A Servomotor with Adjustable Stiffness for Humanoid Robotics Application

Abstract:
The actuation system we propose is based on the combination of a compact high-power and high-speed BLDC motor equipped with a planetary gearbox and a tunable elastic element. As a novelty, with respect to other state-of-the-art actuation systems that integrate fixed elastic components, the servomotor we developed is based on a pneumatic rotary actuator which stiffness can be regulated by controlling the inner pressure. The elastic element is connected in parallel to the output shaft of the motor’s gearbox by means of a rigid connection. This allows to reduce the backlash of the gearbox by 62%, lower the output impedance of the joint, and reduce the robot energy consumption. By effectively reducing the output impedance of the joints, the elastic elements will also increase the robot safety in case of collision with humans or objects present in the environment.