MPU-6050 Measurement, Long Angle Stabilization Phase

Hello,

using MPU-6050 for angle measurements the angle value starts with significant offset (about 10 degree) and will stabilize to expected value (around 0 degree) after a quite long time of about 1.5 seconds.
Is it possible to avoid this long stabilization phase?

  • I'm using complementary filter to calculate the final angle value
  • there is no delay() in the loop slowing down the measurement
// determine angle arround y-axis through gyro
void determineYAngleAndTime() {
    float accX,accY,accZ,gyroY;                           
    float accYAngle,gyroYAngle;
    Wire.beginTransmission(MPU);
    Wire.write(0x3B);                                     // Start with register 0x3B (ACCEL_XOUT_H)
    Wire.endTransmission(false);
    Wire.requestFrom(MPU, 6, true);                       // Read 6 registers total, each axis value is stored in 2 registers
    //For a range of +-2g, we need to divide the raw values by 16384, according to the datasheet
    accX = (Wire.read() << 8 | Wire.read()) / accSens;    // X-axis value
    accY = (Wire.read() << 8 | Wire.read()) / accSens;    // Y-axis value
    accZ = (Wire.read() << 8 | Wire.read()) / accSens;    // Z-axis value

    // read gyro value for Y-axis only
    Wire.beginTransmission(MPU);                          // begin transmission to I2C slave device
    Wire.write(0x45);                                     // Gyro data first register address 0x45 --> gyro Y axis data
    Wire.endTransmission(false);                          // restarts transmission to I2C slave device
    Wire.requestFrom(MPU,2,true);                         // request 2 registers in total, 2 registers for each axis value
    
    previousTime = atTimeStamp;                             // Previous time is stored before the actual time read    
    gyroY = (Wire.read() << 8 | Wire.read()) / gyroSens;  // For a 250deg/s range we have to divide first the raw value by 131.0, according to the datasheet
    atTimeStamp = millis();                               // timeStamp for angle measurement event
    elapsedTime = atTimeStamp - previousTime;               // Divide by 1000 to get seconds?
    
    // calculate y-Angle from acc data
    accYAngle = (atan(-1 * accX / sqrt(pow(accY, 2) + pow(accZ, 2))) * 180 / PI); //+ accXError?
    // calculate y-Angle from gyro data
    // gyroY = gyroY + gyroYError;

    gyroYAngle = yAngle + gyroY * float(elapsedTime) / 1000.0; // deg/s * s = deg

    // Complementary filter - combine accelerometer and gyro angle values
    yAngle = 0.96 * gyroYAngle + 0.04 * accYAngle;
}

yAngleGraph.png

yAngleGraph.png

I somehow feel like this is not the full code. Also for the complimentary filter, you should use "alpha".

Something like this:

alpha = 0.04;
yAngle = (1-alpha) * gyroYAngle + alpha * accYAngle;

You should also show how the gyro angle reacts with the comp. filter.

K = .97f
k1 = 1.0f - K
angle = (K)*(angle + gyro*dt) + (k1)*(x_acc);

Notice the use of dt in the complementary filter?
The proper integration of time into the filter is an important aspect of using the filter.
I have found that using millis() may result in a zero for dt . Instead, for dt, use micros() , millis() can cause 0’s to be spit out.

If your using a MCU that handles floats, than a simple Kalman filter would be better use of your calculating power instead of the complementary filter. GitHub - denyssene/SimpleKalmanFilter: A basic implementation of Kalman Filter for single variable models.. You’d make one instance of each thing, one instance for x and one instance for y, your are filtering.

Hello Idahowalker,
thank you. The answer make sense for the moment. I will check that out.

Hello Idahowalker,

changing the code according your proposal doesn't change anything. Still the same behavior.

Sorry that did not help.