A review on prognostic techniques for non-stationary and non-linear rotating systems

The field of prognostics has attracted significant interest from the research community in recent times. Prognostics enables the prediction of failures in machines resulting in benefits to plant operators such as shorter downtimes, higher operation reliability, reduced operations and maintenance cost, and more effective maintenance and logistics planning. Prognostic systems have been successfully deployed for the monitoring of relatively simple rotating machines. However, machines and associated systems today are increasingly complex. As such, there is an urgent need to develop prognostic techniques for such complex systems operating in the real world. This review paper focuses on prognostic techniques that can be applied to rotating machinery operating under non-linear and non-stationary conditions. The general concept of these techniques, the pros and cons of applying these methods, as well as their applications in the research field are discussed. Finally, the opportunities and challenges in implementing prognostic systems and developing effective techniques for monitoring machines operating under non-stationary and non-linear conditions are also discussed.

Adaptive fuzzy ship autopilot for track-keeping

A fuzzy logic based general purpose modular control architecture is presented for underwater vehicle autonomous navigation, control and collision avoidance. Three levels of fuzzy controllers comprising the sensor fusion module, the collision avoidance module and the motion control module are derived and implemented. No assumption is made on the specific underwater vehicle type, on the amount of a priori knowledge of the 3-D undersea environment or on static and dynamic obstacle size and velocity. The derived controllers account for vehicle position accuracy and vertical stability in the presence of ocean currents and constraints imposed by the roll motion. The main advantage of the proposed navigation control architecture is its simplicity, modularity, expandability and applicability to any type of autonomous or semi-autonomous underwater vehicles. Extensive simulation studies are performed on the NPS Phoenix vehicle whose dynamics have been modified to account for roll stability.

Fuzzy-Logic Based Navigation of Underwater Vehicles

Neural predictive controller of a two-area load frequency control for interconnected power system

Improved Fuzzy Autopilot for Track-Keeping

Fuzzy Autopilot for Ships Experiencing Shallow Water Effect in Manoeuvering

Automatsko upravljanje : analiza linearnih sustava

The stability analysis of nonlinear system that is harmonically linearised is given[10, 3, 11]. With the introduction of fuzzy regulator the nonlinear system consists of linear part and two nonlinear parts. The stability analysis is conducted by use of describing function method and Hurwitz stability criterion. Proportional and derivative parameters of Mamdani type fuzzy regulator gains were preliminary tuned (pre-tuned) by Cohen-Coon and Ziegler-Nichols methods [1, 13]. Stability analysis was conducted for the power system secondary load-frequency control model. The proposed stability analysis presents a good starting point for the design of fuzzy regulator for nonlinear systems.

Design of Fuzzy Regulator for Power System Secondary Load Frequency Control

Engineering procedure for approximate analytical determination of describing function of nonlinear systems with odd static characteristics is presented in the paper. Generalized mathematical expressions for determining such describing function with error estimation are given. The procedure is illustrated on determination of describing function, and corresponding error estimation, of nonlinear structure consisting of fuzzy element and typical nonlinear element.

Ljubomir Kuljaca

Papers

Improved Fuzzy Autopilot for Track-Keeping

Fuzzy Autopilot for Ships Experiencing Shallow Water Effect in Manoeuvering

Automatsko upravljanje : analiza linearnih sustava

Design of Fuzzy Regulator for Power System Secondary Load Frequency Control

Engineering procedure for analysis of nonlinear structure consisting of fuzzy element and typical nonlinear element