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

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

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

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

Real-life Implementation and Comparison of Authenticated Path Following for Automated Vehicles based on Galileo OSNMA Localization

We present a comparative analysis of EGNSS-based path tracking with and without open service navigation message authentication (OSNMA), which was recently made available in mass market EGNSS (Galileo) receivers. The EGNSS receivers provide dual-band GPS L1/L2 and Galileo E1/E5a RTK positioning for cm-level GNSS localization. The path following task utilizes mainly the accurate RTK-assisted EGNSS position and heading information to track a reference path. The lateral error from the reference path is used as the correction signal for the tracking controller. We compare the performance of the tracking controller in an open-sky and urban setting within the Graz University of Technology Inffeldgasse campus using an automated driving demonstrator vehicle. The positioning utilized two different OSNMA schemes, namely “strict” OSNMA solution that utilize only authenticated Galileo satellites or not using authentication, implying utilisation of all the available GNSS satellites