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Design and Numerical and Dynamic Analysis of Marine Suspension System

Abbasian, Ahmad | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58073 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Khorasanchi, Mahdi; Sayyaadi, Hassan
  7. Abstract:
  8. As we know, ride comfort plays an important role in the evaluation of terrestrial vehicles. Many researchers have devoted their research to researching and improving devices to absorb shocks or eliminating of vibrations. Currently, suspension systems, including springs and dampers, are commonly used in such systems. Comparing the road surface profile with the ocean surface, we find that the raging sea level is much rougher and can easily lead to severe shocks; however, suspension systems have rarely been used in marine vehicles to increase convenience, improving the ride, stability of vessel and safety of passengers. In this research, a software code is first presented for the mathematical model developed by Zarnich to simulate the dynamic behavior of planing vessels. This software code is then validated with Friedsma's laboratory data. This mathematical model is used to generate linear and angular oscillations in planing vessels. Suspension modeling is then applied to Adams software, using the Co-simulation technology between mathematical model of planing vessel in MATLAB software and the nonlinear dynamics of simulated suspension system in Adams software. In this way, the fluctuations created in the planing vessel are induced to the suspension system by this technique. Initially, the passive model is simulated in two configurations. Next, the mathematical model of the suspension system is derived and then stabilized by a nonlinear sliding mode controller. After demonstrating the proper performance of the controller and satisfaction of control signals, the controller is applied to a nonlinear suspension model in Adams using a platform developed with Co-simulation technology. The goal is online controlling the deck oscillations. The considered model of planing vessel is Friedsma's model with dead rise angle of 20 degrees. In this particular geometry in passive state, at best case, when the ratio of velocity to squared length (v/√L=6) and wavelength to boat length ratio (λ/L=0.965), the decreasing of heave acceleration amplitude is 24.8% and pitch acceleration amplitude reduction is 37%. With the same test specification, in active mode, the amount of heave acceleration amplitude reduction is 38.46% and pitch acceleration amplitude reduction is 62.22%. In the empirical tests part, an oil damping coefficient measurement device has been constructed and the damping coefficient has been successfully measured by applying the logarithmic decrement method.
  9. Keywords:
  10. Suspension System ; Sliding Mode Controller ; Monohull planing Vessel ; Nonlinear Robust Controller ; Co-Simulation Technology ; Dynamic Analysis

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