Motor Controller for Differential Drive Robot

Description

This Motor Controller project is designed to work seamlessly with a differential drive robot Perceptron Bot. It offers a comprehensive suite of features, including a motor driver implementation, a serial communication protocol, a timer API for simplified timer creation, and a PID controller. Additionally, the timer and PID controller functionalities are designed to become external libraries for wider use.

The motor driver component assumes the use of an L298N driver to facilitate communication between the Arduino and the actual motors. It can operate in both open and closed-loop modes, with encoder feedback required for closed-loop control. An implementation of an Encoder class is provided for this purpose.

The Motor Controller manages two instances of the motor driver, calculating the robot's pose based on the distances traveled by the wheels. It also accepts velocity commands, specifically linear x and angular z velocities.

A very simple serial communication protocol is also available, which is to be used to make the communication via serial with the motor_controller. The main idea is to have a ROS2 node running and communicating via serial with the arduino. Then, this node will subscribe to velocity commands, which will be sent to the motor_controller and also publish odometry. For more information on the protocol, check Serial Protocol section.

This entire repo has been developed on YouTube, for the series Building and Autonomous Robot From Scratch

Table of Contents

• Motor Controller for Differential Drive Robot
  • Description
  • Table of Contents
  • Getting Started
    • Prerequisites
    • Installation
  • Usage
  • Configuration
  • Serial Protocol
    • Possible Acknowledgment Errors
  • Doxygen Documentation
• Contributing
• License

Getting Started

To get started with this Motor Controller project, follow these steps:

Prerequisites

Before you begin, ensure you have the following:

• Hardware: Arduino, L298N driver, differential drive robot
• Software: PlatformIO

Installation

1. Clone this repository to your local machine.
2. Configure your hardware connections as specified in the configuratin.hpp file, or change the configuration to match your connections.

Usage

At this moment in time, you can use the main.cpp as an example how how to use the motor controller. Essentially, you need to call the method run on every main loop iteration. To command the robot, you can then use set_cmd(cmd_vel) to make your robot/motors move.

In case you upload the current code to a board, the robot should be going on a circle.

Configuration

You can configure various aspects of the Motor Controller by editing the configuration.hpp file located in the ./include directory. This file allows you to specify pin configurations and PID controller settings, among other things.

Serial Protocol

The serial protocol is quite straight forward. The sender will need to send a command in a specific format which will always start with a flag. Some commands, like velocity commands will also include some values in the command itself. For the moment, these are the available commands:

• c x w:

  • c: is the flag indicating closed-loop control
  • x: is the linear velocity x (-1000mm/s - 1000mm/s) [interger type]
  • w: is the angular velocity z (-1000mm/s - 1000mm/s) [integer type]
  • Acknowledgment: OK

• o left_pwm right_pwm:

  • o: is the flag indicating open-loop control
  • left_pwm: is the PWM value to be sent to the left motor (0-254)
  • right_pwm: is the PWM value to be sent to the right motor (0-254)
  • Acknowledgment: OK

• q: Get robot's pose/odometry.

  • Returned format: x y z
  • Acknowledgment: the pose

• m: Get motor's data.

  • Returned format: left_rpm left_velocity left_angular_velocity left_distance left_angle,right_rpm right_velocity right_angular_velocity right_distance right_angle
  • Acknowledgment: the data

• r: Reset robot pose.

  • Acknowledgment: OK

Possible Acknowledgment Errors

• ERR: Invalid command: In case the command does not exist or as an invalid format.
• ERR: PWM values out of range: In case the pwm values are not between 0-254.
• ERR: Unknown error: In case none of the above occured. This could be related to arduino and not directly to the command sent.

Doxygen Documentation

The project includes Doxygen documentation, which can be found in the ./doxygen/doxygen_generated/html directory. To view the documentation, you need to install doxygen using sudo apt install doxygen (for Debian based systems), and then start a Python server as follows:

$ cd doxygen && doxygen && cd doxygen_generated/html && python3 -m http.server

Then, open your web browser and navigate to http://localhost:8000 to access the Doxygen documentation.

Contributing

Contributions are welcome. Help us make this Motor Controller even better!

License

This project is licensed under the MIT License. Feel free to use, modify, and distribute it in accordance with the license terms.