TimedPID

A simple PID controller for the Arduino IDE featuring different time step calculation options.

Version 1.0.0

By Julien de la Bruère-Terreault (drgfreeman@tuta.io)

Summary

This library for the Arduino IDE provides a simple Proportional - Integral - Derivative (PID) controller. The controller features three options for time step calculation (the time step is used for integral and derivative error terms calculation):

1. Non-specified (unit) time step (getCmd() method)
2. Auto time step calculation (uses time between calls to getCmdAutoStep() method)
3. Defined time step (passed as argument to getCmdStep() method)

Examples

Two example sketches are provided with the library:

• Minimum.ino
  This example shows the minimum code lines to declare, setup and get the command from the PID controller.

• DemoTimedPID.ino
  This example shows how to use the library with a defined time step. It includes a fake mechanical system simulation to demonstrate how the PID controls the force to apply on a mass object subject to inertial and drag forces to have the mass object achieve a desired speed function.

Library Reference

• TimedPID(float Kp = 1.0, float Ki = 0.0, float Kd = 0.0)
  Constructor: Kp, Ki and Kd are the proportional, integral and derivative gains respectively.

• float getCmd(float setPoint, float procVar)
  Returns the system command. setPoint is the desired "target" value for the process variable being controlled. procVar is the current value of the process variable being controlled. This method uses unit time step for integral and derivative error terms calculation.

• float getCmdAutoStep(float setPoint, float procVar)
  Similar to getCmd method except this method automatically calculates the time step based on the time between two calls to this method. The calculated time step is in seconds units.

• float getCmdStep(float setPoint, float procVar, float timeStep)
  Similar to getCmdAutoStep method except the time step is passed to the method via the timeStep argument. The time step can be in any units.

• void reset()
  Resets the PID error terms. The method also resets to the current time the time variable used by the getCmdAutoStep to calculate the time step.

• void setCmdRange(float cmdMin, float cmdMax)
  Sets the min and max command values that can be returned by the getCmd, getCmdAutoStep and getCmdStep methods to the range defined by the arguments cmdMin and cmdMax. Unless this method is called, the command range will not be limited.

• void setGains(float Kp, float Ki, float Kd)
  Sets the PID controller gains. Kp, Ki and Kd are the proportional, integral and derivative gains respectively.

Version history

• 1.0.0 (2017-04-25) Initial release