International Journal of Vehicle Systems Modelling and Testing (23 papers in press)

Regular Issues

• 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;.
  
  
• 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.
  
  
• 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.
  
  
• Scale simulation of battery performance for electric vehicles  
  by Carlos Armenta-Deu, Juan Pedro Armenta-Deu Carriquiry 
  Abstract: This work simulates the performance of lithium batteries for electric vehicles under different charge and discharge rates. The simulation is based on scale factors for power, voltage and current, reproducing the real operation conditions of an electric vehicle at the model scale. Most current driving modes have been analysed corresponding to discharge rates from 0.1 to 0.37 C. The simulation has also been applied to determine charging time using charge power in real conditions, from 6.1 kW to 18.3 kW (0.1 to 0.3 C). Driving conditions are obtained using equations for vehicle motion including all forces. Tests have been run under two configurations, continuous and alternate current circuits, to reproduce the two types of engine that electric vehicles use. The simulation shows very good agreement in charge and discharge processes, with an average deviation of 3% related to real conditions, and 1.6% between them, which proves the validity of the simulation process.
  Keywords: electric vehicle battery performance simulation; charge and discharge time prediction.
  
  
• Research on vehicle safe speed based on real-time ramp information  
  by Chang Lv, Shuo Liu, Peng Liu, Qiong-qiong Liu, Jin Yan, Si-da Zhu, Xiao-ming Hu, Jun Ni, Jiang Chang 
  Abstract: The influence of longitudinal gradient is ignored in the ramp safe speed control of tank trucks. To solve this problem, taking CLW9390GYQA tank truck as an example, the image recognition technology is used to obtain the ramp curvature radius, transverse gradient and longitudinal gradient at one time. The model is used to calculate the safe speed, and the weight of the impact of the three ramp geometric parameters on the safe speed is calculated. Considering the influence of the longitudinal gradient, the ramp safety speed model is built by combining other ramp geometric parameters and vehicle parameters, and the safe speed is calculated in real time. Compared with the calculation result without considering longitudinal gradient, the results show that the safe speed model considering longitudinal gradient is more in line with the actual working condition of the tank truck, and the result is more accurate. The results are also applied to other vehicles and curves with universal characteristics, and provide a basis for intelligent vehicle speed control.
  Keywords: tank truck; ramp; safe speed; image recognition; transverse gradient; longitudinal gradient.
  
  
• Investigation of various passive steering modes for a multi-wheeled combat vehicle  
  by Moataz Ahmed, Mohamed Omar, Mustafa El-Gindy 
  Abstract: This paper investigates the manoeuverability of a multi-wheeled combat vehicle using various steering modes. Three steering modes are developed and evaluated against the conventional vehicle steering system (front steering). The first steering mode uses a parallel steering of all wheels (crab steering). The second mode exploits the steering of the front and the rear fourth axle with a fixed third axle, while the third mode uses the steering of all wheels (counter steering) to satisfy Ackermann steering condition. The manoeuvrability of the vehicle is assessed at low speed through curb-to-curb, minimum road width, and slalom manoeuvres. Moreover, the vehicle performance is assessed at high speed through a slalom manoeuvre. The results show the limitations and advantages of each steering mode and based on the obtained results, and suggestions have been made to recommend which steering mode should be employed to exploit the best performance at different driving conditions.
  Keywords: counter steering; crab steering; passive steering; steering limitations; multi-wheeled vehicles; combat vehicles.
  
  
• A missing link between fidelity and realism: an experts assessment of an advanced motion-based driving simulator  
  by Miguel Luzuriaga, Stefanie Trunzer, Bernhard Schick 
  Abstract: A major concern about advanced motion-based simulators is their level of fidelity i.e., how close the motion sensation in a simulator is to the one perceived in a real vehicle. In this study, we collect the assessment from an exceptional sample (n = 33) of automotive industry experts, who were asked to evaluate the fidelity in terms of steering, braking and speed. Given the subjective nature of our measure, we propose a censored-data Tobit regression model that accounts for this issue, thus providing more accurate estimations. Our results show that, on average, experts evaluated the steering actions close to the maximum level of fidelity. However, braking and speed were evaluated lower in realism, and in fact both diminished the overall fidelity judgement by up to 50%. Moreover, coefficients indicate that steering contributes more to the judgement of fidelity than braking and speed actions. Heterogeneity in the experts responses and general implications are discussed.
  Keywords: driving simulator; fidelity; real-world driving; motion-based simulator; validity; subjective driving measures.
  
  
• Feedback linearisation and disturbance observer based path following control for autonomous ground vehicle  
  by Pengpeng Feng, Jianwu Zhang, Tongli Lu 
  Abstract: In this paper, a feedback linearisation and nonlinear disturbance observer based controller is proposed for the path following of an autonomous ground vehicle. The path following is realised through the tracking of the designed yaw rate and lateral velocity generated by a upper layer controller according to the path information. A feedback linearisation controller is designed considering the nonlinearity in the vehicle model. Then the disturbance caused by external disturbance and tyre model error is estimated by a nonlinear disturbance observer, and the corresponding compensation is added into the control input to improve the performance of the controller in disturbance rejection. The stability of the comprehensive system is proved using Lyapunov method. Simulations and comparisons performed in a Carsim-Simulink joint platform verify the effectiveness of the present controller.
  Keywords: autonomous ground vehicle; path following; feedback linearisation; nonlinear disturbance observer; robust compensation.
  
  
• A smart procedure for data analysis relative to a vehicle 'coast-down' test  
  by Salvatore Lomartire, Nicola Ivan Giannoccaro, Antonio Toma 
  Abstract: This paper introduces an innovative algorithm to automate the phases of collecting and analysing the data related to a 'coast-down' test. It was possible to achieve this goal thanks to a collaboration between the University of Salento and a private company (Nard
  Keywords: lean testing; coast-down test; vehicle testing standards; post-processing algorithms; statistical analysis; routines; split; interface; SAE standards for vehicle testing; EN standards for vehicle testing.
  
  
• An experimental inverse and direct kinematics analysis of multi-axial simulation table  
  by Deniz Sönmez 
  Abstract: This paper presents the inverse and direct kinematics analysis and experimental study of a parallel manipulator of Multi-Axial Simulation Table (MAST). The numerical simulation was used to predict the workspace analysis and path planning hydraulic cylinder advancement and the workspace of the centre of MAST. Following the numerical simulations, the results were compared with experimental measurements. The results indicate that the numerical and 3D CAD kinematic simulation results show good compatibility with experimental measurements obtained from MAST.
  Keywords: 6-6 Stewart platforms; multi-axial simulation table; inverse and direct kinematics; Jacobian analysis; position analysis.
  
  
• 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.
  DOI: 10.1504/IJVSMT.2016.10000460