Tham khảo tài liệu 'underwater vehicles part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 7 A Survey of Control Allocation Methods for Underwater Vehicles Thor I. Fossen1-2 Tor Arne Johansen1 and Tristan Perez3 1Dept. of Eng. Cybernetics Norwegian Univ. of Science and Techn. 2Centre for Ships and Ocean Structures Norwegian Univ. of Science and Techn. 3Centre of Excellence for Complex Dyn. Syst. and Control Univ. of Newcastle 12Norway 3Australia 1. Introduction A control allocation system implements a function that maps the desired control forces generated by the vehicle motion controller into the commands of the different actuators. In order to achieve high reliability with respect to sensor failure most underwater vehicles have more force-producing actuators than the necessary number required for nominal operations. Therefore it is common to consider the motion control problem in terms of generalised forces independent forces affecting the different degrees of freedom and use a control allocation system. Then for example in case of an actuator failure the remaining ones can be reconfigured by the control allocation system without having to change the motion controller structure and tuning. The control allocation function hardly ever has a close form solution instead the values of the actuator commands are obtained by solving a constrained optimization problem at each sampling period of the digital motion control implementation loop. The optimization problem aims at producing the demanded generalized forces while at the same time minimizing the use of control effort power . Control allocation problems for underwater vehicles can be formulated as optimization problems where the objective typically is to produce the specified generalized forces while minimizing the use of control effort or power subject to actuator rate and position constraints power constraints as well as other operational constraints. In addition singularity avoidance for vessels with rotatable thrusters represents a challenging problem since a non-convex nonlinear program must be .
