PID Arduino UNO

Question

I want to implement a PD controller in Arduino using the PID library. Should I put Ki=0 and the rest of the constants as desired?

/*
BALL BALANCING USING A PID CONTROL with 6" resistive Touchscreen
*/
//////////////////////////////////////////////////////
///Libraries///
#include <PID_v1.h>
#include <stdint.h>
#include <TouchScreen.h>
#include <Servo.h>
//______________________________________________________________
// Definitions TOUCH PINS
#define YP A1 //brown
#define XM A2 //black
#define YM 7 //yellow
#define XP 6 //red
//______________________________________________________________
// For better pressure precision, we need to know the resistance
// between XP and XM Use any multimeter to read it
// For the 6" its 273 ohms across the X plate
#define Rx 273 // Resistance in Ohm of Touchscreen measured in X-Direction
TouchScreen ts = TouchScreen(XP, YP, XM, YM, Rx); 
// Coordinates Touchscreen 
TSPoint p; 
double xmin = 146.0; //154
double xmax = 854.0; //851
double xLength = 160.0; //Width of Touchscreen in mm at 6.0" 158
double ymin = 63.0; //63.0 
double ymax = 953.0; //950.0
double yLength = 96.0; //Length of Touchscreen in mm at 6.0" 94
double convertX = xLength / (xmax - xmin); // converts raw x values to mm. found through manual calibration 0.2295 0.225988
double convertY = yLength / (ymax - ymin); // converts raw y values to mm. found through manual calibration 0.1082 0.107865
//______________________________________________________________
//Center-Position
double x0=74.35; double y0=42.71; //center Correct: 0.5//-7 double x0=74.35; double y0=42.71
//______________________________________________________________
int state = 0;
// servos variables
Servo servoX; //X axis
Servo servoY; //Y axis
/////TIME SAMPLE
int Ts = 45; //Delay between taking samples/measurements
unsigned long Stable=0;
unsigned int noTouchCount = 0; //variable for noTouch
//______________________________________________________________
double Kpx = 0.08; //Kpx = 0.08; //Proportional (P) Get the ball to set point 
double Kix = 0.02; //Kix = 0.02 0.022 //Integral (I) 
double Kdx = 0.035; //Kdx = 0.035; //Derivative (D) Stop the ball at set point 
double Kpy =0.08; //Kpy = 0.08 
double Kiy =0.02; //Kiy = 0.02 0.022; 
double Kdy =0.035; //Kdy = 0.035;
//______________________________________________________________
//INIT PID
double SetpointX, InputX, OutputX; //for X
double SetpointY, InputY, OutputY; //for Y
PID myPIDX(&InputX, &OutputX, &SetpointX, Kpx, Kix, Kdx, REVERSE);
PID myPIDY(&InputY, &OutputY, &SetpointY, Kpy, Kiy, Kdy, REVERSE);
//______________________________________________________________
void setup(){ 
servoX.attach(9);
servoY.attach(10);
 OutputX=92;
 OutputY=100;
 servoX.write(OutputX); // Make Plate flat in X-Direction
 servoY.write(OutputY); // Make Plate flat in Y-Direction
 
 //INIT OF TOUSCHSCREEN
 p = ts.getPoint();
 
 
 //INIT SETPOINT, Center of Plate
 SetpointX = 0.0;
 SetpointY = 0.0;
 
 //Setup PID Controller
 myPIDX.SetMode(AUTOMATIC); 
 myPIDX.SetOutputLimits(77, 107); // 83 107
 myPIDY.SetMode(AUTOMATIC); 
 myPIDY.SetOutputLimits(85, 115); // -- 81 105
 
 // TIME SAMPLE
 myPIDX.SetSampleTime(Ts); 
 myPIDY.SetSampleTime(Ts); 
 delay(100);
 state=0;
 setDesiredPosition();
} // end of setup
void loop()
{
 while(Stable < 15) //REGULATION LOOP 
 { 
 p = ts.getPoint(); //measure pressure on plate
 if (p.x > 0 ) //ball is on plate
 {
 servoX.attach(9); servoY.attach(10); //connect servos
 setDesiredPosition(); 
 noTouchCount = 0; 
 p = ts.getPoint(); // measure actual position 
 InputX = (p.x - xmin) * convertX; // read and convert X coordinate
 InputY = (p.y - ymin) * convertY; // read and convert Y coordinate 
 if((InputX == SetpointX && InputY == SetpointY )) 
 
 { Stable = Stable + 1;}
 
 myPIDX.Compute(); // action control X compute
 myPIDY.Compute(); // action control Y compute 
 }
 else //if there is no ball on plate
 {
 noTouchCount++; //increment no touch count
 if(noTouchCount == 150) 
 {
 noTouchCount++; 
 OutputX=92; OutputY=100; //make plate flat
 servoX.write(OutputX); servoY.write(OutputY);
 }
 if(noTouchCount == 300) //if there is no ball on plate longer, detach servos
 { servoX.detach(); servoY.detach(); }
 }
 servoX.write(OutputX); servoY.write(OutputY); //control 
 
 } // END OF REGULATION LOOP
servoX.detach(); servoY.detach(); //detach servos
///STABILITY////
 while(Stable==15) //if is stable 
 { //still measure actual postiion
 setDesiredPosition(); 
 p = ts.getPoint();
 InputX = (p.x - xmin) * convertX; // read and convert X coordinate
 InputY = (p.y - ymin) * convertY; // read and convert Y coordinate
 if(InputX < SetpointX || InputX > SetpointX || InputY > SetpointY || InputY < SetpointY ) //if ball isnt close to setpoint
 {
 servoX.attach(9); //again attach servos
 servoY.attach(10);
 Stable=0; //change STABLE state
 }
 
 }//end of STABLE LOOP
}//loop end
//______________________________________________________________
//#### DESIRED POSITION ####
void setDesiredPosition(){
 switch(state){
// Start-Sequence 
 case 0: SetpointX = x0;
 SetpointY = y0;
 p = ts.getPoint();
 if (p.x > 0)
 { 
 state = 1; 
 } // if ball is on plate
 else if (p.x <= 0)
 { 
 state = 0; 
 setDesiredPosition(); 
 } // if no ball is on plate 
 break;
// Center-Position 
 case 1: SetpointX = x0; 
 SetpointY = y0;
 state = 1;
 break;
 default : state = 0; break;
 
 } //end of switch state
} //end of setDesiredPosition()
//______________________________________________________________

• Dave Newton: Maybe? Without any context it's impossible to help.
• John C.: I'm doing a project on ball balancing using a PID controller in arduino UNO My plant is of type-2 and fifth order system.
• John C.: you can check the code above

Answer 1

Yes, you can use the PID library with Ki=0; to get a PD controller.