Progress in design and development of automatic vertical steering systems for underground coal cutters

Although control systems for steering coal cutters through undulating coal seams have been in use since the early 1960s, it is only since Webb´s paper (Proceedings of the 3rd UKAC control convention, April 1968) in 1968 that the 3-dimensional dynamic nature of the process has been appreciated. The process model, previously expressed in terms of two independent variables, I and n, is here converted into a model in the single independent variable v. This, for the first time, permits analytical stability studies and proves the fundamental instability of analogue control, which arises from the profound effects of the coal-sensor delay. The technical case for stored-data digital control is therefore one of the main objectives of the paper.