Agent-Based Dynamic Scheduling for Earth-Observing Tasks on Multiple Airships in Emergency

Abstract

Airships are becoming promising platforms for Earth observing in emergency (e.g., nature disaster surveillance). Dynamic scheduling plays a very critical role in dealing with emergent tasks. In this paper, we devise a novel agent-based scheduling mechanism. In contrast to the traditional contract net protocol, our mechanism has a bidirectional announcement mechanism, and the collaborative process consists of forward announcements from the perspective of tasks and backward announcements from the perspective of resources to jointly accomplish the scheduling. Additionally, we devise calculation rules of the bidding values in both forward and backward announcements and two heuristics for selecting contractors. Based on the bidirectional announcement mechanism, we propose an agent-based dynamic scheduling (ABDS) strategy for scheduling Earth-observing tasks on multiple airships. The ABDS scheme employs the fair competition principle of a roulette wheel and the dynamic adjustment principle of a buffer pool to solve the problem of local searching and to improve the load balancing of resources. Extensive experiments were carried out to evaluate the performance of ABDS by comparing it with a unidirectional announcement (UA) scheduling algorithm and a genetic algorithm. In addition, the sensitivity of the priority parameter to the system performance is evaluated. Experimental results show that ABDS significantly outperforms the scheduling quality of UA and that it is suitable for the Earth-observing task scheduling on multiple airships in emergency.