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AP_Math: re-work quaternion functions to be more C++ like 

thanks to Adam for the suggestion!
This commit is contained in:
Andrew Tridgell 2012-03-10 16:44:22 +11:00
parent 9e30b5e4a5
commit 9f0cb78f08
4 changed files with 96 additions and 79 deletions
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66
libraries/AP_Math/AP_Math.cpp
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@ -69,69 +69,3 @@ void calculate_euler_angles(const Matrix3f &m, float *roll, float *pitch, float
}
}
// create a quaternion from Euler angles
void quaternion_from_euler(Quaternion &q, float roll, float pitch, float yaw)
{
float cr2 = cos(roll*0.5);
float cp2 = cos(pitch*0.5);
float cy2 = cos(yaw*0.5);
// the sign reversal here is due to the different conventions
// in the madgwick quaternion code and the rest of APM
float sr2 = -sin(roll*0.5);
float sp2 = -sin(pitch*0.5);
float sy2 = sin(yaw*0.5);
q.q1 = cr2*cp2*cy2 + sr2*sp2*sy2;
q.q2 = sr2*cp2*cy2 - cr2*sp2*sy2;
q.q3 = cr2*sp2*cy2 + sr2*cp2*sy2;
q.q4 = cr2*cp2*sy2 - sr2*sp2*cy2;
}
// create eulers from a quaternion
void euler_from_quaternion(const Quaternion &q, float *roll, float *pitch, float *yaw)
{
*roll = -(atan2(2.0*(q.q1*q.q2 + q.q3*q.q4),
1 - 2.0*(q.q2*q.q2 + q.q3*q.q3)));
// we let safe_asin() handle the singularities near 90/-90 in pitch
*pitch = -safe_asin(2.0*(q.q1*q.q3 - q.q4*q.q2));
*yaw = atan2(2.0*(q.q1*q.q4 + q.q2*q.q3),
1 - 2.0*(q.q3*q.q3 + q.q4*q.q4));
}
// convert a quaternion to a rotation matrix
void quaternion_to_rotation_matrix(const Quaternion &q, Matrix3f &m)
{
float q3q3 = q.q3 * q.q3;
float q3q4 = q.q3 * q.q4;
float q2q2 = q.q2 * q.q2;
float q2q3 = q.q2 * q.q3;
float q2q4 = q.q2 * q.q4;
float q1q2 = q.q1 * q.q2;
float q1q3 = q.q1 * q.q3;
float q1q4 = q.q1 * q.q4;
float q4q4 = q.q4 * q.q4;
m.a.x = 1-2*(q3q3 + q4q4);
m.a.y = 2*(q2q3 - q1q4);
m.a.z = - 2*(q2q4 + q1q3);
m.b.x = 2*(q2q3 + q1q4);
m.b.y = 1-2*(q2q2 + q4q4);
m.b.z = -2*(q3q4 - q1q2);
m.c.x = -2*(q2q4 - q1q3);
m.c.y = -2*(q3q4 + q1q2);
m.c.z = 1-2*(q2q2 + q3q3);
}
// convert a vector in earth frame to a vector in body frame,
// assuming body current rotation is given by a quaternion
void quaternion_earth_to_body(const Quaternion &q, Vector3f &v)
{
Matrix3f m;
// we reverse z before and afterwards because of the differing
// quaternion conventions from APM conventions.
v.z = -v.z;
quaternion_to_rotation_matrix(q, m);
v = m * v;
v.z = -v.z;
}

13
libraries/AP_Math/AP_Math.h
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@ -30,17 +30,4 @@ void rotation_matrix_from_euler(Matrix3f &m, float roll, float pitch, float yaw)
// calculate euler angles from a rotation matrix
void calculate_euler_angles(const Matrix3f &m, float *roll, float *pitch, float *yaw);
// create a quaternion from Euler angles
void quaternion_from_euler(Quaternion &q, float roll, float pitch, float yaw);
// create eulers from a quaternion
void euler_from_quaternion(const Quaternion &q, float *roll, float *pitch, float *yaw);
// convert a quaternion to a rotation matrix
void quaternion_to_rotation_matrix(const Quaternion &q, Matrix3f &m);
// convert a vector in earth frame to a vector in body frame,
// assuming body current rotation is given by a quaternion
void quaternion_earth_to_body(const Quaternion &q, Vector3f &v);
#endif

85
libraries/AP_Math/quaternion.cpp Normal file
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@ -0,0 +1,85 @@
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
* quaternion.cpp
* Copyright (C) Andrew Tridgell 2012
*
* This file is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This file is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "AP_Math.h"
// return the rotation matrix equivalent for this quaternion
void Quaternion::rotation_matrix(Matrix3f &m)
{
float q3q3 = q3 * q3;
float q3q4 = q3 * q4;
float q2q2 = q2 * q2;
float q2q3 = q2 * q3;
float q2q4 = q2 * q4;
float q1q2 = q1 * q2;
float q1q3 = q1 * q3;
float q1q4 = q1 * q4;
float q4q4 = q4 * q4;
m.a.x = 1-2*(q3q3 + q4q4);
m.a.y = 2*(q2q3 - q1q4);
m.a.z = - 2*(q2q4 + q1q3);
m.b.x = 2*(q2q3 + q1q4);
m.b.y = 1-2*(q2q2 + q4q4);
m.b.z = -2*(q3q4 - q1q2);
m.c.x = -2*(q2q4 - q1q3);
m.c.y = -2*(q3q4 + q1q2);
m.c.z = 1-2*(q2q2 + q3q3);
}
// convert a vector from earth to body frame
void Quaternion::earth_to_body(Vector3f &v)
{
Matrix3f m;
// we reverse z before and afterwards because of the differing
// quaternion conventions from APM conventions.
v.z = -v.z;
rotation_matrix(m);
v = m * v;
v.z = -v.z;
}
// create a quaternion from Euler angles
void Quaternion::from_euler(float roll, float pitch, float yaw)
{
float cr2 = cos(roll*0.5);
float cp2 = cos(pitch*0.5);
float cy2 = cos(yaw*0.5);
// the sign reversal here is due to the different conventions
// in the madgwick quaternion code and the rest of APM
float sr2 = -sin(roll*0.5);
float sp2 = -sin(pitch*0.5);
float sy2 = sin(yaw*0.5);
q1 = cr2*cp2*cy2 + sr2*sp2*sy2;
q2 = sr2*cp2*cy2 - cr2*sp2*sy2;
q3 = cr2*sp2*cy2 + sr2*cp2*sy2;
q4 = cr2*cp2*sy2 - sr2*sp2*cy2;
}
// create eulers from a quaternion
void Quaternion::to_euler(float *roll, float *pitch, float *yaw)
{
*roll = -(atan2(2.0*(q1*q2 + q3*q4),
1 - 2.0*(q2*q2 + q3*q3)));
// we let safe_asin() handle the singularities near 90/-90 in pitch
*pitch = -safe_asin(2.0*(q1*q3 - q4*q2));
*yaw = atan2(2.0*(q1*q4 + q2*q3),
1 - 2.0*(q3*q3 + q4*q4));
}

11
libraries/AP_Math/quaternion.h
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@ -33,5 +33,16 @@ public:
bool is_nan(void)
{ return isnan(q1) || isnan(q2) || isnan(q3) || isnan(q4); }
// return the rotation matrix equivalent for this quaternion
void rotation_matrix(Matrix3f &m);
// convert a vector from earth to body frame
void earth_to_body(Vector3f &v);
// create a quaternion from Euler angles
void from_euler(float roll, float pitch, float yaw);
// create eulers from a quaternion
void to_euler(float *roll, float *pitch, float *yaw);
};
#endif // QUATERNION_H