Abstract

To reduce injury in physical human–robot interactions (pHRIs), a common practice is to introduce compliance to joints or arm of a robotic manipulator. In this paper, we present a robotic arm made of parallel guided beams whose stiffness can be continuously tuned by morphing the shape of the cross section through two four-bar linkages actuated by servo motors. An analytical lateral stiffness model is derived based on the pseudo-rigid-body model and validated by experiments. A physical prototype of a three-armed manipulator is built. Extensive stiffness and impact tests are conducted, and the results show that the stiffness of the robotic arm can be changed up to 3.6 times at a morphing angle of 37 deg. At an impact velocity of 2.2 m/s, the peak acceleration has a decrease of 19.4% and a 28.57% reduction of head injury criteria (HIC) when the arm is tuned from the high stiffness mode to the low stiffness mode. These preliminary results demonstrate the feasibility to reduce impact injury by introducing compliance into the robotic link and that the compliant link solution could be an alternative approach for addressing safety concerns of physical human–robot interactions.

References

References
1.
Colgate
,
E.
,
Wannasuphoprasit
,
W.
, and
Peshkin
,
M. A.
,
1996
, “
Cobots: Robots for Collaboration With Human Operators
,”
International Mechanical Engineering Congress and Exhibition, Atlanta, GA, Nov. 17–22
, pp.
433
439
.
2.
Chu
,
A.
,
Kazerooni
,
H.
, and
Zoss
,
A.
,
2005
, “
On the Biomimetic Design of the Berkeley Lower Extremity Exoskeleton (Bleex)
,”
IEEE International Conference on Robotics and Automation (ICRA)
,
Barcelona, Spain
,
Apr. 18–22
, pp.
4345
4352
. 10.1109/robot.2005.1570789
3.
Frisoli
,
A.
,
Rocchi
,
F.
,
Marcheschi
,
S.
,
Dettori
,
A.
,
Salsedo
,
F.
, and
Bergamasco
,
M.
,
2005
, “
A New Force-Feedback Arm Exoskeleton for Haptic Interaction in Virtual Environments
,”
First Joint Eurohaptics Conference, Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, World Haptics (WHC)
,
Pisa, Italy
,
Mar. 18–20
, pp.
195
201
. 10.1109/whc.2005.15
4.
Roderick
,
S.
, and
Carignan
,
C.
,
2007
,
Designing Safety-Critical Rehabilitation Robots
,
InTech
,
Vienna, Austria
.
5.
Wolbrecht
,
E. T.
,
Chan
,
V.
,
Reinkensmeyer
,
D. J.
, and
Bobrow
,
J. E.
,
2008
, “
Optimizing Compliant, Model-Based Robotic Assistance to Promote Neurorehabilitation
,”
IEEE Trans. Neural Syst. Rehabil. Eng.
,
16
(
3
), pp.
286
297
. 10.1109/TNSRE.2008.918389
6.
Yamada
,
Y.
,
Konosu
,
H.
,
Morizono
,
T.
, and
Umetani
,
Y.
,
1999
, “
Proposal of Skill-Assist: A System of Assisting Human Workers by Reflecting Their Skills in Positioning Tasks
,”
IEEE International Conference on Systems, Man, and Cybernetics
,
Tokyo, Japan
,
Oct. 12–15
, Vol.
4
, pp.
11
16
. 10.1109/icsmc.1999.812368
7.
Kaipa
,
K. N.
,
Morato
,
C.
,
Liu
,
J.
, and
Gupta
,
S. K.
,
2014
, “
Human-Robot Collaboration for Bin-Picking Tasks to Support Low-Volume Assemblies
,”
Human-Robot Collaboration for Industrial Manufacturing Workshop, Held at Robotics: Science and Systems Conference (RSS 2014)
,
Rome, Italy
,
July 16–17
. 10.1115/detc2014-34671
8.
Bicchi
,
A.
,
Peshkin
,
M. A.
, and
Colgate
,
J. E.
,
2008
, “Safety for Physical Human–Robot Interaction,”
Springer Handbook of Robotics
,
Springer
,
New York
, pp.
1335
1348
.
9.
Versace
,
J.
,
1971
, “
A Review of the Severity Index
,”
Proceedings of the 15th Stapp Conference, SAE Paper No. 710881
, pp.
771
796
.
10.
Newman
,
J. A.
,
Shewchenko
,
N.
, and
Welbourne
,
E.
,
2000
, “
A Proposed New Biomechanical Head Injury Assessment Function—The Maximum Power Index
,”
Proceedings of the 44th Stapp Car Crash Conference, Atlanta, GA, SAE paper 2000-01-SC16
, pp.
215
247
. 10.4271/2000-01-sc16
11.
International Organization for Standardization
,
2006
, “
Robots for Industrial Environments—Safety Requirements. Part I: Robot
,” ISO10218-1:2006.
12.
Zheng
,
Y.-F.
, and
Hemami
,
H.
,
1985
, “
Mathematical Modeling of a Robot Collision With Its Environment
,”
J. Rob. Syst.
,
2
(
3
), pp.
289
307
. 10.1002/rob.4620020307
13.
She
,
Y.
,
Meng
,
D.
,
Cui
,
J.
, and
Su
,
H.-J.
,
2017
, “
On the Impact Force of Human-Robot Interaction: Joint Compliance vs. Link Compliance
,”
2017 IEEE International Conference on Robotics and Automation (ICRA), Marina Bay Sands
,
Singapore
,
May 29–June 3
, pp.
6718
6723
. 10.1109/icra.2017.7989795
14.
Gao
,
D.
, and
Wampler
,
C. W.
,
2009
, “
Head Injury Criterion
,”
IEEE Rob. Autom. Mag.
,
16
(
4
), pp.
71
74
. 10.1109/MRA.2009.934824
15.
Haddadin
,
S.
,
Albu-Schäffer
,
A.
, and
Hirzinger
,
G.
,
2007
, “
Approaching Asimov’s 1st Law: The Impact of the Robot’s Weight Class
,”
Robotics: Science and Systems Conference Workshop: Robot Manipulation: Sensing and Adapting the Real World (RSS2007)
,
Atlanta, GA
,
June 27–30
.
16.
Pervez
,
A.
, and
Ryu
,
J.
,
2008
, “
Safe Physical Human Robot Interaction—Past, Present and Future
,”
J. Mech. Sci. Technol.
,
22
(
3
), pp.
469
483
. 10.1007/s12206-007-1109-3
17.
Iwata
,
H.
,
Hoshino
,
H.
,
Morita
,
T.
, and
Sugano
,
S.
,
2001
, “
Force Detectable Surface Covers for Humanoid Robots
,”
2001 IEEE/ASME International Conference on Advanced Intelligent Mechatronics
,
Como, Italy
,
July 8–12
, Vol.
2
, pp.
1205
1210
. 10.1109/aim.2001.936882
18.
Zinn
,
M.
,
Roth
,
B.
,
Khatib
,
O.
, and
Salisbury
,
J. K.
,
2004
, “
A New Actuation Approach for Human Friendly Robot Design
,”
Int. J. Rob. Res.
,
23
(
4–5
), pp.
379
398
. 10.1177/0278364904042193
19.
Shepherd
,
R. F.
,
Ilievski
,
F.
,
Choi
,
W.
,
Morin
,
S. A.
,
Stokes
,
A. A.
,
Mazzeo
,
A. D.
,
Chen
,
X.
,
Wang
,
M.
, and
Whitesides
,
G. M.
,
2011
, “
Multigait Soft Robot
,”
Proc. Natl. Acad. Sci.
,
108
(
51
), pp.
20400
20403
. 10.1073/pnas.1116564108
20.
Tolley
,
M. T.
,
Shepherd
,
R. F.
,
Mosadegh
,
B.
,
Galloway
,
K. C.
,
Wehner
,
M.
,
Karpelson
,
M.
,
Wood
,
R. J.
, and
Whitesides
,
G. M.
,
2014
, “
A Resilient, Untethered Soft Robot
,”
Soft Robot.
,
1
(
3
), pp.
213
223
. 10.1089/soro.2014.0008
21.
Filippini
,
R.
,
Sen
,
S.
, and
Bicchi
,
A.
,
2008
, “
Toward Soft Robots You Can Depend On
,”
IEEE Rob. Autom. Mag.
,
15
(
3
), pp.
31
41
. 10.1109/MRA.2008.927696
22.
Ham
,
R. v.
,
Sugar
,
T. G.
,
Vanderborght
,
B.
,
Hollander
,
K. W.
, and
Lefeber
,
D.
,
2009
, “
Compliant Actuator Designs
,”
IEEE Rob.Autom. Mag.
,
16
(
3
), pp.
81
94
. 10.1109/MRA.2009.933629
23.
Tsagarakis
,
N. G.
,
Morfey
,
S.
,
Cerda
,
G. M.
,
Zhibin
,
L.
, and
Caldwell
,
D. G.
,
2013
, “
Compliant Humanoid Coman: Optimal Joint Stiffness Tuning for Modal Frequency Control
,”
2013 IEEE International Conference on Robotics and Automation (ICRA)
,
Karlsruhe, Germany
,
May 6–10
, pp.
673
678
. 10.1109/icra.2013.6630645
24.
Pratt
,
G. A.
, and
Williamson
,
M. M.
,
1995
, “
Series Elastic Actuators
,”
1995 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human Robot Interaction and Cooperative Robots
,
Pittsburgh, PA
,
Aug. 5–9
, Vol.
1
, pp.
399
406
. 10.1109/iros.1995.525827
25.
Haddadin
,
S.
,
Albu-Schäffer
,
A.
, and
Hirzinger
,
G.
,
2009
, “
Requirements for Safe Robots: Measurements, Analysis and New Insights
,”
Int. J. Rob. Res.
,
28
(
1112
), pp.
1507
1527
. 10.1177/0278364909343970
26.
Rodríguez
,
A. G.
,
Chacón
,
J.
,
Donoso
,
A.
, and
Rodríguez
,
A. G.
,
2011
, “
Design of an Adjustable-Stiffness Spring: Mathematical Modeling and Simulation, Fabrication and Experimental Validation
,”
Mech. Mach. Theory
,
46
(
12
), pp.
1970
1979
. 10.1016/j.mechmachtheory.2011.07.002
27.
Wu
,
Y.-S.
, and
Lan
,
C.-C.
,
2014
, “
Linear Variable-Stiffness Mechanisms Based on Preloaded Curved Beams
,”
J. Mech. Design
,
136
(
12
), p.
122302
. 10.1115/1.4028705
28.
Ayoubi
,
Y.
,
Laribi
,
M. A.
,
Courrèges
,
F.
,
Zeghloul
,
S.
, and
Arsicault
,
M.
,
2016
, “
A Complete Methodology to Design a Safety Mechanism for Prismatic Joint Implementation
,”
2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
,
Daejeon, South Korea
,
Oct. 9–14
, pp.
304
309
. 10.1109/iros.2016.7759071
29.
Ayoubi
,
Y.
,
Laribi
,
M. A.
,
Courrèges
,
F.
,
Zeghloul
,
S.
, and
Arsicault
,
M.
,
2018
, “
Complete Design Methodology of Biomimetic Safety Device for Cobots Prismatic Joints
,”
Rob. Auton. Syst.
,
102
, pp.
44
53
. 10.1016/j.robot.2018.01.008
30.
López-Martínez
,
J.
,
Blanco-Claraco
,
J. L.
,
García-Vallejo
,
D.
, and
Giménez-Fernández
,
A.
,
2015
, “
Design and Analysis of a Flexible Linkage for Robot Safe Operation in Collaborative Scenarios
,”
Mech. Mach. Theory
,
92
, pp.
1
16
. 10.1016/j.mechmachtheory.2015.04.018
31.
Park
,
J.-J.
,
Kim
,
B.-S.
,
Song
,
J.-B.
, and
Kim
,
H.-S.
,
2008
, “
Safe Link Mechanism Based on Nonlinear Stiffness for Collision Safety
,”
Mech. Mach. Theory
,
43
(
10
), pp.
1332
1348
. 10.1016/j.mechmachtheory.2007.10.004
32.
Zhang
,
M.
,
Laliberté
,
T.
, and
Gosselin
,
C.
,
2016
, “
Force Capabilities of Two-Degree-of-Freedom Serial Robots Equipped With Passive Isotropic Force Limiters
,”
ASME J. Mech. Robot.
,
8
(
5
), p.
051002
. 10.1115/1.4032120
33.
She
,
Y.
,
Su
,
H.-J.
, and
Hurd
,
C. J.
,
2015
, “
Shape Optimization of 2D Compliant Links for Design of Inherently Safe Robots
,”
Proceedings of IDETC/CIE
,
Boston, MA
,
Aug. 2–5
, p.
V05BT08A004
, ASME Paper No. DETC2015-46622. 10.1115/detc2015-46622
34.
She
,
Y.
,
Su
,
H.-J.
,
Meng
,
D.
,
Song
,
S.
, and
Wang
,
J.
,
2018
, “
Design and Modeling of a Compliant Link for Inherently Safe Corobots
,”
J. Mech. Robot.
,
10
(
1
), p.
011001
. 10.1115/1.4038530
35.
Galloway
,
K. C.
,
Clark
,
J. E.
, and
Koditschek
,
D. E.
,
2013
, “
Variable Stiffness Legs for Robust, Efficient, and Stable Dynamic Running
,”
J. Mech. Robot.
,
5
(
1
), p.
011009
. 10.1115/1.4007843
36.
Kim
,
Y.-J.
,
Cheng
,
S.
,
Kim
,
S.
, and
Iagnemma
,
K.
,
2013
, “
A Novel Layer Jamming Mechanism With Tunable Stiffness Capability for Minimally Invasive Surgery
,”
IEEE Trans. Rob.
,
29
(
4
), pp.
1031
1042
. 10.1109/TRO.2013.2256313
37.
Hines
,
L.
,
Arabagi
,
V.
, and
Sitti
,
M.
,
2012
, “
Shape Memory Polymer-Based Flexure Stiffness Control in a Miniature Flapping-Wing Robot
,”
IEEE Trans. Rob.
,
28
(
4
), pp.
987
990
. 10.1109/TRO.2012.2197313
38.
Stilli
,
A.
,
Wurdemann
,
H. A.
, and
Althoefer
,
K.
,
2017
, “
A Novel Concept for Safe, Stiffness-Controllable Robot Links
,”
Soft Robot.
,
4
(
1
), pp.
16
22
. 10.1089/soro.2016.0015
39.
She
,
Y.
,
2018
, “
Compliant Robotic Arms for Inherently Safe Physical Human-Robot Interaction
,” Ph.D. thesis,
The Ohio State University
,
Columbus, OH
.
40.
Song
,
S.
,
Zeng
,
X.
,
She
,
Y.
,
Wang
,
J.
, and
Su
,
H.-J.
,
2019
, “
Modeling and Control of Inherently Safe Robots With Variable Stiffness Links
,”
Rob. Auton. Syst.
,
120
, p.
103247
. 10.1016/j.robot.2019.07.017
41.
She
,
Y.
,
Su
,
H.-J.
,
Lai
,
C.
, and
Meng
,
D.
,
2016
, “
Design and Prototype of a Tunable Stiffness Arm for Safe Human-Robot Interaction
,”
Proceedings of IDETC/CIE
,
Charlotte, NC
,
Aug. 21–24
, p.
V05BT07A063
, ASME Paper No. IDETC2016-59523. 10.1115/detc2016-59523
42.
Haddadin
,
S.
,
Albu-Schäffer
,
A.
, and
Hirzinger
,
G.
,
2007
, “
Safety Evaluation of Physical Human-Robot Interaction via Crash-Testing
,”
Robotics: Science and Systems Conference Workshop
,
Atlanta, GA
,
June 27–30
, Vol.
3
, pp.
217
224
. 10.15607/rss.2007.iii.028
43.
Haddadin
,
S.
,
Albu-Schaffer
,
A.
, and
Hirzinger
,
G.
,
2008
, “
The Role of the Robot Mass and Velocity in Physical Human-Robot Interaction-Part I: Non-Constrained Blunt Impacts
,”
2008 IEEE International Conference on Robotics and Automation (ICRA)
,
Pasadena, CA
,
May 19–23
, pp.
1331
1338
. 10.1109/robot.2008.4543388
44.
Gao
,
D.
, and
Wampler
,
C.
,
2009
, “
Head Injury Criterion
,”
IEEE Rob. Autom. Mag.
,
16
(
4
), pp.
71
74
. 10.1109/MRA.2009.934824
45.
Howell
,
L. L.
, and
Midha
,
A.
,
1994
, “
A Method for the Design of Compliant Mechanisms With Small-Length Flexural Pivots
,”
J. Mech. Design
,
116
(
1
), pp.
280
290
. 10.1115/1.2919359
46.
Howell
,
L. L.
, and
Midha
,
A.
,
1995
, “
Parametric Deflection Approximations for End-Loaded, Large-Deflection Beams in Compliant Mechanisms
,”
J. Mech. Design
,
117
(
1
), pp.
156
165
. 10.1115/1.2826101
47.
Howell
,
L. L.
,
2001
,
Compliant Mechanisms
,
Wiley-Interscience
,
New York, NY
.
48.
Waldron
,
K. J.
,
Kinzel
,
G. L.
, and
Agrawal
,
S. K.
,
2016
,
Kinematics, Dynamics, and Design of Machinery
,
John Wiley & Sons
,
New York, NY
.
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