Safe multi-robot area coverage for cars with movement limits
Density-Driven Area Coverage for Nonholonomic Multi-Robot Systems with Safety Guarantee
RoboticsMultiagent Systems
Summary
Getting many robots to spread out safely over an area is tricky when the robots can't move directly sideways, like cars that must turn to change direction. The authors found that controlling safety rules on the actual driving commands, rather than on a simpler planned path, stops robots from getting too close while still covering the area efficiently. They combined a special safety filter with the robot’s controls and calculated safe distances considering the robot’s shape and how it moves. They tested this method in simulations and real robot experiments, showing it works well to keep robots safe while guiding them where they need to be.
What this means in practice
- •For industrial robot operators: Operate fleets of wheeled robots safely while covering nonuniform factory floors or warehouses efficiently without collisions or missed spots.
- •For search and rescue teams: Deploy multiple ground robots in complex environments with guaranteed safe distances while directing them to areas with varying importance for coverage.
Authors
Julian Martinez, Kooktae Lee
Abstract
Density-Driven Optimal Control (D2OC) provides a principled approach to distributing multi-robot teams over non-uniform spatial distributions. Applying D2OC to nonholonomic robots, however, creates a gap between safety constraints imposed on a reference motion and the physical inputs that determine the actual robot motion. We address this issue by enforcing the safety constraint directly on the robot's physical inputs while preserving the density-driven coverage objective. The proposed framework combines D2OC with a control barrier function safety filter through a feedback-linearizing look-ahead point, allowing safety and actuator limits to be considered together during control. We further derive a safety margin that accounts for the look-ahead geometry, robot footprint, and motion during each control interval. Simulation results show that the proposed method maintains the required physical separation while achieving coverage performance comparable to a conventional reference-tracking approach, which can satisfy safety on the reference motion yet violate the corresponding physical clearance. Experiments on multiple nonholonomic robots in the Robotarium further demonstrate safe execution while driving the robots toward the desired spatial distribution. These results show that enforcing safety directly on the physical inputs can eliminate the mismatch between safety certification and physical robot motion in density-driven multi-robot coverage.