My ROS Robot Project

Raspberry Pi based robot running ROS1 Noetic (LTS) on Ubuntu Focal 20.04 64bit (LTS) with motor drivers and encoders connected directly to the Pi.

Running the code

Edit bringup.launch file and select one of:

• test_odom - Just for testing different odometry sources against Lidar to see how accurate it is
• hector_mapping - Generate a map using hector_mapping and joystick to drive
• navigation_stack - Encoder odometry, map_server static map, AMCL localisation & move_base navigation stack
• gmapnav - Encoder odometry, gmapping live mapping and localisation & move_base navigation stack
• hectornav - Hector odometry, live mapping and localisation & move_base nav with explore_lite self exploration
• amclhectornav - Hector odometry, map_server static map, AMCL localisation & move_base navigation stack
• cartographer - Encoder odometry, Cartographer live mapping and localisation

then run with: 'start.sh' or 'roslaunch edukit_bot bringup.launch'

Notes:

• My encoder based odometry (and associated transform) has never been very accurate, despite lots of work in that area (encoders fixed and confirmation that Pi is seeing every pulse)
• If you are having encoder issues, use an oscilloscope to check the encoders are pulsing correctly, and push the magnets closer to the sensors if you have issues with missing pulses
• Hector works well at the slow speeds my robot moves at and produces the best odometry I have had - hence I use it in later launch options
• Launch options of hectornav (for live mapping) and amclhectornav (for localisation to an existing map) work pretty well, with explore_lite giving navigation goals to move_base to do self exploration too
• cartographer looked promising, but is very complicated to configure and didn't localise at all well when turning
• I always ran graphical stuff (rviz, rqt_graph, etc) from a VM on the PC, not from Pi
• Best motors I found were 6v B45 603 ratio 30 RPM Micro Metal Gear Motors like these - aliexpress or these - amazon

Example early map from Hector:

Usefull files:

• Setup info and usefull commands I have listed here: https://github.com/KevWal/ROS-Bot-Workspace/blob/master/etc/update-motd.d/motd.txt
• Fan setup: https://github.com/KevWal/ROS-Bot-Workspace/blob/master/boot/firmware/usercfg.txt
• USB Power off on boot (to save Lidar spinning endlessly) https://github.com/KevWal/ROS-Bot-Workspace/blob/master/etc/rc.local
• An example layout of frames https://github.com/KevWal/ROS-Bot-Workspace/blob/master/Frames.txt
• All of my ROS nodes, parameters and launch files https://github.com/KevWal/ROS-Bot-Workspace/tree/master/src/edukit_bot