Abstract:

：In order to improve the accuracy of the direct feed axis driven by double linear motors, an online compensation method of full-stroke thermal error for dual direct feed axis is proposed. The factors that influence full-stroke thermal error of dual feed axis are analyzed. And then a hybrid KPLS and fuzzy logic method is applied to improvement of the positioning accuracy of the feeding axis. In the method, a laser interferometer is utilized to obtain the axial thermal deformation of some evenly discrete points. Some thermocouples and infrared thermometers are used to measure the temperatures of the mechanism. KPLS is used to establish a thermal error identification model for these discrete points. The prediction magnitude for on-line error compensation is acquired through the real-time calculation. On the basis of the relevance of any position and key positions, the fuzzy logic is applied to the prediction of the full-stroke thermal error. Compensation decision function and compensation system are established based on the theory. Compensation value is intelligent inferred through the decision function. Compensation code is sent to CNC system to realize online compensation. To demonstrate the procedure of the proposed approach, an experiment is conducted on the self-construction gantry double direct feed axis test rig. The results show that the hybrid KPLS and fuzzy logic method effectively reduces the direct feed axis thermally induced error by 50 % with a random test.

Key words: fuzzy logic, KPLS, linear motor, on-line compensation, thermal error