Analysis of vehicle use patterns during field training exercises to identify potential roads

In October of 2001, global positioning system (GPS) – based vehicle tracking systems (VTS) were placed on 20 vehicles involved in an 8-day field training exercise at Yakima Training Center, Washington. Based on the GPS data, an analysis of the potential for identifying new roads was conducted. Analysis of vehicle use patterns within selected 25-m grids was utilized to identify new formed or previously unidentified roads in the training area. The factors used to determine the existence of these new roads were (1) if a vehicle actually passed through the grid, (2) the number of vehicles following the same trail segment, (3) if the vehicles passed on different days, (4) if the vehicles were in different troops, and (5) if the vehicles traveled in both directions. A site visit was conducted and confirmed the existence of new roads along segments that met all five criteria levels. Military road class 4 and 5 roads were identified at sites meeting all five criteria.     

Predicting the stability of low volume road embankments in contingency areas

The US Army often operates heavy vehicles in rural areas, operating on low-volume roads having limited load carrying capacity. Many of these roads, such as the ones on the outskirts of Baghdad, have been raised to prevent flooding from nearby canals or irrigated fields. Sections of the roads have collapsed under the weight of armored vehicles, resulting in injuries and even fatalities. For the selected area studied, 2½% of the low-volume road sections were determined to be high risk given typical wheel loads of heavy vehicles for soil strength conditions modeled as low. The goal of the research was to develop a method for rapidly evaluating the stability of a road based on soil conditions, wheel load, and the dimensions of a vehicle. A model for road stability was developed to assist in performing analysis of the canal roads outside of Baghdad. This analysis was then used to create maps and charts characterizing road stability to assist the drivers. The procedure described in this paper can be used to evaluate elevated roads in other parts of the world.     

Vehicle impacts on the environment at different spatial scales: observations in west central Georgia, USA

Roads and vehicles change the environmental conditions in which they occur. One way to categorize these effects is by the spatial scale of the cause and the impacts. Roads may be viewed from the perspective of road segments, the road network, or roads within land ownership or political boundaries such as counties. This paper examines the hypothesis that the observable impacts of roads on the environment depend on spatial resolution. To examine this hypothesis, the environmental impacts of vehicles and roads were considered at four scales in west central Georgia in and around Fort Benning: a second-order catchment, a third-order watershed, the entire military installation, and the five-county region including Fort Benning. Impacts from an experimental path made by a tracked vehicle were examined in the catchment. Land-cover changes discerned through remote sensing data over the past three decades were considered at the watershed and installation scales. A regional simulation model was used to project changes in land cover for the five-county region. Together these analyses provide a picture of the how environmental impacts of roads and vehicles can occur at different spatial scales. Following tracked vehicle impact with a D7 bulldozer, total vegetation cover responded quickly, but the plant species recovered differently. Soils were compacted in the top 10 cm and are likely to remain so for some time. Examining the watershed from 1974 to 1999 revealed that conversion from forest to nonforest was highest near unpaved roads and trails. At the installation scale, major roads as well as unpaved roads and trails were associated with most of the conversion from forest to nonforest. For the five-county region, most of the conversion from forest to nonforest is projected to be due to urban spread rather than direct road impacts. The study illustrates the value of examining the effects of roads at several scales of resolution and shows that road impacts in west central Georgia are most important at local to subregional scales. The insights from these analyses led to several questions about resource management at different spatial scales.     

A method for real-time condition monitoring of haul roads based on Bayesian parameter estimation

Current haul road management techniques, such as routine, periodic and urgent maintenance have shortcomings in many complex haul road environments. Real-time road condition monitoring may significantly reduce maintenance costs, both to the road and to the vehicles. A recent idea is that vehicle on-board data collection systems could be used to monitor haul roads on a real-time basis by means of vibration signature analysis. This paper proposes a methodology based on Bayesian regression to isolate the effect of varying vehicle speed on the measured vehicle response metric. A key feature of the proposed methodology is that it avoids the costly need to generate analytical or empirical vehicle models.     

基于SHAP-RF框架的越野车辆路面识别算法研究

根据越野车辆在不同路面上行驶时的动力学响应特征,可以实现路面类型的在线识别,为面向路面特征调整底盘控制子系统参数从而获取更好的行驶性能奠定基础.但越野环境地面特征复杂,车辆响应机理分析困难,给基于车辆动力学响应进行路面准确识别带来挑战.提出了一种SHAP-RF路面识别算法设计框架,通过SHAP (Shapley additive explanations)模型解释方法实现高维随机森林(random forest, RF)路面识别模型的降维化:首先采集了试验车在压实土路、沙地、良好沥青路与冰雪路4种路面上的行驶数据并计算了3个次级行驶特征;进一步计算了行驶数据的共计105个时域特征和频域特征,并以此为输入特征建立了高维随机森林路面识别模型;利用SHAP解释法分析高维模型输入特征对识别结果的影响从而提炼出各个特征与路面类型的关联性,完成特征筛选;最后,利用筛选后的特征设计降维随机森林路面分类器.基于实车数据的算法验证试验表明,设计的降维路面识别模型对4种路面的识别精确率在94%以上,召回率在93%以上,相比高维的随机森林路面识别模型,各种路面上的精确率和召回率最大降幅不超过3.2%,证明本...     

Tyre rubber friction on a rough road

One of the most challenging aspects of vehicle dynamics is accurate modelling of the tyre-road interface. Forces between the tyre and road need to be accurately represented in simulation. This is challenging over rough roads since the friction changes along the road due to large surface asperities.The Heinrich/Klüppel friction coefficient estimation model has been implemented on smooth roads in the past. However, this study investigates the applicability of using this model over a rough but hard terrain, such as Belgian paving or cobblestones. The model is based on physical properties that can be determined mathematically or experimentally. The study includes detailed terrain topography and the difference between the top and bottom topography is used to determine the radially averaged PSD. Emphasis is placed on finding and implementing the flash temperature in a practical manner that could also be used in further studies.An experimental setup is built to validate the model. The experimental friction coefficient is compared to the friction coefficient calculated using the Heinrich/Klüppel model. The relative percentage error difference between experimental and friction model results is found to be less than 10% on a smooth concrete road and 20% on a rough road (concrete Belgian paving).     

Suspension settings for optimal ride comfort of off-road vehicles travelling on roads with different roughness and speeds

This paper reports on an investigation to determine the spring and damper settings that will ensure optimal ride comfort of an off-road vehicle, on different road profiles and at different speeds. These settings are required for the design of a four stage semi-active hydro-pneumatic spring damper suspension system (4S₄). Spring and damper settings in the 4S₄ can be set either to the ride mode or the handling mode and therefore a compromise ride-handling suspension is avoided. The extent to which the ride comfort optimal suspension settings vary for roads of different roughness and varying speeds and the levels of ride comfort that can be achieved, are addressed. The issues of the best objective function to be used when optimising and if a single road profile and speed can be used as representative conditions for ride comfort optimisation of semi-active suspensions, are dealt with. Optimisation is performed with the Dynamic-Q algorithm on a Land Rover Defender 110 modelled in MSC.ADAMS software for speeds ranging from 10 to 50 km/h. It is found that optimising for a combined driver plus rear passenger seat weighted root mean square vertical acceleration rather than using driver or passenger values only, returns the best results. Results indicate that optimisation of suspension settings using one road and speed will improve ride comfort on the same road at different speeds. These settings will also improve ride comfort for other roads at the optimisation speed and other speeds, although not as much as when optimisation has been done for the particular road. For improved ride comfort damping generally has to be lower than the standard (compromised) setting, the rear spring as soft as possible and the front spring ranging from as soft as possible to stiffer depending on road and speed conditions. Ride comfort is most sensitive to a change in rear spring stiffness.     

Experimental investigation of pneumatic tire performance on ice: Part 1 – Indoor study

Currently, the probability of accident occurrence is much higher when driving on icy roads than on asphalt. Since the tire is the only element of the vehicle that contacts the icy road, it is crucial to thoroughly comprehend the friction mechanism at the tire–ice interface for improved tires and safety systems for icy roads. This study investigates the available friction levels at the tire–ice interface by varying operational parameters through the indoor testing program conducted at the Advanced Vehicle Dynamics Laboratory, Virginia Tech (in part I) and the outdoor testing program conducted at the Keweenaw Research Center (in part II). This two-part article presents the design of experiment, the indoor and outdoor test programs, and friction–slip ratio curves obtained from both test programs for different conditions. The effects of operational parameters and their inter-dependency for the entire slip ratio range during operation on ice is explained, as studied from the two test programs. This article (part I) details the indoor test method consisting of the ice creation procedure, pre-test procedures, the test procedure and analysis of the obtained friction–slip ratio curves. This experimental investigation performs the necessary groundwork and builds a strong foundation towards making driving on ice safe.     

Turbulent travel speeds in nonlinear vehicle dynamics

Quarter car models of vehicles rolling on wavy roads lead to limit cycles of travel speed and acceleration with period doublings and bifurcation effects for appropriate driving force parameters. In case of narrow-banded road excitations, speed jumps occur, additionally. This has the consequence that the driving speed becomes turbulent. Bifurcation and jump effects vanish with growing vehicle damping. The same happens for increasing bandwidth of road excitations when, e.g., on flat highways there are no big road waves but only small noisy slope processes generated by rough road surfaces. The paper derives a new stability condition in mean. Numerical time integrations are stabilized by means of polar coordinates. Equivalently, Fourier series expansions are introduced in the angle domain. Phase portraits of travel speed and acceleration show new period-doublings of limit cycles when speed gets stuck before resonance. The paper extends these investigations to the stochastic case that road surfaces are random generated by filtered white noise. By means of Gaussian closure, a nonlinear mean speed equation is derived which includes the extreme cases of wavy roads and road noise.

     

Autocorrelation model of road roughness

Road surface roughness is the excitation source for the dynamic response of a moving vehicle system. Driving comfort is indicated by either the driver absorbed power level or the vehicle vertical acceleration level. An autocorrelation function model for road roughness is proposed to specify the road surface random characteristics. Subsequently, the power spectral densities (PSDs) for both road roughness and vehicle response, the driver-absorbed power level, are formulated. A road quality index (RQI) in accordance with such energy considerations is defined to catalog the road grade. The laboratory test results show the applicability of the RQI method for road classification using the ISO criteria as a comparison check.     

Improving off-road vehicle handling using an active anti-roll bar

To design a vehicle’s suspension system for a specific, well defined road type or manoeuvre is not a challenge any more. As the application profile of the vehicle becomes wider, it becomes more difficult to find spring and damper characteristics to achieve an acceptable compromise between ride comfort and handling. For vehicles that require both good on- and off-road capabilities, suspension design poses a significant challenge. Vehicles with good off-road capabilities usually suffer from poor on-road handling. These vehicles are designed with a high centre of gravity due to the increased ground clearance, soft suspension systems and large wheel travel to increase ride comfort and ensure traction on all the wheels. All of these characteristics contribute to bad handling and increased rollover propensity even on good level roads. It is expect from these vehicles to have the same handling characteristics as a normal on-road vehicle. This paper analyses the use of an active anti-roll bar as a means of improving the handling of an off-road vehicle without sacrificing ride comfort. The proposed solution is simulated, designed, manufactured, implemented and tested to quantify the effect of the active anti-roll bar on both the handling and ride comfort of an off-road vehicle.     

Haul road defect identification using measured truck response

Current management techniques for the maintenance of mine haul roads, such as ad hoc blading, scheduled blading and even maintenance management systems, have shortcomings in complex mining environments. This paper investigates the possibility of using the response of haul trucks to aid the management of haul road maintenance. The question arises as to whether truck response data can be used to recognize road defects at specific locations, in terms of type and size. This is important since different defect types require different road maintenance strategies. A modeling methodology based on dynamic equilibrium of the unsprung mass of a haul truck is proposed and investigated.     

Dynamic interactions of an integrated vehicle–electromagnetic energy harvester–tire system subject to uneven road excitations

An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electro-magnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by:(1) the natural modes and frequencies of the vehicle;(2) the vehicle rolling and pitching motions;(3) different road exci-tations on four wheels;(4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guide-lines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.     

Vehicle movement patterns and vegetative impacts during military training exercises

The operation of off-road vehicles during military training exercises can affect the environmental conditions of training lands by removing or disturbing vegetation. The use of global positioning systems (GPS)-based vehicle tracking systems can help to characterize the movement of vehicles during training exercises for the purpose of quantifying vegetative impacts. The combination of GPS positions of vehicles in the field during a training exercise, and geographic information system (GIS) maps of the training installation can provide information about vehicle-specific vegetation impacts of a training exercise, as related to vehicle locations, turning radius and velocity. Such relationships can be used to estimate off-road vegetation impacts. Twenty GPS-based vehicle tracking systems were installed on vehicles of the US Army 3rd Brigade 1/14 Cavalry to evaluate vegetation impacts during a 10 day reconnaissance training exercise at Yakima Training Center in Yakima, WA. The vehicle tracking systems were programmed to record the position of the vehicles every second. The resulting vehicle tracking data were analyzed for quantity of travel per day of the training activity, quantity of travel on and off roads, off-road vehicle dynamic properties turning radius and velocity, and off-road vegetation removed. The vehicles were in motion an average of 8.4% (approximately 2 h per day) of the training exercise time. The average distance traveled per day on roads was 33.5 km, and the average distance traveled per day off-roads was 7.7 km. On average, the vehicles spent 16% of their off-road traveling time at turning radii less than 20 m. Vegetation impacts were compared for different missions. The zone reconnaissance mission produced the highest vegetation impact per distance traveled.     

基于车桥耦合理论的梁式桥阻尼比识别研究

提出一种基于车桥耦合动力学理论的梁式桥阻尼比识别方法. 首先按照动力学理论将测试车设计为单自由度体系, 然后利用安装在测试车上的传感器采集信号, 从测试车与桥梁接触点响应信号中得到梁式桥响应的信号, 基于车桥耦合动力学原理滤波处理得到包含梁式桥第一阶频率的信号, 最后假定梁式桥阻尼比值, 通过假定的梁式桥阻尼比值获取假定的梁式桥第一阶振型, 不断循环直至假定的阻尼比值下计算的第一阶振型最大值点居中, 即为识别的梁式桥真实阻尼比. 本文首先从车桥耦合动力学理论推导上说明了该方法的可行性, 然后考虑在不同车速与非恒定车速、路面粗糙度、环境噪音等影响因素下进行车桥耦合动力学模型分析, 最后通过实桥试验进行了初步验证. 研究结果表明: 该方法能一定程度上克服外界不利因素的影响, 达到识别梁式桥阻尼比的目的, 为识别梁式桥阻尼比提供一种更优方法, 其具有参数设置较少、操作简单方便以及更高测试精度等优点, 同时有助于推动基于车桥耦合的车桥耦合动力学理论技术在梁式桥模态参数识别工作中的实际工程应用.      

Parameterization and modelling of large off-road tyres for ride analyses: Part 2 – Parameterization and validation of tyre models

Every mathematical model used in a simulation is an idealization and simplification of reality. Vehicle dynamic simulations that go beyond the fundamental investigations require complex multi-body simulation models. The tyre–road interaction presents one of the biggest challenges in creating an accurate vehicle model. Many tyre models have been proposed and developed but proper validation studies are less accessible. These models were mostly developed and validated for passenger car tyres for application on relatively smooth roads. The improvement of ride comfort, safety and structural integrity of large off-road vehicles, over rough terrain, has become more significant in the development process of heavy vehicles. This paper investigates whether existing tyre models can be used to accurately describe the vertical behaviour of large off road tyres while driving over uneven terrain. [1] Presented an extensive set of experimentally determined parameterization and validation data for a large off-road tyre. Both laboratory and field test are performed for various loads, inflation pressures and terrain inputs. The parameterization process of four tyre models or contact models are discussed in detail. The parameterized models are then validated against test results on various hard but rough off-road terrain and the results are discussed.     

Reconstruction of road defects and road roughness classification using vehicle responses with artificial neural networks simulation

The road damage assessment methodology in this paper utilizes an artificial neural network that reconstructs road surface profiles from measured vehicle accelerations. The paper numerically demonstrates the capabilities of such a methodology in the presence of noise, changing vehicle mass, changing vehicle speeds and road defects. In order to avoid crowding out understanding of the methodology, a simple linear pitch-plane model is employed. Initially, road profiles from known roughness classes were applied to a physical model to calculate vehicle responses. The calculated responses and road profiles were used to train an artificial neural network. In this way, the network renders corresponding road profiles on the availability of fresh data on model responses. The results show that the road profiles and associated defects can be reconstructed to within a 20% error at a minimum correlation value of 94%.     

Identification of superfluous roads in terms of sustainable military land carrying capacity and environment

A great challenge the US military land managers are often faced with is how to optimize road networks in order to maintain roads (including all roads, trails, and paths) for the purpose of military training and reducing negative impacts on environment. In this study, a methodology was developed to identify superfluous roads for being closed in terms of both sustainable military land carrying capacity and environment for Fort Riley. In this method, Geographic Information Systems (GIS), remote sensing, and landscape analysis technologies were combined to derive various spatial data layers of factors that had significant impacts on both military training and environment. The factors included maintenance cost of roads, road access area, military training intensity, soil erosion, water quality, landscape fragmentation, and noise production. The factors were quantified and normalized. A spatial multicriteria decision was then developed to obtain the weights of the factors, combine the data layers, and derive a priority map of all the roads for being closed. This map summarized the negative and positive impacts of the factors on environment and military land carrying capacity and can provide the US military land managers with useful guidelines and tools for determining superfluous roads in terms of both sustainable military training and environment. It is expected this effort can provide a method to quickly ascertain which roads are most cost-effective for being closed without hindering the mission and at the same time with benefits for environmental protection and thus provide the land managers with a comprehensive analysis and assessment of alternatives at their disposal.     

The influence of the soil stratification on free field traffic-induced vibrations

Summary  This paper deals with the influence of the soil stratification on the free field vibrations generated by the passage of a vehicle on an uneven road. A two-stage solution procedure is applied for the numerical prediction of the free field traffic-induced vibrations. First, a 2D vehicle model is used for the calculation of the axle loads from the longitudinal road profile. Next, the free field response is calculated with the dynamic Betti-Rayleigh reciprocity theorem, using a transfer function between the road and the receiver. The dynamic road-soil interaction problem is solved with a substructure method. The road is modelled as a beam of infinite length, while the boundary element method, based on the Green's functions for a horizontally layered linear elastic halfspace is used for the soil. The influence of the soil stratification is demonstrated by a numerical example where the free field vibrations during the passage of a vehicle on a traffic plateau are calculated. Three different cases are considered for the layering of the soil: a homogeneous halfspace, a layer built in at its base and a layer on a halfspace. Special emphasis goes to the dynamic interaction between the road and the soil. It is demonstrated that the stratification of the soil has a considerable influence on both the peak particle velocity and the frequency content of the free field vibrations. Received 28 November 2000; accepted 24 April 2001     

基于DRBF-EKF算法的车辆质心侧偏角与路面附着系数动态联合估计

车辆质心侧偏角和路面附着系数是实现车辆底盘智能化所需要的关键参数. 车辆质心侧偏角对于提高车辆安全性和操控性至关重要, 轮胎-路面附着系数决定轮胎力的峰值, 进而确定汽车的动力学稳定性边界. 本文针对四轮独立驱动电动汽车提出了一种基于惯性测量单元、轮毂电机内置转速/转角传感器的车辆质心侧偏角和路面附着系数动态联合估计方法. 对四轮独立驱动电动汽车进行车辆动力学分析, 结合Dugoff轮胎计算模型得到车辆质心侧偏角估计器; 利用机器学习中高维数据降维PCA多元分析方法, 提取主元特征参数, 建立路面附着系数估计器. 采用可自适应调节网络结构的双径向基神经网络和扩展卡尔曼滤波DRBF-EKF方法, 通过K-means算法改进RBF神经网络结构, 扩展卡尔曼滤波进行噪声滤波提高估计精度, 实现车辆质心侧偏角和路面附着系数的动态联合估计. 通过仿真和实车实验表明, 所设计的DRBF-EKF动态联合估计器实时性和估计精度均优于扩展卡尔曼滤波算法, 可以适应车辆行驶过程中路面附着特性与车速的变化, 表现出较强的鲁棒性; 与DRBF方法相比, 显著提高了估计精度; 并且分析了可以同时满足估计精度和实时性要求的最佳隐含层神经元个数.