Modified comments

TimedPID.cpp

@@ -1,6 +1,6 @@
 /*
 TimedPID.cpp
-Source: https://github.com/DrGFreeman/RasPiBot202.V2
+Source: https://github.com/DrGFreeman/TimedPID
 
 MIT License
 

TimedPID.h

@@ -1,6 +1,6 @@
 /*
 TimedPID.h
-Source: https://github.com/DrGFreeman/RasPiBot202.V2
+Source: https://github.com/DrGFreeman/TimedPID
 
 MIT License
 

examples/DemoTimedPID/DemoTimedPID.ino

@@ -1,37 +1,88 @@
+/*
+DemoTimedPID.ino
+Source: https://github.com/DrGFreeman/TimedPID
+
+MIT License
+
+Copyright (c) 2017 Julien de la Bruere-Terreault <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+/*
+This example demonstrates how to use the TimedPID class to control the speed of
+a mass subject to inertial and drag forces by controlling the force applied to
+the mass. The controller reacts to changes in the desired speed.
+
+The getCmdStep() is used as the time step is calculated in the main loop and
+used to calculate the speed of the mass.
+*/
+
 #include <TimedPID.h>
 
+// Define the PID controller proportional, integral and derivative gains
 float Kp = 10.0;
 float Ki = 0.15;
 float Kd = 5.0;
 
+// Create a TimedPID object instance
 TimedPID pid(Kp, Ki, Kd);
 
-float speed = 0;
-float accel = 0;
-float force = 0;
-float fDrag = 0;
-float mass = 0.2;
+// Initialize the mass system variables
+float speed = 0;    // the speed of the mass
+float accel = 0;    // the acceleration of the mass
+float fDrag = 0;    // the drag force on the mass
+float mass = 0.2;   // the mass value
+float force;        // the force applied to the mass by the control system
 
+// Define the maximum force the system can apply
 float fMax = 300;
 
+// Variables used for set point control and time step calculation
 unsigned long initialTime;
 unsigned long lastTime;
 
 void setup() {
+  // Open Serial communication and wait for monitor to be opened
   Serial.begin(9600);
   while(!Serial);
-
+
+  // Set the PID controller command range
   pid.setCmdRange(-fMax, fMax);
+
+  // Initialize time variables
   initialTime = micros();
   lastTime = initialTime;
   delay(1);
 }
 
 void loop() {
+
+  // Calculate the time step between passes of the main loop
+  // Get current time
   unsigned long currentTime = micros();
+  // Calculate time step in seconds (micro seconds / 1 000 000)
   float timeStep = float(currentTime - lastTime) / 1E6;
+  // Store current time as last time for next pass of the loop
   lastTime = currentTime;
-
+
+  // Define the target speed as function of time
   float targetSpeed = 0;
   if (currentTime - initialTime > 8E6){
     // Reset initial time
@@ -48,22 +99,30 @@ void loop() {
   else if (currentTime - initialTime > 3E6) {
     targetSpeed = 200;
   }
-
+  // Add continuous variation of the target speed
   targetSpeed += 5 * sin(micros() / 2.5E5);
-
+
+  // Calculate drag force proportional to speed squared
   fDrag = .003 * speed * speed;
+
+  // Get the system command from the PID based on target speed and current speed
   force = pid.getCmd(targetSpeed, speed);
+
+  // Calculate mass acceleration using Newton's third law (f=ma -> a=f/m)
   accel = (force - fDrag) / mass;
+  // Update mass speed based on acceleration and time step
   speed += accel * timeStep;
 
+  // Print target speed, force command and mass speed to Serial port
   Serial.print(targetSpeed);
   Serial.print("\t");
-  //Serial.print(force);
-  //Serial.print("\t");
+  Serial.print(force);
+  Serial.print("\t");
   Serial.println(speed);
+
+  // Ensure a constant time step of the main loop (10 milliseconds)
   while (micros() - currentTime < 10000)
   {
     // Wait until time step is reached
   }
 }
-