通过slam同步建图程序看ros2节点参数传递生效顺序

缘起：

ros2 节点参数可以通过启动节点添加，也可以通过launch文件添加，还可以通过配置文件.yaml文件添加，或者是几种方式套用添加，给初学者带来很大的困惑具体是哪个生效了呢，我们拿slam_toolbox  包的online_sync_launch.py来剖析。

程序安装参考这里

(SLAM) 建图时导航 — Navigation 2 1.0.0 文档

我们这里采用源码编译安装，方便随时修改代码编译运行看效果

源码下载地址：https://github.com/SteveMacenski/slam_toolbox/tree/foxy-develhttps://github.com/SteveMacenski/slam_toolbox/tree/foxy-devel

 文件目录结构

 online_sync_launch.py  # 同步建图launch文件源码

import os

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument, LogInfo
from launch.conditions import UnlessCondition
from launch.substitutions import LaunchConfiguration, PythonExpression
from launch_ros.actions import Node
from ament_index_python.packages import get_package_share_directory
from nav2_common.launch import HasNodeParams


def generate_launch_description():
    use_sim_time = LaunchConfiguration('use_sim_time')
    params_file = LaunchConfiguration('params_file')
    default_params_file = os.path.join(get_package_share_directory("slam_toolbox"),
                                       'config', 'mapper_params_online_sync.yaml')

    declare_use_sim_time_argument = DeclareLaunchArgument(
        'use_sim_time',
        default_value='true',
        description='Use simulation/Gazebo clock')
    declare_params_file_cmd = DeclareLaunchArgument(
        'params_file',
        default_value=default_params_file,
        description='Full path to the ROS2 parameters file to use for the slam_toolbox node')

    # If the provided param file doesn't have slam_toolbox params, we must pass the
    # default_params_file instead. This could happen due to automatic propagation of
    # LaunchArguments. See:
    # https://github.com/ros-planning/navigation2/pull/2243#issuecomment-800479866
    has_node_params = HasNodeParams(source_file=params_file,
                                    node_name='slam_toolbox')

    actual_params_file = PythonExpression(['"', params_file, '" if ', has_node_params,
                                           ' else "', default_params_file, '"'])

    log_param_change = LogInfo(msg=['provided params_file ',  params_file,
                                    ' does not contain slam_toolbox parameters. Using default: ',
                                    default_params_file],
                               condition=UnlessCondition(has_node_params))

    start_sync_slam_toolbox_node = Node(
        parameters=[
          actual_params_file,
          {'use_sim_time': use_sim_time}
        ],
        package='slam_toolbox',
        executable='sync_slam_toolbox_node',
        name='slam_toolbox',
        output='screen')

    ld = LaunchDescription()

    ld.add_action(declare_use_sim_time_argument)
    ld.add_action(declare_params_file_cmd)
    ld.add_action(log_param_change)
    ld.add_action(start_sync_slam_toolbox_node)

    return ld

这里我们只看节点配置部分

 start_sync_slam_toolbox_node = Node(
        parameters=[
          actual_params_file,
          {'use_sim_time': use_sim_time}
        ],
        package='slam_toolbox',
        executable='sync_slam_toolbox_node',
        name='slam_toolbox',
        output='screen')

lanuch文件节点参数传递语句：

parameters=[

actual_params_file,

{'use_sim_time': use_sim_time}

],

这里我们只拿最常用的一个参数use_sim_time举例，看看是哪一步的设置生效了，其他参数逻辑是一样的。

启动这个节点

ros2 launch slam_toolbox online_sync_launch.py

[INFO] [launch]: All log files can be found below /home/m/.ros/log/2023-09-06-01-39-24-649989-ubun-44795
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [sync_slam_toolbox_node-1]: process started with pid [44797]
[sync_slam_toolbox_node-1] [INFO] [1693935564.841328831] [slam_toolbox]: Node using stack size 40000000
[sync_slam_toolbox_node-1] [INFO] [1693935564.869237603] [slam_toolbox]: Using solver plugin solver_plugins::CeresSolver
[sync_slam_toolbox_node-1] [INFO] [1693935564.869558263] [slam_toolbox]: CeresSolver: Using SCHUR_JACOBI preconditioner.

查看节点下载参数

m@ubun:~/ros2_ws$ ros2 node list
/slam_toolbox
/transform_listener_impl_563889db4b50
m@ubun:~/ros2_ws$ ros2 param dump slam_toolbox
Saving to:  ./slam_toolbox.yaml

下载的slam_toolbox节点参数详情

/slam_toolbox:
  ros__parameters:
    angle_variance_penalty: 1.0
    base_frame: base_footprint
    ceres_dogleg_type: TRADITIONAL_DOGLEG
    ceres_linear_solver: SPARSE_NORMAL_CHOLESKY
    ceres_loss_function: None
    ceres_preconditioner: SCHUR_JACOBI
    ceres_trust_strategy: LEVENBERG_MARQUARDT
    coarse_angle_resolution: 0.0349
    coarse_search_angle_offset: 0.349
    correlation_search_space_dimension: 0.5
    correlation_search_space_resolution: 0.01
    correlation_search_space_smear_deviation: 0.1
    debug_logging: false
    distance_variance_penalty: 0.5
    do_loop_closing: true
    enable_interactive_mode: true
    fine_search_angle_offset: 0.00349
    interactive_mode: false
    link_match_minimum_response_fine: 0.1
    link_scan_maximum_distance: 1.5
    loop_match_maximum_variance_coarse: 3.0
    loop_match_minimum_chain_size: 10
    loop_match_minimum_response_coarse: 0.35
    loop_match_minimum_response_fine: 0.45
    loop_search_maximum_distance: 3.0
    loop_search_space_dimension: 8.0
    loop_search_space_resolution: 0.05
    loop_search_space_smear_deviation: 0.03
    map_file_name: ''
    map_frame: map
    map_name: /map
    map_start_at_dock: null
    map_start_pose: null
    map_update_interval: 5.0
    minimum_angle_penalty: 0.9
    minimum_distance_penalty: 0.5
    minimum_time_interval: 0.5
    minimum_travel_distance: 0.5
    minimum_travel_heading: 0.5
    mode: mapping
    odom_frame: odom
    paused_new_measurements: false
    paused_processing: false
    resolution: 0.05
    scan_buffer_maximum_scan_distance: 10.0
    scan_buffer_size: 10
    scan_topic: /scan
    solver_plugin: solver_plugins::CeresSolver
    tf_buffer_duration: 30.0
    throttle_scans: 1
    transform_publish_period: 0.02
    transform_timeout: 0.2
    use_response_expansion: true
    use_scan_barycenter: true
    use_scan_matching: true
    use_sim_time: true

看最后一项：

use_sim_time: true

launch文件默认设置：

 declare_use_sim_time_argument = DeclareLaunchArgument(
        'use_sim_time',
        default_value='true',
        description='Use simulation/Gazebo clock')

如果我们启动这个launch文件加上参数

 m@ubun:~/ros2_ws$ ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=false

[INFO] [launch]: All log files can be found below /home/m/.ros/log/2023-09-06-01-48-36-038660-ubun-45408
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [sync_slam_toolbox_node-1]: process started with pid [45410]
[sync_slam_toolbox_node-1] [INFO] [1693936116.286793795] [slam_toolbox]: Node using stack size 40000000
[sync_slam_toolbox_node-1] [INFO] [1693936116.307085638] [slam_toolbox]: Using solver plugin solver_plugins::CeresSolver
[sync_slam_toolbox_node-1] [INFO] [1693936116.307325365] [slam_toolbox]: CeresSolver: Using SCHUR_JACOBI preconditioner.

再次下载参数配置文件

m@ubun:~/ros2_ws$ ros2 param dump slam_toolbox
Saving to:  ./slam_toolbox.yaml

/slam_toolbox:
  ros__parameters:
    angle_variance_penalty: 1.0
    base_frame: base_footprint
    ceres_dogleg_type: TRADITIONAL_DOGLEG
    ceres_linear_solver: SPARSE_NORMAL_CHOLESKY
    ceres_loss_function: None
    ceres_preconditioner: SCHUR_JACOBI
    ceres_trust_strategy: LEVENBERG_MARQUARDT
    coarse_angle_resolution: 0.0349
    coarse_search_angle_offset: 0.349
    correlation_search_space_dimension: 0.5
    correlation_search_space_resolution: 0.01
    correlation_search_space_smear_deviation: 0.1
    debug_logging: false
    distance_variance_penalty: 0.5
    do_loop_closing: true
    enable_interactive_mode: true
    fine_search_angle_offset: 0.00349
    interactive_mode: false
    link_match_minimum_response_fine: 0.1
    link_scan_maximum_distance: 1.5
    loop_match_maximum_variance_coarse: 3.0
    loop_match_minimum_chain_size: 10
    loop_match_minimum_response_coarse: 0.35
    loop_match_minimum_response_fine: 0.45
    loop_search_maximum_distance: 3.0
    loop_search_space_dimension: 8.0
    loop_search_space_resolution: 0.05
    loop_search_space_smear_deviation: 0.03
    map_file_name: ''
    map_frame: map
    map_name: /map
    map_start_at_dock: null
    map_start_pose: null
    map_update_interval: 5.0
    minimum_angle_penalty: 0.9
    minimum_distance_penalty: 0.5
    minimum_time_interval: 0.5
    minimum_travel_distance: 0.5
    minimum_travel_heading: 0.5
    mode: mapping
    odom_frame: odom
    paused_new_measurements: false
    paused_processing: false
    resolution: 0.05
    scan_buffer_maximum_scan_distance: 10.0
    scan_buffer_size: 10
    scan_topic: /scan
    solver_plugin: solver_plugins::CeresSolver
    tf_buffer_duration: 30.0
    throttle_scans: 1
    transform_publish_period: 0.02
    transform_timeout: 0.2
    use_response_expansion: true
    use_scan_barycenter: true
    use_scan_matching: true
    use_sim_time: false

use_sim_time: false   

重新修改参数启动节点

m@ubun:~/ros2_ws$ ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=true

再次下载配置文件

use_sim_time: true 

这里可以看出use_sim_time 的值生效顺序ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=true 或者use_sim_time:=false 是大于launch内的默认配置的。所以我们可以不管launch内的默认配置，直接在启动launch文件时在后面加上参数配置。

这里还有另外一种情况，launch内导入了配置文件的.yaml文件，我们还拿use_sim_time举例。

 start_sync_slam_toolbox_node = Node(
        parameters=[
          actual_params_file,
          {'use_sim_time': use_sim_time}
        ],

actual_params_file其实就是导入的下面的文件

default_params_file = os.path.join(get_package_share_directory("slam_toolbox"),

'config', 'mapper_params_online_sync.yaml')

mapper_params_online_sync.yaml

slam_toolbox:
  ros__parameters:

    # Plugin params
    solver_plugin: solver_plugins::CeresSolver
    ceres_linear_solver: SPARSE_NORMAL_CHOLESKY
    ceres_preconditioner: SCHUR_JACOBI
    ceres_trust_strategy: LEVENBERG_MARQUARDT
    ceres_dogleg_type: TRADITIONAL_DOGLEG
    ceres_loss_function: None

    # ROS Parameters
    odom_frame: odom
    map_frame: map
    base_frame: base_footprint
    scan_topic: /scan
    mode: mapping #localization

    # if you'd like to immediately start continuing a map at a given pose
    # or at the dock, but they are mutually exclusive, if pose is given
    # will use pose
    #map_file_name: test_steve
    #map_start_pose: [0.0, 0.0, 0.0]
    #map_start_at_dock: true

    debug_logging: false
    throttle_scans: 1
    transform_publish_period: 0.02 #if 0 never publishes odometry
    map_update_interval: 5.0
    resolution: 0.05
    max_laser_range: 20.0 #for rastering images
    minimum_time_interval: 0.5
    transform_timeout: 0.2
    tf_buffer_duration: 30.
    stack_size_to_use: 40000000 #// program needs a larger stack size to serialize large maps
    enable_interactive_mode: true

    # General Parameters
    use_scan_matching: true
    use_scan_barycenter: true
    minimum_travel_distance: 0.5
    minimum_travel_heading: 0.5
    scan_buffer_size: 10
    scan_buffer_maximum_scan_distance: 10.0
    link_match_minimum_response_fine: 0.1  
    link_scan_maximum_distance: 1.5
    loop_search_maximum_distance: 3.0
    do_loop_closing: true 
    loop_match_minimum_chain_size: 10           
    loop_match_maximum_variance_coarse: 3.0  
    loop_match_minimum_response_coarse: 0.35    
    loop_match_minimum_response_fine: 0.45

    # Correlation Parameters - Correlation Parameters
    correlation_search_space_dimension: 0.5
    correlation_search_space_resolution: 0.01
    correlation_search_space_smear_deviation: 0.1 

    # Correlation Parameters - Loop Closure Parameters
    loop_search_space_dimension: 8.0
    loop_search_space_resolution: 0.05
    loop_search_space_smear_deviation: 0.03

    # Scan Matcher Parameters
    distance_variance_penalty: 0.5      
    angle_variance_penalty: 1.0    

    fine_search_angle_offset: 0.00349     
    coarse_search_angle_offset: 0.349   
    coarse_angle_resolution: 0.0349        
    minimum_angle_penalty: 0.9
    minimum_distance_penalty: 0.5
    use_response_expansion: true
    #临时在下面添加的参数
    use_sim_time: true

我们在.yaml后面添加了use_sim_time: true

再次启动节点

ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=true 或者use_sim_time:=false

下载参数

ros2 param dump slam_toolbox
Saving to:  ./slam_toolbox.yaml 

/slam_toolbox:
  ros__parameters:
    angle_variance_penalty: 1.0
    base_frame: base_footprint
    ceres_dogleg_type: TRADITIONAL_DOGLEG
    ceres_linear_solver: SPARSE_NORMAL_CHOLESKY
    ceres_loss_function: None
    ceres_preconditioner: SCHUR_JACOBI
    ceres_trust_strategy: LEVENBERG_MARQUARDT
    coarse_angle_resolution: 0.0349
    coarse_search_angle_offset: 0.349
    correlation_search_space_dimension: 0.5
    correlation_search_space_resolution: 0.01
    correlation_search_space_smear_deviation: 0.1
    debug_logging: false
    distance_variance_penalty: 0.5
    do_loop_closing: true
    enable_interactive_mode: true
    fine_search_angle_offset: 0.00349
    interactive_mode: false
    link_match_minimum_response_fine: 0.1
    link_scan_maximum_distance: 1.5
    loop_match_maximum_variance_coarse: 3.0
    loop_match_minimum_chain_size: 10
    loop_match_minimum_response_coarse: 0.35
    loop_match_minimum_response_fine: 0.45
    loop_search_maximum_distance: 3.0
    loop_search_space_dimension: 8.0
    loop_search_space_resolution: 0.05
    loop_search_space_smear_deviation: 0.03
    map_file_name: ''
    map_frame: map
    map_name: /map
    map_start_at_dock: null
    map_start_pose: null
    map_update_interval: 5.0
    minimum_angle_penalty: 0.9
    minimum_distance_penalty: 0.5
    minimum_time_interval: 0.5
    minimum_travel_distance: 0.5
    minimum_travel_heading: 0.5
    mode: mapping
    odom_frame: odom
    paused_new_measurements: false
    paused_processing: false
    resolution: 0.05
    scan_buffer_maximum_scan_distance: 10.0
    scan_buffer_size: 10
    scan_topic: /scan
    solver_plugin: solver_plugins::CeresSolver
    tf_buffer_duration: 30.0
    throttle_scans: 1
    transform_publish_period: 0.02
    transform_timeout: 0.2
    use_response_expansion: true
    use_scan_barycenter: true
    use_scan_matching: true
    use_sim_time: true

不管怎么修改launch的启动参数，use_sim_time: true不变，说明launch文件内加载的.yaml 的权重是大于launch文件后面的启动参数的。

注意我们每次修改完程序都需要重新编译，要不然修改是不生效的。

我们这么反复测试只是为了验证参数在传递过程中哪里生效了，因为launch文件经过层层套娃，一个参数传递了好多次。

参数生效顺序 launch内的.yaml文件大于 ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=true  大于launch文件内的默认参数配置

declare_use_sim_time_argument = DeclareLaunchArgument(

'use_sim_time',

default_value='true',

description='Use simulation/Gazebo clock')

虽然yaml文件的权重最大，但是yaml文件可以在launch文件内进行替换，

 # Create our own temporary YAML files that include substitutions
 # 创建我们自己的临时YAML文件，其中包括替换
    param_substitutions = {
        'use_sim_time': use_sim_time,
        'yaml_filename': map_yaml_file}

    configured_params = RewrittenYaml(
        source_file=params_file,
        root_key=namespace,
        param_rewrites=param_substitutions,
        convert_types=True)

经过这样替换yaml文件的某些参数，使yaml文件的某些参数权重不再是最大。而变成

ros2 launch slam_toolbox online_sync_launch.py use_sim_time:=true  这样的后缀参数权重最大。