| Rotator workpieces are widely used in aerospace, machinery manufacturing and other fileds. It is difficult to detect the rotator workpiece with high precision and high efficiency.Because of the inflexible of its probe and the great impact of the environment, the orthogonal Coordinate Measuring Machine(CMM) is unable to meet the requirement of the quick detection. Our group presents a non-orthogonal coordinate measuring machine for measuring the large complex rotator workpiece that we call it Articulated Arm Revolving Coordinate Measuring Machine(AARCMM). The AARCMM has the characteristics of simple structure,large scale, easy to measure on site, ect. However, compared with the traditional orthogonal CMM, the measurement accuracy of AACMM is relatively low. Kinematic calibration and error compensation are the key methods to reduce the measurement error of the AACMM.The paper focuses on the calibration technology of the AARCMM, and the main contents are as follows.Firstly, this paper introduces the structure and working principle of the AARCMM. Then the kinematic model of the AARCMM based on D-H modeling is established and verifies the correct of the model. The paper analyses the influences on precision of the AARCMM with the errors of joint angular, joints twist angle, rod length and angle encoder to get the accuracy of angle encoder. On the basis of kinematic model the error model is established. Using a known height standard boss as the reference to calculate the altitude difference of the actual height and height calculation, and then the nonlinear equations of kinematics parameter errors is set up and the objective function is constructed as well. Based on the Particle Swarm Optimization(PSO), the nonlinear equations are solved and the values of kinematic parameters error are got. The experiments results show that this method has a greatpracticability to improve the accuracy of the AARCMM and meet the accuracy requirements of the AARCMM. |
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