Abstract:

CPS is a novel complex realtime distributed system consisting of computing,communication and control,in which computation process and physical process interacts and integrates in an open environment.In order to respond to the physical world information in real time, the system usually adopts preemptive scheduling methods to guarantee the implementation of crucial tasks before deadline.However,in the distributed environment,preemptive scheduling methods easily lead to frequent task switching, thus affecting the system’s real-time performance. We propose a realtime scheduling algorithm based on protection threshold to maximize the execution time of low priority tasks by establishing a protection threshold model which can reduce the frequency of task switching. Experimental results show that the proposed algorithm effectively reduces the frequency of task switching, thus improving the realtime performance of CPS system. 

Key words: CPS;real time characteristics;relaxation time;protection threshold;task switches