Evaluation of profile error for free-form surface

On the basis of summarizing the principle of profile error evaluation, the geometrical evaluation rule of the least condition is proposed for the profile error, which are the "triangle principle" and "cross principle". The algorithm for evaluating the least condition of the profile error is studied. First, the feature points are pre-positioned, followed by rough matching by least square method and self adaptation between the measured subject and the theoretical surface based on the least condition principle. At last an example is validated the correctness of the geometry rule and feasibility of this algorithm.