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    Novel robust control using a fractional adaptive PID regulator for an unstable system
    (Institute of Advanced Engineering and Science, 2022) Bensafia, Yassine; Idir, Abdelhakim; Khettab, Khatir; Akhtar, Muhammad Saeed; Sarwat, Zahra
    Recent advances in fractional order calculus led to the improvement of control theory and resulted in the potential use of a fractional adaptive proportional integral derivative (FAPID) controller in advanced academic and industrial applications as compared to the conventional adaptive PID (APID) controller. Basically, a fractional order adaptive PID controller is an improved version of a classical integer order adaptive PID controller that outperformed its classical counterpart. In the case of a closed loop system, a minor change would result in overall system instability. An efficient PID controller can be used to control the response of such a system. Among various parameters of an instable system, the speed of the system is an important parameter to be controlled efficiently. The current research work presents the speed control mechanism for an uncertain, instable system by using a fractional-order adaptive PID controller. To validate the arguments, the effectiveness and robustness of the proposed fractional order adaptive PID controller have been studied in comparison to the classical adaptive PID controller using the criterion of quadratic error. Simulation findings and comparisons demonstrated that the proposed controller has superior control performance and outstanding robustness in terms of percentage overshoot, settling time, rising time, and disturbance rejection
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    Rheological and flow behavior of water-in-oil Pickering emulsions stabilized with organo-hectorite clay
    (Elsevier, 2021) Merad, B.; Bekkour, K.; François, P.; Gareche, M.; Lawniczak, F.
    The rheological and flow behaviors of Pickering emulsions are studied as a function of their water concentration. The studied emulsions are water-in-gasoil inverse emulsions stabilized with organo-hectorite clay. An in-line emulsion preparation was performed and a novel emulsification system was used. The emulsification system was tested and confirmed before performing pipe-flow measurements. A stress-controlled rheometer was used to study the rheological behavior of organoclay stabilized inverse emulsions. It was found that the emulsions exhibited a shear thinning with yield stress non-Newtonian rheological behavior and that the flow curves were well correlated using the Herschel-Bulkley model. Pressure loss and axial velocity measurements were studied to investigate the pipe-flow behavior of the emulsions. Axial velocity of the fluids was measured using an Ultrasonic Pulsed Doppler Velocimeter. It was shown that, up to 50 wt% water mass concentration, an exponential increase of yield stress and viscosity values is noticed, and the phase inversion point is not reached. In the range of the applied flow rates, turbulence took place only in the case of the lowest water cut (0 wt%). The Herschel-Bulkley rheological parameters were used to simulate the pipe-flow behavior of the studied fluids, and showed a satisfactory correlation with the in-line measurements. Furthermore, wall shear stress and velocity profiles were used to study the short-, medium-, and long-term stability of the emulsions. © 2021 Elsevier B.V.
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    Rheological and flow behavior of water-in-oil Pickering emulsions stabilized with organo-hectorite clay
    (Elsevier, 2021) Boutheina, Merad; Bekkour, Karim; Pierre, François; Gareche, Mourad
    The rheological and flow behaviors of Pickering emulsions are studied as a function of their water concentration. The studied emulsions are water-in-gasoil inverse emulsions stabilized with organo-hectorite clay. An in-line emulsion preparation was performed and a novel emulsification system was used. The emulsification system was tested and confirmed before performing pipe-flow measurements. A stress-controlled rheometer was used to study the rheological behavior of organoclay stabilized inverse emulsions. It was found that the emulsions exhibited a shear thinning with yield stress non-Newtonian rheological behavior and that the flow curves were well correlated using the Herschel-Bulkley model. Pressure loss and axial velocity measurements were studied to investigate the pipe-flow behavior of the emulsions. Axial velocity of the fluids was measured using an Ultrasonic Pulsed Doppler Velocimeter. It was shown that, up to 50 wt% water mass concentration, an exponential increase of yield stress and viscosity values is noticed, and the phase inversion point is not reached. In the range of the applied flow rates, turbulence took place only in the case of the lowest water cut (0 wt%). The Herschel-Bulkley rheological parameters were used to simulate the pipe-flow behavior of the studied fluids, and showed a satisfactory correlation with the in-line measurements. Furthermore, wall shear stress and velocity profiles were used to study the short-, medium-, and long-term stability of the emulsions