A Compact Variable Stiffness Actuator for Agile Legged Locomotion

TL;DR

This paper introduces a compact, efficient variable stiffness actuator for legged robots, enabling versatile and energy-efficient locomotion with improved control and rapid stiffness modulation.

Contribution

A novel leaf-spring based variable stiffness actuator (VLLSA) that is compact, lightweight, and capable of fast, wide-range stiffness modulation with low energy use.

Findings

Validated through hopping experiments

Demonstrated wide stiffness variation range

Achieved low energy consumption in stiffness modulation

Abstract

The legged robots with variable stiffness actuators (VSAs) can achieve energy-efficient and versatile locomotion. However, equipping legged robots with VSAs in real-world application is usually restricted by (i) the redundant mechanical structure design, (ii) limited stiffness variation range and speed, (iii) high energy consumption in stiffness modulation, and (iv) the lack of online stiffness control structure with high performance. In this paper, we present a novel Variable-Length Leaf-Spring Actuator (VLLSA) designed for legged robots that aims to address the aforementioned limitations. The design is based on leaf-spring mechanism and we improve the structural design to make the proposed VSA (i) compact and lightweight in mechanical structure, (ii) precise in theoretical modeling, and (iii) capable of modulating stiffness with wide range, fast speed, low energy consumption and high control performance. Hardware experiments including in-place and forward hopping validate advantages of the proposed VLLSA.