Expressive navigation and Local Path-Planning of independent steering autonomous systems

Abstract

This paper presents a novel Local-Path Planning approach for an independent four-wheel steering (I4WS) mobile base. The approach smoothly drives and rotates the platform while still following a given path and avoiding obstacles. I4WS vehicles are omnidirectional vehicles, similar to shopping carts, if one neglects the time needed to steer the wheels. However, due to the danger of mechanical parts breaking while actuating the wheels, they are commonly controlled in a stop-and-go fashion, where the vehicle stops to turn its wheels perpendicular to a desired instantaneous center of curvature (ICC) before starting to move again. The approach overcomes this limitation and ensures an ICC-based kinematic constraint during continuous motion using a flat-input controller running at 100 Hz. Therefore, the trajectory of the ICC is both predictable and suitable for model predictive control (MPC). The MPC implemented generates optimized collision-free trajectories of up to several meters ahead at 10 Hz, given a set of points along a path and laser contour readings. Furthermore, the planner realized here is able to deal with additional constraints such as the vehicle's view direction to focus on attention points while driving. Experimental results highlight the capabilities of the approach on a simulated robot, using GazeboSim, and demonstrate its applicability for the field of service robotics.