  Dynamic balancing under uncertain disturbances is important for a humanoid
robot, which requires a good capability of coordinating the entire body
redundancy to execute multi tasks. Whole-body control (WBC) based on
hierarchical optimization has been generally accepted and utilized in
torque-controlled robots. A good hierarchy is the prerequisite for WBC and can
be predefined according to prior knowledge. However, the real-time computation
would be problematic in the physical applications considering the computational
complexity of WBC. For robots with proprioceptive actuation, the joint friction
in gear reducer would also degrade the torque tracking performance. In our
paper, a reasonable hierarchy of tasks and constraints is first customized for
robot dynamic balancing. Then a real-time WBC is implemented via a
computationally efficient WBC software. Such a method is solved on a modular
master control system UBTMaster characterized by the real-time communication
and powerful computing capability. After the joint friction being well covered
by the model identification, extensive experiments on various balancing
scenarios are conducted on a humanoid Walker3 with proprioceptive actuation.
The robot shows an outstanding balance performance even under external impulses
as well as the two feet of the robot suffering the inclination and shift
disturbances independently. The results demonstrate that with the strict
hierarchy, real-time computation and joint friction being handled carefully,
the robot with proprioceptive actuation can manage the dynamic physical
interactions with the unstructured environments well.

Robotics