Self-Balancing Cube

A self-balancing cube controlled by an STM32 microcontroller, using IMU feedback and internal reaction wheels to balance on an edge or corner.

info

Author: Ana-Maria-Raluca Lupu
GitHub Project Link: acs-project-2026-lupuana

Description

This project implements a self-balancing cube based on reaction-wheel control. The system reads motion and orientation data from an IMU sensor, estimates the cube state, and computes corrective motor commands in real time. Three internal motors spin reaction wheels to generate stabilizing torques, allowing the cube to recover balance and remain upright on an edge or corner.

Motivation

I chose this project because it combines embedded programming, control systems, electronics, mechanical design, and real-time testing in a single system. It is a good practical challenge because it requires both hardware integration and software development, especially sensor processing, feedback control, and actuator coordination on an STM32 platform.

Architecture

The main architecture components of the project are:

• Sensing layer
  Reads acceleration and angular velocity data from the IMU.

• State estimation layer
  Processes raw IMU data and computes the current orientation and angular motion of the cube.

• Control layer
  Runs the balancing algorithm and computes correction values for each axis.

• Actuation layer
  Sends control signals to the three reaction-wheel motors.

• Communication and tuning layer
  Allows calibration and parameter adjustment through a Bluetooth serial connection.

• Power layer
  Supplies the motors directly from the battery and powers the logic through a regulated 5V rail.

Architecture Diagram

Log

Week 14 - 29 April

• Finalized project theme and received approval.
• Researched and ordered components.

Week 4 - 10 May

• Components arrived

Week 11 - 17 May

• Tested components separately
• Started assembling the project

Hardware

The hardware platform is built around an STM32 microcontroller, an MPU6050 IMU for motion sensing, three brushless motors with encoders for the reaction wheels, a 3S LiPo battery for power, a 5V regulator for the logic section, a Bluetooth module for tuning, and a buzzer for status feedback.

Schematics

Bill of Materials

Device	Usage	Price	Link
Dupont wire kit	Prototyping and signal wiring	24.39 RON	AliExpress
2x MPU6050 GY-521	IMU sensing	48.84 RON	AliExpress
3x Nidec 24H brushless servo motors	Reaction-wheel actuation	138.57 RON	AliExpress
HC-05 Bluetooth module	Wireless tuning and calibration	24.35 RON	AliExpress
3S LiPo 11.1V 500mAh battery	Main power source	85.33 RON	AliExpress
Active 5V buzzer	Audio feedback / status signal	15.72 RON	AliExpress
LM7805 5V regulator module	Logic power regulation	16.72 RON	AliExpress
3S LiPo balance charger	Battery charging	28.24 RON	AliExpress
ON/OFF switch	Main power control	21.29 RON	AliExpress

Software