Inter-vehicular Distance Research Articles

Multi-objective platoon maneuvering using artificial potential fields

Nowadays, there is an increasing societal demand for smart mobility solutions which can increase the throughput, comfort, and safety of driving on a road. As one of these solutions, vehicle following technologies like cooperative adaptive cruise control (CACC) are introduced. with the help of vehicle-to-vehicle (V2V) communication, CACC can reduce the safe minimal inter-vehicular distance. Additionally, sharing the vehicle intentions through V2V, enables multi-vehicle maneuvers to be cooperatively executable. In this paper, using the concept of artificial potential fields, a longitudinal control scheme for performing a cooperative merging maneuver will be suggested. Artificial potential fields are powerful enough for modeling and solving such a complex problem, where in addition to vehicle following other objectives such as merging should be addressed. The designed algorithms for vehicle cooperative maneuvering are verified through simulations.

An adaptive cruise control for connected energy-saving electric vehicles

We present an energy-saving cooperative adaptive cruise control (eco-CACC), which minimizes the energy consumption of autonomous electric vehicles. The approach leverages a trajectory preview from the preceding vehicle, and conciliates inter-vehicular distance reduction and speed profile smoothing. The problem is tackled with a nonlinear MPC approach. Rather than tracking a reference trajectory, our approach allows variations of distance and speed between vehicles, as long as the powertrain energy consumption is minimized and collision avoidance is guaranteed. Simulations show that this formulation can successfully handle real-world driving conditions, with limited computational complexity.

Characteristics of lateral vehicular interactions in heterogeneous traffic with weak lane discipline

Heterogeneous traffic conditions prevail in developing countries. Vehicles maintain weak lane discipline which increases lateral interactions of vehicles significantly. It is necessary to study these interactions in the form of maintained lateral gaps for modeling this traffic scenario. This paper aims at determining lateral clearances maintained by different vehicle types while moving in a heterogeneous traffic stream during overtaking. These data were collected using an instrumented vehicle which runs as a part of the stream. Variation of obtained clearance with average speed of interacting vehicles is studied and modeled. Different instrumented vehicles of various types are developed using (1) ultrasonic sensors fixed on both sides of vehicle, which provide inter-vehicular lateral distance and relative speed; and (2) GPS device with cameras, which provides vehicle type and speed of interacting vehicles. They are driven on different roads in six cities of India, to measure lateral gaps maintained with different interacting vehicles at different speeds. Relationships between lateral gaps and speed are modeled as regression lines with positive slopes and beta-distributed residuals. Nature of these graphs (i.e., slopes, intercepts, residuals) are also evaluated and compared for different interacting vehicle-type pairs. It is observed that similar vehicle pairs maintain less lateral clearance than dissimilar vehicle pairs. If a vehicle interacts with two vehicles (one on each side) simultaneously, lateral clearance is reduced and safety of the vehicles is compromised. The obtained relationships can be used for simulating lateral clearance maintaining behavior of vehicles in heterogeneous traffic.

Unsupervised video summarization using cluster analysis for automatic vehicles counting and recognizing

Automatic Vehicles Counting and Recognizing (AVCR) is a very challenging topic in transport engineering having important implications for the modern transport policies. Implementing a computer-assisted AVCR in the most vital districts of a country provides a large amount of measurements which are statistically processed and analyzed, the purpose of which is to optimize the decision-making of traffic operation, pavement design, and transportation planning. Since, the advent of computer vision technology, video-based surveillance of road vehicles has become a key component in developing autonomous intelligent transportation systems. In this context, this paper proposes a Pattern Recognition system which employs an unsupervised clustering algorithm with the objective of detecting, counting and recognizing a number of dynamic objects crossing a roadway. This strategy defines a virtual sensor, whose aim is similar to that of an inductive-loop in a traditional mechanism, i.e. to extract from the traffic video streaming a number of signals containing anarchic information about the road traffic. Then, the set of signals is filtered with the aim of conserving only motion’s significant patterns. Resulted data are subsequently processed by a statistical analysis technique so as to estimate and try to recognize a number of clusters corresponding to vehicles. Finite mixture models fitted by the EM algorithm are used to assess such clusters, which provides important information about the traffic such as the instantaneous number of vehicles, their weights, velocities and intervehicular distances.

Real traffic-data based evaluation of vehicular traffic environment and state-of-the-art with future issues in location-centric data dissemination for VANETs

Extensive investigation has been performed in location-centric or geocast routing protocols for reliable and efficient dissemination of information in Vehicular Adhoc Networks (VANETs). Various location-centric routing protocols have been suggested in literature for road safety ITS applications considering urban and highway traffic environment. This paper characterizes vehicular environments based on real traffic data and investigates the evolution of location-centric data dissemination. The current study is carried out with three main objectives: (i) to analyze the impact of dynamic traffic environment on the design of data dissemination techniques, (ii) to characterize location-centric data dissemination in terms of functional and qualitative behavior of protocols, properties, and strengths and weaknesses, and (iii) to find some future research directions in information dissemination based on location. Vehicular traffic environments have been classified into three categories based on physical characteristics such as speed, inter-vehicular distance, neighborhood stability, traffic volume, etc. Real traffic data is considered to analyze on-road traffic environments based on the measurement of physical parameters and weather conditions. Design issues are identified in incorporating physical parameters and weather conditions into data dissemination. Functional and qualitative characteristics of location-centric techniques are explored considering urban and highway environments. Comparative analysis of location-centric techniques is carried out for both urban and highway environments individually based on some unique and common characteristics of the environments. Finally, some future research directions are identified in the area based on the detailed investigation of traffic environments and location-centric data dissemination techniques.

Cooperative Range Extension Autonomous Driving of Electric Vehicles Considering Inter-Vehicular Distance

Cooperative Range Extension Autonomous Driving of Electric Vehicles Considering Inter-Vehicular Distance

String Stability and a Delay-Based Spacing Policy for Vehicle Platoons Subject to Disturbances

A novel delay-based spacing policy for the control of vehicle platoons is introduced together with a notion of disturbance string stability. The delay-based spacing policy specifies the desired intervehicular distance between vehicles and guarantees that all vehicles track the same spatially varying reference velocity profile, as is for example required for heavy-duty vehicles driving over hilly terrain. Disturbance string stability is a notion of string stability of vehicle platoons subject to external disturbances on all vehicles that guarantees that perturbations do not grow unbounded as they propagate through the platoon. Specifically, a control design approach in the spatial domain is presented that achieves tracking of the desired spacing policy and guarantees disturbance string stability with respect to a spatially varying reference velocity. The results are illustrated by means of simulations.

CAR FOLLOWING TECHNIQUES: THE ROLE OF THE HUMAN FACTOR RECONSIDERED

Engineering and psychophysiological car following models emerge in the late 1950s (Saifuzzaman & Zheng, 2014). Such models differ in their ground concepts and explanatory mechanisms, but both assume a fundamental tenet: following each other, drivers invariably attempt to couple, keeping safety distance. More recent models focus on the spontaneous emergence of traffic jams that results from the properties of a system of interacting vehicles (i.e., without bottlenecks). In an experimental setting Sugiyama et al., (2008) have successfully recreated the conditions that allow the observation of the typical soliton wave going backwards through several car clusters. When certain speed, density and inter-vehicular distance join, so do traffic jams. Some of us have built upon these and other factors (e.g., wave movement in nature) exploring the mathematical properties of a system with three incognita that also needs three variables to be solved (Melchor & Sanchez, 2014). Two canonical car-following techniques emerge as a consequence: Driving to keep safety Distance (DD) vs Inertia (DI). Also a basic question: can drivers actually understand and follow either way, or do they stick to a basic normative driving behavior? This paper summarizes the results after three experimental studies done with a driving simulator. Several performance measures from individual drivers (accelerations, decelerations, average speed, distance to leader, and so on) were taken. As an overall indicator, results consistently announce in the three studies that DI trips consume less fuel (about 20%) than DD ones. DOI: http://dx.doi.org/10.4995/CIT2016.2016.3406

Modeling chain collisions in vehicular networks with variable penetration rates

The vehicular ad hoc network has great potential in improving traffic safety. One of the most important and interesting issues in the research community is the safety evaluation with limited penetration rates of vehicles equipped with inter-vehicular communications. In this paper, a stochastic model is proposed for analyzing the vehicle chain collisions. It takes into account the influences of different penetration rates, the stochastic nature of inter-vehicular distance distribution, and the different kinematic parameters related to driver and vehicle. The usability and accuracy of this model is tested and proved by comparative experiments with Monte Carlo simulations. The collision outcomes of a platoon in different penetration rates and traffic scenarios are also analyzed based on this model. These results are useful to provide theoretical insights into the safety control of a heterogeneous platoon.

Heavy-Duty Vehicle Platooning for Sustainable Freight Transportation: A Cooperative Method to Enhance Safety and Efficiency

The current system of global trade is largely based on transportation and communication technology from the 20th century. Advances in technology have led to an increasingly interconnected global market and reduced the costs of moving goods, people, and technology around the world [1]. Transportation is crucial to society, and the demand for transportation is strongly linked to economic development. Specifically, road transportation is essential since about 60% of all surface freight transportation (which includes road and rail transport) is done on roads [2]. Despite the important role of road freight transportation in the economy, it is facing serious challenges, such as those posed by increasing fuel prices and the need to reduce greenhouse gas emissions. On the other hand, the integration of information and communication technologies to transportation systems-leading to intelligent transportation systems-enables the development of cooperative methods to enhance the safety and energy efficiency of transportation networks. This article focuses on one such cooperative approach, which is known as platooning. The formation of a group of heavy-duty vehicles (HDVs) at close intervehicular distances, known as a platoon (see Figure 1) increases the fuel efficiency of the group by reducing the overall air drag. The safe operation of such platoons requires the automatic control of the velocity of the platoon vehicles as well as their intervehicular distance. Existing work on platooning has focused on the design of controllers for these longitudinal dynamics, in which simple vehicle models are typically exploited and perfect environmental conditions, such as flat roads, are generally assumed. The broader perspective of how platooning can be effectively exploited in a freight transportation system has received less attention. Moreover, experimental validations of the fuel-saving potential offered by platooning have typically been performed by reproducing the perfect conditions as assumed in the design of the automatic controllers. This article focuses on these two aspects by addressing the following two objectives.

A302 経路追従誤差を考慮した車間距離制御(OS10 ビークルの運動と制御1)

Traffic jam on highway causes environmental pollution, economic and time losses. Moreover, car drivers are exhausted by traffic jam. To improve road traffic problems including traffic jam, a work on ITS (Intelligent Transport System) is now in progress. Inter-vehicular distance control is one of approaches in ITS: Vehicles make a platoon and are running with keeping appropriate inter- vehicular distance. In this paper, we propose inter-vehicular distance control considering path tracking error. By considering path tracking error, we can calculate appropriate reference velocity which keeps inter-vehicular distance correctly. To show effectiveness of proposed method, we conducted two simulations: one with consideration of path tracking error and one without consideration.

Cooperative Look-Ahead Control for Fuel-Efficient and Safe Heavy-Duty Vehicle Platooning

The operation of groups of heavy-duty vehicles at a short inter-vehicular distance, known as platoon, allows one to lower the overall aerodynamic drag and, therefore, to reduce fuel consumption and greenhouse gas emissions. However, due to the large mass and limited engine power of trucks, slopes have a significant impact on the feasible and optimal speed profiles that each vehicle can and should follow. Maintaining a short inter-vehicular distance, as required by platooning, without coordination between vehicles can often result in inefficient or even unfeasible trajectories. In this paper, we propose a two-layer control architecture for heavy-duty vehicle platooning aimed to safely and fuel-efficiently coordinate the vehicles in the platoon. Here, the layers are responsible for the inclusion of preview information on road topography and the real-time control of the vehicles, respectively. Within this architecture, dynamic programming is used to compute the fuel-optimal speed profile for the entire platoon and a distributed model predictive control framework is developed for the real-time control of the vehicles. The effectiveness of the proposed controller is analyzed by means of simulations of several realistic scenarios that suggest a possible fuel saving of up to 12% for follower vehicles compared with the use of standard platoon controllers.

Control of platoons of heavy-duty vehicles using a delay-based spacing policy

The formation of groups of heavy-duty vehicles driving at close inter-vehicular distances (known as a platoon) reduces the fuel consumption due to a decreased aerodynamic drag and has the potential to increase traffic flow. This paper motivates the use of a novel spacing policy, which specifies the desired distance between vehicles as a function of their states. Particularly, a delay-based spacing policy is introduced, which guarantees that all vehicles in the group follow the same velocity profile in space. It is shown that the proposed spacing policy offers advantages in the platoon control for non-constant reference velocities, which are common when driving over hilly terrain. A controller is designed to achieve this spacing policy, hereby exploiting an analysis of the vehicle dynamics in the spatial domain rather than time domain. Moreover, the controller is shown to attenuate the effect of disturbances as they propagate through the platoon. Simulations are used to illustrate the effectiveness of the proposed spacing policy and controller.

Fundamental study on effect of preceding vehicle information on fuel consumption reduction of a vehicle group

It is a concern that eco-driving vehicles, because their driving behavior differs from other vehicles due to e.g. e-start, may inhibit smooth traffic flow. Therefore, it is necessary to study the cooperative eco-driving done by a vehicle group, putting “vehicle-to-vehicle communication” and “road-to-vehicle communication” into perspective. Based on these factors, this study aimed to: 1) Analyze fuel consumption rates and driving behaviors of more than one vehicle following an Eco-Driving vehicle. 2) Examine the effect of information on the fuel consumption rate of the preceding vehicles on the following vehicles. As a result, the following findings were obtained: 1) By providing information to multiple following vehicles, the fuel consumption rate of the second vehicle was not lowered, while that of the third one was. 2) It is possible that, when information on fuel consumption of a preceding vehicle is provided to the following one, an inter-vehicular distance is shortened during deceleration to contribute to smooth traffic flow. From the above results, it is suggested that, when targeting a vehicle group, sharing the information on preceding vehicles is effective.

PDdE-based analysis of vehicular platoons with spatio-temporal decoupling

The paper provides exact analytical solutions of wave-like PDdE-based (partial differential-difference equation) models of several popular vehicular platooning problems with bidirectional distributed control. Efficient evaluation of eigenvalues, eigenfunctions and wave velocities is proposed for a finite vehicular platoon without an approximation by a continuum model. Thanks to the decoupling of spatial and temporal dynamics, closed-loop stability can be analyzed by looking at a characteristic polynomial using a root-locus-like graphical technique. Although the paper only contains discussions for static state feedback controllers (using measurements of inter-vehicular distances and relative velocities), extensiona to higher-order (dynamic) controllers is straighforward and will be included in the extended version of the paper.

DBR: Distance Based Routing Protocol for VANETs

Vehicular Ad-Hoc network mainly involves Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communication. This communication facilitates in reducing number of accidents, avoiding traffic congestion, enhancing the transport facility with the aid of infotainment and entertainment application. One of the major challenges of VANET application is in routing the packet in efficient and effective manner since the network topology is dynamic. In this paper we present Distance Based Routing (DBR) protocol designed especially for Vehicular Ad hoc Networks (VANET). The proposed algorithm adopts both position based and map based routing technique. In DBR, a connectivity graph based on the intervehicular distance, the duration of connectivity between neighbouring vehicles and the information from the digital map are collectively used to route the data. In proposed protocol the network traffic is reduced due to the relative position information of the neighbouring vehicle. The stability of the route path is high due to intervehicular distance based next hop selection technique as implemented in this protocol. The proposed routing protocol is simulated using NS2 simulator to analyze the efficiency and effectiveness of the protocol.

Toward an Effective Risk-Conscious and Collaborative Vehicular Collision Avoidance System

In this paper, we introduce a cooperative collision-avoidance (CCA) scheme for intelligent transport systems. Unlike contemporary strategies, the envisioned scheme avoids flooding the considered vehicular network with high volumes of emergency messages upon accidental events. We present a cluster-based organization of the target vehicles. The cluster is based upon several criteria, which define the movement of the vehicles, namely, the directional bearing and relative velocity of each vehicle, as well as the inter-vehicular distance. We also design a risk-aware medium-access control (MAC) protocol to increase the responsiveness of the proposed CCA scheme. According to the order of each vehicle in its corresponding cluster, an emergency level is associated with the vehicle that signifies the risk of encountering a potential emergency scenario. To swiftly circulate the emergency notifications to collocated vehicles to mitigate the risk of chain collisions, the medium-access delay of each vehicle is set as a function of its emergency level. Due to its twofold contributions, i.e., the cluster-based and risk-conscious approaches, our adopted strategy is referred to as the cluster-based risk-aware CCA (C-RACCA) scheme. The performance of the C-RACCA system is verified through mathematical analyses and computer simulations, whose results clearly verify its effectiveness in mitigating collision risks of the vehicles arising from accidental hazards.

Intelligent transportation systems: a safe, robust and comfortable strategy for longitudinal monitoring

An original non-cooperative longitudinal control strategy, based on a new, non-linear and second-order reference model, is studied. The control strategy yields analytical dynamic solutions and pays extreme care to safety constraints. It lowers the safe inter-vehicular distance and is also robust towards errors of sensors when measuring the speed of obstacles. This robustness, valid for slow-moving obstacles as well as fast-moving ones, is a decisive benefit of this strategy. The strategy consists of two main phases depending on vehicles relative interdistance. Considering acceleration and jerk (time derivative of acceleration) as comfort metrics, it is also shown that the control strategy proves comfortable. Simulation results validate the control strategy.

A COLLISION WARNING SYSTEM BASED ON AN INTER-DISTANCE REFERENCE MODEL

In this paper we introduce a new collision warning system which permits to warn the driver with sufficient anticipation about some inter-vehicular distance danger. The warning system is based on the future predictions from a 5-DOF (Degree Of Freedom) vehicle dynamics. The future inter-distance and the future relative velocity are compared with respect to certain safe conditions which are calculated from a dynamic inter-distance reference model. Some simulations with real measure data illustrate the behavior of the proposed driver assistance system.