20 research outputs found

    The Recent Advances in Magnetorheological Fluids-Based Applications

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    The magnetorheological fluids (MRF) are a generation of smart fluids with the ability to alter their variable viscosity. Moreover, the state of the MRF can be switched from the semisolid to the fluid phase and vice versa upon applying or removing the magnetic field. The fast response and the controllability are the main features of the MRF-based systems, which make them suitable for applications with high sensitivity and controllability requirements. Nowadays, MRF-based systems are rapidly growing and widely being used in many industries such as civil, aerospace, and automotive. This study presents a comprehensive review to investigate the fundamentals of MRF and manufacturing and applications of MRF-based systems. According to the existing works and current and future demands for MRF-based systems, the trend for future research in this field is recommended

    Modeling and Testing of a Series Elastic Actuator with Controllable Damping

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    Compliant Actuators are much safer than traditional stiff joint actuators, but at the cost of high overshoot, positional accuracy, and speed. A damper that varies its damping torque during motion is introduced to alleviate these downsides. The equations of motion for the system are derived and simulated. The simulations demonstrated a decrease in the overshoot and ringing time. A physical proof of concept was manufactured and tested. The results from the physical model were inconclusive due to a fault in the physical model. A more accurate physical test model is proposed, and is simulated

    Conception et évaluation d’un simulateur à réalité virtuelle d’intervention laparoscopique actionné par des embrayages magnétorhéologiques

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    La laparoscopie est une technique chirurgicale qui offre une alternative moins invasive à la chirurgie abdominale traditionnelle, en permettant aux patients de récupérer plus rapidement et avec moins de douleur. Dès son arrivée, cette nouvelle technique a su révolutionner le monde de la chirurgie, mais cette révolution est d'ailleurs venue avec un cout, une formation longue et difficile. Des simulateurs haptiques ont tenté de rendre cet apprentissage plus facile, mais leur cout élevé et leurs grosses dimensions les rendent difficiles d'accès pour les étudiants moyens. Afin de résoudre ce problème, des concepts qui utilisent des dispositifs haptiques sont offerts sur le marché pour concevoir des plateformes de simulation d'interventions laparoscopiques. Ces plateformes sont toutefois peu fidèles à la réalité et n'atteignent pas simultanément les performances dynamiques et cinétiques nécessaires à un apprentissage adéquat. En effet, les moteurs électriques utilisés obligent les concepteurs de dispositifs haptiques à faire un compromis entre la force produite et la réponse dynamique du système. Cette approche pourrait par contre être utilisée avec un dispositif haptique nouvelle-génération, le T-Rex. Ce dernier a été développé récemment par Exonetik, une compagnie issue de recherches de l'Université de Sherbrooke. Contrairement aux dispositifs haptiques offerts sur le marché, le T-Rex utilise la technologie d'actionneurs magnéto-rhéologiques développée par Exonetik. Cette technologie pourrait permettre d'atteindre les performances dynamiques et cinétiques nécessaires à la formation de chirurgiens. Ce projet de recherche présente l'analyse préliminaire du T-Rex d'Exonetik en tant que simulateur à réalité virtuelle d'interventions laparoscopiques. Un simulateur à réalité virtuelle d'interventions laparoscopiques utilisant le T-Rex d'Exonetik en tant qu'interface haptique a été conçu. Des critères de performances ont été établis à l'aide de la littérature pour faire une évaluation quantitative du système. Des simulations utilisant la méthode des éléments finis ont aussi été développées pour faire une évaluation qualitative du système auprès de résidents et de chirurgiens. L'évaluation quantitative du système démontre qu'il répond aux quatre critères cinématiques ainsi qu'à trois des quatre critères cinétiques. Les résultats démontrent donc que l'utilisation d'actionneurs magnéto-rhéologiques dans les simulateurs à réalité virtuelle d'interventions laparoscopiques a beaucoup de potentiel. Par contre, la friction dans le système se doit d'être adressée dans les itérations futures du système

    Development of Rotary Variable Damping and Stiffness Magnetorheological Dampers and their Applications on Robotic Arms and Seat Suspensions

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    This thesis successfully expanded the idea of variable damping and stiffness (VSVD) from linear magnetorheological dampers (MR) to rotary magnetorheological dampers; and explored the applications of rotary MR dampers on the robotic arms and seat suspension. The idea of variable damping and stiffness has been proved to be able to reduce vibration to a large degree. Variable damping can reduce the vibration amplitude and variable stiffness can shift the natural frequency of the system from excitation and prevent resonance. Linear MR dampers with the capacity of variable damping and stiffness have been studied by researchers. However, Linear MR dampers usually require larger installation space than rotary MR dampers, and need more expensive MR fluids to fill in their chambers. Furthermore, rotary MR dampers are inherently more suitable than linear MR dampers in rotary motions like braking devices or robot joints. Hence, rotary MR dampers capable of simultaneously varying the damping and stiffness are very attractive to solve angular vibration problems. Out of this motivation, a rotary VSVD MR damper was designed, prototyped, with its feature of variable damping and stiffness verified by experimental property tests in this thesis. Its mathematical model was also built with the parameters identified. The experimental tests indicated that it has a 141.6% damping variation and 618.1% stiffness variation. This damper’s successful development paved the way for the applications of rotary MR dampers with the similar capability of variable damping and stiffness

    Sensitivity analysis and optimal design of conventional and magnnetorheological fluid brakes

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    Mechanical and electrical brakes have dominated the braking industry for many years and will most likely continue to do so for the foreseeable future due to their low cost and adequate operating performance, wide range of applications, vehicle engineering, civil engineering, and biomedical engineering. Simple mechanical drum brake and magnetorheological (MR) fluid brake have presented in the current work. The main objective of this work is to increase braking torque, and to develop a new optimal design of MR fluid brake with better design and design control of the MR fluid design. To do so, four important steps have been accomplished. In the first step, a mathematical modeling of the conventional frictional brake and MR fluid brake has been developed to study and specify all design parameters. In the second step, a nondimensional, closedform analysis and a Taylor series expansion have used to examine the effects of perturbing dimensionless design parameters on the overall brakes performance. In the third step, two optimal designs for MR fluid brakes have been developed by taking advantage of sensitivity analysis and the design of experiments method also known as the Taguchi method. In the fourth step, controlling a MR fluid brake is performed by using two parallel PI controls for controlling the magnetic current and MR fluid thickness simultaneously. It was concluded that sensitivity analysis is a good method for identifying the parameters that have the greatest impact on brake performance and can be used as one method for the designer to obtain an optimal design. Four nondimensional design parameters were successfully used to describe the conventional frictional brake and seven nondimensional design parameters for MR fluid brake. Only two parameters for the conventional brake and five parameters for the MR fluid brake affect the performance and the others can be neglected. Two new designs for the MR fluid brake are presented and shown to be very simple in design, low in cost by removing a lot of additional auxiliaries for the frictional brake, and easy for control. By simultaneously controlling the MR fluid thickness and the electric current, a large range of brake torque is achieved without increasing the radial envelop for the brake, and saturation conditions in one controller are compensated for by the other controller. High angular velocities of the brake are primarily controlled by increasing the MR fluid thickness, while low angular velocities are primarily controlled by increasing the electric current. Good transient responses for regulating a constant speed (high, moderate, and low), and good stability while seeking to track a sinusoidal input have been achieved. In summary, the proposed control system for the MR fluid brake has demonstrated good controllability for the MR fluid brake.Includes bibliographical reference

    Development, characterization and applications of magnetorheological fluid based "smart" materials on the macro-to-micro scale

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2007.Includes bibliographical references (p. 193-208).Magnetorheological fluids belong to the class of field-responsive fluids that undergo large, reversible and fast changes in their rheological properties when acted upon by an external magnetic field. 'Smart' or controllable composite materials have been obtained by doping polymers, foams, fabrics etc. with these field-responsive fluids. The resulting composite materials have potential applications in numerous fields ranging from adaptive energy absorption, automotive crash protection to microfluidic valves, mixers and separation devices. A series of stable magnetorheological (MR) fluids have been systematically characterized under steady shearing, creep and large amplitude oscillatory shear (LAOS) flow conditions. A rheometer fixture for applying nearly uniform magnetic fields up to 0.4 T has been fabricated to measure both steady-state and transient changes in the fluid properties under applied fields. Stable MR fluids with a markedly improved dynamic response (yield stress as a function of magnetic field) compared to commercial fluids have been formulated by increasing the constituent particle size and by stabilizing the system against sedimentation. A new "soft-glassy rheology" model has been used to model the fluid response time and visco-elasto-plastic response under creep conditions and oscillatory loadings.(cont.) The experiments and model show that the evolution of chain structure and plastic collapse in these suspensions exhibits a universal scaling with the dimensionless stress s = [sigma]/[sigma]y. Structure evolution, pattern formation and dynamics of MR fluid flow in microchannel geometries has been analyzed using high-speed digital video microscopy. In order to elucidate the mechanisms that control MR structure formation, experiments have been performed while varying the magnetic field, particle size, channel geometry, concentration and fluid composition. Excellent qualitative agreement has been obtained with Brownian Dynamics simulations and useful scalings based on interplay of magnetostatic & viscous forces have been extracted to understand the field-dependent fluid response on the macro & micro scale. Novel MR elastomeric materials and microparticles have been synthesized by doping photo-curable or thermo-curable polymers with field-responsive fluids. A high-throughput micromolding technique for synthesis of controllable particles of anisotropic shapes and sizes has been developed. Flexible and permanent chain-like structures have also been synthesized using amidation chemistry. Potential microfluidic applications such as field-responsive valves, mixers and separation devices using these 'smart' materials have also been investigated.by Suraj Sharadchandra Deshmukh.Ph.D

    On semi-active inerters for improving machining productivity

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    The inerter is a mechanical element, synthesised in 2002 as an analogue to the electrical capacitor. Originally used in Formula 1 racing as the `J-damper', its potential has since been explored in other vehicles, as well as for vibration control of civil structures. In very recent years, some study has been given to the design and control of semi-active inerters. Such devices would be capable of varying their inertance in response to a control signal. To date, no study has been made of the semi-active inerter in the context of machining chatter. This undesirable form of vibration, leading to poor surface finish on machined parts, is a major issue in machining. The growing requirements of high speed machining of lightweight, flexible parts mean that the need to develop new strategies to tackle chatter will only increase. This thesis seeks to fill this gap in the literature. As a feasibility study, two chatter suppression strategies are developed using a simplified single degree of freedom chatter model. Both strategies assume the existence of an ideal semi-active inerter placed between the vibrating element and ground, allowing the natural frequency to be adjusted on-line. The first of these strategies, discrete inertance variation, is analogous to an existing lobe seeking strategy conducted by changing the spindle speed. It is shown that, with relatively modest ranges of inertance, this is an achievable strategy for high speed machining. The second strategy relies on cyclically adjusting the natural frequency to disrupt self-excited vibration. It is found that the amplitude of this variation is the important characteristic, rather than the ratio of the frequency of inertance variation to the tooth passing frequency. In both cases, the need to be able to rapidly control inertance is noted. The design needs of a semi-active helical inerter are considered, with magnetorheological fluid providing the semi-active control. Three different layouts are studied using quasi-static models. The bypass valve type layout is selected as the most promising for future study. The design of the valve is considered and a new optimisation scheme is developed which better suits the need of the bypass valve than previous schemes. The inerter model is extended into a quasi-dynamic model, which allows the varying inertance to be considered. This model would be key for developing any practical control scheme. Prototype inerters were designed and tested. Initially an oil-based designed is built, followed by a design using magnetorheological fluid. The prototype was tested using a servo-hydraulic actuator, with the goal of validating the models developed in the previous chapter. Unfortunately, trapped air in both systems led to these results being inconclusive in both cases. The use of magnetorheological fluid for flow directional control in this way is unusual at this scale and this work is important for any future researchers who wish to work with the fluid in this way. With this in mind, the issues encountered with the experimental rig are further analysed. Improvements to the design and filling method are proposed. Some more substantial design changes are also presented. Finally, some focus is given to the practical issues of implementing semi-active inerters in machining. The need to miniaturise the design to fit into modern machine tools is highlighted. Two areas in which this would be less of an issue -- fixturing and robotic machining -- are discussed. Notably, key challenges for robotic machining include the number and placement of the inerters, and whether new strategies would be needed to tackle mode-coupling chatter

    Emerging Trends in Mechatronics

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    Mechatronics is a multidisciplinary branch of engineering combining mechanical, electrical and electronics, control and automation, and computer engineering fields. The main research task of mechatronics is design, control, and optimization of advanced devices, products, and hybrid systems utilizing the concepts found in all these fields. The purpose of this special issue is to help better understand how mechatronics will impact on the practice and research of developing advanced techniques to model, control, and optimize complex systems. The special issue presents recent advances in mechatronics and related technologies. The selected topics give an overview of the state of the art and present new research results and prospects for the future development of the interdisciplinary field of mechatronic systems

    Mechatronic Systems

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    Mechatronics, the synergistic blend of mechanics, electronics, and computer science, has evolved over the past twenty five years, leading to a novel stage of engineering design. By integrating the best design practices with the most advanced technologies, mechatronics aims at realizing high-quality products, guaranteeing at the same time a substantial reduction of time and costs of manufacturing. Mechatronic systems are manifold and range from machine components, motion generators, and power producing machines to more complex devices, such as robotic systems and transportation vehicles. With its twenty chapters, which collect contributions from many researchers worldwide, this book provides an excellent survey of recent work in the field of mechatronics with applications in various fields, like robotics, medical and assistive technology, human-machine interaction, unmanned vehicles, manufacturing, and education. We would like to thank all the authors who have invested a great deal of time to write such interesting chapters, which we are sure will be valuable to the readers. Chapters 1 to 6 deal with applications of mechatronics for the development of robotic systems. Medical and assistive technologies and human-machine interaction systems are the topic of chapters 7 to 13.Chapters 14 and 15 concern mechatronic systems for autonomous vehicles. Chapters 16-19 deal with mechatronics in manufacturing contexts. Chapter 20 concludes the book, describing a method for the installation of mechatronics education in schools

    Soft Robotics: Design for Simplicity, Performance, and Robustness of Robots for Interaction with Humans.

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    This thesis deals with the design possibilities concerning the next generation of advanced Robots. Aim of the work is to study, analyse and realise artificial systems that are essentially simple, performing and robust and can live and coexist with humans. The main design guideline followed in doing so is the Soft Robotics Approach, that implies the design of systems with intrinsic mechanical compliance in their architecture. The first part of the thesis addresses design of new soft robotics actuators, or robotic muscles. At the beginning are provided information about what a robotic muscle is and what is needed to realise it. A possible classification of these systems is analysed and some criteria useful for their comparison are explained. After, a set of functional specifications and parameters is identified and defined, to characterise a specific subset of this kind of actuators, called Variable Stiffness Actuators. The selected parameters converge in a data-sheet that easily defines performance and abilities of the robotic system. A complete strategy for the design and realisation of this kind of system is provided, which takes into account their me- chanical morphology and architecture. As consequence of this, some new actuators are developed, validated and employed in the execution of complex experimental tasks. In particular the actuator VSA-Cube and its add-on, a Variable Damper, are developed as the main com- ponents of a robotics low-cost platform, called VSA-CubeBot, that v can be used as an exploratory platform for multi degrees of freedom experiments. Experimental validations and mathematical models of the system employed in multi degrees of freedom tasks (bimanual as- sembly and drawing on an uneven surface), are reported. The second part of the thesis is about the design of multi fingered hands for robots. In this part of the work the Pisa-IIT SoftHand is introduced. It is a novel robot hand prototype designed with the purpose of being as easily usable, robust and simple as an industrial gripper, while exhibiting a level of grasping versatility and an aspect comparable to that of the human hand. In the thesis the main theo- retical tool used to enable such simplification, i.e. the neuroscience– based notion of soft synergies, are briefly reviewed. The approach proposed rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive underactuated mechanisms, which is called the method of adaptive synergies, is discussed. This ap- proach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the method of adaptive syner- gies, the Pisa–IIT SoftHand is then described in detail. The design and implementation of the prototype hand are shown and its effec- tiveness demonstrated through grasping experiments. Finally, control of the Pisa/IIT Hand is considered. Few different control strategies are adopted, including an experimental setup with the use of surface Electromyographic signals
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