Appendix - Catapult

Table 1: Bill of materials for final build

The code does the following:

Sets a desired RPM and maintains this using a PID
Outputs the current value of acceleration being collected by the IMU
Runs the mechanism for one full throwing cycle and records the acceleration data

Pauses the code after running one cycle
Prints recorded acceleration data during this time
Wipes data from memory to improve speed

Continues to power the motor and output accel data after data has been collected to throw more balls

#include <Wire.h>

#include <Adafruit_MPU6050.h>

#include <Adafruit_Sensor.h>

#include <PID_v1_bc.h>

#include <Encoder.h>

// MPU-6050 setup

Adafruit_MPU6050 mpu;

// Motor and encoder setup

const uint8_t motorPinA = 8;

const uint8_t motorPinB = 9;

const uint8_t encoderPinA = 3;

const uint8_t encoderPinB = 2;

const uint8_t motorPWMPin = 5;

Encoder encoder(encoderPinA, encoderPinB);

// PID setup for constant motor speed

const int desiredRPM = 400;

const int countsPerRevolution = 950;

double Setpoint, Input, Output;

double Kp = 0.5, Ki = 5, Kd = 0.01;

PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);

unsigned long previousMillis = 0;

long previousEncoderCount = 0;

uint16_t revolutions = 0;

const int maxDataPoints = 50;

const uint8_t maxRevolutions = 20;

const uint8_t samplesPerRev = maxDataPoints/maxRevolutions;

const int samplesPerStep = countsPerRevolution / samplesPerRev;

int revolutionCounter = 0;

long datapreviousEncoderCount =0;

int dataIndex = 0;

bool recording = true;

unsigned long dataTimes[maxDataPoints];

double accelDataX[maxDataPoints];

double accelDataY[maxDataPoints];

double accelDataZ[maxDataPoints];

void setup() {

Serial.begin(19200);

Wire.begin();

// Initialize MPU-6050

if (!mpu.begin()) {

Serial.println("Failed to find MPU6050 chip");

while (1) {

delay(10);

}

mpu.setAccelerometerRange(MPU6050_RANGE_8_G);

mpu.setGyroRange(MPU6050_RANGE_250_DEG);

mpu.setFilterBandwidth(MPU6050_BAND_21_HZ);

// Configure PID

Setpoint = desiredRPM;

Serial.print(Setpoint);

myPID.SetMode(AUTOMATIC);

myPID.SetSampleTime(100);

myPID.SetOutputLimits(0, 255);

// Motor pins

pinMode(motorPinA, OUTPUT);

pinMode(motorPinB, OUTPUT);

pinMode(motorPWMPin, OUTPUT);

}

void loop() {

Serial.println();

unsigned long currentMillis = millis();

unsigned long deltaTime = currentMillis - previousMillis;

// Read accelerometer and gyroscope data

sensors_event_t a_event, g_event, temp_event;

mpu.getEvent(&a_event, &g_event, &temp_event);

// Convert raw values to Gs

float accel_x = a_event.acceleration.x / 9.81;

float accel_y = a_event.acceleration.y / 9.81;

float accel_z = a_event.acceleration.z / 9.81;

// Print accelerometer values in Gs

Serial.print("Accel X: ");

Serial.print(accel_x);

Serial.print(" Accel Y: ");

Serial.print(accel_y);

Serial.print(" Accel Z: ");

Serial.println(accel_z);

// Calculate and print the magnitude of acceleration

float magnitude = sqrt(pow(accel_x, 2) + pow(accel_y, 2) + pow(accel_z, 2));

Serial.print("Magnitude: ");

Serial.println(magnitude);

if (deltaTime >= 100) {

// Read encoder value and calculate counts per second

long currentEncoderCount = encoder.read();

long deltaEncoderCount = currentEncoderCount - previousEncoderCount;

previousEncoderCount = currentEncoderCount;

double countsPerSecond = (deltaEncoderCount / (double)deltaTime) * 1000;

// Calculate current RPM

Input = (countsPerSecond / countsPerRevolution) * 60;

Serial.print("Input: ");

Serial.println(Input);

// Update revolution counter

revolutions = currentEncoderCount / countsPerRevolution;

Serial.print("Revolutions: ");

Serial.println(revolutions);

// Record acceleration data

if (recording && dataIndex < maxDataPoints) {

int deltaEncoderCount = currentEncoderCount - datapreviousEncoderCount;

if (deltaEncoderCount >= samplesPerStep) {

datapreviousEncoderCount = currentEncoderCount;

dataTimes[dataIndex] = millis();

accelDataX[dataIndex] = accel_x;

accelDataY[dataIndex] = accel_y;

accelDataZ[dataIndex] = accel_z;

dataIndex++;

}

} else if (recording && revolutions >= maxRevolutions) {

recording = false;

endRecording();

}

// Compute PID

myPID.Compute();

// Control motor

controlMotor(Output);

Serial.print("PID OUTPUT (PWM): ");

Serial.println(Output);

// Print current encoder speed, encoder value, and RPM

Serial.print("Encoder Speed (counts/s): ");

Serial.print(countsPerSecond);

Serial.print(" | Encoder Value: ");

Serial.print(currentEncoderCount);

Serial.print(" | RPM: ");

Serial.println(Input);

// Update revolution counter

revolutions = currentEncoderCount / countsPerRevolution;

Serial.print("Revolutions: ");

Serial.println(revolutions);

previousMillis = currentMillis;

}

void controlMotor(int speed) {

if (speed > 0) {

digitalWrite(motorPinA, HIGH);

digitalWrite(motorPinB, LOW);

analogWrite(motorPWMPin, speed);

} else {

digitalWrite(motorPinA, LOW);

digitalWrite(motorPinB, LOW);

analogWrite(motorPWMPin, 0);

}

void endRecording() {

// Print the recorded data

controlMotor(0);

Serial.println("Recorded Data:");

for (int i = 0; i < maxDataPoints; i++) {

//Serial.print(" Time: ");

Serial.print(" ");

Serial.print(dataTimes[i]);

}

Serial.println(" ");

for (int i = 0; i < maxDataPoints; i++) {

//Serial.print(" Accel X: ");

Serial.print(" ");

Serial.print(accelDataX[i]);

}

Serial.println(" ");

for (int i = 0; i < maxDataPoints; i++) {

//Serial.print(" Accel Y: ");

Serial.print(" ");

Serial.print(accelDataY[i]);

}

Serial.println(" ");

for (int i = 0; i < maxDataPoints; i++) {

//Serial.print(" Accel Y: ");

Serial.print(" ");

Serial.print(accelDataZ[i]);

}

Serial.println(" ");

// Reset the data arrays and counters

memset(dataTimes, 0, sizeof(dataTimes));

memset(accelDataX, 0, sizeof(accelDataX));

memset(accelDataY, 0, sizeof(accelDataY));

}