Modeling of Generic Offshore Vessel in Crane Operations With Focus on Strong Rigid Body Connections

Abstract

Abstract-Both marine surface vehicles and underwater vehicles are often equipped with cranes, robotic manipulators or similar equipment. Much attention is given to modeling of both the dynamics of marine vehicles and the dynamics of manipulators, cranes and other equipment. However, less attention is given to the interconnected behaviour of the vehicle and the equipment, even though such equipment may have a considerable impact on the vehicle dynamic behaviour, and therefore risk, or conversely, the vehicle may have a considerable impact on the equipment dynamic behaviour. With main focus on ships equipped with cranes, this paper presents a framework for modeling the interconnected dynamics of rigid body systems, based on Lagrangian dynamics. The resulting equations of motion are implemented as a bond graph template to which any subsystem of interest, such as actuators, hydrodynamics, and controllers may be interfaced. An example on how this framework can be used in order to develop a high fidelity simulator of an offshore installation vessel with a heavy duty crane is presented. This work represents the first bond graph implementation of crane and vessel dynamics where the interconnections are modeled according to true physical rigid body principles without non-physical limitations such as diagonal mass-inertia matrix.

Nonangular MPC-Based Thrust Allocation Algorithm for Marine Vessels—A Study of Optimal Thruster Commands

“…To simulate the performance of the two thrust allocation algorithms, the vessel model derived in [26] is to be utilized. This vessel model is briefly presented in section III-A in order to demonstrate the model fidelity.…”

“…The main case study presented in this work, which includes a high fidelity vessel model with all relevant auxiliary systems as the one presented in [26], provides reasonable and realistic results which is crucial when optimizing system integration such as the interaction between the measurements, the filter, the DP-controller, the thrust allocation algorithm and the local thruster controllers, as done in this work, where the thrust allocation algorithm is the main integrator between the different systems. Different key performance indicators (KPI's) such as total power consumption, position and orientation errors, and power spectral density (PSD) analysis of the thrust command outputs, are used to compare different sets of cost function weights in the thrust allocation algorithm.…”

Virtual prototyping of maritime systems and operations: applications of distributed co-simulations

“…Such systems are characterized as tightly coupled systems, and are not recommended for distribution. In [29] a generic method for combining a crane and a vessel into one single model is presented, but this reduces the modularity of the models since it is not straightforward to replace one crane design with another.…”

“…Since such control layers in real life are affected by sampling dynamics and sampling delays, the use of co-simulation works perfectly in simulating the interaction between the different parts of the total control system. One such case was studied in the ViProMa project, where the vessel model derived in [29], with the main parameters as given in TABLE III, was connected to the power plant model derived in [31]. In addition, electrical motors and propulsors, constituting each thruster, two azimuths at the stern and one tunnel thruster Upper wave spectra period 50 s Fig.…”

“…An Arduino microcontroller [39] was used as hardware and a DP control law for controlling a vessel in DP operations was implemented and uploaded to the microcontroller. In this case the focus was the interaction between the DP controller and the wave filter, hence, simplified thruster models and a static thrust allocation were implemented directly into the vessel model, the same as derived in [29]. Since a static thrust allocation algorithm is used, meaning that the main thrusters placed at the stern have fixed azimuth angles, the vessel was to keep its heading northwards during the whole study.…”