| The auto-rudder is the indispensable part to the ship. With the increasing need of safety navigating and service, demand of people to auto-rudder improves gradually. Hydraulic control system had the advantage of high response speed, wide frequency band, large stiffness, strong ability to resist interference, high power-weight rate and high torque-inertia rate of etc. It have been extensive used in the transfer function of auto-rudder. The Electro-hydraulic control servo unit of ship is the core part of auto-rudder, which links the rudder and operate device. It operates the control single and feedback control. This paper analyzed the output error of Electro-hydraulic control servo unit, made the suitable control plan, and give some advise to the afterward study.This paper analyze the characteristics of 3 port valve and 4 port valve, made a choice to the valve of Electro-hydraulic control servo unit. Consider the valve wick's axial motion. Study the fiction force, flow force and the force of spring reply, build the force balance equation and the motion equation. Build the mathematics model. Then do the simulations to the system with Matlab. Analyze the frequency domain characteristics and time domain characteristics of system. And analyze the stable of the model determined by Routh criterion. After that, analyze the Steady-State Error and static error of system, to know the weak part of system.Aiming at characteristic of the system, choose the suitable control plan. The PID control plan and fuzzy control plan are adopted an outlined, then combine the two plans as Fuzzy-PID. Design the Fuzzy-PID controller to control the system. Then use the different kind of signal to simulate the system. The result shows, in the different situation, the Fuzzy-PID decrease the error of system, increase the response time, and it has better control function then traditional PID. |
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