Design And Implementation Of Two-wheeled Self-balanced Robot Based On Mindstorms NXT

Two-wheeled self-balanced robot is a kind of simple robot which belongs to wheeled mobile robot. It is also a non-linear, multivariable, strong coupling and natural instability system. Because it needs efficient control methods to keep itself balanced, two-wheeled self-balanced robot has become typical device to test a variety of algorithms. It has received many attentions all over the world and become one of the most challenging topics since 1980s.In this paper, two-wheeled self-balanced robot is built by LEGO Mindstorms NXT set, and the whole control systems are designed based on NXT-G. As two-wheeled self-balanced robot and the traditional inverted pendulum share common features, the original system can be simplified as a two-wheeled inverted pendulum. The kinetic model of the system can be set up by Lagrangian analysis. To achieve the state-space equations of the system, the kinetic model has to be linearized near the balanced points. The linearized system is the theoretical basis for the next strategy controls and algorithm researches.The original open-loop system is controllable, observable and unstable. In this paper, two control methods are applied to make the unstable open-loop system stable and closed. They are linear quadratic optimal control and state feedback control with a asymptotical state observer. To test these two methods, control systems are simulated in the Simulink. The results of the simulations turn out to be that these two methods can ensure the stability of two-wheeled self-balanced robot.