Open Access
Symbolic multibody methods for real-time simulation of railway vehicles
(Springer, 2018) Ros Ganuza, Javier; Plaza Puértolas, Aitor; Iriarte Goñi, Xabier; Pintor Borobia, Jesús María; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
In this work, recently developed state-of-the-art symbolic multibody methods are tested to accurately model a complex railway vehicle. The model is generated using a symbolic implementation of the principle of virtual power. Creep forces are modeled using a direct symbolic implementation of the standard linear Kalker model. No simplifications, such as base parameter reduction, partial-linearization or lookup tables for contact kinematics, are used. An Implicit–Explicit integration scheme is proposed to efficiently deal with the stiff creep dynamics. Real-time performance is achieved: the CPU time required for a very robust 1 ms integration time step is 203 µs.
Open Access
Mode-displacement method for structural dynamic analysis of bio-inspired structures: a palm-tree stem subject to wind effects
(Taylor & Francis, 2022) Plaza Puértolas, Aitor; Vargas Silva, Gustavo Adolfo; Iriarte Goñi, Xabier; Ros Ganuza, Javier; Ingeniería; Ingeniaritza
Biological materials (orthotropic materials), like wood, can offer good mechanical properties with a minimum amount of material, making their internal structure the suitable one to be applied on bio-inspired structures. The knowledge of the exceptional structural performance of palm trees, and specially its response to different loading conditions, provides useful information when lightweight structures with high slenderness ratio are desired. Recent researches focused on the analysis of palm trees subject to static loading conditions, ignoring the fluctuating nature of the wind speed. The purpose of this study is to simulate in a computational efficient way the effect of dynamic loading conditions applied on palm trees. Using the mode displacement method, the number of degrees of freedom of a dynamic finite element analysis can be drastically reduced with a minimal loss of accuracy. It was applied to simulate the behavior of structures comprised of an orthotropic material subject to a stochastic dynamic load. The influence of the number of selected degrees of freedom has also been studied. In addition, an exponential integration method is proposed to perform the time integration procedure. The results obtained show that a properly reduced model suitably represents the full finite element model without any appreciable loss of accuracy; it is also shown that computational cost can be drastically reduced. This method could give an appropriate computational representation of the behavior of orthotropic structures, and it could be used for studying more complex bio-inspired structures.
Open Access
Along-the-path exponential integration for Floquet stability analysis of wind turbines
(IOP Publishing, 2022) Ros Ganuza, Javier; Olcoz Alonso, Álvaro; Plaza Puértolas, Aitor; Zientziak; Institute of Smart Cities - ISC; Ciencias; Gobierno de Navarra / Nafarroako Gobernua
Traditionally, stability assessment of wind turbines has been performed by eigenanalysis of the azimuthally-averaged linearized system after applying the Multi-Blade Coordinate (MBC) transformation. However, due to internal or external anisotropy, the MBC transform does not produce an exact Linear Time-Invariant (LTI) system, and a Floquet analysis is required to capture the influence of all periodic terms, leading to a more accurate stability analysis. In this paper exponential integration methods that use system linearizations at different blade azimuth positions are used to integrate the perturbed system state and compute the Floquet monodromy matrix. The proposed procedure is assessed for a simple 6 DOF wind turbine model and a more complex aeroelastic model of a 5MW onshore wind turbine. The defined along-the-path or moving-point exponential integrator is found to be the suitable in order to perform a Floquet stability analysis even using a coarse linearization grid.
Open Access
Dynamic considerations of heel-strike impact in human gait
(Springer, 2015) Ros Ganuza, Javier; Font-Llagunes, Josep M.; Plaza Puértolas, Aitor; Kövecses, József; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
Based on the impulsive-dynamics formulation, this article presents the analysis of different strategies to regulate the energy dissipation at the heel-strike event in the context of human locomotion. For this purpose, a seven-link 2D human-like multibody model based on anthropometric data is used. The model captures the most relevant dynamic and energetic aspects of the heel-strike event in the sagittal plane. The pre-impact mechanical state of the system, around which the analysis of the heel impact contribution to energy dissipation is performed, is defined based on published data. In the context of the proposed impulsive-dynamics framework, different realistic strategies that the subject can apply to modify the impact dynamics are proposed and analyzed, namely, the trailing ankle push-off, the torso configuration and the degree of joint blocking in the colliding leg. Detailed numerical analysis and discussions are presented to quantify the effects of the mentioned strategies.
Open Access
Triaxial accelerometer based azimuth estimator for horizontal axis wind turbines
(Elsevier, 2023) Plaza Puértolas, Aitor; Ros Ganuza, Javier; Gainza González, Gorka; Fuentes Lárez, José David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
One of the elements that receives the greatest stresses is the main shaft. Its damage is directly related to the cyclical nature of its rotational motion. However, the vast majority of horizontal axis wind turbines (HAWT) do not have sensors to measure the main-shaft angular position (azimuth), or they are not always easily accessible. Using a main-shaft placed single triaxial accelerometer for the estimation of the azimuth is proposed as a low intrusion approach that can be easily deployed in machines already in use. An approach using a tandem of two extended Kalman filters (calibration/prediction), aiming for a precise and robust estimation, is presented. The estimator is able to calibrate for accelerometer positional and orientation errors, as well as for bias drift. To simplify the burden of deployment, a simple procedure is proposed to determine the covariance matrices for a particular HAWT from those determined in a synthetic case. The proposed approach is analyzed using synthetic data, OpenFAST simulation of NREL-5MW HAWT. It outperforms the ATAN naive approach by an order of magnitude, showing errors smaller than 0.4o. The filter shows a good behavior, coherent with that of the synthetic setup, when tested on experimental data obtained from a 3MW HAWT.
Open Access
Inertia transfer concept based general method for the determination of the base inertial parameters
(Springer, 2015) Ros Ganuza, Javier; Plaza Puértolas, Aitor; Iriarte Goñi, Xabier; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper presents a new algorithm to obtain the symbolic expressions of any of the possible base inertial parameter sets of a multibody system. Based on the ¿inertia transfer concept¿, a procedure is proposed to write a system of equations from which the base parameters are obtained. This leads to an automatizable and general method to obtain these parameters symbolically. The method can also be used to determine base inertial parameters numerically, and it can be even more straightforward to implement and use than the standard numerical methods. An example is presented to illustrate in detail the application of the algorithm, and to compare its results with those of a standard numerical procedure. The symbolic base inertial parameters can be of interest in symbolic simplification of the dynamic equations for real-time applications, design optimization, dynamic parameter identification, model reduction, and in other fields.