scholarly journals Controlling the Movement of a TRR Spatial Chain With Coupled Six-Bar Function Generators for Biomimetic Motion

2015 ◽  
Author(s):  
Mark M. Plecnik ◽  
J. Michael McCarthy
Keyword(s):  
Constant Velocity ◽  
Joint Angle ◽  
Synthesis Process ◽  
Function Generator ◽  
Single Degree Of Freedom ◽  
Wing Motion ◽  
Serial Chain ◽  
Function Generators ◽  
Synthesis Procedure ◽  
Velocity Input

This paper describes a synthesis technique that constrains a spatial serial chain into a single degree-of-freedom mechanism using planar six-bar function generators. The synthesis process begins by specifying the target motion of a serial chain that is parameterized by time. The goal is to create a mechanism with a constant velocity rotary input that will achieve that motion. To do this we solve the inverse kinematics equations to find functions of each serial joint angle with respect to time. Since a constant velocity input is desired, time is proportional to the angle of the input link, and each serial joint angle can be expressed as functions of the input angle. This poses a separate function generator problem to control each joint of the serial chain. Function generators are linkages that coordinate their input and output angles. Each function is synthesized using a technique that finds 11 position Stephenson II linkages, which are then packaged onto the serial chain. Using pulleys and the scaling capabilities of function generating linkages, the final device can be packaged compactly. We describe this synthesis procedure through the design of a biomimetic device for reproducing a flapping wing motion.

scholarly journals Controlling the Movement of a TRR Spatial Chain With Coupled Six-Bar Function Generators for Biomimetic Motion

2016 ◽  
Vol 8 (5) ◽  
Author(s):  
Mark M. Plecnik ◽  
J. Michael McCarthy
Keyword(s):  
Constant Velocity ◽  
Joint Angle ◽  
Synthesis Process ◽  
Function Generator ◽  
Single Degree Of Freedom ◽  
Wing Motion ◽  
Serial Chain ◽  
Function Generators ◽  
Synthesis Procedure ◽  
Velocity Input

This paper describes a synthesis technique that constrains a spatial serial chain into a single degree-of-freedom mechanism using planar six-bar function generators. The synthesis process begins by specifying the target motion of a serial chain that is parameterized by time. The goal is to create a mechanism with a constant velocity rotary input that will achieve that motion. To do this, we solve the inverse kinematics equations to find functions of each serial joint angle with respect to time. Since a constant velocity input is desired, time is proportional to the angle of the input link, and each serial joint angle can be expressed as functions of the input angle. This poses a separate function generator problem to control each joint of the serial chain. Function generators are linkages that coordinate their input and output angles. Each function is synthesized using a technique that finds 11 position Stephenson II linkages, which are then packaged onto the serial chain. Using pulleys and the scaling capabilities of function generating linkages, the final device can be packaged compactly. We describe this synthesis procedure through the design of a biomimetic device for reproducing a flapping wing motion.

Five Position Synthesis of a Slider-Crank Function Generator

2011 ◽  
Author(s):  
Mark M. Plecnik ◽  
J. Michael McCarthy
Keyword(s):  
Full Range ◽  
Linear Actuator ◽  
Tolerance Zone ◽  
Function Generator ◽  
Front End ◽  
Input And Output ◽  
Function Generators ◽  
Synthesis Procedure ◽  
Position Synthesis ◽  
Branching Solutions

In this paper, we present a synthesis procedure for the coupler link of a planar slider-crank linkage in order to coordinate input by a linear actuator with the rotation of an output crank. This problem can be formulated in a manner similar to the synthesis of a five position RR coupler link. It is well-known that the resulting equations can produce branching solutions that are not useful. This is addressed by introducing tolerances for the input and output values of the specified task function. The proposed synthesis procedure is then executed on two examples. In the first example, a survey of solutions for tolerance zones of increasing size is conducted. In this example we find that a tolerance zone of 5% of the desired full range results in a number of useful task functions and usable slider-crank function generators. To demonstrate the use of these results, we present an example design for the actuator of the shovel of a front-end loader.

scholarly journals Design of a Novel Task-Based Knee Rehabilitation Exoskeleton Device

2018 ◽  
Author(s):  
Visharath Adhikari ◽  
Yimesker Yihun ◽  
Hamid M. Lankarani
Keyword(s):  
Structural Parameters ◽  
Parallel Mechanisms ◽  
Single Degree Of Freedom ◽  
Kinematic Data ◽  
Knee Rehabilitation ◽  
Serial Chain ◽  
Implicit Equations ◽  
Synthesis Procedure ◽  
Serial Chains ◽  
Synthesis Approach

This study is aimed at the design of a novel task-based knee rehabilitation device. The desired trajectories of the knee have been obtained through a vision-based motion capture system. The collected experimental kinematic data has been used as an input to a spatial mechanism synthesis procedure. Parallel mechanisms with single degree-of-freedom (DOF) have been considered to generate the complex 3D motions of the lower leg. An exact workspace synthesis approach is utilized, in which the parameterized forward kinematics equations of each serial chains of the parallel mechanisms are to be converted into implicit equations via elimination. The implicit description of the workspace is made to be a function of the structural parameters of the serial chain, making it easy to relate those parameters to the desired trajectory. The selected mechanism has been verified for the accuracy of its trajectory through CAD modeling and simulations. This design approach reduces alignment and fitting challenges in an exoskeleton as the mechanism does not require alignment of each robotic joint axis with its human counterpart.

A New Methodology for Rapid Synthesis of Function Generators

1992 ◽  
Vol 206 (6) ◽  
pp. 391-398 ◽  
Author(s):  
J R McGarva ◽  
G Mullineux
Keyword(s):  
Harmonic Analysis ◽  
Optimization Technique ◽  
Performance Criteria ◽  
Performance Information ◽  
Rapid Synthesis ◽  
Single Degree Of Freedom ◽  
Performance Requirement ◽  
Single Degree ◽  
Function Generators ◽  
Fine Tune

This paper presents the application of a new methodology for the rapid synthesis of a single-degree-of-freedom function generating linkages. Harmonic analysis and normalization are used as a means of evaluating linkage performance. The performance information for a large number of linkage types and dimensional variants are stored in a software-based library. A means whereby this library can he searched for linkages to meet prescribed performance criteria is discussed. The use of an optimization technique to ‘fine tune’ the library selections is introduced. Finally, an example of the use of the methodology is given for the synthesis of a linkage required to reproduce a particular performance requirement.

Forced Response of a SDOF Friction Oscillator Colliding With a Hysteretic Obstacle

2001 ◽  
Author(s):  
Ugo Andreaus ◽  
Paolo Casini
Keyword(s):  
Constant Velocity ◽  
Driving Force ◽  
Practical Interest ◽  
Forced Response ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Moving Base ◽  
Friction Oscillator ◽  
Sample Application ◽  
Made In

Abstract The forced dynamics of non-smooth oscillators have not yet been sufficiently investigated, when damping is simultaneously due to friction and impact. Because of the theoretical and practical interest of this type of systems, an effort is made in this paper to lighten the behaviour of a single-degree-of-freedom oscillator colliding with a hysteretic obstacle and excited by an harmonic driving force and by a moving base with constant velocity. A friction-contact model has been proposed which allows simulating an exponential velocity-dependent friction law, and a deformable (hysteretic) obstacle. This model has been numerically tested via a sample application.

On the Design of a Portable Force Illusion Device for Navigation Aids

2013 ◽  
Author(s):  
Jacobus W. M. Wever ◽  
Clement Gosselin ◽  
Just L. Herder
Keyword(s):  
Constant Velocity ◽  
Visual Cues ◽  
Objective Evaluation ◽  
Strong Force ◽  
Large Numbers ◽  
Force Profile ◽  
Reaction Forces ◽  
Working Principle ◽  
Synthesis Procedure ◽  
Brute Force Approach

Navigation aids rely mostly on (audio)visual cues when it comes to communication with the user. An alternative and more intuitive communication modality may be provided by means of haptic guidance generated by a portable mechatronic device. Especially visually impaired and blind people may benefit from a device that generates the illusion of an external force; it may possibly eliminate the need for a guide dog. This paper investigates constant-velocity crank-driven mechanisms which are able to generate such a force illusion by means of a reciprocating mass. The focus of this paper is on the generation of the illusion itself rather than manipulating the direction of this force. The force illusion is a result of successive positive and negative reaction forces with unequal amplitude, generated by a reciprocating mass. The acceleration ratio of the mass is selected as the main evaluation criterion for comparing different types of candidate mechanisms. Because the input is a simple motor rotating at a constant velocity, the synthesis of the mechanism is key to generating proper acceleration profiles. A brute-force approach is used for the synthesis procedure, i.e., characteristic distances and link lengths are varied with steps of 1mm for each of the candidate mechanisms, thereby generating very large numbers of variants. Kinematic performance reveal typical acceleration ratios in the range of 1 to 19; where a ratio of one does not result in a force illusion while a ratio of 19 might be demanding on the physical design. An objective evaluation leads to selecting the Square Recti-Linear mechanism as the overall most promising candidate mechanism. A prototype of this mechanism is then presented to demonstrate the working principle. The shape of the prototype’s force profile over time is measured experimentally and is shown to be very similar to the profile obtained by simulation. The reciprocating mass accounts for almost one fifth of the total mass of the prototype, resulting in a strong force illusion in comparison with gravitational forces.

Kinematic Efficiency of Non-Circular Geared Transmissions

1981 ◽  
Vol 103 (1) ◽  
pp. 170-176 ◽  
Author(s):  
R. J. Ferguson ◽  
J. H. Kerr
Keyword(s):  
Power Flow ◽  
High Efficiency ◽  
Function Generator ◽  
Function Generators ◽  
Kinematic Efficiency

Infinitely-variable transmissions of high efficiency can be made using non-circular gears combined in function generators. The efficiency of a function generator depends on the gear parameters, the ratio of the differential, and the direction of power flow. The paper shows how the factors influence the total gear meshing losses and explain how efficiency is calculated. No-load losses are not included.

Dynamics of an automotive transmission consisting of a tripod joint and a ball joint. A symbolic approach

2002 ◽  
Vol 216 (3) ◽  
pp. 203-211 ◽  
Author(s):  
J-P Mariot ◽  
J-Y K'nevez
Keyword(s):  
Constant Velocity ◽  
Joint Angle ◽  
Driving Forces ◽  
Infinite Length ◽  
Ball Joint ◽  
Constant Input ◽  
Shaft Length ◽  
Intermediate Shaft ◽  
Automotive Transmission ◽  
Output Torque

The present paper deals with the zero friction dynamics of an automotive transmission consisting of an inboard ball joint close to the wheel and an outboard tripod joint close to the gearbox, connected by an intermediate shaft. The ball joint is a constant-velocity joint (CVJ) whereas the tripod joint is not. In the idealized case of an intermediate shaft of infinite length, the tripod joint behaves like a CVJ and has the following properties: the input and output torque are equal, the transverse forces generating the output torque are equal and there are no shudder vibrations or inertial shaft effects. For a real transmission with a finite-length shaft, deviations from constant-velocity (CV) properties are due to tripod joint angle variation which causes static and dynamic perturbations; these perturbations are expressed symbolically using first-order approximations in terms of tripod joint angle and ratio of shaft length to tulip radius. For most of the front drive cars equipped, the angle of the tripod joint remains close to 0.1 rad; considering a constant input torque at a 100rad/s input velocity, the perturbations are found to be less than 3 per cent for the driving forces when compared with the CVJ.

Direct Analytic Synthesis of Four-Bar Function Generators With Optimal Structural Error

1973 ◽  
Vol 95 (2) ◽  
pp. 563-571 ◽  
Author(s):  
Richard S. Rose ◽  
George N. Sandor
Keyword(s):  
Conventional Method ◽  
Function Generator ◽  
Arbitrary Choice ◽  
Usual Procedure ◽  
Structural Error ◽  
Function Generators ◽  
Conventional Optimization ◽  
Four Bar Linkage ◽  
Additional Constraints

This paper is a departure from the usual procedure for obtaining the optimal dimensions of a four bar function generator by iteration. In the usual procedure, the accuracy points are first chosen by means of Chebishev spacing or some other means. Using these accuracy points, a four bar linkage is synthesized and the error calculated. Freudenstein’s respacing formula may then be used to respace the accuracy points so as to minimize the errors. After the respacing of the accuracy points is calculated, a new mechanism is synthesized. The process is repeated until the magnitudes of the extreme errors occurring between accuracy points are equalized. The procedure adopted in this paper is to immediately force the extreme errors between accuracy points to be equal in magnitude by imposing additional constraints upon the problem. These constraints eliminate the arbitrary choice of the first set of accuracy points. This procedure results in a more extensive set of equations to be solved than the conventional method. However, once the equations are solved, they lead directly to equalized (and thus minimized) extrema of the magnitude of structural errors between the precision points. Thus there is no need to perform the iterative steps of conventional optimization. The proposed method is illustrated with an example.

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