Lateral Load Transfer Research Articles

Modelling of a Partially Loaded Road Tanker during a Braking-in-a-Turn Maneuver

Road safety depends on several factors associated with the vehicle, to the infrastructure, as well as to the environment and experience of vehicle drivers. Concerning the vehicle factors influencing the safety level of an infrastructure, it has been shown that the dynamic interaction between the carried liquid cargo and the vehicle influences the operational safety limits of the vehicle. A combination of vehicle and infrastructure factors converge when a vehicle carrying liquid cargo at a partial fill level performs a braking maneuver along a curved road segment. Such a maneuver involves both longitudinal and lateral load transfers that potentially affect both the braking efficiency and the lateral stability of the vehicle. In this paper, a series of models are set together to simulate the effects of a sloshing cargo on the braking efficiency and load transfer rate of a partially filled road tanker. The model assumes the superposition of the roll and pitch independent responses, while the vehicle is equipped with Anti-lock braking System brakes (ABS) in the four wheels. Results suggest that cargo sloshing can affect the performance of the vehicle on the order of 2% to 9%, as a function of the performance measure considered. A dedicated ABS system could be considered to cope with such diminished performance.

Rollover speed prediction on curves for heavy vehicles using mobile smartphone

Inappropriate speed selection on a curved road is a main cause of rollover accidents for heavy vehicles due to their relative higher centers of gravity, comparing with those of passenger cars. Traditional driving safety improvement methods on curves include static/dynamic roadside speed limit signs that lack individual vehicle’s characteristics, and the high-cost anti-rollover stability control systems that cannot take road geometric parameters like superelevation of a vehicle’s upcoming curve into consideration. In this paper,a new rollover speed prediction model based on the derivation of three-degree-of-freedom vehicle dynamics and lateral load transfer ratio (LTR) index is presented. Through numerical experiments, the results show that this model could guarantee the vehicle roll stability with the calculated speed for entering a curve whose road radius is even 50 m, in which the vehicle’s LTR never exceeds 0.72 and lateral acceleration is always less than 0.63 g. Moreover, the proposed model built in a mobile smartphone app can calculate curve radius at first, then provide an early alarming to the driver with an appropriate speed if rollover accident is imminent on the curve. The field tests on freeway off-ramps show that this smartphone-based rollover speed warning system can calculate the curve radii, and alert the driver with appropriate curve speeds that are partially equivalent to professional skilled drivers’ speed choices.

Unidirectional GFRP composite connections between precast concrete wall panels under simulated seismic loads

A method of connecting precast concrete walls with Glass Fiber Reinforced Polymer (GFRP) composite sheets is investigated. The method can be used either as a seismic retrofit of existing welded steel plate connections or in new construction. The specimens consisted of two precast concrete wall panels connected with either two or four layers of unidirectional GFRP composite sheets. Eight specimens were subjected to quasi-static cyclic loads to explore the effect of the following variables on the connection capacity: concrete surface preparation; application of surface pressure to the GFRP laminate; number and orientation of GFRP composite layers; and use of carbon fiber reinforced polymer (CFRP) spike anchors. The performance of the composite connection was acceptable in terms of lateral load, lateral displacement, and shear transfer capacity. Application of surface pressure during curing of the GFRP laminate and the use of CFRP spike anchors improved the lateral load and displacement capacity of the composite connection significantly. An empirical expression is proposed to determine the capacity of the composite connection.

H∞ control of integrated rollover prevention system based on improved lateral load transfer rate

A rollover dynamic model that merges the active front steering model and differential braking model is established in this paper. After analyzing and improving the existing rollover evaluation method, a new evaluation method that takes both sprung mass and under-sprung mass into consideration is proposed. The reliability of the improved LTR (lateral load transfer rate) is confirmed by simulation results obtained from MATLAB and CARSIM where, all of three evaluation methods are taken under the same condition. The accuracy of the rollover evaluation index depends on the centroid height of under-sprung mass and the ratio of under-sprung mass and under-sprung mass. In order to achieve the desired tracking effect and anti-jamming capability, an integrated rollover control system based on active steering and differential braking is designed where a H∞ controller is adopted. The results of simulation under J-turn condition indicate that the control system has strong stability and robustness. When the vehicle is under the risk of rollover and reaches the setting threshold, the designed H∞ controller will actively keep the vehicle under the critical state.

Multi-performance analyses and design optimisation of hydro-pneumatic suspension system for an articulated frame-steered vehicle

ABSTRACTThis study investigates the coupled ride and directional performance characteristics of an articulated frame-steered vehicle (AFSV). A three-dimensional multi-body dynamic model of the vehicle is formulated integrating the hydro-mechanical frame steering and hydro-pneumatic suspension (HPS) systems. The model parameters are obtained from field-measured data acquired for an unsuspended AFSV prototype and a validated scaled HPS model. The HPS is implemented only at the front axle, which supports the driver cabin. The main parameters of the HPS, including the piston area, and flow areas of bleed orifices and check valves, are selected through design sensitivity analyses and optimisation, considering ride vibration, and roll- and yaw-plane stability performance measures. These include the frequency-weighted vertical vibration of the front unit, root-mean-square lateral acceleration during the sustained lateral load transfer ratio period prior to absolute rollover of the rear unit, and yaw-mode oscillation frequency following a lateral perturbation of the vehicle. The results suggested that the implementation of the HPS to the front unit alone could help preserve the directional stability limits compared to the unsuspended prototype vehicle and reduce the ride vibration exposure by nearly 30%. The results of sensitivity analyses revealed that the directional stability performance limits are only slightly affected by the HPS parameters. Further reduction in the ride vibration exposure was attained with the optimal design, irrespective of the payload variations. The vehicle operation at relatively higher speeds, however, would yield greater vibration exposure.

Rollover detection and control on the non-driven axles of trucks based on pulsed braking excitation

ABSTRACTThe major challenges for rollover detection are the accurate modelling of vehicle dynamics and the real-time estimation of the varied parameters. To circumvent the dependence on vehicle parameters, a novel rollover detection method based on the pulsed braking excitation is proposed. With the lateral load transfer ratio (LTR), the relationship between rollover risks and non-driven wheel rotational dynamics is deduced, which is the basis to apply braking excitation on wheels. The lateral acceleration is adopted as the first criterion to activate the rollover detection. Once the pulsed braking is applied to the non-driven wheels, the braking pressure and wheel angular speeds are measured to estimate the LTR on the non-driven axle. In case of emergency, the differential braking-based anti-rollover is implemented. Experiments were conducted on a Hardware-in-Loop bench. The results show that, the pulsed braking can be activated timely, and the LTR on the non-driven axle is estimated accurately. With the anti-rollover control, the roll stability is improved considerably.

Driver Model-Based Fault-Tolerant Control of Independent Driving Electric Vehicle Suffering Steering Failure

This paper presents a fault-tolerant control (FTC) strategy for a four-wheel independent driving electric vehicle suffering steering failure. The method is based on the functional redundancy of driving and braking actuators to recover the vehicle’s steering ability. A dynamic vehicle model is derived with the function of four-wheel driving. A sliding mode controller with a combined sliding surface is employed as a motion controller, allowing the desired vehicle motion to be tracked by the adaptive driver model. An extended Kalman filter-based state estimator is adopted to virtually measure the sideslip angle while considering the nonlinear tire force. A new allocation strategy, involving two distribution modes of coordination, is designed. In addition, a weight coefficient adjustment strategy is implemented in optimal mode based on the lateral load transfer, thus improving the steering performance. Simulations are conducted to verify the proposed FTC algorithm. The results demonstrate that steering failure can be effectively covered by the functional redundancy of the driving/braking actuators.

Modeling of Lateral Stability of Tractor-Semitrailer on Combined Alignments of Freeway

The objective of this research was to investigate the impact of roadway geometrics and speed on lateral stability of tractor-semitrailer on combined alignments of freeways since the current design guidelines of combined alignments are not available in China. A closed-loop vehicle dynamic simulation model was established using TruckSim multibody dynamics software. The maximum wheel side friction demand and lateral load transfer ratio were used to measure the skidding and rollover risks, and the variation laws of each indicator were determined by developing the controlled variable simulation scenarios. Based on the theory of statistical analysis, an orthogonal test was designed, and the effects of various impact factors on the lateral stability of the tractor-semitrailer were analyzed. The models for lateral stability indicators were developed by multiple linear regression analysis and applied to evaluate the driving risk of tractor-semitrailer on a wet road surface. The results showed that the radius and speed have significant effects on the lateral stability while the effect of the downgrade is of general significance. In addition, lower safe speed should be adopted on wet road surfaces of curved downgrade. This paper proposed a surrogate approach to road safety analysis and the models can be used for building the freeway driving security system.

A general rollover index for tripped and un-tripped rollovers on flat and sloped roads

In order to develop a rollover prevention system, it is essential to have a reliable index that properly indicates real-time rollover danger during vehicle maneuvers. The existing rollover indices are mainly for un-tripped rollovers and have limitations in detecting tripped rollovers. This study introduces a general rollover index (GRI) for the detection of rollover in both tripped and un-tripped cases and also on flat and sloped roads. Based on the lateral load transfer ratio, the proposed index is analytically derived in terms of measurable vehicle parameters and state variables. The general rollover index considers both lateral and vertical road inputs and thus can indicate tripped rollovers in the instance of curbs, soft soil or bumps. Sensitivity analysis for the proposed index is also provided to evaluate the effects of different vehicle parameters and different state variables on tripped and un-tripped rollovers. The introduced index can be used not only for the development of active rollover prevention systems, but also for rollover analysis and design of vehicles. The performance of the introduced general rollover index is validated through simulations using a high-fidelity CarSim model for a SUV.

Effects of pile shape and pile end condition on the lateral response of displacement piles in soft clay

A series of lateral tests conducted in a centrifuge on displacement piles in kaolin is used to examine the effects of pile shape, pile end-condition and clay overconsolidation on the lateral load transfer (p–y) curves in soft clay. These experimental tests are supported by finite-element analyses, which examine the responses of the circular, square and H pile sections used in the centrifuge tests. The experimental and numerical results reveal an important effect of pile shape on p–y curves, but no discernible effect of the pile end condition. These results also indicate comparable dependencies of net ultimate pressures on normalised depth and undrained shear strength. The findings enable development of a new formulation for p–y curves in soft clay, which incorporates the effects of pile shape and uses the triaxial compression consolidated undrained shear strength as the reference undrained strength.

Shear performance of embedded anchor plates in reinforced concrete tilt-up panels under monotonic and cyclic loadings

Cast-in-place steel plates with headed steel studs constitute a common type of connection system in tilt-up members. These connection systems used in composite construction play an important role in vertical and lateral load transfer mechanisms and in the energy dissipation of seismic responses by allowing sufficient ductility and controlling cracks in the concrete elements. Due to the relatively thin concrete panel thickness, it is difficult to attain adequate ductility in connection system. This study examined design parameters, including the embedment depth-to-stud diameter ratio (hef/d), panel thickness, and supplementary reinforcement, in order to propose effective reinforcing methods to prevent premature failure such as pry-out failure. In addition, this study investigated the feasibility of current existing formulas, including those found in the American Concrete Institute 318M-14 provisions and in the Precast/Prestressed Concrete Institute Handbook with respect to the design variables. This study also investigated the difference between monotonic and cyclic test results and compared the results obtained from the literature.

A LQR-Based Controller with Estimation of Road Bank for Improving Vehicle Lateral and Rollover Stability via Active Suspension.

In this article, a Linear Quadratic Regulator (LQR) lateral stability and rollover controller has been developed including as the main novelty taking into account the road bank angle and using exclusively active suspension for both lateral stability and rollover control. The main problem regarding the road bank is that it cannot be measured by means of on-board sensors. The solution proposed in this article is performing an estimation of this variable using a Kalman filter. In this way, it is possible to distinguish between the road disturbance component and the vehicle’s roll angle. The controller’s effectiveness has been tested by means of simulations carried out in TruckSim, using an experimentally-validated vehicle model. Lateral load transfer, roll angle, yaw rate and sideslip angle have been analyzed in order to quantify the improvements achieved on the behavior of the vehicle. For that purpose, these variables have been compared with the results obtained from both a vehicle that uses passive suspension and a vehicle using a fuzzy logic controller.

H∞ control of anti-rollover strategy based on predictive vertical tire force

The mainstream rollover evaluation index, lateral load transfer rate (LTR), is commonly used in the rollover control field. However, it is not instant enough to reflect the rollover tendency since it can only reflect the load transfer rate of one side wheels while single rear wheel leaves the ground first during rollover happens. In order to monitor the rollover tendency more instantly and improve the reliability of anti-rollover control system, a new evaluation index called predictive vertical tire force (PVTF) is proposed, which is based on the single vertical tire force and merges both iterative prediction and derivative prediction methods. Meanwhile, an optimization is taken to solve the contradiction between prediction time and deviation. Secondly, using the PVTF as the measurement output, an anti-rollover control system based on active steering is established in this paper. In order to achieve the desired tracking effect and anti-jamming capability, a two-way H∞ controller is adopted in the anti-rollover control system. Lastly, the simulation results of J-turn condition and NHTSA (national highway traffic safety administration) condition are conducted and the results indicate that the anti-rollover control system has strong stability and robustness. Meanwhile, benefit from the pre-warning function of PVTF, the controller is triggered earlier and the vertical tire forces of four wheels are controlled to be positive all the time, which is beneficial for handling stability.

Effect of Overspeeding on the Lateral Stability of a Bus Running on a Curve

A bus running on straight roads, general curves, or sharp curves is subjected to vehicle dynamics simulation tests under different overspeeding degrees to study the effects of different overspeeding degrees on driving safety when a bus runs on a curve. TruckSim software is used in the simulation, and lateral offset and tire load transfer rate are selected as analysis indicators. The effects of different overspeeding degrees on lateral stability when the bus runs on curves are quantitatively analyzed. Simulation results indicate that (1) overspeeding degree is negatively correlated with the lateral stability of a bus running on a general curve or a sharp curve. (2) A high overspeeding degree corresponds to poor lateral stability and high likelihood of an accident. (3) Under the same overspeeding degree, a bus running on a general curve likely deviates from the curve path and causes accidents, such as running off roads and enter into adjacent or oncoming driveways. A bus running on a sharp curve easily experiences a rollover accident.

A robust observer based on H∞ filtering with parameter uncertainties combined with Neural Networks for estimation of vehicle roll angle

Abstract Nowadays, one of the main objectives in road transport is to decrease the number of accident victims. Rollover accidents caused nearly 33% of all deaths from passenger vehicle crashes. Roll Stability Control (RSC) systems prevent vehicles from untripped rollover accidents. The lateral load transfer is the main parameter which is taken into account in the RSC systems. This parameter is related to the roll angle, which can be directly measured from a dual-antenna GPS. Nevertheless, this is a costly technique. For this reason, roll angle has to be estimated. In this paper, a novel observer based on H ∞ filtering in combination with a neural network (NN) for the vehicle roll angle estimation is proposed. The design of this observer is based on four main criteria: to use a simplified vehicle model, to use signals of sensors which are installed onboard in current vehicles, to consider the inaccuracy in the system model and to attenuate the effect of the external disturbances. Experimental results show the effectiveness of the proposed observer.

Sensor Fusion Based on an Integrated Neural Network and Probability Density Function (PDF) Dual Kalman Filter for On-Line Estimation of Vehicle Parameters and States.

Vehicles with a high center of gravity (COG), such as light trucks and heavy vehicles, are prone to rollover. This kind of accident causes nearly of all deaths from passenger vehicle crashes. Nowadays, these vehicles are incorporating roll stability control (RSC) systems to improve their safety. Most of the RSC systems require the vehicle roll angle as a known input variable to predict the lateral load transfer. The vehicle roll angle can be directly measured by a dual antenna global positioning system (GPS), but it is expensive. For this reason, it is important to estimate the vehicle roll angle from sensors installed onboard in current vehicles. On the other hand, the knowledge of the vehicle’s parameters values is essential to obtain an accurate vehicle response. Some of vehicle parameters cannot be easily obtained and they can vary over time. In this paper, an algorithm for the simultaneous on-line estimation of vehicle’s roll angle and parameters is proposed. This algorithm uses a probability density function (PDF)-based truncation method in combination with a dual Kalman filter (DKF), to guarantee that both vehicle’s states and parameters are within bounds that have a physical meaning, using the information obtained from sensors mounted on vehicles. Experimental results show the effectiveness of the proposed algorithm.

Analysis of soil resistance on drilled shafts using proposed cyclic p-y curves in weathered soil

A fundamental study of drilled shafts-soil systems subjected to lateral cyclic loading in weathered soil was conducted using numerical analyses. The emphasis was on quantifying the soil resistance of laterally cyclic loaded pile using 3D finite element analysis. The appropriate parametric studies needed for verifying the cyclic p-y characteristic are presented in this paper. A framework for determining the cyclic lateral load transfer curve (p-y curves) on the basis of numerical analyses is proposed. Through comparisons with results of field load tests, the three-dimensional numerical methodology in the present study is in good agreement with the general trend observed by in situ measurements and thus, represents a realistic soil-pile interaction for laterally loaded piles in soil than that of existing p-y method. It can be said that a rigorous present analysis can overcome the limitations of existing cyclic p-y methods to some extent by considering the effect of realistic three-dimensional combination of pile-soil forces. The proposed cyclic p-y curve is shown to be capable of predicting the behavior of the drilled shafts in weathered soil.

Rollover stabilities of three-wheeled vehicles including road configuration effects

This study investigates the rollover stabilities of three-wheeled vehicles including the effects of road configurations. Tripped and untripped rollovers on flat and sloped roads are studied, and a new rollover index is introduced. To explore the unique dynamic behaviours of three-wheeled vehicles, the rollover stability is investigated on the basis of the lateral load transfer ratio, and the proposed rollover index is expressed in terms of measurable vehicle parameters and state variables. In addition to the effects of the lateral acceleration and the roll angle, the proposed rollover index takes the effects of the longitudinal acceleration and the pitch angle into account as well as the effects of banked roads and graded roads. Lateral and vertical road inputs are also considered since they can represent the effects of kerbs, soft soil and road bumps as the main causes of tripped rollovers. Sensitivity analysis is also provided in order to evaluate and compare the effects of different vehicle parameters and different state variables on the rollover stabilities of three-wheeled vehicles. To evaluate the proposed rollover index, simulations are also conducted using a high-fidelity CarSim model for a three-wheeled vehicle.

Design of an integrated control system to enhance vehicle roll and lateral dynamics

Besides lateral instability, one major threat to all ground vehicles, especially SUVs, is the danger of rollover during cornering. A coordination strategy based on fuzzy logic has been devised to coordinate the sub-controls; namely, active steering, active differential, active brake and a novel active roll control system. Independent study of each sub-control as well as an analysis of their inter-relationship has been carried out. The coordination strategy is supposed to resolve the conflict among control targets – which are sideslip regulation, yaw rate tracking, lateral acceleration tracking and roll motion control – all of which are to be done while maintaining the driver’s desired longitudinal acceleration. Thus, a compromise must be reached. Vehicle sideslip angle and yaw rate were considered to be the criteria for lateral stability; and a combination of roll angle, roll rate and lateral load transfer was selected as the criterion for roll stability. The results of simulations on two SUV models in CarSim software indicate that the integrated controller can successfully restore vehicles’ stability in critical condition.

State estimation in roll dynamics for commercial vehicles

ABSTRACTAccurate lateral load transfer estimation plays an important role in improving the performance of the active rollover prevention system equipped in commercial vehicles. This estimation depends on the accurate prediction of roll angles for both the sprung and the unsprung subsystems. This paper proposes a novel computational method for roll-angle estimation in commercial vehicles employing sensors which are already used in a vehicle dynamic control system without additional expensive measurement units. The estimation strategy integrates two blocks. The first block contains a sliding-mode observer which is responsible for calculating the lateral tyre forces, while in the second block, the Kalman filter estimates the roll angles of the sprung mass and those of axles in the truck. The validation is conducted through MATLAB/TruckSim co-simulation. Based on the comparison between the estimated results and the simulation results from TruckSim, it can be concluded that the proposed estimation method has a promising tracking performance with low computational cost and high convergence speed. This approach enables a low-cost solution for the rollover prevention in commercial vehicles.