【作者】 杜昌雄；

【导师】 张军；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2012， 硕士

【摘要】 姿控发动机启动、关机频繁,而且主要以脉冲方式工作,产生一系列持续时间不等的脉冲力调整姿态,并且推力随时间快速变化,这就对测试系统提出了比较高的要求,不仅要求推力测试系统的灵敏度要高,更要求系统的动态性能良好。分析了发动机动态推力测试的难点,分别从力敏元件的选择、测试台架的结构以及信号采集单元对推力测试系统进行总体方案的讨论。针对研制成功的以压电传感器为核心的新型发动机推力测试系统,本文对其动态性能进行了研究。数学模型是研究系统性能的基础,采用机理分析法建立了压电测力平台的二阶传递函数模型,分析了其阶跃响应性能。采用系统辨识法建立了整个测试系统的高阶数学模型,并对模型进行了回归效果验证,结果表明理论模型与实测曲线吻合较好。根据建立的数学模型,采用仿真与实验结合的方法对系统的动态特性进行了研究。在MATLAB中仿真分析了推力测试系统的阶跃响应和梯形脉冲响应。采用矩形脉冲力模拟实际推力进行了动态标定试验,获得了矩形力激振时测试系统的动态响应曲线。研究了阻尼比对测试系统动态性能的影响。结果表明,压电式推力测试系统具有高刚度、高固有频率的特性,满足推力测试要求,但是阻尼比低,有一定超调误差。为了减小测试误差,采用阻尼补偿的方法对系统的动态特性进行改善,对补偿前后系统的阶跃响应、梯形响应以及动态标定结果进行比较,结果表明,对于压电式推力测试系统,采用阻尼补偿的方法改善了系统的动态性能,减小了动态推力测试的误差。更多还原

【Abstract】 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.更多还原