Finance

Electrical engineering

Physics

Control engineering

Torque

Deflection (physics)

Feed forward

Agronomy

Structural engineering

Biology

Optics

Lever

Engineering

Actuator

Artificial intelligence

Position (finance)

Economics

Controller (irrigation)

Control (management)

Stiffness

Computer science

Control theory (sociology)

Mechanical engineering

Thermodynamics

IEEE/ASME Transactions on Mechatronics

This paper presents a novel rotational serial variable stiffness actuator (SVSA) based on an Archimedean spiral relocation mechanism (ASRM), which is applied to linearly change the position of the pivot point of a lever as well as obtain a large range of motion and adjustable stiffness. Consequently, the ASRM introduced in this work contributes to a compact structure of the mechanical design without sacrificing the continuity of adjustable stiffness. In terms of the variable stiffness mechanism, two linear springs are assembled antagonistically on a spring shaft and rotate simultaneously with the output link. To improve the spring force transmission efficiency, these displacements of the springs are set to be perpendicular to the output link. A large deflection angle can therefore be achieved to obtain high passive energy storage ability. Moreover, the SVSA is also modeled to investigate the theoretical capabilities of the output stiffness and passive energy capability. Further control experiments are performed to quantitatively evaluate the physical performance of the SVSA. Our results demonstrate that the SVSA with a proportional-derivative feedback plus feedforward controller exhibits a fast response and high accuracy for both position and stiffness regulation and tracking tasks. In addition, the real output torque measurement verifies the fidelity of the SVSA for torque generation.

A Novel Design of Serial Variable Stiffness Actuator Based on an Archimedean Spiral Relocation Mechanism