International Journal of Vehicle Systems Modelling and Testing (9 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.
Truck tyre-terrain interaction modelling and testing: literature survey
by Zeinab El-Sayegh, Moustafa El-Gindy, Inge Johansson, Fredrik Öijer
Abstract: The interaction between tyre and terrain is the primary factor affecting the efficiency of the ride. The terrain on which the vehicle operates can range between dry or wet road to soil or clayey, depending on the vehicle application whether it is off-road or on-road. The terrain properties affect the vehicle ride significantly, and thus it is highly important to investigate this aspect. This paper focuses on studying the tyre-terrain interaction from several aspects. The truck tyres used in this study were previously modelled and validated by previous research. The terrains used are modelled in a virtual performance software Pam-Crash. The terrains include the hard surface (road); soils such as sand and clayey; snow; and water. The tyre-terrain interaction is modelled in Pam-Crash using contact definition, and several parameters are collected. The hydroplaning speed of the tyre is studied under different conditions of inflation pressure, vertical load, and water depth. The rolling resistance over several terrains is computed and compared. The soil mixing/layering concept is presented and investigated. This work is a preliminary step for an expanded investigation that will be applied during this research.
Keywords: truck tyre; tyre-terrain interaction; smoothed-particle hydrodynamics; finite element analysis; soil modelling and calibration; hydroplaning; Matlab/Simulink.
Aerodynamic analysis of an active rear split spoiler for improving lateral stability of high-speed vehicles
by Divya Teja Ayyagari, Yuping He
Abstract: This paper examines an active rear split spoiler designed for improving lateral stability of high-speed vehicles under high lateral acceleration (high-g) scenarios, such as a tight cornering manoeuvre at high speeds. Downforces produced by the spoiler can enhance the lateral stability of the vehicle under a high-g cornering manoeuvre. On the other hand, the spoiler may introduce additional drags on the vehicle. Aerodynamic analysis and wind tunnel testing are conducted to evaluate the dynamic effects of the active spoiler on a high-speed car. The downforce and drag, as well as their relationship are investigated using CFD simulations of the car with the active rear split spoiler at different spoiler angle of attack and at different speeds. Then, the achieved CFD simulation results are compared with the experimental data derived from the wind tunnel on the physical car and the spoiler prototype. The observations and findings achieved from the study may provide valuable guidelines for developing active aerodynamic control systems to increase safety of high-speed vehicles.
Keywords: aerodynamic analysis; CFD simulations; active rear split spoilers; lateral stability; high-speed vehicles.
The effect of swingarm stiffness on motorcycle stability: experimental measurements and numerical simulations
by Luca Taraborrelli, Valerio Favaron, Alberto Doria
Abstract: This paper focuses on the effect of swingarm deformability on motorcycle stability and in particular on the weave mode. Multibody models for the analysis of stability and handling of single track vehicles require a lumped element representation of the deformability of the critical structural elements of the vehicle. The twist axis method is used to identify lumped stiffness and damping elements able to represent bending and torsion deformability of the swingarm. Experimental tests and identification results dealing with two different swingarms are presented. The identified lumped stiffness and damping elements are implemented in a multibody code and some numerical stability analyses are carried out. Calculated results show that swingarm deformability has a small effect on the stability of super sport motorcycles, whereas the stability of the weave mode of enduro motorcycles is affected by swingarm deformability in a specific range of speeds.
Keywords: motorcycle; swingarm; weave; stability; twist axis; identification.
ABS performance evaluation taking braking, stability and steerability into account
by Herman Hamersma, Schalk Els
Abstract: Extensive research on the design and development of antilock brake systems (ABS) has been done in the past. ABS has been developed not to reduce stopping distance, but rather to stop as quickly as possible whilst maintaining some directional stability and steering control during hard braking. There is however not a single, quantifiable, scientific method in which the performance of these ABS control systems can be compared with one another that takes all the important aspects into account. This investigation proposes an evaluation technique that considers the ABS control systems exploitation of the entire friction circle. Five scenarios are investigated and the performances of two ABS algorithms are compared with one another and with a conventional brake system without ABS. The resulting technique is a clear and concise, multi-parameter comparative tool that can be used to critically compare the performance of various brake systems under the same testing conditions.
Keywords: antilock brake systems; ABS performance evaluation; braking simulations; braking tests; friction circle.
Modelling of optimal tyres selection for a certain truck and transport application
by Zuzana Nedelkova, Peter Lindroth, Bengt Jacobson
Abstract: The main aim of the research leading to this paper is to select, for a truck and its transport application, a configuration of the tyres such that the energy losses caused by these are minimised. We show that neither the rolling resistance coefficient (RRC) classes provided by tyre suppliers nor any other nominal values of RRC evaluated for specific operating conditions are sufficient to do the selection of tyres. Therefore, a surrogate model of the RRC is developed. A tyre model based on the RRC model is introduced in this paper. The modularity of the tyre model is demonstrated by coupling it with two different vehicle models and an operating environment model. The usage of the joint vehicle, tyres, and operating environment model is demonstrated by solving a few illustrative instances of the tyre selection problem. The potential savings with respect to energy losses when the selected tyre configurations are used are presented.
Keywords: tyre; vehicle; simulation; modelling; optimisation; road generator.
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.
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.
Special Issue on: Modelling and Optimisation of Kinematics and Kinetics of Off-Road Vehicle Mobility and Performance by Artificial Intelligence
Path-planning in autonomous electric vehicles using nonlinear state estimation and behaviour-based controllers
by N. Muthukumar, G. Saravanakumar, Seshadhri Srinivasan, B. Subathra, K. Ramkumar
Abstract: Autonomous vehicle navigation in an unknown environment is a challenging task. This investigation presents two algorithms for autonomous vehicle navigation in unknown environments with obstacles. Basic building blocks of the path-planning algorithms are the behaviour-based controller and nonlinear state estimator. Measurements from sensors mounted on the vehicle are used as the input to the state estimator, whereas the estimated position of the vehicle with respect to the obstacle is the output. The estimate is then used to decide the possible control action from a family of behaviour-based controllers for navigating the vehicle. The first path-planning algorithm uses the Extended Kalman Filter (EKF) for estimating the vehicle position using measurements on obstacle position. The second path-planning algorithm uses the Unscented Kalman Filter (UKF) to estimate the vehicle position. Our results indicate that UKF-based path-planning algorithm performs better than the EKF-based algorithm in terms of both performance and fuel consumption. This is indicated by a 9% reduction of the control effort. Path-planning algorithms presented in this investigation can be used to build reliable autonomous vehicle navigation systems.
Keywords: autonomous vehicle, behaviour-based controller, unscented
Kalman filter, extended Kalman filter, path-planning, obstacle avoidance