A COP-based controller for adaptive motion planning of a single-legged robot

This paper presents a motion planning and control method for determining the joint velocities of a single-legged robot based on the desired Centre of Pressure (COP) motion, the Centre of Mass (COM) dynamics and the ground reaction forces. A closed-loop inverse kinematics algorithm is implemented using the Centre of Gravity (COG) Jacobian, while the control system relies on the reaction force data to estimate the real COP. The main idea is to manipulate the dynamics of the COM such as the COP shows a desired behavior. The implementation of the COP-based controller is described to demonstrate the possibility of keeping a single-legged robot in balance, while adapting to unexpected changes in a slope surface or during execution of a specified motion task. Simulation results are illustrated throughout the paper to validate the proposed controller.