抄録
This study has proposed a new coordinate measuring machine (CMM) based on a three-degree-of-freedom parallel mechanism. This paper describes two kinematic calibration methods using a double-ended ball bar (DEBB) with a fixed ball distance. The CMM with a touch trigger probe measures the sun ball and the planet ball of the DEBB, and calculates position errors and distance errors between the two balls using kinematic parameters. The least square method using Jacobian matrices corrects gradually the kinematic parameters so that the errors are minimized. The above calculations have been repeated in both numerical simulations and experiments. After the calibration, the position errors of the DEBB decreased from 123μm_<RMS> to 6μm_<RMS> and the distance errors of two balls decreased from 123μm_<RMS> to 19μm_<RMS> in the experiments. Furthermore, accuracy of length measurement with gauge blocks have been improved after the calibration.
