Frequency spectrum distortion of random signals in non-linear feedback systems

The paper considers the distortion introduced by torque saturation in a servo mechanism when responding to a randomly varying input signal, with emphasis on the spectral distribution of this distortion. It is shown that low-frequency errors are produced by the application of an input signal whose spectrum extends beyond the pass band of the system. An approximate expression is derived which enables the magnitude of the low-frequency errors to be evaluated in a simple manner. Experimental results are presented for a particular system.