Study of the dynamic performance of a thrust stand for small-thrust liquid-pulsed thrusters

Abstract

Small-thrust liquid-pulsed thrusters can achieve higher efficiency and more accurate control when operating in pulsed mode. However, the pulsed characteristic makes it challenging to measure the thrust. This paper describes a thrust stand for directly measuring the pulsed thrust from small-thrust liquid-pulsed thrusters. The proposed stand is based on a unique piezoelectric dynamometer on which the thruster is mounted through a connecting frame. A thrust experiment is conducted by applying a trapezoidal pulsed force, similar to the thrust generated by small-thrust liquid-pulsed thrusters, to the thrust stand. The experimental results show that the thrust stand can quickly trace the input trapezoidal force signal, although its output waveform exhibits obvious oscillations. Based on the experimental frequency response data, a thrust stand transfer function model is constructed, and this model is used to analyze the dynamic response performance of the thrust stand. The step response and trapezoidal pulse response of the thrust stand are obtained, and the influence of the damping ratio on the dynamic performance of the thrust stand is analyzed. A damping compensation transfer function is established to improve the dynamic measurement performance of the thrust stand. Compensated results are obtained by using the raw output from the thrust stand as the input to the damping compensation transfer function. The damping compensation method does not change the natural frequencies of the thrust stand, does not need any additional filtering process, effectively eliminates the waveform oscillations of the thrust stand output, and ensures good consistency between the input and output signals.