The demand for redundant hydraulic manipulators that can implement complex heavy-duty tasks in unstructured areas is increasing;however,current manipulator layouts that remarkably differ from human arms make intuitive...The demand for redundant hydraulic manipulators that can implement complex heavy-duty tasks in unstructured areas is increasing;however,current manipulator layouts that remarkably differ from human arms make intuitive kinematic operation challenging to achieve.This study proposes a seven-degree-of-freedom(7-DOF)redundant anthropomorphic hydraulically actuated manipulator with a novel roll-pitch-yaw spherical wrist.A hybrid series-parallel mechanism is presented to achieve the spherical wrist design,which consists of two parallel linear hydraulic cylinders to drive the yaw/pitch 2-DOF wrist plate connected serially to the roll structure.Designed as a 1R£RRR-1S£U mechanism(“R”,“P”,“S”,and“U”denote revolute,prismatic,spherical,and universal joints,respectively;the underlined letter indicates the active joint),the 2-DOF parallel structure is partially decoupled to obtain simple forward/inverse kinematic solutions in which a closed-loop subchain“R£RR”is included.The 7-DOF manipulator is then designed,and its third joint axis goes through the spherical center to obtain closed-form inverse kinematic computation.The analytical inverse kinematic solution is drawn by constructing self-motion manifolds.Finally,a physical prototype is developed,and the kinematic analysis is validated via numerical simulation and test results.展开更多
The synchronous tracking control problem of a hydraulic parallel manipulator with six degrees of freedom (DOF) is complicated since the inclusion of hydraulic elements increases the order of the system.To solve this p...The synchronous tracking control problem of a hydraulic parallel manipulator with six degrees of freedom (DOF) is complicated since the inclusion of hydraulic elements increases the order of the system.To solve this problem,cascade control method with an inner/outer-loop control structure is used,which masks the hydraulic dynamics with the inner-loop so that the designed controller takes into account of both the mechanical dynamics and the hydraulic dynamics of the manipulator.Furthermore,a cross-coupling control approach is introduced to the synchronous tracking control of the manipulator.The position synchronization error is developed by considering motion synchronization between each actuator joint and its adjacent ones based on the synchronous goal.Then,with the feedback of both position error and synchronization error,the tracking is proven to guarantee that both the position errors and synchronization errors asymptotically converge to zero.Moreover,the effectiveness of the proposed approach is verified by the experimental results performed with a 6-DOF hydraulic parallel manipulator.展开更多
基金This work was supported in part by the National Natural Science Foundation of China(Grant Nos.91748210 and 51922093)in part by the Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyj-msxmX0780)in part by the Fundamental Research Funds for the Central Universities,China(Grant No.2021CDJKYJH019).
文摘The demand for redundant hydraulic manipulators that can implement complex heavy-duty tasks in unstructured areas is increasing;however,current manipulator layouts that remarkably differ from human arms make intuitive kinematic operation challenging to achieve.This study proposes a seven-degree-of-freedom(7-DOF)redundant anthropomorphic hydraulically actuated manipulator with a novel roll-pitch-yaw spherical wrist.A hybrid series-parallel mechanism is presented to achieve the spherical wrist design,which consists of two parallel linear hydraulic cylinders to drive the yaw/pitch 2-DOF wrist plate connected serially to the roll structure.Designed as a 1R£RRR-1S£U mechanism(“R”,“P”,“S”,and“U”denote revolute,prismatic,spherical,and universal joints,respectively;the underlined letter indicates the active joint),the 2-DOF parallel structure is partially decoupled to obtain simple forward/inverse kinematic solutions in which a closed-loop subchain“R£RR”is included.The 7-DOF manipulator is then designed,and its third joint axis goes through the spherical center to obtain closed-form inverse kinematic computation.The analytical inverse kinematic solution is drawn by constructing self-motion manifolds.Finally,a physical prototype is developed,and the kinematic analysis is validated via numerical simulation and test results.
基金Project(50375139) supported by the National Natural Science Foundation of ChinaProject(NCET-04-0545) supported by the New Century Excellent Talent Plan of the Ministry of Education of China
文摘The synchronous tracking control problem of a hydraulic parallel manipulator with six degrees of freedom (DOF) is complicated since the inclusion of hydraulic elements increases the order of the system.To solve this problem,cascade control method with an inner/outer-loop control structure is used,which masks the hydraulic dynamics with the inner-loop so that the designed controller takes into account of both the mechanical dynamics and the hydraulic dynamics of the manipulator.Furthermore,a cross-coupling control approach is introduced to the synchronous tracking control of the manipulator.The position synchronization error is developed by considering motion synchronization between each actuator joint and its adjacent ones based on the synchronous goal.Then,with the feedback of both position error and synchronization error,the tracking is proven to guarantee that both the position errors and synchronization errors asymptotically converge to zero.Moreover,the effectiveness of the proposed approach is verified by the experimental results performed with a 6-DOF hydraulic parallel manipulator.
