Artículos de revista ISC - ISC aldizkari artikuluak

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Open Access
4P operational harmonic and blade vibration in wind turbines: a real case study of an active yaw system and a concrete tower
(Elsevier, 2024) Torres Elizondo, Antonio; Gil Soto, Javier; Plaza Puértolas, Aitor; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This study aims to comprehensively investigate the impact of mechanical loads on the performance and lifetime of wind turbines, with particular emphasis on blade vibration at the 4P operational harmonic. Experiments and advanced aeroelastic simulations are combined to assess how active yaw systems and concrete towers affect this specific vibration. Contrary to previous assumptions, field tests have shown that there is a resonance phenomenon in the blade. Specifically, the first edgewise mode of the blade resonates at the 4P frequency, which did not happen in the aeroelastic simulations. Remarkably, thorough aeroelastic simulations show that this resonance is triggered by the excitation of the Edgewise Backward Whirling mode of the rotor, which occurs at the 3P operating harmonic. This study highlights the need for accurate and precise modelling using aeroelastic simulations to reproduce the resonance phenomenon and analyse the contributing factors. A major breakthrough is the discovery that stiffening the active yaw system significantly reduces the 3P hub fixed motions, resulting in reduced blade vibration at the 4P frequency. Furthermore, the simulations show the sensitivity of the 4P vibration to different wind characteristics, providing valuable insights for the design of wind turbines in different environmental conditions.
Open Access
Characterization and optimization of cutting depth in passive-compliant robotic belt grinding
(Springer, 2024-12-30) Torres Izu, Ramón; Aginaga García, Jokin; Mata Cantón, Sara; Barrenetxea Azpeitia, David; Inziarte Hidalgo, Ibai; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
Robotic belt grinding offers numerous advantages, such as operational versatility and the ability to work in complex spaces. Its implementation in the modern industry aims to surpass manual grinding tasks and enhance overall productivity. Among these processes, compliant techniques offer adaptive solutions, where the tool can adapt to complex surfaces, besides providing more efficient grinding solutions for industrial applications. This paper focuses on an easy characterization of the cutting depth in a robotic belt grinding application using a portable passive-compliant tool. To this end, a cutting depth belt grinding model based on process parameters is presented. Experimental tests are conducted to correlate the depth of material removal with the belt wear behavior and analysis on Inconel 718 specimens. Then, the solution presented is validated through additional tests. Furthermore, the model is utilized for a productivity optimization that takes into account the belt wear, searching for optimal process variables that minimize cycle time.
Embargo
Compensation strategy to minimize over-cut effects in robotic belt grinding with passive-compliant tools
(Elsevier, 2025-03-19) Torres Izu, Ramón; Iriarte Goñi, Xabier; Mata Cantón, Sara; Aginaga García, Jokin; Barrenetxea Azpeitia, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
At the beginning of the robotic belt grinding path, passive-compliant tools can generate an over-cut effect. The transient state from the first contact point between tool and workpiece to the grinding steady state can generate an excess of material removal at the workpiece border. If successive grinding passes are made, this effect will accumulate, increasing the shape deviation at the workpiece border. Therefore, the purpose of this research is to analyze this phenomenon and develop an easy-to-implement compensation strategy to avoid removing an excess of material at the beginning of grinding paths. Specifically, a geometric model of the contact has been developed that, together with the material removal model, allows to reproduce the cut-in effect for a robot-operated passive-compliant tool case. In turn, the compensation strategy that has been designed, avoids removing an excessive amount of material by means of a cut-in path that adjusts the feed velocity to the instantaneous contact force. This path is based on the tool geometry and grinding process parameters. In order to validate the proposed strategy, several experiments have been performed for different process conditions. Results show how the proposed solution significantly reduces the over-cut effect providing a homogeneous material removal since the beginning of the grinding.
Embargo
D-optimal strain sensor placement for mechanical load estimation in the presence of nuisance loads and thermal strain
(Elsevier, 2024-12-08) Iriarte Goñi, Xabier; Bacaicoa Díaz, Julen; Aginaga García, Jokin; Plaza Puértolas, Aitor; Szczepanska-Álvarez, Anna; Ingeniería; Ingeniaritza; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
The measurement of loads in circular cross-section geometries using strain gauges or other types of strain sensors is well-known in the field of mechanical engineering. Typical stress measurement configurations use 4 strain sensors strategically placed on the surface of the shaft and connected in the form of a complete Wheatstone bridge. Thus, 4 strain sensors are used to estimate each of the six load components to which a shaft may be subjected. Some typical configurations are designed to compensate for temperature effects, making them robust to temperature changes. Despite being used for decades, there is no record of any algorithm that serves to calculate these configurations, demonstrate that they are optimal or determine new configurations with other requirements. In this article, an algorithm is developed that allows calculating the optimal configurations of strain sensors to estimate one or several load components, compensating for the effect of other loads and temperature variations. This algorithm is based on the measurement of the strain of each gauge using Wheatstone quarter bridges and uses the same set of sensors for the estimation of various load components. The results are two-fold: on the one hand the traditional configurations are shown to be optimal and on the other hand a series of additional optimal configurations are obtained to estimate various sets of load components compensating for the influence of the rest. Additionally, a means of calculating the estimation variance of the loads of interest is provided.
Open Access
Design, manufacturing, validation of a multi-orientation tilt test bench for testing vehicles rollover and tests of ATV-Quad for agricultural applications
(MDPI, 2021) Bacaicoa Díaz, Julen; Ballesteros Egüés, Tomás; Arana Navarro, Ignacio; Aginaga García, Jokin; Latorre Biel, Juan Ignacio; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
A rollover test bench has been designed, manufactured, and validated for analyzing the all-terrain vehicle (ATV)-Quad overturn of diverse vehicles in different configurations, such as installing a rollover protection system (ROPS), considering drivers of different physical constitutions, the appropriate use of safety belts, or having a full or empty fuel tank. The main purpose of this research is to determine the tilt angle of the vehicle that triggers the ATV-Quad overturn. The scope of the design and development of the newly conceived bench include the mechanical structure, the electronics and the control. It can simulate static and dynamic rollover in different directions. As a main conclusion, it can be stated that the performance of the test bench was successful, since it allowed for the development of several ATV models, equipped with different dummies, in a variety of configurations. In particular, it was possible to assess the effectivity of the AD-ROPS system (automatically deployed ROPS), regarding the protection of the driver of the vehicle. Moreover, multiple tests, performed with diverse ATV-Quads in the developed bench and in different configurations, have been reported and their results discussed.
Open Access
Effects of playing football matches with two balls on spatial exploration: average and one-by-one analyses
(Palacký University in Olomouc, 2024-07-02) González-Artetxe, Asier; Los Arcos Larumbe, Asier; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
Background: football task design lies in manipulating the relevant features of the game considering the consequences these modifications can have on players' performance. Adding an extra ball may boost academy footballers' possibilities of interaction and challenge them to readjust their motor conduct according to the uncertainty of a novel game scenario. Objective: this study compared young footballers¿ spatial exploration index (SEI) overall and one by one during simulated matches played with one or two balls. Methods: forty-four association football players from U14 and U16 teams of the same club played two 60-minute matches with all the official game rules and regulatory conditions. The unique difference was that one match was played with a single ball and the other with two balls simultaneously. Positional data were gathered during matches using a Global Positioning System (GPS) to assess each footballer's SEI central tendency and approximate entropy (ApEn) measures. Results: the average SEI of both U14 (p = .01; -2 = .066, medium) and U16 (p < .001; -2 = .187, large) players was lower, and its ApEn higher (U14: p < .001, -2 = .014, small; U16: p < .001, -2 = .035, small), during the two-ball match in comparison to the standard one-ball match. The graphical representation shows how their relative positioning changed between matches, breaking team formation in two during the two-ball condition. From an individual perspective, the second ball affected defenders mainly. Most of them reduced their intervention area, acted more unpredictably within this, and got closer to their target compared with the standard one-ball match. Conclusions: adding an extra ball led young footballers to explore less space more unpredictably, especially defenders. So, a one-by-one analysis may assist coaches in evaluating each player¿s tactical response to football training.
Open Access
Exploring the impact of social relationship modification on young female soccer players' performance in small-sided games
(Termedia, 2024-12-06) Los Arcos Larumbe, Asier; González-Artetxe, Asier; Lombardero, Sara; Esnal-Arrizabalaga, Oihan; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This study compared young female soccer players' tactical, conditional, and emotional responses during two small-sided games (SSGs), without restrictions (SSGfree), and introducing an additional rule (SSGrelationship: if a player touches an opponent just before she receives the ball, her team wins the ball back with an indirect free kick). Fourteen developmental U14 players participated in two 4 × 6-min seven-a-side games (six each, plus goalkeepers) on a 50-m long × 30-m wide field. Players' positional data were collected using a GPS to assess their tactical performance (central tendency and entropy measures of the surface area, distance between players and to the nearest opponent, and stretch and spatial exploration indices) and conditional performance (total and low-moderate, high, very high speed, sprinting distance covered, and the number of accelerations and decelerations). Participants also rated their perceived enjoyment and competence using the BECS scale. Tactical central tendency measures were higher during SSGfree (p < 0.05) than in SSGrelationship, but no differences were apparent for entropy and conditional measures (p > 0.05). From bout to bout, central tendency measures of tactical variables decreased more frequently during SSGfree than SSGrelationship. Entropy measures and conditional performance hardly varied between bouts. Enjoyment and perceived competence levels were similar for both SSGs. The findings indicate that modifying the interaction between opponents affects players' tactical responses more than conditional responses when compared with free play. Specifically, touching an opponent before they receive the ball may encourage players to play closer to their opponents during training tasks.
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
Kinematic design of a new four degree-of-freedom parallel robot for knee rehabilitation
(ASME, 2018) Aginaga García, Jokin; Iriarte Goñi, Xabier; Plaza Puértolas, Aitor; Mata, Vicente; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza; Institute of Smart Cities - ISC
Rehabilitation robots are increasingly being developed in order to be used by injured people to perform exercise and training. As these exercises do not need wide range movements, some parallel robots with lower mobility architecture can be an ideal solution for this purpose. This paper presents the design of a new four degree-of-freedom (DOF) parallel robot for knee rehabilitation. The required four DOFs are two translations in a vertical plane and two rotations, one of them around an axis perpendicular to the vertical plane and the other one with respect to a vector normal to the instantaneous orientation of the mobile platform. These four DOFs are reached by means of two RPRR limbs and two UPS limbs linked to an articulated mobile platform with an internal DOF. Kinematics of the new mechanism are solved and the direct Jacobian is calculated. A singularity analysis is carried out and the gained DOFs of the direct singularities are calculated. Some of the singularities can be avoided by selecting suitable values of the geometric parameters of the robot. Moreover, among the found singularities, one of them can be used in order to fold up the mechanism for its transportation. It is concluded that the proposed mechanism reaches the desired output movements in order to carry out rehabilitation maneuvers in a singularity-free portion of its workspace.
Embargo
Modal Complexity Factors as indexes for modal parameter identification in operational modal analysis of coupled dynamic systems
(Elsevier, 2024-11-28) Ibarrola Chamizo, Javier; Agirre Olabide, Iker; Merino Olagüe, Mikel; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
Vibration analysis seeks to extract the modal parameters of a mechanical system by means of experimental measurements. Natural frequencies, damping ratios and mode shapes are identified from the measurements data from experimental or operational modal analysis. Modal shapes can show real or complex values. The degree of complexity of a modal shape can be measured by the Modal Complexity Factors (MCF). Among others, modal complexity can be due to non-uniformly distributed damping. In complex mechanical systems like a robot, complex modes are expected due to its active and non distributed damping. In turn, in a metallic workpiece real modes are expected. In the robotic machining of thin workpieces, both the robot and the workpiece constitute a coupled dynamic system, operating within the same frequency range. This work proposes the use of MCFs as indexes to determine if each mode corresponds to the workpiece or the robot. Experimental results of an operational modal analysis show a lower mode complexity for the workpiece modes and a higher complexity for the robot frequencies. MCFs show a good performance in separating modes of such coupled systems due to the different damping nature of the robot and the workpiece.
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
Robotic application for abrasive belt machining of complex aircraft metal parts
(Publicaciones DYNA, 2024) Torres Izu, Ramón; Mata Cantón, Sara; Aginaga García, Jokin; Barrenetxea Azpeitia, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
Surface finishing applications are still cumbersome manual tasks, therefore, robotization of the process is of great interest as it allows for automation and increased versatility. However, finishing processes are difficult to automate, mainly because of the variation in material removal. In particular, the variables involved undergo changes that modify the material removal rate. This paper proposes a methodology for modeling material removal automatically based on experimental data. The procedure consists of monitoring the material removed from the parts under study that are in an automated precision measuring system during the finishing process. Based on the experimental models, a control algorithm for continuous material removal is presented. It guarantees a homogeneous surface finish by varying the robot feed rate. Finally, the results of several experimental material removal models under different process conditions and the validation of the proposed control algorithm are presented. The results show that the proposed method achieves a substantial improvement in the homogeneity of the finish.
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
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.

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