June 14, 2009
June 14, 2009
June 17, 2009
14.156.1 - 14.156.10
In applied process control engineering curriculums, such as programmable logic controllers, MR fluids are easily activated and deactivated by controllers to maintain process set points. Using these fluids in conjunction with proportional–integral– derivative programming accurately removes hysteresis effects on the process being controlled. In statics and dynamics curriculums, sheering force calculations during fluid transitions provides remarkable insight into the clutching and dampening capabilities of the fluid.
Magneto-rheological (MR) fluids are a form of “intelligent” material that change their flow characteristics when subjected to a magnetic field. Response, which takes only milliseconds, is in the form of a progressive gelling that is proportional to field strength. MR fluids can be produced that are capable of giving high shear stresses at low applied magnetic fields. The unique nature of this class of magnetic fluids allows dramatic changes in rheology to occur within the bulk of the fluid on application of a relatively modest magnetic field. The material can change from being fluid to solid almost instantaneously, the rheology of the material reverting to its original state upon removal of the field.
“Response, which takes only milliseconds, is in the form of a progressive gelling that is proportional to field strength. With no field present, the fluid flows as freely as hydraulic oil”.1 As a result, MR technology provides fast and infinitely variable control of energy dissipation of industrial and automotive devices.2 This change of state has the potential to revolutionize the control aspects of vibration and the responsiveness of hydraulic power transmission systems. “The application of magneto-rheological fluids for damping is a unique and novel approach to an age-old problem”. 3
MR fluids have existed for over fifty years. However, it is only now that fluids are available that are stable and give shear stresses that are adequate in demanding applications such as automotive damping. In fact, one automotive manufacturer is equipping several of its new (2007) vehicles with a “MagneRide Suspension” that utilizes MR fluid technology. The manufacturer claims that the MagneRide suspension provides continuous variable real-time suspension damping based on road and driving conditions. 2
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