Force and motion control of a constrained flexible manipulator.

Abstract

This dissertation reports the results of a comprehensive research study on the combined joint motion control, vibration control, and force control of a constrained rigid-flexible robot arm. An efficient and accurate approach to modeling for controller design is provided. Both regulation and tracking problems are considered, and a modified version of a Corless-Leitmann controller is developed. Experimental studies, which demonstrate the effectiveness of the proposed methods, are presented. In this work, the dynamic modeling of a constrained spherical coordinate robot arm, whose last link is very flexible, is studied for the purpose of combined force and motion control. The model is derived using a consistent modeling procedure which accounts for the axial force effects due to contact, and the coupling due to the effects of flexible motions on the rigid body motions. These effects are shown to be important in the prediction of the vibration frequencies. Galerkin's method is employed for spatial discretization of the flexible link deflections. A convergence study is presented to evaluate the appropriateness of the spatial approximating functions and to determine the number of modes required for obtaining accurate simulation results. Linear control design methods are shown to be adequate for solving the problem of hybrid force and position regulation for the constrained flexible robot arm. However, nonlinear control strategies show advantages (i.e., good response of the joint motion and contact force, and small magnitude of the structural vibration) in the tracking control of motion and force. A modified Corless-Leitmann controller is presented to enhance the control of the flexible motion using only joint actuators. Finally, an experimental implementation is used to validate the proposed controller designs, to assess the merit of measuring and feeding back the flexible motion and the contact force, and to evaluate the feasibility of combined force and motion control strategies for the constrained flexible robot arm. These experimental results are in good agreement with the theory, and demonstrate the effectiveness of the proposed control strategies.