Intelligent Balancing and Trajectory Tracking Control for Unicycle Robots

Unlike two-wheeled balancing robots, which are mechanically stable in one direction, unicycle robots use only one bottom wheel to maintain pitching balance, leaving the robot unable to maintain rolling balance. This study proposes an intelligent balancing control (IBC) system to address the highly nonlinear and underactuated behavior of the unicycle robot through the fuzzy control approach. The IBC system comprises three controllers: the fuzzy movement control (FMC), the fuzzy rolling control (FRC) and the fuzzy steering control (FSC). The FMC enables the unicycle robot to move at a desired speed in the longitudinal direction while maintaining balance, the FRC causes the roll angle to approach zero in the lateral direction, and the FSC controls the robot to rotate in place in the yaw direction. In addition, because the movement of bicycle robot is relatively complex, most of them only tend to simple movement patterns or linear movements. Further, this study proposes a trajectory tracking control (TTC) system using the fuzzy control approach to enable the bicycle robot to track a desired trajectory with high accuracy. Finally, the proposed control strategy is implemented using a 32-bit STM32F446RE microcontroller. Six experimental scenarios are studied to help test the robot's stability and maneuverability. The experimental results not only proved the balance of the IBC system in challenging terrain, but also proved the accuracy of the TTC system in tracking the command trajectory.