Robust Fractional-order Control of Flexible-Joint Electrically Driven Robots

This paper presents a novel robust fractional PIλ controller design for flexible joint electrically driven robots. Because of using voltage control strategy, the proposed approach is free of problems arising from torque control strategy in the design and implementation. In fact, the motor's current includes the effects of nonlinearities and coupling in the robot manipulator. Therefore, cancellation of motor current by feedback linearization in voltage control strategy can cancel the highly nonlinear dynamics of manipulators. Thus, it can guarantee robustness of control system to both structured and unstructured uncertainties associated with robot dynamics. As a result, the proposed control is simple, fast response and superior to torque control approaches. The control method is verified by stability analysis. Simulations on a two-link actuated flexible-joint robot show the effectiveness of the proposed control approach. Compared with ordinary controller, the fractional type shows a better tracking performance.