Two wheel differential robot

The project goal was to create a simple mobile robot with a use of 3D printing, which uses basic components commonly used in robotics.

Assembled robot

3D model of the robot in Fusion 360

Components

All devices are connected with wires. Mechanical parts are 3D printed in PLA and connected with M3 screws.

• Microcontroller STM32F411RE Nucleo board
• Motor driver L298N
• 2x The cheapest DC motors + wheels
• Distance sensor HC-SR04p
• IMU device MinIMU-9 v5 9DOF with LSM6DS33 and LIS3MDL
• BT module HC-05
• 2x Battery cells Li-ion Samsung INR18650-26J 2600mAh + basket
• Ball Caster 1/2'' Pololu 953

Features

• Wireless control via bluetooth
• Drive forward, backward, left, right
• Distance measurement
• Drive and maintain set distance from the obstacle before the robot

Programming

Whole program was written with a use of HAL library. Each functionality is in seperate files in my_lib folder:

• Button.c/h
• complex_parser.c/h
• HCSR04p.c/h
• L298N.c/h
• LSM6DS33.c/h
• RingBuffer.c/h
• Robot.c/h
• utils.c/h

Used peripheriales:

• GPIO
  • Motors revolution direction
  • Nucleo blue button to enable/disable robot operation
• Timers
  • PWM to control motors speed and to trigger distance sensor measurement
  • Input capure to measure pulse width from distance sensor echo pin and convert it to distance value
• USART
  • Bluetooth SPP communiation with HC-05 module to send commands from terminal
• I2C
  • Read IMU device data

Both button and motors operation control are written with a use of simple "state machine" notion.

Software

• STM32CubeIDE with built-in CubeMX ver 1.13.2 - programming and configuration
• Realterm - terminal to send commands via BT
• Fusion 360 - 3D modeling

Bluetooth/serial Commands

All commands must end with newline "\n" character.

  Enable robot

Parameter	Type	Description
ENABLE=X	string	Enable robot operation, where X is a 1 (enable) or 0 (disable)

  Move robot

Parameter	Type	Description
MOVE=F	string	Move forward
MOVE=B	string	Move backward
MOVE=L	string	Move left
MOVE=R	string	Move right

  Hold distance mode

Parameter	Type	Description
HOLD=XX.X	string	Maintain distance from obstacle where XX.X is a numerical distance value

Peripherials documentation

Motor drawing

HC-05

HC-SR04

LSM6DS33

L298N