Capítols de llibre
http://hdl.handle.net/2117/4018
2024-03-28T11:41:50ZHas the teaching innovation carried out during the pandemic been consolidated? DEM-UPC Subjects
http://hdl.handle.net/2117/400478
Has the teaching innovation carried out during the pandemic been consolidated? DEM-UPC Subjects
Jordi Nebot, Lluïsa; Puig Ortiz, Joan; Pàmies Vilà, Rosa
The alert situation due to Covid-19 caused traditional university teaching to go from face-to-face to on-line in less than a week. This article presents the experience and the measures adopted in this change of type of teaching in some subjects of the Barcelona School of Industrial Engineering of the UPC that depend on the Department of Mechanical Engineering (DEM). The subjects adopted different forms to face the new situation; those analyzed also made efforts to ensure quality teaching by developing new materials and adapting teaching and assessment systems. In some cases, it was decided to promote activities aimed at developing skills, emphasizing student self-management and, ultimately, promoting their active learning. Another aspect of this work is that it analyzes whether, really, the effort made during confinement has represented a teaching innovation in these subjects or has been just a mirage. For this, the results of two surveys carried out among the professors of the department in which they are asked about the tools they used, and still use, and their interest in sharing the experiences are presented. These results indicate that the resources used have served to improve and innovate in some aspects of DEM teaching.
2024-01-30T08:16:49ZJordi Nebot, LluïsaPuig Ortiz, JoanPàmies Vilà, RosaThe alert situation due to Covid-19 caused traditional university teaching to go from face-to-face to on-line in less than a week. This article presents the experience and the measures adopted in this change of type of teaching in some subjects of the Barcelona School of Industrial Engineering of the UPC that depend on the Department of Mechanical Engineering (DEM). The subjects adopted different forms to face the new situation; those analyzed also made efforts to ensure quality teaching by developing new materials and adapting teaching and assessment systems. In some cases, it was decided to promote activities aimed at developing skills, emphasizing student self-management and, ultimately, promoting their active learning. Another aspect of this work is that it analyzes whether, really, the effort made during confinement has represented a teaching innovation in these subjects or has been just a mirage. For this, the results of two surveys carried out among the professors of the department in which they are asked about the tools they used, and still use, and their interest in sharing the experiences are presented. These results indicate that the resources used have served to improve and innovate in some aspects of DEM teaching.Capítulo VI: Procesos de fusión en lecho de polvo aplicados a polímeros
http://hdl.handle.net/2117/396334
Capítulo VI: Procesos de fusión en lecho de polvo aplicados a polímeros
Minguella Canela, Joaquim; Fenollosa i Artés, Felip
Los procesos de fusión selectiva de polvo aplicados a polímeros se agrupan, en la clasificación de tecnologías propuesta en la norma ISO/ASTM 52900, en la categoría denominada “fusión de lecho de polvo” (en inglés Powder Bed Fusion). La aparición de la primera de estas tecnologías supuso el segundo gran impacto psicológico sobre lo que la impresión 3D podría suponer: si la primera aparición de la estereolitografía (1986) permitía imprimir prototipos para visualizar diseños, la aparición de la fusión selectiva de polvo en el año 1992[ ] demostró que las piezas podían ser algo más que prototipos: eran válidas como producto final, basándose en polímeros técnicos perfectamente conocidos. Si hasta entonces la impresión 3D era conocida como “Rapid Prototyping” (Prototipado Rápido), gracias a la fusión selectiva de polímeros parecía posible hablar de “Rapid Manufacturing” (Fabricación Rápida). El mito (absurdo pero estimulante) de que la impresión 3D reemplazaría la inyección de plásticos se abría paso en el imaginario del mundo de la ingeniería. Lo cierto es que hubo, gracias a esta nueva tecnología, un cambio de visión: el discurso respecto a la fabricación aditiva dejó de centrarse exclusivamente en la aceleración de los procesos de diseño para entrar en cómo productos finales podían beneficiarse de ser hechos mediante impresión 3D, tanto a efecto de que su diseño no se viera limitado por las restricciones de los procesos de fabricación actuales, como por otras cualidades más interesantes aún: la personalización de los productos y las posibilidades en cuanto a funcionalidad que proporcionaba la libertad de trazar cualquier geometría. En los primeros momentos, y aún hoy en buena medida, la tecnología facilitó prototipos que permitían someter a los diseños a pruebas de ensayo. Es decir, si los prototipos fabricados mediante otras tecnologías como la Estereolitografía (SLA) servían para validar diseños conceptuales, sobre todo en cuanto a geometrías a escala o a tamaño real, sin poder verificar aún funciones técnicas complejas, los prototipos hechos por fusión selectiva de polvo permitían los ensayos típicos (resistencia mecánica, térmica…) que validan la funcionalidad de los productos, reduciendo al mínimo las incógnitas sobre si serían homologadas las piezas una vez obtenidas en sus materiales y procesos finales. El mensaje era muy potente: si el prototipo falla, hay que rediseñar el producto. En consecuencia, no habrá posibilidad de error cuando se tengan que fabricar los utillajes (moldes) para la fabricación seriada. En este capítulo abordamos el primer paso dado en esta línea, la relativa a materiales poliméricos. La aplicación con materiales metálicos no tardó mucho más tiempo en ser posible, y se describe en el capítulo 8. Los apartados que se verán aquí se refieren a la descripción general del proceso y a sus variantes, para ver luego más en detalle el procesado, los materiales y casos de uso.
2023-11-14T08:29:49ZMinguella Canela, JoaquimFenollosa i Artés, FelipLos procesos de fusión selectiva de polvo aplicados a polímeros se agrupan, en la clasificación de tecnologías propuesta en la norma ISO/ASTM 52900, en la categoría denominada “fusión de lecho de polvo” (en inglés Powder Bed Fusion). La aparición de la primera de estas tecnologías supuso el segundo gran impacto psicológico sobre lo que la impresión 3D podría suponer: si la primera aparición de la estereolitografía (1986) permitía imprimir prototipos para visualizar diseños, la aparición de la fusión selectiva de polvo en el año 1992[ ] demostró que las piezas podían ser algo más que prototipos: eran válidas como producto final, basándose en polímeros técnicos perfectamente conocidos. Si hasta entonces la impresión 3D era conocida como “Rapid Prototyping” (Prototipado Rápido), gracias a la fusión selectiva de polímeros parecía posible hablar de “Rapid Manufacturing” (Fabricación Rápida). El mito (absurdo pero estimulante) de que la impresión 3D reemplazaría la inyección de plásticos se abría paso en el imaginario del mundo de la ingeniería. Lo cierto es que hubo, gracias a esta nueva tecnología, un cambio de visión: el discurso respecto a la fabricación aditiva dejó de centrarse exclusivamente en la aceleración de los procesos de diseño para entrar en cómo productos finales podían beneficiarse de ser hechos mediante impresión 3D, tanto a efecto de que su diseño no se viera limitado por las restricciones de los procesos de fabricación actuales, como por otras cualidades más interesantes aún: la personalización de los productos y las posibilidades en cuanto a funcionalidad que proporcionaba la libertad de trazar cualquier geometría. En los primeros momentos, y aún hoy en buena medida, la tecnología facilitó prototipos que permitían someter a los diseños a pruebas de ensayo. Es decir, si los prototipos fabricados mediante otras tecnologías como la Estereolitografía (SLA) servían para validar diseños conceptuales, sobre todo en cuanto a geometrías a escala o a tamaño real, sin poder verificar aún funciones técnicas complejas, los prototipos hechos por fusión selectiva de polvo permitían los ensayos típicos (resistencia mecánica, térmica…) que validan la funcionalidad de los productos, reduciendo al mínimo las incógnitas sobre si serían homologadas las piezas una vez obtenidas en sus materiales y procesos finales. El mensaje era muy potente: si el prototipo falla, hay que rediseñar el producto. En consecuencia, no habrá posibilidad de error cuando se tengan que fabricar los utillajes (moldes) para la fabricación seriada. En este capítulo abordamos el primer paso dado en esta línea, la relativa a materiales poliméricos. La aplicación con materiales metálicos no tardó mucho más tiempo en ser posible, y se describe en el capítulo 8. Los apartados que se verán aquí se refieren a la descripción general del proceso y a sus variantes, para ver luego más en detalle el procesado, los materiales y casos de uso.A Method for the Complete Set of Solutions of the Finite-Position Synthesis Problem
http://hdl.handle.net/2117/376314
A Method for the Complete Set of Solutions of the Finite-Position Synthesis Problem
Pérez Gracia, Alba
The equations that appear in the formulation of finite-position synthesis problems tend to increase their complexity and become quite large when solving for multiple-joint systems. In this work, we create a new set of equations that are suited to find all solutions for very large synthesis problems, targeting interval branch-and-cut algorithms. We obtain a system of equations in which all the variables are naturally bounded. Here we present the formulation and preliminary results, while its application to interval analysis is still a work in progress.
2022-11-15T12:26:12ZPérez Gracia, AlbaThe equations that appear in the formulation of finite-position synthesis problems tend to increase their complexity and become quite large when solving for multiple-joint systems. In this work, we create a new set of equations that are suited to find all solutions for very large synthesis problems, targeting interval branch-and-cut algorithms. We obtain a system of equations in which all the variables are naturally bounded. Here we present the formulation and preliminary results, while its application to interval analysis is still a work in progress.A novel method for integrated multicriteria decision-making with uncertainty: A case study on sustainable agriculture in Colombia
http://hdl.handle.net/2117/374885
A novel method for integrated multicriteria decision-making with uncertainty: A case study on sustainable agriculture in Colombia
Juanpera Gallel, Marc; Ferrer Martí, Laia; Garfi, Marianna; Domenech Léga, Bruno; Pastor Moreno, Rafael
Multicriteria decision-making usually requires a set of experts to evaluate the importance of selected criteria and the adequacy of feasible alternatives according to the criteria. Uncertainty can arise in these evaluations, since experts can be hesitant about their responses due to the difficulty of quantifying human language or lack of required knowledge. The Methodology for Integrated Multicriteria Decision-making with Uncertainty (MIMDU) tackles both factors of uncertainty by using non-predefined fuzzy numbers that are continuously adapted taking into account the level of confidence of the experts’ opinions. The methodology also offers useful and complementary information to lead to a robust decision-making. This chapter proposes a novel methodology and provides a sample use case to demonstrate its capability to model uncertainty during decision-making process. In particular, a sensitivity analysis is included, which demonstrates (i) how uncertainty is incorporated into alternatives evaluation, and (ii) that the integrated multicriteria decision-making with uncertainty can be more reliable for decision-makers. The methodology is applied to the robust selection of the most sustainable technology to improve agriculture efficiency in rural areas by means of a case study of a low-cost biogas digester in a small-scale farm in Colombia.
2022-10-24T12:55:58ZJuanpera Gallel, MarcFerrer Martí, LaiaGarfi, MariannaDomenech Léga, BrunoPastor Moreno, RafaelMulticriteria decision-making usually requires a set of experts to evaluate the importance of selected criteria and the adequacy of feasible alternatives according to the criteria. Uncertainty can arise in these evaluations, since experts can be hesitant about their responses due to the difficulty of quantifying human language or lack of required knowledge. The Methodology for Integrated Multicriteria Decision-making with Uncertainty (MIMDU) tackles both factors of uncertainty by using non-predefined fuzzy numbers that are continuously adapted taking into account the level of confidence of the experts’ opinions. The methodology also offers useful and complementary information to lead to a robust decision-making. This chapter proposes a novel methodology and provides a sample use case to demonstrate its capability to model uncertainty during decision-making process. In particular, a sensitivity analysis is included, which demonstrates (i) how uncertainty is incorporated into alternatives evaluation, and (ii) that the integrated multicriteria decision-making with uncertainty can be more reliable for decision-makers. The methodology is applied to the robust selection of the most sustainable technology to improve agriculture efficiency in rural areas by means of a case study of a low-cost biogas digester in a small-scale farm in Colombia.On the use of mesh-based joint contact models within simulations using automatic differentiation
http://hdl.handle.net/2117/372872
On the use of mesh-based joint contact models within simulations using automatic differentiation
Serrancolí, Gil; Torner Ribé, Jordi; Perelli, Simone; Monllau, Joan Carles
Biomechanical simulations integrating computations of joint contact pressures within optimizations typically use mesh-based contact models.However, these models are usually not continuous, which could make convergence difficult. Moreover, they can be difficult to tackle when using expression graphs to calculate derivatives (e.g., when using automatic differentiation) during the resolution of optimization problems. This is due to the computational need to use branches when dealing with conditionals. This study presents a mesh-based contact model adapted to deal with gradient-based optimizations and automatic differentiation.A tracking example of a knee prosthesis contact, integrated into a full-body muscle-driven model, is presented. Kinematics and dynamics data were tracked during an overground gait trial. The results show that the accuracy of knee contact force estimations is comparable to other studies (RMSE medial contact force = 50.8 N, RMSElateral=81.6 N), and the computational time (3 h and 20 min) is acceptable to be run in a conventional PC. Future work is oriented to formulate predictive simulations of muscle-driven full-body models to predict kinematics and dynamics data of subjects post-surgery simultaneously.
2022-09-15T13:15:14ZSerrancolí, GilTorner Ribé, JordiPerelli, SimoneMonllau, Joan CarlesBiomechanical simulations integrating computations of joint contact pressures within optimizations typically use mesh-based contact models.However, these models are usually not continuous, which could make convergence difficult. Moreover, they can be difficult to tackle when using expression graphs to calculate derivatives (e.g., when using automatic differentiation) during the resolution of optimization problems. This is due to the computational need to use branches when dealing with conditionals. This study presents a mesh-based contact model adapted to deal with gradient-based optimizations and automatic differentiation.A tracking example of a knee prosthesis contact, integrated into a full-body muscle-driven model, is presented. Kinematics and dynamics data were tracked during an overground gait trial. The results show that the accuracy of knee contact force estimations is comparable to other studies (RMSE medial contact force = 50.8 N, RMSElateral=81.6 N), and the computational time (3 h and 20 min) is acceptable to be run in a conventional PC. Future work is oriented to formulate predictive simulations of muscle-driven full-body models to predict kinematics and dynamics data of subjects post-surgery simultaneously.Prevention of Failures in the Footwear Production Process by Applying Machine Learning
http://hdl.handle.net/2117/366334
Prevention of Failures in the Footwear Production Process by Applying Machine Learning
Tierra Arévalo, Marcelo; Ayala Chauvin, Manuel Ignacio; Nacevilla, Carmen; Fuente Morató, Albert de la
At present, the handcrafted footwear sector is affected by the high competitiveness due to the increasing automation of companies. In this sense, in order to improve its competitiveness, a system was proposed to predict the failures of a production system and to carry out preventive maintenance actions. Samples were taken from 25 productions and 7 activities were established: cutting, stitching, pre fabrication, final preparation, gluing, assembly and finishing. The company produces batches of 90 pairs per day, with a standard time of 274.53 min and a promised productivity of 1.8. A support vector machine model was developed to predict the possible failures of the process taking as a reference the standard time of each stage. Finally, the results allow predicting the faults to optimise the production process by applying Support Vector Machine (SVM).
2022-04-26T11:20:57ZTierra Arévalo, MarceloAyala Chauvin, Manuel IgnacioNacevilla, CarmenFuente Morató, Albert de laAt present, the handcrafted footwear sector is affected by the high competitiveness due to the increasing automation of companies. In this sense, in order to improve its competitiveness, a system was proposed to predict the failures of a production system and to carry out preventive maintenance actions. Samples were taken from 25 productions and 7 activities were established: cutting, stitching, pre fabrication, final preparation, gluing, assembly and finishing. The company produces batches of 90 pairs per day, with a standard time of 274.53 min and a promised productivity of 1.8. A support vector machine model was developed to predict the possible failures of the process taking as a reference the standard time of each stage. Finally, the results allow predicting the faults to optimise the production process by applying Support Vector Machine (SVM).Quaternions and Clifford Algebras
http://hdl.handle.net/2117/366329
Quaternions and Clifford Algebras
Pérez Gracia, Alba
Quaternions are a type of hypercomplex numbers. Unit quaternions, which describe rotations, were called versors by Hamilton. The concept of versor can be generalized as the product of invertible vectors in the Clifford algebra. Clifford algebras are also named geometric algebras, when referring to the subset of nondegenerate Clifford algebras. Quaternions are four-dimensional elements that form an algebra. Unit quaternions are used to express three-dimensional rotations in a compact way, and their algebraic structure allows performing all related operations, such as composition of rotations, inverse rotations, and action of a rotation on a geometric object
2022-04-26T10:45:15ZPérez Gracia, AlbaQuaternions are a type of hypercomplex numbers. Unit quaternions, which describe rotations, were called versors by Hamilton. The concept of versor can be generalized as the product of invertible vectors in the Clifford algebra. Clifford algebras are also named geometric algebras, when referring to the subset of nondegenerate Clifford algebras. Quaternions are four-dimensional elements that form an algebra. Unit quaternions are used to express three-dimensional rotations in a compact way, and their algebraic structure allows performing all related operations, such as composition of rotations, inverse rotations, and action of a rotation on a geometric objectEvolution of Additive Manufacturing Processes: From the Background to Hybrid Printers
http://hdl.handle.net/2117/365056
Evolution of Additive Manufacturing Processes: From the Background to Hybrid Printers
Buj Corral, Irene; Tejo Otero, Aitor; Fenollosa i Artés, Felip
The Additive Manufacturing (AM) field is revolutionizing the industrial sector in different areas such as automotive, aeronautics, medicine, etc. Many patents aboutAMprocesseswere granted at the end of the XXth century. However, until their release, the use ofAMwas very limited, mainly because of the high cost of the equipment. From that moment on, many 3D printing technologies started to bloom and, along with it, the commercialization of new3D printers, including hybrid 3D printers. They are defined as a combination of AM and subtractive technologies within the same machine, but also as a merge of different AM technologies. With all this in mind, the present chapter first presents an overviewof the differentAMtechnologies, as well as the history of AM, including recent advances. Then, the description of the possible future trends with the use of hybrid 3D printers is discussed.
2022-03-30T17:10:47ZBuj Corral, IreneTejo Otero, AitorFenollosa i Artés, FelipThe Additive Manufacturing (AM) field is revolutionizing the industrial sector in different areas such as automotive, aeronautics, medicine, etc. Many patents aboutAMprocesseswere granted at the end of the XXth century. However, until their release, the use ofAMwas very limited, mainly because of the high cost of the equipment. From that moment on, many 3D printing technologies started to bloom and, along with it, the commercialization of new3D printers, including hybrid 3D printers. They are defined as a combination of AM and subtractive technologies within the same machine, but also as a merge of different AM technologies. With all this in mind, the present chapter first presents an overviewof the differentAMtechnologies, as well as the history of AM, including recent advances. Then, the description of the possible future trends with the use of hybrid 3D printers is discussed.Exoskeleton Design Using Subject-Specific Synergy-Driven Neuromusculoskeletal Models
http://hdl.handle.net/2117/362167
Exoskeleton Design Using Subject-Specific Synergy-Driven Neuromusculoskeletal Models
Arones, Marleny; Font Llagunes, Josep Maria; Fregly, Benjamin Jon
Most assistive devices available today are unable to improve gait asymmetries due to the lack of knowledge on how to directly enforce kinematic symmetry in the formulation of cost functions. We designed a cost function to potentially target kinematic symmetry, and observed improvements in gait asymmetries specifically at the hip and ankle.
2022-02-11T12:51:10ZArones, MarlenyFont Llagunes, Josep MariaFregly, Benjamin JonMost assistive devices available today are unable to improve gait asymmetries due to the lack of knowledge on how to directly enforce kinematic symmetry in the formulation of cost functions. We designed a cost function to potentially target kinematic symmetry, and observed improvements in gait asymmetries specifically at the hip and ankle.Virtual human hand: wrist movements
http://hdl.handle.net/2117/354018
Virtual human hand: wrist movements
Peña Pitarch, Esteve; Puig de la Bellacasa, Inmaculada; Padilla Magaña, Jesús Fernando; Al Omar Mesnaoui, Anas; Alcelay Larrión, José Ignacio
Hand model with 25 Degrees of Freedom (DOF) was developed and implemented considering forward and inverse kinematics. However, the model, after some experience and use need to add new DOF. The proposed model is with 29 DOF, these new DOF serve to simulate the arc of the palm in the part of the wrist.
Once we locate a new coordinates system in the end of the radius close to scaphoid we apply Denavit-Hartenberg for all the joints. Forward and inverse kinematics will be applied. Ligaments to apply restrictions in wrist movement are included. This affect to the fingertip position.
New model of virtual human hand with more accuracy in presented and validated with a Cyberglove™ and Leap Motion.
2021-10-20T13:24:47ZPeña Pitarch, EstevePuig de la Bellacasa, InmaculadaPadilla Magaña, Jesús FernandoAl Omar Mesnaoui, AnasAlcelay Larrión, José IgnacioHand model with 25 Degrees of Freedom (DOF) was developed and implemented considering forward and inverse kinematics. However, the model, after some experience and use need to add new DOF. The proposed model is with 29 DOF, these new DOF serve to simulate the arc of the palm in the part of the wrist.
Once we locate a new coordinates system in the end of the radius close to scaphoid we apply Denavit-Hartenberg for all the joints. Forward and inverse kinematics will be applied. Ligaments to apply restrictions in wrist movement are included. This affect to the fingertip position.
New model of virtual human hand with more accuracy in presented and validated with a Cyberglove™ and Leap Motion.