PID-Py 0.1.4

Simple (but complete) PID controller in Python

PID_Py

PID_Py provide a PID controller wrote in Python. This PID controller is simple to use, but it's complete.

Installation

python3 -m pip install PID_Py

Usage

Minimum usage

from PID_Py.PID import PID

# Initialization
pid = PID(kp = 0.0, ki = 0.0, kd = 0.0)

...

# PID execution (call it as fast as you can)
command = pid(processValue = feedback, setpoint = targetValue)

In this usage the PID as no limitation, no history and the PID is in direct action (Error increasing -> Increase output).

Indirect action PID

If you have a system that required to decrease command to increase feedback, you can use indirectAction parameters.

from PID_Py.PID import PID

# Initialization
pid = PID(kp = 0.0, ki = 0.0, kd = 0.0, indirectAction = True)

...

# PID execution (call it as fast as you can)
command = pid(processValue = feedback, setpoint = targetValue)

Limiting output

If your command must be limit you can use outputLimits parameters.

from PID_Py.PID import PID

# Initialization
pid = PID(kp = 0.0, ki = 0.0, kd = 0.0, outputLimits = (0, 100))

...

# PID execution (call it as fast as you can)
command = pid(processValue = feedback, setpoint = targetValue)

By default the value is (None, None), wich implies that there is no limits. You can activate just the maximum limit with (None, 100). The same for the minimum limit (-100, None).

Historian

If you want to historize PID values, you can configure the historian to record values.

from PID_Py.PID import PID
from PID_Py.PID import HistorianParameters

# Initialization
historianParameters = HistorianParamters.SETPOINT | HistorianParameters.PROCESS_VALUE
pid = PID(kp = 0.0, ki = 0.0, kd = 0.0, historianParameters = HistorianParameters)

...

# PID execution (call it as fast as you can)
command = pid(processValue = feedback, setpoint = targetValue)

...

# PID Historian
import matplotlib.pyplot as plt

plt.plot(pid.historian["TIME"], pid.historian["SETPOINT"], label="Setpoint")

plt.plot(pid.historian["TIME"], pid.historian["PROCESS_VALUE"], label="Process value")

plt.legend()
plt.show()

In the example above, the PID historian records setpoint, processValue and time. Time is the elapsed time from the start. After that a graphic is draw with matplotlib.

Historian parameters list

• P : proportionnal part
• I : integral part
• D : derivative part
• ERROR : PID error
• SETPOINT : PID setpoint
• PROCESS_VALUE : PID process value
• OUTPUT : PID output

Integral limitation

The integral part of the PID can be limit to avoid overshoot of the output when the error is too high (When the setpoint variation is too high, or when the system have trouble to reach setpoint).

from PID_Py.PID import PID

# Initialization
pid = PID(kp = 0.0, ki = 0.0, kd = 0.0, integralLimit = 20.0)

...

# PID execution (call it as fast as you can)
command = pid(processValue = feedback, setpoint = targetValue)

In the example above, the integral part of the PID is clamped between -20 and 20.