DMS*: Minimizing Makespan for Multi-Agent Combinatorial Path Finding
This work addresses path planning for multi-agent systems where minimizing makespan is critical, such as in robotics, but it is incremental as it builds on existing MS* methods.
The paper tackles the Multi-Agent Combinatorial Path Finding (MCPF) problem by proposing a min-max variant, MCPF-max, to minimize the makespan (maximum arrival time) of agents, and introduces DMS* with deferred target sequencing to expedite computation, achieving results tested with up to 20 agents and 80 targets and demonstrated on differential-drive robots.
Multi-Agent Combinatorial Path Finding (MCPF) seeks collision-free paths for multiple agents from their initial to goal locations, while visiting a set of intermediate target locations in the middle of the paths. MCPF is challenging as it involves both planning collision-free paths for multiple agents and target sequencing, i.e., solving traveling salesman problems to assign targets to and find the visiting order for the agents. Recent work develops methods to address MCPF while minimizing the sum of individual arrival times at goals. Such a problem formulation may result in paths with different arrival times and lead to a long makespan, the maximum arrival time, among the agents. This paper proposes a min-max variant of MCPF, denoted as MCPF-max, that minimizes the makespan of the agents. While the existing methods (such as MS*) for MCPF can be adapted to solve MCPF-max, we further develop two new techniques based on MS* to defer the expensive target sequencing during planning to expedite the overall computation. We analyze the properties of the resulting algorithm Deferred MS* (DMS*), and test DMS* with up to 20 agents and 80 targets. We demonstrate the use of DMS* on differential-drive robots.