Suboptimal control based output feedback assist control for flexible structures

Power assist systems have been introduced to reduce workers´ load in industrial production. The authors have studied on control systems based on the modern control (LQ control) theory for power assisted conveyance of flexible structures. However, the LQ control often requires precise state space modeling of a controlled object and an observer for estimating undetected state variables. Therefore, in general, it is not easy to apply the LQ based controller to many kinds of controlled objects. In order to overcome such a drawback, this paper introduces a practical output feedback control design method based on a simplified vibration system model, a suboptimal control theory, and a robust control system structure based on a disturbance observer and a reaction force controller. As one of the suboptimal control methods, the minimum norm method is utilized to realize a simple output feedback controller. This paper adopts a power assist cart with a one-degree-of-freedom flexible structure as a controlled object example. The effectiveness of the proposed design method is verified by experiments and their corresponding simulations.