  Aerospace production volumes have increased over time and robotic solutions
have been progressively introduced in the aeronautic assembly lines to achieve
high-quality standards, high production rates, flexibility and cost reduction.
Robotic workcells are sometimes characterized by robots mounted on slides to
increase the robot workspace. The slide introduces an additional degree of
freedom, making the system kinematically redundant, but this feature is rarely
used to enhance performances. The paper proposes a new concept in trajectory
planning, that exploits the redundancy to satisfy additional requirements. A
dynamic programming technique is adopted, which computes optimized
trajectories, minimizing or maximizing the performance indices of interest. The
use case is defined on the LABOR (Lean robotized AssemBly and cOntrol of
composite aeRostructures) project which adopts two cooperating six-axis robots
mounted on linear axes to perform assembly operations on fuselage panels.
Considering the needs of this workcell, unnecessary robot movements are
minimized to increase safety, the mechanical stiffness is maximized to increase
stability during the drilling operations, collisions are avoided, while joint
limits and the available planning time are respected. Experiments are performed
in a simulation environment, where the optimal trajectories are executed,
highlighting the resulting performances and improvements with respect to
non-optimized solutions.
