Abu Bakar, Muhamad Husaini
(2017)
Hybrid Cfd-Nnarx Modelling Of Single Mrf Valve For Visual Servoing.
PhD thesis, Universiti Sains Malaysia.
Abstract
Magnetorheological fluid (MRF) actuator emerged in the last decade as a
potential system to replace electro-hydraulic servo system in precision applications. A
complete closed-loop control system is necessary to support the accuracy of the
system. Modelling of the valve is a crucial task in developing an optimal control
system for the valve, but the knowledge of fluid behaviour inside the valve channel
remains scarce. This research aims to develop a plant model of MRF actuator using
the system identification approach, where the Computational Fluid Dynamics (CFD)
result is used as an input. The plant model is then used to design a closed-loop control
system for the MRF actuator. To achieve this objective, a 3D CFD model was
developed, and a steady state analysis was run to study fluid behaviours in the channel.
Transient analysis with dynamic input was further performed to study the correlation
between the current input and the volume flow rate as an output. Neural network
nonlinear autoregressive network with exogenous inputs (NNARX) used data from the
CFD to identify the plant model of an MRF valve. The result acquired from the CFD
simulation and plant model gave good agreement with the experimental result with an
error of less than 3%. The velocity in the MRF valve reduced 85% when the current
varied from 0 to 0.8A. The hybrid CFD-NNARX model shows a small deviation from
the experimental result with an average error of 4%. As a conclusion, the hybrid CFDNNARX
has been proven useful in modelling the MRF actuator. The main
contribution of this work is the plant model of an MRF actuator, which can be utilised
as an input in controller design process of MRF actuator.
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