JP7736035B2 - Method and device for testing vibration characteristics of automobile body - Google Patents

Description

The present invention relates to a method and device for testing the vibration characteristics of an automobile body to determine the vibration and noise characteristics generated in the automobile body.

Measurements of the vibrations and cabin noise that occur in the body of an automobile and are felt by passengers while the automobile is in motion are mostly conducted on the completed vehicle, such as through actual vehicle running tests or bench tests in which the completed vehicle is placed on a vibration stand and vibrations are input to the wheels (see, for example, Patent Document 1). In contrast, at the design stage of an automobile body structure, there are not many tests conducted to evaluate the effects of the materials used in the body structure and body parts on vibration characteristics such as the vibrations and noise generated in the automobile body.

Tests are also conducted in which vibrations are input to a single point on the fixed floor of a vehicle body to determine the vibration characteristics occurring in each part of the vehicle body. However, in these tests, it is not possible to apply a large excitation force to the vibration input part (hereinafter referred to as the "vibration input part"), given the local elastic deformation near the part of the vehicle body that receives the vibration. As a result, the vibration level excited in parts distant from the vibration input part tends to be small due to insufficient excitation force.

Furthermore, if a vibration mode analysis of the entire vehicle body is performed using the vibration levels of the vehicle body obtained when the excitation force is insufficient, there is a risk that the deformation state of the vehicle body estimated by the vibration mode analysis will be biased. To eliminate this bias, tests are conducted repeatedly while changing the vibration input location on the vehicle body to multiple locations, and the vibration data obtained for the multiple vibration input locations is averaged to determine the true natural vibration mode.

However, the vibrations that enter the vehicle body from the road surface when the completed vehicle is actually being driven are input to the points that connect the tires and suspension to the vehicle body. In contrast, vibration mode analysis, which is obtained by inputting vibrations to a single point on the vehicle body and applying excitation, is merely a means of identifying the body structure's natural vibration modes, particularly its low-order vibration modes, and therefore cannot be said to reproduce the vibration phenomena that occur when the completed vehicle is being driven.

In addition, the road noise and booming sounds that occur when a completed vehicle is being driven are noise in the audible range (20 Hz to 2.0 kHz) within the vehicle cabin, and are generated by vibrations input from the tires, vibrations of body frame components, and vibrations of panel components that are transmitted through the body frame components. In order to evaluate noise levels in the 20 Hz to 2.0 kHz range within the vehicle cabin, it is important to evaluate the vibration characteristics of the body structure under vibration conditions similar to those experienced when a completed vehicle is being driven.

Patent Document 2 discloses a steering stability evaluation technology that uses a bench test on a fully assembled automobile vehicle to simulate vibrations input from the road surface during driving. This technology simulates the rotational motion of a vehicle body suspended on a four-wheel suspension—roll (around the front-to-rear axis), pitch (around the left-to-right axis), and yaw (around the up-to-down axis)—through periodic steering (steering operations) such as continuous lane changes and slalom driving, primarily for evaluating tire and suspension performance. Each tire is mounted on multiple vibration exciters that vibrate the fully assembled automobile. A vibration controller individually controls the multiple vibration exciters, and vibration waveforms (sine waves) input to the left, right, front, and rear tires are shifted by half a cycle to evaluate steering stability performance. While steering during driving is typically performed slowly for safety and ride comfort reasons, steering during slalom driving and emergency lane changes requires the fastest steering, equivalent to a frequency of approximately 1.0 Hz. For this reason, the handling stability evaluation technology in Patent Document 2 does not anticipate evaluating the vibration characteristics of the vehicle body structure in the frequency range of in-vehicle noise (20 Hz to 2.0 kHz). Furthermore, the vibration excitation method in Patent Document 2 excites the vehicle body structure (body-in-white) via the tires and suspension, so when evaluating the audible frequency range of 20 Hz and above, vibration attenuation is large and the vibration response of the object being observed is small, making it an unsuitable evaluation method.

Therefore, in order to input vibrations into an automobile body and evaluate the differences in vibration and noise due to the body structure and materials used in body parts, it is appropriate to conduct tests in which vibrations are input simultaneously to multiple vibration input points on the automobile body, reproducing the vibration phenomena that occur when the completed vehicle is in operation.

Japanese Patent Application Laid-Open No. 2000-88697 JP 2011-247262 A

Typically, evaluation of vehicle body vibration and cabin noise is primarily based on sensory evaluation or acoustic measurements during road tests of completed vehicles, and there have been few cases where vibration characteristics have been evaluated using the vehicle body structure alone, or the so-called body-in-white.
Therefore, in order to understand the vibration characteristics of the vehicle body, such as the vibrations generated in the vehicle body and the noise inside the vehicle, it is necessary to create an analytical model that is close to the finished vehicle and then make predictions using CAE (Computer Aided Engineering) analysis.This CAE analysis makes it possible to evaluate how the vibration characteristics of the vehicle body will change when changes are made to the body structure or the materials used in the body parts.

To guarantee the predicted values of vibration characteristics of an automobile body through CAE analysis and ensure their accuracy, measurement data on the vibration characteristics of the completed vehicle through road tests or bench tests is essential. However, obtaining such measurement data has traditionally been time-consuming and costly.
On the other hand, if vibration characteristic tests using a body-in-white of the vehicle structure are possible, it will be possible to significantly reduce the time required to create the analytical model used in CAE analysis and to perform the CAE analysis, making it easier to determine the vibration characteristics of the automobile body at the design stage of the vehicle structure.

In tests to determine the vibration characteristics of such car bodies, the key is to recreate the vibration conditions that occur in the car body when the completed vehicle is in operation. However, there were two challenges to overcome in conducting vibration characteristics tests using such car bodies:

The first challenge is to reproduce the constraints on the vehicle body caused by peripheral parts such as the suspension. This challenge is solved by using air cushions (air springs) to support the vehicle body.

The second issue is the excitation method for exciting vibrations and noise into the vehicle body. Regarding this issue, there is a method for reproducing the vibration input waves (vibration waveform, frequency, etc.) input to the vehicle body based on measurement data of vibration characteristics obtained through actual vehicle running tests. However, this method is limited to tests in which the vehicle body is vibrated by inputting vibrations of waveforms acquired under a few specified road surface conditions. Therefore, tests in which the vehicle body is vibrated by parametrically changing countless different road surface conditions, vibration input locations, and vehicle running conditions (running speed, etc.) have not been conducted.
Therefore, in tests that vibrate a vehicle body to determine its vibration characteristics, it is desirable to be able to appropriately change the vibration input locations on the vehicle body and the input vibration waves, and to reproduce the various road conditions and vehicle driving conditions that occur when an actual vehicle is running.

The present invention was made to solve the above-mentioned problems, and aims to provide a method and device for testing the vibration characteristics of an automobile body that can accurately reproduce road surface conditions and vehicle driving conditions during actual vehicle driving to determine the vibration characteristics of the automobile body.

(1) A method for testing vibration characteristics of an automobile body according to the present invention inputs vibration to an automobile body to determine the vibration characteristics of the automobile body,
a vibration application step of setting a plurality of vibration input locations on the automobile body supported by air cushions, and inputting vibrations into each of the plurality of vibration input locations to vibrate the automobile body;
a vibration measuring step of measuring data relating to vibration characteristics of the automobile body vibrated in the vibration applying step,
In the vibration excitation process, the vibration input wave input to a part of the vibration input portion of the automobile body is delayed relative to the vibration input wave input to the other vibration input portions.

(2) In the above (1),
The vibration applying step includes:
The vibration input portions are set on the right and left rear sides of the vehicle body,
generating a plurality of sine wave or random wave reference signals to be used as references for the vibration input waves input to each of the vibration input portions;
generating delayed signals by delaying some of the generated reference signals;
Vibration having the reference signal as an input wave is input to the vibration input portion on either the left or right rear side of the automobile body,
The vibration input portion on the other of the left and right rear sides of the automobile body receives vibration with the delayed signal as an input wave.

(3) In the above (1),
The vibration applying step includes:
The vibration input portions are set at the front and rear of the automobile body,
generating a plurality of sine wave or random wave reference signals to be used as references for the vibration input waves input to each of the vibration input portions;
generating delayed signals by delaying some of the generated reference signals;
a vibration having the reference signal as an input wave is input to the vibration input portion at the front of the automobile body;
The vibration input portion at the rear of the automobile body is input with the delayed signal as an input wave.

(4) In any one of (1) to (3) above,
The vibration measurement process is characterized by installing an accelerometer on the automobile body to measure the vibration acceleration generated in the automobile body, and/or installing a microphone inside the automobile body to measure the sound pressure of noise generated from the automobile body, as data related to the vibration characteristics.

(5) The vibration characteristic testing device for an automobile body according to the present invention inputs vibration into an automobile body to determine the vibration characteristics of the automobile body,
a vibration excitation device that inputs vibrations to each of a plurality of vibration input portions set on the automobile body supported by air cushions to vibrate the automobile body;
a vibration measuring device that measures data related to the vibration characteristics of the automobile body excited by the vibration excitation device,
The vibration device is
a plurality of vibration exciters that input predetermined input wave vibrations to the plurality of vibration input portions of the automobile body to excite them;
a signal generating device that generates a plurality of reference signals that serve as references for the vibration input waves input to each of the vibration input portions;
a delay processing device that delays some of the generated reference signals to generate delayed signals;
a plurality of vibration exciter control devices that respectively drive and control the plurality of vibration exciters using the generated reference signal or delay signal;
The vibration measuring device is
an accelerometer installed in the automobile body to measure vibration acceleration generated in the automobile body, and/or a microphone installed inside the automobile body to measure data related to noise generated from the automobile body;
an excitation force/input accelerometer that measures an excitation force and input acceleration that excites the automobile body due to vibration input to the automobile body;
and a data logger that acquires the vibration acceleration measured by the accelerometer and/or the sound pressure of the noise measured by the microphone, and the excitation force and input acceleration measured by the excitation force/input accelerometer.

According to the present invention, it is possible to reproduce the vibration state excited in the vehicle body under road surface conditions and vehicle running conditions when the vehicle is actually running, and to obtain vibration characteristics such as vibration and noise generated in the vehicle body. This makes it possible to obtain changes in the vibration characteristics of the vehicle body due to changes in the vehicle body structure and materials at the design stage of the vehicle body.
In addition, since the vibration input conditions that simulate the road surface conditions and driving conditions (driving speed, etc.) when a real vehicle is running can be changed parametrically, it becomes easier to create analytical models to be used in CAE analysis.
Furthermore, since it is easy to specify the vibration input waves and their delay times input to each of the multiple vibration input points on the automobile body, the standardization and reproducibility of the vibration input conditions related to the vibration input to the automobile body in vibration characteristic tests are also good.

In addition, by directly vibrating the body frame at the body suspension points and the areas surrounding the suspension connections, this invention makes it possible to reduce the vibrator output and excitation force, enabling efficient vibration testing. In particular, despite the small measured signal response, it is possible to accurately evaluate noise levels in the audible range of 20 Hz to 2.0 kHz, where differences are likely to occur in sensory evaluations, and the vibration characteristics of the body frame.

1 is a flowchart illustrating a process flow of a vibration characteristic testing method for an automobile body according to an embodiment of the present invention. 1 is a diagram illustrating a first aspect of a plurality of vibration input locations that input vibrations to an automobile body in a method and device for testing vibration characteristics of an automobile body according to an embodiment of the present invention; 10 is a diagram illustrating a second aspect of a plurality of vibration input locations on an automobile body in a method and apparatus for testing vibration characteristics of an automobile body according to an embodiment of the present invention. FIG. 1 is a block diagram illustrating the configuration of an automobile body vibration characteristic testing device according to an embodiment of the present invention. 1 is a diagram showing an example of an installation state of a vibrator that inputs vibration to an automobile body in an automobile body vibration characteristic testing device according to an embodiment of the present invention; 1A and 1B are diagrams showing specific examples of how vibration is input to an automobile body to generate vibration in an automobile body vibration characteristic testing device according to an embodiment of the present invention ((a) first mode, (b) second mode). FIG. 10 is a block diagram illustrating another configuration of the vehicle body vibration characteristic testing device according to the embodiment of the present invention (part 1). FIG. 2 is a block diagram illustrating another configuration of the vehicle body vibration characteristic testing device according to the embodiment of the present invention (part 2). Graphs showing the frequency response spectrum of vibrations generated in the vehicle body when random wave vibrations are input to the front and rear vibration input points of the vehicle body in Example 1 ((a) delay time 125 ms, (b) delay time 90 ms). 1A and 1B are diagrams showing the locations where sine wave vibrations are input to vibration input locations on the right and left rear sides of the vehicle body to measure the vibration acceleration generated in the vehicle body in Example 1 ((a) side view, (b) top view). 10 is a graph showing the peak amplitude ratio of vibration acceleration generated at each location when vibration is input with delay processing of phase differences of 0°, 90°, and 180° to the vibration input locations on the right and left rear sides of the automobile body in Example 1. 10A and 10B are diagrams showing the parts in Example 2 where sine wave vibrations are input to vibration input parts at the front and rear of the vehicle body to measure the vibration acceleration generated in the vehicle body ((a) side view, (b) top view). 10A and 10B are graphs showing the frequency response spectra of vibrations generated in an automobile body when random wave vibrations are input to vibration input locations at the front and rear of the automobile body in Example 2 ((a) 20 to 100 Hz low frequency band, (b) 100 to 400 Hz mid frequency band).

<Automobile body>
In the present invention, the automobile body that is the subject of vibration characteristics testing is a so-called automobile body frame (body-in-white) that does not include a chassis, suspension parts, drivetrain parts, interior parts, etc. In the embodiment of the present invention described below, an automobile body 100 shown in Fig. 2 is used as an example. The automobile body 100 includes automobile body frame parts such as a front side member 101, a rear side member 103, a bumper reinforcement 105, and a rear floor cross member 107, as well as panel parts such as a body floor 109.

As shown in Figure 2, the vehicle body 100 has a body floor 109 supported by four air cushions 211 installed on the floor surface 201. Therefore, when vibration is input to the vehicle body 100, the vehicle floor 109 supported by the air cushions 211 is not restrained, and the vehicle body 100 is vibrated.

However, the present invention does not limit the locations and methods for supporting the automobile body 100 to these, and the locations and methods for supporting the automobile body 100 may be selected appropriately depending on the vibration characteristics to be evaluated.

The following describes the vibration characteristics testing method and device for an automobile body according to the present invention (hereinafter referred to as the "vibration characteristics testing method" and the "vibration characteristics testing device," respectively) for the case where an automobile body 100 is the subject of a vibration characteristics test.

<Vibration characteristics test method>
As shown in FIG. 2, the vibration characteristic testing method according to this embodiment involves inputting vibrations into an automobile body 100 and determining the vibration characteristics of the automobile body 100.
As shown in FIG. 1, the vibration characteristics testing method according to this embodiment includes a vibration applying step S1 and a vibration measuring step S3.

≪Vibration process≫
2, in the vibration application step S1, a plurality of vibration input portions 111 (111a, 111b) are set in an automobile body 100 having a body floor 109 supported by air cushions 211 installed on a floor surface 201. Then, in the vibration application step S1, vibration is input to each of the plurality of vibration input portions 111 that have been set, thereby vibrating the automobile body 100.

Furthermore, in the vibration excitation step S1, the vibration input wave input to some of the vibration input parts 111 (e.g., 111b) among the multiple vibration input parts 111 is delayed relative to the vibration input wave input to the other vibration input parts 111 (e.g., 111a).

<Vibration measurement process>
The vibration measurement step S3 is a step of measuring data relating to the vibration characteristics of the automobile body 100 that has been vibrated in the vibration excitation step S1.

In this embodiment, the vibration measurement process S3 involves installing an accelerometer on the automobile body 100 and measuring the vibration acceleration occurring in the automobile body 100 as data related to the vibration characteristics of the automobile body 100.

Next, we will explain the multiple vibration input locations 111 set on the automobile body 100 and the vibration input waves input to each vibration input location in the vibration excitation step S1 of the vibration characteristics testing method according to this embodiment.

Vibrations that occur in the automobile body 100 when the vehicle is actually running tend to be more pronounced when vibrations with waveforms excited by, for example, periodic grooves in the road surface or periodic sipe patterns on the tire surface are input, rather than when vibrations with completely random waveforms are input independently to the four wheels. Furthermore, if a resonance point with the same frequency as the vibrations input from the road surface exists in the automobile body 100, there is a risk that the vibrations excited in the automobile body 100 and the noise inside the vehicle cabin will increase.

Therefore, in order to simulate the vibrations input to the automobile body 100 when the actual vehicle is running, in the vibration application process S1, (a) multiple vibration input locations 111 and (b) the vibrations input to each vibration input location 111 are set as follows:

(a) Setting of Vibration Input Locations There are two types of vibration input locations 111 that can be set on the automobile body 100: the first type illustrated in FIG. 2 and the second type illustrated in FIG.

In the first mode, as shown in Figure 2, vibration input portions 111a and 111b are set on the right and left rear sides of the automobile body 100. This is intended for off-road driving or driving on rough roads such as cobblestone roads in front-engine, front-drive vehicles (FF vehicles), which have drivetrain body parts such as the engine and transmission located at the front of the vehicle.

When driving on rough roads such as off-road or cobblestone roads, the vibrations input from the left and right tires can be considered to be significantly out of phase. In the case of front-wheel drive vehicles, because a heavy load is suspended at the front of the vehicle, vibrations at the front of the vehicle are suppressed, whereas the rear of the vehicle, which has a lower weight distribution, is more susceptible to vibration and tends to have a larger amplitude (displacement) of vibration compared to the front of the vehicle. Therefore, when driving on rough roads, the displacement at the front of the vehicle, which is heavy, is small, while the displacement at the rear of the vehicle is relatively large, which increases the contribution of modes that cause deformation in the torsional direction in the vehicle body.
In the first mode, in order to reproduce a vibration state in which vibration is centered around the rear of a front-wheel drive vehicle, in the vibration excitation step S1, a vibration input portion 111a and a vibration input portion 111b are set on the right and left sides of the rear of the automobile body 100. Then, vibrations are input to the vibration input portions 111a and 111b, with the phase of the vibration input wave input to the left vibration input portion 111b delayed compared to the phase of the vibration input wave input to the right vibration input portion 111a, and the automobile body 100 is vibrated.

In the second mode, as shown in Figure 3, vibration input locations 111c and 111d are set at the front and rear of the automobile body 100, respectively. This assumes that vibrations with the same waveform are input to the vehicle from the front and rear tires due to unevenness in the road surface.

When an actual vehicle is traveling, the vibration waveforms input to the front and rear of the vehicle due to road surface irregularities are the same, but there is a slight time difference between the vibrations input to the front and rear. Therefore, in the second mode, to reproduce a vibration state in which vibrations of the same waveform are input to the front and rear of the vehicle with a time difference, vibration input parts 111c and 111d are set at the front and rear of the automobile body 100, respectively, in the vibration excitation process S1. The phase of the vibration input wave input to vibration input part 111d at the rear of the automobile body 100 is then delayed relative to the phase of the vibration input wave input to vibration input part 111c at the front, and vibration is input to each of vibration input parts 111c and 111d, thereby vibrating the automobile body 100.

(b) Vibration Method As a method for inputting vibrations to each vibration input part 111 of the automobile body 100, (b-i) a method for inputting a sine wave vibration of a predetermined frequency for a certain period of time to excite steady vibration, and (b-ii) a method for inputting a random wave vibration continuously for a certain period of time to excite vibration can be applied.

(b-i) Excitation by sine wave vibration input of a predetermined frequency Excitation by sine wave vibration input is effective for tests that simulate vibrations that are input to a car body due to periodic structures on the road surface, such as drainage ditches, when the car is actually running, and for tests that determine vibration characteristics related to a predetermined frequency at which significant vibrations or noise are observed during CAE analysis or when the car is actually running. Excitation by sine wave vibration input is particularly useful in the frequency band of approximately 200 Hz or less, where the natural frequency peak of the vibration generated in the car body is clear.

As shown in Figure 3, vibration input parts 111c and 111d are set at the front and rear of the automobile body 100, and a method for inputting sine wave vibrations to each vibration input part 111c, 111d is described.

First, a sine wave reference signal of a predetermined frequency is generated as a reference for the vibration input wave input to each of the vibration input portions 111c and 111d.
The vibration input wave input to the vibration input portion 111c at the front of the automobile body 100 is a reference signal. On the other hand, the vibration input wave input to the vibration input portion 111d at the rear of the automobile body 100 is a delayed signal obtained by delaying the reference signal.

When the reference signal is a sine wave, the delayed signal can be generated by delaying the reference signal by giving it a phase difference of 0° to 180°. By setting the phase difference between the vibration input waves input to the vibration input portions 111c and 111d at the front and rear of the automobile body 100 between 0° and 180°, various vibration modes can be reproduced in the automobile body 100.
Note that delaying a sine wave reference signal by imparting a phase difference is synonymous with delaying the reference signal by imparting a delay time equivalent to the phase difference, and therefore a delayed signal may be generated by imparting a predetermined delay time to the reference signal.

Next, as shown in Figure 2, vibration input parts 111a and 111b are set on the right and left rear sides of the automobile body 100, respectively, and a method for inputting sine wave vibrations to each vibration input part 111a, 111b will be described.

First, a sine wave reference signal of a predetermined frequency is generated as a reference for the vibration input wave input to each of the vibration input portions 111a and 111b.
The vibration input wave input to the vibration input portion 111a on the rear right side of the automobile body 100 is set as a reference signal. On the other hand, the vibration input wave input to the vibration input portion 111b on the rear left side of the automobile body 100 is set as a delayed signal obtained by delaying the reference signal.

To reproduce complete torsional mode deformation in the automobile body 100 in the vibration excitation process S1, the vibration input waves input to the vibration input portion 111a and the vibration input portion 111b are made sine waves, and the phase difference between the input waves is set to 180°, and the phase is inverted.

However, it is expected that vibration input during actual vehicle operation often excites vibration modes that combine vertical or horizontal bending in addition to torsion. To reproduce these various vibration modes in the automobile body 100, the vibration input wave in the excitation step S1 can be set to a sine wave, and the phase difference between the vibration input waves input to vibration input portion 111a and vibration input portion 111b can be set between 0° and 180°.

(b-ii) Excitation by Random Wave Vibration Input Excitation by random wave vibration input is effective mainly in tests assuming a paved road surface with little unevenness, and in tests simulating vibrations input to an automobile body at a relatively high traveling speed. Random wave vibration input makes it possible to collectively measure a wide frequency band of vibrations generated in the automobile body 100, and is particularly effective when determining vibration characteristics in the high frequency band above 200 Hz, where multiple natural vibration peaks appear and are difficult to separate.

However, when the automobile body 100 is vibrated by a vibration input of a random wave, it is difficult to control or adjust the phase of the input random wave for each individual frequency.
3, for example, when vibration input portions 111c and 111d are set at the front and rear of the automobile body 100, the vibration input wave input to the front vibration input portion 111c is a random wave reference signal, and the vibration input wave input to the rear vibration input portion 111d is a delayed signal obtained by delaying the reference signal by a predetermined delay time.

In other words, when the vibration input wave is a random wave, a reference signal generated by the same signal generating device (oscillation source) such as a function generator is used as the vibration input wave input to the front vibration input part 111c. Furthermore, a delayed signal obtained by delaying the reference signal is used as the vibration input wave input to the rear vibration input part 111d.

This allows the automobile body 100 to be vibrated with random waves and frequency components of the same waveform at both the front and rear of the automobile body 100, simulating the vibration of random waves input to the automobile body when the actual vehicle is running. The delay time applied to generate the delayed signal can be determined from the vehicle speed of the actual vehicle and the distance between the front and rear wheels (distance between the front and rear axles).

As described above, the vibration characteristic testing method for an automobile body according to this embodiment can reproduce the vibration state excited in the automobile body 100 under road surface conditions and vehicle driving conditions during actual vehicle operation, and determine vibration characteristics such as vibration and noise generated in the automobile body 100. This makes it possible to determine changes in the vibration characteristics of the automobile body 100 due to changes in the body structure and materials at the design stage of the automobile body 100.

Furthermore, in the vibration characteristic testing method for an automobile body according to this embodiment, the vibration input waves (input waveform, frequency, and amplitude) input to the multiple vibration input locations 111 and the delay time of the vibration input waves input to each vibration input location can be changed as appropriate. This allows the vibration input conditions that simulate road surface conditions and driving conditions (driving speed, etc.) when an actual vehicle is running to be changed parametrically, facilitating analytical modeling for use in CAE analysis.

Furthermore, since it is easy to specify the vibration input waves and their delay times that are input to each of the multiple vibration input points on the vehicle body, standardization and reproducibility of vibration input conditions related to vibration input to the vehicle body in vibration characteristic tests are also good.

<Vibration characteristic test equipment>
The vibration characteristic testing method according to this embodiment can be carried out using a vibration characteristic testing apparatus 1 as shown in Fig. 4. The configuration of the vibration characteristic testing apparatus 1 will be described below for the case where a vibration characteristic test is carried out on an automobile body 100 shown in Fig. 2.

The vibration characteristics testing device 1 according to this embodiment is used to implement the vibration characteristics testing method according to this embodiment, and as shown in FIG. 4, includes a vibration excitation device 10 and a vibration measurement device 20.

<Vibration device>
As shown in Fig. 2, the vibration excitation device 10 vibrates the automobile body 100 by inputting vibrations to a plurality of vibration input portions 111 (111a, 111b) in the automobile body 100, whose body floor 109 is supported by air cushions 211. As shown in Fig. 4, the vibration excitation device 10 has a plurality of vibration exciters 11 (11a, 11b), a function generator 13, a delay processing device 15, and a plurality of vibration exciter control devices 17 (17a, 17b).

(vibrator)
The vibrator 11 inputs vibration of a predetermined input wave (vibration input waveform and frequency) to each of a plurality of vibration input portions 111 of the automobile body 100 to vibrate it.

In this embodiment, vibrators 11a and 11b (see Figure 4) are provided at the rear right and left vibration input locations 111a and 111b (see Figure 2) of the automobile body 100, respectively, to input vibrations.

Furthermore, as shown in FIG. 5 as an example, each vibrator 11 is installed on the floor surface 201 via vibration-isolating rubber 203. Each vibrator 11 is also connected via a steel vibration rod 19 to a mounting bracket 103a adhered to a rear side member 103, which is part of the underframe of the automobile body 100. As a result, when the vibrator 11 is driven, vibration is input via the vibration rod 19 to a vibration input portion 111 set on the rear side member 103 of the automobile body 100, causing vibrations in the automobile body 100.

An example of the vibrator 11 is an electrodynamic vibrator, but the present invention is not limited to this.

(function generator)
The function generator 13 functions as a signal generating device 13 a that generates a plurality of reference signals that serve as the reference for the vibration input waves input to each vibration input portion 111 of the automobile body 100 .
The function generator 13 is capable of appropriately setting the waveform and frequency of the reference signal, and is capable of selecting a sine wave or a random wave as the waveform of the reference signal.

In this embodiment, as shown in Fig. 4, the function generator 13 generates two reference signals PA and PB that serve as references for the vibration input waves input to the vibration input portion 111a on the right side and the vibration input portion 111b ( _see Fig. 2 ₎ on the left side at the rear of the automobile body 100. In the following description, the two reference signals _PA and _PB will also be collectively referred to as reference signal P.

(Delay Processing Device)
The delay processing device 15 generates a delayed signal by delaying a part of the reference signals generated by the signal generating device 13a.
In this embodiment, the delay processing device 15 is incorporated into the function generator 13. As shown in Fig. 4, the delay processing device 15 delays one reference signal P B of two reference signals P _A and P _B generated by the signal generating device 13a in the function generator 13 to generate _a delayed signal Q _B.

(Vibrator control device)
The vibrator control device 17 controls the driving of each of the plurality of vibrators 11 using the reference signal generated by the signal generating device 13 a or the delayed signal generated by the delay processing device 15 .
In this embodiment, as shown in FIG. 4, the vibration exciter control device 17a drives and controls the vibration exciter 11a using a reference signal P _A generated by the signal generating device 13a, and the vibration exciter control device 17b drives and controls the vibration exciter 11b using a delay signal Q _B generated by the delay processing device 15.
When an electrodynamic vibrator is used as the vibrator 11, the vibrator control device 17 generates an input power pattern of the power to be input to the electrodynamic vibrator based on the reference signal or the delayed signal.

As explained in the vibration characteristic testing method according to this embodiment regarding the setting of the vibration input portion, there are two modes for vibrating the automobile body 100 using the vibration excitation device 10, as shown in Figure 6 (see Figures 2 and 3).

In the first mode, as shown in Figure 6(a), vibrations are input to vibration input points 111a and 111b located on the right and left rear sides of the automobile body 100. As mentioned above, this first mode assumes a vibration state in which vibrations are input mainly from the rear of a front-wheel drive vehicle (FF vehicle) (see Figure 2).

In the first mode, a reference signal P generated by the function generator 13 is input to the vibration exciter control device 17a to drive and control the vibration exciter 11a, and vibration is input to a vibration input portion 111a set on the rear right side of the automobile body 100. Furthermore, a delay signal Q generated by the function generator 13 is input to the vibration exciter control device 17b to drive and control the vibration exciter 11b, and vibration is input to a vibration input portion 111b set on the rear left side of the automobile body 100.
Here, the reference signal P is a sine wave, and the delayed signal is obtained by delaying the reference signal P by a phase difference of 180° in the function generator 13 .

In the second mode, as shown in Figure 6(b), vibrations are input to vibration input locations 111c and 111d located at the front and rear of the automobile body 100. As mentioned above, the second mode assumes a vibration state in which vibrations of the same waveform are input to the vehicle from the front and rear tires due to unevenness in the road surface (see Figure 3).

In the second mode, first, a reference signal P and a delayed signal Q obtained by delaying the reference signal P are generated by the function generator 13. Here, the reference signal P is a sine wave, and the delayed signal Q is delayed by a delay process that gives the reference signal P a phase difference of 45° (equivalent to a phase angle of -45°).

The generated reference signal P is then input to the vibration exciter control device 17a to drive and control the vibration exciter 11a, which inputs vibration to the vibration input location 111c located at the front of the automobile body 100. Meanwhile, the generated delayed signal Q is input to the vibration exciter control device 17b to drive and control the vibration exciter 11b, which inputs vibration to the vibration input location 111d located at the rear of the automobile body 100.

The above two embodiments involve generating two sine wave reference signals using the function generator 13, and delaying one of the reference signals P by imparting a phase difference (45° or 180°) to generate the delayed signal Q. However, the vibration device according to the present invention may also generate multiple random wave reference signals, perform delay processing to impart a delay time to some of the generated reference signals, and generate delayed signals that are delayed relative to the reference signals.

<Vibration measuring device>
4, the vibration measuring device 20 measures data relating to the vibration characteristics of the automobile body 100 excited by the vibration excitation device 10, and includes an accelerometer 21, an excitation force/input accelerometer 23, and a data logger 25. In this embodiment, the vibration measuring device 20 further includes a data processing device 27.

(accelerometer)
The accelerometer 21 is installed on the automobile body 100 and measures vibration acceleration occurring in the automobile body 100 as data relating to the vibration characteristics of the automobile body 100 .
The accelerometers 21 may be installed at multiple locations on the automobile body 100 .

(Excitation force/input accelerometer)
The excitation force/input accelerometer 23 measures the excitation force and input acceleration that vibrate the automobile body 100 due to vibrations input to the automobile body 100 using the vibrator 11 of the vibration excitation device 10 .
In this embodiment, the excitation force/input accelerometer 23 is installed between the excitation rod 19 and the mounting bracket 103a, as shown in FIG.

(data logger)
The data logger 25 acquires the vibration acceleration of the automobile body 100 measured by the accelerometer 21 and the excitation force and input acceleration of the vibration input to the automobile body 100 measured by the excitation force/input accelerometer 23 .
In this embodiment, the data logger 25 synchronously acquires time history data of vibration acceleration measured by the accelerometer 21 and time history data of vibration excitation force and input acceleration measured by the excitation force/input accelerometer.

(Data Processing Device)
The data processing device 27 processes the time history data of the vibration acceleration of the automobile body 100 acquired by the vibration measuring device 20 and the time history data of the vibration excitation force and input acceleration, and determines the vibration characteristics of the automobile body 100.
The data processing device 27 may be configured by a CPU (Central Processing Unit) of a computer (such as a PC). In this case, the above-mentioned components function when the CPU of the computer executes a predetermined program.

As described above, the vehicle body vibration characteristic testing device according to this embodiment can implement the vehicle body vibration characteristic testing method according to this embodiment. This makes it possible to reproduce the vibration state excited in the vehicle body due to road surface conditions and vehicle driving conditions when the vehicle is actually running, and to determine vibration characteristics such as vibration and noise generated in the vehicle body. Furthermore, it becomes possible to determine changes in the vibration characteristics of the vehicle body due to changes in the vehicle body structure and materials at the design stage of the vehicle body.

In addition, the vehicle body vibration characteristics testing device according to this embodiment can appropriately change the vibration input waves (input waveform, frequency, and amplitude) input to multiple vibration input locations, as well as the delay time of the vibration input waves input to each vibration input location. This allows for parametric changes to the vibration input conditions that simulate road surface conditions and driving conditions (driving speed, etc.) when an actual vehicle is traveling.

Furthermore, in the vibration characteristics testing device according to this embodiment, the vibration input wave and delay time input to the automobile body 100 can be easily specified using the vibration excitation device 10, making it possible to standardize vibration input conditions and perform vibration characteristics testing with good reproducibility.

The above description has been given of a case where vibration acceleration is measured by an accelerometer installed in the automobile body 100 as the vibration characteristics of the automobile body 100. However, the present invention may also be applied to a case where a microphone is installed inside the automobile body 100 and data related to noise generated by the automobile body 100 is measured.
In this case, the sound pressure of the noise is measured by a microphone, and the time history data of the sound pressure is acquired by the data logger 25. Then, by processing the time history data of the sound pressure by the data processing device 27, the noise level can be obtained as the vibration characteristic of the automobile body 100.

Furthermore, in the vibration characteristics testing apparatus 1 described above, the delay processing device 15 was incorporated into the function generator 13, but it may also be provided separately from the function generator 31, as in the vibration characteristics testing apparatus 3 shown in Figure 7, for example.

In this case, as shown in FIG. 7, it is sufficient that a function generator 31 generates two reference signals P _A and P _B , and one of the reference signals P _B is delayed by a delay processing device 15 to generate a delayed signal Q _B.
Alternatively, the vibration characteristic testing device according to the present invention may have a delay processing device incorporated in a vibration exciter control device that controls the vibration exciter using a delayed signal (not shown).

In the present invention, the reference signal input to the vibrator control device refers to a reference signal among the vibration input waves input to each of a plurality of vibration input locations set on the automobile body. The vibration characteristic testing device 5 shown in Fig. 8 generates delayed signals _QA and _QB by delay processing devices 15a and 15b for reference signals _PA and _PB generated by a signal generating device 13a. In this vibration characteristic testing device 5, when delayed signal _QB is delayed more than delayed signal QA, delayed signal _QA is regarded as _the reference signal.

Tests were conducted to verify the effectiveness of this invention, which are described below.

In Example 1, as shown in Figures 2 and 3, the automobile body 100 is loaded onto four air cushions 211 installed on the floor surface 201. Then, using the vibration characteristics testing device 1 according to the embodiment of the present invention described above, vibrations are input to and excited by multiple vibration input locations 111 in the automobile body 100, and the vibration characteristics of the automobile body 100 are determined.

The automobile body 100 used for the test was a commercially available compact car (length 4.0 m, width 1.7 m, vehicle weight 1.0 ton, front-to-rear axle distance 2.5 m) that was disassembled and all parts other than body parts such as the drivetrain, interior, functional parts, and electrical parts were removed.

As shown in Figures 2 and 3, the automobile body 100 was vibrated by the vibration excitation device 10 of the vibration characteristic test device 1. The vibration excitation device 10 includes a vibration exciter 11, a function generator 13, and a vibration exciter control device 17.

The function generator 13 functions as a signal generator 13a that generates a reference signal and a delay processor 15 that delays the reference signal to generate a delayed signal. The reference signal or delayed signal generated by the function generator 13 is then input to the vibrator control device 17 to drive and control the vibrator 11, inputting vibration to the automobile body 100. The vibrator 11 and automobile body 100 are connected by a steel vibrator rod 19, and an excitation force/input accelerometer 23 is installed between the vibrator rod 19 and the vibration input portion 111, which is the mounting portion of the vibrator rod 19 on the automobile body 100. Figure 5, mentioned above, shows an example of the connection between the vibrator rod 19 and the automobile body 100.

An accelerometer that measures vibration acceleration was installed on the automobile body 100. A small piezoelectric accelerometer was used and attached to each part of the automobile body 100 with adhesive.

The vibration acceleration detection signals from the accelerometers were simultaneously recorded in a multi-channel data logger 25 at a sampling frequency of 2.0 kHz, and time history data of the vibration acceleration was obtained.
The acquired time history data of vibration acceleration was then converted into a frequency response spectrum by Fourier transform in the data processing device 27, and the frequency and amplitude intensity of the natural vibration peak were determined.

In this Example 1, vibration characteristics tests were conducted on multiple vibration input locations 111 set on the automobile body 100, both when random wave vibrations were input and when sine wave vibrations were input.

<Excitation by random input wave (part 1)>
Two engine frame mounting points at the front of the vehicle floor 109 of the automobile body 100 were set as vibration input locations 111c, and two torsion beam mounting points at the rear were set as vibration input locations 111d (see FIG. 3). Random wave vibrations were then input continuously for a certain period of time by the vibrator 11 to each of the two front vibration input locations 111c and the two rear vibration input locations 111d, thereby vibrating the automobile body 100.

The vibration input waves input to the two front and two rear vibration exciters 11 were all in phase and had the same waveform. Here, the vibration exciter 11a, which inputs vibration to the two front vibration input locations 111c, was driven and controlled by inputting a reference signal P generated by a signal generating device 13a (see Figure 4) in the function generator 13 to the vibration exciter control device 17a. Meanwhile, the vibration exciter 11b, which inputs vibration to the two rear vibration input locations 111d, was driven and controlled by inputting a delayed signal Q generated by delaying the reference signal P using the delay processing device 15 (see Figure 4) in the function generator 13 to the vibration exciter control device 17b (Figure 6(b)).

Delay signal Q was generated by delaying reference signal P with delay times of 125 ms and 90 ms, assuming actual vehicle speeds of 72 km/h and 100 km/h.

The vibration characteristics test involved applying vibration continuously for 10 minutes, measuring the vibration acceleration using an accelerometer 21 installed on the roof side rail MID (location A7 in Figure 10) of the automobile body 100, and obtaining time history data of the vibration acceleration. The obtained time history data of the vibration acceleration was then Fourier transformed to obtain the frequency response spectrum of the vibration acceleration generated in the roof side rail MID of the automobile body 100.

FIG. 9 shows the results of the frequency response spectrum of the vibration acceleration generated in the roof side rail MID of the automobile body 100 when the delay time of the delay signal Q is set to 125 ms and 90 ms.
When the delay time was 125 ms (traveling speed 72 km/h), as shown in FIG. 9( a), the transmissibility (ratio of acceleration amplitude) based on the vibration acceleration input to the front vibration input part 111 c increased in peak values near 80 Hz and 160 Hz, and decreased in peak value near 100 Hz.

In contrast, when the delay time was 90 ms (equivalent to a driving speed of 100 km/h), as shown in Figure 9 (b), the peak values of the transmissibility around 100 Hz and 165 Hz increased, while the peak values around 50 Hz and 128 Hz decreased.

From the above, it has been shown that in a vibration characteristics test that reproduces the differences in driving speeds in actual vehicle driving tests, it is possible to reproduce conditions in which different vibrations occur in the automobile body 100, and to obtain differences in vibration characteristics relative to driving speed.

<Excitation by sine wave input>
Two torsion beam attachment points on the right and left sides at the rear of the automobile body 100 were set as vibration input locations 111a and 111b, respectively (see FIG. 2). The automobile body 100 was then vibrated by inputting sinusoidal vibrations of a predetermined frequency to the vibration input locations 111a and 111b for a fixed period of time using the vibrator 11 to excite steady-state vibrations.

The vibration input wave input to the vibration input portion 111a on the right side (driver's seat side) was a reference signal P generated by the function generator 13. On the other hand, the vibration input wave input to the vibration input portion 111b on the left side (passenger's seat side) was a delayed signal Q obtained by delaying the reference signal by giving a phase difference using the delay processing device 15 inside the function generator 13.
The waveforms of the reference signal and the delayed signal were both sine waves, and their frequencies (excitation frequencies) were set to the frequencies (40 Hz, 48 Hz, or 103 Hz) observed as resonant peaks in the frequency response spectrum obtained when the automobile body 100 was vibrated by a random wave input wave.

Accelerometers 21 for measuring vibration acceleration were installed on the automobile body 100 at measurement locations A1 to A6 shown in Figure 10. Here, A1 is the right end of the rear roof header in the left-right direction of the vehicle body, A2 is the rear right side of the rear floor, and A3 is the center of the front roof header in the left-right direction of the vehicle body. Furthermore, A4 is the front end of the right front side member, A5 is the center of the rear floor cross in the left-right direction of the vehicle body, and A6 is the center of the right center pillar in the up-down direction of the vehicle body.

In each test, vibration was applied using a sine wave of the same frequency continuously for 100 seconds, and the vibration acceleration was measured using accelerometers 21 installed on the vehicle body 100A1-A6, with the time history data acquired by a data logger. The time history data of the vibration acceleration acquired for each part A1-A6 was then Fourier transformed to obtain a frequency response spectrum, and the average value of the peak amplitude was calculated.

In addition, the vibration input wave input to the vibration input portion 111b on the passenger seat side was delayed by giving it a phase difference in the range of 0° to 180° relative to the vibration input wave input to the vibration input portion 111a on the driver's seat side, and the vibration characteristics of each portion A1 to A6 were compared.

Figure 11 shows the peak amplitude intensity obtained when vibration was applied with a phase difference of 0° (no phase difference, synchronized), 90°, and 180°. Here, the peak amplitude intensity shown in Figure 11 is shown as a ratio, with the amplitude intensity obtained at the phase difference where a prominent peak was observed being set to 1.0. This is done to eliminate differences in amplitude intensity between vehicle parts and positions, and focus on differences in the phase difference of the vibration input wave that is input to the vibration input point.

As shown in Figure 11, at an excitation frequency of 40 Hz, the peak amplitude intensity at measurement sites A1 and A2 reached its maximum at a phase difference of 180°. In contrast, the peak amplitude intensity at measurement site A3 was little affected by the phase difference. Also, at an excitation frequency of 48 Hz, the peak amplitude intensity at measurement sites A4 and A5 reached its maximum value at no phase difference (0°), and decreased as the phase difference increased. Furthermore, at an excitation frequency of 103 Hz, the peak amplitude intensity at measurement site A6 reached its maximum value at a phase difference of 90°.

The above shows that vibration characteristics in response to the influence of periodic vibration input in the low-frequency band transmitted from the left and right rear wheels, which reproduces the condition of the automobile body 100 when traveling on a rough road, can be obtained by a vibration characteristics test using an automobile body-in-white.

<Excitation by random input wave (part 2)>
In Example 2, a vibration characteristics test was conducted on a paved road surface (traveling road surface) with little unevenness, simulating periodic road surface unevenness (for example, stepped pavement, rumble strips, etc.) that exists at intervals shorter than the distance between the front and rear axles of the automobile body 100. In this vibration characteristics test, two vibration input locations 111c at the front and two vibration input locations 111d at the rear were set on the body floor 109 of the automobile body 100 (see FIG. 3 ). Random wave vibrations (equivalent to vibrations input from the paved road surface) were then input continuously for a certain period of time by the vibrator 11 to each of the vibration input locations 111c and 111d, thereby vibrating the automobile body 100.

The vibration input waves input to the two front vibration input locations 111c and the two rear vibration input locations 111d were all in phase and had the same waveform. Here, the vibrator 11a that inputs vibration to the two front vibration input locations 111c was driven and controlled by inputting a reference signal P to the vibrator control device 17a. Meanwhile, the vibrator 11b that inputs vibration to the two rear vibration input locations 111d was driven and controlled by inputting a delayed signal Q to the vibrator control device 17b (Figure 6(b)).

When the axle distance and the interval between periodic road irregularities are equal, the random wave vibration input from the tires to the body is equivalent to input at the same timing (phase synchronization) at the front and rear of the automobile body 100. In contrast, when the interval between periodic road irregularities is shorter than the axle distance, the input timing at the rear of the automobile body 100 is delayed more than at the front depending on the traveling speed, and the delay time of delay signal Q was determined based on this.

In this Example 2, the vehicle body 100's axle distance (2500 m), actual vehicle speed of 100 km/h, and intervals between periodic road surface irregularities were assumed to be 1860 mm, 2180 mm, and 2330 mm, and the delay times of the delay signal Q were determined to be 23.0 ms, 11.5 ms, and 6.1 ms, respectively. The reference signal P was then delayed according to these delay times to generate the delay signal Q.

Accelerometers 21 for measuring vibration acceleration were installed on the automobile body 100 at measurement locations A3, A8 to A10 shown in Figure 12. Here, A3 is the center of the front roof header in the left-right direction of the vehicle body, and A8 is the center of the roof cross in the left-right direction of the vehicle body. Furthermore, A9 is the center of the back panel in the left-right direction of the vehicle body, and A10 is the center of the side sill inner in the fore-and-aft direction of the vehicle body.

The vibration characteristics test involved applying random vibrations with the same waveform for 10 minutes, measuring the vibration acceleration using accelerometers 21 installed at A3, A8 to A10 on the automobile body 100, and obtaining time history data for the vibration acceleration. The obtained time history data for the vibration acceleration was then subjected to a Fourier transform to obtain the frequency response spectrum of the vibration acceleration generated at A3, A8 to A10.

Figure 13 shows graphs of the frequency response spectra of the vibration accelerations generated at (i) A3, (ii) A8, (iii) A9, and (iv) A10. In Figure 13, the horizontal axis represents the frequency of the vibration acceleration (Hz), and the vertical axis represents the transmissibility of the vibration acceleration ((m/ ^s² )/(m/ ^s² )). Figure 13(a) shows the frequency response spectra in the frequency range of 20 to 100 Hz, and Figure 13(b) shows the frequency response spectra in the frequency range of 100 to 400 Hz. The frequency range of 20 to 100 Hz in Figure 13(a) is considered to be a low frequency range within the audible frequency range. In contrast, the frequency range of 100 to 400 Hz in Figure 13(b) is a frequency range where human hearing sensitivity is higher than that in Figure 13(a), and where cabin noise becomes a problem.

In the frequency band of 20 to 100 Hz, as shown in Figure 13(a), when the vibration delay signal Q input to the vibration input portion 111d at the rear of the automobile body 100 is changed between delay times of 6.1 ms and 23.0 ms, the frequency response spectrum distribution changes, and the frequency with the highest transmissibility (peak frequency) also changes. For example, in the frequency response spectrum of the vibration acceleration generated at A3 shown in Figure 13(a)(i), the peak frequencies change to 69 Hz, 47 Hz, and 41 Hz for delay times of 6.1 ms, 11.5 ms, and 23.0 ms, respectively.

In contrast, in the 100-400 Hz frequency band, as shown in Figure 13(b), no change in the frequency response spectrum distribution was observed as in the 20-100 Hz frequency band, but the transmissibility of certain frequencies increased depending on the delay time. For example, in the frequency response spectrum of the vibration acceleration generated at A10 in Figure 13(b)(iv), the transmissibility in the 240-290 Hz and 310 Hz range increased when the delay time was 11.5 ms and 23.0 ms compared to 6.1 ms.

As described above, it can be seen that changing the delay time of the delayed signal Q sent to the rear of the automobile body 100 significantly changes the frequency response spectrum. These results demonstrate that the present invention can reproduce and evaluate situations in which the vibration and noise conditions felt by the driver vary depending on the interval between periodic road surface irregularities.

REFERENCE SIGNS LIST 1 vibration characteristic test device 3 vibration characteristic test device 5 vibration characteristic test device 10 vibration excitation device 11 vibration exciter 11a vibration exciter 11b vibration exciter 13 function generator 13a signal generation device 15 delay processing device 15a delay processing device 15b delay processing device 17 vibration exciter control device 17a vibration exciter control device 17b vibration exciter control device 19 vibration exciter rod 20 vibration measuring device 21 accelerometer 23 excitation force/input accelerometer 25 data logger 27 data processing device 30 vibration exciter 31 function generator 40 vibration exciter 41 function generator 100 automobile body 101 front side member 103 rear side member 103a mounting bracket 105 bumper reinforcement 107 rear floor cross member 109 vehicle floor 111 vibration input portion 111a Vibration input portion 111b Vibration input portion 111c Vibration input portion 111d Vibration input portion 201 Floor surface 203 Anti-vibration rubber 211 Air cushion

Claims (1)

A vibration characteristic testing method for an automobile body, which inputs vibration to an automobile body and determines the vibration characteristics of the automobile body, comprising:
a vibration application step of setting a plurality of vibration input locations on the automobile body supported by air cushions, and inputting vibrations into each of the plurality of vibration input locations to vibrate the automobile body;
a vibration measuring step of measuring data relating to vibration characteristics of the automobile body vibrated in the vibration applying step,
The vibration applying step includes:
The vibration input portions are set at the front and rear of the automobile body,
generating a plurality of sine wave or random wave reference signals to be used as references for the vibration input waves input to each of the vibration input portions;
generating delayed signals by delaying some of the generated reference signals;
a vibration having the reference signal as an input wave is input to the vibration input portion at the front of the automobile body;
vibration having the delayed signal as an input wave is input to the vibration input portion at the rear of the automobile body,
Furthermore, the excitation step is performed by changing the delay time of the delayed signal,
The vibration measurement process is a method for testing the vibration characteristics of an automobile body, characterized in that an accelerometer is installed on the automobile body to measure the vibration acceleration in the frequency band of 20 to 400 Hz generated on the automobile body as data on the vibration characteristics, thereby making it possible to reproduce and evaluate the fact that the vibration and noise conditions felt by the driver differ depending on the interval between periodic road surface irregularities.