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Coordinate measuring system

  • US 5,148,377 A
  • Filed: 06/12/1989
  • Issued: 09/15/1992
  • Est. Priority Date: 12/10/1986
  • Status: Expired due to Term
First Claim
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1. A three-dimensional coordinate measuring system comprising an articulated device including a base member adapted to be fixed to, or relative to, a body relative to which coordinates are to be measured, a first arm rotatable about a first axis relative to the base, a second arm rotatable about a second axis relative to the first arm, a third arm slidingly engaged to said second arm along a third axis, said first, second and third axes being approximately parallel, first second and third electrical pulse generating rotary encoders two of which respectively measuring rotary displacement of the first arm about the base and the second arm about the first arm and the third encoder being driven by a wheel frictionally engaging the third arm with the encoder fixed within the second arm so as to measure relative translation of the third arm relative to the second arm, and a microprocessor held within the base and programmed to collect and retain a set of summed pulsed values being the algebraic sum of pulses initiated by the three rotary encoders since their last initiation, the system further including a host computer communicating with the microprocessor and obtaining therefrom upon request by the host computer, when initiated by a user of the system, the current set of summed pulses values, performing on the set of summed pulsed values a mathematical transformation so as to produce an output being the coordinates of a probe end of the third arm at the time of request of the set of summed pulsed values and wherein the mathematical transformation is modified by a set of error terms so as to produce a coordinate output being electronically corrected in order to correct inaccuracies resulting from non-perfect construction of the articulated device.

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