Attitude Reconstruction of Free-Flight CFD Generated Trajectories Using Non-Linear Pitch Damping Coefficient Curves

2022 ◽  
Author(s):  
Quincy E. McKown ◽  
Cole Kazemba ◽  
Eric Stern ◽  
Joesph Brock
Keyword(s):  
Damping Coefficient ◽  
Free Flight ◽  
Non Linear ◽  
Pitch Damping

Grey-box identification of the pitch damping coefficient from free flight tests

2014 ◽  
Author(s):  
Marie Albisser ◽  
Simona Dobre ◽  
Claude Berner ◽  
Magalie Thomassin ◽  
Hugues Garnier
Keyword(s):  
Damping Coefficient ◽  
Free Flight ◽  
Flight Tests ◽  
Pitch Damping

A New Damping Model for Non-Linear Stiffness Systems With Variable Preload Displacements and Constant Amplitude Decay Ratios

1992 ◽  
Author(s):  
T. Xu ◽  
G. G. Lowen
Keyword(s):  
Energy Loss ◽  
Mathematical Description ◽  
Damping Coefficient ◽  
Constant Amplitude ◽  
Damping Force ◽  
Non Linear ◽  
Linear Damping ◽  
Damping Model ◽  
Good Agreement

Abstract This study of the behavior of non-linear stiffness systems with variable preload displacements and constant amplitude decay ratios showed that the energy loss per cycle is dependent on these preload displacements. By introducing a non-linear damping force, which is a function of both displacement and velocity, the associated work per cycle can be made approximately the same function of the preload displacement as is the case for the energy loss. In this manner, it becomes possible to make the resulting damping coefficient essentially independent of the preload displacement. This new damping model was incorporated into the mathematical description of an over-running sprag clutch. Confirming experimentation showed very good agreement with computed results.

scholarly journals Influence of Variable Damping Coefficient on Efficiency of TMD with Inerter

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6175
Author(s):  
Piotr Brzeski ◽  
Mateusz Lazarek ◽  
Przemyslaw Perlikowski
Keyword(s):  
Oscillation Amplitude ◽  
Maximum Amplitude ◽  
Relative Displacement ◽  
Tuned Mass Damper ◽  
Damping Coefficient ◽  
Main Body ◽  
Mass Damper ◽  
Different Types ◽  
Non Linear ◽  
Variable Damping

In this paper, we study the dynamics of a two-degree freedom system consisting of the main body and tuned mass damper with inerter (TMDI). We add the dash-pot with variable damping coefficient to TMDI to study the overall efficiency of the device. We investigate different types of the non-linear characteristic of the dash-pot. We investigate devices in which damping coefficient change according to the relative displacement or the relative velocity between the damped mass and tuned mass damper. We also include in the investigation of different types of control functions. We show the two-parameter diagrams presenting the main body’s maximum amplitude versus the frequency of excitation of the damped body and different control parameter. We show how the application of a non-linear damper lets us control the main system’s oscillation amplitude.

scholarly journals Pitch damping identification in high speed regimes with a free-to-tumble rig

2020 ◽  
Vol 12 (4) ◽  
pp. 261-265
Author(s):  
Catalin PIRVU ◽  
Mihai Victor PRICOP ◽  
Jean-Philippe PRÉAUD ◽  
Louis WALPOT
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Dynamic Stability ◽  
Curve Fitting ◽  
High Speed ◽  
Oscillatory Behavior ◽  
Damping Coefficient ◽  
Test Conditions ◽  
Nonlinear Dynamic Stability ◽  
Pitch Damping

Many re-entry bodies, even if they are debris or not, have nonlinear dynamic stability characteristics that produce oscillations in flight. The free-to-tumble techniques can be used to extract damping coefficient of specific body for planetary entry. The curve fitting approach is used to predict oscillatory behavior and the damping coefficient for the various test conditions of the wind tunnel obtained after the experimental data. The analysis presented provides an overview of the free-to-tumble test techniques and illustrates the effects of dynamic stability of the inter-stage tronconical system. It is proposed that these test techniques and curve fitting solution be refined in the future to better define the dynamic stability curves for the re-entry bodies.

scholarly journals Power take-off damping control performance on the power conversion of oscillating-buoy wave energy converter

2021 ◽  
Vol 25 (6 Part A) ◽  
pp. 4107-4115
Author(s):  
Weijie Sun ◽  
Yujie Zhou ◽  
Zhengang Wan ◽  
Xiaoguo Zhou ◽  
Wanchao Zhang
Keyword(s):  
Wave Energy ◽  
Power Conversion ◽  
Low Frequency ◽  
Expansion Method ◽  
Damping Coefficient ◽  
Width Ratio ◽  
Damping Capacity ◽  
Low Velocity ◽  
Eigenfunction Expansion Method ◽  
Non Linear

The power take-off (PTO) damping mechanism is very important to the motion and power conversion for the wave energy converters. Based upon the potential flow theory, the series expression with unknown Fourier coefficients of velocity potential function of the basin where the cylindrical floating buoy is located is obtained by using the eigenfunction expansion method. According to the characteristics of the PTO damper, the motion and wave energy conversion characteristics of the float under the linear and non-linear PTO damping are studied, respectively, and the over-damping problem under the linear PTO damping is emphatically explored. The results show that the influence of PTO system with low velocity index on the motion of the device is mainly reflected in the PTO damping coefficient. With the increase of damping coefficient, the resonance frequency of the wave energy device decreases gradually, but the decrease amplitude is very small. The non-linear characteristics of PTO system cannot change the optimal capture width ratio of the float, but the large velocity index can effectively improve the damping capacity of PTO system. At lower and higher frequencies, the optimal PTO damping obtained by the analytic algorithm will make the device in an over-damped state. The highest frequency in the low frequency part and the lowest frequency in the high frequency part which need to be modified will gradually decrease with the increase of radius and draught.

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