Mousa Rezaee, , , ,
Volume 11, Issue 3 (9-2011)
Abstract
In this paper, considering a half car model with 3-DOF, the effects of vehicle velocity, wheelbase, and the vibration parameters of the passenger seat on the statistical characteristics of the vehicle body and the seat responses are investigated. In the previous studies, 2-DOF model was generally used for vibration analysis of the vehicle under the road random excitation. However, science these models ignore the DOF corresponding to the seat, they are not suitable for ride comfort analysis. Here, in order to overcome this shortage and make it possible to study the ride comfort, considering an additional DOF for the seat, a half car 3-DOF model has been used. Moreover, in order to investigate the Root Mean Square Acceleration Response (RMSAR) of the vehicle body and the seat, a mathematical relation is proposed for the power spectral density (PSD) of the actual highway- type road excitation. Finally, by applying the proposed PSD, the ride comfort of a special passenger car (Samand) has been studied. The results show that the range of variations of RMSAR of the vehicle body and that of the seat are completely different from each other, and by choosing reasonable values for the stiffness and damping coefficients of the seat, one can improve the ride comfort.
Reza Hassannejad, Abolfazel Seifi, Mohammad Ali Hamed,
Volume 15, Issue 6 (8-2015)
Abstract
Passive suspension system is used in most vehicles due to its low energy consumption and low cost in most vehicles. Therefore, today there is a challenge in order to enhance the suspension system. The aim of this study is to present a new method for Multi-Objective design of vehicle suspension based on the use of asymmetrical dampers (Nonlinear). Hence, It is shown that using these type of dampers with a choice of two type coefficient by which one of them is in compression and another one in expansion, will lead to a more optimal design compared to those in the literature. For this purpose, vehicle was modeled using full model with eleven degree of freedom under random road excitation. Then, since the tasks of suspension system are reduction of vertical acceleration exerted on passengers, reduction of pitch acceleration of sprung mass, improving road holding and reduction of the change of four wheel work space. Therefore, the problem is defined as a Multi-Objective problem with conflicting objectives which formulated and solved by NSGA-II algorithm. The obtained results indicated that using asymmetrical dampers leads to more efficient design compared to those methods with symmetrical dampers.
