An Research On Embedded Linux And Field-bus Based Open Architecture CNC System

Nowadays, open architecture CNC systems are becoming one of the most important trend of CNC technology. The research purpose of open CNC systems is to build a modular, reconfigurable and expandable architecture to improve the system's flexibility, and enable the systems to be re-developed,in order that CNC systems can be responsive to the market quickly and economically. After researching the recent situation of the abroad and domestic open CNC system, and the characteristic and the existential shortage of the current open architecture system, according to the way of realizing the characteristic of openness, flexibility, modularization, standardize for open CNC system, together with the feature of field-bus and embedded Linux system, this dissertation presents an open CNC system, which is basing on embedded Linux system and field-bus. Further more, some of the features and ways, such as architecture, hardware configuration, software platform, data format and interpolation,and how to realize the openness of system are also discussed. Adopting the modular and layers architecture design method, incorporate with the communication need between modules, as well as the characteristic of field-bus , this dissertation discusses two possible solutions, which are adopt CAN bus which called modularized structure and adopt PROFIBUS called unitization structure, for CNC control system. The comparison between these two solutions including the aspects of the features of control system, real-time characteristic, openness, extensibility and cost is conducted for integrative evaluation. Subsequently, the control system which called modular structure basing on CAN bus is selected to do further design. Research on the communication module , the types and bulk of data exchanging between modules,and then design a simple and practical data exchange agreement. Analyze the hardware structure of functional modules and then design the relative hardware circuit. Using the extensible and configurable programming method, realize programmable I/O, and allow user function subprograms insertion at the same time. On the software platform of open CNC system based on Linux, we divide the software system into several functional layers and software modules. Subsequently, introduce hardware abstract layer to the system, for separating application from hardware platform. Adopt multithreading as CNC system task scheduling mechanism,then develop a CNC graphical user interface based on MiniGUI, it realize the alternating function for systematical management, configuration, display etc. Discuss the translating method of NURBS as uniform internal data interface for different kinds of curves. Further more, introduce the mode of rawness interpolating by man-machine interface module and extractive interpolation by motion control module, for proceeding demonstration of NURBS curve interpolation based on explicit formulation matrices representation. Simultaneity, in order to satisfaction the requirement of modern manufacture for high precision processing,this dissertation do some preliminary study on forecast-adjustment adaptive interpolation algorithm for NURBS curve. The research demonstrates that modular design based on CAN bus,as well as programmable I / O interface,which bring favorable openness and exchangeability to the system. The platform of system software application based on embedded Linux, has better configurable and clipping function compared to the common PC and desktop Operating System, reduce the redundancy of software and hardware. Using uniform interpolation data format, so as to merge different kinds of curves interpolation into single interpolation program.