Development of a navigation algorithm with dead reckoning for unmanned ground vehicles

A navigation algorithm is indispensable for Unmanned Ground Vehicles (UGVs). During driving, UGVs follow a global path. In this study, we propose a navigation algorithm using Real Time Kinematic (RTK)-Differential Global Positioning System (DGPS) units and encoders to complement global path planning. Sometimes GPS systems lose their signals and receive inaccurate position data due to many factors, such as edifice and barrier obstructions. This paper shows that GPS deviations can be solved using a Dead Reckoning (DR) navigation method with encoders and that position errors can be decreased through the use of RTK-DGPS units. In addition to this method, we will introduce a new waypoint update algorithm and a steering algorithm using RTK-DGPS units.     

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.     

A dummy for the objective ride comfort evaluation of ground vehicles

A new device for an objective evaluation of ground vehicle ride comfort is presented. In this study, the ride comfort (frequency range 0–30 Hz) has been referred to the acceleration acting along the vertical axis (subject spine) and to the longitudinal acceleration (acting at the subject shoulders). Based on the experimental measurements of such accelerations on different human subjects seated on a car seat, a proper mechanical/mathematical model of the seat+subject has been derived. The derivation of the model has been performed by minimising the error between the measured and the computed accelerations. A prototype of the derived mechanical model has been actually built. Particular attention has been devoted to the construction of the springs, of the moving members and of the magnetic damper. All of the device parameters (mass, stiffness, damping) can be easily tuned. Finally, an experimental validation of the device has been performed. The device, while seated with the same posture of the corresponding human subject is able to reproduce (with reasonable accuracy) both the acceleration along the subject spine and the acceleration at the subject shoulders.     

Integrated control of ground vehicles dynamics via advanced terminal sliding mode control

An integrated vehicle dynamics control (IVDC) algorithm, developed for improving vehicle handling and stability under critical lateral motions, is discussed in this paper. The IVDC system utilises integral and nonsingular fast terminal sliding mode (NFTSM) control strategies and coordinates active front steering (AFS) and direct yaw moment control (DYC) systems. When the vehicle is in the normal driving situation, the AFS system provides handling enhancement. If the vehicle reaches its handling limit, both AFS and DYC are then integrated to ensure the vehicle stability. The major contribution of this paper is in improving the transient response of the vehicle yaw rate and sideslip angle tracking controllers by implementing advanced types of sliding mode strategies, namely integral terminal sliding mode and NFTSM, in the IVDC system. Simulation results demonstrate that the developed control algorithm for the IVDC system not only has strong robustness against uncertainties but also improves the transient response of the control system.     

Robust gain-scheduling automatic steering control of unmanned ground vehicles under velocity-varying motion

Owing to the fact that unmanned ground vehicles have the features of time-varying, parametric uncertainties and external disturbances, this paper mainly studies robust automatic steering control of unmanned ground vehicles. Firstly, a linear parameter varying lateral model for unmanned ground vehicle is constructed, in which the longitudinal velocity is represented by a polytope with finite vertices. Secondly, a robust gain scheduling automatic steering control scheme based on the linear matrix inequality technique is proposed to deal with the characteristics of time-varying and external disturbances. Finally, Simulation results based on Adams–Matlab joint platform using a nonlinear full vehicle model have demonstrated that the proposed control approach can simultaneously ensure the control accuracy and strong robustness of system.     

Creep force modelling for rail traction vehicles based on the Fastsim algorithm

The evaluation of creep forces is a complex task and their calculation is a time-consuming process for multibody simulation (MBS). A methodology of creep forces modelling at large traction creepages has been proposed by Polach [Creep forces in simulations of traction vehicles running on adhesion limit. Wear. 2005;258:992–1000; Influence of locomotive tractive effort on the forces between wheel and rail. Veh Syst Dyn. 2001(Suppl);35:7–22] adapting his previously published algorithm [Polach O. A fast wheel–rail forces calculation computer code. Veh Syst Dyn. 1999(Suppl);33:728–739]. The most common method for creep force modelling used by software packages for MBS of running dynamics is the Fastsim algorithm by Kalker [A fast algorithm for the simplified theory of rolling contact. Veh Syst Dyn. 1982;11:1–13]. However, the Fastsim code has some limitations which do not allow modelling the creep force – creep characteristic in agreement with measurements for locomotives and other high-power traction vehicles, mainly for large traction creep at low-adhesion conditions. This paper describes a newly developed methodology based on a variable contact flexibility increasing with the ratio of the slip area to the area of adhesion. This variable contact flexibility is introduced in a modification of Kalker's code Fastsim by replacing the constant Kalker's reduction factor, widely used in MBS, by a variable reduction factor together with a slip-velocity-dependent friction coefficient decreasing with increasing global creepage. The proposed methodology is presented in this work and compared with measurements for different locomotives. The modification allows use of the well recognised Fastsim code for simulation of creep forces at large creepages in agreement with measurements without modifying the proven modelling methodology at small creepages.     

Modelling,simulation and evaluation of ground vibration caused by rail vehicles*

ABSTRACT

There is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequence. Compared with airborne noise, the related problem of ground vibration is much more complex. The properties of the ground vary significantly from one location to another. There is no common assessment criterion or measurement quantity and no equivalent to the noise maps. Ground-borne vibration is transmitted into buildings and perceived either as feelable whole-body vibration or as low frequency noise; it can also affect sensitive equipment but it is generally at a level that is too low to cause structural or cosmetic damage to buildings. A review is given of evaluation criteria for both feelable vibration and ground-borne noise, empirical and numerical prediction methods, the main vehicle and track parameters that can affect the vibration levels and a range of possible mitigation methods.     

Dynamic modelling and experimental validation of three wheeled tilting vehicles

The present paper describes the study of the stability in the straight running of a three-wheeled tilting vehicle for urban and sub-urban mobility. The analysis was carried out by developing a multibody model in the Matlab/SimulinkSimMechanics environment. An Adams-Motorcycle model and an equivalent analytical model were developed for the cross-validation and for highlighting the similarities with the lateral dynamics of motorcycles. Field tests were carried out to validate the model and identify some critical parameters, such as the damping on the steering system. The stability analysis demonstrates that the lateral dynamic motions are characterised by vibration modes that are similar to that of a motorcycle. Additionally, it shows that the wobble mode is significantly affected by the castor trail, whereas it is only slightly affected by the dynamics of the front suspension. For the present case study, the frame compliance also has no influence on the weave and wobble.     

A study on model fidelity for model predictive control-based obstacle avoidance in high-speed autonomous ground vehicles

This paper investigates the level of model fidelity needed in order for a model predictive control (MPC)-based obstacle avoidance algorithm to be able to safely and quickly avoid obstacles even when the vehicle is close to its dynamic limits. The context of this work is large autonomous ground vehicles that manoeuvre at high speed within unknown, unstructured, flat environments and have significant vehicle dynamics-related constraints. Five different representations of vehicle dynamics models are considered: four variations of the two degrees-of-freedom (DoF) representation as lower fidelity models and a fourteen DoF representation with combined-slip Magic Formula tyre model as a higher fidelity model. It is concluded that the two DoF representation that accounts for tyre nonlinearities and longitudinal load transfer is necessary for the MPC-based obstacle avoidance algorithm in order to operate the vehicle at its limits within an environment that includes large obstacles. For less challenging environments, however, the two DoF representation with linear tyre model and constant axle loads is sufficient.     

Operating speed pattern optimization of railway vehicles with differential evolution algorithm

The railway transportation system has much advantage in eco-friendliness, punctuality and safety compared to any other transportation system. Most of the railway system administrators have to control and operate under limited resources such as trains and facilities. It is necessary to control traveling time and energy consumption for efficient operation in the railway systems, because the board rate of passenger is inconstant with time variance. It is common that the shorter traveling time causes the greater energy consumption. In this study, a new optimization method considering operation time or energy consumption is proposed by using differential evolution algorithm and some cases are reviewed. The total energy change due to operation time variation are investigated by using the proposed optimization method for tangent and gradient track conditions. Both cases, the total energy decreases exponentially. However, because of gradient the total energy are saturated after a certain time for gradient track.     

Dynamic simulation of railway vehicles: wheel/rail contact analysis

The multibody simulation of railway vehicle dynamics needs a reliable and efficient method to evaluate the contact points between wheel and rail, because their positions have a considerable influence on the direction and intensity of the contact forces. In this work, an innovative semi-analytic procedure for the detection of the wheel/rail contact points (named the DIFF method) is presented. This method considers the wheel and the rail as two surfaces whose analytic expressions are known and is based on the idea that in the contact points the difference between the surfaces has local minima and is equivalent to solving an algebraic two-dimensional system. The original problem can be reduced analytically to a simple scalar equation that can be easily solved numerically (since the problem dimension is one, even elementary non-iterative algorithms can be efficient).     

Dynamic programming-based method for extraction of license plate numbers of speeding vehicles on the highway

In the last decade, vehicle identification systems have become a central element in many applications involving traffic law enforcement and security enhancement, such as locating stolen cars, automatic toll management, and access control to secure areas. As a method of vehicle identification, license plate recognition (LPR) systems play an important role and a number of such techniques have been proposed. In this paper, we describe a method for segmenting the main numeric characters on a license plate by introducing dynamic programming (DP) that optimizes the functionality describing the distribution of the intervals between characters, the alignment of the characters, and the threshold difference used to extract the character blobs. The proposed method functions very rapidly by applying the bottom-up approach of the DP algorithm and also robustly by minimizing the use of environment-dependent image features such as color and edges.     

基于Cruise纯电动手动挡汽车的动力性、经济性换挡浅析

为了更加准确的计算纯电动手动挡汽车的动力性、经济性,利用Cruise软件分类搭建模型,优化手动变速器的换挡车速,通过对计算后的数据对比分析,得到更精确的计算结果.     

软土地基上含反射裂缝沥青道路的动力响应分析

假定车辆荷载为正弦均匀分布,软土和复合地基变形行为服从DRUCKER-PRAGER弹塑性屈服准则,基于动力学、线弹性断裂力学和弹塑性力学理论,采用平面应变有限单元法,对含反射裂缝的沥青路面结构进行了分析。为了计算应力强度因子,在裂缝尖端设置了奇异单元。分析过程中,以路表、基层底、软土地基顶最大竖向位移和I型应力强度因子作为表征参量,探讨了车辆单周期动荷载作用下,道路结构的阻尼比、复合地基的回弹模量、粘聚力、内摩擦角和厚度的改变对道路结构工作性状的影响。     

乘用车不断升级,商用车渐成气候——2007第六届青岛国际车展特别报道

2007年5月18～22日,由中国汽车工程学会、山东省汽车行业协会联合主办,山东省汽车工程学会、青岛嘉路博国际会展有限公司共同承办的第六届青岛国际汽车工业展览会在青岛国际会展中心隆重举办.本届青岛国际车展以"引领汽车生活风尚,构筑和谐汽车生活"为主题.     

新能源汽车发展得失对燃料电池汽车的启示

新能源汽车是我国战略性新兴产业之一,2009年以来,我国逐步建立了以财税政策为主的支持政策体系,推动了我国新能源汽车产业从无到有,逐步发展壮大。新能源汽车产业政策对推动我国产业快速发展起到了关键性作用,但也面临“干预市场”、“干预技术路线”、“透支消费”等质疑,出现了“骗补谋补”、“补贴依赖症”等问题。目前我国燃料电池汽车仍处于市场起步期,大规模推广的条件尚未成熟,产业发展离不开国家政策的支持。如何继续发挥新能源汽车领域的先发优势,吸取前期产业发展经验教训,在下一步推广燃料电池汽车时少走弯路,加快推动产业发展,是当前燃料电池汽车产业发展面临的重大课题。     

碳纤维在汽车上的应用

碳纤维（CF）是纤维状的碳素材料，含碳量在90％以上，它是利用各种有机纤维在惰性气体中、高温状态下碳化而制得。具有十分优异的力学性能。特别是在2000℃以上高温惰性环境中，是唯一强度不下降的物质。碳纤维和碳纤维增强复合材料（CFRP）做为21世纪的新材料，其高强度、高弹性模量和低比重性能，     

超级电容器在电动汽车上的应用

超级电容器是一种介于传统电容器和蓄电池之间的新型储能元件,具有功率密度高、充电迅速、使用温度范围宽、寿命长等特性。本文主要介绍了超级电容器的基本原理及特点,超级电容器在电动汽车上的应用状况及应用中面临的主要问题。     

基于RFID和IMU技术的室内定位方法研究与应用

针对在室内停车场等GPS信号较差的工况,行驶车辆无法实时获取准确定位的问题,文章结合RFID和IMU两种定位技术,使用卡尔曼滤波器耦合该两组定位系统信号,并将该方法应用在某款车型上,结果表明在室内停车场能够获得实时准确的位置信息.     

军用车载计算机环境及可靠性试验方法浅析

简要介绍了我军新型车载计算机的考核试验方法,阐述了军用车载计算机环境试验、可靠性试验的试验条件、试验方法及判定标准,为我军新研车载电子设备的考核试验提供参考。