Toward innate leg stability on unmodeled and natural terrain: hexapod walking

A Force Threshold-based Position (FTP) controller is presented for cyclic legged locomotion over irregular terrain. Force feedback in the form of threshold comparison is used to control each leg independently. The FTP controller decouples the control of individual legs and uses only localized feedback to generate joint torques. No feedback of body state is needed and no multi-leg Jacobian is computed. Preliminary results suggest that the FTP controller is robust to terrain elevations without extracting any information about the ground or inertial sensing of the body. The algorithm is applied to a simulated hexapod walking blindly on irregular terrain, and an experimental system has been built. The controller has also been applied and tested on different gaits without modification. The FTP controller also has potential for expansion to bipeds, quadrupeds and other biologically-inspired forms.