Continuous time state-space model identification with application to magnetic bearing systems

This thesis presents the identification of continuous time linear multi-variable systems using state-space models. A data-driven approach in realization by the subspace methods is carried out in developing the models. In this thesis, the approach by subspace methods is considered for both open-loop and closed-loop continuous time system identification. The Laguerre filter network, the instrumental variables and the frequency sampling filters are adopted in the framework of subspace model identification. More specifically, the Laguerre filters play a role in avoiding problems with differentiation in the Laplace operator, which leads to a simple algebraic relation. It also has the ability to cope with noise at high frequency region due to its orthogonality functions. The instrumental variables help to eliminate the process and measurement noise that may occur in the systems. The frequency sampling filters are used to compress the raw data, eliminate measurement noise so to obtain a set of clean and unbiased step response data. The combination of these techniques allows for the estimation of high quality models, in which, it leads to successful performance of the continuous time system identification overall. The application based on a magnetic bearing system apparatus is used to demonstrate the efficacy of the proposed techniques

Performance Measure Of Some Subspace-Based Methods For Closed-loop System Identification.

This paper presents some of the methods under subspace-based family to perform closed-loop system identification. Three methods have been observed; those are the ORT method, MOESP method and CCA method

Effect of Machining Parameters on Surface Quality of Aluminium Puncher for Microchannel Fabrication Using Micro Cutting Process

Precision and surface finish plays an important role in modern industry. Both of these elements are more challenging to achieve in micro-sized machining due to their extremely small size and ease of damage. The quality of surface roughness and accuracy is directly influenced by the machining parameters used. The present work involves a detailed experimental analysis of surface quality for microchannel fabrication. This experiment was formed using the Response Surface Methodology (RSM) method by using three main machining parameters namely spindle speed (r/min), feed rate (mm/min), and depth of cut (µm) to produce an Aluminium microchannel puncher. The results of the study show that the best surface roughness is obtained by the combination of the following parameters; spindle 14,000 r/min, feed rate of 90 mm/min, and depth of cut 50 µm. This study concludes that the surface roughness of Al6061 steel is greatly influenced by two main parameters, namely depth of cut and feed rate

Variable Gain Super Twisting Sliding Mode Control (VGSTW) application in longitudinal plane of Autonomous Underwater Glider (AUG)

904-913This paper presents a robust control design using variable gain super twisting sliding mode control application in Autonomous Underwater Glider (AUG). AUGs are known as underactuated systems and very nonlinear in nature make difficult to control. The controller is designed for longitudinal plane of an AUG that tracks the pitching angle and net buoyancy of a ballast pump for nominal system, system in existence of external disturbance and parameter variations in hydrodynamic coefficients. The Lyapunov stability theorem has proved that the proposed control law is satisfied the stability sufficient condition. The simulation results have shown that the proposed controller has improved the transient response, reduced steady error and chattering effects in control input and sliding surface in all cases

Variable Gain Super Twisting Sliding Mode Control (VGSTW) application in longitudinal plane of Autonomous Underwater Glider (AUG)

This paper presents a robust control design using variable gain super twisting sliding mode control application in Autonomous Underwater Glider (AUG). AUGs are known as underactuated systems and very nonlinear in nature make difficult to control. The controller is designed for longitudinal plane of an AUG that tracks the pitching angle and net buoyancy of a ballast pump for nominal system, system in existence of external disturbance and parameter variations in hydrodynamic coefficients. The Lyapunov stability theorem has proved that the proposed control law is satisfied the stability sufficient condition. The simulation results have shown that the proposed controller has improved the transient response, reduced steady error and chattering effects in control input and sliding surface in all cases

Environmental Factors and Students\u27 Learning Approaches: a Survey on Malaysian Polytechnics Students

Several studies have shown the impact of environmental factors on student learning approaches. Despite the importance of such studies, studies on technical learners are few. Thus, this study aimed to determine the influence of learning environment on Polytechnics students\u27 learning approaches in Malaysia. Learning environment plays an important role in the cognitive, effective and social domains of students because it could improve students\u27 learning outcomes. Learning approaches refer to the ways students deal with academic tasks that are related to learning outcomes. This study used Course Experience Questionnaire (CEQ) and Revised Two-Factor Study Process Questionnaire (RSPQ-2F) to collect the research data. Data were analyzed using AMOS Version 18. Multiple regressions were conducted to predict learning environment factors that influenced the level of students\u27 learning approaches. The result shows that effective teaching is a major factor that influences students\u27 deep approach followed by the assessment, learning resources and clear objectives

Sempadan dan pertikaian pemilikan tanah adat di Sarawak

Pertikaian pemilikan tanah adat secara jelasnya berpunca daripada tiga faktor utama iaitu status, kesahihan pemilikan dan keluasan sebenar tanah yang dimiliki. Konflik masyarakat berhubung dengan perkara tersebut boleh dikaitkan dengan cara informasi tanah diperoleh. Kebanyakan pemilik tanah adat mendapatkan informasi tanah milik mereka secara lisan iaitu melalui informasi mulut ke mulut. Hal ini akhirnya menjadi satu cabaran yang besar kepada masyarakat apabila timbul pelbagai anggapan dan intepretasi yang berbeza berkait dengan status dan kesahihan tanah adat yang dimiliki. Justeru kajian ini menelit i maklumbalas pemilik tanah adat berhubung dengan cara penentuan sempadan tanah dalam kalangan masyarakat Bidayuh di daerah Serian Sarawak. Selain itu kajian juga memberikan perhatian terhadap pertikaian persempadanan tanah adat serta impilkasinya dalam kalangan pemilik tanah adat. Maklumat yang berkait dengan tujuan kajian telah diperoleh melalui FGD serta temuselidik mendalam dengan pemilik tanah adat di kawasan kajian. Hasil kajian mendapati wujud beberapa cara penentuan sempadan dalam kalangan pemilik tanah. Sehubungan itu, dapat dirumuskan bahawa pertikaian tanah di kawasan kajian banyak didorong oleh isu status dan kesahihan pemilikan tanah yang dimiliki oleh pemilik tanah adat. Bagi mengurangkan konflik maka dicadangkan agar tanah-tanah yang ada dibuat sukatan oleh juruukur bertauliah. Apabila tanah telah disukat, pemilik tanah akan memperoleh surat hakmilik tanah yang lebih jelas dari segi status dan kesasihan pemilikan

PERFORMANCE EVALUATION OF AN IMPROVED ITU-R RAIN ATTENUATION PREDICTION MODEL OVER MALAYSIA EQUATORIAL REGION

Attenuation due to rainfall is one of the most fundamental constraints on the performance of satellite links above 10 GHz. This work presents the results of rain attenuation measurement using radar data collected from MMD and DIDM Malaysia. The results were compared with newly improved ITU-R P530-16 and four other selected tropical rain attenuation prediction models. The statistical analysis showed that ITU-R P 530-16 has significantly addressed the problem of rain attenuation underestimation prediction as presented by older version of the recommendatio

Dehydration of potato slices following brief dipping in osmotic solutions: effect of conditions and understanding the mechanism of water loss

A novel variant of osmotic dehydration, named here as post-dipping dehydration – where a material is dipped in a salt or sugar solution for a very short time followed by simple exposure to ambient conditions was explored with the aim of lowering water content of potato slices but at the same time not gain a high level of sugar/salt. The rate of water loss, which was rapid initially, was found to approach equilibrium. This paper also explored whether the water loss process could subsequently be kick started once again, by employing a multi-stage process, where each stage consisted of osmotic solution dipping followed by ambient holding of the potato slices that had reached equilibrium in the earlier stage. Water loss values comparable to conventional osmotic dehydration could be achieved thus, but with significantly lower overall solid gain (less than 50%) – which can potentially yield a significantly healthy product option

Predictive control of plug-in electric vehicle chargers with photovoltaic integration

This paper presents a model predictive control (MPC) for off-board plug-in electric vehicle (PEV) chargers with photovoltaic (PV) integration using two-level four-leg inverter topology. The PEV charger is controlled by a unified controller that incorporates direct power and current MPC to dynamically control decoupled active-reactive power flow in a smart grid environment as well as to control PEV battery charging and discharging reliably. PV power generation with maximum power tracking is seamlessly integrated with the power flow control to provide additional power generation. Fast dynamic response and good steady-state performance under all power flow modes and various environmental conditions are evaluated and analyzed. From the results obtained, the charger demonstrates less than 1.5% total harmonic distortion as well as low active and reactive power ripple of less than 7% and 8% respectively on the grid for all power flow modes. The PEV battery also experiences a low charging and discharging current ripple of less than 2.5%. Therefore, the results indicate the successful implementation of the proposed charger and its control for PV integrated off-board PEV chargers