Design and analysis of a lightweight lower extremity exoskeleton with novel compliant ankle joints

2021 ◽  
pp. 1-14
Author(s):  
Yong He ◽  
Jingshuai Liu ◽  
Feng Li ◽  
Wujing Cao ◽  
Xinyu Wu
Keyword(s):  
Lower Extremity ◽  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Theoretical Models ◽  
Six Degrees Of Freedom ◽  
Movement Performance ◽  
Ankle Joints ◽  
Design Values ◽  
Flexible Deformation ◽  
Limb Rehabilitation

BACKGROUND: The exoskeleton for lower limb rehabilitation is an uprising field of robot technology. However, since it is difficult to achieve all the optimal design values at the same time, each lower extremity exoskeleton has its own focus. OBJECTIVE: This study aims to develop a modular lightweight lower extremity exoskeleton (MOLLEE) with novel compliant ankle joints, and evaluate the movement performance through kinematics analysis. METHODS: The overall structure of the exoskeleton was proposed and the adjustable frames, active joint modules, and compliant ankle joints were designed. The forward and inverse kinematics models were established based on the geometric method. The theoretical models were validated by numerical simulations in ADAMS, and the kinematic performance was demonstrated through walking experiments. RESULTS: The proposed lower extremity offers six degrees of freedom (DoF). The exoskeleton frame was designed adjustable to fit wearers with a height between 1.55 m and 1.80 m, and waist width from 37 cm to 45 cm. The joint modules can provide maximum torque at 107 Nm for adequate knee and hip joint motion forces. The compliant ankle can bear large flexible deformation, and the relationship between its angular deformation and the contact force can be fitted with a quadratic polynomial function. The kinematics models were established and verified through numerical simulations, and the walking experiments in different action states have shown the expected kinematic characteristics of the designed exoskeleton. CONCLUSIONS: The proposed MOLLEE exoskeleton is adjustable, modular, and compliant. The designed adjustable frame and compliant ankle can ensure comfort and safety for different wearers. In addition, the kinematics characteristics of the exoskeleton can meet the needs of daily rehabilitation activities.

Study on Motion Simulation of HOV

2013 ◽  
Vol 694-697 ◽  
pp. 158-162
Author(s):  
Feng Liu ◽  
Duan Feng Han
Keyword(s):  
Degrees Of Freedom ◽  
Hydrodynamic Force ◽  
Equations Of Motion ◽  
Control System Design ◽  
Motion Simulation ◽  
Six Degrees Of Freedom ◽  
Movement Performance ◽  
Motion Characteristics ◽  
Motor Effects ◽  
Important Basis

It will be to bear several forces when Human Occupied Vehicle (HOV) moves underwater, So the movement performance forecast and research becomes more difficult when HOV under environment disturbances,this paper regards a certain HOV as the research object,researches the HOV actual situation, the comprehensive consideration of the hydrodynamic force, gravity, propeller thrust, environmental interference force for HOV motor effects, establishes the six degrees of freedom equations of motion for HOV, several typical motion states are studied , finally the simulation work is carried out, the simulation results can reflect the HOV motion characteristics , provide important basis for HOV motion control system design.

Determination of Hydrodynamic Parameters for Remotely Operated Vehicles

2016 ◽  
Author(s):  
Ole A. Eidsvik ◽  
Ingrid Schjølberg
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Analytical Data ◽  
Relative Difference ◽  
Accurate Estimate ◽  
Six Degrees Of Freedom ◽  
Hydrodynamic Parameters ◽  
Planar Motion Mechanism ◽  
Rotational Degrees Of Freedom

In this paper the hydrodynamic parameters that characterize the behavior of a typical unmanned underwater vehicle are evaluated. A complete method for identifying these parameters is described. The method is developed to give a brief and accurate estimate of these parameters in all six degrees of freedom using basic properties of the vehicle such as dimensions, mass and shape. The method is based on both empirical and analytical results for typical reference geometries (ellipsoids, cubes, etc.). The method is developed to be applicable for a wide variety of UUV designs as these typically varies substantially. The method is then applied to a small observation class ROV. The results are first verified using an experimental method in which the full scale ROV is towed using a planar motion mechanism. An additional verification is performed with numerical simulations using Computational Fluid Dynamics and a radiation/diffraction program. The method shows promising results for both damping and added mass for the tested case. The translational degrees of freedom are more accurate than the rotational degrees of freedom which are expected as most empirical and analytical data are for translational degrees of freedom. The case study also reveals that the relative difference between the numerical simulations and the experimental results are similar to the relative difference between the proposed method and the experiment.

An Experiment for the Study of Free-Flying Supercavitating Projectiles

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Peter J. K. Cameron ◽  
Peter H. Rogers ◽  
John W. Doane ◽  
David H. Gifford
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Measurement Techniques ◽  
Theoretical Models ◽  
Dynamics Simulation ◽  
Small Scale ◽  
Successful Operation ◽  
Six Degrees Of Freedom ◽  
Impact Location ◽  
Simulation Based

Applications and research utilizing supercavitation for high-speed underwater flight has motivated study of the phenomenon. In this work, a small scale laboratory experiment for studying supercavitating projectiles has been designed, built, and tested. Similar existing experimental work has been documented in literature but using large, elaborate facilities, or has been presented with ambiguous conclusions from test results. The projectiles were 63.5 mm in length and traveled at speeds on the order of 145 m/s. Measurement techniques are discussed and used to record projectile speed, supercavity dimensions, and target impact location. Experimental observations are compared with a six degrees-of-freedom dynamics simulation based on theoretical models presented in literature for predicting supercavity shape and hydrodynamic forces on the supercavitating projectile during flight. Experimental observations are discussed qualitatively, along with quantitative statistics of the measurements made. Successful operation of the experiment has been demonstrated and verified by agreement with theoretical models.

scholarly journals Prediction of Ship Unsteady Maneuvering in Calm Water by a Fully Nonlinear Ship Motion Model

2012 ◽  
Vol 2012 ◽  
pp. 1-11
Author(s):  
Ray-Qing Lin ◽  
Tim Smith ◽  
Michael Hughes
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Ship Motion ◽  
Ship Motions ◽  
Motion Model ◽  
Forward Speed ◽  
Fully Nonlinear ◽  
Six Degrees Of Freedom ◽  
Calm Water

This is the continuation of our research on development of a fully nonlinear, dynamically consistent, numerical ship motion model (DiSSEL). In this study we will report our results in predicting ship motions in unsteady maneuvering in calm water. During the unsteady maneuvering, both the rudder angle, and ship forward speed vary with time. Therefore, not only surge, sway, and yaw motions occur, but roll, pitch and heave motions will also occur even in calm water as heel, trim, and sinkage, respectively. When the rudder angles and ship forward speed vary rapidly with time, the six degrees-of-freedom ship motions and their interactions become strong. To accurately predict the six degrees-of-freedom ship motions in unsteady maneuvering, a universal method for arbitrary ship hull requires physics-based fully-nonlinear models for ship motion and for rudder forces and moments. The numerical simulations will be benchmarked by experimental data of the Pre-Contract DDG51 design and an Experimental Hull Form. The benchmarking shows a good agreement between numerical simulations by the enhancement DiSSEL and experimental data. No empirical parameterization is used, except for the influence of the propeller slipstream on the rudder, which is included using a flow acceleration factor.

Effect of Wind Loads on the Performance of Free-Fall Lifeboats

2014 ◽  
Author(s):  
Thomas Sauder ◽  
Eloise Croonenborghs ◽  
Sebastien Fouques ◽  
Nabila Berchiche ◽  
Svein-Arne Reinholdtsen
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Free Fall ◽  
Offshore Structures ◽  
Water Entry ◽  
Forward Speed ◽  
Cfd Simulations ◽  
Six Degrees Of Freedom ◽  
Complete Set ◽  
Water Exit

The paper presents a model describing the launch of free-fall lifeboats from offshore structures in strong environmental wind. Six-degrees-of-freedom numerical simulations of the lifeboat launch are performed using the free-fall lifeboat simulator VARUNA with a complete set of wind coefficients for the lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry. It is shown by means of numerical simulations that wind-induced loads on the lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the lifeboat, and on its forward speed after water exit. It is concluded that the effect of wind-induced loads on the lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.

Numerical Simulations of OC3 Spar and OC4 Semi-Submersible Type Platforms Under Extreme Conditions in the East Sea, Korea

2019 ◽  
Author(s):  
Hyunkyoung Shin ◽  
Youngjae Yu ◽  
Thanh Dam Pham ◽  
Junbae Kim ◽  
Rupesh Kumar
Keyword(s):  
Renewable Energy ◽  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Reanalysis Data ◽  
Environmental Data ◽  
Offshore Wind ◽  
East Sea ◽  
Mooring Line ◽  
Six Degrees Of Freedom ◽  
Floating Offshore Wind Turbines

Abstract Since the Paris Conference of the parties in 2015, interest in renewable energy around the world is higher than ever. Korea also has plans to increase the proportion of renewable energy to 20% by 2030 through the renewable energy 3020 policy. Of these, 16.5GW is filled with wind power, the installation area is expanding from land to sea. Among them, some of big plans are using floating offshore wind turbines based on the marine environments in Korea. In this study, numerical simulations of the NREL 5MW wind turbine were performed using NREL FAST V.8. A comparison was made between two types of floaters, spar and semi-submersible, installed 58km off the Ulsan Coast with 150m water depth in the East Sea, Korea. The environmental data were obtained from the Meteorological Administration’s measured data and NASA’s reanalysis data, MERRA-2. Design Load Cases were selected by referring to IEC 61400-3. Maximum moments at both blade root and tower base, six-degrees of freedom motions and three mooring line tensions were compared.

Kinematics study of a 10 degrees-of-freedom lower extremity exoskeleton for crutch-less walking rehabilitation

2021 ◽  
pp. 1-9
Author(s):  
Jingshuai Liu ◽  
Yong He ◽  
Feng Li ◽  
Wujing Cao ◽  
Xinyu Wu
Keyword(s):  
Lower Extremity ◽  
Lower Limb ◽  
Degrees Of Freedom ◽  
Leg Extension ◽  
Closed Form Solutions ◽  
Kinematic Characteristics ◽  
Movement Characteristics ◽  
Movement Performance ◽  
Walking Rehabilitation ◽  
Limb Structure

BACKGROUND: Wearable lower extremity exoskeletons can provide walking assistance for the physical rehabilitation of paralyzed individuals. However, most of the existing exoskeletons require crutches to maintain balance, thus a self-balancing type is needed to improve applicability. OBJECTIVE: The purpose of this work is to study the kinematic characteristics of a novel lower extremity exoskeleton for crutch-less walking rehabilitation, and evaluate the movement performance through practical experiments. METHODS: Based on the human lower limb structure and movement characteristics, a fully actuated 10 degrees-of-freedom (DoF) lower extremity exoskeleton was proposed. The kinematic characteristics of the exoskeleton were analyzed by the D-H method and geometric method, and the model validity was verified through simulations and experiments. RESULTS: The closed-form solutions for both forward and inverse kinematics models were obtained. The consistent results of theoretical calculation and numerical simulation have shown the accuracy of the established models. The practical experiments regarding six trials have demonstrated the movement performance of the proposed exoskeleton, including sit, stance, leg extension/flexion, and left/right swing. CONCLUSIONS: The kinematic characteristics of the proposed 10-DoF lower extremity exoskeleton are similar to the human lower limb, and it could meet the motion demands of crutch-less walking rehabilitation.

Influence of Wave-Induced Skid Motions on the Launch of Free-Fall Skid Lifeboats From Floating Hosts: Experimental and Numerical Investigations

2014 ◽  
Author(s):  
Neil Luxcey ◽  
Svein-Arne Reinholdtsen ◽  
Thomas Sauder ◽  
Sébastien Fouques ◽  
Jingzhe Jin ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Model Test ◽  
Degrees Of Freedom ◽  
Free Fall ◽  
Weather Conditions ◽  
Norwegian Sea ◽  
Six Degrees Of Freedom ◽  
Offshore Installations ◽  
Storm Condition ◽  
Wave Induced

The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations. This paper investigates the effects of the wave-induced skid motion on the launch of free-fall lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.

scholarly journals Controlador robusto para el seguimiento de trayectorias para un exoesqueleto de extremidades inferiores

2019 ◽  
pp. 1-8
Author(s):  
Andrés Blanco-Ortega ◽  
Demetrio Pérez-Vigueras ◽  
Edgar Antúnez-Leyva ◽  
Jorge Colín Ocampo
Keyword(s):  
Cell Death ◽  
Lower Extremity ◽  
Muscle Atrophy ◽  
Human Body ◽  
Degrees Of Freedom ◽  
Severe Damage ◽  
Six Degrees Of Freedom ◽  
Adams Software ◽  
Simulation Results ◽  
The Brain

Currently, robotics has shown that it can increase the efficiency in the specific rehabilitation of some of the limbs of the human body, in this case assisting people who have suffered a stroke, by using devices such as exoskeletons, to provide continuous, smooth and controlled movements. Stroke is the result of a shortage of the brain that leads in just a few minutes to cell death, causing severe damage to the human body, even death of the patient. People who have suffered a stroke have difficulty rising from a chair. An exoskeleton is a mechanical structure designed to be used on the human body as a garment, it serves as a support and is used to assist movements or accentuate strength as a support in a person. Lower extremity exoskeleton can assist patients with hemiplegia to get up or sit on a chair, thus avoiding muscle atrophy and possible spasticity. This paper proposes the use of a robust Generalized Proportional Integral (GPI) controller for trajectory tracking for controlling a six degrees of freedom exoskeleton, to assist patients when getting up and sitting down from a chair. Simulation results obtained with the virtual prototype of the exoskeleton, under the environment of the MSC Adams software in co-simulation with Matlab are presented.

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