Deadline and Period Assignment for Guaranteeing Timely Response of the Cyber-Physical System

Abstract

Cyber-physical systems (CPSs) need to respond to each change of each monitored object in time. The entire response process can be divided into two stages: the update stage and the control stage. Tasks in CPSs can thus be divided into two kinds: update tasks and control tasks. Assigning deadlines and periods for tasks to ensure a timely response to each change of each monitored object is an important problem in CPS research. Existing methods can ensure that all changes of all objects can receive timely responses if tasks are schedulable. However, these methods have not made efforts to ensure the schedulability of tasks. Therefore, some tasks that can actually receive services cannot be serviced under these methods. In this article, we study the problem of assigning deadlines and periods for tasks while ensuring timely responses and maximizing the schedulability of tasks. Specifically, we find that the delayed deadline assignment for update tasks is the main factor that causes the low scheduling capability of existing methods. A new deadline and period assignment method is proposed based on an optimized deadline calculation scheme and an advanced deadline determination mechanism. Theoretical analysis proves the correctness and superiority of the proposed method. Experimental results show that the new method can improve 30.02% acceptance ratio and save 98.48% runtime on average, as compared to the state-of-the-art deadline and period assignment method.