• Controller:

  • Raspberry Pi 4B (with 2GB RAM)
  • STM32F405

• Motor:

  • BLDC motor
  • HS-485 motor driver

• Sensor:

  • LDLIDAR: LD06

• Protocol:

  • RS-485

• Test Environment

  • Ubuntu 20.04 mate
  • ROS Noetic

If the speed of 2GB RPi doesn't feed you well, See also Running Ubuntu Desktop on a 2GB Raspberry Pi 4, which to some extent, solves the problem of low memory Raspberry PI.

• See ldlidar_stl_ros

Both are based on Lidar.

• laser_scan_matcher
• rf2o_laser_odometry

We deploy on a 4-mecanum-wheel-drive vehicle. Inverse and direct kinematics can be easily googled

Further info see files under stm32_car_control/ directory.

• STM32

Set baudrate same as below or configure yourself.

 115200  8bits 1stop no parity

• ROS node

Set baudrate in /ros_ws/src/ros_rpi_to_stm32/my_serial_node/src/my_serial_node.cpp, in line 80. Make sure it's the same as STM32's

ROS node is named my_serial_node ，which needs serial library. Clone serial and place it under the same directory as my_serial_node.

Go back to ~/ros_ws and compile my_serial_node only:

$ catkin_make -DCATKIN_WHITELIST_PACKAGES="my_serial_node"

If you want to compile all the packages at the same time, do:

$ catkin_make

Now, my_serial_node node is generated.

First make sure RPi serial port is set to a+x right, e.g.

 $sudo chmod a+x /dev/ttyAMAO

Caution: ttyAMA0 should be set to your own serial port name, e.g. ttyUSB0.

Then make sure roscore and lidar SDK are both already running.

You can also run those nodes by roslaunch.

$ cd ~/ros_ws

$ source devel/setup.bash

$ roslaunch ldlidar_stl_ros ld06.launch

Then run my_serial_node.

$ rosrun my_serial_node my_serial_node

New 2 terminal at the same time and enter respectively(make sure roscore is already running):

$ rosrun turtlesim turtlesim_node

$ rosrun turtlesim turtle_teleop_key

Now you can send Twists message through the arrow keys of your keyboard.

You can also directly publish the cmd_vel topic by doing:

$ rostopic pub -r 1 turtle1/cmd_vel geometry_msgs/Twist -- '[1.0, 0, 0]' '[0, 0, 0.8]'

Note that only $v_x$, $v_y$ and $\omega_z$ can be set to not zero.