Control Systems Engineering

Strength and stability of spherical pressure hulls with different viewport structures

The PMMA frustums applied as observation windows in the deep-sea manned cabins are vital substructures.The accurate measurement and calculation of the real displacement of PMMA frustums are importa...

Time-dependent axial displacement of PMMA frustums designed for deep-sea manned cabin based on finite element analysis

Viewport window in pressure hull is susceptible to high stress and can experience cracks at its corner. For studying the viewport behaviour at its corner a numerical analysis is carried out on the ...

Numerical and experimental study on the safety of viewport window in a deep sea manned submersible

Digital twin for ship life-cycle: A critical systematic review

Manned submersibles are important platforms for exploration and research under the oceans. One of the most important components of the manned submersible is the viewport, which develops high stresses due to the nature of its design. The basic dimensions of the viewport window and its flange are determined using ASME PVHO-1. Analysis of the viewport for given basic dimensions, shows that the corners of the low-pressure face of the viewport window and the notch regions of the flange are subjected to high stresses. Using the fillet radius method at the notch region results in stress reduction by 64%. The biological growth method helps in getting the naturally optimised shape at the corner. The use of the biological growth method for structural shape modification reduces the stress acting on the acrylic viewport by 71%. The same method applied to the flange notch region reduces its sharpness and the stress there by a considerable amount. This also helps in increasing the number of cycles of operation.

Structural analysis of spherical pressure hull viewport for manned submersibles using biological growth method

Steering ship models are important for the study of autonomous ship manoeuverability and design of ship motion control system. It is always a difficult task to find the mathematical model by first ...

Steering model identification and control design of autonomous ship: a complete experimental study

This paper presents an hardware-in-the-loop (HIL) simulation system tool to test and validate an autonomous free running model system for ship hydrodynamic studies with a view to verification of the code, the control logic and system peripherals. The computer simulation of the plant model in real-time computer does not require the actual physical system and reduces the development cost and time for control design and testing purposes. The HIL system includes: the actual programmable embedded controller along with peripherals and a plant model virtually simulated in a real-time computer. With regard to ship controller design for ship model testing, this study describes a plant model for surge and a Nomoto first order steering dynamics, both implemented using Simulink software suit. The surge model captures a quasi-steady state relationship between surge speed and the propeller rpms, obtained from simple forward speed towing tank tests or derived analytically. The Nomoto first order steering dynamics is obtained by performing the standard turning circle test at model scale. The control logic obtained is embedded in a NI-cRIO based controller. The surge and steering dynamics models are used to design a proportional-derivative controller and an LQR controller. The controller runs a Linux based real-time operating system programmed using LabVIEW software. The HIL simulation tool allows for the emulation of standard ship hydrodynamic tests consisting of straight line, turning circle and zigzag to validate the combined system performance, prior to actual for use in the autonomous free-running tests.

https://publications.drdo.gov.in/ojs/index.php/dsj/article/download/14926/7322

Anantha V. Subramanian

Papers

Structural analysis of spherical pressure hull viewport for manned submersibles using biological growth method

Steering model identification and control design of autonomous ship: a complete experimental study

Hardware in the Loop Simulation and Control Design for Autonomous Free Running Ship Models