Friction coefficient measurement for autonomous winter road maintenance

Real-time measurement of tyre–road friction coefficient is extremely valuable for winter road maintenance operations, since knowledge of tyre–road friction coefficient can be used to optimise application of deicing chemicals to the roadway. In this paper, a wheel-based tyre–road friction coefficient measurement system is developed for snowploughs. Unlike a traditional Norse meter, this system is based on measurement of lateral tyre forces, has minimal moving parts and does not use a brake actuator. Hence, it is reliable and inexpensive. A key challenge is quickly detecting changes in the estimated tyre–road friction coefficient while rejecting the high levels of vibratory noise in the measured force signal. Novel filtering and signal processing algorithms are developed to address this challenge, including a biased quadratic mean filter and an accelerometer-based vibration removal filter. Detailed experimental results are presented on the performance of the friction estimation system on different types of road surfaces. It is also shown that disturbances due to lateral and longitudinal vehicle manoeuvres on the estimated friction coefficient can be removed by using accelerometer-based filtering.     

Closed-loop snowplow applicator control using road condition measurements

Closed-loop control of a snowplow applicator, based on direct measurement of the road surface condition, is a valuable technology for the optimisation of winter road maintenance costs and for the protection of the environment from the negative impacts of excessive usage of de-icing chemicals. To this end, a novel friction measurement wheel is designed to provide a continuous measurement of road friction coefficient, which is, in turn, utilised to control the applicator automatically on a snowplow. It is desired that the automated snowplow applicator deploy de-icing materials right from the beginning of any slippery surface detected by the friction wheel, meaning that no portion of the slippery road surface should be left untreated behind, as the snowplow travels over it at a reasonably high speed.

This paper describes the developed wheel-based measurement system, the friction estimation algorithm and the expected performance of the closed-loop applicator system. Conventional and zero velocity applicators are introduced and their hardware time delays are measured in addition to the time delay of the friction estimation algorithm. The overall performance of the closed-loop applicator control system is shown to be reliable at typical snowplowing speeds if the zero velocity applicator is used.     

Developing a safer road user behaviour index

Road user behaviour is an essential factor of increasing the rate of traffic accidents worldwide. Road safety experts and scientists consider aspects of road users' behaviour to be the main risk factors for road fatalities. These factors include drinking alcohol, speeding, not wearing seat belts, not wearing helmets when riding two-wheeled vehicles, not using child restraints, consuming illegal drugs, and being distracted by mobile phone use. This paper aims to investigate the role of these factors in assessing the road user behaviour through aggregating them and build a composite indicator that can be used in countries benchmarking and cross countries comparison, then identifying most successful practises. To achieve this aim, data related to the selected indicators, life-saving rate, and real crash data were collected. The indicators were weighted using simple and theoretical methods. The weighted indicators were aggregated using simple additive method. The developed index was applied to 12 European countries to test the validation of the index through investigation the correlation between index’ ranking of countries with the ranking according to the rate of fatalities. It is concluded that the developed composite indicator can be used to assess the role of using the protection system and speeding in the severity of the road crashes. However, the role of the remaining factors in the likelihood of crashes occurrence needs more investigation. It can be concluded also that the road users' behaviour is not the only factor of reducing the road fatalities in some countries. This enhances the multidimensional system approach of defining the road safety. Based on this, it is recommended to consider other factors in conducting research, developing indices of road safety, and in recommending solutions. The results show also that the UK, Sweden, Ireland and Ireland have the most successful strategies to improve the road user behaviour among the selected countries; therefore, it is recommended to take lessons from these practices.     

On model-based longitudinal feed-forward motion control for low velocities on known road profiles

ABSTRACT

So far, longitudinal motion control has focused on situations like highway driving, where disturbances of the road profile can be neglected. In this paper, we show how the Two Point Tire Model can be used to derive a novel feed-forward control law for a vehicle's longitudinal motion that considers the effects of the road profile and can complement existing control approaches. For this purpose, we recapitulate the basic model assumptions and equations and briefly discuss how it can be used on arbitrary road profiles. Two approaches for implementation in a real vehicle are presented. Comparisons of these approaches in simulation and to a human driver of an experimental vehicle show that the controller can deal with stepped obstacles of up to 14?cm in height. However, the control performance is essentially limited by the actuator delay and human drivers outperform the controller due to their ability of sensing subtle vehicle motions. The results indicate that the control performance can be further improved by using a preview on the necessary drive torque, which can be provided by the solution that we propose.     

SP彩色压花荧光路面施工技术

SP彩色压花荧光路面施工技术通过将SP彩色涂料喷涂于沥青表面,改变了传统沥青的黑色表面,使路面更加美观;通过沥青压花工艺,在沥青路面路口及边缘印出各种图案,既增加了道路防滑性,又使道路更具提示性和美观性;通过将荧光材料填充于预留图案中,白天兼顾装饰美观作用,夜间发出彩色荧光,大大提高了观赏性和道路行驶安全性。本文对SP彩色压花荧光路面施工技术的工艺流程及操作要点进行了阐述,可对该技术的推广应用起到一定的借鉴作用。     

The use of vehicle acceleration measurements to estimate road roughness

Road roughness is a broad term that incorporates everything from potholes and cracks to the random deviations that exist in a profile. To build a roughness index, road irregularities need to be measured first. Existing methods of gauging the roughness are based either on visual inspections or using one of a limited number of instrumented vehicles that can take physical measurements of the road irregularities. This paper proposes the collection of data from accelerometers fixed in a specific vehicle type and the use of this data to estimate the road condition. Although the estimate is approximate, accelerometers are being increasingly used by car manufacturers to improve suspension performance and the proposed method is relatively inexpensive to implement and provide road managers with constantly updated measurements of roughness. This approach is possible due to the relationship between the power spectral densities of road surface and vehicle accelerations via a transfer function. This paper shows how road profiles can be accurately classified using axle and body accelerations from a range of simulated vehicle–road dynamic scenarios.     

The impact of road improvements on road safety and related characteristics

This paper presents the historical and cultural background relating to road improvement and road safety characteristics in Kenya, a developing country in East Africa. Some who come from low-developed areas of developing countries often take time to comprehend the modern transportation infrastructure, especially roads, and have difficulty assimilating and customizing the same to their culturally tailored modes.This paper discusses two case studies: one on the socio-economic impact following improvements to a 50-km, high-class, high-traffic-volume road and the other on the monitoring and evaluation of road safety aspects along the Northern Corridor in Kenya also following major road improvements.The road improvements to the Nairobi-Thika Highway (a trunk road) have attracted many investors along the highway corridor. The high-speed road has also brought with it the unfortunate consequence of speeding vehicles colliding with pedestrians crossing the road at undesignated locations.The Northern Corridor, the transportation corridor that links the Great Lakes Countries of the Democratic Republic of Congo, Burundi, Rwanda, and Uganda from the port of Mombasa in Kenya, has had high accident rates for a considerable amount of time. The results of monitoring and evaluation exercises on the Northern Corridor have shown that drivers are the major contributors in causing accidents, with a component ratio of 49.4%; pedestrians are next at 21.7%. Data also shows that 24% of the accidents along the Northern Corridor are fatal, which is of major concern. The study additionally indicated that the majority of road users have not been exposed to education or training on road safety.This paper presents a number of recommendations arising from the road safety study regarding possible improvements in aspects of road safety along the corridor and potential applications of those changes to other roads in general. For example, there are recommendations related to the geometric design of the road, driver training and behavior, vehicle maintenance, and the need to enhance road safety through the utilization of road safety parks where road users can undergo training and drills on road safety aspects.In conclusion, we argue that the rehabilitation of the Northern Corridor from Mombasa on the Kenyan coast to the border with Uganda has led to significant road safety improvement.     

New design of a road profiler

Macro and micro road profiles are of significant importance for vehicular motion studies, reliable calculations of vehicle system properties, and ensuring vehicular safety. As such, road profiles should be considered carefully. Macro profiles consider the spatial geometry of the road (curves, longitudinal and lateral slopes) while micro profiles consider roughness in longitudinal and lateral directions. These profiles have random characteristics that can be quantified under onroad and off-road conditions using a road profiler. This paper presents an analysis of a new concept for a universal profiler without gyroscopic stabilizers.     

Digital map as a virtual sensor – dynamic road curve reconstruction for a curve speed assistant

While digital map has been applied to many advanced driver assistance system applications, one critical attribute – road/lane curvature—is not available in the existing digital maps. Curvature derivation using splines is a well-known method in the computer graphics modelling community; however, it was also found that the direct application of the spline method is often not appropriate for real-time safety applications due to the resultant discontinuities in the curvature estimates and the lack of robustness against map data errors [CAMP, Enhanced digital mapping project final report, United States Department of Transportation, Washington, DC, 2004]. This paper presents a method to reconstruct road curvature attributes in real time using digital map data based on the proposed circle centre search and circle selection algorithms. Simulation and experimental results demonstrated that the proposed method can deliver curvature estimates that meet the desired accuracy. The method was also applied to the curve over-speed warning system in an on-going research project: Vehicle Infrastructure Integration—California. Some preliminary experimental results are also presented in this paper.     

Slip regulation for anti-lock braking systems using multiple surface sliding controller combined with inertial delay control

In this paper, a multiple surface sliding controller is designed for an anti-lock braking system to maintain the slip ratio at a desired level. Various types of uncertainties coming from unknown road surface conditions, the variations in normal force and the mass of the vehicle are estimated using an uncertainty estimation technique called the inertial delay control and then the estimate is used in the design of the multiple surface sliding controller. The proposed scheme does not require the bounds of uncertainties. The ultimate boundedness of the overall system is proved. The proposed scheme is validated by simulation under various scenarios of road friction, road gradient and vehicle loading followed by experimentation on a laboratory anti-lock braking set-up for different friction conditions.     

Comparative study of vehicle tyre–road friction coefficient estimation with a novel cost-effective method

This paper qualitatively and quantitatively reviews and compares three typical tyre–road friction coefficient estimation methods, which are the slip slope method, individual tyre force estimation method and extended Kalman filter method, and then presents a new cost-effective tyre–road friction coefficient estimation method. Based on the qualitative analysis and the numerical comparisons, it is found that all of the three typical methods can successfully estimate the tyre force and friction coefficient in most of the test conditions, but the estimation performance is compromised for some of the methods during different simulation scenarios. In addition, all of these three methods need global positioning system (GPS) to measure the absolute velocity of a vehicle. To overcome the above-mentioned problem, a novel cost-effective estimation method is proposed in this paper. This method requires only the inputs of wheel angular velocity, traction/brake torque and longitudinal acceleration, which are all easy to be measured using available sensors installed in passenger vehicles. By using this method, the vehicle absolute velocity and slip ratio can be estimated by an improved nonlinear observer without using GPS, and the friction force and tyre–road friction coefficient can be obtained from the estimated vehicle velocity and slip ratio. Simulations are used to validate the effectiveness of the proposed estimation method.     

基于视频的城市道路智能照明控制系统设计

实时的城市道路智能照明控制技术是现代智能交通系统的重要内容之一。该方法与道路交通视频监控技术一起,不仅能够保障驾驶员在雾天、雨天和夜间的行车安全,同时也可以实现城市照明节能。文中提出一种基于视频的城市道路智能照明控制方法,并在此基础上设计了相应的系统,能够根据当前的道路交通流情况,动态控制路灯系统的工作功率。经过大量交通图像序列的测试,显示本智能控制算法是鲁棒而且实时的,可以有效地调节当前道路的照明条件。     

Creating models of road sections and their use in driving dynamics simulations

The paper describes a system for measuring road section parameters in a way that the results can be used in driving dynamics simulations. The system consists of sensorics and a data acquisition subsystem supported by software for generating 3D road section geometrical models. These models are then used as driving surfaces in dynamics simulation packages to investigate and analyse different aspects of road design and its role in traffic accident analysis, reconstruction and prevention. The paper presents examples of measurements, road section modelling and simulation results, obtained by means of different software simulation tools. It discusses possibilities of further development and improvement of the system.     

Suspension system state estimation using adaptive Kalman filtering based on road classification

This paper provides a new method to solve the problem of suspension system state estimation using a Kalman Filter (KF) under various road conditions. Due to the fact that practical road conditions are complex and uncertain, the influence of the system process noise variance and measurement noise covariance on the estimation accuracy of the KF is first analysed. To accurately estimate the road condition, a new road classification method through the vertical acceleration of sprung mass is proposed, and different road process variances are obtained to tune the system’s variance for the application of the KF. Then, road classification and KF are combined to form an Adaptive Kalman Filter (AKF) that takes into account the relationship of different road process noise variances and measurement noise covariances under various road conditions. Simulation results show that the proposed AKF algorithm can obtain a high accuracy of state estimation for a suspension system under varying International Standards Organisation road excitation levels.     

Estimation of longitudinal speed robust to road conditions for ground vehicles

This article seeks to develop a longitudinal vehicle velocity estimator robust to road conditions by employing a tyre model at each corner. Combining the lumped LuGre tyre model and the vehicle kinematics, the tyres internal deflection state is used to gain an accurate estimation. Conventional kinematic-based velocity estimators use acceleration measurements, without correction with the tyre forces. However, this results in inaccurate velocity estimation because of sensor uncertainties which should be handled with another measurement such as tyre forces that depend on unknown road friction. The new Kalman-based observer in this paper addresses this issue by considering tyre nonlinearities with a minimum number of required tyre parameters and the road condition as uncertainty. Longitudinal forces obtained by the unscented Kalman filter on the wheel dynamics is employed as an observation for the Kalman-based velocity estimator at each corner. The stability of the proposed time-varying estimator is investigated and its performance is examined experimentally in several tests and on different road surface frictions. Road experiments and simulation results show the accuracy and robustness of the proposed approach in estimating longitudinal speed for ground vehicles.     

Development of a self-driving car that can handle the adverse weather

Lane and road recognition are essential for self-driving where GPS solution is inaccurate due to the signal block or multipath in an urban environment. Vision based lane or road recognition algorithms have been studied extensively, but they are not robust to changes in weather or illumination due to the characteristic of the sensor. Lidar is a sensor for measuring distance, but it also contains intensity information. The road mark on the road is made to look good with headlight at night by using a special paint with good reflection on the light. With this feature, road marking can be detected with lidar even in the case of changes in illumination due to the rain or shadow. In this paper, we propose equipping autonomous cars with sensor fusion algorithms intended to operate in a different weather conditions. The proposed algorithm was applied to the self-driving car EureCar (KAIST) in order to test its feasibility for real-time use.     

Total dynamic response of a PSS vehicle negotiating asymmetric road excitations

A planar suspension system (PSS) is a novel automobile suspension system in which an individual spring–damper strut is implemented in both the vertical and longitudinal directions, respectively. The wheels in a vehicle with such a suspension system can move back and forth relative to the chassis. When a PSS vehicle experiences asymmetric road excitations, the relative longitudinal motion of wheels with respect to the chassis in two sides of the same axle are not identical, and thus the two wheels at one axle will not be aligned in the same axis. The total dynamic responses, including those of the bounce, pitch and the roll of the PSS vehicle, to the asymmetric road excitation may exhibit different characteristics from those of a conventional vehicle. This paper presents an investigation into the comprehensive dynamic behaviour of a vehicle with the PSS, in such a road condition, on both the straight and curved roads. The study was carried out using an 18 DOF full-car model incorporating a radial-spring tyre–ground contact model and a 2D tyre–ground dynamic friction model. Results demonstrate that the total dynamic behaviour of a PSS vehicle is generally comparable with that of the conventional vehicle, while PSS exhibits significant improvement in absorbing the impact forces along the longitudinal direction when compared to the conventional suspension system. The PSS vehicle is found to be more stable than the conventional vehicle in terms of the directional performance against the disturbance of the road potholes on a straight line manoeuvre, while exhibiting a very similar handling performance on a curved line.     

Investigating the road safety management capacity: Toward a lead agency reform

An efficient management system and leadership body is one of the key requirements for a road safety improvement program. In low- and middle-income countries, the organizational structure of the management system may suffer from deficiencies weakening the institutional functions across key road safety players. Hence, it is necessary to form an inner- and inter-organization evaluation framework encompassing all the processes, events, dependencies, and causation among road safety players. In this paper, a (three-stage) system thinking approach is developed to evaluate the behavior of inter-organizational complex system and to determine major deficiencies in the role of the road safety lead agency. The first stages of the system thinking approach starts with drawing diagrams (i.e. multiple-effect and multiple-criteria trees) that allows identifying the chains of reasoning behind events or consequences. The next stage of the system thinking approach embodies the analytic network process (ANP), an advanced multi-criteria decision-making technique, which handles the lead agency capacity evaluation and helps to determine how and by what magnitude any of the players can affect the national road safety. The proposed method applies to the case of Iran, a middle-income developing country in the Middle East. Since in Iran, the Road Safety Commission (RSC) has been established as the lead agency, it was expected that RSC owns the greatest influence on the status of road safety. However, our results show that the overall influence of RSC on road safety is far less than what was expected. Subsequently, a supplementary procedure is proposed to specify institutional reforms in order to avoid such organizational inefficiencies.     

自适应前照明系统道路最小可见度评估

自适应前照明系统(AFS)是一种通过光型改变来改善道路交通的智能灯具,其作为当今世界最先进的汽车照明系统,能够有效地降低驾驶者在夜晚行车的疲劳程度,从而明显提升夜晚行车的安全性。文章以高速路段驾驶状态为基准,比较了普通近光光型和高速近光光型,对其道路照明进行最小可见度性能分析,并得出装用AFS车辆夜间道路照明最小可见度的研究结论。     

Robust estimation of maximum tire-road friction coefficient considering road surface irregularity

An accurate estimation of the maximum tire-road friction coefficient may provide higher performance in a vehicle active safety control system. Unfortunately, real-time tire-road friction coefficient estimation is costly and necessitates additional sensors that must be installed and maintained at all times. This paper proposes an advanced longitudinal tire-road friction coefficient estimation method that is capable of considering irregular road surfaces. The proposed algorithm uses a stiffness based estimation method, however, unlike previous studies, improvements were made by suggesting a third order model to solve problems related to nonlinear mu-slip curve. To attain the tire-road friction coefficient, real-time normalized force is obtained from the force estimator as exerted from the tire in the low slip region using the recursive least squares method. The decisive aspect of using the suggested algorithm lies in its low cost and versatility. It can be used under irregular road conditions due to its capability of easily obtaining wheel speed and acceleration values from production cars. The newly improved algorithm has been verified to computer simulations as well as compact size cars on dry asphalt conditions.