Design Of Embedded CNC System Bottom Software Based On Linux

CNC is a complex control system, especially for advanced CNC. It is not only required that there are high machining precision,high reliability and the calculating ability for complex curves, but also that personal and operable interface is offered. Therefore, CNC system is a complex combination of computer science and electrical and mechanical systems.The paper is based on 5-axis CNC system which is developed by Beihang Universty for GSK CNC Equipment co., LTD. Based on 5-axis CNC system, the bottom software design of embedded CNC is studied in this paper. The CNC has used ARM+FPGA+DSP+Linux embedded structure. Linux is ported into ARM and schedules processor to work. MiniGUI is offered as the GUI (Graphical User Interface).In the embedded CNC, the bottom software has undertaken the role to connect application software (for example , interpolation,coding etc.) with hardware. The design of bottom software relates to the design methods of the circuit. Whether the design is good or not realates to the stability and efficiency of the upper application software. Therefore, the bottom software is very important in the entire system. The paper introduces the design of the bottom software from four aspects.1. CNC is a system that meets multitasks and strong realtime. In the CNC systems nowadays, there are two designs to solve the problem, which are RTLinux and Linux+DSP. The paper analyzes the advantages and disadvantages in the Linux and RTLinux from memory management,schedule of the processor etc., tells the feasibility of Linux+DSP, and introduces the partition methods of strong realtime models and the weak realtime models.2. In order to make the strong realtime models and the weak realtime models work well on ARM and DSP. The paper analyzes the hardware interface between DSP HPI and ARM. According to the accessing method, software communication between them is designed.3. In order to offer users the excellent GUI, MiniGUI is ported to Linux OS as GUI. The paper analyzes the interface principles between MiniGUI and hardware. From the hardware design of man-machine interface, the transplant of MiniGUI and the realization method of Linux drivers are introduced.4. FPGA is a bridge between DSP and server motors. The paper introduces in details how to design each control logical model in FPGA.Through FPGA, ARM and DSP can control server motors by closed loop.The ARM+FPGA+DSP+Linux structure introduced in the paper breaks through the localization of ARM+FPGA+RTLinux, and enhances the system function and the interpolation calculation ability. The structure can be applied to various machining center. Nowadays the software and hardware of 5-axis CNC system primarily conforms to system requirement. And now it is under the period of being perfected.