Research On Task Scheduling In Real-time Multi-priority Cyclical Interchangeable

In recent years, microprocessor was introduced to all areas of the electronics industry along with the improvement of digital and intelligent degree. Generally speaking, electronic systems with a microprocessor are collectively called embedded systems. The tasks need to be processed by the microprocessor increased with the increasing of functions integrated in a system.At present, there are many mature algorithms aimed at multitask scheduling. In a real-time operating system, there are multiple real-time tasks require the system scheduling, and different tasks have different matched priorities which are established to meet requirements of each task in real-time system. All of the real-time task scheduling in real-time operation system are based on preemptive priority driven. High-priority tasks can peel away the execution time of a lower-priority task, which can meet the strict time limits of high-priority. The execution time of each task has a big difference for the difference of priority level, the execution time of the high-priority task is very short, and the execution time of the low-priority task is long, it is more serious in the system with preemptive priority scheduling algorithm. It is common that low-priority tasks consume more time and appear delay question during the executing processes in all of the real-time systems. How to solve these problems is the research object of this article.In this paper, the priority periodic swap scheduling algorithm is proposed based on the research and analysis of the commonly used multiple task scheduling algorithms. The principle of this algorithm derives from the time slice rotation scheduling algorithm, and the problem-solving method is to swap the priority between the low-priority tasks priority and the high-priority task priority periodically so that the low-priority task can be executed in a time period. For the verifying of the priority periodic swap task scheduling algorithm, the simulation software of Ptolemy Ⅱ is used to simulate the actual control system, and the response curves for each task are plotted through scheduling three PID controllers to control the three controlled objects, it verifies the rationality and advantages of the priority periodic swap scheduling algorithm.