Dynamic Modeling And Simulation Of The Gas Catapult

ABSTRACT:The catapult is one of the most important equipment on the aircraft carrier, it is the guarantee and the essential factor of a heavy aircraft that can take off normally, it can greatly shorten the aircraft take-off sliding distance, to ensure the take-off speed within the prescribed displacement. The use of the modern aircraft carrier is the USA’s steam catapult, only American master all technologies of the steam catapult, and be strictly confidential to the other countries.Based on this situation, this paper proposes a new catapult, the ejection medium is the liquid nitrogen, and use the design of closed cylinder, the traction rope drives the aircraft to accelerate to the reach of take-off speed within a certain displacement. Among them, the ejection cylinder and brake equipment are the two key difficulties of the catapult, this paper focuses on the study of these two factors.Ejection cylinder is a nonlinear process in the ejection process, the aircraft’s lift changes with the aircraft speed nonlinearly, the air resistance varies with the speed of nonlinearly, the pressure changes with the speed of piston and inlet velocity of the cylinder nonlinearly, the intake rate changes with the cylinder’s pressure, the opening rate of the valve and the valve orifice’s area nonlinearly, the leakage rate changes with the cylinder’s pressure nonlinearly. Based on these nonlinear factors, we establish the nonlinear mathematical model of the ejection process, then simulate with Simulink of Matlab toolbox, reflect the specific values of these nonlinear factors and influence on the ejection by the number directly. In order to verify the validity of the mathematical model, we use AMESim to build simulation model in corresponding with the parameters of the mathematical model, then get the curve, the similarity of the both curves to judge outcomes correct or not. Then according to these correct parameters to design the structure the cylinder.The braking process of the brake hydraulic cylinder is also a nonlinear process, the discharge rate varies with the pressure of the hydraulic cylinder and valve orifice area nonlinearly, and the hydraulic oil compressibility varies with the pressure of the hydraulic cylinder nonlinearly, so the braking acceleration is nonlinear. According to the nonlinear factors, we can establish the mathematical model of the braking process, and build the simulation model in Simulink, and then use AMESim to build model to check the results of Simulink, and then get the parameters of the structure of hydraulic cylinder. The results of this paper have theoretical significance and application value for the deep research of Chinese aircraft carrier catapult.