Design and experimental study of a passive power-source-free stiffness-self-adjustable mechanism
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RESEARCH ARTICLE
Yuwang LIU, Dongqi WANG, Shangkui YANG, Jinguo LIU, Guangbo HAO
Design and experimental study of a passive power-source-free stiffness-self-adjustable mechanism
© The Author(s) 2020. This article is published with open access at link.springer.com and journal.hep.com.cn
Abstract Passive variable stiffness joints have unique advantages over active variable stiffness joints and are currently eliciting increased attention. Existing passive variable stiffness joints rely mainly on sensors and special control algorithms, resulting in a bandwidth-limited response speed of the joint. We propose a new passive power-source-free stiffness-self-adjustable mechanism that can be used as the elbow joint of a robot arm. The new mechanism does not require special stiffness regulating motors or sensors and can realize large-range self-adaptive adjustment of stiffness in a purely mechanical manner. The variable stiffness mechanism can automatically adjust joint stiffness in accordance with the magnitude of the payload, and this adjustment is a successful imitation of the stiffness adjustment characteristics of the human elbow. The response speed is high because sensors and control algorithms are not needed. The variable stiffness principle is explained, and the design of the variable stiffness mechanism is analyzed. A prototype is fabricated, and the associated hardware is set up to validate the analytical stiffness model and design experimentally. Keywords variable stiffness mechanism, stiffness self-regulation, bionic robot, modeling
Received April 21, 2020; accepted August 3, 2020
✉), Dongqi WANG, Shangkui YANG, Jinguo LIU, Guangbo HAO (✉)
Yuwang LIU (
State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang 110169, China E-mails: [email protected]; [email protected] Guangbo HAO School of Engineering-Electrical and Electronic Engineering, University College Cork, Cork, Ireland
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Introduction
Even in traditional industrial production, robots are no longer limited to structured environments; they have gradually become free of closed operating spaces by cooperating with humans and working with them in unstructured environments. Traditional industrial robots with high-stiffness joints usually excel in precision positioning and anti-disturbance but lack shock buffering and energy absorption functions. When directly used in cooperative and unstructured environments, such robots can easily collide with the surrounding objects and people; the robot body may become damaged by the strong collision, and the surrounding users may suffer from fatal injuries [1]. The use of flexible joints in robots is an effective approach to resolve the safety problems inherent to the process of human–machine cooperation in unstructured environments. The German Aerospace Center proposed the concept of active variable stiffness and successfully applied it to a KUKA robot [2]. This meth
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