METROLOGY DEVICE AND A METHOD FOR COMPENSATING FOR BEARING RUNOUT ERROR

摘要

A system and method for determining the angular position of a bearing assembly and compensating measurements for bearing runout error in metrology devices, such as an articulated arm coordinate measurement device and a laser tracker, is provided. The system and method includes measuring the bearing runout error and defining a waveform from encoder readings for a first set of rotations. In one embodiment, a transfer function is created based on an analysis of the bearing runout error, such as with a Fourier analysis for example. In another embodiment the bearing runout error is mapped to an absolute angular position. During operation, the angular position of the bearing assembly is determined by comparing a waveform to the waveform from the first set of rotations. With the angular position determined, the bearing runout error may be used to compensate the measurements of the metrology device.

主权项

1. A method of determining an angular rotation position of a metrology device, the method comprising:
providing an encoder coupled to at least one bearing, the encoder having at least a first read head and a second read head, the encoder configured to measure in operation an angular rotation of the at least one bearing; rotating the at least one bearing for a predetermined number of rotations; generating a first signal with the first read head and a second signal with the second read head in response to the rotation of the at least one bearing; defining a first waveform by subtracting the first signal from the second signal; perform a Fourier analysis on the first waveform to define a series of sinusoidal waves for the predetermined number of rotations; generate a transfer function based on the series of sinusoidal waves as a function of absolute angular position; and storing, in a memory operably coupled to the metrology device, the first waveform and the transfer function.