Relationship between positive position feedback and output feedback controllers

The vibration control of structures may be approached in many ways. Often a robust controller is difficult to design as spillover from modes not considered in the controller design can cause the closed loop system to be unstable. One great advantage of positive position feedback (PPF) control is that the frequency response of the controller rolls off quickly, making the closed loop system robust to spillover. Unfortunately methods to design a PPF controller are not as advanced as other approaches in the control literature. This paper shows that a PPF controller may be formulated as an output feedback controller, and both centralized and decentralized controllers are considered. Optimal control methods are used to demonstrate how control design algorithms for output feedback systems may be used to design PPF controllers. The method is demonstrated using a single-degree-of-freedom system.