Principle And Method Of Optical Fiber Distributed Dynamic Monitoring For Thermal Errors In Heavy-duty CNC Machine Tools

Heavy-duty CNC machine tool is the basic and strategic equipment for national economy and national defense construction.Thermal error is the most important factor restricting the machining accuracy of heavy-duty CNC machine tools.It is of great strategic significance and economic value to reduce the thermal error and improve the machining accuracy of heavy-duty CNC machine tools.To study the thermal error of heavy-duty CNC machine tool,not only should the time-varying,time-delay,strong non-linearity,coupling characteristics of the thermal error be considered like traditional small and medium-sized CNC machine tool,but also we need to solve thermal error modeling difficulty and monitoring challenge due to its huge body,decentralized heat source and complicated mechanical boundary conditions.This thesis aimed to break through the limits of the traditional thermal error modeling method and monitoring technology for heavy-duty CNC machine tool.Based on the advantages of fiber Bragg grating(FBG)distributed sensing technology,new techniques were developed for temperature,deformation monitoring of heavy-duty CNC machine tools.From the perspective of the heat mechanism,combined with advanced detecting technology,the new thermal error modeling principle and method for heavy-duty CNC machine tool were established.The main research work of this thesis is as follows:1.Based on the relative position between the heat sources and the heated structural parts,a new heat sources classification method for heavy-duty CNC machine tools was proposed;Based on analyzing the thermoelastic elongation characteristics of structural parts heated at the end,the thermoelastic elongation-bending composite deformation characteristics with asynchronous time-delay of structural parts heated at the side were studied.Based on analyzing the thermoelastic elongation characteristics of symmetrical beam structural parts under ambient temperature,the thermoelastic elongation-bending composite deformation characteristics of asymmetric beam structural parts under ambient temperature were studied.2.The wavelength division multiplexing(WDM)criteria for FBG distributed detection technology was established.An accurate temperature sensitivity model of FBG was proposed,and the response of FBG to dynamic temperature was analyzed theoretically and experimentally.The strain transfer equation and temperature decoupling equation for thermally induced strain measurement using FBG were derived theoretically and verified experimentally.The sensitivity enhanced FBG temperature sensor and sensitivity enhanced FBG strain sensor for heavy-duty CNC machine tools were developed.The FBG multi-parameter distributed sensing system for heavy-duty CNC machine tools was established.3.Based on the virtual work principle(VWP)and FBG distributed temperature measurement,the spatial composite thermal deformation construction method of gantry structure in heavy-duty CNC machine tools was proposed to obtain six thermal error elements.Based on the principle of least square variation(LSV)and FBG distributed strain measurement,the thermoelastic elongation-bending composite deformation construction method of ram structure in heavy-duty CNC machine tools was proposed to obtain three thermal error elements.4.Considering the difference in the heat dissipation forms when spindle rotates and stops,the heating model and cooling model of spindle were unified,and the dynamic temperature rise-temperature drop theoretical recursive model of machine tool spindle was established.Based on Sage-Husa adaptive Kalman filter(SHAKF)theory,the fusion method of theoretical spindle temperature and test temperature data was proposed.The thermal error model of spindle was established,with spindle fusion estimation temperature as input and ram temperature and ambient temperature as dual disturbance factors.The parameter identification method of spindle thermal error model based on bee algorithm(BA)was proposed.Based on the multi-body theory(MBT),combined with the thermal error model of motorized spindle and the thermal coupling error matrix of large structural parts of machine tool body,the integrated thermal error model of heavy-duty CNC machine tool was established.5.Taking the ZK5540 A heavy-duty drilling and milling machine tool as the experimental object,spindle thermal error experiments was carried out,as well as environment temperature caused thermal error experiments,and the internal and external heat source caused thermal error experiments.The proposed integrated thermal error model of heavy-duty CNC machine tool was verified experimentally.This thesis enriches the theory of thermal deformation of machine tools,helps to develop new method and technology for machine tool thermal deformation detection,and expands heavy-duty CNC machine tool thermal error robust modeling,which has great scientific significance.At the same time,it guides to improve machining precision for heavy-duty CNC machine tools,thus to improve the performance of large or extra large high-end engineering equipment,which has important practical application value.