Algorithm for Pressure PID control:


//initialize
kP=0.1; kI=1; kD=0.01; cummulativeError = 0; lastError=0;

//main body of code
while (true) {
    read currentPressure
    error = setPressure - currentPressure;

    //proportional section (distance between curve and 0)
    pCorrection = kP * error

    //integral section (accumulation of error --- area under curve)
    cummulativeError += error
    iCorrection = kI * cummulativeError

    //derivative section (finds out rate of change of error --- slope of curve)
    slope = error - lastError
    dCorrection = kD * slope
    lastError = error

    //decision making time
    correction = pCorrection + iCorrection + dCorrection;
    if correction > 80 //limit max and min correction
        correction = 80
        display "limiting max correction to 80"
    elseif correction < -80 {
        correction = -80
        display "limiting min correction to -80"

    if error > 0.5 { //sets deadband and chooses solenoid for correction
        if time passed >= 30 ms //make sure at least 30ms has passed by before taking any action
            if correction > 0
                turn ON solenoid 1 for correction amount then turn it off
            elseif correction < 0
                turn ON solenoid 2 for correction amount then turn it off
            else
                display "deadband is active"
    }
}