2 * Copyright (c) 2014, Olivier MATZ <zer0@droids-corp.org>
\r
3 * Copyright (c) 2011-2012, SOH Madgwick
\r
5 * This program is free software: you can redistribute it and/or modify
\r
6 * it under the terms of the GNU General Public License as published by
\r
7 * the Free Software Foundation, either version 3 of the License, or
\r
8 * (at your option) any later version.
\r
10 * This program is distributed in the hope that it will be useful,
\r
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
\r
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
\r
13 * GNU General Public License for more details.
\r
15 * You should have received a copy of the GNU General Public License
\r
16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
\r
20 //============================================================================
\r
22 //============================================================================
\r
24 // Implementation of Madgwick's IMU and AHRS algorithms.
\r
25 // See: http://www.x-io.co.uk/node/8#open_source_ahrs_and_imu_algorithms
\r
27 // Date Author Notes
\r
28 // 29/09/2011 SOH Madgwick Initial release
\r
29 // 02/10/2011 SOH Madgwick Optimised for reduced CPU load
\r
30 // 19/02/2012 SOH Madgwick Magnetometer measurement is normalised
\r
32 //============================================================================
\r
34 #include "MadgwickAHRS.h"
\r
37 //#define sampleFreq 512.0f // sample frequency in Hz
\r
38 //#define sampleFreq 46.0f // sample frequency in Hz
\r
39 #define sampleFreq 85.0f // sample frequency in Hz
\r
40 #define betaDef 0.1f // 2 * proportional gain
\r
42 static float invSqrt(float x)
\r
44 return 1.0f / sqrtf(x);
\r
47 /* AHRS algorithm update */
\r
48 void MadgwickAHRSupdate(const struct imu_info *imu, struct quaternion *quat)
\r
51 float s0, s1, s2, s3;
\r
52 float qDot1, qDot2, qDot3, qDot4;
\r
54 float _2q0mx, _2q0my, _2q0mz, _2q1mx, _2bx, _2bz, _4bx, _4bz;
\r
55 float _2q0, _2q1, _2q2, _2q3, _2q0q2, _2q2q3, q0q0, q0q1, q0q2, q0q3;
\r
56 float q1q1, q1q2, q1q3, q2q2, q2q3, q3q3;
\r
57 float mx, my, mz, ax, ay, az, gx, gy, gz;
\r
58 float q0, q1, q2, q3;
\r
60 /* Use IMU algorithm if magnetometer measurement invalid (avoids NaN in
\r
61 * magnetometer normalisation) */
\r
62 if ((imu->mx == 0.0f) && (imu->my == 0.0f) && (imu->mz == 0.0f)) {
\r
63 MadgwickAHRSupdateIMU(imu, quat);
\r
67 /* use local variables, it's more readable */
\r
68 q0 = quat->q0; q1 = quat->q1; q2 = quat->q2; q3 = quat->q3;
\r
69 gx = imu->gx; gy = imu->gy; gz = imu->gz;
\r
70 ax = imu->ax; ay = imu->ay; az = imu->az;
\r
71 mx = imu->mx; my = imu->my; mz = imu->mz;
\r
73 /* Rate of change of quaternion from gyroscope */
\r
74 qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz);
\r
75 qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy);
\r
76 qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx);
\r
77 qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx);
\r
79 /* Compute feedback only if accelerometer measurement valid (avoids NaN
\r
80 * in accelerometer normalisation) */
\r
81 if (!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
\r
83 /* Normalise accelerometer measurement */
\r
84 recipNorm = invSqrt(ax * ax + ay * ay +
\r
90 /* Normalise magnetometer measurement */
\r
91 recipNorm = invSqrt(mx * mx + my * my +
\r
97 /* Auxiliary variables to avoid repeated arithmetic */
\r
98 _2q0mx = 2.0f * q0 * mx;
\r
99 _2q0my = 2.0f * q0 * my;
\r
100 _2q0mz = 2.0f * q0 * mz;
\r
101 _2q1mx = 2.0f * q1 * mx;
\r
106 _2q0q2 = 2.0f * q0 * q2;
\r
107 _2q2q3 = 2.0f * q2 * q3;
\r
119 /* Reference direction of Earth's magnetic field */
\r
120 hx = mx * q0q0 - _2q0my * q3 + _2q0mz * q2 + mx * q1q1 + _2q1 * my * q2 + _2q1 * mz * q3 - mx * q2q2 - mx * q3q3;
\r
121 hy = _2q0mx * q3 + my * q0q0 - _2q0mz * q1 + _2q1mx * q2 - my * q1q1 + my * q2q2 + _2q2 * mz * q3 - my * q3q3;
\r
122 _2bx = sqrt(hx * hx + hy * hy);
\r
123 _2bz = -_2q0mx * q2 + _2q0my * q1 + mz * q0q0 + _2q1mx * q3 - mz * q1q1 + _2q2 * my * q3 - mz * q2q2 + mz * q3q3;
\r
124 _4bx = 2.0f * _2bx;
\r
125 _4bz = 2.0f * _2bz;
\r
127 /* Gradient decent algorithm corrective step */
\r
128 s0 = -_2q2 * (2.0f * q1q3 - _2q0q2 - ax) + _2q1 * (2.0f * q0q1 + _2q2q3 - ay) - _2bz * q2 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q3 + _2bz * q1) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q2 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
\r
129 s1 = _2q3 * (2.0f * q1q3 - _2q0q2 - ax) + _2q0 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q1 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + _2bz * q3 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q2 + _2bz * q0) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q3 - _4bz * q1) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
\r
130 s2 = -_2q0 * (2.0f * q1q3 - _2q0q2 - ax) + _2q3 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q2 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + (-_4bx * q2 - _2bz * q0) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q1 + _2bz * q3) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q0 - _4bz * q2) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
\r
131 s3 = _2q1 * (2.0f * q1q3 - _2q0q2 - ax) + _2q2 * (2.0f * q0q1 + _2q2q3 - ay) + (-_4bx * q3 + _2bz * q1) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q0 + _2bz * q2) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q1 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
\r
133 /* normalize step magnitude */
\r
134 recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3);
\r
140 /* Apply feedback step */
\r
141 qDot1 -= betaDef * s0;
\r
142 qDot2 -= betaDef * s1;
\r
143 qDot3 -= betaDef * s2;
\r
144 qDot4 -= betaDef * s3;
\r
147 /* Integrate rate of change of quaternion to yield quaternion */
\r
148 q0 += qDot1 * (1.0f / sampleFreq);
\r
149 q1 += qDot2 * (1.0f / sampleFreq);
\r
150 q2 += qDot3 * (1.0f / sampleFreq);
\r
151 q3 += qDot4 * (1.0f / sampleFreq);
\r
153 /* Normalise quaternion */
\r
154 recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
\r
160 /* update quaternion in structure */
\r
167 /* IMU algorithm update (does not take magneto in account) */
\r
168 void MadgwickAHRSupdateIMU(const struct imu_info *imu, struct quaternion *quat)
\r
171 float s0, s1, s2, s3;
\r
172 float qDot1, qDot2, qDot3, qDot4;
\r
173 float _2q0, _2q1, _2q2, _2q3, _4q0, _4q1, _4q2 ,_8q1, _8q2, q0q0, q1q1, q2q2, q3q3;
\r
174 float ax, ay, az, gx, gy, gz;
\r
175 float q0, q1, q2, q3;
\r
177 /* use local variables, it's more readable */
\r
178 q0 = quat->q0; q1 = quat->q1; q2 = quat->q2; q3 = quat->q3;
\r
179 gx = imu->gx; gy = imu->gy; gz = imu->gz;
\r
180 ax = imu->ax; ay = imu->ay; az = imu->az;
\r
182 /* Rate of change of quaternion from gyroscope */
\r
183 qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz);
\r
184 qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy);
\r
185 qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx);
\r
186 qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx);
\r
189 /* Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) */
\r
190 if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
\r
192 /* Normalise accelerometer measurement */
\r
193 recipNorm = invSqrt(ax * ax + ay * ay + az * az);
\r
198 /* Auxiliary variables to avoid repeated arithmetic */
\r
213 /* Gradient decent algorithm corrective step */
\r
214 s0 = _4q0 * q2q2 + _2q2 * ax + _4q0 * q1q1 - _2q1 * ay;
\r
215 s1 = _4q1 * q3q3 - _2q3 * ax + 4.0f * q0q0 * q1 - _2q0 * ay - _4q1 + _8q1 * q1q1 + _8q1 * q2q2 + _4q1 * az;
\r
216 s2 = 4.0f * q0q0 * q2 + _2q0 * ax + _4q2 * q3q3 - _2q3 * ay - _4q2 + _8q2 * q1q1 + _8q2 * q2q2 + _4q2 * az;
\r
217 s3 = 4.0f * q1q1 * q3 - _2q1 * ax + 4.0f * q2q2 * q3 - _2q2 * ay;
\r
218 recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); /* normalise step magnitude */
\r
225 /* Apply feedback step */
\r
226 qDot1 -= betaDef * s0;
\r
227 qDot2 -= betaDef * s1;
\r
228 qDot3 -= betaDef * s2;
\r
229 qDot4 -= betaDef * s3;
\r
232 /* Integrate rate of change of quaternion to yield quaternion */
\r
233 q0 += qDot1 * (1.0f / sampleFreq);
\r
234 q1 += qDot2 * (1.0f / sampleFreq);
\r
235 q2 += qDot3 * (1.0f / sampleFreq);
\r
236 q3 += qDot4 * (1.0f / sampleFreq);
\r
238 /* Normalise quaternion */
\r
239 recipNorm = invSqrt(q0 * q0 + q1 * q1 +
\r
240 q2 * q2 + q3 * q3);
\r
246 /* update quaternion in structure */
\r