Reduction of Jerk Through Optimization of a Knee Assistive Device Designed Using Four-Bar Controlled Compliance Actuator

2018 ◽  
Author(s):  
Saikat Sahoo ◽  
Aditya Jain ◽  
Dilip Kumar Pratihar
Keyword(s):  
Knee Joint ◽  
Stance Phase ◽  
Reaction Force ◽  
Swing Phase ◽  
Damping Coefficient ◽  
Assistive Device ◽  
Spring Stiffness ◽  
Design Variables ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping

Two major responsibilities are taken by a knee joint during level ground walking of a human being. At stance phase, knee joint is locked in order to provide stability against ground reaction force, and in swing phase, knee flexes for ground clearance of the foot. In this study, a four-bar controlled compliance actuator (FCCA) has been configured for assisting the knee joint during walking. The main focus of FCCA design is the reduction of required mechanical power through a compliance actuation strategy and amplification of motor power. The proposed design consists of two linear spring-damper systems, out of which, one controls the locking of knee during stance phase and another takes care of knee flexion at swing phase. Without a proper selection of stiffness and damping coefficient for both the springs, the knee may be subjected to jerk during flexion, which may give rise to discomfort to the user and consequently, he/she may fall during walking. This study aims to ensure smooth knee operation in both stance phase as well as swing phase by assigning the proper spring stiffness and damping coefficient for both the springs. The responsibility is given to a non-traditional optimization tool, namely particle swarm optimization (PSO). The optimization is carried out using a co-simulation approach between Matlab and ADAMS. The aim of PSO (run in Matlab) is to minimize both the frequency as well as amplitude of the jerk by finding a suitable set of design variables, that is, spring stiffness and damping coefficient of two spring-damper systems.

Biomechanical responses of young adults with unilateral transfemoral amputation using two types of mechanical stance control prosthetic knee joints

2020 ◽  
Vol 44 (5) ◽  
pp. 314-322
Author(s):  
Jan Andrysek ◽  
Daniela García ◽  
Claudio Rozbaczylo ◽  
Carlos Alvarez-Mitchell ◽  
Rebeca Valdebenito ◽  
...  
Keyword(s):  
Young Adults ◽  
Knee Joint ◽  
Stance Phase ◽  
Pelvic Tilt ◽  
Swing Phase ◽  
Knee Joints ◽  
Transfemoral Amputation ◽  
Phase Duration ◽  
Prosthetic Knee ◽  
Stance Control

Background: Prosthetic knee joint function is important in the rehabilitation of individuals with transfemoral amputation. Objectives: The objective of this study was to assess the gait patterns associated with two types of mechanical stance control prosthetic knee joints—weight-activated braking knee and automatic stance-phase lock knee. It was hypothesized that biomechanical differences exist between the two knee types, including a prolonged swing-phase duration and exaggerated pelvic movements for the weight-activated braking knee during gait. Study design: Prospective crossover study. Methods: Spatiotemporal, kinematic, and kinetic parameters were obtained via instrumented gait analysis for 10 young adults with a unilateral transfemoral amputation. Discrete gait parameters were extracted based on their magnitudes and timing. Results: A 1.01% ± 1.14% longer swing-phase was found for the weight-activated braking knee (p < 0.05). The prosthetic ankle push-off also occurred earlier in the gait cycle for the weight-activated braking knee. Anterior pelvic tilt was 3.3 ± 3.0 degrees greater for the weight-activated braking knee. This range of motion was also higher (p < 0.05) and associated with greater hip flexion angles. Conclusions: Stance control affects biomechanics primarily in the early and late stance associated with prosthetic limb loading and unloading. The prolonged swing-phase time for the weight-activated braking knee may be associated with the need for knee unloading to initiate knee flexion during gait. The differences in pelvic tilt may be related to knee stability and possibly the different knee joint stance control mechanisms. Clinical relevance Understanding the influence of knee function on gait biomechanics is important in selecting and improving treatments and outcomes for individuals with lower-limb amputations. Weight-activated knee joints may result in undesired gait deviations associated with stability in early stance-phase, and swing-phase initiation in the late stance-phase of gait.

Study on Dynamics Characteristics of SINS Damping System in Shock Environment

2013 ◽  
Vol 397-400 ◽  
pp. 355-358
Author(s):  
Xia Qing Tang ◽  
Jun Qiang Gao ◽  
Li Bin Guo ◽  
Huan Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Optimal Design ◽  
Vibration Isolation ◽  
Damping Coefficient ◽  
Shock Environment ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping ◽  
Element Method

Dynamics characteristics of SINS damping system in shock environment were analyzed by finite element method, as the deformation of dampers may leads to the accuracy loss of SINS. In addition, the influence of absorber stiffness and damping coefficient on dynamics characteristics were studied. The results indicate that the decoupling of vibrations is significant for the accuracy of SINS. However, considering the almost impossible of completely decoupled vibrations, its necessary to carry out an optimal design of the absorber stiffness and damping coefficient to maintain the accuracy of SINS while meeting the requirement of vibration isolation.

Vehicle Moving Along an Infinite Beam With Random Surface Irregularities on a Kelvin Foundation

2001 ◽  
Vol 69 (1) ◽  
pp. 69-75 ◽  
Author(s):  
L. Andersen ◽  
S. R. K. Nielsen ◽  
R. Iwankiewicz
Keyword(s):  
Equations Of Motion ◽  
Response Functions ◽  
Spring Stiffness ◽  
Euler Beam ◽  
Random Surface ◽  
Single Degree Of Freedom ◽  
Surface Irregularities ◽  
Stiffness And Damping Coefficient ◽  
Mass Spring ◽  
Stiffness And Damping

The paper deals with the stochastic analysis of a single-degree-of-freedom vehicle moving at a constant velocity along an infinite Bernoulli-Euler beam with surface irregularities supported by a Kelvin foundation. Both the Bernoulli-Euler beam and the Kelvin foundation are assumed to be constant and deterministic. This also applies to the mass, spring stiffness, and damping coefficient of the vehicle. At first the equations of motion for the vehicle and beam are formulated in a coordinate system following the vehicle. The frequency response functions for the displacement of the vehicle and beam are determined for harmonically varying surface irregularities. Next, the surface irregularities are modeled as a random process. The variance response of the mass of the vehicle as well as the displacement variance of the beam under the oscillator are determined in terms of the autospectrum of the surface irregularities.

RELATIONSHIPS BETWEEN KINETIC VARIABLES AND SMOOTHNESS OF KNEE JOINT MOVEMENT IN THE STANCE PHASE

2014 ◽  
Vol 14 (05) ◽  
pp. 1450079 ◽  
Author(s):  
TAKASHI FUKAYA ◽  
HIROTAKA MUTSUZAKI ◽  
HAJIME ITO ◽  
YASUYOSHI WADANO
Keyword(s):  
Knee Joint ◽  
Ground Reaction Force ◽  
Stance Phase ◽  
Reaction Force ◽  
Vertical Component ◽  
Correlation Coefficients ◽  
The Other ◽  
Joint Movement ◽  
Important Index ◽  
Three Phases

The purposes of this study were to clarify which period of the stance phase shows the greatest decrease in the smoothness of the knee joint movement and to analyze the relationships between kinetic variables and the smoothness of the knee joint movement during the stance phase using the angular jerk cost (AJC). The study subjects were 11 healthy adults. To clarify the relationships between the kinetic variables and the AJC, Pearson's product correlation coefficients were calculated for the AJC and three kinetic variables. The AJC in the early stance phase was significantly larger than those in the other three phases, and it was confirmed that the early stance phase showed the greatest decrease in smoothness of the knee joint movement. Furthermore, there was a positive correlation between the AJC and the vertical component of the ground reaction force in the early stance phase. Correlations between the AJC and the kinetic variables were also found in the other three phases. Regarding evaluation of the smoothness of the knee joint movement using the AJC based on the present results, the AJC may be an important index for understanding the dynamics of the knee joint in the early stance phase.

scholarly journals Active Control Method Based on Equivalent Stiffness and Damping Coefficient for an Electromagnetic Isolation System

2020 ◽  
Vol 10 (22) ◽  
pp. 7953
Author(s):  
Lei Zhang ◽  
Xiangtao Zhuan
Keyword(s):  
Control Method ◽  
Dynamic Performance ◽  
Damping Coefficient ◽  
Stiffness Coefficient ◽  
Equivalent Stiffness ◽  
Isolation System ◽  
Performance Indexes ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping ◽  
Active Control Method

For improving the performance of an electromagnetic isolation system with reasonable parameters and avoid the parameter tuning problem of a PID controller, an active control method is put forward based on equivalent stiffness and damping coefficient. In this paper, the range of equivalent stiffness coefficient and damping coefficient of the electromagnetic force are calculated based on the required range of dynamic performance indexes. According to the nonlinear expression between electromagnetic force and coil current and gap, the relationships between the coil current and equivalent stiffness coefficient and damping coefficient are established. Then, the equivalent stiffness coefficient and damping coefficient can be satisfied by the controlled current in different gaps for meeting the required dynamic performance indexes. For reducing the maximum overshoot and the number of oscillations of the system, the active control method with the piecewise equivalent stiffness and damping coefficient is proposed based on the piecewise control strategy to realize the variable control parameters of the isolation system. Simulation and experimental results verify that the control method based on the equivalent stiffness and damping coefficient can obtain the desired dynamic performance indexes and the proposed control method with the piecewise strategy can not only reduce the setting time of the system, but also ensure the stability of the system.

SMOOTHNESS USING ANGULAR JERK COST OF THE KNEE JOINT MOVEMENT AFTER A REDUCTION IN WALKING SPEED

2013 ◽  
Vol 13 (03) ◽  
pp. 1350037 ◽  
Author(s):  
TAKASHI FUKAYA ◽  
HIROTAKA MUTSUZAKI ◽  
YASUYOSHI WADANO
Keyword(s):  
Knee Joint ◽  
Ground Reaction Force ◽  
Stance Phase ◽  
Walking Speed ◽  
Reaction Force ◽  
Angular Acceleration ◽  
Time Dependent ◽  
Initial Contact ◽  
Joint Movement ◽  
Important Index

The angular jerk cost (AJC) was proposed to objectively represent the smoothness of joint movement by calculating the time-dependent changes in acceleration during motion. There are currently no reports focusing on smoothness using AJC measurements of the knee joint movement during the stance phase of gait. The purpose of this study was to verify whether a reduced walking speed affects the smoothness of the knee joint movement during the stance phase of gait. The gaits of 12 healthy adults were assessed. A slower walker showed a significant reduction in the AJC value in the period between the initial contact and the loading response, as compared with someone walking at a comfortable speed. The maximum ground reaction force of the stance phase at a comfortable walking speed was significantly larger than that at a slower walking speed. Thus, although the smoothness of the knee joint was impaired by a rapid load in the early stance phase, a slower walking speed reduced the ground reaction force and angular acceleration of the knee joint and created a smoother movement. The AJC can be an important index for understanding the smoothness of the knee joint in the early stance phase.

Sign in / Sign up

Export Citation Format

Share Document