  This paper presents a simplified model-based trajectory optimization (TO)
formulation for motion planning on quadruped mobile manipulators that carry
heavy payload of known mass. The proposed payload-aware formulation
simultaneously plans locomotion, payload manipulation and considers both robot
and payload model dynamics while remaining computationally efficient. At the
presence of heavy payload, the approach exhibits reduced leg outstretching
(thus increased manipulability) in kinematically demanding motions due to the
contribution of payload manipulation in the optimization. The framework's
computational efficiency and performance is validated through a number of
simulation and experimental studies with the bi-manual quadruped CENTAURO robot
carrying on its arms a payload that exceeds 15 % of its mass and traversing
non-flat terrain.
