A Compact, Modular Series Elastic Actuator

Abstract

This paper presents the development of a compact, modular rotary series elastic actuator (SEA) design that can be customized to meet the requirements of a wide range of applications. The concept incorporates flat brushless motors and planetary gearheads instead of expensive harmonic drives and a flat torsional spring design to create a lightweight, lowvolume, easily reconfigurable, and relatively highperformance modular SEA for use in active impedance controlled devices. The key innovations include a Hall effect sensor for direct spring displacement measurements that mitigate the negative impact of backlash on SEA control performance. Both torque and impedance controllers are developed and evaluated using a 1degreeoffreedom (DoF) prototype of the proposed actuator package. The results demonstrate the performance of a stable firstorder impedance controller tested over a range of target impedances. Finally, the flexibility of the modular SEA is demonstrated by configuring it for use in five different actuator specifications designed for use in the uBot7 mobile manipulator requiring spring stiffnesses from 3 N آ·â€‰m/deg to 11.25 N آ·â€‰m/deg and peak torque outputs from 12 N آ·â€‰m to 45 N آ·â€‰m.