Ship Fuzzy Track Keeping Controller System Design And Simulation

Autopilot has become an indispensable one of the important equipment of modern ship. With the rapid development of the global shipping industry, the demand of autopilot is becoming bigger and bigger. Track keeping control is one of the main functions of the autopilot function, especially for long ocean voyage. Track control autopilot has important significance, in reducing the seafarer’s labor intensity, improving efficiency and increasing security. So researching and designing a track keeping controller with good control performance, low dynamic steering frequency and strong anti-interference ability is very necessary.In this paper, it uses indirect track keeping control method. The outer loop of track keeping control is based on LOS algorithm to calculate the ship heading angle needed to keep the track; the inner loop of track keeping control selects fuzzy control as the control strategy. By using fuzzy control advantage of the requirements of the original model accuracy not high, having higher robustness to disturbances and parameter changes and easy to understand, this paper finally designs a ship track control system of good control performance, low dynamic steering frequency, strong anti-jamming capability.LOS algorithm in N.K Haled’s improvements already has the characteristic of quickly reaching the track, but between the track sections, the ship in large turning angle changes will have a large flare phenomenon because of fixed advance distance. For this, this paper designs an improved LOS algorithm, finally achieving the purpose of small flare between the track sections.The fuzzy controller’s vibration problem in stability control stage is a key problem for controller design. Aiming at this problem, design improvements do in the two aspects in this paper. At first, this paper puts forward a kind of modified fuzzy membership functions of expansion of fuzzy input variables and output variables in the partition "Z". This improvement strategy makes the sensitivity of the controller under the small input signal reduced, which significantly reduces vibration, problem within the stability control, and also makes the stationary time before vibration extended. The other improvement is a "self-damping type fuzzy controller". Self-damping strategy is to use the output value before to influence the output value of the current time. Under the action of this self-damping strategy, The vibration problem in the stability control of the fuzzy controller is solved completely.Simulation results show that through the above three improvements, the eventual fuzzy track keeping controller has the characteristics of small tracking error, smooth course changing and without vibration in stability control stage.