This work focuses on vibration elimination, bifurcation control, and stability achievement in a harmonically forced self-excited nonlinear oscillator. A novel control technique called the Integral Resonant Positive Position Feedback... more
This work focuses on vibration elimination, bifurcation control, and stability achievement in a harmonically forced self-excited nonlinear oscillator. A novel control technique called the Integral Resonant Positive Position Feedback Controller ( IRPPFC ) has been introduced in this study. The proposed controller is composed of second-order and first-order filters, integrated into the targeted oscillator in nonlinear form. Then, the averaging equations governing the slow-flow dynamics of the coupled systems are deduced. Subsequently, the relevant nonlinear algebraic system, which characterizes the static bifurcation, is obtained. The effectiveness of the controller in eliminating system vibrations, controlling nonlinear bifurcations, and stabilizing the unstable motion is investigated through bifurcation diagrams, two-dimensional stability charts, and numerical simulations of the instantaneous vibrations. The conducted analyses approved that the IRPPFC not only can stabilize the unst...
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Over 50% of the total energy consumed by buildings in a hot and dry climate goes toward the cooling regime during the harsh months. Non-residential buildings, especially houses of worship, need a tremendous amount of energy to create a... more
Over 50% of the total energy consumed by buildings in a hot and dry climate goes toward the cooling regime during the harsh months. Non-residential buildings, especially houses of worship, need a tremendous amount of energy to create a comfortable environment for worshipers. Today, mosques are regarded as energy-hungry buildings, whereas in the past, they were designed according to sustainable vernacular architecture. This study was aimed at improving the energy performance of mosques in a hot and dry climate using bioclimatic principles and architectural elements. To achieve this aim, a process-based simulation approach was applied together with a generate and test technique on 86 scenarios based on 10 architectural elements, with various arithmetic transition rates organized in 9 successive steps. Starting from a simplified hypothetical model, the final model of the mosque design was arrived at based on a holistic bioclimatic vision using 10 architectural elements. The findings of...
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Loop delays are taken into our consideration when positive position feedback controller is used to control the vibrations of forced and self-excited nonlinear beam. External excitation is a harmonic excitation caused by support motion of... more
Loop delays are taken into our consideration when positive position feedback controller is used to control the vibrations of forced and self-excited nonlinear beam. External excitation is a harmonic excitation caused by support motion of the cantilever beam. Self-excitation is caused by fluid flow and modeled by a nonlinear damping with a negative linear part (Rayleigh’s function). The multiple timescales perturbation technique is applied to obtain a first-order approximate solution. Effects of time delay on the system are extensively studied, and optimal conditions for the system operation are deduced. The equilibrium solution curves are plotted for several values of controller parameters. The stability of the steady-state solution is investigated using frequency-response equations. The analytical results are validated by numerical integration of the original closed-loop system model equations, time histories and Poincaré map for the system. We realized that all predictions from analytical solutions are in good agreement with the numerical simulation.
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; "> In this work, a passive vibration absorber is used to control the vibrations of a harmonically excited nonlinear shakerwhich emulates a machine. A linear and nonlinear vibration absorberswere considered to suppress the... more
; "> In this work, a passive vibration absorber is used to control the vibrations of a harmonically excited nonlinear shakerwhich emulates a machine. A linear and nonlinear vibration absorberswere considered to suppress the primary resonancevibrations of the shaker in presence ofone to one internal resonance and a comparison between the results of two cases was obtained.The multiple time scales perturbation MTSP techniquewas used to analyze the system and to obtain a first order approximate solution of the closed loop system in presence of one to one internal resonance. In addition,the stability of the systemwas studied using frequency response equations,theeffect of absorber’s parameters on system performanceis discussed to choose the optimal absorber parameters for vibration control process.We also discussed the role of cubicnonlinearity in vibration absorber in suppression of shaker’s vibrations when frequency of the harmonic excitation is well above the resonance frequency of the shaker. All analytical results are validated using numerical solution and the results are convincing. Finally we deduced the best cases for using linear vibration absorber and the best cases for using nonlinear