Stability Of Car Research Articles

Computational aero-acoustic analysis of a passenger car with a rear spoiler

This study proposes an effective numerical model based on the Computational Fluid Dynamics (CFD) approach to obtain the flow structure around a passenger car with wing type rear spoiler. The topology of the test vehicle and grid system is constructed by a commercial package, ICEM/CFD. FLUENT is the CFD solver employed in this study. After numerical iterations are completed, the aerodynamic data and detailed complicated flow structure are visualized using commercial packages, Field View and Tecplot. The wind effect on the aerodynamic behavior of a passenger car with and without a rear spoiler and endplate is numerically investigated in the present study. It is found that the installation of a spoiler with an appropriate angle of attack can reduce the aerodynamic lift coefficient. Furthermore, the installation of an endplate can reduce the noise behind the car. It is clear that the vertical stability of a passenger car and its noise elimination can be improved. Finally, the aerodynamics and aero-acoustics of the most suitable design of spoiler is introduced and analyzed.

Comparison and evaluation of brake yaw motion controllers with an antilock brake system

Two brake yaw motion controllers (BYMC1 and BYMC2) designed to enhance the lateral stability and controllability of cars on slippery roads were evaluated. The motion controllers control the inner rear wheel slip of a vehicle engaged in turning manoeuvres or running on a split-μ road. Their performance was compared with that of a vehicle equipped with an antilock brake system under various road and driving conditions. The results show that the motion controllers reduce the vehicle slip angle and tyre slip angle under all conditions. They also reduce the yaw rate and the lateral acceleration on a split-μ road, and decrease the response variation during lane-change manoeuvres. BYMC1 and BYMC2 extended the limits of adhesion between tyre and road, and increased lateral stability and controllability.

Some remarks on vehicle following control systems with delays

In this paper, we consider the problem of vehicle following control with delay. To solve the problem of traffic congestion, one of the solutions to be considered consists in organizing the traffic into platoons, that is groups of vehicles including a leader and a number of followers "tightly" spaced, all moving in a longitudinal direction. Excepting the stability of individual cars, the problem of avoidance of slinky type effects will be explicitly discussed. Sufficient conditions on the set of control parameters to avoid such a phenomenon will be explicitly derived in a frequency-domain setting. ©2007 IFAC.

Fuzzy sliding mode control of real vehicle semi-active suspensions: comparison with output feedback sliding mode control

The design of a suspension system is very important for the ride-comfort and driving stability of automobiles. Many active and semi-active suspension systems have been studied and results reported. Since an active suspension requires a large amount of energy, semi-active suspension systems have recently received attention because of their lower energy consumption. This paper presents a new fuzzy sliding mode controller based on the theory of output feedback sliding mode control for a semi-active suspension system with variable dampers which have undesirable non-linear properties. In the experiment, the performance of the proposed fuzzy sliding mode control for the semi-active suspension has been examined by comparing it with passive control and also with the output feedback sliding mode control method. The experimental results illustrate the effectiveness of the controller.

Car Stability Detection from Tyre Stresses

In the framework of on-board active systems to control vehicle dynamics, a new approach is presented here. The study and developed application are dedicated to Electronic Stability Program field. This paper gives a feasibility study of the detection and quantification of the trajectory stability via stresses generated in the wheel-road interface. The approach chosen is based on fault diagnosis tools and fuzzy logic due to strong non-linear and coupling aspects. Finally a "detector" of stability (potential dangerous situation), essentially based on the measurement of lateral stresses, is given and tested on real measurements.

On the design and testing of a smart car damper based on electro-rheologicaltechnology

This paper presents the different steps involved in designing, building and testing anintelligent damper, which is originally a classic passive damper retrofitted withelectro-rheological (ER) technology, that can be used for semi-active car suspensions.Following an overview of the essential features of ER fluids, this paper examines thedifferent design details required in building an efficient ER car damper. This particularmodel, filled with a ‘Rheobay VP AI3565’ ER fluid, was experimentally testedfor different speeds and under different electric fields. The experimental resultsobtained clearly show that, when the high electric field is turned on, the generateddissipative force, and hence the damping characteristics, could be greatly increased.The dynamics of this first ER damper prototype model were numerically analysed, with anemphasis placed on evaluation of the influence of the electrical field on the resultingdynamic response. The results show that the damping ability could be easily increased byincreasing the height of the moving electrode. However, this damping increase, whichincreases the stiffness of the ER damper, should be handled carefully by both the designerand the user. Indeed, there is always an optimal damping value which provides acompromise between car stability and ride comfort. Moreover, the simulation shows thatthe controller used to control the damper should not only apply an on/off policybut should also be able to deliver a variable value of the applied high voltage.

Research of braking peculiarities of used cars

Abstract This paper briefly describes some analysis of a car braking process — the peculiarities of car wheel-to-road adhesion, the influence of distiibution of braking forces on car stability between front and rear axles. The requirements of EU Directive 71/320/EEC to braking force coefficients of car front and rear axles are exposed. Structural designs of braking systems are analyzed with respect to their meeting the EU standards. Experimental measurements ofbraking force coefficients for some models of cars which are used in Lithuania, are presented with the analysis how these coefficients meet the EU standards. The analysis of test results, suggestions for the ratio of braking forces of car front and rear axles are presented.

RESEARCH OF BRAKING PECULIARITIES OF USED CARS

This paper briefly describes some analysis of a car braking process — the peculiarities of car wheel-to-road adhesion, the influence of distiibution of braking forces on car stability between front and rear axles. The requirements of EU Directive 71/320/EEC to braking force coefficients of car front and rear axles are exposed. Structural designs of braking systems are analyzed with respect to their meeting the EU standards. Experimental measurements ofbraking force coefficients for some models of cars which are used in Lithuania, are presented with the analysis how these coefficients meet the EU standards. The analysis of test results, suggestions for the ratio of braking forces of car front and rear axles are presented.

1108 等価コーナリングパワーを用いたソーラーカーの操縦安定性に関する研究

1108 等価コーナリングパワーを用いたソーラーカーの操縦安定性に関する研究

Study on the Tire Design Methodology Improving Vehicle Dynamics. On the Driving Index and Tire Characteristics related to the Straight Running Stability of Passenger Cars.

In the present study, following efforts have been made, relating to the unsteady straight running stability of a passenger car. To build a model, on-road vehicle experiment is performed and the straight running stability of a vehicle is verified. Also, to investigate a driving index, sensory test and evaluations of heart rate variability by a driver are performed. To investigate the relationships between vehicle dynamics and tire characteristics, a model for the straight running stability has been built. A 3-degree-of-freedom vehicle model together with a general drivers model are utilized for the analysis. Next, the proposed human-vehicle-model is investigated and the index to quantify straight running stability is determined. Also, by identifying the tire characteristics that improves straight running stability, the effectiveness of the proposed human-vehicle-model is demonstrated. Lastly, tire test is performed against the same operational conditions used for the on-road vehicle test, to verify the validity of the developed human-vehicle-model.

Bilinear Disturbance-Accommodating Optimal Control of Semi-Active Suspension for Automobiles.

The design of suspension very important for ride-comfort and driving stability of automobiles. A lot of active and semi-active suspensions have been studied. In recent years, the cars with active or semi-active suspension have been put into practice. Since an active suspension needs large power and space, a semi-active suspension have recently received attention because of less power consumption. In this study, the bilinear disturbance accommodating optimal control method is established and it is applied to the semi-active control of suspension for automobiles. A half car body model with 4-DOF is used in order to examine the performance of this mothod. In this model, bounce, pitch and hop mode are considered. In the simulation, performance of the proposed bilinear disturbance accommodating optimal control to the semi-active suspension is examined by comparing it with passive control, skyhook control and Karnopp's control method. As a result, the proposed method showed better performance for ride-comfort and driving stability than the other control methods.

LATERAL STABILITY OF A BRAKING VEHICLE ON THE FRICTION LIMIT

A method for calculating the probability of wheel lock during braking with car is presented Car stability might be jeopardized or completely lost when one or more wheels exceed the friction limit. Generating of force in the tire contact depends on number of parameters, and some of them could be random. The paper deals with the behavior of the vehicle on the lateral stable and unstable areas.

Vehicle Cornering Characteristics in Acceleration and Braking through Attitude Control of Front and Rear Tires

A new active control method for the attitude angles of wheels is proposed to improve the maneuverability and stability of automobiles. From theoretical analysis and computer simulation, it is clarified that this control yields satisfactory vehicle cornering performances during steering, acceleration and braking. The dynamics of lateral movement and yawing of the vehicle as a result of tire attitude control are investigated using a quasi-steady-state analysis model for the case of tractive or braking force. An extended stability factor related to the characteristics of toe and camber angles of wheels is defined, which is applicable to circular turnings with lateral and longitudinal accelerations. Effects of control are analyzed using this factor. Furthermore, a modified control method is proposed, which makes it possible not only to improve vehicle dynamics but also to decrease actuating values of attitude angles in actual driving.

Integration of Neural Network and Linear Control Theory Applied to Four-Wheel-Steering Vehicles.

In order to improve handling and stability of automobiles, four-wheel-steering (4WS) systems have been studied and developed with remarkable success. Most of the control methods require a linearized two-wheel model of the actual vehicle system which is however strongly influenced by tire nonlinearity especially in critical situations such as emergency maneuvering or collision avoidance on slippery road surface. We propose a new method of designing the four-wheel-steering system, taking into account the nonlinear characteristics of tires and suspensions. For this purpose a new method using an artificial neural network and linear control theory is analyzed and applied to the identification and control of a nonlinear vehicle model structured using software for multibody dynamics (ADAMS). This model takes into account the nonlinear characteristics of actual vehicles with tires which are modeled by the Magic Formula. The results of computer simulation show that the proposed method using neural networks can be efficiently applied to improve the performance of the vehicle.

Vehicle Cornering Characteristics in Acceleration and Braking through Attitude Control of Front and Rear Tires.

A new active control method for the attitude angles of wheels is proposed to improve the maneuverability and stability of automobiles. From theoretical analysis and computer simulation, it is clarified that this control yields satisfactory vehicle cornering performances during steering, acceleration and braking. The dynamics of lateral movement and yawing of the vehicle as a result of tire attitude control are investigated using a quasi-steady-state analysis model for the case of tractive or braking force. An extended stability factor related to the characteristics of toe and camber angles of wheels is defined, which is applicable to circular turnings with lateral and longitudinal accelerations. Effects of control are analyzed using this factor. Furthermore, a modified control method is proposed, which makes it possible not only to improve vehicle dynamics but also to decrease actuating values of attitude angles in actual driving.

Adaptive Traction Control.

The driving force of an automobile depends ultimately upon the relationship between the tire and road surface. Therefore, traction control, which prevents tire slip, is becoming an important issue from the point of view of driving performance and stability of automobiles. Fuzzy traction control, developed by one of the authors and a co-worker, has excellent performance that can be adapted to any road conditions. It became clear, however, that fuzzy traction control is still poor under abnormal conditions of light vehicle load or of low tire pressure. Therefore, another algorithm for traction control carried out through the detection of the gradient between driving force and tire slip, was proposed in this paper. Relatively good results were obtained.

Fuzzy Tranction Control.

The driving force of an automobile depends ultimately upon the relationship between the tire and road surface. Therefore, traction control which prevents tire slip is becoming an impotrant issue from the point of view of driving performance and the stability of automobiles. Reported here is the traction control method using fuzzy control theory. Fuzzy control is "rule governed", and is said to be suitable for strong nonlinear objects such as this. Another special feature of this traction control is the use of the acceleration signal of the automobile, and this optimizes the engine performance even under the conditions of different slip characteristics. The investigation was carried out by experiment as well as by simulation. In the experiment, an electrical motor scooter on a chassis dynamometer was used instead of an actual automobile and road. Relatively good results were obtained.

Traffic dynamics through human interaction: Reflections on some complex problems

A brief essay based on a discussion of some highlights in the development of traffic flow theory over the last thirty-five years. Of especial interest are flow and stability in single-lane car following, collective effects in a kinetic theory of vehicular traffic on multi-lane highways and in a two-fluid model of traffic in urban street networks. Remarks are made concerning modeling and the remarkable simplifications that often arise from collective effects. It is pointed out that vehicular traffic is an excellent example of a system involving human interaction with consequent behavioral effects that have been effectively described in mathematical terms.

Analysis of dynamical character of car steering system and synthesis of 4-wheel-steering system.

In this paper the active control technology is applied to automovile vehicle dynamics. First, the transient response of the conventional 2-wheel-steering car is studied theoretically using a mathematical model. Results shows that the 2-wheel-steering system is non-minimum phase shift system and makes reverse reaction phenomena. Next, we propose a 4-wheel-steering system in which rear wheels are controlled as a function of rear steering. This system makes zero the horizontal angle of center of gravity and improve stability and control of cars.

渦格子法による自動車周りの流れの計算

Maneuvering stability of a passenger car is threatened when it is subjected to intensive oblique wind.In this study the flow around an automobile body in the oblique wind was carried out by numerical calculation with vortex lattice method. Visualization by the experiment with oil film method and tuft grid on a 1/8 scale model was also carried out to compare with the results of calculation. Good coincidence was obtained between the experimental results and the calculation.