Adaptive cascade control of a hydraulic actuator with an adaptive dead-zone compensation and optimization based on evolutionary algorithms

Abstract. This work presents a cascade controller for the trajectory tracking control of a hydraulic actuator by using adaptive algorithms to deal with parametric uncertainties together with an adaptive dead-zone compensation scheme. The hydraulic actuator is modeled as a forth order nonlinear system including the valve dynamic as a first order linear system and considering a valve with a dead-zone. Some hydraulic actuator parameters are difficult to be determined or measured, leading to the necessity of considering parametric uncertaities in the design process. Furthermore, the valve dead-zone causes trajectory tracking errors. In the cascade strategy, the hydraulic actuator mathematical model is interpreted as a mechanical subsystem (mass and damper) driven by a hydraulic one (valve and cylinder). From this interpretation, one uses a cascade controller by combining two different adaptive control laws for each subsystem and an adaptive algorithm to compensate the dead-zone. Simulation results illustrate the main characteristics of the proposed controller.