US-Egypt Cooperative Research: Application of the Saturation- Based Controller to Self-Excited Oscillators and Systems with Limited Energy Sources

该奖项支持弗吉尼亚州布莱克斯堡弗吉尼亚理工学院和州立大学工程科学与机械系AliNayfeh教授与埃及开罗爱资哈尔大学机械工程系Ayman El-Badawy博士之间的合作研究项目。他们计划研究抑制自激系统和有限电源系统的大振幅振动。控制策略将基于具有二对一自参数共振的二次非线性多自由度系统所表现出的饱和现象。该策略包括引入二阶控制器，并通过传感器和执行器将其耦合到工厂，其中反馈和控制信号都是二次的。因此，期望的非线性可以被引入到完整的装置/控制系统中，即使装置没有表现出任何非线性行为。当装置被迫接近共振时，其响应在一个小值处饱和，剩余的振荡能量被执行器引导和吸收。研究人员将使用数字信号处理板和建模软件来实现这项技术。他们将开发一种自适应控制策略，使用有效的频率调谐机制来维持二比一的内部共振条件。自适应控制使系统（或结构）能够适应变化的环境，以不断优化其性能。研究人员将研究在输入端使用具有施密特触发作用的逻辑门来测量系统频率，因为它的准确性和对噪声干扰的免疫。范围：该项目涉及分析和实验方法，并结合了美国和埃及科学家的互补专业知识。在许多重要的工程系统中都会遇到自激振荡，而抑制这些振荡，特别是在有限电源的约束下，是一个重要的问题。主动非线性反馈控制的发展将具有广泛的应用前景。该项目将支持一名埃及科学家在弗吉尼亚理工大学工作，并将包括两所大学学生的互动。

0322101 NayfehDescription: This award supports a cooperative research project between Professor AliNayfeh, Department of Engineering Sciences and Mechanics, Virginia Polytechnic Institute and State University (Virginia Tech.), Blacksburg, Virginia and Dr. Ayman El-Badawy, Department of Mechanical Engineering, Al-Azhar University, Cairo, Egypt. They plan to study the suppression of the large-amplitude vibrations of self-excited systems and systems with limited power supplies. The control strategy will be based on the saturation phenomenon exhibited by multi-degree-of-freedom systems with quadratic nonlinearities possessing a two-to-one autoparametric resonance. The strategy consists of introducing a second-order controller, and coupling it to the plant through a sensor and an actuator, where both the feedback and control signals are quadratic. Therefore, the desired nonlinearities can be introduced into the complete plant/control system even when the plant does not exhibit any nonlinear behavior. When the plant is forced near resonance, its response saturates at a small value, and the remaining oscillatory energy is channeled and absorbed by the actuator. The investigators will implement the technique by using a digital signal processing board and a modeling software. They will develop an adaptive control strategy using an effective frequency-tuning mechanism to maintain the two-to-one internal-resonance condition. Adaptive control makes it possible for the system (or structure) to adapt to a variable environment in the interest of continuously optimizing its performance. The investigators will examine the use of a logic gate with Schmitt-trigger action on the input to measure the system frequency because of its accuracy and because it is immune to noise disturbances.Scope: The project involves analytical and experimental approaches, and combines the complementary expertise of the US and Egyptian scientists. The self-excited oscillations are encountered in a number of important engineering systems, and the suppression of these oscillations, especially under the constraint of limited power supplies, is an important problem. The development of the active nonlinear feedback control will have many applications. The project will support an Egyptian scientist to work at Virginia Tech and will include interaction of students at both universities.