diff --git a/Makefile b/Makefile index 7eb78eb..2b11aac 100644 --- a/Makefile +++ b/Makefile @@ -35,7 +35,7 @@ VERSION = 0.01 endif -OBJS = visualize.o serialdata.o rawdata.o magcal.o matrix.o fusion.o quality.o +OBJS = visualize.o serialdata.o rawdata.o magcal.o matrix.o fusion.o quality.o mahony.o all: $(ALL) @@ -72,5 +72,6 @@ magcal.o: magcal.c imuread.h matrix.o: matrix.c imuread.h fusion.o: fusion.c imuread.h quality.o: quality.c imuread.h +mahony.o: mahony.c imuread.h diff --git a/fusion.c b/fusion.c index c85151c..3adaf4e 100644 --- a/fusion.c +++ b/fusion.c @@ -32,6 +32,8 @@ #include "imuread.h" +#ifdef USE_NXP_FUSION + // kalman filter noise variances #define FQVA_9DOF_GBY_KALMAN 2E-6F // accelerometer noise g^2 so 1.4mg RMS #define FQVM_9DOF_GBY_KALMAN 0.1F // magnetometer noise uT^2 @@ -1490,4 +1492,4 @@ static float fatan_15deg(float x) } - +#endif // USE_NXP_FUSION diff --git a/imuread.h b/imuread.h index adafef5..1791f5b 100644 --- a/imuread.h +++ b/imuread.h @@ -149,6 +149,8 @@ typedef struct } GyroSensor_t; +//#define USE_NXP_FUSION +#define USE_MAHONY_FUSION void fusion_init(void); void fusion_update(const AccelSensor_t *Accel, const MagSensor_t *Mag, const GyroSensor_t *Gyro, diff --git a/mahony.c b/mahony.c new file mode 100644 index 0000000..b0e86d6 --- /dev/null +++ b/mahony.c @@ -0,0 +1,299 @@ +//============================================================================================== +// MahonyAHRS.c +//============================================================================================== +// +// Madgwick's implementation of Mayhony's AHRS algorithm. +// See: http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/ +// +// From the x-io website "Open-source resources available on this website are +// provided under the GNU General Public Licence unless an alternative licence +// is provided in source." +// +// Date Author Notes +// 29/09/2011 SOH Madgwick Initial release +// 02/10/2011 SOH Madgwick Optimised for reduced CPU load +// +// Algorithm paper: +// http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4608934&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D4608934 +// +//============================================================================================== + +//---------------------------------------------------------------------------------------------- + +#include "imuread.h" + +#ifdef USE_MAHONY_FUSION + +//---------------------------------------------------------------------------------------------- +// Definitions + +#define twoKpDef (2.0f * 0.01f) // 2 * proportional gain +#define twoKiDef (2.0f * 0.0f) // 2 * integral gain + +//---------------------------------------------------------------------------------------------- +// Variable definitions + +static float twoKp = twoKpDef; // 2 * proportional gain (Kp) +static float twoKi = twoKiDef; // 2 * integral gain (Ki) +static float q0 = 1.0f, q1 = 0.0f, q2 = 0.0f, q3 = 0.0f; // quaternion of sensor frame relative to auxiliary frame +static float integralFBx = 0.0f, integralFBy = 0.0f, integralFBz = 0.0f; // integral error terms scaled by Ki + + +//============================================================================================== +// Functions + +static float invSqrt(float x); +static void mahony_init(); +static void mahony_update(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz); +void mahony_updateIMU(float gx, float gy, float gz, float ax, float ay, float az); + + + +void fusion_init(void) +{ + mahony_init(); +} + +void fusion_update(const AccelSensor_t *Accel, const MagSensor_t *Mag, const GyroSensor_t *Gyro, + const MagCalibration_t *MagCal) +{ + int i; + float ax, ay, az, gx, gy, gz, mx, my, mz; + float factor = M_PI / 180.0; + + ax = Accel->Gp[0]; + ay = Accel->Gp[1]; + az = Accel->Gp[2]; + mx = Mag->Bc[0]; + my = Mag->Bc[1]; + mz = Mag->Bc[2]; + for (i=0; i < OVERSAMPLE_RATIO; i++) { + gx = Gyro->YpFast[i][0]; + gy = Gyro->YpFast[i][1]; + gz = Gyro->YpFast[i][2]; + gx *= factor; + gy *= factor; + gz *= factor; + mahony_update(gx, gy, gz, ax, ay, az, mx, my, mz); + } +} + +void fusion_read(Quaternion_t *q) +{ + q->q0 = q0; + q->q1 = q1; + q->q2 = q2; + q->q3 = q3; +} + + +//---------------------------------------------------------------------------------------------- +// AHRS algorithm update + +static void mahony_init() +{ + twoKp = twoKpDef; // 2 * proportional gain (Kp) + twoKi = twoKiDef; // 2 * integral gain (Ki) + q0 = 1.0f; + q1 = 0.0f; + q2 = 0.0f; + q3 = 0.0f; + integralFBx = 0.0f; + integralFBy = 0.0f; + integralFBz = 0.0f; +} + +static void mahony_update(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz) +{ + float recipNorm; + float q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3; + float hx, hy, bx, bz; + float halfvx, halfvy, halfvz, halfwx, halfwy, halfwz; + float halfex, halfey, halfez; + float qa, qb, qc; + + // Use IMU algorithm if magnetometer measurement invalid + // (avoids NaN in magnetometer normalisation) + if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) { + mahony_updateIMU(gx, gy, gz, ax, ay, az); + return; + } + + // Compute feedback only if accelerometer measurement valid + // (avoids NaN in accelerometer normalisation) + if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { + + // Normalise accelerometer measurement + recipNorm = invSqrt(ax * ax + ay * ay + az * az); + ax *= recipNorm; + ay *= recipNorm; + az *= recipNorm; + + // Normalise magnetometer measurement + recipNorm = invSqrt(mx * mx + my * my + mz * mz); + mx *= recipNorm; + my *= recipNorm; + mz *= recipNorm; + + // Auxiliary variables to avoid repeated arithmetic + q0q0 = q0 * q0; + q0q1 = q0 * q1; + q0q2 = q0 * q2; + q0q3 = q0 * q3; + q1q1 = q1 * q1; + q1q2 = q1 * q2; + q1q3 = q1 * q3; + q2q2 = q2 * q2; + q2q3 = q2 * q3; + q3q3 = q3 * q3; + + // Reference direction of Earth's magnetic field + hx = 2.0f * (mx * (0.5f - q2q2 - q3q3) + my * (q1q2 - q0q3) + mz * (q1q3 + q0q2)); + hy = 2.0f * (mx * (q1q2 + q0q3) + my * (0.5f - q1q1 - q3q3) + mz * (q2q3 - q0q1)); + bx = sqrtf(hx * hx + hy * hy); + bz = 2.0f * (mx * (q1q3 - q0q2) + my * (q2q3 + q0q1) + mz * (0.5f - q1q1 - q2q2)); + + // Estimated direction of gravity and magnetic field + halfvx = q1q3 - q0q2; + halfvy = q0q1 + q2q3; + halfvz = q0q0 - 0.5f + q3q3; + halfwx = bx * (0.5f - q2q2 - q3q3) + bz * (q1q3 - q0q2); + halfwy = bx * (q1q2 - q0q3) + bz * (q0q1 + q2q3); + halfwz = bx * (q0q2 + q1q3) + bz * (0.5f - q1q1 - q2q2); + + // Error is sum of cross product between estimated direction and measured direction of field vectors + halfex = (ay * halfvz - az * halfvy) + (my * halfwz - mz * halfwy); + halfey = (az * halfvx - ax * halfvz) + (mz * halfwx - mx * halfwz); + halfez = (ax * halfvy - ay * halfvx) + (mx * halfwy - my * halfwx); + + // Compute and apply integral feedback if enabled + if(twoKi > 0.0f) { + integralFBx += twoKi * halfex * (1.0f / SENSORFS); // integral error scaled by Ki + integralFBy += twoKi * halfey * (1.0f / SENSORFS); + integralFBz += twoKi * halfez * (1.0f / SENSORFS); + gx += integralFBx; // apply integral feedback + gy += integralFBy; + gz += integralFBz; + } + else { + integralFBx = 0.0f; // prevent integral windup + integralFBy = 0.0f; + integralFBz = 0.0f; + } + + // Apply proportional feedback + gx += twoKp * halfex; + gy += twoKp * halfey; + gz += twoKp * halfez; + } + + // Integrate rate of change of quaternion + gx *= (0.5f * (1.0f / SENSORFS)); // pre-multiply common factors + gy *= (0.5f * (1.0f / SENSORFS)); + gz *= (0.5f * (1.0f / SENSORFS)); + qa = q0; + qb = q1; + qc = q2; + q0 += (-qb * gx - qc * gy - q3 * gz); + q1 += (qa * gx + qc * gz - q3 * gy); + q2 += (qa * gy - qb * gz + q3 * gx); + q3 += (qa * gz + qb * gy - qc * gx); + + // Normalise quaternion + recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); + q0 *= recipNorm; + q1 *= recipNorm; + q2 *= recipNorm; + q3 *= recipNorm; +} + +//--------------------------------------------------------------------------------------------- +// IMU algorithm update + +void mahony_updateIMU(float gx, float gy, float gz, float ax, float ay, float az) +{ + float recipNorm; + float halfvx, halfvy, halfvz; + float halfex, halfey, halfez; + float qa, qb, qc; + + // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation) + if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) { + + // Normalise accelerometer measurement + recipNorm = invSqrt(ax * ax + ay * ay + az * az); + ax *= recipNorm; + ay *= recipNorm; + az *= recipNorm; + + // Estimated direction of gravity and vector perpendicular to magnetic flux + halfvx = q1 * q3 - q0 * q2; + halfvy = q0 * q1 + q2 * q3; + halfvz = q0 * q0 - 0.5f + q3 * q3; + + // Error is sum of cross product between estimated and measured direction of gravity + halfex = (ay * halfvz - az * halfvy); + halfey = (az * halfvx - ax * halfvz); + halfez = (ax * halfvy - ay * halfvx); + + // Compute and apply integral feedback if enabled + if(twoKi > 0.0f) { + integralFBx += twoKi * halfex * (1.0f / SENSORFS); // integral error scaled by Ki + integralFBy += twoKi * halfey * (1.0f / SENSORFS); + integralFBz += twoKi * halfez * (1.0f / SENSORFS); + gx += integralFBx; // apply integral feedback + gy += integralFBy; + gz += integralFBz; + } + else { + integralFBx = 0.0f; // prevent integral windup + integralFBy = 0.0f; + integralFBz = 0.0f; + } + + // Apply proportional feedback + gx += twoKp * halfex; + gy += twoKp * halfey; + gz += twoKp * halfez; + } + + // Integrate rate of change of quaternion + gx *= (0.5f * (1.0f / SENSORFS)); // pre-multiply common factors + gy *= (0.5f * (1.0f / SENSORFS)); + gz *= (0.5f * (1.0f / SENSORFS)); + qa = q0; + qb = q1; + qc = q2; + q0 += (-qb * gx - qc * gy - q3 * gz); + q1 += (qa * gx + qc * gz - q3 * gy); + q2 += (qa * gy - qb * gz + q3 * gx); + q3 += (qa * gz + qb * gy - qc * gx); + + // Normalise quaternion + recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3); + q0 *= recipNorm; + q1 *= recipNorm; + q2 *= recipNorm; + q3 *= recipNorm; +} + +//--------------------------------------------------------------------------------------------- +// Fast inverse square-root +// See: http://en.wikipedia.org/wiki/Fast_inverse_square_root + +static float invSqrt(float x) { + float halfx = 0.5f * x; + float y = x; + long i = *(long*)&y; + i = 0x5f3759df - (i>>1); + y = *(float*)&i; + y = y * (1.5f - (halfx * y * y)); + y = y * (1.5f - (halfx * y * y)); + return y; +} + +//============================================================================================== +// END OF CODE +//============================================================================================== + +#endif // USE_MAHONY_FUSION