Abstract
In quadruped robot locomotion using parallel mechanisms, researchers have used equal link lengths as legs for walking. However, force requirements are not the same in the forward and return strokes. An unsymmetrical parallel mechanism can be considered to accommodate such requirements. This work presents optimized dimensions of a 5R planar parallel mechanism (5R-PPM) with two degrees of freedom (DoF). Optimized dimensions are determined by formulating an optimization problem using kinematics and dynamics equations for the 5R-PPM. Genetic algorithm is considered to obtain solutions for the optimization problem formulated in this study. The constraint condition expressed here for optimization will attempt to minimize the peak torque essential to displace the links in the mechanism for the given height of the robot body and the path to be traced by the end-effector. After analysing all the four possible working modes for the same end-effector movement, the best working mode is selected for the quadruped legs. The equations are formulated and solved in MATLAB, and validated in the MATLAB Simscape Multibody toolbox.
Highlights
Mechanisms used in robots are highly inspired by locomotion in humans and animals
We will present the results of this study obtained by the application of Genetic Algorithm, with the conclusions pertaining to this study offered in the final section
As the range of 0.2 to 1 meter was given as bounds to the optimization algorithm, all the link lengths in the solution lie within this range
Summary
Mechanisms used in robots are highly inspired by locomotion in humans and animals. Most robots have open-loop mechanisms or serial mechanisms that have larger workspaces and dexterity than closed-chain mechanisms [1]. In an open-chain mechanism, accurately placing the end effector is slightly compromised, with low stiffness, and a notable amount of actuator power getting wasted, decreasing the dynamic performance. Owing to these predominant shortcomings, many engineering tasks requiring an excellent positional accuracy of end-effector are not implemented using serially connected mechanisms. The 5R-PPM is prone to singularities, and the control and trajectory planning are more involved. The most critical issue for the parallel mechanism is to avoid singularity due to control uncertainty that manifests in poor force transmission [5]
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