Robust Dynamic Positioning of offshore vessels using mixed-μ synthesis modeling, design, and practice

Abstract

This paper describes a procedure to design robust controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads using H ∞ and mixed-µ techniques. The proposed method will increase operational weather window and robustness of the DP vessel and associated DP system. To this effect, practical assumptions are exploited in order to obtain a linear design model with parametric uncertainties describing the dynamics of the vessel. Appropriate frequency weighting functions are selected to capture the required performance specifications at the controller design phase. The proposed model and weighting functions are then used to design robust controllers. The problem of wave filtering is also addressed during the process of modeling and controller design. The key contribution of the paper is threefold: i) it affords system designers a new method to efficiently obtain linearized design models that fit naturally in the framework of H ∞ control theory, and ii) it describes, in a systematic manner, the different steps involved in the controller design process for DP systems operating under different sea conditions, and iii) it contains the details of simulations and results of experimental model tests in a towing tank equipped with a hydraulic wave maker.

Robust Output-Feedback Control in a Dynamic Positioning System via High Order Sliding Modes: Theoretical Framework and Experimental Evaluation

“…In whichη is the velocity of the vessel midship position expressed in the GRF, ν = u v r T ∈ R 3 is the velocity of the vessel midship position expressed in the LRF andν its accelerations in the same frame. Vectors F thrust ∈ R 3 and F env ∈ R 3 are respectively the propeller thrust forces and the environmental forces, both expressed in the LRF. The environmental force vector is composed by…”

“…To achieve enhanced performances in DP, linear robust control methods have been proposed, such as H ∞ [1], [2] and mixed-µ synthesis [3]. Despite providing robust behavior, such controllers are synthesized over linearized plants around a set of operational points, imposing a large amount of workload when determining tuning parameters.…”

Network-Based T–S Fuzzy Dynamic Positioning Controller Design for Unmanned Marine Vehicles

“…Note that sampler-to-controller and controller-to-actuator network-induced characteristics are taken into full consideration in closed-loop systems (16) and (19). If one considers only controller-to-actuator network-induced characteristics, the global dynamics of the observer in (18)…”

“…By using multiple unidirectional tugboats, robust dynamic positioning of an unactuated surface vessel was studied in [17]. In [18], robust controller design for dynamic positioning of ships and offshore rigs using H ∞ and mixed-µ techniques was considered. A novel continuous robust controller for dynamically positioned surface vessels with added mass terms was constructed in [19].…”

Fault Diagnosis Observer and Fault-Tolerant Control Design for Unmanned Surface Vehicles in Network Environments

“…Under the mode of completely autonomous operation, some problems are accompanied by characteristics of completely unmanned and autonomous operation of USVs. A robust controller for ship dynamics and offshore drilling platform positioning had been designed in [26]. Reference [27] had proposed a robust nonlinear coordinated control law for ship dynamic control system under unknown input saturation and time-varying disturbances.…”