Search Results

Rollover crash and accident studies identify significant roof-to-ground impacts adjacent to the vehicle occupant as a potential cause of severe injuries. It is not possible with existing dynamic rollover test methods to specifically repeat or recreate a particular roof-to-ground impact in a controlled fashion. Variations associated with tire-to-dolly, tire/wheel-to-ground, and vehicle-to-ground interactions early in current rollover test methods tend to produce unpredictable and unrepeatable roof-to-ground impacts later in the test. A new test device now enables researchers to bypass the uncertainty of these first ground interactions by beginning each test with the desired roof-to-ground impact conditions as a test input. The new rollover test method releases a rotating vehicle onto the ground from the back of a moving semi-trailer.

A mathematical model for a hydraulic power steering system was constructed and numerical analysis was performed for self-excited vibration caused by rapid steering in the power steering system. From the examination, the guide of the prevention against the vibration was derived, such as positioning the rather long hose at near the power steering gear in the supply line, and the mechanism of the prevention was clarified. Moreover, the mathematical model and the guide of the prevention were verified by bench tests.

Even if the brake judder is an often analyzed problem from the mechanical point of view, its influence on the hydraulic elements such as the braking and steering systems is not fully established. The aim of this paper is to present models of the hydraulic components connected to a model of the front suspension and thus having a view of the influence of these hydraulic elements on the amplification of the brake judder vibrations. Each models of the front suspension, the braking circuit and the hydraulically powered steering assistance are validated separately versus or measurements or other softwares. The introduction of the disc thickness variation (DTV) generates the braking judder of interest. Some first simulation results are shown to see couplings or influence of hydraulic components on vibration propagations.

This paper presents a new motor current control strategy for Electric Power Steering (EPS) to reduce current fluctuation. Such current fluctuation may cause undesirable steering torque ripple and acoustic noise, if an inexpensive microprocessor is used. Using a DC-motor, current fluctuation associated with change in the battery voltage, etc., may occur. We have developed a new current control strategy which effectively alleviates current fluctuations of the motor without using higher performance microprocessors. The new controller is based on the estimation of disturbance voltage and compensation for this disturbance voltage. We have bench-tested the performance of this control strategy and confirmed that current fluctuation is reduced below that using conventional PI controller. The PI gain for the proposed controller is the same as that for the conventional controller.

Mathematical modeling of the mesh friction of a rack and pinion system has been carried out in order to predict the mesh friction of a steering gear. The three dimensional gear geometry and force diagram of a rack and pinion gear is represented in vector form. With proper boundary conditions applied to the equations, the mathematical model simulates the friction forces resulting from the mesh. An experimental apparatus was also built to measure mesh friction between a rack and pinion. A number of rack and pinion steering gears have been tested under several load conditions. Experimental results are then compared with the simulation results to verify the mathematical model.

Front road wheel toe dynamics directly affects tire wear and steering wheel vibration, which in turn negatively impacts customer satisfaction. Though static toe can be preset in assembly plants, the front road wheels can vibrate around steering axes or kingpin axes due to tire mass unbalance and nonuniformity. The frequency of the vibration depends on the wheel size and vehicle speed, while the amplitude of the vibration is not only dictated by the tire forces, but also by suspension and steering parameters. This paper presents a study on the sensitivities of the front road wheel toe dynamics to the parameters of a short-long-arm suspension (SLA) and a parallelogram steering system. These parameters includes hard point shift, steering gear compliance, gear friction, control arm bushing rates, friction in control arm ball joints, and compliance in tie rod outboard joints.

Recently, EPS (Electrical Power Steering) is being widely applied in order to reduce fuel consumption and decrease installation problems of the power steering system. EPS also decreases development time and cost of the steering system due to its ease of tuning. As we mentioned in the former paper “2000-01-0824”, the larger output motors are required. Upon developing the higher output motors, Mitsubishi realized that the EPS Systems brought about high acoustic noise, vibration, large torque ripple and friction loss. We have developed a very silent motor based on our unique technology. This involved a very unique electromagnetic force and mechanical vibration analysis method. Our super silent motor is so quiet, that the occupants of a vehicle can not distinguish the motor noise even when the motor is installed in the vehicle cabin.

This paper describes the method used to design the basic control algorithm of a lane-keeping support system that is intended to assist the driver's steering action. Lane-keeping control has been designed with steering torque as the control input without providing a minor loop for the steering angle. This approach was taken in order to achieve an optimum balance of lane-keeping control, ease of steering intervention by the driver and robustness. The servo control system was designed on the basis of H2 control theory. Robustness against disturbances, vehicle nonlinearity and parameter variation was confirmed by μ - analysis. The results of computer simulations and driving tests have confirmed that the control system designed with this method provides the intended performance.

The automotive shock absorber has various functions in car performance. Particularly, it is a dominant tuning parameter to get good primary and secondary ride characteristics within 1-35Hz ranges in car development. Thus, understanding of characteristics of shock absorber in this frequency range is indispensable to both test and analysis engineers for an effective and systematic approach. In this study, tire is also investigated from the same point of view. Frequency dependent stiffness and damping coefficient are extracted by discrete sine swept test under constant velocity of 25, 50, 100mm/sec which represent typical road surface conditions[1]. The responses are analyzed on frequency domain and the basic theoretical background for this approach is introduced.

Prior theoretical work relating barrier equivalent velocity (BEV) and change in vehicle velocity, ΔV, has either neglected restitution or mischaracterized its role. Based on fundamental structural dynamics principles, improved relationships between BEV, ΔV, coefficient of restitution, and vehicle mass and stiffness are formulated. These corrected relationships are then utilized in the assessment of four classes of vehicular impact testing: vehicle to vehicle (VTV), vehicle to infinitely massive rigid barrier (VRB), vehicle to infinitely massive compliant barrier (VCB) and vehicle to finite mass movable rigid barrier (VFMB).

Traditionally coil springs were used for applications to exert one-dimensional force along a given spring coil axis. However, in recent years, there has been an increasing trend in using coil springs to provide forces in a multi-dimensional space. In this paper, an approach to construct a model of a coil spring for suspension systems using a spatial six degree-of-freedom parallel mechanism is presented. In kinematics and dynamics simulation, the use of a parallel mechanism to model a coil spring allows a designer to simulate six degrees of freedom spring characteristics with vehicle kinematics without using FEA feature embedded in the simulation software. This requires a significant amount of computational load and maybe a file format converter.

As for the McPherson strut, a force from the tire acts on the shock absorber producing a bending moment, which causes an increase in the friction acting on the shock absorber. Reducing the friction is one of the most important issues to improve the riding comfort of an automobile. The bending moment can be reduced by controlling the load axis of the coil spring assembled with the shock absorber. In order to control the load axis, several types of coil springs have been recently reported. This paper proposes another shape-controlled coil spring, called L-shape. The L-shape spring has the following advantages: (1) The load axis can be precisely controlled with ease; (2) Additional space is unnecessary; (3) Manufacturing tractability is increased. The proposed L-shape spring is validated analytically and experimentally in this paper. The effect of the L-shape spring for reducing the friction on a shock absorber is also experimentally confirmed.

A method for predicting body deformation during operation, which cannot be measured by conventional methods, has been developed. The method creates a body model based on the characteristics extracted by modal analysis of the results of a vibration testing of an actual vehicle. The model is combined with a suspension model, using multibody dynamics software, and body deformation calculations are performed. In this paper, the influence of body deformation on vehicle controllability and stability is studied and the usefulness of the method is verified.

For concept and design of modern suspension systems many different demands have to be considered. Beside package and lightweight construction especially the real scopes of a suspension system, kinematics and compliance, are getting more and more important to fulfill all technical needs coming from the automotive market. In particular the development of suspension systems for Sports Utility Vehicles (SUVs) has to satisfy very high demands and strong characteristics criteria coming from the On-Road and Off-Road driving. As many different load cases have to be taken into account, an analytic approach can only be used for first concept steps to design a SUV-suspension system. After that it is necessary to verify and tune all suspension and bushing characteristics by the use of multibody simulation tools like e. g. ADAMS. Therefore adequate models of all suspension components have to be available [6].

Friction caused by side force on a damper axis results in riding discomfort. In order to cancel the side force, accurate shape control for coil springs have been recently become crucial. After designing a target coil shape using a finite element analysis (FEA), actual coiling processes can be done by a NC coiling machine(C/M). The problem with this method is that the NC coiling machine has its own characteristics which coiling experts have to consider when adjustments are made to the control points of the NC machine. This adjustment process usually takes significant amounts of time in order to meet the target coil shape, because the coiling experts do their adjustments by a conventional method based on their experience. This paper describes how to automate the control point design process to reduce the coiling effort and to save time. An ARMA model is used for the coiling machine modeling and its dimensions are determined by the physical dimension of the actual coiling machine.

The University of Texas Center for Electro-mechanics (UT-CEM) has been developing active suspension technology for high-speed off-road applications since 1993. The UT-CEM system uses controlled electromechanical actuators to control vehicle dynamics with passive springs to support vehicle static weight. The program is currently in a full vehicle demonstration phase on a military high mobility multipurpose wheeled vehicle (HMMWV). This paper presents detailed test results for this demonstration vehicle, compared to the conventional passive HMMWV, in a series of tests conducted by the U.S. Army at Yuma Proving Grounds. Extensive data in plotted form are discussed, including accelerometer readings from 6 vehicle mounted accelerometers, corner displacement transducers, and current and power plots for the actuators.

One of the main drawbacks of the NOx adsorber technology vs. the other leading approach for high level NOx conversion, namely selective catalytic reduction, is its high sensitivity to sulfur. In spite of the likely availability of ultra-low sulfur fuel and protecting devices like sulfur traps, and furthermore taking into consideration additional sulfur sources such as engine oil and lubricants, a desulfurization strategy will be essential to the commercial implementation of NOx adsorber catalysts on diesel vehicles. The results presented in this paper were obtained on NOx adsorbers with proven thermal durability and efficiency in diesel engine exhaust. They show NOx performance recovery following severe sulfur poisoning, after desulfation under temperature and air/fuel mixture conditions compatible with diesel engine operation. In addition, different desulfurization tactics, tested on a synthetic gas bench simulating diesel exhaust, are depicted and discussed.

HVE 1 and PC-Crash 2 have been the subject of numerous SAE papers. Both programs have been offered to reconstructionists for the purpose of analyzing vehicle accidents and presenting the resulting motions in 3D graphical form. This paper will give an overview of the theoretical basis for the two computerized accident reconstruction and simulation tools, the user interfaces, the way they present the results, and how they compare in the analysis of different types of accidents.

Frontal, side, rear, pole and offset car to car data sets are examined using familiar damage analysis models: constant stiffness, bilinear stiffness, and force saturation. In addition to these, a non-linear power-law formulation is introduced and compared to the others. The power-law provides a nonlinear stiffness coefficient that transitions between a constant force model and constant stiffness model as the power goes from 0 to 1. It also provides a continuous, single valued function that is easily integrated and used in the analysis. Power-law nonlinearity can be used to smoothly fit low through high crush data. Geometric integral parameters are developed which represent irregular crush profiles. These permit graphical comparison of tests with non-uniform crush data (such as offset, side, and narrow object) with uniform crush test data. They also provide a means for comparison of accident damage with the test data set.

SIMON is a new vehicle dynamic simulation model. Applications for SIMON include single- and multi-unit vehicle handling simulation in severe limit maneuvers (including rollovers) and 3-dimensional environments. Applications also include vehicle-to-vehicle and vehicle-to-barrier collisions. This paper provides the technical background for the SIMON engineering model. The 3-dimensional equations of motion used by the model are presented and explained in detail. The calculations for suspension, tire, collision, aerodynamic and inter-vehicle connection forces and moments are also developed. The integration of features available in the HVE Simulation Environment, such as DyMESH, the Driver Model, Brake Designer and Steer Degree of Freedom, is also explained. Finally, assumptions and limitations of the model are presented.