Objective： To compare differences of acupotomy loosing combined with medication treatment, electroacupuncture combined with medication treatment and simple medication treatment in effects on rheumatoid arthritis pati...Objective： To compare differences of acupotomy loosing combined with medication treatment, electroacupuncture combined with medication treatment and simple medication treatment in effects on rheumatoid arthritis patients with elbow joint stiffness and investigate the anti-inflammatory mechanism of the acupotomy loosing.Methods： A total of 60 cases of rheumatoid arthritis（RA） patients with elbow joint stiffness were randomly assigned into the group receiving acupotomy loosing（group A）, group with electroacupuncture（group B） and the one undergoing medication treatment（group C） with 20 cases for each group. Based on the medication treatment, all patients underwent continuous oral administration with Methotrexate（MTX）, Leflunomide（LEF） and Bitongding capsules for 3 weeks. And no other treatments were given to group C. In addition to medications treatment, the electroacupuncture was performed in group B. The acupoints of Tianzhu（天柱 BL 10）,DAzhui（大椎 GV 14）; Fengchi（风池 GB 20）,Quchi（曲池 LI 11）,Quze（曲泽 PC 3）,Chize（尺泽 LU 5）, Shousanli（手三里 LI 10）, Xiaohai（小海 SI 8）, Shaohai（少海 HT 3）, Tianjing（天井 TE 10）,Qinglengyuan（清冷渊 TE 11） and Hegu（合谷 LI 4） in the affected side were selected. A pair of electrodes were connected to LI 11 and LI 10, and another pair of electrodes were connected to PC 3 and LU 5, and the continuous wave with frequency of 2 Hz was designed, the needle retention for 30 min was performed, and the acupuncture was performed for 6 times per week with 3 weeks for one course,and there was one course totally. Besides the medication treatment, group A underwent the acupotomy loosing therapy. The tender point in lateral elbow joint, etc. were taken as the treatment point, and 6-8 treatment points being taken for each time, and longitudinal dredging and transverse exfoliation were conducted for 2-3 times with the acupotomy. The treatment was given for one time per week with three weeks for one course, and there was one course totally. The changes of maximum angle of active extension position, maximum angle of active flexion position and range of motion were observed, and levels of IL-6, IL-10 and TNF-a in affected synovial fluid of elbow joint were tested before the treatment and 2 weeks after the treatment in the groups.Results： ① Compared with those before treatment, the maximum angle of active extension position were smaller, the maximum angle of active flexion position were larger and the range of motion were wider of the affected elbow joints of the patients in the 3 groups on the 2 weeks after the treatment.There were statistical significances for the differences（All P 0.05）. Two weeks after the treatment,as compared with those in group C, the affected elbow joint for patients in the group B and group A was smaller in maximum angle of active extension position, larger in maximum angle of active flexion position and wider in range of motion and there were statistical significances for the differences（All P 0.05）. Comparing with those in the group B, the affected elbow joint for patients in the group A was smaller in maximum angle of active extension position, larger in maximum angle of active flexion position and wider in range of motion and there were the statistical significances for the differences（All P 0.05）. ② Compared with those before treatment, the levels of TNF-a and IL-6 were lower and the level of IL-10 was higher of the 3 groups on the 2 weeks after the treatment. There were the statistical significances for the differences（All P 0.05）. For 2 weeks after the treatment, compared with those in the group C, group B and group A were lower in levels of TNF-α and IL-6 and higher in level of IL-10 and there were the statistical significances for the differences（All P 0.05）. As compared with those in the group B, group A was lower in levels of TNF-a and IL-6 and higher in level of IL-10 and there were the statistical significances for the differences（All P 0.05）.Conclusions： The combination of acupotomy loosing can improve the maximum angle of active extension position, maximum angle of active flexion position and range of motion in affected elbow joint for RA patients with elbow joint stiffness, whose efficacy was superior to single basic treatment and electroacupuncture combined with basic treatment. Meanwhile, the levels of proinflammatory cytokines,such as TNF-α and IL-6 can be decreased, and the level of anti-inflammatory cytokines, such as IL-10 can be increased, playing a role in regulating the imbalance between proinflammatory cytokines and anti-inflammatory cytokines in RA patients, which may be one of mechanisms regarding treating RA and improving the range of motion for stiff joints.展开更多
Recent research has shown that circular hollow section(CHS) joints may exhibit non-rigid behavior under axial load or bending. The non-rigid behavior significantly affects the mechanical performance of structures. Thi...Recent research has shown that circular hollow section(CHS) joints may exhibit non-rigid behavior under axial load or bending. The non-rigid behavior significantly affects the mechanical performance of structures. This paper is concerned with the parametric formulae for predicting axial stiffness of CHS X-joints while braces are in tension. The factors influencing the axial stiffness of CHS X-joints under brace axial tension are investigated,including the joint geometric parameters,the axial force of the chord,and bending moments of braces in two directions,etc. Effects of various parameters on axial stiffness of CHS X-joints are examined by systematic single-parameter nonlinear analysis using shell finite element methods. The analysis is implemented in a finite element code,ANSYS. The observed trends form the basis of the formulae for calculating the joint axial stiffness under brace axial tension by multivariate regression technique. In order to simplify the formulae,two non-dimensional variables are introduced. The proposed formulae can be used to calculate the joint axial stiffness in the design of single-layer steel tubular structures.展开更多
The relative stiffness between underground structures and surrounding soil may significantly influence the dynamic response of such structures.In this study,two underground pipelines were fabricated using rubber joint...The relative stiffness between underground structures and surrounding soil may significantly influence the dynamic response of such structures.In this study,two underground pipelines were fabricated using rubber joints with varying stiffness,and the corresponding dynamic response was evaluated.Model soils were prepared based on similarity ratios.Next,reduced-scale shaking table tests were conducted to investigate the impact of circular underground structures with varying stiffness joints on the amplification of ground acceleration,dynamic response,and deformation patterns of the underground pipelines.The comparative analysis showed that structures with lower stiffness exert less constraint on the surrounding soil,resulting in a higher amplification factor of ground acceleration.The seismic response of less stiff structures is generally 1.1 to 1.3 times the response of the stiffer structures.Therefore,the seismic response of the variable stiffness pipeline exhibits pronounced characteristics.Rubber joints effectively reduce the seismic response of underground structures,demonstrating favorable isolation effects.Consequently,relative stiffness plays a crucial role in the seismic design of underground structures,and the use of rubber materials in underground structures is advantageous.展开更多
Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between h...Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between human and robots,rather than strictly limiting the human-robot motion.However,most researchers focus on the variable stiffness features of flexible joints,but few evaluate the performance of the flexible joint in the human-robot collision.Therefore,the performance of two typical flexible joints,including the series elastic joint(SEJ)and the passive variable stiffness joint(PVSJ),are compared through dynamic collision experiments.The results demonstrate that the SEJ absorbs 40.7%-58.7%of the collision force and 34.2%-45.2%of the collision torque in the driven-torque below 4 N·m and driven-speed of 3-7(°)/s,which is more stable than PVSJ.In addition,the stiffness error of SEJ is measured at 5.1%,significantly lower than the 23.04%measured in the PVSJ.The huge stiffness error of PVSJ leads to its unreliability in buffering collision.Furthermore,we analyze results and confirm that SEJ has a more stable human-robot safety performance in buffering dynamic collision.Consequently,the SEJ is suitable in SRLs for human-robot safety in our scenario.展开更多
To evaluate the columnar jointed basalts in the dam site of Baihetan hydropower station in southwest China, we developed a basic conceptual model of single jointed rock mass. Considering that the rock mass deformation...To evaluate the columnar jointed basalts in the dam site of Baihetan hydropower station in southwest China, we developed a basic conceptual model of single jointed rock mass. Considering that the rock mass deformation consists of rock block deformation and joints deformation, the linear mechanical characteristics of the cell (including the elastic joints and the nonlinear mechanical behaviors of the cell) with a combined frictional-elastic interface were analyzed. We developed formulas to calculate the rock block deformation, which can be adapted for multiple jointed rock mass and columnar jointed basalts. The formulas are effective in calculating the equivalent modulus of multiple jointed rock mass, and precisely reveal the anisotropic properties of columnar jointed basalts. Furthermore, the in situ rigid bearing plate tests were analyzed and calculated, and the types of loading-unloading curves and the equivalent modulus along different directions of columnar jointed basalts were obtained. The analytical results are in close compliance with the test results.展开更多
In the process of 2-D compressional wave propagation in a rock mass with multiple parallel joints along the radian direction normal to the joints, the maximum possible wave amplitude corresponding to the points betwee...In the process of 2-D compressional wave propagation in a rock mass with multiple parallel joints along the radian direction normal to the joints, the maximum possible wave amplitude corresponding to the points between the two adjacent joints in the joint set is controlled by superposition of the multiple transmitted and the reflected waves, measured by the maximum rebound ratio. Parametric studies on the maximum rebound ratio along the radian direction normal to the joints were performed in universal distinct element code. The results show that the maximum rebound ratio is influenced by three factors, i.e., the normalized normal stiffness of joints, the ratio of joint spacing to wavelength and the joint from which the wave rebounds. The relationship between the maximum rebound ratio and the influence factors is generalized into five charts. Those charts can be used as the prediction model for estimating the maximum rebound ratio.展开更多
The stability and ductility of four buckling-restrained braces (BRBs) with brace joints were studied. The load-carrying element of BRB was fabricated with steel (Chinese Q235), and a layer of colloidal silica sheet (0...The stability and ductility of four buckling-restrained braces (BRBs) with brace joints were studied. The load-carrying element of BRB was fabricated with steel (Chinese Q235), and a layer of colloidal silica sheet (0.5 mm in thickness) or four layers of plastic film (0.2 mm in thickness) were used as unbonding materials to provide space to prevent the buckling of inner core in higher modes and facilitate its lateral expansion in case of compression. Based on the equation of BRBs with brace joints of different restrained stiffnesses, the buckling load is calculated considering the initial geometric imperfections and residual stress, and the theoretical values agree well with the experiment results. It is concluded that the buckling load and ductility of BRBs are influenced greatly by the restrained stiffness of brace joints. If the restrained stiffness is deficient, the unstrained segment of BRBs with less stiffness will buckle firstly. As a result, the ultimate load of BRBs decreases, and the maximum compression load is reduced to about 65% of the maximum tension load; the stiffness also degenerates, and there is a long decreasing stage on the back-bone curve in compression phase; the ductility decreases, i.e., the ultimate tension ductility and ultimate compression ductility are approximately 15 and 1.3 respectively, and the cumulative plastic ductility is only approximately 200. If the restrained stiffness of joint is large enough, the stability will be improved as follows: the yielding strength and ultimate strength of BRBs are nearly the same, and there is an obvious strain intensification in both tension and compression phases; the ductility of brace also increases obviously, i.e., the ultimate tension ductility and ultimate compression ductility are both approximately 14, and the cumulative plastic ductility reaches 782.展开更多
Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in the...Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in theoretical and numerical analysis of wave propagation across rock discontinuity.However,the circumstance under which the DDM is applicable to predict wave propagation across rock discontinuity remains poorly understood.In this study,theoretical analysis and ultrasonic laboratory tests were carried out to examine the theoretical applicability of the DDM for wave propagation,where specimens with rough joints comprising regular rectangular asperities of different spacings and heights were prepared by 3D printing technology.It is found that the theoretical applicability of the DDM to predict wave propagation across rock discontinuity is determined by three joint parameters,i.e.the dimensionless asperity spacing(L),the dimensionless asperity height(H)and the groove density(D).Through theoretical analysis and laboratory tests,the conditions under which the DDM is applicable are derived as follows:and,.With increase in the groove density,the thresholds of the dimensionless asperity spacing and the dimensionless asperity height show a decreasing trend.In addition,the transmission coefficient in the frequency domain decreases with increasing groove density,dimensionless asperity spacing or dimensionless asperity height.The findings can facilitate our understanding of DDM for predicting wave propagation across rock discontinuity.展开更多
ABSTRACT:Knee osteoarthritis(KOA),a complicated peripheral joint disorder,can be caused by non-modifiable and modifiable risk factors.At present,the treatment for osteoarthritis is mainly to manage symptoms and improv...ABSTRACT:Knee osteoarthritis(KOA),a complicated peripheral joint disorder,can be caused by non-modifiable and modifiable risk factors.At present,the treatment for osteoarthritis is mainly to manage symptoms and improve quality of life.Although some patients with osteoarthritis may choose pharmacological agents for pain relief,it has been confirmed that a variety of preparations and doses of pharmacological agents were ineffective.In recent years,Traditional Chinese medicine(TCM)has been shown unique superiorities in the treatment of osteoarthritis,including KOA.Therefore,this article primarily investigated the key points of common syndromes,TCM nursing methods and healthy guidance of KOA,aiming at maintaining and developing the strengths of TCM,improving its efficacy and standardizing its behavior.展开更多
In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidim...In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidimensional translational spring model, in which each finger is constructed with prismatic joints. Human hands and the most developed mechanical hands are constructed with revolute joints. In this paper, the effects of fingertip rotation and a revolute joint spring model are investigated. A grasp stiffness matrix is analytically derived by considering not only frictional rolling contact but also frictionless sliding contact. The difl＇erence between the frictional stiffness matrix and the frictionless one is analytically obtained. The effect of local curvature at contact points is analytically derived. The grasp displacement directions affected by the change in curvature and the contact condition are also obtained. The derived stiffness matrix of the revolute joint model is compared with that of the prismatic joint model, and then the stiffness relation is clarified. The gravity effect of the object is also considered. The effectiveness of our method is demonstrated through numerical examples. The stability is evaluated by the eigenvalues of the grasp stiffness matrix, and the grasp displacement direction is obtained by the corresponding eigenvectors. The effect of joint angle is also discussed.展开更多
The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleratio...The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.展开更多
The physical compliance of interaction is an important requirement for safe and efficient collaboration between robots and humans,and the realization of human–robot compliance requires robot joints with variable stif...The physical compliance of interaction is an important requirement for safe and efficient collaboration between robots and humans,and the realization of human–robot compliance requires robot joints with variable stiffness similar to those of human joints.In this study,based on the tissue structure and driving principle of the human arm muscle ligament,a robot joint with variable stiffness is designed,consisting of an elastic belt and serial elastic actuator in parallel.The variable stiffness of the joint is realized by adjusting the tension length of the elastic belt.Surface electromyography(sEMG)signals of the human arm are used as the characterization quantity of joint stiffness to establish the pseudostiffness model of the elbow joint.The stiffness of the robot joints is adjusted in real-time to match the human arm stiffness based on the changes in sEMG signals of the human arm during operation.Real-time compliant interaction of human–robot collaboration is realized based on an end stiffness matching strategy.Additionally,to verify the effectiveness of the human joint stiffness matching-based compliance control strategy,a human–robot cooperative lifting experiment was designed.The bionic variable stiffness joint shows good stiffness adjustment,and the human–robot joint stiffness matching strategy based on human sEMG signals can improve the effectiveness and comfort of human–robot collaboration.展开更多
Objective: the theme of this study is to explore the clinical effect of systematic rehabilitation training for children with various types of cerebral palsy. Methods: all the children involved in this study were 130 c...Objective: the theme of this study is to explore the clinical effect of systematic rehabilitation training for children with various types of cerebral palsy. Methods: all the children involved in this study were 130 children with cerebral palsy aged 6 to 16 years old who were adopted by our hospital from 2012 to 2019, including 62 children with spasmodic cerebral palsy (47 of whom underwent tendon release), 13 children with athetosis of hand and foot, and the rest 55 children with mixed type. Review the children's participation in rehabilitation training, whether to adhere to rehabilitation training was divided into two equal groups: control group and experimental group. 65 children in the control group received intermittent rehabilitation training due to foster care and other reasons, and 65 children in the experimental group received continuous rehabilitation training. At the same time, the differences of movement, posture and self-care ability between the two groups were observed and compared. Results: after using different rehabilitation training methods, the movement, posture and self-care ability of children in the two groups changed, but the total effective rate of children in the control group after intermittent rehabilitation training was 78.5%, while the total effective rate of children in the experimental group after continuous and systematic rehabilitation training was 95.4%. The data between the two groups were processed by statistical tools, and the results showed significant (P < 0.05). Conclusion: according to the above description, the application of continuous rehabilitation training in children with cerebral palsy can significantly improve movement disorders and poor posture, prevent joint stiffness and muscle atrophy, and effectively improve self-care ability.展开更多
基金Supported by 2014 Wuhan clinical medical research project:WZ14C01~~
文摘Objective： To compare differences of acupotomy loosing combined with medication treatment, electroacupuncture combined with medication treatment and simple medication treatment in effects on rheumatoid arthritis patients with elbow joint stiffness and investigate the anti-inflammatory mechanism of the acupotomy loosing.Methods： A total of 60 cases of rheumatoid arthritis（RA） patients with elbow joint stiffness were randomly assigned into the group receiving acupotomy loosing（group A）, group with electroacupuncture（group B） and the one undergoing medication treatment（group C） with 20 cases for each group. Based on the medication treatment, all patients underwent continuous oral administration with Methotrexate（MTX）, Leflunomide（LEF） and Bitongding capsules for 3 weeks. And no other treatments were given to group C. In addition to medications treatment, the electroacupuncture was performed in group B. The acupoints of Tianzhu（天柱 BL 10）,DAzhui（大椎 GV 14）; Fengchi（风池 GB 20）,Quchi（曲池 LI 11）,Quze（曲泽 PC 3）,Chize（尺泽 LU 5）, Shousanli（手三里 LI 10）, Xiaohai（小海 SI 8）, Shaohai（少海 HT 3）, Tianjing（天井 TE 10）,Qinglengyuan（清冷渊 TE 11） and Hegu（合谷 LI 4） in the affected side were selected. A pair of electrodes were connected to LI 11 and LI 10, and another pair of electrodes were connected to PC 3 and LU 5, and the continuous wave with frequency of 2 Hz was designed, the needle retention for 30 min was performed, and the acupuncture was performed for 6 times per week with 3 weeks for one course,and there was one course totally. Besides the medication treatment, group A underwent the acupotomy loosing therapy. The tender point in lateral elbow joint, etc. were taken as the treatment point, and 6-8 treatment points being taken for each time, and longitudinal dredging and transverse exfoliation were conducted for 2-3 times with the acupotomy. The treatment was given for one time per week with three weeks for one course, and there was one course totally. The changes of maximum angle of active extension position, maximum angle of active flexion position and range of motion were observed, and levels of IL-6, IL-10 and TNF-a in affected synovial fluid of elbow joint were tested before the treatment and 2 weeks after the treatment in the groups.Results： ① Compared with those before treatment, the maximum angle of active extension position were smaller, the maximum angle of active flexion position were larger and the range of motion were wider of the affected elbow joints of the patients in the 3 groups on the 2 weeks after the treatment.There were statistical significances for the differences（All P 0.05）. Two weeks after the treatment,as compared with those in group C, the affected elbow joint for patients in the group B and group A was smaller in maximum angle of active extension position, larger in maximum angle of active flexion position and wider in range of motion and there were statistical significances for the differences（All P 0.05）. Comparing with those in the group B, the affected elbow joint for patients in the group A was smaller in maximum angle of active extension position, larger in maximum angle of active flexion position and wider in range of motion and there were the statistical significances for the differences（All P 0.05）. ② Compared with those before treatment, the levels of TNF-a and IL-6 were lower and the level of IL-10 was higher of the 3 groups on the 2 weeks after the treatment. There were the statistical significances for the differences（All P 0.05）. For 2 weeks after the treatment, compared with those in the group C, group B and group A were lower in levels of TNF-α and IL-6 and higher in level of IL-10 and there were the statistical significances for the differences（All P 0.05）. As compared with those in the group B, group A was lower in levels of TNF-a and IL-6 and higher in level of IL-10 and there were the statistical significances for the differences（All P 0.05）.Conclusions： The combination of acupotomy loosing can improve the maximum angle of active extension position, maximum angle of active flexion position and range of motion in affected elbow joint for RA patients with elbow joint stiffness, whose efficacy was superior to single basic treatment and electroacupuncture combined with basic treatment. Meanwhile, the levels of proinflammatory cytokines,such as TNF-α and IL-6 can be decreased, and the level of anti-inflammatory cytokines, such as IL-10 can be increased, playing a role in regulating the imbalance between proinflammatory cytokines and anti-inflammatory cytokines in RA patients, which may be one of mechanisms regarding treating RA and improving the range of motion for stiff joints.
文摘Recent research has shown that circular hollow section(CHS) joints may exhibit non-rigid behavior under axial load or bending. The non-rigid behavior significantly affects the mechanical performance of structures. This paper is concerned with the parametric formulae for predicting axial stiffness of CHS X-joints while braces are in tension. The factors influencing the axial stiffness of CHS X-joints under brace axial tension are investigated,including the joint geometric parameters,the axial force of the chord,and bending moments of braces in two directions,etc. Effects of various parameters on axial stiffness of CHS X-joints are examined by systematic single-parameter nonlinear analysis using shell finite element methods. The analysis is implemented in a finite element code,ANSYS. The observed trends form the basis of the formulae for calculating the joint axial stiffness under brace axial tension by multivariate regression technique. In order to simplify the formulae,two non-dimensional variables are introduced. The proposed formulae can be used to calculate the joint axial stiffness in the design of single-layer steel tubular structures.
基金Key International(Regional)Joint Research Project under Grant No.52020105002National Natural Science Foundation of China under Grant No.51991393。
文摘The relative stiffness between underground structures and surrounding soil may significantly influence the dynamic response of such structures.In this study,two underground pipelines were fabricated using rubber joints with varying stiffness,and the corresponding dynamic response was evaluated.Model soils were prepared based on similarity ratios.Next,reduced-scale shaking table tests were conducted to investigate the impact of circular underground structures with varying stiffness joints on the amplification of ground acceleration,dynamic response,and deformation patterns of the underground pipelines.The comparative analysis showed that structures with lower stiffness exert less constraint on the surrounding soil,resulting in a higher amplification factor of ground acceleration.The seismic response of less stiff structures is generally 1.1 to 1.3 times the response of the stiffer structures.Therefore,the seismic response of the variable stiffness pipeline exhibits pronounced characteristics.Rubber joints effectively reduce the seismic response of underground structures,demonstrating favorable isolation effects.Consequently,relative stiffness plays a crucial role in the seismic design of underground structures,and the use of rubber materials in underground structures is advantageous.
基金supported by the Na⁃tional Natural Science Foundation of China(No.U22A20204)the Innovation Foundation from National Clinical Research Center for Orthopedics,Sports Medicine&Rehabilitation Foundation(No.23-NCRC-CXJJ-ZD3-8)。
文摘Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between human and robots,rather than strictly limiting the human-robot motion.However,most researchers focus on the variable stiffness features of flexible joints,but few evaluate the performance of the flexible joint in the human-robot collision.Therefore,the performance of two typical flexible joints,including the series elastic joint(SEJ)and the passive variable stiffness joint(PVSJ),are compared through dynamic collision experiments.The results demonstrate that the SEJ absorbs 40.7%-58.7%of the collision force and 34.2%-45.2%of the collision torque in the driven-torque below 4 N·m and driven-speed of 3-7(°)/s,which is more stable than PVSJ.In addition,the stiffness error of SEJ is measured at 5.1%,significantly lower than the 23.04%measured in the PVSJ.The huge stiffness error of PVSJ leads to its unreliability in buffering collision.Furthermore,we analyze results and confirm that SEJ has a more stable human-robot safety performance in buffering dynamic collision.Consequently,the SEJ is suitable in SRLs for human-robot safety in our scenario.
基金Project (Nos. 50911130366 and 2011CB013504) supported by the National Natural Science Foundation of Chinathe Postdoctoral Advanced Research Programs Class Ⅱ of Zhejiang Province (No. BSH1302013), China
文摘To evaluate the columnar jointed basalts in the dam site of Baihetan hydropower station in southwest China, we developed a basic conceptual model of single jointed rock mass. Considering that the rock mass deformation consists of rock block deformation and joints deformation, the linear mechanical characteristics of the cell (including the elastic joints and the nonlinear mechanical behaviors of the cell) with a combined frictional-elastic interface were analyzed. We developed formulas to calculate the rock block deformation, which can be adapted for multiple jointed rock mass and columnar jointed basalts. The formulas are effective in calculating the equivalent modulus of multiple jointed rock mass, and precisely reveal the anisotropic properties of columnar jointed basalts. Furthermore, the in situ rigid bearing plate tests were analyzed and calculated, and the types of loading-unloading curves and the equivalent modulus along different directions of columnar jointed basalts were obtained. The analytical results are in close compliance with the test results.
基金Projects(50278057) supported by the National Natural Science Foundation of China project(2002CB412703) supported by Major State Basic Research Development Program of China
文摘In the process of 2-D compressional wave propagation in a rock mass with multiple parallel joints along the radian direction normal to the joints, the maximum possible wave amplitude corresponding to the points between the two adjacent joints in the joint set is controlled by superposition of the multiple transmitted and the reflected waves, measured by the maximum rebound ratio. Parametric studies on the maximum rebound ratio along the radian direction normal to the joints were performed in universal distinct element code. The results show that the maximum rebound ratio is influenced by three factors, i.e., the normalized normal stiffness of joints, the ratio of joint spacing to wavelength and the joint from which the wave rebounds. The relationship between the maximum rebound ratio and the influence factors is generalized into five charts. Those charts can be used as the prediction model for estimating the maximum rebound ratio.
基金Supported by the "Eleventh Five-Year Plan" for Science and Technology Research of China (No. 2006BAJ01B02-02-03)Natural Science Foundation of Heilongjiang Province (No. ZJG0701)+1 种基金National Natural Science Foundation of China (No. 90715021, No. 50678057, No. 50978080)Natural Scientific Research Innovation Foundation of Harbin Institute of Technology (No. HIT. NSRIF. 2009)
文摘The stability and ductility of four buckling-restrained braces (BRBs) with brace joints were studied. The load-carrying element of BRB was fabricated with steel (Chinese Q235), and a layer of colloidal silica sheet (0.5 mm in thickness) or four layers of plastic film (0.2 mm in thickness) were used as unbonding materials to provide space to prevent the buckling of inner core in higher modes and facilitate its lateral expansion in case of compression. Based on the equation of BRBs with brace joints of different restrained stiffnesses, the buckling load is calculated considering the initial geometric imperfections and residual stress, and the theoretical values agree well with the experiment results. It is concluded that the buckling load and ductility of BRBs are influenced greatly by the restrained stiffness of brace joints. If the restrained stiffness is deficient, the unstrained segment of BRBs with less stiffness will buckle firstly. As a result, the ultimate load of BRBs decreases, and the maximum compression load is reduced to about 65% of the maximum tension load; the stiffness also degenerates, and there is a long decreasing stage on the back-bone curve in compression phase; the ductility decreases, i.e., the ultimate tension ductility and ultimate compression ductility are approximately 15 and 1.3 respectively, and the cumulative plastic ductility is only approximately 200. If the restrained stiffness of joint is large enough, the stability will be improved as follows: the yielding strength and ultimate strength of BRBs are nearly the same, and there is an obvious strain intensification in both tension and compression phases; the ductility of brace also increases obviously, i.e., the ultimate tension ductility and ultimate compression ductility are both approximately 14, and the cumulative plastic ductility reaches 782.
基金supported by the National Key R&D Program of China (No.2022YFC3004602)the National Natural Science Foundation of China (No.52325404)the Shenzhen Science and Technology Program (No.JCYJ20220818095605012).
文摘Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in theoretical and numerical analysis of wave propagation across rock discontinuity.However,the circumstance under which the DDM is applicable to predict wave propagation across rock discontinuity remains poorly understood.In this study,theoretical analysis and ultrasonic laboratory tests were carried out to examine the theoretical applicability of the DDM for wave propagation,where specimens with rough joints comprising regular rectangular asperities of different spacings and heights were prepared by 3D printing technology.It is found that the theoretical applicability of the DDM to predict wave propagation across rock discontinuity is determined by three joint parameters,i.e.the dimensionless asperity spacing(L),the dimensionless asperity height(H)and the groove density(D).Through theoretical analysis and laboratory tests,the conditions under which the DDM is applicable are derived as follows:and,.With increase in the groove density,the thresholds of the dimensionless asperity spacing and the dimensionless asperity height show a decreasing trend.In addition,the transmission coefficient in the frequency domain decreases with increasing groove density,dimensionless asperity spacing or dimensionless asperity height.The findings can facilitate our understanding of DDM for predicting wave propagation across rock discontinuity.
文摘ABSTRACT:Knee osteoarthritis(KOA),a complicated peripheral joint disorder,can be caused by non-modifiable and modifiable risk factors.At present,the treatment for osteoarthritis is mainly to manage symptoms and improve quality of life.Although some patients with osteoarthritis may choose pharmacological agents for pain relief,it has been confirmed that a variety of preparations and doses of pharmacological agents were ineffective.In recent years,Traditional Chinese medicine(TCM)has been shown unique superiorities in the treatment of osteoarthritis,including KOA.Therefore,this article primarily investigated the key points of common syndromes,TCM nursing methods and healthy guidance of KOA,aiming at maintaining and developing the strengths of TCM,improving its efficacy and standardizing its behavior.
文摘In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidimensional translational spring model, in which each finger is constructed with prismatic joints. Human hands and the most developed mechanical hands are constructed with revolute joints. In this paper, the effects of fingertip rotation and a revolute joint spring model are investigated. A grasp stiffness matrix is analytically derived by considering not only frictional rolling contact but also frictionless sliding contact. The difl＇erence between the frictional stiffness matrix and the frictionless one is analytically obtained. The effect of local curvature at contact points is analytically derived. The grasp displacement directions affected by the change in curvature and the contact condition are also obtained. The derived stiffness matrix of the revolute joint model is compared with that of the prismatic joint model, and then the stiffness relation is clarified. The gravity effect of the object is also considered. The effectiveness of our method is demonstrated through numerical examples. The stability is evaluated by the eigenvalues of the grasp stiffness matrix, and the grasp displacement direction is obtained by the corresponding eigenvectors. The effect of joint angle is also discussed.
基金Supported by Key Program of National Natural Science Foundation of China(Grant No.51235009)National Natural Science Foundation of China(Grant No.51605374).
文摘The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.
基金supported by the Science and Technology Innovation 2030-"Brain Science and Brain-like Research"Major Project,China(2021ZD0201403).
文摘The physical compliance of interaction is an important requirement for safe and efficient collaboration between robots and humans,and the realization of human–robot compliance requires robot joints with variable stiffness similar to those of human joints.In this study,based on the tissue structure and driving principle of the human arm muscle ligament,a robot joint with variable stiffness is designed,consisting of an elastic belt and serial elastic actuator in parallel.The variable stiffness of the joint is realized by adjusting the tension length of the elastic belt.Surface electromyography(sEMG)signals of the human arm are used as the characterization quantity of joint stiffness to establish the pseudostiffness model of the elbow joint.The stiffness of the robot joints is adjusted in real-time to match the human arm stiffness based on the changes in sEMG signals of the human arm during operation.Real-time compliant interaction of human–robot collaboration is realized based on an end stiffness matching strategy.Additionally,to verify the effectiveness of the human joint stiffness matching-based compliance control strategy,a human–robot cooperative lifting experiment was designed.The bionic variable stiffness joint shows good stiffness adjustment,and the human–robot joint stiffness matching strategy based on human sEMG signals can improve the effectiveness and comfort of human–robot collaboration.
文摘Objective: the theme of this study is to explore the clinical effect of systematic rehabilitation training for children with various types of cerebral palsy. Methods: all the children involved in this study were 130 children with cerebral palsy aged 6 to 16 years old who were adopted by our hospital from 2012 to 2019, including 62 children with spasmodic cerebral palsy (47 of whom underwent tendon release), 13 children with athetosis of hand and foot, and the rest 55 children with mixed type. Review the children's participation in rehabilitation training, whether to adhere to rehabilitation training was divided into two equal groups: control group and experimental group. 65 children in the control group received intermittent rehabilitation training due to foster care and other reasons, and 65 children in the experimental group received continuous rehabilitation training. At the same time, the differences of movement, posture and self-care ability between the two groups were observed and compared. Results: after using different rehabilitation training methods, the movement, posture and self-care ability of children in the two groups changed, but the total effective rate of children in the control group after intermittent rehabilitation training was 78.5%, while the total effective rate of children in the experimental group after continuous and systematic rehabilitation training was 95.4%. The data between the two groups were processed by statistical tools, and the results showed significant (P < 0.05). Conclusion: according to the above description, the application of continuous rehabilitation training in children with cerebral palsy can significantly improve movement disorders and poor posture, prevent joint stiffness and muscle atrophy, and effectively improve self-care ability.
