用传递函数估计小阻尼的新方法

提出一种对冲激响应函数信号采一段连续样本 ,对样本从起始点和隔 L点为新起始点分别进行两次同样点数的傅立叶变换 ,再分别与输入的力信号进行两次传递函数分析 ,利用其对应谱峰处的幅值计算出阻尼的方法。不考虑模态耦合 ,这是一种精确估计小阻尼的方法 ,不受时域截断产生的能量泄漏的影响 ,能应用于多自由度系统阻尼的求解。仿真结果表明 :阻尼识别精度高 ,当无噪声干扰时 ,最大误差只有 1.6 3% ;有噪声时 ,选取合适的采样频率和延迟点数 ,阻尼的最大误差也只有 1.33%。在两个频率成分靠得很近和大阻尼情况下 ,不能使用这种方法

A New Method for Exactly Estimating Small Damping by Transfer Function

This paper presents a new method for estimating small damping of freedom transient response signal. We sample a length of continuous free transient response signal, and perform FFT analysis from the starting point. Then we lag behind the starting point with L points and perform FFT analysis again. Finally we perform transfer function analysis through the results of these FFT analyses with the input force signal, and estimate the damping by making use of the amplitudes of two corresponding peak lines. If not considering the model coupling, the method is a precise solution, and the estimating damping will not change with spectral leakage. The method can also apply to the multi-frequency system. Simulation result shows that the method is easily carried out with high precision. If the signal is not affected by noise, the maximum error is only 1.63%. Even if the signal is affected by noise, with suitable sampling frequency, the maximum error is only 1.33%. The method can not be used if one frequency is very close to the other or if the damping of one mechanical system is very large.