视频测试系统在结构风洞测试应用的可行性研究

Feasibility Study on Application of Video Test System in Structural Wind Tunnel

基于非接触式精密位移测量系统,对典型直立悬臂结构进行自由振动动力特性标定试验,将激光位移计与非接触式精密位移测量系统在结构典型位置处的自由衰减位移时程测试结果与傅里叶变换后的频谱结果进行吻合度对比,并进一步分析非接触式精密位移测量系统的高频识别适用性、抗噪性能、镜头焦距与测量精度的相关性。试验结果表明,非接触式精密位移测量系统最大采样频率与镜头焦距呈负相关,16 mm焦距镜头仅能实现200 Hz最大采样频率,表明大焦距镜头对于结构高阶频率的识别有一定限制性。在结构自由衰减位移时程大振幅区间,激光位移计与非接触式精密位移测量系统的测量数据吻合度高,小振幅区间下非接触式精密位移测量系统受环境噪声干扰,振幅测量结果呈放大趋势,可通过更换大焦距镜头实现一定程度的抗噪性能,16 mm焦距镜头相较于8 mm焦距镜头在自由振动测试结果小振幅区间可实现70%降噪率效果。风振响应风洞试验中,对于结构低阶频率的识别,视频位移计与加速度计吻合度极高,误差小于1‰。

Based on non-contact precision displacement measurement system,the dynamic characteristics calibration test of free vibration was conducted on typical vertical cantilever structure.The free attenuation displacement time history test results of laser displacement meter and non-contact precision displacement measurement system at the typical position of the structure were compared with the spectrum results after Fourier transform.The applicabili-ty of high frequency identification,anti noise performance and the correlation between lens focal length and measurement accuracy of non-contact precision displacement measurement system were furtherly analyzed.The test results indicate that the maximum sampling frequency is negatively correlated with the lens focal length and the 16 mm focal length lens can only achieve the maximum sampling frequency of 200 Hz which indicate the large focal length lens has certain limitations on the identification of structural high-order frequency.In the large amplitude range of free attenuation displacement time history of the structure,the measurement data of the laser displacement meter and the non-contact precision displacement measurement system are highly consistent.In the small amplitude range,the non-contact precision displacement measurement system is disturbed by environmental noise,and the amplitude measurement results show an amplification trend,which can achieve a certain degree of anti-noise performance by replacing the large focal length lens,Compared with 8 mm focal length lens,16 mm focal length lens can achieve70%noise reduction rate in the small amplitude range of free vibration test results.In the wind tunnel test of wind-induced vibration response,for the identification of low-order frequency of structure,the coincidence degree between video displacement meter and accelerometer is very high and the error is less than 1‰.