Modeling, Analysis, and Experimental Validation of an Electric Linear Series Elastic Actuator for an Exoskeleton

Exoskeletons and humanoid robots require high-power, low-weight, and back-driveable actuators. This paper describes the design and analysis of a high-force linear series elastic actuator for a lower body exoskeleton. The actuator is powered by two motors and utilize a liquid cooling system to increase its maximum continuous torque. The actuator is capable of outputting a maximum continuous force of 4800N and a maximum speed of 0.267 m/s with a maximum continuous motor current of 18A. The Titanium leaf spring was used in the actuator to provide compliance. The spring has a median stiffness of 587 N/mm with standard deviation of 38 N/mm, validated by experiments. Dynamic model was created to analyze the normal modes and can be used for developing model-based controllers.