ISO/TS 21476:2018 道路車両—IR-TRACCデバイスの変位校正方法 | ページ 6

3.1

IR-TRACC

Infra-Red Telescoping Rod for the Assessment of Chest Compression

non-ratiometric displacement transducer used to measure chest deflection in crash dummies

Note 1 to entry: The technology of the transducer was described in a paper by Rouhana et al. [1998]^[1]. The measurement principle is based on emission of infra-red light by an LED and a phototransistor sensitive to irradiance. The transducer is a non-linear device, as the irradiance and output voltage is proportional to the inverse square of the distance between the emitter and the phototransistor. The distance between the phototransistor and the LED is theoretically proportional to the inverse square root of the phototransistor output voltage: d = C/√U_IR. The inverse square root of the output voltage can also be written as the output voltage to the power of minus 0,5, therefore d = C × U_IR^−0,5

3.2

Displacement Calibration

classic compression method where the zero mm starting point is defined close to the extended range of the sensor

Note 1 to entry: When the IR-TRACC overall length decreases (IR-TRACC compresses), its calibrated mm output increases. The IR-TRACC linearized output is negatively proportional to its length. During displacement calibration components are used to fix the transducer to a calibration fixture. These components do not necessarily belong to the final assembly of the sensor as used in the dummy. The displacement calibration therefore is not an absolute point to point (distance) calibration against a fixed reference. This is not necessary as the chest deflection of the dummy is calculated with respect to the IR-TRACC displacement at time zero. The IR-TRACC displacement output is associated with the ISO MME^[2] Code DS for Displacement.

3.3

Displacement Calibration Fixture

fixed head to which the large diameter end of the IR-TRACC is attached through an interface, and a moveable cross head parallel to the sensitive axis of the IR-TRACC to which the small diameter end of the IR-TRACC is attached through another interface

3.4

Nominal Linearization Exponent

theoretical parameter to linearize the phototransistor voltage output as an inverse square root function, or the voltage output U_IR to the power of −0,5

Note 1 to entry: See 3.1. The theoretical linearization exponent is -0,5 [−]. During inception of the IR-TRACC it was found based on a certain quantity of examples or prototypes that in practise the exponent to linearize IR-TRACCs was not −0,5, but was close to −0,428 57.

Note 2 to entry:d = C * U_IR^{−0,428 57}

Note 3 to entry: This value has been used for some time as a fixed exponent to linearize the voltage output, but due to minimal individual differences of IR-TRACC components, this fixed value did not give the smallest linearization error for each individual transducer. Up to this date this value is now applied as a starting exponent for optimization of the exponent (see 3.5 and 3.6).

3.5

Optimized Linearization Exponent

calibration parameter based on the actual calibration data (output voltage over calibration range) of one individual sensor, giving the least linearization error over the entire calibration range

3.6

Exponent Optimization

optimization of the Linearization Exponent by applying data processing, for instance (but not limited to) numerical optimization

Note 1 to entry: The method finds the best linearization exponent that minimises the linearization errors over the entire calibration range. The result of the process is the optimized linearization exponent EXP, Calibration Factor C_IR, Displacement Intercept I_DS, Sensitivity S_IR and Displacement Intercept Voltage I_DSV. The optimization method is explained in 6.3.

3.7

Forced Lateral Manipulation Test

test implemented to ensure an IR-TRACC is not overly sensitive to bending of the tubes in a direction perpendicular to the axis of displacement measurement

Note 1 to entry: The test is executed at the zero displacement point. A force of 4,45 N ± 0,15 N is exerted to the IR-TRACC tube pulling perpendicular to the axis of compression about halfway between the fixed head and the moving cross head (the distance of the lateral loading point does not have to be exact, as the applied force is adequate to manipulate the tubes in bending extremes). The IR-TRACC lateral test output voltages (U_IR-LAT) are recorded pulling in four directions spaced 90 degrees.

3.8

Tubes In-Out Calibration Method

calibration procedure that takes two extreme tube position conditions into account at each calibration interval (tubes-in and tubes-out position) to ensure an IR-TRACC is not overly sensitive to the individual positions of the telescope tubes

Note 1 to entry: Tubes-in: all free tubes are moved to the largest diameter end (to fixed cross head); Tubes-out: all free tubes are moved to the smallest diameter end (to moving cross head).

Note 2 to entry: In any length of the IR-TRACC displacement range (except fully extended/fully collapsed) the intermediate telescope tubes are free to move position.