pid.py

# p=PID(3.0,0.4,1.2)
# p.setPoint(5.0)
# while True:
#     pid = p.update(measurement_value)


class PID:
    """ Discrete PID control """

    def __init__(self, P=2.0, I=0.0, D=1.0, Derivator=0, Integrator=0, Integrator_max=500, Integrator_min=-500):

        self.Kp = P
        self.Ki = I
        self.Kd = D
        self.Derivator = Derivator
        self.Integrator = Integrator
        self.Integrator_max = Integrator_max
        self.Integrator_min = Integrator_min

        self.set_point = 0.0
        self.error = 0.0

    def update(self, current_value):
        """ Calculate PID output value for given reference input and feedback """

        self.error = self.set_point - current_value

        self.P_value = self.Kp * self.error
        self.D_value = self.Kd * (self.error - self.Derivator)
        self.Derivator = self.error

        self.Integrator = self.Integrator + self.error

        if self.Integrator > self.Integrator_max:
            self.Integrator = self.Integrator_max
        elif self.Integrator < self.Integrator_min:
            self.Integrator = self.Integrator_min

        self.I_value = self.Integrator * self.Ki

        PID = self.P_value + self.I_value + self.D_value

        return PID

    def setPoint(self, set_point):
        """ Initilize the setpoint of PID """

        self.set_point = set_point
        self.Integrator = 0
        self.Derivator = 0

    def setIntegrator(self, Integrator):
        self.Integrator = Integrator

    def setDerivator(self, Derivator):
        self.Derivator = Derivator

    def setKp(self, P):
        self.Kp = P

    def setKi(self, I):
        self.Ki = I

    def setKd(self, D):
        self.Kd = D

    def getPoint(self):
        return self.set_point

    def getError(self):
        return self.error

    def getIntegrator(self):
        return self.Integrator

    def getDerivator(self):
        return self.Derivator