An understanding of human seated posture is important across many fields of scientific research. Certain demographics, such as pregnant women, have special postural limitations that need to be considered. Physics-based posture prediction is a tool in which seated postures can be quickly and thoroughly analyzed, as long the predicted postures are realistic. This paper proposes and validates an optimization formulation to predict seated posture for pregnant women considering ground and seat pan contacts. For the optimization formulation, the design variables are joint angles (posture); the cost function is dependent on joint torques. Constraints include joint limits, joint torque limits, the distances from the end-effectors to target points, and self-collision avoidance constraints. Three different joint torque cost functions have been investigated to account for the special postural characteristics of pregnant women and consider the support reaction forces (SRFs) associated with seated posture. Postures are predicted for three different reaching tasks in common reaching directions using each of the objective function formulations. The predicted postures are validated against experimental postures obtained using motion capture. A linear regression analysis was used to evaluate the validity of the predicted postures and was the criteria for comparison between the different objective functions. A 56 degree of freedom model was used for the posture prediction. Use of the objective function minimizing the maximum normalized joint torque provided an R2 value of 0.828, proving superior to either of two alternative functions.

References

References
1.
Aissaoui
,
R.
,
Kauffmann
,
C.
,
Dansereau
,
J.
, and
Guise
,
J. a. D.
, 2001, “
Analysis of Pressure Distribution at the Body-Seat Interface in Abled-Bodied and Paraplegic Subjects Using a Deformable Active Contour Algorithm
,”
Med. Eng. Phys.
,
23
, pp.
359
367
.
2.
Carcone
,
S.
, and
Keir
,
P.
, 2007, “
Effects of Backrest Design on Biomechanics and Comfort During Seated Work
,”
Appl. Ergon
,
38
(
6
), pp.
755
764
.
3.
Ferguson-Pell
,
M.
, and
Cardi
,
M. D.
, 1993, “
Prototype Devlopment and Comparitive Evaluation of Wheelchair Pressure Mapping System
,”
Assist Technol.
,
5
(
2
), pp.
78
91
.
4.
Gyi
,
D. E.
, and
Porter
,
J. M.
, 1999, “
Interface Pressure and the Prediction of Car Seat Discomfort
,”
Appl. Ergon
,
30
, pp.
99
107
.
5.
Hobson
,
D. A.
, 1992, “
Comparitive Effects of Posture on Pressure and Shear at the Body-Seat Interface
,”
J. Rehabil. Res.
,
29
(
4
), pp.
21
31
.
6.
Hostens
,
I.
,
Papaioannou
,
G.
,
Spaepen
,
A.
, and
Ramon
,
H.
, 2001, “
Buttock and Back Pressure Distribution Tests on Seats of Mobile Agricultural Machinery
,”
Appl. Ergon
,
32
, pp.
347
355
.
7.
Verver
,
M. M.
,
Hoof
,
J. V.
,
Oomens
,
C. W. J.
,
Wismans
,
J. S. H. M.
, and
Baaijens
,
P. P. T.
, 2004, “
A Finite Element Model of the Human Buttocks for Prediction of Seat Pressure Distributions
,”
Comput. Methods Biomech. Biomed. Eng.
,
7
(
4
), pp.
193
203
.
8.
Fujimaki
,
F.
, and
Mitsuya
,
R.
, 2002, “
Study of Seated Sosture for VDT Work
,”
Displays
,
23
, pp.
17
24
.
9.
Hsiao
,
H.
, and
Keyserling
,
W. M.
, 1991, “
Evaluating Posture Behavior During Seated Tasks
,”
Int. J. Ind. Ergon
,
8
(
4
), pp.
313
334
.
10.
Reidel
,
S. A.
,
Harris
,
G. F.
, and
Jizzine
,
H. A.
, 1992, “
An Investigation of Seated Postural Stability
,”
IEEE Eng. Med. Biol.
,
11
(
4
), pp.
42
47
.
11.
Son
,
K.
,
Miller
,
J. a. A.
, and
Schultz
,
A. B.
, 1988, “
The Mechanical Role of the Trunk and Lower Extremities in a Seated Weight-Moving Task in the Sagittal Plane
,”
J. Biomech. Eng.
,
110
(
2
), pp.
97
103
.
12.
Bush
,
T. R.
, and
Hubbard
,
R. P.
, 2007, “
Support Force Measures of Midsized Men in Seated Positions
,”
J. Biomech. Eng.
,
129
(
1
), pp.
58
65
.
13.
Pope
,
M. H.
,
Wilder
,
D. G.
,
Jorneus
,
L.
,
Broman
,
H.
,
Svensson
,
M.
, and
Andersson
,
G.
, 1987, “
The Response of the Seated Human to Sinusoidal Vibration and Impact
,”
J. Biomech. Eng.
,
109
(
4
), pp.
279
284
.
14.
Gilleard
,
W.
,
Crosbie
,
J.
, and
Smith
,
R.
, 2008, “
A Longitudinal Study of the Effect of Pregnancy on Rising to Stand from a Chair
,”
J. Biomech.
,
41
(
4
), pp.
779
787
.
15.
Gilleard
,
W. L.
,
Crosbie
,
J.
, and
Smith
,
R.
, 2002, “
Static Trunk Posture in Sitting and Standing During Pregnancy and Early Postpartum
,”
Arch. Phys. Med. Rehabil.
,
83
(
12
), pp.
1739
1744
.
16.
Lee
,
Y. H.
,
Her
,
L.-L.
, and
Tsuang
,
Y.-H.
, 1999, “
A Comparison of Sitting Posture Adaptations of Pregnant and Non-Pregnant Females
,”
Int. J. Ind. Ergon
,
23
, pp.
391
396
.
17.
Lou
,
S.-Z.
,
Chou
,
Y.-L.
,
Chou
,
P.-H.
,
Lin
,
C.-J.
,
Chen
,
U.-C.
, and
Su
,
F. C.
, 2001, “
Sit to Stand at Different Periods of Pregnancy
,”
Clin. Biomech.
,
16
, pp.
194
198
.
18.
Klinich
,
J. D. a. S. L. W.
,
Ebby
,
B.
,
Rupp
,
J. D.
, and
Peralman
,
M. D.
, 1999, “
Seated Anthropometry During Pregnancy
,” Technical Report No. UMTRI-99-16, University of Michigan Transportation Institute, Ann Arbor, MI.
19.
Kim
,
J.
,
Yang
,
J.
, and
Abdel-Malek
,
K.
, 2009, “
Multi-Objective Optimization Approach for Predicting Seated Posture Considering Balance
,”
Int. J. Veh. Des.
,
51
(
3/4
), pp.
287
291
.
20.
Yang
,
J.
, and
Kim
,
J.
, 2010, “
Static Joint Torque Determination of a Human Model for Standing and Seating Tasks Considering Balance
,”
ASME J. Mech. Rob.
,
2
(
3
), p.
031005
.
21.
Yang
,
J.
,
Verma
,
U.
,
Marler
,
T.
,
Beck
,
S.
,
Rahmatalla
,
S.
, and
Harrison
,
C.
, 2009, “
Workspace Zone Differentiation Tool for Visualization of Seated Postural Comfort
,”
Int. J. Ind. Ergon
,
39
(
1
), pp.
267
276
.
22.
Gragg
,
J.
,
Yang
,
J.
, and
Howard
,
B.
, 2012, “
Hybrid Method for Driver Accommodation Using Optimization-Based Digital Human Models
,”
Comput.-Aided Des.
,
44
(
1
), pp.
29
39
.
23.
Gragg
,
J.
,
Yang
,
J.
, and
Long
,
J.
, 2011, “
Optimization-Based Approach for Determining Driver Seate Adjustment Range
,”
Int. J. Veh. Des.
,
57
(
2/3
), pp.
148
161
.
24.
Howard
,
B.
, and
Yang
,
J.
, 2011, “
Optimization-Based Seated Posture Prediction Considering Contact With Environment
,”
Proceedings of the ASME 2011 International Design Engineering Technical Conference & Computer and Information in Engineering Conference
, Washington, D.C., Paper no. DETC2011-48685, pp.
557
566
.
25.
Howard
,
B.
,
Yang
,
J.
, and
Gragg
,
J.
, 2010, “
Toward a New Digital Pregnant Woman Model and Kinematic Posture Prediction
,”
V.
Duffy
, Ed., ed:CRC Press, Miami, Fl., 2010, pp.
293
303
.
26.
Hollerbach
,
J.
, 1980, “
A Recursive Lagrangian Formulation of Manipulator Dynamics and a Comparative Study of Dynamics Formulation Complexity
,”
IEEE Trans. Syst. Man Cybern.
,
10
, pp.
730
736
.
27.
Xiang
,
Y.
,
Arora
,
J.
, and
Abdel-Malek
,
K.
, 2009, “
Optimization-Based Motion Prediction of Mechanical Systems: Sensitivity Analysis
,”
Struct. Multidiscip. Optim.
,
37
, pp.
595
608
.
28.
Yang
,
J.
,
Xiang
,
Y.
, and
Kim
,
J.
, 2009, “
Determining the Static Joint Torques of Digital Human Models Considering Balance
,”
Proceedings of the ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference
, San Diego California, Paper No. DETC2009-87529.
29.
Liu
,
Q.
,
Marler
,
T.
,
Yang
,
J.
, and
Harrison
,
C.
, 2009, “
Posture Prediction With External Loads- a Pilot Study
,”
SAE Int. J. Passenger Cars-Mech. Syst.
,
2
(
1
), pp.
1014
1023
.
30.
Howard
,
B.
, and
Yang
,
J.
, 2011, “
Formulation of Human Performance Measures for Full Body Pregnant Women Standing Posture Prediction
,”
Proceedings of the SAE 2011 World Congress and Exhibition Detroit
, MI, Paper No. 2011-01-0062.
31.
Yang
,
J.
,
Marler
,
T.
, and
Rahmatalla
,
S.
, 2011, “
Multi-Objective Optimization Base Method for Upper Body Postuer Prediction: Devlopment and Validation
,”
Robotica
,
29
(
2
), pp.
245
253
.
32.
Yang
,
J.
,
Rahmatalla
,
S.
,
Marler
,
T.
,
Abdel-Malek
,
K.
, and
Harrison
,
C.
, 2007, “
Validation of Predicted Posture for the Virtual Human Santos
,”
Proceedings Of The 1st International Conference On Digital Human Modeling.
, Beijing, China, pp.
500
510
.
33.
Marler
,
T.
,
Yang
,
J.
,
Rahmatalla
,
S.
,
Abdel-Malek
,
K.
, and
Harrison
,
C.
, 2007, “
New Validation Protocol for Predicted Posture
,”
Proceedings of SAE Digital Human Modeling for Design and Engineering
.,
University of Washington
,
Seattle, WA
.
34.
Yang
,
J.
,
Marler
,
T.
,
Arora
,
J.
, and
Abdel-Malek
,
K.
, 2004, “
Multi-Objective Optimization for Upper Body Posutre Prediction
,”
American Institute of Aeronautics and Astronautics
, 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, Aug. 30-Sept. 1, 2004,
Albany
,
New York
, pp.
1
18
.
35.
Rupp
,
J.
, 1990, “
Desing, Development, and Testing of a New Pregnant Abdomen for the Hybrid Iii Small Female Crash Dummy
,” Technical Report No. UMTRI-2001-07, University of Michigan Transportation Institute, Ann Arbor, MI.
36.
Syddall
,
H. E.
,
Sayer
,
A. A.
,
Simmonds
,
S. J.
,
Osmond
,
C.
,
Cox
,
V.
,
Dennison
,
E. M.
,
Barker
,
D. J.
, and
Cooper
,
C.
, 2005, “
Birth Weight, Infant Weight Gain, and Cause-Specific Mortality: The Hertfordshire Cohort Study
,”
Am. J. Epidemiol.
,
161
(
11
), pp.
1074
1080
.
37.
Brace
,
R. A.
, and
Wolf
,
E. J.
, 1989, “
Normal Amniotic Fluid Volume Changes Throughout Pregnancy
,”
Am. J. Obstet. Gynecol.
,
161
(
2
), pp.
382
388
.
38.
Denavit
,
J.
, and
Hartenberg
,
R. S.
, 1955, “
A Kinematic Notation for Lower-Pair Mechanisms Based on Matrices
,”
J. Appl. Mech.
,
77
, pp.
215
221
.
39.
Riemer
,
R.
, and
Hsiao-Wecksler
,
E. T.
, 2008, “
Improving Joint Torque Calculations: Optimization-Based Inverse Dynamics to Reduce the Effect of Motion Errors
,”
J. Biomech.
,
41
(
7
), pp.
1503
1509
.
40.
Riemer
,
R.
, and
Hsiao-Wecksler
,
E. T.
, 2009, “
Improving Net Joint Torque Calculations through a Two-Step Optimization Method for Estimating Body Segment Properties
,”
J. Biomech. Eng.
,
131
(
1
), p.
011007
.
41.
Dumas
,
R.
,
Cheze
,
L.
, and
Verriest
,
J.
, 2007, “
Adjustments to Mcconville et al. And Young et al. Body Segment Inertial Parameters
,”
J. Biomech.
,
40
(
3
), pp.
543
553
.
42.
Howard
,
B.
, and
Yang
,
J.
, 2012, “
Calculating Support Reaction Forces in Physics-Based Seated Posture Prediction for Pregnant Women
,”
Int. J. Rob. Autom.
,
27
(2)
, pp.
247
260
.
43.
Gragg
,
J.
,
Yang
,
J.
, and
Boothby
,
R.
, 2011, “
Posture Reconstruction Method for Mapping Joint Angles of Motion Capture Experiments to Simulation Models Digital Human Modeling
,” Vol. 6777, Ed.,
V.
Duffy
, ed.,
Springer Berlin/Heidelberg
, pp.
69
78
.
44.
Gill
,
P. E.
,
Murray
,
W.
, and
Saunders
,
M. A.
, 2002, “
SNOPT: An SQP Algorithm for Large Scale Constrained Optimization
,”
SIAM J. Optim.
,
12
, pp.
979
1006
.
45.
Zhang
,
X.
, and
Chaffin
,
D.
, 2000, “
A Three-Dimensional Dynamic Posture Prediction Model for in-Vehicle Seated Reaching Movements: Development and Validation
,”
Ergonomics
,
43
(
9
), pp.
1314
1330
.
46.
Parkinson
,
M. B.
,
Chaffin
,
D. B.
, and
Reed
,
M. P.
, 2006, “
Center of Pressure Excursion Capability in Performance of Seated Lateral-Reaching Tasks
,”
Clin. Biomech.
,
21
(
1
), pp.
26
32
.
47.
Sardain
,
P.
, and
Bessonet
,
G.
, 2004, “
Forces Acting on a Biped Robot. Center of Pressure-Zero Moment Point
,”
IEEE Trans. Syst. Man Cybern., Part A. Syst. Humans
,
34
(
5
), pp.
630
637
.
48.
Howard
,
B.
, and
Yang
,
J.
,
A New Stability Criterion for Human Seated Tasks With Given Postures, International Journal of Humanoid Robotics
, (in press).
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