A stabilization control of underactuated system using sliding mode differentiator based disturbance observer

There are many studies on underactuated systems that control input number is less than output one. That system leads cost reduction and space-saving. Previously, an observer was used widely to control an underactuated system; moreover, time delay occurs because of a low-pass filter. Generally, we use a low-pass filter to obtain the derivative. Recently, Levant suggested a sliding mode differentiator that can estimate the derivative of a input signal, and its time delay is low. Therefore, a new construction of a observer using sliding mode differentiator is proposed, and we investigate how to design the gain of the differentiator. The proposed method was evaluated via a crane experiment. Furthermore, the result showed that the proposed method is effective for controlling an underactuated system.