上文提到特别注意map_builder_bridge_.AddTrajectory(x,x)，查看其中的代码。
int MapBuilderBridge::AddTrajectory(const std::unordered_set<std::string>& expected_sensor_ids, const TrajectoryOptions& trajectory_options)
{
const int trajectory_id = map_builder_.AddTrajectoryBuilder(expected_sensor_ids, trajectory_options.trajectory_builder_options, ::std::bind(&MapBuilderBridge::OnLocalSlamResult, this,
::std::placeholders::_1, ::std::placeholders::_2,
::std::placeholders::_3, ::std::placeholders::_4,
::std::placeholders::_5));
LOG(INFO) << "Added trajectory with ID ‘" << trajectory_id << "‘.";
// Make sure there is no trajectory with ‘trajectory_id‘ yet.
CHECK_EQ(sensor_bridges_.count(trajectory_id), 0);
sensor_bridges_[trajectory_id] = cartographer::common::make_unique<SensorBridge>(
trajectory_options.num_subdivisions_per_laser_scan,
trajectory_options.tracking_frame,
node_options_.lookup_transform_timeout_sec, tf_buffer_,
map_builder_.GetTrajectoryBuilder(trajectory_id));
auto emplace_result = trajectory_options_.emplace(trajectory_id, trajectory_options);
CHECK(emplace_result.second == true);
return trajectory_id;
}
其中map_builder_.AddTrajectoryBuilder(...)是Cartographer项目中的代码了。
int MapBuilder::AddTrajectoryBuilder( const std::unordered_set<std::string>& expected_sensor_ids, const proto::TrajectoryBuilderOptions& trajectory_options, LocalSlamResultCallback local_slam_result_callback)
{
const int trajectory_id = trajectory_builders_.size();//生成trajectory_id
if (options_.use_trajectory_builder_3d())
{
CHECK(trajectory_options.has_trajectory_builder_3d_options());
trajectory_builders_.push_back(common::make_unique<CollatedTrajectoryBuilder>(
&sensor_collator_, trajectory_id, expected_sensor_ids,
common::make_unique<mapping::GlobalTrajectoryBuilder<
mapping_3d::LocalTrajectoryBuilder,
mapping_3d::proto::LocalTrajectoryBuilderOptions,
mapping_3d::PoseGraph>>(
trajectory_options.trajectory_builder_3d_options(),
trajectory_id, pose_graph_3d_.get(),
local_slam_result_callback)));//注意此处的push_back()方法
}
else
{
CHECK(trajectory_options.has_trajectory_builder_2d_options());
trajectory_builders_.push_back(common::make_unique<CollatedTrajectoryBuilder>(
&sensor_collator_, trajectory_id, expected_sensor_ids,
common::make_unique<mapping::GlobalTrajectoryBuilder<
mapping_2d::LocalTrajectoryBuilder,
mapping_2d::proto::LocalTrajectoryBuilderOptions,
mapping_2d::PoseGraph>>(
trajectory_options.trajectory_builder_2d_options(),
trajectory_id, pose_graph_2d_.get(),
local_slam_result_callback)));//注意此处的push_back()方法
}
if (trajectory_options.pure_localization())
{
constexpr int kSubmapsToKeep = 3;
pose_graph_->AddTrimmer(common::make_unique<PureLocalizationTrimmer>(trajectory_id, kSubmapsToKeep));
}
if (trajectory_options.has_initial_trajectory_pose())
{
const auto& initial_trajectory_pose = trajectory_options.initial_trajectory_pose();
pose_graph_->SetInitialTrajectoryPose(trajectory_id, initial_trajectory_pose.to_trajectory_id(),
transform::ToRigid3(initial_trajectory_pose.relative_pose()), common::FromUniversal(initial_trajectory_pose.timestamp()));
}
return trajectory_id;
}
注意，trajectory_builders_是根据trajectory_id添加的。以后调用的时候根据trajectory_id调用。
在ROS的主循环运行过程中，会不断处理传感器传入的数据。
以IMU数据为例，auto sensor_bridge_ptr = map_builder_bridge_.sensor_bridge(trajectory_id)，根据trajectory_id获取sensor_bridge_ptr。
void Node::HandleImuMessage(const int trajectory_id, const std::string& sensor_id, const sensor_msgs::Imu::ConstPtr& msg)
{
carto::common::MutexLocker lock(&mutex_);
if (!sensor_samplers_.at(trajectory_id).imu_sampler.Pulse())
{
return;
}
auto sensor_bridge_ptr = map_builder_bridge_.sensor_bridge(trajectory_id);
auto imu_data_ptr = sensor_bridge_ptr->ToImuData(msg);
if (imu_data_ptr != nullptr)
{
extrapolators_.at(trajectory_id).AddImuData(*imu_data_ptr);
}
sensor_bridge_ptr->HandleImuMessage(sensor_id, msg);
}
