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.

The thermodynamics of intracrystalline sorption I. Models of the sorbed state

1956 ◽  
Vol 234 (1196) ◽  
pp. 24-34 ◽  
Keyword(s):  
Mobile Phase ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Translational Degree ◽  
Sorbate Concentration ◽  
The Ideal

Three basic models of the intracrystalline sorbed state are discussed: a localized phase, a mobile phase possessing two translational degrees of freedom, and a mobile phase with one translational degree of freedom. The isotherm and entropy of each of these models have been investigated for the ideal phase, and where possible the influence of sorbate-sorbate interactions has been considered. Expressions for the molal and differential entropies of each model are given as a function of sorbate concentration. The method of comparing theoretical isotherms and entropies with experimental observations is outlined.

scholarly journals Jumping in frogs: assessing the design of the skeletal system by anatomically realistic modeling and forward dynamic simulation

2002 ◽  
Vol 205 (12) ◽  
pp. 1683-1702 ◽  
Author(s):  
William J. Kargo ◽  
Frank Nelson ◽  
Lawrence C. Rome
Keyword(s):  
Degrees Of Freedom ◽  
The Body ◽  
Joint Torque ◽  
Rotational Degree ◽  
Skeletal System ◽  
Dynamic Simulations ◽  
Inverse Dynamic ◽  
Maximal Distance ◽  
Out Of Plane ◽  
Rotational Degrees Of Freedom

SUMMARY Comparative musculoskeletal modeling represents a tool to understand better how motor system parameters are fine-tuned for specific behaviors. Frog jumping is a behavior in which the physical properties of the body and musculotendon actuators may have evolved specifically to extend the limits of performance. Little is known about how the joints of the frog contribute to and limit jumping performance. To address these issues, we developed a skeletal model of the frog Rana pipiens that contained realistic bones, joints and body-segment properties. We performed forward dynamic simulations of jumping to determine the minimal number of joint degrees of freedom required to produce maximal-distance jumps and to produce jumps of varied take-off angles. The forward dynamics of the models was driven with joint torque patterns determined from inverse dynamic analysis of jumping in experimental frogs. When the joints were constrained to rotate in the extension—flexion plane, the simulations produced short jumps with a fixed angle of take-off. We found that, to produce maximal-distance jumping,the skeletal system of the frog must minimally include a gimbal joint at the hip (three rotational degrees of freedom), a universal Hooke's joint at the knee (two rotational degrees of freedom) and pin joints at the ankle,tarsometatarsal, metatarsophalangeal and iliosacral joints (one rotational degree of freedom). One of the knee degrees of freedom represented a unique kinematic mechanism (internal rotation about the long axis of the tibiofibula)and played a crucial role in bringing the feet under the body so that maximal jump distances could be attained. Finally, the out-of-plane degrees of freedom were found to be essential to enable the frog to alter the angle of take-off and thereby permit flexible neuromotor control. The results of this study form a foundation upon which additional model subsystems (e.g. musculotendon and neural) can be added to test the integrative action of the neuromusculoskeletal system during frog jumping.

The thermodynamics of intracrystalline sorption II. Argon in chabazite

1956 ◽  
Vol 234 (1196) ◽  
pp. 35-45 ◽  
Keyword(s):  
Experimental Data ◽  
Mobile Phase ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Translational Degree ◽  
Sorbed Phase

The experimentally observed isotherms and entropies of the intracrystalline sorbed phase of argon in natural and calcium chabazites are compared with those predicted by models. For sorbate concentrations between approximately θ = 0.1 and 0.7, the experimental data are incompatible with the properties of a localized phase but are in agreement with those of a mobile phase. It is demonstrated that it is impossible for the argon to possess two degrees of translational freedom and that it is best described as having one translational degree of freedom and two vibrational degrees of freedom each with a frequency of 1 x 10 12 to 2 x 10 12 s -1 . The examination of the entropy of the system also shows that at concentrations greater than θ = 0.7 the mobile concept breaks down and it is probable that the translational degree of freedom passes to a vibration due to the mutual caging action of sorbate molecules, so that the phase becomes a system of oscillators.

Develop a Vision Based Auto-Recharging System for Mobile Robots

2010 ◽  
Vol 44-47 ◽  
pp. 1340-1344 ◽  
Author(s):  
Kuo Lan Su ◽  
Yung Chin Lin ◽  
Yi Lin Liao ◽  
J. Hung Guo
Keyword(s):  
Mobile Robot ◽  
Mobile Robots ◽  
Degrees Of Freedom ◽  
Control Device ◽  
Degree Of Freedom ◽  
Usb Interface ◽  
Compression Spring ◽  
Real Time Image ◽  
Wireless Rf Interface ◽  
Time Image

The article develops a vision based auto-recharging system for mobile robots, and programs a new docking processing to enhance successful rate. The system contains a docking station and a mobile robot. The docking station contains a docking structure, a control device, a charger and a detection device and a wireless RF interface. The mobile robot contains a power detection module (voltage and current), an auto-switch, a wireless RF interface, a control system and a camera. The docking structure is designed with one active degree of freedom and two passive degrees of freedom. The active degree of freedom can move forward to contact the recharging connect points that are arranged in the mobile robot. The two passive degrees of freedom can rotation in the Z-axis and use compression spring moving on various docking condition. In image processing, the mobile robot uses a webcam to capture the real-time image; and transmits the image signal to the computer via USB interface, and uses Otsu algorithm to recognize the position of the docking station. In the experiment results, the system had been successfully guided the mobile robot moving to the docking station using the proposed method.

A Low Computational Cost Nonlinear Formulation for Multibody Railroad Vehicle Systems

2007 ◽  
Author(s):  
Graham G. Sanborn ◽  
Jason R. Heineman ◽  
Ahmed A. Shabana
Keyword(s):  
Coordinate System ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Computational Cost ◽  
Space Curve ◽  
The Body ◽  
Degree Of Freedom ◽  
Arbitrary Body ◽  
Resistance Forces ◽  
Low Computational Cost

In this investigation, a multibody system formulation for the nonlinear dynamics of railroad vehicles is developed. This formulation, which permits developing simplified models for the forces acting on rail cars, allows the analysis of long trains at a low computational cost. In the dynamic models developed using the formulation proposed in this investigation, each rail car can be represented as a single rigid body. The configurations of the bodies in a train model are defined with respect to trajectory coordinate systems which follow a space curve whose geometry is defined at a preprocessing stage. In the formulation presented in this study, the number of degrees of freedom of an arbitrary body can be varied from one to six degrees of freedom. The principal degree of freedom of an arbitrary body is the arc length along the space curve. This degree of freedom defines the location of the origin and the orientation of the body trajectory coordinate system. The other five degrees of freedom define the location and orientation of the body with respect to the body trajectory coordinate system. The nonlinear equations of motion of the bodies in a train model are developed using the three-dimensional Newton-Euler equations. These equations are then expressed in terms of the trajectory coordinates and their derivatives. To this end, a velocity transformation is obtained by expressing the Cartesian and angular velocities of the bodies in terms of the time derivatives of the trajectory coordinates. Various force element models particular to rail cars are developed in this study. These forces include tractive effort, and air brake and dynamic brake forces, as well as a model of available wheel-rail adhesion. Additionally, various types of couplers are formulated as force elements, allowing the modeling of connections between cars. Resistance forces are also modeled in order to be able to simulate rolling, curve, and air resistance forces that may act on the cars during the train operations.

Controlling the Rotational DOF of Laminar Jamming Structures With End Clamping Mechanism

2020 ◽  
Author(s):  
Emily A. Allen ◽  
John P. Swensen
Keyword(s):  
Pressure Gradient ◽  
Variable Stiffness ◽  
Degree Of Freedom ◽  
Rotational Degree ◽  
Beam Structure ◽  
Preliminary Results ◽  
High Stiffness ◽  
Additional Mode ◽  
Translational Degree ◽  
Rotational Freedom

Abstract Variable stiffness structures lie at the nexus of soft robots and traditional robots as they enable the execution of both high-force tasks and delicate manipulations. Laminar jamming structures, which consist of thin flexible sheets encased in a sealed chamber, can alternate between a rigid state when a vacuum is applied and a flexible state when the layers are allowed to slide in the absence of a pressure gradient. In this work, an additional mode of controllability is added by clamping and unclamping the ends of a simple laminar jamming beam structure. Previous works have focused on the translational degree of freedom that may be controlled via vacuum pressure; here we introduce a rotational degree of freedom that may be independently controlled with a clamping mechanism. Preliminary results demonstrate the ability to switch between three states: high stiffness (under vacuum), translational freedom (with clamped ends, no vacuum), and rotational freedom (with ends free to slide, no vacuum).

scholarly journals Design and Analysis of Steering and Lifting Mechanisms for Forestry Vehicle Chassis

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Wenhao Li ◽  
Feng Kang
Keyword(s):  
Complex Terrain ◽  
Degrees Of Freedom ◽  
The Body ◽  
Degree Of Freedom ◽  
Working Environment ◽  
Steering Mechanism ◽  
Working Principle ◽  
Turning Radius ◽  
And Function ◽  
Vehicle Chassis

Due to its special topographical structure, the forest working environment requires a vehicle chassis that can adapt well to complex terrain conditions. This article describes the key components of a chassis that was designed to adapt to complex terrain. The working principle and structural design of the steering structure and the lifting structure are analyzed in detail, and function verification is carried out. The steering mechanism has three degrees of freedom, and the first degree of freedom reduces the body’s inclination by 30°. The second degree of freedom can increase the steering angle of the chassis to 47°, decreasing the turning radius of the chassis. The third degree of freedom reduces the body rollover inclination by 30°. The entire steering mechanism enhances the ride and stability of the chassis. With the lifting mechanism, the wheel-legs are lifted so that the chassis can pass a limit height of 187 mm, and the wheel-legs are lowered to raise the center of gravity of the vehicle chassis by 244 mm. The entire lifting mechanism greatly improves the vehicle's ability to cross forest terrain. The size is reduced by 10% compared to other structures, and the lifting height and obstacle resistance are improved by 12.7%.

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.

Bio-Inspired Locomotion of Circular Robots With Diametrically Translating Legs

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Eric Steffan ◽  
Sudeshna Pal ◽  
Tuhin Das
Keyword(s):  
Mobile Robots ◽  
Degrees Of Freedom ◽  
Analytical Framework ◽  
Degree Of Freedom ◽  
Translational Degree ◽  
Simulation Results ◽  
Cellular Locomotion ◽  
Kinetics Of ◽  
Kinematics And Kinetics

Abstract In this paper, we develop an analytical framework for designing the locomotion of mobile robots with a circular core and equispaced diametral legs, each having a radial translational degree of freedom. The mechanism has resemblance with certain cellular locomotion. The robot travels by radial actuation of the legs in a sequential and synchronized manner. Two elementary regimes of motion are first designed using the geometry and degrees of freedom of the mechanism. Overall motion of the robot is generated by repeated switching between the two regimes. The paper addresses both kinematics and kinetics of the mechanism, enabling the prediction of trajectories and computation of constraint as well as actuation forces. Simulation results are provided in support of the theory developed.

scholarly journals FINITE ELEMENTS OF THE PLANE PROBLEM OF THE THEORY OF ELASTICITY WITH DRILLING DEGREES OF FREEDOM

2020 ◽  
Vol 16 (1) ◽  
pp. 48-72
Author(s):  
Виктор Карпиловский
Keyword(s):  
Finite Elements ◽  
Plane Problem ◽  
Degrees Of Freedom ◽  
Theory Of Elasticity ◽  
Degree Of Freedom ◽  
Rotational Degree ◽  
Design Models ◽  
Numerical Examples ◽  
Drilling Degrees Of Freedom ◽  
Dimensional Instability

Twelve new finite elements with drilling degrees of freedom have been developed: triangular and quadrangular elements based on a modified hypothesis about the value of approximating functions on the sides of the element, which made it possible to avoid dimensional instability when all rotation angles are zero; incompatible and compatible triangular and quadrangular elements which can have additional nodes on the sides. Approximating functions satisfy the following condition: the value of the rotational degree of freedom of a node is nonzero and equal to one only for one of them. Numerical examples illustrate estimated minimum orders of convergence for displacements and stresses. All created elements retain the existing symmetry of the design models.

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