Analysis of a Motor Speed-Control System with an Analog Computer

In order to obtain maximum productivity, longest tool life, and high-quality surface finish on a lathe, it is necessary that the machining be done at a constant surface cutting speed. This is particularly true with the use of carbide cutting tools where deviations from optimum cutting speed must be maintained within extremely close limits. A system was proposed using a direct current motor in conjunction with a multistage field regulator in a closed loop system to provide constant cutting speed on an automatic copy lathe. An analog study of the system was made in order to determine what performance could be expected and how performance could be improved. This paper presents a qualitative discussion of the analog study, together with the results obtained and the conclusions reached.