Computing the feasible configurations of a 7-DOF arm subject to joint limits

A seven-degree-of-freedom (7-DOF) anthropomorphic arm requires the control of the relative orientation of the elbow to satisfy task, kinematic, and dynamic constraints. While prior work has dealt primarily with iterative repulsive schemes to avoid joint limit stops, a geometric algorithm for explicitly computing the set of feasible configurations of a zero-offset arm at an arbitrary position with respect to the current position is presented. The data facilitates trajectory planning that takes into account a wide range of factors, including the limit stops, rather than reacting to limit stops encountered during trajectory execution. The algorithm was implemented to run on the JIFFE robotics processor. JIFFE computes the feasible configuration set and, mostly for testing, uses the data for inverse kinematics in 10 μs