Any smart attenuator has its constraints and therefore does the one with magnetorheological fluid inside it. Some of the most vital concerns pertaining to the magnetorheological damper characteristics are the two of these: How fast will it be? How powerful is it?
I will respond to these concerns in this article.
Magnetorheological Damper Reaction Time
There are tests made by a research team in Aalto University with a square reference signal on actuators that have magnetorheological fluid. Over these experiments, the rising edge response time varied from 0.8 ms to 1.9 ms dependent on if the experiment concerned a valve or a membrane actuator joined together with the valve. The falling edge response time varied respectively from 1.5 ms to 7.4 ms. From what I know, these are by far the shortest response times noted down for actuators relying upon magnetorheological fluid.
At my personal findings, the vibration frequency that I ultimately wipe out, is 25 Hz. My actuator simply by itself can function at a lot higher frequencies - I have verified it up to 70 Hz - but the resonance peak in my precise situation is particularly troubling at this frequency. But what is excellent in dampers with magnetorheological fluid, is that they can be designed to kill whatever frequency you want provided that you stay beneath the uppermost frequency the damper can attenuate.
The groundhook control principle is applied in my implementation by presuming that the ground stays still. If we even further expect the vibration of the engine being sinusoidal, the control law then results in that this damper ought to stiffen itself in the negative half of the vibration acceleration curve. At 167 Hz (the absolute maximum frequency to be dampened), the time for the magnetorheological fluid to get to its hard state, is something like 3 ms.
This identifies a prerequisite for the damper reaction time. It is going to have 1/4 period time (ca. 1,5 ms) to rise and another 1/4 period to drop (even though commonly rising edge is a lot quicker than declining edge).
Magnetorheological Damper Strength Precondition
As documented in my estimations, damping a motor of 800 kg vibrating at 167 Hz calls for a counteracting damper force of 19.6 N if 60% attenuation is reached. If this force is divided into four sustaining corners of a motor bedplate, the force prerequisite for one particular actuator would be approximately 5 N. Nevertheless, due to the superposition of the frequencies, the force at a single instant would be higher. Thus, the force criteria here was multiplied with the factor 10 because after discussions with the vendor, I learned that it is still in the scale that magnetorheological fluid dampers of this size are able to achieve.
As an overview, these damper requirements may be set for this type of an example motor:
- Force 50 N
- Reaction time 1.5 ms
Fortunately, a damper that contains magnetorheological fluid complies with these kind of specs. Naturally, those are not exclusively the factors you will want to think about when developing or purchasing your damper. But in my opinion these definitely are the minimum criteria that you have to certainly set. It demands measurements to specify these, but I will not go deep into those features here.
For extra details on magnetorheological dampers and associated equipment, go to Magnetorheological Damper Laboratory. It gives a group of hints for everybody who wishes to buy or develop a damper dependant on magnetorheological fluid. In choosing your damper technologies, choose magnetorheological!
