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

申请人最近几年的研究计划主要关注的是开发一种逼真的现代直升机旋翼叶片的结构和动力学模型，该模型可以用来模拟这些叶片的各种动态行为，并具有高度的保真度。这种模型的一个主要用途是研究舰载直升机的叶片滑行现象。在船舶甲板上直升机旋翼叶片的启动和关闭操作期间，由于旋翼的低速，叶片可能会受到高风致气动力，而在较高的正常运行速度下没有离心力的好处。这种激励与船舶甲板运动和风力条件相结合，有可能导致旋翼叶片过度变形，称为BSP。因此，旋翼叶片可能会接触到直升机的机身或尾梁，导致机身严重损坏，有可能使飞行器的适航性受到质疑，并严重危及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，建立了直升机、舰船运动和空气动力相互作用的系统模型。这一模型将主要用于调查战略规划编制局的性质，以便了解促成这一现象的各种组成部分之间的相互作用。基于变分渐近方法的第二个连续梁模型将被用来模拟弹性叶片的结构特性。在该模型中，将使用基于精确固有动力学方程的混合变分公式来模拟旋转叶片的动态行为。第二个模型还包括集成的压电纤维作为活性纤维复合材料(AFC)，它将被用来研究如何通过使用压电致动器来影响叶片的操作及其动态性能来控制航行现象。利用遗传算法，提出了一种新的方法来优化叶片中必要的AFC的配置和布置。

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.