Optimizing the inter-distances between vehicles is very important to reduce traffic congestion on highways. Variable spacing and constant spacing are the two policies for the longitudinal control of platoons. Variable spacing doesn't require a lot of data (position, speed...) from other vehicles, and string stability can be obtained using on-board information only. However, inter-vehicle distances are very large, and hence traffic density is low. Constant spacing offers string stability with high traffic density, but it requires data communication between the vehicles, at least from the leader. In this paper, a new platoon model and a modification of the variable spacing policy are proposed. This modification is effective to decrease the distances between the cars, making them nearly equal to the constant spacing policy. It also enables increasing string stability. This new approach doesn't require heavy communication between the vehicles. The new model is based on an unidirectional spring-damper model between vehicles, with the vehicles loaded on a virtual flatbed tow truck. From this configuration, conditions of stability and safety of homogeneous platoon are derived. Based on this new model, a control has been derived and evaluated by simulation with a perfect system model using Matlab, and with a more realistic vehicle model using TORCS (The Open Racing Car Simulator). The simulation consists of a platoon of ten vehicles, moving on highways, with a desired inter-vehicle distance equal to 1 meter. The stability and the safety of the platoon are tested during platoon creation, changing the speed and emergency stop. The good results demonstrate the effectiveness of the new approach.

This paper describes a novel projection model based on the so-called unified projection model. The new model applies to catadioptric systems and wide-angle fish-eye cameras, it does not require additional mapping to model distortions, and it takes just two projection parameters more than a simple pinhole model to represent radial distortion (one parameter more than the unified model). Here we provide a study of different mathematical aspects of the model, its application limits, and explicit closed-form inversion. The latter allows to apply all the notions of epipolar geometry with no difficulties. Also we introduce a concept of projection surface, which is a useful notion to study and compare different projection models with radial distortion. Using developed software, several different lenses were calibrated using the proposed model, and in all cases sub-pixel precision was achieved.

A good path tracker is one of the keys for the successful development of a self-driving car. In the literature, there exists a wide variety of techniques, some complex and some simple and yet effective in particular scenarios. The choice of the path tracker influences the performance in terms of precision, stability and passenger comfort. This paper addresses the lateral control of a self-driving car in an urban environment, where speed is not high but variations in velocity and curvature are frequent. In choosing a lateral controller, simplicity, efficiency and robustness are considered as the main criteria. In this paper, three classical techniques used for controlling the lateral error are analyzed: pure pursuit, Stanley and a simplified kinematic steering control. Additionally, a novel kinematic controller based on the lateral speed is proposed. A home-made realistic simulation environment has been developed to allow rapid testing of the control laws. The relevance of this work has been demonstrated for all controllers through realistic simulations and experiments. The experimental site is the campus of Ecole Centrale de Nantes, where all control laws have been compared along the same path. A longer path, involving a portion of the ring road of Nantes (France) has been simulated. It involves speeds up to 90 km/h, allowing to extrapolate the comparison results to higher velocities.

A 2D mobile robot localization system which uses odometry and the azimuth angles of known landmarks is presented. Observability analysis helps to determine situations where such a system may undergo difficulties, and gives information on its behavior when one of the beacons is hidden. Experimental results are presented.

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