Research And Application On Optimization Technologies For Real-time Operating System In Open CNC System

The Real-time Operating System (RTOS) is one of the core components of OpenComputerized Numerical Controller (CNC) and the key technology to ensure the CNCsystem's characteristics of high-speed, high-accuracy, openness and intelligence.Therefore, many domestic and foreign researching organizations have been researchingthe related technologies of RTOS for the open CNC system. Several research topics ofNational Science and Technology Major Project on "High-end CNC machine tools andbasic manufacturing equipment" have proposed that RTOS based on the open sourcesoftware is one of the important research subjects. However, the existing RTOS studiespay too much attention to the average real-time capability, without thoroughlyconsidering the special requirements of the open CNC system. Thence, it is the keyresearch problem to optimize the existing RTOS subject to the demand of the majoritykinds of open CNC systems. By improving the compatibility, scalability, adaptabilityand the ability of supporting the multicore processors, RTOS will become the basis ofthe software platform of open CNC system. This dissertation focuses on the researchand application on optimization technologies for RTOS in CNC systems. The maincontributions of this dissertation are summarized as follows:1. Research and implementation on the function optimizations for RTOS. Theexisting RTOS cannot satisfy the specific requirements on openness and performanceevaluation of open CNC system. They cannot support the open CNC system'sinteroperability, scalability and portability. In order to solve these common requirements,3function extensions are presented in this dissertation. The RTOS API Abstract Layerdynamically transforms the API functions between the different API systems. Differentkinds of open CNC system will use different real-time scheduling algorithms. An openscheduling scheme is presented in this dissertation to solve the above problem. Areal-time system performance evaluation tool which could acquire the hardware levelperformance data and the OS level performance data is designed to evaluate theperformance of RTOS and open CNC system.2. Research and implementation on the data flow feedback scheduling model foropen CNC System. The core functions of the open CNC system's software are based onthe data flow model. In the standard open CNC system whose hardware resources arenot sufficient, the data flow would be interrupted in certain specific scenarios, which degrades the velocity and accuracy of the machine process. A data flow feedbackscheduling model is presented in this dissertation to solve this problem. An experimentin standard open CNC system verified the validity of the model.3. Research and implementation on the adaptive feedback scheduling modelbased on Lebesgue sampling. In the standard open CNC system, the dynamic change ofreal-time workload might cause some non-real-time tasks is long-term lack of execution.In this case, the overall performance of the open CNC system can no longer be ensured.This dissertation presents an adaptive feedback scheduling model that can automaticallybalance the workload of ONC system. The overhead of the model itself is decreased bya Lebesgue sampling method. This model is verified by an experiment in a standardopen CNC system.4. Research and implementation on Cache-aware hard real-time schedulingalgorithm for dual-core processor. While a hard real-time task set is executed by adual-core processor, the concurrent tasks would disturb each other by competing for theshared Cache. The interference would degrade the predictability and the machinequality of the open CNC system. In order to optimize the predictability of the hardreal-time task set in the dual-core processor, a cache-aware hard real-time schedulingalgorithm and a judgment condition for the scheduability are presented in thisdissertation. An experiment verified the validity of the algorithm.5. Research and implementation on the real-time optimization method for theopen CNC system based on multi-core processor. While the open CNC system isimplemented by a single multi-core processor, the non-real-time tasks would disturb theexecution of the real-time tasks through the shared Cache. This interference restricts thereal-time performance of the open CNC system. This dissertation proposes a real-timememory manager and a Cache-aware multi-level scheduling scheme. The real-timememory manager can partition the shared Cache. On the basis of Cache partition, aCache-aware soft real-time scheduling algorithm in the multi-level scheduling schemefurther decrease Cache access conflict by a heuristic method. The real-time memorymanager and the Cache-aware multi-level scheduling scheme are verified by anexperiment in a CNC system based on a quad-core processor.