38 research outputs found
RESEARCH TOWARDS THE DESIGN OF A NOVEL SMART FLUID DAMPER USING A MCKIBBEN ACTUATOR
Vibration reducing performance of many mechanical systems, decreasing the quality of manufactured products, producing noise, generating fatigue in mechanical components, and producing an uncomfortable environment for human bodies. Vibration control is categorized as: active, passive, or semi-active, based on the power consumption of the control system and feedback or feed forward based on whether sensing is used to control vibration.
Semi-active vibration control is the most attractive method; one method of semi-active vibration control could be designed by using smart fluid. Smart fluids are able to modify their effective viscosity in response to an external stimulus such as a magnetic field. This unique characteristic can be utilised to build semi-active dampers for a wide variety of vibration control systems. Previous work has studied the application of smart fluids in semi-active dampers, where the kinetic energy of a vibrating structure can be dissipated in a controllable fashion.
A McKibben actuator is a device that consists of a rubber tube surrounded by braided fibre material. It has different advantages over a piston/cylinder actuator such as: a high power to weight ratio, low weight and less cost. Recently McKibben actuator has appeared in some semi-active vibration control devise. This report investigates the possibility of designing a Magnetorheological MR damper that seeks to reduce the friction in the device by integrating it with a McKibben actuator. In this thesis the concept of both smart fluid and McKibben actuator have been reviewed in depth, and methods of modelling and previous applications of devices made using these materials are also presented. The experimental part of the research includes: designing and modelling a McKibben actuator (using water) under static loads, and validating the model experimentally. The research ends by presenting conclusions and future work
Investigation of actuators with smart links
Principal schemes of actuators with smart links have been designed. Equations are presented for describing motion of a pneumatic actuator with viscous magnetorheological liquid and the vibration actuator with a smart link with shape memory. Amplitude-frequency characteristics of the vibration actuator and the pressure developed by the magnetorheological liquid vane have been determined. Application areas of the devices are propose
Conception et validation expĂ©rimentale dâun gant haptique alimentĂ© par des actionneurs magnĂ©torhĂ©ologiques pour la manipulation dâobjets dans un environnement virtuel
En rĂ©alitĂ© virtuelle (VR), les systĂšmes haptiques sont en mesure de fournir un retour de force Ă lâutilisateur pour des applications de jeux et dâentrainement (simulation). Les interfaces haptiques pour la main sont limitĂ©es par les technologies dâactionnement dâaujourdâhui. En effet, la vaste majoritĂ© des systĂšmes robotiques est actionnĂ©e par des moteurs DC couplĂ©s Ă un ratio de dĂ©multiplication (« gearbox »). Ces systĂšmes font face Ă un compromis inĂ©vitable entre la densitĂ© de couple et la rĂ©ponse dynamique.
De rĂ©centes recherches ont dĂ©montrĂ©es que les embrayages magnĂ©torhĂ©ologiques (MR) couplĂ©es Ă une source de puissance (ex : moteur DC) sont une alternative prometteuse pour lâobtention dâune haute rĂ©ponse dynamique Ă un coĂ»t moindre. JusquâĂ prĂ©sent, la technologie MR nâa pas Ă©tĂ© dĂ©montrĂ©e pour des systĂšmes robotiques ayant de multiple (6 et +) degrĂ©s-de-libertĂ© (ddls).
Ce mĂ©moire a pour but dâĂ©tudier le potentiel de la technologie des embrayages MR pour des applications dâinterfaces haptiques VR pour la main.
Dâabord, les requis de conception sont Ă©tablis par la littĂ©rature. Ensuite, un systĂšme haptique complet permettant aux utilisateurs de manipuler des objets virtuels a Ă©tĂ© dĂ©veloppĂ© basĂ© sur un actionnement Ă tendons alimentĂ©s par des embrayages MR (« tendon-driven manipulator powered by MR actuators », TDM-MR). Ce systĂšme haptique utilise un actionnent Ă configuration semi-distribuĂ©e qui permet Ă deux moteurs DC, couplĂ©s Ă un ratio de dĂ©multiplication, de fournir la puissance nĂ©cessaire pour alimenter 10 embrayages MR actionnant 7 ddls. Ce systĂšme haptique a dâailleurs Ă©tĂ© testĂ© expĂ©rimentalement. Les rĂ©sultats dĂ©montrent dâexcellentes rĂ©ponses dynamiques, de hautes forces gĂ©nĂ©rĂ©es et une tolĂ©rance aux impacts. Pour finir, un jeu VR consistant Ă dĂ©monter la performance du prototype auprĂšs de 10 utilisateurs a Ă©tĂ© dĂ©veloppĂ© et trĂšs bien reçu par ceux-ci
Magneto-Rheological Actuators for Human-Safe Robots: Modeling, Control, and Implementation
In recent years, research on physical human-robot interaction has received considerable attention. Research on this subject has led to the study of new control and actuation mechanisms for robots in order to achieve intrinsic safety. Naturally, intrinsic safety is only achievable in kinematic structures that exhibit low output impedance. Existing solutions for reducing impedance are commonly obtained at the expense of reduced performance, or significant increase in mechanical complexity. Achieving high performance while guaranteeing safety seems to be a challenging goal that necessitates new actuation technologies in future generations of human-safe robots.
In this study, a novel two degrees-of-freedom safe manipulator is presented. The manipulator uses magneto-rheological fluid-based actuators. Magneto-rheological actuators offer low inertia-to-torque and mass-to-torque ratios which support their applications in human-friendly actuation. As a key element in the design of the manipulator, bi-directional actuation is attained by antagonistically coupling MR actuators at the joints. Antagonistically coupled MR actuators at the joints allow using a single motor to drive multiple joints. The motor is located at the base of the manipulator in order to further reduce the overall weight of the robot. Due to the unique characteristic of MR actuators, intrinsically safe actuation is achieved without compromising high quality actuation. Despite these advantages, modeling and control of MR actuators present some challenges. The antagonistic configuration of MR actuators may result in limit cycles in some cases when the actuator operates in the position control loop. To study the possibility of limit cycles, describing function method is employed to obtain the conditions under which limit cycles may occur in the operation of the system. Moreover, a connection between the amplitude and the frequency of the potential limit cycles and the system parameters is established to provide an insight into the design of the actuator as well as the controller. MR actuators require magnetic fields to control their output torques. The application of magnetic field however introduces hysteresis in the behaviors of MR actuators. To this effect, an adaptive model is developed to estimate the hysteretic behavior of the actuator. The effectiveness of the model is evaluated by comparing its results with those obtained using the Preisach model. These results are then extended to an adaptive control scheme in order to compensate for the effect of hysteresis. In both modeling and control, stability of proposed schemes are evaluated using Lyapunov method, and the effectiveness of the proposed methods are validated with experimental results
A Review on the Magnetorheological Fluid, Damper and Its Applications for Seismic Mitigation
Magnetorheological (MR) fluids and dampers have wide advances as smart materials because of its unique properties, notably, viscosity increases in the presence when magnetic field applied MR Fluids composed of three key components, including carrier fluid, surfactants and metal particles. The major applications of MR Fluids are in brakes, dampers, journal bearings, fluid clutches, pneumatic artificial muscles, aerospace etc. where electrical energy is converted to mechanical energy (Damping Force) in a controlled manner. Within a few milliseconds the fluid converts from liquid to semi solid state. Over the years, researchers were concerned on the ways to enhance the modelling precision. Though the proposed Dynamic models of MR Dampers represent displacement and force behaviour. In this review paper, the advances of MR Fluids, MR Damper, Damper Models, Energy harvesting and their applications for seismic resistance of structures are briefly discussed in the present study
Conception et évaluation d'actionneurs à embrayages magnétorhéologiques pour la robotique collaborative
La robotique collaborative se dĂ©marque de la robotique industrielle par sa sĂ©curitĂ© dans le but de travailler en collaboration avec les humains. Toutefois, la majoritĂ© des robots collaboratifs sĂ©riels reposent sur un actionnement Ă haut ratio de rĂ©duction, ce qui augmente considĂ©rablement la masse reflĂ©tĂ©e Ă lâeffecteur du robot, et donc, nuit Ă la sĂ©curitĂ©. Pour pallier cette masse reflĂ©tĂ©e et maintenir un seuil minimal de sĂ©curitĂ©, les vitesses dâopĂ©ration sont abaissĂ©es, nuisant ainsi directement Ă la productivitĂ© des entreprises. Afin de minimiser la masse reflĂ©tĂ©e Ă lâeffecteur, les masses des actionneurs ainsi que leur inertie reflĂ©tĂ©e doivent ĂȘtre minimisĂ©s. Les embrayages Ă fluide magnĂ©torhĂ©ologique (MR) maintenus en glissement continus dĂ©couplent lâinertie provenant de la source de puissance, souvent un moteur et un rĂ©ducteur, offrant ainsi un actionneur possĂ©dant un haut rapport couple-inertie. Toutefois, les embrayages MR, utilisĂ©s de façon antagoniste, ajoutent des composantes Ă lâactionneur ce qui rĂ©duit la densitĂ© de couple, et donc, augmente la masse reflĂ©tĂ©e Ă lâeffecteur du robot. Certains actionneurs MR [1â3] ont Ă©tĂ© dĂ©veloppĂ©s, mais leur basse densitĂ© de couple contrebalance leur faible inertie lorsquâutilisĂ©s comme actionneurs aux articulations de robots collaboratifs sĂ©riels. Cette constatation a menĂ© Ă ma question de recherche : Comment profiter de la faible inertie des actionneurs MR pour maximiser les performances dynamiques des robots collaboratifs sĂ©riels?
Lâobjectif de ce projet de recherche vise donc Ă Ă©tudier le potentiel des embrayages MR en robotique collaborative. Pour ce faire, deux architectures MR sont dĂ©veloppĂ©es et testĂ©es expĂ©rimentalement. La premiĂšre architecture consiste en une articulation robotisĂ©e modulaire comportant des embrayages MR en glissement continu et possĂ©dant un rapport couple/masse et une taille Ă©quivalente Ă lâactionneur dâUniversal Robots (UR) de couple Ă©gal, mais possĂ©dant un rapport couple/inertie 150 fois supĂ©rieur. Ă lâintĂ©rieur de lâarticulation, deux chaines de puissance (2 moteurs et 2 embrayages MR) indĂ©pendantes se rejoignent Ă la sortie du joint offrant ainsi une redondance et augmentant la densitĂ© de couple comparativement Ă une architecture standard (1 moteur pour 2 embrayages MR).
La deuxiĂšme architecture Ă©tudiĂ©e consiste en un actionnement dĂ©localisĂ© du robot oĂč les embrayages MR sont situĂ©s Ă la base du robot et une transmission hydrostatique Ă membranes dĂ©roulantes achemine la puissance aux articulations. Cette architecture a Ă©tĂ© testĂ©e expĂ©rimentalement dans un contexte de bras robotisĂ© surnumĂ©raire. Contrairement Ă lâarticulation MR, cette architecture nâoffre pas une modularitĂ© habituellement recherchĂ©e en robotique sĂ©rielle, mais offre la possibilitĂ© de rĂ©duire lâinertie de la structure avec la dĂ©localisation de lâactionnement.
Finalement, les deux architectures dĂ©veloppĂ©es ont Ă©tĂ© comparĂ©es Ă une architecture standard (haut ratio avec rĂ©ducteur harmonique) afin de situer le potentiel du MR en robotique collaborative. Cette analyse thĂ©orique a dĂ©montrĂ© que pour un robot collaboratif sĂ©riel Ă 6 degrĂ©s de libertĂ©, les architectures MR ont le potentiel dâaccĂ©lĂ©rer 6 et 3 fois plus (respectivement) que le robot standard dâUR, composĂ© dâactionneurs Ă hauts ratios
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Robotic Actuation and Control with Programmable, Field-Activated Material Systems
This dissertation presents novel, field-activated smart material systems for the actuation and control of autonomous robots. Smart materials, a type of material whose properties can be changed with an external stimuli, represent a promising direction to expand upon existing robotic control and actuation methods, particularly in the sub-fields of soft robotics and robotic grasping. Specifically, this work makes the following contributions: i) a literature review that synthesizes recent work on field-activated smart materials and their use in soft robotics; ii) an electrorheological fluid (ERF) valve to control soft actuators; iii) magnetic elastomers (MEs) to increase the grip strength of soft grippers; and iv) a low-power method for torque transmission enabled by magnetorheological fluid (MRF) and electropermanent magnet arrays. After the introduction, this dissertation presents a comprehensive literature review paper (Chapter 2) regarding the use of field-activated materials in soft robotics, with an emphasis on magnetic elastomers. The second paper (Chapter 3) describes the development of a 3D-printed pressure valve intended to leverage the pressuring-holding properties of ERF when under the influence of a high voltage field to actuate soft actuators. The third paper (Chapter 4) demonstrates how magnetic elastomers and magnetic fields can enhance soft robotic grip strength and versatility. The fourth paper (Chapter 5) models, fabricates, and characterizes a MRF-containing clutch device able to rapidly and reversibly module the amount of torque transmitted from an input shaft to an output by leveraging low-power electropermanent magnet arrays. Each work focuses on a field-activated smart material to perform a specific robotic function, with particular emphasis given to compliant mechanisms and soft robotics, as well as to reducing cost and improving ease of fabrication with the use of modern fabrication techniques. In these described papers, field-activated materials are first modeled and then deployed in functional prototypes, and their robotic utility is described in detail after extensive experimental characterization
Advances on mechanical designs for assistive ankle-foot orthoses
Assistive ankle-foot orthoses (AFOs) are powerful solutions to assist or
rehabilitate gait on humans. Existing assistive AFO technologies include
passive, quasi-passive, and active principles to provide assistance to the
users, and their mechanical configuration and control depend on the eventual
support they aim for within the gait pattern. In this research we analyze the
state-of-the-art of assistive AFOs and classify the different approaches into
clusters, describing their basis and working principles. Additionally, we
reviewed the purpose and experimental validation of the devices, providing the
reader with a better view of the technology readiness level. Finally, the
reviewed designs, limitations, and future steps in the field are summarized and
discussed.Comment: Figures appear at the end. Article submitted to Frontiers in
Bioengineering and Biotechnology (currently under review
Development of force feedback device for hands using air-jet mechanism
application/pdfdepartmental bulletin pape
Comparative study of actuation systems for portable upper limb exoskeletons.
During the last two decades, a large variety of upper limb exoskeletons have been developed. Out of these, majority are platform based systems which might be the reason for not being widely adopted for post-stroke rehabilitation. Despite the potential benefits of platform-based exoskeletons as being rugged and reliable, stroke patients prefer to have a portable and user-friendly device that they can take home. However, the types of actuator as well as the actuation mechanism used in the exoskeleton are the inhibiting factors why portable exoskeletons are mostly non-existent for patient use. This paper presents a quantitative analysis of the actuation systems available for developing portable upper arm exoskeletons with their specifications. Finally, it has been concluded from this research that there are not many stand-alone arm exoskeletons which can provide all forms of rehabilitation, therefore, a generic solution has been proposed as the rehabilitation strategy to get best out of the portable arm exoskeletons