International Journal of Vehicle Design (13 papers in press)
Comparison of dual and single clutch transmission based on global transport application mission profiles
by Pär Pettersson, Sixten Berglund, Henrik Ryberg, Gunnar Karlsson, Lennart Brusved, Johan Bjernetun, Bengt Jacobson
Abstract: Global Transport Application (GTA) is a common language used to define transport missions for development, sales and aftermarket processes. To achieve a light weight and low-cost powershifting transmission for the targeted heavy vehicle applications, GTA was used in the development of the I-Shift Dual Clutch (I-Shift DC). Using a well-defined transport mission enables relevant modelling and simulation for performance assessment. This paper outlines the methods and shows some examples of technical implications. Firstly, the results from real world measurements in one specific scenario are presented. This shows the difference between a single clutch (SC) and a dual clutch (DC) transmission for heavy-duty vehicles. Secondly, a full vehicle simulation model is built to extend the results to longer transport missions. The measurement results are used to parametrise and calibrate the model. Finally, the calibrated model is used to evaluate the performance in detail by using GTA to select appropriate transport missions for simulation.
Keywords: commercial vehicles; dual clutch transmission; transport mission; powertrain optimisation; global transport application; I-Shift DC.
Optimal design of power-split hybrid tracked vehicles using two planetary gears
by Zhaobo Qin, Yugong Luo, Ziheng Pan, Keqiang Li, Huei Peng
Abstract: Power-split hybrid powertrains have been thus far successfully used for production passenger cars and SUVs but not for tracked vehicles. For example, track-type dozer (TTD) models available on the market tend to use series hybrid powertrains, which frequently require a separate steering mechanism, resulting in lower operating efficiency and the need for large space arrangements. Looking to the future, power-split hybrid technologies have high potential for tracked vehicles to circumvent the limitation. This paper proposes a design process for multi-mode power-split powertrains for TTDs. The powertrain consists of one engine, two motors, and two outputs connected independently to the left and right tracks. This powertrain is designed to achieve separate control of the two sides of the tracks to enable skid steering. In addition, multi-mode ensures that the powertrain can realize central steering and driving backwards using the engine power. To systematically search for all possible designs with two planetary gears, an optimal methodology is proposed. By establishing two characteristic matrices, an automated modeling process is proposed to obtain the dynamic equations quickly and efficiently. A near-optimal energy management strategy call PEARs+ is used to achieve near-optimal fuel economy. The approach successfully identifies two designs that achieve better overall performance compared with the benchmark.
Keywords: hybrid tracked vehicles; power-split hybrid vehicles; optimal design.
Trajectory tracking control of four-wheel steering under high speed emergency obstacle avoidance
by Runqiao Liu, Minxiang Wei, Wanzhong Zhao
Abstract: In order to solve the problem of trajectory tracking for 4WS autonomous vehicles under high speed emergency obstacle avoidance, an improved trajectory tracking controller combined four-wheel steering (4WS) feed-forward control and linear quadratic regulator (LQR) feed-back control is proposed. First, a polynomial obstacle avoidance trajectory of small radius and sharp curve is established and its several variables are analysed. Second, in order to make actual yaw rate follow a steady-state value based on the reference model, the steering gain of the improved 4WS feed-forward control can change with steering angular frequency and vehicle speed. Third, combined with the LQR feed-back control, the deviations between actual lateral displacement and desired lateral displacement are controlled under 0.05 m. Finally, CarSim
Keywords: 4WS autonomous vehicle; emergency obstacle avoidance; steering angular frequency; linear quadratic regulator; trajectory tracking.
Re-optimisation of occupant restraint system for Chinese statures by reducing airbag inflator power
by Yuan Huang, Yi Huang, Peijun Ji, Qing Zhou
Abstract: The current design of automotive occupant restraint systems is only optimised for protecting some specific occupant statures to best meet requirements of crash safety regulations and consumer rating tests. This paper studies whether occupant restraint systems designed for specific statures can protect occupants with other statures. An occupant restraint system was first optimised to achieve satisfactory protection for US 50th percentile male dummy and US 5th percentile female dummy. Such a restraint system can provide adequate protection to Chinese 50th percentile male dummy, but not Chinese 5th percentile female dummy. Then through a re-optimisation design, it has been demonstrated that, using an airbag inflator with lower mass flow-rate, a restraint system originally optimised for US body sizes can be modified into a restraint system for protection of Chinese body sizes.
Keywords: occupant restraint system; driver-side; frontal collision; US population; Chinese population; airbag inflator power.
Development and validation of a dynamic thermal model of a minibus using TRNSYS
by Daniela C. Vásconez-Nunez, José Gonzálvez-Maciá, José Miguel Corberán, Jorge Payá
Abstract: This paper presents a dynamic thermal model of a vehicle including two thermal zones, one for the front region (driver) and one for the back (passengers). The model, developed in TRNSYS, is able to predict the cabins thermal behaviour under variable ambient temperatures and solar radiation. A minibus was used to validate the model using experimental data for ambient temperature, solar radiation and the indoor temperature of a minibus parked both inside and outside a garage in Torino (Italy). The proposed model accurately reproduces the warm-up and cool-down of the cabin. In addition, the model has been used to calculate the cooling load of the cabin during a summer day, and to quantify the thermal loads under variable ambient conditions. In future work, the model will be used to predict the dynamic performance of the air conditioning system in an urban driving cycle and to optimise the compressor control strategy.
Keywords: automotive; dynamic thermal model; TRNSYS; experimental validation; vehicle air conditioning.
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.
Optimization 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.
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.