Control of physical interaction between a deformable finger-tip and a rigid object

Aims at solving a problem of impedance control for a class of robotic tasks where a soft and deformable tip of a 3 DOF finger robot interacts physically with a fixed rigid object or environment. It is assumed that dynamics of the robot finger are unknown and the characteristics of the reproducing force of the deformable tip in its displacement are unknown and nonlinear. In the first scheme, an impedance control law is proposed to regulate the interaction force between this soft tip and the object to attain a given set-point value. Secondly, impedance control via an iterative learning scheme is proposed to track a prespecified force trajectory of a periodic function. Theoretical findings prove that the first control law guarantees asymptotical stability of the overall dynamics of the objective system. Choosing of parameters for the control input in the case of force tracking is suggested to ensure asymptotic stability. Results of computer simulation illustrate the effectiveness of the proposed control methods.