Referring to Problem 38.1, the mechanical inaccuracies in the open-loop positioning system can be described by a normal distribution whose standard deviation = 0.005 mm. The range of the worktable axis is 500 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) 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 becomes the limiting component on control resolution?

Problem 38.1

A leadscrew with a 7.5 mm pitch drives a worktable in a numerical control positioning system. The leadscrew is powered by a stepping motor which has 200 step angles. The worktable is programmed to move a distance of 120 mm from its present position at a travel speed of 300 mm/min. Determine

(a) the number of pulses required to move the table the specified distance and

(b) the required motor speed and pulse rate to achieve the desired table speed.