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Working Logmap !

release/4.3a0
dellaert 2015-07-21 16:09:56 -04:00
parent c7bc497014
commit 2dbad989d1
1 changed files with 29 additions and 7 deletions
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36
gtsam/navigation/NavState.cpp
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@ -101,27 +101,49 @@ NavState NavState::Expmap(const Vector9& xi, OptionalJacobian<9, 9> H) {
Eigen::Block<const Vector9, 3, 1> v = dP(xi);
Eigen::Block<const Vector9, 3, 1> a = dV(xi);
// NOTE(frank): mostly copy/paste from Pose3
Rot3 nRb = Rot3::Expmap(n_omega_nb);
double theta2 = n_omega_nb.dot(n_omega_nb);
if (theta2 > std::numeric_limits<double>::epsilon()) {
double omega_v = n_omega_nb.dot(v); // translation parallel to axis
// Expmap implements a "screw" motion in the direction of n_omega_nb
Vector3 n_t_parallel = n_omega_nb * n_omega_nb.dot(v); // component along rotation axis
Vector3 omega_cross_v = n_omega_nb.cross(v); // points towards axis
Point3 n_t = Point3(omega_cross_v - nRb * omega_cross_v + omega_v * n_omega_nb)
Point3 n_t = Point3(omega_cross_v - nRb * omega_cross_v + n_t_parallel)
/ theta2;
double omega_a = n_omega_nb.dot(a); // translation parallel to axis
Vector3 n_v_parallel = n_omega_nb * n_omega_nb.dot(a); // component along rotation axis
Vector3 omega_cross_a = n_omega_nb.cross(a); // points towards axis
Vector3 n_v = (omega_cross_a - nRb * omega_cross_a + omega_a * n_omega_nb)
/ theta2;
Vector3 n_v = (omega_cross_a - nRb * omega_cross_a + n_v_parallel) / theta2;
return NavState(nRb, n_t, n_v);
} else {
return NavState(nRb, Point3(v), a);
}
}
Vector9 NavState::Logmap(const NavState& p, OptionalJacobian<9, 9> H) {
Vector9 NavState::Logmap(const NavState& nTb, OptionalJacobian<9, 9> H) {
if (H)
throw std::runtime_error("NavState::Logmap derivative not implemented yet");
return Vector9::Zero();
TIE(nRb, n_p, n_v, nTb);
Vector3 n_t = n_p.vector();
// NOTE(frank): mostly copy/paste from Pose3
Vector9 xi;
Vector3 n_omega_nb = Rot3::Logmap(nRb);
double theta = n_omega_nb.norm();
if (theta * theta <= std::numeric_limits<double>::epsilon()) {
xi << n_omega_nb, n_t, n_v;
} else {
Matrix3 W = skewSymmetric(n_omega_nb / theta);
// Formula from Agrawal06iros, equation (14)
// simplified with Mathematica, and multiplying in n_t to avoid matrix math
double factor = (1 - theta / (2. * tan(0.5 * theta)));
Vector3 n_x = W * n_t;
Vector3 v = n_t - (0.5 * theta) * n_x + factor * (W * n_x);
Vector3 n_y = W * n_v;
Vector3 a = n_v - (0.5 * theta) * n_y + factor * (W * n_y);
xi << n_omega_nb, v, a;
}
return xi;
}
Matrix9 NavState::AdjointMap() const {