Showing papers in "Vehicle System Dynamics in 2004"

Performance Benefits in Passive Vehicle Suspensions Employing Inerters

Abstract: A new ideal mechanical one-port network element named the inerter was recently introduced, and shown to be realisable, with the property that the applied force is proportional to the relative acceleration across the element. This paper makes a comparative study of several simple passive suspension struts, each containing at most one damper and inerter as a preliminary investigation into the potential performance advantages of the element. Improved performance for several different measures in a quarter-car model is demonstrated here in comparison with a conventional passive suspension strut. A study of a full-car model is also undertaken where performance improvements are also shown in comparison to conventional passive suspension struts. A prototype inerter has been built and tested. Experimental results are presented which demonstrate a characteristic phase advance property which cannot be achieved with conventional passive struts consisting of springs and dampers only.

Optimal power management for a hydraulic hybrid delivery truck

Abstract: Hydraulic hybrid propulsion and energy storage components demonstrate characteristics that are very different from their electric counterparts, thus requiring unique control strategies. This paper presents a methodology for developing a power management strategy tailored specifically to a parallel Hydraulic Hybrid Vehicle (HHV) configured for a medium-size delivery truck. The Hydraulic Hybrid Vehicle is modelled in the MATLAB/SIMULINK environment to facilitate system integration and control studies. A Dynamic Programming (DP) algorithm is used to obtain optimal control actions for gear shifting and power splitting between the engine and the hydraulic motor over a representative urban driving schedule. Features of optimal control signal trajectories are then studied to derive implementable rules. System behaviour demonstrates that the new control strategy takes advantage of high power density and efficiency characteristics of hydraulic components, and minimizes disadvantages of low energy density, to achieve enhanced overall efficiency. Simulation results indicate that the potential for fuel economy improvement of delivery trucks with hydraulic hybrid propulsion can be as high as 47%. (A)

A new wheel/rail spatially dynamic coupling model and its verification

Abstract: Based on the theory of vehicle-track coupling dynamics, a new wheel/rail spatially dynamic coupling model is established in this paper. In consideration of rail lateral, vertical and torsion vibrations and track irregularities, the wheel/rail contact geometry, the wheel/rail normal contact force and the wheel/rail tangential creep force are solved in detail. In the new wheel/rail model, the assumption that wheel contacts rail rigidly and wheel always contacts rail is eliminated. Finally, by numeric simulation comparison with international well-known software NUCARS, comparison with vehicle-track vertical coupling model, and comparison with running test results by China Academy of Railway Sciences, the new wheel/rail spatially dynamic coupling model is shown to be correct and effective.

A Fuzzy Logic Direct Yaw-Moment Control System for All-Wheel-Drive Electric Vehicles

Abstract: Summary In-wheel-motors are revolutionary new electric drive systems that can be housed in vehicle wheel assemblies. Such E-wheels permit packaging flexibility by eliminating the central drive motor and the associated transmission and driveline components, including the transmission, the differential, the universal joints and the drive shaft. Apart from many advantages of such a system, unequalled independent wheel control allows vehicle dynamic improvement to assist the driver in enhancing cornering and straight-line stability on slippery roads and in adverse ground conditions. In this paper a Fuzzy logic driver-assist stability system for all-wheel-drive electric vehicles based on a yaw reference DYC is introduced. The system assists the driver with path correction, thus enhancing cornering and straight-line stability and providing enhanced safety. A feed-forward neural network is employed to generate the required yaw rate reference. The neural net maps the vehicle speed and the steering angle to give t...

Driving Pattern Recognition for Control of Hybrid Electric Trucks

Abstract: The design procedure for an adaptive power management control strategy, based on a driving pattern recognition algorithm is proposed. The design goal of the control strategy is to minimize fuel consumption and engine-out NOx and PM emissions on a set of diversified driving schedules. Six representative driving patterns (RDP) are designed to represent different driving scenarios. For each RDP, the Dynamic Programming (DP) technique is used to find the global optimal control actions. Implementable, sub-optimal control algorithms are then extracted by analyzing the behavior of the DP control actions. A driving pattern recognition (DPR) algorithm is subsequently developed and used to classify the current driving pattern into one of the RDPs; thus, the most appropriate control algorithm is selected adaptively. This 'multi-mode' control scheme was tested on several driving cycles and was found to work satisfactorily.

A 3D Brush-type Dynamic Tire Friction Model

Abstract: The use of advanced dynamic friction models can improve the brush-type tire friction models. This paper presents a 3D dynamic brush model based on the LuGre friction model. The model describes the dynamics of longitudinal and lateral tire friction forces, as well as the self aligning torque dynamics. It has been originally derived in a distributed-parameter form, and then transformed to a simpler lumped-parameter form with only three internal states. Both uniform and non-uniform normal pressure distributions are considered. The model has analytical solution for steady-state conditions. The steady-state behavior is validated with respect to “magic” formula static model, which served as an “ideal” benchmark. The lumped model dynamic behavior is validated by comparing its time-responses with original distributed model responses. The model parameterization with respect to normal force and other tire/road parameters is considered as well.

Combined type self-powered active vibration control of truck cabins

Abstract: A self-powered active suspension, which produces control force using energy regenerated by dampers, is applied to truck suspensions. Such systems do not require external energy to produce control force. To discuss its feasibility, the balance between the regenerated and the consumed energy is examined and active controllers that can achieve active control with regenerated energy are obtained. Control schemes for the self-powered system are presented, and their performances are examined through numerical simulations. The results show that the system achieves active vibration control without external energy, and has better suppression performance than passive or semi-active control systems. (A)

Synthesis of a Model-based Tire Slip Controller

Abstract: The Anti-lock Braking System is an important component of the steering system in a modern car. In the latest generation of brake-by-wire systems, the performance requirements on the ABS are much higher. The controllers have to be able to maintain a specified tire slip for each wheel during braking. The authors propose a design model and based on that a gain-scheduled controller that regulates the tire-slip. Simulation and test results are presented.

Automated Vehicle Merging Maneuver Implementation for AHS

Abstract: Summary This paper presents a real-time implementation of a general merging algorithm for automated highway systems. A merging control problem is proposed first. A real-time algorithm is then presented, which is used to calculate a smooth reference speed trajectory for the merging vehicle based on the speed of the main lane vehicle. This algorithm can also be applied even when the main lane vehicles change speed. To make the algorithm adapt to different road layouts and to increase safety, a concept of virtual platooning is proposed. It effectively shifts the time of platoon formation forward prior to the start of real merging. Aspects closely related to real-time implementation are discussed, such as the controller adopted, the use of magnetometer based distance measurement and information passing by communication from main lane vehicles. Test results are presented and briefly analyzed.

Neuromuscular dynamics and the vehicle steering task

Abstract: The paper describes part of a research programme aimed at understanding and modelling the role of steering torque feedback in the vehicle-driver system. Measurement and data analysis procedures for identifying the passive properties (inertia, damping and stiffness) of the driver's arms are presented. A linearised model is found to be satisfactory. In addition, the adaptive properties of the driver's arm dynamics are identified. In particular the driver is able to stiffen the arms by co-activating opposing muscle pairs. By measuring muscle activity using electromyography, the muscles involved in the steering task have been identified and muscle co-activation during a simulated driving task has been observed. For the covering abstract see ITRD E122482.

Design of a predictive semiactive suspension system

Abstract: SUMMARY In this paper we present an original design procedure for semiactive suspension systems. Firstly, we consider a target active control law that takes the form of a feedback control law. Secondly, we approximate the target law by controlling the damper coefficient f of the semiactive suspension. In particular, we examine two different kinds of shock absorbers: the first one uses magneto-rheological fluid instead of oil, while the second one is a solenoid valve damper. In both cases the nonlinear characteristics force-velocity of the damper are used to approximate the target law. To improve the efficiency of the proposed system, we take into account the updating frequency of the coefficient f and compute the expected value of f using a predictive procedure. We also address the problem of designing an asymptotic state observer that can be used not only to estimate the current state but also to predict the value that the state will take at the next sampling time.

Modelling the contact between wheel and rail within multibody system simulation

Abstract: In modern railway industry the simulation of the behaviour of railway vehicles has become an important design method during the last years. Modern simulation packages offer modelling elements that are highly adapted for standard and unusual simulation scenarios. A specific application case is the simulation of a railway vehicle travelling through a switch. It makes high demands on the simulation software due to the inconvenient modelling elements needed: the changing rail profiles on the blade rail and in the crossing vee area as well as the guard rail with its additional contact at the back of the wheel. The article gives an overview over the state of the art in railway vehicle simulation and presents a simulation of a passenger car running through a switch as an application example.

Optimisation of railway wheel profiles using a genetic algorithm

Abstract: This paper presents the procedures and preliminary results of a novel method for designing wheel profiles for railway vehicles using a genetic algorithm. Two existing wheel profiles are chosen as parents and genes are formed to represent these profiles. These genes are mated to produce offspring genes and then reconstructed into profiles that have random combinations of the properties of the parents. Each of the offspring profiles are evaluated by running a computer simulation of the behaviour of a vehicle fitted with these wheel profiles and calculating a penalty index. The inverted penalty index is used as the fitness value in the genetic algorithm. The method has been used to produce optimised wheel profiles for two variants of a typical vehicle, one with a relatively soft primary suspension and the other with a relatively stiff primary suspension.

Nonlinear Backstepping Active Suspension Design Applied to a Half-Car Model

Abstract: A fresh nonlinear backstepping design scheme, which is developed for the control of half-car active suspension systems to improve the inherent tradeoff between ride quality and suspension travel, is proposed in this paper. Since ride quality is dependent on a combination of vertical and angular displacements of a vehicle body, the design of active suspensions must have the potential to minimize heave and pitch movements in order to guarantee the ride comfort of passengers. The other important factor to be emphasized in the design of active suspensions is the suspension travel which means the space variation between the car body and the tires. In order to avoid damaging vehicle components and generating more passenger discomfort, the active suspension controllers must be capable of preventing the suspension from hitting its travel limits. Our design strategy, with two intentionally additional nonlinear filters, shows the potential to achieve these conflicting control objectives. The novelty of our active s...

Active steering systems based on model reference adaptive nonlinear control

Abstract: This paper presents a model reference adaptive nonlinear control strategy for active steering of a two wheel steering car which is realized by steer-by-wire technology. The ideal fixed property of a steering system, which is provided by a reference model, is attained by D * control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are very important under critical situations. Some results of realtime simulation with a steering equipment show the effectiveness of the proposed method.

An Alternative Method to Determine the Magic Tyre Model Parameters Using Genetic Algorithms

Abstract: SUMMARY Tyre behavior plays an important role in vehicle dynamics research. Knowledge of tyre properties is necessary to properly design vehicle components and advance control system. For that purpose mathematical models of the tyre are being used in vehicle simulation models. The Magic Formula Tyre Model is a semi-empirical tyre model which describes tyre behavior quite accurately. The Magic Formula Tyre Model needs a set of parameters to describe the tyre properties; the determination of these parameters is dealt with in this paper. A new method based on genetic techniques is used to determine these parameters. The main advantages of the method are its simplicity of implementation and its fast convergence to optimal solution, with no need of deep knowledge of the searching space. So to start the search, it is not necessary to know a set of starting values of the Magic Formula parameters. The comparison between analytical optimization methods and the method proposed is discussed in this paper.

Model-Based Road Friction Estimation

Abstract: The tire/road friction coefficient, μ, has a significant role in vehicle longitudinal and lateral control, and there has been associated efforts to measure or estimate the road surface condition to provide additional information for stability augmentation systems of automobiles. In this paper, a model based road friction estimation algorithm is proposed from easily measured signals such as yaw rate and wheel speed. For the development of the estimator, a low order vehicle model incorporated with simple but effective tire model. Field tests of the estimator using actual vehicle measurements show promising results.

A 3D contact force safety criterion for flange climb derailment of a railway wheel

Abstract: A revision on the railway safety criteria evolution has shown that the fundamentals of wheel/rail contact phenomena have not been completely addressed. Limitations encountered on the available criteria for safety against derailment have motivated a deeper analysis on the wheel rolling mechanism. The contact mechanics were completely modelled with two tangential components, lateral and longitudinal forces, including spinning effects. An extended three-dimensional formula for the railway wheel flange climb derailment process is derived. Results show that calculated values agree with the classical formulation, and extend its application. This formulation allows the identification of L/V limit values for a three-dimensional rolling-contact mechanism. It can help to identify more reliable limits, relocating the safety margin for the dynamic operation of a railway vehicle.

The dynamics of the three-piece-freight truck

Abstract: The paper provides a model to describe the dynamical performances of the three-piece-fright truck. The model has 19 rigid bodies and 81 degrees of freedom. The focus is put on the two-dimensional dry friction on the surfaces of the wedges in the lateral and vertical directions, and on the contact surfaces between the side frames and the adapters(wheelsets). The stick- slip motion between the corresponding components caused by the friction and the structure varying systems occurring together with the stick-slip motion are considered. The friction direction angle, the switch condition and the acting friction force are used in the model. The critical speed is determined through Hopf bifurcation analysis. The phase diagram and first return map are used to verify the chaotic motion of the systems. The dynamic responses and the wheel/rail contact forces to the irregularity track are provided.

Overview of Coupling of Multibody and Control Engineering Tools

Abstract: The role of Computer Aided Engineering in vehicle development has been significantly increased during the last decade. Specialised simulation tools became very complex, however, growing demands on complexity and particularly interdisciplinarity of vehicles and their simulation models have led to a number of approaches trying either to develop multidisciplinary simulation tools or to connect various specialised simulation tools by interfaces. This paper addresses some aspects of interconnection of the specialised simulation tools as one possibility for simulating complex mechatronic vehicle systems. It classifies the interfaces between specialised software packages in general, mentions some historical development of the interfacing and further discusses the examples of the implemented couplings between the Multibody System codes and Computer Aided Control Engineering tools. Finally, the performance of selected interfaces is compared on an example simulation of a controlled vehicle suspension.

A study of active steering strategies for railway bogie

Abstract: This paper presents a fundamental study of active steering for a railway bogie and is focussed on the development of control strategies to provide a perfect curving performance. A number of active steering strategies are considered. One is to control the wheelset and the bogie to follow desired yaw movements on curves; the second is to control the lateral motion of the wheelset to take the pure rolling line; the third is to control the actuators such that low frequency zero force in the primary suspensions is achieved; and finally a control method using relative motions between the two wheelsets is also investigated to improvement of the performance robustness against parameter variations. A comprehensive assessment of the steering strategies is carried out. For the covering abstract see ITRD E122482.

Automotive steering control in a split-μ manoeuvre using an observer-based sliding mode controller

Abstract: Summary In this paper a sliding mode integral action controller and sliding mode observer are used to enhance vehicle stability in a split- µ manoeuvre. Anti-lock braking systems (ABS) have become an integral part of modern cars, and they have dramatically improved vehicle handling in braking manoeuvres. However, when a vehicle attempts to brake on a surface with uneven friction coefficient such as on wet or icy roads, a so-called split- µ scenario, the yaw moment generated by the asymmetric braking can prove demanding for an inexperienced driver. The controller presented hereworks in conjunction with a conventional ABS system to provide safe and effective braking through steer-by-wire. This paper extends previous state-feedback work by only using certain measurable quantities in the controller, estimating further signals by employing an observer.

Study on electromagnetic damper for automobiles with nonlinear damping force characteristics: (Road test and theoretical analysis)

Abstract: This paper presents study on the electromagnetic damper (EMD) with nonlinear damping force characteristics for automobiles and its road tests. The authors proposed EMD for automobiles for improved ride comfort and compatibility between stability and isolation. General dampers for automobiles have nonlinear damping force characteristics to satisfy this compatibility. The power electronic circuits for the EMD were developed to achieve any nonlinear damping force characteristics. These circuits have the following characteristics: 1) No external power source is required for circuits because the EMD regenerate power, 2) High controllability and tuning of nonlinear damping characteristics were made. The experiments with shaker and road tests proved that the proposed EMD system achieves the nonlinear damping force characteristics for automobiles, and has suitable ability for automobiles dampers.

Practical string stability for longitudinal control of automated vehicles

Abstract: This paper considers string stability for vehicle longitudinal control from a practical implementation viewpoint. A different parameterization is used compared to previous work. Two following strategies are considered, i.e. Adaptive Cruise Control (ACC) and vehicle platooning with inter-vehicle communication. A simplified model and transfer function are used for analysis. It shows that ACC cannot achieve string stability while platooning with communication can achieve it, which agrees with practical test. For the covering abstract see ITRD E122482.

Analysis of active suspension systems with hydraulic actuators

Abstract: 2SUMMARY Most of the existing active suspension studies assume that an ideal force actuator exists and will carry out the commanded force accurately. In reality, due to the interaction between the hydraulic actuator and suspension system, the lightly damped modes of the plant will generate lightly damped zeros (LDZ) for the servo-loop system, which confines the closed-loop performance to a low frequency range. Converting the active suspension problem formulation into a displacement control problem, as suggested by several recent papers, will not solve this problem. Four candidate remedies to reduce the effect of the LDZ are studied and their potentials and limitations are discussed.

Process save reduction by macro joint approach: the key to real time and efficient vehicle simulation

Abstract: Applying a non-linear model reduction method to the tire suspension system of road vehicles enables an automatic transfer of complex offline simulation vehicle models to a mathematical model, which fits the real time simulation requirements. The basic assumption, that high frequent inner suspension dynamics are not relevant to handling manoeuvres, converts the differential algebraic equation system (DAE) of suspensions with kinematical closed loops into pure elasto-kinematical linkage equations. The equations of motions can be represented as an ordinary differential equation system (ODE) and considerable simulation time reductions are obtained for the off-line simulation and real time simulation is enabled. This so-called macro joint approach is an alternative modelling method to the well-known look-up table representation of suspension kinematics but it keeps the parameterisation of the original suspension model and is suitable to parameterised real time MBS models. With a second step the dynamics, caused by compliance in the suspension bushings, are reduced to their quasi-static behaviour. The consideration of these quasi-elasticity has nearly no influence on the necessary simulation time. This contribution shows the theoretical background and demonstrates the advantage of the macro joint model reduction approach on a typical vehicle example. (A)

Analysis and method of the analysis of non-linear lateral stability of railway vehicles in curved track

Abstract: The paper is a contribution into the question of stability in curves and into breaking down the traditional approach to it. It shows that considering stability in curves is reasonable, justifiable and worthwhile. Formal shape of the original method of stability analysis in curved track is presented. Straight track case is just a circular curve of infinite radius here. The method is based on results of numerical simulation. Authors use such results to verify and present corresponding procedure applied while investigating stability in curves. Results of simulation enabled to show how the problem looks for a particular vehicle as well as to analyse stability for objects' variants. The analysis includes influence of angle of attack, cant deficiency and excess as well as suspension parameters on vehicle's stability properties and also comparison of stability for 2-axle vehicle and a bogie of 4-axle one. For the covering abstract see ITRD E122482.

Identification of transient road obstacle distributions and their impact on vehicle durability and driver comfort

Abstract: This paper presents methods that enable identification of the distribution of transient obstacles in a set of public roads. The roads are considered as non-stationary random profiles with superimposed transients of varying depths or heights and lengths. The transient obstacles are detected from both road profiles and vehicle responses by use of wavelet analysis. The impact of the identified distributions on vehicle durability and driver comfort shows a clear potential for differentiating the designs for different road conditions.

Active roll mode control implementation on a narrow tilting vehicle

Abstract: This paper describes work carried out on the development of a narrow tilting vehicle at the University of Minnesota. The project had two objectives. One objective was to better understand the dynamics of two-passenger leaning vehicles. The other was to use this understanding to design and implement leaning control on such a vehicle. The desire was to make a tilting vehicle as easy, in some sense, to drive as a non-leaning vehicle. The scope of this work was fourfold. First, a model of such a system was developed and linearized to obtain a fourth-order linear model. Second, a tilt controller was designed to stabilize a tilting vehicle's unstable rolling mode. Third, the system and controller were simulated using both Simulink and a real time simulator written with Visual Basic. Fourth, and most importantly, an experimental vehicle was built and used for implementation. Comparisons were made between the simulated system and the experimental vehicle. This illustrated the limitations encountered in the simula...

Design and experimental implementation of an active stability system for a high speed bogie

Abstract: This paper describes an experimental active stability system for a high speed railway vehicle. Two models are developed in the study: one for control system design and one for control system performance assessment. A number of possible control schemes are described, these include single axle control schemes and modal control schemes. Results both from comprehensive simulations and for the stability controller functioning on an experimental vehicle during a testing phase are presented. For the covering abstract see ITRD E122482.