Open drf5n opened 1 year ago
Here's an easier-to-fiddle with simulation example:
https://wokwi.com/projects/359088752027305985
The Auto/Manual, Minus/Plus and "Manual/Output=0/Auto" trick controls used in this simulation are all available with the stock PID_v1 code. This sim only adds exposing the outputSum internal variable to the UI.
/********************************************************
PID Basic simulated heater Example
Reading simulated analog input 0 to control analog PWM output 3
********************************************************/
// This simulates a 20W heater block driven by the PID
// Vary the setpoint with the Pot, and watch the heater drive the temperature up
//
// Simulation at https://wokwi.com/projects/359088752027305985
//
// Based on
// Wokwi https://wokwi.com/projects/357374218559137793
// Wokwi https://wokwi.com/projects/356437164264235009
#include "PID_v1.h" // https://github.com/br3ttb/Arduino-PID-Library
// local copy of .h and .cpp are tweaked to expose the integral per
// https://github.com/br3ttb/Arduino-PID-Library/pull/132#issuecomment-1453839425
#define USE_HACK // access the PID.outputSum variable
//Define Variables we'll be connecting to
double Setpoint, Input, Output;
//Specify the links and initial tuning parameters
//double Kp = 20, Ki = .01, Kd = 10; // works reasonably with sim heater block fo 220deg
double Kp = 25.5, Ki = 0.1, Kd = 0; // +/-10°proportional band
//double Kp = 255, Ki = 0.05, Kd = 0; // works reasonably with sim heater block
//double Kp = 255, Ki = .0, Kd = 0; // +/-1° proportional band works reasonably with sim heater block
//double Kp = 10000, Ki = 0.0, Kd = 0.0; // bang-bang
//double Kp = 2, Ki = 0.0, Kd = 0.0; // P-only
//double Kp = 2, Ki = 5, Kd = 1; // commonly used defaults
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, P_ON_E, DIRECT);
const int PWM_PIN = 3; // UNO PWM pin for Output
const int INPUT_PIN = -1; // Analog pin for Input (set <0 for simulation)
const int SETPOINT_PIN = A1; // Analog pin for Setpoint Potentiometer
const int AUTOMATIC_PIN = 8; // Pin for controlling manual/auto mode, NO
const int OVERRIDE_PIN = 12; // Pin for integral override, NO
const int PLUS_PIN = 4; // Pin for integral override, NO
const int MINUS_PIN =7; // Pin for integral override, NO
#include <LiquidCrystal_I2C.h>
#define I2C_ADDR 0x27
#define LCD_COLUMNS 20
#define LCD_LINES 4
LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);
void setup()
{
Serial.begin(115200);
Serial.println(__FILE__);
myPID.SetOutputLimits(0, 255); // -4 for
pinMode(OVERRIDE_PIN, INPUT_PULLUP);
pinMode(AUTOMATIC_PIN, INPUT_PULLUP);
pinMode(MINUS_PIN, INPUT_PULLUP);
pinMode(PLUS_PIN, INPUT_PULLUP);
Setpoint = 0;
//turn the PID on
myPID.SetMode(AUTOMATIC);
if(INPUT_PIN>0){
Input = analogRead(INPUT_PIN);
}else{
Input = simPlant(0.0,1.0); // simulate heating
}
lcd.init();
lcd.backlight();
Serial.println("Setpoint Input Output Integral");
}
void loop()
{
// gather Input from INPUT_PIN or simulated block
float heaterWatts = Output * 20.0 / 255; // 20W heater
if (INPUT_PIN > 0 ) {
Input = analogRead(INPUT_PIN);
} else {
float blockTemp = simPlant(heaterWatts,Output>0?1.0:1-Output); // simulate heating
Input = blockTemp; // read input from simulated heater block
}
if (myPID.Compute())
{
//Output = (int)Output; // Recognize that the output as used is integer
analogWrite(PWM_PIN, Output);
}
Setpoint = analogRead(SETPOINT_PIN) / 4; // Read setpoint from potentiometer
if(digitalRead(OVERRIDE_PIN)==LOW) mySetIntegral(&myPID,0); // integral override
if(digitalRead(AUTOMATIC_PIN)==HIGH != myPID.GetMode()==AUTOMATIC){
myPID.SetMode(digitalRead(AUTOMATIC_PIN)==HIGH ? AUTOMATIC :MANUAL);
}
static uint32_t lastButton = 0;
if(myPID.GetMode()==MANUAL && millis() - lastButton > 250){
if(digitalRead(PLUS_PIN)==LOW){
Output += 1;
lastButton = millis();
}
if(digitalRead(MINUS_PIN)==LOW){
Output -= 1;
lastButton = millis();
}
}
report();
reportLCD();
}
void report(void)
{
static uint32_t last = 0;
const int interval = 250;
if (millis() - last > interval) {
last += interval;
// Serial.print(millis()/1000.0);
Serial.print("SP:");Serial.print(Setpoint);
Serial.print(" PV:");
Serial.print(Input);
Serial.print(" CV:");
Serial.print(Output);
Serial.print(" Int:");
#if defined(USE_HACK)
Serial.print(myPID.outputSum);
#endif
Serial.print(' ');
Serial.println();
}
}
void reportLCD(void)
{
static uint32_t last = 0;
const int interval = 250;
if (millis() - last > interval) {
last += interval;
// Serial.print(millis()/1000.0);
// lcd.clear();
lcd.setCursor(0,0);
lcd.print("PV:");
lcd.print(Input,3);
lcd.print(" CV:");
lcd.print(Output,3);
lcd.print(" ");
lcd.setCursor(0,1);
lcd.print("SP:");
lcd.print(Setpoint,3);
lcd.print(myPID.GetMode()==AUTOMATIC? " Automatic ":" Manual ");
lcd.print(" ");
lcd.setCursor(0,3);
lcd.print("Int:");
#if defined(USE_HACK)
lcd.print(myPID.outputSum,4);
#endif
lcd.print(' ');
lcd.println();
}
}
float simPlant(float Q,float hfactor) { // heat input in W (or J/s)
// simulate a 1x1x2cm aluminum block with a heater and passive ambient cooling
// float C = 237; // W/mK thermal conduction coefficient for Al
float h = 5 *hfactor ; // W/m2K thermal convection coefficient for Al passive
float Cps = 0.89; // J/g°C
float area = 1e-4; // m2 area for convection
float mass = 10 ; // g
float Tamb = 25; // °C
static float T = Tamb; // °C
static uint32_t last = 0;
uint32_t interval = 100; // ms
if (millis() - last >= interval) {
last += interval;
// 0-dimensional heat transfer
T = T + Q * interval / 1000 / mass / Cps - (T - Tamb) * area * h;
}
return T;
}
void mySetIntegral(PID * ptrPID,double value ){
ptrPID->SetMode(MANUAL);
Output = value;
ptrPID->SetMode(AUTOMATIC);
}
Here's an example of using user-space hacking to implement conditional integration:
https://wokwi.com/projects/362722038135838721
The key bit of code is:
float outputSumSave = myPID.outputSum; /// save for conditional integration
if (myPID.Compute())
{
if(Output == 255 || Output == -4){ // undo integral update at limits
myPID.outputSum = outputSumSave;
}
...
Based on the discussion in https://github.com/br3ttb/Arduino-PID-Library/pull/132#issuecomment-1452803503 I realized that a low impact way of handling the issues would be to just move some features out of the black box.
Moving the
PID::Initialize()
function out to public makes theSetMode(MANUAL);Output=value;SetMode(MANUAL);
trick easier to discuss and handle.Moving the
PID::outputSum
variable from private to public makes it possible to examine (or hack on) the internal integrator state.Since these functions already exist, it should be a no-cost change and enables easy understanding of what the algorithm does and easy adaptation to special uses.
A live example:
https://wokwi.com/projects/358190033668210689
This minimal-impact change would obviate https://github.com/br3ttb/Arduino-PID-Library/pull/132