Self-Balancing Electric Unicycle

Abstract

The design and development of a self-balancing electric unicycle (EUC) aimed at improving safety, durability, and user customization compared to existing personal electric vehicles is presented in this paper. Current commercially available unicycles often prioritize cost reduction and mass production, resulting in limited repairability, reduced structural integrity, and insufficient user-centered design features. To address these limitations, a multidisciplinary engineering approach integrating mechanical and electrical designs is presented in this paper. The EUC was designed around an architecture that incorporates a programmable brushless motor controller derived from the 100V/250A variant of the open-source VESC project. The controller was designed to support a maximum phase current of 300A and a maximum battery current of 120A. Real-time balance control is achieved using an inertial measurement unit (IMU) to measure pitch angle and angular velocity. A closed-loop proportional–integral–derivative (PID) control algorithm processes sensor data and regulates motor current to implement balance and acceleration. It uses a 24s battery configuration with a maximum operating voltage of 100.8 V and EVE 40PL “tabless” 21700 lithium-ion cells. The robust aluminum frame used in the design improves its structural reliability while maintaining manufacturability and cost efficiency. Additionally, a modular accessory system was employed to enhance utility, including features such as storage integration, ergonomic improvements, and customizable external components. Computer-aided design tools, specifically Fusion 360, were used extensively to model the system and evaluate component integration. Electrical subsystems, including an LED lighting system and power distribution, were designed and validated through schematic development. Analytical modeling and subsystem validation indicated that the design met all its intended performance objectives. The maximum speed was estimated to be around 43mph / 70kmh. It weighs about 35kg and has a capacity exceeding 140kg. A road test of the final design was successfully performed.

Introduction

The text presents the design and development of a self-balancing electric unicycle (EUC) intended primarily for short-distance urban transportation. The research focuses on creating a vehicle that is affordable, portable, safe, reliable, maintainable, and environmentally friendly.

• Electric unicycles offer an alternative to conventional vehicles for urban commuting, particularly for students and short-distance travelers. They produce very low direct emissions, reduce traffic congestion, require little space, and can provide physical benefits by improving balance and core strength.
• Despite their growing popularity, existing EUCs have limitations including high cost, poor repairability, excessive use of plastic, proprietary components, limited terrain adaptability, safety concerns, and lack of customization.
• Safety is a major concern because loss of balance is a common cause of injuries. Therefore, the proposed design emphasizes self-balancing control, structural strength, visibility, and user-friendly features.
• The proposed EUC operates as a closed-loop electromechanical system. Gyroscopes and accelerometers in an IMU continuously monitor rider movement and orientation. A microcontroller processes this information and controls the motor to generate corrective torque and maintain balance.
• The main electrical components include a brushless DC motor, lithium-ion battery pack, gyroscopic sensors, accelerometers, microcontroller, motor controller, LED lighting, and voltage regulation circuitry.
• The mechanical structure uses a strong and lightweight aluminum frame, while stainless steel is used at high-stress locations. ABS and TPU 3D-printed components are used for protective housings, vibration damping, and other external components.
• Fusion 360 is used to develop and refine the CAD models. The frame is subsequently analyzed using ANSYS to identify stress concentrations and verify structural behavior under expected loads.
• The design considers important operating loads such as rider weight, acceleration, braking, turning, and external impacts. Iterative redesign is used to reduce stress concentrations and improve structural integrity.
• The battery system uses 21700 lithium-ion cells, selected because they provide higher continuous discharge and power capabilities than 18650 cells. The cells are spot-welded using nickel connectors and integrated into a custom 3D-printed battery enclosure.
• The battery enclosure is positioned carefully to achieve appropriate weight distribution and a low center of gravity, which is important for maintaining self-balancing stability.
• Additional components include a mudguard and kickstand assembly, aluminum pedal spacers, a protective cover plate, accessory mounting points, and provisions for future additions such as a seat or storage rack.
• The design also incorporates LED front and rear lighting to improve visibility and safety in urban environments.
• Special attention is given to thermal management, cable routing, component accessibility, weather protection, and modularity, making the vehicle easier to maintain and customize.

Conclusion

This project successfully demonstrates the design and development of a self-balancing electric unicycle that addresses key limitations found in existing personal electric vehicles. By integrating mechanical, electrical, and control systems, the design achieves a balance between performance, durability, and usability. The use of an aluminum structural frame improved strength and reliability, while the high-voltage electrical system enabled efficient power delivery. The incorporation of a programmable controller with real-time feedback allowed the system to maintain balance and respond dynamically to user input. In addition to technical improvements, user-centered design is emphasized through the development of customizable features and ergonomic enhancements. This approach differentiates the design from existing solutions and highlights the importance of considering both engineering performance and user experience. Analytical validation and subsystem development indicated that the design met all its intended objectives. The final prototype was road-tested and was found to operate successfully. Our system can draw about 8.8KW out of the battery, with the limit being the motor controller. The maximum speed was estimated to be about 43mph / 70kmh based on the motor Kv (velocity constant), the tire diameter and the battery voltage. It weighs about 35kg and has a capacity exceeding 140kg. Advancements in battery technology are expected to enhance performance, reducing charging times, and extending battery life. While the current design demonstrates strong potential, several areas can be improved in future development phases. PID tuning can be refined further for smoother and more responsive balancing behavior. The development of external housing and accessory integration features can be improved further. Heat dissipation for the battery and controller systems can be improved for better thermal management. Implementing a fully functional display system and user controls will make it a more user-friendly mode of transportation. Future work may also include additional features such as suspension systems for improved ride comfort, smartphone connectivity and app integration, GPS tracking and real time monitoring and expanded modular accessory systems. Overall, this project provides a solid foundation for future development and highlights the potential for improved, user-focused micro-mobility solutions.

References

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Copyright

Copyright © 2026 Evan Kharlamb, Aneysies DeMore, David De la Cruz, Aliana Jimenez-Mcoy, Sara Bernabe, Graham Werner, Damodaran Radhakrishnan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.