Arduino Nano PID Controller with Potentiometer + IBT-2 Motor Control Board

Using Arduino Motors, Mechanics, Power and CNC
1

I have a potentiometer connected to an analog pin A1 and would like to implement PID Control to move a robot arm up and down based on to a given serial command. For this to work I will need PID out produce a direction and speed output.

#include <AutoPID.h>

// PID settings and gains
#define OUTPUT_MIN 0
#define OUTPUT_MAX 255
#define KP 0.12
#define KI 0.8
#define KD 0.003


// Variables on PID values
float analogReadValue, setPoint, outputVal;

int SENSOR_PIN = A0; // center pin of the potentiometer

int RPWM_Output = 10; //IBT-2 Motor Control 
int LPWM_Output = 11; // 

bool BarUp;
bool BarLow;
bool BarStop;

char c;

// Input/output variables passed by reference, so they are updated automatically
AutoPID myPID(&analogReadValue, &setPoint, &outputVal, OUTPUT_MIN, OUTPUT_MAX, KP, KI, KD);

void setup()
{
  Serial.begin(9600);

  //Motor Direction controls
  pinMode(RPWM_Output, OUTPUT);
  pinMode(LPWM_Output, OUTPUT);

  myPID.setTimeStep(500);
}

float AnalogSensor()
{
    // read the input on analog pin 0:
    int sensorValue = analogRead(SENSOR_PIN);
    // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
    float voltage = sensorValue * (5.0 / 1023.0);

    return voltage;
}

void loop()
{
   analogReadValue=AnalogSensor(); 

  //Reading serial command
  if(Serial.available())
  {
     char c = Serial.read();

     if(c=='r')
     {
         BarLow=false;
         BarUp=true;
         Serial.println("Arm is Rising");
     }
     else if(c=='l')
     {
         BarUp=false;
         BarLow=true;
         Serial.println("Arm is lowering");
     }
}

if(BarUp)
{
  setPoint=UpperLimit;
  myPID.run(); 
}

if(BarLow)
{
  setPoint=LowerLimit;
  myPID.run(); 
}
}


void RaiseArm()
{
   analogWrite(LPWM_Output, 0);
   analogWrite(RPWM_Output, 20);

   delay(1000);

   StopArm();

   BarUp=false;
 }


 void LowerArm()
 {
   analogWrite(LPWM_Output, 20);
   analogWrite(RPWM_Output, 0);

   delay(1000);

   StopArm();

   BarLow=false;

 }

 void StopArm()
 {
    analogWrite(LPWM_Output, 0);
    analogWrite(RPWM_Output, 0);
 }

Ideally I would like to set the Setpoint to analog 5.0 for raising arm and analog 0 for lower arm. Baring in mind.

   analogWrite(LPWM_Output, 20);
   analogWrite(RPWM_Output, 0);

Is for raising arm and

   analogWrite(LPWM_Output, 20);
   analogWrite(RPWM_Output, 0);

Is lowering arm. Hope you can help as the current system is not implementing PID that can potentially work. The question is how can I change the current code to raise and lower arm to the setpoints.

2

This is the code but in the text You tell A1 is the input. That simple mistake?

3

Hi Railroader,

Sorry about that. A simple mistake. Hope you can help.

4

Wrong typing or wrong connection?

No, Your project is outside my comfort zone.

5

I’d suggest a google of how PID works followed by some of the PID examples available for Arduino .

6

Hi Hammy

The code is from the online PID examples. I wanted to find out if some one know more and can guide me through to whats wrong the current code.

7

Well you probably need to actually use outputVal...

Perhaps

if (outputVal < 0.0)
{
   analogWrite(LPWM_Output, constrain (-outputVal, 0, 255));
   analogWrite(RPWM_Output, 0);
}
else
{
   analogWrite(LPWM_Output, 0);
   analogWrite(RPWM_Output, constrain (outputVal, 0, 255));
}
8

Hi MarkT

Thank you so much for the response. I will give it a go.

9

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