Research On Motion Control And Path Planning Of Four-axis Blade Measuring Device

Aero-engine blades have various specifications,different sizes and many applications.At the same time,more stringent requirements are put forward for the manufacturing accuracy and measuring effect of aero-engine blades.In order to improve the integration level of blade processing,manufacturing and measurement,promote the digitalization of blade measurement,and accurately present the error between the actual measurement point and the theoretical measurement point,this paper developed a four-axis blade measurement device by means of laser scanning measurement and studied its key technologies.The main contents are as follows:1)Firstly,a four-axis vane measuring device test bed was built,and relevant components were selected.The servo control adopted a closed-loop control system composed of "upper computer + motion control card".PID gain coefficient was optimized by genetic algorithm PID control,and pulse interpolation algorithm improved point-by-point comparison method was adopted to realize single axis motion and multi-axis linkage of the measuring device.2)Secondly,the mathematical model of laser scanning measurement is established,and the measurement coordinate system is established.At the same time,the nearest neighbor iteration algorithm of ICP is adopted to precisely align the measurement coordinate system.By establishing the blade space coordinate system,the calculation formula of the measured points of the blade relative to the world coordinate system is derived through the transformation of the basic coordinates,and the three-dimensional coordinate information of the profile of the blade is obtained.3)Thirdly,the contour method is adopted to segment the blade profile,the measurement path is planned according to the blade theoretical model,the chord height tolerance method is adopted to distribute the measurement points,and the maximum stride length parameter is introduced to limit the measurement point spacing.A four-part measurement strategy is proposed to reduce the number of head pose adjustment.A special software for blade measurement is developed and the control accuracy of interpolation algorithm is verified.4)Finally,the example of laser scanning measurement is verified,and the automatic data collection and processing of measurement points are completed.The NURBS curve fitting method is proposed,and the measured error values are obtained by comparing the theoretical contour curves of the blades.The research shows that the laser scanning method realizes the intellectualization of the four-axis blade measuring device from determining the position and order of measuring points,to planning the measuring path,and then to the acquisition and processing module of measuring data.The step response overshoot of PID control optimized by genetic algorithm is small and the control effect is good.The measured points are distributed by the string-height tolerance method to ensure that the curve can be distributed adaptively according to the change of curvature.According to the characteristics of high sampling frequency of laser measuring head,the measurement path of continuous scanning acquisition is planned and the measurement speed is faster.The developed blade measurement software has high motion control accuracy and data processing efficiency,and can realize the whole process of blade automatic measurement.The actual blade profile was obtained through NURBS curve fitting,and the measurement accuracy of the device reached 0.05 mm.Compared with the contact measurement,the measurement time of the same section profile was about 2 minutes,which was only 20% of the three-coordinate measurement of the contact probe,greatly improving the efficiency of blade detection.