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An Active Independent Front Steering (AIFS) offers attractive potential for realizing improved directional control performance compared to the conventional Active Front Steering (AFS) system, particularly under more severe steering maneuvers. The AIFS control strategy adjusts the wheel steer angles in an independent manner so as to utilize the maximum available adhesion at each wheel/road contact and thereby compensate for cornering loss caused by the lateral load transfer. In this study, the performance potentials of AIFS are explored for vehicles experiencing greater lateral load transfers during steering maneuvers such as partly-filled tank trucks. A nonlinear yaw plane model of a two-axle truck with limited roll degree-of-freedom is developed to study the performance potentials of AIFS under different cargo fill conditions.

Technological developments in road vehicles over the last two decades have received considerable attention towards pushing the safe performance limits to their ultimate levels. Towards this goal, Active Front Steering (AFS) and Direct Yaw-moment Control (DYC) systems have been widely investigated. AFS systems introduce corrective steering angles to conventional system in order to realize target handling response for a given speed and steering input. It is thus expected that such an action under severe maneuvers may cause one tire to reach saturation while the other tire may be capable of developing more force. This study, therefore, proposes an Active Independent Front Steering (AIFS) system capable of controlling a wheel independently. At low speeds, the proposed AIFS system will modify the steer angle with speeds while maintaining pro-ackerman geometry similar to an AFS system. In doing so, it will realize a target response defined as one provided by a neutral steer system.

Dynamic interactions of urban buses with urban roads are investigated in view of the vibration environment for the driver and dynamic tire forces transmitted to the roads. The static and dynamic properties of suspension component and tires are characterized in the laboratory over a wide range of operating conditions. The measured data is used to derive nonlinear models of the suspension component, and a tire model as a function of the normal load and inflation pressure. The component models are integrated to study the vertical and roll dynamics of front and rear axles of the conventional and modern low floor designs of urban buses. The resulting nonlinear vehicle models are thoroughly validated using the fieldmeasured data on the ride vibration and tire force response of the buses.

In this study, the enhancement of road friendliness of Heavy Goods Vehicle is investigated using two methods to control the resonant forces: (i) Determination of optimal asymmetric force velocity characteristics of the suspension dampers to control the wheel forces corresponding to the resonant modes; (ii) Optimal design of an axle vibration absorber to control the wheel forces corresponding to the unsprung mass resonance mode. An analogy between the dynamic wheel loads and ride quality performance characteristics of heavy vehicles is established through analysis of an in-plane vehicle model. A weighted optimization function comprising the dynamic load coefficient (DLC) and the overall rms vertical acceleration at the driver's location is formulated to determine the design parameters of the damper and absorber for a range of vehicle speeds. The results show that implementation of tuned axle absorbers can lead to reduction in the DLC ranging from 11.5 to 21%.

The longitudinal load transfer encountered in a partly-filled ellipsoidal tank truck, subject to a straight-line braking maneuver, is investigated as a function of the location of partition walls, deceleration and the fill level. The response characteristics of the truck equipped with a compartmented tank are evaluated in terms of dynamic load transfer, stopping distance, braking time and time lag between the front and rear axle wheel lock-up. The braking response characteristics are derived as a function of the load shift, and number and location of partition walls. Road tests were performed on an airport fuel truck, equipped with a 3 m long tank with two movable partition walls. The simulation results derived from the test vehicle model are compared to the road test data to demonstrate the validity of the analytical model. The results show good correlation with the measured data acquired under straight-line braking maneuvers performed under different fill levels and initial speeds.

Ride quality of articulated vehicles is investigated via computer simulation in view of secondary suspension parameters. A tractor-semitrailer vehicle is modelled incorporating primary as well as secondary suspension. The ride vibration levels at the cab floor and at the driver-seat interface are evaluated using power spectral density approach. The effect of various vehicle parameters, such as secondary suspensions, primary suspensions, axle loads and tires on the vehicle ride quality is presented, and the significance of secondary vehicle suspension is specifically emphasized. A software package is developed to evaluate and assess the ride performance of articulated vehicles with suspended seat and cab. A limited validation of the computer ride model is achieved via field measurements.