报告题目：Two Examples of Nonlinear Engineering Systems; Dynamics and Control
Vahid Vaziri是英国阿伯丁大学讲师、英国阿伯丁大学应用动力学研究中心成员、International Conference on Engineering Vibrations (ICoEV2020), 18-21 August 2020, Aberdeen, UK 会议组委会成员、Nonlinear Dynamics and Control of Engineering Systems at International Conference on Vibration Engineering and Technology of Machinery (VETOMAC XIV), 10-13 September 2018, Lisbon, Portugal会议组委会成员、Vibration and Control in Downhole Drilling Processes at International Conference on Engineering Vibration (ICoEV 2017), 4-7 September 2017, Sofia, Bulgaria 会议组委会成员、英国国家自然科学基金评审专家、加拿大国家自然科学基金评审专家。发表论文40余篇。
“Suppression of torsional vibrations occurring in a drill-string”, (40 min)
The first problem deals with drill-string torsional vibrations while drilling, which is conducted in the experimental drilling rig developed at University of Aberdeen. A realistic model of the experimental setup is then constructed, taking into account the dynamics of the drill-string and top motor. Physical parameters of the experimental drilling rig are estimated to calibrate the model to ensure the correspondence of the research results to the experimental conditions. Consequently, a control method is introduced to suppress torsional and stick-slip oscillations exhibited in the experimental drilling rig. The experimental and numerical results considering delay of the actuator are shown to be in close agreement, including the success of the controller in significantly reducing the vibrations.
“Vibrational energy extraction from rotating pendulum systems”, (40 min)
The second problem relates to initiating and maintaining the rotational motion of a parametric pendulum as an energy harvesting system. Several possible control methods to initiate and maintain the rotational motion of a harmonically-excited pendulum are proposed and then verified experimentally. The time-delayed feedback method is shown to maintain quite well the rotational motion of a sinusoidally excited parametric pendulum, even in the presence of noise. A control method for the wave-excited pendulum system is then suggested and tested in order to increase the probability of its rotational motion. This proposed control method succeeds in significantly raising the probability of rotational motion of the wave-excited pendulum.