Low Lateral Acceleration Research Articles

Exploring behavioral validity of driving simulator under time pressure driving conditions of professional drivers

Driving simulators have become an important tool in human factors research, given that they are appropriately validated. Therefore, this study aims to explore the behavioral (absolute and relative) validity of a fixed-base driving simulator by analyzing different driving behavior measures such as speed, longitudinal acceleration, lateral acceleration, and brake pedal force. Thirty professional drivers participated in the experiment and the data was collected in real and simulated worlds under No Time Pressure (NTP) and Time Pressure (TP) driving conditions. Initially, comparative analyses were conducted on different driving behavior measures using Wilcoxon-signed rank test to examine absolute validity of the driving simulator. Finally, Generalized Linear Mixed (GLM) models were developed for computing the effective distance between real and simulated worlds by quantifying the parameters and for establishing relative validity. In general, the continuous profiles of driving behavior measures followed similar trends in real and simulated worlds and comparative analyses indicated relative validity of the driving simulator. The GLM models showed significant interaction effect of driving environments (real-world and simulated world) and driving conditions (NTP and TP) where high driving speed, high brake pedal force, and low lateral acceleration were observed in simulated world under TP driving condition than real-world under TP driving condition. Overall, the statistical analyses showed qualitative correspondence (relative validity) of the driving behavior measures in between real and simulated worlds. The findings from the current study showed expediency of the driving simulator and its effectiveness in conducting research on human factors and driver safety.

Vehicle roll centre estimation with transient dynamics via roll rate

The roll centre (RC) is a core parameter for vehicle lateral dynamics and control, which can be obtained via suspension geometry configuration or suspension kinematics and compliance (K&C) test. However, these methodologies are used for laboratory tests and are suitable at low lateral acceleration. In other words, the RC is hard to measure directly while the vehicle is running on the road. In this paper, the online RC estimation methodologies including the adaptive sliding mode observer (ASMO) and the extended Kalman filter (EKF) only with roll rate are proposed considering vehicle transient dynamics. The performance of these algorithms is evaluated and compared with the recursive least square with disturbance observer algorithm (RLSDA) via vehicle dynamics study. Simulation results manifest that, compared with the RLSDA with three roll signals, the proposed ASMO and EKF, only with roll rate, can estimate RC successfully for both the transient and steady-state cases and can be applied for online vehicle RC estimation. In detail, the proposed ASMO is recommended for the steady-state case, and the proposed EKF is recommended for the transient case. Furthermore, the static RC is recommended as the estimation initial value to improve estimation.

Automated Lane Changing With a Controlled Steering-Wheel Feedback Torque for Low Lateral Acceleration Purposes

To bridge the gap between autonomous and normal steering during low lateral acceleration maneuvers, a steering-wheel torque controller is developed. It consists of three controllers in series, a high-gain feedback steering-wheel torque controller, a nonlinear steering-angle controller, and a linear yaw-rate controller. A validated two degrees of freedom steering-system model, in combination with a single-track vehicle model, is used to determine the controller parameters. Driving tests with different drivers have been executed to find a comfortable steering-wheel torque/angle relation. This relation is maintained throughout the lane change by specifying the steering-wheel torque as a function of the steering-wheel angle tracking error. Experiments show promising results regarding the driver/vehicle interaction, but also show that a system to detect the lanes and the vehicle position on the road is required for further improvement.

Derivation of a multi-body model of an articulated vehicle

In this research, a five degree-of-freedom vehicle dynamics bicycle model is developed for a double tractor-trailer vehicle. Lagrange's equations are used to develop the equations of motion. Due to their complexity, the equations are symbolically derived using Maple. The equations are linearised and placed in state-space form; and, are numerically simulated using Matlab. Validation with TruckSim demonstrates the model's performance. At low forward speeds, the model closely represents the motions of the non-linear reference. As speed is increased, the model over-predicts the response, but the trends are similar. The differences are more pronounced with a heavy load condition. The model can be used to perform parametric stability studies and full numerical simulations, whereby state trajectories can be investigated at low lateral acceleration levels.

Energy-Efficiency Optimization of Torque Vectoring Control for Battery Electric Vehicles

We propose a novel torque vectoring concept for battery electric vehicles propelled by wheelindividual electric machines. Under consideration of vehicle dynamics and electric machine efficiency, this paper focuses on taking advantage of the provided degrees of freedom to reduce energy consumption. The proposed approach improves energy efficiency by introducing two functional elements: Firstly, an optimization problem based on a detailed nonlinear four-wheel vehicle model is solved to create reference sideslip angle and yaw rate that minimize the energy consumption due to wheel slip. A subsequent Linear Quadratic Controller calculates a yaw torque around the vehicle's vertical axis to follow the desired reference. To generate both, the acceleration demanded by the driver and the yaw torque requested by the LQR, a torque allocation algorithm is required. The proposed torque allocation algorithm takes into account the energy efficiency characteristics of the electric machines to provide the required propulsion force and the yaw torque with minimized loss power. Based on experimental results, the proposed torque vectoring control system leads to an energy consumption reduction of around 10% for many typical driving situations containing both, high and low lateral acceleration scenarios.

Energy-Efficiency Optimization of Torque Vectoring Control for Battery Electric Vehicles

We propose a novel torque vectoring concept for battery electric vehicles propelled by wheelindividual electric machines. Under consideration of vehicle dynamics and electric machine efficiency, this paper focuses on taking advantage of the provided degrees of freedom to reduce energy consumption. The proposed approach improves energy efficiency by introducing two functional elements: Firstly, an optimization problem based on a detailed nonlinear four-wheel vehicle model is solved to create reference sideslip angle and yaw rate that minimize the energy consumption due to wheel slip. A subsequent Linear Quadratic Controller calculates a yaw torque around the vehicle's vertical axis to follow the desired reference. To generate both, the acceleration demanded by the driver and the yaw torque requested by the LQR, a torque allocation algorithm is required. The proposed torque allocation algorithm takes into account the energy efficiency characteristics of the electric machines to provide the required propulsion force and the yaw torque with minimized loss power. Based on experimental results, the proposed torque vectoring control system leads to an energy consumption reduction of around 10% for many typical driving situations containing both, high and low lateral acceleration scenarios.

Sources of power loss during torque-vectoring for fully electric vehicles

Continuous wheel torque control of fully electric vehicles (FEV) offers potential improvements in vehicle dynamics and energy efficiency. Various studies have shown benefits from torque–vectoring for minimising vehicle power consumption by considering the losses from the electric motor drives. However, during vehicle operation, various sources of power loss exist such as dissipations due to longitudinal and lateral tyre slip which are strongly influenced by the wheel torque control system. In this study, the different power loss types during steady–state and transient manoeuvres of a case study four–wheel–drive FEV are quantified. The motor drive losses are a major contributor at low lateral acceleration but represent a secondary factor at significant lateral acceleration at which the tyre slip power losses are the most significant contribution. Future control allocation methods seeking to reduce power consumption should consider tyre slip in addition to actuator losses.

Fault classification method for the driving safety of electrified vehicles

A fault classification method is proposed which has been applied to an electric vehicle. Potential faults in the different subsystems that can affect the vehicle directional stability were collected in a failure mode and effect analysis. Similar driveline faults were grouped together if they resembled each other with respect to their influence on the vehicle dynamic behaviour. The faults were physically modelled in a simulation environment before they were induced in a detailed vehicle model under normal driving conditions. A special focus was placed on faults in the driveline of electric vehicles employing in-wheel motors of the permanent magnet type. Several failures caused by mechanical and other faults were analysed as well. The fault classification method consists of a controllability ranking developed according to the functional safety standard ISO 26262. The controllability of a fault was determined with three parameters covering the influence of the longitudinal, lateral and yaw motion of the vehicle. The simulation results were analysed and the faults were classified according to their controllability using the proposed method. It was shown that the controllability decreased specifically with increasing lateral acceleration and increasing speed. The results for the electric driveline faults show that this trend cannot be generalised for all the faults, as the controllability deteriorated for some faults during manoeuvres with low lateral acceleration and low speed. The proposed method is generic and can be applied to various other types of road vehicles and faults.

A theoretical investigation into the handling characteristics of snowboards at low lateral acceleration

In this work, a model of a rider and snowboard is presented. The snowboard is modelled as two rigid one-dimensional sections connected by a frictionless pin-joint linked by a torsional stiffness and the rider by a mass at a fixed height above the snowboard, which can move longitudinally. The model is simplified to allow the fundamental behaviour of the snowboard and rider to be investigated for a number of manoeuvres used by learners. The behaviour of the rider is shown to be related to the angle of lean and it is conjectured that the rider might attempt to achieve consistency of response by moving their centre of mass longitudinally. The response of the model in open-loop is difficult to control, and to overcome this, two control loops are designed for the lateral velocity and yaw angle of the snowboard. The model is shown to recreate a number of manoeuvres that are used to help people to learn to ride snowboards.

Influence of size scale on stable steering characteristic in miniature electric vehicle

To research the influence of size scale on stable steering characteristic (SSC) of the miniature electric vehicle (MEV), based on multi–body system dynamics and ADAMS/View software, multi–body system model of MEV was established, and steady circular was simulated and analysed. Compared with traditional large–size scale vehicles, the changes of vertical load and lateral acceleration can lead to a great change in SSC that the MEV at half–load is 'understeer', whereas the higher the lateral acceleration is the more significant it is; the MEV at full–load is 'oversteer' under low lateral acceleration, but 'understeer' for high lateral acceleration. After comparative simulation analyses of models with different sizes, study results indicate that the smaller the MEV's size scale is, the more the SSC can change owing to the changes of vertical load and lateral acceleration. The study results can provide a theoretical guidance for the design of the MEV.

Extension of the Honda-DRI “Safety Impact Methodology” (SIM) for the NHTSA Advanced Crash Avoidance Technology (ACAT) II Program and Application to the Evaluation of a Pre-Production Head-On Crash Avoidance Assist System - Progress Report

This paper reports on the interim progress of the Honda-DRI ACAT-II program initiated by the National Highway Traffic Safety Administration (NHTSA). The objectives of the ACAT-II program were further development of a formalized Safety Impact Methodology (SIM) for estimating the capability of advanced technology applications installed in vehicles to address specific types of motor vehicle crashes, and to evaluate driver acceptance of the technologies. This particular ACAT study extended earlier work by Honda and DRI in the NHTSA ACAT-I program by extending the SIM so as to be able to analyze head-on crashes more completely, and by using the extended SIM to evaluate of a preproduction version of a Honda Head-on Crash Avoidance Assist System (HCAAS). More than 25 substantial SIM extensions and refinements were implemented, including: updated and extended FARS and NASS database extractions; improving the accident reconstruction process for NASS/CDS cases and developing a new special purpose reconstruction algorithm applicable to head-on cases with low lateral acceleration drifts; extending the driver-vehicle- ACAT environment simulation to include a post-conflict recovery phase; and further automating the overall safety benefits evaluation steps. The extended SIM and results from objective tests were used to evaluate the safety impact of Honda's pre-production H-CAAS based on a large number of simulations of a sample of reconstructed real-world head-on crashes. The effectiveness of the H-CAAS in reducing the number of two-vehicle Same Trafficway, Opposite Direction crashes (including non-H-CAAS technology relevant crashes) and fatalities if the H-CAAS were installed on one of the crash involved vehicles were estimated based on simulation results. The overall benefits of the H-CAAS, in terms of reduction in number of crashes and fatalities, when projected to the US level were also determined. Overall, this ACAT-II program was successful in extending a methodology that can be used to estimate the safety benefits and driver acceptance of frontal crash avoidance and mitigation countermeasures. Language: en

A STUDY OF THE CLOSED-LOOP DIRECTIONAL STABILITY OF VARIOUS COMMERCIAL VEHICLE CONFIGURATIONS

SUMMARY Computer analysis of the closed-loop directional stability of four common commercial vehicle configurations was performed using 1) a disturbance input technique to study low lateral acceleration driving conditions, and 2) a lane-change maneuver for studying system response at elevated lateral acceleration conditions. The results of the disturbance input calculations indicated, that under low lateral acceleration conditions, drivers of different commercial vehicle configurations should be capable of providing adequate control compensation to achieve more or less equal stability margins for most systems. Evaluation of directional stability, based upon the transient lane-change maneuver, indicated systematic reduction in system damping for all vehicles with Increased levels of lateral acceleration. The 5-axle tractor-semitrailer system exhibited the greatest level of directional damping and rollover immunity during the lane-change maneuver. The truck full-trailer was the least damped system while als...