The Study On A Position Disturbance Type Of Electro-hydraulic Servo Force Loading Control System

The force loading control servo system of flight simulator is a typical position disturbance type of force loading system. In this system the corresponding force needed to the pilot stick should be loaded according to the displacement of stick. Due to the motion of object, a high displacement disturbance would be produced, called as extraneous force, which could be larger than the need force if correct treatments are absent. In many cases, the extraneous force will reduced the precision of the system. The extraneous force will affect track precision of the system. The quality of the force loading control system will have a great impact on the effect of simulation to the pilot stick, and then the quality of the flight simulator.With the background of control loading system of flight simulator, the position disturbance type of electro-hydraulic servo force loading system is studied deeply in this thesis. A mathematical model of force loading control system has been established. And then analyses are placed on the extraneous force due to position disturbance, non-liner of electro-hydraulic servo-valve and the impact of friction of hydraulic cylinder. Aiming at these factors, controlling strategies were put forward to compensate them.For the problem of extraneous force, the structure-invariable principle is used for compensation. And with a hybrid control strategy of the improved structure-invariable principle and the Proportional-Integral-Differential (PID), errors of the electro-hydraulic servo-valve's non-liner and real-time of the load flux are compensated. With regard to the hydraulic cylinder's friction force, a friction observer is designed based on LuGre model and theory of state observation. The simulation results indicated that the extraneous force can be restrained effectively by the structure-invariable principle; the non-liner factor of electro-hydraulic servo-valve has a great impact on the system; and the combination of improved structure-invariable principle with PID could cut down extraneous force sharply, but do not have a remarkable effect on reducing track error resulting from non-liner factor; and that compensating system for the friction could further reduce output error and improve the track precision of system.