Open Access
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.
Open Access
The Yeregui family (18th-twentieth century)
(Springer, 2023) Aginaga García, Jokin; Claver Alba, Adrián; Pintor Borobia, Jesús María; Iriarte Goñi, Xabier; Ingeniería; Ingeniaritza
Since their appearance in the Middle Ages, mechanical clocks and watches have been ingenious devices with complex assemblies of gears, cams and actuators, some of which have survived to the present day. Over the centuries, advances in mechanical engineering were applied to clockmaking, achieving clocks with ever-increasing precision. In the north of Navarre, the Yeregui family formed an outstanding family of mechanical clockmakers who, from the end of the eighteenth century until the middle of the twentieth century, designed, built, assembled and maintained tower clocks for five generations. Their first recorded clock was designed and assembled by José Francisco Yeregui Zabaleta for the village of Betelu and its deed dates from 15th April 1796. Subsequently, different members of the family manufactured numerous clocks for towns and cities in and around Navarre, including the old clock of Pamplona Town Hall, in operation for more than 150 years until 1991 and recently restored. This chapter briefly describes the most significant advances in mechanical clockmaking and delves into the history and work of the Yeregui clockmaking lineage.
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
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.
Open Access
Comprehensive analysis of rotor edgewise whirling mode interaction with rotor speed harmonics
(IOP Publishing, 2024) Torres Elizondo, Antonio; Gil Soto, Javier; Plaza Puértolas, Aitor; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper presents a model that investigates the interaction between rotor edgewise whirling modes and rotor speed harmonics in wind turbines. The model is based on kinematic and dynamic principles, with a focus on the multi-blade coordinate transformation, which is critical for simulating the behaviour of the rotor whirling modes in wind turbines. The research has two objectives: to investigate the interaction between the rotor edgewise whirling modes and the rotor speed harmonics, and to provide clearer graphs that explain the complex nature of this non-intuitive rotor dynamics. The paper concludes by highlighting the practical implications of the research findings, in particular the effectiveness of visualisation techniques in identifying and explaining unexpected interactions.
Embargo
Modal Complexity Factors as indexes for modal parameter identification in operational modal analysis of coupled dynamic systems
(Elsevier, 2025-03-31) 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
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
AI training for application to industrial robotics: trajectory generation for neural network tuning
(Springer, 2023) Merino Olagüe, Mikel; Ibarrola Chamizo, Javier; Aginaga García, Jokin; Hualde Otamendi, Mikel; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
In the present work robot trajectories are generated and kinematically simulated. Different data (joint coordinates, end effector position and orientation, images, etc.) are obtained in order to train a neural network suited for applications in robotics. The neural network has the goal of automatically generating trajectories based on a set of images and coordinates. For this purpose, trajectories are designed in two separate sections which are conveniently connected using Bezier curves, ensuring continuity up to accelerations. In addition, among the possible trajectories that can be carried out due to the different configurations of the robot, the most suitable ones have been selected avoiding collisions and singularities. The designed algorithm can be used in multiple applications by adapting its different parameters.
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
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.