In an effort to reduce cost involving repetitive prototype build-test cycles, it is inevitable that simulation on full vehicle will be carried out during the product development stage. Desired suspension kinematic profiles of a given vehicle parameter are often unknown at the initial design stage. This paper demonstrates a simple methodology to obtain optimized kinematic characteristics against quality of handling performance using this model as predictive model in earliest design stage. A full vehicle model that is inclusive of suspension kinematic profiles and nonlinear damper profiles has been derived to enable the engineer to study the characteristics of the nonlinear elements against the vehicle performance when only limited vehicle data are available in the initial stage. Results suggest that the handling characteristics of a vehicle are sensitive to the changes in suspension kinematic profile. Additionally, the proposed vehicle model is able to provide satisfactory handling objective when measured in transient handling and frequency response compared to other vehicle models. A robust prediction model of the vehicle responses in frequency domain is proposed. It is coupled with the vehicle model employed as predictive model to optimize front toe angle profile against vehicle quality of handling performance measured in frequency domain. Keywords 10-degree-of-freedom full vehicle model, suspension kinematic profiles, design of experiment, vehicle handling Date

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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.

A passive vehicle suspension has constant spring and damper properties that compromise either ride or road holding ability, depending on whether the suspension is designed to be hard or soft. This study examines the implementation of a gear mechanism in a vehicle suspension system to alter its suspension characteristic while keeping the same spring and damper properties. In the study, a rack-and-pinion mechanism was used to modify the suspension force which acted between the sprung and unsprung masses of a quarter vehicle model. The system with proposed suspension layout was modeled mathematically and solved to obtain the vehicle response due to step excitation for various gear ratios. Results indicated that the use of such a mechanism was capable of changing the equivalent suspension force of the system. It was noted that different gear ratios would amplify or reduce the equivalent suspension force, hence emulating a harder or softer suspension setting compared to that of the original suspension. Additionally, it was found that with optimized gear ratio and gear mass, the implementation was capable of overcoming the compromise between the ride and road holding ability associated with conventional passive suspensions, as simultaneous improvement on both criteria was observed.

Inerter is a recent advancement in vehicle suspension that have been shown to be capable of improving vehicle ride comfort, however its ride improvement is less encouraging in the parallel layout. This study investigated the possibility of further ride improvement brought by vehicle suspensions with a switchable parallel inerter instead. In this theoretical study, the inerter was assumed to be on-off switchable based on semi-active force cancellation strategy. A two-degree-of-freedom quarter vehicle model was used to evaluate several cases of suspension system, which included ordinary passive suspension as reference, a system with switchable inerter and a system with both switchable damper and inerter. The model was solved mathematically with random road profile and step profile as ground excitations. Results showed that the use of switchable inerter in parallel to spring and damper in the different test cases was capable of reducing vertical sprung mass acceleration by a healthy 12 %, which is far superior to a mere 2 % achieved by a passive parallel inerter, as well as comparable to that achieved by a switchable damper. When both sprung mass acceleration and dynamic tire load were considered, comparison made on the Pareto fronts indicated that the switchable capability of an inerter managed to further improve the Pareto optimal sets over those obtained for cases with passive inerter.