Feedback loop NI DAQ mx

Hi, I'm here to get some help on my program.... since our lab did not have control toolkit,
I had to build my simple PID program.. question is (I'm not sure if it's program question or not)
1. Will my pid work fine ? I just took the basic concept of PID and built it.. just like the picture above...
2. after let pid take care of the error, should I directly send it to the DAQ output ? or should I add something on to it ?
this might be a control question.. but I was really confused.. whetere I have to just send the pure error to my output(in this case, amplifier)
or I have to do something with either setpoint or the previous sesor reading(uncorrected)
we're trying to get the control toolkit sooner or later, but in the mean time, I have no choice but stick to this program..
please help me mr. NI
Thank you

Hi johnny,
Your PID logic seems to be sound and you should be able to take the output of the PID loop and wire it to the DAQ output. I'm not sure what you would do to it before you send it to the DAQ output anyways. Thanks.
Stephen Meserve
National Instruments

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A problem with delays in timed loops and DAQ

I am programming a simulation for nuclear rewetting for a visitor centre at my company in Switzerland. It involves heating a "fuel rod" and then filling the chamber with water. The pump automatically starts once the rod core reaches 750C. After this, a requirement stipulates that flow rate be checked to ensure the pump is operating at the necessary conditions. If it isn't, the heater must be shutdown to avoid, well... meltdown. However, we must allow 10 seconds for the pump to respond, while still allowing a DAQ rate of 10-100Hz.
The challenge is that I can't add a delay in my main loop else delay all acquisition, but I can't figure out how to trigger a peripheral loop (with DAQ for the single channel of checking flow) from the main loop, and when the peripheral loop determines if flow has initalised, respond back to the main loop with the okay.
I think much of my confusion is in the interaction of the loops and the default feedback nodes that labview is putting in willy nilly. Would the only solution be to have two 'main' loops that don't communicate with eachother but rather do the same thing while operating on different timing? Tell me if you want me to post the file (although its on an unnetworked computer and I didn't think it would be too useful).
Thanks+ Curran
Solved!
Go to Solution.

Here it is! It is not in any form of completion unfortunately.
So reading in the temp with NI9213 and watercolumn height with NI9215, we determine to turn on the pump with NI9472. NI9421 determines whether the pump is on (there is flow) and I must respond accordingly.
I have 3 scenarios similar to this one as well, so having redundant loops with different timing like I mentioned would be way to heavy. I think I may have though up of a solution? At the time the pump is initiated, we record the iteration and wait for a number of iterations that correspond to 10s to pass before fulfilling the pump shutoff requirement?
Attachments:
rewettin1.vi ‏15 KB

MIDI feedback loops

Per a different thread discussion, I've started using Plogue Bidule to host most of my Audio units and I'm using IAC to send MIDI from MainStage to Blogue.
However, I frequently get popup dialogs warning me that there is a MIDI feedback loop and I'm prompted to "go online" or "stay offline". I'm doing the latter and everything works fine but I'm wondering how to fix this problem (or at least get rid of the dialog).
I'm not near the machine at the moment but I'm wondering if MainStage is automatically receiving MIDI back from those IAC ports and just blindly sending events out again? If that's what's happening, I can probably create some more dummy MIDI devices and associate them with those ports but it's a pity to have to do this.

This doesn't really answer your question, but I am using Reason with MainStage through rewire and can remote control reason fine with MIDI. Once I launch Reason I can create an external instrument channel strip in MainStage. Then I can set the port to Reason and choose a channel, and then map one of my knobs to send a specific midi controller on this external channel strip. Then Reason receives this midi controller whenever I turn the knob on screen. I imagine you should be able to do something pretty similar with Live in slave mode...

Any way to save data in loop without using shift register or feedback loop

Hello all
I was thinking, is it possible to save data in a loop to next iteration without the use of a shift register or a feedback loop?
I need the possibility to reload data within a loop from a lvm file, but I want to use the same data until i load some new ones.
The reason why I don't want to use the shift register or feedback node is due to speed, even though I am not sure if the shift register
actually moves all the data from one register to another, or if it is stationary until a change in the data occur.
The data I want to reuse is medium-large (6 force measurements, 2 pressure, 1 flow channels)of about 10sec data in each file with samplingsrate of 2kHz..
In my analysis program I have many CPU demanding calculations and 3D graphs, so I just want to minimize the CPU load as much as I can for each part of the
software..
I have attached a small VI to explain what I am talking about.
I now I shouldn't use the express VI, and I am going to change that as well - this is just a proof of concept!
Hope you guys can help me understand this shift register better...
Thanks!
- Tommy
Running LabVIEW 2009 32bit SP1 on Windows 7 64Bit
Solved!
Go to Solution.
Attachments:
visual.vi ‏34 KB

tombech wrote:
[...]The reason why I don't want to use the shift register or feedback node is due to speed[...]
Tommy,
shift register are the fastest you can ever get...........
Norbert
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.

Plug-Ins in a delay feedback-loop

I would like to set plug-Ins in a feedback loop from a delay plug-In
maybe in a simalar way like this:
from a audio track "send", i route the send signal in a delay. the delay output goes after in other plugins (filter, reverb, pitch shifter) and comes back in the delay input, but only maybe maybe 20%-30% of the output volume.
Does anybody know how to do this routing?

Admittedly, I had not tried the routing I had posted. I was just "thinking it through"... evidentially, not very well...
I knew I'd read multiple posts over at Sonikmatter about this sort of thing. Here's the first one I came across doing a quick search:
http://community.sonikmatter.com/forums/index.php?showtopic=7282
See if that gets you closer to what you had in mind...

Gmail IMAP "Copying message" feedback loop

Yesterday I sent an email with 10mbs of attachments from mail.app through gmail imap. after the message sent, I noticed that the spinning icon next to the gmail inbox was perpetually spinning. in the 'activity' window, it says:
Gmail Synchronizing with server
copying message
I figured mail.app and gmail were synchronizing the email. so i let the process go for a few hours yesterday, when I noticed that no new email had come in via gmail, so i checked the account through the web browser. sure enough to find new email, but nothing coming through to mail.app. so i cancelled the process and but the activity status just said "STOPPING: copying message" and didn't go away. So I restarted mail.app. as soon as mail.app was back up and running, the "copying message" status reappeared.
Last night, I let the operation go throughout the night, to wake up this morning with nothing changed. So this morning I checked my "recovered messages (Gmail).mobx" folder to see several 345mb message files. I removed the whole "recovered messages (Gmail).mobx" folder to the desktop and restarted mail.app but I still have the same error.
Incidentals:
The original message with the 10mbs of attachments was a series of 47 photos. Originally, I had dragged full res photos(6-7mbs/photo) into a mail.app message and chose "medium" from the "image size" pop-up at the bottom pane of the message.
My theory is that in between placing the photos in the message and mail.app resizing them, mail.app and gmail tried to save a draft of the message to the server with all the photos at their original size (they might have been somewhere around that 345mb mark). And somehow mail.app is freaking out continually trying to upload a draft of the message with 345mbs of attachments. just a theory.
how do i get mail.app and gmail imap out this weird feedback loop?
Message was edited by: Ed Fladung

I had the same problem myself, except that the message contained over 200 pictures. The actual email was only 7MB, but Mail must have decided to create a draft before it resized the pictures. I only noticed the problem after Mail had consumed over 1.5GB of my limited bandwidth and was taking up almost 4GB in RAM, and a lot more in swap. The solution here worked, but it's unfortunate that I needed it at all. Why would I ever want Mail to upload attached photos to an IMAP server at their original size, especially after the final version of the email with resized photos has already been sent? This NEEDS to be fixed, since it could be a huge problem for someone who is less computer savvy.

What is the block diagram of the feedback loop when op mode is set to velocity?

On 7344s, is the feedback loop changed when the operation mode is set to velocity? Is it still a “position feedback” loop with just a ramp at the input? Or is there an additionnal derivitive to find the speed and the input command is a speed?

When making a move where the encoder is not configured for velocity feedback, the control loop uses actual position vs. expected position as a function of time to correct for the velocity output. However, when the encoder is configured for velocity feedback, we actually use the velocity based on encoder feedback in the control loop and this also allows us to use the functionality of the Kv term to smooth velocity response.
Best Regards,
Chris D
NI Applications Engineer

Speedy-33 feedback loop

Hi, i'm using speedy-33 as my DSP target and i wish to perform a feedback loop. i tried the example found in the NI website but it shows error that the array size is mismatch.
Does anyone know how the data flows?
Let say when i create an analog input, it is a 1-D array. Inorder to create a feedback loop i need to create an array of known size 1st, am i right to say that?? From there onwards, wat are some of the ways that i can can my array size or when do i need to alter my array?
Can anyone pls help??
Thanks

Hi steven,
Thanks for the reply,
Using labview 8.2, DSP target speedy-33
Currently i'm trying to get a feed back from my sample delay function then add back to my signal to create a reverberation effect.
problem
1)the waveform i see from my waveformchart are square wave.
2)I try to set my frame size at 1024 but the programm just run for a few sec and stop.
3)my audio signal sounds like transformer singing!!
can someone help me point out where my problem lies on??
Thanks in advance.
Attachments:
Feedback using for loop.vi ‏49 KB

Feedback loop for taking integral

Hello. I'm trying to model some mathematical equations in LabVIEW and trying to the find the integral using feedback node.
Here is the equation I'm trying to model:
i = integral([VBATT - i*R - i*(dL/dt)]/L), where L is a function as well.
At the output of i I get 0. I'm assuming I have to put an input into the feedback loop but I'm not sure what to do here. Any help would be appreciated. Attached is my VI as well.
Attachments:
project3.vi ‏24 KB

OriolesFan wrote:
Why are you using a feedback node?
Feedback nodes are for storing information from one iteration and using it in the next. Since you don't have any loop and your VI runs once, it will return the default value that the feedback node is initialized with. Thuse zero.
The i I solved for is needed as an input. Those are differential equations.
I think I did this wrong actually. I modeled these equations in Simulink but used a transient response to get the results, so I think I need some other module in my LabVIEW to do this. I was trying to take my equations from Simulink and trying to model it in LabVIEW.

How do I implement a feedback loop to control a DC motor?

I have a couple of 1 hp PMDC motors that I need to control. I have a VI set up that can take an RPM input, convert it to a 0-5V signal that is sent through my USB-2008 DAQ to an amplifier then to the motor. It also displays the actual RPM of the motor by converting the frequency of a signal sent by a rotary encoder attached to the motor. I need it to be able to adjust the applied voltage when a load is applied and keep within a 1 RPM window. What would be the best way to accomplish this.
Dewayne

Hi Dewayne,
I cut out the PID part of your code and used simulated signals. When I did that the PID loop operated as expected. What does your actual RPM profile look like? Have you tried using the PID autotuning VI instead of the PID VI? I looked at your DAQ assistants and they are set up for different connection types (some are RSE and others are differential). I would also double check to make sure that you have all of the connections set up correctly. If you can post another copy of your VI with simulated signals that look like what you are actually getting I can take a look at the code again to see where you are running into problems. Below is a link that will help you verify that your connections are correct.
Field Wiring and Noise Considerations for Analog Signals
http://zone.ni.com/devzone/cda/tut/p/id/3344
Nick Keel
Applications Engineering
National Instruments
Nick Keel
Product Manager - NI VeriStand and Model Interface Toolkit
National Instruments

How to kill feedback loop?

I'm working on a project - no files are selected for recording, but there is feedback always on that's driving me nuts. Sorry, novice user here and I can't find a clue in the manual. Any idea?

Don't have a MBP but ut sounds to me like the internal microphone is feeding back.
Go into Utilities/AudioMIDI Setup and change the input to Line-IN, and or bring down the input volume.
Just a guess.
pancenter-

Using a Phidget Motor Controller and attempting to get a feedback loop

Hello! Recently, I aquired a Phidgets 1065 motor controller and a compatible motor with built-in encoder. Currently, I am trying to write a program that allows me to input a position, and the motor moves at a user-specified speed until the encoder reaches that position. However, the original instructions to the Phidget VI's are so vague, I'm not entirely sure how to tackle this problem. Any help would be appreciated!
Thanks!

It looks like Phidget has a lot of documentation on its website. This webpage might be helpful to get started: http://www.phidgets.com/docs/1065_User_Guide . This user guide shows how to connect the wires. Notice that both the motor control cables and the encoder cables are connected to the motor controller. I believe that the position control loops are performed on this controller/drive itself.
Phidget also has LabVIEW VIs that you can use to set the motor position. This new position is sent to the motor controler through the USB connection and the motor controller will control the motion to that new target position. See this document to get started with the LabVIEW API http://www.phidgets.com/docs/Language_-_LabVIEW#Quick_Downloads . See this document for more information about each of the Phidget VIs: http://www.phidgets.com/documentation/web/LabVIEWDoc/index.html I believe that you would need to look at the section that talks about the servo control module.
Take care,
Jeremy P.
Applications Engineer
National Instruments

After iOS 7 update, trying to call just results in echo feedback loop.

It's happening to both my wife and I. She has a 4S, I have a 5.

I have the same issue. Phone echo's like a toy mic after call ends. I am on the iPhone 5 with version 7.0.4. I even swapped for a new handset and it did not fix the issue. This never happened iOS 6.
Can someone please help as it is very annoying and deters you from making the next immediate call.

DAQ Assistant with multichannels causing Simulation Loop slow?

Hi, another LabView newbie here.
I have in a Real Time Target (NI 9132) a Control & Simulation Loop with DAQ Assistant block inside, whose signals are fed into a Discrete State Space block. The discrete state space model has 1 second time step. I have set the Simulation Loop parameters so that it executes every 1 second as well (see Fig. A below). *sorry for the big white gap under the figures..
The DAQ assistant acquisition mode is set as "1 Sampe (On Demand)".
However, when I run the VI, the plot seemed to be updated much slower than 1 second rate. To confirm this, I put an "Elapsed Time" block inside the Simulation Loop. The "elapsed time" shows the actual time in seconds while the simulation plot show slower time (see Fig. B below).
I tried to isolate the problem by removing the block one by one. Finally, I found out that this problem was caused by (at least) the DAQ Assistant which acquires multichannels data of NI 9214. When I remove some channels and leave one or two channels, the VI runs at the actual time (see Fig. C below). But when I added more channels reading, it became slower again.
Here is the snippet of the block diagram (after all other blocks were removed):
What am I doing wrong here? I'm going to use all of NI 9214 channels so how not to have similar problem like this?
I look forward to hearing any relevant comments from the members. Thanks in advance.
Tian

Hi Tian,
why do you need a Sim loop anyway?
- When it comes to speed you shouldn't use the DAQAssistent. Use basic DAQmx functions…
- Use parallel running loops for each task. Put DAQmx functions in their own loop, running in parallel to your Sim loop…
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

DAQ and timed loop

Hi,
I have a question about DAQ and timed loop. I used timed loop while acquiring data. I need timed loop since I have tvo more loops in my application and ı need give some priority to them.
Data acquisition should have a high priority. But the example codes about DAQ always use wlile loop. Is this wrong to use timed loop in DAQ application, or there is a unexpected result about
this usage.

You could use timed loops in Data acquisition operations as well
But, one thing you will have to watch is the 'number of samples per channel' terminal of DAQmx Read function.
Suppose you have rate as 1000 samples /sec, in your DAQmx timing vi
In continuous acquisition, if you specify number of samples per channel as 500, instead of performing 2 iterations / sec to get your 1000 samples as your nor mal while loop would, your Timed loop will run for 1 sec and you will get an error that all samples could not be acquired

Feedback loop NI DAQ mx

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