Design and Analysis of a Novel Compliant Actuator With Variable Stiffness by Spring Pretension Adjustment

Variable stiffness actuators (VSA) are an emerging advanced driving method for robotic joint in physical human-robot interaction scenarios. This paper proposes a VSA based on adjusting the pre-tightening force of the driving ropes by rotating the linear springs to change the angle of its axis relative to the input frame. By adjusting the spring angle within a small relative rotation angle stroke, the angle between the spring axis and the transmission rope can be changed, thereby achieving rapid stiffness adjustment in a large range. The characteristics analysis shows that the proposed VSA has good stiffness adjustment independence. The mechanical design scheme of the VSA is introduced in detail. Simulations based on a proportional derivative (PD) controller demonstrated the effectiveness of the design.