Abstract: The measurement and compensation of straightness error of long guideways is usually difficult to perform in the field of ultra-precise manufacture and measurement. On the basis of systematic study of the existing measurement methods of straightness, a new approach is introduced for the measurement of straightness of long guideways by using a short benchmark. With this method, we divide the global straightness profile into several sections with overlaps, and measure the local straightness profiles respectively with a short ultra-precise physical benchmark. Then the global profile can be reconstructed with the local profiles. With spatial coordinates transforming relations, the least square (LS) reconstruction algorithm and the mathematical model of the effect of the relative mechanical motion errors are built. And the effect of the error of dual-sampling points and the sampling frequency in the overlaps is researched. The straightness error of an ultra-precise air-guideway of 550 mm long is tested by using this method. Both simulation and practical experiments indicate that the technique has a good performance, and is simple and practical.

Key words: Air guideway, Least square method, Profile measurement, Straightness error