Hi guys.
I've been trying to use this library for getting pitch and roll angles from my MPU-6050 using Kalman filter,
but the data I'm getting off of it is just ridiculously delayed. If I rotate my MPU it takes 5+ seconds to stabilize! The gyro and accelerometer data are displayed in real time so I have no idea what could be slowing down the filters, I guess in case of Kalman it could be the math behind it but with complementary it's just one equation so why would it be so slow? Was anyone playing around with this example and could give me an advice? Thanks.
EDIT: OK I solved the issues, I may have written the thread hastily without looking into the code properly, sorry for the mess, you can delete the thread.
#include <Wire.h>
#include "Kalman.h" // Source: https://github.com/TKJElectronics/KalmanFilter
Kalman kalmanX; // Create the Kalman instances
Kalman kalmanY;
double accX, accY, accZ;
double gyroX, gyroY, gyroZ;
int16_t tempRaw;
double gyroXangle, gyroYangle; // Angle calculate using the gyro only
double compAngleX, compAngleY; // Calculated angle using a complementary filter
double kalAngleX, kalAngleY; // Calculated angle using a Kalman filter
uint32_t timer;
uint8_t i2cData[14]; // Buffer for I2C data
void setup() {
Serial.begin(9600);
Wire.begin();
TWBR = ((F_CPU / 400000L) - 16) / 2; // Set I2C frequency to 400kHz
i2cData[0] = 7; // Set the sample rate to 1000Hz - 8kHz/(7+1) = 1000Hz
i2cData[1] = 0x00; // Disable FSYNC and set 260 Hz Acc filtering, 256 Hz Gyro filtering, 8 KHz sampling
i2cData[2] = 0x00; // Set Gyro Full Scale Range to ±250deg/s
i2cData[3] = 0x00; // Set Accelerometer Full Scale Range to ±2g
while (i2cWrite(0x19, i2cData, 4, false)); // Write to all four registers at once
while (i2cWrite(0x6B, 0x01, true)); // PLL with X axis gyroscope reference and disable sleep mode
while (i2cRead(0x75, i2cData, 1));
if (i2cData[0] != 0x68) { // Read "WHO_AM_I" register
Serial.print(F("Error reading sensor"));
while (1);
}
delay(100); // Wait for sensor to stabilize
/* Set kalman and gyro starting angle */
while (i2cRead(0x3B, i2cData, 6));
accX = (i2cData[0] << 8) | i2cData[1];
accY = (i2cData[2] << 8) | i2cData[3];
accZ = -(i2cData[4] << 8) | i2cData[5];
double roll = atan2(accY, accZ) * RAD_TO_DEG;
double pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
kalmanX.setAngle(roll); // Set starting angle
kalmanY.setAngle(pitch);
gyroXangle = roll;
gyroYangle = pitch;
compAngleX = roll;
compAngleY = pitch;
timer = micros();
}
void loop() {
/* Update all the values */
while (i2cRead(0x3B, i2cData, 14));
accX = ((i2cData[0] << 8) | i2cData[1]);
accY = ((i2cData[2] << 8) | i2cData[3]);
accZ = -((i2cData[4] << 8) | i2cData[5]);
tempRaw = (i2cData[6] << 8) | i2cData[7];
gyroX = (i2cData[8] << 8) | i2cData[9];
gyroY = (i2cData[10] << 8) | i2cData[11];
gyroZ = (i2cData[12] << 8) | i2cData[13];
double dt = (double)(micros() - timer) / 1000000; // Calculate delta time
timer = micros();
double roll = atan2(accY, accZ) * RAD_TO_DEG;
double pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
double gyroXrate = gyroX / 131.0; // Convert to deg/s
double gyroYrate = gyroY / 131.0; // Convert to deg/s
// This fixes the transition problem when the accelerometer angle jumps between -180 and 180 degrees
if ((roll < -90 && kalAngleX > 90) || (roll > 90 && kalAngleX < -90)) {
kalmanX.setAngle(roll);
compAngleX = roll;
kalAngleX = roll;
gyroXangle = roll;
} else
kalAngleX = kalmanX.getAngle(roll, gyroXrate, dt); // Calculate the angle using a Kalman filter
if (abs(kalAngleX) > 90)
gyroYrate = -gyroYrate; // Invert rate, so it fits the restriced accelerometer reading
kalAngleY = kalmanY.getAngle(pitch, gyroYrate, dt);
gyroXangle += gyroXrate * dt; // Calculate gyro angle without any filter
gyroYangle += gyroYrate * dt;
//gyroXangle += kalmanX.getRate() * dt; // Calculate gyro angle using the unbiased rate
//gyroYangle += kalmanY.getRate() * dt;
compAngleX = 0.9 * (compAngleX + gyroXrate * dt) + 0.1 * roll; // Calculate the angle using a Complimentary filter
compAngleY = 0.9 * (compAngleY + gyroYrate * dt) + 0.1 * pitch;
// Reset the gyro angle when it has drifted too much
if (gyroXangle < -180 || gyroXangle > 180)
gyroXangle = kalAngleX;
if (gyroYangle < -180 || gyroYangle > 180)
gyroYangle = kalAngleY;
Serial.print(accX); Serial.print(":");
Serial.print(accY); Serial.print(":");
Serial.print(accZ); Serial.print(":");
Serial.print(roll); Serial.print(":");
Serial.print(pitch); Serial.print(":");
Serial.print(gyroXangle); Serial.print(":");
Serial.print(gyroYangle); Serial.print(":");
Serial.print(compAngleX); Serial.print(":");
Serial.print(compAngleY); Serial.print(":");
Serial.print(kalAngleX); Serial.print(":");
Serial.println(kalAngleY);// Serial.print("\t");
//Serial.print("\r\n");
delay(2);
}
Kalman.h:
#ifndef _Kalman_h
#define _Kalman_h
class Kalman {
public:
Kalman() {
/* We will set the variables like so, these can also be tuned by the user */
Q_angle = 0.001f;
Q_bias = 0.003f;
R_measure = 0.03f;
angle = 0.0f; // Reset the angle
bias = 0.0f; // Reset bias
P[0][0] = 0.0f; // Since we assume that the bias is 0 and we know the starting angle (use setAngle), the error covariance matrix is set like so - see: http://en.wikipedia.org/wiki/Kalman_filter#Example_application.2C_technical
P[0][1] = 0.0f;
P[1][0] = 0.0f;
P[1][1] = 0.0f;
};
// The angle should be in degrees and the rate should be in degrees per second and the delta time in seconds
float getAngle(float newAngle, float newRate, float dt) {
// KasBot V2 - Kalman filter module - http://www.x-firm.com/?page_id=145
// Modified by Kristian Lauszus
// See my blog post for more information: http://blog.tkjelectronics.dk/2012/09/a-practical-approach-to-kalman-filter-and-how-to-implement-it
// Discrete Kalman filter time update equations - Time Update ("Predict")
// Update xhat - Project the state ahead
/* Step 1 */
rate = newRate - bias;
angle += dt * rate;
// Update estimation error covariance - Project the error covariance ahead
/* Step 2 */
P[0][0] += dt * (dt*P[1][1] - P[0][1] - P[1][0] + Q_angle);
P[0][1] -= dt * P[1][1];
P[1][0] -= dt * P[1][1];
P[1][1] += Q_bias * dt;
// Discrete Kalman filter measurement update equations - Measurement Update ("Correct")
// Calculate Kalman gain - Compute the Kalman gain
/* Step 4 */
float S = P[0][0] + R_measure; // Estimate error
/* Step 5 */
float K[2]; // Kalman gain - This is a 2x1 vector
K[0] = P[0][0] / S;
K[1] = P[1][0] / S;
// Calculate angle and bias - Update estimate with measurement zk (newAngle)
/* Step 3 */
float y = newAngle - angle; // Angle difference
/* Step 6 */
angle += K[0] * y;
bias += K[1] * y;
// Calculate estimation error covariance - Update the error covariance
/* Step 7 */
float P00_temp = P[0][0];
float P01_temp = P[0][1];
P[0][0] -= K[0] * P00_temp;
P[0][1] -= K[0] * P01_temp;
P[1][0] -= K[1] * P00_temp;
P[1][1] -= K[1] * P01_temp;
return angle;
};
void setAngle(float newAngle) { angle = newAngle; }; // Used to set angle, this should be set as the starting angle
float getRate() { return rate; }; // Return the unbiased rate
/* These are used to tune the Kalman filter */
void setQangle(float newQ_angle) { Q_angle = newQ_angle; };
void setQbias(float newQ_bias) { Q_bias = newQ_bias; };
void setRmeasure(float newR_measure) { R_measure = newR_measure; };
float getQangle() { return Q_angle; };
float getQbias() { return Q_bias; };
float getRmeasure() { return R_measure; };
private:
/* Kalman filter variables */
float Q_angle; // Process noise variance for the accelerometer
float Q_bias; // Process noise variance for the gyro bias
float R_measure; // Measurement noise variance - this is actually the variance of the measurement noise
float angle; // The angle calculated by the Kalman filter - part of the 2x1 state vector
float bias; // The gyro bias calculated by the Kalman filter - part of the 2x1 state vector
float rate; // Unbiased rate calculated from the rate and the calculated bias - you have to call getAngle to update the rate
float P[2][2]; // Error covariance matrix - This is a 2x2 matrix
};
#endif
while (i2cWrite(0x19, i2cData, 4, false)); // Write to all four registers at once
while (i2cWrite(0x6B, 0x01, true)); // PLL with X axis gyroscope reference and disable sleep mode
Hey don't blame me I haven't written the code, just using it. If you want more detailed info what the author had in mind I suggest you ask him. Besides there are other ways of plugging things in except actually sticking the cables into the board.
i2cWrite and i2cRead both return zero if they succeed. If they fail, they print an error message and try again. The use of the while loop seems to presume that either the fault won't last or if it does the user will get tired of seeing error messages and they'll unplug it and try again.