报告题目：Stability Analysis of Nonlinear Rotating Systems Using Lyapunov Characteristic Exponents Estimated From Multibody Dynamics
报告人：Prof.Pierangelo Masarati(米兰理工大学）
报告时间：12月15日（周四）15:00-17:00
报告地点：Zoom Meeting
https://polimi-it.zoom.us/j/97002784193?pwd=d1lhK291cTdMZEM2NFc4OTA1dlJZQT09
Meeting ID: 970 0278 4193
Passcode: 625685
报告内容简介：
The use of Lyapunov Characteristic Exponents to assess the stability of nonlinear, time-dependent mechanical systems is discussed. Specific attention is dedicated to methods capable of estimating the largest exponent without requiring the Jacobian matrix of the problem, which can be applied to time histories resulting from simulations performed with existing multibody solvers. Helicopter ground resonance is analyzed as the reference application. Improvements over the available literature are: the problem is formulated in physical coordinates, without eliminating periodicity through multiblade coordinates; the rotation of the blades is not linearized; the problem is modeled considering absolute positions and orientations of parts. The dynamic instability that arises at some angular velocities when the isotropy of the rotor is broken (e.g., caused by the failure of one lead-lag damper, a design test condition) is observed to evolve into a large amplitude limit cycle, where the usual Floquet-Lyapunov analysis of the linearized time-periodic simply predicts instability.
报告题目：Rotorcraft-Pilot Couplings
报告人：Prof.Pierangelo Masarati（米兰理工大学）
报告时间：12月19日（周一）15:00-17:00
报告地点：Zoom Meeting
https://polimi-it.zoom.us/j/93456091660?pwd=Nk5Hc0xWSERMOUsxVGpWd0dHSTJtQT09
Meeting ID: 934 5609 1660
Passcode: 936027
报告内容简介：
The design of rotorcraft, especially when the human-machine interaction is concerned, has to take into account the possible interactions between the pilot biomechanics and the rotorcraft dynamics. To this end, existing and novel design techniques and procedures geared toward robustness to Rotorcraft-Pilot Couplings need experimental validation to enable their effective application by OEMs. For this purpose, an experimental test bench, providing means to measure the biodynamic feedthrough of pilot-rotorcraft systems is presented. The system has been designed to easily reconfigurable in order to represent different cockpit designs. Results obtained with a professional test pilot on two different cockpit layouts are presented. The identified biodynamic feedthrough transfer functions are then exploited along with a simplified representation of the helicopter heave dynamics to stability assessments regarding the collective bounce phenomenon.
报告人简介：
Pierangelo Masarati，博士，米兰理工大学航空宇航工程系教授。现担任米兰理工大学航空宇航博士生项目系主任、米兰理工大学博士生院委员会委员。欧洲航空航天学会(CEAS)旋翼飞行器分会主席、欧洲旋翼飞行器论坛（ERF）意大利负责人、美国机械工程师协会(ASME)多体系统和非线性动力学技术委员会委员。现担任RAeS Aeronautical Journal、CEAS Aeronautical Journal、Multibody System Dynamics、ASME Journal of Computational and Nonlinear Dynamics、International Journal of Mechanical System Dynamics等期刊的副主编。
主要研究方向为旋翼飞行器的空气动力学、气动弹性、人机交互、飞行模拟和多体动力学。主持完成了多体动力学开源软件MBDyn的开发、建立了米兰理工大学FRAME实验室。
