104 lines
3.3 KiB
C++
104 lines
3.3 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/base/LieVector.h>
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#include <gtsam/nonlinear/NonlinearFactor.h>
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#include <gtsam_unstable/dynamics/PoseRTV.h>
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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 NoiseModelFactor2<POSE, POSE> {
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public:
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typedef NoiseModelFactor2<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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Vector accel_, gyro_;
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double dt_; /// time between measurements
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public:
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/** Standard constructor */
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IMUFactor(const Vector& accel, const Vector& 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 Vector& 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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virtual ~IMUFactor() {}
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/** Check if two factors are equal */
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virtual bool equals(const NonlinearFactor& e, double tol = 1e-9) const {
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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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fabs(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 {
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std::string a = "IMUFactor: " + s;
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Base::print(a, formatter);
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gtsam::print(accel_, "accel");
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gtsam::print(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 Vector& gyro() const { return gyro_; }
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const Vector& accel() const { return accel_; }
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Vector z() const { return concatVectors(2, &accel_, &gyro_); }
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const Key& key1() const { return this->key1_; }
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const Key& key2() const { return this->key2_; }
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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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virtual Vector evaluateError(const PoseRTV& x1, const PoseRTV& x2,
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boost::optional<Matrix&> H1 = boost::none,
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boost::optional<Matrix&> H2 = boost::none) const {
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const Vector meas = z();
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if (H1) *H1 = numericalDerivative21<LieVector, PoseRTV, PoseRTV>(
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boost::bind(This::predict_proxy, _1, _2, dt_, meas), x1, x2, 1e-5);
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if (H2) *H2 = numericalDerivative22<LieVector, PoseRTV, PoseRTV>(
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boost::bind(This::predict_proxy, _1, _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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boost::optional<Matrix&> H1 = boost::none,
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boost::optional<Matrix&> H2 = boost::none) const {
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assert(false); // no corresponding factor here
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return zero(x1.dim());
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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 LieVector predict_proxy(const PoseRTV& x1, const PoseRTV& x2,
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double dt, const Vector& meas) {
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Vector hx = x1.imuPrediction(x2, dt);
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return LieVector(meas - hx);
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}
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};
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} // \namespace gtsam
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