Mohieddine Benammar

A high precision resolver-to-DC converter

A newly developed resolver converter, providing a pseudolinear voltage proportional to the shaft angle, is presented. This converter is based on a new concept involving the absolute values of the demodulated sine and cosine resolver signals together with a dedicated linearization technique. The converter enables instantaneous determination of the mechanical angle with a theoretical error of nonlinearity below 0.011/spl deg/ over the 360/spl deg/ range. The practical performance of this converter is compared to that of a 10/sup 5/ pulses per revolution optical encoder arrangement. The theory of operation, computer simulation, full circuit details, and experimental results are given.

A novel resolver-to-360/spl deg/ linearized converter

A novel and simple resolver-to-dc converter is presented. It is shown that by appropriate processing of the sine and cosine resolver signals, the proposed converter may produce an output voltage proportional to the shaft angle. A dedicated compensation method is applied to produce an almost perfectly linear output. This enables determination of the angle with reasonable accuracy without a processor and/or a look-up table. The tests carried out under various operating conditions are satisfactory and in good agreement with theory. This paper gives the theoretical analysis, the computer simulation, the full circuit details, and experimental results of the proposed scheme.

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 pi/2. 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.

Ultrahigh Aspect Ratio Copper-Nanowire-Based Hybrid Transparent Conductive Electrodes with PEDOT:PSS and Reduced Graphene Oxide Exhibiting Reduced Surface Roughness and Improved Stability.

UNLABELLED Copper nanowires (CuNWs) with ultrahigh aspect ratio are synthesized with a solution process and spray-coated onto select substrates to fabricate transparent conductive electrodes (TCEs). Different annealing methods are investigated and compared for effectiveness and convenience. The CuNWs are subsequently combined with the conductive polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) ( PEDOT PSS) or with reduced graphene oxide (rGO) platelets in order to reduce the surface roughness and improve the durability of the fabricated TCEs. Our best-performing PEDOT PSS/CuNW films have optical transmittance T550 = 84.2% (at λ = 550 nm) and sheet resistance Rs = 25 Ω/sq, while our best CuNW/rGO films have T550 = 84% and Rs = 21.7 Ω/sq.

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.

Techniques for measurement of oxygen and air-to-fuel ratio using zirconia sensors. A review

The various techniques for measurement of oxygen concentration/partial pressure using sensors employing zirconia electrolytes are reviewed. Zirconia-based air-to-fuel ratio sensors used in combustion applications are also discussed. A solid electrolyte cell incorporating two electrodes on each opposing side may be used as a potentiometric oxygen sensor; this requires a reference gas and provides a logarithmic output. An oxygen pump-gauge device normally consists of two solid electrolyte cells assembled to enclose an internal volume. Pump-gauge devices can be operated in various modes requiring simple electronic circuitry. Devices operating in steady state modes incorporate a diffusion path between the internal volume and the sample gas and provide an output proportional to the oxygen concentration in the sample gas. Pump-gauges operating in oscillatory modes may be fully sealed or may incorporate a diffusion path; they enable both oxygen concentration and partial pressure to be determined.

A novel amplitude-to-phase converter for sine/cosine position transducers

Resolvers and various other types of sine/cosine encoders are used for both angular and linear position sensing. These devices provide analogue signals in the form of the sine and the cosine of an angle θ related to the position of the moving part of the transducer. A novel converter is described for the linearization of the sensor signals. The scheme converts the co-sinusoids into a nearly perfect triangular signal from which θ is determined using simple linear equation. The proposed converter makes use of the alternating pseudo-linear segments of the sensor signals, together with a dedicated and simple linearization technique to further improve the linearity of these segments. This enables unambiguous determination of θ over the full 360 degree range, with an absolute error of non-linearity of 0.041 degree. The conversion technique may be implemented numerically or electronically. The proposed converter was built using basic analogue electronic circuitry, and was successfully tested using both an electronic transducer model and a commercial resolver. The principle and theory of operation, computer simulation, and experimental results are given.

Transient Gas Turbine Performance Diagnostics Through Nonlinear Adaptation of Compressor and Turbine Maps

Gas turbines are faced with new challenges of increasing flexibility in their operation while reducing their life cycle costs, leading to new research priorities and challenges. One of these challenges involves the establishment of high fidelity, accurate, and computationally efficient engine performance simulation, diagnosis, and prognosis schemes, which will be able to handle and address the gas turbines ever-growing flexible and dynamic operational characteristics. Predicting accurately the performance of gas turbines depends on detailed understanding of the engine components behavior that is captured by component performance maps. The limited availability of these maps due to their proprietary nature has been commonly managed by adapting default generic maps in order to match the targeted off-design or engine degraded measurements. Although these approaches might be suitable in small range of operating conditions, further investigation is required to assess the capabilities of such methods for use in gas turbine diagnosis under dynamic transient conditions. The diversification of energy portfolio and introduction of distributed generation in electrical energy production have created need for such studies. The reason is not only the fluctuation in energy demand but also more importantly the fact that renewable energy sources, which work with conventional fossil fuel based sources, supply the grid with varying power that depend, for example, on solar irradiation. In this paper, modeling methods for the compressor and turbine maps are presented for improving the accuracy and fidelity of the engine performance prediction and diagnosis. The proposed component map fitting methods simultaneously determine the best set of equations for matching the compressor and the turbine map data. The coefficients that determine the shape of the component map curves have been analyzed and tuned through a nonlinear multi-objective optimization scheme in order to meet the targeted set of engine measurements. The proposed component map modeling methods are developed in the object oriented MATLAB/SIMULINK environment and integrated with a dynamic gas turbine engine model. The accuracy of the methods is evaluated for predicting multiple component degradations of an engine at transient operating conditions. The proposed adaptive diagnostics method has the capability to generalize current gas turbine performance prediction approaches and to improve performance-based diagnostic techniques. Copyright © 2015 by ASME.

Multiple sensor fault diagnosis by evolving data-driven approach

Sensors are indispensable components of modern plants and processes and their reliability is vital to ensure reliable and safe operation of complex systems. In this paper, the problem of design and development of a data-driven Multiple Sensor Fault Detection and Isolation (MSFDI) algorithm for nonlinear processes is investigated. The proposed scheme is based on an evolving multi-Takagi Sugeno framework in which each sensor output is estimated using a model derived from the available input/output measurement data. Our proposed MSFDI algorithm is applied to Continuous-Flow Stirred-Tank Reactor (CFSTR). Simulation results demonstrate and validate the performance capabilities of our proposed MSFDI algorithm.

Dynamic Performance Simulation of an Aeroderivative Gas Turbine Using the Matlab Simulink Environment

In fossil fuel applications, such as air transportation and power generation systems, gas turbine is the prime mover which governs the aircrafts propulsive and the plants thermal efficiency, respectively. Therefore, an accurate engine performance simulation has a significant impact on the operation and maintenance of gas turbines as far as reliability and availability considerations are concerned. Current trends in achieving stable engine operation, reliable fault diagnosis and prognosis requirements do motivate the development and implementation of real-time dynamic simulators for gas turbines that are sufficiently complex, highly nonlinear, have high fidelity and include fast response modules. This paper presents a gas turbine performance model for predicting the transient dynamic behavior of an aero derivativ e engine that is suitable for both mechanical drive and power generation applications. The engine model has been developed in the Matlab/Simulink environment and combines both the inter-component volume and the constant mass flow methods. Dynamic equations of the mass momentum and the energy balance are incorporated into the steady state thermodynamic equations. This allows one to represent the engine model by a set of first order differential and algebraic equations. The developed Simulink model in an object oriented environment, can be easily adapted to any kind of gas turbine configuration. The model consists of a number of subsystems for representing the gas turbines components and the thermodynamic relationships among them. The components are represented by a set of suitable performance maps that are available from the open literature. The engine model has been validated with an established gas turbine performance simulation software. Time responses of the main variables that describe the gas turbine dynamic behavior are also included. The proposed gas turbine model with its dynamic simulation characteristics is a useful tool for development of real-time model-based diagnostics and prognostics technologies. Copyright © 2013 by ASME.