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Motion Simulation Simulations, Analysis, Model & Full-Scale Testing VT Maritime Dynamics, Inc.'s (MDI) experience in motion simulation and control started with the development of frequency and time domain motion simulations of surface effect ships operating in waves in support of the U.S. Navy Surface Effect Ship Progream. Over its 30 year history, these capabilities have been refined and extended in support of the company's developments of ride control systems for monohulls, catamarans, SWATHs and Trimarans.
MDI can provide an analysis of a vessel's motion and assess the requirement for the stabilization of pitch, heave, roll, and yaw motions by means of trim tabs, interceptors, fins, T-foils, rudders or any similar control device. The programs predict the statistical properties of a vessel's motions with and without active ride control while the vessel is running at any heading relative to a unidirectional random seaway. The MDI simulation program first models the bare hull and simulates the design's uncontrolled state. The predicted uncontrolled motions can be compared to model test results to validate the simulation program. At this time adjustments to the mathematical model are made, if necessary. Next using the active roll, pitch and yaw control devices driven by an MDI controller, the motions are predicted for the same sea conditions. A technical memorandum summarizing the results of the simulations and discussing any design recommendation for improving seakeeping or directional control problems is provided to the customer. The results can be presented in graphical presentation fo the standard deviation of heave, pitch, roll, sway and yaw motions, as well as vertical and lateral accelerations at customer selected locations. The vertical and lateral acceleration results may be used to calculate the Motion Sickness Incidence (MSI) and Motion Induced Interruption (MII). In addition, Response Amplitude Operators (RAO) of the vessel motions can be presented.
Estimations of the control surface resistance and power requirements are also available. If ride control is deemed necessary, a technical specification and quotation of the recommended system is provided. MDI simulation programs have been validated against both model and full-scale test data both with and without active ride control for a variety of hull forms.
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