International Journal of Vehicle Design (21 papers in press)
The effect of circlip-induced contact pressure on the temperature distribution in multi-disc clutches
by Jianpeng Wu, Biao Ma, Heyan Li, Mingyang Li
Abstract: The phenomenon of non-uniform pressure distribution among multi-disc friction pairs is investigated focusing on the effect produced by the circlip using a theoretical model and a 3D FEM model. A temperature field computational model of the discs is established based on the non-uniform pressure distribution. Sliding experiments are conducted to investigate the influence of the circlip on non-uniform pressure distribution among the discs in the multi-disc clutches, and the temperature simulation results are verified by the experimental results. The obtained results show that the concentrated circlip constraint leads to a non-uniform pressure distribution in both the radial and axial directions, which in turn affects the temperature fields of the discs. Unlike uniform pressure, the non-uniform pressure caused by the concentrated circlip constraint will lead to different temperature fields in different discs. Furthermore, the highest temperature and the maximum radial temperature difference both occur on the disc next to the circlip. Besides, the ratio coefficient of temperatures can effectively represent the pressure transfer coefficient among discs.
Keywords: multi-disc clutches; non-uniform surface pressure; temperature field; concentrated load; experimental study.
Optimisation of a small radial turbine impeller of a turbocharger on a 0.8 L two-cylinder gasoline engine
by Omer Faruk Atac, Jeong-Eui Yun, Taehyun Noh
Abstract: The aim of this study is to optimise the very small turbine impeller of a turbocharger used in a 0.8 L two-cylinder gasoline engine by presenting an additional design parameter (rake angle), that has not been used thus far in traditional design studies, as well as other conventional design parameters. The design points, which are constructed for ten assigned parameters through the Design of Experiment (DOE), are evaluated using the surrogate-based single-objective optimisation technique incorporating three-dimensional Reynolds-average Naver-Stokes (RANS) analyses to maximise the isentropic efficiency. The results show that each of the assigned parameters has a considerable effect on the efficiency; in particular, the rake angle can increase the efficiency up to 2.5% and 2% improvement can be achieved with optimal wrap angle. In addition, optimised parameters for hub and shroud curves can lead to improved flow pattern in the inlet and outlet regions of the blade passage, and hence, the efficiency.
Keywords: turbocharger; optimisation; radial turbine; wrap angle; rake angle; blade angle; CFD; DOE; response surface; meridional plane.
Study on parameters affecting steering feel of column assist electric power steering
by Yijun Li, Taehyun Shim, Dexin Wang, Timothy Offerle
Abstract: In recent years, the electric power assist steering (EPAS) system, because of its fuel efficiency, cost effectiveness, and additional safety and convenience features, has rapidly replaced the conventional hydraulic power assist steering (HPAS) system. However, there is still need for improvement of the steering feel of EPAS systems compared with HPAS systems. In this paper, the steering feel of the EPAS system is studied by investigating the steering feel metrics. We first introduce a comprehensive model of a column-assisted EPAS (C-EPAS) system consisting of the major components in the system. The steering feel of the C-EPAS system is then investigated through simulation of on-centre steering tests based on the proposed mechanical model with basic power assist control strategies. Various factors affecting the steering feel responses are identified. Finally, by using this knowledge, it is shown that on-centre steering feel can be improved by adjusting the proper parameters in the C-EPAS system.
Keywords: electric power steering; steering feel; steering system; vehicle steering systems; steering friction; steering model.
Modelling, validation and characterisation of high-performance suspensions by means of a suspension test rig
by Christoph Zauner, Johannes Edelmann, Manfred Plochl
Abstract: To meet the high demands and expectations on ride comfort and handling, detailed analysis of the vibrational behaviour of advanced suspension systems is required. Therefore, component modelling and testing, as well as full vehicle tests, go hand in hand. The present study addresses possible benefits, when a suspension test rig is available, and how it may be used to better analyse and characterise the vibrational behaviour of particular isolated suspensions. Respective synthetic excitation spectra map the dynamic behaviour of the suspension from full vehicle tests to the suspension test rig. Component models are presented that show a reasonable compromise between modelling and parametrisation effort. By using the suspension test rig it is revealed that frictional effects must be considered when assembling the components of a full suspension model. Two high-performance suspensions have been chosen to propose appropriate analysis methods of their vibrational behaviour. In this way, insight into the modal behaviour is revealed, and vibrational characteristics, which can directly be assigned to the respective suspension, become obvious, which may allow comparison with follow-up similar suspensions. Finally, the suspension models are evaluated with full vehicle tests.
Keywords: suspension characterisation; suspension test rig; ride comfort; vibration analysis; double wishbone suspension; multi-link suspension.
A study of robust design of exhaust manifold for gasket leakage
by Chulho Yang
Abstract: Engine output performance is dependent on how the gas flow of an exhaust manifold is managed. Exhaust manifold design mainly aims for structural sturdiness by maintaining the appropriate stiffness and low operating temperatures. Maintaining appropriate sealing pressures at the gasket is another key issue in exhaust manifold design to resolve emissions, power, and fuel consumption. The proper sealing pressure of a gasket is required in order to maintain engine performance. This paper describes the design factors affecting the behaviour of an exhaust gasket in an internal combustion engine and shows the way of obtaining a robust design of the gasket by using finite element analysis and the Taguchi method. The behaviour of an exhaust manifold gasket is affected by the interaction with bolt load, vibration, and thermal loads. A reliable approach is suggested in order to develop the methodology for improving the gasket sealing pressure of an exhaust manifold by understanding the design factors affecting the sealing pressure losses. It is shown that an adequate sealing pressure distribution along the exhaust manifold ports can be obtained and that a highly efficient, durable sealing gasket joint is possible.
Keywords: exhaust manifold; robust design; Taguchi method; gasket sealing pressure; gasket sealing; finite element analysis.
Collision probability prediction algorithm for cooperative overtaking based on TTC and conflict probability estimation method
by Ke Wang, Zhoubing Xiong
Abstract: This paper focuses on the feasibility and methodology of critical issues of overtaking behaviour using inter-vehicle communication technology. The main innovation of this work is the integration of a collision probability model with the overtaking procedure. In detail, the overtaking process was divided into two successive stages: the approaching stage and the passing stage. In the approaching stage, linear assumption between collision probability and time to collision was proposed to release the computational load. In the passing stage, a conflict probability estimation method is used as the safety quantitative indicator to estimate the collision probability. To support the proposed method, we ran many experiments on synthetic data. The result shows that our method achieves better accuracy especially in the unpredictable nature of the road environment, including the capability of making correct behaviour decisions and avoiding collisions with nearby vehicles, which makes the proposed method sufficient for real-world implementation.
Keywords: collision probability prediction; conflict probability estimation; cooperative overtaking; inter-vehicular communication.
Surface interpolation and procedure used in the generative engineering design of surface-based automotive components
by Jana Gulanová, Miroslav Vereš, Ladislav Gulan
Abstract: This new design and innovation method has become very important in the automotive industry. As in art or architecture previously, generative engineering design has been adopted in mechanical engineering as the name used for this method. A common feature of all these fields is to use new programming environments, scripting capabilities, and feedback loops. The method ranges from simple mechanisms, where the model uses its own output as input, to relatively complex systems incorporating design evaluation routines. This paper focuses on the part of routine used for surface interpolation employing modern CAD software. The individual steps in the generative design method procedure of simple plastic parts are also described. Firstly, schemes and definitions for the generative engineering design of surface-based automotive components are defined. Secondly, the paper deals with the procedure for accurate surface interpolation using 3D scanning of the designers draft. The output is a class B surface of a shaped component appropriate for fitting functional parts to. Finally, the paper describes the procedure of generative design using simple illustrations of plastic shaped parts in CAD software.
Keywords: surface interpolation; cloud of points; generative engineering design; class A surface; class B surface.
Modal analysis and structure optimisation of vehicle seat frame based on mass distribution method
by Zheng Zhang, Dong Ye, Congda Lu, Feng Li, Yi Huang, Huaping Wu, Shaofei Jiang
Abstract: The vehicle seat is not only one of the important parts of vehicle interiors, but also the main component that connects occupants and the car body directly. The vibration characteristics of the vehicle seat severely affect the security and dynamic comfort of drivers/passengers. For this reason, the design and optimisation of the vehicle seat have been become increasingly necessary and attractive. A vehicle seat frame developed in the cooperative company is selected as the research object in this paper. The mode of vehicle seat frame is compared by experimental modal test and finite element analysis in order to verify the correctness of the finite element model of vehicle seat. Then, the influence of mass distribution on the vehicle seat frame modal characteristics is investigated by changing the local mass distribution of the vehicle seat through finite element modelling. By optimising the structure of the vehicle seat frame based on the analysis results, the dynamic characteristics of vehicle seat can be improved and the security and dynamic comfort can be enhanced.
Keywords: vehicle seat; experimental modal test; finite element analysis; mass distribution; structure optimisation.
Relation between power spectral density of road roughness and international roughness index and its application
by Jie Li, Zhenwei Zhang, Xiong Gao, Peide Wang, Jiantong Li
Abstract: To address issues on the relation between the power spectral density (PSD) of road roughness and international roughness index (IRI), a simple method based on stochastic mathematics is used to derive the relation between the IRI and relative vertical velocity of sprung and unsprung masses of a quarter-car vibration system. The relation between the PSD of road roughness and IRI is also derived. Furthermore, two new concepts comprising time and spatial frequency IRI suitable for any form of longitudinal road-profile PSD are proposed. Based on the up-to-date ISO road classification and the proposed concepts, car-based and truck-based road classifications are presented. Compared with IRI, a new index named IRItr is found to be a better index for ranking road roughness from the perspective of the dynamic wheel load of a truck.
Keywords: road roughness; international roughness index; power spectral density; time frequency; spatial frequency; road classification; stochastic mathematics; random vibration; pavement management; vehicle manufacture; frequency response function; Gaussian distribution; dynamic wheel load.
Preliminary evaluation research of a powertrain system with electrically controlled planetary gear
by A. Lechowicz, Andrzej Augustynowicz
Abstract: This paper presents a concept of a simple hybrid system intended for use in a light vehicle. The basic element of the proposed system is an electrically controlled planetary gear, which combines input from a combustion engine and an electric motor. The transmissions combine the power from two sources, a gasoline engine and an electric motor. The proposed hybrid solution is characterised by a simple construction that allows its use in small vehicles. This solution can maximise the performance of combustion engine.
Keywords: energy management; hybrid system; hybrid vehicle powertrain configurations.
Lateral stability control of vehicles based on the calculation and allocation of component forces
by Guang Xia, Xiwen Tang, Yangying Hua, Wuwei Chen
Abstract: A vehicle lateral stability control method for real-time calculation and dynamic allocation of the longitudinal force and yaw moment of vehicle tyres is proposed. The achievable range of the longitudinal force and yaw moment of the tyre are calculated in real time through off-line numerical optimisation and nonlinear programming. The calculated values are then adjusted to within the available range and allocated dynamically. A controller for the slip rate and front wheel slip angle is used to ensure that the tyre friction can trace each component force. The proposed method avoids estimating the lateral force of vehicle rear wheels while ensuring accuracy. The results of simulations and driver-in-loop tests demonstrated that the proposed method can improve the track-holding ability while reducing the influence of a road surface with a low adhesion coefficient on vehicle stability. The method ensures high and dynamic tracking performance and lateral stability.
Keywords: longitudinal force component; yaw torque; calculation and allocation of component forces; lateral stability control.
The vehicle frontal impact safety evaluation and design method based on the coupling effect between crash pulse and restraint system characteristic
by Junyuan Zhang, Danqi Wang, Yang Jin, Linan Wu, Hao Zhou
Abstract: The coupling effect analysis between crash pulse and restraint system characteristics has a great significance to guide structural design and restraint system matching in the safety design of vehicles. This paper presents a new method to evaluate and design stiffness of vehicle structure and restraint system from the perspective of coupling effect, at the preliminary stage of safety design. The equivalent dual-trapezia wave (EDTW) and three-segment stiffness curve (TSSC) are defined as the stiffness of the vehicle structure and the restraint system, respectively. The fast iteration algorithm is established by a simple occupantvehicle model to calculate occupant response database. According to the database analysis, the expressions about three indexes, which can evaluate the crash pulse, restraint system and the coupling effect between them, are derived by the parameters of EDTW and TSSC. Based on the data from NHTSA frontal crash impact tests, the star-estimate map is established to estimate the star rating and achieve the design of EDTW and TSSC. Finally, a safety design example of M6 model is optimised to verify the validity of the proposed method. The results show that the relative risk score of the designed solution decreases by 43.6%. The proposed method can be used in the phase of conceptual design, greatly reducing the calculation amount of CAE analysis and shortening the product development cycle.
Keywords: vehicle impact; coupling; evaluation; equivalent dual-trapezia wave; three-segment stiffness curve.
High dimensional expression of combined approximation model
by Weiping Li, Bei Gu
Abstract: In this paper, a new high dimensional model representation (HDMR), combining TPS, SVR and Kriging (TSK) by weighted combination method based on generalised mean square error (GMSE) is proposed, called TSK-HDMR. TSK-HDMR could not only take advantage of the robustness of the combined approximation model but also reveal the correlation relationships among input variables. The model and the algorithm fundamentally change the exponentially growing computation cost to be polynomial. Numerical examples are given to verify the robustness and modelling efficiency of the modelling method. Compared with the classical high-dimension model techniques, in the application of the modelling of air resistance characteristic of a car, the efficiency and accuracy are improved.
Keywords: GMSE; combined approximation model; robustness; air resistance characteristic of car.
An analytical review on automatic gear shifting in automatic transmission
by Debraj Bhattacharjee, Prabha Bhola, Pranab K. Dan
Abstract: This article presents a literature overview of factors, both internal and extraneous, modelled for improving the quality of gear shifting in an automobile through the development of a robust electronic transmission control unit. Such robustness, designed with considerations of internal and external factors, is essential for safety, fatigue reduction and comfort of driving. As automobiles are becoming more sophisticated, the application of electronics and embedded systems is increasing for different functional control system designs, including the gear-shifting mechanism. Automotive transmission system equipped with electronic or electrohydraulic actuators, controlled by an electronic control unit or a computing system provides clutch-less driving experience to the driver for the shifting above operation. Electronic shift controllers are used for automatic speed and torque control in different driving situations, and reduce the human error in gear selection. Less human error and desired shifting provide safe and comfortable driving. In the development of such a mechatronic controller, it is critical to find a desired robust control strategy in the context of semi-autonomous vehicles.
Keywords: automotive transmission; shift control; shift quality; software-in-loop; electronic transmission control unit; vehicular transmission control.
Finite element analysis of thermal buckling characteristics of automotive 430 dry clutch pressure plate
by Yubing Gong, Wencheng Ge, Yun-Bo Yi
Abstract: The thermal buckling analysis of the automotive dry clutch pressure plate is performed by the finite element method based on the thermal buckling theory. According to the temperature distribution of the pressure plate under the realistic conditions, two typical thermal loads are assumed and applied in the thermal buckling analysis of the pressure plate. The thermal buckling characteristics of the pressure plate, including critical temperature and buckling mode under these two typical thermal loads, are comprehensively investigated. The influence of the temperature distribution along the pressure plate thickness direction on the thermal buckling characteristics of the pressure plate is analysed. The effect of boundary constraints on the thermal buckling modes is further studied. The analysis results show that (1) the temperature distribution on the thickness of the pressure plate has a negligible effect on its thermal buckling characteristics; (2) the boundary condition of the pressure plate has a significant effect on the thermal buckling mode of the pressure plate; and (3) the thermal buckling of the pressure plate occurs more readily in its cooling stage than in the heating stage. Since the critical buckling temperature far exceeds the actual possible temperature of the pressure plate, the thermal buckling in the pressure plate will probably not occur in actual applications. Therefore it is concluded that the concave deformation of automobile dry clutch pressure plate is not induced by the thermal buckling mechanism.
Keywords: automotive dry clutch; temperature distribution; buckling mode; pressure plate；boundary constraints; thermal buckling；critical buckling temperature; finite element method；concave deformation.
Analysis on driving stability of micro-vehicle based on human-seat dynamics system
by Hongyu Shu, Shuang Luo, Zejie Yao
Abstract: To study the influence of dynamics interaction between a driver and a micro-vehicle on the driving stability, the driver was modelled as a rigid body and elastically connected to the vehicle. A 5-DOF (degree of freedom) mathematical model was presented for the driver micro-vehicle system. Afterwards, a vibration test was conducted and a corresponding vibration model was developed for the human-seat system, based on which the biomechanical parameters at human-seat interface were obtained. Eventually, the mathematical model was computed by MATLAB in line with those parameters. Influences of the dynamics interaction on the roll and yaw characteristics of the micro-vehicles were analysed. According to the research results, the dynamics interaction prolongs the response time, increases the overshoot and steady-state value of roll angle, and generates less understeer. With the decrease in curb weight of the micro-vehicles, the influences will be more significant.
Keywords: micro-vehicle; driver; human-seat system; driving stability; stable steering characteristic; numerical analysis; dynamics interaction; biomechanical parameters; roll angle; yaw rate.
Attitude motion control of a vehicle including the active passenger seat system
by Wu Liang, Muhammad Arshad Khan, Edward Youn, Iljoong Youn, Masayoshi Tomizuka
Abstract: This research focuses on improving the attitude motion of a vehicle using active suspension and active seat together. The proposed attitude-tracking controller eliminates the unpleasant lateral and longitudinal forces acting on passengers by tilting the vehicle against the direction of the centrifugal forces created in cornering, braking, and accelerating. In addition to the enhancement of ride comfort, better road-holding capability is also achieved by evenly distributing forces on all wheels. An active seat system is added to the car body in order to accommodate angles larger than the available body angle. A nonlinear model is used to simulate the performance that more resembles the actual system, and the difference between linear and nonlinear models is analysed by comparing the simulation. The simulation results show that using an active passenger seat with the attitude-tracking controller can improve ride comfort more than using attitude-tracking controller alone.
Keywords: attitude motion control; tracking control; ride comfort; handling capability; nonlinear model; active passenger seat.
Special Issue on: Recent Advances in Sensing Technology, Vehicle Control Systems and Tyre Design Considerations for Electric and Autonomous Vehicles
Vehicle longitudinal force estimation using adaptive neural network nonlinear observer
by Mourad Boufadene, Mohammed Belkheiri, Abdelhamid Rabhi, El Hajjaji Ahmed
Abstract: This paper presents an adaptive neural network (ANN) nonlinear observer to estimate the longitudinal tyre forces as well as the lateral speed, which is not measured on standard vehicles. The proposed ANN observer uses the longitudinal speed, yaw rate and the steering angle dynamics of the vehicle as measured states. It is used to estimate the states, and the longitudinal tyre forces, which are unknown dynamics, with high performance. The obtained simulation results show the effectiveness of the proposed neural network nonlinear observer.
Keywords: adaptive observer; adaptive neural network; radial basis function
approximation; nonlinear observer; vehicle force estimation; tyre forces
estimation; longitudinal vehicle force estimation.
Integrated control of AFS and DYC for in-wheel-motor electric vehicles based on operation region division
by Jianjun Hu, Zhihua Hu, Chunyun Fu, Fuqian Nan
Abstract: The integrated chassis control system can improve vehicle handling and stability effectively. This paper proposes an integrated control system based on operation region division of AFS and DYC for in-wheel-motor electric vehicles. The control system adopts a two-layer hierarchical control structure. The decision layer employs a modified sliding mode controller to calculate the required corrective yaw moment, and determines operating regions of the two subsystems based on the driving conditions (road adhesion coefficient, tyre load and wheel slip ratio). The execution layer generates the corrective steer angle and the driving/braking toques for the AFS and DYC subsystems respectively. Simulation results show that on the high-adhesion-coefficient road, the integrated control system appropriately adopts subsystems to improve handling, while attenuating the workload of barking system; on the slippery road, the integrated control system maintains vehicle stability and provides superior control performance to those resulting from the single systems.
Keywords: driving stability; AFS; DYC; yaw rate; hierarchical control; operation region division; lateral tyre force; Magic Formula; sliding mode control.
Pressure control of integrated electro-hydraulic braking system considering driver braking behaviour
by Hao Pan, Xuexun Guo, Xiaofei Pei, Daoyuan Sun
Abstract: This paper proposes a pressure controlling strategy for the Integrated Electro-Hydraulic Braking (IEHB) system when considering driver braking behaviour. Firstly, the representative feature parameters of braking behaviour are extracted from various vehicle data and clustered by manoeuvre characteristics. Seven brake pedal operation training libraries are self-learned adaptively by hidden Markov model for driver braking behaviour recognition. Then, a self-tuning function based on recognition results is proposed to adjust the PWM parameters of the PI controller for the motor and valve. Eventually, the hardware-in-loop results of IEHB system show the accuracy of braking behaviour recognition algorithm, and the feasibility of self-tuning control strategy. In addition, the effectiveness of pressure regulation for the IEHB system is verified.
Keywords: electro-hydraulic braking system; braking behaviour; hidden Markov model; pressure control; self-tuning PI.
Active steering control system for an independent wheel drive electric vehicle
by M.A. Khan, M.F. Aftab, E. Ahmad, Iljoong Youn
Abstract: This research presents an active steering control system (ASCS) for an independent wheel drive electric vehicle (EV). The ASCS will manoeuvre the independently actuated (IA) all-wheel drive (AWD) EV via coordinating the angular velocities of the four wheels plus active front steering (AFS). Owing to the physical and mechanical limitations of the steering input in conventional AFS, the differential speed between left and right wheels of an IA EV is used to generate the additional steering effects. The ASCS is designed using the linear model of the vehicle and is tested in simulations using the nonlinear vehicle model. The proposed ASCS is a combination of forward speed and yaw rate controllers, designed using the robust $H_infty$ control methodology. The effectiveness of the proposed control system is analysed by comparing the performance of an AWD IA EV with ASCS, a rear wheel drive (RWD) IA EV with ASCS, a vehicle with AFS only, and a vehicle with no controller. The simulations results using a high-fidelity vehicle model under different driving conditions and road disturbances, indicates that the proposed system can significantly improve the vehicle performance by tracking the desired yaw rate and speed.
Keywords: differential steering control; active front steering; electric vehicle; four wheel drive; nonlinear vehicle model; steering control; vehicle dynamics; yaw rate tracking.