Contact force measurement noise in the partial feedback linearization control of humanoid robots

This paper examines the technique of partial feedback linearization for the positional control of the joints of a humanoid robot. The unique dynamical model of the humanoid robot is first presented. The dynamics have an Euler-Lagrange form but also contain mixed-continuous/ discrete forces that arise due to contact constraints. The mixed-continuous/discrete contact forces are modeled by using linear restoring and damping elements on the bottom of the feet of the humanoid upon contact with the ground. Also, the robot has six degrees-of-freedom that are not directly actuated. The collocated partial feedback linearization scheme is utilized to provide joint-level position control. Implementation of this control law relies upon contact force measurements. It is suggested that partial feedback linearization is a viable option for joint level control even in the presence of significant noise arising from the contact force measurements.