A force threshold-based position controller for legged locomotion

Abstract

Taking inspiration from local leg feedback control loops present in animal legs, a force threshold-based position (FTP) controller is presented to aid with legged locomotion over irregular terrain. The algorithm uses pre-planned position trajectories and force feedback to either elevate or depress the foot. The FTP controller isolates the control of each leg to use only localized feedback, which can result in greater responsiveness to the terrain when compared to a centralized controller arbitrating all of the joint positions in a high degree of freedom system. The controller is robust to terrain elevations without using visual sensors, a priori terrain information, inertial sensing or inter-leg communication. Results of the FTP controller applied to a hexapod system in simulation and on an experimental system are shown in this paper. The algorithm also has the potential for expansion to bipeds, quadrupeds and other biologically-inspired forms.