Identification of periodic nonstationary antenna stabilisation control systems by crosscorrelation techniques

A novel crosscorrelation technique of obtaining dynamic measurements on the systems controlling a 2-axis stable platform carrying a large antenna is reported. Rotation of the antenna causes platform control parameters to be periodically time varying, the periodicity being comparable with control-system time constants. A theoretical analysis of the technique is reported that shows that measurements are realistic, uncorrupted and suitable for determining the nature of compensating device such as a digital filter. Results from measurements on the system, together with results from offline and online simulations, are presented.