Novel Lockable and Stackable Compliant Actuation Unit for Modular +SPEA Actuators

On compliant robotic systems, modularity is recently adopted for the ease of up- and downscaling and the possibility to downgrade the costs, by moving towards the combination of standard units instead of custom designs. However, modularity on the actuator level itself lacks more thorough evaluation. We have developed a novel lockable and stackable compliant actuation unit which can be used to form modular series-parallel elastic actuators (+SPEA). This letter describes the modular +SPEA layer architecture and discusses its two-way overrunner and rubber springs in detail, while providing experimental validation on each component as well. First experiments show the layer can deliver up to 20 Nm. Finally, we present how a manipulator can be equipped with the modular +SPEA layers.