Research On The Key Technologies Of Machine Tool Volumetric Error Online Monitoring And Compensation

For the manufacturing industry,machine tools are indispensable industrial production equipment.The volumetric performance of machine tool is the basis of manufacturing industry processing accuracy.Therefore,research of improving the volumetric performance of machine tools is very important.At present,while measuring volumetric error,the measurement instruments need to occupy the working space of machine tool,so that the error measurement can only be carried out in the method of "interim checks",and it is impossible to measure the actual volumetric performance of the machine tool in the working state.Therefore,in order to make up for the shortcomings of the traditional "interim checks"machine tool error measurement method,it is of great significance to study the volumetric error monitoring-compensation technology of machine tool.This thesis has carried out the research on the error monitoring technology,error transfer modeling technology and real-time volumetric error compensation order calculation algorithm needed to establish the machine tool error online monitoring and compensation system,integrated error monitoring and compensation system on the machine tool to carry out verification experiments.The main research contents are as follows:(1)Aiming at the problem that the current commercial multi-degree-of-freedom error measurement system(MDFMS)cannot meet the volume,cost,and stability requirements of the machine tool error monitoring system.In this thesis,methods to improve the measuring accuracy and stability of compact collimation and auto-collimation MDFMS were developed.The systematic error generated by device manufacturing defects and assembly errors were analyzed and compensated to improve the accuracy of the low-cost compact MDFMS.A small beam drift active suppression module was developed to improve the stability of the measurement system.Based on the above technologies,compact,high-precision,high-stability error monitoring systems were developed.(2)Aiming at the problem of the unclear definition of error parameters in current machine tool error modeling methods,the non-coincidence point error,non-coaxial error,and non-common reference error caused by the error measurement conditions and the error parameter definition were analyzed and compensated.In this thesis,take the machine tool measurement framework composed by the positioning feedback sensors as the core,the measurement set-up of geometric error as the elements,the machine tool error analysis frame system is built.Based on this,the non-coincidence error caused by the mismatch of the error measurement point and the origin of the error analysis coordinate system,the non-coaxial error caused by the misalignment of the error measurement axis and the ideal direction of error analysis coordinate system,the non-common reference error caused by reference coordinate system of error measurement and error modeling are not the same is analyzed and compensated.Provides a method for correcting the unsatisfactory measurement setup error in the machine tool error-monitoring system.(3)Aiming at the problem that the computing efficiency of current error modeling methods cannot meet the real-time calculation requirements of the machine tool error monitoring-compensation system,Based on the theory of differential motion analysis which has high computing efficiency,the Error Vector Transfer modeling method is proposed.The relationship between the machine tool error measurement value and the different definition of the error motion is analyzed,and the formula for calculating the right multiplication error motion vector from the error measurement value is given.It is proved that the small error of the main motion transformation in the differential motion transfer does not affect the transfer result of the error fretting and the compensation fretting.Examples of different configurations of CNC machine tools verify the universality of the error vector transfer model.(4)Based on the above work,the error monitoring-compensation system was integrated on a small three-axis machine tool in a laboratory environment and a T-5 drilling center in an industrial production environment.A series of verification experiments were carried out.Experimental results carried out on the three-axis machine tool experiment platform in a laboratory environment show that after compensation,the accuracy is close to positioning repeatability,and the compensation rate of body diagonal positioning error reaches 70%～95%.The verification experiment results of the T-5 drilling center show that after compensation,the positioning error of each axis after compensation is within ±3 μm,and the body diagonal positioning error is within ±4μm,the compensation rate of positioning error and body diagonal error reaches about 90%.