基于机器视觉的扭摆法转动惯量测量技术研究

Research on moment of inertia measurement technology based on machine vision and torsion pendulum method

针对阻尼条件下刚体转动惯量的测量问题,提出一种融合机器视觉和扭摆法原理的新方法。根据扭摆法的测量原理,建立了摆角θ关于时间t、阻尼比ζ、无阻尼自振频率ω_(n)的数学模型,最终推导出了线性阻尼条件下转动惯量的计算方法。利用高分辨率工业相机和成像系统对扭摆台进行摄像,经图像边缘捕获、特征点提取、摆角计算后得到摆角θ关于时间t的曲线,根据该曲线计算出阻尼比ζ、周期T和转动惯量I。搭建了一套实验系统,针对转动惯量不大于4.00×10^(-3)kg·m^(2)的被测物体进行转动惯量测量实验,结果表明测量误差的绝对值不超过4.55×10^(-5)kg·m^(2);对于4种被测物进行了多次重复性测量实验,测量的标准差优于1.2×10^(-4)kg·m^(2)。该方法可用于工程中刚体惯量的测量问题,对某型无人机进行了Z轴转动惯量实测,进一步验证了所述方法的有效性。

To measure the moment of inertia of rigid body under damping condition,a new method combining machine vision and torsional pendulum method is proposed.According to the measuring principle of the torsional pendulum method,the mathematical model of the pendulum swing angleθwith respect to time t,the damping ratioζand the undamped natural frequencyω_(n) is established.Finally,the calculation method of the moment of inertia under the linear damping condition is deduced.A high-resolution industrial camera and an imaging system were used to photograph the torsion pendulum.The curve of the pendulum swing angleθwith respect to time t was obtained by capturing the image edge,extracting the feature points and calculating the pendulum swing angle.According to the curve,the damping ratioζ,the period T and the moment of inertia I were calculated.A set of experimental system is set up to measure the moment of inertia of the measured object whose moment of inertia is less than 4.00×10^(-3)kg·m^(2).The results show that the absolute value of the measurement error is less than 4.55×10^(-5)kg·m^(2).Repeated measurement experiments were carried out for four kinds of tested objects,and the standard deviation was better than 1.2×10^(-4)kg·m^(2).This method can be used to measure the rigid body inertia in engineering.The Z-axis rotation inertia of an unmanned aerial vehicle is measured,and the validity of the method described is further verified.