BioFilter Human Vibration

Module BIOFILT

Biodynamics

Issue 6.5 Module Reference

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BIOFILT

Applies the vibration weightings defined in ISO8041:2005 to acceleration signals. These are used in the assessment of the effects of vibration on human beings (see ISO2631, ISO5394, ISO6954 and similar). See also VIBQ for various quality measures.

Parameters • Weight Class

Wb Z seat (rail) Wb Z seat (rail BS6841) Wc X seat back Wd XY seat surface We rotation Wf Z motion sickness Wf Z motion sickness (BS6841) Wg Z seat (BS6841) Wh hand arm Wj recumbent head Wk Z seat surface Wm building & ship vibration X, Y and Z (formerly WBC) WBC whole body combined (retained for compatibility)

• k Factor k factor Scaling Factor [Default 1.0]

• Strict ISO8041: compliance? [Default Yes]

Notes General The input signal must be an acceleration signal with units of m/sec

2. It must have been

sampled at an adequate rate for the required filter and weight class to be applied. The signal is initially band limited with a high pass (low frequency, f1) filter, low pass (high frequency, f2) filter and then the relevant weighting filters using frequencies f3, f4, f5 and f6 are applied. See the Algorithm Notes for the definition of the frequencies fk, and their associated Qk factors. ISO8041:2005 gives precise details and allowable tolerances of the vibration weightings in terms of frequency response (Annexe B), response to saw tooth signal bursts (Section 5.7, Tables 6, 7 and 8) and Time Weighting Decay Rates (Section 5.13, Table 10). The BIOFILT module meets all of these requirements.

k Factor For some situations an additional multiplying factor, the k Factor, needs to be applied to

meet an ISO requirement. For example, in ISO2631-1 a factor of 1.4 is required for a seated person in the x and y directions. In most situations the k Factor is unity. The non- unity factors and the relevant regulations and conditions are shown below.

Standard Type Condition Signal Weighting k Factor

ISO2631-1 Health Seated Seat-x Wd 1.4 ISO2631-1 Health Seated Seat-y Wd 1.4 ISO2631-1 Comfort Seated Rotation-x We 0.63 ISO2631-1 Comfort Seated Rotation-y Wd 0.4 ISO2631-1 Comfort Seated Rotation-z Wd 0.2 ISO2631-1 Comfort Seated Back-x Wc 0.8 ISO2631-1 Comfort Seated Back-y Wd 0.5 ISO2631-1 Comfort Seated Back-z Wd 0.4 ISO2631-1 Comfort Seated Back_sim-x Wk 1.4 ISO2631-1 Comfort Seated Back_sim-y Wk 1.4 ISO2631-1 Comfort Seated Feet_Sitting-x Wk 0.25 ISO2631-1 Comfort Seated Feet_Sitting-y Wk 0.25

Module BIOFILT

Module Reference Issue 6.5

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ISO2631-1 Comfort Seated Feet_Sitting-z Wk 0.4 Strict ISO8041 Compliance In order to achieve strict ISO8041:2005 compliance the critical item is the data sample rate with respect to the low pass pre filter cut off frequency, f2. For reference the Low Pass cut off frequencies are 100 Hz for all Classes with the exception of Class Wf where it is 0.63 Hz and Class Wh where it is 1258.9 Hz. If the default Strict ISO8041 compliance is set then the minimum sample rate factor is set to nine times the relevant low pass frequency. If strict compliance is not required then the sample rate factor is set to 2.2 times the low pass frequency. If the sample rate is too low the module exists with an appropriate error message. ISO8041:2005 defines both modular and phase characteristics of the weighting functions and also gives tolerance margins for an acceptable operation. In order to meet these tolerances it is essential that the sample rate is more than nine times the nominal cut off frequency (f2) of the band limiting filter, as listed below. The reason why a factor as high as nine times is needed is because the low pass filter is just a second order filter giving a rejection of 12dB per octave. As typically 60dB rejection is required then a sample rate of ten times the nominal cut off frequency would be expected. The tolerances and the bilinear method used to implement the filters reduce the multiple to nine.

Weight Classes The full details of the Weight Classes are given in ISO8041:2005. Their uses are given

in ISO 2631:1997, BS 6841:1987, ISO5349:2001 and related publications. Different input weightings are used for different input sources. A general guide to the use of individual weightings is summarised in the notes below where the x axis of the body is the normal forward direction, y is lateral positive on the left side and z is vertical with positive from toe to head as shown in the diagram.

All of the weightings are defined in IS0 8041:2005.

Wb is typically used for fixed track vehicles (eg, trains)used for vertical (z) vibrations input at the seat when sitting or the feet when standing.

Wc is used for x axis input from seat back. Wd is usually for x and y inputs at the seat or at the feet. We is for seat rotational inputs. Wf is z input for motion sickness. Wg Is used for z axis vibrations. Wh is used for effects on Hand-Arm vibration. Wj is used for x input to head when recumbent. Wk is used for vertical (z) vibrations input at the seat when sitting or the feet

when standing.

Module BIOFILT

Biodynamics


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Wm is used for all axes in building (ISO2631-2) and ship (ISO6954) vibration measurements Note Wm was previously known as WBC. It was re-designated in ISO2631-2:2003.

WBC is an old notation for whole body combined. See also Wm above The frequency response curves for each weight class are shown below. Each curve

shown matches the curves given in ISO8041:2005 almost exactly and is well within the tolerances allowed. The graphs are formatted over the same range as given in ISO8041:2005.

10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wb

WbBandLim

Whole Body (rail) Vertical z

Type Wb

Wb

WbBandLim

Whole Body (rail) Vertical z

Type Wb

10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wc

WcBandLim

Whole Body Seat Back Horizontal x

Type Wc

Wc

WcBandLim

Whole Body Seat Back Horizontal x

Type Wc

Module BIOFILT


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10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wd

WdBandLim

Whole Body Horizontal x & y

Type Wd

Wd

WdBandLim

Whole Body Horizontal x & y

Type Wd

10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

We

WeBandLim

Whole Body rotational

Type We

We

WeBandLim

Whole Body rotational

Type We

Module BIOFILT

Biodynamics


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10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-2

10-1

100

Frequency [Hz]

Wf

WfBandLim

Motion Sickness vertical z

Type Wf

Wf

WfBandLim

Motion Sickness vertical z

Type Wf

10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

100

101

102

103

Frequency [Hz]

Wh

WhBandLim

Hand Arm x, y & z

Type Wh

Wh

WhBandLim

Hand Arm x, y & z

Type Wh

Module BIOFILT


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10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wj

WjBandLim

Head Recumbent Vertical x

Type Wj

Wj

WjBandLim

Head Recumbent Vertical x

Type Wj

10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wk

WkBandLim

Whole Body Vertical z

Type Wk

Wk

WkBandLim

Whole Body Vertical z

Type Wk

Module BIOFILT

Biodynamics


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10-3

10-2

10-1

100

101

We

igh

tin

g F

act

or

[]

-200

0

200

Ph

ase

[°]

10-1

100

101

102

Frequency [Hz]

Wm

WmBandLim

Building & Ship Vibration X,Y and Z

Type Wm

Wm

WmBandLim

Building & Ship Vibration X,Y and Z

Type Wm

Module BIOFILT


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Algorithm Notes The band limiting filters are Butterworth characteristic 2 pole high pass at f1 and a 2 pole

low pass at f2. If the cut off frequency of these is written as 1ω and 2ω respectively

then the filter transfer function HHL(s) is given by

( ) ( )( ) ( ) ( ) ( )

++

++=

2

22

2

11

2

1

//21

1

//21

/

ωωωω

ω

ssss

sSH HL .

where the frequencies 1ϖ = 2πf1 and ω2 = 2πf2 are given below for each class.

Class F1 F2 Wb 0.4 100 Wc 0.4 100 Wd 0.4 100 We 0.4 100

Wf 0.08 0.63 Wg 0.8 100 Wh 10^0.8 10^3.1 Wj 0.4 100 Wk 0.4 100 Wm 10^-0.1 100 WBC 10^-0.1 100

The generalised form of the weighting functions Hx are given for each class as

( )( )( )

( ) ( )( ) ( )[ ]( )

( ) ( )

++

++

++

+=

2

666

2

65

2

555

2

444

3

//1

///1

//1

/1

ωωβ

ωωωωβ

ωωβ

ω

ss

ss

ss

sKsH

g

x

The values of ωn = 2πfn and βn = 1/Qn are given below for each class. Not all components are used in each class. Where a frequency is infinite in the table below then that component is not used.

Class f3 f4 f5 f6 Q4 Q5 Q6 Kg

Wb 16 16 2.5 4 0.55 0.9 0.95 1.024

Wb_6841 16 16 2.5 4 0.55 0.9 0.95 0.4

Wc 8 8 ∞ ∞ 0.63 1.0 1.0 1.0

Wd 2 2 ∞ ∞ 0.63 1.0 1.0 1.0

We 1 1 ∞ ∞ 0.63 1.0 1.0 1.0

Wf ∞ 0.25 0.0625 0.1 0.86 0.8 0.8 1.0

Wf_6841 ∞ 0.25 0.0625 0.1 0.86 0.8 0.8 0.4

Wg 1.5 5.3 ∞ ∞ 0.68 - - 0.42

Wh 100/2π 100/2π ∞ ∞ 0.64 1.0 1.0 1.0

Wj ∞ ∞ 3.75 5.32 - 0.91 0.91 1.0

Wk 12.5 12.5 2.37 3.35 0.63 0.91 0.91 1.0

Wm 1/0.056π 1/0.056π ∞ ∞ 1.0 1.0 1.0 1.0

WBC 1/0.056π 1/0.056π ∞ ∞ 1.0 1.0 1.0 1.0

ISO8041:2005 provides a set of reference calibration frequencies and the expected

Weighting. The Table below details the results obtained using the BIOFILT module. The

Module BIOFILT

Biodynamics


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measurements show excellent agreement with errors less than 0.1% which is well within the + 3% tolerance allowed by ISO8041:2005.

Weighting Frequency (radians/sec)

Measured Factor

ISO8041 Factor

Wb 100 0.8124 0.8126

Wc 100 0.5141 0.5145

Wd 100 0.1259 0.1261

We 100 0.0629 0.0629

Wf 2.5 0.3885 0.3888

Wh 500 0.2018 0.2020

Wj 100 1.0184 1.0190

Wk 100 1.0374 1.0371

Wm 100 0.3359 0.3362

WBC 100 0.3359 0.3362

Named Elements Named Element Type Description $BioFilter text set to Wb ,Wk ,Wd ,Wf ,WBC ,Wc ,We ,Wj ,Wh ,Wm ,Wg

, Wb_BS6841, Wf_BS6841, as appropriate. $HumanBio_Weight_Class text set to Wb ,Wk ,Wd ,Wf ,WBC ,Wc ,We ,Wj ,Wh ,Wm ,Wg

, Wb_BS6841, Wf_BS6841, as appropriate. $HumanBio_Weighting text BS6841 if Wb_BS6841, Wf_BS6841 or Wg,

ISO2631-2 if Wm , otherwise ISO8041. $HumanBio_Weight_Usage text set as appropriate to

Whole Body (rail) Vertical Z, Whole Body Vertical Z, Whole Body Horizontal X & Y, Motion Sickness Vertical Z, Whole Body Combined Directions, Whole Body Seat Back Horizontal X, Whole Body Rotational, Head Recumbent Vertical X, Hand Arm X, Y and Z, Building & Ship vibration X, Y and Z.

$HumanBio_Weight_Reference text set as appropriate to ISO8041 ISO2631-1, ISO2631-1, ISO2631-1, ISO2631-2, ISO2631-1, ISO2631-1, ISO2631-1, ISO5349, ISO2631-2, ISO6954 BS6841, BS6841, BS6841.

$LPBV text Set to the low pass cut off frequency of the

appropriate weight class.

Layout Control The output signal will have a #$LAYOUT_STYLE as the input signal.

Module BIOFILT


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Analysis Menu Location Human Biodynamics

Human Body Vibration

Vibration Weighting

References ISO8041:2005 Human Response to Vibration – Measuring instrumentation. ISO2631-1: 1997 Measurement and evaluation of human exposure to whole body

mechanical vibration and repeated shock - Part 1. ISO2631-2: 2003 Measurement and evaluation of human exposure to whole body




mechanical vibration and repeated shock - Part 5. BS6841 : 1987 Measurement and evaluation of human exposure to whole body

mechanical vibration and repeated shock. ISO8041:1990 Human Response to Vibration. Measuring Instrumentation (also known as

DD ENV 28041:1993). ISO8041:1999 Human Response to Vibration. Measuring Instrumentation Amendment ISO5439-1:2001 Mechanical Vibration – Measurement and evaluation of human exposure

to hand transmitted vibration – Part 1: General Requirements ISO6954:2000 Mechanical Vibration – Guidelines for the measurement, reporting and

evaluation of vibration with regard to habitability on passenger and merchant ships

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BioFilter Human Vibration