0
Research Papers

A Nonlinear Stiffness Safe Joint Mechanism Design for Human Robot Interaction

[+] Author and Article Information
Jung-Jun Park

School of Mechanical Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713, Koreahantiboy@korea.ac.kr

Jae-Bok Song1

School of Mechanical Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713, Koreajbsong@korea.ac.kr

1

Corresponding author.

J. Mech. Des 132(6), 061005 (May 25, 2010) (8 pages) doi:10.1115/1.4001666 History: Received July 22, 2009; Revised April 08, 2010; Published May 25, 2010; Online May 25, 2010

Service robots used in human environments must be designed to avoid collisions with humans. A safe robot arm can be designed using active or passive compliance methods. A passive compliance system composed of purely mechanical elements often provides faster and more reliable responses for dynamic collision than an active one involving sensors and actuators. Because positioning accuracy and collision safety are equally important, a robot arm should have very low stiffness when subjected to a collision force that could cause human injury but should otherwise maintain very high stiffness. A novel safe joint mechanism (SJM) consisting of linear springs and a double-slider mechanism is proposed to address these requirements. The SJM has variable stiffness that can be achieved with only passive mechanical elements. Analyses and experiments on static and dynamic collisions show high stiffness against an external torque less than a predetermined threshold value and an abrupt drop in stiffness when the external torque exceeds this threshold. The SJM enables the robotic manipulator to guarantee positioning accuracy and collision safety and it is simple to install between an actuator and a robot link without a significant change in the robot’s design.

Copyright © 2010 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 17

Experimental results on static collision for robot arm with SJM-II and torque limiter: (a) collision force and (b) angular displacement of robot link

Grahic Jump Location
Figure 16

Experimental setup for comparison between SJM-II and torque limiter

Grahic Jump Location
Figure 15

Experimental results on dynamic collision: (a) with SJM-II and (b) without SJM-II

Grahic Jump Location
Figure 14

Experimental results for static collision for robot arm: (a) collision force versus time with and without SJM-II and (b) collision force versus angular displacement of SJM-II

Grahic Jump Location
Figure 13

Experimental setup for robot arm with SJM-II

Grahic Jump Location
Figure 12

Prototype of the SJM-II

Grahic Jump Location
Figure 11

Analytical results showing impact force versus time during collision with robot arm: (a) with SJM-II and (b) without SJM-II

Grahic Jump Location
Figure 10

Collision model between human head and robot arm: (a) concept collision model (b) simplified collision model

Grahic Jump Location
Figure 9

Operation of SJM-II: (a) before collision and (b) after collision

Grahic Jump Location
Figure 8

Dynamic analysis of the nonlinear spring system: (a) angular displacement versus input torque and (b) comparison between input torque and torque by spring force

Grahic Jump Location
Figure 7

Dynamic analysis of the nonlinear spring system: (a) input torque versus time and (b) angular displacement of input link and displacement of output slider versus time

Grahic Jump Location
Figure 6

Approximate dynamic analysis of nonlinear spring system

Grahic Jump Location
Figure 5

(a) Spring torque and force versus transmission angle and (b) equivalent stiffness of nonlinear spring system as a function of angular displacement

Grahic Jump Location
Figure 4

Nonlinear spring system composed of a double-slider mechanism with a spring: (a) zero configuration and (b) general configuration

Grahic Jump Location
Figure 3

Force ratio as a function of transmission angle

Grahic Jump Location
Figure 2

(a) Double-slider mechanism and (b) zero configuration and general configuration

Grahic Jump Location
Figure 1

Comparison between linear and nonlinear springs

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In