NSF Award
2328671
Coordinating a large team of robots to perform navigation tasks in a congested environment is a critical problem in many settings such as automated warehouses. An increasing number of Artificial Intelligence (AI) researchers have been attracted to study an abstract model of this problem, called Multi-Agent Path Finding (MAPF), and made significant progress in the past decade. State-of-the-art MAPF solvers can generate paths in seconds for hundreds of mobile agents (which are simplified versions of robots) in highly congested environments and yet provide important theoretical guarantees such as soundness and even optimality. Yet, these solvers cannot be directly applied to real robots. They ignore constraints on robot dynamics such as limits on acceleration and do not account for the uncertainty in execution such as potential slippage, latency in coordination, and delays in trajectory following. Consequently, in practice, engineers commonly ignore these advanced MAPF solvers and instead opt for much simpler techniques that can often generate poor-quality solutions but are easy to adapt. This project aims to close this gap by investigating how to provide a safe and effective multi-robot path planning and execution framework that enables hundreds of heterogeneous robots to move to their desired locations in the presence of complex obstacles, non-holonomic dynamics, actuation limits, and disturbances while minimizing their travel times and communication efforts.<br/><br/>This project builds on the recent work on Temporal Plan Graphs (TPGs), which relaxes an MAPF plan by allowing arbitrary modifications to the robot speeds as long as the ordering with which each robot visits each location is preserved. This project leverages some insights behind TPG but aims to develop a coordination-aware algorithmic framework that interleaves multi-robot planning with coordination and control. The first thrust focuses on handling robot dynamics and temporal tracking errors by developing relaxed and adaptive TPGs that enforce only critical precedence constraints and allow for the re-optimization of TPGs on the fly. The second thrust extends the first one by further considering spatial tracking errors and integrating reachability analysis and controller optimization into MAPF and TPG algorithms. The third thrust aims at developing MAPF algorithms that provide provably fast planning and re-planning times by extending a recently introduced concept of Provably Constant-Time Motion Planning to the domain of multi-agent planning. The last thrust develops an open-source platform for testing MAPF algorithms in a more realistic setting that includes constraints on robot dynamics and uncertainty in execution.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
