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

近年来，申请人的研究计划的主要关注点是开发现代直升机旋翼桨叶的现实结构和动态模型，该模型可用于以高度的保真度模拟这些桨叶的各种动态行为。该模型的主要用途是研究舰载直升机的叶片航行现象。在船舶甲板上的直升机转子叶片的启动和关闭操作期间，由于转子的低速度，叶片可能受到高的风引起的空气动力，而没有在较高的正常操作速度下存在的离心加强的益处。这种激励与船舶甲板运动和风力条件相结合，有可能导致转子叶片过度变形，称为BSP。结果，旋翼桨叶可能与直升机的机身或尾梁接触，导致机身严重损坏，可能使飞行器的适航性受到质疑，并严重危及飞行机组人员和船舶甲板人员的安全。利用刚体多体动力学原理，建立了一个能够模拟直升机、船舶运动和空气动力学相互作用的系统模型。该模型将主要用于研究BSP的性质，以了解导致这一现象的各种组件的相互作用。基于变分渐近法的第二个连续梁模型将用于模拟弹性叶片的结构特性。在该模型中，将采用基于精确的固有动力学方程的混合变分公式来模拟旋转叶片的动力学行为。这第二个模型，也纳入了集成的压电纤维作为主动纤维复合材料（AFC）将被用来研究如何航行现象可以通过使用压电致动器来控制，以影响叶片的操作和它们的动态性能。使用遗传算法的一种新的方法，建议优化配置和必要的AFC在叶片中的位置。

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.