Paparazzi UAS  v5.15_devel-109-gee85905
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stabilization_attitude_quat_transformations.c
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1 /*
2  * Copyright (C) 2013 Felix Ruess <felix.ruess@gmail.com>
3  *
4  * This file is part of paparazzi.
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6  * paparazzi is free software; you can redistribute it and/or modify
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14  * GNU General Public License for more details.
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18  * the Free Software Foundation, 59 Temple Place - Suite 330,
19  * Boston, MA 02111-1307, USA.
20  */
21 
27 
28 void quat_from_rpy_cmd_i(struct Int32Quat *quat, struct Int32Eulers *rpy)
29 {
30  struct FloatEulers rpy_f;
31  EULERS_FLOAT_OF_BFP(rpy_f, *rpy);
32  struct FloatQuat quat_f;
33  quat_from_rpy_cmd_f(&quat_f, &rpy_f);
34  QUAT_BFP_OF_REAL(*quat, quat_f);
35 }
36 
37 void quat_from_rpy_cmd_f(struct FloatQuat *quat, struct FloatEulers *rpy)
38 {
39  // only a plug for now... doesn't apply roll/pitch wrt. current yaw angle
40 
41  /* orientation vector describing simultaneous rotation of roll/pitch/yaw */
42  const struct FloatVect3 ov = {rpy->phi, rpy->theta, rpy->psi};
43  /* quaternion from that orientation vector */
45 
46 }
47 
48 void quat_from_earth_cmd_i(struct Int32Quat *quat, struct Int32Vect2 *cmd, int32_t heading)
49 {
50  // use float conversion for now...
51  struct FloatVect2 cmd_f;
52  cmd_f.x = ANGLE_FLOAT_OF_BFP(cmd->x);
53  cmd_f.y = ANGLE_FLOAT_OF_BFP(cmd->y);
54  float heading_f = ANGLE_FLOAT_OF_BFP(heading);
55 
56  struct FloatQuat quat_f;
57  quat_from_earth_cmd_f(&quat_f, &cmd_f, heading_f);
58 
59  // convert back to fixed point
60  QUAT_BFP_OF_REAL(*quat, quat_f);
61 }
62 
63 void quat_from_earth_cmd_f(struct FloatQuat *quat, struct FloatVect2 *cmd, float heading)
64 {
65 
66  /* cmd_x is positive to north = negative pitch
67  * cmd_y is positive to east = positive roll
68  *
69  * orientation vector describing simultaneous rotation of roll/pitch
70  */
71  const struct FloatVect3 ov = {cmd->y, -cmd->x, 0.0};
72  /* quaternion from that orientation vector */
73  struct FloatQuat q_rp;
75 
76  /* as rotation matrix */
77  struct FloatRMat R_rp;
78  float_rmat_of_quat(&R_rp, &q_rp);
79  /* body x-axis (before heading command) is first row */
80  struct FloatVect3 b_x;
81  VECT3_ASSIGN(b_x, R_rp.m[0], R_rp.m[1], R_rp.m[2]);
82  /* body z-axis (thrust vect) is last row */
83  struct FloatVect3 thrust_vect;
84  VECT3_ASSIGN(thrust_vect, R_rp.m[6], R_rp.m[7], R_rp.m[8]);
85 
87 
88  /*
89  * Instead of using the psi setpoint angle to rotate around the body z-axis,
90  * calculate the real angle needed to align the projection of the body x-axis
91  * onto the horizontal plane with the psi setpoint.
92  *
93  * angle between two vectors a and b:
94  * angle = atan2(norm(cross(a,b)), dot(a,b)) * sign(dot(cross(a,b), n))
95  * where the normal n is the thrust vector (i.e. both a and b lie in that plane)
96  */
97 
98  // desired heading vect in earth x-y plane
99  const struct FloatVect3 psi_vect = {cosf(heading), sinf(heading), 0.0};
100 
101  /* projection of desired heading onto body x-y plane
102  * dot(b,n) = 0
103  */
104  float dot = VECT3_DOT_PRODUCT(psi_vect, thrust_vect);
105 
106  struct FloatVect3 b;
107  VECT3_ASSIGN(b, psi_vect.x, psi_vect.y, -dot/thrust_vect.z);
108 
109  dot = VECT3_DOT_PRODUCT(b_x, b);
110  struct FloatVect3 cross;
111  VECT3_CROSS_PRODUCT(cross, b_x, b);
112  // norm of the cross product
113  float nc = FLOAT_VECT3_NORM(cross);
114  // angle = atan2(norm(cross(a,b)), dot(a,b))
115  float yaw2 = atan2(nc, dot) / 2.0;
116 
117  // negative angle if needed
118  // sign(dot(cross(a,b), n)
119  float dot_cross_ab = VECT3_DOT_PRODUCT(cross, thrust_vect);
120  if (dot_cross_ab < 0) {
121  yaw2 = -yaw2;
122  }
123 
124  /* quaternion with yaw command */
125  struct FloatQuat q_yaw;
126  QUAT_ASSIGN(q_yaw, cosf(yaw2), 0.0, 0.0, sinf(yaw2));
127 
128  /* final setpoint: apply roll/pitch, then yaw around resulting body z-axis */
129  float_quat_comp(quat, &q_rp, &q_yaw);
130  float_quat_normalize(quat);
132 
133 }
#define VECT3_CROSS_PRODUCT(_vo, _v1, _v2)
Definition: pprz_algebra.h:244
#define VECT3_DOT_PRODUCT(_v1, _v2)
Definition: pprz_algebra.h:250
float phi
in radians
Quaternion transformation functions.
void float_quat_comp(struct FloatQuat *a2c, struct FloatQuat *a2b, struct FloatQuat *b2c)
Composition (multiplication) of two quaternions.
#define VECT3_ASSIGN(_a, _x, _y, _z)
Definition: pprz_algebra.h:125
float psi
in radians
#define FLOAT_VECT3_NORM(_v)
#define ANGLE_FLOAT_OF_BFP(_ai)
euler angles
Roation quaternion.
float theta
in radians
static float heading
Definition: ahrs_infrared.c:45
void quat_from_rpy_cmd_i(struct Int32Quat *quat, struct Int32Eulers *rpy)
void float_rmat_of_quat(struct FloatRMat *rm, struct FloatQuat *q)
euler angles
#define QUAT_ASSIGN(_q, _i, _x, _y, _z)
Definition: pprz_algebra.h:580
#define QUAT_BFP_OF_REAL(_qi, _qf)
Definition: pprz_algebra.h:752
static void float_quat_normalize(struct FloatQuat *q)
void quat_from_earth_cmd_i(struct Int32Quat *quat, struct Int32Vect2 *cmd, int32_t heading)
signed long int32_t
Definition: types.h:19
float m[3 *3]
void quat_from_earth_cmd_f(struct FloatQuat *quat, struct FloatVect2 *cmd, float heading)
void float_quat_of_orientation_vect(struct FloatQuat *q, const struct FloatVect3 *ov)
Quaternion from orientation vector.
static void float_quat_wrap_shortest(struct FloatQuat *q)
void quat_from_rpy_cmd_f(struct FloatQuat *quat, struct FloatEulers *rpy)
rotation matrix
Rotation quaternion.
#define EULERS_FLOAT_OF_BFP(_ef, _ei)
Definition: pprz_algebra.h:709