Structural dynamics and optimization of placement and configuration of actuators in smart structures

点击翻译按钮获取中文摘要

A major concern of the applicant's research program in the recent years has been the development of a realistic structural and dynamic model of a modern helicopter rotor blade that can be used to simulate various dynamic behaviours of these blades with a high degree of fidelity. A main use of such a model is in the investigation of Blade Sailing Phenomenon (BSP) in shipboard helicopters. During start-up and shut-down operations of helicopter rotor blades on ship decks, due to low speeds of the rotor the blades can be subjected to high wind-induced aerodynamic forces without the benefit of the centrifugal stiffening present at the higher normal operating speeds. This excitation combined with ship deck motion and wind conditions has the potential of resulting in excessive deformations in rotor blades that is referred to as BSP. As the result, the rotor blades can come into contact with the fuselage or tailboom of the helicopter resulting in substantial levels of airframe damage with the possibility of bringing the airworthiness of the vehicle into question, as well as compromising the safety of flight crew and the ship deck personnel quite seriously. Using the principles of rigid multibody dynamics a system model that can simulate the dynamic interaction of the helicopter, the ship motion and aerodynamics will be developed. This model will be used primarily to investigate the nature of BSP in order to understand the interaction of the various components contributing to this phenomenon. A second continuous beam model that is based on variational asymptotic method will be used to model the structural characteristics of the elastic blade. Mixed variational formulation that is based on exact intrinsic dynamic equations will be used to model the dynamic behaviour of rotating blades in this model. This second model that also incorporates integrated piezoelectric fibres as Active Fibre Composites (AFC) will be used to investigate how the sailing phenomenon can be controlled by using the piezoelectric actuators to influence the operation of the blades and their dynamic performance. Using genetic algorithms a novel approach is suggested for optimizing the configuration and placement of the necessary AFC in the blade.