A COMPARATIVE STUDY OF PARAMETRIC MODELS OF MAGNETORHEOLOGICAL FLUID SUSPENSION DAMPERS
Magnetorheological dampers more commonly called, MR dampers, are being developed for a wide variety of applications where controllable damping is desired. MR damper is an intelligent damper, which is used as automobile suspension for vibration control. MR fluids represent a class of smart materials whose rheological properties change in response to the application of a magnetic field. MR fluid dampers are new type of vibration control elements, having the advantages of rapid damping and stiffness changing in the presence of an applied magnetic field. MR dampers have received a great deal of attention in the last two decades due to their being a potential technology to conduct semi-active control. It is therefore vitally important to understand the dynamic behavior of such devices whose nonlinear hysteresis is a rather complicated phenomenon. Models can accurately represent the behaviour of MR dampers are essential in understanding the operation and working principles of the device. Such models can eliminate a great deal of uncertainties during the design process, which can subsequently enable control strategies for the damper to be developed efficiently and reliably. In this paper, MR fluid structure, damper description and parametric models have been presented.
Semi-active H∞ control of vehicle suspension with magneto-rheological dampers
Semi-active H∞ control of vehicle suspension with magneto-rheological (MR) damper is studied in this paper. First, an experiment is conducted on an MR damper prototype subjected to cyclic excitation. Then, a polynomial model is adopted to characterize the dynamic response of the MR damper. Such a model has an advantage that it can represent the inverse dynamics of the MR damper analytically, so that the desired output in the open-loop control scheme can be realized easily. Finally, a static output feedback H∞ controller which utilizes the measurable suspension deflection and sprung mass velocity as feedback signals for active vehicle suspension is designed. The active control force is realized with the MR damper using the obtained polynomial model. A quarter-car suspension model is considered in this paper for analysis and simulation. The proposed scheme is further validated by numerical simulation under random excitation. Simulation results showed that the designed static output feedback H∞ controller realized by the MR damper can achieve good active suspension performance.
Flow and Compaction During the Vacuum Assisted Resin Transfer Molding Process
The flow of an epoxy resin and compaction behavior of carbon fiber preform during vacuum- assisted resin transfer molding (VARTM) infiltration was measured using an instrumented tool. Composite panels were fabricated by the VARTM process using SAERTEX(R)2 multi-axial non- crimp carbon fiber fabric and the A.T.A.R.D. SI-ZG-5A epoxy resin. Resin pressure and preform thickness variation was measured during infiltration. The effects of the resin on the compaction behavior of the preform were measured. The local preform compaction during the infiltration is a combination of wetting and spring-back deformations. Flow front position computed by the 3DINFIL model was compared with the experimental data.