Uncertainty analysis of on-machine motion and profile measurement with sensor reading errors

Straightness and guideway straightness motion errors of an x-y table or lathe are difficult to measure accurately. A novel error separation technique (Fung and Yang, Measurement Science & Technology, 11 (10) Oct 2000, p.1515-21) is evaluated by uncertainty analysis when the measurement is subject to sensor reading errors. The variance of the resulting profile estimation error is investigated both in the frequency domain and the spatial domain. Theoretical analysis and computer simulation reveal that the profile estimation error, though adversely affected by the sensor noise, is not cumulative in the sense that the error will not build up as a result of increasing the number of sample points as in the 2-step method (Tanaka and Sato, Trans. ASME, J. Eng. Ind. 108, 1986, p.176-82). Experiments have been performed to confirm this finding.