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Articles by Z. Yeo
Total Records ( 14 ) for Z. Yeo
  O. Asseu , M. Koffi , Z. Yeo , X. Lin-Shi , M.A. Kouacou and T.J. Zoueu
  This study presents a feedback linearization strategy and a robust controller to permit a decoupling and regulation of the motor states in order to assure a good dynamic performance and stability of the global system. As the control required the knowledge of the instantaneous flux of the rotor and the rotor parameter estimation can improve the control quality, a six-dimensional discrete-time extended sliding mode observer is proposed for on-line estimation of rotor fluxes and rotor time constant. The simulation results for a 1.8 kW induction motor are presented to illustrate the validity and the high robustness of the proposed approach against parameter variations and disturbances.
  O. Asseu , T.R. Ori , K.E. Ali , Z. Yeo , S. Ouattara and X. Lin-Shi
  The aim of this study is to present a high dynamic current control and speed estimation strategy for Permanent Magnet Synchronous Motor (PMSM) drives without a speed transducer. The strategy is based on the exact linearization methodology and Extended Sliding Mode Observer (ESMO) algorithm. The performances of the proposed control strategy are analysed by simulations for a 1.6 kW PMSM. The obtained results show the effectiveness of the proposed robust current control approach and speed observation algorithm under load torque and stator resistance variation.
  O. Asseu , A. Tanoh , M. Koffi , Z. Yeo , T.R. Ori and X. Lin-Shi
  In this study, a reduced-order discrete-time Extended Sliding Mode Observer (ESMO) is introduced for on-line estimation of rotor fluxes and rotor time constant. The satisfying simulations and experimental results carried out on a 5.5 kW induction motor demonstrate the excellent performance and high robustness of the proposed ESMO against parameter variations, modeling uncertainty and measurement noise. It is concluded that the implementation in real-time of this reduced-order ESMO in the industrial applications, compared with the full-order ESMO, permit on the one hand to overcome the heavy computational effort, complexity and hard tuning of the estimation algorithm and on the other hand, to reduce the execution time of the observation with a good accuracy and considerable rapidity.
  M.A. Kouacou , A.A. Koua , Z. Yeo , A. Akichi , A. Tanoh and M. Koffi
  The aim of this study is to investigate magnetic properties of an example of half-metallic and ferromagnetic compounds, namely, the half Heusler PtMnSb. From the magnetic measurements, it can be shown a change from a localized magnetism due to the spin waves thermally excited, to an itinerant magnetism with spin fluctuations is to reduce the moments in this compound. Furthermore, the electrical and thermal resistivity measurements were performed. The resistivity results with respect to the magnetic properties are confirmed and a transition of a half-metallic state to a metallic state at 100 K is observed.
  M. Koffi , Z. Yeo , A. Tanoh , A.D. Ochou , O. Asseu , D.K. Konan and M.A. Kouracou
  The raindrop size distribution (DSD) measurements were collected in the tropical and mid-latitude rain system. Comparisons of measured values and estimated values of polarimetric parameters (ZH and ZDR) shows that kinematic peaks are the main cause of the variability of ZH but they do not influence much ZDR. The influence of the peak number on the variance of the radar parameters is based on the relations between time and averaging. It consists to examine how many DSDs have to be averaged in order to suppress the peaks and what are the consequences on the radar parameters. The study shows that averaging improves the validity of the polarimetric parameters.
  Z. Yeo , M. Koffi , M.A. Kouacou , O. Asseu , A. Tanoh and D. Konan
  This study built a computer program in order to carry out accurate calculations of the magnetic field according to time, space and the load of a three-phase line (3 or 6 conductors). The theorem of Ampere and the superposition one were used. We obtained the variations of the magnetic field according to time at a given space point and the magnetic field at a given moment on both sides of the line. These results enabled us to define security distance with respect to critical values used in the literature. The number of parameters did not allow us to calculate standard security distances. For the tested pylons, if reference value is 0.2 μT, the security distance can exceed several hundred meters.
  A. Tanoh , D.K. Konan , M. Koffi , Z. Yeo , M.A. Kouacou , B.K. Koffi and K.R. N`guessan
  This study deals with the early detection of damages in rolling bearings of an asynchronous machine. It presents a neuronal network based application for motor bearing fault diagnosis. Vibration simulation is used to assist in the design of various motor rolling bearing fault strategies. These simulation results indicate that neural networks can be effective agents in the diagnosis of motor bearing fault through vibration signature.
  O. Asseu , Z. Yeo , M. Koffi , M.A. Kouacou and K.E. Ali
  This study proposes a novel method to achieve good performance for rotor time constant and flux estimation in induction motor sensorless control, using a reduced order Extended Kalman Filter (EKF) instead of a full-order EKF. This new algorithm uses a reduced order state-space model that is discretized in a particular and innovative way proposed in this study. With this model structure, only the rotor flux components are estimated while the full order EKF also estimates stator current components. Thus, as compared with the full order EKF, this new approach strongly reduces the execution time of the observation and simplifies the tuning of covariance matrices, since, the number of elements to be adjusted is reduced. The satisfying simulations results on Matlab-Simulink environment for a 1.8 kW induction motor, demonstrate the good performance and stability of the proposed reduced order EKF algorithm against parameter variation, modeling uncertainty, measurement and system noises.
  D.K. Konan , B.K. Koffi , A. Tanoh , M. Koffi , M.A. Kouacou , Z. Yeo , K. Konan , A.A. Koua and R.K. N`guessan
  This study deals with the determination of the phase and the amplitude of a diffracted field. We build a simple setup in order to measure the phase of a diffracted field. This setup can be used with different direction of the incident beam.
  B.K. Koffi , D.K. Konan , R.K. N’guessan , J.K. Saraka , A. Tanoh , M.A. Kouacou , Z. Yeo , M. Koffi and A.A. Koua
  This study presents theoretical consideration and results of solar water distiller system. Device was composed of glass which served as a condenser and an aluminium plate in black paint as an absorber. It was also composed of a tank of brine and a tank of distilled water. Solar water distiller system was modelled and simulated using an implicit numerical scheme, the Diabolo-Sablier algorithm. Simulation results showed that accumulated mass water greatly depended on the ambient temperature. Thus, for an increasing of 5°C of the ambient temperature, accumulated mass water roughly doubled. This inexpensive device permitted to produce 6 kg of water per day with a commonly used of collector of 2 m2. Condensed mass water became significant for relative humidity of 40% at 308K temperature corresponding to conditions of dry season in the Abidjan zones.
  D.K. Konan , B.K. Koffi , A. Tanoh , M. Koffi , M.A. Kouacou , Z. Yeo , K. Konan , A.A. Koua and R.K. N`guessan
  .
  Z. Yeo , M. Koffi , O. Asseu , A. Tanoh , D. Konan and B. Koffi
  Some discharge models suppose that the discharge is developed mainly according to an electric field`s line. In this study, a computer program is built in order to carry out accurate determination of the electric field`s lines. Finite element method is implemented to solve the Laplace equation and then the electric field is derivate. Field`s lines are built by successive jumps and their parameters are calculated by a polynomial approximation. Results are successfully compared to empirical formula established by earlier researches in rod to plane geometry. The field`s lines and what could be a discharge line for an aerial insulator are also investigated and discussed.
  D.K. Konan , B.K. Koffi , A. Tanoh , M. Koffi , Z. Yeo , K. Konan and R.K. N`guessan
  This study presents a new technique to measure the phase difference between two diffracted fields: The field diffracted by a reference object and the field diffracted by an unknown object. For that we use the interferential technique of Young slits. We measured the phase difference between the diffracted fields of two rods of resin. And knowing the phase of the diffracted field of the reference object helps deducing the phase of the field diffracted by the sample. This setup is simple and it is very strong in the presence of disturbances because both objects are illuminated with the same incident beam. Moreover, this technique allows us measuring the phase of the diffracted field on a wide range of angle so that a high resolution of the image can be obtained.
  O. Asseu , S. Ouattara , K.E. Ali , Z. Yeo and M. Koffi
  This study uses a robust input-output linearization via feedback control in order to assure a good dynamic performance, stability and a decoupling of the stator currents for an induction motor in a field-oriented (d, q) coordinate. However, this control requires the knowledge of certain variables (rotor flux, torque) that are difficult to access or simply impossible to measure and also the rotor time constant variation can induce a performance degradation of the system. Thus, a fifth-order Discrete-time extended Kalman filter approach is proposed for on-line estimation of rotor flux, currents, rotor time constant and torque in an induction motor. The interesting simulations and experimental results obtained on a testing bench for a 5.5 kW induction motor permit to validate the effectiveness and good performance of the proposed nonlinear control and extended Kalman filter algorithm in the presence of parameter variation, modeling uncertainty and measurement noise.
 
 
 
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