| 摘要 |
A method is disclosed whereby a probe head which articulates a probe on the moveable arm of a coordinate measuring machine is calibrated to reduce the effect of errors, such as misalignment of the rotary axes of the head, and droop of the head and the probe. The method involves measurement of the probe position at a number of orientations of the head, the angle of orientation being determined by encoders within the head. Pairs of adjacent orientations at which the probe position is measured define segments, over which it is assumed that all errors change linearly. From the measured probe positions, a value of actual angular displacement between measured probe positions is calculated. The position of the probe at a given angular orientation within a segment may then be determined from the encoder reading at that orientation, and the ratio of the actual angular displacement between measured probe positions to the difference in the encoder readings at the orientations defining the segment (and corresponding to these measured positions). The size of the segments depends upon the linearity with which the droop changes with changing angular orientation of the head; as the change in droop becomes less linear, the segment size decreases in order to ensure that the assumption of linearity remains valid.
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