定位误差, 机构学建模, 等价机构, 映射关系

Workpiece-fixture system was represented by mechanism model, where fixture was the frame of the mechanism, the contact pairs between workpiece and locators constructed the kinematic pairs between side links and mechanism frame. The dimensional lines between location datum and location contact point become the side links, the dimensional lines between process datum and location datum become middle links or mechanism structure, and the process dimensional lines between workpiece surface and process datum were the objective links of the mechanism. By calculating the length and angle variation of objective links, the location errors of process system were obtained. The rules mapping from contact pairs to mechanism components were established. By analyzing the position relations between machining surface and process datum and the position relations between process datum and location datum, the rules controlling the conversion from dimension relations to equivalent mechanism components were explored. According to the mapping rules mentioned above, an equivalent mechanism model was established automatically, and the automatic solution of location error can be realized by means of the accuracy analysis methods of mechanism.