Multi-Robot Task Allocation Based on Swarm Intelligence

Abstract

In the field of cooperative robotics, task allocation is an issue receiving much attention. When researchers design, build, and use cooperative multi-robot system, they invariably try to answer the question of which robot should execute which task. This is in fact a multirobot task allocation problem (MRTA). The task allocation problem addresses the question of finding the task-to-robot assignments that optimize global cost or utility objectives. Finding an optimal task allocation, even in a relatively simplified case, is an NP-hard problem. Therefore, the majority of common approaches are approximate or heuristic in nature. Those approaches usually give suboptimal solutions. MRTA is a fundamental issue of the multi-robot systems, which embodies the high-level system organization and operation mechanism. The quality of task allocation algorithm directly affects the performance of multi-robot system. With an increase in the number of robots and difficulty of tasks within a system, the issue of task allocation has risen to prominence and become a key research topic in the multi-robot domain. In 2005, the International Conference on Robotics and Automation (ICRA 2005) set special panels on multi-robot task allocation, in which the latest research and the progress are discussed. Gerkey and Mataric (2004) presented a particular taxonomy for the task allocation problem. It is described as follows: • Single-task robots (ST) vs. multi-task robots (MT): ST means that each robot is capable of executing at most one task at a time, while MT means that some robots can execute multiple tasks simultaneously. • Single-robot tasks (SR) and multi-robot tasks (MR): SR means that each task requires exactly one robot to achieve it, while MR means that some tasks can require multiple robots. • Instantaneous (IA) and time-extended (TA) assignment: In the instantaneous assignment, robots do not plan for future allocations and are only concerned with the one task they are carrying out at the moment (or for which they are considering executing). In the time-extended assignment, robots have more information and can come up with longer-term plans involving task sequences or schedules. Based on above categorization, there are eight types of task allocation combination. ST-SRIA is the simplest, as it is actually a trivial instance of the Optimal Assignment Problem