GB2194637A - Measuring fender deformation using a docking sonar system - Google Patents

Abstract

A method for measuring fender deformation uses a conventional docking sonar system in which a distance and a moving speed of a vessel 1 are measured from elapsed time for reciprocation of ultrasonic waves which are transmitted from at least one transmitting-receiving transducer 5-1 (5-2) disposed underwater at a berth 2 etc. and received thereby as reflection waves from the vessel. A normalized distance D between a reference position 7, which is set at a predetermined distance from the transmitting-receiving transducer, and the vessel 1 is calculated from a distance L between the transmitting-receiving transducer and the vessel and a distance A between the transmitting-receiving transducer and the reference position. The normalized distance is output as a displacement data of the vessel after the vessel has reached the reference position 7 or a preset position proximate to the reference position. A deformation amount of the fender 3 is obtained from the displacement data, using D</=0. <IMAGE>

Description

SPECIFICATION Method and apparatus for measuring fen: der deformation using docking sonar system Field of the Invention This invention relates to a method and apparatus for measuring fender deformation, using a docking sonar system for measuring for example a distance of a vessel from a pier, jetty, etc. or a moving speed of the vessel when the vessel is being berthed or docked.

Prior Arts A place where the vessel is berthed or docked is generally as illustrated in Fig.5. In this berthing or docking place 2, a mooring position alon9 a line of a bow and a stern of the vessel 1 is called a mooring normal 6.

The berthing or docking place 2 may, in general, be a pier, a wharf, a quay, a berth, a jetty, a dolphin or the like. The berthing or docking place 2 is usually equipped with fenders 3 made of resilient materials such as a synthetic rubber, for buffering shocks caused by the collision at the time of docking of the vessel or for protecting various facilities provided around the berthing or docking place 2.

The berthing or docking operation should be safe as well as speedy. Safety is crucial, especially in the berthing or docking of a large vessel such as a supertanker or a very large crude carrier which carries inflammable materials such as oil, LPG or LNG, because even the slightest misoperation or misjudgment would possibly lead to a serious accident. If the speed of the vessel being docked or the distance of the vessel from the pier or jetty to which the vessel is being moored to is wrongly estimated, the vessel will possibly collide against the pier or jetty, which will possibly cause strain in the body of the vessel or do damage to the cargo etc. due to the shock of the collision. In the most serious case, there might be a danger of ignition of inflammable gases or oil carried on the vessel. Thus, a fatal accident may possibly be caused.

To prevent such- an accident, expensive fenders 3 are provided in the berthing or docking place 2 at positions corresponding to the bow and the stern of the vessel for buffering the shock by the collision. In addition, an ultrasonic docking sonar system for informing a speed of the vessel or a distance of the vessel to the pier or jetty is provided so that the vessel can be berthed more accurately and safely in the place 2.

The docking sonar system generally includes transmitting-receiving transducers 5-1, 5-2 which are installed at positions corresponding to the bow and the stern of the vessel to be docked as illustrated in Figs.5 and 6. The large tanker or large crude carrier, etc. as described above is usually berthed at a similar position in the same berthing or docking place, so that the transmiiting-receiving transducers may be installed fixedly at such posi -tions. The docking sonar system measures the distance and the speed of the vessel which is being docked to the berthing or docking place 2. The system further includes a large display (not shown) such as an electrically illuminated numerical display board which is provided on the pier or jetty and visible at a distance as far as 100 or 200m away from the pier or jetty.

In the docking sonar system, a central ar main measuring unit 4 is installed on the pier or jetty and the transmitting-receiving transducers 5-1, 5-2 are installed underwater to horizontally transmit ultrasonic waves from the berthing or docking place 2 to the vessel 1 and receive the wave reflected from the vessel 1.

This kind of ultrasonic docking sonar system as arranged above will operate as follows: First, an electric signal generated from the central measuring unit 4 is supplied through a signal line to the transmitting-receiving transducers 5-1, 5-2 which are installed underwater at the berthing or docking place 2 at the positions corresponding to the bow and the stern of the vessel, respectively. The electric signal supplied to the transmitting-receiving transducers is then converted into an ultrasonic signal and the ultrasonic signal of a narrow beam width is trasmitted in water towards the vessel 1. The ultrasonic beam is partly reflected from the body of the vessel 1. The reflected wave from the vessel 1 returns to the transmitting-receiving tansducers 5-1, 5-2 and is converted to an electric signal and returned to the central measuring unit 4 again.

The elapsed time from the transmission of the ultrasonic signal from the transmitting-receiving transducers 5-1, 5-2 to the receipt of the reflection signal is proportional to the distance between the transmitting-receiving transducers 5-1, 5-2 and the vessel 1. Thus, the elapsed time may be measured to obtain the distances of the bow and the stern to the pier or jetty 2. Moreover, changes of such distances per unit time may be measured to know the moving speed of the vessel towards the berthing or docking place 2. These results of the measurement are numerically indicated on the large display board (not shown) on the pier or jetty.

With the aid of such indication, a pilot can maneuver the vessel so that it may approach the pier or jetty in parallel therewith at a suitable speed.

In fact, however, it is sometimes quite difficult to dock or moor the Vessel accurately to the berthing or docking position even if the pilot knows the distance and the speed of the vessel. This difficulty is often due to an influence of inertia of the vessel or an influence of waves, a tide or a wind. This often causes collision of the vessel against the fenders 3 when it is docked The fenders 3 are buffers for absorbing shock at the collision and function to absorb kinetic energy of the vessel to prevent the vessel from crashing into the pier or jetty.

When shock is applied to the fenders 3, strain is caused by an internal stress. The strain is left in the fenders 3 when shocks have been applied repeatedly. This gives fatigue to the materials of the fenders 3, eventually leading to breakage of the fenders after they are subjected to shock repeatedly. Or, even in the case where the stress application does not occur so frequency, if extraordinarily large strain is caused at a time, the strain remains in the fenders, giving fatigue to the materials and finally leading to breakage of the fenders afterwards. Moreover, when the fender 3 gets to failure, the fenders 3 can not function as buffers and can not prevent the vessel from crashing into the pier or jetty. The shock due to the crashing will possibly cause strain in the body of the vessel or damage the cargo.In an extreme case, there may be a danger that inflammable gases or oil of the cargo will catch fire.

Furthermore, even after completion of the docking, the vessel is subjected to rocking due to influences of waves, tides, waves, etc.

and the vessel repeats collision against the fenders 3. These collisions again cause strain within the fenders 3, which strain may possi bly be accumulated to a dangerous level as the case may be.

To avoid serious accident as described above, it is necessary to replace the fenders with new ones before they have been broken.

For this purpose, the status of the accumu Iat & strain within the fenders 3 should be detected The detection of the strain in the fenders 3 may be attained by detecting hys terns'is of displacement of tip ends of the fenders 3 or deformation of the fenders 3 due to compression and/or deflection of the fenders.

More specifically, the displacement amount or deformation amount of the fenders 3 may be recorded to know the amount of strain re maining within the fenders.

The record of the fender displacement or deformation will also be helpful to know the magnitude of the stress applied to the fenders or the past status of strain in the fenders when the fenders get broken and to clear up the cause of the breakage.

However, special equipments are necessary to record the detected data and considerable costs are needed to provide such' equipments.

By this reason, the recording equipments have not been provided in the conventional docking sonar system.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for measuring fender displacement or deformation, which is capable of easily detecting a displacement or deformation amount of a fender, by utilizing measurement data of an existing docking sonar system, without providing special equipments.

It is another embodiment of the present invention to provide an apparatus for carrying out the method as described above.

The present invention features a method for measuring fender deformation using a docking sonar system in which a distance and a moving speed of a vessel are measured on the basis of an elapsed time for reciprocation of ultrasonic waves which are transmitted from at least one transmitting-receiving transducer disposed underwater at a berthing or docking place and received thereby as reflection waves from the vessel, which method comprises:: calculating a normalized distance between a reference position, which is set at a predetermined distance from the transmitting-receiving transducer, and the vessel on the basis of a distance between said transmitting-receiving transducer and the vessel and a distance between the transmitting-receiving transducer and said reference position; outputting the normalized distance as a displacement data of the vessel after the vessel has reached said reference position or a preset position proximate to said reference position; and obtaining a displacement amount of a tip end of the fender from said displacement data.

The present invention further features, in an ultrasonic docking sonar system including at least one transmitting-receiving transducer installed at a berthing or docking place for a vessel for transmitting and receiving ultrasonic waves and a central measuring unit for measuring a distance of the vessel from said transmitting-receiving transducer and a moving speed of the vessel on the basis of an elapsed time of the ultrasonic waves transmitted and received by said transducer, an apparatus for measuring fender deformation which comprises: : a normalized distance calculating means for calculating a normalized distance between a reference position, which is set at a predetermined distance from the transmitting-receiving transducer, and the vessel on the basis of a distance between said transmitting-receiving transducer and the vessel and a distance between the transmitting-receiving transducer and said reference position; a judging means for judging whether the vessel has reached said reference position or a preset position proximate to said reference position; and a displacement data outputting means for outputting the normalized distance as a displacement data for the vessel when said judging means has judged that the vessel has reached said reference position or preliminarily set proximate region; whereby the fender deformation is detected on the basis of said displacement data.

In the present invention, preferably, when the distance from the transmitting-receiving transducers to the vessel is equal or less than the distance from the transmitting-receiving transducers to the reference position, the displacement data as specified above is used as a displacement amount of the tip end of the fender to measure fender deformation.

The reference position, however, may be set at a position nearer to the pier or jetty than said tip end position and a region between this reference position and the tip end of the fender may be preliminarily set as a proximate region. Alternatively, the reference position may be set at a position more remote from the pier or jetty than said tip end position.

The fender deformation is obtained in the form of an amount of displacement of the tip end of the fender and it may be indicated by a display or recorded by a recorder such as a printer.

A limit value of the deformation amount, which is determined at the time of designing, may be set so that it may be judged whether the measured displacement data reaches the set deformation limit. When the measured value reaches the set value, an alarm may be given. Furthermore, accumulation of the deformation amount reaches a preliminarily set cautionary value, an alarm may be given.

Operation The measurement of the fender deformation amount is based on the measurement of the displacement of the vessel because the fender deformation is caused only by depression by the vessel. For this purpose, the measrement data by the docking sonar system is utilized in the present invention.

More specifically, the reference position is set at a predetermined distance from the transmitting-receiving transducers and a distance from these transmitting-receiving transducers to the vessel is normalized to a distance from the reference position. This normalized distance represents the displacement of the vessel from the reference position. The displacement of the tip end of the fender and accordingly the deformation of the fender are obtained on the basis of the displacement data of the vessel. The normalized distance is calculated on the basis of the distance between the transmitting-receiving transducers and the vessel and the distance between the transmitting-receiving transducers and the reference position, and, in general, the normalized distance is obtained by subtracting the latter distance from the former distance.

When the vessel is outside the reference position, the sign of the normalized distance is positive and when the vessel is inside the reference position, the sign of the normalized distance is negative.

The detection of the displacement of the fender tip end or the deformation of the fender is started when the vessel has come into the reference position or the preliminarily set proximate region and the normalized distance is calculated as described above and then output as the displacement or deformation data.

In this respect, the reference position may be set at any of various positions as described above, but, in general, it is set at a position corresponding to the tip end of the fender.

Whether the vessel has reached the reference position or not, can be judged from that the normalized distance has been changed from positive to zero.

When the reference position is set at the fender tip end position, the negative value of the normalized distance represents the displacement amount or deformation amount of the fender after the normalized distance has been changed from zero to negative. In this case, therefore, the record of the normalized distance can be used as a record of a change of the fender displacement or deformation.

In the case where the reference position is set at a position inside the fender tip end position or nearer to the pier or jetty than the fender tip end position and the region between this reference position and the fender tip end position is preliminarily set as the proximate region, the reference position may preferably be set at a position where the fender is displaced or deformed at its maximum extent within an elastic limit which is determined according to the design of the fender.

If such a position is selected as the reference position, the displacement or deformation which hardly leaves strain in the fender may be omitted from the measurement of the fender displacement or deformation.

When the reference position is set at a position outside the fender tip end position or more remote from the pier or jetty than the fender tip end position, the motion of the vessel before its collision against the fender may be recorded as the vessel displacement data.

If necessary, a change of the momentum and/or kinetic energy of the vessel before and after the collision may be detected on the basis of the recorded displacement data. Thus, the record can provide a more detailed data for the damage of the fender.

As described above, the measurement data of the docking sonar system may effectively be utilized to detect the fender deformation easily without providing special equipments for this purpose.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a block diagram of a formation of one embodiment of the present invention; Fig.2A is a plan view showing the arrange ment of a docking sonar system employable in the embodiment; Fig.2B is a side view of the arrangement of the docking sonar system as shown in Fig.2A; Fig.3A is a block diagram of a concrete circuit arrangement for carrying out the embodiment; Fig.3B is a block diagram of a receiver provided in a central measuring unit employable in the present embodiment; Fig.3C is a block diagram of a signal processing circuit provided in the central measuring unit employable in the present embodiment; Fig.4 is a flowchart showing an operation of the embodiment; Fig.5 is a plan view showing an arrangement of a conventional ultrasonic sonar system; and Fig.6 is a side view of the arrangement of the conventional ultrasonic sonar system of Fig.5.

PREFERRED EMBODIMENTS A preferred form of fender deformation measuring method and apparatus using a docking sonar system will now be described.

Configuration of Embodiment The arrangement.of the ultrasonic docking sonar system employed in the present embodiment will now be described, while referring to Figs.2A and 2B.

Fender means 3 made of a resilient material such as a synthetic rubber are installed in a berthing or docking place (referred to as "berth" in this embodiment) 2 in which the ultrasonic docking sonar system employable in the present embodiment is installed. The ultrasonic docking sonar system comprises transmitting-receiving transducers 5-1 and 5-2 which are provided underwater at positions corresponding to two mooring positions for a bow and a stern of a vessel 1 to be docked, respectively, and a central measuring unit 4 provided at a suitable position in the berth 2.

An apparatus for measuring a fender deformation according to the present invention comprises, as illustrated in Fig.1, the docking sonar system including the transmitting-receiving transducers 5 and the main measuring unit 4 and a normalized-distance calculating means 30, a judging means 40 and a deformation data outputting means 50, which are incorporated in the docking sonar system. The normalized-distance calculating means 30, the judging means 40 and the deformation data outputting means 50 are implemented by a microcomputer 14 in the present embodiment as will be described in detail later.

For calculation of the normalized distance, a reference position 7 is set at a predetermined distance from the transmitting-receiving transducers 5-1, 5-2. The normalized-distance calculating means 30 calculates the normalized distance D between the reference position 7 and the vessel 1 from a distance L between the transmitting-receiving transducers 5-1, 5-2 and the vessel 1 and a distance A between the transmitting-receiving transducers 5-1, 5-2 and the reference position 7. The calculation is carried out by the following formula: D=L-A The reference position 7 is set so that it may coincide with a mooring normal 6 in the present embodiment. As a result of this, the reference position 7 is set so as to coincide with positions of tip ends of the fenders 3.

The judging means 40 judges whether the vessel 1 has reached the reference position 7 or not. In other words, it determines whether DO or not. If D is O or minus, the judging means 40 supplies a judgment signal indicative of D $ 0 to the deformation data outputting means 50.

In response to the judgment signal, the deformation data outputting means 50 outputs the calculated normalized distance D as a displacement or deformation information. More specifically, the normalized distance D (D =( 0) is output as the deformation data. The present embodiment further comprises a printer as an output means as will be described in detail later. The deformation data is output by the printer 21.

The deformation measuring apparatus according to the present embodiment and the main measuring unit 4 of the docking sonar system employed in the apparatus are illustrated more specifically in Fig.3A.

In Fig.3A, the central measuring unit 4 comprises a timing signal generating circuit 9 for generating a transmission timing signal for ultrasonic pulses and a switching signal for the transmitting-receiving transducers 5-1, 5-2; a pulser circuit 10 which is responsive to the transmission timing signal to generate exciting current pulses for producing the ultrasonic pulses; a selector 11 for switching the transmitting-receiving transducer 5-1 for the bow and the transmitting-receiving transducer 5-2 for the stern; a receiver 12 for receiving reflected waves from signals input from the transmitting-receiving transducers 5-1, 5-2; a signal processing circuit 13 for processing the received signals to measure an elapsed time of the reciprocated ultrasonic pulse; a microcomputer 14; a driver circuit 20; a printer 21; and a display 22.

The selector 11 is for switching the operation between the bow and the stern transmitting-receiving transducer and comprises for example a mercury relay. A switching instruction is supplied from the timing signal generating circuit 9.

The receiver 12 includes a limiter 12a for protecting an amplifier 12b of a later stage from a high-voltage signal from the pulser cir cuit 10; the amplifier 12b, and a detector 12c.

When there is a difference in sensitivities between the two transmitting-receiving transducers, the amplifier 12b may include two amplifier systems having different amplification degrees so as to correct or compensate the difference. These two amplifier systems may be switched in synchronism with the selector 11.

The signal processing circuit 13 comprises a comparator 1 3a for pulsing the input signal, a pulse-width discriminating circuit 13b for discriminating whether the pulse is of a predetermined width or more to eliminate pulses of smaller widths, a gate control circuit 1 3c for setting a gating width based on the transmission timing signal from the timing signal generating circuit 9 and the pulse discriminated as being of the predetermined width or more, and a counter 1 3d which counts clock pulses during the gate is opened with the gatingwidth or duration as set above.The signal processing circuit 13 further comprises a noise level determining circuit for determining a noise included in the received signal, an echo level determining circuit for determining an echo level of the received signal, and a status signal producing circuit for producing a status signal from the determination results, which circuits are not shown in the drawings.

The status signal is input to the microcomputer 14 together with a count value of the counter 13d.

The microcomputer 14 calculates the elapsed time of the reciprocated ultrasonic pulses from the count value of the counter 13d. The microcomputer 14 further has functions of calculating the distance between the transmitting-receiving transducer 5-1, 5-2 and the vessel 1 and a speed of the vessel based on changes in distance with time. It also functions as the normalized-distance calculating means 30, the judging means 40 and the deformation data outputting means 50 in the present embodiment.

The microcomputer 14 comprises an input/output circuit 15, a central processing unit (hereinafter referred to as CPU) 16, a readonly memory (ROM) -17, a writable and readable memory (RAM) 18, and a clock generator 19 for generating a clock pulse which is used as a reference for the calculation. The signal processing circuit 13 and the display 22 are connected to the input/output circuit 15. The printer 21 for recording the data is connected to CPU 16 through the driver circuit 20 which amplifiers the data such as the distance and the moving speed.

ROM 17 stores an operation control program for CPU 16 and data A indicative of the set position of the reference position 7 together with fixed data such as switching data for switching the measured distance units between "m" and "cm".

RAM 18.stores an operation parameter for program for calculating the elapsed time of the reciprocated ultrasonic pulse from the count value of the counter 13d, an operation parameter for program for calculating the distance L from the elapsed time and the speed of sound, and an operation parameter for program for calculating the speed from changes in distance with time. It further stores an operation parameter for program for calculating the normalized distance D by subtracting the distance between the transmitting-receiving transducers 5-1, 5-2 and the reference position 7 from the distance L, a judging program for judging whether the normalized distance D is within a range of D =( O or not, and a program for carrying out various signal processing functions in the main measuring unit 4.This implements the function as the docking sonar system and the functions as the normalized distance calculating means 30, the judging means 40 and the deformation data outputting means 50.

The display 22 comprises a large numerical display board, for example, an electrically illuminated display board, which can be read from far away.

Operation of Embodiment The operation of the embodiment as arranged above will now be described, referring to Fig.4 as well as Figs.1 to 3.

When the vessel 1 is being docked alongside the berth 2, the ultrasonic docking sonar system measures a distance of the bow and the stern from the berth 2 and the moving speed of the bow and the stern, by using ultrasonic waves transmitted from the transmitting-receiving transducers 5-1, 5-2 provided underwater, measuring an elapsed time during which the ultrasonic waves propagate to the vessel 1 and return to the transducers after reflection, and calculating the distance and speed based on the measured results.

First, the elapsed time of the reciprocated ultrasonic pulse is measured by the centralmeasuring unit 4 under the control of the microcomputer 14 (Step 1).

More specifically, the pulser circuit 10 and the selector 11 are operated by a transmission timing signal transmitted from the timing signal generating circuit 9. The bow and stern transmitting-receiving transducers 5-1, 5-2 are switched alternatingly by the selector 11 and driven by a high-voltage pulse from the pulser circuit 10 to transmit ultrasonic waves and receive reflected waves. The so received reflection waves are received by the receiver 12 and the received signal is input to the signal processing circuit 13.

The transmission timinig signal is also supplied to the gate control circuit 13c of the signal processing circuit 13 to open an input gate of the counter 13d. This allows the clock pulses from the timing signal generating circuit 9 to be input to the counter 13d. The clock pulses thus input are counted in the counter 13d.

The received signal from the receiver 13 is shaped into pulses by the comparator 1 3a and the pulses are subjected to the discrimination as to whether the pulse duration is a predetermined width or more. Since the transmitted waves have the predetermined width, the received waves of less than the predetermined width might be considered as noises. This discrimination is for preventing possible false measurement due to such noises.

When the received signal is a pulse having the predetermined width or more, it is input to the gate control circuit 13c. As a result of this, the input gate of the counter 13d is closed and the counting of the clock pulses is terminated. The counted value is input to the microcomputer 14.

CPU 16 of the microcomputer 14 calculates the distance and speed on the basis of the counted value (Step 2). The distance and speed are calculated for the bow and the stern independently, according to the operation parameter for program stored in RAM 18, based on fixed data stored in ROM 17.

For example, the distance data for the bow and the stern from the transmitting-receiving transducers 5-1 and 5-2 are obtained independently as L1 and L2, respectively. The calculation results are once stored at a predetermined region of RAM 18.

CPU 16 reads out the calculated distance data from RAM 18 to obtain the normalized distance D of the vessel 1 from the reference position 7 based on the data (Step 3). The distance data L1, L2 are subtracted by the distance A between the transmitting-receiving transducers 5-1, 5-2 and the reference position A to obtain the normalized distances D1, D2 between the vessel and the reference position 7.

The calculation results are supplied to the display 22 through the input/output circuit 15 and numerically indicated (Step 4). In this case, the calculation results are indicated in the unit of "meter" in the present embodiment. However, another unit system such as a feet-inch system may be used alternatively.

Or, the meter-centimeter system and the feetinch system may be switched if desired.

According to necessity, the calculation results may be output through the driver circuit 20 to be printed out by the printer 21.

The operation of the present embodiment as given above is due to the function of the present embodiment as an ordinary docking sonar. An operation of the present embodiment due to its characteristic function will now be described.

After calculation of the normalized distances D1 and D2, CPU 16 judges based on the normalized distances D1 and D2 as to whether the bow and the stern of the vessel 1 have already reached the reference position or not (Step 5). More particularly, CPU 16 carries out the judgment as to whether D1 ~ 0, D2 4 0.

When both D1 and D2 are larger than 0, the vessel 1 is outside the reference position 7 and the process returns to step 1 to continue the measurement. However, if either of D1 and D2 is 0 or minus, a judgment signal is output, which indicates that the distance D1 and/or D2 is 0 or minus.

Then, CPU 16 outputs the normalized distance Dl and/or D2, which is O or less, as deformation data associated with the vessel 1 (Step 6). More particularly, the normalized distance or distances D which is or are within the range of D $ 0 is or are output as deformation data. Since the printer 21 is provided as the 'output means in the present embodiment, the deformation data is printed out by the printer 21.

In this connection, it is to be noted that the values of the normalized distances D1 and D2 are generally several meters or less. By this reason, the indication unit for the normalized distances D1, D2 is switched from "m" to "cm" by CPU 16 in the present embodiment.

CPU 16 then judges as to whether an instruction for measurement termination has externally been input or not (Step 7). If the measurement terminating instruction has been input, the measurement is then ended. However, when there has been no terminating instruction, the process returns to step 1 to continue the measurement.

As described above, the apparatus of the present embodiment functions as the ordinary docking sonar system until the vessel 1 has reached the tip end positions of the fenders 3, while the normalized distances D are output as the deformation data after the vessel 1 has reached the tip end positions of the fenders 3. In this case, the normalized distances D indicate that the vessel 1 is located inside the reference position 7, nearer to the land. This also indicates that the body of the vessel 1 is being pressed against the fenders 3. In this respect, the value D also represents an amount of deformation of the fenders 3. The deformation data may be monitored to watch and detect the degree of the damage given to the fenders 3.

The detection of the damages may be attained simply by checking the record output from the printer 21 periodically. Of course, it is possible to carry out the detection automatically. For example, a deformation amount which corresponds to an elastic limit of the fenders 3 may preliminarily be stored in RAM 18 or ROM 17 and CPU 16 may be adapted to keep a watch as to whether the normalized distance D exceeds the stored value and give an alarm when it exceeds the value. As to aging, for example, the normalized distances D may be cumulatively added and when the sum has reached a preset value, a message to repace the fenders 3 with new ones will be given.

Although the reference position 7 is set at the tip end position of the fenders, 3 in the present embodiment, the reference position 7 is not limited to that and it may be set, for example, at a position corresponding to an intermediate position of the fender or a bit farther off the land.

When the position intermediate the length of the fender 3 is selected, the reference position may preferably be set at a position where the fender is deformable to its greatest extent within the elastic limit which is determined by the design of the fender. In this case, deformation amount data as to the deformation within a limit wherein the fender hardly undergoes residual strain can be distinguished from deformation amount data as to the deformation which causes damages on the fender.

In this case, a region between the so selected reference position and the tip end of the fender may be set as a proximate region, so that the normalized distance D may be output as deformation data only after the vessel has reached this proximate region. With this arrangement, the normalized distance D may be obtained in the sign of plus before the reference position and it may be obtained in the sign of minus after the reference position.

When the reference position is set at a position a bit farther off the land, the movement of the vessel before collision against the fenders may be recorded as deformation data.

This deformation data can provide changes in momentums and kinetic energies of the vessel before and after the collision, according to necessity. In this case, more detailed information about the damages of the fenders can be obtained.

As described above, according to the present embodiment, the deformation amount of the fender can be easily known, by utilizing the measurement data of the docking sonar system, without providing a special equipment.

It is to be noted that the sound speed of the ultrasonic waves in seawater varies with a temperature of the seawater. In order to measure the propagation time accurately, the seawater temperature is preferably measured to change the clock frequency based on the measured temperature for correcting or compensating the change with temperature of the sound speed. In the present embodiment, the correction of the measured data is made in the calculating operation, according to an output from a seawater temperature sensor (not shown).

In the embodiment as described above, the position of the vessel is indicated by the normalized distance D, but it may alternatively be indicated by the distance L between the transmitting-receiving transducers and the vessel.

Moreover, the number of the transmittingreceiving transducers to be employed in the present embodiment is not limited to two, but it may be one or more than two.

The reference position set for the calculation of the normalized distance is stored in ROM 17 in the abovementioned embodiment, but it may alternatively be stored in RAM 17, or an external memory means. Or, it may be input through a digital switch etc.

Claims (14)

1. A method for measuring fender deformation using a docking sonar system in which a distance and a moving speed of a vessel are measured from elapsed time for reciprocation of ultrasonic waves which are transmitted from at least one transmitting-receiving transducer disposed underwater at a berthing or docking place and received thereby as reflection waves from the vessel, which method comprises:: calculating a normalized distance between a reference position, which is set at a predetermined distance from the transmitting-receiving transducer, and the vessel on the basis of a distance between said transmitting-receiving transducer and the vessel and a distance between the transmitting-receiving transducer and said reference position; outputting the normalized distance as a displacement data of the vessel after the vessel has reached said reference position or a preset position proximate to said reference position; and obtaining a deformation amount of the fender from said displacement data.

2. A method for measuring fender deformation as claimed in claim 1, in which said reference position is set so as to coincide with a mooring normal.

3. A method for measuring fender deformation as claimed in claim 1, in which said reference position is set so as to coincide with a position of a tip end of the fender.

4. A method for measuring fender deformation as claimed in claim 3, in which said displacement data is used as the deformation amount of the fender when the distance between the transmitting-receiving transducer and the vessel is equal to or smaller than the distance between the transmitting-receiving transducer and the reference position.

5. A method for measuring fender deformation as claimed in claim 1, in which said reference position is set nearer to a pier, jetty, etc. than a tip end of the fender and a region between said reference position and said tip end of the fender is preliminarily set as the proximate region.

6. A method for measuring fender deformation as claimed in claim 1, in which said reference position is set at a position outside a tip end of the fender or farther than the same.

7. In an ultrasonic docking sonar system including at least one transmitting-receiving transducer installed at a berthing or docking place for a vessel for transmitting and receiving ultrasonic waves and a central measuring unit for measuring a distance of the vessel from said transmitting-receiving transducer and a moving speed of the vessel on the basis of an elapsed time of the ultrasonic waves transmitted and received by said transducer, an apparatus for measuring fender deformation which comprises:: a normalized distance calculating means for calculating a normalized distance between a reference position, which is set at a predetermined distance on the basis of the transmitting-receiving transducer, and the vessel from a distance between said transmitting-receiving transducer and the vessel and a distance between the transmitting-receiving transducer and said reference position; a judging means for judging whether the vessel has reached said reference position or a preset position proximate to said reference position; and a displacement data outputting means for outputting the normalized distance as a displacement data for the vessel when it is judged by said judging means that the vessel has reached said reference position or preliminarily set proximate region; whereby the fender deformation is detected on the basis of said displacement data.

8. A method for measuring fender deformation as claimed in claim 7, in which said reference position is set so as to coincide with a mooring normal.

9. A method for measuring fender deformation as claimed in claim 7, in which said reference position is set so as to coincide with a position of a tip end of the fender.

10. A method for measuring fender deformation as claimed in claim 9, in which said displacement data is used as the deformation amount of the fender when the distance between the transmitting-receiving transducer and the vessel is equal to or smaller than the distance between the transmitting-receiving transducer and the reference position.

11. A method for measuring fender deformation as claimed in claim 7, in which said reference position is set nearer to a pier, a jetty, etc. than a tip end of the fender and a region between said reference position and said tip end of the fender is preliminarily set as the proximate region.

12. A method for measuring fender deformation as claimed in claim 7, in which said reference position is set farther than a tip end of the fender.

13. A method for measuring fender deformation substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.

14. An apparatus for measuring fender deformation substantially as hereinbefore described with reference to, or as illustrated in, Figs. 1 to 4 of the accompanying drawings.