  Last decades of humanoid research has shown that humanoids developed for high
dynamic performance require a stiff structure and optimal distribution of
mass--inertial properties. Humanoid robots built with a purely tree type
architecture tend to be bulky and usually suffer from velocity and force/torque
limitations. This paper presents a novel series-parallel hybrid humanoid called
RH5 which is 2 m tall and weighs only 62.5 kg capable of performing heavy-duty
dynamic tasks with 5 kg payloads in each hand. The analysis and control of this
humanoid is performed with whole-body trajectory optimization technique based
on differential dynamic programming (DDP). Additionally, we present an improved
contact stability soft-constrained DDP algorithm which is able to generate
physically consistent walking trajectories for the humanoid that can be tracked
via a simple PD position control in a physics simulator. Finally, we showcase
preliminary experimental results on the RH5 humanoid robot.
