Magnetic-Rheological (MR) Fluid Shock Absorber
This project is supported by LORD Corporation to develop a force VS v_rel plot for a MR-Fluid sample with different compounds.
Magneto-Rheological fluid (MR fluid) is a suspension of micron size iron spherical particles. The carrier fluid is typically an oil of some kind. If the fluid is within some passage way and a magnetic field is across the passage, the iron particles align with the magnetic field and it is difficult to create fluid flow until some breakaway pressure drop is established.
This characteristic is idealized for this demonstration but it does show that the slope of the force/velocity curves does not change with the current thus these fluids are not variable viscosity as sometimes referred to in the literature.
In the schematic, the dotted damper at the top of the figure is the idealized inertial damper we would like on the sprung mass. This is called an inertial or skyhook damper and of course it is not physically achievable. We use the force this damper would generate as the target force for the MR damper.
The purpose for this project is to design a scaled-down MR-Fluid shock absorber with force feedback by using a load cell. It is worth to notice that all of the MR-Fluid active suspension system on the market is using feedward control, meaning a look-up chart is developed through experiments such that the current output is based on the relative velocity. However, the particals in the MR-Fluid tends to wear off as time goes on, which results in a inaccurate performance with the feedward control. With the force feedback, it can be guaranteed that the force output will always be as desired since the current is no longer fixed based on a look-up chart.
Figure above shows a prototype of the scaled-down MR-Fluid shock absorber that has a load cell on the right end. Such a damper will first be tested to generate a force VS v_rel plots for Lord Corp's interests and then it will be put on a RC vehicle which is commanded by Raspberry Pi with a set of gyroscope sensors attached to apply any desired controller. This is an on-going project and results will be updated. Stay TUNED...