The development of a powerful new magnetorheological fluid (MRF), together with recent progress in the understanding of the behavior of such fluids, has convinced researchers and engineers that MRF dampers are among the most promising devices for semi-active automotive suspension vibration control, because of their large force capacity and their inherent ability to provide a simple, fast and robust interface between electronic controls and mechanical components.In this paper, theoretical and experimental studies are performed for the design, development and testing of a completely new MRF damper model that can be used for the semi-active control of automotive suspensions. The MR damper technology presented in this paper is based on a completely new approach where, in contrast to in the conventional solutions where the coil axis is usually superposed on the damper axis and where the inner cylindrical housing is part of the magnetic circuit, the coils are wound in a direction perpendicular to the damper axis. The paper investigates approaches to optimizing the dynamic response and provides experimental verification.Both experimental and theoretical results have shown that, if this particular model is filled with an 'MRF 336AG' MR fluid, it can provide large controllable damping forces that require only a small amount of energy. For a magnetizing system with four coils, the damping coefficient could be increased by up to three times for an excitation current of only 2 A. Such current could be reduced to less than 1 A if the magnetizing system used eight small cores. In this case, the magnetic field will be more powerful and more regularly distributed. In the presence of harmonic excitation, such a design will allow the optimum compromise between comfort and stability to be reached over different intervals of the excitation frequencies.

This article presents a new concept design for magnetorheological dampers, where the excitation circuit and magnetic field are applied from outside the magnetorheological chamber. This magnetorheological damper was designed and built to decrease the intrusive manufacturing operations and to maximize the working efficiency. The experimental tests made on the first prototype featuring this new technology was promising. The excitation of a set of 12 coils surrounding the body of the damper, by an electric current of 5 A, managed to increase the damping coefficient by up to 75%. A similar performance could be obtained by a current 9.4 times lower if the magnetic circuit is designed correctly. Compared to other devices, the actual design tolerates more the temperature elevation caused by the feeding of coils with high-intensity current, just because the heat is radiated outwards instead of being transferred directly to the magnetorheological fluid like in conventional designs. Finally, the numerical simulations made on Matlab show that the new magnetorheological damper, when mounted on a commercial vehicle, can considerably enhance its dynamic behavior and bring it back quickly to its stable position when the tires hit a bump on the road.

No abstract

This paper presents the different steps involved in designing, building and testing an intelligent damper, which is originally a classic passive damper retrofitted with electro-rheological (ER) technology, that can be used for semi-active car suspensions. Following an overview of the essential features of ER fluids, this paper examines the different design details required in building an efficient ER car damper. This particular model, filled with a ‘Rheobay VP AI3565’ ER fluid, was experimentally tested for different speeds and under different electric fields. The experimental results obtained clearly show that, when the high electric field is turned on, the generated dissipative force, and hence the damping characteristics, could be greatly increased. The dynamics of this first ER damper prototype model were numerically analysed, with an emphasis placed on evaluation of the influence of the electrical field on the resulting dynamic response. The results show that the damping ability could be easily increased by increasing the height of the moving electrode. However, this damping increase, which increases the stiffness of the ER damper, should be handled carefully by both the designer and the user. Indeed, there is always an optimal damping value which provides a compromise between car stability and ride comfort. Moreover, the simulation shows that the controller used to control the damper should not only apply an on/off policy but should also be able to deliver a variable value of the applied high voltage.

This study presents the design and performance evaluation of a new design of intelligent damper that can be used for semi-active vehicle suspensions.This damper is a modified version of anordinary model, for which electro-rheological (ER) technology was incorporated. The key features of this particular design are the use of an efficient homemade homogeneous organic/inorganic ER fluid together with four electrodes mounted electrically in parallel and could be excited separately and independently from each other.An electro-rheological fluid (ERF) was prepared using modified silica particles dispersed in silicon oil. Molecules with mesogens groups were grafted on the surface of silica using polymethylhrosiloxane (PMHS) as interface. A net improvement of the stability of the suspension was then observed with an appreciable ER effect. FTIR and Zeta potential measurements confirmed the silica surface change.The characteristics of the fluid and the damper are experimentally obtained. The results show that the damping ability could be easily increased by increasing the number of excited electrodes.Incorporating the ER damper into a quarter-car suspension system represented by a single-degreeof-freedom model show that the optimum between comfort and stability depends on the excitation frequency. Because a continuous varying damping device is difficult and expensive to achieve, the innovative idea to use a fragmented long electrode could be an original approach to deliver a stepped (discrete) damping which values are depending on the number of excited electrodes.