|
| 1 | +//============================================================================================= |
| 2 | +// MadgwickAHRS.c |
| 3 | +//============================================================================================= |
| 4 | +// |
| 5 | +// Implementation of Madgwick's IMU and AHRS algorithms. |
| 6 | +// See: http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/ |
| 7 | +// |
| 8 | +// From the x-io website "Open-source resources available on this website are |
| 9 | +// provided under the GNU General Public Licence unless an alternative licence |
| 10 | +// is provided in source." |
| 11 | +// |
| 12 | +// Date Author Notes |
| 13 | +// 29/09/2011 SOH Madgwick Initial release |
| 14 | +// 02/10/2011 SOH Madgwick Optimised for reduced CPU load |
| 15 | +// 19/02/2012 SOH Madgwick Magnetometer measurement is normalised |
| 16 | +// |
| 17 | +//============================================================================================= |
| 18 | + |
| 19 | +//------------------------------------------------------------------------------------------- |
| 20 | +// Header files |
| 21 | + |
| 22 | +#include "MadgwickAHRS.h" |
| 23 | +#include <math.h> |
| 24 | + |
| 25 | +//------------------------------------------------------------------------------------------- |
| 26 | +// Definitions |
| 27 | + |
| 28 | +#define sampleFreqDef 512.0f // sample frequency in Hz |
| 29 | +#define betaDef 0.1f // 2 * proportional gain |
| 30 | + |
| 31 | + |
| 32 | +//============================================================================================ |
| 33 | +// Functions |
| 34 | + |
| 35 | +//------------------------------------------------------------------------------------------- |
| 36 | +// AHRS algorithm update |
| 37 | + |
| 38 | +Madgwick::Madgwick() { |
| 39 | + beta = betaDef; |
| 40 | + q0 = 1.0f; |
| 41 | + q1 = 0.0f; |
| 42 | + q2 = 0.0f; |
| 43 | + q3 = 0.0f; |
| 44 | + invSampleFreq = 1.0f / sampleFreqDef; |
| 45 | + anglesComputed = 0; |
| 46 | +} |
| 47 | + |
| 48 | +void Madgwick::update(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz, float dt) { |
| 49 | + float recipNorm; |
| 50 | + float s0, s1, s2, s3; |
| 51 | + float qDot1, qDot2, qDot3, qDot4; |
| 52 | + float hx, hy; |
| 53 | + float _2q0mx, _2q0my, _2q0mz, _2q1mx, _2bx, _2bz, _4bx, _4bz, _2q0, _2q1, _2q2, _2q3, _2q0q2, _2q2q3, q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3; |
| 54 | + |
| 55 | + // Use IMU algorithm if magnetometer measurement invalid (avoids NaN in magnetometer normalisation) |
| 56 | + if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) { |
| 57 | + updateIMU(gx, gy, gz, ax, ay, az, dt); |
| 58 | + return; |
| 59 | + } |
| 60 | + |
| 61 | + // Convert gyroscope degrees/sec to radians/sec |
| 62 | + gx *= 0.0174533f; |
| 63 | + gy *= 0.0174533f; |
| 64 | + gz *= 0.0174533f; |
| 65 | + |
| 66 | + // Rate of change of quaternion from gyroscope |
| 67 | + qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz); |
| 68 | + qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy); |
| 69 | + qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx); |
| 70 | + qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx); |
| 71 | + |
| 72 | + // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) |
| 73 | + if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { |
| 74 | + |
| 75 | + // Normalise accelerometer measurement |
| 76 | + recipNorm = invSqrt(ax * ax + ay * ay + az * az); |
| 77 | + ax *= recipNorm; |
| 78 | + ay *= recipNorm; |
| 79 | + az *= recipNorm; |
| 80 | + |
| 81 | + // Normalise magnetometer measurement |
| 82 | + recipNorm = invSqrt(mx * mx + my * my + mz * mz); |
| 83 | + mx *= recipNorm; |
| 84 | + my *= recipNorm; |
| 85 | + mz *= recipNorm; |
| 86 | + |
| 87 | + // Auxiliary variables to avoid repeated arithmetic |
| 88 | + _2q0mx = 2.0f * q0 * mx; |
| 89 | + _2q0my = 2.0f * q0 * my; |
| 90 | + _2q0mz = 2.0f * q0 * mz; |
| 91 | + _2q1mx = 2.0f * q1 * mx; |
| 92 | + _2q0 = 2.0f * q0; |
| 93 | + _2q1 = 2.0f * q1; |
| 94 | + _2q2 = 2.0f * q2; |
| 95 | + _2q3 = 2.0f * q3; |
| 96 | + _2q0q2 = 2.0f * q0 * q2; |
| 97 | + _2q2q3 = 2.0f * q2 * q3; |
| 98 | + q0q0 = q0 * q0; |
| 99 | + q0q1 = q0 * q1; |
| 100 | + q0q2 = q0 * q2; |
| 101 | + q0q3 = q0 * q3; |
| 102 | + q1q1 = q1 * q1; |
| 103 | + q1q2 = q1 * q2; |
| 104 | + q1q3 = q1 * q3; |
| 105 | + q2q2 = q2 * q2; |
| 106 | + q2q3 = q2 * q3; |
| 107 | + q3q3 = q3 * q3; |
| 108 | + |
| 109 | + // Reference direction of Earth's magnetic field |
| 110 | + hx = mx * q0q0 - _2q0my * q3 + _2q0mz * q2 + mx * q1q1 + _2q1 * my * q2 + _2q1 * mz * q3 - mx * q2q2 - mx * q3q3; |
| 111 | + hy = _2q0mx * q3 + my * q0q0 - _2q0mz * q1 + _2q1mx * q2 - my * q1q1 + my * q2q2 + _2q2 * mz * q3 - my * q3q3; |
| 112 | + _2bx = sqrtf(hx * hx + hy * hy); |
| 113 | + _2bz = -_2q0mx * q2 + _2q0my * q1 + mz * q0q0 + _2q1mx * q3 - mz * q1q1 + _2q2 * my * q3 - mz * q2q2 + mz * q3q3; |
| 114 | + _4bx = 2.0f * _2bx; |
| 115 | + _4bz = 2.0f * _2bz; |
| 116 | + |
| 117 | + // Gradient decent algorithm corrective step |
| 118 | + 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); |
| 119 | + 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); |
| 120 | + 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); |
| 121 | + 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); |
| 122 | + recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude |
| 123 | + s0 *= recipNorm; |
| 124 | + s1 *= recipNorm; |
| 125 | + s2 *= recipNorm; |
| 126 | + s3 *= recipNorm; |
| 127 | + |
| 128 | + // Apply feedback step |
| 129 | + qDot1 -= beta * s0; |
| 130 | + qDot2 -= beta * s1; |
| 131 | + qDot3 -= beta * s2; |
| 132 | + qDot4 -= beta * s3; |
| 133 | + } |
| 134 | + |
| 135 | + // Integrate rate of change of quaternion to yield quaternion |
| 136 | + //q0 += qDot1 * invSampleFreq; |
| 137 | + //q1 += qDot2 * invSampleFreq; |
| 138 | + //q2 += qDot3 * invSampleFreq; |
| 139 | + //q3 += qDot4 * invSampleFreq; |
| 140 | + q0 += qDot1 * dt; |
| 141 | + q1 += qDot2 * dt; |
| 142 | + q2 += qDot3 * dt; |
| 143 | + q3 += qDot4 * dt; |
| 144 | + |
| 145 | + // Normalise quaternion |
| 146 | + recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); |
| 147 | + q0 *= recipNorm; |
| 148 | + q1 *= recipNorm; |
| 149 | + q2 *= recipNorm; |
| 150 | + q3 *= recipNorm; |
| 151 | + anglesComputed = 0; |
| 152 | +} |
| 153 | + |
| 154 | +//------------------------------------------------------------------------------------------- |
| 155 | +// IMU algorithm update |
| 156 | + |
| 157 | +void Madgwick::updateIMU(float gx, float gy, float gz, float ax, float ay, float az, float dt) { |
| 158 | + float recipNorm; |
| 159 | + float s0, s1, s2, s3; |
| 160 | + float qDot1, qDot2, qDot3, qDot4; |
| 161 | + float _2q0, _2q1, _2q2, _2q3, _4q0, _4q1, _4q2 ,_8q1, _8q2, q0q0, q1q1, q2q2, q3q3; |
| 162 | + |
| 163 | + // Convert gyroscope degrees/sec to radians/sec |
| 164 | + gx *= 0.0174533f; |
| 165 | + gy *= 0.0174533f; |
| 166 | + gz *= 0.0174533f; |
| 167 | + |
| 168 | + // Rate of change of quaternion from gyroscope |
| 169 | + qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz); |
| 170 | + qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy); |
| 171 | + qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx); |
| 172 | + qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx); |
| 173 | + |
| 174 | + // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) |
| 175 | + if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { |
| 176 | + |
| 177 | + // Normalise accelerometer measurement |
| 178 | + recipNorm = invSqrt(ax * ax + ay * ay + az * az); |
| 179 | + ax *= recipNorm; |
| 180 | + ay *= recipNorm; |
| 181 | + az *= recipNorm; |
| 182 | + |
| 183 | + // Auxiliary variables to avoid repeated arithmetic |
| 184 | + _2q0 = 2.0f * q0; |
| 185 | + _2q1 = 2.0f * q1; |
| 186 | + _2q2 = 2.0f * q2; |
| 187 | + _2q3 = 2.0f * q3; |
| 188 | + _4q0 = 4.0f * q0; |
| 189 | + _4q1 = 4.0f * q1; |
| 190 | + _4q2 = 4.0f * q2; |
| 191 | + _8q1 = 8.0f * q1; |
| 192 | + _8q2 = 8.0f * q2; |
| 193 | + q0q0 = q0 * q0; |
| 194 | + q1q1 = q1 * q1; |
| 195 | + q2q2 = q2 * q2; |
| 196 | + q3q3 = q3 * q3; |
| 197 | + |
| 198 | + // Gradient decent algorithm corrective step |
| 199 | + s0 = _4q0 * q2q2 + _2q2 * ax + _4q0 * q1q1 - _2q1 * ay; |
| 200 | + s1 = _4q1 * q3q3 - _2q3 * ax + 4.0f * q0q0 * q1 - _2q0 * ay - _4q1 + _8q1 * q1q1 + _8q1 * q2q2 + _4q1 * az; |
| 201 | + s2 = 4.0f * q0q0 * q2 + _2q0 * ax + _4q2 * q3q3 - _2q3 * ay - _4q2 + _8q2 * q1q1 + _8q2 * q2q2 + _4q2 * az; |
| 202 | + s3 = 4.0f * q1q1 * q3 - _2q1 * ax + 4.0f * q2q2 * q3 - _2q2 * ay; |
| 203 | + recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude |
| 204 | + s0 *= recipNorm; |
| 205 | + s1 *= recipNorm; |
| 206 | + s2 *= recipNorm; |
| 207 | + s3 *= recipNorm; |
| 208 | + |
| 209 | + // Apply feedback step |
| 210 | + qDot1 -= beta * s0; |
| 211 | + qDot2 -= beta * s1; |
| 212 | + qDot3 -= beta * s2; |
| 213 | + qDot4 -= beta * s3; |
| 214 | + } |
| 215 | + |
| 216 | + // Integrate rate of change of quaternion to yield quaternion |
| 217 | + //q0 += qDot1 * invSampleFreq; |
| 218 | + //q1 += qDot2 * invSampleFreq; |
| 219 | + //q2 += qDot3 * invSampleFreq; |
| 220 | + //q3 += qDot4 * invSampleFreq; |
| 221 | + q0 += qDot1 * dt; |
| 222 | + q1 += qDot2 * dt; |
| 223 | + q2 += qDot3 * dt; |
| 224 | + q3 += qDot4 * dt; |
| 225 | + |
| 226 | + // Normalise quaternion |
| 227 | + recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); |
| 228 | + q0 *= recipNorm; |
| 229 | + q1 *= recipNorm; |
| 230 | + q2 *= recipNorm; |
| 231 | + q3 *= recipNorm; |
| 232 | + anglesComputed = 0; |
| 233 | +} |
| 234 | + |
| 235 | +//------------------------------------------------------------------------------------------- |
| 236 | +// Fast inverse square-root |
| 237 | +// See: http://en.wikipedia.org/wiki/Fast_inverse_square_root |
| 238 | + |
| 239 | +float Madgwick::invSqrt(float x) { |
| 240 | + float halfx = 0.5f * x; |
| 241 | + float y = x; |
| 242 | + long i = *(long*)&y; |
| 243 | + i = 0x5f3759df - (i>>1); |
| 244 | + y = *(float*)&i; |
| 245 | + y = y * (1.5f - (halfx * y * y)); |
| 246 | + y = y * (1.5f - (halfx * y * y)); |
| 247 | + return y; |
| 248 | +} |
| 249 | + |
| 250 | +//------------------------------------------------------------------------------------------- |
| 251 | + |
| 252 | +void Madgwick::computeAngles() |
| 253 | +{ |
| 254 | + roll = atan2f(q0*q1 + q2*q3, 0.5f - q1*q1 - q2*q2); |
| 255 | + pitch = asinf(-2.0f * (q1*q3 - q0*q2)); |
| 256 | + yaw = atan2f(q1*q2 + q0*q3, 0.5f - q2*q2 - q3*q3); |
| 257 | + anglesComputed = 1; |
| 258 | +} |
| 259 | + |
| 260 | + |
0 commit comments