String-stable automated steering in cooperative driving applications

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Abstract

The ever-increasing road transport demand in the developing and the developed world has resulted in road-traffic networks nearing maximum capacity. Traditional approaches to this problem, such as increasing road capacity, do not offer long-term solutions. Combined with rising environmental concerns, the demand for smarter solutions has never been higher. One such solution, which has gained significant ground in the past decades, is automated vehicle platooning.

A vehicle platoon is an interconnected dynamical system consisting of automated vehicles driving in close proximity, coordinating their movement through measurements and sometimes inter-vehicular communication. By allowing driving in close proximity, platoons have the potential to increase road capacity, whilst reducing fuel consumption. Platoons are subject to safety and performance requirements. In order to meet these requirements the vehicle platoon needs be string stable, such that effects of disturbances are not amplified in the upstream direction of the string of vehicles. String-stable platoons also help preventing ghost traffic jams, typically caused by human driver behaviour. Advancements in vehicle platooning research have mostly been concerned with longitudinal automation, and consequently with longitudinal string stability. However, driving at small inter-vehicular gaps also requires lateral automation. Naturally, this means that string stability in the lateral sense is required.

Therefore, the objective of this MSc thesis is to develop a lateral control method for automated vehicle platoons that yield string-stable behaviour. In the first part, an error model based on a vehicle-following control strategy, which uses vehicle path following, is derived. This model is then used to describe the path-following problem within a platoon. In the second part, a control strategy is proposed using the H∞ framework, such that path following and lateral string stability are guaranteed a-priori.

The robustness properties and the performance of the designed controller are analysed by means of frequency-domain analysis and time-domain simulations. Finally, path following and the string-stability properties of the controller have been validated experimentally. The experiments performed confirm the theoretical analysis, thereby showing that lateral string stability is obtainable using the proposed method.

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