Effect of Gyroscopic Couple on Aircraft Landing Gear Shimmy

This article presents the effect of gyroscopic couples on the shimmy response of landing gear. The gyroscopic effect between the rotational motions of the aircraft’s longitudinal and vertical axes may be one of the causes of shimmy. The vertical load acting on the wheel axle plays a significant role in a tire’s dynamic characteristics, which may influence shimmy oscillation. So, vertical dynamics also need to be considered for shimmy analysis along with lateral and torsional modes. Suitable mathematical models are required to study the system’s shimmy oscillation and stability nature. The mathematical model was developed by introducing a gyroscopic couple with 5 degrees of freedom (DOF). A numeric analysis was made to investigate the influence of gyroscopic couples on the landing gear model. The simulation results of the model with and without gyroscopic couple are compared and the effect of each parameter on shimmy is studied

Effect of grinding wheel on the dynamic performance of high-speed spindle system with an improved FE model

The grinding wheel is a key factor which should be considered in the process of predicting the dynamic performance of the high-speed spindle system. Currently, most research is mainly focuses on shaft and bearing using Timoshenko’s beam and Jones’ bearing model. In this research, considering the effect of grinding wheel on the dynamic behavior of the high-speed motorized spindle system, a dynamic model of spindle system has been established by utilizing the finite element method (FEM). The model is improved by optimizing the relevant parameters of spindle system and validated by measuring FRF using impact hammer test. The reported results are well matched (maximum error is 5 %). Using the improved model, the effect of grinding wheel on the critical speeds, mode shapes, centrifugal force and gyroscopic effects of spindle system are analyzed. In addition, the impact of different diameters, materials and fixed methods of grinding wheel on the dynamic property of spindle system are also carried out. The result shows the affect of grinding wheel and design guideline of the spindle and grinding wheel

CFD investigation of a complete floating offshore wind turbine

This chapter presents numerical computations for floating offshore wind turbines for a machine of 10-MW rated power. The rotors were computed using the Helicopter Multi-Block flow solver of the University of Glasgow that solves the Navier-Stokes equations in integral form using the arbitrary Lagrangian-Eulerian formulation for time-dependent domains with moving boundaries. Hydrodynamic loads on the support platform were computed using the Smoothed Particle Hydrodynamics method. This method is mesh-free, and represents the fluid by a set of discrete particles. The motion of the floating offshore wind turbine is computed using a Multi-Body Dynamic Model of rigid bodies and frictionless joints. Mooring cables are modelled as a set of springs and dampers. All solvers were validated separately before coupling, and the loosely coupled algorithm used is described in detail alongside the obtained results

A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone

Modeling of the youBot in a serial link structure using twists and wrenches in a bond graph

We present a walk-through tutorial on the modeling of a complex robotic system, like the newly developed desktop mobile manipulator youBot developed by KUKA[5, 4]. The tutorial shows the design of models for typical robotic elements, done in a reusable object-oriented style. We employ an energy-based approach for modeling and its bondgraph notation to ensure encapsulation of functionality, extendability and reusability of each element of the model. The kinematic representation of mechanical elements is captured using screw theory. The modeling process is explained in two steps: first submodels of separate components are elaborated and next the model is constructed from these components

Dynamic model of a railway wheelset for corrugation problem analysis

[EN] In the present work a model of flexible shafts is adapted for modelling the railway wheelset. The dynamic properties of the solid are obtained from a solid finite element model of a real wheelset. The model adopts an Eulerian coordinate set for numerical efficiency. Results of the crossed-receptance and mobility functions are presented, where the excitation is the vertical wheel-rail contact force and the displacement (or velocity) is measured in the wheel-rail contact plane. These results let us know that the gyroscopic effect may contribute to define the wavelength-fixing mechanism in some corrugation problems, even if the train speed is low.This work was sponsored by Projects T79/2006 (Ministerio de Fomento - Metro de Madrid- CDM) and TRA2007-67167 (Ministerio de Educación y Ciencia - FEDER).Vila Tortosa, MP.; Rovira, A.; Fayos Sancho, J.; Baeza González, LM. (2009). Dynamic model of a railway wheelset for corrugation problem analysis. Noise & Vibration Worldwide. 40(11):10-18. https://doi.org/10.1260/095745609790251579S1018401

Thermal Effects for Shaft-Pre-Stress on Rotor Dynamic System

This Paper outlines study behaviour of rotating shaft with high speed under thermal effects. The method of obtaining the frequency response functions of a rotor system with study whirl effect in this revision the raw data obtained from the experimental results (using Smart Office program) are curve-fitted by theoretical data regenerated from some of the experimental data and simulating it using finite element (ANSYS 12). (FE) models using the Eigen analysis capability were used to simulate the vibration. The results were compared with experimental data show analysis data with acceptable accuracy and performance. The rotating effect causes un-symmetry in the system matrices, resulting in complexity in decoupling the mathematical models of the system for the purpose of modal analysis. Different method is therefore required, which can handle general system matrices rather than symmetrical matrices, which is normal for passive structures. Mathematical model of the system from the test data can be assembled. The frequency response functions are extracted, Campbell diagram are draw and simulated. (FE) is used to carry out such as simulation since it has good capability for Eigen analysis and also good graphical facility. Keywords: Thermal effects, Modelling, Campbell diagram, Whirl, Rotor dynamics.Comment: Published by: Academic Research Publishing Agency. All rights reserved, 6 pages, 4 figures, 1 pictur

Stabilization of biped dynamic walking using gyroscopic couple

This paper presents a new strategy for dynamic walking where a gyroscope mounted on top of the biped is precessed to achieve balancing both in the Coronal and Sagittal planes. A gait is devised and simulation results are provided to show the feasibility of proposed balancing method.published_or_final_versio

Influence of the Gyroscopic Effects on Friction Induced Vibration in Aircraft Braking in System

International audienceAeronautical brakes are subject to non-linear unstable vibrations. In particular, two modes appear and present a risk for the structure. Firstly, the whirl modes consist of a rotating bending motion of the axle out-of-phase with the brake torque tube. It is due to a coupling of two bending modes of the axle in orthogonal directions. Secondly, the brake squeal mode resulting from stick-slip or sprag-slip phenomena consists of a rotational motion of the brake around the axle. Those vibrations are not resulting from an external excitation but are friction-induced self-excited. Hence, they are dependent on tribological phenomena specific to carbon disks and are in particular controlled by the friction coefficient μ.In order to take into account the dynamical aspect in brake design, Messier-Bugatti-Dowty wants to simulate modes and acceleration g's levels. This article deals with the improvement of such a model.A finite element of the brake exists. It is able to reproduce whirl modes and squeal mode. In order to improve it, physical phenomena must be introduced. Here, the impact of gyroscopic effects is evaluated. For this, an analytical model is built to determine the consequences on frequencies and stability