Research On The Dynamic Stability And Control Techniques Of A Submarine Emergency Ascent

The submarine is a kind of the most important military forces. Every country's navy makes an effort to develop the submarine. In the recent years, the submarine accidents happened frequently in the world. The safety of a submarine is a more interesting problem. The study on motion laws and control methods of a submarine under casualty condition is a fundamental work to solve the safety problem of a submarine. The purpose of this dissertation is to make the theoretical research and investigation on the safety of a submarine under casualty condition.At first, the physical model of the pneumatic blowing system of the submarine's ballast tanks is simplified with reason, and then through analyzing the dynamic process of the pneumatic blowing system of the ballast tanks, the mathematical models for flooding of damaged compartments and corresponding emergency blowing of the submarine are derived by means of aerodynamics, hydrodynamics and thermodynamics laws. The software MSC. EASY5 is used to simulate this system comparing with the former mathematical model simulation. The both simulation results are in agreement with practice in the submarine. The full mathematical model was developed for the submarine's emergency ascent. It provided a foundation to investigate on motion laws and control methods of a submarine blowing water ballast.In this dissertation the motion stability and bifurcation theory and its numerical methods of a nonlinear system were applied to stable state response and motion stability analysis of a submarine during emergency ascent. The stability analysis results were verified by simulations using direct numerical integrations of the fully nonlinear, coupled six degrees-of-freedom equations of motion for the submarine. The control surface deflections, excess buoyancy and speed effects on the stability of the submarine during emergency ascent show that emergency rising motion is not always restricted in the vertical plane even under port/starboard symmetric conditions. Complicated out-of-plane motions may be generated, and the submarine may lose the stability under some critical conditions. The singularity and bifurcation theory was used to explain the mechanism for these phenomena. These laws provide a theoretical basis for maneuvering and controlling submarine during emergency ascent.The motion state after taking the emergency measures of the damaged submarine is simulated. The significant results were obtained. These results will be of great help to practical maneuver and control of the submarine under flooding emergency condition and design of the automatic control system.Finally, a sliding mode fuzzy controller was developed for the submarine during emergency ascent. A new sliding mode fuzzy grey predictive controller was also proposed in order to compensate the delay of the actuators such as rudder, drainage and the pneumatic blowing system, etc. The simulation results show that the control approach not only remains robustness of sliding mode control, but also avoids the effects of chattering phenomenon, and possess better performance of the system.