四元数+互补滤波

四元数

圆点博士小四轴之四元数算法。四元数算法在小四轴上一般直接采用Madgwick的算法就差不多。

这是一个居于GPL的协议，大家可以自由使用。

//================
// IMU.c
// S.O.H. Madgwick
// 25th September 2010
//=================

转载如下：

void IMUupdate(float gx, float gy, float gz, float ax, float ay, float az) {
float norm;
float vx, vy, vz;
float ex, ey, ez;

// normalise the measurements
norm = sqrt(ax*ax + ay*ay + az*az);
ax = ax / norm;
ay = ay / norm;
az = az / norm;

// estimated direction of gravity
vx = 2*(q1*q3 - q0*q2);
vy = 2*(q0*q1 + q2*q3);
vz = q0*q0 - q1*q1 - q2*q2 + q3*q3;

// error is sum of cross product between reference direction of field and direction measured by sensor
ex = (ay*vz - az*vy);
ey = (az*vx - ax*vz);
ez = (ax*vy - ay*vx);

// integral error scaled integral gain
exInt = exInt + ex*Ki;
eyInt = eyInt + ey*Ki;
ezInt = ezInt + ez*Ki;

// adjusted gyroscope measurements
gx = gx + Kp*ex + exInt;
gy = gy + Kp*ey + eyInt;
gz = gz + Kp*ez + ezInt;

// integrate quaternion rate and normalise
q0 = q0 + (-q1*gx - q2*gy - q3*gz)*halfT;
q1 = q1 + (q0*gx + q2*gz - q3*gy)*halfT;
q2 = q2 + (q0*gy - q1*gz + q3*gx)*halfT;
q3 = q3 + (q0*gz + q1*gy - q2*gx)*halfT;

// normalise quaternion
norm = sqrt(q0*q0 + q1*q1 + q2*q2 + q3*q3);
q0 = q0 / norm;
q1 = q1 / norm;
q2 = q2 / norm;
q3 = q3 / norm;
}