88 lines
2.3 KiB
C
88 lines
2.3 KiB
C
/*
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* Copyright 2022 Oleg Borodin <borodin@unix7.org>
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*/
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#include <stdio.h>
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#include <math.h>
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#include <geometry.h>
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static double inv_sqrt(double x) {
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return 1.0 / sqrt(x);
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}
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void madgwick(double dt, quaternion_t* q, imuvec_t* m) {
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double q0 = q->w;
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double q1 = q->x;
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double q2 = q->y;
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double q3 = q->z; // quaternion of sensor frame relative to auxiliary frame
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double gx = m->gx;
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double gy = m->gy;
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double gz = m->gz;
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double ax = m->ax;
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double ay = m->ay;
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double az = m->az;
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double beta = 0.1f; // 2 * proportional gain (Kp)
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double recipNorm;
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double s0, s1, s2, s3;
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double qDot1, qDot2, qDot3, qDot4;
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// Rate of change of quaternion from gyroscope
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qDot1 = 0.5 * (-q1*gx - q2*gy - q3*gz);
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qDot2 = 0.5 * ( q0*gx + q2*gz - q3*gy);
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qDot3 = 0.5 * ( q0*gy - q1*gz + q3*gx);
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qDot4 = 0.5 * ( q0*gz + q1*gy - q2*gx);
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// Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
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if (!((ax == 0.0) && (ay == 0.0) && (az == 0.0))) {
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// Normalise accelerometer measurement
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recipNorm = inv_sqrt(ax*ax + ay*ay + az*az);
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ax *= recipNorm;
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ay *= recipNorm;
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az *= recipNorm;
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// Gradient decent algorithm corrective step
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s0 = 4.0*q0*q2*q2 + 2.0*q2*ax + 4.0*q0*q1*q1 - 2.0*q1*ay;
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s1 = 4.0*q1*q3*q3 - 2.0*q3*ax + 4.0*q0*q0*q1 - 2.0*q0*ay - 4.0*q1 + 8.0*q1*q1*q1 + 8.0*q1*q2*q2 + 4.0*q1*az;
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s2 = 4.0*q0*q0*q2 + 2.0*q0*ax + 4.0*q2*q3*q3 - 2.0*q3*ay - 4.0*q2 + 8.0*q2*q1*q1 + 8.0*q2*q2*q2 + 4.0*q2*az;
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s3 = 4.0*q1*q1*q3 - 2.0*q1*ax + 4.0*q2*q2*q3 - 2.0*q2*ay;
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// Normalise step magnitude
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recipNorm = inv_sqrt(s0*s0 + s1*s1 + s2*s2 + s3*s3);
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s0 *= recipNorm;
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s1 *= recipNorm;
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s2 *= recipNorm;
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s3 *= recipNorm;
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// Apply feedback step
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qDot1 -= beta * s0;
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qDot2 -= beta * s1;
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qDot3 -= beta * s2;
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qDot4 -= beta * s3;
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}
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// Integrate rate of change of quaternion to yield quaternion
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q0 += qDot1 * dt;
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q1 += qDot2 * dt;
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q2 += qDot3 * dt;
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q3 += qDot4 * dt;
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// Normalise quaternion
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recipNorm = inv_sqrt(q0*q0 + q1*q1 + q2*q2 + q3*q3);
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q0 *= recipNorm;
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q1 *= recipNorm;
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q2 *= recipNorm;
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q3 *= recipNorm;
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q->w = q0;
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q->x = q1;
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q->y = q2;
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q->z = q3;
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}
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