A KINEMATIC ANALYSIS OF THE SPACE STATION REMOTE MANIPULATOR SYSTEM (SSRMS)

An efficient reverse analysis of three 6-degree-of-freedom (dof) subchains of the 7-dof SSRMS is presented. The first subchain is formed by locking the seventh joint. The second subchain is formed by locking the second joint, while the third subchain is formed by locking the first joint (the grounded joint is counted as the first joint in the chain). There are a maximum of eight different arm configurations in each of the three subchains, and these were determined by employing a computer-efficient algorithm, which required the rooting of only at most quadratic polynomials. The algorithms were implemented, and the SSRMS was employed in an animated environment to perform and practice a number of useful tasks for space station servicing. The locking of the second joint has the advantage in that an operator could, at the outset, choose the orientation of the plane that contains the two longest links (the upper arm and forearm) so as to avoid collisions with obstacles. However, it has the disadvantage that when the second joint angle equals 0-degrees or 180-degrees, the manipulator is in a singularity configuration (a singularity analysis of the SSRMS is presented in a second article). It is interesting to note that this plane can also be oriented by specifying the first joint angle. This has the distinct advantage that the plane can be oriented arbitrarily and, in this way, the singularity is avoided.