Abstract
Seven-degree-of-freedom redundant manipulators with link offset have many advantages, including obvious geometric significance and suitability for configuration control. Their configuration is similar to that of the experimental module manipulator (EMM) in the Chinese Space Station Remote Manipulator System. However, finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult. This study proposes a high-precision, semi-analytical inverse method for EMMs. Firstly, the analytical inverse kinematic solution is established based on joint angle parameterization. Secondly, the analytical inverse kinematic solution for a non-offset spherical-roll-spherical (SRS) redundant manipulator is derived based on arm angle parameterization. The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator. Thirdly, the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization. After selecting the stride and termination condition, the precise inverse solution is computed for the EMM based on arm angle parameterization. Lastly, case solutions confirm that this method has high precision, and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.
Highlights
Space robots play an irreplaceable role in human space exploration [1,2,3,4]
We propose a numerical method to correct the solution errors of the experimental module manipulator (EMM) based on arm angle parameterization in Section 3 so that actual arm angle ψ~ is infinitely close to nominal arm angle ψ
This study proposes a high-precision, semi-analytical inverse method for 7-DOF redundant manipulators with link offset on the basis of arm angle parameterization
Summary
Space robots play an irreplaceable role in human space exploration [1,2,3,4]. The Space Station Remote Manipulator System (SSRMS) [5], special purpose dexterous manipulator [6], and European Robotic Arm [7] applied to the International Space Station [8] are all 7-degree-of-freedom (7-DOF) redundant manipulators. Shimizu et al [32] solved the inverse kinematics of the SRS manipulator via arm angle parameterization and reported that this method is suitable for joint limits. The method is based on damped least-squares, and the inverse kinematic solution is solved by iterative calculation in the velocity domain This method was verified through a simulation in which the end-effector tracked a circle with a constant orientation and arm angle. No previous study has presented a method to solve the precise solution for the EMM on the basis of arm angle parameterization. The hand-eye-camera coordinate systems at the beginning and end of this manipulator, respectively
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