Using gear mechanism in vehicle suspension as a method of altering suspension characteristic

Abstract

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.