HRP-4 Walks on Soft Feet

The majority of humanoid robots adopt flat feet, a choice that can limit their performance when maneuvering over uneven terrains. Recently, a soft robotic foot designed to adapt to the ground was proposed to overcome part of these limitations. This paper presents the results of testing two such feet on the humanoid robot HRP-4, and compares them to what obtained with the original flat feet of the robot. After describing the SoftFoot and how it has been adapted to the robot, the biped is tested while balancing, stepping and walking. Tests are carried out on flat ground and on obstacles of different heights. For comparison purposes, the original HRP-4 controller has been used for both types of feet with no changes (except for re-evaluation of the CoM position). Analysis of the ankle pitch angle, ankle pitch torque, knee pitch angle, knee pitch torque, waist roll angle and waist pitch angle, show a substantial improvement in obstacle negotiation performance of HRP-4, when using the SoftFoot, even without optimizing the controller to exploit the SoftFoot features.