Characterization, validation, and stability analysis of maximized reachable workspace of radially symmetric hexapod machines

Abstract

Walking machines may be used for both walking and manipulation objectives. A walking robot can walk to a target and then do manipulation. For the manipulation objectives, hexapod robots are potential solutions as they show intrinsic stability in addition to providing six degrees of freedom to the top platform. On the other hand, when the robot does in-situ manipulation without walking, it has a confined workspace due to its parallel structure. This paper presents how to design a radially symmetric hexapod walking robot to achieve the maximum possible workspace when a limited size of the robot is intended. After an analytical characterization of the workspace, an optimization algorithm is used to calculate a set of kinematic and structural parameters with which the maximum reachable workspace is theoretically guaranteed given a desired size of the robot. A prototype of the robot is fabricated based upon the calculated parameters to experimentally test and measure the reachable workspace of the robot. The results confirm that the robot achieves the maximum workspace as far as physical constraints allow. It is also shown that the stability consideration of the robot constrains the reachable workspace of the hexapod robot.