LQR Design for an Experimental Planar Elastic Arm with a Large Payload

This paper presents initial results on the modeling and control of a two-link planar elastic manipulator. Experimental and analytical open-loop transfer functions relating actuator torques to joint angles and strain-gauges are compared for the arm in a given configuration. Good agreement between the experimental and the simulated closed-loop response with a 2-DOF proportional and derivative (PD) controller is obtained. An optimal full-state feedback controller is then designed for a linearized model of the arm. The choice of weightings in the quadratic performance index using the location of the asymptotic regulator poles is then discussed. Closed-loop simulations demonstrate the performance improvement obtained with a full-state feedback controller (based on a combination of joint sensors, strain gauges, and tip sensors) compared to a PD design. Future work will address the issue of estimator designs.