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Hydraulic power steering systems traditionally are sized in a straightforward manner with easily verifiable results. The source of power in conventional systems is an engine driven pump that is effectively a source of hydraulic flow. As energy consumption of auxiliary functions becomes significant, on-demand power sources are considered. Best typified by hydraulic pumps driven by electric motors, these on-demand sources are often power limited, and established sizing practices should be re-visited.

Brake judder is about oscillations excited by brake application, which are generated in the contact area between brake pad and brake disc and are transmitted by the elements of the suspension to body and steering system. The driver perceives these perturbations as brake pedal pulsations, steering wheel rotational and body vibrations. The evaluation of a suspension concerning brake judder often takes place for the first time in road tests, since established simulation processes with a high significance concerning ride comfort are missing. At such a late moment necessary modifications in the development process are only hardly possible and very expensive. For avoiding brake judder a systematic development process is needed for brake and suspension. Each one can separately be improved in measurably borders so that their assembly is free of cold brake judder. The present paper shows appropriate test and simulation methods to achieve this.

Scope of the DRESS project is to research, develop and validate a distributed and redundant electrical steering system technology for an aircraft nose landing gear. The new system aims to: • reduce system weight at aircraft level, replacing the current hydraulic actuation system with an electric one. • improve aircraft safety, achieving higher system redundancy levels compared to the current technology capabilities. This paper presents an outline of different activities occurring in the DRESS project and also shows preliminary results of the new system performance.

Patents granted recently to Mr. Rode have changed the industry capability to adjust and verify wheel-end bearings on trucks. Until now it was believed1 that there was nothing available to confirm or verify the most desirable settings of preload on these bearings. The new, breakthrough invention is a tool and spindle-locking nut that permit quick and accurate wheel bearing adjustment by utilizing direct reading force measurement. Bearings can be set to either SAE recommended preloads or specific endplay settings. The author has been working on bearing adjustment methods for industrial applications for over forty years, and considers these inventions to be his most important breakthrough for solving this elusive bearing adjustment problem. Consistent wheel bearing preload adjustment was not possible before, even though it was widely known to achieve the best wheel performance as noted in SAE specification J2535 and re-affirmed in 2006 by the SAE Truck and Bus Wheel Subcommittee.

The timing and associated levels of braking between initial brake pedal application and actual maximum braking at the wheels for a tractor-semitrailer are important parameters in understanding vehicle performance and response. This paper presents detailed brake timing information obtained from full scale instrumented testing of a tractor-semitrailer under various conditions of load and speed. Brake timing at steer, drive and semitrailer brake positions is analyzed for each of the tested conditions. The study further seeks to compare the full scale test data to predicted response from detailed heavy truck computer vehicle dynamics simulation models available in commercial software packages in order to validate the model's brake timing parameters. The brake timing data was collected during several days of full scale instrumented testing of a tractor-semitrailer performed at the Transportation Research Center, in East Liberty, Ohio.

The paper presents linear and non-linear driveline models for Heavy Goods Vehicles (HGVs) in order to evaluate the main parameters for optimal tuning, when considering the drivability. The implemented models consider the linear and non-linear driveline dynamics, including the effect of the engine inertia, the clutch damper, the driveshaft, the half-shafts and the tires. Sensitivity analyses are carried out for each driveline component during tip-in maneuvers. The paper also analyses the overall frequency response using Bode diagrams and natural frequencies. It is demonstrated that the most basic model capable of taking into account the first order dynamics of the driveline must consider the moments of inertia of the engine, the transmission and the wheels, the stiffness and the damping properties of the clutch damper, driveshaft and half-shafts, and the tires (which link the wheel to the equivalent inertia of the vehicle).

Recently Michelin has been developing a new airless, integrated tire and wheel combination called the Tweel® tire. The Tweel tire aims at performance levels beyond those possible with conventional pneumatic technology because of its shear band design, added suspension, and potentially decreased rolling resistance. In this paper, we will focus on the environmental impact of the Tweel tire during its life-cycle from manufacturing, through use and disposal. Since the Tweel tire is currently still in the research phase and is not manufactured and used on a large scale, there are uncertainties with respect to end-of-life scenarios and rolling resistance estimates that will affect the LCA. Nevertheless, some preliminary conclusions of the Tweel tire's environmental performance in comparison to a conventional radial tire can be drawn.

This paper describes a driving controller to improve vehicle lateral stability and maneuverability for a six wheel driving / six wheel steering (6WD/6WS) vehicle. The driving controller consists of upper and lower level controller. The upper level controller based on sliding control theory determines front, middle steering angle, additional net yaw moment and longitudinal net force according to reference velocity and steering of a manual driving, remote control and autonomous controller. The lower level controller takes desired longitudinal net force, yaw moment and tire force information as an input and determines additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and has considered the friction circle related to vertical tire force and friction coefficient acting on the road and tire.

This paper presents an integrated design method for active trailer steering (ATS) systems of articulated heavy vehicles (AHVs). Of all contradictory design goals of AHVs, two of them, i.e. path-following at low speeds and lateral stability at high speeds, may be the most fundamental and important, which have been bothering vehicle designers and researchers. To tackle this problem, a new design synthesis approach is proposed: with design optimization techniques, the active design variables of ATS systems and passive design variables of trailers can be optimized simultaneously; the ATS controller derived from this approach has two operational modes, one for improving lateral stability at high speeds and the other for enhancing path-following at low speeds. To demonstrate the effectiveness of the proposed approach, it is applied to the design of an ATS system for an AHV with a tractor and a full trailer.

The adhesion control is the basic technology of active safety for the four-wheel driven EV. In this paper, a novel adhesion control method based on fuzzy logic control is proposed. The control system can maximize the adhesion force without road condition information and vehicle speed signal. Also, the regulation torque to prevent wheel slip is smooth and the vehicle driving comfort is greatly improved. For implementation, only the rotating speed of the driving wheel and the motor driving torque signals are needed, while the derived information of the wheel acceleration and the skid status are used. The simulation and road test results have shown that the adhesion control method is effective for preventing slip and lock on the slippery road condition.

Hydrostatic (hydraulic hybrid) drives have demonstrated energy efficiency and emissions reduction benefits. This paper investigates the potential of an independent hydrostatic wheel drive system for implementing a traction-based vehicle lateral stability control system. The system allows an upper level vehicle stability controller to produce a desired corrective yaw moment via a differential distribution of torque to the independent wheel motors. In cornering maneuvers that require braking on any one wheel of the vehicle, the motors can be operated as pumps for re-generating energy into an on-board accumulator. This approach avoids or reduces activation of the friction brakes, thereby reducing energy waste as heat in the brake pads and offering potential savings in brake maintenance costs. For this study, a model of a 4×4 hydrostatic independent wheel drive system is constructed in a causal and modular fashion and is coupled to a 7 DOF vehicle handling dynamics model.

The paper presents a method for the indoor testing of road vehicle suspension systems. A suspension is positioned on a rotating drum which is located in the Laboratory for the Safety of Transport at Politecnico di Milano. Special six-axis load cells have been designed and used for measuring the forces/moments acting at each suspension-chassis joints. The forces/moments, wheel accelerations, displacements are measured up to 100 Hz. Two different types of test can be performed. The tire/wheel unbalance effect on the suspension system behavior (Vibration and Harshness, VH) has been analyzed by testing the suspension system from zero to the vehicle maximum speed on a flat surface and by monitoring the forces transmitted to the chassis. In the second kind of test, the suspension system has been excited as the wheel passes over different cleats fixed on the drum.

With the objective of establishing the ultimate steering operation system for drivers, we developed, based on bioengineering considerations, the Twin Lever Steering (TLS) system which mimicks the bi-articular muscles, as shown in Fig. 1 . The bioengineering advantages are as follows: (1) force can be exerted more easily, (2) the steering can be accomplished quickly, (3) the positioning can be done accurately, and (4) the burden on the driver can be reduced (less fatigue). The advantages of the vehicle in terms of its motion are as follows: (1) the line-traceability is improved, (2) the drift control is improved, (3) the lane-change capability is improved, and (4) the lap time and stability are improved. We would like to report on these advantages of the TLS system from a bioengineering standpoint, and also describe the results of some verification test results obtained from vehicles equipped with this new steering system.

This work details the process employed to design the 2009 Cooper Union FSAE® suspension system, spanning the overarching design philosophy, configuration selection, analysis, fabrication, and implementation, while offering recommendations to those especially new to the field. The design methodology illustrated here provides a systematic approach to suspension geometry, material selection, packaging, and construction. Though this paper serves as a starting point for FSAE® suspension designers, it provides a succinct overview for those interested in general suspension design fundamentals. The design process began with the selection of a suspension configuration, geometries, and kinematics, which were driven in part by tire data, desired bulk vehicle dynamics characteristics, and overall geometric variability. The springs and adjustable dampers were then selected as the front and rear anti-roll bar properties were concurrently designed.

In response to the growing demand for fuel economy, we are developing a high-efficient variable displacement pump for hydraulic power steering systems. In order to develop a quiet variable displacement pump which generates lower noise for better vehicle interior sound quality, we have been developing a simulation tool which includes hydraulic analysis, vibration analysis, and vehicle interior noise analysis which combines simulation outputs and measured noise transfer functions of the targeted vehicle. This paper provides both validation results of the simulation tool and application examples to design improvement to conclude the effectiveness of the simulation tool developed.

Multiple-ribbed V belts have been widely used in automotive accessory drive systems to transmit power from crankshaft to power steering pump, alternator, and air conditioning (A/C) compressor. Overload under severe environmental conditions can lead to excessive slippage in the belt pulley interface in poorly designed accessory drive systems. This can lead to undesirable noise that increases warranty cost substantially. The mechanisms of this tribology phenomenon, noise features and system response are of utmost interest to the accessory drive system engineers. As accessory belt systems are usually used in ambient condition, the presence of water or moisture on belt is unavoidable under rainy or highly humid conditions. It has been found that the wet friction with negative coefficient of friction (cof)-velocity slope can lead to self-excited vibrations and squeal noise.

This paper concerns a torque control of a rear wheel of a motorcycle equipped with a rubber/aramid belt electronically-controlled continuous variable transmission where a primary sheave position is controlled by an electric motor. In particular, the paper discusses a method to calculate a required engine torque and a required primary sheave position, given reference values of a rear-wheel torque and an engine rotational velocity. The method forms a foundation of a hierarchized traction control where a higher control layer decides an optimal motorcycle motion (rear-wheel torque and engine rotational velocity) and a lower control layer realizes the motion by actuators (engine torque and primary sheave position). Difficulties of the control are due to large mechanical compliance of the rubber/aramid belt, which leads to an inevitable lag from the primary sheave position to a speed reduction ratio.

This paper describes the development of a new concept two-wheel steering system for realizing motorcycle motion control. By considering the whole of the main frame as the rear-wheel steering axis, it was possible to move the rear-wheel steering system from the conventional installation position at the rear arm to the head pipe. As a result, the developed two-wheel steering system is both lightweight and compact. This two-wheel steering system was installed in a motorcycle, and starting and stopping tests were carried out with two people riding on the motorcycle. The test results confirmed that the two-wheel steering system is capable of changing the motion characteristics of the motorcycle in actual riding. Furthermore, by calculating the equivalent wheel alignment of this system, this paper also theoretically demonstrates that these changes in motion characteristics are caused by changes in caster and trail.

In the automobile industries, weight reduction has been investigated to improve fuel efficiency together with reduction of CO2 emission. In such circumstance, it becomes necessity to make an electric power steering (EPS) more compact and lightweight. In this study, we aimed to have a smaller and lighter EPS gear size by focusing on an impact load caused at steering end. In order to increase the shock absorption energy without increase of stopper bush size, we propose new theory of impact energy absorption by not only spring function but also friction, and a new stopper bush was designed on the basis of the theory. The profile of the new stopper bush is cylinder form with wedge-shaped grooves, and when the new stopper bush is compressed by the end of rack and the gear housing at steering end, it enables to expand the external diameter and produce friction. In this study, we considered the durability in the proposed profile.

The adoption of the electronic controlled steering systems with new technologies has been extended in recent years. They have interactions with other complex vehicle subsystems and it is a hard task for the vehicle developer to find the best solution from huge number of the combination of parameter settings with track tests. In order to improve the efficiency of the steering system development, the authors had developed a steering bench test method for steering system using a Hardware-In-the-Loop Simulation (HILS). In the steering HILS system, vehicle dynamics simulation and the tie rod axial force calculation are required at the same time in the real-time simulation environment. The accuracy of the tie rod axial force calculation is one of the key factors to reproduce the vehicle driving condition. But the calculation cannot be realized by a commercial software for the vehicle dynamics simulation.