scholarly journals A symbolic framework for flexible multibody systems applied to horizontal axis wind turbines

2021 ◽  
Author(s):  
Emmanuel Branlard ◽  
Jens Geisler
Keyword(s):  
Multibody Systems ◽  
Controller Design ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Flexible Bodies ◽  
Non Linear ◽  
Horizontal Axis Wind Turbines ◽  
Non Linear Equations

Abstract. The article presents a symbolic framework that is used to obtain the linear and non-linear equations of motion of a multibody system including rigid and flexible bodies. Our approach is based on Kane's method and a nonlinear shape function representation for flexible bodies. The method yields compact symbolic equations of motion with implicit account of the constraints. The general and automatic framework facilitate the creation and manipulation of models with various levels of fidelity. The symbolic treatment provides analytical gradients and linearized equations of motion. The linear and non-linear equations can be exported to Python code or dedicated software. The application are multiple such as: time-domain simulation, stability analyses, frequency domain analyses, advanced controller design, state observers, digital twins, etc. In this paper, we describe the method we used to systematically generate the equations of motion of multibody systems. We apply the framework to generate illustrative onshore and offshore wind turbine models. We compare our results with OpenFAST simulations and discuss the advantages and limitations of the method. A Python implementation is provided as an opensource project.

scholarly journals Multi-parametric Dynamic Analysis of a Rolling Bearings System

2021 ◽  
Vol 67 (9) ◽  
pp. 421-432
Author(s):  
Almatbek Kydyrbekuly ◽  
Gulama-Garip Alisher Ibrayev ◽  
Tangat Ospan ◽  
Anatolij Nikonov
Keyword(s):  
Harmonic Balance ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Stiffness Coefficient ◽  
Rolling Bearings ◽  
Linear Characteristic ◽  
Non Linear ◽  
Linear Equations Of Motion ◽  
Oscillation Frequencies ◽  
Non Linear Equations

A method for calculating amplitudes and constructing frequency characteristics of forced and self-excited vibrations of a rotor-fluid-foundation system on rolling bearings with a non-linear characteristic based on the method of complex amplitudes and harmonic balance has been developed. Non-linear equations of motion of the rotor-fluid-foundation system are derived, and analytical methods of their solution are presented. Frequencies of fundamental and ultra-harmonic resonances are determined. The intervals between self-oscillation frequencies are estimated. The dependence of amplitudes on the amount of fluid in the rotor cavity, the mass of the foundation, linear imbalance, the value of the stiffness coefficient, and the damping coefficient is shown.

scholarly journals Application of harmonic balance method for solving non-linear equations of motion

2018 ◽  
Vol 182 ◽  
pp. 02024
Author(s):  
Robert Kostek
Keyword(s):  
Harmonic Balance ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Harmonic Balance Method ◽  
Time History ◽  
Balance Method ◽  
Non Linear ◽  
Time Histories ◽  
History Of ◽  
Non Linear Equations

This article presents the advantages and limitations of a harmonic balance method applied for solving non-linear equations of monition. This method provides an opportunity to find stable and unstable periodic solutions, which was demonstrated for a few equations. An error of solution decreases rapidly with increase of number of harmonics for smooth time history of acceleration, which shows convergence; whereas, for discontinuous time histories, this method is not effective.

Stability and vibration of a non-linear vehicle and passenger system

2002 ◽  
Vol 216 (2) ◽  
pp. 109-116 ◽  
Author(s):  
K Yu ◽  
A C J Luo ◽  
Y He
Keyword(s):  
Equations Of Motion ◽  
Linear Equations ◽  
Dynamic Responses ◽  
Spring Stiffness ◽  
Torsional Spring ◽  
Non Linear ◽  
Linear Equations Of Motion ◽  
Safety Belts ◽  
The Stability ◽  
Non Linear Equations

A non-linear dynamic model to predict the passenger's response in a vehicle travelling on a rough pavement surface (or a rough terrain) is developed. The corresponding equilibrium and stability are investigated through the non-linear equations of motion for a vehicle and passenger system with impacts. The stability with respect to the torsional spring stiffness of safety belts is illustrated. Based on such a stability condition, the dynamic responses for the vehicle and passenger system with and without impacts are simulated numerically. This investigation shows that a strong torsional spring is required in order to reduce the vibration amplitudes of passengers and to avoid impacts between the vehicle and passenger.

Benchmarking Bicycle and Motorcycle Equations of Motion

2011 ◽  
Author(s):  
Andrew E. Dressel ◽  
Adeeb Rahman
Keyword(s):  
Numerical Solutions ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Linearized Equations ◽  
Cornell University ◽  
Class Project ◽  
Bicycle Model ◽  
Non Linear ◽  
Eigenvalue Condition ◽  
Non Linear Equations

In 2007, Meijaard, et al. [1] presented the canonical linearized equations of motion for the Whipple bicycle model along with test cases for checking alternative formulations of the equations of motion or alternative numerical solutions. This paper describes benchmarking three other implementations of bike equations of motion: the linearized equations for bicycles written by Papadopoulos and Schwab [2] in JBike6, the non-linear equations for bicycles outlined by Schwab [3] and implemented in MATLAB as a Cornell University class project, and the non-linear equations for motorcycles implemented in FastBike from the Motorcycle Dynamics Research Group at the University of Padua. [4] Some implementations are easier to benchmark than others. For example, JBike6 is designed to produce eigenvalues and easily exposes the coefficients of its linearized equations of motion. At the other extreme, the class project non-linear equations were not originally intended to generate eigenvalues and are implemented in a single 48×48 matrix. Finally, while FastBike does generate eigenvalues, its equations of motion incorporate tire and frame compliance, which cannot be completely disabled. Instead, the tire stiffness parameters must be increased, but not so much as to cause convergence errors in FastBike. In the end, all three implementations generate eigenvalues that match the published benchmark values to varying degrees. JBike6 comes the closest, with agreement of 12 digits or more. The class project is second, with agreement of 12 digits for most forward speeds, but with a loss of measurable agreement near the capsize speed due to a peak in the eigenvalue condition number. Unfortunately, FastBike is limited at this time to exporting eigenvalues with no more than two decimal places, and so agreement can only be found to ±0.005.

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