Keeping constant speed with variable voltage using Phidgets

I have 4 motors, 3 of which are being monitored using encoders. What I want to be done is have the user input certain variables and then have those variables control the process. My main program is the first attachment. My control is the second attachment. I call the phidget that I'm using to power my motors, Motor Controller, and it has a 0-10VDC range. I'm using signal isolators that act as the pots for DC drive boxes that then control 90VDC motors.
The problem I'm having is I'm not sure how to control the voltage properly. After the user inputs the variables, I then want the signal isolators to ramp up the voltage to get the motors to drive at the user input run speed. All the speeds won't be exactly the same, which is why I use the "Equal-Greater-Less" VI 4 different times. (ie. The desired run speed might be 15 ft/min, but the chopper speed might need to be faster or slower depending on application.) Once the voltage is ramped up enough to keep the motors at the desired levels, I want it to slighly adjust, if needed, to make sure that the encoders are showing the same measured speed as the desired speeds. Currently the way I have it now, I have either 0 V or 10 V outputs. I don't want the voltages to be extremes. If the puller encoder is showing that the the measured speed is 14.5 and I want it to be at 15, I don't want 10V to be output to that signal isolator. Basically, my question is, how can I have a variable voltage control for the code to try to keep the measured speed at the desired speed.
*I have three attachments for reference, but my main question is in the Equal-Great-Less Vi. Also, I know there are other little things that still need to be done. I know that my program won't run at this time. The Event structure will also be removed at the end. I have it in there now so I can manually control each motor by itself for testing.
Attachments:
Pre-preg Machine Program.vi ‏95 KB
Equal-Greater-Less.vi ‏31 KB
EncoderEvents.vi ‏20 KB

Hi ggpoly,
on your "Equal Great Less"-VI:
- It's RubeGoldberg to convert boolean conditions to enums just to select one of two cases…
- By moving index and output outside the inner case structure you don't need local variables…
- Comparing floats for equality is very dangerous as has been explained a lot of times before…
Best regards,
GerdW
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