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]);
+}
+