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

Vibrational Behaviour of a Quarter Car Travelling over Road Humps with Different Suspension Systems Waleed Dirbas α , Hamza Diken σ & Khalid Alnefaie ρ Abstract- Due to the unawareness of some vehicles’ drivers to abide by the limited speeds, many authorities have had to set up road speed humps to calm down the vehicles flow, especially in densely populated areas. And as a result, bad vehicles ride comfort is produced from the suspension system. Therefore, researchers and car manufacturers were interested in improving the vibrational behaviour of the vehicle while traveling over humps. In this study, the vibrational behaviour of the vehicle was studied while traveling over different types of road humps using passive, semi-active and active suspension systems. A mathematical model was introduced to study the vibrational behaviour of the vehicle when traveling over various types of road humps such as the circular hump, trapezoidal hump, and cat-eye hump, using a passive, semi-active and active model. The parameters that were investigated in this study to evaluate the ride comfort are the body vertical acceleration, the suspension working space, the dynamic tire load, and the body displacement. The results show that the ride comfort is greatly affected by driving over humps especially at high speeds. The impact was most evident and tangible when traveling over the road humps, even at low speeds. Traveling over humps, whether circular or trapezoidal, has a great impact on the vehicle ride comfort as well as the stability of the car. There is a tangible improvement when using a semi-active and active suspension system. These improvements were obtained in the body vertical acceleration, the suspension working space, and the displacement of the body. While there was no significant change in the dynamic tire load levels. In the case of active suspension system, there is a greater improvement in both the suspension working space, the body vertical acceleration, and the body displacement. Keywords: vehicle ride comfort, quarter car model, road humps, vehicle stability, and vehicle vibrational behavior. I. I ntroduction uring the last century, the vehicle has become one of the basics of daily life. Wherever we are, the vehicle is considered as the companion of man in all parts of the earth. Wherever the human found the vehicle inherent to him. The vehicle is one of the ways to add more comfort and ease human life. Since the beginning of the production of vehicles, scientists and vehicle manufacturers have been interested in ride comfort as one of the most important factors in adding driving a pleasure.[1] Author α σ ρ: King Abdulaziz University, Mechanical Engineering Department, Jeddah, KSA. e-mail: waleedahmedderbas@hotmail.com Due to the unawareness of some vehicles’ drivers to abide by the limited speeds, many authorities have had to set up road speed humps to calm down the vehicle's flow, especially in densely populated areas. And as a result, bad vehicle ride comfort is produced for the vehicle components . [2] Semi-active suspension is a type of vehicle suspension system in which the force generated by the damping is variable to achieve better ride comfort and reduce the amplitude of the shock amplitude of the generated vibrations. The damping force is varied depending on the input outgoing naturally changing road surfaces. The purpose of this system is to apply the adaptive active suspension using variable shock absorbers that produce variable damping force. The semi-active suspension system can be managed in a variety of control methodologies. One of these methods is a rather ideal technology referred to as the Skyhook control system . [3] As for the active suspension system, it is fundamentally different from other previous types, as it depends mainly on a control system that works to regulate the generation of additional power that is produced by an electrical or hydraulic actuator organized by a control algorithm based on the signals of the sensors indicating the road and driving conditions of the vehicle. In addition to the main suspension components; spring and damper; the active suspension includes the actuator to provide additional force to spring and damper forces that contribute to improving ride comfort. The active suspension is characterized by the generation of additional power from the actuator to reduce the impact of vertical forces generated by unexpected changes in road inputs.[4] There are two main types of humps, the short type which is known as bumps that are typically used to smooth lanes in low-speed areas such as school fronts and shopping mall parking lots. This type of bump is designed to force cars to travel at extremely low speeds less than10 km/h. As for the other type of humps, it is to slow down traffic on a larger scale and is characterized by its large dimensions, relatively to the short type, and is used in the streets within the city to force cars over a range of 10-20 km/h. The humps usually lead to a sharp jolt in the car’s suspension system, especially the short bumps, and it can reach severe damage to the D Global Journal of Researches in Engineering (A ) Volume XxXII Issue I Version I 45 Year 2022 © 2022 Global Journals