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Topic: MPU6050 axis drift problem (Read 163 times) previous topic - next topic

DimitrisTzam

Hi all,
I'm using the the followns code to control 2 servos (pitch and roll) with mpu6050. Pitch and roll takes values from acelerometer and gyroscope too. The problem is that there are drifts on values if I turn the sensor rapidly and the servo doesn't follow. For example If I turn the sensor rapidly 90 degrees the servo will stay immobilized. Also value on serial monitor will not change. I trying to explain it as better I can so if you can't understand just ask me.
Thanks



DimitrisTzam

Code: [Select]
Power (5V) is provided to the Arduino pro mini by the FTDI programmer

Gyro - Arduino pro mini
VCC  -  5V
GND  -  GND
SDA  -  A4
SCL  -  A5

LCD  - Arduino pro mini
VCC  -  5V
GND  -  GND
SDA  -  A4
SCL  -  A5
*//////////////////////////////////////////////////////////////////////////////////////

//Include LCD and I2C library

#include <Wire.h>
#include "Servo.h"
Servo RollServo, PitchServo;
//Declaring some global variables
int gyro_x, gyro_y, gyro_z;
long acc_x, acc_y, acc_z, acc_total_vector;
int temperature;
long gyro_x_cal, gyro_y_cal, gyro_z_cal;
long loop_timer;
int lcd_loop_counter;
float angle_pitch, angle_roll;
int angle_pitch_buffer, angle_roll_buffer;
boolean set_gyro_angles;
float angle_roll_acc, angle_pitch_acc;
float angle_pitch_output, angle_roll_output;


void setup() {
  Wire.begin();                                                        //Start I2C as master
  Serial.begin(115200);                                               //Use only for debugging
  pinMode(13, OUTPUT);                                                 //Set output 13 (LED) as output
  RollServo.attach(8);
  PitchServo.attach(9);
  setup_mpu_6050_registers();                                          //Setup the registers of the MPU-6050 (500dfs / +/-8g) and start the gyro

  digitalWrite(13, HIGH);                                              //Set digital output 13 high to indicate startup

 
  Serial.print("  MPU-6050 IMU");                                         //Print text to screen
 
  Serial.print("     V1.0");                                              //Print text to screen

  delay(1500);                                                         //Delay 1.5 second to display the text
 
 
 
  Serial.print("Calibrating gyro");                                       //Print text to screen
  for (int cal_int = 0; cal_int < 2000 ; cal_int ++){                  //Run this code 2000 times
    if(cal_int % 125 == 0)Serial.print(".");           
                     //Print a dot on the LCD every 125 readings
    read_mpu_6050_data();                                              //Read the raw acc and gyro data from the MPU-6050
    gyro_x_cal += gyro_x;                                              //Add the gyro x-axis offset to the gyro_x_cal variable
    gyro_y_cal += gyro_y;                                              //Add the gyro y-axis offset to the gyro_y_cal variable
    gyro_z_cal += gyro_z;                                              //Add the gyro z-axis offset to the gyro_z_cal variable
    delay(3);                                                          //Delay 3us to simulate the 250Hz program loop
  }
  gyro_x_cal /= 2000;                                                  //Divide the gyro_x_cal variable by 2000 to get the avarage offset
  gyro_y_cal /= 2000;                                                  //Divide the gyro_y_cal variable by 2000 to get the avarage offset
  gyro_z_cal /= 2000;                                                  //Divide the gyro_z_cal variable by 2000 to get the avarage offset

 
  Serial.print("Pitch:");                                                 //Print text to screen
 
  Serial.print("Roll :");                                                 //Print text to screen
 
  digitalWrite(13, LOW);                                               //All done, turn the LED off
 
  loop_timer = micros();                                               //Reset the loop timer
}

void loop(){

  read_mpu_6050_data();                                                //Read the raw acc and gyro data from the MPU-6050

  gyro_x -= gyro_x_cal;                                                //Subtract the offset calibration value from the raw gyro_x value
  gyro_y -= gyro_y_cal;                                                //Subtract the offset calibration value from the raw gyro_y value
  gyro_z -= gyro_z_cal;                                                //Subtract the offset calibration value from the raw gyro_z value
 
  //Gyro angle calculations
  //0.0000611 = 1 / (250Hz / 65.5)
  angle_pitch += gyro_x * 0.0000611;                                   //Calculate the traveled pitch angle and add this to the angle_pitch variable
  angle_roll += gyro_y * 0.0000611;                                    //Calculate the traveled roll angle and add this to the angle_roll variable
 
  //0.000001066 = 0.0000611 * (3.142(PI) / 180degr) The Arduino sin function is in radians
  angle_pitch += angle_roll * sin(gyro_z * 0.000001066);               //If the IMU has yawed transfer the roll angle to the pitch angel
  angle_roll -= angle_pitch * sin(gyro_z * 0.000001066);               //If the IMU has yawed transfer the pitch angle to the roll angel
 
  //Accelerometer angle calculations
  acc_total_vector = sqrt((acc_x*acc_x)+(acc_y*acc_y)+(acc_z*acc_z));  //Calculate the total accelerometer vector
  //57.296 = 1 / (3.142 / 180) The Arduino asin function is in radians
  angle_pitch_acc = asin((float)acc_y/acc_total_vector)* 57.296;       //Calculate the pitch angle
  angle_roll_acc = asin((float)acc_x/acc_total_vector)* -57.296;       //Calculate the roll angle
 
 
  //Place the MPU-6050 spirit level and note the values in the following two lines for calibration
  angle_pitch_acc -= 0.0;                                              //Accelerometer calibration value for pitch
  angle_roll_acc -= 0.0;                                               //Accelerometer calibration value for roll

  if(set_gyro_angles){                                                 //If the IMU is already started
    angle_pitch = angle_pitch * 0.9996 + angle_pitch_acc * 0.0004;     //Correct the drift of the gyro pitch angle with the accelerometer pitch angle
    angle_roll = angle_roll * 0.9996 + angle_roll_acc * 0.0004; //Correct the drift of the gyro roll angle with the accelerometer roll angle
 
  }
  else{                                                                //At first start
    angle_pitch = angle_pitch_acc;                                     //Set the gyro pitch angle equal to the accelerometer pitch angle
    angle_roll = angle_roll_acc;                                       //Set the gyro roll angle equal to the accelerometer roll angle
    set_gyro_angles = true;                                            //Set the IMU started flag
  }
 
  //To dampen the pitch and roll angles a complementary filter is used
  angle_pitch_output = angle_pitch_output * 0.9 + angle_pitch * 0.1;   //Take 90% of the output pitch value and add 10% of the raw pitch value
  angle_roll_output = angle_roll_output * 0.9 + angle_roll * 0.1;      //Take 90% of the output roll value and add 10% of the raw roll value
 
  Serial.print("  Pitch= "); Serial.print(angle_pitch_output); Serial.print("\t");
  Serial.print("  Roll= "); Serial.print(angle_roll_output); Serial.print("\n");
int Roll12, Pitch;
Roll12 = map(angle_roll_output, -114, 0, 120, 179);
RollServo.write(Roll12);
Serial.print(" ROLL= ");
Serial.print(Roll12);
Pitch = map(angle_pitch_output, -7, 57, 50, 130);
PitchServo.write(Pitch);

  while(micros() - loop_timer < 4000);                                 //Wait until the loop_timer reaches 4000us (250Hz) before starting the next loop
  loop_timer = micros();                                               //Reset the loop timer
}



DimitrisTzam

Code: [Select]



void read_mpu_6050_data(){                                             //Subroutine for reading the raw gyro and accelerometer data
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x3B);                                                    //Send the requested starting register
  Wire.endTransmission();                                              //End the transmission
  Wire.requestFrom(0x68,14);                                           //Request 14 bytes from the MPU-6050
  while(Wire.available() < 14);                                        //Wait until all the bytes are received
  acc_x = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_x variable
  acc_y = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_y variable
  acc_z = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_z variable
  temperature = Wire.read()<<8|Wire.read();                            //Add the low and high byte to the temperature variable
  gyro_x = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_x variable
  gyro_y = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_y variable
  gyro_z = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_z variable

}



void setup_mpu_6050_registers(){
  //Activate the MPU-6050
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x6B);                                                    //Send the requested starting register
  Wire.write(0x00);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
  //Configure the accelerometer (+/-8g)
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x1C);                                                    //Send the requested starting register
  Wire.write(0x10);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
  //Configure the gyro (500dps full scale)
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x1B);                                                    //Send the requested starting register
  Wire.write(0x08);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
}



I couldn't post all the code so I posted it in two parts

DimitrisTzam


jremington

I'll bet you just cut and pasted this program, don't understand it and now want us to fix it for you.

But if I'm wrong, please explain this crap:

Code: [Select]
int Roll12, Pitch;
Roll12 = map(angle_roll_output, -114, 0, 120, 179);
RollServo.write(Roll12);
Serial.print(" ROLL= ");
Serial.print(Roll12);
Pitch = map(angle_pitch_output, -7, 57, 50, 130);
PitchServo.write(Pitch);

DimitrisTzam

Yes something like this I'm new on programming and thanks for your help. This is to map servo and make it move

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