Global Journal of Researches in Engineering, A: Mechanical & Mechanics, Volume 22 Issue 1

et al [23] have used PID controller in their work to control semi-active suspension system. The active suspension system is characterized by the presence of a linear actuator beside the spring and damper. The linear actuator can be either a hydraulic actuator or an electric motor. The role of the linear actuator is to generate the force required for the suspension system to be more comfortable and the vehicle more stable during varied driving conditions [19- 21] Tremendous development has occurred in vehicle technology in most of the vehicle's components, especially the suspension system. Firstly, the suspension system has been presented in the economic vehicles as a major part of the vehicle's parts. The main role of the suspension system is to isolate or reduce the vibrations resulting from the movement of the vehicle is travelling over different roads according to the quality of the asphalt. Conventional suspension system is consisting of sprung mass and un-sprung mass connected by a spring and damper. The un-sprung mass is attached to the bottom by means of a tire stiffness. The conventional system is called the passive suspension system. To enhance the performance of the suspension system, a semi-active suspension system has been applied, in which the value of the damping coefficient is adapted based on changing operating conditions such as vehicle speed and road quality. Many references have proven the effectiveness of the semi-active suspension system . On the other hand, the quality of roads in residential areas and highways is increasing day by day, which encourages some vehicle drivers to drive at high speeds more than the recommended limits set by the authorities. Therefore, decision makers have been forced to extend road humps, especially where accidents are frequent. Several shapes of humps and bumps have been presented such as circular, trapezoidal and circular bumps. Of course, these humps greatly affect the vehicle ride comfort, especially when traveling over them at high speeds . Therefore, the aim of this work is to present a theoretical study (a mathematical model) using the MATLAB Simulink program to investigate the vibrational behaviour of a quarter a car with passive suspension and a semi-active suspension system with a comparison between each system when driving over the types of bumps by calculating - : • Body Vertical Acceleration (m/s 2 ) . • Tire Dynamic Loads (N) . • Suspensions Working Space (m) . • Body Displacement (m) . III. M odeling & A nalysis Table 1: Below shows a medium sedan passenger car specification that will be used in this study.[6] Table 1: Sedan vehicle specifications Many types of road humps are globally used in urban areas. In this study, three well known types of road humps are used: circular hump, trapezoidal hump, and cat-eye hump. a) Circular Hump The circular humps are one of the common humps that are used in urban areas and cities. The circular hump is characterized by the arc radius “R”, the hump length, and hump height. It is required to calculate the time required that the vehicle is travelling over the hump. The time is the input of the model. The time can be expressed as follow: Parameters Value Suspension Stiffness (k s ) 30000 (N/m) Damping Coefficient (c s ) 3500 (N ⋅ s/m) Sprung Mass ( 2 ) 381 (kg) Un-Sprung Mass ( 1 ) 50 (kg) Tire Stiffness (k t ) 220000 (N/m) Tire Damping Coefficient (c t ) 140 (N.s/m) Moment of Inertia ( ) 1000 (kg.m 2 ) Wheelbase ( ) 2.69 (m) Vibrational Behaviour of a Quarter Car Travelling over Road Humps with Different Suspension Systems © 2022 Global Journals Global Journal of Researches in Engineering (A ) Volume XxXII Issue I Version I 48 Year 2022 .