Introduction: Ball and Beam W/LabVIEW & Arduino

This was a school project, the assignment was to construct a ball and beam control system.

A ping pong ball sits on top of the beam rolling forwards and backwards according to the pitch of the beam. The pitch is controlled by a servo that is connected to an Arduino. The position of the ball is measured by a distance sensor mounted at the end of the beam.

An PID controller is used to control the position of the ball on the beam.

Step 1: Parts

Electronics

  • Distance sensor - SHARP 2Y0A21
  • Parallax Standard Servo (#900-00005)
  • Arduino
  • 5V powersupply

3D printed parts

Infill - 20%
Resolution - 0.15mm
Filament Material - PLA

  • Arm
  • Servo arm
  • Servo holder
  • Endplate with sensor
  • Endplate without sensor
  • Hinge

Mechanicall

  • 6x - M4x5mm
  • 1x - M3x45mm
  • 1x - M3x35mm
  • 1x - M3x10mm
  • 4x - 1,5x5mm wood screw
  • 4x - 3,5x15mm woood screw
  • Aluminum profile angle 520mm 15x15x2mm
  • Flanged bearings - 4mm Radial Ball Bearing 8mm O.D
  • 650x95x30mm wood board
  • 145x30x47mm wood stud
  • Ping pong ball

Attachments

Step 2: Assembling

The design was 3D modelled with Fusion 360

Step 3: Electrical

You need to use an external 5 volt power supply to supply power the servo and distance sensor.

Attachments

Step 4: PID Controller

LabVIEW

Using the LINX in LabVIEW to connect to the arduino.

Arduino

Using a modified version of SharpIR.h library, originaly by Dr. Marcal Casas-Cartagena

Step 5: LabVIEW Code

Select the COM port to the arduino and the servo and sensor pin.

Attachments

Step 6: Arduino Code

// Libraries
#include      <SharpIR.h>
#include      <Servo.h>
// Defines
#define       PIN_SERVO                   3
#define       PIN_SENSOR                  0
#define       PIN_LED                     13
#define       DEBUG_ACTIVE                1
#define       IR_MODEL                    1080
// Running average
const int     numReadings               = 3;
int           readings[numReadings];               // The readings from the analog input
int           readIndex                 = 0;       // The index of the current reading
double        total                     = 0;       // The running total
int           sensorRunningAverage      = 0;
// Constants
const double  Kp                        = 1;
const double  Ki                        = 0.1;
const double  Kd                        = 15;
const double  sampleTime                = 100;     // ms
const double  setpoint                  = 20;      // cm
const int     sensorMax                 = 57;      // cm
// Floating variables
double        error                     = 0;
double        oldError                  = 0;
double        diffError                 = 0;
double        sumError                  = 0;
unsigned long lastTime                  = 0;
unsigned long standbyTime               = 0;
unsigned long runningTime               = 0;
double        u                         = 0;       // Output of the PID controller
int           servoOutput               = 0;       // Output to the servo
double        dis                       = 0;
// Functrions
Servo servo;
SharpIR SharpIR(sensorRunningAverage, IR_MODEL);
void setup() {
  servo.attach(PIN_SERVO);
  pinMode(OUTPUT, PIN_LED);
  startup();
  for (int thisReading = 0; thisReading < numReadings; thisReading++) {
    readings[thisReading] = 0;
  }
  lastTime = millis();
  if (DEBUG_ACTIVE) {
    Serial.begin(9600);
  }
}
void loop() {
  sensorRunningAverage = getSensorRunningAverage(analogRead(PIN_SENSOR));
  dis = SharpIR.distance(); // this returns the distance to the object you're measuring
  /*How long since we last calculated*/
  unsigned long now = millis();
  double timeChange = (double)(now - lastTime);
  lastTime = now;
  if (dis >= sensorMax) {
    error = 0;
    sumError = 0;
    diffError = 0;
    standbyTime = millis() + 2000;
  }
  else if (standbyTime < now) {
       error = dis - setpoint;
      sumError += (error * (timeChange / 1000));
      diffError = error - oldError;
      oldError = error;
  }
  if (sampleTime + runningTime < now) {
      if (!(error <= 1  && error >= -1 && servoOutput == 26 && diffError <=0.5 && diffError >=-0.5)) { //tweaking of the regulator so that it stands still if the ball is within +-1 Cm.
    u = (Kp * error) + (Ki * sumError) + (Kd * diffError);
      }
    servoOutput = constrain(-u + 26, 0, 65);
    servo.write(servoOutput);
    runningTime = millis();
  }
  if (DEBUG_ACTIVE) {
    printStatus();
  }
}
void startup() {
  for (int i = 75; i >= 15; i--) {
    servo.write(i);
    if ((i / 2 & 1) == 0) {
      ledPinOn(PIN_LED);
    } else {
      ledPinOff(PIN_LED);
    }
    delay(50);
  }
}
int getSensorRunningAverage(int sensorValue) {
  total = total - readings[readIndex];
  readings[readIndex] = sensorValue;    // read from the sensor:
  total = total + readings[readIndex];  // add the reading to the total:
  readIndex = readIndex + 1;            // advance to the next position in the array:
  if (readIndex >= numReadings) {       // if we're at the end of the array...
    readIndex = 0;                      // ...wrap around to the beginning:
  }
  float average = total / numReadings;   // calculate the average:
  return average;
}
void printStatus() {
  Serial.print("Distance:  ");
  Serial.print(dis);
  Serial.print("\t");
  Serial.print("Error:  ");
  Serial.print(error);
  Serial.print("\t");
  Serial.print("Sum error:  ");
  Serial.print(sumError);
  Serial.print("\t");
  Serial.print("Diff error:  ");
  Serial.print(diffError);
  Serial.print("\t");
  Serial.print("u(t):  ");
  Serial.print(u);
  Serial.print("\t");
  Serial.print("Output:  ");
  Serial.println(servoOutput);
}
void ledPinOn(int led) {
  digitalWrite(led, HIGH);
}
void ledPinOff(int led) {
  digitalWrite(led, LOW);
}

Attachments