof four-bar mechanisms. The objective in this work is to minimize position error defined by the coordinates of coupler point subjected to satisfaction of constraints such as Grashof criterion and sequence on input link angles in addition to geometrical constraints on the design variables. A generalized approach is formulated such that the minimization of objective is carried-out only after a feasible solution has been obtained. Two benchmark examples for path synthesis with and without prescribed timings (input link angles for each precision point) are considered to illustrate the effectiveness of the method.

Keywords: Path synthesis, Position error, Crank-rocker mechanism, Constrained-Optimization, Harmony search.

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In this paper, a methodology is presented for synthesis of planar link's geometry for prescribed inertia parameter values subject to given geometric constraints and having the flexibility of varying topology if desired. Synthesis starts with an initial geometry that satisfies the geometric constraints but not the inertial requirements. As the geometry evolves, topology has to change according to the geometric constraints. The challenge here is to have a controlled change of topology to avoid splitting of domain into multiple components. A novel method of achieving control over the topological evolution of the domain is identified in this work using two types of transformations namely domain preserving transformation and domain splitting transformation. Link geometry is represented as a set of non-intersecting closed polygons consisting of a set of vertices and directed edges (loops), one of which is the outer boundary and the others are holes. The desired inertial properties of the domain are achieved through iterative gradient based optimization.Results obtained from kinematic synthesis provide joint locations, outcome of link geometry synthesis for interference free motion provides the allowable domain; these together form the set of geometric constraints. The results of dynamic synthesis provide the optimal (target) values of inertial parameters for the present geometry synthesis procedure. The methodology presented in this work enables exploration of multiplicity of solutions.

Keywords: Geometry Synthesis, Dynamic Balancing, Shape Optimization

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Abstract

This paper investigates the optimization of toggle mechanisms by energy approach. Circuit breaker mechanism is the classical example of toggle mechanisms. High degree of reliability is required for circuit breaker mechanism to ensure safety of the electrical circuit and human life. Extra available (reserved) energy in the toggle mechanisms can be used during life of the product to ensure high degree of reliability. Total available energy in the mechanism is used to find the dynamic response of spring operated mechanism from the known value of spring stiffness called forward dynamics. The equation of motion, second order non linear differential equation and special form of Lagrange equation, used to analyze the dynamic response of the spring type operating mechanism. Equation of motion is solved in MATLAB gives the motion of the system as a function of time. Result of closing operation is comparable with those obtained numerically by Nastran Working Model as well as by experiment. These results of equation of motion used to find the frictional energy loss in the mechanism. Next step is to find out the extra available energy called energy margin in the toggle mechanisms.

Keywords: Toggle Mechanism, Lagrange, Dynamic, Virtual work

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Abstract

The paper presents a methodology to synthesis simple planar linkage mechanism involving a multi objective optimization model considering cost associated with mechanical tolerances and the reliability based robustness of generating the intended path. An adapted probabilistic model for the deviation of the actual path generated by a coupler point from the desired one, by considering the structural and mechanical errors due to tolerances and clearances is considered. A synthesis procedure of the linkages is formulated as a multi objective non-linear optimization problem with robustness subject to a reliability level and cost as objectives. The reliability index of the mechanism is based on the probability with which a linkage will generate its intended design motion with specified precision. The robustness is based on the ratio of the mean to standard deviation of the error in the traced path with respect to the target. The cost index is based on manufacturing and assembly cost, which are functions of tolerances and clearances in joints. Multi objective genetic algorithm (MOGA) is employed as the search tool. A Four-bar path generating mechanism is selected for numerical illustration.

Keywords: Mechanism synthesis; tolerances; reliability; cost; multi objective genetic algorithm

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Abstract

Nonlinear elastic transmission is an essential component of mechanisms meant for passively variable stiffness. Variable-stiffness-actuation finds applications in areas like human friendly robots, legged machines, artificial prostheses, vibration control etc. Most of the designs in literature use nonlinearity in transmission for the sake of nonlinearity only − there does not exist any guideline for choosing the function. In this article, design of an elastic transmission is presented with an objective and a functional specification for an optimal stiffness behaviour. A principle is derived from passive properties of biological muscles to obtain the elastic function. Consequently, a general method is explained to synthesize a cam profile for the obtained function, followed by description of the spring design. Finally, an antagonistic implementation is presented with initial result.

Keywords: Nonlinear elastic transmission, Exponential spring, Variable-Stiffness-Actuation, Antagonistic actuation

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Abstract

Closed link mechanisms are widely used in machines and manipulators. The presence of clearance at the joints in mechanisms is inevitable. Joint clearance produces positional deviation along with other effects like vibration and wear. It is needed to study its effect as positional deviation caused due to it is unpredictable and random. It is needed to model possible highest positional error due to joint clearance and identify respective positions of mechanisms in workspace.This paper presents formulation of joint clearances in single-DOF planar mechanism. An orientation of coupler and follower is obtained for respective position of input link. Each clearance link is allowed to rotate fully about respective pivot centre. Shift in joint positions and mathematical expression of its motion is obtained. Formulation is implemented through soft computing. Highest positional deviation of coupler point with and without joint clearance is anticipated. It is observed that maximum error at any point on coupler is almost equal to sum of error due to individual joint clearances with almost equal contribution of all joint clearances in total error.

Keywords: Four bar mechanism formulation, clearance consideration, mechanism mapping, positional deviation, Maximum error.

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Abstract

This paper presents a simple second order, curvature based mobility analysis of planar curves for rotation. The underlying theory and methods are purely geometrical, dealing with penetration and separation of curves with multiple contacts, based on relative configuration of osculating circles at points of contact for rotation about each point of the plane. Starting with a single contact, partitioning of the plane into four types of mobility regions has been shown. Using point based composition operations based on dual-number matrices; analysis has been extended to computationally handle multiple contacts scenario. A novel coloured directed line has been proposed to capture the contact scenario. Multiple contacts mobility is obtained through intersection of the mobility half spaces. It is derived that mobility region comprise a pair of open or a single closed convex polygon. The theory has been used for analysis of form closure and synthesis of revolute pairs.

Keywords: mobility analysis, form closure, kinematic pair.

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Abstract

aPosition analysis and the evaluation of various performance indices are integral parts of iterative design of mechanisms using computers. To perform these tasks, one relies upon either a commercially available software or self-written codes. While the first option suffers from the lack of flexibility in terms of integration with other external modules such as an optimiser, the second one requires significant amounts of time and effort in terms of planning, programming, debugging, and code maintenance. In this paper, a unique solution to this problem is proposed, via the introduction of a meta-programming language called MML, developed for the specific purpose of modelling and analysing mechanisms. A few lines of codes in MML is enough to describe a mechanism, solve its position kinematic problem, and also to generate automatically programmes in C language that can be either compiled externally to create stand-alone analysis modules, or be integrated with any other system accepting a C module. Further, to complete the framework as a stand-alone analysis package, a Qt-based visualisation interface is added. It allows dynamic manipulation of the design parameters via the GUI elements, and updates the screen with the corresponding effects on motion and/or some pre-defined output function or performance index in the real time. The features and the usage of the framework is illustrated with the example of a Stephenson-III six-bar mechanism. The framework, however, is capable of handling more generic mechanisms and is designed to be easily extendable. It is hoped that the mechanism design community would find this framework of some interest and utility.

Keywords: Planar mechanisms, Graph theory, Dynamic visualisation, flex, Bison, Qt, Meta-programmingdfdfd

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Abstract

In this paper a brief account of historical development of TMM in Italy is presented by discussing main aspects with peculiarities of Italian frames by using significant illustrative examples of personalities and works. This historical background is the base for the current activity of the Italian community working on MMS as linked also to IFToMM. Research, teaching, and application development on MMS are today carried out by teams in 32 Italian Universities with success both within national frames and with international collaborations.

Keywords: History of TMM, History of Kinematics, Italian Developments

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Abstract

There have been wide applications of threaded fasteners since its inception few centuries back. However, under hostile vibrating condition, threaded fasteners loosen clamping force leading to failure of the system. Many researchers investigated the mechanism of loosening, and found out the factors behind the loosening. With this understanding, many investigators tried to develop threaded fasteners having locking characteristics. In the present work, loosening characteristics of M16 high tension steel bolt (HTS) with conventional nut, nylock nut, hybrid double nut (one conventional nut and one nylock nut), flat washer, spring washer, inside serrated washer and outside serrated washer are tested under accelerated vibrating conditions using an indigenously made test rig for 11000 oscillations. The loss of clamping force from the initial one indicates the extent of loosening. Hybrid double nut using one conventional nut and one nylock nut has been found out to show remarkably good anti-loosening characteristics over the others tested. On the other hand, the nylock nut applied on a conventional bolt shows better anti-loosening ability than the other nuts and washers tested apart from hybrid double nuts.

Keywords: Metric thread, Washer, Loosening, Accelerated test, Vibration

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Abstract

This paper presents the use of neural network for condition monitoring of ball bearings using statistical parameters. The time domain vibration data corresponding to normal running and various fault conditions (ball fault, inner race fault, outer race fault in O3, O6, and O12 relative position) were used. The data were segmented into groups and statistical features like Kurtosis, Skewness, Variance, RMS and normalized 6th moment were calculated for each of these groups. These five parameters were used as input for a neural network consisting of one hidden layer with sixteen neurons and one output layer with one neuron. The network was first trained for single faults and then by combination of faults. This trained network was then tested by another set of data which was unknown to the network and the success rates were calculated for each type of input. The results proved the effectiveness of the neural networks in diagnosis of the bearing condition. After testing success of the network for fault diagnosis, the effectiveness of each parameter was tested. This helped to relatively grade the five parameters and also confirmed that only a single parameter was not sufficient for accurate fault diagnosis. Also, relative grading of the parameters provided flexibility to eliminate less significant parameters, leading to lesser number of inputs, thus reducing the computation required. This makes the neural network suitable for being adopted for on-line condition monitoring.

Keywords: Neural Network, Ball Bearing, Condition Monitoring, Vibration Data, Statistical Parameters.

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Abstract

To provide a stable hydrodynamic pressure on a parallel thrust bearing, one of the viable method is providing the surface textures on one of the bearing surface. The work is carried out experimentally to study the effect of positive square shaped textures on the performance characteristics like film thickness and frictional torque of thrust bearing by varying load and speed. The result shows that at low loads, film thickness decreases as speed increases however at high loads, film thickness increases as speed increases. Frictional torque increases as both speed and load increases. By providing textures on the thrust pad bearing, the load carrying capacity increases and frictional torque decreases than that of the plain thrust pad bearing.

Keywords: Lubrication, Surface texture, Thrust pad

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Abstract

Extensive uses of composite structures can be found in weight-sensitive structural applications due to its high specific strength and high specific stiffness. Laminated composite shallow conical shell with low aspect ratio can be idealized as turbomachinery blades. Delamination or inter-laminar debonding is the most feared damage mode in composites. This paper presents a finite element method to investigate the effects of delamination on free vibration characteristics of eight layered graphite-epoxy composite pre-twisted conical shells with bending stiff and torsion stiff configurations. The formulation is based on eight noded isoparametric plate bending element applying Mindlin's theory and neglecting Coriolis effect for moderate rotational speeds. The Multi-point Constraint algorithm is employed to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The QR iteration algorithm is utilized to solve the standard eigen value problem. Finite element codes are developed to obtain the numerical results concerning the effects of twist angles and rotational speeds. Numerical results obtained for eight layered bending stiff and torsion stiff laminates with mid-plane delamination are the first known non-dimensional frequencies for the type of analyses carried out here.

Keywords: Finite Element, Delamination, Conical Shell, Bending Stiff, Torsion Stiff, Multi-point Constraint

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Abstract

This paper explores to relate total fatigue damage and frequency of vibration resulting from excitation of a cantilever beam. From recent studies on damage mechanics, it is found that the magnitude of total fatigue damage of a component not only depends on the induced dynamic strain but also on the severity of vibrations. The Hybrid I-kaz method provides a two dimensional graphical representation of the measured strain and vibration signal. Hybrid I-kaz parameter (Zh) provides a measure for the degree of data scattering and thus incorporating strain-vibration effects into the relation between frequency and total fatigue damage. The comparative study is implemented using strain-life approach, and Hybrid Integrated kurtosis based algorithm for Z notch filter technique (Hybrid I-kaz). Two sets of the experiments are conducted, considering the frequencies near first mode and second mode of the beam. The pattern obtained by frequency variation with the Hybrid kurtosis parameter is useful in finding hybrid kurtosis parameter at any given frequency of vibration. It is found that the total fatigue damage is varying linearly with the hybrid kurtosis parameter. This relation is proved to be useful in predicting fatigue damage of a beam at any frequency of vibration.

Keywords: Vibrations, Hybrid I-Kaz Method, Total Fatigue Damage.

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Abstract

In diagnosing mechanical faults of rotating machinery, it is very important to know the vibration feature of the machine with various forms of fault. A rotor system with fault is generally a complicated non-linear vibrating system. Its vibration is in a very complex form. Rotating machinery is very popular in industrial applications. Most of the mechanical failures are due to vibrations. It is more so in case of rotating machinery. Main cause of vibrations is faults in the rotating systems like unbalance, looseness, etc.. In this paper Artificial Neural Networks (ANN) are used to identify unbalance and looseness in rotor bearing system. Here it is considered as two class classification problem. Experiments are conducted to collect the vibration data in both horizontal and vertical directions, from the rotating system. Statistical features are extracted from the vibration data and fed to neural networks for classifying the unbalance and looseness. These results are useful for making maintenance decision.

Keywords: Unbalance, Looseness, Rotor, and Neural Networks

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Abstract

The present work deals with stability analysis of a spinning viscoelastic rotor mounted on a rotating (precessing) base under the effect of axial centrifugal tension, where the spin axis and precession axis intersect at right angle. The nutation speed is zero, the spin and precession speeds are considered to be uniform and the precession axis is located at one end of the shaft. The axial centrifugal force on the disc due to precession speed has been considered. The properties of the shaft material correspond to those of a linear viscoelastic model of four element type. The shaft-disc system is assumed to be axially and torsionally stiff. For analysis, a simple supported rotor has been considered with a rigid disc on a massless viscoelastic shaft. The governing 3rd order parametric equations for such a rotor are derived in the simultaneously spinning and precessing frame by using the principle of virtual work. The stability borderlines are computed using the generalized eigenvalue problem considering spin speed, precession speed and the centrifugal force on the disc as parameters. Variation in axial centrifugal tension is effected by varying the location of the disc from the precession axis on the shaft.

Keywords: Precession, Spin, Viscoelastic , Centrifugal tensile force

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Abstract

This paper presents the design and analysis of a compliant mechanism using hyperbolic flexural hinges. The flexural joint study is carried for the general Stewart platform with 6-6 configuration which has six degrees of freedom. The paper is aimed at designing a flexural joint using finite element method. First the maximum joint forces required for a particular movement of the Stewart platform is obtained from using MSC ADAMS software. The solid model developed in MSC ADAMS is validated with respect to the analytical Newton-Euler formulation for a set of motion. The results are in good match with each other for the extensions of legs. Then the forces are used to determine maximum stresses induced in the joints for different neck dimensions and lengths utilizing FEA software ABAQUS.

Keywords:Stewart Platform, Flexural Joint, Hyperbolic, FEMfdfd

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Abstract

Gear contact surface wear is one of the important failure modes in gear systems. The procedure implemented in this work includes finite element multi pair contact modeling to predict the load sharing between the simultaneously contacting pairs and mathematical programming method to estimate the gear surface wear in high contact ratio gear drives for particular number of cycles. A method to find out the new tooth profile and the worn out volume after some particular number of wear cycles is also presented. The parametric study based on the pre established center distance and also for the fixed pitch circle radius are discussed. The variation of wear depth at various contact point along the path of contact shows the maximum wear depth at the beginning and end of the contact in gear drive, but the highest wear occurs at the dedendum flank portion or root portion of tooth surface.

Keywords: Wear, Finite element analysis, High contact ratio, Spur gear.

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Abstract

The present work aims at eigenvalue analysis of three-dimensional finite element rotor models using a simple mass-lumping scheme frequently used in structural dynamics. Finite element analysis of spinning systems is more complicated than the conventional structural ones due to the presence of the anti-symmetric gyroscopic or Coriolis matrices. In the present work, the mass matrix is lumped keeping the gyroscopic/Coriolis matrix intact. Unlike structural dynamics, in order to take care of the anti-symmetric terms the eigenvalue analysis needs to be performed in state space. For rotors on isotropic or rigid bearings, the matrices in the state space becomes 2n  2n in size, where the mass, stiffness and gyroscopic/Coriolis matrices are of the order n  n. If the bearings are orthotropic, the size of the eigenvalue problem further increases depending on the terms considered in the assumed solution. In this case the mass matrix appears twice in the final eigenvalue problem and only one of them requires to be lumped. It is shown in this work that in both the above cases, a diagonal mass matrix considerably reduces the computational effort. It is observed that the results using conventional and lumped mass matrices match particularly well when the rotor has different bending stiffness in two perpendicular planes.

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Many materials empirically exhibit rate-independent per-cycle dissipation under periodic loading. Towards developing micromechanically motivated models for damping under general triaxial periodic stress, here we consider small frictional cracks in a linearly elastic solid under arbitrary far-field time-periodic tractions. Detailed simulations in 2D and 3D are conducted using ABAQUS, with both zero- and nonzero-mean loading. A simple pseudostatic spring-block model is also studied analytically. Results from the latter, up to one fitted constant, accurately predict all the simulation results from ABAQUS, suggesting that the entire crack face essentially sticks or slips together. These results may lead, in future work, to useful constitutive relations for damping under triaxial periodic loading.

Keywords: Vibration damping, internal dissipation, friction, microcrack, ABAQUS

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Abstract

Due to the demand in increased load carrying capacity with reduced weight, size and vibration, asymmetric gear design is getting significance for the engineering applications where unidirectional load requirement exists. Unlike symmetric gears, different base circle diameter of drive and coast side gear tooth profile necessitates optimization of asymmetric gear root circle diameter. In this work, finite element analysis is performed to optimize the dedendum for the chosen module of 3, 18 teeth, 20-34 asymmetric spur gears.

Keywords: Asymmetric gear, Finite element analysis, Optimization

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Abstract

Large aperture deployable mesh reflectors have potential use for satellite communication. These are light weight and flexible. These reflectors need to be stowed to a compact volume and held to the spacecraft deck through hold down and release mechanism (HDRM) at multiple locations during launch due to space constraints in launch vehicle and also to meet the necessary frequency requirement. HDRM will be released, deployed and latched to the intended position in the orbit. The dynamics and latching of one such HDRM is analysed in this paper. The mechanism consists of two deployable, spring driven circular plates connected by a pre-tensioned bolt. Upon deployment these circular plates latch into their intended position. The flexibility of the circular plate is modelled during its deployment. The velocity of the deploying plates is estimated and a transient dynamic analysis is carried out, imposing the velocity as initial condition to estimate the latching forces and moments. The latching loads form input for the design of HDRM mechanism.

Keywords: Dynamics, Deployment Mechanism, Transient dynamics, Latching and Shock

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Abstract

Seminal works in biped walking such as [1] had assumed favorable initial conditions on a limit cycle to start with. A more practical approach would be to start the biped from a static resting position. This paper proposes a simplified and straightforward approach for taking a biped robot from an initial resting position to a stable walking limit cycle. The biped model selected for the study is the 'kneeless biped with torso'. The problem is tackled in two stages - gait initiation from rest followed by convergence to stable walking. Walking is divided into various sub-phases depending on the state of the biped and simple state feedback control laws are proposed for each phase. The individual control laws are mathematically accrued into a single control law valid throughout the walking phase. Simulation results validating the approach are presented.

Keywords: Knee-less biped, Walking robots, limit cycle

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Abstract

This paper describes the formulation of equations of motion of a spatial pendulum using Euler-Lagrange formulation. Note that the pendulum has one spherical joint with three rotational degrees of freedom. Out of 12 possible Euler-Angles combinations available to represent the spherical joint, the ZYZ Euler angles were used to describe the rotations of the link. The equations of motions involving partial differentiations, etc. were obtained using symbolic computations. Such symbolic expressions help in interpreting the effect of parameters on the overall dynamic behavior of the system at hand. For the spatial pendulum, simulations were performed by varying the different rotational angles. The Coriolis and centrifugal forces were evaluated symbolically. After four-stage simplifications about 1000 terms could be brought down to less than 100 terms using the "simplify" command of MATLAB in a systematic way which will be shown in the paper.

Keywords: Spatial pendulum, symbolic computations, forward dynamics

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Abstract

This paper presents design and development of a novel two axis servo-control mechanism. A sphere is used to which a a panel is coupled which is to be driven about two axes mutually perpendicular to each other. The two axis control applicable for the solar panel is sought. A prototype is developed. Two limited angle servomotors are used to drive the wheels which generate the necessary friction torque for the spherical ball to rotate about the two mutually perpendicular axes. A control algorithm is developed and verified in simulations using Proteus software. The complete setup is developed. The controller is validated experimentally using micro-controller.

Keywords: Servomechanism, Two axis control, Spherical ball drive.

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Abstract

Managing bedridden patients is an important issue as many people are involved in it and patients need round the clock assistance. An attempt is being made by the authors, to reduce the amount of assistance required in managing these patients by designing a new bed. This paper presents analysis and synthesis of mechanisms for realizing such bed.

Keywords: Design of bed, Mechanism synthesis, Bedridden patient, Bed with commode

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Abstract

kadwa is hay cut into small pieces for feeding to livestock. It is a good fodder, and at its best when it is cleanly and evenly cut, free of dust, of good colour and with a fresh aroma. kadwa can be purchased from commercial kadwa cutting mills. Cutting kadwa can be done by manually and electric operated cutting machine, as far as cutting manually is concerned. Traditionally for the operator it is done manually which is physically demanding through it energy and postural requirements and is commonly regarded as source of drudgery. Many farmers associated with this task reported back, shoulder and wrist discomfort. It may also cause clinical or anatomical disorders and may affect worker's health. The machine consists of a human powered flywheel motor using a bicycle-drive mechanism with speed increasing gearing and a flywheel, which drives the process unit through a spiral jaw clutch and torque-increasing gearing. Manually energized flywheel motor has been adopted for many designs of rural applications in the last two decades, establishing functional feasibility and economic viability of energized process machines. The paper presents experimental work executed for establishing generalized experimental based empirical model for kadwa-cutting operation. Estimation of mathematical model and its simulation. Some third world development projects currently transform used bicycles into pedal powered tools for sustainable development. The articles discuss about the applications for pedal power technology.

Keywords: Flywheel, Spiral Jaw Clutch ,Kadwa Cutter.

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Abstract

One of the basic problems of user on manual wheelchair is overcoming architectural barriers (kerbs, stairs etc.) on its way. Even though many research studies have been reported in different fields to increase the independence of wheelchair users, the question of overcoming obstacles by a wheelchair always remains as topic of discussion for many researchers. In this paper, the author has proposed a manual stair climbing wheelchair concept which can overcome the architectural barriers to a considerable extent. Major part of the paper focuses on the proposed creative design concept and concludes by discussing upon the physical working model developed for the proposed design solution.

Keyword: Convertible Wheelchair, Stair Climbing Manual Wheelchair, Design for Barrier, Inclusive design.

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Abstract

This paper demonstrates the investigation of autonomous motion, in special autonomous oscillation of plane mechanisms, by using two computer-programs in combination with common software. The first part gives a short introduction with respect to the first computer-program, which can be installed at any notebook. This program allows the investigation of plane mechanisms up to 20 links, starting from the type-synthesis till the analysis; considering geometrical, differential-geometrical, kinematical and kinetostatical tasks. The definition of elementary groups (EGs) includes the specification of a link-fixed coordinate system at any link. On the basis of explicit equations the solution of significant tasks is included to this restricted universal computer program. The second part of the paper demonstrates the advantages in researching special topics of autonomous motion of an oscillating slider-crank mechanism by using the announced two computer-programs.

Keywords: Mechanism, linkage, elementary group (EG), prime core-structure, position geometry, differential geometry, kinetics, kinematics, position-parameters, mass-parameters, force-parameters, type-synthesis, autonomous motion, autonomous oscillation, generalized force, kinetic energy, time-calculation, position of equilibrium PE, stationary motion.

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Abstract

Manually powered hand tricycles are commonly used vehicles used by the mobility challenged for conveyance and transportation in India. However, the existing models are inadequate in many essential features. The authors have developed a new design, which can be configured according to the user's requirement and comfort. The features that are adjustable are the driving mechanism, seat height, and inclination, back-rest inclination, and foot-rests. Telescopic tubes are used in all the modular features.

Keywords: Tricycle, Wheelchair, Mobility-disabled, Physically-disabled.

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Abstract

Lightweight power tillers have been introduced recently in the country. Most models of the light weight power tiller being manufactured in India have been provided with a front or rear mounted powered rotary unit for forward movement as well as for tillage operation. There is scope for these power tillers to be used as seedbed preparation and inter culture operation in wide spaced row crops like cotton and sugarcane. In order to assess the performance of lightweight power tiller, one such model was evaluated at Central Mechanical Engineering Research Institute, Durgapur under various soil conditions. The model was extensively used for seedbed preparation, inter culture operation etc. This paper presents the results of the study. The field capacity found to be 0.1 ha/day (10 hrs.). The fuel consumption was 1 lit/hr.

Key words: Tiller, tillage, Power, lightweight, rotary tiller

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Abstract

Truck, tipper, dump truck are used to transport loose material from one place to another place at construction site in mines or in dump yards to accomplish the actual site requirement. If one can understand the ground condition and availability of space in mines and on construction site, it is very tough task to unload loose material at appropriate place, adjustment of truck is needed which take considerable time and effort to unload loose material. As everyone knows that tipper is mostly used for unloading loose material on construction site, mines and dump yards. The Existing system available is to unload material on back side. As considering the mines space available is very less due to which unloading material on left or right side is not possible to take this as a problem Multiside tipper tilting is the need of time. To overcome one side tilting of trolley, multiside tilting mechanism is come into focus. This will help to reduce the efforts to unload loose material one side of tipper. Propose work is on placing three hydraulic cylinders each on front side, right side and left side of trolley to unload loose material on back side, left side and right side of trolley respectively. Some design modification is needed in existing system to work on multiside tipper tilting mechanism.

Keywords: Design, Mechanisms, Hydraulic power pack

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Abstract

In fast breeder reactors, spent fuel subassemblies are replaced with fresh subassemblies during fuel handling. Three types of machines namely, straight pull, offset arm and collapsible type or pantograph are used for in-vessel handling operations. The pantograph type uses a collapsible link system identical to a Scott-Russel mechanism. Though design is very complex with many links working inside sodium, use of pantograph type machine is being considered in the recent advanced reactor designs due to overall economic benefits. Kinematic analysis of the link system is very important in order to meet the accuracy of positioning of gripper and to arrive at the basic dimensions of the machine including its drive system. Displacement, velocity and acceleration diagrams were generated for the gripper assembly connected to output end of the link system in relation to the movement of the input link (lower carriage) using Multibody Dynamics analysis software and the same was verified analytically. The displacement, velocity and acceleration at the output link (gripper) vary non-linearly. Analysis showed that the maximum velocity of the link system is very small within the operating range of the machine and hence does not influence the positional accuracy of the gripper for a velocity of 50mm/s at the lower carriage. The inertia force developed on the gripper assembly is negligibly small.

Keywords: Fast breeder reactors, Prototype fast breeder reactor, Fuel handling, In-vessel handling machine, Kinematic analysis of mechanisms.

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Abstract

While many state governments in India, like Tamilnadu, Karnataka, Punjab & Haryana, going for compulsory inclusion of speed controllers in vehicles, commercial speed controllers is priced between Rs 10000 to Rs. 20000, which imposes a financial burden to the vehicle owners. In the proposed system, by using economical elements like a microcontroller (Rs.250), a motor driving circuit (Rs.100), 12V motor with gearbox (Rs. 300), springs (Rs. 40) & other miscellaneous items (< Rs.180), in innovative manner the total amounts to Rs. 870. Incorporating other costs, the market price would be Rs. 3500, which is 65% to 80% less when compared to the present product's market price. It is achieved through replacing a rigid link between the linear cable and the cap of the carburettor/fuel-injector by a spring link whose stiffness is selected with respect to that of inside the carburettor/fuel-injector. So, when the current speed exceeds the desired speed, by compressing the spring link with the aid of a motor, the speed of the vehicle can be reduced/controlled without the need for the driver to change the throttle's position. Detailed force analysis along with a video proof shows the innovation behind this small modification. Thus when the proposed product, which can be easily incorporated & does not affect the engine's performance, is commercialized, after making some market ready alterations, will benefit the vehicle owners in large & also in successful implementation of the law.

Keywords: speed control, automobile speed control system, low-cost speed control system

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Abstract

This paper describes the design, prototyping, and testing of a single-piece compliant ring-actuator that can deform radially to grasp and release objects of regular polygonal shapes. The ring-actuator comprises a compliant mechanism that converts circumferential motion to radial motion of its multiple contact pads, two shape-memory-alloy (SMA) wires that provide circumferential actuation, and insulating roller guides. A new feature of this actuator is that its contact pads move in unison because of the uniform deformation of the underlying compliant mechanism. The outer diameter of the ring-actuator is 90 mm while the diameter of the circle made by the inner contact pads is 59 mm. Thus, it has a radial span of 15.5 mm. The weight of the ring-actuator is 52 g. With 2% strain in the SMA wires, the pads can move radially outwards by 1.5 mm. This means that there is a displacement of about 10% of the radial span. The experimental prototype had about 1.2 mm radial displacement for an induced strain of 1.75%. One of the uses of this ring-actuator is in grasping an object externally and thereby enabling an external pipe-crawling device with inchworm motion.

Keywords: compliant mechanism, shape memory alloy, deployable actuator, pipe crawler, robotic system

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Abstract

We present a compliant end-effector that helps in cutting soft tissues and sensing the cutting forces. The design of the end-effector is such that it has an upper threshold on cutting forces to facilitate safe handling of tissue during automated cutting. This is shown with nonlinear finite element analysis and experimental results obtained by cutting inhomogeneous phantom tissue. The cutting forces are estimated using a vision-based technique that uses deformation of the compliant end-effector. Furthermore, we demonstrate an immersive tele-operated tissue-cutting system together with a haptic device that gives real-time force feedback to the user.

Keywords: Compliant mechanisms, Tissue-cutting, Tele-operation, Haptics.

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Abstract

Kinematic synthesis techniques that include springs to model elastic deformation, and solid mechanics and optimization-based techniques developed so far for compliant mechanism design are general enough for initial or conceptual design but are not, at this point of time, capable of easily handling practical requirements. Furthermore, they cannot judge a priori whether a set of user-specifications has a solution or not. To address these issues, we have recently developed a lumped input-output model of compliant mechanisms and a comprehensive method of design based on selection and re-design of entries stored in a database of compliant mechanisms. The method is capable of informing the user if the specifications given to it are feasible or not. It also enables the user, when it is possible, to select a topology of choice and re-design it interactively with due attention to maximum stress, manufacturing considerations, and material selection. To make this method accessible to designers at large, this paper presents an online implementation of the method with graphical user interface (GUI) (http://www.mecheng.iisc.enet.in/~m2d2/CMdesign). The necessary theoretical background is included and a case-study is presented.

Keywords: Compliant mechanisms, spring-lever model, design by selection, interactive design

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Abstract

In this work, we present the design of the Force-amplifying Compliant Mechanisms (FaCMs) that are integrated into micromachined resonant accelerometers to increase their sensitivity. An FaCM is a mechanical amplifier that utilizes the force applied at one point to give an amplified force at another point in an elastic continuum. The inertial force acting on the accelerometer device causes a shift in the resonant frequency of the sensing beams by exerting an axial load on the beams. The role of an FaCM is to amplify this axial force and thus enhance the frequency-shift in the beams. In this work, we present FaCMs that are synthesized using topology optimization procedure for compliant mechanisms. A comparison of these FaCMs with existing force-amplifier lever mechanism is presented. One of the FaCMs outperforms the lever by a factor of six. In order to further improve the designs of the FaCM, we use the selection-map technique. Selection-map is a newly developed method used in place of shape and size optimization for re-designing single-input-single-output (SISO) compliant mechanisms as per user specifications. The evaluations of the re-designed FaCMs indicate better performance as compared to the original one.

Keywords: Compliant mechanisms, Topology Optimization, Selection map, Resonant accelerometer.

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Abstract

We present here an overview of the work done on the development of a meso-scale dual-axis spring steel in-plane accelerometer equipped with Hall-effect sensors. The design of the accelerometer has the unique feature that there is perfect de-coupling of the motions in the two in-plane orthogonal directions. One more extra feature is the use of rechargeable Li-ion batteries as a part of the proof-mass in addition to serving as the power source. The mechanical element of the accelerometer is made of EN J42/AISI 1080 spring steel foil machined using Wire-cut Electro-Discharge Machining (EDM) process. Allegro A1395 linear Hall-effect sensors are used to transduce the displacement of the proof-mass into voltage. The packaged sensor has an overall dimension of 73 mm × 73 mm × 28.5 mm. The packaged sensor can detect an acceleration signal as small as 25 milli-g with a measured sensitivity of 78 mV/g and 102 mV/g along X and Y axes respectively. Reason for asymmetry and scope for improvement in performance, reduction in size, and batch production are also discussed in this paper.

Keywords: Accelerometer, meso-scale, dual-axis, Hall-effect sensor, mechanism and Wire-cut EDM

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Abstract

Flexure mechanism systems with ultra-high precision motion stages are increasingly being used for several applications including micro-measurement, micro/nano manipulation, microfabrication, data reading, writing on CD and so on. Flexure linkages offer inherent advantages of being frictionless, highly repeatable, and having great design flexibility. Their main advantage is that they can be manufactured monolithic which is extremely crucial for micro and nano-scale applications. But Monolithic fabrications of these mechanisms limit the use of multiple materials in the system and hence become expensive especially for three dimensional mechanisms. For large range flexure mechanisms monolithic fabrication is a costlier affair. Efforts have been made by researchers to come up with assembly procedure to assemble these mechanisms without over constraining them. Our paper discusses one such type of method to design and assemble various components of these mechanisms. The proposed guidelines which are based on criterion similar to Grubler's include a very simple formulation to determine number of locating pins to be used in assembly and also their locations of these pins. A z-stage flexure mechanism was fabricated and assembled using these guidelines and found it to be working perfectly with repeated assembly and dis-assembly.

Keywords: Flexure, bending, micro-fabrication, kinematics of linkages, constraints

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Abstract

Rovers provide a mobile platform for exploring planetary bodies. The rover performance on uneven terrain depends on mobility limits on slopes and obstacles which in turn is dictated by the rover configuration. This includes the number of wheels, the dimensions of the rover, wheel size, presence of active joints and the like. In this study, to evaluate the performance of rover on lunar terrain which is uneven and covered with regolith and boulders, benchmark obstacles have been considered that are rigid and regular in shape like inclined and stepped terrain. A quasi-static analysis is carried out where equilibrium equations are solved to obtain the normal contact forces. Subsequently, the friction coefficient required to develop traction to overcome obstacle resistance and the wheel drive torques are obtained. The toppling limits for the longitudinal and lateral directions are also obtained. Consequent to analysis, the rover hardware is tested on benchmark obstacles. To control the rover, an active open loop algorithm has been developed using an external motion controller for the motors used to drive the rover. This study provides a validation to the analytical model besides proving the performance of rover hardware on obstacles.

Keywords: Rover, Traction, Drive torque, CAN, Quasi-static analysis

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Abstract

The present paper deals with the coordination issues of multiple wheeled robots working in a common dynamic environment, in a decentralized manner. Two different motion planners, one based on Neural Network and other using the potential field method have been developed to plan the motion of the robots. A strategic approach has been proposed to develop the decision making support. Performance of the developed approaches have been tested through computer simulations. Proposed strategy has been found to solve the conflicts and induced coordination among the agents.

Keywords: Mobile Robots, Coordination, Robot Motion Planning, Neural Network,
Potential Field Method.

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Abstract

In this paper an attempt has been made to design a three legged vertical robot. Each leg of the robot is considered to have two links connected each other and with the trunk by revolute joint. The legs are symmetrically distributed over the trunk body. Movement of the Center of Gravity (CG) of the robot has been ensured considering one leg is moving at a time and other two are providing necessary support to the robot body. Motion equations of the robot have been derived using the concept of Newtonian mechanics. Thereafter, stability of the robot is analysed. Computer simulations have been carried out to test the navigation capability of the robot on a vertical surface. Performances are found to be satisfactory and computational complexity of the developed algorithms is found to be low.

Keywords: Tripod Robot, Kinematics, Gait Planning, Dynamics, Stability.

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Abstract

The paper presents path planning of dual arm free flying space robot using smooth functions of time. Kinematic and dynamic modeling of dual arm free flying space robot is presented first. Using kinematic model the Jacobian of the system and using dynamic model equation of motion are derived. A path planning methodology for planar system is developed using smooth function of time such as polynomials. Due to nonholonomic behavior of the manipulator in the zero gravity environment linear and angular momentum are conserved. The proposed method yields input trajectories that drive both the manipulator and the base to a desired configuration. Joint torque curves can be obtained by introducing this joint trajectory curves in equation of motion of the space robot.

Keywords: Free-flying space robot, Dynamics, Polynomial

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Abstract

Path planning of holonomic robot is a difficult task particularly when the robot has a finite size with holonomic characteristics. Basically the kinematic configuration in each stepwise movement is difficult to predict before the findings of gait constraints. So far the path planners are available those are worked on the movement of geometric CG vector but in our analysis CG becomes the secondary parameter rather the centre points of front and rear plays an important role in path planning. Moreover the analysis results show that the path obtained in this methodology is more stable than the earlier analysis. In each instant the pose variants are calculated and the related required data are handed over to find out the decisive variable in respect of its pose. The algorithm developed is based on geometric intervention of various curves and geometric figures. The chronology of this development is maintained and elaborated sequentially.

Keywords: Robot, trajectory, CG, path planning, potential field, heading anglefdfd

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Abstract

Boombot comprising four wheels and a rotating boom in the middle has been developed as a mobile robot for stair climbing application. The boom can rotate continuously to provide flipping motion to the main body. Stair climbing with low friction co-efficient between the wheels and the ground has been implemented by weight distribution between the rear and front wheels. To arrive at the optimum weight distribution, static analysis of the Boombot over stairs has been carried out using linear programming. It is found that redistribution of weight results in static equilibrium with low friction co-efficient.

Keywords: Wheeled robot, Stair climbing, Friction, Linear programming

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Abstract

Robotics has emerged as a major field of research and application over the years, and has also found a place in the curriculum of universities. Robotics as a course is challenging both for the teachers to teach and the students to learn as it involves 3D transformations, algebraic and differential equations, etc., which are difficult to understand. Several robotics learning software have been developed have helped to ease the learning of robotics as a subject. A similar attempt was made in developing RoboAnalyzer, a 3D model based robotics learning software that modelled a serial robot based on its DH-parameters. It could perform forward kinematics and show animation and graph plot as outputs. In this paper, further development of RoboAnalyzer is reported in the form of addition of inverse and forward dynamics analyses of a generic serial manipulator. The important contributions of this paper lie in the development of algorithms using an object oriented modelling approach and the Decoupled Natural Orthogonal Complement (DeNOC)-based recursive formulation. A KUKA KR5 robot was modelled in the proposed software, and the results were verified with those obtained using the Dynamic Simulation module of Autodesk Inventor. RoboAnalyzer can be downloaded for free from http://www.roboanalyzer.com and can be used almost instantly.

Keywords: DeNOC, DH Parameters, Recursive Robot Dynamics, Robot Analysis, Robotics Learning Software.

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Abstract

This paper presents a design and analysis approach for micropositioning stage based on 3-RPR parallel kinematic linkage. The dimensions of the stage are first obtained and static, dynamic characteristics of the stage are predicted. The objective here is to maximize the workspace (for ranges of both position and orientation) and minimize the singularities inherent in the system. After arriving the dimensions, the finite element model of linkage is developed in ANSYS and its resonant frequencies and deflections are also predicted to identify the effects of flexure hinges on overall performance.

Keywords: Planar positioning stage, Compliant parallel linkage, Electrostatic actuation, Flexure hinges, Finite element analysis.

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Abstract

This paper reports the biomimetic design and development of an extreme upper limb prosthesis. The motivation for developing a new prosthetic hand is provided by the fact that low functionality and low controllability are the most important reasons why amputees do not use their prosthetic hands. In addition, although multifingered hand prosthesis has appeared in the market, the cost is exorbitantly high and out of reach of common people, which is particularly true for developing countries like India. The paper presents an anthropomorphic design of a prosthetic hand with 15 degrees of freedom using underactuated mechanism. Control is through electromyogram signals based on support vector machine for classification of six grasp types involved in 70% of daily living activities.

Keywords: Biomimetic, Prosthetic hand, Electromyogram, Grasps

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Abstract

In this work, shape optimization is carried out of a single link flexible revolute flexible manipulator. Robotic link is considered as an Euler-Bernoulli beam and finite element formulation is done for its dynamics analysis using Newmark's scheme. Sequential quadratic programming (SQP) method is used to minimize the dynamic maximum tip deflection in order to have vibration suppression. Optimized revolute robotic manipulator may be preferred in the real world applications as per vibration issue is concerned due to its flexible nature.

Keywords: Flexible revolute manipulator, Euler-Bernoulli beam, Shape optimization, Finite Element Method, Sequential quadratic programming

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Abstract

This paper presents the study results on the handover movement informing a receiver of the weight load as an example of the informative motion for the humansynergetic robot. To design and generate the movement depending on the weight load, the human movement is measured and analyzed, and four items are selected as the parameter to vary – the distance between target point and transferred point (in front-back direction), the distance between highest point and transferred point (in vertical direction), the elbow rotation angle, and the waist joint angle. The fitted curve of the parameter variation depending on the weigh load is obtained from the tendency of the subjects' movement data. The movement data for an arbitrary weight load is generated processing the standard data at 0 kg of weight load so that each parameter follows the fitted curve. From the questionnaire survey, although it is difficult for a receiver to estimate the exact weight load, he may distinguish the heavy weight load from the light weight load so that the package will be received safely and certainly.

Keywords: Human-Synergetic Robot, Informative Motion, and Handover Task

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Abstract

A recursive dynamic modeling of a three-DOF parallel robot, namely, three-Revolute-Prismatic-Spherical (3-RPS) parallel manipulator is reported in this work. Euler parameters are utilized to define the 3-DOF orientation of its moving platform, because the coordinates are free of singularity. For the dynamic modeling, the concept of the Decoupled Natural Orthogonal complement (DeNOC) matrices is employed. The necessity of the concept is to use a set of independent coordinates, while Euler parameters are not. Hence, the improved recursive dynamic modeling reported somewhere else is utilized. This is especially useful for forward dynamic modeling. Finally, the results obtained are compared with those achieved from ADAMS model to validate them.

Keywords: 3-RPS manipulator; Euler parameters; Dynamic modeling, DeNOC matrices;

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Abstract

In this paper, we revisit the 3-Degrees of freedom (DOF) pure translational mechanism. The mathematical model and the design considerations are discussed. A detailed sensitivity analysis is carried out and the results are discussed in a new perspective. The theoretical model makes a strong case for feasibility of simple and practical 3-DOF pure translational mechanism. We validate the theoretical observations with prototype models and experiments. The results concur with the theoretical observations in contrast to what is presented in [6].

Keywords: 3 DOF Spatial Parallel Mechanism, Sensitivity Analysis, Prototype developmentdfdfd

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Abstract

This study addresses the forward kinematics problem of a new type of 3-UPU parallel manipulator. Orientation and position vector loop equations are derived using exponential rotation matrices. It is found that for generic dimensions the manipulator has 4 (Schönflies type) or 3 degrees-of-freedom (dof) depending on whether the platform is assembled parallel to the base or not. There are several assembly modes in both of the cases. When the base and the platform are identical the manipulator is overconstrained with 4 dof. This study also compares vector and quaternion approaches via analysis of the 3-UPU manipulator.

Keywords: Parallel manipulator, Forward kinematics, Exponential rotation matrices

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Abstract

Singularity analysis is the study of gain or loss in degrees of freedom of a mechanism at a particular configuration. Singularity analysis is related to the degeneracy of Jacobian matrices relating configuration variables with task space variables. In this paper, we present an improved Jacobian formulation which can be used to identify not only the gain or loss of degrees of freedom, but, in addition, can be used to determine if the gain results in redundant degree of freedom. The approach and its advantages are illustrated with several examples.

Keywords: Degree of freedom (DOF), Manipulator, Kinematics, Singularity, Actuated,
Passive joints, Redundant

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Abstract

In this paper, the forward and inverse kinematic relations of a hybrid 6-DOF robotic manipulator, named the H6AR, are presented. The H6AR consists of twin 2-DOF anthropomorphic arms that can move in the vertical plane. These arms are connected, at one end, to a 1-DOF waist and constrained, at the other end, by a novel wrist assembly. The wrist contains an actuator only for the pitching motion and due to its unique design, by moving only the twin arms, the yaw and roll motions are generated. Closed-form forward and inverse kinematic relations are presented by following the Denavit-Hartenberg technique.

Keywords: Hybrid Manipulator, Kinematics, Closed-form solutions

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Abstract

A 3-RPS manipulator is a three degree of freedom (DOF) parallel manipulator. It consists of a equilateral triangular fixed platform and a similar moving platform connected by 3 identical RPS (revolute-prismatic-spherical) legs. This manipulator has got a lot of attention in the literature. But as it turns out all of the papers are incomplete. This paper closes the gap and gives a complete description of the forward kinematics and of all operation modes of this manipulator, using Study's kinematic mapping. For this purpose algebraic constraint equations for each RPS leg are derived. The constraint equations together with the Study equation and a normalization term determine an ideal, representing the complete algebraic and kinematic description of the manipulator. This ideal is tested for possible decomposition to reveal different operation modes and then the different corresponding systems of equations are solved. Furthermore all singular poses and transitions between the operation modes are computed using the Jacobian of the aforementioned system.

Keywords: 3-RPS-manipulator, Direct Kinematics, Working Modes, Singularities

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Abstract

The co-operation among a set of robots is for the purpose of achieving a common goal. The intent of cooperation and objective of effective co-operation would set up a functional relationship among the co-operative robots. This paper presents a new trajectory planning scheme based on inter-relationship that has to exist in achieving a goal in cooperation. Apart from conceptualization of the scheme, the paper presents an analytical scheme and experimentally validates the concept using two in-parallel robots in cooperation. The development is based on the robotics in nuclear industry.

Keywords: Mirroring motions, Cooperative Robotics, Task Space Trajectory, Robot Trajectory Program.

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Abstract

This paper reports experimental results of a newly built BAPAMAN1 (Binary Actuated PArallel MANipulator). This is a 3-DOF (Degree Of Freedom) modular spatial parallel manipulator with low-cost and easy-operation design features. BAPAMAN1 is driven by SMA (Shape Memory Alloy) at its flexure joints. Several experimental tests have been carried out with the aims to validate the proposed mechanical design and to evaluate the practical operation performances and characteristics of the built prototype. Experimental results show that the tested prototype can perform eight binary configurations and it has a suitable reachable workspace for the prescribed applications.

Keywords: Flexure Joints, Binary Actuators, Parallel Manipulators

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Abstract

The presence of backlash in the gearheads is an inherent problem in manipulators using geared motors. This paper looks at a potential solution to this problem via the implementation of a dual-loop control strategy, in which feedback is taken from the motors as well as the end-effector of the manipulator. Using the redundant sensed information, the actual error in the joint-space is computed and used to rectify the desired trajectory for the joint-space trajectory-tracking control scheme. Experiments done on a 3-RRR planar parallel manipulator show significant improvement in the tracking performance due to the introduction of dual-loop control scheme.

Keywords: Dual-loop, trajectory tracking, backlash correction, parallel manipulators

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Abstract

Trajectory-tracking control of parallel manipulators is more difficult than in the case of serial ones due to the presence of the loop-closure constraints and constraint forces resulting from them. One needs to eliminate these forces to get to the equation of motion, and then apply a control scheme. In this paper, such a control scheme is presented through application on a semi-regular Stewart platform manipulator (SRSPM). The manipulator has six degrees-of-freedom; however, it is modelled by a system of 18 coupled nonlinear ordinary differential equations (ODE) using the constrained Lagrangian formulation. The model is then linearised through feedback, and controlled by a linear PD servo scheme. Numerical simulations over a non-singular path show that the scheme is fairly accurate, at the cost of being computationally expensive. The scheme is general in nature, and as such, it is expected to work in the case of other parallel manipulators as well.

Keywords: Stewart platform, Computed torque control, Feedback linearisation, Control-law partitioning, Parallel manipulator, Lagrangian dynamics, Trajectorytracking

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Abstract

Farm Tractors undergo dynamic, vibration energy changes during operation of farm implements. With the help of mechanical equilibrium and weight shift reactions of tractor different parameters of force, wheel base, tyre reactions and CG were calculated. During the vibration analysis of the tractor system (vibration on the chassis or due to air flow resistance-Ra=CAv2) by assuming tractor as spring mass system, the vibration noted was of the scale of ω1, 2 = 36.0 radians/sec, and 21.5 radians/sec i.e. 5.73 Hz and 3.43 Hz. Piezoelectric materials can convert mechanical stress and vibration movements of the tractor (normal load on the tyres and vibration on the chassis) into electrical energy of high voltage output. When such a material (Quartz, PZT), Ferroelectric in nature, was subjected to mechanical stress or vibrations on lateral or transverse axis, a multilayer generator of a size of 5×5×2 mm under a normal load of 10kN could generate energy of 12mJ.This electrical energy was thereafter formatted by a static converter before supplying to a storage system or directly to the site of application, which can also be harnessed by rubber brush actuators and thus can be stored in the super capacitors, lead batteries or super conducting magnetic energy storage devices and hence was used to drive the PTO, AC compressors, portable and non portable electric devices, Gauge and Thermostat valves. Thus reducing the engine load and increasing the fuel efficiency of a farm tractor by manifold thereby decreasing carbon footprints and operational cost.

Keywords: vibration, dynamic, piezoelectric-generators, tractor, fuel- efficiency

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Abstract

Stereotactic surgery is a technique used for diagnosis and treatment of brain tumors. This paper gives survey on evaluation of art and science of neuro-surgery and proposes the need of stereotaxy to replace the outmoded conventional surgery. Stereotaxy makes use of a system of three-dimensional coordinates to locate a site (usually within the brain) with high precision for conducting biopsy or surgery. The evolution of frame to frameless stereotaxy till its current form has been explained. The paper gives a detailed account of how the imaging and image processing software has complimented the advances in neuro-navigation based stereotactic surgery. The important contributions and developments in the past and the current practices in the area of neuro-navigation and registration techniques have been presented in this paper. The development in the author's laboratory on robotics based stereotactic surgery has been discussed.

Keywords: Frame and Frameless Stereotaxy, Neuro-Navigation, Robots for Surgery

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Abstract

In shuttle less weaving machine, the threads are inserted along width of the cloth by using two rapiers placed on its flexible tape wound on oscillating rapier wheels which are situated at both sides of the machine. A mechanism driving each rapier wheel consists of a slider-crank engaged with the helicoids variable pitch screw. The kinematical study of the mechanism is divided into the analysis of two sub-mechanisms: 1) a slider-crank 2) the slider engaged with screw. At the end of the axis of the screw the rapier wheel is fixed. The displacement of the slider-crank along the axis of the screw and rotation of the screw are calculated. Three types of variable helix geometry namely a) cycloidal b) 2-3 polynomial c) 3-4-5 polynomial type is considered. The relations between rotation of crank (input) and the corresponding angular rotation of the screw (output) producing oscillatory motion of the screw are obtained for three cases of helix geometry by graphical method and the output is symmetrical about the crank rotation of 180 . It is found that the polynomial type produces lower acceleration and velocity but a considerable dwell of screw and also the rapier wheel than that of cycloidal type.

Keywords: Rapier weaving, Slider-crank mechanism, Screw mechanism, Variable pitch screw

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Abstract

PFBR, India's first commercial fast breeder reactor is equipped with two independent, fast acting and diverse shutdown systems. A shutdown system comprises of sensors, logic circuits, drive mechanisms and neutron absorbing rods. The absorber rods of the first shutdown system are called as Control & Safety rods (CSR) and their drive mechanisms are called as Control & Safety Rod Drive Mechanisms (CSRDM). CSR are normally partially inserted in the active core & held by CSRDM. CSR and its Drive Mechanism (CSRDM) are used for reactor control and for safe shutdown of the reactor by scram action. The safety of the reactor is primarily dependent on shutdown system and heat removal system; hence these systems should be highly reliable systems. In order to improve the safety of future reactors further, active and passive safety features are added to the existing shutdown system design. The stroke limiting device is one such active safety device which safeguards the reactor against Unprotected Transient Over Power (UTOP) event resulting from uncontrolled withdrawal of one control rod. It is an add-on device for CSRDM. This is a mechanical device, which physically limits the upward movement of CSR to a specified value and allows further upward travel on resetting by plant operator. The paper presents the principle & design features of SLD. Three concepts of SLD are discussed with their pros & cons

Keywords: Stroke limiting device, CSRDM, CSR, Fast reactor, PFBR

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Abstract

Design of Spacecraft components is multidisciplinary in nature involving many iterative engineering fields in the process of product realization. Development of spacecraft components includes rigorous optimization to meet the stringent multifunctional requirement like high strength, stiffness, low mass, eased manufacturing, ease in assembly and functional needs. The spacecraft payload components are integrated with RF cables of various sizes, length and diameters. These cables form heavy RF/DC harnesses integrated with space payload and cause many practical problems like joint breaks, solder cracks and arcing during operational and environmental testing of payload. A similar problem is faced in the recent development of Electronic Power Conditioner (EPC) scheduled for the GEOSAT payload of ISRO's mission. The solution to the problem has culminated in an innovative product called Controlled Compressible Collet Clamp Micro Mechanism (C4μM) which could successfully eliminate joint breaks, cracks and arcing problems. The product design of C4μM is rigorously parameterized, optimized, simulated and analyzed using state of art CAE tools. The product (C4μM) is manufactured, assembled and successfully tested. Presently this design is slated for flight in the upcoming GEOSAT Satellite. This paper describes the challenge faced in the development and realization of the product.

Keywords: Finite Element Method, Collet, Spacecraft, Electronic Power Conditioner, clamp, RF cables, Mechanism

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Abstract

Bent pipes as in fig 1 are used for structural (sometimes decorative) purposes like bicycle handlebars, furniture frames, grab bars, roll bars, etc. or as passageways carrying fluids or gases like hydraulic lines, fuel lines, exhaust pipes, water lines, etc. Industries typically using bent pipes are automotive, aircraft, off-road and farm equipment, boiler, air conditioning, ship building, furniture, power generation, recreational vehicle, railroad, etc.[1] The objective is to design and develop a mechanism which can bend a pipe using manually energized flywheel motor, which consist of energy unit and transmission mechanism. Development of such an energy source which has tremendous utility in energizing many rural based process machines in places where reliability or availability of electric energy is much low . The real challenge is accurately placing the tubing into the bender so that the bend comes out in the right position. Relation deduced predicts the performance of pedal powered pipe bending mechanism and all the parameter needs to be optimized to get the best performance of the machine. A new theory of Pedal Powered pipe bending machine is proposed. This human energized unit can be useful for other purposes as lifting water by pump, rice mill. The advantage of this machine is that this will generate employment. It helps in keeping the environment pollution free.

Keywords: Pedal, Pipe Bending, transmission mechanism

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Abstract

Precise positioning and tracking find applications in several areas including robotics. This paper presents robust stabilization and tracking using integral sliding mode control(ISMC). A second order position servo mechanism is considered. A sliding mode control is known to be robust during sliding, however the reaching phase is not robust. Integrals sliding mode ensures sliding right from the beginning thus ensures robust performance in the entire state space. Effectiveness of the method is validated in simulation as well as by experiment.

Keywords: ISMC, Stabilization, Tracking

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Abstract

The paper discusses a method for the dynamic simulation of a KUKA KR5 industrial robot using MATLAB SimMechanics. As it is difficult to model complicated 3D objects directly in SimMechanics environment, Autodesk Inventor was used to develop CAD model of KUKA KR5 robot parts and its assembly. Details of the CAD assembly and importing to the MATLAB environment are explained. The assembly of robot required joint constraints that were fed with cycloidal joint trajectories to perform inverse dynamics. The same system was also allowed to fall freely under gravity for which simulation results were obtained. The above inverse dynamics and simulation results were verified using those obtained from the model developed.

Keywords: CAD Assembly, MATLAB SimMechanics, Dynamic Simulation

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Abstract

Legged locomotion is used by most of the animals and human beings on the earth. Legged locomotion is preferred over the wheeled locomotion as it can be used for both flat and rough terrains. In this paper, an attempt has been made for the dynamic modelling and simulation of four legged jumping robots with compliant legs. Sagittal plane and bounding gait has been used. For energy saving passive dynamics has been used with the help of compliant legs (linear spring). Different state variables have been obtained for analysis. Control strategies have been implemented on dynamic modelling for forward velocity control.

Keywords: passive dynamics, legged locomotion, sagittal plane, control,

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Abstract

Vibration suppression of piezoelectric laminated beam is presented in the present work. A one-dimensional finite element model for the dynamic analysis and control of a hybrid beam with surface mounted piezo-layers is developed. The coupled efficient layer-wise (zigzag) theory is used for making the model. Piezoelectric layers are used as sensing and actuating elements. Each node of beam element has four mechanical degrees of freedom and a variable number of electrical degrees of freedom. Cubic Hermite interpolation is used for the deflection and electric potentials. Linear interpolation is used for the axial displacement and the shear rotation. Eigen Value problem using subspace iteration method is solved for a beam with clamped-clamped end conditions to obtain the natural frequencies. Based on the structure responses determined by finite element method, a state space model of the system is developed by converting the equations in modal model. The linear quadratic Gaussian (LQG) algorithm is employed for controller design. The control model assumes that the upper layer acts as sensor and the bottom layer as actuator, and the signal generated through is used as a feedback reference in the closed loop control system. The formulation is validated by comparing the results with the 2D-FE results, obtained using ABAQUS, for a beam with clamped-clamped end conditions.

Keywords: Zigzag Theory, FEM, Smart Beam, ABAQUS, LQG controller

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Abstract

Common method of limiting the stroke of a machine/mechanism by physically providing stoppers at the extreme limits is a proven concept to avoid unsafe manoeuvres. However, in some applications, it may be necessary to provide periodic stoppers while travelling in unsafe direction & their resetting after ensuring the safety of further travel and freewheeling from any position in the safe direction. The stroke limiting device is one such active safety device which safeguards the Reactor against uncontrolled withdrawal of one or all control rods resulting in unprotected transient over power (UTOP) accident. This is a mechanical device, which physically limits the upward movement of control rod to a specified maximum and allows further upward travel only on authorization by the plant operator, at the same allowing the freewheeling for downward movement from any given position. In this paper, design and development of the device are brought out.

Keywords: Stroke Limiting Device (SLD), Prototype Fast Breeder Reactor (PFBR), Control and Safety Rod (CSR), CSR Drive Mechanism (CRSDM), One-Way Clutch

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Abstract

The paper describes the design of a Stewart Gough Platform for isolating sensitive payloads from onboard vibration-emanating-components of a spacecraft e.g. cryogenic coolers and momentum wheel etc. The design is for isolating onboard milli g level vibrations primarily in three orthogonal translational axes and to survive the launch loads. The six legs connecting moving and base plates using spherical joints with axial rotation of legs constrained, contains linear actuator collocated with force sensor. A decentralized force feedback controller which uses PID control law with single gain for all six loops is used for actively attenuation the vibration coming from base platform. The transfer functions defined between base plate and moving plate accelerations is considered as a measure of isolation. An isolation of more than 20 dB beyond 40 Hz was demonstrated.

Keywords: Vibration Isolation, Stewart Gough Platform, PID controller

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Abstract

This paper investigates the Dynamic Analysis and optimization of electromechanical switching systems. It is a critical simulation activity which saves time, cost and improves efficiency of the design process. Auxiliary is an indication device for circuit breaker, which have mechanism to indicate whether circuit breaker is in tripped or ON/OFF state. There are many parameters which govern the performance of mechanism inside circuit breaker auxiliary such as material, stiffness of mechanism springs, interference of flexible links and friction. The purpose of the study is to investigate the effect of the above parameters on circuit breaker Auxiliary performance. Auxiliary performance is measured by functional requirements such as Toggle Torque, Response time for manual switching and rotation angle of Toggle. Toggle ON Torque for auxiliary should be always lessthan associated protection devices. Toggle Torque is applied on the toggle axis to change state of auxiliary from OFF to ON. Transfer function is developed for Toggle torque (Manual Switch ON) as a function of parameters with the help of Design of Experiments (DOE). Dynamic Analysis of the mechanism predicts the toggle torque and confirms with the test results, as well as transfer function is validated. Mechanism simulation effectively captured the product performance and assisted in enhancing the performance.

Keywords: Circuit breaker auxiliary, Dynamic Analysis, Toggle Torque, Design of Experiments

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Abstract

This paper proposes a neural network-based controller to enhance the effectiveness of antilock braking systems. Simulations of integrated controller of vehicle anti-lock braking system are illustrated first with traditional continuous PID controller and then with the proposed back-propagation neural network model controller. The slip ratio is selected as the main control parameters. Effects of vehicle speed and slip ratio are investigated on braking torque to reveal the performance of anti-lock braking system. Quarter vehicle single-wheel system is studied in this paper to illustrate the controller performance in maintaining the required slip reference trajectory. This can provide a guideline to design an anti-lock braking system.

Keywords: Antilock braking system, Wheel slip, Nonlinear control, Neural network

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Abstract

This paper presents kinematic analysis of a three-leg structure, namely, three- Revolute-Prismatic-Spherical (3-RPS) parallel manipulator using relative Euler parameters. Since, coordinates which are chosen to define orientation of platform, directly affect singularity of the manipulator, Euler parameters are utilized for this purpose. It is well-known that defining rotational motion of a moving coordinate system with respect to another using the Euler parameters causes singularity free formulation. The kinematic constraint equations are performed and solved numerically. The results are compared with the same of the manipulator simulation in ADAMS environment to validate the analysis. The algorithm is practical for dynamic modeling of the system as describe separately.

Keywords: 3-RPS; Parallel manipulator; Euler parameters; Kinematic analysis

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Abstract

Vehicle stability and performance have always been an active area of research for the automotive industry. The steering system is one of the key elements that determine the handling of a vehicle. A better understanding and modelling of tyres along with advances in techniques to actively determine the tyre characteristics has made it possible for a designer to better exploit the tyres capability. A four wheel independent steer-by-wire system is a system where all four wheels of the vehicle can be steering independently by separate actuators responding to computer generated signals. It has been shown in this work that in case of a vehicle with four wheel independent steer-by-wire system, the individual steady state slip angles of the four wheels can be directly controlled by an active system in the steady state. This can be used to help conserve tyres at off-limit cornering manoeuvres and boost maximum cornering speeds at on-limit cornering.

Keywords: Vehicle dynamics, steer-by-wire, four wheel steering, independent steering, tyre dynamics, slip angle control.

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Abstract

Flexural mechanisms have become popular due to their unique advantages over the conventional rigid body mechanisms. Due to absence of friction, stiction, and backlash as against conventional mechanism, compliant mechanisms are unprecedented in precision and reduction in wear and tear. However they face limitation in terms of range of possible displacements. Displacement-amplifying compliant mechanisms are used to get enhanced displacement (2-3 times) at the output as compared to the input. Researchers [2] in the past have proposed various designs of Displacement amplifying compliant mechanisms (DaCMs) which are based on structural optimization. However these are fabricated in a monolithic way. In this paper we consider design, analysis, and fabrication of DaCMs in an alternative assembly route instead of monolithic way. Based on evaluation of various monolithic mechanism proposed previously [2], one of the mechanisms giving highest displacement amplification is selected for analysis and fabrication of a equivalent compliant mechanism made of several assembled parts. The mechanism is designed to give displacement amplification in the range of 3 to 4. Overall size being the important criteria is kept within 300mm X 300 mm and height 100mm Copper beryllium strips are used as flexural links and aluminium clamps are used to connect the flexural links together to form the compliant mechanism. The analysis of the proposed mechanism is carried out using ANSYS to make sure the stresses are well within the limits and to determine geometric nonlinearity in the mechanism. Analysis shows that the overall amplification of about 3.5 is obtained though the relationship between input and output displacement is nonlinear and the stresses are well within limits. Successful assembly of mechanism without warping has been carried out. Further characterization of mechanism would be carried out in the near future.

Keywords: Compliant mechanism, flexural mechanism, displacement amplifying compliant/flexural mechanism.

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Abstract

Rotary electro-mechanical actuator is configured with stepper motor and four stage compound gear train for the Mixture Ratio Control (MRC) application of oxidizer & fuel for the liquid engines of satellite launch vehicle. Qualification tests conducted based on the detailed test plan confirms the design adequacy of actuator meeting the performance requirements. The actuator has been successfully inducted into the flight after successful ground validation tests.

Keywords: Actuator, Stepper motor, Bearings, Rotary Potentiometer, Limit switches, qualification

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Abstract

In this paper we suggest an effective method to measure dexterity index of parallel manipulators. A commonly used criterion for dimensional synthesis is the dexterity, which refers to the capacity of a Parallel Manipulator (PM) to provide a large range of orientation to its end-effector and describes a PM's motion accuracy, controllability (singularity) and manipulability. The earliest definition of dexterity is introduced by Salisbury and Craig , in which the dexterity is evaluated by the Local Condition Number (LCN) of kinematics Jacobian matrix. As LCN is configuration specific, various authors have used Global Condition Number (GCN) or Global Condition Index (GCI) which is reciprocal of GCN as the performance index. While studying the effect of change in design parameters, on performance of a 6-dof fully parallel manipulator, of Stewart Platform Architecture, we have found that GCN does not quantify the actual corresponding change in performance. We have tried to establish this by comparing change in GCN and change in frequency of various ranges of LCN. In cases, where we see a considerable change in frequency of undesirable ranges of LCN value due to dimensional changes, there is very little change in GCN, may be because of averaging effect. As we are more interested in examining if there are higher LCN values, GCN is unable to bring out this fact clearly. We suggest a concept of Weighted Average Condition Number (WACN) which can more effectively bring out this fact and can be used for optimization purpose.

Keywords: Parallel Manipulators, Dexterity, Local Condition Number, Global Condition Number, Weighted Average Condition Number

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Abstract

With advancement of technology life has become complex and redefinition of what is luxury and what is not luxury. Fuzzy. Examples are colour TV, mobile phones etc. Even in families and households below poverty line these white goods find presence. Consequently it is not confined to advanced technologies, the need for fail safe system. It is important to innovate fail safe systems in every technological environment. One of the early control mechanism is the fuse wire in an electrical network which has given way to trip switches. It is unfortunate that in spite of these advancement a house wife who was using an electric iron was electrocuted and the baby who was put to sleep and crawling on waking up to touch the mother also got electrocuted. Needless to say absence of proper fuse, earthing or tripping mechanism invited the calamity. At the other end of the spectrum is the burn out of Columbia on re entering into earth's atmosphere all because of a foam piece separating and falling on the heat shield and creating a crack. This paper drives home the importance of failsafe systems sto effective robust control mechanisms i.e. "meet the purpose and not fail to meet the purpose" which has been echoed in the statement "we need to have a high level of expectation that things will work the way we expect them to work" in the lead statement to the World Standards Day Message of 14th Oct 2011 by the Presidents of IEC. ISO and ITU.

Keywords: Fail safe mechanisms, Design elegance, Fail safe controls, Product quality, Process quality, Procedure quality, Value driven design.

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