Path Following Control Of Underactuated AUVs Based On ADRC

An underactuated autonomous underwater vehicle’s (AUV) actuating mechanisms areusually designed as a combination of rudders, propellers and wings. The propellers can offerthe power of the linear surge motion, and the sway movement and the heave movement canbe achieved by the control of rudders and wings. The underactuated AUV’s motion is highlynon-linear and strong coupling, and its working condition is easily disturbed by the oceancurrent and the signal’s transportation, which makes the underactrated AUV’s control verydifficult. Further more, in some certain tasks, such as the examination of the sub-sea oil pipes,the exploration of the sub-sea geomorphology and some military applications, we need tofind some suitable methods to ensure that the AUV can efficiently and accurately follow acertain path. So that we select the active disturbance rejection control, which is invented bythe Researcher Han Jingqing and his team from the Institute of Systems Science, ChineseAcademy of Sciences.Active disturbance rejection control (ADRC) doesn’t rely on the object’s motion modeltoo much and it can combine the internal and external disturbance of the system as one.ADRC can improve the system’s robustness and anti-interference by building Extended StateObserver and Non-Linear State Error Feedback. ADRC has been successfully applied in anumber of areas so far.In this paper, we focus on the research of the underactuated AUV’s path following basedon ADRC. Firstly, we build the AUV’s six-degree-of-freedom motion model according to thetheories of Newtonian mechanics, rigid body motion mechanics and fluid mechanics andsimplify the motion model by the plane assumption; Secondly, we build a suitable pathfollowing error equation based on the Serret-Frenet coordinate system, and use thesecond-order ADRC to design the path following controller in horizontal plane and thevertical plane for a certain underactuated AUV; Thirdly, we use S-function to achieve ADRCin MATLAB/Simulink; Finally, we make a simulation compared with the traditional PIDcontrol method.From the simulation results, we can realize that the underactuated AUV’s path followingcontroller based on ADRC can achieve the goal of path following in different disturbance, no mater the path is curve or straight. Compared with traditional PID path following controller,the controller based on ADRC is more efficient in overcoming the chattering, overshoot andother phenomena caused by disturbance.