Modal control of an electrohydrostatic flight simulator motion system

Valve-controlled electro-hydraulic actuators in a Stewart platform configuration have become established as a good way of meeting the performance required for flight simulator motion systems. However, valve-controlled actuators are very inefficient, and thus an electrohydrostatic motion system, controlled using servomotor driven pumps, has been developed by Thales, and is now in production. This paper presents a simulation study of a multi-axis controller which can improve the dynamic response of the new motion system. A modal control approach is used - i.e. the modes of vibration of the system are controlled individually. These modes are dependent on the inertial properties of the platform and the compliance of the actuators. The modes change as the motion system moves throughout its workspace, and so the controller has to adapt to the current operating point. Simulation results are presented based on a partially validated model of the motion system.