Two equivalent control structures for an electrohydraulic actuator

Abstract

Two non-linear control structures are considered for position control of an electrohydraulic actuator. The first control structure is derived from a direct near input-output (IO) linearization of the actuator model with position as output. The second control structure is a cascade of a near IO linearizing pressure force controller as an inner loop to a feedback plus feedforward outer-loop position controller. In the present paper, it is shown that the two control structures are theoretically equivalent. Then, it is highlighted that the equivalence can be exploited to extract a simple and intuitive tuning procedure for selecting the gains of one control structure from the gains of the other structure. This result is particularly useful for tuning the near IO linearizing position controller as the interpretation of its gains is obscured by the non-linear state transformation of the feedback linearization. Some numerical simulation and experimental results are included to demonstrate the identified tuning procedure.