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`44 1EST A-,fN
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`4 i IM
`
`Petitioner Ex. 1085 Page 1
`
`

`
`UNCLASSIFIED
`SECURITY CLASSIFICATION OF' THIS PAGE (1W1en Datee Entered)
`
`REPORT DOCUMENTATION PAGE
`
`READ INSTRUCTIONS
`BEFORE COMPLETING FORM
`
`I. REPORT NUMBER
`
`2. GOVT ACCESSION NO. S. RECIPIENT.S CATALOG NUMBER
`
`NATICK/TR-82/022
`4C TITLE (wnd SubItle)
`S. TYPE OF REPORT & PERIOO COVERED
`A MATHEMATICAL MODEL OF THE INERTIAL Final Report for Period Oct-
`IV.
`VOLUME
`ober 1, 1979 to August 31,198
`PROPERTIES OF A CARRIER-BACKPACK SYSTEM
`
`
`
`r,/_) -i'
`
`/J
`
`, 3
`
`7. AUTHOR(.) '.
`Philip E. Martin, M.S., Richard N. Hinrichs, M.S.,
`In-Sik Shin, B.S., and Richard C. Nelson, Ph.D.
`
`9. PERFORMING OR3ANIZATION NAME AND ADDRESS
`BIomechanics Labo-atory
`The Pennsylvania State University
`16802
`University Park, Pennsylvania
`
`6. PERFORMING ORG, REPORT NUMBER
`IPL-252
`CONTRACT OR GRANT NUMBER(e)
`DAAK60-79-C-0131
`
`10. PROGRAM ELEMENT, PROJECT, TASK
`AREA 6 WORK UNIT NUMBERS
`6.2,
`1L!62723AH98AJ005
`
`II. CONTROLLING OFFICE NAME AND ADDRESS
`US Army Natick Research and Development Laboratorie
`ATTN: DRDNA-ICCH
`Natick, Massachusetts 01760
`14. MONITORING AGENCY NAME 4 ADORESS(II diflent from Controllind Office)
`
`12. REPORT DATE
`May 1982
`Is. NUMBER OF PAGES
`83
`IS. SECURITY CLASS. (of thli report)
`
`UNCLASSIFIED
`
`IS.' DECL ASS$II C ATI ON/ DOWN GRADING
`bCNEOULE
`
`I0. DISTRIBUTION STATEMENT (of this Report)
`
`Approved for public release; distribution unlimited.
`
`17. DISTRIBUTION STATEMENT (of the ebetrect entered In Black 20. it d(cid:127)fferent hfm Rep.*t)
`
`19. SUPPLEMENTARY NOTES
`
`IS. KrY WORDS (Cnimgue On revere @Ode Itf nf(cid:127)cesar and' Idni'fy by block nlaumber)
`Backpacks
`Loads
`Backpack Systrm
`Human Backpack System
`Mathematic Models
`Load Carrying
`Carrier Backpack System
`Inertial Properties
`\ Computer Models
`~.
`2* ~UAT(~n
`dIt? by block numober)
`This
`is a report on the development of a mathematical model and Fortran
`program to examine the inertial properties of a human-backpack system. A twelve-
`segment model was formulated to represent a soldier carrying a backpack and
`other objects often carried during military operations. This computer model is
`used to generate values of tha following variables:
`system mass, system center
`of mass location, system inertia tensor, and principal moments of inertia for
`the system.
`The model can be used to simulate both a male and a female human
`body.
`Any one of four backpack systems, each containing a 20-1b load, can be
`W . I W43
`cEnQ CIF 9, NOV 46 IS OeoLWTIE
`
`UNCLASSIFIED
`SICUmNrY CLASUIPICATION OF TNIS PAGEC (3bw. Doca SnteaeE
`
`Petitioner Ex. 1085 Page 2
`
`

`
`MI.LASSIFIED
`SKCURITY CLASSIFICATION OP THIS PAOIE(Wrhe Date Eatert.)
`
`examincd. Three of the backpacks have external frames and one has an internal
`frame. One or two loads,
`the weights of which are determined by the program
`user can be added to the 20-lb pack load. The positioning of these added loads
`is also user-determined.
`In this report, the development of the model is
`discussed and results of executions of the program are presented.
`In addition,
`the report contains a listing of the Fortran program.
`/
`
`UNCLASSIFIED
`SKCURITY CLASSIFICATION OF T1IS PAGglrllnen Data Entm.
`
`Petitioner Ex. 1085 Page 3
`
`

`
`PREFACE
`
`the fourth of four volumes comprising the final report of
`This is
`res;earch performed under Contract Number DAAK60-79-C-0131 with the
`Individual Protection Laboretory, US Army Natick Research and Development
`Laboratories, Natick, Massachusetts.
`The work was formulated and
`directed hy Drs. Carolyn K. Bensel and Richard F. Johnson, Human Factors
`Group, Individual Protection Laboratory. Dr. Bensel was the contract
`monitor and Dr. Johnson was the alternate.
`
`r -°
`
`IN
`
`o~ N
`
`Petitioner Ex. 1085 Page 4
`
`

`
`Table of Contents
`
`Preface
`
`List of Figures
`
`List of Tables
`
`Introduction
`
`Procedures
`
`Twelve Segment Model
`Human Body
`Helmet
`Fighting Gear Elements
`Boots
`Rifle
`Backpacks
`Added Loads
`Loading Configuraticns
`Calculated Variables
`
`Results and Discussion
`
`Gender
`Backpacks
`Added Loads
`Loading Configurations
`Products of Inertia
`
`Summary and Conclusions
`
`Recommendations for rarther Study
`
`Cited References
`
`Appendices
`
`A. Clothing and Equipment Used in This Study
`
`B.
`
`IMSL Policy Statement
`
`C. The Biomechanica of Load Carrying Behavior:
`3D Program
`System Inertial Characteristics --
`
`3
`
`Page'
`
`1
`
`4
`
`5
`
`7
`
`8
`
`8
`9
`10
`10
`12
`12
`13
`16
`16
`17
`
`19
`
`19
`28
`28
`29
`29
`
`30
`
`30
`
`31
`
`33
`
`49
`
`51
`
`Petitioner Ex. 1085 Page 5
`
`

`
`List of Figures
`
`Figure 1.
`
`Representation of the fixed coordinate axes for
`the entire carrier-pack system.
`
`Figure 2.
`
`Figure 3.
`
`Position of the four fignting gear elements along
`the transverse (Y) and dorso-ventral
`MX) axes.
`
`Representation of the rifle
`and three points on the rifle
`vectors along the three axes.
`
`local coordinate system
`used to define unit
`
`Figure A-I.
`
`ALICE Fighting Gear.
`
`Fisure A-2.
`
`ALICE Pack.
`
`Figure A-3.
`
`ALICE LC-2 Frame.
`
`Figure A-4.
`
`ALICE LC-l Frame.
`
`Figure A-5.
`
`PACKBOARD.
`
`Figure A-6.
`
`LOCO.
`
`Page
`
`10
`
`12
`
`13
`
`35
`
`37
`
`39
`
`42
`
`44
`
`46
`
`4
`
`Petitioner Ex. 1085 Page 6
`
`

`
`List of Tables
`
`Table 1.
`
`Inertial Properties for the Nine Fixed Segments
`of the Human-Backpack System
`
`Table
`
`2.
`
`Table
`
`Table
`
`Table
`
`3.
`
`4.
`
`5.
`
`Table
`
`6.
`
`Table 7.
`
`Table
`
`Table
`
`8.
`
`9.
`
`Table 10.
`
`Inertial Properties of the Four Backpacks
`
`Inertial Properties for Male with ALICE LC-2
`
`Inertial Properties for-Male with ALICE LC-I
`
`Inertial Properties for Male with LOCO
`
`Inertial Properties for Male with PACKBOARD
`
`Inertial Properties for Female with ALICE LC-2
`
`Inertial Properties for Female with ALICE LC-l
`
`Inertial Properties for Female with LOCO
`
`Inertial Properties for Female with PACKBOARD
`
`Page
`
`14
`
`15
`
`20
`
`21
`
`22
`
`23
`
`24
`
`25
`
`26
`
`27
`
`5
`
`Petitioner Ex. 1085 Page 7
`
`

`
`A Mathematical Model of the Inertial
`Properties of a Carrier-Backpack System
`
`INTRODUCTION
`
`In the field of biomechanics, researchers use a variety of research
`techn iques to evaluate various aspects of physical performance. Mathematical
`modeling is one analysis technique which is available to the biomechanics
`researcher for relating performnance to the mechanical characteristics of
`the system under investigation.
`
`According to Olinick,1 a researcher may develop conclusions about a
`situation under observation by conducting controlled experiments and recording
`th2 results or by developing a model which, when carefully designed, will
`eventually lead to the same conclusions as experimentation. The advantage
`of mathematical modeling is that a model is free of the physical limitations
`often associated with experimentalJ research. Selected variables of interest
`can be isolated and carefully controlled.
`
`There are basically two classifications of mathematical models which are
`commonly used: deterministic and probabilistic. Deterministic models are
`those which are based on exact relationships sucIb that, for any given input,
`the exact end result may be determined. Probabilistic models, as the name
`implies, are based on the assumption that an observation or system under
`investigation can occupy one of several different states with different
`probabilities at any given moment. Consequently, inferential statistics play
`an important role in the development and evaluation of these models. In either
`case, the goal of the researcher is to develop the most accurate, yet simple,
`model possible.
`
`In this project a deterministic model was developed to examine the
`inertial characteristics of a human-backpack system. In any system, the accelera-
`tion of a body is related to the inertial propertieý of the body. In the case
`of linear motion, the mass of an object repreientr the resistance iLo linear
`acceleration. When considering angular motion, however, one must be concerned
`not only with tie magnitude of the object's mass, but also with how that mass is
`distributed about some axis of rotation. The moment of inertia of an object
`takes into consideration both mass and the distribution of that mass and thus
`represents the resistance of that object to angular acceleration.
`
`The inertial properties of a human-pack system are quite important to
`the ability of an individual to make rapid movements, either linear or angular
`in nature. For example, a soldier in a combat situation may be required to
`make some evasive maneuver. A greater mass and greater moment of inertia of
`the soldier-pack system would inhibit the ability of the soldier to make~
`rapid linear and angular accelerations, respectively.
`
`1 Olinick, M., An Introduction to Mathematical Models in the Social and Life
`Sciences. Reading, Massachusetts: Addison Wesl.ey Publishing Company, 1978.
`
`7
`
`-
`
`Petitioner Ex. 1085 Page 8
`
`

`
`Because a pack can be loaded in various ways, an individual has some
`control over the inertial properties of a pack and the influence of the
`pack inertial properties on the entire carrier-pack system. Consequently,
`it was the purpose of this project to examine the inertial characteristics
`of the total carrier-backpack sys;tem using a mathematical model.
`The system
`,was designed so that both male and female models could be examined in conjunc-
`tion with four different backpacks.
`
`The work performed in this3 project was an2 extension of that done
`previously by Hinrichs, Lallemant, and Nelson.
`In their work they examined
`the inertial properties of three backpacks of different design while
`manipulating the loading configurations of the packs.
`In discussing the
`results,
`they summarized certain inertial properties which are desirable in
`a backpack, based on mechanical principles. These included having the smallest
`possible mass, having the dorso-ventral center of gravity (CG)
`component as
`close to the body as possible, having the pack symmetrically loaded from side
`to side, having the longitudinal CG component as low as nossible, and having
`the smallest possible moments of inertia. The authors were quick to point out
`that these desirable characteristics are not always feasible. With this
`limitation in mind,
`their results suggested that the most desirable combinations
`of the loading configurations examined would be to load the equipment low and
`place any added weight on the sides and/or the bottom of the pack.
`In addition,
`any extra weight should be placed as close to the pack frame as possible.
`
`PROCEDURES
`
`In this phase of the work on load carrying behavior, a computer model
`was developed to estimate the inertial properties of a human-backpack system.
`In order to understand the methods used in
`this phase,
`the reader should have
`some basic understanding of rigid body dynamics. Because this information can
`be obtained from any number of texts (eg., Synge and Griffith, 1942; Greenwood,
`1970; or Beer and Johnston, 1977),
`it will not be discussed in this write-up.
`The reader is a so referred to Hinrichs et al. for discussion of basic mechanical
`considerations.
`Their discussion is quite appropriate for this project.
`
`Twelve Segment Model
`
`For the purpose of this phase of the project, a twelve segment model was
`developed to represent a soldier wearing a pack and other common objects
`normally carried in combat.
`Information on the items included is presented
`in Appendix A. Because the principal objective of this phase was to estimate
`
`'Ilinrirlhs, R.N., S.R. Lallemant, and R.C. Nelson. An Investigation of the
`Inertial Properties of Backpacks Loaded
`in Various Configurations.
`(Tech.
`Rep. NATICK/TR-82/G23). Natick, Massachusetts: U.S. Army Natick Research
`and Development Laboratories, May 1982.
`
`8
`
`Petitioner Ex. 1085 Page 9
`
`

`
`the influence of the backpack type and load on the inertial characteristics
`of the entire system,
`the values of inertial variables for all segments,
`excer,
`the backpack and added load, were fixed. The computer model was
`developed so that one of four backpacks, ALICE LC-2, ALICE LC-1, LOCO, and
`PACKBOARD, could be used in conjunction with one,
`two, or no added loads.
`The
`backpack systems are described in Appendix A.
`In addition,
`the program allowed
`for the incorporation of either a male or femalp human body.
`
`In developing the model, a common coordinate system was used so that each
`segment could be appropriately positioned relative to all other segments.
`The
`origin of the coordinate system was fixed at a point between the feet of the
`body at ground level. The X-axis represented a dorso-ventral axis, the Y-axis
`a transverse axis, and the Z-axis a longitudinal axis. Figure 1 gives a general
`representation of these three ax"s relative to a human body model.
`
`A description of each of the twelve segments incorporated into the model
`follows.
`
`(Segment 1). The human body was treated as a rigid body in
`Human Bod;
`this project. Several sources of information were used to construct both
`male and female models. The stature, mass, and necessary body coordinates
`were obtained or derived using the anthropometric data from two separate reports:
`The Body Size of Soldiers: U.S* Army Anfhropometry - 19663 and Anthropometry
`of Women of the U.S. Army - 1977.1 For both the male and the female models,
`50th percentile data wcre used. These values were also adjusted for the inclusion
`of the Army-issue utility shirt and trousers. These anthropometric data were then
`used in corjunction with the inertial data reported by ilanavan 5 who developed a
`mathematical model of the human body in an attempt to estimate the inertial
`properties of the body in rany different lixed positions. For this model,
`Hanavan's position 21, which is that shown in Figure 1, was selected. This
`body position seemed to most closely approximate the position of a soldier
`carrying a rifle in front of his body. Again using 50th percentile data, the
`location of the body center of gravity and the body moments of inertia were
`derived from Hanavan's data. Because the available inertia values were for an
`individual with a body mass of 74.2 kg and a stature of 1.755 m, they had to be
`
`3White, R.M. and E. Ch.rhill. The Body Size of Soldiers: U.S. Army
`Anthropometry - 1966 (Tech. Rep. 72-81-CE). Natick, Massachusetts: United
`States Army Natick Laboratories, December 1971.
`
`4 Churchill, E., T. Churchill, J.T. McConville, and M. White. Anthropometry
`of Women of the U.S. Arm
`- 1977 (Tech. Rep. NATICK/TR-77/024). Natick,
`Massachusetts: United States Army Natick Research and Development Command,
`June 1977.
`5 Hanavan, E.P. A Mathematical Model of the Human Body (Tech. Rep. AMRL-TR-64-102).
`Wrigth-Patterson Air Force Base, Ohio: Aerospace Medical Research Laboratories,
`1964.
`
`Petitioner Ex. 1085 Page 10
`
`

`
`Figure 1. Representation of the fixed coordinate axes for the entire
`carrier-pack system.
`
`10
`
`Petitioner Ex. 1085 Page 11
`
`

`
`adjusted for the male and the female rnodels used in this study. These adjustments
`were made by using correction factors based on stature and bidy mass.
`These can
`be shown mathematically as follows:
`
`I TAS2
`
`TH
`
`IDA M[.S2
`
`IDH
`
`2 . J LH
`
`L [
`
`where ILA,
`ITA, and IDA are the adjusted moment of Anertia values for the
`longitudinal,
`trausver3e, and dorso-ventral axes, respectively;
`ILH,
`ITH,
`
`IDH are the inertia values from Hanavan; MA and SA are the male or
`and
`female model mass and stature values; and MH and SH are the mass and stature
`values from Hanavan.
`This adjustment is
`a minor one for the male model but
`
`is reiatively large for the female model. Because of the lack of inertia
`data for females,
`this adjustment for the female model represents a limita-
`tion.
`It was felt, however,
`that it would have a relatively minor effect on
`the results. The rationale for this adjustment method was provided by
`Hinrichs.6
`
`Helmet (Segment 2). Many of the twelve segments were modeled as point
`masses rather than rigid bodies. This greatly simplifies the necessary input
`data since a point mass has no moments or products of inertia. This is an
`appropriate assumption as long as the transfer term from a local co~ordinate
`system to a coordinate system located at the total system center of mass
`dominates the segment's moments of inertia. This simplifying assumption will not
`lead to any significant error when applied to those segments of relatively
`small size and mass.
`The helmet was one such segment aad consequently was
`represented as a point mass.
`The center of mass location for the helmet was
`determined using the reaction-board
`technique. This center of mass location
`was then used to locate the helmet relative to the top of the head.
`
`Fighting Gear Elements (Segments 3-6). Each of the four fightli:g gear
`elements wa6 represented as a point mass. Rather than determining center of
`mass positions for the four elements, each was considered as a regular
`rectangular shape with the center of mass coincident with the geometric center.
`The four elements were then positioned around the (cid:127)runk of the body using
`selected anthropometric measures presented in the 1966 and 1977 anthropo-
`metric reports.
`(Ref.
`3 and 4).
`Figure 2 shows the positioning of the four
`elements in
`the transverse and dorso-ventral directions.
`The location of the
`
`elements in these two directions was based on measures of hip breadth (transverse)
`and waist depth (dorso-ventral). All four elements'were positioned along the
`longitudinal axis at the level of the trochanters of(cid:127) the femurs.
`
`6 Hinrichs, R.N.
`"Principal Axes and Moments of Inertia of the Human Body: An
`Investigation of the Stability of Rotary Motions." Unpublished Masters
`Thesis, University of Iowa,
`Iowa City, Iowa, 1978.
`
`11
`
`-
`
`.•-.
`
`-*/,.
`
`-
`
`.-
`
`e
`
`Petitioner Ex. 1085 Page 12
`
`

`
`+ X
`
`Amino 8CM25c
`Pouch25
`
`cm
`
`Amino
`Pouch
`
`Tool
`
`!-A'
`
`'(cid:127)
`
`10C
`
`A a Hip Breadth
`B W Wait Depth
`
`Figure 2. Position of the four fighting gear elements along
`the transverse (Y) and dorso-ventrall (X) axes.
`
`Boots (Segments 7-8). Both boots were modelcd as point masses as well.
`Because the center of mass of the boot was quite cLose to the approximated
`the coordinates of the foot center of
`center of mass of the foot segment,
`mass were used to represent the location of the boot.
`
`Since the rifle is much larger and has a greater
`Rifle (Segment 9).
`it was more appropriately
`mass than those segments treated as point masses,
`By using the reaction-board technique,
`the
`modeled as a rigid body.
`location of the center of mass was determined.
`Then, by using an oscillation
`technique which was previously used by Hinrichs et al. (Ref. 2),
`the moments
`In order to define unit vectors along
`and products of inertia were derived.
`the three local axes of the rifle, three points were established on the
`rifle. Figure 3 shows the location of these points (A,B,C) and the local
`coordinate axes. Point A was also used to position the rifle relative to
`the body since it was assumed that the right hand gripped the rifle at
`In this model the rifle was positioned horizontally in front
`this point.
`of the body. Consequently, knowledge of the location of the right hand on
`the rifle determines the position of the left hand on the rifle. By knowing
`the fixed coordinate system, the
`the coordinates of the right hand in
`location of the center of mass of the rifle was easily transformed from
`local to system coordinates.
`
`12
`
`Petitioner Ex. 1085 Page 13
`
`

`
`+ Y
`
`C
`
`+ X
`
`Figure 3. Representation of the rifle local coordinate system
`and three points on the rifle used to define unit
`vectors along the three axes.
`
`The nine segments defined thus far are those which were assumed to be
`fixed in
`the computer model. Their inertial properties are sutmarized in
`Table 1.
`
`lackpacks (Segment 10).
`The origin of the local coordinate axes for
`each backpack was located at the center of mass of the backpack with the
`axes oriented parallel to the fixed coordinate axes. The local z-axis of
`the backpack was aligned parallel to the line connecting the contact points
`of the pack on the body at the shoulders and hip. This assured the backpacks
`would have the proper orientation relative to the body.
`The same reaction-
`board and oscillation techniques were used to estimate center of mass
`location and the inertial properties for each backpack.
`For these tests,
`each pack was loaded with a sleeping bag, mattress, waterproof clothes bag,
`poncho, socks and undershirt. These items, excluding the backpack, totalled
`9.07 kg. Estimates were then made of the location of each pack relative to
`the shoulder joints.
`In
`the dorso-ventral direction, the edge of each pack
`closest to the body was positioned 10 centimeters from the X coordinate of
`the shoulder. For the transverse direction, each pack was assumed to be
`centered on the logitudinal axis of the body. Along the longitudinal axis,
`the tops of the ALICE LC-2, ALICE LC-l, and PACKBOARD were positioned at the
`same level as the shoulders. Only the top of the LOCO was positioned
`differently.
`It was posit'oned 10 centimeters above the level of the shoulders
`because of its greater length.
`By representing the local centers of mass as
`proportions of the dimensions of the packs and then relative to the shoulders,
`the center of mass locatious were traneformed to the system coordinate axes.
`Table 2 summarizes the inertial properties of the four packs.
`
`13
`
`Petitioner Ex. 1085 Page 14
`
`

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`Petitioner Ex. 1085 Page 15
`
`

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`
`Petitioner Ex. 1085 Page 16
`
`

`
`The computer model allows for the
`Added Loads (Segments 11-12).
`the
`possible addition of one or two loads of variable mass to the pack in
`The loads can be placed in any position uithin the
`form of point masses.
`pack by specifying the locations as proportions of the pa,k's three diuiensions.
`In this way, a variety of loading conditions could be simulated.
`
`Loading Configurations
`
`To examine the influence of different loading conditions on the
`Inertial prope.ties of the human-backpack s13tem, seven loading configurations
`were simulated for both a male and a female model and for each of four back-
`the loading configurations were simulatLd under
`packs. With one exception,
`Each added load was 6.80 kg. Thus,
`conditions of one and of two added loads.
`the pack loads simulated totalled 9.07, 15.87, and 22.67 kg. These values
`were chosen because they are identical to pack load weights used in other
`studies conducted under this contract. 7' 8'9
`These studies entailed analyses
`of the effects of load carrying on the performance capabilities of men and
`For confi.gurations 2 through 7, the positioning of the added loads
`women.
`For the dorso-ventral
`were represented as a proportion of the pack dimensions.
`For
`direction (X), 0% represented the edge of the pack closer to the body.
`0% would be on the side of the pack representing
`the transverse direction (Y),
`the models left side. Finally, for the longitudinal direction (Z), 0%
`represented the top of the pack. The following is a brief summary of the
`seven loading configurations. Values in parentheses represent the proportions
`the X, Y and Z directions, respectively.
`used in locating the added loads in
`
`1.
`
`No added load. Both of the added loads were set to zero so that
`only the basic, 9.07-kg load was included within the pack.
`
`2.
`
`a,b.
`
`The added loads were
`Performance testing position (PTP).
`positioned such that they estimated the positioning of loads
`added to the packs during the performance testing studies
`(Refs. 7,8,9). This position was near the top of the pack
`.50,
`.20).
`(.10,
`and close to the body.
`
`3.
`
`a,b.
`
`High loading. The added loads were positioned near the top
`the pack with respect to its
`of the pack and were centered in
`.10).
`(.50,
`.50,
`dorso-ventral (X) and transverse (Y) axes.
`
`7 Nelson, R.C. and P.E. Martin. Volume I. Effects of Gender and Load on
`(Tech. Rep. NATICK/TR-82/0OI). Natick,
`Combative Movement Performance
`US Army Natick Research and Development Laboratories,
`Massachusetts:
`February 1982.
`
`8 Nelson, R.C. and P.E. Martin. Volume II. Effects of Gender. Load, and
`Backpack on Easy Standing and Vertical Jump Performance (rech. Rep.
`NATICK/TR-82/016). Natick, Massachusetts: US Army Natick Research and
`Development Laboratories, March 1982.
`
`9 Martin, P.E. and R.C. Nelson. Volume III. EffectA of Gender, Load, and"
`Backpack on the Temporal and Kinematic Characterfatics of Walking Gait
`US Army Natick
`(Tech. Rep. NiATICK/TR-82/021). Natick, Massachuisetts:
`Research and Development Laboratories, April 1982.
`
`/
`
`...
`
`_
`
`16
`
`..
`
`Petitioner Ex. 1085 Page 17
`
`

`
`4.
`
`a,b.
`
`Low loading.
`The positioning of the added loads was the same
`as that for *he high loading, except along the longitudinal
`(Z)
`axis, where the loads were placed near the bottom of the
`pack.
`(.50,
`.50,
`.90).
`
`5.
`
`a,b.
`
`Front loading.
`The added loads were centered with respect to
`the longitudinal (Z)
`and transverse (Y) axes of the pack, but
`were position2d close to the body.
`(.10,
`.50,
`.50)
`
`6.
`
`a,b.
`
`7.
`
`a,b.
`
`Back loading.
`The added loads were again centered with respect
`to the longitudinal (Z) and transverse (Y) axes, but were
`positioned near the edge of the pack farthest from the body.
`(.90,
`.50,
`.50).
`
`Side-to-Side loading (S-to-S).
`The added joads were pos(cid:127)i-oned
`near the left
`and the right edges of the pack and were cetered
`along the longicudinal (Z)
`and dorso-ventral (X)
`axes of the
`.10,
`body.
`(.50,
`.50 for half of the load and
`.50,
`.90,
`.50
`for the other half).
`
`Calculated Variables
`
`The computer model developed for this phase of the project was adapted
`from a similar program written by Richard N. Hinrichs
`(Ref.
`6)
`for his
`investigation of the stability
`of rotary motion.
`The computer model generated
`values for the following variables which described the inertial
`characteristics
`cf the entire human-pack system:
`i.
`System mass -
`the total mass of all
`components of the model.
`2.
`System center of mass location -
`the X, Y, and
`Z values of the center of mass of the system with respec* to the fixed
`coo:dinate system.
`3.
`System inertia
`tensor represented at the system
`ce:Lter of mass, which includes the moments and products of inettia
`for a
`rystem of axes parallel
`to the three fixed axes and whose origin lies
`at
`the center of mass. These describe how the total
`mass
`is distributed
`about the three axes.
`4.
`Principal moments of inertia
`and their direction
`cosines from the three f'xed axes. These represent moments of inertia
`of
`the total mass about a new set of axes oriented such that the products of
`inertia
`are eliminated.
`The system inertia
`tensor and principal moments
`of inertia
`with direction cosines provide the same information to the
`program user but in different formats. For this
`reason, oaly the values
`of the ine-tia
`tensor will be reported and discussed in
`this
`document.
`The reade(cid:127)
`is agaiu referred to such sources as Greenwood
`(1970) or Beer and
`Johnston (1977)
`for details
`of inertia
`tensors and principal moments of
`inertia
`and their
`interpretation.
`
`In addition, the model was developed so that it would have a certain
`degree of flexibility.
`the program user has the option of selecting either
`a male or a female model and any one of the four backpacks used in
`the testing,
`and of using no, one, or two added loads of variable magnitude positioned
`anywhere within the pack. Separate data decks were developed for the male
`and the female models so the user need only incorporate the appropriate deck
`in
`the computer analysis.
`The other options can be selected simply by
`adjusting input values of selected variables in a few cards of the data deck.
`For example,
`the subroutine LDDAT of the computer program reads in values
`
`17
`
`Petitioner Ex. 1085 Page 18
`
`

`
`of thi* extra loads desired and calculates their location based on information
`specified by the user. If the user prefers to use no added load, the
`magnItudes for the added loads in the data deck must be set to zero. To
`establish the location of any non-zero load, the user must manipulate the
`proportions of the three pack dimensions to be read in from the data deck.
`These adjustments are all quite simple to make as long as the user takes
`care in selecting the appropriate cards-from the data deck to be changed.
`
`Although a certain rPmount of flexibility has been created in the
`development of the computer model, there are limitations to the use of the
`model. This is particularly true when considering the characteristics of
`the carrier used in the model. The human body (Segment 1 of the model) was
`deve~loped as being a 50th percentile male or female in stature and body mass.
`Becaiuse the emphasis of the model was to examine the effects of gender, back-
`pack, and load on the inertial properties of the total system, no attempt
`was made to incorporate other percentile levels for the human body, although
`this could be done if desired. In additton, some limits are not established
`by the program itself but should be by the user. For example, there is no
`sp-acific limit on the possible magnitude of added loads except that imposed
`by the format used in reading this data in the program. It makes little
`sense however, to incorporate loads beyond those typically used in the
`mi~litary.
`
`Petitioner Ex. 1085 Page 19
`
`

`
`RESULTS AND DISCUSSION
`
`In two other studies conducted under this contract, the effects of
`three main factors - gender, backpack, and load - on selected characteristics
`of standing, vertical jumping, and walking were examined (Refs. 8,9). Because
`of the design of the computer model developed for this study, the effects of
`these same three factors on the interial properties of the rarrier-backpack
`system can be examined. In addition, a fourth factor, loaiing position, is
`included. The influence of these four factors will be discussed in terms of
`three basic variables: mass, center of mass location, and moments of inertia.
`
`Tables 3 through 10 present results obtained from executions of the
`computer model. Because the trends are quite similar across the four factors,
`specific results will no 't be discussed for each condition examined. Rather,
`general trends found in the data will be presented.
`
`Gender
`
`Comparing the results for the male model presented in Tables 3 to 6 with
`those for the female model shouvn in Tables 7 to 10 demonstrated that the male
`values for system mass and the threc moments of inertia were greater th'an
`the female values for the same variables under all conditions tested. These
`results provide no new information since it is common knowledge that an
`average male has a greater body mass than an average female. This difference
`in body mass is responsible not only for the difference in system mass but
`also for the difference in the values for movent of inertia.
`
`These greater values for the male model indicated a greater resistance
`to both linear and angular accelerations existed for the male than for the
`female. This does not indicate, however, that it is easier for the female to
`accelerate in thesi! directions. Since the ability to produce a linear,
`acceleration is directly proportional to the force acting to cause the
`acceleration, one must consider the force-producing capab