Re: LVDT Transfer Function

"David Corliss" <dcorliss@xxxxxxxx> wrote in message
news:LYWdnVfro-gt6MHZRVn-vA@xxxxxxxxxxxxxx
| Consider the following proposition or experiment:
| Find a small DC motor with a shaft to which you can affix a piece of
| wood, plastic, or other 'shapeable' material. In some way, shape the shaft
| attachment into a cam, that is a form which has a 'lobe' that will allow
| the LVDT armature to rise and fall some arbitrary distance when placed at
an
| appropriate position adjacent to the armature piece.

This does not provide information that allow one to ID the resolver alone.

Run the motor at
| varying speed settings and see if there are any interesting features of
the
| output variable, that is the LVDT output voltage. ...It would be useful to
| be able to measure the angular speed of the motor. This can be done with a
| simple Hall Effect device, a magnet, and an oscilloscope.

Why not use an encoder?

| If you have an A
| to D converter board, you should be able to record the LVDT voltage
waveform
| so that you can study its characteristics on a computer.

Yes, but the encoder and analog device BOTH need to be phyically measuring
the same position. No cams no springs yets. That is a different problem.

| If you do observe a significant signal characteristic at some frequency of
| the output variable, try to relate this to the characterists of a spring,
| mass damper system ... resonant frequency or whatever. Maybe you can
obtain
| values for the spring and armature mass of the LVDT, and see if they are
| relevant to your observations.

This is what you don't want if you want to ID the LVDT alone

| I guess the first question to ask is what characteristics of the output
| variable, in relation to the input, will you observe? ....
|
| ... The motivation for suggesting this scheme is that it approximates a
| fundamental systems identification experiment that is commonly used to
| characterize unknown plants.
|
| ... glad to be of assistance if possible,
| Dave

In Shay's original post he said he wants to ID the LVDT, not a mass on the
spring
or cam etc. The connection between the encoder and the LVDT must provide a
1 to 1
linkage so only the LVDT transfer function is being computed.

Everyone is dodging how one computes the transfer function.

Peter Nachtwey


.

Relevant Pages

  • Re: LVDT Transfer Function
    ... In some way, shape the shaft ... Run the motor at ... that is the LVDT output voltage. ... when I probe the position of a sheet of metal, ...
    (sci.engr.control)
  • Re: LVDT Transfer Function
    ... Peter Nachtwey wrote: ... Run the motor at ... that is the LVDT output voltage. ... Everyone is dodging how one computes the transfer function. ...
    (sci.engr.control)
  • Re: equations for inertial simulator
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  • equations for inertial simulator
    ... Imagine a horizontal shaft on ball bearings, with an unbalanced mass ... motor attached to an optical encoder. ... to a wheel mounted on the bell. ...
    (sci.physics)