Hi.
I am building a self-balancing robot and it is a part of my final year project at university.
I finally managed to get some codes from youtube since many used the library functions such as
a. I2Cdev
b. MPU6050_6Axis_MotionApps20.h
c. PID_v1.h
Well, successfully I have balanced the robot with only adjusting the Kp value. Soon I will adjust the Ki and Kd values.
I'm quite curious about why the motor rotates very fast for a second before even entering the loop. Sometimes even back and forth. The rotation is very fast until it made my robot quite hard hold before the balancing point. I have stated both motors at rest condition in the setup function. Kindly assist. Thanks. Below attached is the code.
I am using 10A dual channel motor driver, 12V DC motor at 336 RPM, Arduino Nano, 3 X 3.7V 18650 battery, 3S 25A battery management system (BMS), MPU6050 6 axis gyro and accelerometer and wooden frame (simple one to support the robot).
#include "I2Cdev.h"
#include <PID_v1.h> //From https://github.com/br3ttb/Arduino-PID-Library/blob/master/PID_v1.h
#include "MPU6050_6Axis_MotionApps20.h" //https://github.com/jrowberg/i2cdevlib/tree/master/Arduino/MPU6050
MPU6050 mpu;
// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer
// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorFloat gravity; // [x, y, z] gravity vector
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector
/*********Tune these 4 values for your BOT*********/
double setpoint = 177; //set the value when the bot is perpendicular to ground using serial monitor.
//Read the project documentation on circuitdigest.com to learn how to set these values
double Kp = 25; //Set this first
double Kd = 0; //Set this secound
double Ki = 0; //Finally set this
/******End of values setting*********/
double input, output;
PID pid(&input, &output, &setpoint, Kp, Ki, Kd, DIRECT);
volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void dmpDataReady()
{
mpuInterrupt = true;
}
void setup() {
Serial.begin(115200);
// initialize device
Serial.println(F("Initializing I2C devices..."));
mpu.initialize();
// verify connection
Serial.println(F("Testing device connections..."));
Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));
// load and configure the DMP
devStatus = mpu.dmpInitialize();
// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1742);
// make sure it worked (returns 0 if so)
if (devStatus == 0)
{
// turn on the DMP, now that it's ready
Serial.println(F("Enabling DMP..."));
mpu.setDMPEnabled(true);
// enable Arduino interrupt detection
Serial.println(F("Enabling interrupt detection (Arduino external interrupt 0)..."));
attachInterrupt(0, dmpDataReady, RISING);
mpuIntStatus = mpu.getIntStatus();
// set our DMP Ready flag so the main loop() function knows it's okay to use it
Serial.println(F("DMP ready! Waiting for first interrupt..."));
dmpReady = true;
// get expected DMP packet size for later comparison
packetSize = mpu.dmpGetFIFOPacketSize();
//setup PID
pid.SetMode(AUTOMATIC);
pid.SetSampleTime(10);
pid.SetOutputLimits(-255, 255);
}
else
{
// ERROR!
// 1 = initial memory load failed
// 2 = DMP configuration updates failed
// (if it's going to break, usually the code will be 1)
Serial.print(F("DMP Initialization failed (code "));
Serial.print(devStatus);
Serial.println(F(")"));
}
//Initialise the Motor outpu pins
pinMode (3, OUTPUT);
pinMode (4, OUTPUT);
pinMode (5, OUTPUT);
pinMode (6, OUTPUT);
//By default turn off both the motors
digitalWrite(4, LOW);
digitalWrite(3, 0);
digitalWrite(6, LOW);
digitalWrite(5, 0);
}
void loop() {
// if programming failed, don't try to do anything
if (!dmpReady) return;
// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize)
{
//no mpu data - performing PID calculations and output to motors
pid.Compute();
//Print the value of Input and Output on serial monitor to check how it is working.
//Serial.print(input); Serial.print(" =>"); Serial.println(output);
if (input > (setpoint - 30) && input < (setpoint + 30)) { //If the Bot is falling
if (output > 0) //Falling towards front
Forward(); //Rotate the wheels forward
else if (output < 0) //Falling towards back
Reverse(); //Rotate the wheels backward
}
else //If Bot not falling
Stop(); //Hold the wheels still
}
// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();
// get current FIFO count
fifoCount = mpu.getFIFOCount();
// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024)
{
// reset so we can continue cleanly
mpu.resetFIFO();
Serial.println(F("FIFO overflow!"));
// otherwise, check for DMP data ready interrupt (this should happen frequently)
}
else if (mpuIntStatus & 0x02)
{
// wait for correct available data length, should be a VERY short wait
while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);
// track FIFO count here in case there is > 1 packet available
// (this lets us immediately read more without waiting for an interrupt)
fifoCount -= packetSize;
mpu.dmpGetQuaternion(&q, fifoBuffer); //get value for q
mpu.dmpGetGravity(&gravity, &q); //get value for gravity
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity); //get value for ypr
input = ypr[1] * 180 / M_PI + 180;
}
}
void Forward() //Code to rotate the wheel forward
{
analogWrite(3, output);
digitalWrite(4, HIGH);
analogWrite(5, output);
digitalWrite(6, LOW);
//Serial.print("F"); //Debugging information
}
void Reverse() //Code to rotate the wheel Backward
{
analogWrite(3, -output);
digitalWrite(4, LOW);
analogWrite(5, -output);
digitalWrite(6, HIGH);
//Serial.print("R");
}
void Stop() //Code to stop both the wheels
{
analogWrite(3, 0);
digitalWrite(4, LOW);
analogWrite(5, 0);
digitalWrite(6, LOW);
//Serial.print("S");
}
I2Cdev.zip (13.3 KB)
MPU6050.zip (49.8 KB)
PID_v1.zip (3.82 KB)