International Journal of Vehicle Systems Modelling and Testing (21 papers in press)
Comparing the calibration methods for intelligent driver model using Beijing data
by Md. Mijanoor Rahman, Mohd. Tahir Ismail, Majid Khan Majahar Ali
Abstract: Safe and comfortable journeys in the traffic systems greatly depend on the drivers behaviour. The Car Following Model (CFM) describes the drivers behaviour by following the path of the preceding driver in a traffic flow. The Intelligent Driver Model (IDM) is the most popular CFM for safe and comfortable journeys. This research compares the calibrated methods with each other for Beijing data by using Genetic Algorithm (GA), Sequential Quadratic Programming (SQP) and Simultaneous Perturbation Stochastic Approximation (SPSA). Findings reveal that the IDM simulation parameters, such as maximum acceleration, maximum deceleration, desired speed, minimum headway and minimum jam distance, differ from the IDM calibration parameters by -66.21%, -36.57%, -44.98%, -98.77%, and -9.76%, respectively, for SPSA. Findings also show that the negative percentage values represent the decrease from the IDM simulation parameters, and the positive percentage values represent the increase from the same parameters. The comparison results show that the IDM calibration parameters are more precise with SPSA than GA and SQP for safe and comfortable journeys.
Keywords: car-following; calibration; vehicle dynamics; intelligent driver model.
Vehicle dynamics: experimental analysis of sedan and sport utility vehicle
by Thiago Antonio Fiorentin, Maikol Funk Drechsler
Abstract: Sport utility vehicles (SUVs) have off-road features such as superior ground clearance, a high driving position, and towing capability, which have increased sales in emerging markets. However, their high centres of gravity (CGs) can reduce the ease of handling, safety, and comfort of this type of vehicle. Despite this consideration, the comfort and handling of SUVs as compared with other classes of vehicles has not been explored in the literature. Hence, in this study, we compared two kinds of vehicles, the SUV and the sedan, and analysed them with respect to static construction parameters such as mass, CG, and suspension characteristics. We then performed a second evaluation by measuring their vertical accelerations and rotation movements. The dynamic tests were divided into three manoeuvres to enable the separate evaluation of the vertical acceleration, roll, and pitch of the vehicles. Based on our results, we can conclude that the behaviour of the SUV is similar to that of the medium sedan, but we highlight the differences in their CG heights and damping ratios. The lower damping ratio available in the SUV suspension brings greater vertical acceleration and pitch movement. The higher CG height of the SUV shows no significant influence, owing to the low speeds used in these tests. However, at high speeds, the higher CG can change the handling of the SUV.
Keywords: sport utility vehicle; vehicle handling; vehicle comfort; acceleration.
Hydropneumatic semi-active suspension system with continuously variable damping
by Andre Gerhard Vosloo, Pieter Schalk Els
Abstract: A hydropneumatic semi-active suspension system for an off-road vehicle, which can switch between two discrete damping characteristics as well as two discrete spring characteristics, has been successfully developed and implemented previously. This paper investigates the feasibility of expanding the concept to include four discrete spring characteristics as well as continuously variable damping by controlling two proportional solenoid valves, which can variably restrict flow paths to two accumulators. Spring, damping and response time characteristics are determined experimentally, modelled mathematically and validated with experimental measurements. The model incorporates an iterative solver to determine the flow rate through each valve and the change in the accumulator volumes. The accumulator model uses real gas theory, while also taking compressibility of the oil and heat transfer into account. Damping is calculated by a velocity and solenoid current dependant curve-fit model, parameterised from experimental data.
Keywords: semi-active suspension; hydropneumatic; continuously variable damping; accumulator model; flow split; real gas model.
Development and validation of a real-time capable vehicle dynamics simulation environment for road and test bench applications
by Alexander Ahlert, Alexander Fridrich, Werner Krantz, Jens Neubeck
Abstract: Holistic, real-time capable models, which are able to describe the overall 3D vehicle dynamics and nonlinear wheel suspension behaviour, are necessary for different applications, such as control system design and HIL test system operation. In this paper, a vehicle dynamics modelling approach is presented together with a methodology to derive the equations of motion and adapt them to special applications such as simulating a vehicle on a test bench. With the presented methodology and by using symbolic computation, the equations are obtained in analytical form with a minimal set of ordinary differential equations. The equations can be easily manipulated, simplified and evaluated according to the given task. This is especially valuable for overall vehicle test benches, wherefore the equations are needed for model-based control design and parameter identification. To prove the validity of the simulation environment, the resulting vehicle model for road applications is compared with commercial, state of the art vehicle dynamics simulation tools.
Keywords: nonlinear multibody vehicle model; real-time simulation; modeling and simulation methodology; multi-purpose modelling; LEICHT wheel suspension;.
Active stabilisation of a car-trailer system by means of torque vectoring
by Michele Vignati, Sidharth Dave, Federico Cheli
Abstract: The addition of a trailer to a vehicle introduces significant changes to its dynamic behaviour. Therefore, the response of the vehicle to driver inputs and external excitation differ and are in turn functions of the parameters of the system. The lateral response of the system is of significant interest as unfavourable conditions may lead to instability in the system. The instability introduced may cause the vehicle to stray from the intended path, and in extreme situations may even cause the vehicle to topple over. This instability may be introduced by means of manoeuvres performed by the driver, such as a lane change, or may even be triggered by external factors such as lateral forces arising because of wind. This phenomenon has been studied in-depth, and numerous active systems have been proposed. However, the systems in use exploit brake distribution in the wheels of the vehicle. Electric vehicles with independent motors provide the opportunity of achieving the same through torque vectoring. This paper proposes a feedback-loop control system as an active driver assistance system that enables stabilisation of the system by means of torque vectoring for an independent motor two-wheel drive electric vehicle.
Keywords: vehicle dynamics; control system; vehicle-trailer system; torque vectoring.
Design and testing of a braking control logic for an independently driven electric wheel
by Michele Vignati, Gabriele Canonico, Angelo Omid Salustri, Edoardo Sabbioni, Davide Tarsitano
Abstract: Anti-lock braking control strategies have the aim of avoiding the wheel locking condition, in order to reduce the stopping distance and preserve the handling of the vehicle during the braking manoeuvres. Furthermore, the spread of electric vehicles offers the possibility of adopting new powertrain layouts. Among those, the most interesting is represented by vehicles with independently driven wheels, i.e. one motor per wheel. This paper proposes a braking control logic particularly intended for independently driven electric wheels, in which the electric motor brakes the wheel and handles the wheel dynamics to avoid locking in braking. The control strategy is based on the estimation of the longitudinal force exchanged between the tyre and the road made possible by the motor torque estimation. The knowledge of the braking force allows to improve the braking performance with respect to conventional acceleration-based strategies. The effectiveness of this strategy has been verified both in numerical simulation with a full car vehicle model and in a dedicated test-bench that reproduces the quarter car longitudinal dynamics.
Keywords: active braking; anti-slip control system; electric motors.
Tyre inflation pressure effects on the transient handling performance of a multipurpose protected vehicle.
by Manuel Tentarelli, Alessio Pizzi
Abstract: One of the main requirements for military vehicles is the capability to move over all types of terrain. For this purpose, many military vehicles allow the driver to change tyre inflation pressure to improve the mobility over soft soils. Although various studies have investigated the effect of the inflation pressure on the interaction between tyre and soil, to date there has not been an adequate analysis on the effects on lateral vehicle dynamics on the road. A Multipurpose Protected Vehicle (MPV) was instrumented and tested with a campaign of sweep steer tests at different tyre inflation pressures; experimental data were analysed in order to evaluate modifications on lateral handling performance. Although our tests did not show any compromise in directional stability, MPV dynamics on the road were found to be globally degraded by reducing tyre inflation pressure.
Keywords: military vehicles; multipurpose protected vehicles; vehicle dynamics; tyre inflation pressure; transient handling performance.
Rear wing spoiler effects on vehicle stability and aerodynamic performance
by Hossam Ragheb, Moustafa El-Gindy
Abstract: Nowadays, it is useful to understand the aerodynamic effects of the rear vehicle spoiler because of financial protection as well as environmental issues. The rear spoiler plays a major role in vehicle aerodynamics, improving agility, driving stability, handling, fuel consumption, acceleration and braking by optimal angle, size and shape to achieve the best performance of the vehicle. In the last decade, substantial efforts have been invested in the restrictions of modern wind tunnel tests and prompted advances in computer technology to research vehicle aerodynamics computationally. This paper uses commercial fluid dynamic software ANSYS FLUENT
Keywords: aerodynamics; CFD; spoiler; lift coefficient; drag coefficient.
Research on speed estimation of hub-motor vehicle based on multi-sensor information fusion
by Mingyue Zhang, Xiaobin Fan, Jing Gan
Abstract: Accurate acquisition of the longitudinal and lateral velocity of a vehicle plays an important role in the modern automobile control system. In this paper, the vehicle speed test system is composed of multiple sensors, data acquisition board (NI cDAQ9137) and LabView software. The real-time acquisition of front-wheel angle, wheel speed, longitudinal acceleration, lateral acceleration, and yaw velocity of the hub-motor vehicle is completed by using the speed measuring system. Based on the real road test results, the vehicle speed estimation is obtained by Kalman filter technology and compared with the reference vehicle dynamics model. The comparison results show that the vehicle speed estimation has high accuracy and can meet the requirements of state parameter estimation. The algorithm has the advantages of simple structure, small computation, and easy implementation and can provide more information for the automobile control system.
Keywords: LabVIEW; speed test system; multi-sensor information fusion; speed estimation; Kalman filter.
Theoretical analysis on cornering properties of the mechanical elastic wheel based on a mixed modelling method
by Hongxun Fu, Zifeng Zhang, Xuemeng Liang
Abstract: The mechanical elastic wheel (MEW) is a new type of the non-pneumatic tyre, and its structure is characterised by elastic-rings and hinge-groups to replace the compressed air in the ordinary tyre. In the paper, a mixed modelling method is used to theoretically analyse the steady-state cornering properties of MEW. On the basis of fully considering structure properties and using the basic theory of the brush model, a simplified theoretical model on steady-state cornering properties of MEW is set up. Test data for MEW cornering properties under different vertical load conditions is used to establish the fitting models on half contact length, lateral stiffness and sliding friction coefficient. Based on the steady-state cornering simplified theoretical model and the fitting models, the MEW cornering mixed model is constructed. Comparing simulation results of the theoretical model with test results of the MEW prototype, it is indicated that the MEW cornering mixed model has relatively high prediction accuracy, and can express the steady-state cornering mechanical properties of the MEW. In this paper, details are provided for optimising the MEW structure and improving cornering performance.
Keywords: tyre; security tyre; non-pneumatic tyre; tyre model; steady-state cornering properties; mixed modelling method.
ONCAR: an ontology-based approach for car automation modelling
by Achraf Lyazidi, Salma Mouline
Abstract: Smart cars are vehicles conceived with technological components to ease the driving and the management of the car, and to assist drivers with safety and security, energy saving and comfort services. However, the design of these complex systems involves diverse aspects, including automated behaviours and user's needs and information. A modelling language with a semantic aspect will allow a close modelisation to these requirements. Also, adequate design methods to ensure the effectiveness of such systems are needed. Yet, research to design intelligent vehicles is still limited. In this paper, we aim to offer a complete design method. For that, we define a complete ontology for car automation.
Keywords: car automation; intelligent vehicles; smart cars; ontology.
On aerodynamic drag reduction of road vehicles in platoon
by Wei Gao, Zhaowen Deng, Ying Feng, Yuping He
Abstract: With the spiking of fuel price and stringent requirements on greenhouse gas emissions, we are confronted with a daunting challenge to reduce the aerodynamic drag of road vehicles. When vehicles are travelling in a platoon, the wake of the preceding vehicle can affect the aerodynamic characteristics of the following vehicle. Owing to the interaction of the airflow field of the platoon and the involved vehicles, the drag of each vehicle changes, affecting the vehicle's fuel consumption. In the study, the Motor Industry Research Association (MIRA) car models, namely notchback, fastback, and squareback, are generated. The airflow fields for these isolated single-vehicle models are imitated by CFD simulation. The numerical results of the drag coefficients are compared with wind tunnel test results. The drag coefficient errors between the simulation and the experiment results are less than 6%, implying that the simulation and the wind tunnel tests achieve a good agreement. Using CFD simulation, we explore the effects on the aerodynamic properties of vehicles in platooning due to the factors of non-uniform inter-vehicle separating distance, number of vehicles, and vehicle shape. Insightful findings derived from the study will provide guidelines for the development of intelligent transportation systems and autonomous vehicle platoons.
Keywords: automotive aerodynamics; drag reduction; platoon driving; CFD simulation; impact factors.
Vehicle directional stability control: a literature survey
by Moataz Ahmed, Haoxiang Lang, Moustafa El-Gindy
Abstract: Lateral dynamic control for ground vehicles has been under study for more than three decades to ensure safe driving. Lateral dynamic control is involved in automotive engineering in two areas of study. The first is lateral stability control to enhance the vehicle directional stability when turning. The second is vehicle autonomy to secure stability while tracking at high speed. The state of the art and development in control methodologies of the most notable researches will be reviewed in this paper. Also, a comprehensive review for direct yaw control, active steering, and integrated chassis control systems will be introduced for both two-axle and multi-axle ground vehicles. Finally, the inclusion of lateral dynamic control in autonomous applications will be discussed to show the area of research that is not covered yet and requires more attention to improve both stability and tracking performance of ground vehicles.
Keywords: stability control; vehicle handling; vehicle directional control; direct yaw control; torque vectoring; active steering; path following.
Study on the air flow characteristics of the in-wheel motor drive system of electric vehicles
by Di Tan, Fan Song, Shuaishuai Liu
Abstract: The in-wheel motor is installed in the wheels. The air flow field around the in-wheel motor shows strong time-variance and non-linearity with the wheel rolling, and the flow field characteristics will change with different vehicle velocities. This is quite different from the current empirical estimates, and the accuracy of the analysis results of the thermal characteristics for the in-wheel motor is further affected. Based on this, an electric vehicle driven by a rear-drive in-wheel motor is taken as the research object in this paper. Based on the development of the vehicle model with the critical components, the air flow field characteristics around the in-wheel motor and the influence of vehicle velocity are obtained by analysing the flow field of vehicle at different vehicle velocities. Meanwhile, the heat dissipation coefficient of each surface of the in-wheel motor is calculated at different velocities according to the results of the flow field analysis. The results show that the distribution trend of the flow field on each surface of in-wheel motor is basically the same when the vehicle runs at different velocities. The air flow velocity on each surface of the in-wheel motor increases linearly with the vehicle velocity, and the velocity difference on each surface of the in-wheel motor is larger. The highest and average velocities of each surface are in the order from large to small and left cover, right cover and house. This paper provides a theoretical basis on the research of heat generation and heat dissipation of the in-wheel motor drive system.
Keywords: in-wheel motor drive system; electric vehicle; flow field characteristics; heat dissipation coefficient.
Exploring effects of distribution of mass and driving torque on tyre wear for electric vehicles using simulations
by Vishal Venkatachalam, Erfan Nikyar, Lars Drugge, Jenny Jerrelind
Abstract: Faster tyre wear in electric vehicles is a concern not only for the individual customers who need to buy new sets of tyres earlier, but also from an environmental perspective. Changing certain vehicle parameters can help to reduce the tyre wear. This paper investigates how tyre wear would vary if the centre of gravity position and drivetrain configuration are changed. To calculate tyre wear, a non-linear brush tyre model is used in conjunction with Reyes wear method. To analyse the effect of the parameters on wear, a full vehicle model was constructed and is simulated with the wear model. The simulations performed are constant velocity, straight line acceleration and steady-state cornering events. As expected, the results show that equally distributing the vertical load and the driving torque between the front and rear axles gives the lowest wear rate in most scenarios. Further, an increase in acceleration has the dominating effect on wear followed by torque distribution and lastly mass distribution according to the simulations. Torque and mass distribution have a larger effect on tyre wear during the straight line tests than the cornering tests.
Keywords: tyre wear; electric vehicles; driving torque; mass distribution; brush model.
Effects of international roughness index on vehicle emissions
by Priscilla Oliveira Azevedo, Ernesto Ferreira Nobre Junior, Arielle Arantes
Abstract: Road surface conditions, such as roughness, measured by the International Roughness Index (IRI) play an essential role in improving vehicle fuel economy and greenhouse gas emission reduction. Considering this, the objective of this study was to investigate the relationship between IRI and vehicle emissions, derived from the HDM-4 model. IRI and speed values were collected for every 100 m for two road segments located on Brazil, State of Cear
Keywords: international roughness index; greenhouse gas emissions; HDM-4 model; fuel consumption; tailpipe emissions.
Optimisation of robust and LQR control parameters for discrete car model using genetic algorithm
by Mohammed Kaleemullah, Waleed Faris
Abstract: Active suspension systems are a main feature in modern cars and will be the main stream in the future, and the optimisation of their performance requires many studies about the different types of controller. Robust H-infinity and LQR controllers are used to control the suspension system and to reduce the vibrations in the car and to improve handling. A half-car discrete model is considered in this research to study the effects on passengers due to different road profiles. The weights of the two controllers are obtained using genetic algorithm on a half-car model with two different types of common road disturbance. The design parameters of both the active controllers vary with various road profiles. This proves that particular design parameters in robust and LQR controllers do not have the ability to adapt to the variations in road surface. Furthermore, active controllers significantly improve the performance of the system in all aspects when compared with passive systems.
Keywords: vehicle dynamics; vehicle control; modelling.
Vehicle yaw stability control: literature review
by Mohamed Omar, Moustafa El-Gindy
Abstract: Vehicle dynamics control can be realised through controlling the vehicle in longitudinal, lateral and/or vertical motion. The focal point of this study is vehicle lateral dynamics control, where yaw stability control has a great influence on vehicle handling and stability performance. Vehicle dynamics control is experiencing an ongoing evolution to ensure vehicle safety and ride comfort. Consequently, several research studies have been proposed to improve vehicle lateral dynamics via yaw stability control. Based on these previous studies in the past three decades, this review paper aims to investigate the main fundamental elements of vehicle yaw stability control structure, in terms of the used vehicle models, control objectives, various control systems implemented for active chassis control and control allocation strategies.
Keywords: active chassis control; vehicle dynamics control; direct yaw control; active steering control; integrated chassis control; torque vectoring; differential braking; active front steering; active rear steering.
Remaining energy estimation strategy for lithium-ion battery pack based on RLS-UKF algorithm
by Qiuting Wang, Wei Qi, Duo Xiao
Abstract: This paper focuses on a modelling method and online estimation strategy to estimate the remaining energy of a lithium-ion battery pack. the new estimation method is based on system complexity analysis and it can describe the external characteristics of different temperatures and frequencies for the battery model. The recursive least squares (RLS) algorithm is introduced to update the battery parameters online. The relationship equations between the remaining energy of the battery pack and the state of charge of the single cell is established. Meanwhile, the Unscented Kalman Filtering(UKF) algorithm is used to estimate the remaining energy online. The influences of temperature and charge/discharge ratio is considered. Finally, the inconsistency influence between different cells are analysed. The validity and reliability of our new model and estimation strategy are verified under UDDC experiments. The experimental results are compared under real-time conditions.
Keywords: vehicle system; lithium-ion battery pack; remaining energy; SOC; recursive least squares; UKF; system complexity analysis.
Analysis and comparison of a single-material versus multi-material chassis design for lightweight electric vehicles
by Eftychios Papadokokolakis, Polychronis Spanoudakis, Lefteris Doitsidis, Nikolaos Tsourveloudis
Abstract: In this work we present in detail the design and analysis of a novel multi-material chassis combining different lightweight materials. Our main goal was to achieve a design offering low weight and increased safety factor for lightweight electric vehicles. Structural evaluation of the chassis is accomplished by conducting a series of finite element analyses (FEA), in different loading scenarios. A simple but effective test bench for the experimental validation of simulation results is also presented in detail. A comparative analysis is performed for different chassis designs, evaluating their effects on structural strength, torsional stiffness and natural frequencies. Moreover, a multi-material approach is followed and valuable results are presented, regarding the overall benefits related to weight reduction and structural efficiency, as compared to single material use on chassis design. Our findings indicate 8% weight reduction and 22% higher stiffness to weight ratio in favour of the multi-material use.
Keywords: chassis; lightweight; multi-material; structural analysis; FEA; electric vehicle.
Development of a rolling truck tyre model using an automatic model regeneration algorithm
by Shahram Shokouhfar, Subhash Rakheja, Moustafa El-Gindy
Abstract: A three-dimensional finite element model of a rolling radial-ply truck tyre is developed to predict its vertical and cornering properties at relatively high speeds. The model includes a detailed representation of the tyre complex geometry and multi-layered composite structure including the carcass and belt plies, bead fillers and tread. LS-DYNA, a nonlinear finite element code, is used as the simulation tool. An algorithm is developed for efficient formulation of the model for parametric analyses. The validity of the proposed tyre model is demonstrated by comparing the predicted load-deflection, cornering and free vertical vibration characteristics with the reported experimental data. The simulation results revealed robust behaviour of the tyre model up to rolling speeds of 100 km/h. The verified tyre model is subsequently employed to study the influences of various operating parameters, namely, the inflation pressure, vertical load, rolling speed and road friction on the tyre vertical and cornering properties.
Keywords: rolling truck tyre models; multi-layered tyre structure; vertical tyre properties; cornering properties; parametric studies; finite element method; FEM; LS-DYNA; automatic model regeneration; truck tyres; tyre modelling; radial-ply tyres; carcass plies; belt plies; bead fillers; tyre tread; simulation; rolling speed; load deflection; free vertical vibration; tyre inflation pressure; vertical load; road friction; radial tyres.