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基于快速傅里叶变换(FFT)方法,对系统的输入和输出信号进行快速傅里叶变换,对含有高次谐波的输出信号进行滤波,得到期望主频率的傅里叶频谱,然后进行傅里叶反变换,求得在各主频率下的幅值和相位。利用MATLAB中的非线性最小二乘拟配方法得到含有非线性环节的飞机纵向飞行控制系统的频域等效线性模型。这种方法也为含有非线性环节的飞机纵向飞行控制系统的飞行品质评估提供了一种可行的方法。
Based on the Fast Fourier Transform (FFT) method, the input and output signals of the system are subjected to fast Fourier transform, the output signal containing higher harmonics is filtered to obtain the Fourier spectrum of the desired dominant frequency, and then Fourier In the inverse of the transformation, obtained in the main frequency amplitude and phase. The frequency-domain equivalent linear model of aircraft longitudinal flight control system with non-linear links is obtained by using the nonlinear least squares fitting method in MATLAB. This method also provides a feasible method for flight quality assessment of aircraft longitudinal flight control system with non-linear links.