Abstract—A unicycle robot with an omnidirectional wheel mechanism is explained in this paper, focusing on its design and control. The proposed system combines a main driving wheel for pitch motion and a roller-based mechanism for lateral movement, allowing multi-directional movement while relying on single-wheel balance. A nonlinear dynamic model of the robot is derived using the Euler–Lagrange formulation and linearized around the upright equilibrium point to obtain a state-space representation. A Linear Quadratic Regulator (LQR) controller is designed to stabilize the roll and pitch motions simultaneously. Simulation results demonstrate fast stabilization with settling times of approximately 1.7 s for roll and 1.9 s for pitch. Experimental results on a unicycle robot confirm stable behavior with settling times of approximately 1.2 s and 1.5 s, respectively, and negligible steady-state error. The results support the effectiveness of mechanical design and control strategy for stable omnidirectional balancing.

Keywords—unicycle robot, omnidirectional wheel, Linear Quadratic Regulator (LQR), self-balancing control, nonlinear dynamics

Cite: Phankon Pinkham and Manukid Parnichkun, "Development and Balancing Control of a Unicycle Robot Using Omnidirectional Wheel," International Journal of Mechanical Engineering and Robotics Research, Vol. 15, No. 3, pp. 260-269, 2026. doi: 10.18178/ijmerr.15.3.260-269

Copyright © 2026 by the authors. 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 (CC BY 4.0).