Analysis of an up-down counter used as a velocity-servo error register

The advantages of a medium-speed two-stage up-down counter combined with special digital-to-analog (D-A) conversion are simplicity, better control modes, and elimination of operation limits. The disadvantages of a conventional
m
-stage up-down counter with binary weight D-A conversion are also discussed, and a simple linear analysis of the up-down counter in conjunction with the servo system is presented.