Numerical control resolver position measuring device

Abstract

An absolute resolver position measuring device for a numerical control apparatus that controls a machine having a plurality of movable members. A resolver is operatively connected to each movable member such that the rotor of each resolver rotates as the corresponding member moves. The resolver position measuring device includes a real time counter that provides a multi-digit data word that is cyclically redundant. A first PROM is addressed by the real time counter and provides a sequence of digital data words which represent a sine waveform; and a second PROM is addressed by the real time counter and provides a sequence of digital data words which represent a cosine waveform. A first digital to analog converter is responsive to the first PROM to provide a sine wave to the first stator winding of each resolver, and a second digital to analog converter is responsive to the second PROM to provide a cosine wave to the second stator winding of each resolver. The waveform induced in each resolver rotor is input to a zero crossing detector and the outputs of the zero crossing detectors are multiplexed in a sequential order onto a single conductor. This multiplexed signal is used to store the current count of the real time counter a plurality of times such that the stored counts represent the phase angles between the corresponding resolver stator windings and rotors.