Research On Calibration Algorithm Of Articulated CMM

Articulated Coordinate Measuring Machine is credited with small size, large measuring space and portable. And it is widely applied in modern industrial. At the conclusion of the mechanical structure design and data acquisition system, this article mainly studies a new calibration algorithm of the experimental prototype.First, establish a new coordinate system according to the analysis of traditional DH model, then calculating coordinate is more convenient. Use the graphic method to verify the correctness of the model in several special positions. Analyze error sources of the measurement system, they are mainly the length and angle error in the process of mechaning and assembling and zero deviation of the encoder. Establish an error model to correct the zero deviation and the error of structure parameters.A compare among the exsiting methods is presented. After considering the efficiency and accuracy, this paper brings forward a single-point multi-pose calibration method based on the distance of two points. And a new calibration block with nine holes is designed, and then collects data in the five different locations in the space. After that we calculate each error of the system parameters by using Gauss - Newton method.The measurement accuracy has been greatly improved after calibration. And the angle error has a greater impact on the accuracy than the length error. Choose the good date of the last step, and optimize the date by using genetic algorithms.At last, we use the high-precision ceramic ball to calibrate the results of their test-related indicators,the error is about 1mm. Altough the accuracy is comparartively low, it has reached the stage target of the prototype, and analyse the sources of the error.