78 lines
2.9 KiB
C++
Executable File
78 lines
2.9 KiB
C++
Executable File
/*
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* Copyright 2016 The Cartographer Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "cartographer/mapping/imu_tracker.h"
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#include <cmath>
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#include <limits>
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#include "cartographer/common/math.h"
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#include "cartographer/mapping/internal/eigen_quaterniond_from_two_vectors.h"
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#include "cartographer/transform/transform.h"
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#include "glog/logging.h"
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namespace cartographer {
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namespace mapping {
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ImuTracker::ImuTracker(const double imu_gravity_time_constant,
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const common::Time time)
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: imu_gravity_time_constant_(imu_gravity_time_constant),
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time_(time),
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last_linear_acceleration_time_(common::Time::min()),
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orientation_(Eigen::Quaterniond::Identity()),
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gravity_vector_(Eigen::Vector3d::UnitZ()),
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imu_angular_velocity_(Eigen::Vector3d::Zero()) {}
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void ImuTracker::Advance(const common::Time time) {
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CHECK_LE(time_, time);
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const double delta_t = common::ToSeconds(time - time_);
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const Eigen::Quaterniond rotation =
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transform::AngleAxisVectorToRotationQuaternion(
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Eigen::Vector3d(imu_angular_velocity_ * delta_t));
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orientation_ = (orientation_ * rotation).normalized();
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gravity_vector_ = rotation.conjugate() * gravity_vector_;
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time_ = time;
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}
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void ImuTracker::AddImuLinearAccelerationObservation(
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const Eigen::Vector3d& imu_linear_acceleration) {
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// Update the 'gravity_vector_' with an exponential moving average using the
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// 'imu_gravity_time_constant'.
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const double delta_t =
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last_linear_acceleration_time_ > common::Time::min()
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? common::ToSeconds(time_ - last_linear_acceleration_time_)
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: std::numeric_limits<double>::infinity();
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last_linear_acceleration_time_ = time_;
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const double alpha = 1. - std::exp(-delta_t / imu_gravity_time_constant_);
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gravity_vector_ =
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(1. - alpha) * gravity_vector_ + alpha * imu_linear_acceleration;
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// Change the 'orientation_' so that it agrees with the current
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// 'gravity_vector_'.
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const Eigen::Quaterniond rotation = FromTwoVectors(
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gravity_vector_, orientation_.conjugate() * Eigen::Vector3d::UnitZ());
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orientation_ = (orientation_ * rotation).normalized();
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CHECK_GT((orientation_ * gravity_vector_).z(), 0.);
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CHECK_GT((orientation_ * gravity_vector_).normalized().z(), 0.99);
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}
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void ImuTracker::AddImuAngularVelocityObservation(
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const Eigen::Vector3d& imu_angular_velocity) {
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imu_angular_velocity_ = imu_angular_velocity;
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}
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} // namespace mapping
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} // namespace cartographer
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