Compliant Joint Actuator With Dual Spiral Springs

The main motivation behind the creation of a compliant actuation system is to provide safety, capability of storing energy, and improved performance levels in dynamic tasks. The choice of the proper compliance level pertaining to robots depends on the specific purposes of the robots. In this paper, a dual-spiral-spring actuation system (DSSAS) is proposed to provide high compliance and deformation values for wearable robots. Among many different applications of wearable robotic systems, we aim for systems in which safety and compliance are more important than the control bandwidth of the joints. A spiral spring is selected to take advantage of the characteristics of high levels of compliance and deformation compared to other elastic components. The proposed dual-spiral-spring actuation system uses two spiral springs in opposite directions, as the spiral spring generates torque only in one direction. First, we present the characteristics of the spiral spring for a compliant joint. Then, the design and performance of the DSSAS are demonstrated by experiments.