International Journal of Vehicle Design (61 papers in press)
- Experimental analysi and control development for vehicle rollover prevention
by Corina Sandu, Hegazy Shawky
Abstract: An experimental test rig simulating the whole mechanical steering system was developed. The conventional steering system was replaced by an electric motor connecting the steering wheel and the steering shaft. An electronic control module was proposed, realized, and implemented on this steering system. This module was operated using a control unit and the necessary sensors and actuators through algorithms designed to control the vehicle speed. In the proposed technique, the lateral acceleration was measured and sent instantaneously to the control unit. At a threshold value, a control signal was activated automatically to control the vehicle throttle pedal, decreasing the vehicle speed and locking the steering wheel in the critical direction, thus preventing the steering angle from increasing. The results showed that, controlling the vehicle speed during such a manoeuvre was the main factor in rollover prevention. Controlling the lateral acceleration may prevent the vehicle rollover at critical speeds.
Keywords: vehicle stability, vehicle handling, rollover prevention, experimental rollover, control
- Stochastic modelling of 1-D and 2-D terrain profiles using a polynomial chaos approach
by Lin Li, Corina Sandu
Abstract: One fundamental difficulty in understanding the physics of vehicular off-road traction and in predicting vehicle performance is the variability of the terrain profile. These operating conditions are uniquely defined at a given spatial location and a given time. It is not practically feasible to measure them at a sufficiently large number of points to be able to accurately represent the terrain in models, or to use all the data collected to recreate the terrain profile. This renders traditional analysis tools insufficient when dealing with rough terrain.
In this study, mathematical tools to quantify the impact of uncertainties in the terrain profile on vehicle mobility are developed. A polynomial chaos approach is used to reconstruct one-dimensional (along longitudinal direction) stationary and non-stationary terrain profiles. Also, an efficient mathematical method based on the Karhunen-Loeve expansion and the approach for 1-D stochastic terrain profile is developed to reconstruct two-dimensional (along longitudinal and lateral directions) terrain profiles. The proposed mathematical methods calculate the autocorrelation of terrain profiles, solve eigenvalues and eigenvectors of the autocorrelation function, and obtain the corresponding orthogonal random variables directly. The original terrain profile is reconstructed by Karhunen-Loeve expansions, requesting a small, limited computational effort, without the need to verify the terrain data for Gaussianity, stationary, and linearity, and without the need to choose the order of the expansion and the corresponding fitting coefficient artificially. Promising simulation results based on experimental data are obtained using the proposed methods. The schemes to choose the number of eigenvalues and eigenvectors are discussed. The proposed mathematical methods can be used to simulate the terrain profile for on-road and off-road vehicle dynamics or robotic applications.
Keywords: stochastic terrain profile, Karhunen-Loeve expansion, polynomial chaos, stationary
- Effect of fuel particle magnetization on the overall performance of a four-stroke S.I. engine
by Raed Kafafy, Waleed Faris, Wajdi Ali
Abstract: In this paper, we investigate the effect of fuel particle magnetization on the overall performance of a four-stroke spark ignition engine. To achieve this objective, we have designed a set of experiments using the Mitsubishi 1.5L (4G15) spark ignition engine. Each experiment is performed in two phases; with and without the fuel particle magnetization. The collected data was analyzed to assess the overall performance of the engine at several operating conditions. Our study shows that fuel particle magnetizer can enhance the overall performance of a typical SI engine. However, the enhancement greatly depends on the operating condition of the engine.
Keywords: fuel magnetization; engine performance; fuel economy; spark ignition engine
- Simulation and experimental evaluations on the performance of pneumatically actuated active roll control suspension system for improving vehicle lateral dynamics performance
by Hudha Khisbullah, Zulkiffli Abd. Kadir, Hishamuddin Jamaluddin
Abstract: This paper presents the derivation of a full vehicle model. It consists of ride, handling and tire subsystems to study vehicle dynamics behavior in lateral direction. The full vehicle model is then validated experimentally using an instrumented experimental vehicle based on steering wheel input. Three types of vehicle dynamics test were performed for model validation. These are step steer, slalom and double lane change tests. The validation results show that the behaviors of the model are similar to the real vehicle with acceptable error. An active roll control (ARC) suspension system was developed using the validated full vehicle model to reduce unwanted vehicle motions during steering input maneuvers such as body roll angle, body roll rate, vertical acceleration of the body and body heave. The proposed controller for the ARC system is a combination of PID control with roll moment rejection loop. The results of the study shows that the proposed control structure is able to significantly improve the dynamics performance of the vehicle during step steer, slalom and double lane change maneuvers compared with a passive vehicle system. The additional roll moment rejection loop is found to be able to further improve the performance of the PID ARC system. The effectiveness of the ARC system with the proposed control was also proven experimentally using an instrumented experimental vehicle.
Keywords: ride and handling model; step steer test; slalom test; double lane change test; active roll control; roll moment rejection control
- Non-linear dynamics of a whole vehicle finite element model using a harmonic balance method
by Jean-Jacques Sinou, Franck Barillon, Jean-Marc Duffal, Louis Jézéquel
Abstract: The aim of the present paper is to apply the Harmonic Balance Method (HBM) to a Finite Element Model of a complete vehicle (body, engine and engine mounts) in order to calculate the non-linear response of the assembly. The non-linear effects come from the amplitude-dependent stiffness of the engine mounts.
First, the Harmonic Balance Method is presented. A condensation process on the non-linear degrees-of-freedom is also proposed. This process reduces the original non-linear system by focusing only on the solution of the non-linear equations associated with the system's non-linear components.
Secondly, the engine mount stiffness dependency with amplitude is measured on a test bench to estimate a polynomial stiffness law. Finally, the numerical analysis is performed to analyze the non-linear response of the whole vehicle using the Harmonic Balance Method algorithm with appropriate condensation located only on the non-linear coordinates of the system in order to minimize computer time.
Keywords: harmonic balance method; engine mounts; vehicle finite element model; amplitude-dependent stiffness; Craig and Bampton condensation procedure; condensation on non-linear DOFs
- Stochastic vehicle handling prediction using a polynomial chaos approach
by Lin Li, Corina Sandu
Abstract: One fundamental difficulty in understanding the physics of the off-road traction and in predicting vehicle performance is the indeterminacy of certain important parameters on the interface between tyre and terrain/road surface, for instance, the slip ratio, the slip angle, the normal forces, and the friction coefficients. It is not possible to accurately capture the effect of such uncertainties on the tyre behaviour (resultant force and moments) using a deterministic model. In addition, current measuring techniques have certain limitations and sometimes non-negligible measurement errors could be a source of relatively rough approximations in estimating some important parameters involved in vehicle dynamics simulations and control algorithms.
In this study, mathematical tools to quantify the impact of uncertainties in tyre-terrain interface on vehicle handling were employed. We treated the uncertainty in key parameters associated with the tyre-road interface using a polynomial chaos approach. Two of the most popular semi-empirical models for predicting the pneumatic tyres performance under steady-state and transient conditions, the Friction Ellipse Model (FEM) and the Magic Formula Model (MFM), were selected to be extended from the deterministic to a stochastic workframe, to account for the uncertainties in the tyre-terrain friction coefficient, the slip ratio, the slip angle, and the normal forces in the contact patch. The modelling approach presented in this paper was able to capture the stochastic nature of parameters of interest and to predict the response of the system under those uncertainties, in an effort to provide a better understanding and a more realistic prediction of the tyre-terrain interaction than a deterministic formulation. To illustrate the application of the stochastic tyre-road models on vehicle dynamics, they were simulated in conjunction with a bicycle-car model.
Keywords: Karhunen-Loeve expansion; polynomial chaos; friction ellipse model; magic formula model; probability density function; uncertainty; handling
- Road-frequency based optimisation of damping coefficients for semi-active suspension systems
by Arjon Turnip, Keum-Shik Hong
Abstract: In this paper, a sequential quadratic programming method for determining the optimal damping coefficients of a semi-active suspension system is investigated. Two objective functions (i.e., mean squares of the sprung-mass absolute acceleration and the dynamic load) are minimised under four constraints. By splitting the road frequency range into four regions, the optimal damping coefficients in individual regions are obtained. Simulation results of three cases (passive, semi-active with optimal static damping coefficients, and semi-active with optimal dynamic damping coefficients) show that the semi-active suspension system significantly improve the ride comfort, road holding, and reduce the noise and harshness.
Keywords: suspension control; semi-active damping; road frequency; ride comfort; road holding; optimisation; modified skyhook control.
- Design and optimization of an anti-idling system for police vehicles
by Brian Fan, Amir Khajepour, Mehrdad Kazerani
Abstract: A configurable vehicle model using scalable powertrain components has been developed and modified to create an anti-idling system for police vehicles. Multidisciplinary Design Optimization (MDO) approach is implemented to optimize the anti-idling system. The goal of the optimization study is to select and size an additional battery, while simultaneously determining the power management logic. The objective function seeks to minimize the cost of the battery, fuel consumption, and carbon tax over a period of five years. It is found that depending on the SOC threshold, the duration of time over which the engine is activated varied non-linearly, where local minima and maxima exist. A comparison between different optimization algorithms demonstrated that only global optimization methods were capable of reaching the optimal solution. Finally, it is concluded that the anti-idling system provides significant fuel and cost reduction compared to one without, demonstrating the effectiveness of the design and optimization study.
Keywords: anti-idling; multidisciplinary design optimization; genetic algorithm optimization; vehicle modelling
- Heat transfer effects on the performance of an air-standard irreversible dual cycle
by Yasin Ust, Bahri Sahin, Hasan Kayhan Kayadelen, Guven Gonca
Abstract: The objective of this study is to analyse the effects of heat transfer loss and internal irreversibilites, resulting from adiabatic processes, on an irreversible diesel heat engine. Thermodynamic optimisation has been carried out based on the Maximum Power (MP), Maximum Thermal Efficiency (MEF) and Maximum mean Effective Pressure (MEP) criteria for the dual cycle. Power output, thermal efficiency and mean effective pressure are obtained by introducing variable compression ratio, inlet temperature, combustion and heat transfer constants, and compression and expansion efficiencies. Optimal performance and design parameters of the dual cycle are obtained numerically for the MP, MEF and MEP conditions. The optimal compression ratio and pressure ratio at MEP conditions are compared with those results obtained by using the MP and MEF criteria for different constants of heat transfer and combustion in the characteristic grid curves. The results obtained in this paper may provide a guide to the performance and improvement of practical diesel engines.
Keywords: dual cycle; optimal performance; performance analysis; thermodynamic optimisation; combustion; heat transfer.
- Effect of drum radius variation on the brake torque variation and brake factor
by Muhammad Najib Abdul Hamid, Zaidi Mohd Ripin
Abstract: In the drum brake system analysis, the drum is assumed to be perfectly round and this is the case as reported by simulation work done elsewhere. The true effect of roundness of the drum on the brake torque has not been investigated. In this study, a brake drum of a motorcycle was subjected to the roundness test, the brake torque test and the lining compression test. The effect of roundness of the drum has been analyzed using experimental and FE simulation and showed that the roundness affected the braking torque and this value changes with the rotation of the drum. Correlation between experimental and finite element analysis of the brake torque showed a good relationship with the Pearson coefficient of 0.828. The brake factor values were found to be in the range of 0.5 to 2.0 which is close to the theoretical brake factor value of 2.0 for Âµ=0.3.
Keywords: drum brake; drum radius variation; brake torque variation; brake factor
- Automotive lightweight engineering: a method for identifying lazy parts
by Benjamin Caldwell, Jenkins Richarson, Chiradeep Sen, Thomas Rotenburg, Gregory Mocko, Joshua Summers, Andreas Obieglo
Abstract: This paper presents a method for evaluating the lightweightedness of a vehicle, specifically addressing those components whose primary purpose is to aid in manufacturing and assembly rather than to provide end-user function. Seven specific laziness indicators are described and illustrated: rigid-to-rigid connection, support for a flexible, non-moving part, positioning feature, duplicate geometry, fastener, bridging system, and material flow restriction. These indicators are used to evaluate individual vehicle components as part of a proposed method for identifying mass reduction potential. The indicators do not require extensive knowledge of the functionality of the components being evaluated, focusing instead on the geometry and assembly information available. The purpose of the proposed method is to focus the attention of designers on components or assemblies with high potential for mass reduction. This method is applied to a complete automotive vehicle consisting of approximately 1500 parts, demonstrating a mass savings potential of the overall vehicle of approximately 114 kilograms, or 5% of the total mass of the vehicle. The frequency of use of seven laziness indicators and various combinations of these indicators is also analysed, and it is determined that the greatest potential for mass savings within the vehicle occurs when a part has rigid-to-rigid connection and duplicate geometry indicators. This analysis also demonstrates that entry-level manufacturing engineers can analyse a system based on geometric and assembly relationships, with a limited understanding of functionality, to identify potential mass savings.
Keywords: lightweight, mass reduction, vehicle design, design for assembly, design for manufacturing
- Modelling and testing of arresting process in flexible vehicle arresting systems
by Pak Kin Wong, Lap Mou Tam, Yueqiao Chen, Zhengchao Xie
Abstract: As car bomb incidents become more prevalent globally, in order not only to protect people's lives but also to avoid the complete destruction of the suspect vehicle, a promising solution is to use flexible vehicle arresting systems, which generally absorb the kinetic energy of the suspect vehicle using energy absorbers and an arresting net, so the vehicle can be arrested safely. According to the existing literature, theoretical research on vehicle arresting systems and processes is very limited. This research is the first attempt at developing an analytical model for the arresting system and process, and carrying out experimental validation. Based on the model built, dynamic analysis of arresting process was also carried out. Experimental and simulated results indicate the model developed is valid and can accurately predict arresting distance and the other safety-related parameters. Therefore, the analytical model proposed can provide a foundation for further study of vehicle arresting systems.
Keywords: flexible vehicle arresting system; energy absorber; analytical model; computer simulation
- Fault tree analysis of hydraulic power-steering system
by Dobrivoje Catic, Milomir Gasic, Mile Savkovic, Jasna Glisovic
Abstract: The history development is presented in the introductory part, and it points out the importance of using the Fault Tree Analysis-FTA method for analysis of the reliability and safety of technical systems. By analyzing a number of references relating to the FTA method, it is established the FTA methodology which an algorithm with an explanation of some steps is given in the paper. As an example of the practical application of methods, it is analyzed the failure of the hydraulic power amplifier of the steering system of light commercial vehicles. Based on data from the development phase, by the team approach it was developed the fault tree of hydraulic power steering. Along with an explanation of certain parts of the fault tree, it is done the estimation of the significance of certain events, and it is considered able to eliminate causes of failure or to minimize the consequences of failure.
Keywords: reliability; fault tree analysis; methodology; industrial light vehicle; hydraulic power-steering system; HPS; qualitative analysis
- Overview of electric machines for electric and hybrid vehicles
by K.T. Chau, Wenlong Li
Abstract: This invited paper gives an overview of various electric machines for application to electric vehicles (EVs) and hybrid electric vehicles (HEVs). First of all, the classification and a brief introduction of EVs and HEVs are presented. Then, viable electric machines that have been applied to EVs and HEVs, including the DC, induction, switched reluctance and permanent magnet (PM) brushless types, are reviewed. Next, the advanced PM machines that are promising for application to EVs and HEVs are discussed. Finally, the integrated PM machines are introduced, which are essential for future EVs and HEVs.
Keywords: electric machines; electric motors; electric vehicles; hybrid vehicles.
- Procedure to verify the suspension system on periodical motor vehicle inspection
by José A. Calvo, José L. San Román, Carolina Álvarez-Caldas
Abstract: The suspension system of a vehicle is an essential element which assures driving safety and passenger comfort. The shock absorbers are the key component of this system. A worn out damper reduces the tyre-road contact, resulting in increased stopping distances. Similarly, lateral stability may be compromised as a result of uncontrolled rolling movements. In order to maintain safe driving conditions, it is essential to verify the status of the suspension system during Periodic Motor Vehicle Inspections (PMVI) using efficient procedures. The current method to verify the suspension system at PMVI stations is not reliable. This paper proposes a procedure that uses a new test bench that allows to know the real status of the suspension system of a vehicle and is based on identifying the damping ratio of the shock absorbers. Proposed procedure has been validated by experimental tests.
Keywords: suspension system; vehicle inspection; shock absorber; damping coefficient.
- Dynamics and control of gear upshift in automated manual transmissions
by Bingzhao Gao, Xiaohui Lu, Hong Chen, Xintian Lu, Jun Li
Abstract: Automated Manual Transmission (AMT) is suitable for heavy-duty vehicles to offer an easy drive and good fuel efficiency. After the dynamics and control problems of gear upshift of AMT are described in detail, Model Predictive Control (MPC), together with a shaft torque observer, is adopted to address these challenging control problems. It is demonstrated through simulations that by using the proposed control scheme of gear shifting, a very short torque interruption time can be achieved, while the shift shock is kept small enough.
Keywords: AMT; automated manual transmission; gear shift; clutch; MPC; model predictive control; torque estimation.
- On the impact of the regulatory frontal crash test speed on optimal vehicle design and road traffic injuries
by Steven Hoffenson, Matthew P. Reed, Yannaphol Kaewbaidhoon, Panos Y. Papalambros
Abstract: Many countries have instituted New Car Assessment Programs (NCAPs) to help consumers compare the crashworthiness of automobiles on the market. These typically involve four or five standardised tests, for which each new vehicle is rated on a 5-star scale. The ratings are available to customers and so, automakers strive for high scores by optimising their vehicle designs to the scenarios represented by the tests. The United States NCAP rates vehicles for frontal crashworthiness with a 56 kilometres per hour (35 miles per hour) full-engagement barrier collision, which is a relatively severe test, considering that over 98% of crashes on US roadways occur at slower speeds. This paper presents a methodology for understanding the impact of the NCAP crash test speed on vehicle design and the consequent on-road safety outcomes, using physics-based simulations and optimisation tools. The results suggest that lowering the test speed from the current level to 48 kilometres per hour (30 miles per hour) may decrease the rates of serious injuries to vehicle occupants in the US by up to 21%.
Keywords: automobile safety; crashworthiness; design optimisation; new car assessment program; vehicle design.
- Kineto-dynamic directional response analysis of an articulated frame steer vehicle
by Alireza Pazooki, Subhash Rakheja, Dongpu Cao
Abstract: Owing to their high mass centre, relatively soft tyres, extreme variations in the load and load distributions during work cycles, and greater flexibility of the steering system, the articulated steer vehicles (ASV) exhibit lower directional stability limits than vehicles with conventional steering. In this study, a kineto-dynamic model of the articulated steering mechanism is formulated by considering the kinematics and dynamics of the hydraulic steering struts and valve flows, in conjunction with a nonlinear yaw-plane model of an articulated dump-truck. The vehicle system model also incorporates tyre-lag to account for effects of tyre relaxation. The validity of the model is demonstrated on the basis of the available measured data for an articulated dump truck. The proposed model is initially analysed to derive response characteristics of the steering system in terms of articulation angle, steering valve opening, strut orientations and deflections, fluid pressures in the struts, and resultant strut forces and torque on the articulation joint. The influences of variations in selected operating and design parameters on the steering system responses are investigated under a steady-turning and pulse steering inputs. The results provide important design guidelines with regard to kinematic and dynamic parameters of the steering mechanism, and show that the lateral stability of the ASV is strongly influenced by the kineto-dynamic characteristics of the articulated steering system, apart from the vehicle and tyre properties. The effective damping of the steering mechanism, in particular, affects the steering system responses and yaw stability limit of the vehicle. The effective damping property is determined by the leakage flows across the struts piston, valve flow characteristics and struts' orientations.
Keywords: articulated steer vehicles; steering mechanism; kineto-dynamic model; directional stability; model validation; design guidance
- Robust controller design for an electromagnetic active suspension subjected to mixed uncertainties
by Yongchao Zhang, Fan Yu, Jianyong Cao, Guoguang Zhang
Abstract: This paper focuses on the modelling and robust control of a DC-motor-based electromagnetic active suspension. Owing to the small damping of the motor, the moments of inertia of rotor and nut can significantly affect the high-frequency performance of the suspension system, so they are taken into consideration in system modelling. In addition, parameter variations of the vehicle system and unmodelled high-order dynamics of the actuator could influence the control effectiveness. Thus, the mixed uncertainties composed of both multiple parameter uncertainties and unmodelled high-order dynamics of the suspension and actuator are taken into account in the system model. In order to ensure the robustness and performance of the uncertain suspension system, a robust controller based on mixed mu-synthesis is designed. An easy method of choosing the weighting functions is proposed. The simulation results show the mixed mu-synthesis controller can meet the requirement of robust performance in the presence of the mixed uncertainties, and can achieve good ride comfort.
Keywords: electromagnetic active suspension; DC-motor-based; uncertainty; mu-synthesis; robust control
- Analysis of the torsional rigidity of a dump semi-trailer under unfavourable load conditions
by David Valladares, Marco Carrera, Ramon Miralbes, Luis Castejon
Abstract: The use of dump semi-trailers in their habitual workplace is fraught with risks associated with the unloading of the transported material. The unloading manoeuvre involves raising hydraulically the semi-trailer box bed at its front until it reaches a certain angle. While tipping the semi-trailer, the transported material leaves the box bed and falls to the ground. Factors such as the presence of a transversal slope, a different compression degree of the ground or an irregular unloading caused by the adherence of the material to the box surfaces (due to braking manoeuvres, to the load dead weight or to the existence of vacuum areas) can lead to non-desirable lateral unstability situations. At the same time, the vehicle becomes more unstable because of the elevation of its centre of gravity, which increases the semi-trailer rollover risk. Taking into account this instability risk, it is interesting to analyse the torsional rigidity of the semi-trailer dump bed under unfavourable loads generating torsional compliance. In this kind of vehicle, the hydraulic actuator for the tipping operation is connected to the box bed at its front by means of a pivoting bearing joint that allows a turning movement between the parts comprising this coupling. A non-desirable contact between these components could generate a failure and breakage of the coupling. Therefore, in the present paper, the maximum allowable turn angle between these coupling parts has been geometrically evaluated, and a finite element analysis of the semi-trailer box bed behaviour under torsion loads has been carried out. In this step, the load level necessary to achieve a critical torsion angle at the front of the box bed has been evaluated. Finally, a complete finite element model of the semi-trailer has been analysed, taking into account not only an off-centre load but also the static rollover threshold of the vehicle. It has thus been possible to verify the correct performance of the articulated coupling between the semi-trailer dump bed and the hydraulic actuator in the presence of unfavourable stability conditions.
Keywords: semi-trailer; dump, torsional rigidity; finite element method; rollover; safety; transport; unloading; coupling; off-centre load; unstability.
- Analysis and modelling of tyre in-plane time domain simulation with modal parameter tyre model
by Jin Shang, Dihua Guan, Baojiang Li
Abstract: Virtual proving ground simulation is important in vehicle product development, which requires tyre dynamic simulation in the time domain. This paper uses the modal parameter tyre model (MPTM) to obtain the static vertical properties that match the experimental results well and then presents a complete analytical model based on MPTM for in-plane time domain simulation that involves tyre rolling movement, tyre mechanics and typical working conditions. The computational method is also proposed. Results show that the steady state result is consistent with the convergent result of dynamic simulation. Further, this article presents simulation results in both time and frequency domains and compares them with experimental results, calculating rolling resistance, etc. The model and its computational method can be applied for more complex theoretical analysis and simulation in tyre mechanics.
Keywords: modal parameter; tyre model; time domain simulation; rolling speed; damping ratio; rolling resistance.
- Combined wheel torque and steering control based on model predictive controller using a simplified tyre model
by Taehyun Shim
Abstract: This paper presents a vehicle chassis control system based on model predictive control method that controls both front steer and wheel torques at each wheel, developed to enhance the vehicle yaw motion and the ability to track the desired trajectory. A computationally efficient simplified nonlinear tyre model that is easy to implement in the control algorithms is used, along with an 8 degree of freedom (DOF) vehicle model. The performance of this controller is compared with that based on well known Magic Formula tyre model. The effectiveness and limitations of the proposed controller are discussed through simulation.
Keywords: vehicle dynamics control; model predictive control; simplified tyre
- Suspension design by means of numerical sensitivity analysis and optimisation
by Bernhard Angrosch, Manfred Plöchl, Werner Reinalter
Abstract: The kinematic layout of suspension systems determines the wheel's motion during bounce and rebound, and has thus high influence on the dynamic performance of the vehicle. The presented study uses Design of Experiments (DoE) in order to determine dependencies between the location of the mounting points of the suspension devices and typical suspension indicators. Therefore, MBS models of a McPherson front as well as a multi-link rear suspension are regarded. Then the locations of the mountings are varied by means of numerical optimization by considering target values for chosen suspension indicators. Whereas vehicle handling properties are usually anticipated by regarding suspension indicators, this paper aims to present a shortcut between the positioning of a suspension's mounting points and the resulting consequences on the vehicle handling characteristics by means of DoE. Therefore a virtual full vehicle model is introduced.
Keywords: suspension design; numerical optimization; design of experiments; McPherson suspension; multi-link suspension
- Determinants of US passenger car weight
by Donald MacKenzie, Stephen Zoepf, John Heywood
Abstract: After a precipitous drop from 1976-1982, the weight of US passenger cars has grown steadily. This paper examines multiple conflicting influences on vehicle weight in two categories: technological changes that reduce vehicle weight; and improvements in functionality that, ceterus paribus, add to vehicle weight. The widespread adoption of unibody construction, lightweight materials and smaller engines has been offset by growth in vehicle size and feature content. The best estimates from this work indicate that new features and functionality would have added at least 250 kg (550 lbs) to the weight of the average new car between 1975 and 2009, but for offsetting improvements in technology. Over the same period, it is estimated that alternative materials, more weight-efficient vehicle architectures, and reduced engine sizes have taken 790 kg (1,700 lbs) out of the weight of the average car. These observable influences do not explain the full extent of the drop and subsequent growth in weight, suggesting that substantial non-observed technological improvements were made from 1976-1982, and that unobserved improvements in areas such as crashworthiness and NVH have added substantially to vehicle weight in the past two decades.
Keywords: weight; lightweighting; materials; unibody; features
- Structure and performance of a novel electric power steering system integrated with active steering
by Jianwei Wei
Abstract: Based on a review of the primary functions, as well as defects of the existing electric power steering (EPS) and active steering respectively, a realisation of active steering on an existing EPS system is researched, and a novel EPS system integrated with active steering is introduced. According to the working principle of the double planetary gear train, decoupling control of force and angular displacement is realised. To study the effects of the proposed novel EPS system on a vehicles steering performance, mathematical models are built, and then amplitude-frequency characters of steering feeling and steering sensitivity, as well as stability, are investigated. Results indicate that road information can be measured by the torque sensor without any installation position changing, compared with that of existing EPS system, and no other torque sensor is needed. Meanwhile, perfect combination of force and angular displacement can be obtained by the novel EPS system.
Keywords: electric power steering; active steering; steering feeling; steering sensitivity; road information
- On integral sliding mode control for a unicycle
by Jian-Xin Xu, Zhao-Qin Guo, Tong Heng Lee
Abstract: In this paper we present an integral sliding mode controller (ISMC) that can stabilize an underactuated unicycle system. The unicycle consists of a wheel and a saddle that is modelled as an inverse pendulum. The control objective for unicycle is to achieve position control of the wheel while keeping the pendulum at the balanced position that is an unstable equilibrium. The only driving force is the torque applied to the shaft of the wheel. The proposed ISMC consists of an integral sliding surface, a switching term, a nonlinear compensation term and a LQR stabilizing controller for the sliding manifold. The ISMC can effectively reject the matched disturbance, and reduce the influence from unmatched disturbances, which is verified through rigorous analysis and intensive numerical validation.
Keywords: ISMC; unicycle; underactuated system; LQR.
- Distributed occupant-seat interactions as an objective measure of seating comfort
by Ali Akgunduz, Subhash Rakheja, Anthony Tarczay
Abstract: As part of the interface between the driver and the automobile, the automotive seat must provide the occupant with a comfortable environment in which driving can be performed in a safe and comfortable manner. The characterization of the interactions between the occupant and the seat under various conditions thus constitutes an important goal for enhancing the knowledge of essential design factors that could yield improved seating comfort. This paper investigates the occupant-seat interactions through measurements and analyses of the distributed contact force, and pressure at the body-seat-pan and body-backrest interfaces of three different automotive seats. The contact force, contact area, and peak and mean pressure responses are analysed as a function of the occupant anthropometry, the seated posture and the seat design features. Single and multi-factor statistical analyses are performed to identify the significance of the experimental factors. Finally, users perceived comfort levels for various seating configurations were acquired through a survey, and results were analysed through Analytical Hierarchy Process (AHP) in order to derive a quantitative expression for the perceived comfort level. The correlation between the perceived comfort levels and the measured responses was further analysed, which suggested a strong correlation between the perceived comfort and the peak and mean pressures on the seat-pan.
Keywords: automobile seat design; objective measure of seating comfort; occupant-seat interaction; perceived comfort; multi-criteria evaluations; analytical hierarchy process.
- Robust tracking control of vehicle lateral dynamics
by Haiping Du, Nong Zhang
Abstract: In this paper, a robust yaw moment controller is designed to improve vehicle handling and stability. Three issues regarding to vehicle mass variation, cornering stiffness uncertainty, and tracking control are considered in the controller design process. To deal with these issues, parameter-dependent control strategy, normbounded uncertainty description, and tracking error feedback are applied. The control objective is to stabilise the closed-loop system and to optimise the tracking performance on yaw rate and sideslip angle with respect to their targets. The condition for designing such a controller is derived in terms of linear matrix inequality. Numerical simulations on a nonlinear vehicle model are performed to validate the effectiveness of the proposed approach. The results show that the designed controller can improve vehicle handling and stability despite of the variation of vehicle mass and the change of road surface condition.
Keywords: vehicle lateral dynamics, yaw moment control, uncertainty, vehicle mass, cornering stiffness, tracking control
- Optimum tyre force distribution for four-wheel-independent drive electric vehicle with active front steering
by Yifan Dai, Yugong Luo, Wenbo Chu, Keqiang Li
Abstract: Tyre workload is widely used as a performance index in tyre force distribution because it can reflect the stability margin of vehicle directly. There are kinds of tyre force distribution methods based on the use of tyre workload. These methods are limited by either the uneven distribution result or too many constraints. To maximize vehicle stability margin while not involving too many constraints, an optimum tyre force distribution method based on minimizing the variance and mean value of tyre workload for four-wheel-independent drive electric vehicle with active front steering is proposed. In order to follow the drivers intention, the operations of the driver are explained as the desired total longitudinal and lateral force and yaw moment, which are considered as constraints. The original constrained optimization problem is transformed to an unconstrained optimization for better convergence rate and solution accuracy. The four longitudinal tyre forces and the lateral force of the front axle are obtained by using a quasi-Newton method for solution. A 15-DOF vehicle dynamic model is established for simulation. The simulation results show that the proposed method can increase the maximum safe speed by several percentage points on all kinds of adhesion coefficient roads when compared with existing methods. A vehicle test is carried out to verify the distribution method. The results show that the adhesion margin is kept to a high level, which will enhance the stability performance of the vehicle.
Keywords: tyre workload, force distribution, four-wheel-independent drive, active front steering, quasi-Newton method
- Study of air-cushion system modelling for semi-track air-cushion vehicle body attitude control
by Dong Xie, Zhe Luo, Fan Yu
Abstract: In order to investigate the body attitude control for a semi-track air-cushion vehicle (STACV), a multi-air-cushions design scheme is adopted. Based on the experimental study of the developed single air-cushion (1-AC) STACV prototype, along with its computational fluid dynamics (CFD) simulation, a two air-cushions (2-AC) configuration with controllable orifice valves is examined for the pitch control of the STACV in this paper. Since the air-cushion forces, which can actively control the attitude of the 2-AC STACV, are greatly influenced by the air-cushion system related parameters, their relationships should be acquired first. The relationship between the equivalent clearance height and input air total pressure of air-cushion system is obtained according to the relevant testing and CFD simulations from the 1-AC system. Then, the relationships among the controllable orifice valve diameters, fan rotational speed and generated air-cushion pressures of the 2-AC system are acquired using CFD simulations. Finally, the forward and reverse air-cushion system models are established by neural network, which can be used in real-time control for body pitch control of the STACV. This method can be used as a reference in future body attitude control of the STACV with more air-cushions.
Keywords: semi-track air-cushion vehicle; air-cushion system modelling; CFD; neural network
- Investigation of a driver-oriented adaptive cruise control system
by Liang-kuang Chen, Chih-Chi Dai, Min-Fang Luo
Abstract: The driver-oriented adaptive cruise control (ACC) is developed using the driver drowsy index assessed by an online driver monitoring system. The longitudinal control of the ACC functions is designed using the sliding mode control technique to address the unknown disturbance force in the vehicle longitudinal dynamics. The ACC system parameters are modified according to the instant driver drowsy index to allow safer vehicle range keeping strategy for a more fatigued driver, and less conservative control for a less fatigued driver. The developed control strategies are evaluated using computer simulations and driving simulator experiments. The results indicate that the designed control strategies modifications provide the expected functions both in simulations and experiments, and the sliding mode controller successfully regulates the inter-vehicle range under unknown disturbance. Driving simulator experiment results also show that the alert drivers accept the design modifications with fewer instances of gas pedal intervention and do not intervene in the brake control during stopping.
Keywords: driver-oriented adaptive cruise control, driver assist system, vehicle longitudinal control
- Game-theory-based operation of autonomous vehicles
by Changwon Kim, Reza Langari
Abstract: In this paper, we propose a game-theory-based approach to decision making with application to the operation of autonomous ground vehicles in highway settings. The mixed-motive game theory is used as a decision-making strategy in the context of a two-player game involving autonomous vehicles. The payoff matrices are defined by considering the safety of each players decision combination in view of their desire to stay within a given lane or to change lanes in consideration of the traffic conditions that the vehicles encounter. By analysing the payoff matrix, either a pure (deterministic) strategy or a mixed (probabilistic) strategy is selected. Three 10 km velocity profiles are predefined for simulation purposes. The simulation results demonstrate effective driving performance. In particular, when it is compared with non-game theory cases, game-theory-based results show a larger payoff for both vehicles and smaller payoff differences, securing safe manoeuvring via LCM and ACC.
Keywords: autonomous vehicles, game theory, mixed motive game, virtual bumper
- Design of a rectilinear suspension with automatic length compensation branches
by Jing-Shan Zhao
Abstract: This paper proposes an independent suspension whose alignment parameters are theoretically invariable during jounce and rebound.The suspension is a kind of multilink mechanism each kinematic chain of which consists of a 3-linkage that could automatically compensate for the axial distance change. This kind of linkage is a parallel rectilinear mechanism which provides the knuckle with high alignment capability to trace an expected straight line. The motions of the 3-linkage and the knuckle are investigated from the view points of screw theory and geometry. The equivalent torsional stiffness, bending stiffness and shear stiffness of the 3-linkage are investigated to demonstrate the feasibility of engineering applications. Research results show that this complex linkage has better mechanical properties than a prismatic joint does when used as a passive connection. As a result, the 3-linkage has accurate alignment ability on the one hand and could keep the compact space in design while having the required strength and compliance on the other hand.
Keywords: passive length compensation, rectilinear, suspension, mechanism.
Special Issue on: "Off-Road Vehicle Dynamics"
- Gas damper: potential vehicle performance studied on a full-car model
by Jorge Gonzalez Prada, Jordi Vinolas, Xabier Carrera
Abstract: The main characteristic of a gas damper (GD) is the use of gas as internal fluid, something that provides it with an important dependency on operating frequency and stroke amplitude. The potential performance of GD was analyzed in a previous study using a quarter-car model, and offered a new approach to the traditional ride/handling trade-off, especially in off-road vehicles. However, the use of a more complete vehicle model is needed to confirm the applicability and suitability of GD to that kind of vehicles and also to completely understand the GD behaviour. Consequently, this paper is devoted to study the GD influence on a vehicleâ€™s performance using a full-car model. This performance is evaluated attending to ride isolation, road-holding, body control and rollover stability, and is compared to the performance of a hydraulic suspension. GD dependency on frequency and amplitude is also studied using deterministic inputs.
Keywords: rollover; roll stability; suspension system; vibration control, off-road vehicle dynamics; gas dampers; ride comfort; handling.
- Effects of steering dynamics upon tyre lateral forces on deformable surfaces
by Jaroslaw Pytka
Abstract: Tyre lateral force is one of the most important parameters of the tyre and is critical for vehicleâ€™s handling and stability performance. For wheeled off-road vehicles, the effects of deformable surface on tyre performance must be considered. This paper presents a study on tyre lateral force measurement on three different deformable surfaces: loess soil, sandy soil and wet snow. The lateral force was measured on two front wheels of a light SUV by means of two 6-element rotating wheel dynamometers. The front wheels of the vehicle were turned by a steering robot installed in the vehicle to obtain repeatable excitation of the wheels at various angular speeds (100, 500, and 1500 deg/s) and frequencies (0.5, 1, and 2.5 Hz). During measurements, the test vehicle was pulled by a tractor vehicle of a significantly higher weight to ensure linear movement. This paper presents and discusses the tyre lateral force results and characteristics.
Keywords: off-road vehicles, tyre-soil interaction, tyre-snow interaction, tyre lateral force, measurements, steering
- Snowmobile model for ride dynamic analysis
by Paul-Andre Hebert, Subhash Rakheja, Marc J. Richard
Abstract: Snowmobiling involves exposure to high magnitude vibrations. The ride comfort thus forms a major design requirement, currently met through iterative prototyping and field-testing. This study aims at developing an industry-viable snowmobile ride model to assist designersâ€™ in achieving the desired ride performance. Implemented in ADAMS, the model includes nine degrees-of-freedom and sub-models for: lumped frame, detailed suspension, track, deformable ground, trail surface profile, quasi-steady traction, and simplified rider and seat. Four trails were measured and their roughness was characterized through spatial power spectral density (PSD). Field tests provided the vehicle response data. Comparing them to the model outputs revealed reasonably good agreements for some of the trails, while considerable differences were observed for others. A parametric analysis was performed using the rms vertical acceleration at the seat surface as a measure of the ride comfort. It led to a setup reducing by nearly 58% the rms vertical acceleration.
Keywords: snowmobile; snowmobile model; ride dynamic, ride analysis; ground profiles; trail profiles; ground roughness; track model; traction model; snowmobile suspension; off-road; snowmobile simulation.
- Simulation and experimental validation of a modified terramechanics model for small-wheeled vehicles
by Gareth Meirion-Griffith, Matthew Spenko
Abstract: The ability to model and predict vehicle performance over deformable terrains, which is typically done using terramechanics, is important for planetary exploration, military operations, and off-road vehicle design. This paper details the development of a new vehicle-terrain model that specifically addresses some of the limitations of traditional terramechanics when applied to unmanned ground vehicles (UGVs) with small wheel diameters. Assumptions and limitations of the classical Bekker terramechanics model for wheeled locomotion are discussed. A novel pressure-sinkage model that was recently developed by the authors is detailed and shown to improve sinkage and compaction resistance models significantly. These models are implemented in a numerical simulation, which is used to predict the tractive performance of an experimental UGV. Field tests carried out on sandy terrain are described, and the results are used to validate the simulated predictions.
Keywords: traction; UGVs; Bekker theory; terramechanics; small wheels, pressure-sinkage
- A general model for inferring terrain surface roughness as a root-mean-square to predict vehicle off-road ride quality
by Phillip Durst, Alex Baylot, Burney McKinley, George Mason
Abstract: Vehicle maximum speed for off-road operations is limited by the absorbed power via vertical acceleration to the driver for a given terrain root-mean-square (RMS) surface roughness. RMS calculation requires centimetre-scale terrain elevation data; however, previous work by the authors has shown that RMS can be modelled using a 5-metre terrain profile's fractal dimension (FD) and power spectral density (PSD) DC offset. Presented is a study of the effects of surface elevation data resolution on the model. Forty-nine ride courses were down-sampled from 30 centimetre to 0.91, 1.83, 2.74, 3.66, 4.57, 5.49, 6.40, 7.32, and 8.23 metre spacings, and an RMS model at each spacing was generated using linear regression techniques. The effects of data resolution on the RMS model were studied, and a continuous model for RMS as a function of FD and DC offset across elevation data resolutions for sample spacing of up to 7 metres was developed. Results of the model's use in predicting off road military vehicle mobility are presented.
Keywords: surface roughness; root-mean-square; RMS; fractal dimension; FD; power spectral density; PSD; off-road performance; ride performance; military vehicles; terrain modelling, terrain characterisation.
- Mathematical models for farm tractor rollover prediction
by Giorgio Previati, Massimiliano Gobbi, Gianpiero Mastinu
Abstract: This paper deals with the estimation of the rollover limit of a farm tractor. The rollover phenomenon is investigated by considering the static stability of the farm tractor on a sloped surface. Three mathematical models are derived in order to understand the basic features of the rollover mechanism. The models are able to predict the (static) rollover limit for any orientation of the farm tractor with respect to the slope. The effects of tyre stiffness (vertical and lateral) and non-symmetric implement positioning are analysed. The classical architecture of the farm tractor equipped with a pivoting front axle is compared with the adoption of a passively suspended front axle. In case of a front axle suspension, the rollover limit of the vehicle can be improved, especially when employing non-symmetric implements.
Keywords: roll-over prediction; farm tractor modelling; static stability
- The relationship between vehicle yaw acceleration response and steering velocity for steering control
by Michael Thoresson, Theunis Botha, Schalk Els
Abstract: This paper proposes a novel concept for the modelling of a vehicle steering driver model for path following. The proposed steering driver reformulates and applies the Magic Formula, used for tyre lateral force vs. slip angle modelling as a function of vertical force, to the vehicle's yaw acceleration vs. steering velocity response as a function of vehicle speed. The path-following driver model was developed for use in gradient-based mathematical optimisation of vehicle suspension characteristics for handling. Successful application of gradient-based optimisation depends on the availability of good gradient information. This requires a robust driver model that can ensure completion of the required handling manoeuvre, even when the vehicle handling is poor. The steering driver is applied to a non-linear full vehicle model of a sports utility vehicle, performing a severe double lane change manoeuvre. Simulation results show excellent correlation with test results. The proposed driver model is robust and well suited to gradient-based optimisation of vehicle handling.
Keywords: driver model; Magic Formula; steering response; tyre characteristics; handling; mathematical optimisation.
- Profiling of rough terrain
by Carl Becker, Pieter Els
Abstract: This study concentrates on obtaining three-dimensional (3-D) profiles of rough terrain suitable for vehicle dynamics simulations cost effectively. Commercially available inertial profilometers are unable to profile the terrains of interest owing to the severe roughness of these terrains. A mechanical profilometer is developed and evaluated by profiling obstacles with known profiles as well as rough 3-D test track profiles. Good correlation between the 3-D profiles and actual terrains are achieved. The displacement spectral densities of the profiled terrains are found to contain discrete peaks, and it was found that a straight line fit would not be an accurate estimation for the specific rough terrains. Comparisons between the terrains defined in the International Roughness Index (IRI) and the present study indicate that the roughness index of the terrains profiled with the mechanical profilometer is significantly higher than the terrains normally profiled by inertial profilometers.
Keywords: profilometer, rough terrain, displacement spectral densities, three-dimensional profiles, International Roughness Index, root mean square, photogrammetry, laser
- A study of volumetric contact modelling approaches in rigid tyre simulation for planetary rover application
by Willem Petersen, John McPhee
Abstract: For planetary rover applications, a volumetric contact modelling approach is used to capture the dynamics of the rigid tyre/soil interface. The volumetric contact model allows for determining closed-form expressions for the tyre contact forces. These volumetric force representations contain information about the shape of the contact geometry so that the analytical expressions result in fast simulations. Three different volumetric rigid tyre models are developed and evaluated from a plasticity point of view. The performance of each tyre is tested and compared with respect to the resistance force caused by the ongoing compaction of the soil and the resultant plastic deformation. The quantity used to model the plastic deformation of the soil is represented by the soil rebound. Moreover, each tyre model is compared against experimental data to evaluate its validity.
Keywords: contact mechanics; volumetric contact model; tyre/soil interaction; planetary rover simulation; analytical contact model
- A fatigue failure formula and a new measure of the roughness of a terrain profile
by T. C. Sun, David Gorsich, Milton Chaika, Jinfeng Wei, Shanshan Qiu, Kussiy Alyass
Abstract: There have been complaints that the root mean square (RMS) does not describe well the roughness of terrain profiles. Similar complaints can be made about the international roughness index (IRI) as a measurement of roughness of terrain profiles. In this paper, by using the rainflow count of the oscillations of the terrain profiles, we shall first propose a fatigue failure formula and then we shall modify it to define a new measure of roughness of terrain profiles. We shall show that this new measure can describe the roughness better than the RMS and the IRI and hence can be used, either independently or in conjunction with RMS and IRI, as a new measure of roughness of terrain profiles.
Keywords: terrain roughness, terrain modelling.
Special Issue on: "Advanced Developments in Tyre Modelling, Analysis and Dynamics"
- An intelligent tyre-based adaptive vehicle stability controller
by Mustafa Ali Arat, Kanwar Bharat Singh, Saied Taheri
Abstract: Active safety systems have become an essential part of today's vehicles. Although they have advanced in many aspects, there are still many areas that they can be improved. Especially being able to obtain information about tyre-road conditions (e.g. slip ratio, tyre-slip angle, tyre forces, tyre-road friction) would be significant due to the key role tyres play in providing directional stability and control. Current systems are capable of obtaining such information by means of indirect methods (i.e. vehicle kinematic relations); however, they tend to fail in severe manoeuvres mainly because of the highly non-linear characteristics of tyres. As a result, other methods are sought to directly obtain information about tyre-road interaction. This paper examines such a method where a tyre-attached sensor unit (intelligent tyre system) provides tyre slip information, and the potential performance improvements offered by integrating this system with an adaptive vehicle stability controller.
Keywords: intelligent tyre, sliding mode observer, Lyapunov stability, integrated chassis control
- Development of rational tyre models for vehicle dynamics control design and combined vehicle state/parameter estimation
by S. Caglar Baslamisli
Abstract: In this paper, control-oriented rational tyre models are developed and incorporated in the design of vehicle dynamics estimators and controllers. Previously proposed rational models are used to derive a generic rational tyre model whose parameters are obtained through the optimisation of an increased number of regression terms. The proposed model results in vehicle dynamic responses that closely follow those obtained with a Magic Formula tyre model for a range of driving scenarios, especially on low mu roads. The use of rational tyre models in the design of gain-scheduled active front steering controller working in coordination with a nonlinear observer is demonstrated in the second part of the paper, where the vehicle model is expressed as a linear parameter varying system. This step demonstrates the strength of the rational tyre model's selected structure, allowing the estimation of vehicle states through the estimation of the road adhesion coefficient, which is obtained by simple algebraic computations.
Keywords: Rational Tyre model; Magic Formula Tyre Model; Linear
parameter varying systems; LPV system in descriptor form; active
front steering; road adhesion coefficient; nonlinear observer
- Development and validation of a finite element model of a mining vehicle tyre
by Zhanbiao Li, Aleksander Tonkovich, Sante DiCecco, W. Altenhof, Richard Banting, Henry Hu
Abstract: Owing to the harsh operating conditions and high payload requirements of heavy mining vehicles, extremely durable, stiff, heavy and large-sized tyres are necessary to meet functional requirements. This necessitates the use of multi-piece wheels to allow mounting of the tyre. As part of an on-going study to enhance the safety and design of multi-piece heavy mining vehicle wheels, finite element methods are applied to develop a tyre model of a bias-ply Goodyear 29.5-29 Smooth, D/L 5D (I-5S) 40 ply model used on a Caterpillar R2900G load-haul-dump (LHD) scoop. The model is validated based on manufacturer engineering data, static load testing, and quasi-static testing. Tyre deformation was determined using non-contact displacement transducers and analysis of high speed imagery acquired during testing which was representative of harsh tyre loading. Development of an FE model of the wheel and tyre assembly model was completed and error estimates on the displacement measurements on several locations of the tyre, representing vertical, horizontal and out-of-plane deformations, were typically less than 10% when compared to experimental observations. Maximum values of the vertical and lateral deflections of the tyre in both experimental and numerical investigations, considering the most severe loading case within this investigation, were observed to be approximately 80 mm and 30 mm, respectively. This study details the methodology used in the development of a high fidelity numerical mining vehicle tyre model capable of simulating static and quasi-static loading conditions.
Keywords: heavy mining vehicle, finite element analysis, tyre modelling, wheel assembly modelling, tyre model validation
- Tyre/road interaction model for the prediction of road texture influence on rolling resistance
by Stijn Boere, Ines Lopez Arteaga, Ard Kuijpers, Henk Nijmeijer
Abstract: A modelling approach to predict the influence of road texture on the rolling resistance of car tyres is presented, in which the large static tyre deformations and the small texture-induced tyre vibrations are treated separately. The energy dissipation due to the large continuous cyclic deformation of the tyre cross-section for a treadless tyre on a smooth road subject to the nominal load is determined in a non-linear steady-state rolling analysis on a finite element tyre model. The additional energy dissipation resulting from the contact forces and tyre vibrations due to the combined effect of tread profile and road texture are determined, based on a modal representation of the deformed tyre. The predicted rolling resistance coefficients are compared with experimental data. Although an offset in the absolute rolling resistance levels can be observed, the model predicts the correct trend regarding the increase of rolling resistance with increasing texture depth.
Keywords: rolling; resistance; tyre; road; interaction; vibration; texture.
- A ride comfort tyre model for off-highway vehicles
by Thomas Langer, Thorkil Iversen, Ole Mouritsen, Morten Bak, Michael Hansen
Abstract: Tyre modelling is a major challenge when using time domain multibody simulations models to evaluate ride comfort on off-highway commercial vehicles. Also parameters for these big tyres are difficult to obtain and thus commercial car tyre models are difficult to apply. In this research work a simple vertical tyre model for off-highway ride comfort evaluation is suggested. A displaced volume approach has been developed and combined with slip theory to yield a tyre model that can be characterised by only four parameters. Full scale measurements on a dump truck have been carried out. Force responses from measurements are compared with the simulation results. Also acceleration responses and the level of whole-body vibrations have been compared.
Keywords: tyre modelling; whole-body vibration; ride comfort; off-highway; vehicle dynamics; multibody dynamics simulation
- A new empirical exponential tyre model
by Matthew Best
Abstract: A new and simple formula is presented for empirical modelling of tyre force data. Based on exponential functions, it is capable of matching single slip data for lateral or longitudinal force using three parameters which can be computed in terms of stiffness, peak and saturated force values. Through a factorial study, the three parameters are also reformulated into functions of load and slip to provide full mapping of Fx and Fy across the range of longitudinal slip, lateral slip and vertical load. Significantly, the resulting model does not rely on a total slip calculation, so it retains a simple structure in force vs slip or load derivatives. The new model is compared with two other simple tyre models, and is shown to map forces generated from a reference Pacejka model. It is also used to fit measured tyre force data accurately.
Keywords: tyre model; empirical model; vehicle dynamics; vehicle control
Special Issue on: "Enabling technologies for sustainable vehicle electrification control, optimisation and diagnostics"
- A spatially-reduced dynamic model for the thermal characterisation of Li-ion battery cells
by Matteo Muratori, Marcello Canova, Yann Guezennec
Abstract: Li-ion electrochemical batteries have become the standard for energy storage in transportation and several studies have related the performance and aging behaviour to the cell temperature during utilisation. This paper proposes a methodology to predict the thermal behaviour of Li-ion battery cells through a spatially-reduced model. An electro-thermal model was formulated to predict the dynamics of the cell voltage, state of charge and internal temperature distribution in relation with the current demand and cooling conditions, applying an analytical solution technique. The model calibration was experimentally conducted and validation results are presented to support the proposed modelling approach.
Keywords: energy storage systems; Li-ion batteries; lithium-ion batteries; thermal modelling; thermal management; spatially-reduced models; electro-thermal models; Li-ion thermal properties; dynamic modelling.
Special Issue on: "Recent Advancement in Optimisation Algorithms for Vehicle Design and Manufacturing Processes"
- Simulation-based design optimization to develop a lightweight body-in-white structure focusing on dynamic and static stiffness
by Morteza Kiani, Hirotaka Shiozaki, Keiichi Motoyama
Abstract: Through finite element simulations, static stiffness and vibration frequencies of the body-in-white (BIW) model are investigated. Design of computer experiments through Latin Hypercube Sampling is used to sample the vehicle design space defined by the wall thicknesses of twenty parts. Radial basis function is used to generate separate surrogate models for selected responses, including bending, torsion, lateral, and longitudinal stiffness as well as the fundamental natural frequencies. A nonlinear constrained optimization for mass minimization is formulated and solved under two different cases. In the first case, the BIW model was optimized under just vibration while vibration and stiffness requirements are included in the second case. Results show that the NVH performance of the car improves when both vibration and stiffness requirements are included in the optimization. This guideline not only reduced the mass but also improved the body structure stiffness (static and dynamic) as the basic criterion of body design.
Keywords: car structure; NVH; vibration; stiffness; optimization; surrogate based.
Special Issue on: "Smart Materials and Structures in Automotive Applications"
- Semi-active control of magneto-rheological variable stiffness and damping seat suspension with human-body model
by Xiaomin Dong
Abstract: The potential benefits of a MR seat suspension in improving ride quality are investigated. Two magnetorheological (MR) dampers are devised and manufactured to realize the variable damping and equivalent stiffness capacities of a seat suspension, respectively. After evaluating field-dependent damping characteristics of the MR seat damper, the equivalent variable stiffness is also given. A seat suspension model with a four-DOF human body model is then formulated. A human simulated intelligent controller (HSIC) is proposed to attenuate the unwanted vibration of the variable stiffness and damping seat suspension. To validate the control performance of the proposed seat suspension and the control scheme, a numerical simulation is performed under the bump, random and chirp excitations. The result indicates that the proposed seat suspension system with HSIC can significantly improve the drivers ride quality compared to the passive one.
Keywords: magnetorheological damper, seat suspension, human simulated intelligent controller, HSIC, semi-active control, passive control
- Analysis of a magnetorheological damper incorporating temperature dependence
by Nicholas Wilson, Norman Wereley, Wei Hu, Gregory Hiemenz
Abstract: Aside from external environmental heating, a magnetorheological (MR) damper may internally self-heat due to both resistive heating by the electromagnetic coil and, to a greater extent, by dissipating mechanical energy into thermal energy. Temperature can significantly alter damper behaviour as the fluid viscosity and accumulator gas pressure are highly dependent on temperature. Therefore, to improve the understanding of the behaviour of a linear stroke MR damper designed for a ground vehicle seat suspension, its performance is characterised over temperatures ranging from 00C to 1000C. A hydro-mechanical analysis is used to represent MR damper behaviour when it is subjected to large temperature perturbations, and captures contributions from fluid viscosity, fluid inertia, and pneumatic compressibility. The effect of damper self-heating on the identified model parameters is presented, and the connection of these parameters to physical properties is also discussed.
Keywords: MR damper; temperature; fluid inertia; hydro-mechanical analysis.
- Semi-active control of an integrated full-car suspension with seat suspension and driver body model using electrorheological dampers
by Haiping Du, Weihua Li, Nong Zhang
Abstract: In this paper, an integrated vehicle semi-active suspension control system that includes a full-car suspension model (7 degree-of-freedom (DOF)), a seat suspension model (2 DOF), and a driver body model (4 DOF) is developed. A H∞ static output feedback controller that only uses measurement available variables as feedback signals is designed to improve vehicle ride comfort performance in terms of driver head acceleration under constraints of actuator saturation, suspension deflection limitation, and road holding capability. The controller design conditions, which are expressed as linear matrix inequalities (LMIs), are derived by dealing with each control input separately under a common Lyapunov function so that a feasible solution can be found for the integrated high order system that has five control inputs and ten control outputs. Each control input may require different feedback signals and have different saturation limitations. Furthermore, a semi-active control strategy
is applied to implement the proposed control system with using electrorheological dampers. Numerical simulations are used to evaluate the improvement of ride comfort performance in terms of driver head acceleration responses under typical road disturbances.
Keywords: integrated semi-active control, electrorheological damper, vehicle suspension, seat
suspension, driver body model
- Design of car hood sandwich structures for pedestrian safety
by Tso-Liang Teng
Abstract: Vehicle safety should simultaneously consider the safety of occupants and pedestrians, because pedestrians are the third largest category of traffic fatalities. Most pedestrian deaths occur due to traumatic brain injury resulting from the hard impact of the head against the stiff hood or windshield. Therefore, how to consider a more pedestrian friendly vehicle and then propose a new hood structure is an urgent work for minimizing pedestrian head injury. In this study, three kinds of sandwich hood structures are proposed for reducing pedestrian head injuries, including carbon fibre-reinforced polycarbonate, carbon fibre-reinforced foam and aluminium-reinforced polycarbonate. In assessing the friendliness of vehicle hood, this study adopts the EEVC/WG17 regulations of headform to hood tests. The finite element method is used to simulate the impact between vehicle hood and headform impactor. The software used in simulation is LS-DYNA. The results predicted by the headform to hood tests show that the hood structure with aluminium-reinforced polycarbonate material provides an absorption capability to protect pedestrians during the impact accident. It also is stiff enough to keep a pedestrian's head away from the beneath parts of engine cavity. Analysis models and sandwich materials proposed herein contribute to efforts to design vehicle hood structures and pave the way for developing pedestrian protection technologies.
Keywords: pedestrian; hood; sandwich structures; head injury; headform; EEVC/WG17.
- A magnetorheological-elastomer-based energy absorption device for car crash protection
by Lingyu Sun, Wei Li, Shirong Guo, Weiwei Chen
Abstract: To offer protection during a car crash under various collision scenarios, the energy absorption device should be able to adjust its stiffness and/or damping capacities accordingly. A magnetorheological elastomer (MRE) based adaptive energy absorption device (MREBEAD) is proposed and developed by taking advantage of its controllable characteristics for car bumper system. The distribution and amplitude of magnetic flux density are verified by finite element method. Both the shear and compression stiffness properties of MREs are derived analytically. In addition, a series of these devices are installed behind a car bumper, and the dynamic response and energy storage of the bumper system is demonstrated through MATLAB/Simulink software. The results show that the proposed MREBEAD system for car crash protection at a low speed collision is more effective than traditional metal crash box in avoiding plastic deformation and decreasing damage to passengers, as a result reducing the repair cost.
Keywords: magnetorheological elastomer; adaptive energy storage; car crash; finite element method; optimisation.
- Hydraulic hybrid vehicle vibration isolation control with magnetorheological fluid mounts
by The Nguyen, Shuo Wang, Mohammad Elahinia
Abstract: Hydraulic hybrid vehicle (HHV) is an emerging technology especially for heavy duty vehicles, thanks to its high efficiency and power density. However, one of the main problems that should be solved for the successful commercialization of HHV is the excessive noise and vibration produced by the hydraulic systems. This study focused on using magnetorheological fluid (MRF) technology to reduce the noise and vibration transmissibility from the power sources to the vehicle body. In order to study the noise and vibration of HHV, a hydraulic hybrid vehicle structure in parallel design was analysed. An MRF mount, to use for the engine and pump/motor, was designed, fabricated and tested. The vibration control schemes based on skyhook algorithm were used to reduce the transmissibilities and amplitudes of vibration. The research showed that the MRF mounts played an important role in reducing the transmitted noise and vibration to the vehicle body. Additionally, the locations and orientations of the isolation system also affected the efficiency of the noise and vibration mitigation.
Keywords: vibration isolation, hydraulic hybrid vehicles, magnetorheological fluid, skyhook control
- Magneto-rheological fluid flow through complex valve geometries
by Huseyin Sahin, Xiaojie Wang, Faramarz Gordaninejad
Abstract: In this study, the flow behaviour of a magneto-rheological (MR) fluid through complex valve geometries is investigated by analytical, computational and experimental approaches. A two-dimensional MR valve model is constructed for computational simulation, based on a unique MR device that has circular, radial, and annular flow regions. Compared with analytical solutions, the results of a computational fluid dynamics (CFD) model that has taken into account minor losses of MR fluid flow in different valving areas are in good agreement with those of experimental measurements. It has been shown that the Bingham CFD model works well for complex flow geometries in the two-dimensional domain, and that the CFD method can be greatly beneficial in the design and development of MR devices for practical applications.
Keywords: magneto-rheological fluids, complex valves, computational fluid dynamics
- A compressible magneto-rheological fluid damper - liquid spring system
by Faramarz Gordaninejad, Xiaojie Wang, Mutyala Rao Potnuru, Sreeram Mantripragada
Abstract: In this study, a compressible magneto-rheological fluid damper-liquid spring (CMRFD-LS) system is designed, built and tested. The CMRFD-LS functions as a liquid spring and a controllable fluid damper in a single unit. The CMRFD-LS system has a magneto-rheolgical (MR) valve with tapered annular flow channel. The flow profile and pressure drops due to varying cross sections of the flow path under different applied magnetic fields are studied. To evaluate the spring effect, experiments are carried out using pure silicone oil under different input displacements and frequencies. The spring effect of the liquid spring and the energy dissipated due to damping are obtained from the performance tests conducted with MR fluid, which is composed of 80wt.% iron particles suspended in silicone oil. The equivalent spring coefficient, equivalent damping coefficients, and energy dissipated for different sinusoidal input displacements at different motion frequencies and applied electric currents are determined from these force-displacement loops of experimental results. The effect of the tapered flow path on the pressure drops for compression and rebound is investigated.
Keywords: compressible, magneto-rheological fluid, liquid spring, semi-active damping
- Quasi-steady modelling for magneto-rheological fluid mount based on squeeze mode and experimental testing
by Changrong Liao, Lei Xie, Danxia Zhao
Abstract: A magneto-rheological (MR) fluid mount, based on parallel disk squeeze mode, is put forward to implement the controllable dissipation of vibration energy. The differential equation of the MR fluid squeeze radial flow is theoretically set. The Navier slip boundary condition and compatible condition are respectively used to depict the MR fluid slip at the disk surface and the smoothness of flow characteristics. The interface between the Newtonian flow region and bi-viscous flow region is theoretically determined. An approximate arithmetic of the squeeze force is developed, and the mathematical expression of the squeeze force is also obtained. Some influences of the slip coefficient and radius coordinate on the radial flow velocity profiles are examined. A MR fluid mount is designed and fabricated. The experimental test with sine wave excitation is accomplished. The experimental result reveals that the analytical squeeze forces are in good agreement with the experimental squeeze forces.
Keywords: magneto-rheological fluid; mount; squeeze mode; modelling; squeeze force
- Characterization of friction reduction with tangential ultrasonic vibrations using a SDOF model
by Marcelo Dapino, Shravan Bharadwaj
Abstract: Active control of friction between sliding surfaces is of fundamental and practical interest in automotive applications. It has been shown that the friction force between sliding surfaces decreases when ultrasonic vibration is superimposed on the sliding motion. This principle can be applied to systems in which solid state lubrication or friction modulation is advantageous. The ultrasonic vibration may be applied longitudinally, perpendicularly, or normal to the direction of motion. A number of friction models have been studied and applied in order to analyse this
phenomenon. The degree of friction reduction has been shown to depend on the ratio of the sliding velocity to the vibration velocity. Since friction is a system response, it is necessary to include system dynamics in the analysis of ultrasonic lubrication. A nonlinear single-degree-of-freedom-model is formulated and numerically approximated to quantify the effect on friction reduction of control force, normal load, friction-induced oscillations, tangential stiffness at the sliding interface, system stiffness, and coefficient of friction. Model results are in close
agreement with experimental measurements.
Keywords: ultrasonic lubrication, piezoelectric actuators, system dynamics