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Although many different types of Adaptive Cruise Controller (ACC) have been developed to maintain a constant headway between lead and following vehicles, little is known about the dynamic performance of such controllers during cornering and in adverse environmental conditions. There are currently no standard guidelines for the use of ACC systems in such scenarios. Use of the controller in adverse weather or cornering conditions may lead to braking and handling instabilities, or unwanted accelerations being transmitted to the driver in the forms of pitch and roll. These dynamic characteristics are especially important when one considers that ACC systems are being marketed not as safety devices but to aid driver comfort. This paper presents an ACC algorithm that can be tuned to provide desirable dynamic characteristics as well as high-quality kinematic results. The performance of the controller is evaluated using a high-fidelity 9 degree of freedom vehicle model.

This paper proposes an advanced control strategy to improve vehicle handling and directional stability by integrating either Active Front Steering (AFS) or Active Rear Steering (ARS) with Variable Torque Distribution (VTD) control. Both AFS and ARS serve as the steerability controller and are designed to achieve the improved yaw rate tracking in low to mid-range lateral acceleration using Sliding Mode Control (SMC); while VTD is used as the stability controller and employs differential driving torque between left and right wheels on the same axle to produce a relatively large stabilizing yaw moment when the vehicle states (sideslip angle and its angular velocity) exceed the reference stable region defined in the phase plane. Based on these stand-alone subsystems, an integrated control scheme which coordinates the control actions of both AFS/ARS and VTD is proposed. The functional difference between AFS and ARS when integrated with VTD is explained physically.

The directional stability properties of passenger cars under high speed, straight running conditions form a major contributory factor in overall subjective ratings of vehicle handling, comfort and driveability. The aim of the paper is to investigate the links between straight running properties under random wind loading and vehicle design parameters. A linear, three degree of freedom vehicle model was selected, to which a simple driver model could be incorporated as necessary. The wind loading excitation was modeled using a quasi-static approach, involving a randomly varying side wind with statistical properties taken from existing literature. The response properties of the vehicle with and without driver were characterized by performance indices such as root mean square values of vehicle motions. Finally, these results were analyzed to search for correlation between the performance indices and vehicle chassis design features such as tires, steering system and suspension kinematics.

The current popularity of the Sport Utility Vehicle (SUV) market has led to new developments aiming to increase product performance. Such vehicles pose a significant challenge as they must perform to a high standard over a large variety of road conditions. Previously, emphasis has been placed on off-road ability. However, SUVs are now seen as an alternative to conventional luxury cars, and hence are expected to perform similarly, but without significantly degrading off-road performance. The introduction of a roll control system can achieve body roll levels lower than a conventional sports saloon, whilst improving off-road ability by removing the compromises associated with conventional anti-roll bars. This paper investigates the characteristics of such a system by developing a computer simulation of the vehicle and the associated roll control scheme.

A non-linear example vehicle model including four degrees of freedom (yaw, sideslip, roll and steering), non-linear kinematics and the Magic Formula tyre model has been developed. With the assumption of small perturbations around any steady-state working condition, the linearised equations are derived. A novel approach is used for the linearisation of external forces and moments from the tyres. They are linearised in terms of the state variables rather than the slip angle, camber angle and vertical load which are themselves functions of the state variables. The results of this process are expressed in terms of stability derivatives. In order to use the method, the steady-state solution of the non-linear equations is first obtained for a particular value of lateral acceleration, then after the calculation of the stability derivatives, a linear analysis can be performed for the linear equations in terms of perturbed variables.

The ride dynamics of articulated heavy trucks were studied to assess the benefits of applying electronically controlled suspension elements. Computer simulations were used to compare passive, two-state and continuous semi-active, and fully active suspensions. These results prompted further work to develop a prototype active suspension, operating according to a limited bandwidth strategy, which was tested on a full size, single-wheel-station vibration rig. With the active prototype, root mean square body vertical acceleration was 30% lower than with a production air suspension, during a test simulating travel over a very good road profile. RMS dynamic tyre forces, generated by the active prototype were similarly 20% lower. Mean power consumption during this test was 1.2kW. Further consideration of the limited bandwidth active suspension led to the invention of a substantially passive equivalent.