This study presents the design, fabrication, and test of a magnetorheological (MR) damper utilizing an inner bypass that can simultaneously produce large dynamic range (i.e., ratio of field-on to field-off stroking load) and low field-off stroking load at high piston velocity. These two damper properties, large dynamic range and low field-off stroking load, are critical to achieving high performance in ground vehicle suspensions. The MR damper is comprised of a pair of concentric tubes, a movable piston-shaft arrangement, and an annular MR fluid flow gap between the concentric tubes. The inner tube serves as the piston guide, the inner surface of the annular flow gap, and the bobbin for the five electromagnetic coils used in this design. The outer tube serves as the flux return and the outer surface of the annular flow gap. The annular flow gap is an inner bypass annular valve where the rheology of the MR fluids, and hence the stroking load of the damper, is controlled. The MR damper is analyzed using a Bingham-plastic nonlinear fluid mechanics model. To experimentally validate the analysis of the MR damper with the inner bypass, and to illustrate its advantages over the MR damper with the conventional annular orifice, the prototype damper is tested in terms of controllable damping force or stroking load, dynamic range, and equivalent damping as a function of shaft/piston velocity.

“Functional integration” is to integrate two or multiple systems or mechanisms that are independent with each other and to realize the two or multiple functions using only one actuation system. Maximization of engineering applications of actuation systems could be achieved through the use of the “functional integration” concept-based structural design. In this article, an integrated semi-active seat suspension, mainly composed of a switching mechanism, a transmission amplification mechanism, and a damping force- or torque-controllable rotary magnetorheological (MR) damper working in pure shear mode, for both longitudinal and vertical vibration attenuation, is proposed, designed, and fabricated. The switching mechanism employs the parallelogram frames as a motion guide which keeps the seat moving longitudinally and vertically. Both longitudinal and vertical motions are transformed into a reciprocating rotary motion that is transmitted to the rotary MR damper after an amplification by a gear mechanism. The torque generated by the MR damper can be tuned by adapting the applied current in real time, and hence, effective two-dimensional vibration control of the seat could be realized. The mathematical model of the semi-active seat suspension system is established, and vibration isolation performance of the system is simulated and analyzed. Based on the established experimental test rig, the prototype of the semi-active seat suspension system is tested, and the results of the mathematical model and the experimental test are compared.

This paper presents a mathematical model for a new semi-active vehicle engine mount utilizing magneto-rheological (MR) fluids in squeeze mode (MR mount in short) and validates the model by comparing analysis results with experimental tests. The proposed MR mount is mainly comprised of a frame for installation, a main rubber, a squeeze plate and a bobbin for coil winding. When the magnetic fields on, MR effect occurs in the upper gap between the squeeze plate and the bobbin, and the dynamic stiffness can be controlled by tuning the applied currents. Employing Bingham model and flow properties between parallel plates of MR fluids, a mathematical model for the squeeze type of MR mount is formulated with consideration of the fluid inertia, MR effect and hysteresis property. The field-dependent dynamic stiffness of the MR mount is then analyzed using the established mathematical model. Subsequently, in order to validate the mathematical model, an appropriate size of MR mount is fabricated and tested. The field-dependent force and dynamic stiffness of the proposed MR mount are evaluated and compared between the model and experimental tests in both time and frequency domains to verify the model efficiency. In addition, it is shown that both the damping property and the stiffness property of the proposed MR mount can be simultaneously controlled.

This paper presents a shape function and memory mechanism based approach to design the hysteresis models which are related to the behaviors of smart materials, such as magnetorheological (MR) fluids, electrorheological fluids, piezoelectric materials, and friction forces. The proposed approach is inspired from two general properties of the existing hysteresis models, like Bouc-Wen, Dahl, and LuGre models. The memory mechanism originating from the charging and discharging processes of the resistor-capacitor circuit is constructed by adopting a virtual displacement variable and updating laws for the reference points. The shape function is achieved and generalized from analytical solutions of a simple semilinear Duhem model. Using the proposed approach, the memory mechanism reveals the essence of specific Duhem hysteresis and the general shape function provides a direct and clear means to fit the hysteresis loops. In addition, the proposed approach has a potential capability to formulate the inverse hysteresis model by estimating the virtual displacement. Eventually, as an example within a predefined format of the shape function, the feasibility of the proposed approach is verified through modeling the hysteresis behaviors of a commercial MR damper. A comparative work with Bouc-Wen model is further undertaken to demonstrate superior performances of high computational efficiency and comparable accuracy of the developed model based on the proposed approach.