NOT FINISHED YET!!! My first try to get a self built fully working Quadrocopter based on an mbed, a self built frame and some other more or less cheap parts.
Diff: IMU_Filter/IMU_Filter.cpp
- Revision:
- 34:3aa1cbcde59d
- Child:
- 37:34917f7c10ae
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/IMU_Filter/IMU_Filter.cpp Mon Jun 10 13:22:46 2013 +0000 @@ -0,0 +1,130 @@ +#include "IMU_Filter.h" + +// MARG +#define PI 3.1415926535897932384626433832795 +#define Kp 2.0f // proportional gain governs rate of convergence to accelerometer/magnetometer +#define Ki 0.005f // integral gain governs rate of convergence of gyroscope biases + +IMU_Filter::IMU_Filter() +{ + for(int i=0; i<3; i++) + angle[i]=0; + + // MARG + q0 = 1; q1 = 0; q2 = 0; q3 = 0; + exInt = 0; eyInt = 0; ezInt = 0; +} + +void IMU_Filter::compute(float dt, const float * Gyro_data, const float * Acc_data) +{ + // calculate angles for each sensor + for(int i = 0; i < 3; i++) + d_Gyro_angle[i] = Gyro_data[i] *dt; + get_Acc_angle(Acc_data); + + // Complementary Filter + #if 0 // (formula from http://diydrones.com/m/discussion?id=705844%3ATopic%3A669858) + angle[0] = (0.999*(angle[0] + d_Gyro_angle[0]))+(0.001*(Acc_angle[0])); + angle[1] = (0.999*(angle[1] + d_Gyro_angle[1]))+(0.001*(Acc_angle[1]));// + 3)); // TODO Offset accelerometer einstellen + angle[2] += d_Gyro_angle[2]; // gyro only here TODO: Compass + 3D + #endif + + #if 0 // alte berechnung, vielleicht Accelerometer zu stark gewichtet + angle[0] += (Acc.angle[0] - angle[0])/50 + d_Gyro_angle[0]; + angle[1] += (Acc.angle[1] - angle[1])/50 + d_Gyro_angle[1];// TODO Offset accelerometer einstellen + //tempangle += (Comp.get_angle() - tempangle)/50 + Gyro.data[2] *dt/15000000.0; + angle[2] = Gyro_angle[2]; // gyro only here + #endif + + #if 0 // neuer Test 2 (funktioniert wahrscheinlich nicht, denkfehler) + angle[0] += Gyro_angle[0] * 0.98 + Acc.angle[0] * 0.02; + angle[1] += Gyro_angle[1] * 0.98 + (Acc.angle[1] + 3) * 0.02; // TODO: Calibrierung Acc + angle[2] = Gyro_angle[2]; // gyro only here + #endif + + #if 0 // all gyro only + for(int i = 0; i < 3; i++) + angle[i] += d_Gyro_angle[i]; + #endif + + // MARG + #if 1 // (from http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/) + float radGyro[3]; + + for(int i=0; i<3; i++) // Radians per second + radGyro[i] = Gyro_data[i] * PI / 180; + + IMUupdate(dt/2, radGyro[0], radGyro[1], radGyro[2], Acc_data[0], Acc_data[1], Acc_data[2]); + + float rangle[3]; // calculate angles in radians from quternion output + rangle[0] = atan2(2*q0*q1 + 2*q2*q3, 1 - 2*(q1*q1 + q2*q2)); // from Wiki + rangle[1] = asin(2*q0*q2 - 2*q3*q1); + rangle[2] = atan2(2*q0*q3 + 2*q1*q2, 1 - 2*(q2*q2 + q3*q3)); + + for(int i=0; i<3; i++) // angle in degree + angle[i] = rangle[i] * 180 / PI; + #endif +} + +void IMU_Filter::get_Acc_angle(const float * Acc_data) +{ + // calculate the angles for roll and pitch (0,1) + float R = sqrt(pow((float)Acc_data[0],2) + pow((float)Acc_data[1],2) + pow((float)Acc_data[2],2)); + float temp[3]; + + temp[0] = -(Rad2Deg * acos(Acc_data[1] / R)-90); + temp[1] = Rad2Deg * acos(Acc_data[0] / R)-90; + temp[2] = Rad2Deg * acos(Acc_data[2] / R); + + for(int i = 0;i < 3; i++) + if (temp[i] > -360 && temp[i] < 360) + Acc_angle[i] = temp[i]; +} + +// MARG +void IMU_Filter::IMUupdate(float halfT, float gx, float gy, float gz, float ax, float ay, float az) +{ + float norm; + float vx, vy, vz; + float ex, ey, ez; + + // normalise the measurements + norm = sqrt(ax*ax + ay*ay + az*az); + if(norm == 0.0f) return; + ax = ax / norm; + ay = ay / norm; + az = az / norm; + + // estimated direction of gravity + vx = 2*(q1*q3 - q0*q2); + vy = 2*(q0*q1 + q2*q3); + vz = q0*q0 - q1*q1 - q2*q2 + q3*q3; + + // error is sum of cross product between reference direction of field and direction measured by sensor + ex = (ay*vz - az*vy); + ey = (az*vx - ax*vz); + ez = (ax*vy - ay*vx); + + // integral error scaled integral gain + exInt = exInt + ex*Ki; + eyInt = eyInt + ey*Ki; + ezInt = ezInt + ez*Ki; + + // adjusted gyroscope measurements + gx = gx + Kp*ex + exInt; + gy = gy + Kp*ey + eyInt; + gz = gz + Kp*ez + ezInt; + + // integrate quaternion rate and normalise + q0 = q0 + (-q1*gx - q2*gy - q3*gz)*halfT; + q1 = q1 + (q0*gx + q2*gz - q3*gy)*halfT; + q2 = q2 + (q0*gy - q1*gz + q3*gx)*halfT; + q3 = q3 + (q0*gz + q1*gy - q2*gx)*halfT; + + // normalise quaternion + norm = sqrt(q0*q0 + q1*q1 + q2*q2 + q3*q3); + q0 = q0 / norm; + q1 = q1 / norm; + q2 = q2 / norm; + q3 = q3 / norm; +} \ No newline at end of file