Design And Implementation Of A DSP Control System For Thermal Error Compensation Of CNC Machine Tools

The CNC machine tools will inevitably produce heat while working, result in thermal error and finally affect the machining accuracy. A large number of studies have shown that the thermal error occupies50%～80%of the total error of precise process machines like CNC machine tools. Therefore, studying thermal error compensation technology of CNC machine tools is very important for improving the machining accuracy of CNC machine tools.Through the gray relational analysis of system, the temperature measured points are optimized, and the main temperature measured points affecting thermal error of the spindle can be determined, which simplifies the hardware architecture of the system and effectively improves the robustness of the system. Based on multiple linear regression combining the least squares method, the mathematical model of thermal error prediction is derived. The theoretical basis of the real-time compensation system is established.The real-time feedback interrupt type compensation method of CNC machine tools is researched. Compensation control system as an intelligent module is directly embedded into the position feedback loop of the CNC servo system. The CNC machine tools can have the thermal error compensation function without hardware and software of the original CNC control system being changed. The compensation system has a bright future.High-performance digital signal processor (DSP) as the core IC is used to build the thermal error compensation system. The temperature data of the main temperature measured points is collected by the temperature sensor, and the thermal error caused by temperature rise is calculated based on mathematical model. The thermal error is converted into the corresponding compensation pulses, and through the software control system and real-time compensation hardware circuit the compensation pulses which have the characteristics of original feedback pulse are added to the feedback loop of the servo system to achieve the compensation function.The experimental platform is established, and the actual processing experiments has been done on the precision CNC machining centers. The experimental results shows that the compensation system has good stability and reliability and the system achieves the desired designing goals. The system can be applied in the actual processing.