Research On The Key Technique Of The Reconfigurable CNC Based On Embedded System

The reconfigurable manufacturing system (RMS) is a direction of future manufacturing system. It includes system-level reconfiguration and machine-level reconfiguration. Computerized numerical controlled (CNC) machines are the main parts of manufacturing system. It is possible to realize RMS if a CNC machines has the capability of reconfiguration. This capability has become one of the performance indexes to modem CNC machines.With the development of semiconductors technologies, the embedded micro-processor is becoming the mainstream of the post PC market. It is high-speed, small, powerful, multi functional, and integrates high performance core with a rich set of peripheral functions focused on communication. These advantages greatly satisfy the development of the modem CNC machines. Besides some embedded operating systems, such as embedded Linux, uCOS, based on GNU software,is robust and open sources, provide widely application space for CNC machines controller based on embedded system. As the beginning step based on embedded system at home and abroad, most CNC systems have been developed according to their specific request, together with the resource limit and platform relativity of the embedded system, which make development hard, long time and reconfiguration impossible.This thesis emphasizes on CNC system reconfiguration and its key technology based on embedded system. It analyses the architecture of embedded reconfigurable CNC system from the point of view of the methodology. Then study the software and multi-task schedule algorithm of the reconfigurable CNC system, and a prototype of reconfigurable CNC system IDE (Integrated Development Environment) is built up. In the end the water-jet CNC system and wiring harness CNC system have been developed to verify the research result. The details are organized as follows:The current architecture and complexity of the CNC system have been researched, with the result that the architecture is the fundament of the reconfigurable CNC system. Based on the research of the methodology, the exact polices to solve the complexity of the CNC system have been put forward. With these polices, the thesis analyzes the structure, the communication, the behavior and the connection of the CNC system, and bring forward a light software bus architecture based on activity object. Then a brief description about reconfigurable process has been given.Analyzing current standard component models, and considering the software and hardware characteristic of embedded system, such as limited source, great difference between platforms, high requirement of dependability, ECRNC (Embedded Component for Reconfigurable Numerical Controller) a component model used for embedded reconfigurable numerical controller is proposed in this thesis. The elements of the ECRNC, description of the component and the implement also have been researched. And according the characteristic of the software bus, some key technologies about realization have been given.Analyzing the particularity of multi-task schedule in CNC system, this thesis provides a hierarchical scheduling algorithm of real-time tasks. The algorithm guarantees that the deadlines of real-time tasks will not be missed by using DRM strategy on the first level and makes good use of bandwidth by applying the dynamic programming and greedy strategy to the scheduling of the optional components of real-time tasks on the second level. The algorithm overcomes the difficulties of the traditional hybrid scheduling algorithms such as the restriction of processor utilization, the high system overhead and the long responsive time.Researching the representing methods of software components, the representing method based on facet model for embedded CNC system is suggested. So a method based on tree inclusion is proposed to retrieve reusable components classified in faceted scheme, which combines the theory of tree matching and the feature of faceted classification scheme. And aim at multi schemes from tree matching, an adaptability analyzing model based fuzzy analytic hierarchy process (FAHP) is brought forward to choose optimal adaptability selection. An example is given to demonstrate the feasibility and effectiveness of this model. And a prototype of NC system IDE is built up.Based on the achievements mentioned above, a water-jet CNC system and wiring hamess CNC system with reconfigurable architecture have been developed successfully.