Research On Friction And Control Characteristics Of A New Electro-hydraulic Load Simulator

Load simulator is a type of equipment for hardware-in-the-loop experiments, which is mainly used to generate force or torque to simulate aerodynamic load to test and evaluate actuator systems. Its performance determines the accuracy of the simulated load acting on aircraft or missile actuator. So to develop load simulator with high performance has a profound significance on the defense industry.As a typical passive force servo control system, electro-hydraulic load simulator is affected by actuator motion disturbance, which seriously affects the load simulator load performance. The traditional electro-hydraulic load simulator is unable to eliminate the extraneous torque. And extensive researches have been done to resolve this problem. But extraneous torque has not been completely eliminated. On the basis of consulting a large number of literatures, this paper puts forward a kind of electro-hydraulic load simulator based on friction load to minimize or eliminate the extraneous torque. The new electro-hydraulic load simulator can simulate aerodynamic load acting on the actuator system by friction, which theoretically won’t produce extraneous torque.Based on the existing preliminary research results, some research works and achievements of this paper have been listed as following.First of all, the impact of different friction forms on the stability of friction torque was discussed to determine the friction form and parameters. And in view of the problem that heat production caused by friction disc movement leaded to friction surface temperature rise, which caused a substantial change in the coefficient of friction, and leaded to the generated friction torque instability in the exis ting prototype. The main factors affecting the friction disc temperature were analyzed and a better theoretical performance friction pair was designed with the aid of thermodynamic simulation.Secondly, the main shaft and hydraulic cylinders were separated in the existing prototype, and the hardware selection in the system was modified. Then the linear modeling of loading system was established, and the influence of time-varying parameters on system was analysed by simulation. In order to minimize the “chattering”, reaching law approach was used to design the conventional sliding mode controller based on the simplified transfer function of the system. And the response curves under different loading signal were obtained. Then the superiority of the designed controller was verified by comparative analysis with the PID controller. Later, the integral sliding mode cotroller, the integral sliding mode adaptive cotroller and the differential plus integral sliding mode adaptive cotroller were designed on the basis of the conventional sliding mode control, and the performance of the above-mentioned controller was verified by simulating the tracking performance of the load signal.Finally, the experimental study was carried out on the load prototype. The extra torque caused by movement of the system components and inertia moment of the spindle caused by movement of the steering gear was tested. The test results were compared with the previous and the reasonableness of structural improvement was verified. At the same time the designed conventional sliding mode controller was used in the loading system for the load signal tracking ability test, the superiority of sliding mode control in improving system load performance was verified than the traditional PID control.