Research On The Body Motion Control Based On The Vector Propulsion AUV

Autonomous Undersea Vehicle named AUV has a broad application prospect both in military and civilian.Because of the complexity and uncertainty of underwater environment,it has been playing an important role and replacing humans in underwater detection,underwater construction, underwater rescue,underwater salvage and so on.So it has great economic and social benefits.For the moment,the rudder is widely used to control AUV in the way that the rudder interacts with water to change the attitudes of AUV. Rudder acted as the control input of AUV has good performance in high_speed cruise.But in low_speed cruise,it has poor performance and even that it is out of control in zero_speed cruise.Besides,Rudder acted as the control input of AUV may make propeller thrust disabled when AUV is diving.The AUV gets pitching moment at the same time makes thrust failure.Otherwise,AUV must overcome the moment caused by positive buoyancy.So it is difficult to dive for AUV in low_speed in this way.For these reasons,this paper studys a kind of vector propeller.It changes the direction of thrust to provide manipulation of the force and the moment of AUV instead of the way of operating rudder.It has good performance in controling AUV’s attitudes both in high_speed cruise and low_speed cruise.In theory, it also has good performance even in zero_speed cruise.So,this kind of AUV equipped with vector propeller has good mobility both in high_speed cruise and low_speed cruise.Besides,the propeller thrust of AUV equipped with vector propeller still work when AUV is diving because the propeller is deflected downard at this moment,which increases the time of effect of thrust.Besides,the pitching moment can be improved by incresing rotating speed of propeller to overcome the moment caused by positive buoyancy.For these resons,it is easy to dive for AUV in this way.The main work and innovation of this paper is following:1. First of all,The paper makes a mathematical modeling of vector propulsion AUV.Based on the structure and working principle of vector thruster,the dissertation makes a dynamics and kinematics analysis of this kind of vector propulsion AUV,then based on the classical momentum and angluar momentum theorem,the dissertation makes a mathematical modeling of vector propulsion AUV. Based on the decoupling principle,the space motion of AUV is divided into longitudinal motion in the vertical plane and lateral motion in the horizontal plane.Otherwise, the dissertation deduces the linear equation of longitudinal motion and lateral motion in the state of cruise.2. The second,The paper makes a maneuverability analysis of vector propulsion AUV.Based on the small perturbation principle,the dissertation deduces the perturbation equation of longitudinal motion and lateral motion according to the the linear equation.And then the dissertation gets the transfer function of every motion parameters. The maneuverability analysis of longitudinal motion and lateral motion of vector propulsion AUV is studyed according to the transfer function.The manoeuvrability index of longitudinal motion and lateral motion of AUV is given in different sailing speed and compared with that in rudder propulsion AUV.The result shows that vecotor propeller AUV has more better maneuvering and is more suitable for controlling AUV in therory.3.Then,the paper does a reserch on the body motion control based on vector propulsion AUV. For the inaccuracy of mathematical modeling and the complexity and uncertainty of underwater environment,the fuzzy PID controller and the conventional PID controller have been designed for the longitudinal motion and lateral motion of vector propulsion AUV.The respond curve of depth,pitching angle and course angle in different navigation conditions have been simulated under the two control methods.Besides the dynamic performance and the perturbation resistance analysis of the system have been studyed and compared with each other under the two control methods. The results shows that the fuzzy PID controller can improved the dynamic performance and the perturbation resistance of system.