International Journal of Vehicle Systems Modelling and Testing (24 papers in press)
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.
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.
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.
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.
Study of hybrid electric vehicle energy-saving control based on a multi-agent system
by Limin Niu, Quanquan Zhang, Fentian Zhu, Jianmei Lv, Hongyuan Yang
Abstract: In order to reduce the fuel consumption of hybrid electric vehicles (HEV), a multi-agent energy-saving control method is proposed. A subsystem agent model of the engine, motor, battery and other powertrain components is established, meanwhile, the powertrain coordinated control framework based on multi-agent system is built. A multi-objective optimisation algorithm of power distribution for minimum global energy cost combined with the minimum equivalent fuel consumption (ECMS) is proposed. All agents optimise their operating efficiency to limit the request torque, and the control of HEV powertrain is coordinated by the interaction between different agents about compensation torque information. The hardware in the loop simulation based on D2P (From Development to Production) system of the powertrain multi-agent system is verified. Simulation and bench test results show that the HEV powertrain multi-agent coordinated control algorithm can distribute the power according to different driving cycles adaptively, and the HEV fuel economy is improved effectively.
Keywords: energy-saving control; multi-agent system; powertrain; hybrid electric vehicle.
Kinematics and compliance analysis using a 14 DOF virtual vehicle model: developing a software for simulation and post-processing
by Cádmo Dias, Janes Landre Jr
Abstract: This paper aims to develop software to analyse the influence of the variation of vehicle suspension angles. To do so, a model with 14 degrees of freedom was integrated with a graphical user interface that allows the user to define some parameters of the suspension and the environment. At the end of the work, it was possible to observe that the behaviour of caster bump for vehicles with different caster values is the same. Another conclusion that was already expected and validated the model and the software for this type of analysis is that when the left wheel of a suspension is excited, the load passed to the right side will be much greater if the suspension is dependent than if it is independent. The third and final analysis showed that the MacPherson strut has better responses than the double wishbone suspension when it comes to minimising bump effects.
Keywords: software development; automotive engineering; vehicle dynamics; virtual simulation; virtual vehicle models.
Research on the shift rule of two-speed transmission in a pure electric van
by Long Haiyang, Wang ZhiTao, Wang Jiajun, Li Yongpo, Hui Xuewen, Tan Senqi
Abstract: To balance the dynamic and economic performance of pure electric vehicles, an optimal shift schedule is proposed in this paper for a pure electric van equipped with a two-speed gearbox. The driving motor parameters are calculated based on the vehicle dynamic requirements, and the driving motor characteristic curve is used to establish the optimal shift schedule. To analyse the dynamics of the whole vehicle, the maximum acceleration method is adopted and the relationship between acceleration and speed under different throttle opening degrees is obtained, thus the optimal dynamic shift point is determined. To generate motor efficiency MAP offline, the law of economic shift is obtained using table lookup, thus the optimum economic shift point is determined. The comprehensive dynamic and economic shift schedule is obtained, which considers both dynamic and economic factors. Dynamic and economic simulation verification is performed in MATLAB Simulink, the results show that the integrated shift schedule can meet the dynamic and economic requirements of electric vehicles, and provide a theoretical reference for the formulation of the shift schedule of electric vehicles.
Keywords: pure electric vehicle; dynamic shifting schedule; economical shift schedule; comprehensive shift schedule.
Research on power transmission optimisation of dual motor coupling drive for pure electric car based on genetic algorithm
by Qingyong Zhang, Xingjian Wu, Yiqing Yuan, Saiyun Xu, Zhenfei Lu
Abstract: Based on a pure electric vehicle, we have adopted a new dual motor coupling drive system to realise a smooth switch between the single motor and dual motor modes, without experiencing power interruption, and a switch between dual motor and single motor modes without experiencing power interruption and with minimum impact. Also, the structural characteristics and working mode are analysed, and the parameter matching and control strategy of the new power system is studied. Taking the 100 km power consumption as the optimisation goal, a non-dominated sequencing genetic algorithm (NSGA-II) with elite strategy is adopted to optimise the coupling drive system. The results of the experiment show that the control strategy of the dual motor multi-mode drive system improves the vehicle economy by 12%.
Keywords: control strategy of dual motor coupling drive system; parameter optimisation; CRUISE; NSGA-II.
Control system for determining real driving range in electric vehicles
by Carlos Armenta-Deu, Erwan Cattin
Abstract: The main goal of this project is the design of a control system to determine real energy consumption in electric vehicles, thus to calculate the remaining driving distance. The control system uses specific developed software that takes into account real driving conditions. Data for the software calculation are taken either from a database or from online operating driving conditions. the system is adaptive, thus valid for all electric vehicles, driving conditions, way of driving and type of the road. The system also includes specific hardware to calculate parameter values for the input simulation. The theoretical approach has been correlated to experimental tests within 96% accuracy, thus proving the validity of the proposed method. The new protocol represents a useful tool to determine not only the driving range of electric vehicles, but also the remaining driving distance.
Keywords: electric vehicles; control system design; software design; electronic devices; energy consumption; driving range.
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.