Can I read output from ai channel to control ao channel?

[amproctor]

Hello,

I am using a USB 6211 to aquire two synchronized voltage signals from a LVDT (ai0) and a Load Cell (ai1).The LVDT and Load Cell signals have already been amplified and conditioned before they go into the DAC. The LVDT and Load Cell read displacement and force on a rod whos position is controlled by a linear actuator. The actuator is controlled by a voltage waveform that is output from the 6211 (ao0). Is there a way to reference either input signal (one or the other, perhaps depending on a boolean) to control the amplitude achieved by the output signal?

For example, if I wanted to move the rod a specific distance or press the rod into something with a certain force, could I reference the distance or force input signal from the ai channels to adjust the ao signal amplitude?

I guess what I would really like to do is close the loop on the actuator so that it knows where it is in terms of force and distance. Is this possible using this hardware?

USB-6211 (https://www.ni.com/en-us/support/model.usb-6211.html)

Best,

amproctor

[labview-programmer]

Hi,

Yes, absolutely. You are to use some sort of feedback mechanism, control AO based on what you read from AI.

In case that you are using continuous mode of read/write, you have to influnce parameters of the simulated output to AO based on the wave at AI.

In case of single value, you just have to read AI and then, decide value for AO and then make write for AO in a while loop.

[amproctor]

Thanks Aniket,

I have been messing around with this trying to get it to work but I didnt know if it was possible. I will have to play around with it a bit more.

Do you know of any examples on here for continuous feedback of this sort?

-amproctor

[labview-programmer · Accepted solution]

Whether you are doing it sample to sample or wave to wave? I did not find a typical example...

See the snap, here it is being done sample to sample. The subvi icon has your correction formula.

[amproctor]

Thanks Aniket!

[labview-programmer]

Just, ensure that your actuator does behave as you want!

e.g. consider you r doing a simple stress/compression test. If your test piece just snaps or (other way round) siezes, you really require n intelligent feedb.

[amproctor]

Good point. What would really be great is if I could have realtime feedback to maintain a constant force on a material even if the material creeps. I do not expect that this will work for that.

What do you think?