Force/Position Tracking of a Robot in Compliant Contact with Unknown Stiffness and Surface Kinematics

This work deals with the problem of force/position trajectory tracking under uncertainties arising from surface position and orientation. A robotic finger with a soft hemispherical tip of uncertain compliance parameter is considered in contact with a rigid flat surface. A novel adaptive controller is designed using online estimates of the unknown parameters and is proved to achieve force and position tracking by ensuring the convergence of the estimated normal to the surface direction to its actual value. The performance of the proposed controller is demonstrated by a simulation example.