**6. Conclusions**

In this study, a 2D model of the Ballbot is obtained using the Euler-Lagrange equation and the decoupling method. A robust nonlinear controller based on the hierarchical SMC technique is designed for the Ballbot to control stabilizing and transferring. The capability of the closed-loop system with the hierarchical SMC is achieved using the Lyapunov function. The performance and robustness of the hierarchical SMC are examined under several tests in both simulation and experiment. The simulation and experimental results demonstrate the capabilities of the proposed controller for stabilizing and trajectory tracking.
