ardupilot/ArduCopter/inertia.pde

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#if INERTIAL_NAV == ENABLED
// generates a new location and velocity in space based on inertia
// Calc 100 hz
void calc_inertia()
{
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// rotate accels based on DCM
// --------------------------
accels_rotated = ahrs.get_dcm_matrix() * imu.get_accel();
//accels_rotated += accels_offset; // skew accels to account for long term error using calibration
accels_rotated.z += 9.805; // remove influence of gravity
// rising = 2
// neutral = 0
// falling = -2
// ACC Y POS = going EAST
// ACC X POS = going North
// ACC Z POS = going DOWN (lets flip this)
// Integrate accels to get the velocity
// ------------------------------------
Vector3f temp = accels_rotated * (G_Dt * 100);
temp.z = -temp.z; // Temp is changed to world frame and we can use it normaly
accels_velocity += temp;
// Integrate velocity to get the Position
// ------------------------------------
accels_position += accels_velocity * G_Dt;
/*
* current_loc.lng += accels_velocity.x * G_Dt;
* current_loc.lat += accels_velocity.y * G_Dt;
* current_loc.alt += accels_velocity.z * G_Dt;
*/
}
void xy_error_correction()
{
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// Calculate speed error
// ---------------------
speed_error.x = x_actual_speed - accels_velocity.x;
speed_error.y = y_actual_speed - accels_velocity.y;
// Calculate position error
// ------------------------
//position_error.x = accels_position.x - current_loc.lng;
//position_error.y = accels_position.y - current_loc.lat;
// correct integrated velocity by speed_error
// this number must be small or we will bring back sensor latency
// -------------------------------------------
accels_velocity.x += speed_error.x * 0.03; // g.speed_correction_x;
accels_velocity.y += speed_error.y * 0.03;
// Error correct the accels to deal with calibration, drift and noise
// ------------------------------------------------------------------
//accels_position.x -= position_error.x * 0.08; // g.loiter_offset_correction; //.001;
//accels_position.y -= position_error.y * 0.08; // g.loiter_offset_correction; //.001;
accels_position.x = 0;
accels_position.y = 0;
}
void z_error_correction()
{
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// Calculate speed error
// ---------------------
speed_error.z = climb_rate - accels_velocity.z;
//position_error.z = accels_position.z - current_loc.alt;
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// correct integrated velocity by speed_error
// this number must be small or we will bring back sensor latency
// -------------------------------------------
accels_velocity.z += speed_error.z * 0.0350; //speed_correction_z;
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// ------------------------------------------------------------------
//accels_position.z -= position_error.z * 0.006; //g.alt_offset_correction; // OK
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accels_position.z = 0;
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// For developement only
// ---------------------
if(motors.armed())
Log_Write_Raw();
}
#endif