Designing optimal controls by parameter optimization for a stance-control knee-ankle-foot orthosis

Inverse dynamics simulation is often used in robotic and mechatronic systems to track a desired trajectory by feed-forward control. Musculoskeletal multibody systems are highly overactuated and show a switching number of closed kinematical loops. The method of inverse dynamics is also successfully applied to overactuated systems by parameter optimization for two- and three-dimensional models of the human musculoskeletal system. The presented simulation approach is fully based on optimizationPostprint (published version

Detection of Communities within the Multibody System Dynamics Network and Analysis of Their Relations

Multibody system dynamics is already a well developed branch of theoretical, computational and applied mechanics. Thousands of documents can be found in any of the well-known scientific databases. In this work it is demonstrated that multibody system dynamics is built of many thematic communities. Using the Elsevier’s abstract and citation database SCOPUS, a massive amount of data is collected and analyzed with the use of the open source visualization tool Gephi. The information is represented as a large set of nodes with connections to study their graphical distribution and explore geometry and symmetries. A randomized radial symmetry is found in the graphical representation of the collected information. Furthermore, the concept of modularity is used to demonstrate that community structures are present in the field of multibody system dynamics. In particular, twenty-four different thematic communities have been identified. The scientific production of each community is analyzed, which allows to predict its growing rate in the next years. The journals and conference proceedings mainly used by the authors belonging to the community as well as the cooperation between them by country are also analyzed

Study of the Contribution of Nonlinear Normal Modes (NNMs) in Large Amplitude Oscillations of Simply Supported Beams

Faculty of Civil and Industrial Engineering , Rome; Italy. 10 September 2017 through 13 September 2017This paper focuses on the Nonlinear Normal Modes of simply supported beams with unrestrained axial displacements. Two different configurations are considered, depending on whether longitudinal displacements are allowed at one end of the beam or at both ends. An integro-differential equation is obtained for the transverse displacement of the beam, upon the common assumption of inextensibility. By using a perturbation approach, the NNMs are analytically computed, which yields a frequency-amplitude relation for each NNM. These analytical curves are compared to FE results, showing a remarkable accordance. Noticeably, qualitatively different behaviors are found for the first NNM in both configurations: with one free end, the beam softens; with both ends free, it hardens

Direct Sensitivity Analysis of Multibody Systems With Holonomic and Nonholonomic Constraints via an Index-3 Augmented Lagrangian Formulation With Projections

This is a post-peer-review, pre-copyedit version of an article published in Nonlinear Dynamics. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11071-018-4306-y[Abstract] Optimizing the dynamic response of mechanical systems is often a necessary step during the early stages of product development cycle. This is a complex problem that requires to carry out the sensitivity analysis of the system dynamics equations if gradient-based optimization tools are used. These dynamics equations are often expressed as a highly nonlinear system of Ordinary Differential Equations (ODEs) or Differential-Algebraic Equations (DAEs), if a dependent set of generalized coordinates with its corresponding kinematic constraints is used to describe the motion. Two main techniques are currently available to perform the sensitivity analysis of a multibody system, namely the direct differentiation and the adjoint variable methods. In this paper, we derive the equations that correspond to the direct sensitivity analysis of the index-3 augmented Lagrangian formulation with velocity and acceleration projections. Mechanical systems with both holonomic and nonholonomic constraints are considered. The evaluation of the system sensitivities requires the solution of a Tangent Linear Model (TLM) that corresponds to the Newton-Raphson iterative solution of the dynamics at configuration level, plus two additional nonlinear systems of equations for the velocity and acceleration projections. The method was validated in the sensitivity analysis of a set of examples, including a five-bar linkage with spring elements, which had been used in the literature as benchmark problem for similar multibody dynamics formulations, a point-mass system subjected to nonholonomic constraints, and a full-scale vehicle model.Ministerio de Economía y Competitividad (MINECO); DPI2016-81005-PXunta de Galicia; ED431B2016/03

Linearization-based state-transition model for the discrete extended Kalman filter applied to multibody simulations

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.This study investigates the discrete extended Kalman filter as applied to multibody systems and focuses on accurate formulation of the state-transition model in the framework. The proposed state-transition model is based on the coordinate-partitioning method and linearization of the multibody equations of motion. The approach utilizes the synergies between the integration of states and estimator covariances without overly simplifying the integrator structure. The proposed method is analyzed with a forward dynamics analysis of a four-bar mechanism. The results show that the stability of the state-transition model in the forward dynamics analysis is significantly enhanced with the proposed method compared with the forward Euler-based methods. The computational efficiency of the novel method was significantly lower in comparison to forward Euler-based methods, which was found to be mainly due to the computation of the Jacobian matrix of the nonlinear state equation. However, the increase in computational cost can be considered acceptable in Kalman-filtering applications, where the exact Jacobian of the state equation is needed

An efficient and accurate linearization approach for hydraulically actuated multibody systems with holonomic and nonholonomic constraints

Hydraulics is often used to actuate mechanisms in the applications of heavy machinery. In this work, a linearization approach for hydraulically driven multibody systems is presented. The approach allows linearizing the equations of motion of general multibody systems with holonomic and nonholonomic constraints, augmented with the hydraulic equations of the hydraulic subsystem. The derivation of this linearization approach is of interest in many applications, such as the performance of linear stability analyses. The procedure is tested with a three-dimensional multibody model of a hydraulically actuated four-bar mechanism. The validation of the approach is performed by means of the forward dynamics simulation of the linear and nonlinear systems. The results show the power of the approach, obtaining the linearized equations of motion around the equilibrium position of the four-bar mechanism multibody model in terms of the mechanical and hydraulic parameters. A comparison of the proposed procedure with a conventional counterpart approach is included, demonstrating the great accuracy and computational efficiency of the approach developed in this work

Dissemination of the hispalense university artistic heritage through the participation in national and international exhibitions

Esta comunicación presenta la gestión expositiva del Patrimonio Histórico-Artístico de la Universidad de Sevilla, en el período comprendido entre 2008-2012 y los resultados objetivos de la difusión de su patrimonio a través de las exposiciones temporales participadas. Se describirán los protocolos técnicos internos aplicados a dicha gestión, en cuanto a condiciones del préstamo: plazos, información técnica, conservación preventiva de las piezas (transporte, instalación, correos, pólizas de seguro, etc.). Todo lo cuál nos muestra la diversa naturaleza de la actividad universitaria generada: académica de su profesorado en la gestión de comisariado, inventario, catalogación y difusión en la web. El área de Conservación con el equipo y talleres. El área Técnico-administrativa del Personal de Administración y Servicios (PAS): Gabinete Jurídico, Gabinete de Prensa, Gabinete de Protocolo, etc. Esta información nos suministra datos objetivos concluyentes sobre el positivo impacto socio-económico y cultural de estas exposiciones y el impulso global que la gestión y el rendimiento patrimonial genera. Se trasladará a la mesa el debate sobre la diferenciación u homologación entre las distintas instituciones patrimoniales y museísticas, públicas o privadas. Así como, la obligación legal y moral de las entidades universitarias españolas, no sólo en conservar su patrimonio, sino en exponerlo pública y establemente con las debidas garantías para obra y público. En la necesidad de que exista una dotación en infraestructuras técnicas museológicas y administrativas permanentes e institucionalizadas de las colecciones en igualdad de rango y condiciones con los servicios bibliotecarios y archivísticos, como entidad estable y abierta, al margen de los distintos equipos de gobierno.This communication presents the expositive management of the Historical and Artistic Heritage from University of Seville in the period 2008-2012. Local, national, continental and international exhibitions organized or participated: exhibition content, its core values and museological contributions are shown. Internal technical protocols applied to such management, in terms of preventive conservation conditions of loans (transport, installation, insurance, etc.). Similarly, the internal administrative arrangements with the Faculties and governmental university departments involved are analyzed. All of which shows the diverse nature of university activity generated: academic area in the management of curating, cataloging, etc. Conservation and restoration area with equipment and workshops. Technical-administrative area: Legal Office, Press Office, Office of Protocol, etc. This information provides us with conclusive objective data on the socio-economic and cultural impact of these exhibitions, the overall momentum management and asset performance generated. Finally, the debate on the need for differentiation or standardization between different heritage and museums, public and private institutions is proposed. As the legal and moral obligation of the Spanish university institutions, not only to preserve their heritage, but exhibit it publicly and stably with appropriate safe measures for artwork and audience. The need for an permanent endowment and institutionalized museological and administrative technical infrastructure of the University Museum in equal status and conditions with the librarians and archival services such as stable and open entity, regardless of domestic political changes

A New Electromechanical Analogy Approach Based on Electrostatic Coupling for Vertical Dynamic Analysis of Planar Vehicle Models

Article number 9524572Analogies between mechanical and electrical systems have been developed and applied for almost a century, and they have proved their usefulness in the study of mechanical and electrical systems. The development of new elements such as the inerter or the memristor is a clear example. However, new applications and possibilities of using these analogues remain to be explored. In this work, the electrical analogues of different vehicle models are presented. A new and not previously reported analogy between inertial coupling and electrostatic capacitive coupling is found and described. Several examples are provided to highlight the benefits of this analogy. Well-known mechanical systems like the half-car or three three-axle vehicle models are discussed and some numerical results are presented. To the best of the author’s knowledge, such systems were never dealt with by using a full electromechanical analogy. The mechanical equations are also derived and compared with those of the electrical domain for harmonic steady-state analysis.Ministerio de Ciencia, Innovación y Universidades(España) PGC2018-098813-B-C3

Sistemas constructivos de fachadas que incorporan vegetación. Una revisión del estado del arte

Esta comunicación realiza una revisión del el estado del arte de los sistemas constructivos de fachadas que utilizan vegetación. La integración de vegetación viva en las fachadas de los edificios no es ninguna novedad; a lo largo de la historia han existido múltiples ejemplos de la integración de vegetación en las fachadas de las edificaciones. En la actualidad, la situación de posible catástrofe medio-ambiental en la que estamos inmersos, ha popularizado el desarrollo de fachadas verdes. Existen numerosísimas investigaciones en marcha para valorar las virtudes ecológicas de estos sistemas. Se realizan estudios sobre el efecto de sombreamiento que producen sobre las fachadas, la climatización que generan a través del enfriamiento evaporativo…, pero es importante señalar que los estudios que implican el uso de vegetación son complicados, debido a la dependencia de los factores climáticos, las diferentes especies usadas... Los sistemas de fachadas verdes pueden emplearse tanto en obra nueva como en rehabilitación de envolventes. En ambas situaciones es posible alcanzar una elevada integración de la fachada verde en la envolvente del edificio mediante la combinación adecuada de las funciones de cada sistema