One of the key issues for parallel mechanism is the kinematic characteristics,especially the workspace which varies with configuration parameters.A kind of 4UPS-UPU parallel mechanism is designed and its workspace is ...One of the key issues for parallel mechanism is the kinematic characteristics,especially the workspace which varies with configuration parameters.A kind of 4UPS-UPU parallel mechanism is designed and its workspace is studied in this paper.First,the mobility of the 4UPS-UPU parallel mechanism is analyzed based on the reciprocal screw theory,and the motion and constraint screw systems of the parallel mechanism are obtained.Then the inverse kinematics is derived by the closed-form kinematics chain.The boundary search method in the polar coordinate system is presented to analyze the constant-orientation workspace of the parallel mechanism.Finally,the influence factors relevant to the workspace,such as the structural parameters and kinematics parameters are analyzed in detail.The relationship between the workspace volume and different parameters are obtained.The conclusions can be used for parameters optimization and path planning of the parallel mechanism.展开更多
Purpose. To investigate the peak latency of the orbital presaccadic spike potential (SP) with horizontal eye movement in normals.Methods. Orbital SP was recorded in 28 normal subjects from 8 electrodes around the eyes...Purpose. To investigate the peak latency of the orbital presaccadic spike potential (SP) with horizontal eye movement in normals.Methods. Orbital SP was recorded in 28 normal subjects from 8 electrodes around the eyes with Pz as the reference while performing 5°, 10°, 20°, 30° and 40°horizontal saccades to visual targets. SP peak latency was measured from SP onset to SP peak on averaged data aligned on SP peak.Results. Significant main effects on SP peak latency are found for saccade size (<0. 01), saccade direction (P<0. 01) and electrode site (P<0. 05). No significant main effect on SP peak latency is found for eye (P>0. 05). SP peak latency increases with increasing saccade size from 5°to 40°. SP peak latency is longer with saccades back to center than away from center, and with abducting saccades than with adducting saccades. SP peak latency differs at the electrode sites with an order from shorter to longer as follows: inner canthus (IC); inferior orbit (IO): outer canthus (OC); superior orbit (SO).Conclusicos. The effects on the peak latency of orbital SP can be explained by the saccade dynamic property, volume conduction as well as physiologic and anatomic factors of the eyes and orbits. The peak latency of orbital SP can be used to reflect the temporal characteristics of ocular motor units controlling saccadic eye movement.展开更多
基金Supported by the National High Technology Research and Development Programme of China(No.SS2012AA041604)
文摘One of the key issues for parallel mechanism is the kinematic characteristics,especially the workspace which varies with configuration parameters.A kind of 4UPS-UPU parallel mechanism is designed and its workspace is studied in this paper.First,the mobility of the 4UPS-UPU parallel mechanism is analyzed based on the reciprocal screw theory,and the motion and constraint screw systems of the parallel mechanism are obtained.Then the inverse kinematics is derived by the closed-form kinematics chain.The boundary search method in the polar coordinate system is presented to analyze the constant-orientation workspace of the parallel mechanism.Finally,the influence factors relevant to the workspace,such as the structural parameters and kinematics parameters are analyzed in detail.The relationship between the workspace volume and different parameters are obtained.The conclusions can be used for parameters optimization and path planning of the parallel mechanism.
文摘Purpose. To investigate the peak latency of the orbital presaccadic spike potential (SP) with horizontal eye movement in normals.Methods. Orbital SP was recorded in 28 normal subjects from 8 electrodes around the eyes with Pz as the reference while performing 5°, 10°, 20°, 30° and 40°horizontal saccades to visual targets. SP peak latency was measured from SP onset to SP peak on averaged data aligned on SP peak.Results. Significant main effects on SP peak latency are found for saccade size (<0. 01), saccade direction (P<0. 01) and electrode site (P<0. 05). No significant main effect on SP peak latency is found for eye (P>0. 05). SP peak latency increases with increasing saccade size from 5°to 40°. SP peak latency is longer with saccades back to center than away from center, and with abducting saccades than with adducting saccades. SP peak latency differs at the electrode sites with an order from shorter to longer as follows: inner canthus (IC); inferior orbit (IO): outer canthus (OC); superior orbit (SO).Conclusicos. The effects on the peak latency of orbital SP can be explained by the saccade dynamic property, volume conduction as well as physiologic and anatomic factors of the eyes and orbits. The peak latency of orbital SP can be used to reflect the temporal characteristics of ocular motor units controlling saccadic eye movement.
