10 research outputs found
Design and control of a robotic wrist orthosis for joint rehabilitation
Ageing society in many countries has led to an increasing number of stroke and cerebral palsy patients who require rehabilitation therapy. Affected wrist joints often show an increased spasticity and stiffness, caused by impairments of surrounding muscles and tendons. However, the medical devices for wrist joint assessment and rehabilitation are lacking. This paper proposes a robotic orthosis to assist the patient's wrist to perform rehabilitation exercise in a compliant way. A 1-DOF robotic device with parallel mechanism is designed for the wrist joint by utilising pneumatic artificial muscles (PAMs) that are compliant and lightweight. The mechanical design of the wrist orthosis and the corresponding development of pneumatic control system will be also presented. A model-based pressure close-loop control strategy is implemented for the PAMs in order to track the trajectory in high-performance. Experiments on the orthosis demonstrated that the robot could assist the hand to move along a torque-sensitive trajectory with relatively small errors and the differential forces were also kept stable
Stretch reflex improves rolling stability during hopping of a decerebrate system
When humans hop, attitude recovery can be observed in both the sagittal and frontal planes. While it is agreed that the brain plays an important role in leg placement, the role of low-level feedback (the stretch reflex) on frontal plane stabilization remains unclear. Seeking to better understand the contribution of the soleus stretch reflex to rolling stability, we performed experiments on a biomimetic humanoid hopping robot. Various reflex responses to touching the floor, ranging from no response to long muscle activations, were examined, and the effect of a delay upon touching the floor was also examined. We found that the stretch reflex brought the system closer to stable, straight hopping. The presence of a delay did not affect the results; both the cases with and without a delay outperformed the case without a reflex response. The results of this study highlight the importance of low-level control in locomotion for which body stabilization does not require higher-level signals.This is the accepted manuscript. The final version is available at http://iopscience.iop.org/article/10.1088/1748-3190/10/1/016008/meta;jsessionid=8394D6E9724906C836DC3624B5BF2F90.c1
Lower Limb Rehabilitation Using Patient Data
The aim of this study is to investigate the performance of a 6-DoF parallel robot in tracking the movement of the foot trajectory of a paretic leg during a single stride. The foot trajectories of nine patients with a paretic leg including both males and females have been measured and analysed by a Vicon system in a gait laboratory. Based on kinematic and dynamic analysis of a 6-DoF UPS parallel robot, an algorithm was developed in MATLAB to calculate the length of the actuators and their required forces during all trajectories. The workspace and singularity points of the robot were then investigated in nine different cases. A 6-DoF UPS parallel robot prototype with high repeatability was designed and built in order to simulate a single stride. Results showed that the robot was capable of tracking all of the trajectories with the maximum position error of 1.2âmm
Effect of flow compressibility in convergent-divergent nozzle
: Nozzles come in a range of shapes and sizes based on a purpose such as De Laval nozzle
also known as the converging diverging nozzle. Convergent- divergent nozzle is commonly used in
modern rocket engines that accelerates at high velocity till the supersonic region Ma>1. This paper
aims to investigate numerically the effect of area ratio of the convergent divergent throat and the
Mach number from the incompressible flow to compressible flow. The software that were used to
simulate cases is ANSYS Computational Fluid Dynamics (CFD) code FLUENT. The area ratio
throat (AR= 5mm, 6mm, 7mm, and 8mm) and Mach number (Ma = 0.2, 1.0 and 1.8) was varied to
obtain more specific result. The result from this paper has shown that the most effective Mach
number and area ratio are at the 0.2 Ma with the AR=5mm According to the findings of this research,
the most effective Mach number and area ratio are at 0.2 Ma with AR=5mm. According to the
calculations performed in this research, the percentage variation of velocity at 0.2Ma was larger
than at 1.0 Ma and 1.8 Ma. This happen cause at the sonic and supersonic flow there is factor that
disturb the flow such as the back pressure and normal shoc
Design and control of soft rehabilitation robots actuated by pneumatic muscles: State of the art
Robot-assisted rehabilitation has become a new mainstream trend for the treatment of stroke patients with movement disability. Pneumatic muscle (PM) is one of the most promising actuators for rehabilitation robots, due to its inherent compliance and safety features. In this paper, we conduct a systematic review on the soft rehabilitation robots driven by pneumatic muscles. This review discusses up to date mechanical structures and control strategies for PMs-actuated rehabilitation robots. A variety of state-of-the-art soft rehabilitation robots are classified and reviewed according to the actuation configurations. Special attentions are paid to control strategies under different mechanical designs, with advanced control approaches to overcome PMâs highly nonlinear and time-varying behaviors and to enhance the adaptability to different patients. Finally, we analyze and highlight the current research gaps and the future directions in this field, which is potential for providing a reliable guidance on the development of advanced soft rehabilitation robots
Design and Control of Robotic Systems for Lower Limb Stroke Rehabilitation
Lower extremity stroke rehabilitation exhausts considerable health care resources, is labor intensive, and provides mostly qualitative metrics of patient recovery. To overcome these issues, robots can assist patients in physically manipulating their affected limb and measure the output motion. The robots that have been currently designed, however, provide assistance over a limited set of training motions, are not portable for in-home and in-clinic use, have high cost and may not provide sufficient safety or performance. This thesis proposes the idea of incorporating a mobile drive base into lower extremity rehabilitation robots to create a portable, inherently safe system that provides assistance over a wide range of training motions. A set of rehabilitative motion tasks were established and a six-degree-of-freedom (DOF) motion and force-sensing system was designed to meet high-power, large workspace, and affordability requirements. An admittance controller was implemented, and the feasibility of using this portable, low-cost system for movement assistance was shown through tests on a healthy individual. An improved version of the robot was then developed that added torque sensing and known joint elasticity for use in future clinical testing with a flexible-joint impedance controller
Type-2 Takagi-Sugeno-Kang Fuzzy Logic System and Uncertainty in Machining
RĂSUMĂ: Plusieurs mĂ©thodes permettent aujourdâhui dâanalyser le comportement des Ă©coulements
qui rĂ©gissent le fonctionnement de systĂšmes rencontrĂ©s dans lâindustrie (vĂ©hicules aĂ©riens,
marins et terrestres, gĂ©nĂ©ration dâĂ©nergie, etc.). Pour les Ă©coulements transitoires ou
turbulents, les méthodes expérimentales sont utilisées conjointement avec les simulations
numĂ©riques (simulation directe ou faisant appel Ă des modĂšles) afin dâextraire le plus
dâinformation possible. Dans les deux cas, les mĂ©thodes gĂ©nĂšrent des quantitĂ©s de donnĂ©es
importantes qui doivent ensuite ĂȘtre traitĂ©es et analysĂ©es. Ce projet de recherche vise Ă
amĂ©liorer notre capacitĂ© dâanalyse pour lâĂ©tude des Ă©coulements simulĂ©s numĂ©riquement
et les Ă©coulements obtenus Ă lâaide de mĂ©thodes de mesure (par exemple la vĂ©locimĂ©trie
par image de particules PIV ).
Lâabsence, jusquâĂ aujourdâhui, dâune dĂ©finition objective dâune structure tourbillonnaire
a conduit Ă lâutilisation de plusieurs mĂ©thodes eulĂ©riennes (vorticitĂ©, critĂšre Q,
Lambda-2, etc.), souvent inadaptées, pour extraire les structures cohérentes des écoulements.
Lâexposant de Lyapunov, calculĂ© sur un temps fini (appelĂ© le FTLE), sâest rĂ©vĂ©lĂ©
comme une alternative lagrangienne efficace à ces méthodes classiques. Cependant, la
mĂ©thodologie de calcul actuelle du FTLE exige lâĂ©valuation numĂ©rique dâun grand nombre
de trajectoires sur une grille cartésienne qui est superposée aux champs de vitesse
simulés ou mesurés. Le nombre de noeuds nécessaire pour représenter un champ FTLE
dâun Ă©coulement 3D instationnaire atteint facilement plusieurs millions, ce qui nĂ©cessite
des ressources informatiques importantes pour une analyse adéquate.
Dans ce projet, nous visons Ă amĂ©liorer lâefficacitĂ© du calcul du champ FTLE en
proposant une méthode alternative au calcul classique des composantes du tenseur de
dĂ©formation de Cauchy-Green. Un ensemble dâĂ©quations diffĂ©rentielles ordinaires (EDOs)
est utilisé pour calculer simultanément les trajectoires des particules et les dérivées premiÚres
et secondes du champ de déplacement, ce qui se traduit par une amélioration de
la précision nodale des composantes du tenseur. Les dérivées premiÚres sont utilisées
pour le calcul de lâexposant de Lyapunov et les dĂ©rivĂ©es secondes pour lâestimation de
lâerreur dâinterpolation. Les matrices hessiennes du champ de dĂ©placement (deux matrices
en 2D et trois matrices en 3D) nous permettent de construire une métrique optimale
multi-échelle et de générer un maillage anisotrope non structuré de façon à distribuer efficacement
les noeuds et Ă minimiser lâerreur dâinterpolation.----------ABSTRACT: Several methods can help us to analyse the behavior of flows that govern the operation
of fluid flow systems encountered in the industry (aerospace, marine and terrestrial
transportation, power generation, etc..). For transient or turbulent flows, experimental
methods are used in conjunction with numerical simulations ( direct simulation or based
on models) to extract as much information as possible. In both cases, these methods
generate massive amounts of data which must then be processed and analyzed. This
research project aims to improve the post-processing algorithms to facilitate the study
of numerically simulated flows and those obtained using measurement techniques (e.g.
particle image velocimetry PIV ).
The absence, even until today, of an objective definition of a vortex has led to the
use of several Eulerian methods (vorticity, the Q and the Lambda-2 criteria, etc..), often
unsuitable to extract the flow characteristics. The Lyapunov exponent, calculated on a
finite time (the so-called FTLE), is an effective Lagrangian alternative to these standard
methods. However, the computation methodology currently used to obtain the FTLE
requires numerical evaluation of a large number of fluid particle trajectories on a Cartesian
grid that is superimposed on the simulated or measured velocity fields. The number of
nodes required to visualize a FTLE field of an unsteady 3D flow can easily reach several
millions, which requires significant computing resources for an adequate analysis.
In this project, we aim to improve the computational efficiency of the FTLE field
by providing an alternative to the conventional calculation of the components of the
Cauchy-Green deformation tensor. A set of ordinary differential equations (ODEs) is
used to calculate the particle trajectories and simultaneously the first and the second
derivatives of the displacement field, resulting in a highly improved accuracy of nodal
tensor components. The first derivatives are used to calculate the Lyapunov exponent
and the second derivatives to estimate the interpolation error. Hessian matrices of the
displacement field (two matrices in 2D and three matrices in 3D) allow us to build a
multi-scale optimal metric and generate an unstructured anisotropic mesh to efficiently
distribute nodes and to minimize the interpolation error. The flexibility of anisotropic
meshes allows to add and align nodes near the structures of the flow and to remove
those in areas of low interest. The mesh adaptation is based on the intersection of the
Hessian matrices of the displacement field and not on the FTLE field
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