Browsing by Author "Ghayoor, Najafabadi Farzad."

Now showing 1 - 5 of 5

Implementation of Iterative Learning Control on a Pneumatic Actuator.
(2022) Rwafa, James.; Ghayoor, Najafabadi Farzad.
Pneumatic systems play a pivotal role in many industrial applications, such as in petrochemical industries, steel manufacturing, car manufacturing and food industries. Besides industrial applications, pneumatic systems have also been used in many robotic systems. Nevertheless, a pneumatic system contains different nonlinear and uncertain behaviour due to gas compression, gas leakage, attenuation of the air in pipes and frictional forces in mechanical parts, which increase the system’s dynamic orders. Therefore, modelling a pneumatic system tends to be complicated and challenges the design of the controller for such a system. As a result, employing an effective control mechanism to precisely control a pneumatic system for achieving the required performance is essential. A desirable controller for a pneumatic system should be capable of learning the dynamics of the system and adjusting the control signal accordingly. In this study, a learning control scheme to overcome the highlighted nonlinearity problems is suggested. Many industrial processes are repetitive, and it is reasonable to make use of previously acquired data to improve a controller’s convergence and robustness. An Iterative Learning Control (ILC) algorithm uses information from previous repetitions to learn about the system’s dynamics. The ILC algorithm characteristics are beneficial in real-time control given its short time requirements for responding to input changes. Cylinder-piston actuators are the most common pneumatic systems, which translate the air pressure force into a linear mechanical motion. In industrial automation and robotics, linear pneumatic actuators have a wide range of applications, from load positioning to pneumatic muscles in robots. Therefore, the aim of this research is to study the performance of ILC techniques in position control of the rod in a pneumatic position-cylinder system. Based on theoretical analysis, the design of an ILC is discussed, showing that the controller can satisfactorily overcome nonlinearities and uncertainties in the system without needing any prior knowledge of the system’s model. The controller has been designed in such a way to even work on non-iterative processes. The performance of the ILC-controlled system is compared with a well-tuned PID controller, showing a faster and more accurate response.
Integration of distributed energy resources (Solar PV) a revenue impact study and tariff optimisation analysis for EThekwini Municipality.
(2020) Moodliar, Leshan.; Swanson, Andrew Graham.; Ghayoor, Najafabadi Farzad.
The South African energy generation sector is naturally evolving from a traditionally vertically integrated structure to a more liberalised one via the promotion of local generation. The main drivers of such a transition are the rapid drop in generation technology prices, especially solar photovoltaic (PV) and the corresponding increase in electricity prices. While this transition is unconventional for South Africa, it does bring fresh opportunities for local economic stimulation and job creation. However, as the generation becomes more localised, customers reduce their energy dependency from the network due to their ability to self-consume generated electricity. This self-consumption creates an imbalance in the recovery of network-related charges for the municipality, i.e. creating a revenue loss. The rate of localisation of energy generation will dictate the magnitude of loss for the municipality. To better understand the level of revenue loss associated with customers migrating to solar PV, a solar techno-economic model was designed and analysed with eThekwini Municipality’s unique loading and generation data. The model showed that customers were deemed feasible if their projects met the minimum Internal Rate of Return (IRR) of 15% and a maximum Simple Payback Period (SPBP) of ten years. Based on the number of feasible customers migrating to PV under various scenarios, the municipal revenue loss was quantified. The potential renewable energy (RE) that could be introduced onto the grid for each scenario was also quantified. The electricity tariff structures were optimised for each customer category within eThekwini Municipality to mitigate revenue losses. The optimised tariff structures were focussed on introducing fixed network access charges, based on the PV inverter size and a buy-back tariff for energy exported onto the grid. In instances where customers adopt a long term view for solar PV investing, and accept to calculate the IRR over 25 years, 37% of customers met the feasibility criteria. This resulted in the municipality potentially losing R1.041 billion and gaining 1343 MW of RE, should all feasible customers install solar PV. Applying generation limits as per NRS 097-2-3, resulted in a municipal revenue loss of R959 million and a RE gain of 1251 MW. Introducing RE tariffs to counteract the revenue loss, in conjunction with the generation limits resulted in only 3.9% of customers remaining feasible, with a reduced RE gain of 722 MW. Applying the NRS 097-2-3 generation limits and calculating the IRR over 10 years, resulted in 31% of customers meeting the feasibility criteria. Under these conditions, the municipality could potentially lose R 397 million and gain 684 MW of RE should all feasible customers install solar PV. Introducing RE tariffs to counteract the revenue loss resulted in zero customers meeting the feasibility criteria. The revenue losses were introduced because the current municipal tariffs recover fixed network charges via variable energy rates. Each unit of electricity offset due to self-consumption via solar PV results in fixed network costs incorrectly being offset as well, due to the nature of the current tariff design. RE tariffs were designed to remedy this anomaly. They incorporated fixed network charges and a buy-back energy rate, priced at the avoided cost. The RE tariffs have been optimised to position the municipality in a revenue neutral position as solar PV is introduced, resulting in no windfall gain or inadvertent revenue losses to the municipality.
Non-binary compound codes based on single parity-check codes.
(2013) Ghayoor, Najafabadi Farzad.; Takawira, Fambirai.; Xu, Hongjun.
Shannon showed that the codes with random-like codeword weight distribution are capable of approaching the channel capacity. However, the random-like property can be achieved only in codes with long-length codewords. On the other hand, the decoding complexity for a random-like codeword increases exponentially with its length. Therefore, code designers are combining shorter and simpler codes in a pseudorandom manner to form longer and more powerful codewords. In this research, a method for designing non-binary compound codes with moderate to high coding rate is proposed. Based on this method, non-binary single parity-check (SPC) codes are considered as component codes and different iterative decoding algorithms for decoding the constructed compound codes are proposed. The soft-input soft-output component decoders, which are employed for the iterative decoding algorithms, are constructed from optimal and sub-optimal a posteriori probability (APP) decoders. However, for non-binary codes, implementing an optimal APP decoder requires a large amount of memory. In order to reduce the memory requirement of the APP decoding algorithm, in the first part of this research, a modified form of the APP decoding algorithm is presented. The amount of memory requirement of this proposed algorithm is significantly less than that of the standard APP decoder. Therefore, the proposed algorithm becomes more practical for decoding non-binary block codes. The compound codes that are proposed in this research are constructed from combination of non-binary SPC codes. Therefore, as part of this research, the construction and decoding of the non-binary SPC codes, when SPC codes are defined over a finite ring of order q, are presented. The concept of finite rings is more general and it thus includes non-binary SPC codes defined over finite fields. Thereafter, based on production of non-binary SPC codes, a class of non-binary compound codes is proposed that is efficient for controlling both random-error and burst-error patterns and can be used for applications where high coding rate schemes are required. Simulation results show that the performance of the proposed codes is good. Furthermore, the performance of the compound code improves over larger rings. The analytical performance bounds and the minimum distance properties of these product codes are studied.
Optimal sizing for a grid-connected hybrid renewable energy system.
(2021) Sibanda, Hudson.; Ghayoor, Najafabadi Farzad.; Swanson, Andrew Graham.
Hybrid renewable energy systems (HRESs) refer to power generating systems that integrate several sources of energy, including renewables, to provide electricity to consumers. HRESs can either work as standalone or grid-connected systems. Since wind and solar have complementary characteristics and are available in most areas, they are considered as suitable energy sources to be combined in an HRES. Moreover, the maturity of technologies needed for generating electricity from wind and solar has turned them into more economical options in many locations. Many countries, including South Africa, have introduced policies and incentives to increase their renewable energy capacities in order to address environmental concerns and reduce pollutant emissions into the atmosphere. In addition, consumers in South Africa have faced the ever-increasing price of electricity and unreliability of the grid since 2007 due to the lack of sufficient electricity production. As a result, employing HRESs has gained popularity among consumers in different sectors. This research is focused on grid-connected hybrid energy systems based on solar photovoltaic (PV) panels and wind turbines as a potential solution to reduce the dependency of residential sector consumers on the grid in Durban. The aim of the research is to identify the optimal sizing of such a HRES to be cost-effective for consumers over a certain period of time. Since the energy supplied by renewable sources are intermittent and dependent on the geographical location of the system, identifying optimal sizing becomes a challenging task in HRESs. In this research, Durban’s meteorological data and eThekwini municipality tariff rates have been considered. Moreover, two artificial intelligence methods have been used to obtain the optimal sizing for different types of available PV panels, wind turbines and inverters in the market. The results have shown that the combination of PV panels and battery storage (BS) can become a profitable option for Durban area. Moreover, the systems using higher rated power PV panels can start to become profitable in a shorter lifetime. Considering BS in a system can only become a cost-effective choice if we consider a long enough lifespan for the system.
Power allocation in a QoS-aware cellular-based vehicular communication system.
(2021) Mankge, Sello Leonard.; Ghayoor, Najafabadi Farzad.
The task of a driver assistance system is to monitor the surrounding environment of a vehicle and provide an appropriate response in the case of detecting any hazardous condition. Such operation requires real-time processing of a large amount of information, which is gathered by a variety of sensors. Vehicular communication in future vehicles can pave the way for designing highly efficient and cost-effective driver assistance systems based on collaborative and remote processing solutions. The main transmission links of vehicular communication systems are vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I). In this research, a cellular-based vehicular communication system is proposed where Device-to-device (D2D) communication links are considered for establishing V2V links, and cellular communication links are employed for V2I links. D2D communication is one of the enablers of the next generation of cellular networks for improving spectrum and power utilization. D2D communication allows direct communication between user equipments within a cellular system. Nevertheless, implementing D2D communication should not defect nearby ongoing communication services. As a result, interference management is a significant aspect of designing D2D communication systems. Communication links in a cellular network are supposed to support a required level of data rates. The capacity of a communication channel is directly proportional to the energy of a transmitted signal, and in fact, achieving the desired level of Quality of Service (QoS) requires careful control of transmission power for all the radio sources within a system. Among different methods that are recommended for D2D communications, in-band D2D can offer better control over power transmission sources. In an underlay in-band D2D communication system, D2D user equipments (DUEs) usually reuse the cellular uplink (UL) spectrum. In such a system, the level of interference can effectively be managed by controlling the level of power that is transmitted by user equipments. To effectively perform the interference management, knowledge of the channel state information is required. However, as a result of the distributed nature of DUEs, such information is not fully attainable in a practical D2D system. Therefore, statistical methods are employed to find boundaries on the allocated transmission powers for achieving sufficient spectral efficiencies in V2I and V2V links without considering any prior knowledge on vehicles’ locations or the channel state information. Furthermore, the concepts of massive multiple-input multiple-output and underlay D2D communication sharing the uplink spectrum of a cellular system are used to minimize the interference effect.