The mobile chassis needs to be driven by a program to achieve the navigation of Limo. The chassis driver of Limo has the C++ version and the Python version. Both two versions can control the movement of the Limo.

C++ chassis driver

The folder where the C++ version of the driver is located is ~/agilex_ws/src/limo_ros/limo_base, which can be accessed by the following command.

cd agilex_ws/src/limo_ros/limo_base

The following is the file list of the limo_base package:

├── limo_base
    ├── CMakeLists.txt
    ├── include
    │   ├── limo_driver.h
    │   ├── limo_protocol.h
    │   └── serial_port.h
    ├── launch
    │   └── limo_base.launch
    ├── msg
    │   └── LimoStatus.msg
    ├── package.xml
    └── src
        ├── limo_base_node.cpp
        ├── limo_driver.cpp
        └── serial_port.cpp

There are four folders under limo_base, namely include, launch, msg, and src. The include folder stores the library files called by the driver; the launch folder stores the startup files of the driver; the msg folder stores the message files needed by the driver; the src folder stores the driver source code.

Folder Stored files
include Library files called by the driver
launch Startup files of the driver
msg Message files needed by the driver
src Driver source code

You can control the forward movement of limo with a simple command.

Note: Before running the command, please make sure that the programs in other terminals have been terminated. The termination command is: Ctrl+c.

  1. Launch the chassis, open a terminal, and enter the command in the terminal:
roslaunch limo_base limo_base.launch
  1. Enter the control command, open a terminal, and enter the command in the terminal:
rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: 0.2
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0"

<aside> 📙 Note: Copy the entire command to the terminal and enter it, and don’t enter it manually.

</aside>

  1. After entering the command in the terminal, Limo will move forward for a short distance before stopping.

Functions used in the driver source code:

Name Function
connect() Connect the chassis
readData() Read the data, and get the information feedback from the chassis
processRxData() Receive serial data
parseFrame() Process serial data
sendFrame() Send serial data
setMotionCommand() Set limo’s control mode
enableCommandedMode() Enable control mode
publishOdometry() Publish odometer data
publishLimoState() Publish limo’s state information
publishIMUData() Publish IMU data
processErrorCode() Error detection
twistCmdCallback() Publish speed control data
normalizeAngle() Output a normal angle
degToRad() Turn the angle to radian
convertInnerAngleToCentral() Convert inner angle to central angle
convertCentralAngleToInner() Convert central angle to inner angle

Python chassis driver

The driver of Limo (Python version) is uploaded to pypi, and it can be downloaded through the pip command. The installation directory of the program is ~/.local/lib/python3.6/site-packages/pylimo. Its file list is: