A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight, and most importantly safe. To achieve these goals, an actuator with a good “power to weight” ratio, good mechanical efficiency, good “strength to weight” ratio, and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and heavy weight. However, using the design procedure outlined in this text, both efficiency and weight are improved; thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a power to weight ratio of 277Wkg, approaching that of the dc motor driving it, at 312Wkg, as well as a mechanical efficiency of 0.74, and a maximum strength to weight ratio of 11.3kNkg(1154kgfkg).

1.
Census 2000 Brief, Disability Status. U.S. Census Bureau, 2000, URL ⟨http://www.firstgov.gov/http://www.firstgov.gov/⟩ (online).
2.
Van Hook
,
F. W.
,
Demonbreun
,
D.
, and
Weiss
,
B. D.
, 2003, “
Ambulatory Devices for Chronic Gait Disorders in the Elderly
,”
Am. Fam. Physician
0002-838X,
67
(
8
), pp.
1717
1724
.
3.
Edgerton
,
V. R.
,
Roy
,
R. R.
,
Gregor
,
R. J.
, and
Rugg
,
S.
, 1986, “
Morphological Basis of Skeletal Muscle Power Output
,”
Human Muscle Power
,
N. L.
Jones
,
N.
McCartney
, and
A. J.
McComas
, eds.,
Human Kinetics Publishers, Inc.
, Champaign, IL, Ch. 4, pp.
43
64
.
4.
Tsagarakis
,
N.
, and
Caldwell
,
D. G.
, 2000, “
Improved Modelling and Assessment of Pneumatic Muscle Actuators
,”
IEEE International Conference on Robotics & Automation (ICRA)
, pp.
3641
3646
.
5.
Chou
,
C. P.
, and
Hannaford
,
B.
, 1996, “
Measurement and Modeling of McKibben Pneumatic Artificial Muscles
,”
IEEE Trans. Rob. Autom.
1042-296X,
12
(
1
), pp.
90
102
.
6.
Wang
,
Z.
,
Zhu
,
S.
,
Wang
,
J.
,
Pierson
, Jr,
R. N.
, and
Heymsfield
,
S. B.
, 2003, “
Whole-Body Skeletal Muscle Mass: Development and Validation of Total-Body Potassium Prediction Models
,”
Am. J. Clin. Nutr.
0002-9165,
77
(
1
), pp.
76
82
.
7.
Guyton
,
A. C.
, and
Hall
,
J. E.
, 1996,
Textbook of Medical Physiology
,
9th ed.
,
W. B. Saunders Co.
, Philadelphia.
8.
Winters
,
J. M.
, and
Stark
,
L.
, 1988, “
Estimated Mechanical Properties of Synergistic Muscles Involved in Movements of a Variety of Human Joints
,”
J. Biomech.
0021-9290,
21
(
12
), pp.
1027
1041
.
9.
Sea-23-23 Product Specifications, 2004, Yobotics, Inc., URL ⟨http://www.yobotics.com/http://www.yobotics.com/⟩ (online).
10.
Robinson
,
D. W.
,
Pratt
,
J. E.
,
Paluska
,
D. J.
, and
Pratt
,
G. A.
, 1999, “
Series Elastic Actuator Development for a Biomimetric Walking Robot
,”
IEEE/ASME International Conference on Advanced Intelligent Mechatronics
, pp.
561
568
.
11.
Tsagarakis
,
N.
,
Caldwell
,
D. G.
, and
Medrano-Cerda
,
G. A.
, 1999, “
A 7 DOF Pneumatic Muscle Actuator (PMA) Powered Exoskeleton
,”
8th IEEE International Workshop on Robot and Human Interaction (RO-MAN)
, pp.
327
333
.
12.
Daerden
,
F.
, and
Lefeber
,
D.
, 2002, “
Pneumatic Artificial Muscles: Actuators for Robotics and Automation
,”
Euro. J. Mech. Environ. Eng.
,
47
(
1
), pp.
10
21
.
13.
Kobayashi
,
H.
,
Aoki
,
J.
,
Hosono
,
H.
,
Matsushita
,
T.
,
Ishida
,
Y.
,
Kikuchi
,
K.
, and
Koseki
,
M.
, 2002, “
Concept of Wear-Type Muscular Support Apparatus (Muscle Suit)
,”
IEEE International Conference on Robotics and Automation (ICRA)
, pp.
3236
3241
.
14.
Air Muscle Product Specifications, 2005, Shadow Robot Company Ltd., URL ⟨http://www.shadow.org.uk/http://www.shadow.org.uk/⟩ (online).
15.
Shigley
,
J. E.
, and
Mischke
,
C. R.
, 1989,
Mechanical Engineering Design
,
5th ed.
,
McGraw–Hill
, New York.
16.
Eggert
,
R. J.
, 2003, “
Power Screws
,”
Standard Handbook of Machine Design
,
Shigley
and
Mischke
, Eds.,
2nd Ed.
,
McGraw–Hill
, New York, Ch. 20.
17.
Ball Bearing Catalog, 2004, technical data, NTN Corporation. URL ⟨http://www.ntnamerica.com/http://www.ntnamerica.com/⟩ (online).
18.
Serway
,
J. E.
, 1986,
Physics for Scientists and Engineers
,
2nd ed.
,
Saunders College Publishing
, New York.
19.
Searchable Database, 2004, MatWeb, Material Property Data, URL ⟨http://www.matweb.com/http://www.matweb.com/⟩ (online).
20.
Ugural
,
A. C.
, 1991,
Mechanics of Materials
,
McGraw–Hill
, New York.
21.
Whittle
,
M. W.
, 1996,
Gait Analysis: An Introduction
,
2nd ed.
,
Butterworth–Heinemann
, Oxford.
22.
IMPREGLON 525 plating data sheet, 2004, SR Metal Protection Ltd. URL ⟨http://www.impreglon.com/http://www.impreglon.com/⟩ (online).
23.
Hollander
,
K. W.
, and
Sugar
,
T. G.
, 2004, “
Concepts for Compliant Actuation in Wearable Robotic Systems
,” U.S.–Korea Conference (UKC) CDROM.
24.
Hollander
,
K. W.
,
Ilg
,
R.
, and
Sugar
,
T. G.
, 2005, “
Design of the Robotic Tendon
,”
Design of Medical Devices Conference (DMD 2005)
.
25.
Hollander
,
K. W.
,
Sugar
,
T. G.
, and
Herring
,
D. E.
, 2005, “
A Robotic `Jack Spring'TM for Ankle Gait Assistance
,”
ASME International Design Engineering Technical Conference & Computers and Information In Engineering Conference (IDETC/CIE 2005)
.
You do not currently have access to this content.