Research On High-speed Motion Control Technology Of Open Soft Architecture CNC System Based On Linux

This dissertation analyses the domestic and foreign state of the open architecture CNC system. A PC+rogrammable I/O hardware interface architecture CNC system has bean researched to realize low cost, high speed, high precision, reconfiguration, reconstruction and extention of open soft CNC system with modularization and flexibility. In allusion to the drawbacks of existing research work, the dissertation makes a further research on the aspects such as system software structure, control technique with high velocity and high precision, system working mechanism, interpolation algorithm and communication protocols.In allusion to the drawbacks of existing research work in the software modularization and standardization, hierarchy-designing method is adopted to simplify the CNC system control flow. Dividing the CNC system into four functional layers, then unified standard communication among software functional layers based on RCS is realized, which lay a foundation for the realization of CNC interchangeable, reconfigurable and scalable function. In consideration to the difficulties and transplantability of soft CNC development method based on Linux+RTAI, the software platform based on Linux only is redefined. Then PCI bus is selected as the communication interface to satisfy the requirement of high-velocity and large amount of data transmission between PC and I/O hardware card. Red Cyclone development board with PCI9054is used as the programmable I/O hardware card. According to multitask characteristic of CNC system, the dissertation realizes multitask concurrent scheduling mechanism based on producer/consumer model. As to the CNC bus communication protocol between hardware and software, account for the configurable and extendable characters of motion axises, the interpolation data transport format is extended and defined by Chinese open CNC system bus communication protocol. Furthermore, the data type is treated as integer, which not only simplifies the process of interpolation calculation in I/O hardware card, but also reduces the amount of data transmission. Besides, the Linux device driver of the I/O card is developed.This dissertation analyses the drawbacks of real-time and high-velocity interpolation using PC softeware. According to hardware and software function distribution of coarse and fine interpolation, the timing relationship between them is studied, then high-velocity asynchronous interpolation structure is implemented, which not only meets the requirements of high velocity, high precision movement control and the large amounts of data processing, but also reduces real-time requirement of interpolation, which conducives to the software-based open CNC system development. In the aspect of interpolation algorithm, studys continuous micro-segment interpolation technique for high-velocity and high-precision, the realization methods include continuous coarse interpolation and double velocity look-ahead control algorithm are presented, which enhances the predictive ability of the system. Through simulation analysis, the results show that the proposed algorithm realizes high-velocity smooth transition between segments, and ensures the position accuracy of segment and the uniformity of the feed rate.Now the developed soft CNC system base on Linux realizes3-axis stepping motors simultaneous motion, and runs well both software and the hardware. Besides, for machining the continuous micro-segment, the movement is continuous and smooth, and trajectory error is small.