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

申请人近年来主要关注的研究项目是建立现代直升机旋翼桨叶的真实结构和动力学模型，该模型可用于模拟这些桨叶的各种动态行为，并具有很高的保真度。该模型的主要应用是对舰载直升机桨叶航行现象（BSP）的研究。在船舶甲板上的直升机旋翼叶片的启动和关闭操作期间，由于旋翼的低速，叶片可以受到高风致气动力，而没有在较高的正常运行速度下存在的离心加强的好处。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，即BSP。其结果是，旋翼叶片可以接触到机身或直升机的尾臂，导致机体损伤的实质性水平，并可能使车辆的适航性受到质疑，以及危及飞行机组人员和船舶甲板人员的安全相当严重。利用刚体多体动力学原理，建立一个能够模拟直升机、舰船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成部分的相互作用。第二种基于变分渐近方法的连续梁模型将用于模拟弹性叶片的结构特性。在该模型中，将采用基于精确的内禀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。第二个模型也采用了集成的压电纤维作为活性纤维复合材料（AFC），将用于研究如何通过使用压电致动器来影响叶片的运行及其动态性能来控制航行现象。提出了一种利用遗传算法优化叶片中所需AFC结构和位置的新方法。

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.