scholarly journals Force Analysis and Evaluation of a Pelvic Support Walking Robot with Joint Compliance

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Jiancheng Ji ◽  
Shuai Guo ◽  
Fengfeng (Jeff) Xi
Keyword(s):  
Force Field ◽  
Piecewise Linear ◽  
Linear Method ◽  
Kinematic Model ◽  
Gait Training ◽  
Walking Robot ◽  
Force Analysis ◽  
Interaction Forces ◽  
Joint Compliance ◽  
Pelvic Support

The force analysis of a pelvic support walking robot with joint compliance is discussed in this paper. During gait training, pelvic motions of hemiplegic patients may be excessively large or out of control; however, restriction of pelvic motions is not likely to facilitate successful rehabilitation. A robot-assisted pelvic balance trainer (RAPBT) is proposed to help patients control the range of motion via force field, and force analysis is necessary for the control of the compliant joints. Thus, kinematic model and static model are developed to derive the Jacobian and the relation between the interaction forces and the pelvic movements, respectively. Since the joint compliance is realized through a nontorsional spring, a conventional (linear) Jacobian method and a piecewise linear method are derived to relate the interaction forces with the pelvis movements. Three preliminary experiments are carried out to evaluate the effectiveness of the proposed methods and the feasibility of the RAPBT. The experiment results indicate that the piecewise linear method is effective in the calculation of the interaction forces. Gait with pelvic brace strongly resembles free overground walking and partly decreases motion range via force field. The findings of this research demonstrate that the pelvic brace with joint compliance may provide effective interventions.

scholarly journals Tip-Over Stability Analysis of a Pelvic Support Walking Robot

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Yawei Han ◽  
Shuai Guo ◽  
Leigang Zhang ◽  
Fengfeng (Jeff) Xi ◽  
Weiwei Lu
Keyword(s):  
Stability Analysis ◽  
Optimization Algorithm ◽  
Influence Factors ◽  
Gait Training ◽  
Static Case ◽  
Walking Robot ◽  
Interaction Forces ◽  
Force Moment ◽  
Pelvic Support ◽  
The Stability

Discussed in this paper is the tip-over stability analysis of a pelvic support walking robot. To improve the activities of daily living (ADL) in hemiplegic patients, a pelvic support walking robot is proposed to help patients facilitating their rehabilitation. During the gait training with the robot, the abnormal man-machine interaction forces may lead to the tip-over of the robot, which is not beneficial to the rehabilitation process. A new method is proposed to predict the possibility of tipping over and evaluate the stability of the robot based on statics model, dynamics model, and zero-moment point (ZMP) theory. Through the interaction forces and moments analysis with static case, the safe point (ZMP) is studied, and the influence factors of force/moment are analyzed by dynamics case. An optimization algorithm based on the genetic algorithm (GA) is proposed to reduce the risk of tipping over. The simulation results show that the optimization algorithm can keep the robot from tipping over when the interaction forces exceed the safety threshold.

A New Model for Simulating AC and Surge Properties of ZnO Varistors Based on Microstructural Characteristics

2008 ◽  
Vol 368-372 ◽  
pp. 510-513 ◽  
Author(s):  
Jun Hu ◽  
Jin Liang He ◽  
Feng Chao Luo
Keyword(s):  
Numerical Simulation ◽  
Grain Boundaries ◽  
Conduction Mechanism ◽  
Piecewise Linear ◽  
Linear Method ◽  
Microstructural Characteristics ◽  
Nonlinear Resistor ◽  
Resistor Networks ◽  
Zno Varistors ◽  
The Relationship

The numerical simulation is an effective method for researching the relationship between macroscopic properties of ZnO varistors and their microstructural characteristics. However, the computing efficiency is a big problem for further researches. In this paper, a quick piecewise linear method for solving the complicated nonlinear resistor networks of ZnO varistors is proposed, which can significantly improve the computing efficiency by a hundred times. The simulating models for the microstructural characteristics of ZnO varistors are improved based on actual conduction mechanism of grain boundaries. The simulations of more bulk characteristics of ZnO varistors become possible, such as alternating current (AC) and surge properties.

scholarly journals The Effect of Pelvic Movements of a Gait Training System for Stroke Patients

2021 ◽  
Author(s):  
Choonghyun Son ◽  
Anna Lee ◽  
Junkyung Lee ◽  
DaeEun Kim ◽  
Seung-Jong Kim ◽  
...  
Keyword(s):  
Stance Phase ◽  
Gait Training ◽  
Training System ◽  
Transverse Plane ◽  
Gait Rehabilitation ◽  
Stroke Patients ◽  
Interaction Forces ◽  
Flexion Extension ◽  
Pelvic Movement ◽  
Robotic Gait

Abstract Background: Aging societies lead to higher demand for gait rehabilitation as age-related neurological disorders such as stroke increase. Since conventional methods for gait rehabilitation are physically and economically burdensome, robotic gait training systems have been studied and commercialized, many of which provided movements confined in the sagittal plane. For better outcomes of gait rehabilitation with more natural gait patterns, however, it is desirable to provide pelvic movements in the transverse plane. In this study, a robotic gait training system capable of pelvic motions in the transverse plane was used to evaluated the effect of the pelvic motions on stroke patients. Method: Healbot T, which is a robotic gait training system and capable of providing pelvic movements in the transverse plane as well as flexion/extension of the hip and knee joints and adduction/abduction of the hip joints, is introduced and used to evaluate the effect of the pelvic movement on gait training of stroke patients.Experiment: 23 stroke patients with hemiparesis participated in this study and were assigned into two groups. Pelvis-on group was provided with pelvic motions whereas no pelvic movement was allowed for pelvis-off group during 10 sessions of gait trainings in Healbot T. EMG signals and interaction forces as well as the joint angles of the robot were measured. Gait parameters such as stride length, gait period, cadence, and walking speed were measured after gait training. Result: 37.5 % lower interaction forces of pelvis were observed in the pelvis-on group than the pelvis-off group. Furthermore, the interaction forces at the thighs and calves of both groups showed significant decrease. The EMG signals of gluteus medius of the pelvis-on group increased by 77.2 %. Furthermore, statistically significant increases in various muscles were measured in the pelvis-on group during the stance phase. Conclusion: Gait training using a robotic gait training system with pelvic movements was conducted to study the effects of lateral and rotational pelvic movements in gait training of stroke patients. The pelvic movements made gait training less interfered by the exoskeleton while stimulating the voluntary muscle activation during the stance phase. Clinical trial registration: KCT0003762, 2018-1254, Registered 28 October 2018, https://cris.nih.go.kr/cris/search/search_result_st01_kren.jsp?seq=14310

Kinematic Modeling and Analysis of a Novel Bio-Inspired and Cable-Driven Hybrid Shoulder Mechanism

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
A. S. Niyetkaliyev ◽  
E. Sariyildiz ◽  
G. Alici
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Kinematic Modeling ◽  
Interaction Forces ◽  
Modeling And Analysis ◽  
Shoulder Joints ◽  
Hybrid Mechanism ◽  
Simulation Results

Abstract The robotic shoulder rehabilitation exoskeletons that do not take into consideration all shoulder degrees-of-freedom (DOFs) lead to undesirable interaction forces and cause discomfort to the patient due to the joint axes misalignments between the exoskeleton and shoulder joints. In order to contribute to the solution of this human–robot compatibility issue, we present the kinematic modeling and analysis of a novel bio-inspired 5-DOFs hybrid human–robot mechanism (HRM). The human limbs are regarded as the inner passive restrained links in the proposed hybrid constrained anthropomorphic mechanism. The proposed hybrid mechanism combines serial and parallel manipulators with rigid and cable links enabling a match between human and exoskeleton joint axes. It is designed to cover the whole range of motion of the human shoulder with the workspace free of singularities. The numerical and simulation results from the computer-aided drawing model of the mechanism are presented to demonstrate the validity of the kinematic model, and the kinematic and singularity merits of the proposed mechanism. A three-dimensional printed prototype of the hybrid mechanism was fabricated to further validate the kinematic model and its overall advantages.

An Intuitionistic Fuzzy Multi-Objective Goal Programming Approach to Portfolio Selection

2021 ◽  
pp. 1-21
Author(s):  
Gao-Feng Yu ◽  
Deng-Feng Li ◽  
De-Cui Liang ◽  
Guang-Xu Li
Keyword(s):  
Portfolio Selection ◽  
Piecewise Linear ◽  
Linear Method ◽  
Multiple Objectives ◽  
Programming Approach ◽  
Binary Variables ◽  
Multi Objective ◽  
Intuitionistic Fuzzy ◽  
Solution Methods ◽  
Hard Problems

Portfolio selection can be regarded as a type of multi-objective decision problem. However, traditional solution methods rarely discussed the decision maker’s nonsatisfaction and hesitation degrees with regard to multiple objectives and they require many extra binary variables, which lead to tedious computational burden. Based on the above, the aim of this paper is to develop a new and unified intuitionistic fuzzy multi-objective linear programming (IFMOLP) model for such portfolio selection problems. The nonmembership functions are constructed by the pessimistic, optimistic, and mixed approaches so as to perfect the traditional intuitionistic fizzy (IF) inequalities and IF theory. The decision maker’s hesitation degrees with regard to multiple objectives are represented by using IF inequalities, and the new IFMOLP model based on IF inequalities is proposed. The IFMOLP problems are solved by the S-shaped membership functions without extra binary variables required by the piecewise-linear method. Finally, the portfolio selection model under IF environments based on IFMOLP is established, and a real example is analyzed to demonstrate its validity and superiority. The developed unified IFMOLP model and method can not only effectively solve multi-objective decision problems with nonsatisfaction and hesitation degrees but also remarkably reduce the complexity of the nondeterministic polynomial-hard problems.

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