A Single Leg Model With a Novel Variable Stiffness Element Based on the Dynamics Analysis and its Dynamic Characteristics

2017 ◽  
Author(s):  
Zhang Li ◽  
Yuegang Tan ◽  
Liu Hong ◽  
Jaspreet Singh Dhupia ◽  
Shun Zeng ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Stance Phase ◽  
Variable Stiffness ◽  
Body Motion ◽  
Dynamics Analysis ◽  
Variable Sensitivity ◽  
Variation Characteristics ◽  
Reaction Forces ◽  
Independent Variable ◽  
Vibration Parameters

This paper presents a bio-inspired dynamic leg model with a novel variable stiffness element to create a normal body motion during stance phase. The variable stiffness in the model is implemented through structure-controlled stiffness. It allows to decouple the stiffness from joint motion, which makes the stiffness a independent variable. Sensitivity of leg model to the variable stiffness element is investigated through dynamics analysis. Because of the decoupled structure of dynamics equations, the deflection of ankle joint related to variable stiffness element is planned based on generalized forced vibration motion in order to create the leg’s motion. A detailed study to investigate the dynamic characteristics under different generalized vibration parameters, and the desired variable stiffness function are evaluated. It is found that under the effects of variable stiffness, the ground reaction forces of leg model during stance motion have similar characteristics to those observed for mammals. Furthermore, in order to create a normal motion during stance phase, linear stiffness variation characteristics and small stiffness range are needed for the proposed variable stiffness actuator.

scholarly journals Rotor Dynamics Analysis of Rotating Machine Systems Using Artificial Neural Networks

2003 ◽  
Vol 9 (4) ◽  
pp. 255-262 ◽  
Author(s):  
M. Kalkat ◽  
Ş. Yıldırım ◽  
I. Uzmay
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Vertical Direction ◽  
Rotor Dynamics ◽  
Experimental Setup ◽  
Dynamics Analysis ◽  
Rotating Machine ◽  
Rotating Systems ◽  
Machine Systems ◽  
Vibration Parameters

Adirect-coupled rotor system was designed to analyze the dynamic behavior of rotating systems in regard to vibration parameters. The vibration parameters are amplitude, velocity, and acceleration in the vertical direction. The system consisted of a machine analyzer, shaft, disk, master-trend software, and power unit. Four different points were detected and measured by the experimental setup. The vibration parameters were found and saved from master-trend software. These parameters were employed as the desired parameters of the network. A neural network is designed for analyzing a system's vibration parameters. The results showed that the network could be used as an analyzer of such systems in experimental applications.

Dynamic Characteristics of Stance Phase Gait with Prosthetic Foot for Trans-Tibial Amputee

2011 ◽  
Author(s):  
Hyeon-Seok Cho ◽  
Gyoo-Suk Kim ◽  
Sung-Jae Kang ◽  
Jei-Chung Ryu ◽  
Mu-Sung Mun
Keyword(s):  
Dynamic Characteristics ◽  
Stance Phase ◽  
Prosthetic Foot

A Robotic Cadaveric Flatfoot Analysis of Stance Phase

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Lyle T. Jackson ◽  
Patrick M. Aubin ◽  
Matthew S. Cowley ◽  
Bruce J. Sangeorzan ◽  
William R. Ledoux
Keyword(s):  
Surgical Treatment ◽  
Degrees Of Freedom ◽  
Stance Phase ◽  
Gait Cycle ◽  
Ground Reaction Forces ◽  
Pes Planus ◽  
Reaction Forces ◽  
Vertical Ground

The symptomatic flatfoot deformity (pes planus with peri-talar subluxation) can be a debilitating condition. Cadaveric flatfoot models have been employed to study the etiology of the deformity, as well as invasive and noninvasive surgical treatment strategies, by evaluating bone positions. Prior cadaveric flatfoot simulators, however, have not leveraged industrial robotic technologies, which provide several advantages as compared with the previously developed custom fabricated devices. Utilizing a robotic device allows the researcher to experimentally evaluate the flatfoot model at many static instants in the gait cycle, compared with most studies, which model only one to a maximum of three instances. Furthermore, the cadaveric tibia can be statically positioned with more degrees of freedom and with a greater accuracy, and then a custom device typically allows. We created a six degree of freedom robotic cadaveric simulator and used it with a flatfoot model to quantify static bone positions at ten discrete instants over the stance phase of gait. In vivo tibial gait kinematics and ground reaction forces were averaged from ten flatfoot subjects. A fresh frozen cadaveric lower limb was dissected and mounted in the robotic gait simulator (RGS). Biomechanically realistic extrinsic tendon forces, tibial kinematics, and vertical ground reaction forces were applied to the limb. In vitro bone angular position of the tibia, calcaneus, talus, navicular, medial cuneiform, and first metatarsal were recorded between 0% and 90% of stance phase at discrete 10% increments using a retroreflective six-camera motion analysis system. The foot was conditioned flat through ligament attenuation and axial cyclic loading. Post-flat testing was repeated to study the pes planus deformity. Comparison was then made between the pre-flat and post-flat conditions. The RGS was able to recreate ten gait positions of the in vivo pes planus subjects in static increments. The in vitro vertical ground reaction force was within ±1 standard deviation (SD) of the in vivo data. The in vitro sagittal, coronal, and transverse plane tibial kinematics were almost entirely within ±1 SD of the in vivo data. The model showed changes consistent with the flexible flatfoot pathology including the collapse of the medial arch and abduction of the forefoot, despite unexpected hindfoot inversion. Unlike previous static flatfoot models that use simplified tibial degrees of freedom to characterize only the midpoint of the stance phase or at most three gait positions, our simulator represented the stance phase of gait with ten discrete positions and with six tibial degrees of freedom. This system has the potential to replicate foot function to permit both noninvasive and surgical treatment evaluations throughout the stance phase of gait, perhaps eliciting unknown advantages or disadvantages of these treatments at other points in the gait cycle.

scholarly journals Force Pattern and Acceleration Waveform Repeatability of Amateur Runners

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 136
Author(s):  
Ophelie Lariviere ◽  
Thomas Provot ◽  
Laura Valdes-Tamayo ◽  
Maxime Bourgain ◽  
Delphine Chadefaux
Keyword(s):  
Stance Phase ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Multiple Correlation ◽  
Risk Of Injury ◽  
Straight Line ◽  
Reaction Forces ◽  
Tibial Acceleration ◽  
Acceleration Signals ◽  
Study Performance

Although accelerometers’ responses during running are not perfectly understood, they are widely used to study performance and the risk of injury. To outline the typical tibial acceleration pattern during running, this study aims to investigate the repeatability of acceleration signals with respect to the ground reaction force waveforms. Ten amateur runners were asked to perform ten trials along a straight line. One participant was asked to perform this protocol over ten sessions. Tibial accelerations and ground reaction forces were measured during the stance phase. The coefficient of multiple correlation R was computed to study the intra- and inter-test and subject repeatability of accelerometric and force waveforms. A good (R>0.8) intra- and inter-test repeatability was observed for all measured signals. Similar results were observed for intra-subject repeatability. A good inter-subject repeatability was observed only for the longitudinal acceleration and vertical and antero-posterior forces. Typical accelerometric signatures were outlined for each case studied.

The Double Pendulum Model and Nonlinear Dynamic Characteristics of the Pantograph of High-Speed Train

2013 ◽  
Vol 275-277 ◽  
pp. 767-770
Author(s):  
Hua Li ◽  
Shu Qian Cao
Keyword(s):  
Numerical Simulation ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Lagrange Equation ◽  
Variable Stiffness ◽  
Nonlinear Damping ◽  
Double Pendulum ◽  
High Speed Train ◽  
Pendulum Model ◽  
Damping Torque

In this paper, the double pendulum model of the pantograph was developed, in which a square angular velocity damping torque was used to describe the nonlinear damping torque of the hydraulic vibration damper, and the catenary was described as a variable stiffness spring. Considering the nonlinear factors caused by hydraulic damping and the interaction between the catenary and the pantograph, the motion differential equations based on the double pendulum model were established in Lagrange equation, and then were simplified. The dynamic characteristics were analyzed through numerical simulation. The result of numerical simulation shows that there are quasi-periodic motion and chaos in the system, which are both affected by the pendulum length ratio. The results are helpful to research the dynamic characteristics of the pantograph of high-speed train.

Dynamics analysis of dual-axis positioning mechanism of satellite antenna with joint clearance

2014 ◽  
Vol 10 (1) ◽  
pp. 59-74
Author(s):  
Zheng Feng Bai ◽  
Yang Zhao ◽  
Jun Chen
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Performance ◽  
Engineering Application ◽  
Friction Model ◽  
Joint Clearance ◽  
Force Model ◽  
Dynamics Analysis ◽  
Satellite Antenna ◽  
Content Type ◽  
Continuous Contact

Purpose – The existence of clearance in joints of positioning mechanism is inevitable and the movements of the real mechanism are deflected from the ideal mechanism due to the clearances. The purpose of this paper is to investigate the effects of clearance on the dynamic characteristics of dual-axis positioning mechanism of a satellite antenna. Design/methodology/approach – The dynamics analysis of dual-axis positioning mechanism with clearance are investigated using a computational approach based on virtual prototyping technology. The contact model in joint clearance is established by using a hybrid nonlinear continuous contact force model and the friction effect is considered by using a modified Coulomb friction model. Then the numerical simulation of dual-axis positioning mechanism with joint clearance is carried out and four case studies are implemented for different clearance sizes. Findings – Clearance leads to degradation of the dynamic performance of the system. The existence of clearance causes impact dynamic loads, and influences the motion accuracy and stability of the dual-axis positioning mechanism. Larger clearance induces higher frequency shakes and larger shake amplitudes, which will deteriorate positioning accuracy. Practical implications – Providing an effective and practical method to analyze dynamic characteristics of dual-axis positioning mechanism of satellite antenna with joint clearance and describing the dynamic characteristics of the dual-axis positioning system more realistically, which improves the engineering application. Originality/value – The paper is the basis of mechanism design, precision analysis and robust control system design of dual-axis positioning mechanism of satellite antenna.

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