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Analysis of the effects on the pitching, rolling and yawing rate of a v-tail configured quadcopter
Get PDFMany different projects have been focused on multirotor aircraft, especially on quadcopters, but there are only a few papers relating to the dynamic effects on quadcopters with tilted motors. In this paper, a quadcopter has been modelled to allow flight simulation under differing motor tilt angle configurations. The simulation has also been validated by building a quadcopter of known physical attributes and with on-board instrumentation and telemetry to log its attitude and motor control inputs (PWM signals). The conversion from a PWM signal to the rpm was achieved by determining the relationship between the PWM signal and the thrust generated. Both of these parameters being recorded on a test bench. Thrust is calculated for each motor individually, since the angled motors generate different advance ratios and hence different thrust coefficients. The main focus of this research was on the effect of the different coefficients and the thrust components acting in the x-y plane of the quadcopter body frame
Design and Development of MIMO Antennas for WiGig Terminals
Get PDFThis article presents a design for high-gain MIMO antennas with compact geometry. The proposed design is composed of four antennas in MIMO configuration, wherein, each antenna is made up of small units of microstrip patches. The overall geometry is printed on the top layer of the substrate, i.e., Rogers RT-5880 with permittivity of 2.2, permeability of 1.0, dielectric loss of 0.0009, and depth of 0.508 mm. The proposed design covers an area of 29.5 × 61.4 mm2, wherein each antenna covers an area of 11.82 × 25.28 mm2. The dimensions of the microstrip lines in each MIMO element were optimized to achieve a good impedance matching. The design is resonating at 61 GHz, with a wide practical bandwidth of more than 7 GHz, thereby covering IEEE 802.11ad WiGig (58–65 GHz). The average value of gain ranges from 9.45 to 13.6 dBi over the entire frequency bandwidth whereas, the average value of efficiency ranges from 55.5% to 84.3%. The proposed design attains a compact volume, wide bandwidth, and good gain and efficiency performances, which makes it suitable for WiGig terminals
Direct measurement of current derivative using a delta-sigma modulator for Sensorless Traction Motor Control
Get PDFThis paper discusses a new method of direct measurement of the current derivative applied to determine an electric motor inductance required for efficient and reliable control of sensorless AC electric drives. The method is based on the measurement of the voltage drop across a calibrated inductor implemented into the power circuit of the motor drive inverter. In order to increase accuracy and reduce transients and oscillations the measured voltage drop is processed using a delta-sigma modulator. The data stream generated by the modulator is then transferred to a microcontroller supported demodulation for further processing and filtering. The paper also presents the results of experimental investigations of three different shunt inductors. The results demonstrate a high accuracy and noise immunity of the proposed method
Time and Frequency Domain Simulation, Measurement and Optimization of Log-Periodic Antennas
Get PDFLog-periodic antenna is a special antenna type utilized with great success in many broadband applications due to its ability to achieve nearly constant gain over a wide frequency range. Such antennas are extensively used in electromagnetic compatibility measurements, spectrum monitoring and TV reception. In this study, a log-periodic dipole array is measured, simulated, and then optimized in the 470–860 MHz frequency band. Two simulations of the antenna are initially performed in time and frequency domain respectively. The comparison between these simulations is presented to ensure accurate modelling of the antenna. The practically measured realized gain is in good agreement with the simulated realized gain. The antenna is then optimized to concurrently improve voltage standing wave ratio, realized gain and front-to-back ratio. The optimization process has been implemented by using various algorithms included in CST Microwave Studio, such as Trusted Region Framework, Nelder Mead Simplex algorithm, Classic Powell and Covariance Matrix Adaptation Evolutionary Strategy. The Trusted Region Framework algorithm seems to have the best performance in adequately optimizing all predefined goals specified for the antenna
What Do Audiences Want from a Public Art Gallery in the Digital Age?
Get PDFThis paper outlines the human-centred design approach taken to create a new analytical framework to understand audiences and establish themes, patterns and behaviours at MOSTYN, a public contemporary art gallery in Llandudno, North Wales. Wrexham Glyndwr University PhD student Clare Harding collaborated with Dr Adrian Gradinar, and Dr Mark Lochrie from Media Innovation Studio, University of Central Lancashire, to test the conceptual framework with the EDGE (Experiential Display to Generate Engagement) research project that secured Innovate UK and the Arts Council of Wales funding. EDGE applied a Human Centred Design process to MOSTYN, Wales’ foremost contemporary Art Gallery MOSTYN to investigate audience expectations of a public art gallery in the digital age. EDGE was designed to help MOSTYN define their purpose as a public art gallery in the face of rapidly developing, culturally competing technologies. Phase one of the project used design thinking and iterative processes to explore new and authentic ways in which MOSTYN can co-design their visitor experience with audiences. Phase two, from April 2019, will use findings to build a digital interface within the gallery to create an interactive exhibition of digital art. This will be accompanied by a six-month engagement programme to build links with new audiences and up-skill both the general public and regional artists. The scope and limitation of the research as identified so far are discussed with a focus on how human-centred design approaches were used to create a new analytical framework. The testing of lo-fi prototypes will be discussed within the gallery setting and the insights uncovered by deployment of the framework, tools and MOSTYN’s engagement programme with a critical review of the methodological approach used and findings to date
Reduction of short circuit current using DC transmission and split-winding power transformer
Get PDFThis paper discusses a new scheme to reduce the level of fault currents in the feeder cable and power transformer windings under short-circuit conditions. The proposed scheme suggests splitting the feeder cable in two cables and connecting it to a network through two rectifier units. Therefore, the split windings of the power transformer are supplied by a six-conductor feeder using unidirectional dc current. Unidirectional magnetic flux produced by the windings are summarised in the transformer core resulting ac flux to ensure a normal transformer operation. The proposed scheme was analysed under short and open-circuit faults. It has been shown that the short-circuit currents in the cable conductors and transformer windings are reduced in 1.41 times in comparison to a conventional scheme
Efficient Global Optimisation of Microwave Antennas Based on a Parallel Surrogate Model-assisted Evolutionary Algorithm
Get PDFComputational efficiency is a major challenge for evolutionary algorithm (EA)-based antenna optimisation methods due to the computationally expensive electromagnetic simulations. Surrogate model-assisted EAs considerably improve the optimisation efficiency, but most of them are sequential methods, which cannot benefit from parallel simulation of multiple candidate designs for further speed improvement. To address this problem, a new method, called parallel surrogate model-assisted hybrid differential evolution for antenna optimisation (PSADEA), is proposed. The performance of PSADEA is demonstrated by a dielectric resonator antenna, a Yagi-Uda antenna, and three mathematical benchmark problems. Experimental results show high operational performance in a few hours using a normal desktop 4-core workstation. Comparisons show that PSADEA possesses significant advantages in efficiency compared to a state-of-the-art surrogate model-assisted EA for antenna optimisation, the standard parallel differential evolution algorithm, and parallel particle swarm optimisation. In addition, PSADEA also shows stronger optimisation ability compared to the above reference methods for challenging design cases
Current derivative measurement using closed-loop Hall-effect current sensor
Get PDFThis paper discusses a method of the current derivative measurement using a standard closed-loop Hall-effect current sensor. The proposed method can operate with PWM-driven inverters and provides the estimation of motor-phase inductances required for an encoderless or self-sensing control. The method is based on the current transformation feature of the closed-loop sensor where a sensing inductor is connected in series with the measuring resistor. The voltage drop across the inductor is proportional to the current derivative. The experimental results are demonstrated that the measurement of the current derivative can be performed under a good accuracy, though the measurement should be executed while inverter is in the steady-state condition
Experimental performance analysis of advanced layers for electronic circuit boards
Get PDFThis paper provides an experimental performance analysis of advanced layers for electronic circuit boards. The base material of the advanced layers used in the experiments is Al-5052, with the dimensions of 100mm x 20mm x 1mm. As insulating material between the base and conductor, two aluminium coatings were investigated and the surface structure and thermal conductivity of the coatings were examined. Furthermore, three electroconductive adhesives were applied onto the coatings. Initially, electrical performance is investigated and electrical components were applied onto the new surface structure. Finally, the environmental tests were performed to determine the robustness of the evaluated system
Pomegranate seed oil stabilized with ovalbumin glycated by inulin: Physicochemical stability and oxidative stability
Get PDFPomegranate seed oil is rich of conjugated fatty acids which are highly appealing for a variety of applications in food industry. In this research, ovalbumin (OVA) and ovalbumin-inulin glycoconjugates with different Maillard reaction times were used to stabilize pomegranate seed oil emulsions and their impact on physicochemical stability and oxidative stability of the products was investigated. The OVA-inulin glycoconjugate produced on 10th day of Maillard reaction has exhibited significantly
higher conjugation efficiency, lower surface hydrophobicity and lower surface tension than other glycoconjugates. The secondary conformation of OVA and conjugates determined by far-UV circular dichroism spectroscopy has remarkably changed. The reduction in intensity of Trp-fluorescence observed in glycated proteins with inulin indicated that the glycation affected partially the side chains of protein in tertiary structure through the Maillard reaction without great disruption of native structure. The emulsion stabilized by OVA-inulin glycoconjugate obtained by 10 days Maillard reaction has shown the best physicochemical stability. Compared with the OVA emulsion, the oxidative stability of the glycated OVA emulsion system was significantly improved (p < 0.05). Fatty acid profile results also confirmed that OVA-inulin glycoconjugates were able to prevent the pomegranate seed oil from oxidation. It is suggested that the inulin attached to OVA by glycation played a vital role in physicochemical stability and oxidative stability of pomegranate seed oil emulsions