A high-speed motion control technique for inverted pendulum robots, utilizing instability and a disturbance observer, based on the Kalman filtering technique, is introduced. Inverted pendulums are basically controlled as they do not topple. Shimada et al. developed a contrary idea and presented a controller that deliberately off balanced the robot when it moved. To implement the idea, a controller was designed using zero dynamics, which was derived by partial feedback linearization. However, the control system was not robust or sufficiently reliable. Although they presented a revised method using Hinfin control law, it was complex. Shimada et al. also presented a design method for a disturbance observer using Kalman filtering. However, the technique can be applied to only straight motion. This paper extends the technique on a plane surface using three dimension model.