| Ground gravity compensation is an important aspect of space science andtechnology. With the development of China's space technology, space manipulator playsan important role in space exploration. In order to ensure the reliability of the spacemanipulator in work, low-gravity experiment needs to be done on the ground beforelaunch. Space manipulator is designed to meet the space environment, withoutconsidering the effect of gravity. Therefore, when tested on the ground, the gravitycompensation needs to be done. In this paper, the suspension mechanism is designedand the compensation force is analyzed.The center of mass is not on the axis of rotation, so each manipulator rod gravitycan not be fully compensated, leaving residual joint torque(additional moment andreverse torque). the mathematical expression between the joints torque(additionalmoment and reverse torque) and ideal compensation force is obtained by analyzing thespace manipulator muti-point suspension compensation force model. By setting theideal compensation force as the optimization variables, the joint additional moment andreverse torque less than a certain value constraints, the minimum of the square sum ofeach joint torque as objective function, the ideal compensation force optimization modelis created. The joint angle optimization model contains time-related variables, so theproblem is a muti-condition optimization problem, by using MATLAB and ADAMSco-optimization method, finally got the best of a set of compensation idealcompensation force.After the whole gravity compensation system is outlined,structural design principleis analyzed, suspension mechanism is designed in detail and the strength and stiffness ofthe critical component is checked by using ANSYS software. In order to ensure thereliability of the system and reduce the cost of system development, the adjacentsuspensions are merged with the use of hierarchical principle. Suspension subsystemconsist of five slings, of which one is fixed sling, and the remaining four are followingslings..Causes of gravity compensation force compensating system error sources areanalyzed to establish the expression of the error. Gravity compensation system error isobtained under extremes integrated data errors by the error integration. Athree-dimensional model of the robot arm and suspension subsystem is established byusing PRO/E. Suspension system dynamics simulation is analyzed through ADAMSmulti-body system dynamics software. Analyzing the simulation results, The lift ofconstant tension system is not less than1.35m, the response of velocity and accelerationis not less than110mm/s and16mm/s2, the tracking speed and acceleration of position following system are not less than30mm/s and5.5mm/s2. After gravity compensation,the maximum additional moment torque is72Nm, occurred in the joint1and the amaximum reverse torque is72.5Nm, occurred in the joint4. |
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