Alternate Optimization of Speed Control Hump for Automobiles and Automobile Suspension : Reducing Excessive Shocks to Drivers of Heavy Vehicles by Multiobjective Optimization of Hump

Abstract

In this paper, we propose an optimum design method of humps to reduce the excessive shocks experienced by drivers of heavy vehicles passing over existing circular arc humps with a length of 3.67 m at normal speeds, and to compensate for too few shocks experienced by drivers when light vehicles with semi-active suspensions pass over the same humps at excessive speeds. We take the standpoint of hump design and suspension design alternately, and determine the optimum dimensions of a circular arc hump by optimizing it and the damping coefficient of light vehicle suspension dampers alternately. The maximum acceleration of the driver of the heavy vehicle and that of the light vehicle is set as a multiobjective function for the optimization of the hump, while the maximum acceleration of the driver of the light vehicle is selected as a single objective function for the optimization of the suspension of it. It is found that the optimum hump determined in this study further reduces the excessive shock to drivers of heavy vehicles compared to the existing hump and to the optimum hump obtained in the previous study, in which heavy vehicles were not considered. For the light vehicles, a decrease in the amount of control of vehicle speed was found previously, but the present method is found to overcome this weak point. Speed control effects of the existing hump and the one optimized by the present method on three types of light vehicles with different wheelbases which have two types of conventional passive suspensions are compared using simulation calculations. The optimized hump exhibited less deviation among the above different vehicle types in terms of the speed control effects.