Flatness based control with adaptive load torque compensation for position tracking of electro hydraulic actuators

In this paper, a flatness based control with adaptive load torque compensation is proposed for position tracking of electro hydraulic actuators (EHAs). The proposed method is implemented on a rotational joint driven by a linear type EHA. The proposed method consists of a position tracking controller and a load torque estimator. The position tracking controller is designed to track the desired position and load pressure as a near Input-output linearizing inner-loop load pressure controller and a feedback plus feedforward outer-loop position controller. The desired load pressure is designed using differential flatness property of the EHA mechanical subsystem. The load torque estimator is designed to estimate the unknown amplitude of the sinusoidal load torque. Then the load torque is compensated by a feedforward-loop. The performance of the proposed method is validated via simulations.