Leader-Based Trajectory Following in Unstructured Environments—From Concept to Real-World Implementation

Abstract

In this paper, the problem of vehicle guidance by means of an external leader is described. The objective is to navigate a four-wheeled vehicle through unstructured environments, characterized by the lack of availability of typical guidance infrastructure like lane markings or HD maps. The trajectory-following approach is based on an estimate of the leader’s path. For that, position measurements are stored over time with respect to an inertial frame. A new strategy is proposed to rate the significance of position measurements and ensure that a certain threshold of stored samples is not exceeded. Having an estimate of the leader path is essential to prevent the cutting-corner phenomenon and for exact path following in general. A spline-approximation technique is applied to obtain a smooth reference path for the underlying lateral and longitudinal motion controllers. For longitudinal tracking, a constant time-headway policy was implemented, to follow the leader with a constant time gap along the estimated path. The algorithm was first developed and tested in a simulation framework and then deployed in a demonstrator vehicle for validation under real operating conditions. The presented experimental results were achieved using only on-board sensors of the demonstrator vehicle, while high-accuracy differential GPS-based position measurements serve as the ground truth data for visualization.

A Survey on Path Planning for Autonomous Ground Vehicles in Unstructured Environments

“…Safety constraints contain the collision avoidance constraints [85,104,117] and rollover-free constraints [66,75]. Obstacle avoidance can be met by setting a safe distance from obstacles or limits on speed and acceleration [118]. Rollover can be avoided by limiting the steering angle [75], pitch angle, and roll angle [66].…”

Feasible, Robust and Reliable Automation and Control for Autonomous Systems

“…Finally, in 'Leader-Based Trajectory Following in Unstructured Environments-From Concept to Real-World Implementation', Nestlinger et al described the issue of guiding a vehicle by means of an external leader [12]. A system was proposed and tested in a simulation framework and then deployed in a demonstrator vehicle for validation under real operating conditions.…”