International Journal of Vehicle Design (9 papers in press)
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.
Vehicle parameters identification with particle swarm optimization for four-wheel independent motor-drive vehicle
by Hongliang Zhou, Zhiyuan Liu, Xingwang Yang, Levent Guvenc
Abstract: An identification method for vehicle dynamics parameters that is based on particle swarm optimisation (PSO) is presented in this paper using a four-wheel independent motor-drive (FWIM) vehicle in the tests. The parameters that are identified are vehicle body mass, yaw moment of inertia, position of centre of gravity, rotational inertia of wheels, tyre stiffness coefficients and some coupling parameters. The identification process consists of two steps. In the first step, wheel rotational inertias are identified using test data of motor torque and wheel speed. In the second step, a nonlinear vehicle dynamics model with vehicle longitudinal and lateral dynamics, wheel dynamics model and tyre characteristics, and the parameters related to vehicle body and the tyre, are identified with the test data of motor torque, accelerations, yaw rate and wheel speeds. The model outputs and test data are compared and the parameters seem to be very accurate. A benchmarking study using a commercially available optimisation routine for the same parameter identification task is carried out, and the PSO method presented here is observed to be much more accurate.
Keywords: parameter identification; particle swarm optimisation; four-wheel independent motor-drive vehicle.
Switched anti-roll control design for hydraulically interconnected suspension system with time delay
by Xiaojian Wu, Bing Zhou, Juhua Huang, Xiang Qiu
Abstract: To improve a vehicle's anti-roll performance while consuming less energy, an active/passive dual-mode switched control method based on a hydraulically interconnected suspension (HIS) is proposed. This method has two key components as follows: modelling the "mechanical-liquid-gas" coupled dynamic system consisting of hydraulic cylinders, a hydraulic pump and accumulators; and robustly controlling a time-delayed system with uncertain model and lag time. In this study, the nonlinear characteristics of the underlying HIS system's execution were considered, and a 4 degree-of-freedom (DOF) roll-plane half-car model was employed for the study. The backstepping nonlinear algorithm was adopted to maintain the body in the desired posture. Subsequently, a modified Smith predictor and a Taylor expansion of lateral acceleration were applied to compensate for the time delay caused by the hydraulic transmission and the hydraulic pump fluid pressure increase, respectively. Finally, a double-lane change simulation with uncertain parameters and lag time was performed. The results indicate that the proposed method is robust in the case of an uncertain control system and can effectively improve the vehicle's anti-roll performance.
Keywords: anti-roll; hydraulically interconnected suspension; switched control; time delay; nonlinear dynamics.
Ergonomic intervention in meeting the challenges of elderly drivers: identifying, prioritising and factorising the ergonomic attributes
by Ashish Dutta, A.K. Bhardwaj, A. P. S. Rathore
Abstract: Better life expectancy has caused a demographic shift worldwide and has led to a considerable rise in the proportion of the seniors, aged above 65. The number of elderly drivers has also increased, who, even with physiological limitations, do not want to give up driving. This has necessitated conscious efforts to be made during the car design stage, to analyse their ergonomic needs and challenges. This research was aimed to identify the major ergonomic concern of the aged drivers that will improve their posture, increase attention and decrease fatigue during driving. Their needs were grouped into ten ergonomic attributes and their opinions about each attribute was captured from a consumer survey. Attributes were prioritised and factor analysis was carried out. Three factors were extracted and were named as musculoskeletal factor, safety factor, and man-machine interface factor. This research provides an understanding of the ergonomic needs of senior drivers, which car manufacturers and automobile designers may consider during the design phase to make a car ergonomically more compatible.
Keywords: automobile design and development; car ergonomics; challenges of elders; elder drivers; ergonomic attributes; factor analysis; factorising attributes; participatory ergonomics; prioritising attributes; vehicle design.
Study of the effect of the load distribution on the SMC engine room bracket of an electric vehicle
by Mingde Ding, Cong Gao, Bo Liu
Abstract: The engine room bracket of an electric vehicle supports the charger assembly, battery and so on. Because of lightweight requirements for electric vehicles, the SMC (Sheet Moulding Compounds) component was developed. The structural design of this composite component is much more complex due to more complex load distribution. This is a new problem for electric vehicles. The objective of this paper is to study the effect of load distribution on the SMC component for improving structural design efficiency and obtaining a rational structure for achieving maximum weight reduction. The topology optimisation was used for conceptual design. Three common load cases were used. Finite element (FE) simulation was conducted for strength, stiffness, and model analysis by two kinds of analysis model, and vibration durability test was carried out to verify the performance of the structure. Finally, the rational analysis model and the structures for different suspension weights were obtained. This research can be very useful for the development of this kind of composite component.
Keywords: load distribution; SMC; engine room bracket; structure design; electric vehicle.
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.