A Trajectory Planner for Mobile Robots Steering Non-Holonomic Wheelchairs in Dynamic Environments

Motion planning for mobile robot platforms is one of the long-established research fields in robotics. In this paper, we propose a trajectory planner for mobile holonomic robots to steer non-holonomic conventional passive wheelchairs in dynamic environments. The challenges to overcome when steering a wheelchair are to find smooth feasible trajectories, maintain a fast reactive response to dynamic obstacles and to satisfy a set of additional constraints such as limiting physical forces acting on the wheelchair occupants. Our approach is a variant of the timed-elastic-bands (TEB) planner, which includes a footprint of the wheelchair during optimization, and generates a steering angle which is then consumed by an arm controller to actuate the relative orientation between the wheelchair and the mobile platform. This is realized by posing new non-holonomic and kinodynamic constraints on the TEB planner and an implementation of a suitable real-time dual-arm controller for executing steering commands. We demonstrate our results based on a TEB baseline comparison in simulation using functional models of our robot HoLLiE and a wheelchair.