Frequency domain approach to automatic testing of control systems

The system user must be satisfied that frequency domain data adequately measures the quality of his system in all the performance aspects of interest. This involves the interpretation of transfer functions other than system output/input, and the acquisition of data over a wide frequency band ranging from a few percent of bandwidth to several multiples of bandwidth, the latter for the detection of secondary resonances. However, only a few spot frequencies need be chosen to ensure that system response to actual operational signals is adequate. Careful selection will also maximize the diagnostic potential of the measurements. In noisy systems the measurement time for adequate confidence in gain and phase observations must be established before the test routine can be automated.