 The proposed optimized model for the trajectory tracking control of a wheeled inverted pendulum robot, WIPR, system uses a kinematic controller to track a reference trajectory, a non-linear disturbance observer, NDO, to enhance the system's robustness to external disturbances, and an improved hierarchical sliding mode controller to control the forward rotation subsystem and tilt angle velocity subsystem separately. Simulation experiments show that the proposed method outperforms a common sliding mode control approach in terms of tracking accuracy. This article was authored by Ming Ho, Xue Dong Zhang, Du Chen, and others.