Research On X Rudder AUV’s Motion Control

With the increasing demand for marine resources,the application of Autonomous Underwater Vehicle(AUV)has gradually become an important instrument for humans to explore and exploit the ocean.Regarding the layout of motion actuator,compared with the cross rudder,the X-rudder has the characteristics that the lateral scale is not over-wide,the vertical scale is not prominent,and it has the steering redundancy,hence it is gradually adopted by researchers and applied to the design of new autonomous underwater robots.Compared with the AUV control of the traditional cross rudder layout,the special layout of the X rudder will give rise to many control problems different from the cross rudder,such as X-rudder steering characteristics,rudder control force allocation,and fault-tolerant control when motion actuator fails.Therefore,based on the project requirements,this dissertation sorts out,analyzes and summarizes the current research of typical X-rudder underwater installations,AUV motion control,control distribution,fault diagnosis and fault-tolerant control,and finds out the problems and challenges faced by X-rudder AUV in motion.In this dissertation,the research includes the following aspects:(1)The steering characteristics of the X-rudder AUV are analyzed and summarized.After establishing the motion coordinate system for the X-rudder AUV and the corresponding kinematics and dynamics model,a series of steering simulation experiments were performed on the X-rudder AUV.These include single rudder operation,double rudder combination operation and combined operation of four rudders at different speeds and different steering angles.In addition,according to the layout of the X rudder,the corresponding rudder size cross rudder AUV is established for comparison with the steering situation of the X rudder AUV.According to the experimental results,the motions of the single rudder,double rudder and quadruple-rudder operation carriers of the X-rudder AUV are summarized.(2)Based on the virtual angle and the Extended State Observer(ESO),a non-diagonal linkage control method for the X-rudder AUV is established.By comparing the similarities and differences with the traditional AUV control process of the cross-rudder layout,a diagonal linkage control allocation method and a non-diagonal linkage control allocation method are established for the X-rudder AUV.Based on the virtual angle,a relationship between the controller output and the actual steering angle of the X-rudder is established,thereby completing the non-diagonal linkage control process;the expansion state observer is used to eliminate the coupling problem of the X rudder during steering.In addition,in the non-diagonal linkage control process,the double rudder,triple-rudder and quadruple-rudder control allocation methods are also designed for the X rudder,and the effectiveness of the designed method is verified by simulation experiments.(3)X-rudder AUV quadruple-rudder control optimization method with Levy flight characteristics is studied.Because the X-rudder quadruple-rudder control method that relies solely on the pseudo-reverse design does not take the rudder’s own control ability during the design process into consideration,thus the rudder manipulation may be saturated causing,it difficult to ensure that the output of the X rudder is consistent with the required control force of the carrier during the movement of the carrier.Therefore,combined with the carrier characteristics of the X-rudder AUV,it is optimized with the existing Lagrangian multiplier,and the fixed-point iteration method respectively,both have some problems and cannot be universally applied to various types of X-rudders.AUV.Finally,the X-rudder quadruple-rudder optimization method with Levy flight characteristics is studied,and the effectiveness of the design method is verified by simulation experiments.(4)Fault-tolerant control based on fault compensation for X-rudder AUV reconstruction.For the three typical faults of AUV,including its locked rudder fault,servo shake fault and rudder blade missing,the modified rudder motion control matrix and two kinds of reconstruction fault-tolerant control by changing the X-rudder steering mode are studied to correct and compensate the corresponding rudder fault.And the effectiveness of the two methods is verified through simulation experiments.