Design And Implementation Of Open Architecture Cnc System Based On Rtlinux

Open architecture control has been becoming the essential requirement for modern CNC system. The development of CNC technique has being influenced vitally by the technological system revolution, i.e. from the closure technological system to the open architecture. Open architecture CNC system differs greatly from traditional CNC system on both the integrated system structure and concrete algorithms. This dissertation presents a systematic theoretical frame of the open architecture CNC system, and illustrates the implementation of an open CNC system based on the operating system RTLinux.The concept of open architecture CNC system has been introduced for a few years. However, its exact definition has not yet been presented. And moreover, as a new technology, it has not yet reached the matured and applicable level. The author presents an essential idea of an open architecture CNC system, and analyzes its detailed technical features. Based on the comprehension, both of the advantage and disadvantage comparing to the traditional CNC system are addressed in this dissertation.The hardware and software platforms determine basically the system structure and characteristics of a CNC system. PC has been becoming the preferred hardware platform for CNC systems. Dos and Windows operating systems have been widely used as its software platform. However, neither of them is ideal for the software platform of an open architecture CNC system, because of their limitations for either multi-tasks or real-time control requirements. So, the real-time operating system RTLinux is used to develop the open architecture CNC system.RTLinux is a real-time operating system with excellent performance. It can be used accomplish real-time multi-tasks scheduling without secondary CPU. Its source code is open for end user. Therefore, developing an open CNC system based on RTLinux helps to improve the CNC technology in China. The author addresses the characteristics of RTLinux, describes the key programming techniques for the implementation of an open CNC system based on RTLinux.The software structure, including the logic structure and scheduling structure, of an open CNC system determines its performance. The logic structure involves the function-modules classification and the data-link relationship between the modules. The scheduling structure concerns about time-allocation for multi-tasks, i.e. to ensure the real-time tasks (e.g. interpolation) being processed on time, the non real-time tasks (e.g. display) being processed properly, and all the tasks being scheduled accurately. Quite a lot of new ideas for designing both logic structure and scheduling structure of the open architecture CNC system have been implemented, including the principles of module-classification, large buffer mechanism for data transfer between modules, principles of time-allocation scheduling, and etc.Based on the software structure, the author implemented a few function-modules, such as master-control, interface, decode, interpolation, position-control. Essential techniques about programming the modules are addressedin the dissertation.The interface between the CNC system and the servo system is an essential part of a CNC system. It is vital to select carefully a suitable interface card (hardware) for the system. The author developed an interface driver program (software) for a specific interface card, which is elaborated with laying stress on to stepping servo and digital servo system.Another important control interface of a CNC system is the switching control interface. Instead of using the traditional PLC, a kind of "soft PLC" is implemented to achieve the switching control, which efficiently reduces the cost and boosts the flexibility.IT (Information Technology) is tightly associated with CNC more and more. The application of IT in the field of CNC is explored, then the net function(e.g. far distance control) and the database function(e.g. remote database accessing) of our CNC system are demonstrated.The new CNC system has already been app...