类 Subtree

BT::Tree有一个成员是 std::vector< Subtree::Ptr > subtrees。类BT::Tree::Subtree的成员函数如下：

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Blackboard::Ptr   blackboard
 
std::string   instance_name
 
std::vector< TreeNode::Ptr >  nodes
 
std::string   tree_ID

instance_name的结果:

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subA::5
subB::16
subB::16/SubC::20

tree_ID是把instance_name的数字去掉了。

emitStateChanged

TreeNode::emitStateChanged() 是 TreeNode 类中的一个方法。它用于发出信号，告知树节点的状态已发生变化。此方法对于在行为树中启用响应式和异步行为至关重要。当节点状态发生变化（例如，从running变为成功或失败）时，系统会调用 emitStateChanged() 来通知树，并可能触发进一步的操作或更新。 类似Qt中的信号和槽的机制。

StdCoutLogger

StdCoutLogger 继承 StatusChangeLogger。这个类可以在终端里打印出行为树的日志，相当于Groot Pro的弱化版，可以用来看节点的状态变化，勉强算一个调试工具。

一般这样用，在createTree之后，tick之前。

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auto tree = factory.createTree("main", maintree_bb);
BT::StdCoutLogger cout_logger(tree);
// cout_logger.setEnabled(false);
while (true)
{
  try
  {
    tree.tickOnce();
  }
  catch (BT::RuntimeError &error)
  {
    printf("behavior tree tick Runtime Error: %s \n", 
    error.what());
    break;
  }
  tree.sleep(std::chrono::milliseconds(100));
}

• void setEnabled(bool enabled)     相当于打印日志的开关，结合参数会很有用

• void enableTransitionToIdle(bool enable)

registerSimpleAction

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void BT::BehaviorTreeFactory::registerSimpleAction (const std::string&  ID,
            const SimpleActionNode::TickFunctor &   tick_functor,
            PortsList   ports = {} 
)

typedef std::function<NodeStatus(TreeNode&)> BT::SimpleActionNode::TickFunctor

registerSimpleAction help you register nodes of type SimpleActionNode.

其实就是std::bind的用法，如果在类内的成员函数里注册，应该如下使用

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BT::NodeStatus TestBT()
{
	printf("TestBT\n");
	return BT::NodeStatus::SUCCESS;
}

void memberFunc()
{
	this->registerSimpleAction("TestBT", std::bind(&BtFactory::TestBT, this) );
}

外部调用时，将类对象本身的地址作为this指针传入

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Class a;
obj.registerSimpleAction(std::bind(&Class::TestBT, &a, placeholders::_1, placeholders::_2));

registerNodeType

行为树注册时，是注册节点的ModelName，而不是InstanceName

报错

1. 不识别新添加的Action类

factory.registerNodeType<ActionReportError>("ReportError");报了很多错，都是undefine error。解决方法：到CMake里先把对应的cpp文件去掉，编译后报错，再添加回来，成功

这个警告是因为我们以值捕获的方式(byvalue)捕获了一个多态类型(polymorphic type)的异常（例如std:exception)。在 C++中，多态类型（即具有虚函数的类）通常应该通过引用（最好是const引用）来捕获，以避免对象切片（slicing）问题，并确保正确的多态行为。

代码中写了类似：catch(std:exception e) 按值捕获而正确的做法应该是：catch(const std:exception&e) ，按 const引用捕获

编译器选项—Wcatch—value（被—Wall启用）会对此发出警告，并且有三个级别：—Wcatch—value=1：警告按值捕获多态类型（默认，相当于—Wcatch—value）—Wcatch—value=2：警告按值捕获所有类类型—Wcatch—value=3：警告所有没有通过引用捕获的类型因此，解决这个警告的方法就是将按值捕获改为按引用捕获。

• LogicError is related to problems which require code refactoring to be fixed.

• RuntimeError is related to problems that are relted to data or conditions that happen only at run-time

createTree之后的 catch 应该这样用：

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BT::Tree  tree;
try{
	factory.registerBehaviorTreeFromFile("/home/user/test.xml");
	tree = factory.createTree("maintree", maintree_bb);
} catch (BT::RuntimeError &error) {
	printf("behavior tree RuntimeError: %s", error.what() );
	return false;
} catch (BT::LogicError &error) {
	printf("behavior tree LogicError: %s", error.what() );
	return false;
}
catch (...) {
	printf("create behavior tree failed, check it out");
	return false;
}

ROS2中msg的命名规范：必须以大写字母开头，并且不能有下划线，应当是 ^[A-Z][A-Za-z0-9]*$。像moving_target.msg, Moving_target.msg都是不规范的，应该是MovingTarget.msg

msg文件里的成员命名：只能是小写+下划线，不能出现大写。int32 id_number是合适的，int32 ID_number就不合适

参考 官方教程，注意对package.xml做下面修改

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<build_depend>rosidl_default_generators</build_depend>
<exec_depend>rosidl_default_runtime</exec_depend>
<member_of_group>rosidl_interface_packages</member_of_group>

在其他包使用自定义的msg/Action包的时候，编译完成后，去build文件夹里找到可执行文件，结果发现有一个.so没有链接成功

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ldd libmy_node.so  | grep my_defined
    libmy_defined_msgs__rosidl_typesupport_cpp.so => /home/user/j36_project/install/my_defined_msgs/lib/libmy_defined_msgs__rosidl_typesupport_cpp.so (0x00007a9426d69000)
    libmy_defined_msgs__rosidl_generator_c.so => not found

在launch目录里创建launch文件或py文件后，ros2 launch不能直接找到，会报错

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file 'file.launch' was not found in the share directory of package 'package_name' which is at '/home/user/catkin_ws/install/package_name/share/package_name'

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install(DIRECTORY launch
DESTINATION share/${PROJECT_NAME})

• 使用xml

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<launch>
    <node pkg="nav2_map_server" exec="map_server" name="map_server">
        <param name="yaml_filename" value="/home/zzp/catkin_ws/maps/test.yaml"/>
    </node>

    <node pkg="nav2_planner" exec="planner_server" name="planner_server" >
    </node>
</launch>

args的写法一直查不到，按ROS1的写法是错的，节点会退出: <node pkg ="tf2_ros" exec="static_transform_publisher" name="map_odom_tf" args="1 0 0 0 0 0 map odom 100" />

• 使用python

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cd ~/ros2_ws
mkdir launch
vim launch/both_launch.py

加入下面内容:

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from launch import LaunchDescription
from launch_ros.actions import Node
 
def generate_launch_description():
    return LaunchDescription([
        Node(
            package='duckiebot',
            namespace='duckietown',
            executable='duckiebot_node',
            name='duckiebot_node1'
        ),
        Node(
            package='control',
            namespace='duckietown',
            executable='control_node',
            name='control_node1'
        )
    ])

两个类互相引用的问题，一般用前置声明解决，但是两个不同命名空间的类就有些复杂了，两个类的头文件和源文件这样写:

类A的头文件:

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namespace bbb
{
    class B;
}

namespace aaa {

class A
{
public:
    A();
private:
    bbb::B* b;
};
}

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#include "a.h"
#include "b.h"

namespace aaa {
	A::A()
	{
	    cout << "A" << endl;
	}
}

类B的头文件:

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#include "a.h"

namespace bbb {
	class B
	{
	public:
	    B();
	private:
	    aaa::A* a;
	};
}

类B的源文件

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#include "b.h"

namespace bbb {
	B::B()
	{
	    cout << "B" << endl;
	}
}

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file.cc:19:69:   required from here
/usr/include/c++/13/ext/aligned_buffer.h:93:28: error: invalid application of ‘sizeof’ to incomplete type ‘aaa::A’
   93 |     : std::aligned_storage<sizeof(_Tp), __alignof__(_Tp)>
      |                            ^~~~~~~~~~~
/usr/include/c++/13/ext/aligned_buffer.h:93:28: error: invalid application of ‘sizeof’ to incomplete type ‘aaa::A’ 

解决了带命名空间的两个类互相调用的问题后，编译又出错误。看来是初始化aaa::A时，sizeof计算出错

前置声明告知编译器某个类或者模板的存在，但不提供其完整定义的方式。在初始化前置声明类时，需要分配内存，也就需要使用sizeof，它的计算发生在代码编译时期，此时无法计算，就会报错。解决方法就是在源文件里include前置声明类的头文件，比如这里我们在b.cpp里include "a.h"

可以使用convert_v3_to_v4.py将版本3的xml文件转为版本4，没发现反过来转换的。

• classes / XML tags 发生的变化

• <root> 变成了 <root BTCPP_format="4">

• ControlNodes and Decorators 必须支持新的节点状态 NodeStatus:SKIPPED

The purpose of this new status is to be returned when a PreCondition is not met. When a Node returns SKIPPED, it is notifying to its parent (ControlNode or Decorator) that it hasn’t been executed.

• Ticking in a While Loop

版本3常常是这样进行tick的

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while(status != NodeStatus::SUCCESS || status == NodeStatus::FAILURE)
{ 
	tree.tickRoot();
	std::this_thread::sleep_for(sleep_ms);
}

版本4引入新的sleep函数

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Tree::sleep(std::chrono::milliseconds timeout)

This particular implementation of sleepcan be interrupted if any node in the tree invokes the method TreeNode::emitWakeUpSignal. This allows the loop to re-tick the tree immediately.

Tree::tickRoot() 已经消失了

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//  status = tree.tickOnce();
while(!BT::isStatusCompleted(status) ) 
{
  //---- or, even better ------
  // tree.tickWhileRunning(sleep_ms); 
  tree.tickOnce();
  tree.sleep(sleep_ms);
}

Tree::tickWhileRunning is the new default and it has its own internal loop; the first argument is a timeout of the sleep inside the loop.

或者这两个:

• Tree::tickExactlyOnce(): equivalent to the old behavior in 3.8+
• Tree::tickOnce() is roughly equivalent to tickWhileRunning(0ms). It may potentially tick more than once.

• getInput的变化

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BT::Optional<std::string> port_plugin_name = getInput<std::string>("plugin_name");

原型: Result BT::TreeNode::getInput(const std::string& key, T& destination ) const [inline]

Read an input port, which, in practice, is an entry in the blackboard. If the blackboard contains a std::string and T is not a string, convertFromString<T>() is used automatically to parse the text.

如果没有默认值的InputPort,不能获取值，运行会报错

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BT::Expected<int> t = getInput<int>("ttt");
if(t)
  cout << "Expected ttt: " << t.value() << endl;

• SequenceWithMemory 取代 SequenceStar

Use this ControlNode when you don’t want to tick children again that already returned SUCCESS.

加载行为树的方式变化

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Tree BT::BehaviorTreeFactory::createTree(const std::string& tree_name,
        Blackboard::Ptr  blackboard = Blackboard::create()  )

Tree BT::BehaviorTreeFactory::createTreeFromFile(const std::string&  file_path, Blackboard::Ptr  blackboard = Blackboard::create() )

Tree BT::BehaviorTreeFactory::createTreeFromText(const std::string& text,
           Blackboard::Ptr  blackboard = Blackboard::create() )   

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- void BT::BehaviorTreeFactory::registerBehaviorTreeFromFile(const std::string&  filename)

Load the definition of an entire behavior tree, but don’t instantiate it. You can instantiate it later with BehaviorTreeFactory::createTree(tree_id), where “tree_id” come from the XML attribute <BehaviorTree id="tree_id">

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void BT::BehaviorTreeFactory::registerBehaviorTreeFromText(const std::string &_xml_text_)

Same of registerBehaviorTreeFromFile, but passing the XML text, instead of the filename

• 版本3的用法

auto tree = factory.createTreeFromFile("test.xml", maintree_bb);

版本4的用法如下:

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factory.registerBehaviorTreeFromFile("test.xml");

// xml文件的开头是 <root BTCPP_format="4"  main_tree_to_execute = "test" >
auto tree = factory.createTree("test", maintree_bb);

main_tree_to_execute的值一定要和createTree的第一个参数一致，否则会出错，出错的根源在 Tree XMLParser::instantiateTree(const Blackboard::Ptr& root_blackboard, std::string main_tree_ID)

每次在Groot2里修改行为树后，保存会让main_tree_to_execute部分消失，我认为这是个设计上的bug

tick系列函数

• 版本4不再有函数 BT::Tree::tickRoot(TickOption opt, std::chrono::milliseconds sleep_time)

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enum BT::Tree::TickOption
{
    Enumerator
    EXACTLY_ONCE    
    ONCE_UNLESS_WOKEN_UP    
    WHILE_RUNNING 
}

版本4使用下面3个函数

• BT::NodeStatus BT::Tree::tickWhileRunning(std::chrono::milliseconds sleep_time = std::chrono::milliseconds(10) )

Call tickOnce until the status is different from RUNNING. Note that between one tick and the following one, a Tree::sleep() is used

• BT::NodeStatus BT::Tree::tickExactlyOnce()

Tick the root of the tree once, even if a node invoked emitWakeUpSignal()

• BT::NodeStatus BT::Tree::tickOnce()

by default, tickOnce() sends a single tick, But as long as there is at least one node of the tree invoking TreeNode::emitWakeUpSignal(), it will be ticked again.

类BT::Tree在版本3里有两个成员变量

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std::vector<Blackboard::Ptr>  blackboard_stack

std::vector<TreeNode::Ptr>    nodes

按照这个包的步骤来，最后启动

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ros2 launch gazebo_differential_drive_robot robot.launch.py

手动控制还是用cmd

ubuntu 24.04安装jazzy后，对应的gazebo和以前不太一样了。我们需要安装的是 gazebo Harmonic

安装

安装过程参考 Gazebo Harmonic 和 ROS2 jazzy 安装和测试

最后还要安装

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sudo apt-get install -y ros-jazzy-ros-gz 
sudo apt-get install -y ros-jazzy-ros-gz-sim-demos 
sudo apt-get install -y ros-jazzy-ros-gz-bridge
sudo apt-get install -y ros-jazzy-ros-gz-image
sudo apt-get install -y ros-jazzy-ros-gz-interfaces
sudo apt-get install -y ros-jazzy-ros-gz-sim
sudo apt-get install -y ros-jazzy-joint-state-publisher
sudo apt-get install -y ros-jazzy-xacro
sudo apt-get install -y ros-jazzy-teleop-twist-keyboard
sudo apt-get install -y ros-jazzy-teleop-twist-joy

基础命令

• 启动命令: gz sim 或者 gz sim -v 4. -v: 指定日志详细级别，4 表示最高详细程度。

• 可以使用-s（仅服务器）或-g（仅GUI）参数来分别运行服务器或GUI

插件的加载方式已被更改，需要在模型文件（SDF/URDF）或 Gazebo 的配置中添加。

• 启动制定的sdf文件: gz sim shapes.sdf

启动之后，有3个进程: gz sim, gz sim server, gz sim gui

• ROS2的方式启动: ros2 launch ros_gz_sim gz_sim.launch.py gz_args:=empty.sdf

• 启动图像管道: ros2 launch ros_gz_sim_demos image_bridge.launch.py

重要的sdf文件: diff_drive_skid.sdf, actor.sdf

从ROS 2 Jazzy开始，Gazebo通过vendor包的形式在ROS包仓库中可用。如果您的包直接依赖于Gazebo库，而不是仅依赖于ros_gz，请参考相关文档学习如何使用Gazebo vendor包。

话题相关命令

gazebo的相关命令从ROS2里独立出来了

• gz topic -l 显示所有话题

• gz topic -it /model/tugbot/pose 显示话题信息，结果如下

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Publishers [Address, Message Type]:
  tcp://172.27.36.158:38969, gz.msgs.Pose
No subscribers on topic [/model/tugbot/pose]

• -et echo 话题
• -ft 显示话题频率
• -pt 发布话题

gz topic -h可显示其他命令

在新的架构中，Gazebo Sim 与ROS 2的集成通过ros_gz桥接包实现。该桥接包允许 ROS 2 和 Gazebo Sim 之间的消息传递

问题

docker里运行gazebo报错: libGL error: MESA-LOADER: failed to retrieve device information ，这是本机的显卡没装好