Pid

A PID service allows the tracking and transformation of output in relation to iinput.  This is currently used as one of the tracking strategies in the Tracking service.  Input is sent to PID, a "compute" method is sent and appropriate output is sent to a servo.

References

• Bret Beauregard detailed explanation of PID
• Tuning PID flow diagram
• Original library
• Wikipedia PID controller
• Another great tutorial

Example for develop:

#file : Pid.py edit raw

arduino = Runtime.createAndStart("arduino","Arduino")
arduino.connect("COM5")
# arduino.setSampleRate(30000)


readAnalogPin = 0
arduino.enablePin(readAnalogPin)
arduino.addListener("publishPin", "python", "input")


pid = Runtime.start("pid","Pid")

#set Kp, kd, ki kp = gain, how strong it react kd = how fast it react ki= take care of the sum of errors (differences between target and actual value) in the time
pid.setPID("x", 10.0, 0, 1.0)
pid.setMode("x", 1)
#set the range of the "correction"
pid.setOutputRange("x", -5, 5)

# pid.setControllerDirection("x", 0)

#set a starting analog value, which will pilot the MOSFET on the Gate
heaterValue = 512


def onPin(data):
 thermistorPin = data
 print 'thermistor value is', thermistorPin.value
 global heaterValue
 global futureHeaterValue
 #target of temperature or target value
 pid.setSetpoint(150)
 #input value
 pid.setInput(thermistorPin.value)
 pid.compute()
 correction = pid.getOutput()
 futureHeaterValue = (heaterValue + correction)
 if (futureHeaterValue < 1024) and (futureHeaterValue >0):
  heaterValue = futureHeaterValue
  arduino.analogWrite(4,futureHeaterValue)
  print heaterValue
 else :
  arduino.analogWrite(4,heaterValue)
  print heaterValue