Aball screw with an 8-mm pitch drives a worktable in an nc positioning system. the screw is powered by a stepping motor with 180 step angles. the worktable is programmed to move a distance of 150 mm from its present position at a travel speed of 400 mm/min. the mechanical inaccuracies in the open-loop positioning system can be described by a normal distribution whose standard deviation = 0.006 mm. the range of the worktable axis is 750 mm, and there are 12 bits in the binary register used by the digital controller to store the programmed position. for the positioning system, determine (a) the control resolution, (b) accuracy, and (c) repeatability. (d) what is the minimum number of bits that the binary register should have so that the mechanical drive system is the limitation on control resolution?