LiDAR Mobile Robot

The course project of EE202-17L - Digital Circuits Laboratory.
Lead Author: Shengzhe GAN (Communication, ROS and algorithm implementation)
Collaborators: Xujie WANG (Hardware and embedded systems), Xiaokun LIU (Hardware), Kairui XIAO (Hardware)

Communication between ESP32, Mobile robot base and Laptop

Function of this repo:

• Realize the wireless communication between a Mobile robot and a laptop running Ubuntu 20.04
• In the ROS workspace, a basic LiDAR-slam algorithm will be implemented.

Approach overview

Hardware

• A L150 DIFF Mobile Robot Base by Wheeltech Technology Co., LTD.
• LD14 2-D LiDAR.
• ESP32-Wroom-32 dev board.
• Laptop running ROS noetic.

Strategy

• Communication via multiport strategy to exchange LiDAR data, Base data and command data.
• The command data is sent via Wi-Fi directly.
• The recieved LiDAR and base data are pushed into two pair of virtual serial.
• The ROS packages read these data via virtual serial.

Pipeline

• LiDAR connect to ESP32 dev board via UART.
• The car is embedded with ROS interface, connect to the ESP32 dev board via serial. A converter is used.
• The ESP32 connect to local Wi-Fi which is same to the Laptop running ROS.
• The ESP32 send LiDAR and base date via two port, receive command data via a third data.
• The laptop runs 5 ros packages:
  • communication: Realize the LiDAR and base data reception.
  • vel_control_pkg: Realize the command data transmition.
  • sensor_data_parse: Realize the parse for the feedback base data, publish \odom, \imuamd \battary topics.
  • ldlidar_sl_ros: The official driver for the ld14 2-D LiDAR.
  • slam_and_motion_control_pkg: The slam and ego-motion planning package, is the core algorithm of this project.

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Version Updates and Usage Guidance

version 1.0

Limitation:
Only achieved the serial penetration, single side communication.

Pipeline:

• Sensor send data to ESP32 via uart serial
• ESP32 send these data to WiFi
• Laptop receive these data via WiFi
• Transmit these data via virtual serial
• Resultantly ROS sensor driver can receive these data via the virtual serial

Get started:
Notice:

• Ensure the laptop and ESP32 are connected to same Wi-Fi.
• wifi.py is the MicroPython script running on ESP32.
• wifi_receive_virtual_serial.py is the Python script running on laptop.
• Only send data when the ESP32 receiced uart data.

Steps to implement, in Ubuntu20.04:

• Upload wifi.py to ESP32, change the wifi condition variable's name of SSID and PASSWARD.
• Chanege the uart initiallization to your preferred tx and rx pin.
• Run this program once, write down the ESP32's IP address.
• Then save file to ESP32, rename as main.py to ensure autumatically run after boot.
• Create virtual serial and give them sudo access.
  • Create virtual serial: run in terminal: sudo socat -d -d PTY,raw,echo=0,link=/dev/ttyVIRT0 PTY,raw,echo=0,link=/dev/ttyVIRT1
  • Implement sudo access: run in another terminal: sudo chmod 777 /dev/ttyVIRT*
• Run wifi_receive_virtual_serial.py on laptop
  • Remember to change TCP_IP variable as the noted IP address of you ESP32.
  • Remember to change virtual_com signature in __init__() function as your virtual serial name('/dev/ttyVIRT0')
• You can examine the output by cancel the code comments in run() function.
• Read the virtual serial data in the other virtual serial which is created in pair('/dev/ttyVIRT1')

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version 2.0

Limitation:
Still in prograss. The basic communication logic is finished, using the multiple-port strategy.

What's new? & Pipeline:

• Use different port to communicate in three way --- LiDAR tx, CMD rx and Encoder tx.
• Wrote a python package to utililze the Wi-Fi reciever class, to be easily instantiated both in vel-cmd node and LiDAR receiver.
• Created the ROS node of the vel_cmd subscriber
  1. Directly Use the serial from Laptop linked with the base. (Verified)
  2. Use Wi-Fi port to send data to esp32 and use UART output to the base. (Verified with serial assistant, but due to the cable issue, the data can't received by the base.)
• wifi_receiver.py is not oop one, communication.py is new, and can be run by rosrun.
• wifi_transmitter.py is the code runs on the esp32. This used multi-thread. And used 2 pair of UART pins.

Get started:
Notice:

• Ensure the laptop and ESP32 are connected to same Wi-Fi.
• wifi_transmitter.py is the MicroPython script running on ESP32.
• communication.py is the Python script running on laptop, can be run by rosrun communication communication.py.
• Only send data when the ESP32 receiced uart data.

Steps to implement, in Ubuntu20.04:

• Upload wifi_transmitter.py to ESP32, change the wifi condition variable's name of SSID and PASSWARD.
• Chanege the uart initiallization to your preferred tx and rx pin.
• Run this program once, write down the ESP32's IP address.
• Then save file to ESP32, rename as main.py to ensure autumatically run after boot.
• Create two pairs of virtual serial and give them sudo access.
  • Create virtual serial: run in terminal: sudo socat -d -d PTY,raw,echo=0,link=/dev/ttyVIRT0 PTY,raw,echo=0,link=/dev/ttyVIRT1
  • Create virtual serial: run in terminal: sudo socat -d -d PTY,raw,echo=0,link=/dev/ttyVIRT2 PTY,raw,echo=0,link=/dev/ttyVIRT3
  • Implement sudo access: run in another terminal: sudo chmod 777 /dev/ttyVIRT*
• Run communication.py on laptop
  • Remember to change TCP_IP variable as the noted IP address of you ESP32.
  • Remember to change virtual_com signature in __init__() function as your virtual serial name('/dev/ttyVIRT0')
  • Run in terminal: rosrun communication communication.py.
• You can examine the output by cancel the code comments in run() function.
• Read the virtual serial data in the other virtual serial which is created in pair('/dev/ttyVIRT1')
• Theoretically, the encoder data is streamed into the second pair of virtual serial, but this is not verified yet.

Check data with RViz:

• Run roscore
• After all above finished:
  • cd catkin_workspace Enter the ws, change to your only path.
  • source devel/setup.sh
  • Run the LiDAR's drive: roslaunch ldlidar_sl_ros ld14.launch
  • Open RViz rviz
  • In RViz, change the base to Laser_base
  • Add LaserScan, choose topic /scan
  • Finished.

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Version 2.1

What's new?:

• The serial communication between the base and ESP32 is finished

Get Started:

• Followed by Version2.0
• UART serial communication:
  • Cable connection:
    • Base's pin PA2: Tx, connect to ESP32's Pin 25;
    • Base's pin PA3: Rx, connect to ESP32's Pin 26.

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Version 2.2

2025/5/11 Work

• 修改了odom发布的数据
• 在vel_control_wifi.py的launch文件里加上了tf变换，使得建图可以正常运行，使用的是hector mapping
• 运行顺序：
  1. 创建虚拟串口并设置sudo权限
  2. 确保esp32运行并且与计算机处于同一网络环境下，ip地址在/util/bridge.py下替换为实际地址
  3. 在终端中运行rosrun communication communication.py
  4. 在终端中运行rosrun vel_control_pkg vel_control_wifi.py
  5. 在终端中运行rosrun sensor_data_pkg sensor data parse.py
  6. 如需要自己控制，启动rqt_robot_steering
  7. 运行lidar的驱动
  8. 可以在rviz中验证数据

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