A direct digital design for a multichannel structural test system using the characteristic locus method

Structural test systems are used in aerospace and automotive industries to investigate fatigue and vibration properties of structures. Current control schemes often ignore the multivariable nature of these tests, using sequential closure of PID loops. Earlier work has focused on analog Nyquist array and characteristic locus methods. This paper extends that work by considering a direct digital design using the characteristic locus method. The design process for a two input two output system is described and compared to an earlier analogue design which is shown to be unstable when implemented digitally.