Design And Experiment Analysis Of Thermal Errors Monitoring System For Machine Tool Based On RFID Sensor Tag

With the rapid development of modern manufacturing technology,thermal error has become the main factors that affect the machining accuracy of CNC machine tools.The experimental modeling and compensation method is mainly used for thermal error at present,and the monitoring data of machine tools was transmitted to the monitoring center in the wired way.This method has many shortcomings,such as more lines,complex wiring,difficult maintenance,high cost and so on.The sensor tag technology integrated RFID and sensor,has the characteristics of high degree of identity,fast response speed,non-contact and so on.It not only can overcome the shortcomings of the traditional wired monitoring method,but also have the ability of perception and signal wireless tracking and monitoring.This method has broad application research prospects in the accuracy monitoring of machine tools,structure health monitoring and other fields in recent years.The CNC machine thermal error monitoring system was designed based on RFID sensor tag technology and the laser displacement sensor.The layout of heat sensitive measuring points and optimal conditions of thermal error were studied.The cumulative modeling analysis was done according to the data acquired by the monitoring system,and compared with the results of the least square method.The research can be divided into four aspects:1.The thermal error monitoring system of machine tools spindle was designed.Integrated with the RFID,sensor and embedded technology,a temperature sensor tag was designed to monitor temperature,and the laser displacement sensor was used to monitor thermal deformation simultaneously.The results of accuracy compared with the infrared thermometer,laser interferometer,and other equipments show that all the accuracy index of the temperature sensor tag and laser displacement sensor are good,and it can meet the test requirement of thermal error.2.A new layout method of measuring points was proposed based on golden section of heat sensitive area.According to the distribution of cloud analyzed by the spindle thermal characteristics,the heat sensitive area was quantized preliminarily.The axial direction of spindle was the main heat transfer direction according to the experimental study on heat transfer characteristics of spindle.The gold iterative segmentation for axial spindle was done,and the optimal heat sensitive area was found and it ranged from 54 mm to 84 mm.This new layout method can solve the problems in traditional experiential method,such as data redundancy,unreliability and etc.3.The optimal conditions were determined by orthogonal experimental method and correlation analysis.Orthogonal design table was designed and the test of uniformity layout points was done according to actual test requirements of the factory.The number of measuring points reduced from 4 to 2 through regression analysis.And the thermal error testing optimal conditions were determined through the range analysis,which was the 120 minutes running time,6000r/min speed,and without cooling.4.The cumulative modeling analysis of thermal error was done and compared with the results of least square method.The modeling evaluation program was designed by the cumulative method and the least square method on the platform of Lab VIEW.Then the prediction of spindle thermal drift error was done according to the acquired testing data.The results show that the residual error rate of cumulative modeling is 3.26%,the mean absolute percentage error(MAPE)is 3.18%,both accuracy value are much better than the least square method,and the modeling time of cumulative method was also less than the least square method.