Mechanical actuator for biomimetic propulsion and the effect of the caudal fin elasticity on the swimming performance

This paper presents a mechanical actuator for the biomimetic propulsion of swimming devices and the experimental study of the effect of the caudal fin elasticity on the overall performance. The design of the proposed drive allows the DC motor to operate at constant speed, so all the power of the motor is spent only for the motion of the caudal fin. A prototype of the actuator, in which the caudal fin serves as a driving element, is manufactured and tested in both laboratory and natural conditions. The swimming speed, the thrust efficiency and the maneuverability are evaluated for caudal fins with different stiffness. The caudal fin whose rigidity varies relative to both vertical and horizontal cross-section, exhibits the best performance. The achieved results also confirm that the proposed actuator could be of great interest to applications in the field of underwater operation, ocean investigation and environmental protection.

BR3: a biologically inspired fish-like robot actuated by SMA-based artificial muscles

Los peces son animales, donde en la mayoría de los casos, son considerados como nadadores muy eficientes y con una alta capacidad de maniobra. En general los peces se caracterizan por su capacidad de maniobra, locomoción silencioso, giros y partidas rápidas y viajes de larga distancia. Los estudios han identificado varios tipos de locomoción que los peces usan para generar maniobras y natación constante. A bajas velocidades la mayoría de los peces utilizan sus aletas pares y / o impares para su locomoción, que ofrecen una mayor maniobrabilidad y mejor eficiencia de propulsión. A altas velocidades la locomoción implica el cuerpo y / o aleta caudal porque esto puede lograr un mayor empuje y aceleración. Estas características pueden inspirar el diseo y fabricación de una piel muy flexible, una aleta caudal mórfica y una espina dorsal no articulada con una gran capacidad de maniobra. Esta tesis presenta el desarrollo de un novedoso pez robot bio-inspirado y biomimético llamado BR3, inspirado en la capacidad de maniobra y nado constante de los peces vertebrados. Inspirado por la morfología de los peces Micropterus salmoides o también conocido como lubina negra, el robot BR3 utiliza su fundamento biológico para desarrollar modelos y métodos matemáticos precisos que permiten imitar la locomoción de los peces reales. Los peces Largemouth Bass pueden lograr un nivel increíble de maniobrabilidad y eficacia de la propulsión mediante la combinación de los movimientos ondulatorios y aletas morficas. Para imitar la locomoción de los peces reales en una contraparte artificial se necesita del análisis de tecnologías de actuación alternativos, como arreglos de fibras musculares en lugar de servo actuadores o motores DC estándar, así como un material flexible que proporciona una estructura continua sin juntas. Las aleaciones con memoria de forma (SMAs) proveen la posibilidad de construir robots livianos, que no emiten ruido, sin motores, sin juntas y sin engranajes. Asi es como un pez robot submarino se ha desarrollado y cuyos movimientos son generados mediante SMAs. Estos actuadores son los adecuados para doblar la espina dorsal continua del pez robot, que a su vez provoca un cambio en la curvatura del cuerpo. Este tipo de arreglo estructural está inspirado en los músculos rojos del pescado, que son usados principalmente durante la natación constante para la flexión de una estructura flexible pero casi incompresible como lo es la espina dorsal de pescado. Del mismo modo la aleta caudal se basa en SMAs y se modifica para llevar a cabo el trabajo necesario. La estructura flexible proporciona empuje y permite que el BR3 nade. Por otro lado la aleta caudal mórfica proporciona movimientos de balanceo y guiada. Motivado por la versatilidad del BR3 para imitar todos los modos de natación (anguilliforme, carangiforme, subcarangiforme y tunniforme) se propone un controlador de doblado y velocidad. La ley de control de doblado y velocidad incorpora la información del ángulo de curvatura y de la frecuencia para producir el modo de natación deseado y a su vez controlar la velocidad de natación. Así mismo de acuerdo con el hecho biológico de la influencia de la forma de la aleta caudal en la maniobrabilidad durante la natación constante se propone un control de actitud. Esta novedoso robot pescado es el primero de su tipo en incorporar sólo SMAs para doblar una estructura flexible continua y sin juntas y engranajes para producir empuje e imitar todos los modos de natación, así como la aleta caudal que es capaz de cambiar su forma. Este novedoso diseo mecatrónico presenta un futuro muy prometedor para el diseo de vehículos submarinos capaces de modificar su forma y nadar mas eficientemente. La nueva metodología de control propuesto en esta tesis proporcionan una forma totalmente nueva de control de robots basados en SMAs, haciéndolos energéticamente más eficientes y la incorporación de una aleta caudal mórfica permite realizar maniobras más eficientemente. En su conjunto, el proyecto BR3 consta de cinco grandes etapas de desarrollo: • Estudio y análisis biológico del nado de los peces con el propósito de definir criterios de diseño y control. • Formulación de modelos matemáticos que describan la: i) cinemática del cuerpo, ii) dinámica, iii) hidrodinámica iv) análisis de los modos de vibración y v) actuación usando SMA. Estos modelos permiten estimar la influencia de modular la aleta caudal y el doblado del cuerpo en la producción de fuerzas de empuje y fuerzas de rotación necesarias en las maniobras y optimización del consumo de energía. • Diseño y fabricación de BR3: i) estructura esquelética de la columna vertebral y el cuerpo, ii) mecanismo de actuación basado en SMAs para el cuerpo y la aleta caudal, iii) piel artificial, iv) electrónica embebida y v) fusión sensorial. Está dirigido a desarrollar la plataforma de pez robot BR3 que permite probar los métodos propuestos. • Controlador de nado: compuesto por: i) control de las SMA (modulación de la forma de la aleta caudal y regulación de la actitud) y ii) control de nado continuo (modulación de la velocidad y doblado). Está dirigido a la formulación de los métodos de control adecuados que permiten la modulación adecuada de la aleta caudal y el cuerpo del BR3. • Experimentos: está dirigido a la cuantificación de los efectos de: i) la correcta modulación de la aleta caudal en la producción de rotación y su efecto hidrodinámico durante la maniobra, ii) doblado del cuerpo para la producción de empuje y iii) efecto de la flexibilidad de la piel en la habilidad para doblarse del BR3. También tiene como objetivo demostrar y validar la hipótesis de mejora en la eficiencia de la natación y las maniobras gracias a los nuevos métodos de control presentados en esta tesis. A lo largo del desarrollo de cada una de las cinco etapas, se irán presentando los retos, problemáticas y soluciones a abordar. Los experimentos en canales de agua estarán orientados a discutir y demostrar cómo la aleta caudal y el cuerpo pueden afectar considerablemente la dinámica / hidrodinámica de natación / maniobras y cómo tomar ventaja de la modulación de curvatura que la aleta caudal mórfica y el cuerpo permiten para cambiar correctamente la geometría de la aleta caudal y del cuerpo durante la natación constante y maniobras. ABSTRACT Fishes are animals where in most cases are considered as highly manoeuvrable and effortless swimmers. In general fishes are characterized for his manoeuvring skills, noiseless locomotion, rapid turning, fast starting and long distance cruising. Studies have identified several types of locomotion that fish use to generate maneuvering and steady swimming. At low speeds most fishes uses median and/or paired fins for its locomotion, offering greater maneuverability and better propulsive efficiency At high speeds the locomotion involves the body and/or caudal fin because this can achieve greater thrust and accelerations. This can inspire the design and fabrication of a highly deformable soft artificial skins, morphing caudal fins and non articulated backbone with a significant maneuverability capacity. This thesis presents the development of a novel bio-inspired and biomimetic fishlike robot (BR3) inspired by the maneuverability and steady swimming ability of ray-finned fishes (Actinopterygii, bony fishes). Inspired by the morphology of the Largemouth Bass fish, the BR3 uses its biological foundation to develop accurate mathematical models and methods allowing to mimic fish locomotion. The Largemouth Bass fishes can achieve an amazing level of maneuverability and propulsive efficiency by combining undulatory movements and morphing fins. To mimic the locomotion of the real fishes on an artificial counterpart needs the analysis of alternative actuation technologies more likely muscle fiber arrays instead of standard servomotor actuators as well as a bendable material that provides a continuous structure without joins. The Shape Memory Alloys (SMAs) provide the possibility of building lightweight, joint-less, noise-less, motor-less and gear-less robots. Thus a swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. Likewise the caudal fin is based on SMAs and is customized to provide the necessary work out. The bendable structure provides thrust and allows the BR3 to swim. On the other hand the morphing caudal fin provides roll and yaw movements. Motivated by the versatility of the BR3 to mimic all the swimming modes (anguilliform, caranguiform, subcaranguiform and thunniform) a bending-speed controller is proposed. The bending-speed control law incorporates bend angle and frequency information to produce desired swimming mode and swimming speed. Likewise according to the biological fact about the influence of caudal fin shape in the maneuverability during steady swimming an attitude control is proposed. This novel fish robot is the first of its kind to incorporate only SMAs to bend a flexible continuous structure without joints and gears to produce thrust and mimic all the swimming modes as well as the caudal fin to be morphing. This novel mechatronic design is a promising way to design more efficient swimming/morphing underwater vehicles. The novel control methodology proposed in this thesis provide a totally new way of controlling robots based on SMAs, making them more energy efficient and the incorporation of a morphing caudal fin allows to perform more efficient maneuvers. As a whole, the BR3 project consists of five major stages of development: • Study and analysis of biological fish swimming data reported in specialized literature aimed at defining design and control criteria. • Formulation of mathematical models for: i) body kinematics, ii) dynamics, iii) hydrodynamics, iv) free vibration analysis and v) SMA muscle-like actuation. It is aimed at modelling the e ects of modulating caudal fin and body bend into the production of thrust forces for swimming, rotational forces for maneuvering and energy consumption optimisation. • Bio-inspired design and fabrication of: i) skeletal structure of backbone and body, ii) SMA muscle-like mechanisms for the body and caudal fin, iii) the artificial skin, iv) electronics onboard and v) sensor fusion. It is aimed at developing the fish-like platform (BR3) that allows for testing the methods proposed. • The swimming controller: i) control of SMA-muscles (morphing-caudal fin modulation and attitude regulation) and ii) steady swimming control (bend modulation and speed modulation). It is aimed at formulating the proper control methods that allow for the proper modulation of BR3’s caudal fin and body. • Experiments: it is aimed at quantifying the effects of: i) properly caudal fin modulation into hydrodynamics and rotation production for maneuvering, ii) body bending into thrust generation and iii) skin flexibility into BR3 bending ability. It is also aimed at demonstrating and validating the hypothesis of improving swimming and maneuvering efficiency thanks to the novel control methods presented in this thesis. This thesis introduces the challenges and methods to address these stages. Waterchannel experiments will be oriented to discuss and demonstrate how the caudal fin and body can considerably affect the dynamics/hydrodynamics of swimming/maneuvering and how to take advantage of bend modulation that the morphing-caudal fin and body enable to properly change caudal fin and body’ geometry during steady swimming and maneuvering.

Bridge windshield design to avoid aeroelastic phenomena

Since in 1940 the Tacoma Narrows Bridge was destroyed by the wind, aeroelastic instabilities have been recognized as one of the most challenging aspects of bridge design. They can produce long-term fatigue failure through vortex induced vibrations, or sudden collapse through self-excited flutter. These vibrations may also cause discomfort for the users and temporary closure of the bridge. Wind tunnel studies are a very helpful tool to understand these phenomena. By means of them, the critical wind speed at which vortex induced vibration and flutter appear can be precisely determined and the design of the bridge can be reconsidered in the early steps of the process. In this paper, an optimum design of the bridge section is sought. One of the most relevant parameters that influence the stability of a certain deck is the porosity of the barriers. Section model tests have been carried out to find whether an optimum value of the porosity of the barrier exists. This value or range of values must present neither vortex induced vibration nor flutter.

Safety-related issues for high-speed railway bridges

Railway bridges have specific requirements related to safety, which often are critical aspects of design. In this paper the main phenomena are reviewed, namely vertical dynamic effects for impact effect of moving loads and resonance in high-speed, service limit states which affect the safety of running traffic, and lateral dynamic effects.

Criteria for Ballast Flight Initiation Induced by High Speed Trains

One of the phenomena that limit the velocity of trains in high speed lines is the so- called “ballast pick-up”. It is a ballast train-induced-wind erosion (or BATIWE) that can produce damage to the train under body and the infrastructure surrounding the tracks. The analysis of the measurements taken during several passes of the train allows for a criterion of ballast flight initiation to be obtained. The first rotation of a ballast stone occurs when the impulse given to the stone (arising from the aerodynamic loading produced by the wind gust genera ted by the passing train) overpasses a critical impulse. This impulse depends on the physical properties of the stone (mass, shape, moment of inertia, etc. ...) and its posture on the track bed. The aim of this paper is to report on the experimental results obtained in the ADIF’S Brihuega (Guadalajara) test station, in the Madrid to Barcelona high speed line, and the way they can be used to support the feasibility of the definition of a criterion to evaluate the BA TIWE capability of trains. The results obtained show the feasibility of the proposed method, and contribute to a method of BATIWE characterization, which can be relevant for the development of train interoperability standardization.

Great marquee for high-speed trains in the new railway station of Malaga

The commercial centre VIALIA and the new railway station of the AVE (high speed train) in Malaga was inaugurated in November 2006, just on the place of the former railway station. The new railway station with an investment of 134,7 million Euros occupies a surface of 51.377 m2, five times the surface of the former station. The enclosure is the biggest intermodal and commercial centre of Spain which comprises a parking of 21.000 m2 for 1300 parking places, one commercial area and a hotel with a total extension constructed of approximately 100.000 m2. The spaces of leisure contain cinemas, shops, restaurants, bowling, gymnasium, swimming pool and zones of passenger's traffic.

Aeroacoustics in high speed trains

Este trabajo se centra en el estudio de problemas aeroacústicos en los trenes de alta velocidad. Se han considerado dos escenarios en los que las ondas de presión generadas son críticos para el confort de los pasajeros. Uno es el debido a las ondas de presión que genera el tren cuando entra y sale de un túnel, que a su vez producen saltos de presión de baja frecuencia en el tren (cuando se cruzan con él) y en los alrededores del túnel cuando alcanzan la salida. Se estudia este fenómeno, y se propone un sistema aeroelástico basado en el galope transversal para disminuir la energía de estas ondas, y se analiza la energía extraíble de las ondas utilizando cuerpos con diferentes secciones transversales [Sorribes-Palmer and Sanz-Andres, 2013]. La influencia de la geometría de los portales en la energía radiada hacia el exterior de túnel es analizada experimentalmente, prestando especial atención a las boquillas porosas. Las ondas de presión en el interior del túnel se han analizado mediante el método de las características. Se han realizado ensayos experimentales para estimar la energía reflejada hacia el interior del túnel al alcanzar las ondas de presión el portal de salida del túnel. Se ha estudiado la formación e interacción entre el portal del túnel y la onda de choque generada en los túneles de gran longitud y pequeña fricción. Se propone un método para describir de forma aproximada el ruido radiado al exterior. Por otro lado se ha estudiado el ruido de media y alta frecuencia de origen aerodinámico. Se ha estudiado la influencia del desprendimiento de la capa límite sobre el tren. Se propone una metodología basada en una sección de tren característica para predecir rápidamente el nivel de presión de sonido dentro y fuera del tren para todo el rango de frecuencias. Se han realizado medidas experimentales en vía de los espectros de presión sobre la superficie del tren, y de la transmisibilidad de las uniones entre estructura y revestimiento. Los resultados experimentales se han utilizado en los modelos vibroacústicos. El método de la sección del tren característica es especialmente útil a altas frecuencias cuando todo el tren se puede modelar mediante el ensamblaje de diferentes secciones características utilizando el análisis estadístico de la energía. ABSTRACT This work is focused on the study of aeroacoustic problems in high speed trains. We have considered two scenarios in which the pressure waves generated are critical for passengers comfort. The first one is due to the pressure waves generated by a train entering in a tunnel. These waves generate pressure gauges inside the train (when they find each other) and outside of the tunnel portals. This phenomenon has been studied, and an aeroelastic system based on transverse galloping to reduce the energy of these waves is proposed. The maximum extractable energy by using bodies with different cross-section shapes is analyzed. The influence of the portals geometry in the energy radiated outwards the tunnel is analyzed experimentally, with particular attention to the porous exits. The pressure waves inside the tunnel have been analyzed using the method of characteristics. Experimental tests to estimate the energy reflected into the tunnel when the pressure waves reach the tunnel portal have been performed. We have studied the generation and interaction between the tunnel portal and a shock wave generated in long tunnels with small friction. A method to describe in an approximated way the pressure radiated outside the tunnel is proposed. In the second scenario, middle and high frequency noise generated aerodynamically has been studied, including the influence of the detachment of the boundary layer around the train. A method based on a train section to quickly predict the sound pressure level inside and outside the train has been proposed. Experimental test have been performed on board to evaluate the pressure power spectra on the surface of the train, and the transmissibility of the junctions between the structure and trim. These experimental results have been used in the vibroacoustic models. The low frequency pressure waves generated with the train during the tunnel crossing has been identified in the pressure spectrum. The train characteristic section method is especially useful at high frequencies, when the whole train can be modeled by assembling different sections using the statistical energy analysis. The sound pressure level inside the train is evaluated inside and outside the tunnel.

Aeroacoustic noise prediction in high speed trains due to attached and detached flow

This paper aims to set out the influence of the flow field around high speed trains in open field. To achieve this parametric analysis of the sound pressure inside the train was performed. Three vibroacoustic models of a characteristic train section are used to predict the noise inside the train in open field by using finite element method FEM, boundary element method (BEM) and statistical energy analysis (SEA) depending on the frequency range of analysis. The turbulent boundary layer excitation is implemented as the only airborne noise source, in order to focus on the study of the attached and detached flow in the surface of the train. The power spectral densities of the pressure fluctuation in the train surface proposed by [Cockburn and Roberson 1974, Rennison et al. 2009] are applied on the exterior surface of the structural subsystems in the vibroacoustic models. An increase in the sound pressure level up to10 dB can be appreciated due to the detachment of the flow around the train. These results highlight the importance to determine the detached regions prediction, making critical the airborne noise due to turbulent boundary layer.

Vibroacoustic Problems in High Speed Trains

Passengers comfort in terms of acoustic noise levels is a key train design parameter, especially relevant in high speed trains, where the aerodynamic noise is dominant. The aim of the work, described in this paper, is to make progress in the understanding of the flow field around high speed trains in an open field, which is a subject of interest for many researchers with direct industrial applications, but also the critical configuration of the train inside a tunnel is studied in order to evaluate the external loads arising from noise sources of the train. The airborne noise coming from the wheels (wheelrail interaction), which is the dominant source at a certain range of frequencies, is also investigated from the numerical and experimental points of view. The numerical prediction of the noise in the interior of the train is a very complex problem, involving many different parameters: complex geometries and materials, different noise sources, complex interactions among those sources, broad range of frequencies where the phenomenon is important, etc. During recent years a research plan is being developed at IDR/UPM (Instituto de Microgravedad Ignacio Da Riva, Universidad Politécnica de Madrid) involving both numerical simulations, wind tunnel and full-scale tests to address this problem. Comparison of numerical simulations with experimental data is a key factor in this process.

Lateral Dynamic Models for High-Speed Railway Bridges and Vehicles

The analysis of the running safety of railway vehicles on viaducts subject to strong lateral actions such as cross winds requires coupled nonlinear vehicle-bridge interaction models, capable to study extreme events. In this paper original models developed by the authors are described, based on finite elements for the structure, multibody and finite element models for the vehicle, and specially developed interaction elements for the interface between wheel and rail. The models have been implemented within ABAQUS and have full nonlinear capabilities for the structure, the vehicle and the contact interface. An application is developed for the Ulla Viaduct, a 105 m tall arch in the Spanish high-speed railway network. The dynamic analyses allow obtaining critical wind curves, which define the running safety conditions for a given train in terms of speed of circulation and wind speed