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Motivated by driver-assist systems that warn the driver before taking control action, we study the safety problem for a class of bounded hybrid automata. We show that for this class there exists a least restrictive safe feedback controller that has a simple structure and can be computed efficiently online. The theoretical results are then used to design driver-assist systems for rear-end and merging...
Based on the further research of STCA and F-STCA cellular automata traffic flow model, combined with the actual situation of the symmetric same direction two-lane traffic flow, improved the risk description of vehicle lane-changing in the driving, a more perfect distance constraint rule and cellular automata traffic flow model are proposed, which are more in line with the actual situation of symmetric...
Information exchange for the purpose of creating situational awareness is the backbone of distributed systems that rely on communication. For example, connected vehicle safety systems rely on exchange of information between vehicles to allow each vehicle to create a real time map of its surrounding cars. These systems work by sampling the state of a physical process (vehicle trajectory) and communicating...
A mainline merged two on-ramps is known as three-merge-one road, which three roads merged into one road. The emphasis of this study lies in traffic flow characteristics and the design optimization for buffer lane, which restrict traffic flow of the three-merge-one road that become a congested traffic bottleneck in urban traffic. This study presents traffic flow model with cellular automaton. It is...
A formal mathematical model of an Adaptive Cruise Controller (ACC)in SpaceEx is presented with a view to formally verify it to ensure its safety critical behavior. SpaceEx (an academic open source tool) is a hybrid systems modeling and verification platform which employs efficient implementation of reachability and safety verification algorithms which are scalable under certain assumptions, to circumvent...
We establish two models with Cellular Automaton (CA) to simulate the conditions of multi-lane freeways under the Keep-Right-Except-to-Pass (KRETP) rule and other improved road rules. We establish the Keep-Right-Except-to- Pass (KRETP) model, which takes into consideration human behaviors when simulating the KRETP rule in both light and heavy traffic. In this model we divide drivers into two categories:...
Vehicular Ad-hoc Networks (VANET) are considered as a promising approach for building a variety of applications for Intelligent Transportation Systems (ITS). They are a kind of mobile networks that enables moving vehicles to exchange information about the driving environment. Although the amount of information disseminated through a VANET provides a great opportunity to enhance traffic safety, a study...
Cyber-physical systems (CPS) may interact and manipulate objects in the physical world, and therefore ideally would have formal guarantees about their behavior. Performing static-time proofs of safety invariants, however, may be intractable for systems with distributed physical-world interactions. This is further complicated when realistic communication models are considered, for which there may not...
In this paper, we consider the safety control problem for hidden mode hybrid systems (HMHSs), which are a special class of hybrid automata in which the mode is not available for control. For these systems, safety control is a problem with imperfect state information. We tackle this problem by introducing the notion of nondeterministic discrete information state and by translating the problem to one...
Cyber-Physical Systems (CPS) involve deep interactions between computation cores, communication networks, and physical environments. These systems are inherently complex and highly nondeterministic. This makes the traditional formal verification technology impractical to verify the complete system behavior, and testing alone is insufficient to guarantee correctness. Runtime monitoring, known as a...
In this paper, the problem of collision avoidance between two vehicles is considered, in which one vehicle is autonomous and the other one is human-driven. This problem arises in cooperative active safety systems at traffic intersections, mergings, and roundabouts, in which some vehicles are equipped with on-board communication and automatic control, while others are not capable of communicating and...
This work considers the problem of decentralized coordination between multiple non-holonomic vehicles, each navigating to a specified goal. By augmenting the Generalized Roundabout Policy (GRP), which guarantees collision avoidance, this paper improves the performance and liveness characteristics for such problems. These gains are achieved by integrating a second hybrid policy with GRP that updates...
Cyber-physical systems bridge the gap between cyber components, typically written in software, and the physical world. Software written with traditional development practices, however, likely contains bugs or unintended interactions among components, which can result in uncontrolled and possibly disastrous physical-world interactions. Complete verification of cyber-physical systems, however, is often...
The safety problem in multi-vehicle systems seeks to establish collision-free and live vehicle motion, and it is a prominent problem for many configurations of these environments. Past work studying this problem in the context of free-range vehicular systems through abstractions based on Resource Allocation System (RAS) theory, has implicitly assumed that its resolution through maximally permissive...
In this paper we propose a decentralized control policy for coordinating a group of nonholonomic autonomous vehicles (non necessarily homogeneous) with input constraints moving in ??2, aiming to satisfy individual (trajectory tracking) and common objectives (guaranteed vehicles safety). The proposed policy models the discrete operation modes of each participating vehicle as a hybrid automaton, while...
We consider a parallel composition of two order preserving hybrid automata with imperfect state information. We show that the order preserving properties of the dynamics lead to a separation principle between state estimation and control under safety specifications. We provide a dynamic feedback algorithm that is guaranteed to terminate and whose complexity scales with the number of continuous variables.
In this paper, we employ partial order techniques to develop linear complexity algorithms for guaranteed collision avoidance between vehicles at highway and roundabout mergings. These techniques can be employed by virtue of the rich structure offered by such traffic systems, which constrain vehicles to advance unidirectionally along a path. The algorithms are safe by construction while maintaining...
Based on the basic symmetric two lane cellular automaton model (STCA), we propose a modified STCA (MSTCA) for mixed traffic flow. In MSTCA, the headway also could be used for lane changing, and then the length for safety criterion would be extended a lot. Lane changing region and first cell for lane changing on the other lane could be located. The situation while there are successive vehicles satisfies...
The multi-agent system, which combines the cellular automata model, is of benefit to the simulations of large-scale events. Cars' movements were simulated using cellular automata model and their variability was introduced by superimposing agent. There were two submodels which based on the combined model. The first submodel simulated cars' movement in a park. The other submodel was proposed to simulate...
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