Research On Autonomous Control Unit And Key Technology Based On Full Distribution CNC System

Computer Numerical Control (CNC) technology is the key of advanced manufacturing technology. Its level is the most important indication of a country's industrialization. With the rapid development of PC technology, the open CNC system is widely used and the development is very fast. Contraposing the disadvantages of recent open CNC, we propose the idea of autonomous control unit based on full distribution CNC technology. The following key technologies of the new idea are investigated in this thesis:(1) Based on the analysis of off-line interpolation and full distribution CNC technology, the new concept of autonomous control unit based on full distribution CNC technology is proposed: Interpolation computation of all axes'coordinate data is completed in the PC and the computational results are transferred to every autonomous control unit by high speed bus. One autonomous control unit only controls one motor. Clock synchronization technology is used to ensure all servomotors successive and synchronous running. The autonomous control units realize the loop control of position, velocity and current. The functions model, hardware and software structures are also proposed and researched in the paper based on functions demands analysis. The new structure has good structure flexibility and good openness.(2) The problem of how to communicate between PC and control unit is researched in the paper. The communication model of field bus and properties of CAN bus is analyzed. The solve scheme of autonomous control unit based on CAN bus is proposed and the application layer communication protocol of distribution system based on CAN bus is designed. The communication process between PC and autonomous control unit is researched. Under the condition of the transmitting speed of PC is quicker than the using speed of all control units, the buffer conditions of eight times periods are analyzed in detail. The two buffers technology is used to solve the communication problem.(3)The DMC control theory is used in the position control of autonomous control unit because of the new characteristic of control unit. The DMC controller parameters design process and parameter simulation are researched. Because of changes of model parameters and dynamic characteristics during CNC processing, the method of self-proofread is added into the DMC control to real-timely regulate the parameters. The scheme of STC-PID-DMC is proposed and simulation experiments are done to verify the theory.(4) The whole scheme of autonomous control unit is designed by using S3C44B0 based on ARM core processor. The development is based on control unit function model, hardware and software structures. The two layers structure hardware including core circuit board and interface board are designed. On the other hand, the system boot loader software, driver software and application software are developed and the process of timer, interrupt and communication are analyzed at the same time.(5) Based on the above research, the author design two autonomous control units. A prototype system of full distribution CNC system is successfully developed by using the permanent magnet linear synchronous motor (PMLSM) made by Parker Inc in USA. The CAN bus communication and synchronous functions are tested on the prototype system. The one axis, circle contrail and NURBS curve control experiments are done at the same time. The influence of different control periods and different moving speed on precision are also researched. The results of experiments prove the new structure and autonomous control unit are feasible.