109 lines
3.6 KiB
C++
109 lines
3.6 KiB
C++
/**
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* @file IMUFactor.h
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* @brief Factor to express an IMU measurement between dynamic poses
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* @author Alex Cunningham
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*/
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#pragma once
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#include <gtsam/base/numericalDerivative.h>
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#include <gtsam/nonlinear/NonlinearFactor.h>
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#include <gtsam_unstable/dynamics/PoseRTV.h>
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#include <cassert>
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namespace gtsam {
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/**
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* Class that represents integrating IMU measurements over time for dynamic systems
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* Templated to allow for different key types, but variables all
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* assumed to be PoseRTV
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*/
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template<class POSE>
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class IMUFactor : public NoiseModelFactorN<POSE, POSE> {
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public:
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typedef NoiseModelFactorN<POSE, POSE> Base;
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typedef IMUFactor<POSE> This;
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protected:
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/** measurements from the IMU */
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Vector3 accel_, gyro_;
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double dt_; /// time between measurements
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public:
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// Provide access to the Matrix& version of evaluateError:
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using Base::evaluateError;
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/** Standard constructor */
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IMUFactor(const Vector3& accel, const Vector3& gyro,
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double dt, const Key& key1, const Key& key2, const SharedNoiseModel& model)
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: Base(model, key1, key2), accel_(accel), gyro_(gyro), dt_(dt) {}
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/** Full IMU vector specification */
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IMUFactor(const Vector6& imu_vector,
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double dt, const Key& key1, const Key& key2, const SharedNoiseModel& model)
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: Base(model, key1, key2), accel_(imu_vector.head(3)), gyro_(imu_vector.tail(3)), dt_(dt) {}
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~IMUFactor() override {}
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/// @return a deep copy of this factor
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gtsam::NonlinearFactor::shared_ptr clone() const override {
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return std::static_pointer_cast<gtsam::NonlinearFactor>(
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gtsam::NonlinearFactor::shared_ptr(new This(*this))); }
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/** Check if two factors are equal */
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bool equals(const NonlinearFactor& e, double tol = 1e-9) const override {
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const This* const f = dynamic_cast<const This*>(&e);
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return f && Base::equals(e) &&
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equal_with_abs_tol(accel_, f->accel_, tol) &&
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equal_with_abs_tol(gyro_, f->gyro_, tol) &&
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std::abs(dt_ - f->dt_) < tol;
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}
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void print(const std::string& s="", const gtsam::KeyFormatter& formatter = gtsam::DefaultKeyFormatter) const override {
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std::string a = "IMUFactor: " + s;
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Base::print(a, formatter);
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gtsam::print((Vector)accel_, "accel");
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gtsam::print((Vector)gyro_, "gyro");
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std::cout << "dt: " << dt_ << std::endl;
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}
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// access
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const Vector3& gyro() const { return gyro_; }
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const Vector3& accel() const { return accel_; }
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Vector6 z() const { return (Vector6() << accel_, gyro_).finished(); }
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/**
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* Error evaluation with optional derivatives - calculates
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* z - h(x1,x2)
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*/
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Vector evaluateError(const PoseRTV& x1, const PoseRTV& x2,
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OptionalMatrixType H1, OptionalMatrixType H2) const override {
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const Vector6 meas = z();
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if (H1) *H1 = numericalDerivative21<Vector6, PoseRTV, PoseRTV>(
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std::bind(This::predict_proxy, std::placeholders::_1, std::placeholders::_2, dt_, meas), x1, x2, 1e-5);
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if (H2) *H2 = numericalDerivative22<Vector6, PoseRTV, PoseRTV>(
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std::bind(This::predict_proxy, std::placeholders::_1, std::placeholders::_2, dt_, meas), x1, x2, 1e-5);
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return predict_proxy(x1, x2, dt_, meas);
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}
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/** dummy version that fails for non-dynamic poses */
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virtual Vector evaluateError(const Pose3& x1, const Pose3& x2,
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OptionalMatrixType H1, OptionalMatrixType H2) const {
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assert(false); // no corresponding factor here
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return Vector6::Zero();
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}
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private:
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/** copy of the measurement function formulated for numerical derivatives */
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static Vector6 predict_proxy(const PoseRTV& x1, const PoseRTV& x2,
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double dt, const Vector6& meas) {
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Vector6 hx = x1.imuPrediction(x2, dt);
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return meas - hx;
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}
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};
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} // \namespace gtsam
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