Speakers Information- Controls, Measurement & Calibration Congress
Shocks absorbers with inertial valve in vertical dynamic behavior of a passenger car Guilherme Caravieri de Abreu Magneti Marelli
ABSTRACT This study is intended at investigating the possible benefits of the use of shock absorbers with inertial valves in terms of ride quality and safety. This is aimed to provide a theoretical framework for decision making before large investments are made in experimental evaluations, which are costly. A comparative study of the dynamic response resulting from a car suspension equipped with shock absorber with inertial valves and the one resulting from a suspension with conventional shock absorbers is conducted. For this objective, mathematical models have been developed to investigate the influence of acceleration sensitive shock absorbers on the vertical dynamics of passenger vehicles in terms of ride and handling criteria. A quarter car model with 2DoF is used for an analysis of the dynamic response of the vehicle under different road quality conditions and utilizing performance criteria quantifying comfort and safety. The results reported in this manuscript indicate a good potential for the use of shock absorbers with inertial valves, showing improved ride comfort without sacrificing safety.
INTRODUCTION For physical reasons, comfort and stability are antagonistic in the design of the vehicle suspension. A vehicle with great performance in stability is not comfortable on bumpy roads. The converse of this statement is that the extremely comfortable vehicle, does not have proper grip of the tire to the ground. The dampers and springs of the suspension plays an essential part in this relation, because they determine the compromise between comfort and safety. These two components determine the relative movement between the wheels and the ground and between the wheels and the vehicle body, aiming to keep the wheels as much time in contact with the ground and with minimal disturbance in body, increasing safety and improving comfort, respectively. For some time are applied for suspension systems which use shock absorbers with characteristics of the variable damping coefficient depending on driving conditions, the weight carried and various other information using electromagnetic valves or magneto-rheological fluids. These are called semi-active systems, however, have the disadvantages of very high cost and the need to use sensors in the vehicle suspension and complex electronic controllers. There are also shock absorbers that do not use electronic modulation of damping, but valves which are sensitive to the stroke, frequency or acceleration. One of these shock absorbers that have an internal device that is excited by the movement of the sprung mass or even by the unsprung mass change the damping coefficient for more appropriate level to the current acceleration of the sprung mass in a passive way. These dampers are called shock absorbers with inertial valves and promise a performance positioned between passive and semi-active suspension, but with lower cost and complexity than the latter. The purpose of this study is to provide an objective evaluation of the performance potential of a suspension that uses a system with inertial valves through computer simulations. Through the development and use of relatively simple mathematical models, it is expected to evaluate the potential of a vehicle suspension equipped with shock absorbers with inertial valves subjected to typical situations on the track, using objective performance criteria found in the literature and specific standards used by the vehicles manufacturer.