Power-Based Gravity Compensation for Flexible Joint Manipulators

In this paper, we propose an add-on dynamic gravity compensator for flexible joint manipulators. The compensator pumps sufficient power that matches the gravity power demand on the manipulator links, resulting in a reduced oscillatory response. The proposed power-based gravity (PG) Compensator uses moving window batch least squares to implement the power match. The performance of the proposed PG Compensator was validated when added to a base-line Proportional Derivative (PD) controller and two PD-based benchmark controllers. In every case, the addition of the compensator improves the system response for regulation operation, allowing for faster convergence to steady-state. Experimental testing was performed showing a 23% transient error improvement over the baseline controller without the power compensator.