Research Of Parallel CNC System Based On Embedded Symmetric Multi-Core Processor

With the proposal of new research directions such as high-speed,high precision,multi axis linkage,intellectualizationand other numerical control technologies,the real-time computing ability of embedded CNC system needs to be greatly improved.However,single core processor is unable to provide computational bandwidth which is required by those features,while multi-core processors can provide sufficent computing power for embedded CNC systems.In this thesis,a multi task parallel CNC system is developed based on embedded symmetric multi-core processor.Firstly,the hardware platform architecture of numerical control system is designed using multi-core processor and real-time industrial Ethernet technology.A parpllelization scheme of the CNC system kernel is proposed,and a multi-core parallel CNC system software framework is designed.The CNC system kernel is divided into multiple tasks by function using pipeline technology.Data transfer between tasks is realized via FIFO ring buffer,thus the data dependence relationship between tasks is decoupled.Consequently,the CNC tasks are capable to run independently and concurrently on multiple processor cores.Secondly,through the analysis of task scheduling requirements of multi-core parallel CNC system,a scheduling strategy for mixed real-time task set of CNC system is developed.The scheduling strategy is integrated in the kernel of eCos real-time operating system.In order to maintain stability of the data flow between tasks of CNC system,a data flow feedback task scheduling strategy is proposed by introducing data stream status into task scheduling.Through analyzing the task scheduling mechanism of eCos on a multi-core processor,the kernel scheduler of eCos is reconstructed by adding support for hybrid real-time task scheduling.Meanwhile,a general design framework for two kinds of real-time tasks is proposed.Thirdly,each task module is realized according to the framework of multi-core parallel CNC system.The information transfer mode and data structure between tasks are defined.The software development of the multi-core parallel CNC system is accomplished.An experimental platform of CNC system based on PowerLink real-time Ethernet bus is built.An embedded PowerLink communication card is implemented for network communication between multi-core processor platform and servo system.At last,serval tests are performed towards the hybrid real-time scheduler.Serval scheduling instances are designed to test and verify the correctness and data flow balance effect of the hybrid real-time scheduler.The speedup ratio and efficiency of parallel programs are also tested on the multi-core platform.To verify the correctness of key functions of the developed CNC system,real-time performance tests and processing experiments are conducted.The experimental results have shown the performance and functional correctness of the developed CNC system.