Model Identification for Submarines in Waves
Abstract
The specific objectives of the collaboration are:1. To develop and validate theory and methods to obtain energy-based parametric models for submarine maneuvering in high sea states for use in motion prediction and control. Advanced Mobility is a critical research area under the Naval S&T Focus Area of Platform Design and Survivability. A cost effective strategy is to enhance the mobility of existing platforms through advanced modeling and control, enabling current assets to operate within larger envelopes. This proposal supports an international collaborative research effort, organized under the auspices of The Technical Cooperation Program (TTCP), on submarine maneuvering in a seaway. Under this effort, advanced modeling and control methods are being developed to improve the disturbance rejection and maneuvering performance of submarines operating near the surface. Participating organizations, in addition to Virginia Tech, include Australia’s Defence Science & Technology (DST) Group and Queensland University of Technology (QUT). The goal of the international collaboration is to critically assess the effectiveness of energy-based nonlinear control approaches for motion control of a submarine operating at periscope depth in significant waves. Energy-based nonlinear control methods leverage dynamic models that preserve and exploit the mechanical structure of the underlying system in the closed-loop. The approach can produce control laws that are effective over a much larger operating envelope than one would obtain using control laws designed for linear models. The international team is working (i) to develop a parametric model structure that faithfully represents the motion of a submarine maneuvering in a seaway but is amenable to nonlinear control design, (ii) to design a model-based predictive motion control law, and (iii) to assess the performance of this autopilot design by comparing its performance to conventional designs. Initial efforts at Virginia Tech, sponsored under ONR Grant No. N00014-14-1-0651, have produced a reduced order nonlinear model of the vessel dynamics which may be used to predict and reject wave disturbances while the vessel maneuvers at periscope depth. Efforts to develop the feedforward control strategy are now under way. However, the scope of work that was originally proposed was reduced by 50% due to budget limitations. This proposal aims to restore an important component that was eliminated from the originally proposed effort: computational fluid dynamic (CFD) analysis to support model identification. The DST Group’s Joubert platform, a subscale model of a generic submarine, serves as the example application for this effort. Some experimental data for model validation are already available for the Joubert platform; more will become available in Summer 2016 following captive model tests at the Australian Maritime College. The proposed CFD analysis will provide higher fidelity data sets (relative to strip theory or panel methods) from which to identify model parameters. Moreover, CFD analysis may reveal conditions under which the proposed model structure is inadequate. For example, certain maneuvers in given wave encounter conditions may result in complicated flow interactions that are not adequately predicted. In these cases, CFD might also suggest modifications to the model structure that can better accommodate such effects.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 23, 2016
- Source ID
- N000141612749
Entities
People
- Craig A Woolsey
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech