JP3129782B2 - Control method of road simulation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a road simulation apparatus capable of reproducing an actual road load on a vehicle on a test bench.

[0002]

2. Description of the Related Art A road simulation device can reproduce the actual road load of a completed vehicle on a test bench.
Widely used for endurance tests.

However, for excitation, the transfer function is regarded as linear, an approximate transfer function is obtained, and test excitation and correction calculation are repeated based on the obtained transfer function to obtain a load target value for the vehicle. After obtaining the corresponding input signal, the signal is supplied to the vibration means to vibrate.

[0004]

However, as shown in FIG. 7, the actual transfer function has a non-linear transfer function G.
On the other hand, to approximate with a linear transfer function, for example, when approximating with _a transfer function G _a tangent to the actual transfer function at the input X _a , the input X _c
The must take into input to vibrating means, when receiving an input X _c, load target value generated by using a transfer function G _a is exceeded the load target value Y is aimed, load target value Y is bottoming If the value is just before, there is a problem that the test vehicle is damaged.

Further, there is another problem that the process of obtaining the input signal corresponding to the target load value on the vehicle by repeating the test excitation and the correction calculation does not converge and diverges.

It is an object of the present invention to provide a control method of a road simulation device which increases the possibility that a process for obtaining an input signal corresponding to the load target value converges, and eliminates the risk of damaging a test vehicle. I do.

[0007]

In order to achieve the above object, a control method according to the present invention is directed to a road simulation apparatus for forcibly exciting a vehicle by an exciting means so as to obtain an actual running road surface load. When obtaining a transfer function G _ar (f) used for forcibly exciting, a predetermined noise and the output of a transducer attached to the vehicle when the noise is input to the exciting means and subjected to test excitation. , A provisional transfer function G _a (f) is obtained, an inverse function G _b (f) of the provisional transfer function G _a (f) is calculated, and an output signal y of the transducer mounted on the actual traveling vehicle is calculated.
The signal Y (f) obtained by Fourier-transforming (t) is used to calculate the inverse function G _b
(F) is multiplied, a first step of obtaining an excitation signal x ₍₀₎ (t) obtained by performing Fourier inverse transform of the multiplied output, and an excitation signal x ₍₀₎ (t) obtained in the first step Is an initial value, and a signal Y _(n) obtained by Fourier-transforming the output of the transducer when the vibration signal x ₍₀₎ () t is supplied to the vibration means and vibrated.
The difference signal E between the absolute value of (f) and the absolute value of the signal Y (f)
_(n) a second step of sequentially correcting the excitation signal until (f) falls within a predetermined allowable error range;
_{(n) The} transfer function G _ar (f) is calculated using a noise group having the same distribution of the absolute value of the Fourier spectrum with respect to the excitation signal obtained in the second step when (f) falls within the allowable error range. And a third step to be determined.

Further, in the first step, the excitation signal as an initial value is represented by an inverse function G _b (f) and a safety coefficient k (0 <k ≦
Even if the multiplied output of 1) and the signal Y (f) is obtained by inverse Fourier transform, the correction of the excitation signal in the second step is performed by correcting the signal E _(n) (f) and the inverse function _Gb (f) multiplied by the safety coefficient k (0 <k ≦ 1) multiplied by the absolute value of the signal,
The absolute value of the signal obtained by Fourier-transforming the excitation signal is added, and this signal is subjected to Fourier-inversely-transformed signal. Further, the predetermined noise may be white noise or noise in which the distribution of the absolute value of the Fourier spectrum is inversely proportional to the square of the frequency within the frequency range in which the transfer function is to be calculated.

[0009]

According to the control method of the present invention, in the first step, the provisional transfer function G is defined by the predetermined noise and the output from the transducer when the noise is input to the vibration means and subjected to test vibration. _a (f) is calculated, and then the inverse function G _b (f) of the temporary transfer function G _a (f) is calculated, and the output signal y of the transducer mounted on the actual traveling vehicle is calculated.
(T) is the Fourier-transformed signal Y (f) and the inverse function G
_b (f), and the multiplied signal is subjected to inverse Fourier transform to calculate an excitation signal x ₍₀₎ (t). In the second step, the excitation signal x ₍₀₎ obtained in the first step
A signal Y _{(n) obtained} by Fourier-transforming the output of the transducer when the vibration is applied by the excitation signal with (t) as an initial value.
The difference signal E between the absolute value of (f) and the absolute value of the signal Y (f)
_{(n) The} correction is sequentially performed until (f) falls within a predetermined allowable error range. When the difference signal E _(n) (f) falls within the range of the allowable error by this correction, the distribution of the absolute value of the Fourier spectrum in the third step is Fourier-transformed from the excitation signal obtained in the second step. The transfer function G _ar (f) is obtained with a noise group equal to the absolute value of the signal.

However, the first method for obtaining the transfer function G _ar (f)
Since the output signal y (t) of the transducer mounted on the actual traveling vehicle is used in the step, the divergence does not occur in the second step, and the transfer function G _ar (f) converges and is fast in time. Can be requested.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. The present embodiment illustrates a case where a motorcycle is used as a test vehicle. FIG. 5 is a side view of a road simulation apparatus for implementing the method of the present invention. In the drawing, reference numeral 1 denotes a motorcycle to be vibrated, and the front and rear wheels of the vehicle have been removed in advance. Reference numeral 2 denotes a front axle rotatably supported by a body frame (not shown) of the motorcycle. The axle 2 is supported by a telescopic type telescopic suspension 3. Reference numeral 5 denotes a rear axle, and the axle 5 is attached to a rear fork 6 that is supported by a rear cushion (not shown) combined with a link mechanism so as to be able to vibrate freely.

Reference numeral 10 denotes axle vibration means for directly vibrating the axles 2 and 5 in front and behind the motorcycle 1. The axle vibration means 10 includes a mechanical part 11 for actually vibrating the axle, and a controller 12 for controlling the mechanical part 11.

The mechanical part 11 of the axle vibration means 10
A first vibrator 14 for vertically vibrating the rear axle 5 of the motorcycle 1, a second vibrator 15 for vertically vibrating the front axle 2, and a front axle And a third vibrator 16 for vibrating the second member 2 in the front-rear direction. The first, second, and third vibrators 14, 15, 16
For this purpose, a backward-acting hydraulic cylinder capable of applying both tension and compression forces is used.

The ends of the piston rods 14a, 14b of the first and second vibrators 14, 15 are respectively connected to the ends of connecting rods 17, 17 by pins, and the other ends of the connecting rods 17, 17 are respectively connected to axles. Pins 2 and 5 are connected.
One end 18b of a swing plate 18 is pin-connected to a tip of a piston rod 16a of the third vibrator 16 via a link 16aa. The oscillating plate 18 is formed in a triangular shape in a side view, and has a central base end 18 a rotatably supported on an upper portion of a support 19. The other end 18c of the oscillating plate 18 is connected to the vibrating rod 2 extending substantially in the horizontal direction.
The other end of the vibrating rod 20 is pin-connected to the front axle 2.

That is, when the piston rod 16a of the third vibrator 16 expands and contracts in the vertical direction, the axle 2 on the front side of the motorcycle moves back and forth through the link 16aa, the rocking plate 18 and the vibration rod 20. It is structured to be vibrated in the direction. The vibrating rod 20 is provided with a load detecting means 21.

Reference numeral 25 denotes a rigid reaction force jig for restricting the longitudinal movement of the body of the motorcycle. The rear axle 5 of the motorcycle is connected to the reaction jig 25 via a link bar 26.

Next, a description will be given of a vibration method using the load simulation apparatus having the above structure. The controller 12 of the axle vibration means 10 will be clarified by a vibration method described below, and a description of a single configuration will be omitted.

In the above-described road simulation apparatus, the first to third vibrators 14, 15, 16 can be respectively controlled in displacement. This is because displacement control can perform control at a higher speed or higher acceleration than load control, so that the accuracy of reproducing the actual road load can be further improved.

Here, in the above-described road simulation apparatus, the forward and backward movement of the rear axle 5 is restrained by the link rod 26 pin-connected to the reaction force jig 25, and as shown in FIG. 1, second vibrators 14 and 15
Is operated, the left end of the link bar 26 draws an arc-shaped trajectory, which may cause an unexpected longitudinal compression load or tension load to be applied to the vehicle body (between the front and rear axles 2 and 5). There is. The following copying control is performed to eliminate such a problem. In other words, since the copying control is performed based on the map shown in FIG.
In addition, high-speed displacement control by the third vibrators 14 to 16 can be performed.

That is, the load applied to the third vibrator 16 is controlled by a load detecting means 21 for detecting the load applied to the vibrating rod 20 from the computer incorporated in the controller 12 to the vibrator 16. Issue a command so that the value is always zero.

Next, based on a command from the computer, the first and second vibrators 14 and 15 are operated to move the piston rods 14a and 15a at a low speed from the lowest point to the highest point (No. By operating the third exciter 16 by following the first and second exciters 14 and 15,
It is moved at such a speed that the value of the load detecting means 21 can always be kept at zero). The third vibrator 16 at this time
Of the piston rod 16a is input to the memory of the computer via the A / D converter. FIG. 6 schematically shows the storage map. In this way, the displacement of the third vibrator 16 is input in relation to the displacement of the first and second vibrators 14 and 15.

Next, the third vibration exciter 16 is switched to a displacement control that operates according to the map schematically shown in FIG. 6, and the first and second vibration exciters 14 and 15 are operated. The respective piston rods 14a, 15a are set to reach the vibration neutral point. At this time, the third vibrator 16 moves along the above-mentioned map, and the third vibrator 1
The piston rod 16a of No. 6 reaches the vibration neutral point. Hereinafter, by operating each of the vibrators 14, 15, 16 based on an input signal described later, an actual running road surface load can be applied to the motorcycle.

When the vibrators 14, 15, 16 are stopped, the third vibrator 16 is caused to move along the above-mentioned map and stopped. Note that the map is obtained by one learning operation, and thereafter, it can be stably started or dropped any number of times along the above-described map.

An actual running load is measured from output data of an accelerometer C ₁ , an accelerometer C ₂ and a strain gauge C ₃ as transducers when the motorcycle actually runs. The road simulation apparatus according to the present embodiment sets the actual traveling load as the target signal y (t), and applies the target signals y (t) to the vibrators 14, 15, 16 in order to obtain the target signal. Excitation signal given for vibration (hereinafter referred to as test signal) x
(T) is calculated, and the calculated test signal is sent to the vibrators 14, 1
In addition to 5 and 16, a simulation of actual running is performed on the motorcycle.

In the concentration durability test of a motorcycle, suspension bottoming tends to occur, and a maximum load also occurs at the time of suspension bottoming. It is desirable that the maximum load in actual running can be faithfully reproduced in the simulation of the strength / endurance test.

However, although the suspension bottoming phenomenon is nonlinear, the load simulation apparatus calculates the test signal x (t) from the target signal y (t) by using a linear transfer function.
It is desirable to apply a test signal x (t) immediately before suspension bottoming occurs to the vibrator. This is clear from FIG.

That is, the actual transfer function G is approximated by the transfer function G _a (f) in the case of the test signal value x _a , and the target signal value immediately before the suspension bottoming occurs in the case of the transfer function G _a The test signal value x for y is extremely large, and the test signal value x becomes [test signal value x _b << test signal value x] with respect to the test signal value x _b for the target signal value y. Therefore, if the vibration is applied by the test signal value x, the target signal value at the time of suspension bottoming is exceeded and the vehicle is damaged. However, in the case of the test signal value _xb , it is approximated by the transfer function G _ar (f),
In the vicinity of the test signal value _xb , the transfer function G _ar approaches the actual transfer function G, and has a better approximation to the actual transfer function G. Therefore, the test signal value _xb is obtained by calculating the test signal value for the target signal value y using the transfer function _Gar .

The operation of this embodiment will be described below with reference to the flowchart shown in FIG.
First, a motorcycle is excited by applying white noise, 1 / f ² characteristic noise, or a predetermined noise signal obtained as a result of various experiments as a test signal x _in (t). measuring an output signal y _in (t) from the output signal and the measured y _in (t) because the test signal x _in (t), which is the ratio of the Fourier transform of both the transfer function G _a (f) It is determined (step S1).

For the calculation of the transfer function G _a (f), the case of a single shaft as described above will be described. When the output signal accompanying the vibration of the first vibrator 14 is obtained, the rear fork is used. mounting an accelerometer C ₁ upward corresponding to the position of the axle 5 on 6, measures the behavior of the rear fork 6 by an accelerometer C _1. The transfer function G _a (f) is obtained by dividing the measured value by the noise signal which is the input signal of the vibrator 14. Further, the second vibrator 15 or the third vibrator 1
Similarly, the accelerometer C ₂ is attached to the position above the front axle 2 and the strain gauge C ₃ is attached to the inner pipe 3 a below the bottom bridge of the front suspension 3. Is divided by the input signal to calculate the transfer function G _a (f).

Following step S1, the transfer function G _a (f)
Of calculating the inverse function G _b (f), determining the inverse function G _b (f) safety factor k (0 <k ≦ 1) multiplying by the transfer function H _a (f) (step S2). The reason for multiplying by the safety coefficient k is to set the initial value to a small value so that an excessive load is not applied to the test vehicle by an excessive test signal.

In step S2, the output signal y (t) (preferably the output signal value almost immediately before the occurrence of suspension bottoming) from the transducer measured during actual running is Fourier-transformed to convert the time domain to the frequency domain. (Step S3). The Fourier transform result is indicated by Y (f). Then by obtaining the transfer function H _a multiplies the output signal Y (f) to (f) with the test signal X ₍₀₎ (f) to step S3 (step S4). Next, X ₍₀₎ (f)
Is inverse-Fourier-transformed to convert from the frequency domain to the time domain to obtain a test signal x ₍₀₎ (t) (step S5). The test signal x ₍₀₎ (t) obtained in step S5 is used as an initial value.

After step S5, the test signal x
A test signal x _(n) (t) having ₍₀₎ (t) as an initial value is supplied to a vibrator to vibrate, and an output from the transducer, that is, an output signal y _(n) (t) is measured. And read it (step S6). Subsequent to step S6, the test signal x _(n) (t) is Fourier-transformed, and the read output signal y _(n) (t) is Fourier-transformed.
_(n) (f) and Y _(n) (f) are obtained (step S7). Then, | Y (f) | − | Y _(n) (f) |
_(n) Obtain (f) (step S8). Therefore, in step S8, the absolute value of the output signal | Y
This means that a deviation between (f) | and the absolute value | y _(n) (f) | of the operation output signal has been detected.

Subsequent to step S8, it is checked whether the error E _(n) (f) is within a range of less than a predetermined allowable error ± ε (step S9). If it is determined in step S9 that the error E _(n) (f) is _{equal to} or larger than the allowable error ± ε, then, following step S9, [| X _(n) (f) | + E
_(n) (f) · | H _a (f) |] is calculated, and the phase angle ∠X ₍₀₎ (f) of the Fourier spectrum is set to X _{(n + 1)} (f) (step S10). Here, ∠ indicates the phase angle of the Fourier spectrum. Therefore, the absolute value | X _(n) (f) | of the amplitude of the Fourier spectrum of the test signal X _(n) (f) obtained in step S7 is equal to the error E in step S10.
_(n) (f) is corrected by the product of the absolute value of the transfer function H (f), the absolute value of the amplitude of the Fourier spectrum of the test signal X _(n) (f) is corrected, and | Y (f) | − | Y _(n) (f) |
Is approached or falls within the range of less than ± ε. Further, the phase angle of the Fourier spectrum is fixed at the initial value. This state is schematically shown in FIG.

Subsequent to step S10, X _{(n + 1)} (f) is inversely Fourier-transformed and returned to the time domain, and x _{(n + 1)} (t)
Is obtained (step S11), n is incremented, that is, +1 is added (step S12), and then step S6
And continue until the error E _(n) (f) falls within the range of ± ε. In this case, since Y (f) uses a signal obtained by Fourier-transforming the output signal y (t) measured during actual running, | Y (f) | − | Y _(n) (f) | It does not diverge, but always converges within a range of less than ± ε. Further, when a signal obtained by performing a Fourier transform on the output signal y (t) using a signal almost immediately before the occurrence of suspension bottoming is adopted, | Y () f | − | Y
_{(n) The} time required for (f) | to converge within the range of less than ± ε is short.

As a result of the check in step S9, E
_(n) When it is determined that (f) is within the range of ± ε,
In step S9, the output symbol Y _{(n) is a} noise group whose absolute value distribution of the Fourier spectrum is equal to | X _(n) (f) |
(F) is measured, a transfer function is calculated from the measurement result,
The arithmetic transfer function is arithmetically averaged to calculate a transfer function G _ar (f) (step S13).

In the above, with respect to the phase of the Fourier spectrum, the test signal was calculated by fixing ∠X _(n) (f) as ∠X ₍₀₎ (f). The phase angle ∠X _(n) (f) of the Fourier spectrum is determined for each frequency in the desired frequency range by generating a group of phases randomly distributed in the range of -π to π by a random number generation routine. The transfer function G _ar (f) including the phase is obtained by performing test excitation using the group. Using the transfer function thus obtained, an inverse function G _br (f) of the transfer function G _ar (f) is calculated as shown in the flowchart of FIG.
(T) is Fourier-transformed, and the output signal Y (f) resulting from the Fourier transformation is multiplied by the transfer function G _br (f) to obtain a test signal X
₍₀₎ (f) is obtained, and the Fourier-transformed test signal X is obtained.
₍₀₎ Fourier inverse transform of (f) to initialize test signal x
₍₀₎ (t) is obtained (steps S22 to S25).

Next, a correction calculation is performed by iterative correction.
That is, subsequently, the transducer output signal y _(n) (t) as a result of the excitation with the signal x _(n) (t) having the test signal x ₍₀₎ (t) as the initial value is read, and the test signal x _(n) (T) and the Fourier transform signal X of the read output signal y _(n) (t)
_(n) (f) and Y _(n) (f) using the error E (n) (f) [=
Y (f) -Y _(n) (f)] (steps S26 to S26).
28), [X _(n) (f) -E _(n) (f ₎ for reducing the test excitation and the error until the absolute value of the error E (n) (f) falls below a predetermined allowable error ε. ) .G _br (f)] is repeatedly performed (steps S26 to S32),
A test signal x _(n) (t) is obtained when the error E _(n) (f) falls below the allowable error ε, and a target value load is applied to the test vehicle by applying the test signal value. be able to.

Although the above description has been made in the case of a single axis, for example,
In the case of three axes, a transfer function G _ar (f) is obtained for each axis, and there is mutual crosstalk between the axes.
The transfer function G _ar (f) due to crosstalk is obtained in the same manner as described above. If the element of the transfer function G _ar (f) in this case is indicated by Gmn, the suffix m indicates the number of the vibrator and n indicates the number of the transducer. As a result,
In a matrix display, the test signal X for three axes
The output signal Y (f) for (f) is as shown in FIG. 4A, and the test signal X (f) for the output signal Y (f).
Is as shown in FIG. Here, [G] ^-1 indicates an inverse matrix. FIG. 4B shows a basic formula for the three-axis system, and a simulation of actual traveling can be performed based on this formula.

The transfer function G obtained as described above
_ar (f) is by using a transfer function inverse Fourier transform G _{a r} (f), performing a vibration test corresponding to various running modes.

In the above-described vibration control, bottoming similar to that in actual running is generated, a transfer function is obtained by using the output signal y (t) at that time, and iterative correction processing is performed based on the transfer function. Even a non-linear response system such as a front fork of a motorcycle can excite a state close to the actual road load.

In the above embodiment, the case where the motorcycle is vibrated has been described as an example. However, the object to be vibrated is not limited to the motorcycle, but may be a three- or four-wheeled vehicle. It goes without saying that the present invention can be applied to all kinds of vibration devices.

[0042]

As described above, according to the present invention, the test signal calculated using the output of the transducer measured during actual running is used as the initial value in the calculation processing of the transfer function used for forcibly applying vibration. , The signal during the processing of the transfer function [| Y (f) |-| Y (n) (f)
|] Does not diverge, and has the effect of converging without fail. When the transfer function G _ar (f) is obtained using a signal obtained by multiplying the inverse function G _b by a safety coefficient, the test signal x ₍₀₎ (t)
Is calculated to the smaller eye, and there is an effect that an excessive load is not applied to the test vehicle. In addition, in the calculation process of the transfer function, since the calculation was performed using the output of the transducer immediately before the bottoming measured during actual running,
[| Y (f) |-| Y _(n) during the calculation of the transfer function
(F) |] converges quickly.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the method of the present invention.

FIG. 2 is an explanatory diagram showing the amplitude of a Fourier spectrum when a method according to the present invention is used.

FIG. 3 is a flowchart for obtaining a test signal x (t) using a transfer function obtained by the method of the present invention.

FIG. 4 is a diagram illustrating a relationship between a transfer function matrix and input / output signals and a transfer function inverse matrix and input signals in a multi-axis system.

FIG. 5 is a side view of a road simulation device that implements an embodiment of the present invention.

6 is a schematic diagram showing a storage map used when controlling displacement of a third vibrator in the road simulation apparatus shown in FIG. 5;

FIG. 7 is a characteristic diagram showing an actual transfer function and an approximate transfer function.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Motorcycle 2 Front axle 3 Front suspension 5 Rear axle 6 Rear fork 10 Axle vibration means 11 Mechanical part of axle vibration means 12 Controller of axle vibration means 14 First vibration machine 15 Second 16 Exciter 16 Third exciter 25 Reaction force jig C ₁ Accelerometer provided on rear axle C ₂ Accelerometer provided on front axle C ₃ Strain gauge provided on front suspension

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-144922 (JP, A) JP-A-61-164135 (JP, A) Masayoshi Harashima, 4 others, “Development of general-purpose road simulator”, HONDA R & D Technical Review, Honda R & D Co., Ltd., August 1, 1991, Volume 3, p. 153-162 (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 17/00-17/10 G01M 7/00-7/08 G05D 19/00-19/02

Claims (6)

(57) [Claims] 1. A load simulation device for forcibly exciting a vehicle by an exciting means so as to obtain an actual running road surface load, in obtaining a transfer function G _ar (f) used for forcibly exciting the vehicle. The provisional transfer function G _a (f) is obtained from the predetermined noise and the output of the transducer attached to the vehicle when the noise is input to the vibration means and subjected to test vibration, and the provisional transfer function G is obtained. calculating the _a inverse function of _{(f) G b (f)} , the output signal y of the transducer attached to the actual running vehicle
The signal Y (f) obtained by Fourier-transforming (t) is used to calculate the inverse function G _b
(F) is multiplied, a first step of obtaining an excitation signal x ₍₀₎ (t) obtained by Fourier-inverting the multiplied output, and an excitation signal x ₍₀₎ (t) obtained in the first step Is used as an initial value, and the absolute value of the signal Y _(n) (f) obtained by Fourier-transforming the output of the transducer when the vibration signal x ₍₀₎ (t) is supplied to the vibration means and vibrated, and a second step of sequentially correcting the difference signal E of the absolute value _{(n) (f)} is the excitation signal to fall within the scope of the tolerance predetermined signal Y (f), the difference signal E _{( n) The} transfer function G _{ar in a} noise group in which the distribution of the absolute value of the Fourier spectrum is equal to the excitation signal obtained in the second step when (f) falls within the allowable error range.
A method for controlling a road simulation apparatus, comprising: a third step of obtaining (f). 2. The method according to claim 1, wherein in the first step, the excitation signal as an initial value is converted into an inverse function G _b (f), a safety coefficient k (0 <k ≦ 1), and a signal Y (f A method for controlling a road simulation apparatus, characterized in that the output of the product is multiplied by Fourier inverse transform. 3. The method according to claim 1, wherein the correction of the excitation signal in the second step is performed by adding a safety factor k (0 <k) to the signal E _(n) (f) and the inverse function G _b (f). ≦ 1) The absolute value of the signal obtained by Fourier-transforming the excitation signal is added to the product of the absolute value of the signal multiplied by ≦ 1), and this signal is subjected to the inverse Fourier-transformed signal. . 4. The method according to claim 1, wherein the signal y
(T) is a control method of the road simulation device, wherein the signal is a signal immediately before the occurrence of suspension bottoming during actual running. 5. The method according to claim 1, wherein the predetermined noise is white noise. 6. The method according to claim 1, wherein the predetermined noise is noise in which the distribution of the absolute value of the Fourier spectrum is inversely proportional to the square of the frequency within the frequency range in which the transfer function is to be calculated. Control method for a road simulation device.