EXPERIMENTS IN END-EFFECTOR TRACKING CONTROL FOR STRUCTURALLY FLEXIBLE SPACE MANIPULATORS

An experimental study of a control policy for end-effector trajectory tracking of structurally flexible space-based manipulators is presented. The controller employs a fully feedback-driven approach using a series of steady-state linear regulators. An augmented dynamical description involving derivatives of the control inputs is employed to ensure smooth force and/or torque profiles at the joints. Experiments were performed on Radius, a two-link planar manipulator with flexible links and rotary joints supported on a horizontal table by air pucks. Motivated by the space application of robotics, the facility was established as a testbed for the validation of dynamics models and control algorithms for flexible manipulators. Radius is designed so that its frequencies of vibration are comparable to those of space manipulators. The arm is instrumented with potentiometers for measuring joint angles and rates as well as strain gages for monitoring link deformation. The joints are actuated by DC motors coupled to harmonic drive gear reducers. Experimental results show that the controller is able to track demanding end-effector trajectories very well. These results furthermore agree closely with computer simulations.