Inverse Dynamics Approach for Invariant Control of Constrained Robots

Abstract

A nonlinear feedback control based on inverse dynamics is proposed for redundant robots with rigid or flexible joints during constrained motion task execution. Based on constrained system formalism, the control scheme presented in the paper achieves simultaneous, independent control of both position and contact force at the robot end-effector. The method is based on the introduction of a set of kinematic parameters, which are defined in a new basis of the working space. In this basis, a general inner product characterized by the unity matrix gives rise to the definition of a new set of metrics for the robot task space. Using these metrics, it becomes possible to decompose the twist and wrench spaces into complementary subspaces. This approach contributes to better understanding of the constrained task decomposition, and provides a consistent interpretation of the analytical procedures used for constraint formulation. An example with a three-link robot operating a moving joystick, with constrained orientation of the end-effector, is presented. The results of numerical simulation are used to show the effectiveness of the proposed controller and its robustness to modeling errors.