|
|
Package Summary
| Tags | No category tags. |
| Version | 0.1.7 |
| License | Apache License 2.0 |
| Build type | AMENT_CMAKE |
| Use | RECOMMENDED |
Repository Summary
| Checkout URI | https://github.com/ros-planning/navigation2.git |
| VCS Type | git |
| VCS Version | crystal-devel |
| Last Updated | 2019-03-13 |
| Dev Status | DEVELOPED |
| CI status | No Continuous Integration |
| Released | RELEASED |
| Tags | No category tags. |
| Contributing |
Help Wanted (0)
Good First Issues (0) Pull Requests to Review (0) |
Package Description
Additional Links
Maintainers
- Michael Jeronimo
Authors
Mission Executor
The Mission Executor module is a task server that coordinates other tasks. It can be used to direct the activities of multiple robots as well as other, non-navigation and non-robot tasks. This module would typically reside on a central orchestration computer and direct the operation of remote robots.
Overview
The Mission Executor module is implemented using Behavior Trees. As detailed in Michele Colledanchils's doctoral thesis, Behavior Trees are a Control Architecture (CA) initially used in the video game industry to control non-player characters and now applied to the control of autonomous robots.
The Mission Executor task server receives a MissionPlan and returns whether the plan was successfully executed, failed, or was canceled. The ExecuteMissionTask is defined as follows:
namespace nav2_tasks {
using ExecuteMissionCommand = nav2_msgs::msg::MissionPlan;
using ExecuteMissionResult = std_msgs::msg::Empty;
using ExecuteMissionTaskClient = TaskClient<ExecuteMissionCommand, ExecuteMissionResult>;
using ExecuteMissionTaskServer = TaskServer<ExecuteMissionCommand, ExecuteMissionResult>;
} // namespace nav2_tasks
NOTE: An Empty message is used in the definition of the task client and server if there is no other data required.
The mission plan message consists of a header and a mission plan string:
std_msgs/Header header
string mission_plan
The mission plan itself is an XML string that defines a Behavior Tree. For example, the following XML string specifies a sequence of three NavigateToPose actions:
<root main_tree_to_execute="MainTree">
<BehaviorTree ID="MainTree">
<SequenceStar name="root">
<NavigateToPose position="10;11;0.0" orientation="0.7071;0;0.7071;0"/>
<NavigateToPose position="20;21;0.0" orientation="0.7071;0;0.7071;0"/>
<NavigateToPose position="30;31;0.0" orientation="0.7071;0;0.7071;0"/>
</SequenceStar>
</BehaviorTree>
</root>
Invoking the MissionExecutor
The MissionExecutor is an implementation of the ExecuteMissionTaskServer interface, so the corresponding ExecuteMissionTaskClient is used to communicate with the task server, like this:
// Demonstrate using a task client to invoke the MissionExecutor task
void invokeMission(rclcpp::Node::SharedPtr node, std::string mission_plan)
{
// Create a task client for this particular kind of task
auto task_client_ = std::make_unique<nav2_tasks::ExecuteMissionTaskClient>(node);
// Create the input and output
auto cmd = std::make_shared<nav2_tasks::ExecuteMissionCommand>();
auto result = std::make_shared<nav2_tasks::ExecuteMissionResult>();
// Set the mission_plan field to the XML input
cmd->mission_plan = mission_plan;
// Send this message to the task server
task_client_->sendCommand(cmd);
// Loop until the tasks is complete
for (;; ) {
// Get the status of the remote task server
TaskStatus status = task_client_->waitForResult(result, 100ms);
switch (status) {
case TaskStatus::SUCCEEDED:
printf("Task succeeded\n");
return;
case TaskStatus::FAILED:
printf("Task failed\n");
return;
case TaskStatus::CANCELED:
printf("Task cancelled\n");
return;
case TaskStatus::RUNNING:
// Continue waiting for task to complete
break;
default:
throw std::logic_error("Invalid status value");
}
}
}
Open Issues
- Schema definition and XML document validation - Currently, there is no dynamic validation of incoming XML. The Behavior-Tree.CPP library is using tinyxml2, which doesn't have a validator. Instead, we can create a schema for the Mission Planning-level XML and use build-time validation of the XML input to ensure that it is well-formed and valid.
Wiki Tutorials
Source Tutorials
Package Dependencies
System Dependencies
Dependant Packages
| Name | Repo | Deps |
|---|---|---|
| navigation2 | github-ros-planning-navigation2 |