Abstract
This article presents a robust control method for trajectory tracking and balancing of a ballbot with uncertainty. Since the ballbot is an underactuated system, previous studies have designed controllers using a hierarchical strategy and/or multi-loop approach. However, multi-loop control systems require several controllers and the hierarchical strategy has a local minimum problem that does not guarantee the convergence of all errors globally. To overcome these drawbacks, we introduce a virtual angle and design a sliding mode controller with a single-loop control system. As a result, the proposed controller is simple and can achieve simultaneous tracking and balancing of the ballbot. From Lyapunov stability theory, it is proven that the tracking and balancing errors of the ballbot are uniformly ultimately bounded and can be made arbitrarily small. Finally, simulation results are presented to verify the proposed control system.
Highlights
A ballbot is a mobile robot consisting of a body mounted on a spherical wheel [1]
We introduce the virtual angles that are developed for the trajectory tracking of the ballbot and design the controller using the SMC method for robustness against external disturbances
Since we focus on the controller design for trajectory tracking and balancing of the ballbot with uncertainty, considering unmeasured velocities and input saturation remains a meaningful subject for future research
Summary
A ballbot is a mobile robot consisting of a body mounted on a spherical wheel [1]. Unlike nonholonomic mobile robots, it can be moved in all directions and can be used even in a narrow space. Due to the combination of independent sliding surfaces for trajectory tracking and balancing, it has a local minimum problem that does not guarantee the convergence of all errors globally [18] This means that the ballbot may not achieve trajectory tracking and balancing simultaneously. Park: Robust Control for Trajectory Tracking and Balancing of a Ballbot To this end, a method using a virtual angle is proposed, and by using the virtual angle, trajectory tracking and balancing can be achieved with a single controller, unlike previous studies. The contributions of this article are as follows: 1) Unlike in previous studies using a multi-loop control system, it is possible to design a single controller that can simultaneously achieve trajectory tracking and balancing of the ballbot with a single-loop control system.
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