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Road vehicles have been shown to experience measurable changes in aerodynamic performance when travelling in everyday safe-distance driving conditions, with a major contributor being the lower effective wind speed associated with the wakes from forward vehicles. Using a novel traffic-wake-generator system, a comprehensive test program was undertaken to examine the influence of traffic wakes on the aerodynamic performance of heavy-duty vehicles (HDVs). The experiments were conducted in a large wind tunnel with four primary variants of a high-fidelity 30%-scale tractor-trailer model. Three high-roof-tractor models (conventional North-American sleeper-cab and day-cab, and a zero-emissions-cab style) paired with a standard dry-van trailer were tested, along with a low-roof day-cab tractor paired with a flat-bed trailer.

With the rapid development of the logistics and transportation industry, heavy-duty trucks play an increasingly important role in social life. However, due to the characteristics of large cargo loads, high center of mass and relatively narrow wheelbase, the driving stability of heavy trucks are poor, and it is easy to cause rollover accidents under high-speed driving conditions, large angle steering and emergency obstacle avoidance. To improve the roll stability of heavy trucks, it is necessary to design an active anti-rollover control system, through the analysis of the yaw rate and the load transfer rate of the vehicle, driving states can be estimated during the driving process. Under the intervention of the control system, the lateral transfer rate of heavy trucks can be reduced to correct the driving posture of the vehicle body and reduce the possibility of rollover accidents.

Build variation and tolerance stack up are unavoidable in the vehicle manufacturing process, not only for individual components and assemblies but also for the vehicle at large. Deviations across several components, each within tolerance limits, could ultimately have a significant effect on vehicle aerodynamic performance. The objective of this study is to quantify the impact of several such build variations on vehicle drag. A Lattice-Boltzmann-based simulation method was used in conjunction with design of experiments to construct a Kriging response surface interpolation model to efficiently characterize the impact of 17 different body and chassis build variations on the aerodynamic drag of a VNL 780 tractor trailer at a nonzero yaw angle. The top three parameters with greatest aerodynamic impact were then evaluated at the opposite symmetric yaw angle to understand the impact of build variation on vehicle asymmetry.

Autonomous vehicle operation is dependent upon accurate position estimation and thus a major concern of implementing the autonomous navigation is obtaining robust and accurate data from sensors. This is especially true, in case of Inertial Measurement Unit (IMU) sensor data. The IMU consists of a 3-axis gyro, 3-axis accelerometer, and 3-axis magnetometer. The IMU provides vehicle orientation in 3D space in terms of yaw, roll and pitch. Out of which, yaw is a major parameter to control the ground vehicle’s lateral position during navigation. The accelerometer is responsible for attitude (roll-pitch) estimates and magnetometer is responsible for yaw estimates. However, the magnetometer is prone to environmental magnetic disturbances which induce errors in the measurement.

Advanced driver-assistance systems (ADAS) are becoming an essential part of the modern commercial automobile industry. Vehicle handling and stability are determined by the yaw rate and body slip of the vehicle. This paper is a comparative study of a nonlinear vehicle stability control algorithms for steering control based on two different controllers i.e. fuzzy logic based controller and PID controller. A full vehicle 14DOF model was made in Simulink to simulate an actual vehicle. The control algorithms are based on a two-track 7-DOF model with a non-linear tire model based on Pacejka “Magic tire formula”, which was used to establish the desired response of a full vehicle 14DOF model. It was found that the fuzzy logic-based control algorithm demonstrated an overall superior performance characteristic than a PID based control algorithm; this includes a significant decrease in time lag and overshoot.

Considering the aerodynamic characteristics of the vehicle traveling under the crosswind and the complexity of the flow field change, this paper uses overset mesh of STAR CCM+ software to carry out CFD simulation analysis on the aerodynamic characteristics of heavy commercial vehicles passing through the highway tunnel of which entrance and exit exist crosswind. Corresponding aerodynamic coefficients and flow field changes around the body at different crosswind speeds and different tunnel forms are monitored. The results show that the yaw moment is sensitive to the speed of crosswind. When a heavy commercial vehicle passes through a tunnel where crosswind increases from 10m/s to 13m/s,the yaw moment change rate increases from 34.8 kN•m/s to 45.9 kN•m/s. It also can be seen in these results is that when passing through two tunnels with a distance, the heavy commercial vehicle’s side force, roll moment and yaw moment change because of the surrounding periodic variation of flow field.

Accident reconstructionists rarely have complete data with which to determine vehicle speed, and so the true value must be bracketed within a range. Previous work has shown the effect of friction uncertainty in determining speed from tire marks left by a vehicle in yaw. The goal of the current study was to assess improvements in the accuracy of vehicle speed estimated from yaw marks using progressively more scene and vehicle information. Data for this analysis came from staged S-turn maneuvers that in some cases led to rollover of sport utility vehicles. Initial speeds were first calculated using the critical curve speed (CCS) formula on the yaw marks from the first portion of the S-maneuver. Then computer simulations were performed with progressively more input data: i) the complete tire marks from the whole S-maneuver, ii) measured vehicle mass, iii) measured suspension stiffness and damping, and iv) measured steering history.

In this paper, a new roll-plane hydraulically interconnected suspension (HIS) system is proposed to enhance the roll and lateral dynamics of a two-axle bus. It is well-known that the suspension tuning is of great importance in the design process and has also been explored in a number of studies, while only minimal efforts have been made for suspension tuning for the newly proposed HIS system especially considering lateral stability. This study aims to explore lateral dynamics and suspension tuning of a two-axle bus with HIS system, which could also provide valuable information for roll dynamics analysis. Based on a ten-DOFs lumped-mass full-car model of a bus either integrating transient mechanical-hydraulic model for HIS or the traditional suspension components, three newly promoted parameters of HIS system are defined and analyzed-namely the total roll stiffness (TRS), roll stiffness distribution ratio (RSDR) and roll-plane damping (RPD).

In this paper, a gain-scheduling optimal control approach is proposed to enhance yaw stability of articulated commercial vehicles through active braking of the proper wheel(s). For this purpose, an optimal feedback control is used to design a family of yaw moment controllers considering a broad range of vehicle velocities. The yaw moment controller is designed such that the instantaneous tractor yaw rate and articulation angle responses are forced to track the target values at each specific vehicle velocity. A gain scheduling mechanism is subsequently constructed via interpolations among the controllers. Furthermore, yaw moments derived from the proposed controller are realized by braking torque distribution among the appropriate wheels. The effectiveness of the proposed yaw stability control scheme is evaluated through software-in-the-loop (SIL) co-simulations involving Matlab/Simulink and TruckSim under lane change maneuvers.

Steering returnability is an important index for evaluating vehicle handling performance. A systematic method is presented in this paper to reduce the high yaw rate residue and the steering response time for a light duty truck in the steering return test. The vehicle multibody model is established in ADAMS, which takes into consideration of the frictional loss torque and hydraulically assisted steering property in the steering mechanism, since the friction, which exists in steering column, spherical joint, steering universal joint, and steering gear, plays an important role in vehicle returnability performance. The accuracy of the vehicle model is validated by road test and the key parameters are determined by executing the sensitivity analysis, which shows the effect of each design parameter upon returnability performance.

The development of an integrated controller for a 4WS/4WD electric bus is investigated. The front wheel steering angle is assumed to be controlled by the human driver. The vehicle is controlled by the rear wheel steering and the yaw moment that can be generated by the differential torque/brake control on each wheel. The high speed cornering is used as the testing scenario to validate the designed controller. Due to the highly nonlinear and the multiple-input and multiple-output nature, the control design is separated into different stages using the hierarchical layer control concept. The longitudinal speed is controlled using a PI controller together with a rule-based speed modification. The other two control inputs, namely the rear wheel steering and the DYC moment, are then designed using the state-dependent Riccati equation method. The designed controllers are evaluated using computer simulations first, and the simulations showed promising results.

This paper investigates the yaw dynamic behaviour of a seven axle tractor semitrailer combination vehicle developed by VRDE (Vehicle Research & Development). The semitrailer has four steerable axles which follow command steering law i.e. all axles of semitrailer are steered in a particular relation with articulation of tractor. A 4 dof (degree of freedom) linear yaw plane model was developed for this combination vehicle. Yaw response characteristics such as lateral acceleration, yaw rate and articulation angle for step and sine steer is obtained from this model. Effects of speed on the above parameters are also studied to the same steering inputs. Lateral tyre forces due to semitrailer steering at various speeds are estimated to understand its distribution on each axle. Steady state yaw rate and articulation angle gain are obtained to predict the understeer / oversteer behaviour of combination vehicle.

The prediction in the design phase of the stability of ground vehicles subject to transient crosswinds become of increased concern with drag reduced shapes, lighter vehicles as well as platooning. The objective of this work is to assess the order of model complexity needed in numerical simulations to capture the behavior of a ground vehicle passing through a transient crosswind. The performance of a full-dynamic coupling between aerodynamic and vehicle dynamic simulations, including a driver model, is evaluated. In the simulations a feedback from the vehicle dynamics into the aerodynamic simulation is performed in every time step. In the work, both the vehicle dynamic response and the aerodynamic forces and moments are studied. The results are compared to a static coupling approach on a set of different vehicle geometries. Five car-type geometries and one simplified bus geometry are evaluated.

A novel method was developed to predict the free-stream velocity experienced by a traveling vehicle based on track-side anemometric measurements. The end objective of this research was to enhance the reliability of the prediction of free-stream conditions in order to improve the accuracy of aerodynamic drag coefficient (CD) assessments from track tests of surface vehicles. Although the technique was applied to heavy-duty vehicles in the present work, it is equally applicable to any vehicle type. The proposed method is based on Taylor’s hypothesis, a principle applied in fluid mechanics to convert temporal signals into the spatial domain. It considers that the turbulent wind velocity fluctuations measured at one point are due to the "passage of an unchanging pattern of turbulent motion over the point". The method is applied to predict the wind velocity that the vehicle will experience as it encounters a wind pattern detected earlier by an anemometer located upwind.

Heavy vehicles have the characteristics of with high center of gravity position, large weight and volume, wheelbase is too narrow relative to the body height and so on, so that they always prone to rollover. In response to the above heavy security problems of heavy vehicle in running process, this paper mainly analyzes roll stability and yaw stability mechanism of heavy vehicles and studies the influence of vehicle parameters on stability by establishing the vehicle dynamics model. At the same time, this paper focuses on heavy vehicles stability control methods based on simulation and differential braking technology. At last, verify the effect of heavy vehicle stability control by computer simulation. The results shows that self-developed stability control algorithm can control vehicle stability effectively, so that the heavy vehicles instability can be avoided, the vehicle driving safety and braking stability are improved.

The United States Army Tank Automotive Research, Development and Engineering Center (TARDEC) built systems to measure the suspension parameters, center of gravity, and moments of inertia of wheeled vehicles. This is part of an ongoing effort to model and predict vehicle dynamic behavior. The new machines, the Suspension Parameter Identification and Evaluation Rig (SPIdER) and the Vehicle Inertia Parameter Evaluation Rig (VIPER), have sufficient capacity to cover most heavy, wheeled vehicles. The SPIdER operates by holding the vehicle sprung mass nominally fixed while hydraulic cylinders move an “axle frame” in bounce or roll under each axle being tested. Up to two axles may be tested at once. Vertical forces at the tires, displacements of the wheel centers in three dimensions, and steer and camber angles are measured.

Tractor semi-trailer as a widely-used heavy duty freight vehicle has caused many fatal accidents every year and one of the main factors of which may relate to its relatively poor lateral dynamics performance compared to the passenger cars [1, 2, 3]. In this paper, attention is concentrated on the parametric design for a tractor semi-trailer by optimizing the configuration parameters aiming to comprehensively improve the lateral dynamics performance. According to the previous public reports, the performance measures such as Load Transfer Ratio (LTR), Static Rollover Threshold (SRT), Rearward Amplification Ratio (RAR) and Ratio of Yaw Rate (RYR) are very effective measures and often be used to evaluate the handling and stability performances for tractor-trailer vehicles. However, each of those measures only pays attention to a certain aspect of vehicle lateral dynamics which is closely related to vehicle configuration parameters.

Vehicle jackknifing is generally associated with the loss of yaw stability, and is one of the most common cause of serious traffic accidents involving tractor-semitrailer combinations. In this paper, an active braking control strategy is proposed for jackknifing prevention of a tractor-semitrailer combination on a low friction road. The proposed control strategy is realized via upper-level and lower-level control structures considering braking of both the units. In the upper-level control, the required corrective yaw moments for tractor and semitrailer are generated using a PID controller aiming to reduce errors between the actual yaw rates of tractor-semitrailer and the target yaw rates deduced from a reference model. The corrective yaw moments are achieved through brake torque distribution among the tractor and semitrailer axle wheels in the lower-level control.

The articulated frame steering (AFS) systems are widely implemented in construction, forestry and mining vehicles to achieve enhanced maneuverability and traction performances. The kinematic and dynamic performances of articulated steered vehicles are strongly influenced by properties of the frame steering system. In this paper, a flow volume regulated frame steering system is described and analytically modelled. The analytical model of the steering system is formulated in conjunction with yaw-plane model of a 35 tonnes mining vehicle to investigate steady as well as transient responses of the steering system and the vehicle. A field test program was undertaken to measure responses of the steering system and the vehicle under nearly constant speed turning as well as path-change maneuvers.

Vehicle handling is an important attribute that is directly related to vehicle safety. The rapid development of road infrastructure has resulted in a greater focus on safety and stability. Commercial vehicle stability and safety assumes higher significance because of high center of gravity (CG) and heavier loads. A gamut of parameters influence vehicle handling directly and indirectly. However, it is quite difficult to gauge through physical testing, the extent of each parameter's influence on handling. Therefore, this paper examines vehicle handling by way of a sensitivity analysis through numerical simulation. A prototype vehicle is also instrumented and tested to confirm trends and validate the results of the simulation. An Intermediate Commercial Vehicle (ICV) with Gross Vehicle Weight (GVW) of around 13 tonnes is modeled and parameters like wheelbase and tyre stiffness are altered and the effect of these changes on handling parameters (yaw rate, lateral acceleration) is observed.