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Diffstat (limited to 'mavlink/include/mavlink/v1.0/mavlink_conversions.h')
| -rw-r--r-- | mavlink/include/mavlink/v1.0/mavlink_conversions.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/mavlink/include/mavlink/v1.0/mavlink_conversions.h b/mavlink/include/mavlink/v1.0/mavlink_conversions.h new file mode 100644 index 000000000..1dc9088b7 --- /dev/null +++ b/mavlink/include/mavlink/v1.0/mavlink_conversions.h @@ -0,0 +1,125 @@ +#ifndef _MAVLINK_CONVERSIONS_H_ +#define _MAVLINK_CONVERSIONS_H_ + +#include <math.h> + +/** + * @file mavlink_conversions.h + * + * These conversion functions follow the NASA rotation standards definition file + * available online. + * + * Their intent is to lower the barrier for MAVLink adopters to use gimbal-lock free + * (both rotation matrices, sometimes called DCM, and quaternions are gimbal-lock free) + * rotation representations. Euler angles (roll, pitch, yaw) will be phased out of the + * protocol as widely as possible. + * + * @author James Goppert + */ + +MAVLINK_HELPER void mavlink_quaternion_to_dcm(const float quaternion[4], float dcm[3][3]) +{ + double a = quaternion[0]; + double b = quaternion[1]; + double c = quaternion[2]; + double d = quaternion[3]; + double aSq = a * a; + double bSq = b * b; + double cSq = c * c; + double dSq = d * d; + dcm[0][0] = aSq + bSq - cSq - dSq; + dcm[0][1] = 2.0 * (b * c - a * d); + dcm[0][2] = 2.0 * (a * c + b * d); + dcm[1][0] = 2.0 * (b * c + a * d); + dcm[1][1] = aSq - bSq + cSq - dSq; + dcm[1][2] = 2.0 * (c * d - a * b); + dcm[2][0] = 2.0 * (b * d - a * c); + dcm[2][1] = 2.0 * (a * b + c * d); + dcm[2][2] = aSq - bSq - cSq + dSq; +} + +MAVLINK_HELPER void mavlink_dcm_to_euler(const float dcm[3][3], float* roll, float* pitch, float* yaw) +{ + float phi, theta, psi; + theta = asin(-dcm[2][0]); + + if (fabs(theta - M_PI_2) < 1.0e-3f) { + phi = 0.0f; + psi = (atan2(dcm[1][2] - dcm[0][1], + dcm[0][2] + dcm[1][1]) + phi); + + } else if (fabs(theta + M_PI_2) < 1.0e-3f) { + phi = 0.0f; + psi = atan2f(dcm[1][2] - dcm[0][1], + dcm[0][2] + dcm[1][1] - phi); + + } else { + phi = atan2f(dcm[2][1], dcm[2][2]); + psi = atan2f(dcm[1][0], dcm[0][0]); + } + + *roll = phi; + *pitch = theta; + *yaw = psi; +} + +MAVLINK_HELPER void mavlink_quaternion_to_euler(const float quaternion[4], float* roll, float* pitch, float* yaw) +{ + float dcm[3][3]; + mavlink_quaternion_to_dcm(quaternion, dcm); + mavlink_dcm_to_euler(dcm, roll, pitch, yaw); +} + +MAVLINK_HELPER void mavlink_euler_to_quaternion(float roll, float pitch, float yaw, float quaternion[4]) +{ + double cosPhi_2 = cos((double)roll / 2.0); + double sinPhi_2 = sin((double)roll / 2.0); + double cosTheta_2 = cos((double)pitch / 2.0); + double sinTheta_2 = sin((double)pitch / 2.0); + double cosPsi_2 = cos((double)yaw / 2.0); + double sinPsi_2 = sin((double)yaw / 2.0); + quaternion[0] = (cosPhi_2 * cosTheta_2 * cosPsi_2 + + sinPhi_2 * sinTheta_2 * sinPsi_2); + quaternion[1] = (sinPhi_2 * cosTheta_2 * cosPsi_2 - + cosPhi_2 * sinTheta_2 * sinPsi_2); + quaternion[2] = (cosPhi_2 * sinTheta_2 * cosPsi_2 + + sinPhi_2 * cosTheta_2 * sinPsi_2); + quaternion[3] = (cosPhi_2 * cosTheta_2 * sinPsi_2 - + sinPhi_2 * sinTheta_2 * cosPsi_2); +} + +MAVLINK_HELPER void mavlink_dcm_to_quaternion(const float dcm[3][3], float quaternion[4]) +{ + quaternion[0] = (0.5 * sqrt(1.0 + + (double)(dcm[0][0] + dcm[1][1] + dcm[2][2]))); + quaternion[1] = (0.5 * sqrt(1.0 + + (double)(dcm[0][0] - dcm[1][1] - dcm[2][2]))); + quaternion[2] = (0.5 * sqrt(1.0 + + (double)(-dcm[0][0] + dcm[1][1] - dcm[2][2]))); + quaternion[3] = (0.5 * sqrt(1.0 + + (double)(-dcm[0][0] - dcm[1][1] + dcm[2][2]))); +} + +MAVLINK_HELPER void mavlink_euler_to_dcm(float roll, float pitch, float yaw, float dcm[3][3]) +{ + double cosPhi = cos(roll); + double sinPhi = sin(roll); + double cosThe = cos(pitch); + double sinThe = sin(pitch); + double cosPsi = cos(yaw); + double sinPsi = sin(yaw); + + dcm[0][0] = cosThe * cosPsi; + dcm[0][1] = -cosPhi * sinPsi + sinPhi * sinThe * cosPsi; + dcm[0][2] = sinPhi * sinPsi + cosPhi * sinThe * cosPsi; + + dcm[1][0] = cosThe * sinPsi; + dcm[1][1] = cosPhi * cosPsi + sinPhi * sinThe * sinPsi; + dcm[1][2] = -sinPhi * cosPsi + cosPhi * sinThe * sinPsi; + + dcm[2][0] = -sinThe; + dcm[2][1] = sinPhi * cosThe; + dcm[2][2] = cosPhi * cosThe; +} + +#endif
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