http://hdl.handle.net/2117/3899 Sun, 19 May 2013 11:50:37 GMT 2013-05-19T11:50:37Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/18732 Title: Enhancement in evaluating small group work in courses with large number of students. Machine theory at industrial engineering degrees Authors: Jordi Nebot, Lluïsa; Pàmies Vila, Rosa; Català Calderon, Pau; Puig Ortiz, Joan Tue, 09 Apr 2013 11:49:48 GMT http://hdl.handle.net/2117/18732 2013-04-09T11:49:48Z Jordi Nebot, Lluïsa; Pàmies Vila, Rosa; Català Calderon, Pau; Puig Ortiz, Joan no http://hdl.handle.net/2117/17955 Title: Synthesis of displacement functions by Bézier curves in constant-breadth cams with parallel flat-faced translating and oscillating followers Authors: Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa; Català Calderon, Pau Abstract: The constant-breadth cam mechanisms, which drive a parallel flat-faced double follower, are desmodromic, and guarantee global bilaterality. In the said mechanisms, the law of displacement of the follower can only be freely designed for an interval of the rotation angle of the cam – the designed segment – close or equal to 180°, and the remaining interval – the calculated segment – is obtained through calculation from the first. Guaranteeing the continuity between segments is not a trivial task. This work shows a design procedure which guarantees automatically the global continuity of the law of displacement. This procedure provides the expressions of calculation for both parallel flat-faced double translating follower and parallel flat-faced double oscillating follower. Non-parametric Bézier curves are used for the definition of the displacement functions. For both types of followers, two numerical examples of the design of the displacement functions are given. Furthermore, the corresponding cam profiles are provided. Mon, 25 Feb 2013 10:56:13 GMT http://hdl.handle.net/2117/17955 2013-02-25T10:56:13Z Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa; Català Calderon, Pau no The constant-breadth cam mechanisms, which drive a parallel flat-faced double follower, are desmodromic, and guarantee global bilaterality. In the said mechanisms, the law of displacement of the follower can only be freely designed for an interval of the rotation angle of the cam – the designed segment – close or equal to 180°, and the remaining interval – the calculated segment – is obtained through calculation from the first. Guaranteeing the continuity between segments is not a trivial task. This work shows a design procedure which guarantees automatically the global continuity of the law of displacement. This procedure provides the expressions of calculation for both parallel flat-faced double translating follower and parallel flat-faced double oscillating follower. Non-parametric Bézier curves are used for the definition of the displacement functions. For both types of followers, two numerical examples of the design of the displacement functions are given. Furthermore, the corresponding cam profiles are provided. http://hdl.handle.net/2117/17769 Title: Proyecto de Ingeniería Mecánica integrador de conocimientos. Cuarto cuatrimestre del Grado de Ingeniería en Tecnologías Industriales Authors: Cardona Foix, Salvador; Jordi Nebot, Lluïsa; Puig Ortiz, Joan Thu, 14 Feb 2013 14:41:34 GMT http://hdl.handle.net/2117/17769 2013-02-14T14:41:34Z Cardona Foix, Salvador; Jordi Nebot, Lluïsa; Puig Ortiz, Joan no http://hdl.handle.net/2117/17767 Title: Soporte dinámico para el material docente del profesorado. Teoría de Máquinas y Mecanismos Authors: Jordi Nebot, Lluïsa; Cardona Foix, Salvador; Puig Ortiz, Joan Abstract: Es usual que el material docente para las clases tenga procedencia diversa: publicaciones, material de elaboración propia, acceso a la red, etc. y que varíe en mayor o menor grado de un curso a otro, e incluso que tenga que reelaborarse o reorganizarse durante el curso para hacer frente a situaciones no previstas. Todo ello hace deseable un soporte dinámico de este material. Por estas razones se ha buscado un soporte adecuado para el material utilizado en la impartición de la materia de Teoría de Máquinas y Mecanismos en la Escuela Técnica Superior de Ingeniería Industrial de Barcelona. Se ha optado por una aplicación TiddlyWiki. El contenido se ha estructurado en una introducción más los temas que se corresponden con los capítulos del libro de texto utilizado. Cada tema tiene tres apartados: libro, guión del contenido y ejercicios para realizar en clase. Thu, 14 Feb 2013 14:29:16 GMT http://hdl.handle.net/2117/17767 2013-02-14T14:29:16Z Jordi Nebot, Lluïsa; Cardona Foix, Salvador; Puig Ortiz, Joan no Es usual que el material docente para las clases tenga procedencia diversa: publicaciones, material de elaboración propia, acceso a la red, etc. y que varíe en mayor o menor grado de un curso a otro, e incluso que tenga que reelaborarse o reorganizarse durante el curso para hacer frente a situaciones no previstas. Todo ello hace deseable un soporte dinámico de este material. Por estas razones se ha buscado un soporte adecuado para el material utilizado en la impartición de la materia de Teoría de Máquinas y Mecanismos en la Escuela Técnica Superior de Ingeniería Industrial de Barcelona. Se ha optado por una aplicación TiddlyWiki. El contenido se ha estructurado en una introducción más los temas que se corresponden con los capítulos del libro de texto utilizado. Cada tema tiene tres apartados: libro, guión del contenido y ejercicios para realizar en clase. http://hdl.handle.net/2117/17759 Title: Analysis of different uncertainties in the inverse dynamic analysis of human gait Authors: Pàmies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier; Alonso, F. Javier Thu, 14 Feb 2013 11:56:04 GMT http://hdl.handle.net/2117/17759 2013-02-14T11:56:04Z Pàmies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier; Alonso, F. Javier no http://hdl.handle.net/2117/17736 Title: Dynamic analysis of impact in swing-through crutch gait using impulsive and continuous contact models Authors: Font Llagunes, Josep Maria; Barjau Condomines, Ana; Pàmies Vila, Rosa; Kövecses, József Abstract: The dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of mechanical energy loss during swing-through gait. In this work, a multibody system representing a subject walking with crutches is used to investigate the behavior of two different contact models, impulsive and continuous, used for impact analysis. In the impulsive (discrete) approach, the impact interval is considered to be negligible and, therefore, the system configuration is constant. The postimpact state is directly obtained from the preimpact one through algebraic equations. In the continuous approach, the stiffness and dissipation characteristics of the contact surfaces are modeled through nonlinear springs and dampers. The equations of motion are integrated during the impact time interval to obtain the postimpact state, which, in principle, can differ from that obtained by means of the impulsive approach. Although both approaches have been widely used in the field of biomechanics, we have not found any comparative study in the existing literature justifying the model chosen for impact analysis. In this work, we present detailed numerical results and discussions to investigate several dynamic and energetic features associated with crutch impact. Based on the results, we compare the implications of using one contact model or the other. Wed, 13 Feb 2013 17:14:04 GMT http://hdl.handle.net/2117/17736 2013-02-13T17:14:04Z Font Llagunes, Josep Maria; Barjau Condomines, Ana; Pàmies Vila, Rosa; Kövecses, József no The dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of mechanical energy loss during swing-through gait. In this work, a multibody system representing a subject walking with crutches is used to investigate the behavior of two different contact models, impulsive and continuous, used for impact analysis. In the impulsive (discrete) approach, the impact interval is considered to be negligible and, therefore, the system configuration is constant. The postimpact state is directly obtained from the preimpact one through algebraic equations. In the continuous approach, the stiffness and dissipation characteristics of the contact surfaces are modeled through nonlinear springs and dampers. The equations of motion are integrated during the impact time interval to obtain the postimpact state, which, in principle, can differ from that obtained by means of the impulsive approach. Although both approaches have been widely used in the field of biomechanics, we have not found any comparative study in the existing literature justifying the model chosen for impact analysis. In this work, we present detailed numerical results and discussions to investigate several dynamic and energetic features associated with crutch impact. Based on the results, we compare the implications of using one contact model or the other. http://hdl.handle.net/2117/17673 Title: Synthesis of displacement functions by Bézier curves in constant-breadth cams with parallel flat-faced double translating and oscillating followers Authors: Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa; Català Calderon, Pau Abstract: The constant-breadth cam mechanisms, which drive a parallel flat-faced double follower, are desmodromic, and guarantee global bilaterality. In the said mechanisms, the law of displacement of the follower can only be freely designed for an interval of the rotation angle of the cam – the designed segment – close or equal to 180°, and the remaining interval – the calculated segment – is obtained through calculation from the first. Guaranteeing the continuity between segments is not a trivial task. This work shows a design procedure which guarantees automatically the global continuity of the law of displacement. This procedure provides the expressions of calculation for both parallel flat-faced double translating follower and parallel flat-faced double oscillating follower. Non-parametric Bézier curves are used for the definition of the displacement functions. For both types of followers, two numerical examples of the design of the displacement functions are given. Furthermore, the corresponding cam profiles are provided. Tue, 12 Feb 2013 16:06:32 GMT http://hdl.handle.net/2117/17673 2013-02-12T16:06:32Z Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa; Català Calderon, Pau no The constant-breadth cam mechanisms, which drive a parallel flat-faced double follower, are desmodromic, and guarantee global bilaterality. In the said mechanisms, the law of displacement of the follower can only be freely designed for an interval of the rotation angle of the cam – the designed segment – close or equal to 180°, and the remaining interval – the calculated segment – is obtained through calculation from the first. Guaranteeing the continuity between segments is not a trivial task. This work shows a design procedure which guarantees automatically the global continuity of the law of displacement. This procedure provides the expressions of calculation for both parallel flat-faced double translating follower and parallel flat-faced double oscillating follower. Non-parametric Bézier curves are used for the definition of the displacement functions. For both types of followers, two numerical examples of the design of the displacement functions are given. Furthermore, the corresponding cam profiles are provided. http://hdl.handle.net/2117/17657 Title: Uso de la STFT en el análisis de vibraciones para detectar y caracterizar la presencia de un defecto en la superficie de las ruedas de un tren Authors: Flórez Serrano, Elkin Gregorio; Cardona Foix, Salvador; Jordi Nebot, Lluïsa Tue, 12 Feb 2013 13:17:20 GMT http://hdl.handle.net/2117/17657 2013-02-12T13:17:20Z Flórez Serrano, Elkin Gregorio; Cardona Foix, Salvador; Jordi Nebot, Lluïsa no http://hdl.handle.net/2117/16340 Title: Residual vibration reduction in low damping systems. Generation of regular piecewise algebraic polynomial inputs Authors: Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador Abstract: This paper presents a feedforward technique to generate command inputs to reduce residual vibration after transient maneuvers in mechanical systems. Synthesized inputs base their vibration reduction in zero-frequency content at the system resonances and are obtained taking advantage of the convolution theorem of the Fourier transform (FT). The analyzed systems are those that can be modeled as discrete linear systems with n vibratory degrees-offreedom, and can be described with constant parameter motion equations. Although the complete cancellation of residual vibrations occurs for null damping ratios, the results obtained for low damped systems are quite acceptable. The method is particularized for rest-to-rest maneuvers and is compared to other literature methods. The new profiles present an optimal shape in terms of minimum acceleration fluctuation, which is useful to reduce the fatigue strength of the mechanical parts. By using a pulse as a base signal, the inputs obtained follow piecewise algebraic polynomial functions easily implementable through a B-spline scheme. The development includes a robust approach against the variation of the system parameters and a constraint determination aid for symmetric functions. Finally, some experimental results are presented using a two vibratory degrees-of-freedom test bed. Wed, 25 Jul 2012 11:21:11 GMT http://hdl.handle.net/2117/16340 2012-07-25T11:21:11Z Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador no This paper presents a feedforward technique to generate command inputs to reduce residual vibration after transient maneuvers in mechanical systems. Synthesized inputs base their vibration reduction in zero-frequency content at the system resonances and are obtained taking advantage of the convolution theorem of the Fourier transform (FT). The analyzed systems are those that can be modeled as discrete linear systems with n vibratory degrees-offreedom, and can be described with constant parameter motion equations. Although the complete cancellation of residual vibrations occurs for null damping ratios, the results obtained for low damped systems are quite acceptable. The method is particularized for rest-to-rest maneuvers and is compared to other literature methods. The new profiles present an optimal shape in terms of minimum acceleration fluctuation, which is useful to reduce the fatigue strength of the mechanical parts. By using a pulse as a base signal, the inputs obtained follow piecewise algebraic polynomial functions easily implementable through a B-spline scheme. The development includes a robust approach against the variation of the system parameters and a constraint determination aid for symmetric functions. Finally, some experimental results are presented using a two vibratory degrees-of-freedom test bed. http://hdl.handle.net/2117/16317 Title: Residual vibration reduction in mechanical systems: a time-domain approach Authors: Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador Abstract: This paper presents a time-domain technique to generate command inputs for the reduction of residual vibrations in mechanical systems. The technique is based on the generation of motion profiles with zero-crossing points in their frequency spectra at the system resonances in the same way as the zero-vibration (ZV) command generation methods. By including an appropriate negative exponential time function, which contains the system natural frequency and the damping ratio, the resultant input can be applied to damped systems with a result of zero residual vibration. The signals synthesized can be used as a generic physical magnitude in vibratory systems. However, they were particularized for mechanical systems and engineering metrics were used. Compared to other ZV methods, for a short duration input range, the signals obtained have better performance in terms of minimum-acceleration-switch shape which is translated to a smoother motion profile. The development includes the application to single-mode and multiple-mode mechanical systems and the possibility of handling two functional requirements or constraints in the desired application. The analyzed systems are those that can be modeled as discrete linear ones with several vibratory degrees of freedom and can be described with constant parameter motion equations. Experimental results show the efficacy of the method developed with its application to a damped pendulum test platform. Tue, 24 Jul 2012 11:15:47 GMT http://hdl.handle.net/2117/16317 2012-07-24T11:15:47Z Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador no This paper presents a time-domain technique to generate command inputs for the reduction of residual vibrations in mechanical systems. The technique is based on the generation of motion profiles with zero-crossing points in their frequency spectra at the system resonances in the same way as the zero-vibration (ZV) command generation methods. By including an appropriate negative exponential time function, which contains the system natural frequency and the damping ratio, the resultant input can be applied to damped systems with a result of zero residual vibration. The signals synthesized can be used as a generic physical magnitude in vibratory systems. However, they were particularized for mechanical systems and engineering metrics were used. Compared to other ZV methods, for a short duration input range, the signals obtained have better performance in terms of minimum-acceleration-switch shape which is translated to a smoother motion profile. The development includes the application to single-mode and multiple-mode mechanical systems and the possibility of handling two functional requirements or constraints in the desired application. The analyzed systems are those that can be modeled as discrete linear ones with several vibratory degrees of freedom and can be described with constant parameter motion equations. Experimental results show the efficacy of the method developed with its application to a damped pendulum test platform. http://hdl.handle.net/2117/9932 Title: Determination of the force of the actuators and constraint forces in the inverse dynamic analysis of mechanisms Authors: Jordi Nebot, Lluïsa; Puig Ortiz, Joan; Cardona Foix, Salvador Fri, 22 Oct 2010 13:27:35 GMT http://hdl.handle.net/2117/9932 2010-10-22T13:27:35Z Jordi Nebot, Lluïsa; Puig Ortiz, Joan; Cardona Foix, Salvador no http://hdl.handle.net/2117/8888 Title: Determinación de las rutas de un robot transportador en un sistema productivo Authors: Mateo Doll, Manuel; D'Armas, Mayra; Santos López, M. Antonia de los Abstract: En este trabajo se resuelve un problema de programación de los ciclos producción en un sistema productivo con la presencia de robots transportadores o vehículos autoguiados. Se determinó la secuencia óptima de transporte de las piezas entre las máquinas, a partir de los tiempos de procesamiento y de transporte de las piezas de una etapa a otra del proceso productivo. El objetivo de este trabajo es obtener la secuencia óptima de movimientos del robot transportador para diferentes configuraciones de un sistema productivo (máquinas que pueden estar activas e inactivas, disposiciones lineal y circular de las máquinas). Para la resolución de los diferentes casos se programó en lenguaje Visual Basic un algoritmo Brach and Bound. El algoritmo se experimentó con 214 ejemplares. Los resultados demuestran que existen relaciones entre las diferentes características del sistema productivo, como son los tiempos de ciclo, los tiempos de procesamiento o la distribución de las máquinas dentro del proceso productivo. Estos resultados evidencian las configuraciones del sistema que permiten reducir de manera significativa los tiempos ciclos del robot transportador. Thu, 16 Sep 2010 07:28:49 GMT http://hdl.handle.net/2117/8888 2010-09-16T07:28:49Z Mateo Doll, Manuel; D'Armas, Mayra; Santos López, M. Antonia de los no En este trabajo se resuelve un problema de programación de los ciclos producción en un sistema productivo con la presencia de robots transportadores o vehículos autoguiados. Se determinó la secuencia óptima de transporte de las piezas entre las máquinas, a partir de los tiempos de procesamiento y de transporte de las piezas de una etapa a otra del proceso productivo. El objetivo de este trabajo es obtener la secuencia óptima de movimientos del robot transportador para diferentes configuraciones de un sistema productivo (máquinas que pueden estar activas e inactivas, disposiciones lineal y circular de las máquinas). Para la resolución de los diferentes casos se programó en lenguaje Visual Basic un algoritmo Brach and Bound. El algoritmo se experimentó con 214 ejemplares. Los resultados demuestran que existen relaciones entre las diferentes características del sistema productivo, como son los tiempos de ciclo, los tiempos de procesamiento o la distribución de las máquinas dentro del proceso productivo. Estos resultados evidencian las configuraciones del sistema que permiten reducir de manera significativa los tiempos ciclos del robot transportador. http://hdl.handle.net/2117/7325 Title: Selección de la ventana temporal en la transformada de Fourier en tiempos cortos utilizada en el análisis de señales de vibración para determinar planos en las ruedas de un tren Authors: Flórez Serrano, Elkin Gregorio; Cardona Foix, Salvador; Jordi Nebot, Lluïsa Wed, 19 May 2010 14:25:35 GMT http://hdl.handle.net/2117/7325 2010-05-19T14:25:35Z Flórez Serrano, Elkin Gregorio; Cardona Foix, Salvador; Jordi Nebot, Lluïsa no