A Self-Balancing Tandem-Wheel Mobile Robotic System Using Differential Propeller Thrust for Active Roll Stabilization

Maintaining upright stability in tandem-wheel robotic systems is particularly challenging during stationary and low-speed operation, where steering-induced stabilization and gyroscopic effects become limited. Also, alternative mechanisms such as reaction wheels, control-moment gyroscopes, and movable balancing masses can increase mass and mechanical complexity. To address these limitations, this paper proposes an elevated, vectored differential-propeller-thrust approach for active roll stabilization and presents the design, prototyping, and experimental validation of a self-balancing tandem-wheel mobile robotic system employing the proposed principle. Two laterally oriented ducted propeller fans are mounted above the vehicle’s center of mass to increase the available roll-moment arm, while thrust vectoring provides an additional contribution to the corrective rolling moment. The system integrates a perpendicular drivetrain, front-wheel steering mechanism, inertial sensing, wireless communication, and a real-time proportional–integral–derivative (PID) controller utilizing direct gyroscope roll-rate feedback. The system is characterized through geometry-based roll-moment and dynamic analyses, including open-loop pole analysis and a Routh–Hurwitz assessment of the PID-controlled roll dynamics. A Python-based supervisory interface provides wireless command generation, real-time telemetry visualization, and data logging. Experimental evaluation includes static stability, dynamic roll-reference tracking, and variable-speed driving-performance tests. The analytical results identify an open-loop unstable upright equilibrium and reveal the mechanical and actuator parameter conditions for local asymptotic stability under PID-controlled differential thrust. The results of the experiments demonstrate effective upright stabilization, accurate roll-reference tracking, smooth differential-thrust allocation, and reliable attitude regulation during stationary and low-speed operation. The principal contribution is the development and experimental demonstration of an elevated, vectored differential-thrust stabilization architecture for active roll control of a slender tandem-wheel robotic platform, providing a foundation for further development of dynamically stabilized single-track robotic systems.