79 lines
2.4 KiB
C++
79 lines
2.4 KiB
C++
/* ----------------------------------------------------------------------------
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* GTSAM Copyright 2010, Georgia Tech Research Corporation,
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* Atlanta, Georgia 30332-0415
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* All Rights Reserved
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* Authors: Frank Dellaert, et al. (see THANKS for the full author list)
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* See LICENSE for the license information
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* -------------------------------------------------------------------------- */
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/**
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* @file LIEKF_Rot3Example.cpp
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* @brief Left‐Invariant EKF on SO(3) with state‐dependent pitch/roll control
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* and a single magnetometer update.
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* @date April 25, 2025
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* @authors Scott Baker, Matt Kielo, Frank Dellaert
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*/
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#include <gtsam/base/Matrix.h>
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#include <gtsam/base/OptionalJacobian.h>
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#include <gtsam/geometry/Rot3.h>
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#include <gtsam/navigation/LIEKF.h>
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#include <iostream>
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using namespace std;
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using namespace gtsam;
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// --- 1) Closed‐loop dynamics f(X): xi = –k·[φx,φy,0], H = ∂xi/∂φ·Dφ ---
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static constexpr double k = 0.5;
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Vector3 dynamicsSO3(const Rot3& X, OptionalJacobian<3, 3> H = {}) {
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// φ = Logmap(R), Dφ = ∂φ/∂δR
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Matrix3 D_phi;
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Vector3 phi = Rot3::Logmap(X, D_phi);
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// zero out yaw
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phi[2] = 0.0;
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D_phi.row(2).setZero();
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if (H) *H = -k * D_phi; // ∂(–kφ)/∂δR
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return -k * phi; // xi ∈ 𝔰𝔬(3)
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}
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// --- 2) Magnetometer model: z = R⁻¹ m, H = –[z]_× ---
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static const Vector3 m_world(0, 0, -1);
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Vector3 h_mag(const Rot3& X, OptionalJacobian<3, 3> H = {}) {
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Vector3 z = X.inverse().rotate(m_world);
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if (H) *H = -skewSymmetric(z);
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return z;
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}
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int main() {
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// Initial estimate (identity) and covariance
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const Rot3 R0 = Rot3::RzRyRx(0.1, -0.2, 0.3);
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const Matrix3 P0 = Matrix3::Identity() * 0.1;
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LIEKF<Rot3> ekf(R0, P0);
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// Timestep, process noise, measurement noise
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double dt = 0.1;
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Matrix3 Q = Matrix3::Identity() * 0.01;
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Matrix3 Rm = Matrix3::Identity() * 0.05;
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cout << "=== Init ===\nR:\n"
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<< ekf.state().matrix() << "\nP:\n"
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<< ekf.covariance() << "\n\n";
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// Predict using state‐dependent f
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ekf.predict(dynamicsSO3, dt, Q);
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cout << "--- After predict ---\nR:\n" << ekf.state().matrix() << "\n\n";
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// Magnetometer measurement = body‐frame reading of m_world
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Vector3 z = h_mag(R0);
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ekf.update(h_mag, z, Rm);
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cout << "--- After update ---\nR:\n" << ekf.state().matrix() << "\n";
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return 0;
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}
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