| 主权项 |
1. A method of correcting errors in a bearing cartridge used in a portable articulated arm coordinate measurement machine (AACMM), comprising:
providing the cartridge having a first bearing and a second bearing arranged in a fixed relationship to define an axis, the cartridge further including an angle measurement device configured to measure an angle of rotation of a portion of the cartridge about the axis, the angle measurement device being further configured to transmit an angle measurement signal in response to the rotation of the portion of the cartridge about the axis; rotating the portion of the cartridge about the axis by a plurality of turns in a forward direction and in a reverse direction, each turn being 360 degrees; measuring for each of the plurality of turns a plurality of first rotational values, each of the plurality of first rotational values comprising a first number of turns of the plurality of turns that the portion of the cartridge is rotated in the forward direction minus a second number of turns of the plurality of turns the portion of the cartridge is rotated in the reverse direction; measuring over the plurality of turns a plurality of angles with the angle measurement device; determining a first plurality of displacements at a first position along the axis, each of the first plurality of displacements being associated with one of the plurality of angles and one of the plurality of first rotational values; determining compensation values based at least in part on the measured plurality of angles, the plurality of first rotational values, and the determined first plurality of displacements; storing the compensation values in a memory; providing the AACMM with the cartridge installed between two arm segments and a rotational counter configured to measure a second rotational value of the installed cartridge, the second rotational value being a third number of turns the portion of the cartridge is rotated in the forward direction minus a fourth number of turns the portion of the cartridge is rotated in the reverse direction, wherein the rotational counter is further configured to measure the second rotational value when the AACMM is in a powered off-state and in a powered on-state; and measuring a three-dimensional coordinate of an object with the AACMM based at least in part on the angular measurement signal, the stored compensation values, and the second rotational value. |
