electricpete,
Thanks for the Maple calculations. Very nice. :-)
I almost finished going throught the calcuations, when my lovely Jeannabelle's water broke and we had to leave for the birthing center. I may have one question about the solution using the equivalent circuit. I will re-examine...
electricpete,
This electrical equivalent stuff seems to be quite useful.
What is your source of information for this technique?
Can you suggest a good book or a few good papers?
Thanks
Paul
If the energy in a wave is to be completely extracted, then the wave is completely destroyed. To destroy a wave is to make a wave which is equal and opposite.
Falnes does a good job explaining the idea in the attached paper. See Section 3 on page 190...
The bode plot of the transfer function of the spring/mass/damper definitely shows how changing the damping effects the resonant peak of the system. I don't know how to explain this in terms of the electrical equivalent circuit.
Here is a m-file that varies Ce from zero damping to over...
Okay. I understand the point that you are making about creating an extra node by drawing the damper below the mass. I agree that the mass and damper should be in parallel to create an electrical equivalent.
It has been a busy couple of days for me, so I have only been able to think about this for about a minute and a quarter. There is a lot of info here for me to digest so I have some catching up to do so we are on the same page.
Thanks again for all of your input.
electricpete said... "It leads to an important question - what are we really trying to achieve....what is the purpose of varying resonant frequency? Are we trying to minimize movement of the mass inertia elements? "
I would like to extract the maximum power out of the system by way of the...
Corrected Free Body Diagram
and
Equivalent Free Body Diagram
http://files.engineering.com/getfile.aspx?folder=f18f549b-1a63-428e-888d-d15b975540a0&file=Updated_FBD.pdf
Which mechanical parameters am I interested in?
The original goal of this experiment was to maintain resonance by varying Ce. In other words, vary Ce so that the resonant frequency of the mechanical system is the same as the frequency of the displacement that is driving the free end of the...
CORRECTION
The damping transfers throught the gearbox just like the inertia does.
Ce = c + r^2*(cs + 1/n^2*cm)
In this case I choose to ignore the damping in the rope, rope sheave, and gear box so c = 0 and cs = 0 and then,
Ce = r^2*1/n^2*cm
The damping transfers throught the gearbox just like the inertia does.
Ce = c + r^2*(cs + n^2*cm)
In this case I choose to ignore the damping in the rope, rope sheave, and gear box so c = 0 and cs = 0 and then,
Ce = r^2*n^2*cm
What is effective shaft grounding?
We have used carbon brushes and slip rings on VFD motor shafts with limited success. I suspect that the problem here is that the carbon brush will not conduct until there is a 0.5 volt differential accross the brush and the slip ring, but the grease in the...
It is a little more of a challenge...
... but after all of the variables of the mechanical parameters are transfered to the left of the gearbox and combined then the model becomes more straight forward.
The variable 'bm' was supposed to be the motor damping. I should have wrote 'cm'
The...
Here is the FBD for this project.
The equivalent inertia of the motor, gearbox and sheave is lumped together and called Js.
I will attempt to convert this mechanical system into an electrical equivalent.
Please post an electrical equivalent if anyone is comfortable with this method of...
electricpete said... "My answer is based on the presumption that a generator can be used as a linear damping element characterized by it's damping constant C."
This is a valid presumption because the time constant of the generator and circuit is much, much smaller that the wave period. In this...
The electrical analogy to mechanical vibration is an interesting approach.
The next step in this problem is to choose m, k and c to maintain resonance over a range of wave periods by varying the power that is extracted power from the damper. The electrical analogy might help.
I will try to...
I am trying to simulate a spring-mass-damper system which uses an electric generator connected to a resistive load as a variable damper. The damper is varied by controlling the current to the resistive load.
I seem to have a mental deficiency pertaining to the correlation between the damping...
This is a perfect application for a hydraulic unit and a hydraulic motor. Leave the motor running continuosly. Resize your motor for 25 full load current operations per hour instead of 25 starts per hour.
