Determining the collision-free joint space graph for two cooperating robot manipulators

The problem of path planning for two planar robot manipulators that cooperate in carrying a rectangular object from an initial position and orientation to a destination position and orientation in a 2-D environment is investigated. The two robot arms, the carried object, and the straight line connecting the two robot bases are modeled as a 6-link closed chain. The problem of path planning for the chain is solved by two major algorithms: a collision-free feasible-configuration-finding algorithm and a collision-free path-finding algorithm. The former maps the free space in the Cartesian world space to the robot´s joint space in which all the collision-free feasible configuratiions (CFFCs) for the 6-link closed chain are found. The latter builds a connection graph representing the CFFCs and the transitions between any two groups of CFFCs at adjacent joint intervals. A graph search method is employed to find a collision-free path for each joint of both manipulators