Position Control of Hydraulic Series Elastic Actuator with Parameter Self-Optimization

Series elastic actuator (SEA) can reduce the output impedance of robots when interacting with the environment, thereby improving the force control performance. However, owing to complex dynamics and sensitivity to external disturbance, the application of SEA suffers from poor position control. Therefore, this paper proposes an effective method for high-precision position control. A hydraulic SEA is presented with its dynamic model firstly. Then, we apply a disturbance observer (DOB) to load position control based on the dynamic character. The cylinder extension control is considered as velocity-source, therefore simplifying the system model. In addition, we design a feedback controller based on the measured load position for error compensation. The control parameters are further optimized by using a crowding-based dynNP-DE algorithm, in which a crowding strategy is introduced to improve the population diversity. Experiments are conducted to validate the effectiveness of the proposal.