Output Feedback Control of Hydraulic Driven Flexible Actuator with Imprecise Modeling

In recent years, flexible soft robots have received increasing attention compared to rigid robots. The modeling of flexible actuators has always been difficult to solve. The control problem of hydraulic driven flexible actuators in this paper under the premise of imprecise modeling. In this paper, an innovative output feedback controller based on Unknown System Dynamics Estimator (USDE) is proposed to improve the position tracking accuracy of hydraulic driven flexible actuators with imprecise model. Firstly, the strict feedback high order electro-hydraulic servo system is transformed into a new standard form that incorporates servo valve dynamics. Therefore, controllers designed using traditional backstepping methods are rendered obsolete. Subsequently, a High-Gain Observer (HGO) is introduced for state reconstruction of the new system. To counteract the impact of lumped unknown system dynamics which include imprecise modeling dynamics of hydraulic driven flexible actuator, a USDE with straightforward parameter tuning and robust performance is introduced. Finally, both scalar containing error terms and USDE are integrated into the design of the output feedback controller. Experimental validation is conducted to demonstrate the effectiveness of the proposed method.