Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces Proceedings of a Workshop (1988) / Chapter Skim
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3. Biomechanical Models
3. Biomechanical Models
Pages 19-42
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From page 19... ...
that used Statistical techniques to relate theoretical variables present in a collection of data. This type of model typically employs regression analysis to describe the dynamic behavior of the human body.
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Hence, impact, physim logical, and psychophysical models are not included in this review, nor are all existing models of the musculoskeletal system. Instead, examples are presented that concern bones, joints, body segments, and the whole body.
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Extending the previous principles, he calculated torques and forces around the joint, and then tracked the whole body in a kinetic chain. Most of the later models are two-dimensional static models that represent, to a limited extent, forces and moments acting at each particular articulation to generate internal loading information.
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From page 22... ...
are static, sagittal plane extensions of the major body segments and were expanded to predict the compressive forces sustained by the lumbar spine. They demonstrated how predicted moments generated about the body articulations could be compared with human strength characteristics, and suggested that this method be used
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From page 23... ...
also discussed how multiple-link static models could be used to evaluate reactive moments of the body in both coplanar and nonplanar analyses, how modeling techniques assess the moments experienced by joints during motion, single- and multiple-segment dynamic modeling techniques, and how biodyna~nic analysis techniques could be used to assess pushing tasks. Aunts et al.
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Thus, a rigid beam link analogy may not be the best method of modeling the human system. This is also evident from the previous discussion regarding bone modeling.
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Internal loading refers to the forces supplied by the muscles and ligaments that react to the external loads; thus, both external and internal forces load the body. The significance of internal forces to the loading of the body has been discussed by Cailliet (1968)
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data, minimum total muscular force and/or moment, and minimum total mechanical or metabolic energy are used to reduce the number of unknowns. Equations in dynarn~c models are usually nonlinear differential equations.
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Use of EMG data eliminated the antagonistic muscle forces and ligament functions and allowed calculations of bone contact or joint force. The results were comparable for repeated tests of the same subject but varied from subject to subject.
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Linear programming was used to determine the resultant spinal loads and muscle forces while minimizing spinal compress sign. Large spinal compression forces were predicted for minor activities and were validated with myoelectric activity indicating muscular tension.
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(1978) proposed the use of nonlinear optimization schemes that had closer correlations with EMG data than did linear schemes, and Crowninshield and Brand (1981)
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The problem was solved by linear programming with a variety of objective functions that determined joint forces caused by a unit pinch force between the tips of two fingers or between finger and thumb. One objective function was the minimization of the sum of muscle forces or the sum of constraint moments.
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A direct approach can be taken if the differential equations are solved for unknown kinematic variables and/or joint loads. The problem is generally indeterminate, requiring an optimization scheme with identification of an objective function to create extra equations.
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The disc and soft tissue were represented by a deformable element such as a viscoelastic body, but because of the lack of material properties, no model of either a spinal segment or the spinal column was proposed. Koogle et al.
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proposed a simpler threemass mode! which simulated dual load paths from the head to the pelvis, the spinal column, and the abdominal viscera.
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34 ~ is .
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ANrAGON ANTAGONISTIC AUTO 6EN AUTO-6ENERATION AVAIL AVAlLABlE AX AXIAL AXISYH AXIAL SYHHEIRY IS ASSUMED BEAH THEORY SIMPLIFIED THEORY OF ElASTICITY APPLIED ro ONE DIHENSlONAl PROBLEMS, SUCH AS BEAMS BILAT BILATERAl CALC CALCUlATE OR CAlCUlATED CART CARTIlAGE CLOSED SOlUTION SOLUTIOH ro A SET ~F DIFFERENTIAL EQUATIONS c`R,rEe our ANAlYTICALLY IN [ERHS OF A HATHEHATICAL EXPRESSION COHB COMBINED OR COMBINATION COMB / PE RH COHB I NAT ION/ PERMUTATION COHP COHPRESS1ON OR CO8PRESSIYE COND CONDITION CONf OR CONfI6 CONfI6URATION CONST H OF I THE HASS HOHENT OF INERTIA OF BODY SE6HENTS IS ASSU8ED ro REMAIN CONSTANT DURIN6 LOCOHOllON CONTACT HODEl A TECHNIQUE IN ElASTICITY TO COMPUTE CONTACT STRESSES BETIEEN r~o BODIES rN CONTACT CORT CORTICAL D DYNAMIC DAHP DAHPIN6 DEFl DEFlECTION DIFF EQS DIFFERENTIAL EOUAllONS DOF DE6REES OF FREEDOM DYN EQUIL PRINClPlES OF DYNAMIC EQUILBRIUH dERE USED ro FORMULATE HODEl ElASTIC PROPERTIES THE PROPERTIES OF A HAlERIAL ASSOCIATED VIrH rrs ELASTIC RESPONSE, SUCH AS MODULUS OF ELASTICITY EH6 ELECTROHYOGRAPHY - THE TECHN[QUE OF HONIlORIN6 ElECTRICAL ACTIVITIES OF MUSCLES EQUIL EQUILBRIUH EXT EXTREMITY OR EXTENSION fEH OR FE FrNITE ElEHENT METHODS OR FINITE ElEHENT FLEX FLEXION FUNC SP UNIT FUNCTIONAL SPINAL UNl INDET INDETERMINATE lNDIV INDIVIDUAL INIT INITIAL INV DYN PROB INYERSE DYNAMIC PROBLEM 6RD REACT 6ROUND REACTION M-A-I MODEL OF A HUMAN BODY 1N ~HICH THE HEAD, ARHS AND CONSIDERED AS A SIN6LE HASS TORSO
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BODY SE6HENTS CAN ONlY ROTATE HrrH REsPEcr ro EACH OTHER Jr JO[NT KElYIN MODEL A VTSCOElASTIC HODEl ~HICH HAS A HORE SOlID-LIKE BEHAVIOR ~ IN ~ INEHAT lCS LAT lATERAl LIG lI6AHENT OR lIGAHENTOUS LIN LINEAR LINEAR ELASTIC THE MODEL ASSUMES rHE BIOL06ICAL HATERIAl ro BEHAVE IN A LINEARLY ELASTIC MANNER LINEAR PR06 SOLN SOLUTION ro A SET OF lINEAR AL6EBRAIC EQUATION' LINEARlY ORTHOTROPIC LOC ION LUH HAX HAXlEll MODEL HCP HECH HIN HOD HOH HUSC NON-LIN OBJ FCN PARAH PHYSIOL X-SECT PlANE STRAIN PROB PRON PROPS PROX REDUNDANT MODEL RESONANT FREQUENCY RESP RH£0l RIGID BODY NHICH ARE REDUNDANT, USIN6 THE lINEAR PR06RA8HIN6 METHOD A HATERIAl ~HICH HAS A lINEAR RESPONSE ro srREs~ BUT HAS ~ ro 12 MATERIAL CONSTANTS LOCATION lOdER lUHBAR HAXIHUH A VISCOElASTIC MODEL dHICH HAS A hORE flUID-LI`E BEHAYIOR HETACARPAl HECHANICAl HEDIAl HINIHUH HODEl HOHENT MUSCLE OR MUSCULAR NON-LINEAR OBJECTIVE FUNCTION USED IN OPTIHI2ATION TECHNIQUES PARAMETER PHYSIOL06ICAl CROSS-SECTION A 2-DIHENSIONAl STRAIN ASSUHPlION IN kHICH THE PARTIClES DEFORM IN ONE PlANE AND REMAIN THAI PlANE PROBLEM PRONATAION PROPERTIES PROXIMAL A HAlHEHATICAL MODEL WHICH HAS HORE UNKNOlNS [HAN EQUATIONS TO SOlVE FOR THESE UNKNOINS rHE FREtUENCY AT dHICH A SYSrEH RESONATES OR HAS LAR6E AMPLITUDES OR DISPlACEHENTS RESPONSE RHEOL06ICAl AN ASSUMPTION IS HADE THAT THE BODY SE8HEN!
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39 Rae s SEE SIR star STAT EOUIL STRUCT OPT TECH SUP SUPP SYN [END THOR r-~ TRAB TRANSVERSELY ISOTROPIC OR TRANS ISOf VAR VERT VERIEB ~1 RO [Al ION STATIC SEGhENT SIMULATION STATIC OR STATICALLY PRINCIPLES OF STATIC EQUILIBRIUM HERE USED TO fORHUlATE THE MODEL STRUCTURAL OPTIHIlATION TECHNIQUES SUPINATION SUPPORT SYHHEIRIC OR SYHHEIRY TENDON THORAX OR [HORACIC TEN PORAL -HAND I B AL AR TRABECULAR - fORH Of ANISOTROPY FOR CHICK 5 JO 6 DIFFERENT MATERIAL CONSTANTS ARE NEEDED JO DESCRIBE THE RESPONSE OF THE MATERIAL VARIATION VERTICAL VERTEBRAL WITH
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The analogy of the rigid beam link should be investigated. Instead of viewing the body as a set of rigid links, perhaps a semiflexible spinal column can provide snore accurate assessments of the lifting of loads on the body.
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The hypothesis that an objective function indeed exists needs to be proven before further advances can be made. A secondary problem concerns the use of linear optimization techniques.
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From page 42... ...
A fixed-parameter mode} cannot be applied reliably in situations other than those for which it was calibrated. Deterrn~nation of the difference between the net reaction forces at a given body joint and the actual internal loads (e.g., those generated by the antagonistic muscle groups that are involved)
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