小型FRP船舶夜間導航控制

VISUAL GUIDANCE AND CONTROL OF A SMALL FRP BOAT IN THE NIGHT TIME

本文主旨在以航海人員慣用之前後疊標視覺導航概念，研究在夜間能見度受限之環境下使用影像處理技術並配合船舶自航控制器，用以導引小型玻璃纖維（FRP）船舶自動行駛於進港航道上。為了使船舶能提早駛於航道上，本文提出前後疊標視覺導航法之改良式計算法,並驗證改良法之船舶軌跡收斂改善效果。實驗中增加旋轉機構用以提升CCD攝影機之可視角度範圍，提升機器視覺之導航疊標追蹤能力避免目標物出鏡，強化系統抗風、流干擾之能力，以避免導航用之影像資訊中斷導致船舶暫時失控。實驗流程乃以船艏所架設之一般型CCD攝影機擷取能見度受限之夜間環境岸上影像，透過影像處理程序進行HSV篩選與感興趣區域（RoI, Region of Interest）之影像選取，以濾除背景干擾光源進而擷取正確之導航疊標，並將解算出的疊標質心應用至前後疊標導航法。實驗進行採用原始及改良式疊標導航法解算出航向修正量，並配合模糊與內模式控制架構設計之自航控制器，輸出適當舵角命令而將船舶自動導引於航道上。經先期作業測試歸納出紅色LED光板為夜間環境中較易辨識之目標，LED光板小尺寸之特性亦可減少質心計算偏差量。實驗結果顯示，改良式參考航向角修正量計算法則所解算之角度較原先之影像導航法修正量為大，而且較符合真實操船行為，可確保船舶於較早的時機將船位修正至航道上。 This work adopts the popular concept of visual guidance scheme practiced by the mariners, namely, the fore-aftleading mark as the guiding aid and uses the image process technique along with autopilot to guide the FRP (FiberReinforced Plastic) boat towards a prescribed straight water channel. In order to have the boat steer to the leading lineearlier, a modified algorithm of fore-aft leading mark guidance method is proposed and improvement of the shiptrajectory convergence rate is verified via experimental studies. Use of a rotating stand; hence, improves the field of view of the CCD camera lessens the oscillating problem caused by sea disturbance. Moreover, it can prevent loss sightof the target to ensure the boat is continuously under visual guidance and control. An image processing unit mountedon the bow of the boat is used in capturing a set of targets placed on the shore. Proper thresholds of HSV (Hue,Saturation, and Value) are set and the RoI (Region of Interest) scheme is adopted during the image processing processto enhance identifibility of the leading mark. Moreover, filtering of the background light source disturbance isconsidered. The reference heading angles are calculated by two types of fore-aft leading mark guidance methods andfed into the fuzzy logic autopilot and the Internal Model Control (IMC) autopilot to steer the boat towards the leadingline. Experimental studies indicate adoption of red LED (Light-emitting Diode) improves target recognition possibility,and the small size nature of the LED also reduces the error range of the computed center of leading mark as comparedwith color canvas targets. Specifically, the reference heading angle calculated by the proposed modified algorithm offore-aft leading mark guidance method is larger, thus, reduces the time of convergence to the leading line and betterresembles the real maneuvering behavior.