JP6630203B2 - Displacement measuring device - Google Patents

Description

  The present invention relates to a displacement measuring device that calculates a displacement from an output of an acceleration detecting means.

Vibration applied to the vehicle due to unevenness of the road surface is collected as actual vibration waveform data when the vehicle is actually driven, and the same vibration received during actual driving based on the collected actual vibration waveform data is displayed on the table. By adding to a vehicle on a test machine, a vehicle vibration test, a suspension function evaluation, a suspension control, and the like are performed without actually running the vehicle.
When measuring the displacement of an object using a displacement meter when collecting waveform data of actual vibration, the displacement meter becomes larger in accordance with the displacement of the measurement object, and the displacement is measured for measurement. A large measurement space depending on the size may be required.
For this reason, when measuring the amount of displacement in a limited space such as the inside of a vehicle, a displacement meter may not be installed. Therefore, the amount of displacement is calculated from the output of the acceleration detecting means.
For example, in Patent Literature 1, the amount of displacement (unevenness on the road surface) is calculated by performing time integration twice on the output signal of the acceleration detection means installed in the vehicle. The acceleration detecting means has a small sensor itself and does not require a large measurement space around the sensor to measure acceleration. Therefore, it can be installed in a place where a displacement meter cannot be installed.

JP-A-10-278528 Patent No. 3421559

  By the way, the output signal of the acceleration detecting means is an analog signal, but integration cannot be performed with the analog signal, so that the analog signal must be converted into a digital signal (A / D conversion). However, the digital signal discretized by the A / D conversion includes a quantization error. Then, in order to calculate the displacement amount, the digital signal containing the quantum error is integrated, and the integration result (velocity) is further integrated. For this reason, the quantization errors are integrated, and it has been difficult to calculate an accurate displacement amount.

  The present invention has been made in view of the above points, and has as its object to provide a displacement measurement device that can more accurately calculate the amount of displacement of an object to be measured from an output signal of an acceleration detection unit.

In order to achieve the above object, a displacement measuring device according to the present invention includes an acceleration detecting unit that detects an acceleration of a measuring object to be displaced, and a displacement amount of the measuring object from an output signal of the acceleration detecting unit. Calculating means for converting the output signal from the time axis to the frequency axis, performing second-order integration, and performing inverse conversion from the frequency axis to the time axis to perform the measurement. Calculate the calculated displacement amount as the displacement amount of the object, obtain a response function for the displacement of the measurement object from the output signal and the calculated displacement amount, and reproduce the response function from the acceleration measured by the acceleration detection means and the calculated displacement amount. The residual with the reproduced acceleration as the calculated acceleration is calculated, and based on the response function, the correction of the calculated displacement is repeated until the residual falls within the required accuracy, and the accuracy at which the residual is required is obtained. The calculated displacement amount when it is within Characterized by a displacement amount of the measurement object.

  According to such a configuration, the output signal of the acceleration detecting means is subjected to the second-order integration in the frequency domain to obtain the displacement of the measuring object, whereby the displacement of the measuring object is obtained only by the output signal of the acceleration detecting means. The amount can be calculated more accurately.

  Further, in the displacement measuring device, when converting the output signal from a time axis to a frequency axis, a Fourier transform is performed, and when performing an inverse transform from a frequency axis to a time axis, an inverse Fourier transform may be performed. preferable.

  According to such a configuration, the same operation and effect as those of the above-described configuration can be obtained.

  Further, in the displacement measuring device, the object to be measured is a wheel constituting a vehicle body, and the acceleration detecting means is provided on a vehicle body side of a suspension installed between the vehicle body and an axle supporting the wheel. It is preferable that a vehicle-side acceleration sensor installed on a fixed portion and a wheel-side acceleration sensor installed on a wheel-side fixed portion of the suspension be provided, and the arithmetic unit calculate a vertical displacement of the wheel. .

  According to such a configuration, the displacement amount of the wheel can be more accurately calculated only by the output signal of the acceleration detecting means. Also, by using the calculated wheel displacement, the reproducibility of the real environment in the bench test can be improved, so that the suspension can be accurately evaluated.

  According to the present invention, the displacement amount of the measurement object can be calculated more accurately from the output signal of the acceleration detection means.

It is a test outline figure showing signs that a displacement amount of a test object is measured using a displacement measuring device of this embodiment in a hammering test. It is the graph which compared the test result of the hammering test with the measurement result of the displacement measuring device of this embodiment. It is a test outline figure showing signs that a displacement amount of a wheel is measured using a displacement measuring device of this embodiment during running of a vehicle. It is a schematic diagram which shows the structure of a bench test machine.

  An embodiment of the present invention will be described in detail with reference to the drawings as appropriate. The same components are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, the displacement measuring device 1 of the present embodiment measures the acceleration of a displaced test object 11 (measurement target) in a hammering test, and calculates the amount of displacement of the test object 11 from the acceleration. In the hammering test, the displacement (amplitude) of the vibrating test body 11 is measured by the impact (hammering) with the hammer 12.
The displacement measurement device 1 according to the present embodiment includes an acceleration detection unit 2, a storage unit 3, and a calculation unit 4.
The acceleration detecting means 2 is constituted by an acceleration sensor, and is installed on the test body 11 (measurement target). As a method for detecting the acceleration of the acceleration sensor, various detection methods such as a piezoelectric element type, a capacitance type, and a strain gauge type have been proposed. It can be adopted regardless of the detection method as long as the measurement conditions such as the outer dimensions and the fact that it can be securely fixed to the measurement location can be satisfied. Note that the method of calculating the displacement amount from the acceleration can reduce the size and cost of the sensor as compared with directly measuring the displacement.
The storage unit 3 stores the output signal output from the acceleration detection unit 2 and the calculation result of the calculation unit 4.
The calculating means 4 performs a Fourier transform of the output signal of the acceleration detecting means 2 from the time domain to the frequency domain, performs second-order integration, and performs an inverse Fourier transform from the frequency domain to the time domain, thereby displacing the displacement of the test body 11. Calculate the amount.
That is, the calculating means 4 calculates the displacement of the test body 11 from the output signal of the acceleration detecting means 2.
In the hammering test shown in FIG. 1, a displacement meter 13 that measures a displacement due to hammering is installed on the test body 11 for comparison with the displacement measuring device 1 of the present embodiment.

Next, a procedure for measuring the displacement amount of the test body 11 by a hammering test will be described.
First, the acceleration detecting means 2 is installed on the test body 11.
Next, the test body 11 is hit with a hammer 12 to vibrate, and an output signal output from the acceleration detection means 2 is recorded in the storage means 3.
The calculation means 4 reads the output signal of the acceleration detection means 2 recorded in the storage means 3 and performs discretization (A / D conversion) of the output signal. Here, the discretized output signal is defined as a calculated acceleration. When the output signal is recorded in the storage unit 3, the arithmetic unit 4 may perform discretization (A / D conversion) of the output signal.

演算手段４は、数式２によって、算出加速度を時間領域から周波数領域にフーリエ変換する。なお、角振動数ω＝２πｎ/τとする。
数式２：

次に、演算手段４は、数式３によって、周波数領域に変換された算出加速度の２階積分を行い、周波数領域における変位量を算出する。
数式３：

さらに、演算手段４は、数式４によって、周波数領域における変位量に対して逆フーリエ変換を行い、時間領域における変位量（算出変位量）に変換する。
数式４：

演算手段４は、上記の各数式２〜４について、算出加速度、および各計算式の計算結果を用いてそれぞれの計算を行い、算出加速度から変位量（算出変位量）を算出する。 When discretizing the output signal, the arithmetic unit 4 samples the number N of samples at the sampling period τ. That is, the calculated acceleration is discretized at the sampling period τ.
Formula 1:

The calculation means 4 performs a Fourier transform of the calculated acceleration from the time domain to the frequency domain using Expression 2. Note that the angular frequency ω = 2πn / τ.
Formula 2:

Next, the calculating means 4 calculates the displacement amount in the frequency domain by performing the second-order integration of the calculated acceleration converted into the frequency domain by Expression 3.
Formula 3:

Further, the calculation means 4 performs inverse Fourier transform on the displacement amount in the frequency domain by using Expression 4, and converts the displacement amount into the displacement amount (calculated displacement amount) in the time domain.
Equation 4:

The calculation means 4 calculates each of the above formulas 2 to 4 using the calculated acceleration and the calculation result of each calculation formula, and calculates a displacement (calculated displacement) from the calculated acceleration.

When the calculated displacement amount calculated by the above method is compared with the displacement amount of the actual measurement value by the displacement meter 13, as shown in FIG. 2, the vibration waveform of the calculated displacement amount is similar to the vibration waveform of the actually measured value. It is considered that the actual measurement value could be reproduced by the calculated displacement calculated from the acceleration.
For reference, the calculated acceleration is second-order integrated in the time domain, and the obtained displacement (time domain calculated displacement) is also drawn in the figure. In the time domain calculated displacement, for example, a condition such as "the displacement is zero before the impact is applied" is added for a part of the area, but the calculation diverges in the entire calculation range. Clearly.

  In addition to the above configuration, the output signal of the acceleration detecting means 2 is subjected to second-order integration in the frequency domain to obtain the displacement of the object to be measured. Can be calculated more accurately.

Next, as shown in FIG. 3, the displacement measuring device 1 is installed on the vehicle S, and when the vehicle S travels, the displacement amount of the wheel S1 (measurement target) displaced by the unevenness of the road surface R is measured by displacement measurement. A method of measuring using the device 1 will be described.
The vehicle S includes an axle S2 extending from the vehicle body SS, wheels S1 supported by the axle S2, and a suspension S3 disposed between the vehicle body SS and the wheels S1.
The wheel S1 is rotatably supported by an axle S2, and a tire S1a having elasticity and constituting a mounting surface with a road surface R is fitted around the wheel S1.

The suspension S3 is disposed between the vehicle body SS and the wheels S1, supports the axle S2, absorbs the unevenness of the road surface R transmitted from the wheels S1 to the vehicle body SS during traveling, and appropriately grounds the tire S1a. To keep. The suspension S3 includes a spring S3a and a damper S3b.
The spring S3a is constituted by a coil spring wound in a cylindrical shape.
The damper S3b is disposed inside the cylinder of the spring S3a.
The damper S3b includes a piston (not shown) that moves in accordance with expansion and contraction of the suspension S3 in a cylinder (not shown), and a liquid such as oil is sealed in the cylinder. The piston is provided with an orifice (not shown).
The spring S3a and the damper S3b are arranged to be able to expand and contract between the vehicle-body-side fixing part S3c and the wheel-side fixing part S3d of the suspension S3.
The vehicle body side fixing portion S3c is located at the upper end of the suspension S3 and is fixed to the vehicle body SS.
The wheel-side fixing portion S3d is located at the lower end of the suspension S3, and is fixed to an axle S2 that supports the center of the wheel S1.
The suspension S3 configured as described above absorbs the impact from the road surface R by the expansion and contraction of the spring S3a. Further, the piston moves in the cylinder in synchronization with the expansion and contraction of the spring S3a, and the liquid passes through the orifice by the movement of the piston. Then, the resistance generated when the liquid passes through the orifice causes the damper S3b to attenuate the vibration of the spring S3a.

The acceleration detecting means 2A comprises an acceleration sensor, and detects the vertical acceleration of the wheel S1 displaced by the unevenness of the road surface R when the vehicle S travels. The acceleration detecting means 2A includes a wheel-side acceleration sensor 2Aa installed on the wheel-side fixed portion S3d of the suspension S3, and a vehicle-body-side acceleration sensor 2Ab installed on the vehicle-body fixed portion S3c of the suspension S3.
The wheel-side acceleration sensor 2Aa measures acceleration along the direction in which the suspension S3 expands and contracts.
The vehicle-body-side acceleration sensor 2Ab measures the acceleration along the direction in which the suspension S3 expands and contracts when the suspension S3 moves in the vertical direction (the vehicle body SS moves in the vertical direction).
The acceleration signals output from the acceleration sensors 2Aa and 2Ab are output to the storage unit 3.
When the spring S3a and the damper S3b of the suspension S3 are of a separate type, a vehicle-body-side acceleration sensor and a wheel-side acceleration sensor are respectively installed to measure the vertical acceleration.

The calculation means 4 reads the output signal of the acceleration detection means 2A recorded in the storage means 3 and calculates the vertical acceleration (calculated acceleration) of the wheel S1. The reason for obtaining such a calculated acceleration is as follows.
Since the suspension S3 is installed on the vehicle body SS so as to expand and contract obliquely with respect to the vertical direction, the acceleration signals output from the acceleration sensors 2Aa and 2Ab are inclined obliquely with respect to the vertical direction. is there. Further, since the wheel S1 is supported by the vehicle body SS with a configuration different from that of the suspension S3, the wheel S1 moves differently from the suspension S3. Therefore, in order to calculate the amount of displacement of the wheel S1, the acceleration signals output from the acceleration sensors 2Aa and 2Ab must be converted in accordance with the direction in which the wheel S1 moves.
Further, if the calculated displacement is converted into a vertical displacement, when the calculated displacement is applied to the bench tester 101 described later, the vibration exciter 102 is adjusted in accordance with the direction of the suspension S3. This is convenient because it is not necessary to adjust the position of.
Further, while the vehicle is running, vibrations due to unevenness of the road surface R are input to the vehicle body SS through the wheels S1, but the suspension S3 disposed between the wheels S1 and the vehicle body SS expands and contracts to absorb the vibrations. . However, when the suspension S3 expands and contracts, the vibration due to the unevenness of the road surface R cannot be completely absorbed, so that the vehicle body SS vibrates in the vertical direction.
That is, the suspension S3 while the vehicle is running is displaced in the vertical direction while expanding and contracting. Therefore, the output signal of the wheel-side acceleration sensor 2Aa alone cannot accurately measure the acceleration of the displaced wheel S1. Therefore, the calculating means 4 adds the output signal of the vehicle body-side acceleration sensor 2Ab to the output signal of the wheel-side acceleration sensor 2Aa, and calculates the acceleration (calculated acceleration) of the wheel S1 in consideration of the vibration of the vehicle body SS.

  The calculating means 4 performs a Fourier transform of the calculated acceleration from the time domain to the frequency domain, performs second-order integration, and performs an inverse Fourier transform from the frequency domain to the time domain, thereby obtaining the vertical displacement amount (calculation) of the wheel S1. Displacement).

Next, a method of calculating the amount of displacement of the wheel S1 from the acceleration of the displaced wheel S1 using the displacement measuring device 1 of the present embodiment will be described.
First, the wheel-side acceleration sensor 2Aa is installed on the wheel-side fixed part S3d of each suspension S3, and the vehicle-body-side acceleration sensor 2Ab is installed on the vehicle-body-side fixed part S3c of each suspension S3.
Then, the vehicle S is driven on the set test road, and the output signals output from the acceleration sensors 2Aa and 2Ab are recorded in the storage unit 3.

Next, the calculation means 4 reads the output signals of the acceleration sensors 2Aa, 2Ab recorded in the storage means 3, and calculates the vertical acceleration (calculated acceleration) of the wheel S1.
The arithmetic unit 4 performs discretization (A / D conversion) of the output signal when recording the output signal in the storage unit 3 or calculating the calculated acceleration.
That is, the output signal of the wheel side acceleration sensor 2Aa and the two output signals of the vehicle body side acceleration sensor 2Ab are synchronized, and sampling is performed at the same timing. Then, the vertical acceleration (calculated acceleration) of the wheel S1 is calculated from the sampled output signal of the wheel-side acceleration sensor 2Aa and the output signal of the vehicle-body-side acceleration sensor 2Ab.

The calculating means 4 calculates the displacement from the calculated acceleration.
For this purpose, the calculating means 4 first performs a Fourier transform on the calculated acceleration from the time domain to the frequency domain.
Next, the calculating means 4 performs second-order integration of the calculated acceleration converted into the frequency domain, and calculates the displacement amount in the frequency domain.
Further, the calculating means 4 performs an inverse Fourier transform on the displacement amount in the frequency domain, and converts the displacement amount into the displacement amount in the time domain.

The displacement amount calculated by the displacement measuring device 1 and the method as described above can be applied to the bench tester 101 (road simulator) of the vehicle to reproduce the unevenness of the road surface R.
The bench tester 101 includes a vibrator 102 that applies vibration to the wheel S1 and a vibration control unit 103 that controls the vibrator 102. The vehicle S to be tested is a four-wheeled vehicle.

The vibration exciter 102 is disposed for each wheel S1, and a double-acting hydraulic cylinder or the like that can apply force to both tension and compression is used. The vibration exciter 102 includes a vibration part 102a that can move in the vertical direction. The wheel S1 is installed on the vibration unit 102a, and the vibration unit 102a moves up and down to reproduce the unevenness of the road surface R and apply vibration to the wheel S1.
The vibration control unit 103 controls each of the vibrators 102 to change the position (height) of each of the vibration units 102a. The vibration control unit 103 includes an arithmetic processing unit 103a and a storage unit 103b.
The arithmetic processing unit 103a calculates a vibration control signal for controlling the vibrator 102 based on the calculated displacement amount.
The storage unit 103b stores the calculated control signal.

Further, in the vehicle S, similarly to the above, a wheel-side acceleration sensor 2Aa and a vehicle-body-side acceleration sensor 2Ab as the acceleration detecting means 2A are installed in each part of the suspension S3.
When the calculated displacement is used as the road surface data of the bench tester 101, the displacement in the vertical direction alone is not enough to reproduce the running state, so the six-axis acceleration (X-axis, Y-axis, Physical quantities such as Z axis, roll, pitch, yaw) and vehicle speed are also measured. Further, when measuring accelerations in three axis directions of the X axis (front-back direction), the Y axis (left-right direction), and the Z axis (vertical), as in the present embodiment, an acceleration sensor is used in the direction in which the suspension S3 expands and contracts. Although a method of installing and converting the measured acceleration into acceleration in each axis direction may be used, an acceleration sensor may be installed for each axis direction. With such a configuration, the measurement of the acceleration in each axis direction can be performed more accurately.

Next, road surface data to be reproduced by the bench tester 101 is calculated.
The calculated amount of displacement calculated by the above method is the amount of vertical displacement of the wheel S1 (axle S2).
An elastic tire S1a is mounted on the wheel S1, and the unevenness of the road surface R is absorbed by the tire S1a. For this reason, when the calculated displacement amount is considered as road surface data representing the unevenness of the road surface R, an error is included.
Therefore, in order to reproduce a more realistic running state, an operation of increasing the accuracy of the calculated displacement amount is performed.

In calculating the road surface data, the arithmetic processing unit 103a of the vibration control unit 103 first calculates a vibration control signal from the calculated displacement calculated by the above-described method (control signal input).
Then, the arithmetic processing unit 103a controls the vibrator 102 using the calculated vibration control signal, and applies vibration to the vehicle S from the vibration unit 102a. The acceleration detecting means 2A installed on the vehicle S measures the acceleration of the wheel S1 displaced by the vibration (response measurement).

The arithmetic processing unit 103a calculates a response function to the displacement of the installation point on the road surface R from the measured acceleration and each sensor output.
The arithmetic processing unit 103a compares the acceleration (target) actually measured while traveling with the acceleration (reproduced acceleration) due to the vibration reproduced on the bench tester 101, and calculates the residual between the target and the reproduced acceleration. (Residual calculation with the target).
The arithmetic processing unit 103a corrects the displacement amount based on the response function so as to reduce the residual (update the displacement amount).

The arithmetic processing unit 103a calculates a new vibration control signal from the corrected displacement amount (input of a control signal), and controls the vibrator 102 with the new vibration control signal.
The acceleration of the wheel S1 excited by the new excitation control signal is measured (response measurement), and the residual with respect to the target is calculated (residual with the target).
Here, if the residual is within the required accuracy, the arithmetic processing unit 103a ends the calculation, and records the calculated displacement amount as road surface data in the storage unit 103b.
If the residual is not within the required accuracy, the arithmetic processing unit 103a calculates the response function again, corrects the displacement based on the response function (updates the displacement), and executes the vibration test. Do it again.
The arithmetic processing unit 103a repeats (control signal input) → (response measurement) → (residual difference calculation with target) → (displacement amount update) → (control signal input) →. The difference is reduced to the required accuracy, and road surface data is calculated.

According to the configuration and the calculation method as described above, it is possible to more accurately calculate the amount of displacement of the wheel using only the output signal of the acceleration detection means. Also, by using the calculated wheel displacement, the reproducibility of the real environment in the bench test can be improved, so that the suspension can be accurately evaluated.
In the present embodiment, a Fourier transform is used as a method for converting the time axis to the frequency axis, but the present invention is not limited to this. Various conversion methods such as wavelet conversion can be used according to the frequency characteristics of the vibration to be measured.

DESCRIPTION OF SYMBOLS 1 Displacement measuring device 2A Acceleration detecting means 2Aa Wheel side acceleration sensor 2Ab Body side acceleration sensor 4 Calculation means 11, S1 Measurement target SS Body S2 Axle S3 Suspension S3c Body side fixed part S3d Wheel side fixed part

Claims (3)

Acceleration detection means for detecting the acceleration of the object to be displaced,
Calculating means for calculating an amount of displacement of the object to be measured from an output signal of the acceleration detecting means,
The calculating means includes:
After converting the output signal from the time axis to the frequency axis, the second-order integration is performed, and the inverse conversion is performed from the frequency axis to the time axis to calculate a calculated displacement amount as the displacement amount of the measurement object. And
The output signal, a response function to the displacement of the measurement object from the calculated displacement amount,
Calculate the residual of the acceleration measured by the acceleration detection means and the reproduced acceleration as the acceleration reproduced from the calculated displacement amount,
Based on the response function, repeat the correction of the calculated displacement amount until the residual is within the required accuracy,
The displacement measuring device , wherein the calculated displacement amount when the residual falls within required accuracy is set as the displacement amount of the measurement object. When transforming the output signal from the time axis to the frequency axis, perform a Fourier transform,
2. The displacement measuring apparatus according to claim 1, wherein an inverse Fourier transform is performed when performing an inverse transform from a frequency axis to a time axis. The measurement object is
The wheels that make up the body,
The acceleration detecting means,
A vehicle-body-side acceleration sensor installed on a vehicle-body-side fixed portion of a suspension installed between the vehicle body and an axle that supports the wheels;
A wheel-side acceleration sensor installed on a wheel-side fixed portion of the suspension,
The calculating means includes:
The displacement measuring device according to claim 1 or 2, wherein a vertical displacement amount of the wheel is calculated.

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