Abstract: A system for measuring the accuracy of a machines and mechanisms having a driving member and a driven member is disclosed. The absolute position of the driving member is determined using a first absolute encoder operatively engaged to the driving member. The actual absolute position of the driven member is also determined using a second absolute encoder operatively engaged to the driven member. The theoretical absolute position of the driven member is then calculated based upon the absolute position of the driving member. The actual absolute position of the driven member is compared to the theoretical absolute position of the driven member, preferably by subtraction, to determine the accuracy of the machines and mechanisms. Optical absolute encoders may be used and the process may be performed using a microprocessor which may utilize a ratio function to calculate the theoretical absolute position of the driven member based upon the absolute position of a driving member.

Abstract: An apparatus for measuring kinematic errors in power transmission mechanisms with an input shaft and an output shaft. The apparatus comprises a pair of laser doppler velocimeters (LDV's) (16,34). Each generates a laser beam split into two equal-intensity parallel beams which are projected so as to strike a shaft while the shaft rotates. The shaft produces reflected beams having a frequency which is shifted from that of the incident beams, thereby producing returning beams which are heterodyne. A measuring (20,38) channel is in communication with each LDV. An attenuator (24) is in communication with one of the measuring channels (20) for decreasing the amplitude of a signal generated by the measuring channel (20). A summing and integrating amplifier (28) is connected to the attenuator, the amplifier generating a signal indicative of kinematic error in the gear mechanism.