International Journal of Vehicle Systems Modelling and Testing (7 papers in press)
Simulation of a distance estimator for battery electric vehicles
by Chew Kuew Wai, Yong Yew Rong, Stella Morris
Abstract: Battery Electric Vehicles (BEV) are a promising candidate in reducing air pollution and fossil fuel dependencies. It is a growing market for the automobile manufacturers. Although there are many advantages of driving a BEV, it is still not widely accepted in the market owing to the limited driving range. Other than just improving the technologies that drive the vehicle, an additional range estimation system can calm the range anxiety‟ caused by the limited range of BEVs. Merely predicting the range based on the state of charge of the battery, the average driving speed, and the average power consumption is inadequate. This paper proposes a new range estimator, the dynamic range estimator, which also takes into account the driving behaviour, in addition to the slopes of the trip for its energy estimation. The driving behaviour is obtained based on the response to speed error and the time delay between throttle pedal and brake pedal switching. In this way, the driving behaviour is a fixed response for any driving speeds on the same route, thus allowing the energy consumption to be compared for different speeds.
Keywords: Matlab-Simulink; stateflow; distance estimator; battery electric vehicle; control system; vehicle dynamic; vehicle systems modelling; range anxiety; limited driving range; driving behaviour; energy estimation.
Analytical modelling of twist beam axles
by Xiangfan Fang, Kanlun Tan
Abstract: This paper presents an efficient method for concept design of twist beam axles and other similar mechanical systems by using analytical models. A concept of twist beam axles has been idealised as a beam model with extensive parametric variables. With this model many stiffness and kinematic characteristics that are typically required for twist beam axles can be determined analytically and accurately within a few seconds. Compared with the conventional method with numerous CAD and CAE iterations, this new method can substantially reduce the development time, including human resources and computation time. Several axles have been evaluated and verified. The results are well comparable with those of CAE simulations. This very fast and efficient concept development can be coupled with mathematical optimisation algorithms in order to obtain an ideal starting position for further CAD/CAE based product development in detail.
Keywords: vehicle suspension; twist beam axle; concept design; analytical method; analytical modelling.
Integrated vehicle dynamic controls using active rear wheel steering and four wheel braking
by Jeonghoon Song
Abstract: This paper describes and compares two Integrated Dynamic Controller systems (IDCs; IDCB and IDCR) and one Active Rear wheel Steering system (ARS), developed to stabilise lateral dynamics and maintain steerability on a slippery road. The IDCs make use of a brake system and a rear steering system. A fuzzy logic control method and a sliding mode control method were employed to design the three systems. The performance of the ARS and IDCs was tested under a variety of road and driving conditions. The results show that ARS and IDCs systems tracked the reference yaw rate under all tested conditions. The two IDCs reduced the body slip angle also. When a vehicle ran on a split- road and brake input was applied, IDCB and IDCR virtually eliminated the lateral dynamics. These results indicate that the two IDCs enhanced lateral stability and preserved steerability.
Keywords: active rear wheel steer; fuzzy logic control; integrated dynamics control; sliding mode control; yaw rate; body slip angle; lateral stability; steerability.
E-bikes for steep roads: mid-drive and hub-drive motor efficiency Comparison
by Ivan Arango, Andres Godoy, Carlos Lopez
Abstract: Power input, speed, and efficiency concern people when selecting a transportation means. This study compares multiple e-bikes configurations and presents scientific criteria to choose the one that fits best non-trained cyclists, who want to use e-bikes for everyday transportation in cities with steep roads, assuring that the cyclist takes effective part of the power input. Power development, speeds, energy consumption and efficiency result from a computational model and experimental data. Configurations vary in motor placement, assistance level, cyclist cadence, wheel type and transmission sets. Results indicate that the motor's placement is the most determining factor in the efficiency of the whole system. Placing the motor in the bottom bracket allows both the cyclist and the motor to range in the most efficient rpm. As efficiency for the mid-drive motor is higher than for the hub-drive motor, energy consumption in the hub-drive motor is 18% higher.
Keywords: E-bikes; efficiency test; energy consumption; power development model; electric motor dynamics.
Performance test and analysis of key components of pure electric vehicles
by Wanyou Huang, Guangcan Wang, Mingjin Yu
Abstract: Tests are performed in this article to analyse the lithium iron phosphate (LiFePO4) battery performance and drive motor system performance, so as to give a sufficient understanding of performance characteristics of key components of pure electric vehicles (EV). The EV powertrain system performance test bed is applied for the tests. Applying a LiFePO4 battery (192 V/100 Ah) as the research object, a calculation method is raised for battery charging/discharging efficiency. Tests are performed to analyse the influence of battery temperature on terminal voltage, as well as the influence of battery SOC and charging/discharging current on the battery efficiency. Applying an AC asynchronous motor (rated power 32 kW) as the research object, tests are performed to analyze the influence of battery voltage on the performance of motor system, the efficiency characteristics of drive motor within the high-speed field weakening area, and the efficiency characteristics of drive motor in normal working conditions. Through the tests and analysis for the performance of EV battery and motor, it can provide guidance for the matching of EV powertrain system, and gives a basis for development of high-efficient EV control strategies.
Keywords: pure electric vehicles; performance test and analysis; battery; drive motor system.
A design methodology for space frame through parametric study of torsional stiffness
by Abdelrahman Youssef, Mohamed Elhaddad, Mohammed Anany, Yehia Eldrainy
Abstract: Torsional stiffness is a priority in chassis design as it greatly affects its dynamics. According to the literature survey done in this research, the design methodology of tubular space frame was not performed explicitly, so there is a great need to fill this gap. Therefore, this research aims to develop a methodology for designing a tubular space frame for vehicles and other applications. A finite element model was made to evaluate the torsional stiffness of the vehicle frame, then the model results were validated with experimental data obtained from a previous experiment. A parametric study was conducted using this model to investigate the impact of varying the tube cross-section, length ratio, triangulation, intermediate sections and materials on both frame stiffness and frame stiffness to weight ratio. From this study, several guidelines for designing a tubular space frame were concluded, and a design methodology for tubular space frame was deduced.
Keywords: parametric study; space frame stiffness; torsional stiffness; finite element method; finite element analysis; frame optimisation; chassis design.
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.