An Underactuated AUV-Oriented Region Search Method Based on Electronic Chart

In order to accomplish region search task in a boundary information known area, a global path planning method based on electronic chart suitable for underactuated AUV (autonomous underwater vehicle) is designed. Needing only for a little amount of manual labor, target region environment model is established from corresponding electronic chart, global path planning is accomplished as well. Automatically region search task aiming at geographic information collecting or object detecting is completed after the jointly execution of path tracking and terrain tracking. Firstly, based on the given task parameters, the proposed path planning method can output a comb shaped 2 DOF global path automatically making use of electronic chart. Regardless of how complex the region shape is, even a concave polygon, the algorithm can give reasonable results. Secondly, a decoupled control method (DCM) is adopted, which means velocity, heading and depth are controlled separately. The use of DCM makes it possible to accomplish the horizontal path tracking and vertical terrain tracking simultaneously. Path tracking adopts a proposed Sigmoid function based guidance control method which outputs reference heading in use of both AUV's current heading and the transverse distance deviation between AUV and path. An adaptive S-surface control method is adopted in designing the controller of executive level. The method itself owns robustness and nonlinearity and the adoption not only speeds up system response but also short overshoot, control performance is increased as a result.Last, on the premise of given path planning coverage fraction, tracking simulation experiment results show that tracking error of horizontal comb shaped path tracking guarantees full coverage in the AUV search on mission area. What's more, terrain tracking error on vertical plane meets the requirement of vertical distance for side scan sonar. In conclusion, the feasibility of the path planning algorithm is demonstrated by the combining examples in the process of method introduction. Moreover, tracking simulation test demonstrates that the designed tracking controller works stably and effectively to track both comb shaped path and varying terrain.