Inverted pendulum PID control using Arduino

Hi everyone, I still have a ongoing problem trying to control the inverted pendulum using a self built PID algorithm. The problem is not with the algorithm itself but the program around the algorithm. Anyway this is what IM trying to do.
I want to be able to constantly read the angle of the pendulum, which will be done using the arduino read analog vi. Now the pendulum angle will be represented as a voltage. This is all fine. Now:
1. If the angle(voltage) is inside a specified correction range I want the PID algorithm to turn on and let the algorithm work on the error as it would normally (while updating the angle(voltage) reading after each PID loop.
2. Also when this angle(voltage) goes back outside the specific correction range I would like the PID algorithm to STOP, however at this stage I would like the overall program to continue running and keep checking the angle(voltage) to see if its value comes back into range and if it does switch back again to the PID algorithm.
I don't have great knowledge of labview and IM still learning about it. I have included my program so far below. rev2 is the higher layer and the PID algorithm itself is rev1.
I have tested my program with the arduino but what happens is this:
the checking of the angle range works but once the value is true i.e. Angle is inside correction range , the angle value moves into the PID algorithm however is never updated at this stage and I can not get back out of the PID while loop.
Sorry if what I have been saying does not make sense and was hard to follow, however I have include my code below for help. And I would really appreciate help on this and what I could look at in order to get it working all comments are very welcome.
Thanks
Fran
Attachments:
PID rev2.vi ‏1143 KB
PID rev1.vi ‏1158 KB

ladysman217f wrote:
the checking of the angle range works but once the value is true i.e. Angle is inside correction range , the angle value moves into the PID algorithm however is never updated at this stage and I can not get back out of the PID while loop.
That's a very accurate description of the problem with your code - enough so that I think you could figure out how to solve it. You might find it helpful to run your code with execution highlighting enabled. Remember that values at loop tunnels never change. At the moment you take one measurement of the angle, feed it into the PID loop, and then the PID continues to run in its own loop without ever measuring the angle again. You either need to put the measurement and the PID algorithm in the same loop; you could do this by making the PID run only once per call, or by moving the angle measurement into the loop that implements the algorithm.

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Im using the labview arduino interface and im trying to control the angle of an inverted pendulum using a PID algorithm. the project is part of my FYP and therefore i want to try writing my own PID algo instead of using a labview PID.vi. now the code for the PID algorithm still needs work but my main question is this.
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Attachments:
PID rev1.vi ‏673 KB

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asdfs wrote:
Per my other posts, I am testing a friend's software to see if this is what we would like to use. I would prefer to use their software for our initial work to help offset the cost of the software. Problem is their software is 8.0 pro without the extra PID stuff. I am curious how one gets started creating a custom PID algorithm to be used in series between an input and an output. I have viewed several tutorials but all seem to simply point at the PID toolkit that is not availalbe to me right now. I realize it might be more work to create one but probably the only option at this point.
To simply the process, lets just compare a single input and output where the software will control the output to obtain to desired input. in tutorial, I was following right along until the PID loop was added and that seems to be just a drop and go type of deal in which would rarely apply to a real work application. I am simply trying to learn how PID systems are written into the block diagrams.
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Inverted pendulum PID control using Arduino

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