Design of a Parallel Elastic Actuator with a Continuously-Adjustable Equilibrium Position

TL;DR

This paper introduces an adjustable-equilibrium parallel elastic actuator (AE-PEA) that allows energy-efficient control of the actuator's equilibrium position without external energy, enhancing versatility for robotic applications.

Contribution

The paper presents a novel AE-PEA design with a mechanism for low-energy equilibrium adjustment, overcoming limitations of traditional PEAs.

Findings

Enables energy-efficient operation at multiple equilibrium positions.

Uses a spring rotation mechanism to adjust equilibrium without deformation.

Suitable for applications requiring gravity compensation and oscillatory motion.

Abstract

In this paper, we present an adjustable-equilibrium parallel elastic actuator (AE-PEA). The actuator consists of a motor, an equilibrium adjusting mechanism, and a spring arranged into a cylindrical geometry, similar to a motor-gearbox assembly. The novel component of the actuator is the equilibrium adjusting mechanism which (i) does not require external energy to maintain the equilibrium position of the actuator even if the spring is deformed and (ii) enables equilibrium position control with low energy cost by rotating the spring while keeping it undeformed. Adjustable equilibrium parallel elastic actuators resolve the main limitation of parallel elastic actuators (PEAs) by enabling energy-efficient operation at different equilibrium positions, instead of being limited to energy-efficient operation at a single equilibrium position. We foresee the use of AE-PEAs in industrial robots, mobile robots, exoskeletons, and prostheses, where efficient oscillatory motion and gravity compensation at different positions are required.