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Topic: Motor rotate fast before loop (Read 325 times) previous topic - next topic

KTPovanes

Aug 03, 2019, 09:11 pm Last Edit: Aug 03, 2019, 09:16 pm by KTPovanes Reason: attaching Arduino code
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).

Code: [Select]

#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");
}

Slumpert

Code: [Select]

if (output > 0) //Falling towards front
        Forward(); //Rotate the wheels forward
      else if (output < 0) //Falling towards back
        Reverse(); //Rotate the wheels backward


So "output" is declared as Double and when your code first runs it is = 0
What does your code above do when "output" = 0

KTPovanes

Thanks for the prompt reply. I have changed the code somehow and it still didn't work. If the robot is at a certain angle beyond the given condition, it should stop rotating but when I serial print the input and output, it says a different thing.

Would it be a faulty Arduino Nano or MPU6050?

Code: [Select]

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 > (147) && input < (207))
    {
      //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 (output == 0)
        //Stop();
    }
    else if (input < 147 || input > 207) //If Bot not falling
      Stop(); //Hold the wheels still
  }


[code]

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KTPovanes

Finally, I managed to solve the issue. Somehow, it is reading the output value but not the motor condition at setup. So I added the (output = 0) at the end of the setup. Thanks for the help by the way @Slumpert

MarkT

Another issue that can happen is the motor driver inputs float, so during reset they can be any state.
Adding pull-down or pull-up resistors (as appropriate to disable drive) means the motor controller is well-
behaved before setup() gets to complete.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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