Kinematic Calibration and Compensation of Gravity-induced Errors on a Hexapod-type Parallel Kinematic Machine tool
Soichi Ibaraki, Atsushi Matsubara, Takeshi Yokawa, Masao Nakagawa, Tetsuya Matsushita
Abstract
This paper presents methodologies to calibrate kinematic parameters and to compensate motion errors caused by the gravity on a Hexapod-type parallel mechanism machine tool. In a conventional kinematic calibration method, two major sources of motion error, namely the calibration error of kinematic parameters and the deformation due to the gravity, cannot be explicitly distinguished. This paper presents a kinematic calibration methodology under the cancellation of gravity-induced errors, such that only the calibration error of kinematic parameters can be evaluated in the calibration process. The simulator of gravity-induced errors can be identified by using the prediction method of contouring error trajectories proposed in this paper. Experimental comparison shows the machine's contouring accuracy is significantly improved over the entire workspace by applying the proposed calibration method.
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