Recent experiences have shown that one of the main causes of heavy vehicle crashes is the braking performance. In particular, when having to decelerate in an emergency situation, such as when an unexpected object is in the road. Thus, the capability of a vehicle to come to a safe stop is one of the most important factors in preventing more accidents. Safe braking distance is influenced by many factors, such as brake pedal force, the vehicle's loading conditions, the travel speed and the road surface conditions. The aim of this study was to analyse the effect of the driver's brake pedal force on braking distance during an emergency situation, allowed for a wide range of heavy vehicle's GVW and speed. This study is carried out by using a multi-body dynamics simulation of a Single Unit Truck based on the validated vehicle model. Braking performance was estimated in terms of braking distance on a straight road with a wet surface. The findings from the braking distance simulation suggest a non-linear relationship between brake pedal force and braking distance. Finally, it reveals that, depending on the wheel lock-up situation, braking distance increases with increasing brake pedal force, and that the braking distance on a wet road is significantly affected by both the heavy vehicle's GVW and speed.
Abstract. The skid mark is valuable for accident reconstruction as it provides information about the braking behaviour drivers and the speed of heavy vehicles. However, despite its importance, there is currently no mathematical model available to estimate skidding distance (SD) as a function of vehicle characteristics and road conditions. This paper attempts to develop a non-linear regression model that is capable of reliably predicting the skidding distance of heavy vehicles under various road conditions and vehicle characteristics. To develop the regression model, huge data sets were derived from complex heavy vehicle multi-body dynamic simulation. An emergency braking simulation was conducted to examine the skidding distance of a heavy vehicle model subject to various Gross Vehicle Weight (GVW) and vehicle speeds, as well as the coefficient of friction of the road under wet and dry conditions. The results suggested that the skidding distance is significantly affected by Gross Vehicle Weight, speeds, and coefficient of friction of the road. The improved non-linear regression model provides a better prediction of the skidding distance than that of the conventional approach thus suitable to be employed as an alternative model for skidding distance of heavy vehicles in accident reconstruction.
Numerous studies have proven that the performance of vehicle suspension can be benefited by an inerter in parallel to conventional spring-damper setup, yet its usability in passenger vehicle suspension is still limited by practical consideration in physical implementation. One way of achieving better physical implementation of the parallel inerter suspension layout is to exploit the inerter’s flywheel as a metallic conductor to integrate passive damping in the form of a rotary eddy current damper. However, the feasibility of eddy current damping in this specific application remains unknown. This study investigates the applicability of eddy current damping incorporated in an inerter in terms of the achievable damping rates as required in typical passenger vehicle suspensions. In the study, passive eddy current damping due to constant magnetic field around the flywheel of a mathematically designed inerter was computed through simulation, and the range of achievable damping rates due to parametric variations, for instance air gap and magnetic coverage, was evaluated. Results of the parametric analysis showed that the induced eddy current damping from a rack-and-pinion inerter’s flywheel, considering the designed inertance as prerequisite, was at least capable of achieving 1500 Nsm-1. As the achievable damping was within the range of suitable damping rates for typical passenger vehicles, rotary eddy current damper was deemed applicable in passenger vehicle suspension employing parallel inerter.
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