Relay feedback identification of SOPDT transfer functions with NMP zero

In this paper a second order plus dead time transfer function with a NMP zero is identified. Through a single run of biased relay test exact analytical expressions are written for the unsymmetrical limit cycle and up to five parameters can be driven using fitting conditions simultaneously. By using both frequency and time domain features a clear algorithm is proposed which is applicable to identifying non-minimum phase systems including time delays and inverse responses.