Volume 2 Issue 4
Authors: H. Salarieh; M. T. Ghorbani
Abstract: In the current paper, the problem of path planning of the ESSO, a 190,000 deadweight oil tanker is considered. The path planning of the tanker is a challenging issue both in narrow channels due to collision possibility and in open waters where minimum fuel usage is important. To handle this problem, the vessel and its actuator dynamics in shallow and deep waters, the economy and the waypoint guidance are translated into the optimal control framework. In order to solve the resulted nonlinear constrained optimal control problem (OCP), the Gauss pseudospectral collocation method (GPCM) is used to transcribe the OCP into a nonlinear programming problem (NLP) by discretization of controls and states. The resulted NLP is then solved by a well-developed algorithm known as SNOPT. The procedure for modeling, compilation and solving of resulted OCP is done in Matlab optimal control software known as PROPT. Nonlinear optimal tracking, course-changing autopilot and way point guidance are then designed for the tanker using the proposed method. The obtained results provide fuel economy and better maneuvering performance in a low computational time.
Keywords: Optimal Control; Gauss Pseudospectral Collocation Method; Super-tanker; Path Planning; PROPT
Authors: Werneld Ngongi; Jialu Du; Athuman Mohamed
Abstract: In this paper we propose a linear matrix inequality (LMI) based fuzzy control system design for dynamic positioning (DP) system of surface ships. The stability conditions satisfying decay rate using relaxed stability conditions and theory of parallel distributed compensation (PDC) are used. The nonlinear DP system is firstly transformed into Takagi-Sugeno (T-S) fuzzy model. Then the PDC is employed to design the fuzzy control system from the T-S fuzzy model. The stability analysis used in this paper is reduced to a problem of finding a common Lyapunov function for the set of LMIs. The convex optimization method involving LMIs is applied to find a common Lyapunov function and stable feedback gains which satisfy the decay rate. Then the resulting fuzzy control system is simulated using ship parameters provided and results are analysed. Simulation results obtained show the validity of the proposed fuzzy control technique.
Keywords: Takagi-Sugeno Fuzzy Model; Linear Matrix Inequality; Relaxed Stability Conditions; Decay Rate; Parallel Distributed Compensation