LEARNING ABOUT CONTROL OF LEGGED LOCOMOTION USING A HEXAPOD ROBOT WITH COMPLIANT PNEUMATIC ACTUATORS

Abstract

by GABRIEL MARTIN NELSON This thesis describes efforts to get a biologically-inspired hexapod robot, Robot 3, to walk. Robot 3 is a pneumatically actuated robot that is a scaled-up model of the Blaberus discoidalis cockroach. It uses three-way solenoid valves, driven with PulseWidth-Modulation, and off-the-shelf pneumatic cylinders to actuate its 24 degrees of freedom. Single-turn potentiometers and strain gage load cells provide joint angle sensing and three axis foot force sensing respectively. Robot 3 has two complementary controllers that are well developed. The posture control allows the robot to stabilize its standing posture, even when subjected to sizable disturbances, voluntarily shift and rotate its body around while standing, and lift a payload equal to its own weight. The local control performs position control of single joints, with local and higher-level feedback. It addresses the redundant inverse kinematics of the robot’s legs by appealing to a minimum actuator strain energy paradigm. This allows the robot, while suspended, to move its legs smoothly in an animal-like manner through a coordinated gait. Implementation details for both controllers are described. Future Work discusses possible ways to improve the walking performance of the robot.