Study And Application Of Controller Oriented Real-time Scheduling Jitter Compensation And Scheduling Policies

Computer Numerical Control System(CNC)is a sort of typical hard real-time system, which needs strict real-time processing function and high-class dependability. The correctness of CNC's real-time control lies on both the result and the finish time of real-time computing. Real-time system's real-time performance must be guaranteed so that it can respond in expected time .As an important part of real-time system, real-time scheduling is a key factor to influence the real-time performance, which distributes the system resources. The work goes along under the above background.Firstly, the basic knowledge of real-time system and real-time scheduling is introduced, followed by the introduction of the real-time platform and software level of LT-CNC. Secondly, scheduling jitter is one of the most important performance criterions for RTOS while scheduling jitter exists in all RTOS. The testing and analysis techniques of jitter are discussed; A kind of once scheduling compensating method used to reduce jitter in motion control of CNC is Put forward, and then their effect when used in the motion controller of LT-CNC is illustrated. Thirdly, the tasks in after-upgraded LT-CNC will become more in the future, so it is importance to find a jitter compensation methods for multi-tasks to improve the dependability of the after-upgraded LT-CNC; The process of modeling, analyzing and designing one kinds compensation method for output jitter of multi-tasks is described, followed by the illustration of performance test of the method. Fourthly, real-time scheduling policies are the kernel of real-time scheduling. Serveral kinds of real-time scheduling policies in common use are introduced, and then one kind of the most popular real-time scheduling policies-RM is compared with another one-EDF in some important performances.