RRLAB SEA — A highly integrated compliant actuator with minimised reflected inertia

The Robotics Research Lab (RRLab) is currently striving to bring the Bio-inspired Behaviour-Based Bipedal Locomotion Control (B4LC) to a physical platform. Regarding the actuation, dynamic walking poses specific requirements like impact tolerance and high acceleration capabilities. A linear Series Elastic Actuator (Sea) which is designed to meet the requirements is presented. A design approach to the drivetrain which is taking the reflected motor inertia into account, is depicted in order to achieve a high acceleration capability. The resulting Sea implementation features a drivetrain based on a high pitch ball screw as a single gear reduction. This positively impacts the efficiency, the backdrivability and most importantly reduces the reflected motor inertia. Furthermore, the design features a high degree of integration to achieve a high torque density and allow for a compact integration. To exploit its full potential, the actuator is encapsulated by a dedicated FPGA-based embedded system. In open-loop experiments all unlumped dynamic quantities of the actuator are identified.