欠驱动船舶路径跟踪的非线性模型预测控制

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第14卷第3期 2010年3月 船舶力学 Vo1.14 No.3 Mar.2010 

Article ID:1007—7294(2010)03-0217-11 

Nonlinear Model Predictive Controller Design for 

Path Following of Underactuated Ships 

WANG Xiao-fei a,b L1 Tie—shah .ZOU Zao-jian 一.LUO Wei—lin。山 a.State Key Laboratory of Ocean Engineering;b.School of Naval Architecture,Ocean and Civil Engineering, Shanghai Jiao Tong University,Shanghai 200030,China) 

Abstract:An analytic model predictive controller is presented for path following of an underactuated ship maneuvering along a predefined path.q3ae mathematical model of ship motion is described by HS。 ing Serret—Frenet flame and the output—redefinition is introduced.As a result,the problem of ill—de— fined relative degree is avoided,and the original single-input multiple—output(SIMO)system is trans’ formed into an equivalent single—input single—output(SISO)system.The proposed algorithm provides a systematic method to get appropriate controller parameters to guarantee the stability of the closed— loop system.Numerical simulations demonstrate the validity of the proposed controller. Key words:underactuated ship;path following;model predictive control; Serret-Frenet frame CLC number:U66 1.32 Document code:A 

1 Introduction 

Recently,path following of underactuated surface ships has received increasing attention from the control community.Path following control aims at forcing a vessel to follow a desired 

path.It is more suitable for practical implementation of the guidance and control of vehicles 

than trajectory tracking which needs a suitable virtual vehicle to generate a reference trajec 

tory.This problem has been studied extensively by using different techniques in past years. Path following control along straight lines was explored by Pettersen and Lefeber[1】.They rede— fined the output as a combination of the cross—track error and the heading angle error,and 

used a cascade approach and feedback linearization technique to control the cross——track Y and 

the heading angle converging to zero.Zhang et al【2J addressed the path following control prob— 

lem in restricted waters by using input-output linearization and sliding mode control which 

provides robustness against environmental changes.As pointed out by Do and PanI引.some con— 

Received date:2008—1 0—09 Foundation item:Supported by the National Natural Science Foundation of China(Grant No.50779033);the National Hi—Tech Research and Development Program of China(863 program,Grant No.2007AA1 1Z250); China Postdoctoral Science Foundation(Grant No.20070420101)and Shanghm Postdoctoral Scientific Program(Grant No.07R214128) Biography:WANG Xiao-fei(1 978-),male,Ph.D.candidate of Shanghai Jiao Tong Universit

y 218 船舶力学 第14卷第3期 

trollers require)raw velocity to be nonzero,thus they 

the other hand,good performances of both straight can not be used to track straight lines.On and curve path following can be achieved by introducing the Serret-Frenet framet。-5].Based on the transformation of ship kinematics to 

Sen'et—Frenet frame,some controllers for path following of underactuated ships have been proposed 

in the past few years.A path following controller was presented by Encarnaqgo and PaseoaltaJ for 

autonomous underwater vehicles in the presence of constant but unknown currents.The design 

was built on Lyapunov theory and backstepping technique.Combined the acceleration foedback approach with 3-step baekstepping technique for interconnecting subsystems,a path following 

controller was proposed by Skjetne and Fossen嘲.which can keep the ship on any feasible path. Based on Skjetne and Fossen’s work,Do and Pan[3]modified the out—redefinition to make it I1-ore reasonable.They developed state and output feedback controllers to steer an underaetuat— 

ed surface ship following a predefined path at a constant forward speed controlled by the main 

thruster in the presence of environmental disturbances. However,there are two disadvantages in the above-mentioned control algorithms.Firstly, 

the control parameters k (i=0,…,p-1)(where P is the relative degree)are chosen by numeri— 

cal experiments which are random and are lack of theory foundation,and k have no necessary 

 ̄lationship each other.Especially when P is lmge,it is dificult to choose appropriate后 to guar- 

antee the system’s stability.Secondly,as pointed out by Chen et al[6J,the control order is re— 

stricted to zero.This implies that the nonlinear system can only be approximated by Taylor—se— 

ries expansion to its relative degree.This limitation might result in the poor performance.In view of this,Chen et al[6 ̄proposed an analytic model predictive controller to solve the above—