@ -4,7 +4,7 @@ ArUco markers are a type of fiducials that are used extensively in robotics for
## ArUco Detection
Stretch uses the OpenCV ArUco detection library and is configured to identify a specific set of ArUco markers belonging to the 6x6, 250 dictionary. To understand why this is important, please refer to [this](https://docs.opencv.org/4.x/d5/dae/tutorial_aruco_detection.html) handy guide provided by OpenCV.
Stretch comes preconfigured to identify ArUco markers. The ROS node that enables this is the detect_aruco_markers [node](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/detect_aruco_markers.py) in the stretch_core package. Thanks to this node, identifying and estimating the pose of a marker is as easy as pointing the camera at the marker and running the detection node. It is also possible and quite convenient to visualize the detections with RViz.
Stretch comes preconfigured to identify ArUco markers. The ROS node that enables this is the detect_aruco_markers [node](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/detect_aruco_markers.py) in the stretch_core package. Thanks to this node, identifying and estimating the pose of a marker is as easy as pointing the camera at the marker and running the detection node. It is also possible and quite convenient to visualize the detections with RViz.
## Computing Transformations
If you have not already done so, now might be a good time to review the [tf listener](https://docs.hello-robot.com/0.2/stretch-tutorials/ros2/example_10/) tutorial. Go on, we can wait…
Let's jump into the code to see how things work under the hood. Follow along [here](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/align_to_aruco.py) to have a look at the entire script.
Let's jump into the code to see how things work under the hood. Follow along [here](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/align_to_aruco.py) to have a look at the entire script.
We make use of two separate Python classes for this demo. The FrameListener class is derived from the Node class and is the place where we compute the TF transformations. For an explantion of this class, you can refer to the [TF listener](https://docs.hello-robot.com/0.2/stretch-tutorials/ros2/example_10/) tutorial.
```python
@ -118,4 +118,4 @@ The align_to_marker() method is where we command Stretch to the pose goal in thr
def align_to_marker(self):
```
If you want to work with a different ArUco marker than the one we used in this tutorial, you can do so by changing line 44 in the [code](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/align_to_aruco.py#L44) to the one you wish to detect. Also, don't forget to add the marker in the [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/config/stretch_marker_dict.yaml) ArUco marker dictionary.
If you want to work with a different ArUco marker than the one we used in this tutorial, you can do so by changing line 44 in the [code](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/align_to_aruco.py#L44) to the one you wish to detect. Also, don't forget to add the marker in the [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/config/stretch_marker_dict.yaml) ArUco marker dictionary.
Every Python ROS [Node](http://wiki.ros.org/Nodes) will have this declaration at the top. The first line makes sure your script is executed as a Python script.
Every Python ROS [Node](http://docs.ros.org/en/humble/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html) will have this declaration at the top. The first line makes sure your script is executed as a Python script.
For this example, we will send follow joint trajectory commands for the head camera to search and locate an ArUco tag. In this instance, a Stretch robot will try to locate the docking station's ArUco tag.
## Modifying Stretch Marker Dictionary YAML File
When defining the ArUco markers on Stretch, hello robot utilizes a YAML file, [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/config/stretch_marker_dict.yaml), that holds the information about the markers. A further breakdown of the YAML file can be found in our [Aruco Marker Detection](aruco_marker_detection.md) tutorial.
When defining the ArUco markers on Stretch, hello robot utilizes a YAML file, [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/config/stretch_marker_dict.yaml), that holds the information about the markers. A further breakdown of the YAML file can be found in our [Aruco Marker Detection](aruco_marker_detection.md) tutorial.
Below is what needs to be included in the [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/config/stretch_marker_dict.yaml) file so the [detect_aruco_markers](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/detect_aruco_markers.py) node can find the docking station's ArUco tag.
Below is what needs to be included in the [stretch_marker_dict.yaml](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/config/stretch_marker_dict.yaml) file so the [detect_aruco_markers](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/detect_aruco_markers.py) node can find the docking station's ArUco tag.
```yaml
'245':
@ -27,19 +27,19 @@ To activate the RealSense camera and publish topics to be visualized, run the fo
Next, run the stretch ArUco launch file which will bring up the [detect_aruco_markers](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/detect_aruco_markers.py) node. In a new terminal, execute:
Next, run the stretch ArUco launch file which will bring up the [detect_aruco_markers](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/detect_aruco_markers.py) node. In a new terminal, execute:
```{.bash .shell-prompt}
ros2 launch stretch_core stretch_aruco.launch.py
```
Within this tutorial package, there is an [RViz config file](https://github.com/hello-robot/stretch_tutorials/blob/iron/rviz/aruco_detector_example.rviz) with the topics for the transform frames in the Display tree. You can visualize these topics and the robot model by running the command below in a new terminal.
Within this tutorial package, there is an [RViz config file](https://github.com/hello-robot/stretch_tutorials/blob/humble/rviz/aruco_detector_example.rviz) with the topics for the transform frames in the Display tree. You can visualize these topics and the robot model by running the command below in a new terminal.
```{.bash .shell-prompt}
ros2 run rviz2 rviz2 -d /home/hello-robot/ament_ws/src/stretch_tutorials/rviz/aruco_detector_example.rviz
```
Then run the [aruco_tag_locator.py](https://github.com/hello-robot/stretch_tutorials/blob/iron/stretch_ros_tutorials/aruco_tag_locator.py) node. In a new terminal, execute:
Then run the [aruco_tag_locator.py](https://github.com/hello-robot/stretch_tutorials/blob/humble/stretch_ros_tutorials/aruco_tag_locator.py) node. In a new terminal, execute:
```{.bash .shell-prompt}
cd ament_ws/src/stretch_tutorials/stretch_ros_tutorials/
@ -274,7 +274,7 @@ Now let's break the code down.
#!/usr/bin/env python3
```
Every Python ROS [Node](https://docs.ros.org/en/iron/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html) will have this declaration at the top. The first line makes sure your script is executed as a Python3 script.
Every Python ROS [Node](http://docs.ros.org/en/humble/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html) will have this declaration at the top. The first line makes sure your script is executed as a Python3 script.
```python
import rclpy
@ -291,7 +291,7 @@ from trajectory_msgs.msg import JointTrajectoryPoint
from geometry_msgs.msg import TransformStamped
```
You need to import `rclpy` if you are writing a ROS [Node](https://docs.ros.org/en/iron/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html). Import other python modules needed for this node. Import the `FollowJointTrajectory` from the [control_msgs.action](http://wiki.ros.org/control_msgs) package to control the Stretch robot. Import `JointTrajectoryPoint` from the [trajectory_msgs](https://github.com/ros2/common_interfaces/tree/iron/trajectory_msgs) package to define robot trajectories. The [hello_helpers](https://github.com/hello-robot/stretch_ros2/tree/iron/hello_helpers) package consists of a module that provides various Python scripts used across [stretch_ros](https://github.com/hello-robot/stretch_ros2). In this instance, we are importing the `hello_misc` script.
You need to import `rclpy` if you are writing a ROS [Node](http://docs.ros.org/en/humble/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html). Import other python modules needed for this node. Import the `FollowJointTrajectory` from the [control_msgs.action](http://wiki.ros.org/control_msgs) package to control the Stretch robot. Import `JointTrajectoryPoint` from the [trajectory_msgs](https://github.com/ros2/common_interfaces/tree/humble/trajectory_msgs) package to define robot trajectories. The [hello_helpers](https://github.com/hello-robot/stretch_ros2/tree/humble/hello_helpers) package consists of a module that provides various Python scripts used across [stretch_ros](https://github.com/hello-robot/stretch_ros2). In this instance, we are importing the `hello_misc` script.
Every Python ROS [Node](http://wiki.ros.org/Nodes) will have this declaration at the top. The first line makes sure your script is executed as a Python script.
Every Python ROS [Node](https://docs.ros.org/en/humble/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Nodes/Understanding-ROS2-Nodes.html) will have this declaration at the top. The first line makes sure your script is executed as a Python script.
```python
@ -99,7 +99,7 @@ from hello_helpers.hello_misc import HelloNode
import time
```
You need to import rclpy if you are writing a ROS 2 Node. Import the FollowJointTrajectory from the [control_msgs.action](https://github.com/ros-controls/control_msgs/tree/master/control_msgs) package to control the Stretch robot. Import JointTrajectoryPoint from the [trajectory_msgs](https://github.com/ros2/common_interfaces/tree/rolling/trajectory_msgs/msg) package to define robot trajectories.
You need to import rclpy if you are writing a ROS 2 Node. Import the FollowJointTrajectory from the [control_msgs.action](https://github.com/ros-controls/control_msgs/tree/master/control_msgs) package to control the Stretch robot. Import JointTrajectoryPoint from the [trajectory_msgs](https://github.com/ros2/common_interfaces/tree/humble/trajectory_msgs/msg) package to define robot trajectories.
In this tutorial, we will work with Stretch to explore the Simple Commander Python API to enable autonomous navigation programmatically. We will also demonstrate a security patrol routine for Stretch developed using this API. If you just landed here, it might be a good idea to first review the previous tutorial which covered mapping and navigation using RViz as an interface.
## The Simple Commander Python API
To develop complex behaviors with Stretch where navigation is just one aspect of the autonomy stack, we need to be able to plan and execute navigation routines as part of a bigger program. Luckily, the Nav2 stack exposes a Python API that abstracts the ROS layer and the Behavior Tree framework (more on that later!) from the user through a pre-configured library called the [robot navigator](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_nav2/stretch_nav2/robot_navigator.py). This library defines a class called BasicNavigator which wraps the planner, controller and recovery action servers and exposes methods such as `goToPose()`, `goToPoses()` and `followWaypoints()` to execute navigation behaviors.
To develop complex behaviors with Stretch where navigation is just one aspect of the autonomy stack, we need to be able to plan and execute navigation routines as part of a bigger program. Luckily, the Nav2 stack exposes a Python API that abstracts the ROS layer and the Behavior Tree framework (more on that later!) from the user through a pre-configured library called the [robot navigator](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_nav2/stretch_nav2/robot_navigator.py). This library defines a class called BasicNavigator which wraps the planner, controller and recovery action servers and exposes methods such as `goToPose()`, `goToPoses()` and `followWaypoints()` to execute navigation behaviors.
Let's first see the demo in action and then explore the code to understand how this works!
@ -16,7 +16,7 @@ stretch_robot_stow.py
```
## Setup
Let's set the patrol route up before you can execute this demo in your map. This requires reading the position of the robot at various locations in the map and entering the co-ordinates in the array called `security_route` in the [simple_commander_demo.py](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_nav2/stretch_nav2/simple_commander_demo.py#L30) file.
Let's set the patrol route up before you can execute this demo in your map. This requires reading the position of the robot at various locations in the map and entering the co-ordinates in the array called `security_route` in the [simple_commander_demo.py](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_nav2/stretch_nav2/simple_commander_demo.py#L30) file.
First, execute the following command while passing the correct map YAML. Then, press the 'Startup' button:
@ -24,7 +24,7 @@ First, execute the following command while passing the correct map YAML. Then, p
Since we expect the first point in the patrol route to be at the origin of the map, the first coordinates should be (0.0, 0.0). Next, to define the route, the easiest way to define the waypoints in the `security_route` array is by setting the robot at random locations in the map using the '2D Pose Estimate' button in RViz as shown below. For each location, note the x, and y coordinates in the position field of the base_footprint frame and add it to the `security_route` array in [simple_commander_demo.py](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_nav2/stretch_nav2/simple_commander_demo.py#L30).
Since we expect the first point in the patrol route to be at the origin of the map, the first coordinates should be (0.0, 0.0). Next, to define the route, the easiest way to define the waypoints in the `security_route` array is by setting the robot at random locations in the map using the '2D Pose Estimate' button in RViz as shown below. For each location, note the x, and y coordinates in the position field of the base_footprint frame and add it to the `security_route` array in [simple_commander_demo.py](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_nav2/stretch_nav2/simple_commander_demo.py#L30).
Now, let's jump into the code to see how things work under the hood. Follow along in the [code](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_nav2/stretch_nav2/simple_commander_demo.py) to have a look at the entire script.
Now, let's jump into the code to see how things work under the hood. Follow along in the [code](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_nav2/stretch_nav2/simple_commander_demo.py) to have a look at the entire script.
First, we import the `BasicNavigator` class from the robot_navigator library which comes standard with the Nav2 stack. This class wraps around the planner, controller and recovery action servers.
@ -12,7 +12,7 @@ LaserScanSpeckleFilter - We use this filter to remove phantom detections in the
LaserScanBoxFilter - Stretch is prone to returning false detections right over the mobile base. While navigating, since it’s safe to assume that Stretch is not standing right above an obstacle, we filter out any detections that are in a box shape over the mobile base.
Beware that filtering laser scans comes at the cost of a sparser scan that might not be ideal for all applications. If you want to tweak the values for your end application, you could do so by changing the values in the [laser_filter_params.yaml](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/config/laser_filter_params.yaml) file and by following the laser_filters package wiki. Also, if you are feeling zany and want to use the raw unfiltered scans from the laser scanner, simply subscribe to the /scan topic instead of the /scan_filtered topic.
Beware that filtering laser scans comes at the cost of a sparser scan that might not be ideal for all applications. If you want to tweak the values for your end application, you could do so by changing the values in the [laser_filter_params.yaml](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/config/laser_filter_params.yaml) file and by following the laser_filters package wiki. Also, if you are feeling zany and want to use the raw unfiltered scans from the laser scanner, simply subscribe to the /scan topic instead of the /scan_filtered topic.
Let's jump into the code to see how things work under the hood. Follow along [here](https://github.com/hello-robot/stretch_ros2/blob/iron/stretch_core/stretch_core/avoider.py) to have a look at the entire script.
Let's jump into the code to see how things work under the hood. Follow along [here](https://github.com/hello-robot/stretch_ros2/blob/humble/stretch_core/stretch_core/avoider.py) to have a look at the entire script.
The turning distance is defined by the distance attribute and the keepout distance is defined by the keepout attribute.
hello-jesus
1 year ago