A numerical study on the optimal geometric design of speed control humps

Abstract

The aim of the present paper is to find an optimum speed control hump geometric design by using the sequential quadratic programming method. Theoretical investigation of the dynamic behavior of the driver body components and the vehicle due to crossing speed control humps is presented. The vehicle–driver system represented as a mathematical model consists of 12 degrees of freedom (DOF). Seven DOFs are used for the human body model in the heave mode and the rest are for the vehicle body, suspension system and tires. An optimum design method for the hump geometry is proposed to reduce the excessive shocks experienced by drivers when crossing the hump below the speed limit, while being unpleasant when going over the speed limit. The pleasant or unpleasant ride, or what is called comfort criteria (CC), is modeled by calculating the driver's head acceleration. In this regard, the geometry of the hump will be controlled to match an optimum practical shape that can be implemented economically. Three types of humps are discussed and evaluated in the optimization technique. These humps are Watts, flat-topped and polynomial humps. For Watts and flat-topped humps, different rise and return profiles which are used as design variables, are sinusoidal, harmonic, cycloidal, circular and modified harmonic. The global design was selected from 42 optimal designs which are found by combining different rise/return profiles for the three types of humps. The effect of special cases such as symmetrical roads, design limitations, CC, critical speed (CS) and system parametric variations on the optimal design of speed control humps are presented at the end of this paper.