JPH11337641A - Sonar device for detecting obstacle and underwater navigating body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conserve the power of an underwater navigating body by offloading a sonar sound source to a ship upper part such as a supporting mother ship. SOLUTION: An underwater navigating body 1 operates, together with a ship upper part such as a supporting ship 1. At this time, the ship upper part 2 is the sonar sound source. The underwater navigating body 1 comprises a wave receiving circuit 4 to receive direct waves from the ship upper part and a wave receiving circuit 5 for receiving reflected waves. When there is a presence of an obstacle 3, sound waved from the ship upper part 2 are reflected at the obstacle 3, are delayed by the difference in course from the direct waves, and are received. By measuring this time delay and appropriately correcting the angle of incidence of the direct waves, the relative distance between the navigating body 1 and the obstacle 3 is computed. In addition, by using a narrow-directional wave receiver for the reflected wave receiving circuit 5, it is possible to obtain the direction of an obstacle as well and to specify the location of the obstacle in a polar coordinate system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detection sonar used for forward monitoring, obstacle detection, etc. Obstacle detection sonar in a system for searching for obstacles.

[0002]

2. Description of the Related Art Conventionally, this kind of obstacle monitoring sonar is
It is provided on underwater vehicles such as robots and submersibles that are active in the water, and is used for the purpose of preventing collision with the sea floor and obstacles and detecting underwater targets. The basic principle of this forward obstacle monitoring sonar is that an underwater vehicle emits sound waves in the water,
In this method, a reflected wave (echo) from an obstacle or the like is received, and the relative position of the obstacle or the like is calculated from its return time or direction.

[0003] Also, various techniques have been conventionally developed for improving the operation performance of the forward obstacle monitoring sonar and the detection rate of obstacles. For example, Japanese Patent Application Laid-Open No. 62-247279 describes a technique for improving the performance by reducing the influence of ghost due to the receiver side lobe.

[0004]

A conventional forward obstacle monitoring sonar of this type has a sonar body which has a sonar sound source, and a sound output by a transmitter mounted on the body. Is emitted into the water. Generally, the larger the sound output is, the longer the detection distance is and the higher the resolution is. Therefore, the larger the sound source is, the better.

However, driving a high-output sound source increases power consumption. In the case of a non-voyage vehicle that operates without receiving power supply underwater, the marginal activity time is short due to the limitation of the power supply capacity. In addition, there is a problem that practical performance is significantly impaired because the range of activity is limited.

It is necessary to provide an acoustic transmission system circuit. Generally, the transmission system circuit is composed of a high-output power amplifier and its driving system. It consists of an output power amplifier, a transformer, a transmitter and the like. All of these components are larger in size and weight than other circuit components, and the hardware scale becomes larger. Further, in connection with the first problem, as the power consumption increases, it becomes necessary to mount a large-capacity battery set on the vehicle, which indirectly increases the hardware scale. For this reason,
When applied to marine equipment, which is required to be easy to operate and handle, there will be significant disadvantages in size and weight.

An object of the present invention is to provide a low power consumption forward monitoring sonar system in view of the above problems.

Another object of the present invention is to provide a forward monitoring sonar system capable of reducing the hardware scale.

[0009]

SUMMARY OF THE INVENTION According to the present invention, an acoustic transmission circuit, which is the unit that consumes the most power among the forward obstacle detection sonars, is not incorporated in the underwater navigation unit. Is characterized by performing obstacle detection by receiving an echo wave generated by a sound wave emitted from another alternative sound source without performing acoustic transmission. As this alternative sound source, a short pulse emitted from the upper part of the underwater vehicle such as a support mother ship is used.

Specifically, the underwater traveling unit measures the difference between the time at which the sound wave from the alternative sound source directly arrives at itself and the time at which the sound wave is received after being reflected by an obstacle. From the difference, the relative distance between the underwater navigation unit itself and the obstacle is calculated. At this time, since the path difference changes depending on the incident angle of the direct wave, the incident angle is measured by a general SSBL acoustic positioning device to correct the path difference.

At the same time, by detecting the arrival direction of the reflected wave, the relative position of the obstacle in the polar coordinate format can be grasped.

According to the present invention, since the underwater vehicle does not transmit sound by itself, the power consumption can be greatly reduced as compared with a system that performs transmission by itself. As a result, the time limit for activity in water is lengthened, and activity ability is greatly improved.

In addition, the hardware is small, and the operability is increased. In particular, by improving power savings, the number of batteries mounted on the hull can be reduced, so that the underwater configuration can be significantly reduced in weight and size.

[0014]

FIG. 1 is an overall configuration diagram showing an embodiment of a forward obstacle detection sonar according to the present invention. In FIG. 1, reference numeral 1 denotes an underwater vehicle, reference numeral 2 denotes a mother ship, reference numeral 3 denotes, for example, an obstacle on the sea floor, and reference numerals 4 and 5 denote sound wave receivers provided on the underwater vehicle.

The underwater vehicle 1 receives the direct wave of the short pulse sound wave emitted from the sound wave transmitting device provided in the mother ship 2 by the receiver 4, and receives the reflected wave from the obstacle 3. The distance between the underwater vehicle 1 and the obstacle 3 is measured by measuring the difference between the reception times by receiving the signals by the receiver 5. For example, the underwater navigation is performed so as to avoid the collision with the obstacle 3. The running control of the running body 1 is performed.

FIG. 2 is a block diagram showing a configuration of a received sound wave processing unit provided in the underwater vehicle according to the present invention.
It comprises a direct wave receiving unit 4, a reflected wave receiving unit 5, an SSBL acoustic positioning device 6, and a CPU 6.

The direct wave receiving unit 4 receives the direct wave emitted from the mother ship 2 and continuously outputs data to the CPU 7 and the SSBL acoustic positioning device 6, and mainly includes a receiver array and It comprises a preamplifier, a bandpass filter, and an A / D converter, receives and amplifies an audio signal in a predetermined band, digitizes a received wave level, and outputs it.

The SSBL positioning device 6 is located between the direct wave receiving unit 4 and the CPU 7, receives a signal from the direct wave receiving unit 4, calculates a sound arrival direction, and passes the value to the CPU 7. In addition, a line for directly passing a received signal from the direct wave receiving unit 4 to the CPU 7 is provided in another system.

The reflected wave receiving section 5 is a system for transmitting a received signal to the CPU 7 in a completely different system from the direct wave receiving section, and mainly includes a narrow directional receiver array, a preamplifier, a bandpass filter, / D converter, and has almost the same function and configuration as the direct wave receiving unit 4.

The CPU 7 has a signal input / output unit (SIO) for receiving data from the direct wave receiving unit 4, the reflected wave receiving unit 5, and the SSBL positioning device 6, a memory for temporarily storing the received data, and a time difference measurement. An internal timer and the like are provided.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS. In FIG. 2, the CPU
Reference numeral 7 reads data continuously output from the direct wave receiving unit 4 and the reflected wave receiving unit 5, and sequentially compares the preset threshold value with the value. The threshold value is selected by estimating the minimum value of the sound level obtained when each receiving unit receives an acoustic pulse, and when the data value exceeds this, it is determined that each receiving unit has received an acoustic signal. belongs to.

When a short pulse is emitted from the mother ship in the operation mode shown in FIG. 1, first, the direct wave receiver 4 shown in FIG. 2 receives a direct wave. The received data value output at this time is
The threshold value exceeds a preset value of 7 and the CPU 7 starts an internal timer count and starts a time difference measurement by using this as a trigger. The timer measures the time difference until a reflected wave from the reflected wave receiving unit 5 is received.

On the other hand, the SSBL acoustic positioning device 6 continuously calculates the sound arrival direction from the signal received by the direct wave receiving unit 4 and outputs it to the CPU 7, but when the CPU 7 starts counting the internal timer. Is selected as the arrival direction of the direct wave signal.

Thereafter, when the reflected wave reaches the reflected wave receiving unit 5 and the output data of the reflected wave receiving unit 5 exceeds the threshold value held by the CPU 7, the CPU 7 causes the reflected wave receiving unit to receive the reflected wave. Judgment has been made, the internal timer stops counting,
This elapsed time is obtained as a reception time difference between the direct wave and the reflected wave.

The distance to the obstacle ahead can be calculated from the reception time difference between the direct wave / reflected wave and the arrival direction of the direct wave obtained by the above series of operations. In addition, since the narrow-directional receiver array is used in the reflected wave receiver, the azimuth of the obstacle can be calculated using this characteristic.

FIG. 3 is a block diagram showing an embodiment of the reception sound wave processing section of FIG. The receiver array 4 constituting the direct wave receiving unit receives the direct wave emitted from the mother ship for each of the receiving elements. The received signal of each receiving element is amplified and extracted by the preamplifier 11 and the filter 12, respectively. These signals are input to the SSBL acoustic positioning device 13, and the sound source direction α is calculated based on the phase difference and the like. α is output to the CPU 7 as sound source direction information. The received signal level is digitized by the A / D converter 14 and passed directly to another SIO port of the CPU 7.

On the other hand, the narrow directional receiver 5 constituting the reflected wave receiving section receives the reflected wave from the obstacle 3, and the received signal is amplified and extracted by the preamplifier 21 and the filter 22.
It is digitized by the D converter 23 and output to the CPU 7.

The CPU 7 determines the receiving level and direction of the direct wave,
Then, by taking in the reflected wave level, the receiving time difference between the direct wave and the reflected wave is measured, the sound source direction is corrected, and the distance between the obstacle and itself is calculated. Here, the reception time measurement of the direct wave and the reflected wave is defined as reception at a moment when the reception signal exceeds a preset reception level threshold value.

FIG. 4 shows the path of a sound wave when the sound wave arrives at an incident angle α. Here, β is the angle between the horizontal direction of the receiver and the reflection point R. In FIG. 4, when the navigation body depth L is extremely larger than the detection distance, that is, L >> r
Then, it is approximated as AO // A'O '. At this time, α,
The path difference O′RO between the direct wave and the reflected wave in consideration of β is calculated using the shortest path r as follows: O′RO = r + r ′ = r {1 + cos (α−β)} (1) where Assuming that the receiving time difference between the direct wave and the reflected wave is T, r + r '= cT, so the distance O to be measured is
R = r is given by: r = cT-r '= cT-rcos (α-β) (2) Therefore, r = cT / {1 + cos (α-β)} (3) The distance between the obstacle and the underwater vehicle is: If it is defined as the closest point (shortest reflection path) detected within the directivity width of the receiver 5, r min [−φ ≦ β ≦ φ | cT / ｛1 + cos (where φ is the directivity half width of the receiver 5) α-β)｝] (4).

The CPU 7 calculates the distance r to the obstacle using given c, T, α, and φ according to equation (4). Also,
The obstacle direction is determined by the direction to which the receiver 5 is directed.

FIG. 5 shows time-series data of the received signal taken into the CPU 7 in FIG. Here, signal 1 corresponds to FIG.
Receiving signal of a direct wave obtained from the A / D converter 14 in the inside,
The signal 2 is a received signal of a reflected wave obtained from the A / D converter 23 in FIG.

The CPU 7 has a preset threshold value Th1 for the signal 1, and continuously measures the reception level. The instant TR1 at which the signal level L1 exceeds Th1 is regarded as a direct wave reception. Recognizing the direct wave reception, C
The PU 7 starts measuring the reception level L2 of the signal 2, and
Moment TR exceeds the preset threshold value Th2
2 is the reception of the reflected wave.

The L2 measurement is performed for a preset time-out time to seconds, and when the reception of the reflected wave is recognized within to, the level measurement of the signal 2 is stopped, and the calculation shown in the equation (4) is performed to calculate the distance r. To complete one cycle of obstacle detection. If no reflected wave is recognized within to, no obstacle is detected within the detection range, and one cycle of obstacle detection ends. After one cycle, the CPU 7 returns to measuring the signal 1 again, and starts the next one cycle operation.

The time measurement is performed by an internal timer of the CPU 7, and the reception time difference T between the direct wave and the reflected wave is calculated by T = TR2-TR1 (5). FIG. 6 is a flowchart showing the operation sequence described above.

In the specific example shown in FIG. 3, the reflected wave receiving system is used for detecting the reflected wave direction using a single narrow directional receiver 5, but this is used for the direct wave receiving system. In the same manner as described above, the reflected wave direction can be detected by performing SSBL positioning using a receiver array. In that case, the configurations of the direct wave receiving system and the reflected wave receiving system are almost the same.

As a method of determining the reception times TR1 and TR2 of the acoustic signal shown in equation (5), a specific example uses a determination method based on a comparison between the reception level and threshold values Th1 and Th2. This can be replaced with another method. For example, for each of the received waveforms shown in FIG. 5, level differences DL1 and DL per unit time as shown in FIG.
2 is calculated and compared with threshold values Th1 'and Th2'. That is, DL1> Th
When 1 ′ and DL2> Th2 ′, the times TR1 and TR2 when the direct wave and the reflected wave are received may be used.

[0037]

According to the present invention, there is no acoustic transmission means requiring a large amount of power consumption in the underwater part. As a result, the activity time and activity range of the underwater vehicle can be expanded, and the system performance can be greatly improved.

In the underwater part, since a transmitter, a transmission circuit, a power supply circuit and the like for performing sound transmission are not mounted from the beginning, the hardware scale of the underwater part can be reduced. Therefore, when applied to an underwater vehicle or an underwater robot (ROV) operated in a severe environment, operability is greatly improved.

Further, the capacity of the battery mounted in the underwater part can be reduced by the power saving function.
The scale of the underwater part to which this system is applied can be further reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a forward obstacle detection sonar according to the present invention.

FIG. 2 is a block diagram showing a configuration of a received sound wave processing unit provided in the underwater vehicle according to the present invention.

FIG. 3 is a diagram illustrating an embodiment of a reception sound wave processing unit in FIG. 2;

FIG. 4 is a diagram for explaining an operation for calculating a distance to an obstacle.

FIG. 5 is a diagram illustrating a relationship between a received signal level and a received time according to the embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a received signal level and a received time according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Underwater vehicle 2 Mother ship 3 Obstacle 4 Direct wave receiving part 5 Reflection wave receiving part 6 SSBL acoustic positioning device 7 CPU 11,21 Preamplifier 12,22 Filter 14,23 A / D converter

Claims (7)

[Claims] 1. A means for receiving a direct wave of a sound wave emitted from another sound source, a means for receiving a reflected wave from an obstacle due to the sound wave, and the received direct wave and a reflected wave A means for calculating a reception time difference between the direct wave and the arrival direction of the direct wave, and a means for calculating a relative distance to the obstacle from the obtained reception time difference and the arrival direction of the direct wave. Obstacle detection sonar device. 2. The means for receiving the direct wave and the means for receiving the reflected wave are each constituted by a receiver array, and the means for receiving the reflected wave includes a wave having a narrow directivity characteristic. 2. The device according to claim 1, wherein the device is configured as a container.
Obstacle detection sonar device as described. 3. A means for receiving a direct wave of a sound wave emitted from another sound source, a means for receiving a reflected wave from an obstacle due to the sound wave, and the received direct wave and reflected wave Means for calculating the arrival time difference between the reception time and the direct wave and the reflected wave, and means for calculating the relative position of the obstacle from the obtained reception time difference and the arrival direction of the direct wave and the reflected wave. An obstacle detection sonar device, comprising: 4. The obstacle detecting sonar apparatus according to claim 3, wherein the means for receiving the direct wave and the means for receiving the reflected wave are each constituted by a receiver array. 5. A means for receiving a direct wave or a reflected wave of the sound wave, wherein a difference between a reception level of the sound wave or a reception time per unit time when the reception level of the sound wave becomes a predetermined threshold value or more The obstacle detection sonar device according to claim 1 or 3, wherein the time point when the above is determined is the reception time of the sound wave. 6. An underwater vehicle comprising the sonar device for detecting an obstacle according to claim 1 or 3. 7. The underwater vehicle includes a mother ship and an underwater vehicle, and the underwater vehicle includes a unit that emits a sound wave into the water, and the underwater vehicle receives a direct wave of the sound wave emitted from the mother ship. Means, means for receiving a reflected wave from the obstacle due to the sound wave, means for determining the reception time difference between the received direct wave and the reflected wave, and the arrival direction of the direct wave and the reflected wave, An obstacle detection sonar system comprising: means for calculating a relative position between the underwater vehicle and the obstacle from the reception time difference and the arrival directions of the direct wave and the reflected wave.