Open Access
Impact of strain gauge misalignment and model parameters on load estimation in wind turbines
(Elsevier, 2026-01-15) Bacaicoa Díaz, Julen; Iriarte Goñi, Xabier; Aginaga García, Jokin; Plaza Puértolas, Aitor; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Accurate load estimation in wind turbines is important for understanding the structural behaviour and optimising performance. Loads are commonly measured using strain gauges, but the process is strongly based on accurate placement and alignment. This work explores the influence of geometric, material, misplacement, and misalignment parameters on the performance of different strain gauge configurations for obtaining load estimates. An analytical model for a single gauge is presented which establishes the relationship between exerted loads and measured strain. Using second-order approximations, the sensitivities of the estimated loads are calculated in terms of the uncertainty of the model parameters. The model allows to calculate how the secondary loads affect the estimation of those of interest, which is particularly useful in wind turbines where all three forces and three moments occur simultaneously. When estimating a single load, analytic results show that sensitivities to geometric and material parameters remain consistent regardless of secondary loads, while sensitivities to gauge bonding parameters reveal a cross-talk effect. As these sensitivity results depend on the model parameters and the instantaneous values of the secondary loads (which vary with time) the sensitivities will strongly depend on the application cases. In this paper a horizontal-axis wind turbine is simulated, calculating the loads at the Low Speed Shaft and the Tower Base. The sensitivity results for these subsystems using Montecarlo simulations show that while some loads can be precisely estimated, other loads will be very poorly estimated even when the gauges are bonded with tiny misalignment errors.
Open Access
On the convergence of a modal updating iterative method applied to a vibrating table for food transportation
(2007) Iriarte Goñi, Xabier; Ros Ganuza, Javier; Mekanika, Energetika eta Materialen Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería Mecánica, Energética y de Materiales
This work focuses on the updating of the parameters of a Vibrating Table Multibody model. Modal Analysis has been done to obtain the experimental Modal Parameters of the System (natural frequencies (ωi), damping ratios (ξi) and mode shapes (φi)), and the unknown Dynamic Model Parameters (p) are found through a Newton-Raphson based procedure that fits the Modal Parameters of the dynamic model to those obtained from the Modal Analysis experiment.
Open Access
Determination of the symbolic base inertial parameters of planar mechanisms
(Elsevier, 2017) Iriarte Goñi, Xabier; Ros Ganuza, Javier; Mata, Vicente; Aginaga García, Jokin; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The inertial information of a planar mechanical system is characterised using 4 inertial parameters per solid. Due to the kinematic constraints, this parametrisation turns out be redundant. In order to reduce the computational cost of the model and make it possible to estimate its inertial parameters, the model is usually written in terms of a minimum set of inertial parameters called base inertial parameters. These parameters completely determine the dynamics of motion (kinetics) of a mechanism and, since their contributions are independent to each other, their actual values can be estimated experimentally. The base inertial parameters expressions can be written as a linear combination of the inertial parameters and determining their symbolic expressions provides a deeper insight into their physical meaning. This paper presents a new algorithm to determine the symbolic expressions of the base inertial parameters of planar mechanisms. The approach is based on a very well known numerical method to obtain the base inertial parameters and on the fact that these parameters belong to a class of functions that lets us search for symbolic expressions matching with them. Since the symbolic expressions are a function of the geometric constants of the system, the presented algorithm constitutes a very valuable tool in design optimisation and it is also very interesting in dynamic parameter estimation, model reduction and other fields.
Open Access
Trayectorias de máxima rigidez de un robot redundante actuando como soporte en el mecanizado de paredes delgadas
(Universitat Politècnica de València, 2023) Aginaga García, Jokin; García Cuesta, Iván; Iriarte Goñi, Xabier; Plaza Puértolas, Aitor; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
La precisión de un robot está ligada a su rigidez. En comparación con la máquina herramienta tradicional, los robots industriales tienen un gran espacio de trabajo como ventaja, pero una rigidez reducida como desventaja. Además, la rigidez tiene una gran dependencia y variabilidad con la postura o configuración del robot. De ahí que resulte necesario un análisis de rigidez de los robots, que se evalúa mediante la matriz de rigidez. En este trabajo se presenta un análisis de rigidez de un robot serie. Ante la diversidad de índices representativos extraídos a partir de la matriz de rigidez, se ha propuesto el uso de un índice que tenga en cuenta la dirección de las cargas que soporta el robot y la dirección en que se desea que el robot aporte rigidez en la aplicación específica. Asimismo, se ha utilizado el índice de rigidez para llevar el robot a configuraciones que mejoren la rigidez, hecho que resulta posible en aplicaciones en las que el robot tiene al menos un grado de libertad (GDL) redundante. La metodología se ha aplicado a un robot de 7 GDL utilizado como robot de soporte en el mecanizado de paredes delgadas. Dado que para definir la trayectoria únicamente son necesarios 5 GDL, se utilizan 2 GDL reduntantes para mejorar la rigidez.
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.
Open Access
A unified analytical disk cam profile generation methodology using the Instantaneous Center of Rotation for educational purpose
(Elsevier, 2024) Iriarte Goñi, Xabier; Bacaicoa Díaz, Julen; Plaza Puértolas, Aitor; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Cam design is a fundamental part of the Mechanism and Machine Theory (MMT) and is included in the vast majority of MMT books. Cam profile design is usually determined with graphical and analytical methods. Graphical methods are didactically very successful to introduce the theory of cam profile generation in a simple way. In turn, analytical methods allow computer implementations of cam profile generation in order to reproduce it accurately. Most modern MMT books describe analytical methods using geometric equations and envelope theory. However, the analytical profile definition depends on the specific type of follower and there is a lack of a general formulation. This work presents a unified and general analytical formulation for the disk cam profile determination. Based on the Instantaneous Center of Rotation and the kinematic inversion, the formulation provides analytical expressions of the cam profile and is applicable to any type of follower. Thus, the unified formulation can be used in forthcoming books on this discipline.
Open Access
Comprehensive characterisation of a low-frequency-vibration energy harvester
(MDPI, 2024) Plaza Puértolas, Aitor; Iriarte Goñi, Xabier; Castellano Aldave, Jesús Carlos; Carlosena García, Alfonso; Ingeniería; Ingeniaritza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
In this paper, we describe a measurement procedure to fully characterise a novel vibration energy harvester operating in the ultra-low-frequency range. The procedure, which is more thorough than those usually found in the literature, comprises three main stages: modelling, experimental characterisation and parameter identification. Modelling is accomplished in two alternative ways, a physical model (white box) and a mixed one (black box), which model the magnetic interaction via Fourier series. The experimental measurements include not only the input (acceleration)–output (energy) response but also the (internal) dynamic behaviour of the system, making use of a synchronised image processing and signal acquisition system. The identification procedure, based on maximum likelihood, estimates all the relevant parameters to characterise the system to simulate its behaviour and helps to optimise its performance. While the method is custom-designed for a particular harvester, the comprehensive approach and most of its procedures can be applied to similar harvesters.
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
Optimal strain-gauge placement for mechanical load estimation in circular cross-section shafts
(Elsevier, 2021) Iriarte Goñi, Xabier; Aginaga García, Jokin; Gainza González, Gorka; Ros Ganuza, Javier; Bacaicoa Díaz, Julen; Institute of Smart Cities - ISC
The customary electrical circuit configuration for estimating mechanical loads with strain gauges uses Wheatstone full- or half-bridges. For each mechanical load to be estimated, a dedicated bridge with two or four gauges has to be mounted, placing the strain gauges in specific configurations along the measured part. In this paper the strain of individual gauges is measured by means of quarter-bridges and all the mechanical loads exerted on a shaft are estimated jointly as different linear combinations of the strains of the gauges. The location of the gauges on the shaft are determined optimally and the influence of apparent strain related to temperature variations is avoided. Results show several configurations of reduced sets of gauges capable of optimally estimating the six components of the mechanical loads exerted on a circular cross-section shaft. The validation of the approach in a dedicated rig has shown the complexity of its experimental implementation.
Open Access
Precise and low-cost computationally efficient method for operational modal analysis in wind turbines
(Elsevier, 2026-01-05) Vilella San Martín, Íñigo; Gainza González, Gorka; Zivanovic, Miroslav; Iriarte Goñi, Xabier; Plaza Puértolas, Aitor; Carlosena García, Alfonso; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Structural Health Monitoring of wind turbines using Operational Modal Analysis techniques has become increasingly important in the wind industry. This importance is underscored by the fact that many installed wind farms are nearing the end of their operational lifespan and require life extension strategies that ensure safe operation. However, most existing techniques in the state of the art are either imprecise or necessitate complex calculations and high computational costs. These limitations often require extensive data extraction for external processing, the use of complex processors, and the engagement of external services for data analysis, posing significant challenges for wind farm owners. This paper presents an Operational Modal Analysis algorithm designed for Structural Health Monitoring of wind turbines, addressing the aforementioned issues. The proposed algorithm is highly computationally efficient, allowing for implementation on a low-cost electronic node that can autonomously analyze the structural health of the wind turbine with high precision. To achieve this, the algorithm employs a combination of techniques, some of which are novel, such as the modeling of modes and harmonic elimination using linear Kalman filters. Other techniques, such as the Random Decrement Technique and the Ibrahim Time Domain, are well-established in literature. However, the specific combination of these techniques as presented in this paper is also a novelty. All these techniques involve simple calculations, resulting in an efficient algorithm with low computational cost. Moreover, this paper validates the algorithm using both synthetic signals from OpenFAST and real signals from wind turbines. The results are highly satisfactory, outperforming leading techniques in this context and confirming the algorithm's precision. Notably, the algorithm excels in damping estimation, a challenging aspect of Operational Modal Analysis applied to wind turbines, for which no existing Operational Modal Analysis techniques provide precise estimates. In conclusion, the algorithm presented in this paper offers a precise, efficient, and low-cost solution for Structural Health Monitoring of wind turbines, eliminating the need for extensive data processing and external analysis, thereby simplifying and improving the maintenance and operation of wind farms.