Robust electrohydraulic force control

Electrohydraulic actuators are used where a combination of high speed and high force is required. Controller design to give high-performance position servosystems is often straightforward. However, force control with electrohydraulic actuators is usually much more difficult, as the load dynamics radically affect the closed-loop performance. In this paper, a design method for a force controller is proposed which is insensitive to the load dynamics. Not only does this controller avoid the need for re-tuning for loads exhibiting a wide range of dynamic behaviour, but the tracking and disturbance responses are much higher than a conventional controller would provide. The controller design takes account of stability robustness and noise sensitivity. A detailed case study concerning the emulation of aerodynamic forces in a Formula One car test rig is presented, including experimental results.