Mine Countermeasures Technology (1993)

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20. Motion picture data and grapho-numerical differentiation may be used instead, but the time required to produce results and the loss of accuracy make this method impractical for extensive use in rapid evaluation of knee mechanisms. Accelerometers, on the other hand, are well adapted to this purpose and the use of this method is indicated.

TABLE II COMPARISON OF ACCELEROMETER AND GRAPHO-NUMERICAL METHODS Factor Considered Grapho—Numerical Differentiation of Motion Picture Data Direct Me-enre= ment Using Accelerometers Application in cases where a single member is to be studied Satisfactory Most advantageous Application in cases where several inter- connected manbers are Most advantageous Limit ed to be studied Initial cost of . equipment Intermediate High Operating costs Intermediate Low Required processing of Development None record of film Time required to Intermediate Small reduce record Accuracy Fair Good Sensitivity and response to abrupt changes in Fair Excellent phenomenon Influence of | . “human factor" on - Moderate Slight results

SUSPENDING WIRES— UNBONDED RESISTANCE WIRE STRAIN GAGES (ZERO OUTPUT) FRICTIONLESS SURFACE THIS LEAO NOT CON- NECTED WHEN STRAIN 7 ANALYZER USED —_—-— ; —_— TC — - ——— SENSITIVE AXIS ) E SUSPENDED OUTER CASING WEIGHT w R, = Re*Rs*RyeR (a) ACCELEROMETER AT REST IN (b) INTERNAL BRIOGE FOR (a) HORIZONTAL POSITION #7. (OUTPUT PROPORTIONAL TO a,,) —F-$——_ THIS LEAD NOT CON- NECTED WHEN STRAIN ANALYZER USED R,*R5*R-AR Ro*R4*R+AR (C) ACCELEROMETER WITH ACCEL - (d) INTERNAL BRIDGE FOR (c) ERATION @ INCLINED WITH THE HORIZONTAL FIG. | -OPERATION OF AN UNBONDED RESISTANCE WIRE LINEAR ACCELEROMETER PROSTHETIC DEVICES RESEARCH UNIVERISITY OF CALIFORNIA FIG. |

yi U THESE LEADS NOT CONNECTED WHEN STRAIN ANALYZER USED RECORDER (a) ACCELEROMETERS A AND B WIRED TO ADD OUTPUTS THESE LEADS NOT CONNECTED WHEN STRAIN ANALYZER USED 7 ye 4 ¢ *, a l aa d er? RECORDER (b) ACCELEROMETERS A ANDO 8 WIRED TO SUBTRACT OUTPUTS FIG. 2-WIRING DIAGRAMS FOR COMBINING OUTPUTS OF TWO ACCELEROMETERS PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA

e d ty (a) SINGLE LINEAR ACCELEROMETER (b) TWO LINEAR ACCELEROMETERS — OUTPUTS ADDITIVE RECORDER (c) TWO LINEAR ACCELEROMETERS — OUTPUTS SUBTRACTIVE R;, POWER SOURCE, AND AMPLIFIER ARE IN STRAIN ANALYZER FIG. 3-WIRING DIAGRAMS USING STRAIN ANALYZER PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA FIG. 3

MODEL AP ACCELEROMETERS SINUSOIDAL ANGULAR \ BEAM DISPLACEMENT MOVING PIVOT OSCILLATING BEAM VIBRATING TABLE Se SINUSOIDAL LINEAR ) TABLE DISPLACEMENT Ty RIGID BASE FIG. 4-ANGULAR ACCELEROMETER DYNAMIC CALIBRATION APPARATUS PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA Fie. 4

30 25 | Y | jv FLAT RESPONSE RANGE “ p> E 2oL E a | | v a“ >) | a S Ry b “ | 3 iS sv " rm S w | wi a o ge ! a 10} Fog n® | g v 5 <a i > per i wy Ss S > | s+ Cs “> 1300 ¥ | . | , ( ° j i I i 0 500 1000 1500 2000 INPUT FREQUENCY] [eps]° (ao) ACCELEROMETERS MOUNTED ON VIBRATING TABLE 15 E E = ¢) S ° «anor 2 | FLAT RESPONSE ue _ a RANGE ™ yee = _ iT | ex _— W Sr \ —_— L p? C—-——" — z : wort 400 oO I a | i i O 500 ° 1000 1500 2000 [INPUT FREQUENCY]? [cps]* (b) ACCELEROMETERS MOUNTED ON OSCILLATING BEAM FIG. 5- SYSTEM OUTPUT vs SQUARE OF INPUT FREQUENCY PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA FIG.

10 ° > K = 22.3 RAD. PER SEC.* PER MM = ! Z eb ‘ _ O oad Bar oS y uJ a 2 “ 0 j ! i i i i j | i 0 2 4 6 8 10 12 14 6 18 20 ANGULAR ACCELERATION - RADIANS PER SECOND? (a) DYNAMIC CALIBRATION AT 10.2 CYCLES PER SECOND ATTENUATION 10 10 = 2 K=21.4 RAD. PER SEC® PER MM = > K ° 6 = a 5 | ZF _! a 4k 2S ONE POINT STATIC GALIBRATION ° a ADJUSTED TO ATTENUATION 50 y Q@ ol CALIBRATION AT 10.2 cps ADJUSTED TO ATTENUATION 50 O i i j | | ] i i i 0 to 20 30 40 50 60 TO 80 90 100 ANGULAR ACCELERATION —RADIANS PER SECOND? (b) DYNAMIC CALIBRATION AT 21.4 CYCLES PER SECOND ATTENUATION 50 FIG. 6-DYNAMIC CALIBRATION OF ANGULAR ACCELEROMETER DATA FROM TESTS ON OSCILLATING BEAM PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA FIG. 6

STATHAM TYPE “AP* ACCELEROMETER ACCELEROMETER OUTPUTS STATHAM TYPE "AP" ACCELEROMETER ———___, STATHAM TYPE "C° ACCELEROMETER (a) ACCELEROMETER MOUNTING ASSEMBLY ———_ESTateD POSITION SENSITIVE AXES FOR OF KNEE JOINT TYPE “AP” ACCELEROMETERS ADHESIVE TAPE ESTIMATED POSITION OF C.G. FOR SHANK, FOOT AND SHOE COMBINED \sensirive AXIS FOR TYPE “C" ACCELEROMETER (b) ACCELEROMETER MOUNTING ASSEMBLY ON SHANK FIG. 7 METHOD OF MOUNTING ACCELEROMETERS PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA FIG. 7

es 7 ae 4 Pe J _~* . he ao FIG. 8- TYPICAL ACCELEROMETER TEST RUN NORMAL SUBJECT — LEVEL WALKING PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA FIG. 8

LINEAR ACCELERATION == Least reading -2 ft./sec. 2 Toe Off) ~\— ANGULAR ACCELERATION +150 least reading -5 rad. /sec.” . FIG. 9-TYPICAL ACCELEROMETER RECORD OF PROSTHETIC SHANK DURING SWING PHASE OF LEVEL WALKING SUBJECT 16) NORMAL CADENCE RUN 8-245 APRIL 350, 194) PROSTHETIC DEVICES RESEARCH UNIVERSITY OF CALIFORNIA Fis. 9