scholarly journals Development of an Exoskeleton-Type Assist Suit Utilizing Variable Stiffness Control Devices Based on Human Joint Characteristics

Actuators ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 17
Author(s):  
Seigo Kimura ◽  
Ryuji Suzuki ◽  
Katsuki Machida ◽  
Masashi Kashima ◽  
Manabu Okui ◽  
...  
Keyword(s):  
Joint Stiffness ◽  
Knee Extensor ◽  
Artificial Muscle ◽  
Variable Stiffness ◽  
Lower Limbs ◽  
Joint Characteristics ◽  
Standing Up ◽  
Maximum Decrease ◽  
Control Devices ◽  
The Relationship

In this paper, the prototype of the assistive suit for lower limbs was developed. The prototype was based on an assist method with joint stiffness and antagonized angle control. The assist method comprises a system consisting of a pneumatic artificial muscle and a pull spring, which changes the joint stiffness and the antagonized angle to correspond to the movement phase and aims at coordinated motion assistance with the wearer. First, the characteristics of the developed prototype were tested. It was confirmed that the measured value of the prototype followed the target value in the relationship between torque and angle. In addition, there was hysteresis in the measured value, but it did not affect the assist. Next, the evaluation of standing-up and gait assist by measuring electromyography (EMG) of the knee extensor muscle was conducted using the prototype. In all subjects, a decrease in EMG due to the assist was confirmed. In one subject, the maximum decrease rate at the peak of the EMG was about 50% for standing-up motion and about 75% for gait motion. From the results of these assist evaluations, the effectiveness of the assist method based on the joint stiffness and antagonistic angle control using the prototype was confirmed.

Posture Control Considering Joint Stiffness of a Robotic Arm Driven by Rubberless Artificial Muscle

2016 ◽  
Vol 10 (4) ◽  
pp. 503-510 ◽  
Author(s):  
Naoki Saito ◽  
◽  
Toshiyuki Satoh ◽  
Keyword(s):  
Joint Angle ◽  
Joint Stiffness ◽  
Mathematical Expression ◽  
Artificial Muscle ◽  
Good Control ◽  
Robotic Arm ◽  
Rubber Tube ◽  
Robotic Arms ◽  
Control Scheme ◽  
The Relationship

This paper describes a joint angle control considering the passive joint stiffness of robotic arms driven by rubberless artificial muscle (RLAM), which is a pneumatic actuator. The contraction mechanism of RLAM is the same as that of the McKibben artificial muscle. Unlike the McKibben artificial muscle, RLAM is constructed using an airbag made of a nonelastic material instead of a rubber tube.The objective of this study is to realize a soft contact movement of robotic arms by applying the passive compliance characteristics of RLAMs. In this study, we derive a mathematical expression for the relationship between the output of an RLAM and the joint stiffness of a robotic arm. In addition, we suggest a control scheme for each RLAM. We confirm the validity of these suggestions experimentally. From the result, we observe a good control performance of the joint angle. A robotic arm moves smoothly according to the force added from outside by setting the passive stiffness of the arm.

RESEARCH ON DESIGN AND CONTROL OF A NEW TYPE FLEXIBLE JOINT WITH VARIABLE STIFFNESS

2020 ◽  
Vol 20 (02) ◽  
pp. 2050003
Author(s):  
YUBIN LIU ◽  
GANGFENG LIU ◽  
RUOFAN CAI
Keyword(s):  
Dynamic Stiffness ◽  
Joint Stiffness ◽  
Taylor Series Expansion ◽  
Planetary Gear ◽  
Variable Stiffness ◽  
Application Process ◽  
New Type ◽  
Gear Mechanism ◽  
And Control ◽  
The Relationship

Aiming at non-linear problems existing in the principle of variable stiffness of robot joints, a class crank-slider and planetary gear mechanism are presented. The spring is pre-compressed by using the inter-agency geometric relations of fulcrum movement. The approximate linear variation of stiffness about fulcrum offset is realized. The problems of mechanism clearance, operational stability, and compact space are solved. The joint stiffness calculation method is derived, and the relationship between key parameters and stiffness outputs is analyzed. The stiffness control strategy is researched on, and a trajectory generator is designed based on Taylor series expansion. Static stiffness identification and dynamic stiffness following experiment are designed to test joint stiffness and position characteristics. The feasibility of joint is verified to achieve stiffness and position continuous adjustment within a certain range. This type of joint can be used in the field of medical treatment and rehabilitation to solve the problems of safety and environmental adaptability in the application process.

A Novel Wire-Driven Variable-Stiffness Joint Based on a Permanent Magnetic Mechanism

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Ming Zhang ◽  
Lijin Fang ◽  
Feng Sun ◽  
Koichi Oka
Keyword(s):  
Traditional Approach ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
The Novel ◽  
Adjustment Time ◽  
Stiffness Model ◽  
Wide Range ◽  
Driven System ◽  
The Relationship ◽  
Magnetic Mechanism

The variable-stiffness joint (VSJ) plays an important role in creating compliant and powerful motions. This paper presents a novel wire-driven VSJ based on a permanent magnetic mechanism (PMM). The proposed joint regulates the joint stiffness with lower energy consumption through a wide range via the permanent magnetic mechanism. This effect possibly depends on the novel nonlinear combination of a permanent magnet-spring and wire-driven system that achieves the same stiffness with lower wire tension. A trapezoidal layout of the joint is proposed. Because of the relationship among the stiffness, the position of the joint and the stiffness of the PMM, the stiffness model is also been established. Based on this model, the decoupling controller is built to independently control the position and stiffness of the joint. Experiments show that the VSJPMM achieves position and stiffness independently and also reduces energy and power required to regulate the stiffness compared with the traditional approach. In addition, the proposed mechanism displays a powerful motion and short stiffness adjustment time.

Correction of Posture Deviations in the Sagittal Plane Using the Pilates Method

2019 ◽  
pp. 3-13
Author(s):  
Alexandru Cîtea ◽  
George-Sebastian Iacob
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Postural Control ◽  
Human Body ◽  
Sagittal Plane ◽  
The Body ◽  
Lower Limbs ◽  
Low Back ◽  
Pilates Method ◽  
The Relationship

Posture is commonly perceived as the relationship between the segments of the human body upright. Certain parts of the body such as the cephalic extremity, neck, torso, upper and lower limbs are involved in the final posture of the body. Musculoskeletal instabilities and reduced postural control lead to the installation of nonstructural posture deviations in all 3 anatomical planes. When we talk about the sagittal plane, it was concluded that there are 4 main types of posture deviation: hyperlordotic posture, kyphotic posture, rectitude and "sway-back" posture.Pilates method has become in the last decade a much more popular formof exercise used in rehabilitation. The Pilates method is frequently prescribed to people with low back pain due to their orientation on the stabilizing muscles of the pelvis. Pilates exercise is thus theorized to help reactivate the muscles and, by doingso, increases lumbar support, reduces pain, and improves body alignment.

scholarly journals The superficial venous pump

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Konstantin Mazayshvili
Keyword(s):  
Saphenous Vein ◽  
Great Saphenous Vein ◽  
Lower Limbs ◽  
Superficial Fascia ◽  
Step Cycle ◽  
Cross Sectional ◽  
Blood Flows ◽  
Active Function ◽  
Vein Segment ◽  
The Relationship

The present study has revealed the relationship between the cross sectional area of the great saphenous vein and the degree of tension in the superficial fascia of the thigh. We conducted an ultrasound examination with 27 patients (54 lower limbs) in both standing and walking positions. With an increase and decrease in the degree of tension of the superficial fascia, the blood is pushed to the sapheno-femoral junction. Nearly 200 mm3 of blood flows in, and is pushed out of, a 100-mm great saphenous vein segment in the thigh, towards the sapheno-femoral junction during a step cycle. As a result, the active function of the fascial compartment of the great saphenous vein has been found. We have called this mechanism the superficial venous pump.

FILTERING CALCULATIONS OF WATERLOWERING IN THE CONSTRUCTION OF ENGINEERING COMMUNICATIONS

2021 ◽  
pp. 126-133
Author(s):  
N. P. KARPENKO ◽  
◽  
E. S. BEGLYAROVA ◽  
S. A. SOKOLOVA ◽  
T. I. MATVEEVA
Keyword(s):  
Administrative District ◽  
Microsoft Excel ◽  
Model Calculations ◽  
Factors Affecting ◽  
Infinite Layer ◽  
Linear Scheme ◽  
Maximum Decrease ◽  
Water Catchment ◽  
The Relationship ◽  
Infinite Linear

The purpose of the investigations is an assessment of filtration calculations of water lowering during construction works and laying engineering communications at the water catchment of the Likhoborka and Zhabenka rivers. There are considered hydrogeological questions of filtration calculations at construction and laying urban and rain sewers on the territory of the Dmitrovskoe highway in the Northern administrative district of Moscow. It is revealed that the main factors affecting hydrogeological conditions in the area of construction of engineering communications is water lowering. The dependences on the estimation of filtration calculations of water lowering in the area of construction of engineering communications are analyzed. Analytical dependences for the scheme of an infinite linear source of perturbation in the infinite layer are proposed and improved. It is established that the average costs are proportionally dependent to the level of water lowering in the water lowering area,and the relationship between average costs, regardless of the calculated linear scheme, is linear. A model for filtration calculations has been developed in Microsoft Excel. The model calculations showed that the maximum decrease in the estimated point of a multi-story non-residential administrative building does not exceed the values of the maximum allowable deformations.

scholarly journals Corporate governance and conglomerate diversification strategy – evidence from Vietnam

2018 ◽  
Vol 13 (6) ◽  
pp. 1578-1596 ◽  
Author(s):  
Thi Xuan Trang Nguyen
Keyword(s):  
Corporate Governance ◽  
Stock Exchange ◽  
Board Composition ◽  
Governance Mechanisms ◽  
Content Type ◽  
Unrelated Diversification ◽  
Corporate Governance Mechanisms ◽  
Control Devices ◽  
Interest Alignment ◽  
The Relationship

Purpose The purpose of this paper is to examine the impact of internal corporate governance mechanisms, including interest alignment and control devices, on the unrelated diversification level in Vietnam. Additionally, the moderation of free cash flow (FCF) on these relationships is also tested. Design/methodology/approach The study is based on a balanced panel data set of 70 listed companies in both stock markets, Ho Chi Minh Stock Exchange and Hanoi Stock Exchange, in Vietnam for the years 2007–2014, which gives 560 observations in total. Findings The results show that if executive ownership for CEOs is increased, then the extent of diversification is likely to be reduced. However, the link between unrelated diversification level and executive stock option, another interest alignment device, cannot be confirmed. Among three control devices (level of blockholder ownership, board composition and separation of CEO and chairman positions), the study finds a positive connection between diversification and blockholder ownership, and statistically insignificant relations between the conglomerate diversification level and board composition, or CEO duality. Additionally, this study discovers a negative link between diversification and state ownership, although there is no evidence to support the change to the effect of each internal corporate governance mechanism on the diversification level of a firm between high and low FCF. Practical implications The research can be a useful reference not only for investors and managers but also for policy makers in Vietnam. This study explores the relationship among corporate governance, diversification and firm value in Vietnam, where the topics related to effectiveness of corporate governance mechanisms to public companies has been increasingly attractive to researchers since the default of Vietnam Shipbuilding Industry Group (Vinashin) happened in 2010 and the Circular No. 121/2012/TT-BTC on 26 July 2012 of the Vietnamese Ministry of Finance was issued with regulations on corporate governance applicable to listed firms in this country. Originality/value This research, first, enriches current literature on the relationship between corporate governance and firm diversification. It can be considered as a contribution to the related topic with an example of Vietnam, a developing country in Asia. Second, the research continues to prove non-unification in results showing the relationship between corporate governance and conglomerate diversification among different nations. Third, it provides a potential input for future research works on the moderation of FCF to the effects of corporate governance on diversification.

scholarly journals Design and Analysis of a Novel Variable Stiffness Joint for Robot

2018 ◽  
Vol 249 ◽  
pp. 03005
Author(s):  
Xiang Zhang ◽  
Twan Capehart ◽  
Carl A. Moore
Keyword(s):  
High Frequency ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Robotic Systems ◽  
Compliant Joint ◽  
Variable Transmission ◽  
Application Requirements ◽  
Base Application ◽  
Robotic Applications ◽  
Human Robotic Interaction

As people pay more attention to the safety of human-robotic interaction, the flexibility of machine joints is becoming more and more important. To address the needs of future robotic applications, many kinds of variable stiffness mechanisms have been designed by scientists. But most of the structures are complex. By studying and comparing many different mechanism designs of variable stiffness joint, we recognize the need to miniaturization and reduce weight of variable stiffness joints with high frequency operation. To address this, need a continuously Variable Compliant Joint (CVCJ) was designed. The core of the joint is based on the structure of the spherical continuously variable transmission (SCVT) which is the catalyst to change the stiffness continuously and smoothly. In this paper, we present a compact variable stiffness joint structure to meet the volume and weight requirements of the future robotic systems. We show the connection between the joint stiffness coefficient and the structure parameters by making mathematical analysis, modelling and simulation for the system to verify the ability to satisfy the base application requirements of the compliant joint.

Effect of voluntary vs. artificial activation on the relationship of muscle torque to speed

1990 ◽  
Vol 69 (6) ◽  
pp. 2215-2221 ◽  
Author(s):  
G. A. Dudley ◽  
R. T. Harris ◽  
M. R. Duvoisin ◽  
B. M. Hather ◽  
P. Buchanan
Keyword(s):  
Knee Extensor ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Angular Velocities ◽  
The Central Nervous System ◽  
The Right ◽  
Artificial Activation ◽  
Relationship Of ◽  
The Relationship ◽  
Eccentric Actions

The speed-torque relationship of the right knee extensor muscle group was investigated in eight untrained subjects (28 +/- 2 yr old). Torque was measured at a specific knee angle during isokinetic concentric or eccentric actions at nine angular velocities (0.17-3.66 rad/s) and during isometric actions. Activation was by "maximal" voluntary effort or by transcutaneous tetanic electrical stimulation that induced an isometric torque equal to 60% (STIM 1) or 45% (STIM 2) of the voluntary isometric value. Torque increased (P less than 0.05) to 1.4 times isometric as the speed of eccentric actions increased to 1.57 rad/s for STIM 1 and STIM 2. Thereafter, increases in eccentric speed did not further increase torque. Torque did not increase (P greater than 0.05) above isometric for voluntary eccentric actions. As the speed of concentric actions increased from 0.00 to 3.66 rad/s, torque decreased (P less than 0.05) more (P less than 0.05) for both STIM 1 and STIM 2 (two-thirds) than for voluntary activation (one-half). As a result of these responses, torque changed three times as much (P less than 0.05) across speeds of concentric and eccentric actions with artificial (3.4-fold) than voluntary (1.1-fold) activation. The results indicate that with artificial activation the normalized speed-torque relationship of the knee extensors in situ is remarkably similar to that of isolated muscle. The relationship for voluntary activation, in contrast, suggests that the ability of the central nervous system to activate the knee extensors during maximal efforts depends on the speed and type of muscle action performed.

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