Study On Dynamic Performance Of Piezoelectric Thrust Testing System

Attitude-control rocket starts and shuts frequently, working in the impulse way. It generates a series of impulse force, which is differently lasted and quickly changed, to adjust attitude. These propose higher requirements to thrust testing system:not only high sensitivity, but also good dynamic performance.The difficulties of motor thrust measurement is analysed, and scheme of the thrust testing system is discussed from the aspects of sensor selection, stand structure and signal acquisition. Taking piezoelectric as the core, a novel motor thrust measurement system is developed. Based on this fact, dynamic performance of the new thrust testing stand is studied in this paper. The groundwork of performance studying is mathematical model. The second order transfer function model of the piezoelectric force test platform is established via mechanism analysis, and the step response performance is studied. Besides, the high order mathematical model is built for the whole of the measurement system, and the regression effect of the model is examined. The results indicate that the theoretical model agreed well with the experiment curve. Based on the mathematical model established, dynamic performance of the testing system is studied, combing with simulation and experimental methods. The step response performance and the response of trapezoidal pulse is analysed by the means of simulation in MATLAB. Dynamic calibration is carried out by using square impulse to simulate the engine thrust, and the response curve is obtained. Influence on dynamic performance of the testing system by damping ration is studied. The results show that piezoelectric thrust testing system has advantages of high stiffness and natural frequency, it can meet the requirements of thrust test, but the damping ration is low and the overshoot is big. In order to decrease the measurement error, dynamic performance of the system is improved by the using of the damping compensation. The followings are compared with and without damping compensation:step response, trapezoid impulse response and dynamic calibration curve. The compensation results show that, by the means of damping compensation, dynamic performance of the piezoelectric thrust testing system can be improved and measurement error can be decreased.