Waist Joint Research Articles

Full-scale loading test for shield tunnel segments: Load-bearing performance and failure patterns of lining structures

To explore the load-bearing performance and the failure patterns of the lining structures, a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system. In the experimental study, the segments’ internal force, convergence deformation, and displacement, and the bolts’ internal force, are analyzed. According to the experimental results, the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage. Three stages are specified for the evolution of the segment’s maximum bending moment during the loading process, in which, the elastic stage is the main and longest stage, in which the bending moment of the segment increases the most. There are two stages for convergence deformation development and segment misalignment development. At the end of loading, the segment’s maximum positive and negative convergence values reach 61.22 and −57.69 mm, respectively. Besides, the maximum segment misalignment is 3.67 mm, which occurs in the direction of 90°. The segment cracks when its maximum convergence value reaches 25.03 mm. Moreover, there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm. The concrete at the waist joint starts fracturing in pieces when the segment’s maximum convergence value reaches 38.93 mm, which is defined as the type of shear failure. Finally, the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.

Full-scale experimental and structural characterization study of shield tunnel reinforcement under ground stacking loads

To investigate the internal force response characteristics and reinforcement effects of the shield tunnel segment structure in the presence of ground load disturbances in the Hangzhou Metro, full-scale tests were conducted on three-ring misaligned assembled segments using a self-developed "Shield Tunnel Segment Hydraulic Loading System." The study examined the structural characteristics of tunnel segments under the influence of different ground resistance coefficients (λ) and eccentric loads (P), and explored the reinforcement effects of the internal tension ring method from multiple perspectives. The research results indicate that under different ground resistance coefficients (λ), the sensitivity of internal force response is concentrated in the waist concrete, with a maximum bending moment reduction of 88.8%. The effective rate of bending stiffness tends to flatten, joint bending moment transfer effects strengthen, and the bearing capacity of the segments significantly increases after reinforcement, leading to a more uniform overall structural response. Under different eccentric loads (P), the bending moment of the segments after reinforcement approximates central symmetry with a reduced distribution range. The rate of change of the effective bending stiffness (η) shifts from "rapid" to "slow," and the variation of joint bending moment transfer coefficient (ζ) stabilizes. The reinforcement with steel rings significantly enhances the overall stiffness of the segments and reinforces the joint bending moment transfer effect. The reinforcement effect of the segments can be evaluated through the bending moment transfer coefficient and effective bending stiffness. After reinforcement, the bearing capacity of the segments is noticeably enhanced, and significant forces are observed at two locations in the right waist joint, where the combination of steel plates and segments exhibits optimal performance.

A Torque Control Strategy for a Robotic Dolphin Platform Based on Angle of Attack Feedback.

Biological fish can always sense the state of water flow and regulate the angle of attack in time, so as to maintain the highest movement efficiency during periodic flapping. The biological adjustment of the caudal fin's angle of attack (AoA) depends on the contraction/relaxation of the tail muscles, accompanying the variation in tail stiffness. During an interaction with external fluid, it helps to maintain the optimal angle of attack during movement, to improve the propulsion performance. Inspired by this, this paper proposes a tail joint motion control scheme based on AoA feedback for the high-speed swimming of bionic dolphins. Firstly, the kinematic characteristics of the designed robot dolphin are analyzed, and the hardware basis is clarified. Second, aiming at the deficiency of the tail motor, which cannot effectively cooperate with the waist joint motor during high-frequency movement, a compensation model for the friction force and latex skin-restoring force is designed, and a joint angle control algorithm based on fuzzy inference is proposed to realize the tracking of the desired joint angle for the tail joint in torque mode. In addition, a tail joint closed-loop control scheme based on angle of attack feedback is proposed to improve the motion performance. Finally, experiments verify the effectiveness of the proposed motion control scheme.

특이성을 고려한 엑소수트의 전신 기반 제어 전략 시뮬레이션

Many human movements can be aided by exo-suit. One of them is that humans put a lot of strain on their knee and waist joints while lifting large objects, but using an exo-suit can lessen the risk. However, since the weight of the exo-suit itself acts as an additional burden on body, an appropriate torque distribution strategy considering the entire system is necessary. To solve this problem, this paper proposed an assistive technique based on whole-body control. Meanwhile, when the legs are fully extended during torque control, the system has a singularity problem and the required torque will be highly increased. Singularity is serious problem because it is essential to fully straighten the legs during the lifting operation. In this paper, this problem was solved by adding a straight-leg term to the whole-body control cost function. The feasibility of the proposed method was verified through simulation, and it was shown that the exo-suit could stably perform lifting motions due to the method.

Mechanism design and workspace analysis of a hexapod robot

Mobile robots are essential for inspection, surveillance, and disaster relief. The legged robot can adapt to challenging terrains such as stairs and debris. The hexapod robot has better stability, payload capability, and fault-tolerant ability than the biped and quadruped robot. This paper proposes a novel hexapod robot composed of two walking platforms and an actively actuated waist joint. The mechanical topology of the robot is determined by comprehensively considering the walking stability, energy consumption, and operating dexterity. The modular leg mechanism is selected by analyzing the reachable workspaces of three typical 2-DOF parallel leg mechanisms. Besides, the analytical method of calculating the reachable workspace of the robot body with shank-ground interferences is studied for the first time, which helps to enhance the efficiency of foothold selection. The feasibility of integrating the analytical workspace in obstacle-surmounting is verified by climbing a 45-degree staircase. Simulations including avoiding obstacles, spot turning, and climbing a staircase are carried out to verify the correctness of the theoretical analysis. A robot prototype is fabricated, and the field experiments corroborate the results of the computational simulations.

Investigation of ultimate bearing capacity of shield tunnel based on concrete damage model

Shield tunnel is usually treated as an underground permanent facility with a design service life of 100 years, its bearing capacity and service performance has attracted extensive attention. Previous studies on the mechanical behavior of shield tunnel are mostly carried out within the framework of elastic or elastoplastic theories. However, when these theories are used to explore the ultimate bearing capacity of shield tunnels, large structural deformation is bound to occur, which leads to crack or damage development and finally structural failure. Therefore, to analyze the damage and failure of shield tunnels, the damage and deterioration characteristics of concrete materials should be considered. Also, the damage mechanics theory is more appropriate to deal with this problem. In this paper, a damage–based analysis method for investigating the ultimate bearing capacity of shield tunnels is proposed. A bi–scalar elastoplastic damage constitutive model based on energy–based stress decomposition is introduced to describe the damage and deterioration behavior of concrete materials. Then, an elaborate numerical model of shield tunnel is developed based on the 3D discontinuous contact model. Moreover, the validity of the proposed method is verified by comparing the simulations with the full–scale experimental results. Then, the ultimate bearing capacity and damage characteristics of shield tunnels in practical underground service conditions are discussed. It is found that the numerical results are generally in good agreement with the experimental data, so that the proposed model can effectively reflect the characteristics of structural deformation, internal force transfer, damage evolution process, failure mode and stress redistribution in the loading process. Also, it is found that the failure process of the tunnel structure can be divided into linear elastic phase, yield–damage phase and failure phase. The range of each phase depends on the loading conditions and surrounding soil constraints. In addition, the integrated stiffness and bearing capacity of the tunnel–soil coupled structure increase with the increase of soil elastic modulus and lateral coefficient of earth pressure. The increase of coupled structural stiffness will also shorten the yield–damage phase and decrease the structural toughness (or ductility). The failure modes of the shield tunnel structure are manifested by the bolt yielding, concrete cracking, and finally, the forming joint plastic hinges on the tunnel crown and waist joints.

Optimal Motion of a Motor Cycle Rider on Sudden Halt

In this paper, a new concept has been proposed to theoretically analyze the forces and torques on the upper body of a human riding on a two wheeler while facing a sudden halt/crash. This approach is applied to different joints by using a musculoskeletal model of the upper body. The optimal motion of the upper body during the sudden halt/crash is obtained by converting the multi degree of freedom control problem to a parameter based problem to study the nature and modes of response following a shock. A mathematical model with reduced degrees of freedom is proposed that retains the essential features of the motion most probable in the direction of the original velocity and the same (a non-linear formulation) is numerically investigated to find out the forces and torques on the thorasic trunk and the head-neck with the waist joint together with the displacements.

A 3-DOF Bionic Waist Joint for Humanoid Robot.

In this study, a 3 degree-of-freedom bionic waist joint was developed with coupled tendon-driven mechanism. This bionic waist joint can not only ensure the safety of the human-robot interface, but also increase the load capacity without increasing the weight. The coupled tendon-driven mechanism enables the motion of each joint to be driven by at least two motors together, and enables a maximum torque of 3 times the maximum motor output torque at each joint. The bionic waist joint has similar kinematic characteristics to a human waist, including degrees of freedom (DOF) and range of motion (ROM). The problem of coexistence of coupling and decoupling in the same rotating joint was solved with a novel mechanism that can promote further versatility of the coupled tendon-driven mechanism. The basic movements and characteristics of the waist was validated in the experiment.

Fault tolerant control based on backstepping nonsingular terminal integral sliding mode and impedance control for a lower limb exoskeleton

In this paper, an active fault-tolerant control scheme is proposed for a lower limb exoskeleton, based on hybrid backstepping nonsingular fast terminal integral type sliding mode control and impedance control. To increase the robustness of the sliding mode controller and to eliminate the chattering, a nonsingular fast terminal integral type sliding surface is used, which ensures finite time convergence and high tracking accuracy. The backstepping term of this controller guarantees global stability based on Lyapunov stability criterion, and the impedance control reduces the interaction forces between the user and the robot. This controller employs a third order super twisting sliding mode observer for detecting, isolating ad estimating sensor and actuator faults. Motion stability based on zero moment point criterion is achieved by trajectory planning of waist joint. Furthermore, the highest level of stability, minimum error in tracking the desired joint trajectories, minimum interaction force between the user and the robot, and maximum system capability to handle the effect of faults are realized by optimizing the parameters of the desired trajectories, the controller and the observer, using harmony search algorithm. Simulation results for the proposed controller are compared with the results obtained from adaptive nonsingular fast terminal integral type sliding mode control, as well as conventional sliding mode control, which confirm the outperformance of the proposed control scheme.

Effects of Health Qigong in Improving the Cervical and Lumbar Disc Disease and Mental Health Status of Sedentary Young and Middle-Aged Faculties.

Background:Shoulder, neck, and back discomforts and abdominal obesity caused by sedentariness are increasingly prominent in young and middle-aged population groups. Health Qigong improves physical functions and strengthens the disease resistance of exercisers. This study aims to explore health Qigong intervention’s effects on the cervical vertebra, lumbar vertebra, and mental status.Methods:A total of 108 sedentary young and middle-aged faculties from Yantai University in China were recruited from July to December 2020 and randomly classified into the experimental and control groups. The former received health Qigong exercises for 12 weeks, and the latter was not intervened. The total general skeletal muscle mass, range of neck joint motion, mental health, and range of waist joint motion of all respondents before and after the intervention were tested and calculated.Results:The body fat rate of the experimental group after intervention was significantly lower than that before intervention (P<0.05). The skeletal muscle mass (SMM) value was significantly higher than that before intervention. The experimental group had lower body fat rate but higher SMM value than the control group after the intervention. In addition, the range of motion (ROM) of the cervical vertebra was significantly higher in the experimental group than in the control group after intervention. Somatization, obsessive/compulsive disorder, interpersonal sensitivity, depression, anxiety, hostility, paranoia, and SCL-90 total score of the experimental group after intervention decreased significantly compared with that before intervention (P<0.05).Conclusion:Health Qigong improves the ROM of cervical and lumbar vertebrae and the mental health status of sedentary young and middle-aged groups.

Design and Experimental Validation of a 3-DOF Force Feedback System Featuring Spherical Manipulator and Magnetorheological Actuators

This research focuses on the development of a new 3-DOF (Degree of Freedom) force feedback system featuring a spherical arm mechanism and three magnetorheological (MR) brakes, namely two rotary MR brakes and one linear MR brake. The first rotary MR brake is integrated in the waist joint to reflect the horizontal tangent force, the other rotary MR brake is integrated in the shoulder joint to reflect the elevation tangent force, while the linear MR brake is integrated in the sliding joint of the arm to reflect the radial force (approach force). The proposed configuration can reflect a desired force to the operator at the end-effectors of the arm independently in 3 DOFs by controlling the current applied to the coils of the MR brakes. After the introduction, the configuration of the proposed force feedback system is presented. Afterward, the design and conducted simulation of the MR brakes for the systems are provided. The prototype of the force feedback system, which was manufactured for the experiment, is then presented as well as some of the obtained experimental results. Finally, the proposed control system is presented and its implementation to provide a desired feedback force to the operator is provided.

플로어볼 운동선수의 운동경력에 따른 무릎, 허리관절의 등속성 근기능 연구

이 연구는 5년이상 경력을 가진 플로어볼 남자선수 10명과 1년이하 경력을 가진 플로어볼 남자선수 10명을 대상으로 신전근력과 굴곡 근력을 차이 및 관련성을 검증하기 위해 실시하였다. 차이검증을 위해서 각 집단별 측정 항목의 평균(Mean)과 표준편차(Standard deviation)를 산출하였으며 Independent t-test를 이용하였다. 유의수준은 p.05로 설정하였다. 그 결과 오른쪽 무릎관절 신전과 굴곡 60°/sec의 최대 근력(p.01), 180°/sec의 근지구력비 신전(p.01)이 유의하게 나타났고, 굴곡에서는 유의한 차이는 없는 것으로 나타났다. 왼쪽 무릎관절 신전과 굴곡 60°/sec의 최대 근력(p.01), 180°/sec의 근지구력비 신전(p.05)이 유의하게 나타났고, 굴곡에서는 유의한 차이는 없는 것으로 나타났다. 허리관절 신전과 굴곡 30°/sec에서 등속성 운동능력인 최대근력 신전(p.05)과 굴곡(p.01), 180°/sec에서 등속성 운동능력인 근지구력비의 신전에서 유의한 차이가 나타났으며 굴곡에서는 유의한 차이는 없는 것으로 나타났다. 따라서 5년이상 경력 선수들의 하지의 근력, 근 파워, 근지구력비를 향상시키기 위해 실시되는 운동은 절대근력 향상 및 햄스트링 근력 강화를 통해 근력의 균형적 발달을 모색해야 할 것으로 사료되고, 본 연구를 통하여 플로어볼 선수들의 경기력 증진 및 체력 보강 훈련에 적용할 자료를 제시하고자 한다.

The Gait Design and Trajectory Planning of a Gecko-Inspired Climbing Robot.

Inspired by the dynamic gait adopted by gecko, we had put forward GPL (Gecko-inspired mechanism with a Pendular waist and Linear legs) model with one passive waist and four active linear legs. To further develop dynamic gait and reduce energy consumption of climbing robot based on the GPL model, the gait design and trajectory planning are addressed in this paper. According to kinematics and dynamics of GPL, the trot gait and continuity analysis are executed. The effects of structural parameters on the supporting forces are analyzed. Moreover, the trajectory of the waist is optimized based on system energy consumption. Finally, a bioinspired robot is developed and the prototype experiment results show that the larger body length ratio, a certain elasticity of the waist joint, and the optimized trajectory contribute to a decrease in the supporting forces and reduction in system energy consumption, especially negative forces on supporting feet. Further, the results in our experiments partly explain the reasonability of quadruped reptile's kinesiology during dynamic gait.

The ultimate bearing capacity of rectangular tunnel lining assembled by composite segments: An experimental investigation

In this paper, full-scale loading tests were performed on a rectangular segmental tunnel lining, which was assembled by steel composite segments, to investigate its load-bearing structural behavior and failure mechanism. The tests were also used to confirm the composite effect by adding concrete inside to satisfy the required performance under severe loading conditions. The design of the tested rectangular segmental lining and the loading scheme are also described to better understand the bearing capacity of this composite lining structure. It is found that the structural ultimate bearing capacity is governed by the bond capacity between steel plates and the tunnel segment. The failure of the strengthened lining is the consequence of local failure of the bond at waist joints. This led to a fast decrease of the overall stiffness and eventually a loss of the structural integrity.

腰部の形状を考慮した空気圧アクチュエータによる内骨格型パワーアシストスーツの開発および補助効果検証

Recently, about 60% of worker suffers from low back pain in Japan. Hard working such as lifting and carrying provides a load to waist joint, and worker gets low back pain. So, we developed a power assist suit to reduce the load of waist joint. This assist suit has various futures; endoskeleton, high output and flexibility, because this device moves using two pneumatic actuators. This device generates active and passive assistive force. These forces can assist human motions according as situations. First of all, we analyzed the human motion by motion capturing software. The analysis results are substituted into human link model, and load of human body is estimated. Thus, we decided design and operation method of the assist suit using analysis results and a static assist suit model. The motion of wearer is “lifting up motion” and “carrying motion” in evaluation experiments, because these motions are frequently performed in manufacturing plant work. Each assistive force assists these motions, and effectiveness of assist suit was confirmed from decrease of electromyography (EMG) in wearing.

Fuzzy control-based real-time robust balance for a humanoid robot

This paper studies and implements a real-time robust balance control for a humanoid robot under three environment disturbances which are an external thrust, an inclinable platform, and a see-saw. More precisely to say, the robot with robust control can resist an external thrust, stand on a two-axis inclinable platform, or walk on a see-saw successfully. The main feature of the robot is that it has a waist joint which has three degrees of freedom. With the aids of the proposed fuzzy controllers, the robot can change the posture of the body nimbly by adjusting the waist joint and two ankle joints to strengthen the stabilization capacity. The sensory system of the robot includes eight force sensors and one inertial measurement unit sensor in order to measure the center of pressure and the slant angle of the robot’s body. According to the measured data from the sensors and by imitating human reflex actions, the proposed fuzzy controllers perform real-time balance control for the robot under three environment disturbances. According to the experiment results, the stability of the robot is increased at least 32.2 and 61.7% under the first two environment disturbances, respectively. In addition, the robot walking on a see-saw has a success rate of about 95%.

The effect of waist twisting on walking speed of an amphibious salamander like robot

Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion. A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems (ADAMS) and physical experiments verify the rationality and validity of this expression.

A Wheel-legged Robot with Active Waist Joint: Design, Analysis, and Experimental Results

This paper presents a wheel-legged robot that features an active waist joint. The proposed wheel-legged robot is composed of a front module, a rear module, and an active waist joint. The proposed robot can perform rectilinear motion and turning motion in both wheeled and legged modes. The active waist joint module is added to make the robot pass through the curved narrow channel. Several experiments have been done to evaluate the performance of the proposed wheel-legged robot. The maximum velocities of the proposed robot in wheeled and legged modes are 17.2 and 10.4 m/min respectively. And the average corresponding deflection rates of the proposed robot in wheeled and legged modes are 3.1 and 3.7 % respectively. The mobility efficiencies of the robot in wheeled and legged modes are up to 96.3 and 94.3 % respectively. Compared with the proposed robot in legged mode, the performance in the turning motion with the active waist joint is better when the proposed robot is in wheeled mode. Two approaches of climbing obstacles are proposed for the proposed robot in legged mode. The wheel-legged robot can climb an obstacle with maximum height of 10 cm.

Nonlinear Identification of a PUMA Manipulator Arm MA2000

This article deals with the tuning of a simplified non-linear model that represents the dynamic behavior of the manipulator arm PUMA MA2000, where excitation signals formed by a finite sum of harmonics Fourier series were used in order to obtain arm dynamical responses. Initially, non-linear mathematical model is derived by using the Euler-Lagrange notation, and then a simplified nonlinear model is obtained and tuned by using the experimental angular position measurements for waist, shoulder and elbow robot joints.

허리 구조를 갖는 복합 바퀴-다리 이동형 로봇의 설계

본 논문에서는 허리 구조를 갖는 복합 바퀴-다리 이동형 로봇의 설계 방법을 제안한다. 제안된 복합 이동형 로봇은 비평탄 및 평탄 지형에서의 효과적인 이동을 위하여 로봇의 다리에 바퀴가 결합된 복합 바퀴-다리 구조와 로봇 주행 중 보행 자세로의 안정적인 전환과 비평탄 지형에서 기구적인 제한의 개선을 위하여 허리 관절을 갖는 구조로 설계하였다. 또한 다양한 지형을 인지하기 위하여 LRF센서, PSD센서, CCD 카메라를 사용하였다. 제안한 로봇 시스템의 검증을 위해 지형별 주행과 보행 자세를 선택할 수 있는 운동 계획 기법을 제안하였다. 실제 복합 바퀴-다리 이동형 로봇을 설계 및 제작하고, 제안된 운동계획을 사용한 실험을 통해 지형에 따른 효율적인 이동 성능을 검증하였다. In this paper, we design a hybrid wheeled and legged mobile robot with a waist joint. The proposed hybrid mobile robot is designed to have a hybrid structure with leg and wheel for the efficient movement in flat and uneven surfaces. The proposed robot have a waist joint that is used to stably transform from wheeled driving to legged walking of the robot and to overcome non-flat surface. In order to recognize various environments we use LRF sensor, PSD sensor, CCD camera. Also, a motion planning method for hybrid mobile robot with a waist joint is proposed to select wheeled driving motion and legged walking motion of the robot based the environment types. We verify the efficient mobility of the developed hybrid mobile robot through navigation experiments using the proposed motion planning method in various environments.