Research On The Load Simulators Of The Aircraft Hydraulic System

The load simulators including the flow and rudder load simulators are the important ground simulation platform, which is necessary for analyzing the performance of the aircraft hydraulic system characteristics in complete flight phases can be analyzed. The aircraft hydraulic load requirements at different flight phases were analyzed to design the simulators. The mathematical models of the flow and rudder simulator were built and the controllers were designed. Both simulation and experimental results validated the models and the controllers.The following contents are included in this thesis:Chapter 1:The domestic and international research state of load simulators was reviewed briefly. The significance, objective, research work contents were outlined.Chapter 2:The aircraft hydraulic system configuration and its working status at different flight phases are introduced. Main tasks and user of aircraft hydraulic system at full flight phases are discussed. Flow demands of hydraulic system and pumps working status in normal and fault conditions are analyzed.Chapter 3:Mathematical models of pump source, the flow simulator and system are built for analyzing the characteristics of the system. The pros and cons of two simulators are compared. Moreover, the performance of the aircraft hydraulic system during the full flight phases is simulated tested. For reducing the pressure fluctuation at step response, integral variable PI controller was proposed. The simulation and test results show that the pressure fluctuation of the system with the developed PI controller has been reduced by more than 40% compared to the traditional PI controller.Chapter 4:Simulation and experimental research on rudder load simulator. The characteristic of rudder load simulator was analyzed and its mathematic model of system was built for exploring the surplus force mechanism. The influences of flow gain coefficient and parameter uncertainty on surplus force were analyzed. Meanwhile, the nonlinear optimized feedforward controller was proposed. The research results show that the loading precision and the eliminating ability of the surplus force with the developed feedforward compensation controller has been improved by more than 50% compared to the traditional feedforward compensation controllers.Chapter 5:Research results and programs are summarized, and suggestions about future improvements are given in this paper.