Siti Marhainis Othman
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Siti Marhainis Othman
Official Name
Siti Marhainis, Othman
Alternative Name
Marhainis, Siti
Othman, S. M.
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Scopus Author ID
55210362500
Researcher ID
ABF-6513-2020

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  • Publication
    Identification of ARX Model for Thermoelectric Cooling on Glass Windows
    ( 2022-01-01)
    Mohd Saifizi Saidon
    ;
    Nasrul Amri Mohd Amin
    ;
    ‘Aqilah Che Sulaiman
    ;
    Mohd Rizal Manan
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    ;
    Arith F.
    Thermoelectric cooling (TEC) is a solid-state heat pump that uses the Peltier effect to dissipate the heat generated by the electronic packaging system. TECs are widely used in aerospace, military, scientific work and industry due to small size, lack of moving parts, and ease of integration. In this study, a cooling system integrated with TEC is developed in a testing area (lecturer’s office) with the aim to reduce the temperature of the hot glass window area due to solar radiation that passes through it. This cooling system used direct TEC, for keeping the cooling temperature on the window to about 26 °C which is equivalent to an air conditioning setting temperature of 26 °C set during the experiment. This work includes experimental and modelling studies conducted on cooling systems integrated with TEC. The main target of this study is to develop a dynamic model of a cooling system integrated with TEC. The black box modelling approach in producing a mathematical model was selected based on the ARX model that corresponds to the actual dynamic state of the cooling system. The best model was finalized based on the best match on curve patterns when comparing the real and estimated models using the system identification tools in MATLAB, and also had the least error. The accuracy of the models was compared and analysed. The results showed that the 4th order of the ARX model produced a higher best fitting and standard deviation values of 78.14% and 0.030769. This system accuracy is almost within the acceptable range for most error calculations in the validation method. In addition, the ARX model is found incapable of achieving the highest fitting due to the losses from the dynamic environment and losses from the TEC itself. Still, the use of this black box model used in this study is a significant variation where system parameters can be identified even offline.
  • Publication
    Temperature control using fuzzy controller for variable speed vapor compression refrigerator system
    ( 2022-01-01)
    Siti Qurrata Ain
    ;
    Mohd Saifizi Saidon
    ;
    Siti Marhainis Othman
    ;
    Aziz A.A.
    ;
    Wan Azani Wan Mustafa
    ;
    Wan Khairunizam Wan Ahmad
    Keeping the cold chain vaccine is crucial to a stable immunisation programme; however, faulty processes may occur more frequently than are often thought in developing nations. This paper discusses the quick and accurate control process for designing fuzzy controllers for variable speed vapor compression refrigerator system. The suggested controller is based on the fuzzy logic intended to improve performance while keeping the cooler’s constant internal temperature and increasing the refrigerator efficiency. Despite the external changes such as the outside temperature change or the volume change in the refrigerator vaccine, the fuzzy logic controller is utilised to maintain the interior temperature. However, a variable speed compressor (VSC) must be used to control the thermophysical characteristics, which dramatically alter the temperature with a small pressure change. In this case, fuzzy rules of the sort developed by Mamdani are used to build up the system. The programming platforms utilised to implement the model include MATLAB, SIMULINK, and Fuzzy Logic Toolbox (FLT). The efficiency of fuzzy logic controller design membership will be compared to ensure that the refrigerator temperature is more accurate and until it achieves the best performance, maintains a temperature of 5°C, and adapts to its surroundings. From the research done, the membership 2 with load shows the near accurate temperature of 5°C with steady-state error ±1.97°C.
  • Publication
    Characteristic Study of Supercapacitor's Discharging Process Base on BLDC Motor
    ( 2023-01-01)
    Mohd Azri Abd Aziz
    ;
    Mohd Saifizi Saidon
    ;
    Muhammad Izuan Fahmi Romli
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    ;
    Al-Dolaimy F.
    ;
    Alkhayyat A.
    Energy storage has become a key issue for achieving goals connected with increasing the efficiency of both producers and users. In particular, supercapacitors currently seem to be interesting devices for many applications because they can supply high power for a significant amount of time and can be recharged more quickly than electrochemical batteries. Supercapacitors, as similar to conventional capacitors build on two plates separated by a dielectric and an electrolyte, can store more energy than conventional capacitors because they can produce two distinct layers of separated charges between plates, which are typically made of porous, carbon-based materials. The supercapacitors module serves as the power supply for the discharging process as called Energy Storages (ES). The main purpose of this research is to investigate the behaviour and properties of discharged supercapacitors. The design is created using Simulink and includes a circuit schematic and scope label. Using Brushless Direct Current Motor (BLDCM) as a load, study proposed steady state condition and dynamic state condition of BLDCM operation are investigated. With comparison to battery, preliminary finding state that value of SoC and voltage of battery higher but value of current less than supercapacitor in a certain amount of time.
      34  1
  • Publication
    Design and implementation of closed-loop PI control strategies in real-time for Linear ARMAX Models of Vapour Compression Refrigeration System using R600a Refrigerant
    ( 2022-01-01)
    Rajaie M.N.
    ;
    Mohd Saifizi Saidon
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    The objective of the research undertaken in this paper is to design a control strategy using a Linear Auto-Regressive Moving-Average Exogenous (ARMAX), which is a mathematical modelling method in real time, which to be implemented into the closed-loop Proportional-Integral controller. The ARMAX model is developed using SIMULINK tool from the MATLAB R2020a software. The Vapour Compression Refrigeration System consists of an evaporator, an expansion valve, a condenser and a compressor which was modified to a variable speed compressor. This modification is required due to the usage of R600a refrigerant that has thermophysical properties that can be described as with a slight change in its pressure will cause a considerable change in its temperature [1]. R600a refrigerant was chosen for this paper, despite the difficulty is due to it is more environmental-friendlier refrigerant compared to other types of refrigerant [2]. Two types of ARMAX model were designed, the first type of ARMAX model will have a polynomial order of na= 2, nb= 2, nc= 1 while the second type of ARMAX model will have a polynomial order of na= 2, nb= 2, nc= 2. Both types of controller were tested and compared the performance in terms of settling time, steady-state error, overshoot and peak-time. From the test conducted, it was found that the controller with the ARMAX model will have a polynomial order of na= 2, nb= 2, nc= 1 has a better overall performance.
      2  22
  • Publication
    Optimization of PD Controller based on ARMAX Model for Vapor Compression Refrigeration System using R600a Refrigerant
    ( 2022-01-01)
    Rajaie M.N.
    ;
    Mohd Saifizi Saidon
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    The research undertaken in this paper is to investigates the difference in approaches to the modelling, design and implementation of an adaptive controller tuned using Auto-Regressive Moving-Average Exogenous (ARMAX) 2,1,1 model in an environment simulated in SIMULINK, applied to a variable speed compressor vapor compression refrigeration system running R600a refrigerant. A vapor compression refrigeration system is chosen for this paper research as it’s the most commonly used type of refrigeration system in all over the world, either for domestic, commercial or industrial application. The refrigeration system consists of a condenser, an expansion valve, an evaporator and a compressor which are modified from a fixed speed compressor to a variable speed compressor. The compressor was modified to be able to accommodate the usage of R600a refrigerant. R600a refrigerant has a thermophysical properties which can roughly be define as a slight change in pressure will result in a drastic change in temperature [1]. To be able to control the pressure for R600a with precision, an optimized adaptive controller is required. For the purpose of the simulation, the refrigeration system mathematical model is simplified to a linear polynomials ARMAX model. This is to reduce the complexity of the control design strategies, which in term improve the implementation of the new controller design. The optimization of the adaptive controller design, its simplicity of implementation, speed of convergence and robustness are concluded at the end part of the paper.
      7  32
  • Publication
    Comparative study of controller performance for variable speed compressor using R600a refrigerant
    ( 2022-01-01)
    Rajaie M.N.
    ;
    Mohd Saifizi Saidon
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    R600a is a refrigerant that is more environmental-friendlier compared to other types of refrigerant (Borokinni et al. in NAŠE MORE 65:11–17, 2018). However, it required the use of a Variable Speed Compressor (VSC) in order to be able to regulate its thermophysical properties, which vary the temperature drastically with the slight change in pressure (ASHRAE: 2009 ASHRAE Handbook—Fundamentals (SI). SI edn. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., United States (2009).). In order to efficiently control the speed of VSC, three types of controllers, namely, Adaptive Proportional Controller (P-ARMAX), Fuzzy-Logic (FL) controller and Sliding Mode Controller (SMC) are studied and compared the performance of each controller. The performance of each type of controller was evaluated based on the criteria of its settling time, steady state error, control effort and response temperature. From the studied conducted, it was found that the fuzzy logic controller has the most efficient control effort between the three with an acceptable settling time and steady state error.
      1  28
  • Publication
    The ARX and ARMAX Models for thermoelectric cooling on glass windows: A Comparative study
    ( 2022-01-01)
    Mohd Saifizi Saidon
    ;
    Nasrul Amri Mohd Amin
    ;
    Aqilah Che Sulaiman
    ;
    Mohd Rizal Manan
    ;
    Siti Marhainis Othman
    ;
    Wan Azani Wan Mustafa
    ;
    Wahab N.A.
    Thermoelectric cooling (TEC), in particular, can be combined with a heat sink for local cooling, but they can also be integrated into electronic chips for point-to-point cooling. The study aims to develop a dynamic model of a cooling system integrated with TEC for glass window. The main target of this study is to develop a dynamic model of a cooling system integrated with TEC. The black box modelling approach in producing a mathematical model was selected based on the ARMAX and ARX model that corresponds to the actual dynamic state of the cooling system. The best model was finalized based on the best match on curve patterns when comparing the real and estimated models using the system identification tools in MATLAB, and also having the least error. The accuracy of the models was compared and analysed. The results showed that the 4th order of the ARMAX model produced a higher best fitting and standard deviation values of 80.23% and 0.027592 compared to the 4th order of the ARX model of 78.14% and 0.030769 respectively. This system accuracy is almost within the acceptable range for most error calculations in the validation method. Yet, this cooling system integrated with TEC is found more suitable for the 4th order of the ARMAX model when compared to the ARX model due to the noise parameter in the ARMAX model. Nevertheless, the noise order in this system is not dominant, therefore, whenever the noise order of the system in the ARMAX model is high than the second structure (nb), the number of errors is also high. In addition, the ARMAX model is found incapable of achieving the highest fitting due to the losses from the dynamic environment and losses from the TEC itself. Still, the use of this black box model used in this study is a significant variation where system parameters can be identified even offline.
      1  37