Re: Design of Positive Position Feedback Compensator(filter)
- From: pnachtwey@xxxxxxxxx
- Date: Mon, 03 Sep 2007 09:20:04 -0700
On Sep 3, 12:02 am, user <rs...@xxxxxxxxxxxxxx> wrote:
In article <1188568938.856403.292...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,I told you what a feed forward is. Since the SP is always the steady
pnacht...@xxxxxxxxx says...
On Aug 31, 4:02 am, user <rs...@xxxxxxxxxxxxxx> wrote:
In article <1188472901.228393.90...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
snovite2...@xxxxxxxxx says...
This is my plant (-0.0708s-2.687)/(s^2 + 0.5982s+ 1011)
The sensor & actuator send/pick-up signals from a PC(MATLAB & dSPACE
control desk) via a signal conditioning box.
I m using 2 Piezo electric strips for sensing & actuating.
external excitation: tap the free end of the beam lightly with a
pencil(once)..the vibration is picked by the sensor.The control is
such that the actuator induces vibrations in the opposite direction to
the original- this results in destructive interference & hence vib
suppression.
The first natural frequency of the plant is between 4.89 Hz - 5.1Hz:I
want to damp the first mode vibrations.
Will it work if You make feed-forward control which send CV in natural
frequency (initally, then in ratio to PV acceleration) and advanced in
phase- Hide quoted text -
- Show quoted text -Feed forwards are gain mulitplied by the set point and its derivatives
and added to the output. Since this is a damping system or regulator,
the set point and its dervatives are 0. The questions I have is how
big will the distrubances or initial value of x be? If the initial
distrubance is too big the controller will saturate so its ability to
dampen oscillations is limited.
Peter Nachtwey
By feedforward I ment generating dumping signal, which is approximately
inverse of transfer function.
state position then SP's derivatives are all 0. There is no feed
forward term.
The signal could consist of natural
frequency signal=f(phase(t),natfreq,Amplitude(t))???? This sound like a lot of tweaking and coffee drinking to me. I
Then we need to create few fuzzy rules regarding dumping quality = f
(phase) and f(amplitude)
with this knowledge the system would know which direction to go in case
of excessive error.
can't think of any place where fuzzy logic should be used on a SISO
system with a good transfer function available.
You and snovite are making this too difficult. If you thoroughly
understand the basics of control then neither of you would be
suggesting complicated control scheme for simple problems.
The intersting part would be max systemIn my saturated example, the control output was doing all it could to
decceleration,phase shift betwen control signal and final steady error
if applies.
stop the vibrations. What more can a control algorithm do? BTW,
I did try changing the control output to +/- 1000 and saw that it
works and then changed it back just to see what kind of response I
would get...... from the newsgroup. Not much.
This method could distinquish between various environment changes. ItYes, it is called state. That is the x array in my .pdf files.
has a kind of memory-
I am waiting for snovite to tells us what the units are of his
transfer function, what the control output limits are and what the
desired response is.
I updated the .pdf files so the control output limit is +/-1000. You
can see it dampens nicely if the starting amplitude is 1 or less. I
placed the closed loop poles on the negative real axis to provide a
crititcally damped response. Note, the lead lag has a closed loop
transfer funciton with three poles at -2*PI*50 and the PD feedback
example has only two poles at -2*PI*50. All the calculations
necessary are shown for the PD feedback example. It uses Ackermann's
equation to calculate the P and D gains given the desired pole
location. I referenced the text book where I got the information to
do this.
ftp://ftp.deltacompsys.com/public/NG/Mathcad%20-%20T0C1%20snovite%20leadlag.pdf
ftp://ftp.deltacompsys.com/public/NG/Mathcad%20-%20T0C1%20snovite%20Ack.pdf
This is easy, snovite did the hard part when he calculated the
transfer function.
Peter Nachtwey
.
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