Jetracer Lidar

LIDAR (Vll. Bild des LIDAR)

In diesem Tutorial: Enable the Lidar Node wird beschrieben wie man den LIDAR des JetRacers initial einschaltet und dann überprüft ob Daten gesendet werden. Danach kann dann eine Karte des Raumes erstellt werden. Hierfür kann dem Tutorial SLAM Lidar Mapping gefolgt werden, und es können vier verschiedene Mapping-Algorithmen ausprobiert werden.

Hier bei ist allerdings zu beachten das der im Tutorial gegebene Save Befehl abgeändert werden muss. Das jetbot_pro im Befehl muss auf jetracer_ros geändert werden, sodass der Befehle "cd catkin_ws/src/jetracer_ros/maps" lautet.

LIDAR Node einschalten

• Firstly, you need to power on the lidar and make it rotate.
• Run the following commands to enable the lidar node on the robot.

roslaunch jetracer lidar.launch

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• If the node can not be enabled, please press the RESET key on the expansion board, and reboot it.
• If you want to run Is/dev, please check whether the expansion board is connected to Jetson Nano,and whether or not the ttyACM0 and ttyACM11 device is found. [ttyACM0 is for micro-controller communicationn, and ttyACM1 is for lidar communication.]

 ls /dev

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Daten in RVIZ einsehen

• View radar data through the RVIZ tool in a virtual machine. Please enter the following command to open the RVIZ graphical tool interface.

rosrun rviz rviz

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• Click "Add" to add the LaserScan component, select the /scan topic for the Topic, and select Laser_frame for the Fixed Frame to see the radar data. The red points in the image are the points scanned by the radar.

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• Click "Add" to add the TF component.

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• TF displays two coordinates, where base_footprint is the robot chassis coordinates, laser_frame is the radar coordinates, the radar coordinates, and the chassis coordinates are opposite.

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Daten filtern

• From the above steps, we know the data format and radar data information sent by the radar, so we can choose to filter the unwanted parts.
• [Note: Please close the radar node first, otherwise an error will occur if you start the radar node multiple times.]
• Enter the following command on the robot side to start the radar filter node.

roslaunch jetracer laser_filter.launch        #Start the radar filter node

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• Run the following command on the virtual machine side to open the RVIZ graphical tool interface.

rosrun rviz rviz

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• Add LaserScan component, Topic select /filteredscan topic, Fixed Frame select base_footprint; add TF component to display the coordinates of the robot chassis; the red points in the image are the points scanned by the radar. At this time, it can be found that the radar data is only the first half, and the general data behind is filtered out.

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• Run the following commands to enable the reconfigure parameters interface.

 rosrun rqt_reconfigure rqt_reconfigure    

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• Among which:

1. laserAngle : Set the effective angle range to detect the angle in front of the robot
2. distance: Set the effective distance, data beyond this distance will be filtered

• Drag the slider to adjust the parameters, and you can find that the red dot displayed by the radar also changes.