Optimization of a Motorcycle Rear Suspension Mechanism with Four-bar Linkage

Abstract

In the paper optimization of the motorcycle rear suspension mechanism is presented. The introduction of a four-bar linkage in the classic rear suspension system, composed of a large fork made up of two trailing arms with two spring damper units, one on each side, inclined at a certain angle with respect to the swinging arm, makes it easier to obtain the desired damping and stiffness characteristics of the suspension system. The geometric parameters of the four-bar linkage (Uni-Trak® design of Kawasaki) are used in the paper as the design variables, which are optimized to obtain desired damping characteristics of the rear suspension system. It enables avoiding hitting suspension bumper stops which causes rider's discomfort and also excessive dynamic loads effecting motorcycle parts. Optimization toolbox for use with MATLAB (sequential quadratic programming) and also genetic algorithms were applied to solve the optimization problem. The analysis of numerical results shows that a possibility of varying just one geometric parameter of the four-bar linkage enables tuning the suspension system to different kinds of uneven roads (with different stochastic characteristics).