A smart rig for calibration of gas sensor nodes

Electrochemical gas sensors require regular maintenance to check and secure proper functioning. Standard procedures usually involve testing and recalibration of the sensors, for which working environments are needed. Periodic calibration is therefore necessary to ensure reliable and accurate measurements. This paper proposes a dedicated smart calibration rig with a set of novel features enabling simultaneous calibration of multiple sensors. The proposed calibration rig system comprises a gas mixing system, temperature control system, a test chamber, and a process-control PC that controls all calibration phases. The calibration process is automated by a LabVIEW-based platform that controls the calibration environment for the sensor nodes, logs sensor data, and best fit equation based on interpolation for every sensor on the node and uploads it to the sensor node for next deployments. The communication between the PC and the sensor nodes is performed using the same IEEE 802.15.4 (ZigBee) protocol that the nodes also use in field deployment for air quality measurement. The results presented demonstrate the effectiveness of the sensors calibration rig.Scopu

Copper nanowires and Graphene nano-composite based electrodes with high transparency and conductivity

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.In this paper, we present ITO-free hybrid transparent conducting electrodes that are based on bilayers of reduced Graphene Oxide (rGO) and Copper Nanowires (CuNWs). The unique structural features of these in-house fabricated electrodes allowed for superior performance with an optical transmittance of 84% and sheet resistance of 21.7 Ω/sq obtained, showing their potential of becoming a replacement for ITO based electrodes. The fabricated hybrid electrodes exhibited extreme stability when subjected to various environmental and durability tests. Adoption of such high performance TCEs, will lead to simple, versatile and cost effective solutions for next generation optoelectronics industry.cf201

A Resolver Angle Estimator Based on Its Excitation Signal

A resolver generates a pair of signals proportional to the sine and cosine of the angular position of its shaft. A new low-cost method for converting the amplitudes of these sine/cosine transducer signals into a measure of the input angle without using lookup tables is proposed. The new method takes advantage of the components used to operate the resolver, the excitation (carrier) signal in particular. This is a feedforward method based on comparing the amplitudes of the resolver signals to those of the excitation signal together with another shifted by π. A simple method is then used to estimate the shaft angle through this comparison technique. The poor precision of comparison of the signals around their highly nonlinear peak regions is avoided by using a simple technique that relies only on the alternating pseudolinear segments of the signals. This results in a better overall accuracy of the converter. Beside simplicity of implementation, the proposed scheme offers the advantage of robustness to amplitude fluctuation of the transducer excitation signal. © 2009 IEEE

A New Low Cost Linear Resolver Converter

A new low cost converter topology is proposed for sinusoidal position encoders. The converter enables determination of the angle from the sine and cosine signals of the encoder. When used with resolvers, the implementation of the present scheme takes advantage of the available excitation signal used to operate the device. This trigonometric reference signal is optimally used to generate an analogue signal equivalent to a digital look-up table (LUT). This enables determination of the mechanical angle without using LUT, A/D, and D/A converters. The scheme is optimized in order to achieve highest possible precision. Beside simplicity of its implementation, the proposed converter offers the advantage of robustness to amplitude fluctuation of the transducer excitation signal. The converter was implemented using ordinary low-cost analog components. The theory of operation, computer simulation, and experimental results are given

Development of energy efficient battery electric car for Shell Eco-Marathon competition - Qatar University experience

The paper reports on the participation of Electrical Engineering students of Qatar University students in Shell Eco Marathon (SEM) competition, which aims at designing and racing energy efficient vehicles. This participation has multiple objectives both for improving student technical and soft skills. Details of the design of a three-wheel car for SEM Asia 2014 race in Manila are given. Additionally, a dedicated computer-controlled test bench is developed for testing and optimizing the car design, and for training the drivers for optimum driving strategy that minimizes energy consumption. The process of car and test bench design has gone through various phases of study, modeling and simulation, optimization, and testing. Both mechanical and electrical parts of the test bench as well as the car are designed in-house. The design has to meet SEM technical and safety requirement, which guided the team till the ultimate design. The testing was done on the designed car, which was shipped to Manila/Philippines to participate in the SEM Asia 2014 competition February 3-9, 2014 in Manila. In Manila, the team planned to record so many data from different runs with different driving strategies on the real track circuit. These data will be compared to those that will be obtained using the designed test bench for same conditions for further tuning and improvement of the car model and car design.Scopu

Contributions of competition based complex engineering design experience to leadership development in engineering students

Engineering design activities provide students an opportunity to develop a number of skills. Engineering design experiences not only help students to acquire practical or technical skills, but also may enhance a number of soft (non-technical) attributes and competencies, little is investigated on the impact of engineering design on leadership development. Shell Eco Marathon (SEM) competition is a venue whereby engineering students compete on designing an energy-efficient car that is able to travel furthest given distance within a given time using the least amount of energy. The competition is composed of two categories: First one is a prototype oriented, which focuses on maximum efficiency while passenger comfort takes a back seat. The second category is Urban Concept class that encourages more practical designs. In this paper, analysis of contribution of a complex engineering design experience such as SEM on leadership attributes development is provided. This paper starts with a review on leadership attributes, as well as, recent developments and efforts of incorporating leadership themes in engineering education. Then an overview of the Shell Eco-Marathon competition is provided, with some details on historical background and global organizational structure. Methodology of the impact of SEM on leadership development is then highlighted, and detailed analysis is provided. Impact analysis of the SEM Design Competition incorporates evaluation of data collected through questionnaire with participating students. The paper then discusses students own opinions on leadership skills enhancement spanned over 3 main categories; personality traits, motives, and cognitive factors. The paper concludes with recommendations emerging from the investigation for engineering education academics and engineering curriculum developers.Scopu

A resolver converter based upon a novel open-Loop Technique

The paper presents a novel technique for the determination of the angle from slowly-varying quadrature co-sinusoidal signals produced, for example, by position sensors. In the presented scheme applied to a resolver, the separately generated constant-frequency sine wave used for exciting the resolver together with an additional cosine wave are used as reference against which the amplitudes of the angle-dependent demodulated resolver sine and cosine signals are compared. At the instant equality between respective amplitudes of the signals are detected, two sample and hold circuits sample a voltage proportional to the angle of the shaft of the resolver from a triangular waveform generated from the reference signals. In theory, the sample and hold devices produce identical output voltages proportional to the unknown angle of the transducer. In order to improve the precision of the proposed converter, the two sample and hold circuits outputs are fed into a multiplexer to produce a single output that takes full advantage of the accurate comparison outside the peak regions of the signals. With this method, the validated output is obtained from the accurate comparisons involving the alternating pseudo-linear segments of the trigonometric signals. Another important feature of this converter is its robustness to amplitude fluctuations in the trigonometric reference signals which are used for the excitation of the resolver. A converter based on this technique has been successfully implemented using basic electronic components. Theory of operation, computer simulation and experimental results are given

An open-loop technique for angle determination from position encoders

The paper presents a novel technique for the determination of the angle from low-frequency quadrature cosinusoidal signals produced, for example, by position sensors. In the presented scheme applied to a resolver, the separately generated constant-frequency sine wave used for exciting the resolver together with an additional cosine wave are used as reference against which the amplitudes of the angle-dependent demodulated resolver sine and cosine signals are compared. At the instant equality between amplitudes of respective signals are detected, a sample and hold circuit samples a voltage proportional to the angle of the shaft of the resolver from a triangular waveform generated from the reference signals. This is a feed-forward method, which is an analog equivalent to digital look up table techniques. In order to improve the precision of the proposed converter, a new technique is used to take full advantage of the alternating pseudo-linear segments of the trigonometric signals. With this method, the sampling relies only on the accurate comparison outside the peak regions of the signals. A converter based on this technique has been successfully implemented using basic electronic components. Theory of operation, computer simulation and experimental results are given

Hybrid thin-films of graphene materials and metallic nanowires for next generation transparent electrodes

We report advances in the fabrication and characterization of transparent conductive electrodes based on thin-films of metallic nanowires (copper and silver) encapsulated with graphene, graphene oxide, and reduced graphene oxide, using solution-processed approaches. Renewable Energy and the Environment CongressScopu

Hybrid thin-films of graphene materials and metallic nanowires for next generation transparent electrodes

We report advances in the fabrication and characterization of transparent conductive electrodes based on thin-films of metallic nanowires (copper and silver) encapsulated with graphene, graphene oxide, and reduced graphene oxide, using solution-processed approaches. Renewable Energy and the Environment CongressScopu