px4_autopilot/EKF/utils.cpp

#include "utils.hpp"

matrix::Dcmf taitBryan312ToRotMat(const matrix::Vector3f &rot312)
{
		// Calculate the frame2 to frame 1 rotation matrix from a 312 Tait-Bryan rotation sequence
		const float c2 = cosf(rot312(2)); // third rotation is pitch
		const float s2 = sinf(rot312(2));
		const float s1 = sinf(rot312(1)); // second rotation is roll
		const float c1 = cosf(rot312(1));
		const float s0 = sinf(rot312(0)); // first rotation is yaw
		const float c0 = cosf(rot312(0));

		matrix::Dcmf R;
		R(0, 0) = c0 * c2 - s0 * s1 * s2;
		R(1, 1) = c0 * c1;
		R(2, 2) = c2 * c1;
		R(0, 1) = -c1 * s0;
		R(0, 2) = s2 * c0 + c2 * s1 * s0;
		R(1, 0) = c2 * s0 + s2 * s1 * c0;
		R(1, 2) = s0 * s2 - s1 * c0 * c2;
		R(2, 0) = -s2 * c1;
		R(2, 1) = s1;

		return R;
}

float kahanSummation(float sum_previous, float input, float &accumulator)
{
	const float y = input - accumulator;
	const float t = sum_previous + y;
	accumulator = (t - sum_previous) - y;
	return t;
}

matrix::Dcmf quatToInverseRotMat(const  matrix::Quatf &quat)
{
	const float q00 = quat(0) * quat(0);
	const float q11 = quat(1) * quat(1);
	const float q22 = quat(2) * quat(2);
	const float q33 = quat(3) * quat(3);
	const float q01 = quat(0) * quat(1);
	const float q02 = quat(0) * quat(2);
	const float q03 = quat(0) * quat(3);
	const float q12 = quat(1) * quat(2);
	const float q13 = quat(1) * quat(3);
	const float q23 = quat(2) * quat(3);

	matrix::Dcmf dcm;
	dcm(0, 0) = q00 + q11 - q22 - q33;
	dcm(1, 1) = q00 - q11 + q22 - q33;
	dcm(2, 2) = q00 - q11 - q22 + q33;
	dcm(1, 0) = 2.0f * (q12 - q03);
	dcm(2, 0) = 2.0f * (q13 + q02);
	dcm(0, 1) = 2.0f * (q12 + q03);
	dcm(2, 1) = 2.0f * (q23 - q01);
	dcm(0, 2) = 2.0f * (q13 - q02);
	dcm(1, 2) = 2.0f * (q23 + q01);

	return dcm;
}