Abstract: Aiming at the requirement of high accuracy of in-situ calibration of liquid rocket engines,an automatic force loading device based on hydraulic transmission with servo motor as the execution component was introduced,and the structure and working principle of the system was expounded.The mathematical model of the system was established,the simulation model of the system was built through Matlab and AMEsim,and the fuzzy PID controller was designed on the basis of analyzing the accuracy and stability of thrust loading.The simulation results show that the designed force value loading system can complete the accurate force value loading,the (0~6) kN force value loading time is less than 30 s,and the maximum error of the loading force indication value is ±0.05%,which meets the calibration force value loading requirements.It is proved that the introduction of the fuzzy PID control algorithm into the force loading system can effectively compensate the uncertain disturbance in the system and enhance the robustness of the system.

Key words: Thrust, Automatic calibration, Force value loading, Modeling, Fuzzy PID control