Stability of position-loop based hydraulic Control Loading System

When flying an aircraft, the force feel of the control column provides the pilot with important information about the state of the aircraft. In a flight simulator this force feel needs to be simulated, which is the task of the control loading system. A hydraulic Control Loading System (CLS) was developed and installed on our flight simulator earlier days, but the CLS contains instabilities for some certain conditions. The stability of the CLS has been theoretically analyzed on the basis of the transfer function model founded, and a stability criterion for the CLS has been put forward, which is sufficiently proved valid by experiments. According to the stability criterion, the load mass is one of the key parameters when designing a CLS, which must be limited into a certain range in order that the CLS could operate stably.