0
Research Papers

An Adjustable Constant-Force Mechanism for Adaptive End-Effector Operations

[+] Author and Article Information
Yi-Ho Chen

Department of Mechanical Engineering,  National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan, R.O.C.solzeta@gmail.com

Chao-Chieh Lan1

Department of Mechanical Engineering,  National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan, R.O.C.cclan@mail.ncku.edu.tw

1

Corresponding author.

J. Mech. Des 134(3), 031005 (Feb 29, 2012) (9 pages) doi:10.1115/1.4005865 History: Received June 17, 2011; Revised January 10, 2012; Published February 28, 2012; Online February 29, 2012

Force regulation is a challenging problem for robot end-effectors when interacting with an unknown environment. It often requires sophisticated sensors with computerized control. This paper presents an adjustable constant-force mechanism (ACFM) to passively regulate the contact force of a robot end-effector. The proposed ACFM combines the negative stiffness of a bistable mechanism and positive stiffness of a linear spring to generate a constant-force output. Through prestressing the linear spring, the constant-force magnitude can be adjusted to adapt to different working environments. The ACFM is a monolithic compliant mechanism that has no frictional wear and is capable of miniaturization. We propose a design formulation to find optimal mechanism configurations that produce the most constant-force. A resulting force to displacement curve and maximal stress curve can be easily manipulated to fit a different application requirement. Illustrated experiments show that an end-effector equipped with the ACFM can adapt to a surface of variable height, without additional motion programming. Since sensors and control effort are minimized, we expect this mechanism can provide a reliable alternative for robot end-effectors to interact friendly with an environment.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

(a) Buckling structure, (b) a CFM with three springs, (c) end-effector with an active force controller, (d) end-effector with a passive CFM

Grahic Jump Location
Figure 2

(a) F–Δ curve of a spring, (b) F–Δ curve of a CFM, (c) characterization of the F–Δ curve of a CFM

Grahic Jump Location
Figure 3

CAD model of an optimized CFM

Grahic Jump Location
Figure 4

F–Δ curve of the CFM in Fig. 3

Grahic Jump Location
Figure 5

The proposed ACFM

Grahic Jump Location
Figure 6

Schematic of the ACFM force curves

Grahic Jump Location
Figure 7

Schematic of the bistable beam design

Grahic Jump Location
Figure 8

Optimal shapes of the bistable beam

Grahic Jump Location
Figure 9

Optimal F–Δ curves of the ACFM

Grahic Jump Location
Figure 10

Schematic of the bistable beam design (arc and line)

Grahic Jump Location
Figure 11

Optimal bistable beam shapes (arc and line)

Grahic Jump Location
Figure 12

Optimal F–Δ curves of the ACFM (arc and line)

Grahic Jump Location
Figure 13

Schematic of the linear spring design

Grahic Jump Location
Figure 14

Optimal shape of the linear spring

Grahic Jump Location
Figure 16

Comparison of simulation results

Grahic Jump Location
Figure 17

Effect of bistable beam spacing on lateral stiffness

Grahic Jump Location
Figure 18

Effect of bistable beam spacing on out-of-plane stiffness

Grahic Jump Location
Figure 19

ACFMs symmetrically placed at 120 deg and 90 deg intervals

Grahic Jump Location
Figure 21

Experimental F–Δ curves (compression)

Grahic Jump Location
Figure 22

Experimental F–Δ curves (decompression)

Grahic Jump Location
Figure 23

Constant-force versus adjustment length (Fc –Δa )

Grahic Jump Location
Figure 24

Experiment setup

Grahic Jump Location
Figure 25

Force curves of knife-edge (without preload)

Grahic Jump Location
Figure 26

Force curves of knife-edge (with preload)

Grahic Jump Location
Figure 27

Force curves of roller (without preload)

Grahic Jump Location
Figure 28

Force curves of roller (with preload)

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