Motion planning of ladder climbing for humanoid robots

This paper describes preliminary steps toward providing the Hubo-U+ humanoid robot with ladder climbing capabilities. Ladder climbing is an essential mode of locomotion for navigating industrial environments and conducting maintenance tasks in buildings, trees, and other man-made structures (e.g., utility poles). Although seemingly straightforward for humans, this task is quite challenging for humanoid robots due to differences from human kinematics, significant physical stresses, simultaneous coordination of four limbs in contact, and limited motor torques. We present a planning strategy for the Hubo-U+ robot that automatically generates multi-limbed locomotion sequences that satisfy contact, collision, and torque limit constraints for a given ladder specification. This method is used to automatically test climbing strategies on a variety of ladders in simulation. This planner-aided design paradigm allows us to employ extensive simulation in order to rapidly design, test, and verify novel climbing strategies, as well as testing how candidate hardware changes would affect the robot's ladder climbing capabilities.