JPH0410973B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a wave observation device using an acceleration sensor,
In particular, it relates to those from which trend components have been removed.

(Prior Art) The problem of ocean waves is closely related to the operation and design of ships, coastal structures, seawall structures of ports, etc., and research and elucidation of wave phenomena is an important issue.

Conventionally, wave observation has relied on visual observation by sailing an aircraft to the desired sea area, but wave observation during typhoons etc. not only requires a large amount of expense but also poses danger to the crew. There was a problem.

For this reason, various wave observation methods and devices have been proposed in recent years, one of which is to float a buoy equipped with an acceleration sensor on the sea surface to observe wave height, wave period, or wave direction.

As an example, a conventional wave height observation device using an acceleration sensor, particularly its acceleration/displacement converter, will be explained.

FIG. 2a is a block diagram showing the acceleration/displacement conversion section of a wave height observation device using a conventional acceleration sensor, in which 1 is a vertical acceleration sensor, and its output is passed through a DC amplifier 2 to a double integrator. 3.

This takes advantage of the fact that the velocity component can be obtained by integrating the acceleration component once, and the distance, that is, displacement, can be obtained by integrating the acceleration component once more.The buoy equipped with the acceleration/displacement conversion device follows the waves. The wave height value is determined by extracting the acceleration component that occurs when moving as a vertical displacement.

In addition to the above-mentioned wave height observation device using the vertical acceleration sensor, wave observation using an acceleration sensor may also include a horizontal acceleration sensor to observe the wave direction, or three-dimensional orthogonal three-axes (x, y, z axes). ) An acceleration sensor is provided in each direction, and the acceleration generated in each sensor is separated and extracted into components of each of the three axes, thereby correcting the inclination of the buoy and adjusting the wave height,
Various types of wave observation are possible, including those that more accurately and simultaneously observe the wave direction, wave period, etc.

In this way, wave observation using a buoy equipped with an acceleration sensor floating on the sea surface can be performed using other conventional methods, such as wave height observation methods using pressure (hydraulic) sensors below the sea surface or on the seabed, and ultrasonic pulse observation methods. A sonic observation method that detects the sea surface position by reflecting the wave on the sea surface, or a wave column of several meters with a scale attached to the surface of the sea.
Compared to the Froude wave height meter, which suspends a weight from a 70m wire and fixes a part of the wave column above the sea surface to visually observe the wave height, it has a better ability to track the movement of waves, so it can be measured. It is attracting attention as a means of future wave observation because it has the excellent features of a wide wave height range and accuracy.

However, in the wave observation method using the acceleration sensor as described above, the output of the integrator used to convert acceleration into velocity or displacement may have fluctuations with a period considerably longer than the wave period due to various causes. This method has the disadvantage that so-called trend (also called tred or drift) components are superimposed, complicating subsequent data processing and making the device expensive.

In order to facilitate understanding of the present invention, the occurrence of the trend and conventional countermeasures will be explained in detail below.

That is, a buoy floating on the ocean not only moves by following the waves, but also may generate an excessive acceleration component when it falls from the crest of a large wave and lands on the sea surface, or when it collides with fish or other floating objects. In addition, it has a built-in dry battery as a power source, and in order to reduce current consumption, the electrical impulses generated when the power is turned on intermittently act as if excessive acceleration were generated. Acceleration components caused by such causes are impulse-like single-shot components, unlike continuous acceleration components caused by waves.

On the other hand, when an impulse component is input to an integrator, its output produces a response waveform that reaches its maximum value with a slight delay and then attenuates according to a curve determined by a constant. The response wave is an oscillatory wave because it is common to use an operational amplifier and add a negative feedback function to avoid saturation of the integrated output.

Therefore, when an impact impulse is input to the above-mentioned integrator, an oscillating water-reducing wave component is output as shown in FIG. .

Furthermore, the negative feedback effect applied to the integrator works even when minute noise input components generated from the preceding stage DC amplifier etc. are accumulated over time and reach a predetermined output level, resulting in a signal similar to that shown in Fig. 2b. This produces an oscillating damped wave component, that is, a trend component.

In wave observation using an acceleration/displacement conversion device with such response characteristics, the acceleration component generated by following the wave is output as a waveform superimposed on the trend, so the wave height can be calculated from the absolute value of the determined displacement amount. is impossible to read.

For this reason, conventionally, as shown in Figure 2c, the difference between the highest and lowest values (p-p value) is calculated for each half cycle of the wave component superimposed on the trend component, and then the average value of both is calculated. Furthermore, the result obtained by calculating either the difference between the average value and the maximum value or the sum of the minimum value is regarded as a trend component, and the difference between the component and the maximum value and the minimum value is detected. Therefore, we were working on extracting wave components.

In other words, only the wave component was extracted by using the average value in each period of the short-period wave component superimposed on the long-period trend component as a new reference value.

Generally, these processes are performed during the calculation process,
There was a problem that the amount of data to be processed was large, which not only made the device complicated and expensive, but also made it impossible to achieve high measurement accuracy.

In particular, when the observation buoy is floated in the ocean and data is collected via a wireless line, this poses an extremely serious problem due to limitations on the information that can be transmitted.

(Object of the Invention) The present invention was made in order to solve the problems of the above-mentioned conventional wave observation device using an acceleration sensor, especially its acceleration/velocity or acceleration/displacement converter. It is an object of the present invention to provide a wave observation device that facilitates the extraction of wave components by removing the influence of trend components that have conventionally occurred.

(Summary of the Invention) For this purpose, the present invention provides a wave observation method in which a trend component having a generally long period is removed by interposing a high frequency wave generator or a band wave wave generator having a required band after the integrator. Configure the device.

(Example) The present invention will be described in detail below based on an illustrated example.

FIG. 1 is a block diagram showing an embodiment of the acceleration/displacement conversion section of the wave height observation device according to the present invention.

In the figure, 1, 2, and 3 are vertical acceleration sensors, DC amplifiers, and double integrators as in FIG. (BPF) 4 is inserted and connected.

That is, the BPF 4 has a high frequency filter with a low cutoff period of 20 (seconds) and an attenuation amount of 10 (dB) or more for the period 30 (second) component, and a high frequency cutoff period of 3 (seconds).
And the attenuation in period 1 (seconds) is 20 (dB).
A band wave device is constructed by combining the above-described low band wave device.

For reference, the relationship between period T (seconds) and frequency F (Hz) is F = 1/T, so each of the above periods is T = 30 (seconds) and F = 0.033 (Hz). , T
= 20 (seconds) is F = 0.05 (Hz), T = 3 (seconds) is F =
0.33 (Hz) and T=1 (second), F=1 (Hz).

In addition, such an ultra-low frequency device can be realized by, for example, an active filter using an operational amplifier, and the components used in this case, such as capacitors and resistors, should have excellent DC leakage characteristics. You need to choose.

Furthermore, although any existing filter design method may be used, the maximum flat characteristic design method, that is, the Butterworth filter, is most suitable because of the need to reduce ripples within the passband.

FIGS. 3a, b, and c show circuit diagrams and characteristic diagrams of a fourth-order Butterworth high-frequency filter and a low-frequency filter as an embodiment of the filter.

That is, Figure a is a circuit diagram showing a Butterworth-type high-frequency filter using an operational amplifier OP, and since the active filter stage generally corresponds to two stages of RC filters, the fourth-order Butterworth filter is as shown in the diagram. This can be realized by using two stages of active filters.

Similarly, FIG. 3b shows a circuit diagram of a fourth-order Butterworth type low-band waver, and by connecting the above two wavers in series, a desired band-pass waver can be realized.

For reference, the numerical values of the main elements of the circuit diagram and the band wave characteristics at that time are shown in FIG. 3c.

First, in Figure a, the values of the circuit elements that determine the wave characteristics are R ₁ ≒13KΩ, R ₃ ≒300KΩ, C ₁ ,
C ₂ ≒1μF, R ₅ ≒620KΩ, R ₆ ≒360KΩ, C ₄ , C ₅ ≒
It is 2.2μF.

Also, in the same figure b, R ₉ , R ₁₀ ≒950KΩ, C ₇ ,
C ₁₀ ≒0.47μF, C ₈ ≒0.4μF, R ₁₂ , R ₁₄ ≒2.3MΩ,
C ₁₁ ≒0.068μF. Note that variable resistors VR ₁ and VR ₂ are for level adjustment. The overall characteristics when each circuit element is determined as described above are as shown in FIG. 3c.

By placing the wave generator as described in detail above after the integrator, the trend component included in the integrator output is removed, making it possible to extract only the passband periodic signal of the filter from this output. The wave height value of the wave component can be immediately obtained.

In the above embodiment, the case where a bandpass filter is used is shown, but this is to remove high-frequency noise components at the same time as the trend component.To remove only the trend component, only a high-frequency filter is needed For example, as shown in Figure 3a above, the cutoff period is sufficient.
A Butteras type active filter set to 20 (seconds) may be used.

Furthermore, the present invention is not limited to a wave height observation device, and is not limited to, for example, a device that observes the direction and period of waves using a horizontal acceleration sensor, or a device other than wave observation that integrates acceleration output to obtain velocity components or displacement components. There is no need to explain that the present invention can be widely applied to devices and the like that perform desired measurements.

(Effects of the Invention) As explained above, the present invention uses an extremely simple configuration to remove the trend component that inevitably occurs when integrating the acceleration component and obtaining the displacement component in the velocity component region. Therefore, it is effective in reducing the data processing amount of various devices using these acceleration/velocity or acceleration/displacement conversion devices, facilitating wireless data transmission, and greatly simplifying the devices.

[Brief explanation of drawings]

Figure 1 shows the acceleration/wave height observation device according to the present invention.
A block diagram showing one embodiment of the displacement converter; FIGS. 2a, b, and c are block diagrams of a conventional acceleration/displacement converter, respectively, and a diagram showing its response characteristics and conventional peak value detection principle; FIG. Figures a, b, and c are circuit diagrams and characteristic diagrams showing one embodiment of a wave generator used in the present invention. 1... Acceleration sensor, 2... DC amplifier, 3...
...Integrator, 4... Bandwidth wave generator, OP... Operational amplifier, C ₁ to C ₁₂ ... Capacitor, R ₁ to R ₁₆ ...
Resistors, VR ₁ and VR ₂ ...variable resistors.

Claims (1)

[Claims] 1. An acceleration sensor is used in which an acceleration sensor is mounted on a floating object floating on a liquid surface, and a displacement signal corresponding to the displacement of the liquid surface is obtained by integrating the output of the acceleration sensor twice. A wave observation device using an acceleration sensor, characterized in that the wave observation device is provided with a filter that inputs the displacement signal and removes a trend component superimposed on the displacement signal.