基于动态补偿的半导体应变天平短时测力技术研究

Research on short time force measurement of balance with semiconductor strain gauge based on dynamic compensation

脉冲风洞是模拟高马赫数的重要地面设备,有效试验时间为毫秒量级,天平采集到的信号为气动力信号和振动产生的惯性力的合力,因此提高测量精度的途径之一为提高模型-天平-支杆组成的脉冲风洞测力系统(MBS系统)的固有频率,降低惯性力的占比。固有频率的提高必然导致天平灵敏度下降,对于高马赫数或小攻角的小载荷测量,过小的输出信号可能会淹没在噪音中。针对以上难题,将半导体应变计应用于天平设计中,达到提高天平刚度同时提高输出灵敏度,并应用动态补偿技术,缩短天平响应时间,降低试验不确定度。新天平静态校准表明,法向力校准结果优于3‰,俯仰力矩校准结果优于1‰,各分量输出提高约40倍;针对试验模型进行动态校准,设计动态补偿滤波器,加速试验输出信号收敛,提高数据品质。动态补偿后的测试系统响应时间可缩短至3 ms,可以满足有效试验时间为10 ms量级的脉冲风洞气动数据测量需求。

A new balance with semiconductor strain gauge and the dynamic compensation technique are used to improve the accuracy of the test data and to satisfy the requirement of aerodynamic measurement with the small load and short duration in the impulse tunnel.The static calibration for the new balance shows that the error of the normal force is less than 3‰,that of the pitch moment is less than 1‰and the output of every aerodynamic coefficient increases about 40 times.The dynamic calibration for the system with the new balance and the test model is performed so that the dynamic compensation filter could be designed to accelerate the convergence of the output signal and to improve the quality of the aerodynamic data.The responsible time of the system after the dynamic compensation could be decreased to 3 milliseconds,so the requirement of the aerodynamic measurement in the impulse tunnel with the effective test time of 10 milliseconds could be satisfied.