| The error measurement of the roundness and cylindricity is an important indicator to verify the machining accuracy of the heavy truck axle housing.The methods of manual detection used in the current production are inefficient and inaccuracy.According to the topography characteristics of the heavy truck axle housing,a mechanical transmission device was designed and a control platform using a PLC and a servo drive system was built in this project.The multi-section rotation measurement of the sensor avoids the eccentricity of the rotary positioning which was caused by the dynamic balance of large-scale irregular workpieces during the detection process.With using three-point error separation algorithm as the principle and the least squares method as the assessment standard,the detection devices trips the roundness and cylindricity from the comprehensive error to improve the detection accuracy.The control system has a high degree of automation and integrates various core technologies such as PLC control,HMI configuration,heterogeneous network communication and motion control.In order to ensure the detection accuracy,the laser displacement sensor beam should pass through the axis of the axle housing and be perpendicular to the axis of the axle housing during the measurement process.In the actual inspection application,due to the sensor installation error and the detection equipment being influenced by the machining process,the detector is difficult to ensure the positional relationship between the sensor and the axle of the axle housing,the sensor ray does not pass through the center of the measured section to generate an eccentric error,and the ray does not perpendicular to the contour surface of the axle housing to generate the axis tilt error.The data of the profile with eccentric tilt error will be incorporated into the roundness error of the axle housing,so that the inspection data cannot reflect the real shape of the measured section and also affects assessment results of the roundness and cylindricity error.Aiming at the two factors of error interference we mentioned before,this paper established a mathematical model to detect two(or more)cross-sections of the axle housing,fit least square center of the section and the space axis,and solve the target section eccentricity and axis inclination angle.Eccentricity compensation algorithm used the robot kinematics to construct a space transformation matrix,performed spatial coordinate transformation on the detected section,translated and rotated the original section with eccentric inclination to the ideal normal section,eliminated the errors introduced by the eccentric tilting of the axis of the axle housing.Because of the axial deviation between the detection section and the ideal positive section,this paper established the constraint condition of the eccentric tilt error compensation algorithm,solved the maximum axial deviation of the two sections and converted the axial deviation dimension to the maximum installation declination angle of the sensor to improve the algorithm's compensation accuracy.Four groups of different cross-section data were selected for MATLAB simulation verification,the eccentricity tilt error accounted for 21.7% to 31% of the true section roundness error after the compensation algorithm was processed.The accuracy of the roundness error of the real section is improved by 17.8%-23.4% compared with the roundness error of the original section.The algorithm can effectively eliminate the axle positioning error of the axle housing,and the accuracy of roundness evaluation of the section processed by the compensation algorithms significantly improved. |
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