Robust Force Control of Series Elastic Actuator Using Disturbance Observer

摘要

A series elastic actuator (SEA) has become prevailing in rehabilitation robots, legged robots and cooperative robots to achieve force control and ensure safety. The proposed SEA incorporates brushless DC electric motor and large gear reductions that introduce challenging problems associated with large reflected inertia, friction, backlash and torque ripple. To realize high fidelity force control, a high-gain control method makes system unstable. In this article, a generic model is derived that the friction and backlash are regarded as unmodeled disturbances. The unmodeled and exogenous disturbances are attenuated by disturbance observer (DOB). The solution for high performance force control is based on combinations of feedforward, PID, model-based, and DOB. The proposed approach can address stability issues and improve force tracking accuracy. Simulation and experimental results are provided that verify the proposed method for SEA systems.