Fluent coordination of autonomous vehicles at intersections

In this paper we introduce a new decentralized navigation function for coordination of autonomous vehicles at intersections. The main contribution is a navigation function designed for vehicles with predefined paths that uses expected time to intersection for collision avoidance. In such way, deadlock situations are avoided. Different inertias of the vehicles are taken into account to enable on-board energy optimization for crossing. Heavier vehicles that need more energy and time for acceleration or braking are given an indirect priority at intersections. The proposed decentralized coordination scheme shows a significant improvement in energy consumption and in motion smoothness compared to traditional crossing with human drivers

Information sharing among autonomous vehicles crossing an intersection

In this paper we compare the performance of autonomous vehicles at intersections with respect to the type of information shared. For this purpose we consider the cases where vehicles share or not information about their inertia and their intention at the intersection. An existing control method based on navigation functions is modified in order to take into account such information. The results show that if autonomous vehicles know each other’s inertia they achieve significantly smoother paths, use less fuel and more often avoid full stop

A Virtual Vehicle Based Coordination Framework For Autonomous Vehicles in Heterogeneous Scenarios

This work presents a novel virtual vehicle based decentralized coordination framework for Connected Autonomous Vehicles (CAVs). We explore the idea of CAVs being capable of positioning virtual vehicles to share their intended maneuver as well as request cooperation. This framework has potential to inspire versatile solutions and provides an intuitive interface to interact with reactive and unconnected vehicles. In this context, a preliminary coordination policy is proposed and tested on a three-legged single-lane roundabout. Simulation results show that the presented solution performs outstandingly better when it leverages the freedom at positioning virtual vehicles that our framework provides. Furthermore, the performance degradation resulting from mixing CAVs and unconnected cars is observed, and coordination assessment under this circumstance is discussed

Collision-Free Intersection Crossing of Mobile Robots Using Decentralized Navigation Functions on Predefined Paths

This paper deals with the coordination of a group of mobile robots at an intersection. It focusses on decentralized navigation functions (DNFs) to achieve efficient traffic control. The main challenge is to define virtual potentials, which are used by decentralized navigation functions, such that traffic is both fluent and safe, while taking into account real-world limitations like acceleration, braking and speed limits. Our method consists in defining the navigation function with respect to the desired acceleration profile and is accompanied by a set of visibility conditions that increase the capacity of the intersection in terms of vehicle throughput. Priority conditions have been used to both avoid blockades of robots and to save energy by assigning higher priorities to robots with higher inertias

Collision-Free Coordination of Fiber Positioners in Multi-object Spectrographs

Many ber-fed spectroscopic survey projects, such as DESI, PFS and MOONS, will use thousands of fiber positioners packed at a focal plane. To maximize observation time, the positioners need to move simultaneously and reach their targets swiftly. We have previously presented a motion planning method based on a decentralized navigation function for the collision-free coordination of the fiber positioners in DESI. In MOONS, the end-effector of each positioner handling the ber can reach the centre of its neighbours. There is therefore a risk of collision with up to 18 surrounding positioners in the chosen dense hexagonal conguration. Moreover, the length of the second arm of the positioner is almost twice the length of the rst one. As a result, the geometry of the potential collision zone between two positioners is not limited to the extremity of their end-effector, but surrounds the second arm. In this paper, we modify the navigation function to take into account the larger collision zone resulting from the extended geometrical shape of the positioners. The proposed navigation function takes into account the conguration of the positioners as well as the constraints on the actuators, such as their maximal velocity and their mechanical clearance. Considering the fact that all the positioners' bases are xed to the focal plane, collisions can occur locally and the risk of collision is limited to the 18 surrounding positioners. The decentralizing motion planning and trajectory generation takes advantage of this limited number of positioners and the locality of collisions, hence signicantly reduces the complexity of the algorithm to a linear order. The linear complexity ensures short computation time. In addition, the time needed to move all the positioners to their targets is independent of the number of positioners. These two key advantages of the chosen decentralization approach turn this method to a promising solution for the collision-free motion-planning problem in the next-generation spectroscopic survey projects. A motion planning simulator, exploited as a software prototype, has been developed in Python. The pre-computed collision-free trajectories of the actuators of all the positioners are fed directly from the simulator to the electronics controlling the motors. A successful demonstration of the effectiveness of these trajectories on the real positioners as well as their simulated counterparts are put side by side in the following online video sequence (https://goo.gl/YuwwsE)

Micro-simulation Modeling of Coordination of Automated Guided Vehicles at Intersection

One of the challenging problems with autonomous vehicles is their performance at intersections. This paper shows an alternative control method for the coordination of autonomous vehicles at intersections. The proposed approach is grounded in multi-robot coordination and it also takes into account vehicle dynamics as well as realistic communication constraints. The existing concept of decentralized navigation functions is combined with a sensing model and a crossing strategy is developed. It is shown that, thanks to the proposed approach, vehicles have smoother trajectories when crossing at a four-way intersection. The proposed method is compared to adaptive traffic lights and roundabouts in terms of throughput. Results show that using a decentralized navigation function for the coordination of autonomous vehicles improves the performance by reducing energy consumption and pollution emission

Collision-free motion planning for fiber positioner robots: discretization of velocity profiles

The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber positioners. The navigation function takes into account the configuration of positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (~2.5 seconds with the maximum speed of 30 rpm for the positioner), which is independent of the number of positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs.Comment: SPIE Astronomical Telescopes + Instrumentation 2014 in Montr\'eal, Quebec, Canada. arXiv admin note: substantial text overlap with arXiv:1312.164

Autonomous vehicles share information crossing an intersection

Autonomous vehicles can react faster than humans, they have more accurate perception and do not get distracted, sleepy or intoxicated. Autonomous vehicles could also increase the capacity of our current roads by allowing cars to be driven more closely to each other. Accordingly, driverless cars seem to be imminent. One of the challenges with autonomous vehicles is their performance at intersections. This performance directly depends on the level of cooperation between the vehicles