Swing-up and LQR stabilization of a rotary inverted pendulum

In this article, we consider the swing-up and linear quadratic regulator (LQR) stabilization of a rotary inverted pendulum. A DC motor rotates a rigid arm. At the end of the rigid arm is a joint with a pendulum suspended from it. Two encoders check the degree of the rigid arm and the pendulum every 0.5 ms. This article describes a modified bang-bang control which swings the pendulum up safely and fast. In order to solve the stabilization problem, we used a linear quadratic regulator. When the user gives a large disturbance to the pendulum so that it loses its position, it quickly recovers to the upright position. Experimental results showed that the proposed bang-bang and LQR controllers can stabilize a rotary inverted pendulum system within 3.0 s from any starting point. The system also showed robustness to a large disturbance.