Articles de revista
http://hdl.handle.net/2117/3899
2016-10-28T14:26:12ZA mathematical model to study railway track dynamics for the prediction of vibration levels generated by rail vehicles
http://hdl.handle.net/2117/87591
A mathematical model to study railway track dynamics for the prediction of vibration levels generated by rail vehicles
Otero Yugat, Jesús; Martínez Miralles, Jordi Ramon; Santos López, M. Antonia de los; Cardona Foix, Salvador
This article presents a mathematical model aimed at predicting wheel–rail contact vibration force arising from wheel profile irregularities. Prediction of vibrations caused by a passing train is a basic factor in environmental impact studies related to planning new railway lines. The prediction model is useful during the development of a project as it facilitates selection of the most suitable track for reducing vibration levels. This article presents the model, analyses the influence of the track base on the vibration-generating mechanisms, and compares the dynamic behaviour of the most widely used urban railway tracks.
2016-06-01T12:51:17ZOtero Yugat, JesúsMartínez Miralles, Jordi RamonSantos López, M. Antonia de losCardona Foix, SalvadorThis article presents a mathematical model aimed at predicting wheel–rail contact vibration force arising from wheel profile irregularities. Prediction of vibrations caused by a passing train is a basic factor in environmental impact studies related to planning new railway lines. The prediction model is useful during the development of a project as it facilitates selection of the most suitable track for reducing vibration levels. This article presents the model, analyses the influence of the track base on the vibration-generating mechanisms, and compares the dynamic behaviour of the most widely used urban railway tracks.Evaluation of the influence of a planned interference fit on the expected fatigue life of a conjugate cam mechanism- A case study
http://hdl.handle.net/2117/86677
Evaluation of the influence of a planned interference fit on the expected fatigue life of a conjugate cam mechanism- A case study
Català Calderon, Pau; Santos López, M. Antonia de los; Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador
Due to dynamic effects, clearances, manufacturing and assembly errors in form-closed cam mechanisms, the follower jump can also occur. For conjugate cam mechanisms a technique to avoid the follower jump without the use of a spring involves making the conjugate cam profiles bigger than the kinematical ones by adding an external offset. This strategy produces an interference fit between the conjugate cam profiles and the follower train. This paper presents an ordered procedure to study the influence that the planned interference fit has on the evaluation of the contact forces, the expected fatigue life of the
rollers, contact pressures and the lubrication conditions. The study is based on a conjugate cam mechanism with translational roller followers used in a real automatic process for manufacturing muselets. A three-degree-of-freedom dynamic model is proposed and the Hertzian theory for general profiles is used to model the nonlinear contact stiffness between the cams and the crowned rollers. The dynamic model predicts that it is difficult to obtain conjugate cam mechanisms with an infinite expected fatigue life of the rollers just by considering typical achievable manufacturing errors or clearances, and as happens in reality, a set-up process is highly recommended. The procedure is also tested with measured manufacturing errors on a coordinate measure machine—CMM—and with measured radial internal clearances for the rollers measured by an experimental apparatus.
Also, to evaluate lubrication conditions, surface finishing measurements have been taken of the cams and the rollers with a surface profiler.
2016-05-06T09:39:52ZCatalà Calderon, PauSantos López, M. Antonia de losVeciana Fontanet, Joaquim MariaCardona Foix, SalvadorDue to dynamic effects, clearances, manufacturing and assembly errors in form-closed cam mechanisms, the follower jump can also occur. For conjugate cam mechanisms a technique to avoid the follower jump without the use of a spring involves making the conjugate cam profiles bigger than the kinematical ones by adding an external offset. This strategy produces an interference fit between the conjugate cam profiles and the follower train. This paper presents an ordered procedure to study the influence that the planned interference fit has on the evaluation of the contact forces, the expected fatigue life of the
rollers, contact pressures and the lubrication conditions. The study is based on a conjugate cam mechanism with translational roller followers used in a real automatic process for manufacturing muselets. A three-degree-of-freedom dynamic model is proposed and the Hertzian theory for general profiles is used to model the nonlinear contact stiffness between the cams and the crowned rollers. The dynamic model predicts that it is difficult to obtain conjugate cam mechanisms with an infinite expected fatigue life of the rollers just by considering typical achievable manufacturing errors or clearances, and as happens in reality, a set-up process is highly recommended. The procedure is also tested with measured manufacturing errors on a coordinate measure machine—CMM—and with measured radial internal clearances for the rollers measured by an experimental apparatus.
Also, to evaluate lubrication conditions, surface finishing measurements have been taken of the cams and the rollers with a surface profiler.Modified adaptive input shaping for maneuvering cranes using a feedback MEM gyroscope with null drift
http://hdl.handle.net/2117/82946
Modified adaptive input shaping for maneuvering cranes using a feedback MEM gyroscope with null drift
Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador; Català Calderon, Pau
This paper presents an adaptive algorithm to reduce residual vibrations when the feedback sensor used has null drift along the time. The adaptive approaches are useful to deal with large variations of the system parameters at each maneuver, such as it occurs in cranes. For the feedback sensor, the use of inertial measurement units such as Micro-Electro-Mechanical Systems (MEMS) is increasingly extended because of their cost, size, robustness and power consumption. However, the effectiveness of the adaptive input shaping algorithms is compromised because of this drift, which is a commonly raised issue in this kind of devices. The study presented in this manuscript focuses on the development of an automatic compensation of this drift to obviate frequent calibrations. It is based on a non-asymptotic algebraic identification technique, which does not require initial conditions and has a short convergence time. This study uses the Zero-Vibration (ZV) input shaper technique, and the null drift is added to the algorithm as a parameter to be identified. The proposed method is particularized for single maneuvers of cranes with a gyroscope as feedback sensor, in a real time scenario. Experimental results show the efficacy of the method on a scaled crane test platform.
2016-02-15T14:08:16ZVeciana Fontanet, Joaquim MariaCardona Foix, SalvadorCatalà Calderon, PauThis paper presents an adaptive algorithm to reduce residual vibrations when the feedback sensor used has null drift along the time. The adaptive approaches are useful to deal with large variations of the system parameters at each maneuver, such as it occurs in cranes. For the feedback sensor, the use of inertial measurement units such as Micro-Electro-Mechanical Systems (MEMS) is increasingly extended because of their cost, size, robustness and power consumption. However, the effectiveness of the adaptive input shaping algorithms is compromised because of this drift, which is a commonly raised issue in this kind of devices. The study presented in this manuscript focuses on the development of an automatic compensation of this drift to obviate frequent calibrations. It is based on a non-asymptotic algebraic identification technique, which does not require initial conditions and has a short convergence time. This study uses the Zero-Vibration (ZV) input shaper technique, and the null drift is added to the algorithm as a parameter to be identified. The proposed method is particularized for single maneuvers of cranes with a gyroscope as feedback sensor, in a real time scenario. Experimental results show the efficacy of the method on a scaled crane test platform.The use of hybrid CO2+MQL in machining operations
http://hdl.handle.net/2117/82264
The use of hybrid CO2+MQL in machining operations
Pereira, Octavio; Català Calderon, Pau; Rodríguez, Adrian; Ostra, Txomin; Vivancos Calvet, Joan; Rivero, Asunción; López de Lacalle, Luis Norberto
Nowadays, the environmental concern in machining industry is a fact. Because of that, in this article a new cooling-lubrication
system which combines CO2 cryogenic and MQL technologies is presented. The aim of this new cooling-lubrication system is to
offer an ecological and economic efficient alternative. Two nozzle adapters are proposed with different CO2 outlets. The
developed nozzles are Plug & Play and directly applicable to commercial MQL systems. The behaviors of nozzle adapters were
simulated by CFD (Computational Fluid Dynamics) and the optimal nozzle adapter was tested by milling Inconel 718 ®. In these
milling tests, the tool life was measured and using different main cooling-lubrication techniques: dry, wet, CO2 stand alone, MQL
stand alone and CO2+MQL (proposed alternative).
2016-01-29T11:30:30ZPereira, OctavioCatalà Calderon, PauRodríguez, AdrianOstra, TxominVivancos Calvet, JoanRivero, AsunciónLópez de Lacalle, Luis NorbertoNowadays, the environmental concern in machining industry is a fact. Because of that, in this article a new cooling-lubrication
system which combines CO2 cryogenic and MQL technologies is presented. The aim of this new cooling-lubrication system is to
offer an ecological and economic efficient alternative. Two nozzle adapters are proposed with different CO2 outlets. The
developed nozzles are Plug & Play and directly applicable to commercial MQL systems. The behaviors of nozzle adapters were
simulated by CFD (Computational Fluid Dynamics) and the optimal nozzle adapter was tested by milling Inconel 718 ®. In these
milling tests, the tool life was measured and using different main cooling-lubrication techniques: dry, wet, CO2 stand alone, MQL
stand alone and CO2+MQL (proposed alternative).Use of single board computers as smart sensors in the manufacturing industry
http://hdl.handle.net/2117/82257
Use of single board computers as smart sensors in the manufacturing industry
Gomez, Agustin; Cuiñas Vázquez, Daniel; Català Calderon, Pau; Xin, Lin; Li, Weidong; Conway, Stewart; Lack, Donald
The continuously growing presence of cyber-physical systems in the industry, especially in the field of processes automation and control, represents the paradigm of the so called fourth industrial revolution, in which the systems are smarter, faster and more optimized by means of artificial intelligence, control systems and sensors networks. The presence of ICT and automation systems guarantees energy and other resources efficiency along the whole value chain of industrial processes. Especially important is the case of the smart sensors, in which a conventional sensor is equipped with interfacing methodologies for signal processing and decision making. In this article the capabilities of using a single board computer as a smart sensor are explored.
2016-01-29T09:49:51ZGomez, AgustinCuiñas Vázquez, DanielCatalà Calderon, PauXin, LinLi, WeidongConway, StewartLack, DonaldThe continuously growing presence of cyber-physical systems in the industry, especially in the field of processes automation and control, represents the paradigm of the so called fourth industrial revolution, in which the systems are smarter, faster and more optimized by means of artificial intelligence, control systems and sensors networks. The presence of ICT and automation systems guarantees energy and other resources efficiency along the whole value chain of industrial processes. Especially important is the case of the smart sensors, in which a conventional sensor is equipped with interfacing methodologies for signal processing and decision making. In this article the capabilities of using a single board computer as a smart sensor are explored.Avoiding early failures in conjugate cam mechanism by means of different design strategies
http://hdl.handle.net/2117/82217
Avoiding early failures in conjugate cam mechanism by means of different design strategies
Català Calderon, Pau; Santos López, M. Antonia de los; Veciana Fontanet, Joaquim Maria; Cardona Foix, Salvador
To solve the indetermination of forces existing in a form-closed cam mechanism formed by conjugate cams, where the contact between the cams and the follower rollers is constantly ensured by only the geometry of the elements, dynamic models that consider the elasticity of the elements must be proposed. Because the stiffness of the main elements is associated with the elasticity of the solids, tight variations in manufacturing and assembly errors modify the effective interference fit, which significantly affects the expected fatigue life of the mechanism, leading to a premature failure of the elements due to surface fatigue. Based on a real industrial application of a conjugate cam mechanism and using lumped-parameter models, the objectives of this paper are: first, to show that it is difficult to achieve a pure form-closed conjugate cam mechanism, with the expected fatigue life of the mechanism, by using only standard tolerance specifications; second, to compare the expected fatigue life and motor torque with other cam mechanism design strategies such as force-closed and the combination of force-closed and form-closed strategies, known as force-closed conjugate cam strategy. This paper based on simulation results demonstrates that this latest strategy can, thanks to a better control of the preload, easily achieve results very similar to the theoretical ones of a form-closed conjugate cam mechanism. A prototype of the mechanism of the force-closed conjugate cam strategy is also built.
2016-01-28T11:48:52ZCatalà Calderon, PauSantos López, M. Antonia de losVeciana Fontanet, Joaquim MariaCardona Foix, SalvadorTo solve the indetermination of forces existing in a form-closed cam mechanism formed by conjugate cams, where the contact between the cams and the follower rollers is constantly ensured by only the geometry of the elements, dynamic models that consider the elasticity of the elements must be proposed. Because the stiffness of the main elements is associated with the elasticity of the solids, tight variations in manufacturing and assembly errors modify the effective interference fit, which significantly affects the expected fatigue life of the mechanism, leading to a premature failure of the elements due to surface fatigue. Based on a real industrial application of a conjugate cam mechanism and using lumped-parameter models, the objectives of this paper are: first, to show that it is difficult to achieve a pure form-closed conjugate cam mechanism, with the expected fatigue life of the mechanism, by using only standard tolerance specifications; second, to compare the expected fatigue life and motor torque with other cam mechanism design strategies such as force-closed and the combination of force-closed and form-closed strategies, known as force-closed conjugate cam strategy. This paper based on simulation results demonstrates that this latest strategy can, thanks to a better control of the preload, easily achieve results very similar to the theoretical ones of a form-closed conjugate cam mechanism. A prototype of the mechanism of the force-closed conjugate cam strategy is also built.Integration of product conceptual design synthesis into a Computer-Aided Design system
http://hdl.handle.net/2117/26943
Integration of product conceptual design synthesis into a Computer-Aided Design system
Álvarez Cabrales, Alexis; Zayas Figueras, Enrique Ernesto; Pérez Rodríguez, Roberto; Simeón, Rolando; Riba Romeva, Carles; Cardona Foix, Salvador
Commercial Computer-Aided Design systems have mainly focused to support the process of capturing and representing geometric shapes and incorporating technological information. In contrast, few utilities in these systems are present to facilitate decision making in the early stages of the design process, such as the capture, modeling and conceptual design synthesis of solutions. Typical tasks of the conceptual design process in mechanical design are lead in applications stand-alone or are based on the heuristic knowledge of the designer. Such approaches are non-interoperable with de commercial computer-aided design systems, leading to discontinuous design information of design process. This study addresses this subject and proposes a method to improve the integration of product conceptual design synthesis into a Computer Aided Design system. To validate the feasibility of the approach implemented, a prototype application based on a Computer Aided Design system was developed and a study case was accomplished
2015-03-23T13:33:09ZÁlvarez Cabrales, AlexisZayas Figueras, Enrique ErnestoPérez Rodríguez, RobertoSimeón, RolandoRiba Romeva, CarlesCardona Foix, SalvadorCommercial Computer-Aided Design systems have mainly focused to support the process of capturing and representing geometric shapes and incorporating technological information. In contrast, few utilities in these systems are present to facilitate decision making in the early stages of the design process, such as the capture, modeling and conceptual design synthesis of solutions. Typical tasks of the conceptual design process in mechanical design are lead in applications stand-alone or are based on the heuristic knowledge of the designer. Such approaches are non-interoperable with de commercial computer-aided design systems, leading to discontinuous design information of design process. This study addresses this subject and proposes a method to improve the integration of product conceptual design synthesis into a Computer Aided Design system. To validate the feasibility of the approach implemented, a prototype application based on a Computer Aided Design system was developed and a study case was accomplishedRadius of curvature and sliding velocity in constant-breadth cam mechanisms
http://hdl.handle.net/2117/26852
Radius of curvature and sliding velocity in constant-breadth cam mechanisms
Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa
In constant-breadth cam mechanisms closure of the higher kinematic pairs formed by the bilateral cam-follower contact is guaranteed by the geometry of both cam and follower. A study of the cam profile by means of its radius of curvature and the sliding velocities in the upper pair enables us to predict the correct functioning of the mechanism. This work presents the equations for calculating cam breadth when the translating follower is eccentric with an inclination, the radius of curvature of its profile and the sliding velocities of constant-breadth cam mechanisms with translating and oscillating followers. This study also analyses the influence of the angle of inclination and the offset of the flat-faced translating followers on the size of the cam and the kinematics of the mechanism. Numerical examples are given of constant-breadth cams obtained for distinct values of the mentioned parameters. Additionally, this paper describes the redesign of a cam of a conventional sewing machine and the new cam prototype, with a continuity of an order higher than the original profile, is included. (C) 2014 Elsevier Ltd. All rights reserved.
2015-03-19T13:33:19ZCardona Foix, SalvadorZayas Figueras, Enrique ErnestoJordi Nebot, LluïsaIn constant-breadth cam mechanisms closure of the higher kinematic pairs formed by the bilateral cam-follower contact is guaranteed by the geometry of both cam and follower. A study of the cam profile by means of its radius of curvature and the sliding velocities in the upper pair enables us to predict the correct functioning of the mechanism. This work presents the equations for calculating cam breadth when the translating follower is eccentric with an inclination, the radius of curvature of its profile and the sliding velocities of constant-breadth cam mechanisms with translating and oscillating followers. This study also analyses the influence of the angle of inclination and the offset of the flat-faced translating followers on the size of the cam and the kinematics of the mechanism. Numerical examples are given of constant-breadth cams obtained for distinct values of the mentioned parameters. Additionally, this paper describes the redesign of a cam of a conventional sewing machine and the new cam prototype, with a continuity of an order higher than the original profile, is included. (C) 2014 Elsevier Ltd. All rights reserved.Enhancement in evaluating small group work in courses with large number of students. Machine theory at industrial engineering degrees
http://hdl.handle.net/2117/18732
Enhancement in evaluating small group work in courses with large number of students. Machine theory at industrial engineering degrees
Jordi Nebot, Lluïsa; Pàmies Vila, Rosa; Català Calderon, Pau; Puig Ortiz, Joan
2013-04-09T11:49:48ZJordi Nebot, LluïsaPàmies Vila, RosaCatalà Calderon, PauPuig Ortiz, JoanSynthesis of displacement functions by Bézier curves in constant-breadth cams with parallel flat-faced translating and oscillating followers
http://hdl.handle.net/2117/17955
Synthesis of displacement functions by Bézier curves in constant-breadth cams with parallel flat-faced translating and oscillating followers
Cardona Foix, Salvador; Zayas Figueras, Enrique Ernesto; Jordi Nebot, Lluïsa; Català Calderon, Pau
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.
2013-02-25T10:56:13ZCardona Foix, SalvadorZayas Figueras, Enrique ErnestoJordi Nebot, LluïsaCatalà Calderon, PauThe 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.