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
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
This paper presents some initial solutions to the problem of accuracy and repeatability of the arm position placement in applied kinematics by solving the inverse kinematics problem of a serial jointed manipulator who...This paper presents some initial solutions to the problem of accuracy and repeatability of the arm position placement in applied kinematics by solving the inverse kinematics problem of a serial jointed manipulator whose forward kinematics solution was earlier presented to solve the position placement problem of a mobile manipulator for Lunar Oxygen production. The problem herein is that of identifying a combination of joint angles to effectively position the end-effecter at a specified location in space. The reverse solution as presented in this paper is predicated on DH＇s （Denavit-Hartenberg＇s） technique for robot arm position analysis. The generalized solution for the 5-degrees of freedom DOF （degree of freedom） revolute joint variables which comprises 2-1inks and a spade-like 3-DOF end-effecter was obtained by solving a set of algebraic equations emerging from series of transformation matrices. The proposed solution herein has a high degree of accuracy and repeatability for workspace reachable domains where joint combination is analytic.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
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.
文摘This paper presents some initial solutions to the problem of accuracy and repeatability of the arm position placement in applied kinematics by solving the inverse kinematics problem of a serial jointed manipulator whose forward kinematics solution was earlier presented to solve the position placement problem of a mobile manipulator for Lunar Oxygen production. The problem herein is that of identifying a combination of joint angles to effectively position the end-effecter at a specified location in space. The reverse solution as presented in this paper is predicated on DH＇s （Denavit-Hartenberg＇s） technique for robot arm position analysis. The generalized solution for the 5-degrees of freedom DOF （degree of freedom） revolute joint variables which comprises 2-1inks and a spade-like 3-DOF end-effecter was obtained by solving a set of algebraic equations emerging from series of transformation matrices. The proposed solution herein has a high degree of accuracy and repeatability for workspace reachable domains where joint combination is analytic.
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.
