Abstract

An asymmetric three-degree-of-freedom parallel mechanism is adopted in rehabilitation robots for assisting patients suffering from stroke or trauma in the hip. It is necessary to keep its kinematic singularity out of the workspace of human normal gait and increase the output power efficiency. Therefore, a novel method is proposed to optimize geometrical parameters of the mechanism. To describe the kinematic singularity in a better way, the improved force transmission indexes based on previous methods are proposed using the reciprocal product and mobility condition of the closed-loop mechanism. The indexes mainly represent the force transmission performance of unactuated parts of subchains and moving platform. Together with the driving force transmission indexes and geometrical constraints, the multiobjective optimization model is established. The differential evolution algorithm, which is widely applied to mechanism optimization, is used to achieve optimal results. The Jacobian matrix singularity and output power efficiency along giving trajectory before and after optimization are compared to verify the effectiveness of the method.

References

1.
Sašo
,
J.
,
Gery
,
C.
,
Thierry
,
K.
,
Hansruedi
,
F.
, and
Manfred
,
M.
,
2003
, “
Robotic Orthosis Lokomat: A Rehabilitation and Research Tool
,”
Neuromodulation Technol. Neural Interface
,
6
(
2
), pp.
108
115
. 10.1046/j.1525-1403.2003.03017.x
2.
Veneman
,
J. F.
,
Kruidhof
,
R.
,
Hekman
,
E. E. G.
,
Ekkelenkamp
,
R.
,
Asseldonk
,
E. H. F. V.
, and
Kooij
,
H. V. D.
,
2007
, “
Design and Evaluation of the LOPES Exoskeleton Robot for Interactive Gait Rehabilitation
,”
IEEE Trans. Neural Syst. Rehabil. Eng.
,
15
(
3
), pp.
379
386
. 10.1109/TNSRE.2007.903919
3.
Yu
,
Y.
, and
Liang
,
W.
,
2013
, “
Manipulability Inclusive Principle for Hip Joint Assistive Mechanism Design Optimization
,”
Int. J. Adv. Manuf. Technol.
,
70
(
5–8
), pp.
929
945
.
4.
Zhang
,
W.
,
Zhang
,
W.
,
Shi
,
D.
, and
Ding
,
X.
,
2018
, “
Design of Hip Joint Assistant Asymmetric Parallel Mechanism and Optimization of Singularity-Free Workspace
,”
Mech. Mach. Theory
,
122
, pp.
389
403
. 10.1016/j.mechmachtheory.2017.12.013
5.
Gosselin
,
C. M.
, and
Angeles
,
J.
,
1991
, “
A Global Performance Index for the Kinematic Optimization of Robotic Manipulators
,”
ASME J. Mech. Des.
,
113
(
3
), pp.
220
226
. 10.1115/1.2912772
6.
Kim
,
H. S.
, and
Choi
,
Y. J.
,
2001
, “
Forward/Inverse Force Transmission Capability Analyses of Fully Parallel Manipulators
,”
IEEE Trans. Rob. Auto.
,
17
(
4
), pp.
526
531
. 10.1109/70.954767
7.
Lin
,
C. C.
, and
Chang
,
W. T.
,
2002
, “
The Force Transmissivity Index of Planar Linkage Mechanisms
,”
Mech. Mach. Theory
,
37
(
12
), pp.
1465
1485
. 10.1016/S0094-114X(02)00070-8
8.
Chang
,
W. T.
,
Lin
,
C. C.
, and
Lee
,
J. J.
,
2003
, “
Force Transmissibility Performance of Parallel Manipulators
,”
J. Rob. Syst.
,
20
(
11
), pp.
659
670
. 10.1002/rob.10115
9.
Merlet
,
J. P.
,
2006
, “
Jacobian, Manipulability, Condition Number, and Accuracy of Parallel Robots
,”
ASME J. Mech. Des.
,
128
(
1
), pp.
199
206
. 10.1115/1.2121740
10.
Chen
,
C.
, and
Angeles
,
J.
,
2007
, “
Generalized Transmission Index and Transmission Quality for Spatial Linkages
,”
Mech. Mach. Theory
,
42
(
9
), pp.
1225
1237
. 10.1016/j.mechmachtheory.2006.08.001
11.
Liu
,
X. J.
,
Wu
,
C.
, and
Wang
,
J.
,
2008
, “
A New Index for the Performance Evaluation of Parallel Manipulators: A Study on Planar Parallel Manipulators
,”
World Congress on Intelligent Control and Automation
,
Chongqing, China
,
June 25–27
, pp.
353
357
.
12.
Wang
,
J. S.
,
Liu
,
X. J.
, and
Wu
,
C.
,
2009
, “
Optimal Design of a New Spatial 3-DOF Parallel Robot With Respect to a Frame-Free Index
,”
Sci. China
,
52
(
4
), pp.
986
999
. 10.1007/s11431-008-0305-4
13.
Wu
,
C.
,
Liu
,
X. J.
, and
Wang
,
J.
,
2009
, “
Force Transmission Analysis of Spherical 5R Parallel Manipulators
,”
ASME/IFToMM International Conference on Reconfigurable Mechanisms and Robots
,
Kings College London, London, England
,
June 22–24
, pp.
331
336
.
14.
Wang
,
J.
,
Wu
,
C.
, and
Liu
,
X. J.
,
2010
, “
Performance Evaluation of Parallel Manipulators: Motion/Force Transmissibility and Its Index
,”
Mech. Mach. Theory
,
45
(
10
), pp.
1462
1476
. 10.1016/j.mechmachtheory.2010.05.001
15.
Yu
,
Y.
, and
Liang
,
W.
,
2012
, “
Design Optimization for Lower Limb Assistive Mechanism Based on Manipulability Inclusive Principle
,”
IEEE International Conference on Robotics and Biomimetics
,
Guangzhou, China
,
Dec. 11–14
, pp.
174
180
.
16.
Yun
,
Q.
, and
Dai
,
J. S.
,
2012
, “
Configuration and Actuation Analysis of a 2US+UPS Asymmetrical Parallel Mechanism
,”
ARCHIVE Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science 1989–1996 (vols. 203–210)
,
226
(
9
), pp.
2296
2308
.
17.
Manxin
,
W.
,
Haitao
,
L.
, and
Tian
,
H.
,
2017
, “
Kinematics Performance Evaluation of a 3-SPR Parallel Manipulator
,”
J. Mech. Eng.
,
53
(
5
), p.
108
.
18.
Olds
,
K. C.
,
2017
, “
Global Indices for Kinematic and Force Transmission Performance in Parallel Robots
,”
IEEE Trans. Rob.
,
31
(
2
), pp.
494
500
. 10.1109/TRO.2015.2398632
19.
Kuo
,
C.
, and
Dai
,
J.
,
2010
, “
Jacobian Analysis of Parallel Robotic Manipulators With a Passive Constraint Leg
,”
The First IFToMM Asian Conference on Mechanism and Machine Science
,
Taipei, Taiwan
,
Oct. 21–25
, pp.
21
25
.
20.
Price
,
K. V.
,
Storn
,
R. M.
, and
Lampinen
,
J. A.
,
2005
,
Differential Evolution-A Practical Approach to Global Optimization
, Vol.
141
,
Natural Computing Series
,
Springer Verlag
,
Berlin
.
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