Compact design of a redundant manipulator system and application to multiple-goal tasks with temporal constraint

This paper aims to design a compact manipulator system consisting of a 6 degree-of-freedom (dof) manipulator and a 1-dof rotary table. It proposes a new compactness measure that considers manipulator swept volume or the space occupied by the system while executing task. Swept volume is crucial because a manipulator has a small footprint but can occupy a substantial space due to its large workspace. Moreover, since compactness can negatively impact manipulator motion, the compact design problem is formulated with motion time or temporal constraint. A best-effort search method is proposed to minimize the swept volume and reduce the motion time to the level of temporal constraint setting. It is carried out by a proposed spatial motion coordination (SMC) for minimizing swept volume and temporal motion coordination (TMC) for reducing motion time. The two schemes are integrated with the base placement optimization, tool attachment optimization and goal rearrangement and are evaluated under various temporal constraint settings. A cross-breed algorithm called STMC utilizing SMC and TMC is then proposed to deal with the limitation. Several optimization frameworks including SMC, TMC and STMC are compared with robot motion simulations. It is found that the ability of SMC and TMC is limited by certain range of the constraint values and STMC is better than the others.