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172 lines
7.4 KiB
Markdown
172 lines
7.4 KiB
Markdown
# Navigation using ArUco markers
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> **Note** Documentation for the versions [of image](microsd_images.md), starting with **0.15**. For earlier versions, see [documentation for version **0.14**](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/aruco.md).
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[ArUco-Markers](https://docs.opencv.org/3.2.0/d5/dae/tutorial_aruco_detection.html) is a popular technology for positioning
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robotic systems using computer vision.
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Examples of ArUco markers:
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> **Hint** Use the most matte paper for printing visual markers. Glossy paper may glitter in the light, severely deteriorating the quality of recognition.
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For rapid generation of markers for printing, you may use an online tool: http://chev.me/arucogen/.
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## aruco\_pose
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The `aruco_pose` module allows restoring the position of the copter relative to the map of ArUco markers and communicating it to the flight controller using the [Vision Position Estimation](https://dev.px4.io/en/ros/external_position_estimation.html) mechanism.
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If the source of the copter position by the markers is available, the option appears for precise autonomous indoor navigation by the positions using the [simple_offboard](simple_offboard.md) module.
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### Turning on
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Make sure that in the clever launch file \(`~/catkin_ws/src/clever/clever/launch/clever.launch`\), the start of aruco\_pose and [computer vision cameras](camera.md) is turned on:
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```xml
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<arg name="main_camera" default="true"/>
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```
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```xml
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<arg name="aruco" default="true"/>
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```
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After the launch-file is edited, restart package `clever`:
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```(bash)
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sudo systemctl restart clever
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```
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### Calibrating the ArUco marker map
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An automatically generated [ArUco-board](https://docs.opencv.org/trunk/db/da9/tutorial_aruco_board_detection.html) may be used as a map of marks.
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The map of marks is adjusted using file `~/catkin_ws/src/clever/clever/launch/aruco.launch`. To use ArUco-board, enter its parameters:
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```xml
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<node pkg="nodelet" type="nodelet" name="aruco_pose" args="load aruco_pose/aruco_pose nodelet_manager">
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<param name="frame_id" value="aruco_map_raw"/>
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<!-- the type of the marker field -->
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<param name="type" value="gridboard"/>
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<!-- the number of markets along x -->
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<param name="markers_x" value="1"/>
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<!-- the number of markers along y -->
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<param name="markers_y" value="6"/>
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<!-- ID of the first marker (left top) -->
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<param name="first_marker" value="240"/>
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<!-- the length of the marker side in meters -->
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<param name="markers_side" value="0.3362"/>
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<!-- distance between the murders -->
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<param name="markers_sep" value="0.46"/>
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</node>
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```
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The vertical and horizontal distance between the markers may be set separately:
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```xml
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<!-- the horizontal distance between the markers -->
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<param name="markers_sep_x" value="0.97"/>
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<!-- the vertical distance between the marker -->
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<param name="markers_sep_y" value="1.435"/>
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```
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If a map with a custom order of marker IDs is used, parameter `marker_ids` may be used:
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```xml
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<rosparam param="marker_ids">[5, 7, 9, 11, 13, 15]</rosparam>
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```
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The markers are numbered from the top left corner of the field.
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For monitoring the map that is currently used by the copter for navigation, one can watch the content of topic `aruco_pose/map_image`. In a browser, it may be viewed with [web\_video\_server](web_video_server.md) by following the link [http://192.168.11.1:8080/snapshot?topic=/aruco\_pose/map\_image](http://192.168.11.1:8080/snapshot?topic=/aruco_pose/map_image):
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When flying, make sure that the markers glued to the floor correspond to the map.
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In topic `aruco_pose/debug` \([http://192.168.11.1:8080/snapshot?topic=/aruco\_pose/debug](http://192.168.11.1:8080/snapshot?topic=/aruco_pose/debug)\) the current result of markers recognitions is available:
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TODO
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### The system of coordinates
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According to [agreement](http://www.ros.org/reps/rep-0103.html), the standard ENU system of coordinates is used in the marker field:
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* x — rightward \(conditional East\);
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* y — forward \(conditional North\);
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* z — upward.
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_Note_: the definition above is provided for a situation when the marker field is on the floor.
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First, the zero is the bottom left point of the marker field. The yaw angle is considered zero when the copter is faced rightward\(along the x-axis\).
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### Configuring the flight controller
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Correct Vision Position Estimation requires making sure \(via [QGroundControl](gcs_bridge.md)\) that:
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* **For Pixhawk**: Firmware with LPE \(local position estimator\) is installed. For Pixhawk [download firmware `px4fmu-v2_lpe.px4`](https://github.com/PX4/Firmware/releases).
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**For Pixracer**: parameter `SYS_MC_EST_GROUP` should be set to`local_position_estimator, attitude_estimator_q`.
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> **Note** After changing the value of parameter `SYS_MC_EST_GROUP` restart the flight controller.
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* In parameter `LPE_FUSION` **only** flags `vision position`, `land detector` are enabled. The final value _20_.
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* Compass disabled: `ATT_W_MAG` = 0
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* Complimentary filter external heading weight: `ATT_W_EXT_HDG` = 0.5
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* Orientation by yaw by vision enabled: `ATT_EXT_HDG_M` = 2 `MOCAP`.
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* VPE settings: `LPE_VIS_DELAY` = 0 sec, `LPE_VIS_XY` = 0.1 m, `LPE_VIS_Z` = 0.15 m.
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* Recommended settings for land detector:
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* `COM_DISARM_LAND` = 1 s
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* `LNDMC_ROT_MAX` = 45 deg
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* `LNDMC_THR_RANGE` = 0.5
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* `LNDMC_Z_VEL_MAX` = 1 m/s
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<!--
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For the ease of configuring, you may use a ready settings file for [Clever 2](https://github.com/CopterExpress/clever/blob/master/docs/assets/Clever2LPE_160118.params) or for [Clever 3](https://github.com/CopterExpress/clever/blob/master/docs/assets/Clever3_LPE_020218.params) and upload it to the controller using menu Tools - Load from file in tab Parameters in QGroundControl.
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-->
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### Flight
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A properly configured copter starts holding position by VPE \(in [modes](modes.md) `POSCTL` or `OFFBOARD`\) automatically.
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For [autonomous flights](simple_offboard.md) do you will be able to use functions `navigate`, `set_position`, `set_velocity`. For flying to specific coordinates of the marker field, use frame `aruco_map`:
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```python
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# First, the copter has to take off to see the map of marks
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# and for frame aruco_map to appear:
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navigate(0, 0, 2, frame_id='body', speed=0.5, auto_arm=True) # take off to the altitude of 2 meters
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time.sleep(5)
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# Flying to coordinate 2:2 of the marker field at the altitude of 2 meters
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navigate(2, 2, 2, speed=1, frame_id='aruco_map') # flying to coordinate 2:2 at the altitude of 3 meters
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```
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See [other functions](simple_offboard.md) simple_offboard.
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### Location of markers on the ceiling
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To navigate by the markers placed on the ceiling, you need to set the main camera facing up and [set the corresponding frame of the camera](camera_frame.md).
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To set the map of markers in a "turned over" system of coordinates, change parameter `aruco_orientation` in file `~/catkin_ws/src/clever/clever/aruco.launch`:
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```xml
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<param name="aruco_orientation" value="map_upside_down"/>
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```
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When this parameter is set, frame aruco\_map will also be "turned over". Thus, to fly at the altitude of 2 meters below the ceiling, argument `z` should be set to 2:
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```python
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navigate(x=1, y=2, z=1.1, speed=0.5, frame_id='aruco_map')
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