Design of a 2 DOF Prosthetic Ankle Using Coupled Compliance to Increase Ankle Torque

2012 ◽  
Author(s):  
Shuguang Huang ◽  
Joseph M. Schimmels
Keyword(s):  
Ankle Joint ◽  
Compliant Mechanism ◽  
Lower Leg ◽  
The Body ◽  
Degree Of Freedom ◽  
Spring Constant ◽  
Active Components ◽  
Active Behavior ◽  
Ankle Torque ◽  
Optimization Routine

Current passive prosthetic ankles are lighter, simpler, and less expensive than powered prosthetic ankles. These current passive designs, however, do not provide adequate torque at the instant when it is needed to propel the body forward. This paper presents a novel 2 degree of freedom (DOF) passive compliant prosthetic ankle that uses a network of conventional springs. One DOF allows the lower leg component to compress when the weight of the amputee is applied during walking. The second DOF allows rotation about the prosthetic ankle joint. The force generated along the leg during walking is converted into ankle torque used to propel the body forward during push-off. An optimization routine is used to select the stiffness values and connection locations of the springs used in the compliant mechanism. The optimization yields a design that generates a torque-deflection profile that is very similar to that of a natural ankle. The mechanism demonstrates apparent active behavior (negative spring constant) at the ankle during push-off without using active components.

scholarly journals Flexure wheels for spacecraft attitude control

2021 ◽  
Author(s):  
Patrick Fluckiger ◽  
Simon Henein ◽  
Ilan Vardi ◽  
Hubert Schneegans ◽  
Loïc Tissot-Daguette
Keyword(s):  
Angular Momentum ◽  
Attitude Control ◽  
Compliant Mechanism ◽  
The Body ◽  
Degree Of Freedom ◽  
Centre Of Mass ◽  
Angular Rotation ◽  
Flexure Mechanism ◽  
Fixed Axis ◽  
Two Degree Of Freedom

This paper presents innovative mechanisms capable of advantageously providing attitude control for spacecrafts. These new mechanisms, which we have named flexure wheels, are the dynamic equivalent of a rotating wheel and can be entirely implemented with flexures.A reaction wheel is a well known device for controlling the orientation of spacecrafts. It consists in a motorised fly-wheel which is placed within the spacecraft. To set the wheel into angular rotation, a torque is applied to the wheel which in response applies the opposite torque back to the spacecraft, according to Newton's third law. This reaction torque is how the spacecraft rotates in order to control its orientation. In order to enable this wheel to rotate around a fixed axis, several methods have been implemented such as ball bearings, which suffer from frictional losses and imperfections which lead to vibrations and failure, as well as magnetic bearings which do not suffer from these issues but have an increased power consumption and complexity.The subject of this paper is to introduce alternative mechanisms that are able to produce the same constant angular momentum as a rotating wheel, but which do not suffer from the above defects.In order to reach this goal, our inventions use flexure mechanisms to produce the required constant angular momentum. Note that the term flexure mechanism is exactly equivalent to compliant mechanism. The difficulty in this task is that flexures only have a limited stroke making it virtually impossible for a flexure bearing wheel to rotate around a fixed axis with constant angular momentum. We therefore found alternate methods for generating angular momentum by using flexure mechanisms.Two methods are presented in this paper. The first consists of a rigid body whose centre of mass has a circular trajectory around a fixed point, but the body does not rotate around its centre of mass. The body moves in translation and acts dynamically as a point mass, and thereby generates angular momentum in a constant direction. The second consists of two bodies rotating around their centres of mass, but whose total angular momentum lies in a fixed direction. The first method was successfully exploited in the IsoSpring project whose goal was to introduce new two degree of freedom oscillators in mechanical clocks and watches, in order to remove their traditional escapement mechanism. The second mechanism is also inspired from the IsoSpring project where a sphere oscillating around its centre of mass provided a two degree of freedom oscillator less sensitive to the direction of gravity.The paper presents flexure wheel designs along with their implementations. Moreover, methods to control the uniform circular motion are presented, among which a novel flexure bearing which restricts the motion of a body to translation on a circular orbit. Two prototypes were successfully built and tested. Finally, qualitative results from this proof of concept are presented.

Design and Evaluation of a Passive Ankle Prosthesis With Rotational Power Generation by a Compliant Coupling Between Leg Deflection and Ankle Rotation

2014 ◽  
Author(s):  
Jacob J. Rice ◽  
Joseph M. Schimmels
Keyword(s):  
Degrees Of Freedom ◽  
Gait Cycle ◽  
The Body ◽  
Degree Of Freedom ◽  
Rotational Degree ◽  
Kinematic Data ◽  
Active Behavior ◽  
Ankle Prosthesis ◽  
Compression Spring ◽  
Translational Degree

This paper presents the design and simulation results of a passive prosthetic ankle prosthesis that has mechanical behavior similar to a natural ankle. The presented design achieves active behavior with powered push-off to propel the body forward. The design contains a conventional compression spring network that allows coupling between two degrees of freedom. There is a translational degree of freedom along the leg and a rotational degree of freedom about the ankle joint. During a standard gait cycle, potential energy from the person’s weight is stored in the spring network from deflection along the leg. The energy is released by the spring network as rotation of the foot. With this design, capping the allowable leg deflection at 15 millimeters produces 45% of the rotational work that a natural ankle will produce. This is based on simulation using published average kinetic and kinematic data from gait analyses.

scholarly journals Passive Prosthetic Foot Shape and Size Optimization Using Lower Leg Trajectory Error

2017 ◽  
Author(s):  
Kathryn M. Olesnavage ◽  
Amos G. Winter
Keyword(s):  
Optimal Design ◽  
Compliant Mechanism ◽  
Lower Leg ◽  
Degree Of Freedom ◽  
Analytical Models ◽  
Element Analysis ◽  
Trajectory Error ◽  
Prosthetic Foot ◽  
Two Degree Of Freedom ◽  
Shape And Size

A method is presented to optimize the shape and size of a passive prosthetic foot using the Lower Leg Trajectory Error (LLTE) as the design objective. The LLTE is defined as the root-mean-square error between the lower leg trajectory calculated for a given prosthetic foot by finding the deformed shape of the foot under typical ground reaction forces and a target physiological lower leg trajectory obtained from published gait data for able-bodied walking. In previous work, the design of simple two degree-of-freedom analytical models consisting of rigid structures, rotational joints with constant stiffness, and uniform cantilevered beams, have been optimized for LLTE. However, prototypes built to replicate these simple models were large, heavy, and overly complex. In this work, the size and shape of a single-part compliant prosthetic foot keel made out of nylon 6/6 was optimized for LLTE to produce a light weight, low cost, and easily manufacturable prosthetic foot design. The shape of the keel was parameterized as a wide Bézier curve, with constraints ensuring that only physically meaningful shapes were considered. The LLTE value for each design was evaluated using a custom MATLAB script, which ran ADINA finite element analysis software to find the deformed shape of the prosthetic keel under multiple loading scenarios. The optimization was performed by MATLAB’s built-in genetic algorithm. After the optimal design for the keel was found, a heel was added to structure, sized such that when the user’s full weight acted on the heel, the structure had a factor of safety of two. The resulting optimal design has a lower LLTE value than the two degree-of-freedom analytical models, at 0.154 compared to 0.172, 0.187, and 0.269 for the two degree-of-freedom models. At 412 g, the optimal wide curve foot is nearly half the mass of the lightest prototype built from the previous models, which was 980 g. The design found through this compliant mechanism optimization method is thus far superior to the two degree-of-freedom models previously considered.

Kinematic Analysis of Olympic Hurdle Performance: Women's 100 Meters

1985 ◽  
Vol 1 (2) ◽  
pp. 163-173 ◽  
Author(s):  
Ralph Mann ◽  
John Herman
Keyword(s):  
Elite Athlete ◽  
Olympic Games ◽  
Lower Leg ◽  
The Body ◽  
Performance Variables ◽  
Body Velocity ◽  
The Difference ◽  
Foot Position ◽  
Support Time ◽  
Leg Position

Selected kinematic variables in the performance of the Gold and Silver medalists and the eighth-place finisher in the women's 100-meter hurdles final at the 1984 Summer Olympic Games were investigated. Cinematographic records were obtained for all track hurdling events at the Games, with the 100-meter hurdle performers singled out for initial analysis. In this race, sagittal view filming records (100 fps) were collected at the 9th hurdle of the performance. Computer generated analysis variables included both direct performance variables (body velocity, support time, etc.) and body kinematics (upper leg position, lower leg velocity, etc.) that have previously been utilized in the analysis of elite athlete hurdlers. The difference in place finish was related to the performance variables body horizontal velocity (direct), vertical velocity (indirect), and support time (indirect). The critical body kinematics variables related to success included upper and lower leg velocity during support into and off the hurdle (direct), relative horizontal foot position (to the body) at touchdown into and off the hurdle (indirect), and relative horizontal foot velocity (to the body) at touchdown into the hurdle.

Leg Lift During Non-Overconstrained Pseudo-Static Walking

1996 ◽  
Author(s):  
Chee K. Foo ◽  
Eugene F. Fichter ◽  
Becky L. Fichter
Keyword(s):  
Position Control ◽  
The Body ◽  
Degree Of Freedom ◽  
Walking Machine

Abstract A non-overconstrained pseudo-static walking machine has 1 leg joint under position control for every degree-of-freedom of the body. When 1 joint is position controlled on each of 6 legs, leg lift during a step results in 1 unregulated degree-of-freedom of the body. A second joint in one of the 5 legs that maintain contact with the ground must be switched to active position control at the same time that a foot is lifted. In theory any passively controlled joint in the 5 supporting legs may be chosen. However the requirement that no leg be in tension and practical limits on torques available from joint actuators severely restrict choice of both additional joint to actively position control and possible body positions where legs can be lifted.

Analysis of Parasitic Motion in Compliant Mechanisms Using Eigenwrenches and Eigentwists

2018 ◽  
Author(s):  
Werner W. P. J. van de Sande ◽  
Just L. Herder
Keyword(s):  
Compliant Mechanisms ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Degree Of Freedom ◽  
Compliance Matrix ◽  
Parasitic Motion ◽  
Actual Degree ◽  
Motion Metrics ◽  
Mechanism Kinematic ◽  
Kinematic Information

Parasitic motion is undesired in precision mechanisms, it causes unwanted kinematics. These erroneous motions are especially apparent in compliant mechanisms. Usually an analysis of parasitic motion is only valid for one type of mechanism. Kinematic information is imbedded in the compliance matrix of any mechanism; an eigenscrew decomposition expresses this kinematic information as screws. It uses screw theory to identify the lines along which a force yields a parallel translation and a rotation yields a parallel moment. These lines are called eigenwrenches and eigentwists. Any other load on the compliant mechanism will lead to parasitic motion. This article introduces two parasitic motion metrics using eigenscrew decomposition: the parasitic resultant from an applied screw and the deviation of an actual degree of freedom from a desired degree of freedom. These metrics are applicable to all compliant mechanism and allow comparison between two compliant mechanisms. These metrics are applied to some common compliant mechanisms as an example.

scholarly journals A Custom-Made Lower Limb Dynamometer for Assessing Ankle Joint Torque in Humans: Calibration and Measurement Procedures

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 135
Author(s):  
Iulia Iovanca Drăgoi ◽  
Florina Georgeta Popescu ◽  
Teodor Petrița ◽  
Romulus Fabian Tatu ◽  
Cosmina Ioana Bondor ◽  
...  
Keyword(s):  
Ankle Joint ◽  
Plantar Flexion ◽  
Calibration Procedure ◽  
Measurement Procedure ◽  
Joint Torque ◽  
Ankle Torque ◽  
Offset Voltage ◽  
Interclass Correlation ◽  
Custom Made ◽  
Measurement Protocol

Custom-made dynamometry was shown to objectively analyze human muscle strength around the ankle joint with accuracy, easy portability and low costs. This paper describes the full method of calibration and measurement setup and the measurement procedure when capturing ankle torque for establishing reliability of a portable custom-built electronic dynamometer. After considering the load cell offset voltage, the pivotal position was determined, and calibration with loads followed. Linear regression was used for calculating the proportionality constant between torque and measured voltage. Digital means were used for data collection and processing. Four healthy consenting participants were enrolled in the study. Three consecutive maximum voluntary isometric contractions of five seconds each were registered for both feet during plantar flexion/dorsiflexion, and ankle torque was then calculated for three ankle inclinations. A calibration procedure resulted, comprising determination of the pivotal axis and pedal constant. Using the obtained data, a measurement procedure was proposed. Obtained contraction time graphs led to easier filtering of the results. When calculating the interclass correlation, the portable apparatus demonstrated to be reliable when measuring ankle torque. When a custom-made dynamometer was used for capturing ankle torque, accuracy of the method was assured by a rigorous calibration and measurement protocol elaboration.

scholarly journals Ultrasound assessment of muscle mass in the diagnosis of sarcopenia in cardiovascular patients

2021 ◽  
Vol 20 (3) ◽  
pp. 2699
Author(s):  
A. S. Erokhina ◽  
E. D. Golovanova ◽  
M. A. Miloserdov
Keyword(s):  
Body Mass Index ◽  
Muscle Mass ◽  
Body Mass ◽  
Lower Leg ◽  
The Body ◽  
Russian Society ◽  
Speed Test ◽  
European Working ◽  
Class 1 ◽  
Artery Disease

Aim. To study the advantages of ultrasound versus anthropometric assessment of muscle mass for early diagnosis of sarcopenia in patients >45 years of age.Material and methods. The study included 79 patients aged 4589 years with coronary artery disease (CAD), hypertension, type 2 diabetes, heart failure, class 1-3 obesity. Diagnosis of hypertension was carried out according to the European (2018) and Russian (2019) guidelines; CAD — according to Russian Society of Cardiology (2020) guidelines. Sarcopenia was diagnosed according to 2010 European Working Group on Sarcopenia in Older People (EWGSOP) criteria and 2018 EWGSOP2 guidelines. Muscle mass (MM) was determined by two methods: 1 — by measuring the rectus abdominis muscle (RAM) thickness using the ultrasound; 2 — by measuring the arm and lower leg circumference. Muscle strength was determined by wrist dynamometer. Muscle function was assessed using the 4-m gait speed test.Results. The study showed that in patients aged >45 years admitted to the emergency cardiology department, the body mass index exceeded 25 kg/m2 in 88,6% of cases. The incidence of sarcopenia of varying severity was 55,7% (n=44). The differences in RAM thickness, arm and lower leg circumference between the groups of patients with/without sarcopenia were significant (p<0,001), but were less than the threshold only for RAM thickness. RAM thickness levels progressively decreased with increasing severity of sarcopenia and significantly differed at all stages compared to patients without sarcopenia (p<0,001), regardless of body mass index. A decrease in lower leg circumference below the threshold values determining a MM decrease was observed only in severe sarcopenia, and arm circumference — in both men and women only in severe sarcopenia. There were no significant differences for arm and lower leg circumference depending on sarcopenia stages in overweight and obese patients.Conclusion. MM assessment by measuring RAM thickness with ultrasound in comparison with the anthropometric method makes it possible to diagnose sarcopenia in patients >45 years of age with cardiovascular diseases and obesity at earlier stages and to promptly recommend preventive measures.

scholarly journals Lactococcus lactis, A Tool for the Delivery of Therapeutic Proteins Treatment of IBD

2001 ◽  
Vol 1 ◽  
pp. 216-217 ◽  
Author(s):  
Lothar Steidler
Keyword(s):  
Age Of Onset ◽  
Inflammatory Diseases ◽  
Corticosteroid Treatment ◽  
The Body ◽  
Clinical Image ◽  
Active Components ◽  
Conventional Medical Therapy ◽  
Recurrent Activity ◽  
Important Means ◽  
Loss Of Appetite

Inflammatory bowel disease (IBD) is a group of chronic intestinal inflammatory diseases that consists of ulcerative colitis (UC), an inflammation of the large intestine, and Crohn�s disease (CD), which can affect any part of the gastrointestinal tract. IBD affects approximately 1 in every 1000 individuals in western countries. There is a marked tendency in the age of onset toward gradually younger people. IBD represents a genuine problem in public health because of the absence of etiologic treatment. The clinical image is characterized by recurrent segmental or total inflammatory involvement of the large and/or small intestine, often resulting in a chronic, unpredictable course. The symptoms of both are extremely unpleasant and impact all aspects of quality of life. They include diarrhea, abdominal pain, rectal bleeding, fever, nausea, weight loss, lethargy, and loss of appetite. If left untreated, malnutrition, dehydration, and anemia follow, which, in extreme cases, can even lead to death. Although many patients are managed successfully with conventional medical therapy, such as anti-inflammatory corticosteroid treatment, some stay refractory to treatment, most will have recurrent activity of disease, and two thirds will require surgery. Administered orally or by injection, only a fraction of the active components of most conventional drugs reaches the intended target site, the inflamed intestinal lining. This is not only an inefficient way to deliver drugs, but, more important, means that patients are often subject to a spectrum of unpleasant side effects that result from the high levels of the drugs in other, otherwise healthy tissues and organs of the body.

Biomechanical constraints to stair negotiation

2018 ◽  
Author(s):  
Constantinos Maganaris ◽  
Vasilios Baltzopoulos ◽  
David Jones ◽  
Irene Di Giulio ◽  
Neil Reeves ◽  
...  
Keyword(s):  
Older Adults ◽  
Dynamic Stability ◽  
Ankle Joint ◽  
The Elderly ◽  
The Body ◽  
Centre Of Mass ◽  
Centre Of Pressure ◽  
Younger Adults ◽  
Stair Negotiation ◽  
Biomechanical Constraints

This chapter discusses strategies that older and younger people employ to negotiate stairs based on experiments performed on an instrumented staircase in lab environment aiming at identifying ways to reduce stair fall risk for the elderly. Stair negotiation was found to be more demanding for the knee and ankle joint muscles in older than younger adults, with the demand increasing further when the step-rise was higher. During descent of stairs with higher step-rises, older adults shifted the centre of mass (COM) posteriorly, behind the centre of pressure (COP) to prevent forward falling. A decreased step-going resulted in a slower descent of the centre of mass in the older adults and standing on a single leg for longer than younger adults. A greater reliance on the handrails and rotation of the body in the direction of the handrail was also observed when the step-going was decreased during descent, which allowed this task to be performed with better dynamic stability, by maintaining the COM closer to the COP. These findings have important implications for stair design and exercise programs aiming at improving safety on stairs for the elderly.

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