AHRS library, modified version of Peter Bartz work.
Diff: DCM.cpp
- Revision:
- 0:014ee3239c80
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DCM.cpp Thu Nov 08 18:57:18 2012 +0000 @@ -0,0 +1,129 @@ +/* This file is part of the Razor AHRS Firmware */ +#include "AHRS.h" +#include <math.h> + +// DCM algorithm + +/**************************************************/ +void IMU::Normalize(void) +{ + float error=0; + float temporary[3][3]; + float renorm=0; + + error= -Vector_Dot_Product(&DCM_Matrix[0][0],&DCM_Matrix[1][0])*.5; //eq.19 + + Vector_Scale(&temporary[0][0], &DCM_Matrix[1][0], error); //eq.19 + Vector_Scale(&temporary[1][0], &DCM_Matrix[0][0], error); //eq.19 + + Vector_Add(&temporary[0][0], &temporary[0][0], &DCM_Matrix[0][0]);//eq.19 + Vector_Add(&temporary[1][0], &temporary[1][0], &DCM_Matrix[1][0]);//eq.19 + + Vector_Cross_Product(&temporary[2][0],&temporary[0][0],&temporary[1][0]); // c= a x b //eq.20 + + renorm= .5 *(3 - Vector_Dot_Product(&temporary[0][0],&temporary[0][0])); //eq.21 + Vector_Scale(&DCM_Matrix[0][0], &temporary[0][0], renorm); + + renorm= .5 *(3 - Vector_Dot_Product(&temporary[1][0],&temporary[1][0])); //eq.21 + Vector_Scale(&DCM_Matrix[1][0], &temporary[1][0], renorm); + + renorm= .5 *(3 - Vector_Dot_Product(&temporary[2][0],&temporary[2][0])); //eq.21 + Vector_Scale(&DCM_Matrix[2][0], &temporary[2][0], renorm); +} + +/**************************************************/ +void IMU::Drift_correction(void) +{ + float mag_heading_x; + float mag_heading_y; + float errorCourse; + //Compensation the Roll, Pitch and Yaw drift. + static float Scaled_Omega_P[3]; + static float Scaled_Omega_I[3]; + float Accel_magnitude; + float Accel_weight; + + + //*****Roll and Pitch*************** + + // Calculate the magnitude of the accelerometer vector + Accel_magnitude = sqrt(Accel_Vector[0]*Accel_Vector[0] + Accel_Vector[1]*Accel_Vector[1] + Accel_Vector[2]*Accel_Vector[2]); + Accel_magnitude = Accel_magnitude / GRAVITY; // Scale to gravity. + // Dynamic weighting of accelerometer info (reliability filter) + // Weight for accelerometer info (<0.5G = 0.0, 1G = 1.0 , >1.5G = 0.0) + Accel_weight = constrain(1 - 2*abs(1 - Accel_magnitude),0,1); // + + Vector_Cross_Product(&errorRollPitch[0],&Accel_Vector[0],&DCM_Matrix[2][0]); //adjust the ground of reference + Vector_Scale(&Omega_P[0],&errorRollPitch[0],Kp_ROLLPITCH*Accel_weight); + + Vector_Scale(&Scaled_Omega_I[0],&errorRollPitch[0],Ki_ROLLPITCH*Accel_weight); + Vector_Add(Omega_I,Omega_I,Scaled_Omega_I); + + //*****YAW*************** + // We make the gyro YAW drift correction based on compass magnetic heading + + mag_heading_x = cos(MAG_Heading); + mag_heading_y = sin(MAG_Heading); + errorCourse=(DCM_Matrix[0][0]*mag_heading_y) - (DCM_Matrix[1][0]*mag_heading_x); //Calculating YAW error + Vector_Scale(errorYaw,&DCM_Matrix[2][0],errorCourse); //Applys the yaw correction to the XYZ rotation of the aircraft, depeding the position. + + Vector_Scale(&Scaled_Omega_P[0],&errorYaw[0],Kp_YAW);//.01proportional of YAW. + Vector_Add(Omega_P,Omega_P,Scaled_Omega_P);//Adding Proportional. + + Vector_Scale(&Scaled_Omega_I[0],&errorYaw[0],Ki_YAW);//.00001Integrator + Vector_Add(Omega_I,Omega_I,Scaled_Omega_I);//adding integrator to the Omega_I +} + +void IMU::Matrix_update(void) +{ + Gyro_Vector[0]=GYRO_SCALED_RAD(gyro[0]); //gyro x roll + Gyro_Vector[1]=GYRO_SCALED_RAD(gyro[1]); //gyro y pitch + Gyro_Vector[2]=GYRO_SCALED_RAD(gyro[2]); //gyro z yaw + + Accel_Vector[0]=accel[0]; + Accel_Vector[1]=accel[1]; + Accel_Vector[2]=accel[2]; + + Vector_Add(&Omega[0], &Gyro_Vector[0], &Omega_I[0]); //adding proportional term + Vector_Add(&Omega_Vector[0], &Omega[0], &Omega_P[0]); //adding Integrator term + +#if DEBUG__NO_DRIFT_CORRECTION == true // Do not use drift correction + Update_Matrix[0][0]=0; + Update_Matrix[0][1]=-G_Dt*Gyro_Vector[2];//-z + Update_Matrix[0][2]=G_Dt*Gyro_Vector[1];//y + Update_Matrix[1][0]=G_Dt*Gyro_Vector[2];//z + Update_Matrix[1][1]=0; + Update_Matrix[1][2]=-G_Dt*Gyro_Vector[0]; + Update_Matrix[2][0]=-G_Dt*Gyro_Vector[1]; + Update_Matrix[2][1]=G_Dt*Gyro_Vector[0]; + Update_Matrix[2][2]=0; +#else // Use drift correction + Update_Matrix[0][0]=0; + Update_Matrix[0][1]=-G_Dt*Omega_Vector[2];//-z + Update_Matrix[0][2]=G_Dt*Omega_Vector[1];//y + Update_Matrix[1][0]=G_Dt*Omega_Vector[2];//z + Update_Matrix[1][1]=0; + Update_Matrix[1][2]=-G_Dt*Omega_Vector[0];//-x + Update_Matrix[2][0]=-G_Dt*Omega_Vector[1];//-y + Update_Matrix[2][1]=G_Dt*Omega_Vector[0];//x + Update_Matrix[2][2]=0; +#endif + + Matrix_Multiply(DCM_Matrix,Update_Matrix,Temporary_Matrix); //a*b=c + + for(int x=0; x<3; x++) //Matrix Addition (update) + { + for(int y=0; y<3; y++) + { + DCM_Matrix[x][y]+=Temporary_Matrix[x][y]; + } + } +} + +void IMU::Euler_angles(void) +{ + pitch = -asin(DCM_Matrix[2][0]); + roll = atan2(DCM_Matrix[2][1],DCM_Matrix[2][2]); + yaw = atan2(DCM_Matrix[1][0],DCM_Matrix[0][0]); +} +