JP2011019845A - Fatigue degree measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the degree of fatigue in a continuously seated state on a seat while reducing a load to an occupant. <P>SOLUTION: This fatigue degree measuring device includes a seat acceleration sensor 10 installed at the seat 30 measuring vertical seat acceleration to generate a seat acceleration signal Xn; a head acceleration sensor 12 installed at the occupant's head 32 measuring vertical head acceleration of the head 32 to generate a head acceleration signal Yn; a band pass filter 14 allowing passing of a frequency band BD predetermined on the seat acceleration signal Xn and the head acceleration signal Yn; and a fatigue degree computing part 16 storing the seat acceleration signal Xn and the head acceleration signal Yn for a predetermined fixed time Cn and computing the degree of fatigue TR of the occupant based on a statistical value ST of the seat acceleration signal Xn and head acceleration signal Yn of the fixed time Cn. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technical field for evaluating the degree of fatigue of an occupant, and more particularly to a technique for measuring the degree of fatigue using signal processing.

A car occupant gradually accumulates fatigue as the car ride time increases. The smaller the degree of fatigue accumulation, the more comfortable the car and the higher the merchantability of the car, so evaluating the driver's degree of fatigue at the development stage is an important technology for the development of seats and suspensions. is there.
For this reason, conventionally, many methods have been used to measure an electromyogram or an electrocardiogram and to measure a fatigue state by measuring a chemical substance in blood or saliva.

In Patent Document 1, for the purpose of specifying a muscle fatigue site that affects fatigue feeling, an electrode for measuring myoelectric potential is attached to the occupant's lower back, and the weight is measured before sitting and every unit time (paragraph 0026). A technique is disclosed in which an average power spectrum is calculated (paragraph 0046) for a myoelectric signal (paragraph 0044) in a state in which a load is applied and a correlation with a subjective evaluation of fatigue is obtained.
In Patent Document 2, for the purpose of measuring the fatigue level of the human body seated on the seat in the running state, the amount of adrenaline secretion by urine collection is measured (paragraph 0018), and the cushion characteristics and vibration characteristics of the seat are used as explanatory variables. In particular, a method is disclosed in which vertical accelerations and acceleration change rates of the head and waist are adopted as vibration characteristics (paragraph 0019) and explanatory variables are selected by multiple regression analysis (paragraph 0022). In this patent document, as explanatory variables affecting the amount of adrenaline secretion, the amount of deflection near the back, the amount of deflection near the thigh, the rate of change in lateral acceleration at 2 to 4 [Hz] of the head, and 1 of the seat And the vertical acceleration at 2 [Hz] is disclosed (paragraph 0023).
In Patent Document 3, for the purpose of measuring the degree of fatigue reflecting the effect of sympathetic nerve function on fatigue, the power value of a biological signal such as a heart rate and a pulse wave is corrected for the compensation due to sympathetic nerve activity. A method for calculating the metabolic rate as the degree of fatigue based on the corrected power value is disclosed.

Japanese Patent Laid-Open No. 2002-224072 Japanese Patent Laid-Open No. 2003-118458 JP 2009-22610

In Patent Document 1, an electrode is attached to a human body in order to measure an electromyogram, and wiring from the electrode to the signal processing device is required, and measurement cannot be performed without restraining driving operation without contact.
In Patent Document 2, since urine must be collected and the amount of adrenaline secretion must be measured, it is not possible to measure the degree of fatigue in a state where the seated state is continued. In addition, in the conventional example in which blood or saliva is collected, the burden on the occupant to be measured is large, and data collection for a large number of occupants becomes difficult.
In Patent Document 3, since the heart rate and the pulse wave fluctuate according to various factors, it is difficult to calculate fatigue alone. In particular, the error increases when measuring the degree of fatigue related to sitting for a long time.

[Problem 1] As described above, the conventional example described above has a disadvantage in that it is impossible to measure the degree of fatigue in a state where the seat is continuously seated on the occupant with a low burden.
[Problem 2] Furthermore, the conventional example described above has a disadvantage that the quality of the seat cannot be determined based on the degree of fatigue in the state of being continuously seated on the seat.

  [Object of the invention] An object of the present invention is to measure the degree of fatigue in a state of being continuously seated on a seat while reducing the load on an occupant.

  [Aspects] The inventor of the present invention assumes a transfer function of the human body that is exposed to continuous vibration, positions the head vibration as the output of the transfer function, and examines the correlation with fatigue. We focused on this point. And it came to the idea that the said subject could be solved by devising the signal processing of the signal regarding the vibration of the head.

[Problem Solving Means 1] A first group of the present invention corresponding to the first embodiment includes a seat acceleration sensor that is installed on a seat and generates a seat acceleration signal Xn by measuring a seat acceleration in the vertical direction of the seat; A head acceleration sensor installed on the head and measuring the head acceleration in the vertical direction of the head 32 to generate a head acceleration signal Yn, and the seat acceleration signal Xn and the head acceleration signal Yn are predetermined. A band-pass filter that passes the frequency band, and the seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined time, and based on the statistical values of the seat acceleration signal and the head acceleration signal for the predetermined time. And a fatigue level calculating unit for calculating the fatigue level of the occupant.
Thereby, the said subject 1 was solved.

[Problem Solving Means 2] As in the first group, the second group of the present invention corresponding to Example 2 measures the vertical seat acceleration of the seat and generates the seat acceleration signal Xn. A seat acceleration sensor, a head acceleration sensor installed on the head of an occupant to measure a head acceleration in the vertical direction of the head to generate a head acceleration signal Yn, the seat acceleration signal Xn, and the head acceleration signal A band-pass filter that passes a predetermined frequency band for Yn, the seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined time, and the seat acceleration signal and head acceleration for the predetermined time are stored. And a fatigue level calculation unit that calculates the fatigue level TR of the occupant based on the statistical value of the signal.
The problem solving means 2 has a configuration in which a sheet holding unit that holds a replaceable sheet and a vibration unit that vibrates the sheet are provided.
Thereby, the said subject 2 was solved.

  The present invention interprets the meaning of the terms described in each claim in consideration of the description of the present specification and the drawings, and certifies the invention according to each claim. There are the following advantageous effects in relation to

  [Functional Effect 1 of Invention] In the fatigue level measuring apparatus of Problem Solving Means 1, the bandpass filter passes a predetermined frequency band for the seat acceleration signal Xn and the head acceleration signal Yn, and the fatigue level calculation unit includes: The seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined time, and the fatigue level of the occupant is determined based on the statistical values of the seat acceleration signal Xn and the head acceleration signal Yn for the predetermined time. By calculating the degree of fatigue after sitting on the seat, capturing the characteristics of the head acceleration signal that increases as fatigue accumulates over time, and calculating the degree of fatigue in the seated state without any time constraints Can do.

  [Functional Effect 2 of Invention] In the sheet evaluation apparatus of Problem Solving Means 2, the vibration unit vibrates the evaluation target sheet, and the fatigue calculation unit calculates the seat acceleration signal Xn and the head corresponding to the vibration. Since the fatigue level TR is calculated according to the acceleration signal Yn, the fatigue level of the evaluation target sheet can be quantitatively measured. Thus, the quality of the seat can be determined based on the degree of fatigue in the state where the seat is continuously seated.

It is a block diagram which shows the structural example of embodiment of this invention. (Examples 1 and 2) It is a block diagram which shows the structural example of the hardware resource of this embodiment. (Examples 1 and 2) It is a graph which shows the ratio of each component in three dimensions of a passenger | crew's head vibration. (Examples 1 and 2) It is a graph which shows an example of the head acceleration signal which is a Z-axis component of the vibration of a head. (Examples 1 and 2) 3 is a flowchart illustrating an example of a processing process according to the first embodiment. (Examples 1 and 2) It is explanatory drawing which shows an example of an acceleration signal. (Examples 1 and 2) It is a graph which shows an example of the correlation between the transmission ratio change amount and the subjective fatigue level. (Examples 1 and 2) It is explanatory drawing which shows an example of the relationship between each time tn, transmission ratio Tn, and transmission ratio change amount. (Examples 1 and 2) 10 is a block diagram illustrating a configuration example of Example 2. FIG. (Example 2) It is a graph which shows an example of the time change of the transmission ratio change amount. (Examples 1 and 2)

Two embodiments are disclosed as modes for carrying out the invention. Example 1 is a fatigue measurement apparatus, and Example 2 is a sheet evaluation apparatus. Embodiments including Examples 1 and 2 are referred to as embodiments.
In the present embodiment, the degree of fatigue (fatigue degree TR) of a human body that is continuously exposed to vibration by an input from an engine or road surface such as in a car interior is based on the vibration of the head 32 of the human body. It is to be measured.

The human head 32 is supported from the pelvis through the spine to the top of the human body. However, the spine itself is a flexible structure in which many joints are stacked, and as it is, a soft spring stands upright and a weight is placed on it, and the head 32 is supported stably. Can not. For this reason, the human body has a structure and properties that maintain the posture and keep the head 32 stable by the tension generated by many muscles surrounding the soft spine.
However, since the muscle state changes due to accumulation of stress, fatigue, etc., it is considered that the state in which the head 32 is supported in the human body is also affected by the change in the muscle state.
When the vibration input from the seat 30 to the human body during actual driving of the vehicle and the vibration state of the head 32 are measured and the changes associated with the long-time driving of the vehicle are observed, There was a tendency for the transmission ratio to the head 32 to change.
In the present embodiment, this is used to infer from the result of vibration measurement the change in the muscle state of the human body, specifically the change in the state of fatigue, in an environment where the human body is exposed to vibration such as driving a car.・ I want to quantify.

<1 Fatigue measuring device>
<1.1 Head z-axis statistics>
First, Example 1 of this embodiment is disclosed. In the first embodiment, the seat acceleration and the head 32 acceleration are measured in order to measure the fatigue level TR in a state where the occupant is seated on the seat 30 for a long time, and the fatigue is obtained by signal processing. The degree TR is to be calculated.

The fatigue level measuring apparatus according to the first embodiment includes a seat acceleration sensor 10, a head acceleration sensor 12, a bandpass filter 14, and a fatigue level calculation unit 16 as main elements.
In the example shown in FIG. 1, the seat acceleration sensor 10 is installed on the seat 30 and measures the seat acceleration in the vertical direction of the seat 30 to generate the seat acceleration signal Xn. The seat acceleration is the acceleration of vibration due to the influence of the road surface, the brake and the engine. The head acceleration sensor 12 is installed on the occupant's head 32 and measures the head acceleration in the vertical direction of the head 32 to generate a head acceleration signal Yn. The head acceleration is the acceleration of the head 32 that is reduced by the acceleration of the human body due to the seat acceleration and the seat acceleration when the posture is maintained against the vibration of the seat. The band pass filter 14 removes a noise component by passing a predetermined frequency band BD for the seat acceleration signal Xn and the head acceleration signal Yn.

  The fatigue degree calculation unit 16 accumulates the seat acceleration signal Xn and the head acceleration signal Yn for a predetermined time Cn, and the statistical value ST of the seat acceleration signal Xn and the head acceleration signal Yn for the predetermined time Cn. Based on the above, the fatigue level TR of the occupant is calculated.

  In the example illustrated in FIG. 2, the fatigue measurement apparatus includes, as hardware resources, an acceleration sensor 40 that measures accelerations of the head 32 and the seat 30, and signals from the acceleration sensor 40 (the seat acceleration signal Xn and the head). The amplifier 42 amplifies the acceleration signal Yn), the A / D converter 44 that converts the amplified signal into a digital signal, and the recording analyzer 36 that processes the digital signal.

  The recording / analyzing device 36 is, for example, a computer, and includes a primary memory 46 that temporarily stores digital signals, an arithmetic device 48 such as a CPU that processes the digital signals, and a main storage device 50 that is a main memory of the arithmetic device 48. And an auxiliary storage device 52 such as a hard disk for storing data in a nonvolatile manner. The seat acceleration signal Xn and the head acceleration signal Yn converted into digital signals by the A / D converter 44 are stored in the auxiliary storage device 52. The computing device 48 functions as the fatigue level calculation unit 16 shown in FIG. 1 by executing the fatigue level measurement program, calculates a statistical value ST for a predetermined time Cn, and based on this statistical value ST, the fatigue level Calculate TR.

FIG. 3 shows the vibration ratio of the head 32 of the human body during driving. When driving an automobile, the Z-axis component in the vertical direction is mainly observed in the vibration during traveling transmitted to the head 32. For example, when the vibration component is divided into three dimensions, the Z-axis component becomes 75%. The change in vibration of the Z-axis component shows a good correlation with the fatigue level.
For this reason, in Example 1, first, evaluation is performed using only vibration in the Z-axis direction (vertical direction). In this example, the seat acceleration sensor 10 and the head acceleration sensor 12 shown in FIG. 1 detect acceleration of a Z-axis component that is a vertical component.

  Note that the pitch direction rotation component of the head 32 can be approximated by measuring the movement in the front-rear direction of the portion as high as possible of the head 32, so the reference point near the head 32 such as a headrest and the head 32. The movement of the head 32 may be measured in a non-contact manner by measuring the distance by optical means or the like.

In the first embodiment, secondly, it is preferable to extract only the predetermined frequency band BD for the seat acceleration signal Xn and the head acceleration signal Yn.
Referring to FIG. 4, the frequency band BD that the band pass filter 14 passes is desirably 0.5 [Hz] to 20 [Hz]. Comparison between 0.5 [Hz] and 20 [Hz] is effective because the measurement error is large between the region below 0.5 [Hz] and the region above 20 [Hz].

When a constant vibration is continuously input from the seating surface of the seat 30 to the human body, when the acceleration in the Z-axis direction is observed for the vibration of the head 32, the head acceleration signal of the head 32 at the initial time t1. The power of Y1 is in the state indicated by the dotted line in FIG. 4, and at time t2 when fatigue is accumulated after a predetermined time has elapsed, the head acceleration signal Y2 changes to the state indicated by the solid line in FIG.
In the example shown in FIG. 4, the power of the head acceleration signal Y2 indicated by the solid line at the time point t2 is larger than Y1 in the range indicated by the frequency band BD.

  Furthermore, in the first embodiment, thirdly, in order to obtain frequency components and the like indicated by the dotted line and the solid line in FIG. 4, it is preferable to accumulate the head acceleration signal Yn for a certain period of time Cn and calculate the frequency of the accumulated signal. The fixed time Cn is preferably about several minutes to several tens of minutes.

  As indicated by a dotted line in FIG. 4, at the time t1 immediately after sitting, in the state where the vibration of the seat 30 is attenuated by the human body and the position of the head 32 is stabilized, the vibration component of the head acceleration signal Y1 is small. Thereafter, as shown by a solid line in FIG. 4, when fatigue is accumulated in the occupant after a predetermined time has elapsed, the function of the human body that stabilizes the position of the head 32 is weakened, and the vibration of the head 32 is increased. Then, at time t2, as shown in FIG. 4, the power of the head acceleration signal Y2 becomes larger than the power of the head acceleration signal Y1 at time t1.

  In order to effectively and stably calculate the characteristics of the head acceleration signal Yn with the passage of time by signal processing, in the first embodiment, fourthly, not the head acceleration signal Yn alone but the seat acceleration signal Xn Processing based on the head acceleration signal Yn is performed. That is, first, the vibration component of the head acceleration signal Y1 was attenuated by a component caused by the vibration of the seat 30 and by a muscle strength of the human body that tries to stabilize the position of the head 32 against the vibration of the seat 30. Contains vibration components. This state can be considered as a transmission system in which the vibration of the seat 30 is an input and the vibration of the head 32 is an output. Furthermore, the degree of muscle strength fatigue that stabilizes the head 32 can be more directly quantified by handling the head acceleration signal Y1 in association with the seat acceleration signal Xn instead of handling it alone. As an example of processing based on the seat acceleration signal Xn and the head acceleration signal Yn, if the function of the muscular strength that maintains the head 32 is regarded as a transfer function, a calculation that removes both signals can be applied. In order to detect the amount of the seat acceleration signal Yn remaining in the head acceleration signal Y1, both signals may be subtracted.

  In the first embodiment, fifthly, the statistical value ST of both signals is used in the processing based on the seat acceleration signal Xn and the head acceleration signal Yn. Both signals contain data for a certain time Cn, and even if all data are divided or subtracted between the two signals, the values become unstable. For this reason, in the first embodiment, the statistical value ST is calculated for both signals, and the statistical value ST of both is divided or subtracted. As an example of the statistical value ST, it is desirable to use the statistical value ST in which the difference in power at each time point tn shown in FIG. For example, a single average value or median value is set for the entire fixed time Cn. As the average value, an addition average or a root mean square can be adopted. Alternatively, the predetermined time Cn may be divided into predetermined frequency sections, the statistical value ST may be calculated for each section, and the two signals may be divided or subtracted for each frequency section.

  Thus, firstly, the vibration in the vertical direction (Z-axis direction) of the seat 30 and the head 32 is measured, and secondly, a signal in a predetermined frequency band BD is taken out, and thirdly, constant Accumulate time Cn, and fourth, process based on the seat acceleration signal Xn and the head acceleration signal Yn, and fifth, the statistics of the seat acceleration signal Xn and the head acceleration signal Yn, respectively. By calculating the value ST and dividing or subtracting the statistical value ST, the occupant's fatigue level TR can be calculated satisfactorily. Then, by comparing the division and subtraction values of the statistical value ST at the time points t1, t2, and tn, the fatigue level TR corresponding to the magnitude of fatigue can be calculated.

  In the first embodiment, a 0.5-20 Hz region of translational acceleration in the head Z-axis direction is used as the head vibration used for calculating the fatigue index. The direction of movement) can also be used as an alternative signal for the head Z-axis translation, and a result similar to the measurement of translational vibration in the head Z-axis direction can be obtained.

1.1 Effect of Head Z-Axis Statistics As described above, the bandpass filter 14 passes the predetermined frequency band BD for the seat acceleration signal Xn and the head acceleration signal Yn, and the fatigue level calculation unit 16 The seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined time Cn, and the occupant is based on the statistical value ST of the seat acceleration signal Xn and the head acceleration signal Yn for the predetermined time Cn. By calculating the degree of fatigue TR, the head acceleration signal Yn, which increases as the fatigue accumulates over time after the seat 30 is seated, is captured, and there is no time restriction in the seated state. It is possible to calculate the fatigue level TR. Furthermore, since the fatigue level TR can be calculated if there is a statistical value ST of the constant time Cn of both signals, a plurality of measurements can be performed continuously under the same measurement conditions while in the sitting state.

<1.2 Transmission ratio and transmission ratio change>
In Example 1, it is possible to perform measurement that is highly correlated with fatigue and the degree of fatigue accumulation. In this example, the fatigue level calculation unit 16 includes a power calculation process 18 and a transmission ratio calculation process 20 as main elements. In a preferred example, a transmission ratio change amount calculation process 22 may be provided.

The power calculation process 18 calculates the root mean square XRn of the fixed time Cn of the seat acceleration signal Xn and the root mean square YRn of the fixed time Cn of the head acceleration signal Yn.
The power calculation process 18 uses a bandpass filter 14 that changes the frequency band BD from 0.1 [Hz] to 20 [Hz] on the seat acceleration signal Xn and head acceleration signal Yn measured for a certain time Cn at a certain time t1 from the start of measurement. With respect to the signal after application, when the individual values of the signal are xn and yn, XR1 and YR1 corresponding to the signal power are calculated by the following equations (1) and (2).
$
The A / D converter 44 shown in FIG. 2 performs A / D conversion on the acceleration signal at regular intervals and samples it. Then, the seat acceleration signal Xn and the head acceleration signal Yn are collected as N pieces of numerical data, respectively.

X1 = {x1, x2, x3, ... xN} ... Seat acceleration signal Xn from 0.1 [Hz] to 20 [Hz]
Y1 = {y1, y2, y3, ... yN} ... Head acceleration signal Yn from 0.1 [Hz] to 20 [Hz]

  Similarly, the power calculation process 18 calculates the root mean square XR2 and YR2 at the next certain time point t2. Then, when there are a large number of measurement time points tn, the root mean square is calculated from the values of the individual signals for a fixed time Cn at each measurement time point tn.

  The transmission ratio calculation process 20 divides the root mean square YRn of the head acceleration signal YRn by the root mean square XRn of the seat acceleration signal Xn in accordance with the following equation (3), whereby the head of the vibration of the seat 30 is calculated. A transmission ratio Tn to vibration of the unit 32 is calculated. That is, the transmission ratio calculation process 20 calculates the ratio by dividing XRn corresponding to the input and YRn corresponding to the output, and this is set as the vibration transmission ratio T1 at a certain time. This transmission ratio is a value obtained by quantifying the occupant fatigue level TR at the time point tn.

  In a preferred example, the transmission ratio change amount calculation process 22 further calculates the transmission ratio Tn for two time points tn in the time interval exceeding the certain time Cn, and the two time points according to the following equation (4): The absolute value of the difference between the transmission ratios Tn of tn is calculated as the transmission ratio change amount DTn correlated with the fatigue level TR. That is, at time t2 after a predetermined time has elapsed from time t1, similarly, the transmission ratio T2 is calculated using the seat acceleration signal X2 and the head acceleration signal Y2, and the difference between T2 and T1 calculated at time t1 is calculated. The absolute value is the transmission ratio change amount in the first embodiment.

  Referring to FIG. 5, the fatigue level measuring apparatus is first installed on the seat 30 to measure the seat acceleration in the vertical direction (Z-axis direction) of the seat 30, and the seat acceleration signal Xn shown in FIG. (Step S01, sheet acceleration recording step). In parallel with this step S01, the head acceleration in the vertical direction (Z-axis direction) installed on the head 32 of the passenger is measured, and the head acceleration signal Yn shown in FIG. (Step S02, head acceleration recording step). Then, the noise component is removed by passing a predetermined frequency band BD with respect to the seat acceleration signal Xn and the head acceleration signal Yn (steps S03, S04, band pass filter step). As described above, the frequency band BD is preferably 0.5 [Hz] to 20 [Hz].

  Then, the fatigue level calculation unit 16 calculates the occupant fatigue level TR based on the statistical value ST of the seat acceleration signal Xn and the head acceleration signal Yn for a predetermined time Cn shown in FIG. Fatigue degree calculation process). In this fatigue level calculation step, first, for two time points tn of the time interval exceeding the predetermined time Cn, the statistical value ST of the head acceleration signal Yn is divided by the statistical value ST of the seat acceleration signal Xn, A transmission ratio Tn of the vibration of the seat 30 to the vibration of the head 32 is calculated (step S05, transmission ratio calculation step). The statistical value ST may be, for example, root mean square XRn, YRn.

As for the transmission ratio Tn, when the value of the time point t1 before driving and the value of the time point t2 after elapse of a predetermined time are compared, as shown in FIG. 7, the ratio decreases or increases due to a change in muscle state or a collapse of posture. To do. That is, the absolute value of the difference between the transmission ratios Tn at the two time points tn is calculated as the transmission ratio change amount DTn correlated with the fatigue level TR (step S06, transmission ratio change amount calculation step).
It should be noted that in order to compare two conditions, for example, two types of seats 30 and suspensions, it is not an absolute value of a difference in transmission ratio Tn, but simply a difference, and this difference value is measured in two types. It may be determined whether the results are different.

  This transmission ratio Tn may be increased or decreased by the occupant. However, as a whole, it is considered that the posture of the human skeleton and the state of the muscles that support it change according to the magnitude that has changed from the initial stage (the state that is not fatigued). As shown in FIG. 7, the transmission ratio change amount DTn shows a good correlation with the subjective fatigue level felt by humans.

  In the first embodiment, by utilizing this, the change in the vibration energy ratio of the seat surface of the seat 30 in the vertical direction and the vibration energy ratio of the occupant's head 32 in the frequency band BD of 0.5 [Hz] to 20 [Hz] is obtained. By observing it, the human fatigue level TR is estimated.

  As shown in FIG. 8, in the method described in the first embodiment, a plurality of measurements can be stably performed under the same conditions for a long time seating, and the seat acceleration signal X1 at time points t1, t2, and t3. , X2, X3 and head acceleration signals Y1, Y2, Y3 are obtained and transmission ratios T1, T2, T3 are calculated, and not only transmission ratio change amounts DT1_2, DT2_3 but also DT1_3 can be calculated.

  The processing steps shown in FIG. 5 can be realized by the arithmetic unit 48 shown in FIG. 2 executing the fatigue degree measurement program. This fatigue degree measurement program may include program codes for exhibiting the functions of the power calculation process 18, the transmission ratio calculation process 20, and the transmission ratio change amount calculation process 22 of FIG.

1.2 Effect of Transmission Ratio and Transmission Ratio Change As described above, the transmission ratio calculation process 20 calculates the transmission ratio Tn as the statistical value ST, and the transmission ratio change calculation process 22 calculates the transmission ratio T1 at the time point t1. To calculate the difference (absolute value) DT1_2 from the transmission ratio T2 at time t2 and set this as the fatigue level TR, the fatigue level TR having a high correlation with the subjective fatigue level is set as shown in FIG. The fatigue level TR accumulated between a plurality of time points Tn can be quantified while the measurement environment is continuously constructed for a long time with a small load on the occupant.

  As described above, in the first embodiment, the frequency band from 0.5 [Hz] to 20 [Hz] is extracted for the vertical translational acceleration of the human head 32, and the root mean square (statistical value) for several seconds to several tens of seconds is extracted. ST) is calculated. Similarly, for the seating surface of the seat 30 on which the human body is seated, the root mean square of the vertical translational acceleration is calculated in the frequency band of 0.5-10 Hz. Further, with respect to the calculated mean square value, the value of the human head 32 is divided by the value of the seat 30 to calculate a signal transmission ratio Tn. Then, the absolute value DT1_2 of the difference between the signal transmission ratio T2 after a predetermined time and the initial transmission ratio T1 is calculated, and the fatigue level TR of the human body is estimated from the magnitude.

For this reason, the state of fatigue of the human body can be inferred using acceleration data that can be measured as an electrical signal from the outside without using subjective sensory evaluation, which is laborious and relatively large in error. By limiting the frequency range from 0.5 [Hz] to 20 [Hz], it is possible to measure changes in human vibration due to fatigue without being affected by noise.
Furthermore, the vibration of the human head 32 in the passenger compartment has many components in the vertical translation direction. By measuring and evaluating only this direction, the same effects as measuring and evaluating all three axes can be obtained easily. In addition, since the vibration of the head 32 of the human body is affected by the magnitude of the vibration on the vehicle body side, the influence on the observed value of the vehicle running state is minimized by using the ratio with the seat surface vibration of the seat 30. Limit.
Further, due to the difference in the fatigue state due to the nature of the sheet 30 and individual differences, it is difficult to evaluate the fatigue state by simply increasing or decreasing the numerical value. By taking the initial transmission ratio and the absolute value of the amount of change in the transmission ratio after a lapse of a certain time, a physical value having a good correlation with the subjective fatigue level can be obtained.

<2 Sheet evaluation device>
Next, Example 2 is disclosed.
The sheet evaluation apparatus according to the second embodiment includes a sheet holding unit 24 and a vibration unit 26 as main elements in addition to the main elements according to the first embodiment.
In the example shown in FIG. 8, the screen 28 is further provided, and the amplifier 42 and the recording analyzer 36 shown in FIG.

  The sheet holding unit 24 holds the sheet 30 in a replaceable manner. It is preferable to have a mechanism capable of attaching a seat 30 for a four-wheel vehicle. The vibration unit 26 vibrates the sheet 30. This excitation is an excitation for simulating the actual traveling state of the four-wheeled vehicle, and it is preferable to give the seat 30 vibration according to a preset traveling environment and vehicle speed. It is preferable to provide a pseudo driving environment by storing an image of the driving environment on the screen 28 and providing a computer that displays and controls the driving environment according to the operation of the occupant and displaying the driving environment on the screen 28.

  The configurations of the seat acceleration sensor 10, the head acceleration sensor 12, the bandpass filter 14, and the fatigue level calculation unit 16 (recording analysis device 36) are the same as those in the first embodiment.

  The sheet evaluation apparatus shown in FIG. 9 is a simulator having a vibration function for performing measurement according to the first embodiment. A vibration simulation unit 26 connected to the driver's seat floor surface performs a driving simulation for a predetermined period of time while applying vibrations simulating automobile travel to the human body via the seat 30. Data of the head acceleration signal Xn and the seat acceleration signal Yn is collected by the acceleration sensor 40 fixed to the occupant's head 32. When the head acceleration signal Xn and the seat acceleration signal Yn are collected, the transmission ratio Tn is calculated according to the procedure shown in FIG.

  As a specific use example, for example, when comparing several types of seats 30 for an automobile occupant, after performing a driving experiment for a certain period of time or a simulator experiment simulating the driving vibration of an automobile, By calculating and comparing the transmission ratio change amount DTn using the input vibration from the seat 30 and the vibration of the head 32 of the human body, it is possible to compare the magnitude of the influence on the occupant's fatigue due to the difference in the seat 30. This makes it possible to support the development of an automobile seat 30 that is less tired.

In FIG. 10, using the sheet evaluation apparatus, with respect to two types of sheets 30, the transmission ratio immediately after the start of the experiment is set to T1, and the same simulator experiment is performed, and the transmission ratio is measured three times over time. Shows an example of calculating the transmission ratio change amount with respect to T1. As shown in FIG. 10, for both types of sheets 30, the fatigue level TR increases in proportion to the passage of time, and the sheet 30 indicated by the dotted line brings about a higher level of fatigue. In this way, when there is a difference in the transmission ratio change between the two sheets 30, the sheet 30 in which the amount of change in the transmission ratio change is small with time has little fatigue, and the sheet 30 with much change has a lot of fatigue. It can be estimated that it is 30.
In addition, when performing improvements such as weight reduction and cost reduction of the seat 30, it is possible to evaluate whether or not performance deterioration has occurred that increases the fatigue of the human body due to structural changes.

-2 Effect of Sheet Evaluation Device As described above, in Example 2, the vibration unit 26 vibrates the evaluation target sheet 30, and the fatigue level calculation unit 16 performs the sheet acceleration signal Xn according to the vibration. Since the fatigue level TR is calculated in accordance with the head acceleration signal Yn, the fatigue level TR on the evaluation target seat 30 can be quantitatively measured. Regarding the evaluation of the fatigue level TR, in addition to the same effect as in the first embodiment, the quality of the plurality of seats 30 is compared and determined based on the fatigue level TR in the state of being continuously seated on the seat 30. Can do.

DESCRIPTION OF SYMBOLS 10 Sheet acceleration sensor 12 Head acceleration sensor 14 Band pass filter 16 Fatigue degree calculation part 18 Power calculation process 20 Transmission ratio calculation process 22 Transmission ratio change amount calculation process 24 Sheet holding part 26 Excitation part 28 Screen 30 Sheet 32 Head part 36 Recording analysis device 40 Acceleration sensor 42 Amplifier 44 A / D converter 46 Primary memory 48 Arithmetic device 50 Main storage device 52 Auxiliary storage device
Xn, X1, X2, X3 Seat acceleration signal
Yn, Y1, Y2, Y3 Head acceleration signal
BD frequency band
Cn fixed time
ST statistics
TR fatigue
XRn, YRn root mean square
Tn, T1, T2, T3 transmission ratio
tn, t1, t2, t3
DTn, DT1_2, DT1_3, DT2_3 Transmission ratio change

Claims (6)

A seat acceleration sensor that is installed on the seat and measures a seat acceleration in the vertical direction of the seat to generate a seat acceleration signal Xn;
A head acceleration sensor that is installed on the head of the occupant and measures a head acceleration in the vertical direction of the head to generate a head acceleration signal Yn;
A bandpass filter that passes a predetermined frequency band for the seat acceleration signal Xn and the head acceleration signal Yn;
The seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined period of time, and the degree of fatigue of the occupant is calculated based on statistical values of the seat acceleration signal and the head acceleration signal for the predetermined period of time. A fatigue degree calculation unit,
A fatigue measurement apparatus characterized by the above. The fatigue level calculation unit
A power calculation process for calculating the root mean square of the fixed time of the seat acceleration signal Xn and the root mean square of the constant time of the head acceleration signal Yn;
A transmission ratio calculation process for calculating a transmission ratio of the vibration of the seat to the vibration of the head by dividing the root mean square of the head acceleration signal by the root mean square of the seat acceleration signal Xn. The
The fatigue degree measuring apparatus according to claim 1, wherein: The fatigue level calculation unit
A transmission ratio for calculating the transmission ratio for two time points exceeding the predetermined time and calculating an absolute value of a difference between the transmission ratios at the two time points as a transmission ratio change amount correlated with the fatigue level. With a change amount calculation process,
The fatigue degree measuring apparatus according to claim 2. A sheet acceleration recording step that is installed in the sheet and measures the sheet acceleration in the vertical direction of the sheet and records the sheet acceleration signal Xn;
In parallel with this seat acceleration recording step, a head acceleration recording step that is installed on the occupant's head and measures the head acceleration in the vertical direction of the head and records the head acceleration signal Yn,
A bandpass filter step of passing a predetermined frequency band for the seat acceleration signal Xn and the head acceleration signal Yn;
A fatigue degree calculating step of calculating the degree of fatigue of the occupant based on statistical values of the seat acceleration signal Xn and the head acceleration signal Yn for a predetermined period of time;
This fatigue level calculation process
By dividing the statistical value of the head acceleration signal Yn by the statistical value of the seat acceleration signal Xn at two time points that exceed the predetermined time, the vibration of the seat is transmitted to the vibration of the head. A transmission ratio calculation step for calculating the ratio;
A transmission ratio change amount calculating step of calculating a difference between the transmission ratios at the two time points as a transmission ratio change amount correlated with the degree of fatigue.
A method for measuring fatigue level.   A fatigue degree measuring program for executing the method according to claim 4 using an arithmetic unit. A sheet holding section for holding the sheet in a replaceable manner;
A vibration unit for vibrating the sheet;
A seat acceleration sensor that is installed on the seat and measures a seat acceleration in the vertical direction of the seat to generate a seat acceleration signal Xn;
A head acceleration sensor that is installed on the head of the occupant and measures a head acceleration in the vertical direction of the head to generate a head acceleration signal Yn;
A bandpass filter that passes a predetermined frequency band for the seat acceleration signal Xn and the head acceleration signal Yn;
The seat acceleration signal Xn and the head acceleration signal Yn are accumulated for a predetermined period of time, and the occupant's fatigue level TR is calculated based on statistical values of the seat acceleration signal and the head acceleration signal for the predetermined period of time. A fatigue degree calculation unit,
A sheet evaluation apparatus.

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