PID vi problem (simple question)

[Wottrich]

I am trying to create a boat that maintain a specific direction, for that I use a rudder to change direction of the boat the rudder is controller by a servomotor, and a gyroscope to measure the angle on which the boat is pointing at.

I want to know if the logic of my connection to the PID function are correct :

• my setpoint is 0 degrees
• my process variable is the value of my gyroscope in degrees
• my output range is 0.0525 to 0.675 (the middle point of my rudder is 0.06), ( they have this value to send it to the rubber and change the direction of max of 17.5 degrees of the rudder)
• my output is going to the rudder

the part I am really confuse is: If I put my set point to be 0 degrees I want the rudder to change the direction to stabilize the system if the boat is not at 0 degrees, but I don't know if the PID function knows if the values of the gyroscope and the rudder are related to each other or not, because the process value I am working is from the degrees of the gyroscope and the output I put to be is the rudder with that range of values, when trying in real life the PID it didn't work. and I don't know if it is because of my logic of or what 

[GerdW]

Hi Wottrich,

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@Wottrich wrote:

the part I am really confuse is: If I put my set point to be 0 degrees I want the rudder to change the direction to stabilize the system if the boat is not at 0 degrees, but I don't know if the PID function knows if the values of the gyroscope and the rudder are related to each other or not, because the process value I am working is from the degrees of the gyroscope and the output I put to be is the rudder with that range of values, when trying in real life the PID it didn't work. and I don't know if it is because of my logic of or what 

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And what are your PID gains? They determine the relation between sp, pv and output!

On your VI:

• The "case value" should be blue, aka integer!
• The "gauge" and "PID gains" belong before the case structure, "Turn Duty…" afterwards! No locals needed!
• The wait belongs into the main loop, not just into one case.
• The dt input of the PID is WRONG!
• All those comparisons on ElapsedTime can be simplified using either InRangeAndCoeerce or a simple array function like Threshold1DArray…
• Several controls/indicators are bound to SharedVariables, that makes it very hard to verify your code: we miss all the definitions and connections…

Example: