A compliant humanoid walking strategy based on the switching of state feedback gravity compensation controllers

This paper provides stability analyses for two different types of desired gravity compensation controllers, employing both motor and link feedback, and describes a means by which these controllers can be used to control a compliant humanoid robot in order to ensure the successful execution of walking trajectories. Given the challenging task of controlling compliant bipedal systems, owing to their possession of underactuated degrees of freedom, the full actuator and link dynamics are accounted for. The proposed walking strategy involves a process of switching between three distinct controllers which is contingent upon the force feedback provided by the force/torque sensors embedded in the robot's feet. These controllers were tuned using a simulation model of the robot and were then implemented on the compliant COMAN legs, whose performance of walking confirms the controllers' stability, in addition to the walking scheme's efficacy.