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4 Human-Machine Interface Models Information generated by anthropometric and dynamic biome- chanical modem is needed to build the next level of model in the hierarchical structure, that is, the interface model. Interface mod- els describe the interactions among the anthropometric and the biomechanical modem in a symbiotic relationship with the equip- ment used in system operation. Typical applications of these quantitative anthropometric and biomechanical modem are their use in the development of inter- face modem as COMBIMAN (computerized biomechanical man model), CAPE (computerized accommodated percentage evalua- tion), CAR (crewstation assemment of reach), SAMMIE (system for aiding man-machine interaction evaluation), CREW CHIEF (computer-aided design mode} of an aircraft maintenance tech- nician), and PLAI~TEMPUS (three-dimensional mode} of an interactive environment for the design and evaluation of system design and operation). Each of these interface models relies on an- thropometric and biomechanical data to mode} the relationships among people, tasks, equipment, and the workplace. Early approaches to the development of interface models and their characteristics are shown in Table 4~1 (Kroemer, 1973~. In 1967, Popdirnitrov (Popdirnitrov et al., 1969) reported on one of the first interface models, BULGAR, which was used for calcu- lating the positions of certain parts of the body related to a per- son's posture. Other approaches, such as DYNASTICK (Wartiuft, 43

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45 1971) and TORQUE MAN, LIFT MAN, and FORCE MAN (Chaf- fin, 1969), were based on linkjoint Stick man modeled they repre- sented mass properties and capabilities for exerting forces. MTM MAN (Kilpatrick, 1970) incorporated elementary motion times from tables used by industrial engineers. The ARM MODEL (Ay- oub, 1971) simulated two-link arm movements, using power as an optimization algorithm. CINCT KID (Huston and Passerello, 1971) incorporated kinematic and kinetic aspects of the human body and the effects of gravity. BOEMAN (Boeing Company, 1970; Ryan, 1971) was a complex mode! of a pilot sitting in an aircraft cockpit. This mode} was intended for use in the evaluation of the geometry of aircraft cockpits with respect to their suitability for the aviator. COMBIMAN (Krause and Bogner, 1987; Kroe- mer, 1973; McDaniel, 1976) was developed based largely on the experience of the Boeing Company, hence it has been called "son of BOEMAN." Since 1973, several other interface modem have been devel- oped. They include CAR (Edwards, 1976), CAPE (Bittner, 1975), ATE (Fleck and Butler, 1975; Butler and Fleck, 1980), PLAID- TEMPUS (Lewis 1979 a, b) and, currently under development, CREW CHIEF (Korea and McDaniel, 1985~. These modem and their interrelationships are discussed In the following text. BOEMAN BOEMAN is a computer-based mode} that was developed for the design and evaluation of cockpit and other crewstations (Ryan, 1970, 1971~. Although it provided a broad conceptual framework for the study of diverse variables, its prunary reason for development was aimed at the assessment of the seated operator's ability to move toward and reach controls. The operator model is made up of a system of 31 links that are constrained by hard angular Innits at each body joint. In addition, a time-cost function is associated with each joint. Mathematical programing is used to minimize the total time as the operator reaches from one point to another. The links are typically enfleshed by truncated cones. Cockpit boundary surfaces are defined. Model reaches are made within the boundaries imposed by enfleshment and cockpit surfaces. The result of exercising the mode! is a description of the effort and time required to reach the controls and provides indications of the points

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46 of contact between limbs and cockpit surfaces. This mode! has proven complicated to implement because of the volume of data required and the complexity of the cost of movement algorithms. Consequently, it was typically employed late in the design process. BOEMAN provided the conceptual bases and motivation for other workplace assessment models, for example, CAPE, CAR, and COMBIMAN. COMPUTERIZED ACCOMMODATED PERCENTAGE EVALUATION (CAPE) MODEL The CAPE mode! was developed as a design too! for the as- sessment of cockpit crewstation design in terms of the percentage of the aircrew population that could be accommodated by that design (Bittner, 1975, 1979~. The CAPE program used a multi- variate Monte CarIo simulation to create a typical sample, based on 2,500 "pilots" that matched the means, standard deviations, and correlations of 13 anthropometric variables that are critical for the design of cockpits, that must fit a target population (Gifford et al., 1965~. The Monte Cario simulation component of this model was tested in a series of investigations that compared actual and Monte CarIo estimates of the proportion of a population accornmm dated as various anthropometric exclusions were applied (Bittner, 1974~. The Monte CarIo component was found to be valid based on the results of four evaluation studies (Bittner, 1976~. The CAPE pilot link system component was selected to aug- ment arm and leg reach models in the design standard for military aircraft (Department of Defense, 1969~. This link system was viewed only as a baseline; the development of a later model based on the BOEMAN (Ryan, 1970, 1971) link system was proposed (Bittner and Moroney, 1975~. This proposal was implemented subsequently in the CAR mode] (Edwards, 1976; Harris et al., 1980), which replaced CAPE. CREWSTATION ASSESSMENT OF REACH (CAR) MODEL The CAR model is a design evaluation too! for determining the population percentage that can be accommodated by a particular crewstation design (Edwards, 1976; Harris and lavecchia, 1984; Harris et al., 1980~. The CAR mode! allows the user to define the geometry of

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47 the crewstation and to select an operator sample to evaluate the crewstation design. The CAR mode! consists of an anchorage point, the design eye point (DEP), the line of sight (LOS), seat characteristics, head clearance data, and a set of hand and/or foot controls. The anchorage point is the fixed location in space to which the operator must position a specific body part. Anchorage options include: seated, positioned to DEP (similar to BOEMAN); seated, positioned to a foot control; seated in a nonadjustable seat; standing in a fixed position; shoulder positioning; and hip positioning. The operator's seat consists of a seat back, seat pan, seat adjustment, and harness. The seat adjustment is defined by the seat reference point (i.e., the center of the line segment formed by the intersection of the seat back and the seat pan), the furthest- down forward position of the seat, and the furthest-upward back position of the seat. The user defines the harness by specifying the position along the horizontal shoulder line where the harness meets the shouicler. A maximum of 50 controls can be specified for the crewstation. Controls are defined in terms of body part (hand or foot), the grip that is appropriate for the control (clenched palm open; fingertip; thumb; or pinch, extended, or point), the harness condition flocked or unIocked), and the control location. An additional point representing the lining of the linear range of movement is specified for adjustable controls. The sample population can be generated either by a Monte Cario process based on the means, standard deviations, and corre- ration coefficients of standard anthropometric measurements fol- lowing the procedure developed by Bittner (1975) or by using direct inputs based on the actual measurements of test individu- alm. In either case, body measurements for the sample population are transformed into links, a modification of the procedure used in BOEMAN (Ryan, 1970, 1971~. The 19 links in the CAR link- person mode! (Figure 4-1) represent a simplification of the human skeletal structure from the 31 links used for BOEMAN (Harris and lavecchia, 1984; Harris, et al., 1980; Zachary, 1979~. The CAR mode] analyzes the ability of an operator in the sample to reach a control by starting at the lumbar joint and

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48 1a ;~12 t3) 1LUMBAR 2THORAC1C 3NECK (VERTICAL) ~N ECK ( HOR I ZONTA L) 5HEAD (LOWERS 6_ EYE 7HEAD IUPPER} l~TERCLAVt6VLAR 9CLAVICULAR 10HUMRAL 1 1RAOIA' 12HAND (CLNCHED, 13HAND I F INGE RTIP OR IP' 14HAND (EXTENDED' 15PELVIC 16fEMORAL 17IlBIAL 18ANKLE 19 - FOOT FIGURE 4-1 CAR Link-person model. SOURCE: Harris and Iavecchia (1984~. adding links in succession in the direction of that control. The links are constrained by angular limits of motion associated with each link joint, the harness conditions, and the type of clothing. Since the link lengths calculated for the operator sample are for an unclad operator, CAR allows the user to specify whether the operator Is wearing either summer or winter flight clothing. The clothing specification modifies the appropriate link lengths and the angular limits of motion. Three types of reaches can be incorporated into the CAR model: Zone 1: The shoulder harness is locked, and the operator does

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49 not strain against the harness. The lumbar, thoracic, interciavic- ular, and ciavicular links are immobile. The remaining links are aBowed to move within their angular lignite. Zone 2: The shoulder harness is locked, and the operator strains against the harness. The lumbar, thoracic, and interciav- icular links are i~runobile. The cIavicular link ~ aDowed to move within the confines of the harness. The remaining links are allowed to move within their angular limits. Zone 8: The shoulder harness is unlocked. AD links are aBowed to move within the bounds of their angular limits. Zone ~ and zone 2 reaches are performed for all hand controls, where the shoulder harness is specified as locked by the user. Zone 3 reach is performed for foot controls and hand controls, where the shoulder harness is specified as unlocked. CAR evaluates each operator in the sample to determine the ability to place himself adequately (i.e., with respect to anchorage point, DEP, LOS, and head clearance) and the ability to reach controls for zones 1, 2, and/or 3 reach as appropriate. The results indicate the percentage of the population that can achieve visual accommodation and the percentage that is capable of reaching each control. Guidance in changing control positions for improved accommodation ~ given in the form of reports de- ta~ling the distance and direction of control location alteration to accommodate additional portions of the population. The flexibility of a mode} such as CAR was illustrated in a recent program for flight deck design (Stone and McCauley, 1984~. In that study, data input was based on the anthropometric mea- surement of a broad range of aviation personnel in the U.S. Air Force, Army, and Navy. Stone and McCauley observed that, using the standard numerical link-person analysis provided by CAR, an accurate analysm of reach could be performed. Complete fit and function analyses required both graphic output and enfleshment (Figure 4~2~. The resulting figures are three-dimensional and pos- sess the dimensional characteristics of the people created by the CAR program in terms of both link and body dimensions. For flight deck design, the CAR mode! generates full reach en- velopes in various planes, along with eye and seat reference point locations. All the components are then integrated to allow evalua- tion of alternative designs for placement of controls, displays, and other equipment as a function of operational task requirements.

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so ,7~ FIGURE 4-2 CAR three-dimensional anthropometrically variable crew member. SOURCE: Stone and McCauley (1984: 113. Reprinted with permission ~ 1984 Society of Automotive Engineers, Inc. The resulting three-~nnensional models of the operator, the equipment, and the environment can be viewed on the screen in front, top, and side elevations; in isometric projection; or in perspective from any viewpoint. This capability enables the user to enter and walk around inside the model. The scale of the model can be changed and hidden lines can be removed. All objects within the mode} can be repositioned and regrouped. Further development of the CAR mode! will provide

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51 a building block concept for systematic design and evaluation of various workstations. Efforts are under way to validate the CAR model. For exam- ple, based on the CAPE mode} (Bittner, 1975), the Monte CarIo component has been evaluated by four accommodation studies, which have been summarized by Bittner (1976~. In addition, the anthropometric measurements and reach envelopes for individual subjects are being directly compared with mode] estimates under typical seat, restraint, and workplace conditions. Finally, CAR has been tested for the congruence of mode} reach data and exper- imentally derived anthropometric reach envelopes (Bennett et al., 1982; Kennedy, 1978~. SYSTEM FOR AIDING MAN-MACEINE INTERACTION EVALUATION (SAMMIE) SAMMIE, developed by a team of investigators at the Uni- versity of Nottingham, EnglancI, under the leadership of Maurice Bonney, was produced to evaluate the design of simple workstation layouts (Bonney et al., 1969~. With SAMMIE three-dimensional models of equipment ant} environments can be built by specifying and assembling geometrical shapes. The anthropometric mode! is preprogrammed to represent a male of average height and weight based on data developed by Dempster (1955), but can be modified to represent other anthropometric data. SAMMIE consists of two independent modules: ~ Three-dimenmonal modeling functions: This component builds models of equipment or workplaces by assembling primitive geometric shapes or general shape definitions, as shown in Figure 4-3. Man-model: The human mode] consists of 19 connected links representing a schematic skeleton around which three-dimen- sional solids such as boxes, cones, and cylinders are placed to denote outer contours of the human body. The idealized flesh contours can be varied to simulate body builds from stern to rotund (Sheldon, 1940~. Each link length can be varied to create different body proportions and can be adjusted to any feasible body position. Extreme limits of joint movements and comfort can be included in the model. The body segments are connected by pin joints at the shoulders, hips, neck, knees, .

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52 ~1 ~'4 \\W \ / FIGURE 4-3 Example of a SAMMIE geometrical model. SOURCE: SAM- MIE Human Factors 3-D Design System (1985~. and other articulations. Logical relationships are included so that when an upper arm moves, the lower arm and wrist also move in the expected direction, representing normal human movement, an specified in a user-definable joint constraints table. The limbs can only extend as far as human limbs can reach. It is also possible to mode! factors that limit movement, such as clothing. SAMMIE has the capability to create concave, convex, or plane mirrors superimposed on any surface in the workplace and can then examine the reflections found from any vantage point. Another module is used to assess visibility encompassing 360 de- grees of view horizontally and 180 degrees vertically. The following evaluations can be performed by SAMMIE: ability to reach; fit of a person in a confined workspace, including oper- ator size an] shapes, clearances, and access aperture sizes and positions; . working postures (e.g., seated, standing, bending); . visibility, including head and eye movement constraint, production of two-dimensional vision maps, and three-dimensional vision charts; field of vision; blind spots; and

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53 ~ mirror views. The environmental component of SAMMIE consists of geo- metrical information defining solid objects, location and orienta- tion data, and relationships between objects and humans. The mode! can be viewed in plane parallel projection or in perspective (from either outside or within the model) in front, top, and side elevations or a combination of views. The mode! can be viewed from a specific internal center of interest or from a position that represents the subject's visual view of the environment. The scale clan be changed and hidden lines can be removed. The model, once constructed, can be repositioned and re- grouped as needed. It lends itself to the modeling of human inter- actions with control panels and workplace ergonomic evaluations. Movement can be simulated frame by frame to evalute reach, fit, strength, balance, comfort, or vision for candidate postures. ARTICULAT1:D TOTAL BODY (ATB) MODEL The ATB mode] is a modified version of the crash victim simu- lator program developed by Cal~pan Corporation for the National Highway Traffic Safety Administration (NHTSA) to study human response during automobile crashes (Fleck et al., 1975~. The U.S. Air Force's Armstrong Aerospace Medical Research Laboratory modified this mode} for application to the study of human body dynamics during ejection from high-performance aircraft, devel- oped a three-dimensional projected graphics display capability, and applied the name articulated total body (ATB) mode! to this modified software program (Butler and Fleck, 1980; Butler et al., 1983; Fleck and Butler, 1975~. The three-dimensional ATB mode} is formulated in terms of rigid body equations of motion. The body segments do not deform during motion; all body deformation occurs only at the joints that connect the body segments. The standard configuration consists of 15 segments, but the actual number that can be specified is limited only by the computer memory. The body segments are coupled at joints, the centers of which are specified by three-dimensional coordinates within each segment and with respect to landmarks on that segment. Each segment has its own coordinate system defined with respect to bony anatomical landmarks on that segment. Coordinate systems are also defined

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57 two-dimensional display, two orthogonal views are projected si- multaneously and can be rotated for viewing at any angle and can be magnified. In the model, however, alogrithms exist in three - .lmenslons. The evaluation techniques consist of defining the dimensions of the man-mode! and simulating intended tasks within the work- place. The man-mode} dimensions can be defined in several ways: . Direct Measure: Specific measurements are entered from the keyboard or punched cards. . Data Base Summary Statistics: Percentiles computed from large samples are used to define the man-model. Individual seg- ments may be modeled for groups with different percentiles. ~ User Population: Several anthropometric surveys are in- corporated in the COMBIMAN model. A utility program allows the user to define which survey to use or to add data from other surveys. Computer-Aided Dimensioning: Abstract human models can be generated from anthropometric survey data. A critical body characteristic relevant to the evaluation of a task can be called up and used to construct a proportioned man-mode! based on a series of regression equations. Once the man-mode] is built, it can be positioned by com- mands from a light pen or keyboard. The COMBIMAN hand is made up of three links originating from the wrist: (1) grip center (for whole-hand grasp); (2) func- tional reach (e.g., finger grip, knobs); and (3) fingertip reach (e.g., pushing a button). The program evaluates reach capability as a function of cloth- ing and restraints (harness) in two ways. First, the user can select a control handle or pedal, or even an arbitrary point in space, and the COMBIMAN simulates the process of reaching to that point. Second, the user can select a control panel, and the mode} will compute the maximum reach envelope in the plane of that panel. If a point or control can be reached, the user can evaluate the force which the COMBIMAN can exert in that control location, in a defined direction, and to a specific control. The reach routine applies to the arms, legs, and head. Move- ments can be limited or confined, such as arm-shoulder movement only or arm-shoulder-trunk movement.

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58 A printout and plot of the workplace providing detailed body dimensions of the man-model and coordinates of the workplace in any scale can be generated at any design or evaluation stage. For mapping the visual field of a workplace, COMBIMAN defines a range of three-dimensional head and eye positions with coordinates. The size of the operator, seat adjustment, head pm sition, and visual restrictions can all be varied. This generates realistic visual angles. Other features of the COMBIMAN include the following: . Change View: Views the model and crewstation from any angle. Identify Object: Shows the name and three-dimensional coordinates of any characteristic of the crewstation. Omit Object: Declutters the display. . Retrieve Cremation: Calls up any of the crewstations stored in the library. Visibility Plot: Plots the crewstation as seen by COMBl- MAN. Display Anthropometry: Displays the values of sizes of the body segments. Display Links: Displays the dimensions and angles of the skeletal link system of COMBIMAN. Design Panel: Allows the user to add a new characteristic of modification to an existing crewstation. Modify Posture: Permits the user to manually change the posture of the model. Seat Adjust: Allows the user to reposition the seat. Zoom: Causes a portion of the image to be magnified to fill the entire screen. Plot: Produces paper a plot of the crewstation and COM- BIMAN in any scale. Add Crewstation: A utility program that allows a user to define a new crewstation and add it to the library. CREW CHIE1? The U.S. Air Force Armstrong Aerospace Medical Research Laboratory and the U.S. Air Force Human Resources Laboratory are jointly developing a computer-aided design (CAD) model of an aircraft maintenance technician (McDaniel, 1985; McDaniel and

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59 Askren, 1985~. This three-dimensional interactive graphics mode] would have an interface with existing commercial CAD systems. The developers expect to have an initial version available for use in 1988. The CREW CHIEF model will give the CAD designer the ability to use the computer drawing board to simulate mainte- nance and related human operator interactions with a system. It will represent the correct body size and proportions of the maintenance technician, the encumbrance of clothing and personal protective equipment, mobility limitations for simulating working postures, physical access for reaching into confined areas (with hands, tools, and objects), visual access (seeing around obstruc- tions), and strength capability (for using hand tools and manual materiab-handling tasks). The CREW CHIEF mode! user will be able to select data from a range of body sizes of both male and female maintenance technicians. The initial mode! will have four types of standard clothing to choose from: fatigues, cold weather, arctic, and chemical defense. The clothing interacts with the joint mobility limits for strength and posture to mode] accessibility. The CREW CHIEF mode} will display the visual accessibility of maintenance personnel. For example, inserting a screwdriver into a screw head requires that the technician simultaneously see and reach the screw head. The CREW CHIEF mode} allows the designer to see the task from the maintenance technician's view- point and to determine whether it can be physically accomplished. The 12 CREW CHIEF mode! postures include standing, sit- ting, kneeling on one knee, kneeling on both knees, stooping, squatting, prone, supine, lying on the side, walking, crawling, and climbing. Some of these postures reduce the mobility of the limbs and the strength available to perform the task. These are only starting postures, however, and the designer can manipulate all the body segments as required to achieve the desired posture. Posturing will be automated for accessibility, reach, and strength analyses. The CREW CHIEF mode! will have a realistic simulation of the strength capabilities of a maintenance technician. AAMRL has recently gathered strength data relative to the manual han- dling task (lifting, pushing, and pulling) for the postures described

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60 above. Another major data base includes torque strength with var- ious hand tools. The CREW CHIEF model itself will be three-dimensional. To accurately represent the clothing, the mode! will have a surface of facets (triangles) attached to the 35 links which make up the skeletal link system. A simplifier! three-dimensional mode! will be available whenever the designer wishes to rotate the model, and a hidden line two-dimensional mode! will be available for high- resolution views and plots. PLAID AND TEMPUS PLAID and TEMPUS are modeling programs created specif- ically for the Man-Systems Division, Lyndon B. Johnson Space Center (]SC), National Aeronautics and Space Administration, for use in man-machine interface design and evaluation for the space shuttle and the initial space station configuration. The earliest concept of PLAID was an interactive graphics software system for the design of instrumentation pane} layouts (Lewis, 1979a; PLAID Preliminary Specifications, 1977~. PLAID is currently housed in a VAX 11/785 computer. PLAID will also be used with an auto- mated anthropometric measurement system being developed for DISC (Lewis, 1979b). PLAID is a system for analyzing the crew interaction with crewstations and spacecraft systems and components (Brown, 1982~. It is based on full-scale, three-dimensional, solid-geometry computer software models that are created interactively by the user. The program can represent humans in shirtsleeves and spacer suits, crew workstations, spacecraft, and virtually any structure the user desires to build. These elements, called primitives, are assembled in the computer and viewed on the computer moni- tor. PI,AID provides flexibility in achieving the desired renderings and evaluation products, while the mode! data base stores created primitives and assemblies for subsequent use (Brown, 1981~. The user begins the modeling process by defining the end product. If a primitive that is required for the activity is in the data base, the user can assess its appropriateness for the particular analysis. All primitives are constructed in BUILD, the first major mod- ule of PLAID, from planar polygons created interactively by the user. The polygon can be built either graphically or numerically in

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61 one of six standard orthographic views (front, back, top, bottom, left, or right). Once polygons are created, the user can combine them, either by translation along one, two, or three axes or by rotation about some axis. Hence, a square can be translated along the nonrepresented axis for conversion to a rectangular box, a halcircIe can be rotated about its base to create a sphere; and a circle can be rotated about an offset axis to form a torus. A contour function allows the creation of a solid object by joining planar polygons, essentially creating a surface between the edges of two planes. This function is particularly useful for building objects with complex contours, such as the human body, human reach envelopes, and the space shuttle orbiter. For exam- ple, by using cross-sectional plots (reduced from digitized body mapping data in PLAID's REACH module), a shirtsleeved crew member can be created graphically. A second major module of PLAID, COG (composite object generator), ~ the basis for grouping constructed prirn~tives. The COG file contains primitive parts, COG file (subassembly) parts, or some combinations of primitives and subassemblies. Versatility can be achieved by careful selection of parts and by the COG file structure itself. The use of subassemblies facilitates stop-action articulation or motion in assembly since a subassembly has both its own local coordinate system and a second one in a global coordinate system of the assembly achieved via translation and rotation. By layering subassemblies and parts, a human arm, for example, can attach to the shoulder, yet when rotated, the upper arm primitive and lower arm subassembly move as a unit. At the next level, the lower arm, attached at the elbow, moves itself (a primitive) and the hand assembly attached at the wrist. Each element of the arm has its own local origin and coordinate system to enhance motion commands but can be translated and rotated to attach it to the next element in the tree. Final viewing and conflict checking is performed with a third major PLAID module, DISPLAY. Here, the user identifies the oh ject (i.e., target file) of interest and specifies the other parameters that are required to produce the desired end product. Several alternatives for the final renderings are available, in- cluding a wire frame, in which all assembly lines are visible. This common-form rendition is often satisfactory for simple objects, but interpretation usually suffers from ambiguity. In another rendi- tion, hidden lines are automatically removed or shown as dashed if

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62 behind-the-scene viewing is required. A conflict detector is another user option in which collisions of parts are defined numerically and graphically for ready identification. The PLAID program also cal- culates between-vertex clearance. While these line drawings are appropriate for most applications, PLAID shaded renderings are also available. The REACH module of PLAID serves as the interface with the anthropometric data to render crew reach and body mapping contours and contours from other digitized data. By using PLAID for interface ergonomic models, human body models of various sizes can be built and articulated with respect to workstation layouts. Improvements are sought, however, in the complementary software package TEMPUS to create a basic man- mode! that will interact with the PLAID program and data base elements. The TEMPUS user interfaces allow for a user-specified body to be constructed and more easily manipulated in the desired environment. For example, the PLAID person is articulated by the user on a joint-byjoint basis, with the user being responsible for body size parameters and joint limits. In TEMPOS, the user selects a specific crew member from the data base, one or more anthropometric measurements, or a random body. The internal anthropometric data base governs the constraints for size, range of motion, sex, and other parameters. Thus, the computer can avoid the use of a trial-and-error positioning schema. The body modeling is accomplished by using the data in the CAR mode! (Harris et al., 1980~. Following CAR, TEMPUS cal- culates the body segments by using regression equations. These segments are then used to build a link person. One graphic prm cedure that provides a realistic approach is the use of Bubble people" (BadIer et al., 1980), which are composed of hundreds of small spheres. Enfleshment of the link is proportional to link length; girth measurements are not used. Other graphics models include stickmen (no thickness) and ~polybodies" built of polyhe- drone. In each case, the three-dimensional body is generated by the computer and displayed graphically in the workstation. (For a detailed review of this technique, see Woolford and Lewis [1981] and Stramier and Woolford 1982. Knowledge of the positions of the arms, legs, head, and torso as well as their velocities and vectors are required to specify a body in motion. Specifications of forces requires knowledge of accelerations as well. Data storage and access requires extensive effort, however.

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63 In the initial stages of the study of the biomechanics of astronaut extravehicular activity (EVA), a dictionary of units of motion is constructed. The dictionary entries are isolated motions that can be combined to describe complex tasks. For planning new tasks, the components can be extracted from the dictionary and combined to describe the activity. Information regarding time, forces, restraints, and aids that are required to perform the tasks can be deduced. A major requirement for these modem of human performance is realistic motion data. Some rules of motion can be extracted from the viewing of films of human motion. However, more precise data can be obtained by digitizing data derived from points on the arms, legs, and torso as the subjects move. Automation can play a large role in this regard (O'Rourke, 1980~. TEMPUS has an associated anunation capability in which the movements of subjects and objects in the picture can be coordi- nated with each other and with a soundtrack. The animation Is dependent on the operator drawing key frames in which the stages of motion are displayed. For example, while reaching for a switch the body might be portrayed in the rest position with the arm partly raised and the hand on the switch. The animation facility then generates intermediate frames between these key frames to interpolate motion. One approach to the analyses of changes in body position and force vectors during the performance of a task ~ the use of models rather than traditional tables. For example, the body can be modeled as rigid links connected with rotary motors capable of exerting known forces or moving at known velocities. The kinematics and dynamics of the body can then be modeled by using trigonometry, differential] equations, and linear algebra. Digitized film data taken of astronauts are used to develop models of forces applied in EVA tasks. (See Bowden [1981] for a description of some of the pioneering efforts in this area.) This effort results in equations of motion that can be integrated numer- ically to provide position and orientation information for the body segments. In turn, these data can be used to drive graphic displays of motion to permit assessment of proposed EVA procedures.

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64 DISCUSSION Table 4-2 summarizes many of the important features of these models. The following points describe the state of the art In the development of interface modem. . Current interface models are specific to given designs, pur- poses, or characteristics. The usefuInem of interface modem ~ limited by the anthro- pometric and/or biomechanical data input. The workstation and the operator need to be accurately modeled. Predictive models of the effects of the dynamics of "plat- forms~ (e.g., ships, spacecraft, airplanes) on tasks are not available. There is a paucity of dynamic interface models. Effects of stress and motivation have not been adequately quantified or modeled. Effects of fatigue, trauma, and other injuries have not been adequately quantified or modeled. The effects of environmental factors on human performance are largely unquantified. The impact of complex aspects of vision, audition, and the speed and accuracy of responses to other sensory inputs and signals need to be explored for their impact on human- machme interface modeling. Sociological factors such as habitability that have an effect on human performance are largely unquantified. Mode} validation is a largely unresolved issue.

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65 CONPARISON lAllE Of INlElf~ NODElS T~le 4 - 2 IiIL ~ Of CO8~lR6t I Vt ~N l S IIODELS 2-D 3-. LlKl/OIHEI - 'E DY - lC/S[`rlC LIKIIS JOINTS S llf N6IH V1510# cia 3 D 3i LiNiS ViRiED E*lE~Ni S;iiiC ;oi~i ~E c~sTiii~rs ~o -Ef REfERENCE 17 ~IE CA~O 110 - lldlS IEO~IlIC~-Y`IIOUS tOS1I10~ CIOIHI~, lEST~IKI POIHT - 9 LINE {BlD6. llOC! SI4ULlI10N fROh PRINIII~S ~ CI=ES) SYSIEN Of SICHT SYSTEM) Dir' - Y 1# rHE SIohE NCCAUlEY CiD/C~I lllERtiCE VERS . S - IE 3-D -1161D -19 lill!S . . . -6EONErtlC~ tlIIIIlVES Sr~rlC {CO#ES, CTllNDERS -ViRIOUS ~SITIONS ClRClES) -C" IE SEOUEIlCEt . .. -lO61C~ lElilJOkSHIPS -lr~lr~r'11 Of IIOY11ENI -lol~r CONSTRAJ#T -CLOIH1146 ~0 -HEID ~ ETE NOVENElT COItST~IlT -2-' fISI. MPS -3-D VISI. ~S -fJLD Of VISI~ iI1 3-D -IS 01 "E -IICID -SE6NENTS . . . COI8ItWI {COIIPeterit IIOsesbeeic~l 11611-~o~1) . 3-D -3S YARI~lE LINIS, DFINED I~NUALLl OR flO.I DAll IASE -ElilPSOIDAl fOI -3-DJ8ENSJO" CO#~`CIS, "' ~PE IOD! DI - ICS fOI C~HJC~ DIS~'r -PlK, EULEI ~ 6L~061,PHIC JOJlIS VIrH R^E Of MOTION ~D NOT10# RESISI - E P - EIIIS -IRIEfiULA1 3-D F`CETED -SIiIIC dITH -~l IOJ#TS - ~lE SU8F6CE d/ "ESSElII~ ~1~! D Ll~ tE~ 81 6 DE6REES OF ESSENTI1L lllES CiP~ILII7, ~L FREEDON. H~t' llNES RE~YED llNIS RE - ED CLOrHIN6 ~JLIT' 110 110 ~ . -PREDJCTS 1,S,~, -PLOTS VJEU ~S "D ~TH [0 ~EdSTIT1 - PERCEITILE "E ~IOO DE61EES FE~LE ST~N6TH ~I~T#. -LI8JTS V17H ~TO - TED 1N f~"lD RE~ -~ DECtEES LlKl RE6CN HllSPHERE ELEY`TI~ UITH VISIOII LIMIT OVEILifS, - - ILE HEAD CREN CHiEf 3-i 3S ViRlillE -IRRE6UliR J-0 fiCETED -STiTJC dJTH -RfSTRJCTJO. Ir CLOTH 6 -PREDICTS l,S,SO, -PLOTS YlEN Of LINIS DEfJ#ED SUlfAeCE V/ NONESSENTIAL ~Ur~AT D Ll. REACH 01 PIOTECTIVE EOUIPHT 9S ~ 99TH IT1LE BOIItL" ~1 f~l DiTt IiSE lJ#ES REMOVED CiPAtilITY, All ~IlITr llHJTtT NS ~LE I FE - E AUI - TH' ll~lS REHOKD -RESTRJCrED REACH 11 STRENCIH f~ KA1~ -~ DE61EES 6 DE6REES Of flEEDOII TENAIICE ACTIVITIES ELEVtTION UIIH YIS10# LIMIT OVERLAT5 -t - ILE HE~ . PL1ID/IEHPUS 3-D -NUt I l-l INI tODY HODEl -hAN-HoDEL SANE tS CAR -SIICthAN -POITtODIES/ POl THE ORONS dlilBlE PEOPlEt SPHERES -6EOt~f TRIC ~ODELS-SPKRES -3-D SUREACE KAPPINC SYSrER (liRS} -lASER IASED COORDINATES -sT'rlc, tur SIIIJlllES Norl0N 81 USE Of CE06 ANIBATED SEQUENCE -~OtAI TR`NSLiT H OR ~OIlilON Of ll~ OR tODY . -RON CONSTR1JNTS -COLLECT 6 DAIA -DEfIKITION Of -CONSTRAIN! IT CLOIHIN6 -HoDELIN6 fORCES YIElI~ COOIDI - TES fOR TtSIS - - E~ fUNCTIO! YISUAL ~ESS

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66 COCNIlIvE dORtS11IION fOIICES APPl IED ANIHROPO~IRIC D`Td SCALE/CHAN6l VlEV D`ll IlSE . . ~ . . . . .. .. Ko -CO#1ROLS, DlspLArs No~ -'Nr POPUL'TIoll D'1' -tODr SIIE, CLOTHIN6 -rEs (Il SrONE -Allr VIEV 1# SE`I, ~fSTRAIN! a~sE dHICH INClUKS ~S,RESTRICTIONS, CRfB- AND HccAuEr STONf. A#D acc~LEr VERS10N SrSTE' Sl~llD`RD DEVIllIONS, AIID sr1TloN GEollETRr VERS10~) IJVARI`TE CORREL`TION COEFFICI.flS 01 AClUAL OPERAIOR I1E`SURE~NTS ~o -EWI' OR - rSrAES Of 6EONETRIC SHHES LKAT104 ~16 RfL`TIO~HIP DAT' rES -KllROl rLANE PARALLEL ?Ets?fcTlvE -FRONT -PL" ELEVAlIONS -PL" -SIDE -CO~INAT10N -CE*IER Of lNlEaEsT -VIEdI~ ~INT , _ _ _ _ . . . . . . No -DEFI - LE IN TE - S -CONT`CT FOICES -uS`F FLrlK6 -JOINT CfNTERS DErEalNED Ir -lODr K'lcrED 1' Of FOtCE lHrEucTTyE oll AND 6ETeEEII loor PERSONNEl -SE611ENT INERTI'l D'T' I`SE ELLIrSOIDS OR OTHfl PLA~ES ~ ELLltsoTDs sf6nElTs -V'RIOUS "LE ~ fENALE PROPERIIES USER SPECIFIED SHA~E fO' -~L ?lEssURf ON POPULATIONS -SfCHENT FORCE- SE6nfNTS AND DlsEL,rED SURfm Of ELLIPSOIDS -3 A~D 6 rEil OILD DEfLECIION 111 3-DlNENslolts PIOJECTED -RESTUAlilr SrSTEd CHILDREN C14ARAC1ERISTICS VIE' flON "r VlEllrOlIIT TEL`CTloll -VARIWS TES1 DUmlES -Jolilr HorloN -6uVI r~r lo"L f OtCES RESISTA~CE rRo'ERTlEs -PIESCITIED fORCE o' To~UE oll ANr SE6NENr o -ANr SEATED UORTST`T10. NONE DEf lNEr Ir THE USEI -IST-99TH PERCENTILE lII -lODr SIIE FORCE BALE ~ fEwE -IODY HotlLllr plLors -CLOTH1N6 REsTllciloN -P`PER PLOTS `RHr ~ N'V! IlAtE PILOTS -STREN6TH TO ANY SCAIE -'IR FORCE HoNEN IR1lr ilO~N -OIHfLRS AS DEFINED Ir USER -VISION LlnlTs -CREVSTl110NS #.ONE -A#' MORISTITIO. DEflNETl-6RIVITY fOR IAL"CE -I.S.SO.9S ~ ~1H 2TILE -80DY SIZE tr ~HE WEt c~uT'rloNs ~IR FORCE RALE ~ FE - E -8oDr ~lLlTr ~INlEN - CE TECHNICI"S, -CLOlHTN6 RESTIICT104 IE?RESElIll'N -OTHERS ~S DEFIHED Ir USER-STIEK6TH "r SCALE 0N -VISIO. Ll~lis cir -CREITEI Ir roL26o,5 T~NSLllE' OS ROIlTEt - PUcC5 C2ElTES HDLES - NILL ~DD C 09 SUOT~Cr'6 -Ct~CTERS/LETTESS -CONfO~: CtElTES SURFICE tETNEEN srHElEs ~C-CROUrS PSINITIYE . -NAS' ~STRONAUT FllES rES -~`r IE VIEdED fROH -100N ON c.R.r. ANr AN6LE: t ORT~ VIEIIIN6 PLAIIES -~1r VIE' 2 SIItULT6IlEOUSlY -~Ar BE lOTilE. ~ lCUTE ANCLES TO THE VIEdINC ~ANE -~6Nlf IED -2-D C.~.l. tlSPLAT AlccuR`rE CAN IE VIEIIED fRON A#r SCALE "LE AXES: . fRONT ~ IAC! TOP ~ 80~10K (EFT ~ R16HT HORI ZONTA VER1 ICAL l#/WT SCREEN DINElRIC ~ ISONEIRLC ORTH060N`l ~ PERSPECTIYE

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67 C0KP'RISON RILE Of IkIEREiCE NODElS I ABl ~ 0F C0RPAR' I I VE ~ l S hODELS HIDK. LI~S OUTPUT Rf NOVED CO#TROLL1 D i EAIURi S ASS - 'T. IO#S -COHFUTEl- 17 .. . . . . . . . . CAP -tES, 1K STOHE/ -~011[0# ~ CtEd -1EflO1ID NCC4~EY VERSI~ ,CC~TED I! VISI~ -CAIDS t~lD6. BLOC! AND K - , REA~ -DtSI s rs I EN ~ E - l O~S - TAN -THE SIONE/ bCCAUE, vIlst! REOUIlES l~rEI- ACTIVE CID/C" TE~Illl~l ... . . . S`I~IE TES . . . . All tES -IEACN -aE,l - ES -VlSlilLITr iSSESS~TS COCI'lr lESI~S . . . . . . . . .. . .. ..... . .. . -SEC~11 t1NE68 ,~D -llICH 1~,UI "CULAt lISPLICE~#IS, YElOClilES A. dCCfLER1TIOIIS, Jolllr ollE*rArlo#s. fOICES, - TO - UES ~ r,~cr rol~rs A fOICES, ~ 01~1 f OICES -1017 CEllEI ~ c~vlr~, ~.r~ Aue II.Erlc ENE~! -C",HIC~ DISnAt SNWINC IODY POSITIO# 1N rlNE .. . . . . .... .... -~OUltES S~ClflC -llKl~lY IEOUIRES -ro~re'~ 77 4~THROPO~TRIC D'T' ESTIKATES Oi I - ~S,?-"INf~ 01 L6 - K181 FI. Il16 1ASE 01 SIA~O DEVIArlONS, S~ AS 11N, CDC, V,X, ACTUAL D~tiTOlS "D CO'R~LATIOKS U#IV4C . ... ... . . -~1~ ~ SdEIIES 32 llr C - urE. -~tI-S OPEIlil.C SYSrE, til~Er. ~T~E t-~' - ET salrcHI.c rloroco~ tENOTE JOI EdTtY EItILAT1011 '~S -lEOUItES "1Nf - E KIIIC~rE. -CODE lH f - T" 77 -1~1 1~LENENIlTI~ lil~WE: -Ffill~ELHEI -tEc- -IB! ~C .. .. .. _ . . . . . CO#Ill - ' -6UrOllAlED NI - EN -~ER PLOlS -Ll~l rE! (01 -Nl~ tESOLUT104 IODY -SElTEI -1~ ~1I~ - E { lC01'Poter~z~ llNE IEKOVED -I~ER T"LES OR ALL tlOUSE O# SOKE SllE "D FROtO1110#, O,E1~101 EOUlY`LE#T) ll~eet.eit..l 11 H" NODEL; d1CTIVITIES ,~O DATi IISPLiTS) SItENCIN, VIS10N, -YEClOI C~ICS -~1) KANUALlY RElIOVEI -1~ flLES Of nOIS -AlPHAIHl~IERIC Rf~H -C~NICS ~JItOU1111 PAadC ~r WRItLACE Aal lAI' IETSOARD -FUt.CT l O.i IETIO4ID CREli CHIEf -lUTOItlTED HIDDEN -SII'UL'TE ItilNTEN`NCE -6RIPHICS LINt RfHOVil AS PROVIDED 11 CAD -DISRl~r-CRI IN tUN-ltoKL; SOf IIIAREIH6RDVIRE -L 16HIPEN (OR tlANUALLY REIIOVED NOUSE) 114 WRltPLACE, -tETIOiRD OR OIHER lS -iLPHANURERIC FROVIDED t' CAD fUNC110~1 SOf T`ARE PLAID/ TENPUS YES -CRF. REAC.'i -IODY llAPPING CONI OURS -ANIBlTED MOTIONS -CRElTES ldORIST`IION .. . . . VARIABLE 50DY SltE ~ PROPORTION, STREN6TH, VISION, REACH, lCCFSSltililY, INlfR- ACT10N 11/ HAhD IOOLS OtJECTS, 12 SIIRTIN6 POSTURES ADJUSTED 17 USER . . . .. ... . . . .... . . . -COlOR AV'IIAlLE -DAll lDJUSTED fOR IODY DlFfNSION -CHAN6ES IN GRAVITY -RETENTION t~ ItUlTIPLE COPIES -DISPL'YS REICH DAT' ldlil 9E iVIILA4lE -fOLlO.S CAD SOfT\litE 01 IN 1988 srsTERs CiD" (It~l) . . -V`X 111785 -INPUTS rEITRONIX TERtII"LS