Active control of chaotic vibration in a constrained flexible pipe conveying fluid: Fid-Bau Portal

Active control of chaotic vibration in a constrained flexible pipe conveying fluid

Yau, C.H. / Bajaj, A.K. / Nwokah, O.D.I.

An active vibration control system is designed, and is numerically verified, to suppress the undesirable chaotic vibration in a constrained flexible pipe conveying fluid, which exhibits regions of flutter and chaotic motions at sufficiently high flow velocity. The four-dimensional analytical model obtained from the continuous system by Galerkin's method, that has been previously verified to represent adequately the dynamics, is utilized for designing the control law. Various control design methodologies are investigated for different situations. Firstly, optimal regulator theory is applied to obtain feedback gains to stabilize the system with full state information. The effects of the location and length of the piezoelectric actuators on the efficiency as a vibration damper are theoretically examined in this case. Secondly, a state observer is added to estimate the required state signals. To cover the situation when the states are not directly measurable, dynamic compensators are obtained to control the system with only the output feedback. Finally, a robust controller for such a system with large flow velocity variations, without sensing the flow velocity or gain-scheduling, is developed. The robust control method is based on a newly developed sensitivity-based Quantitative Feedback Theory (QFT) scheme, which allows the controller to make the closed loop system response meet quantitatively specified performance requirements even though the system has large parameter variations. Numerical simulations are carried out for the different controllers and they validate the effectiveness of the proposed control scheme. The QFT scheme yields a remarkable result in stability robustness with respect to flow velocity variations.