Electric drive system for a steerable aerial at a satellite-communication Earth station

The paper describes the control and motor-drive system for the steerable aerial located at the Post Office Earth station, Goonhilly Downs, Cornwall. Specification, performance and control racilities are detailed for the purpose of establishing the general design considerations involved. The arrangement of the principal items of the closed-loop Ward Leonard drive is given briefly, and particular attention is then directed in the remaining sections of the paper to the design and performance of the servosystem. The basic linear equations of the system are developed for the major components, and the nonlinear restrictions are then introduced to establish the complete analogue network for the computer analysis. The simulation of the nonlinear elements is detailed for the particular cases of saturation limits, `dead band¿ and backlash; a useful method of derivative-network simulation is also outlined. The introduction of appropriate stabilising networks, to counteract system instabilities demonstrated by the computer study, is considered, and linear networks are employed in this application. The paper concludes with a brief review of the commissioning procedure and with an example of operational performance data.