mirror of https://github.com/ArduPilot/ardupilot
136 lines
4.2 KiB
C
136 lines
4.2 KiB
C
#ifndef _MAVLINK_CONVERSIONS_H_
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#define _MAVLINK_CONVERSIONS_H_
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/* enable math defines on Windows */
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#ifdef _MSC_VER
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#ifndef _USE_MATH_DEFINES
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#define _USE_MATH_DEFINES
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#endif
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#endif
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#include <math.h>
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#ifndef M_PI_2
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#define M_PI_2 ((float)asin(1))
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#endif
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/**
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* @file mavlink_conversions.h
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*
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* These conversion functions follow the NASA rotation standards definition file
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* available online.
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*
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* Their intent is to lower the barrier for MAVLink adopters to use gimbal-lock free
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* (both rotation matrices, sometimes called DCM, and quaternions are gimbal-lock free)
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* rotation representations. Euler angles (roll, pitch, yaw) will be phased out of the
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* protocol as widely as possible.
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*
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* @author James Goppert
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*/
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MAVLINK_HELPER void mavlink_quaternion_to_dcm(const float quaternion[4], float dcm[3][3])
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{
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double a = quaternion[0];
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double b = quaternion[1];
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double c = quaternion[2];
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double d = quaternion[3];
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double aSq = a * a;
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double bSq = b * b;
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double cSq = c * c;
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double dSq = d * d;
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dcm[0][0] = aSq + bSq - cSq - dSq;
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dcm[0][1] = 2.0 * (b * c - a * d);
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dcm[0][2] = 2.0 * (a * c + b * d);
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dcm[1][0] = 2.0 * (b * c + a * d);
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dcm[1][1] = aSq - bSq + cSq - dSq;
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dcm[1][2] = 2.0 * (c * d - a * b);
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dcm[2][0] = 2.0 * (b * d - a * c);
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dcm[2][1] = 2.0 * (a * b + c * d);
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dcm[2][2] = aSq - bSq - cSq + dSq;
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}
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MAVLINK_HELPER void mavlink_dcm_to_euler(const float dcm[3][3], float* roll, float* pitch, float* yaw)
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{
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float phi, theta, psi;
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theta = asin(-dcm[2][0]);
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if (fabsf(theta - (float)M_PI_2) < 1.0e-3f) {
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phi = 0.0f;
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psi = (atan2f(dcm[1][2] - dcm[0][1],
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dcm[0][2] + dcm[1][1]) + phi);
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} else if (fabsf(theta + (float)M_PI_2) < 1.0e-3f) {
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phi = 0.0f;
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psi = atan2f(dcm[1][2] - dcm[0][1],
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dcm[0][2] + dcm[1][1] - phi);
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} else {
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phi = atan2f(dcm[2][1], dcm[2][2]);
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psi = atan2f(dcm[1][0], dcm[0][0]);
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}
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*roll = phi;
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*pitch = theta;
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*yaw = psi;
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}
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MAVLINK_HELPER void mavlink_quaternion_to_euler(const float quaternion[4], float* roll, float* pitch, float* yaw)
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{
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float dcm[3][3];
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mavlink_quaternion_to_dcm(quaternion, dcm);
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mavlink_dcm_to_euler(dcm, roll, pitch, yaw);
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}
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MAVLINK_HELPER void mavlink_euler_to_quaternion(float roll, float pitch, float yaw, float quaternion[4])
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{
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double cosPhi_2 = cos((double)roll / 2.0);
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double sinPhi_2 = sin((double)roll / 2.0);
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double cosTheta_2 = cos((double)pitch / 2.0);
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double sinTheta_2 = sin((double)pitch / 2.0);
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double cosPsi_2 = cos((double)yaw / 2.0);
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double sinPsi_2 = sin((double)yaw / 2.0);
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quaternion[0] = (cosPhi_2 * cosTheta_2 * cosPsi_2 +
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sinPhi_2 * sinTheta_2 * sinPsi_2);
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quaternion[1] = (sinPhi_2 * cosTheta_2 * cosPsi_2 -
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cosPhi_2 * sinTheta_2 * sinPsi_2);
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quaternion[2] = (cosPhi_2 * sinTheta_2 * cosPsi_2 +
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sinPhi_2 * cosTheta_2 * sinPsi_2);
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quaternion[3] = (cosPhi_2 * cosTheta_2 * sinPsi_2 -
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sinPhi_2 * sinTheta_2 * cosPsi_2);
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}
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MAVLINK_HELPER void mavlink_dcm_to_quaternion(const float dcm[3][3], float quaternion[4])
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{
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quaternion[0] = (0.5 * sqrt(1.0 +
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(double)(dcm[0][0] + dcm[1][1] + dcm[2][2])));
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quaternion[1] = (0.5 * sqrt(1.0 +
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(double)(dcm[0][0] - dcm[1][1] - dcm[2][2])));
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quaternion[2] = (0.5 * sqrt(1.0 +
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(double)(-dcm[0][0] + dcm[1][1] - dcm[2][2])));
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quaternion[3] = (0.5 * sqrt(1.0 +
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(double)(-dcm[0][0] - dcm[1][1] + dcm[2][2])));
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}
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MAVLINK_HELPER void mavlink_euler_to_dcm(float roll, float pitch, float yaw, float dcm[3][3])
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{
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double cosPhi = cos(roll);
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double sinPhi = sin(roll);
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double cosThe = cos(pitch);
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double sinThe = sin(pitch);
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double cosPsi = cos(yaw);
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double sinPsi = sin(yaw);
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dcm[0][0] = cosThe * cosPsi;
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dcm[0][1] = -cosPhi * sinPsi + sinPhi * sinThe * cosPsi;
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dcm[0][2] = sinPhi * sinPsi + cosPhi * sinThe * cosPsi;
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dcm[1][0] = cosThe * sinPsi;
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dcm[1][1] = cosPhi * cosPsi + sinPhi * sinThe * sinPsi;
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dcm[1][2] = -sinPhi * cosPsi + cosPhi * sinThe * sinPsi;
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dcm[2][0] = -sinThe;
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dcm[2][1] = sinPhi * cosThe;
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dcm[2][2] = cosPhi * cosThe;
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}
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#endif
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