CODEWITHSUNDEEP
matlabtiminglabview
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frank_black

Reputation: 43

matlab script node in Labview with different timing

I have a DAQ for Temperature measurment. I take a continuous sample rate and after DAQ, calculating temperature difference per minute (Cooling Rate: CR) during this process. This CR and temperature values are inserted into the Matlab script for a physical model running (predicting the temperature drop for next 30 sec). Then, I record and compare the predicted and experimental values in LabVIEW.

What i am trying to do is the matlab model is executing every 30 sec, and send out its predictions as an output from matlab script. One of this outputs helps me to change the Air Blower Motor Speed until next matlab run( eventually affect the temperature drop for next 30 sec as well, which becomes a closed loop). After 30 sec while main process is still running, sending CR and temperature values to matlab model again, and so on.

I have a case structure for this Matlab script. And inside of case structure i applied an elapsed time function to control the timing for the matlab script, but this is not working.

Code example

Upvotes: 0

Views: 672

Answers (1)

mzu
mzu

Reputation: 723

Yes. Short answer: I believe (one of) the reasons the program behaves weird on changed timing are several race conditions present in the code.

The part of the diagram presented shows several big problems with the code:

  1. Local variables lead to race conditions. Use dataflow. E.g. you are writing to Tinitial local variable, and reading from Tinitial local varaible in the chunk of code with no data dependencies. It is not known whether reading or writing will happen first. It may not manifest itself badly with small delays, while big delays may be an issue. Solution: rewrite you program using the following example:

From Bad:

Bad example

To Good:

enter image description here

(nevermind broken wires)

  1. Matlab script node executes in the main UI execution system. If it is executing for a long time, it may freeze indicators/controls as well as execution of other pieces of code. Change execution system of other VIs in your program (say to "other 1") and see if the situation improves.

Upvotes: 1

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