The Structure Design And Experimental Verification Of 7-DOF Redundant Manipulator

Space manipulators can assist astronauts in carrying loads,spacecraft maintenance and other space operations,objectively space manipulators can reduce workload of astronauts and protects their safety effectively.Therefore,space manipulator is playing an increasingly important role in space exploration activities.This article is based on the manipulator project of Shanghai Institute of Aerospace Systems Engineering.The manipulator in project designed for space manipulator's ground validation experiment is taken as the research object of this article.The research contents of this article include system design of manipulator,structural design of joints and positioning accuracy of manipulator.Firstly,according to the index from duty book and combining the application status of space manipulator,this paper completes the design of the control arm system.According to the design requirements,the configuration of the manipulator is defined as seven degrees of freedom with 3-1-3 joints determined,and then the configuration is analyzed.The parts under load of the manipulator are designed,and then static analysis of these parts is carried out to verify the strength and stiffness indexes.The rotation stiffness of the manipulator joints are estimated and the crossed roller bearing stiffness is verified,then the physical model of the manipulator is simplified based on these stiffness data.Optimize the structure of the joint housing is optimized to improve the stiffness of the whole manipulator system.Simplified physical model of the manipulator is used to simulate the stiffness and fundamental frequency of the manipulator,to verify the fundamental frequency and stiffness index.Then,according to the design index of joint performance,the joints of manipulator and a kind of joint torque sensor with high stiffness for shoulder is designed.According to the requirement of output torque and speed,motors and reducers are selected for the each joint.According to the load of the joints,the type selection of bearings is carried out.The joint torque sensor for shoulder with high is designed.The elastomer of the torque sensor is analyzed and finish the calibration experiment of the torque sensor.According to the principle of the power-off brake,the paper completed the spring type selection and size design of the power-off brake.Then static analysis of the load parts of the joint is completed to verify the strength and stiffness index of each part.Next,accuracy and output torque measurement experiments are carried out to verify the joint performance index.Finally,the error of the manipulator is studied.The kinematics model of the manipulator is established of the manipulator based on D-H parameters.Then the geometric error model of the manipulator is established based on the kinematics model.Combining the structure design,estimating the kinematics parameter error of the manipulator are calculated.Combining with the calculation results of kinematic parameters error,the geometric error of the manipulator is simulated.The kinematic parameters of the manipulator are calibrated.Basing on the simplified physical model of the manipulator,the flexible error of the manipulator is simulated.In order to meets the design requirements,the position accuracy experiment of the manipulator is carried out,including repeated accuracy and absolute position accuracy experiments.