This paper presents the contact-consistent elastic strips (CES) framework, a motion planning approach capable of producing complex multi-contact whole-body humanoid behaviors in dynamic environments. Planning multi-contact motions for humanoid robots is known to be non-trivial since it involves aspects of autonomous balancing, obstacle avoidance, ensuring global connectivity of the workspace and concurrent consideration of the kinematic and dynamic constraints. Previous works at motion planning for humanoid systems tend to focus on joint space planning and deal with obstacle avoidance and contact-point searching as the separated problems. CES framework, however, simultaneously considers all these requirements and constraints in task space while planning a valid sequence of contact-points and corresponding motions. This resulted in considerable improvements to efficiency and significantly reduced planning time. With the use of CES framework, complex multi-contact locomotion behaviors and real-time adjustments to the robot motions in 3D unstructured environments is possible. Several simulations are demonstrated to evaluate and verify the performance of CES framework.

We present a light, actuated smart staff with 5DOF tip force sensing which can be used by a humanoid robot operating in challenging terrain. The staff has an extension mechanism that employs mechanical multiplexing to achieve a high extension ratio in a stiff and compact package. The tip force sensor uses two metal diaphragms to achieve decoupling of axial and radial forces and the ability to tune the maximum range of forces in each direction independently. With the force sensor, the robot can characterize the coefficient of friction and orientation of a surface with simple motion primitives. Two sets of experiments were conducted with the smart staff manipulated by a 7 DOF robot arm. Using the sensor, the robot was able to determine the orientations of sloped surfaces within two degrees in two orthogonal directions.

Maintaining humanoid robot stability in unstructured environments is nontrivial because robots lack humanlike tactile sensing and require complex task-specific controllers to integrate information from multiple sensors. To deploy humanoid robots in cluttered and unstructured environments such as disaster sites, it is necessary to develop advanced techniques in both locomotion and control. This paper proposes to incorporate a pair of actuated smart staffs with vision and force sensing that transforms biped humanoids into tripeds or quadrupeds or more generally, SupraPeds. The concept of SuprePeds not only improves the stability of humanoid robots while traversing rough terrain but also retains the manipulation capabilities. In order to control the potentially numerous contact forces on SupraPeds, we develop a friction-consistent whole-body control framework that implements generic multi-contact control for arbitrary humanoids, which enables autonomous balancing while complying with friction constraints. The simulation results are presented to demonstrate that the proposed control framework can efficiently deal with multi-contact locomotion in 3D unstructured environments.