EP1957358B1 - Method for production of a danger warning against an attacking torpedo - Google Patents

Abstract

The method involves pinpointing a torpedo with an underwater antenna using sonar under output of pinpointing angle and pinpointing time. The cotangent of the pinpointing angles is computed and the pinpointing time is assigned such that slew rate of the cotangent in a center pinpointing angle area is compared with a default value and an operating signal for a warning alarm is released if the cotangent exceeds the value.

Description

The invention relates to a method for generating a danger warning in front of a stern of a vessel attacking, in particular keel water-guided torpedo according to the preamble of claim 1.

Torpedoes are typically capable of attacking a watercraft from all directions. Thus, modern, very quiet torpedoes run the vessel, e.g. a surface ship, usually from a previous sector, whereas jet-water-borne torpedoes attack the ship from the aft sector. For early detection of an incoming torpedo therefore an all-round view of the ship carried by the sonar device is required. Known, on-board Aktivsonare that are usually installed in the bow of the ship or at the bow as so-called Hull Mounted Sonars (HMS) are due to the situation and due to the screw noise of the ship only imperfect all-round visibility with a more or less large gap. This aft sector of the ship is blind to incoming torpedoes.

To cover this vulnerability sector of the ship is in a known method for defense against aft direction of attacking torpedoes ( EP 1 117 587 B1 ) the torpedo by means of a so-called. Schleppsonars having an underwater antenna towed by the ship, passively detected and measured the frequency of at least one of the torpedo radiated, significant spectral line over time. From the Peilwinkeländerungsgeschwindigkeit, the frequency of the measured spectral line and their rate of change, the distance to the torpedo is calculated continuously. When a torpedo distance is detected, which is covered by the area of application of an torpedo-combating effector, the displacement of the effector is triggered by the ship.

The invention has for its object to provide an efficient method for generating a hazard warning in the case of aft-attacking torpedo, which triggers little signal processing at least then a warning alarm when the torpedo overflows the underwater antenna.

The object is achieved by the features in claim 1.

The method according to the invention has the advantage that by monitoring the rate of change of the cotangent of the successively determined bearing angle to the starting torpedo, the overflow of the torpedo via the underwater antenna can be determined by simple means. The detection of the overflow provides data on both the speed of the torpedo, as well as its distance to the stern of the vessel, on the one hand, the rate of change of Kotangens the bearing angle, ie the time differential of Kotangens the bearing angle, is substantially constant and corresponds to the torpedo speed and on the other hand the predetermined by the tow distance of the underwater antenna from the rear of the vehicle and thus the torpedo position at the moment of the antenna overflow is known. As a result, in an effector remote from the vessel for controlling the torpedo, the target data required for combat can be programmed very accurately and the time of settling of the effector for effective control of the torpedo can be maintained relatively accurately.

Advantageous embodiments of the method according to the invention with advantageous developments and embodiments of the invention will become apparent from the other claims.

According to an advantageous embodiment of the invention, the angle of a receiving direction with maximum receiving level, preferably with respect to the longitudinal axis of the underwater antenna, is determined as the bearing angle. This maximum reception level is compared-preferably after smoothing-continuously with a threshold value, and generates a gate signal when the threshold value is exceeded. The gate signal is linked to the trigger signal of the cotangent detection in such a way that a linkage signal arises when the gate signal and the triggering signal generated by the cotangent detection occur together. The logic signal activates the warning alarm. This additional monitoring of the reception level increases the reliability of the torpedo detection, thus reducing the false alarm rate, since the torpedo generates the largest reception level when the underwater antenna overflows.

According to an advantageous embodiment of the invention, it is additionally checked at which bearing angle the logic signal occurs and an additional alarm is output when the logic signal occurs at a bearing angle in the range of 90 °. By this measure, the accuracy of the determination of the distance of the torpedo is increased during the overflow, since at a bearing of the torpedo at 90 °, the torpedo has reached exactly the center of the underwater antenna and with the known distance of the underwater antenna from the rear of the vehicle an exact distance measure can be calculated.

According to an advantageous embodiment of the invention, the underwater antenna has a plurality of juxtaposed in the tow direction of hydrophones or hydrophone groups and from the electrical output signals of the hydrophones or hydrophone groups by means of directional formation of a series of directional characteristics, each of which a direction angle is uniquely associated, clamped on both sides of the underwater antenna , The reception signals obtained via the directional characteristics are normalized, whereby a normalization window used for this purpose for the reception signals from the most aft-directional directional characteristics in comparison with a standardization window for the reception signals used for this purpose is selected to be larger from the remaining directional characteristics. In the normalized received signals, the maximum reception level is determined and the directional angle of the directional characteristic with the maximum reception level is output as the bearing angle.

Due to the normalization constant noise sources are largely suppressed and fast in bearing and level Level and bearing changes highlighted. For this purpose, the median or mean value is formed over a preceding time segment of each received signal as defined by the normalization window, and the current value of the received signal is divided by this median or mean value. The normalization window or the time segment is dimensioned differently, as described above, for directional characteristics having different directional angles. In this way, when approaching a torpedo a slow increase in level of the received signal in the aft directional characteristics, the so-called. Endfire Beams, and the overflow of the antenna, the rapid increase in level due to the rapid passage of the torpedo through the other directional characteristics taken into account.

In accordance with an advantageous embodiment of the invention, the receive levels of the most afferent directional characteristics (Endfire Beams) are monitored and, upon the occurrence of a steep level rise exceeding a threshold, a pre-alarm is issued. As the level increases further, confirmation of the pre-alarm is issued.

Fig. 1

eine schematisierte Draufsicht eines Oberflächenschiffes mit einem bugseitigen Aktivsonar und einem achterlichen Schleppsonar,

Fig. 2

ein Blockschaltbild einer Schaltungsanordnung zur Erzeugung einer Gefahrenwarnung vor einem achterlich angreifenden Torpedo,

Fig. 3

ein Diagramm der Funktion des Peilwinkels zu einem achterlich angreifenden Torpedo (Kurve a) und der Kotangens des Peilwinkels (Kurve b) jeweils in Abhängigkeit von der Zeit.

The invention is described in more detail below with reference to an embodiment shown in the drawing. Show it:

Fig. 1

a schematic plan view of a surface ship with a bow-side active sonar and a stern towed sonar,

Fig. 2

a block diagram of a circuit arrangement for generating a danger warning in front of aft-attacking torpedo,

Fig. 3

a diagram of the function of the bearing angle to aft-attacking torpedo (curve a) and the Kotangens the bearing angle (curve b) respectively as a function of time.

A surface ship 10 equipped as an exemplary embodiment of a general vessel for protection against torpedoes with deflection vectors has a sonar device which, in addition to the location of targets, also serves to detect and locate torpedoes which attack the ship. The sonar device comprises an active sonar 11, which is designed in a known manner as a cylinder base or as a so-called. Hull Mounted Sonar (HMS), and a towed sonar, which called a towed in the water from the surface vessel 10 underwater antenna, hereinafter referred towed antenna 13. Due to the arrangement in the bow of the ship or by the integration in the fore ship's side, the active sonar 11 only covers a sector of about 150 ° from ship to starboard and from ship to port and is in a stern sector α ≈ 60 ° blind. Torpedoes starting from this aft sector are not detected by the active sonar 11.

To close this vulnerability gap of the surface ship 10 in the aft area, the towing sonar, which works exclusively passive. The towed antenna 13 is on a very long trailing cable or Tow rope 14, for example 800m, fixed and has an acoustic effective part of about 6m. At the towed antenna 13 may still be attached a tow brake 15. The attachment of the acoustic part of the towed antenna 13 to tow 14 and drag brake 15 is usually done via not shown here, attenuators, so-called. VIMs. The acoustic part of the towed antenna 13 is supported by a multiplicity of hydrophones 16 (15) arranged next to one another in the towing direction. Fig. 2 ) or hydrophone groups are formed, which are connected via running in the tow 14 signal lines 17 with an installed on board the surface vessel 10 signal processing unit. All hydrophones 16 or hydraulic groups are operated simultaneously, and by means of a direction generator 18, also called Beamförmer, is on both sides of the towed antenna 13 a fan of adjacent directional characteristics 19, also called beams, clamped. For this purpose, the electrical output signals of the hydrophones 16 or hydrophone groups are delayed in time and added in a known manner konphas. Each directional characteristic 19 is a direction angle Θ ( Fig. 1 ). The longitudinal axis of the towed antenna 13 thereby represents the reference line for the directional angles Θ, so that the directional characteristics 19 with the largest directional angles Θ are the furthest aft directional characteristics 19. The received signals received via the individual directional characteristics 19 are evaluated in order to detect a torpedo, which starts in the wake of the surface ship 10 astern, a so-called keilwasserhomenden torpedo, and to generate a danger warning.

In order to largely suppress constant noise sources in the received signals in bearing and level and thus emphasize the rapidly changing torpedo noises, the receive signals from each directional characteristic 19 are normalized in block 20, wherein a Normalisierungsfenster used for the received signals from the most aft-directional characteristics 19, ie from the so-called. Endfire sector, compared to the normalization window for the received signals from the other directional characteristics 19 is selected to be large. As a result, the various mechanisms which lead to level changes in the received signals of the directional characteristics 19 during the torpedo startup are taken into account. In the farthest aft-directional characteristics 19, the so-called Endfire Beams, there is a slow increase in level due to the approaching torpedo. Outside the Endfire Beams results in a rapid level change by the rapid passage of the torpedo through the directional characteristics 19 in the overflow of the trailing antenna 13. Therefore, for the slow level changes a large period, ie a large normalization window, and for the rapid level changes a short period, ie a small normalization window, used. The normalization is performed such that a current signal value of the received signal is divided by the median of the signal values contained in a period of time determined by the normalization window and immediately preceding the current signal value. Instead of the median, the average over the normalization window can also be used.

The core of the procedure for generating the hazard warning is the continuous bearing of the torpedo with the output of the bearing angle and bearing time. For determining the bearing angle θ In the normalized reception signals of the directional characteristics 19, the maximum reception level is determined, and the direction angle θ of the directional characteristics 19 having the maximum reception level is output as a bearing angle θ (block 21). Also, the respective maximum reception level P _{max is} output. The determination of bearing angle θ and receiving level P _max is limited to the directional characteristics 19 whose direction angle Θ in the angular range between 40 ° to 140 °.

The assignment of the detected bearing angle θ to the bearing times t is in Fig. 3 and gives the curve a in the bearing angle range of θ = 40 ° to θ = 140 °. For the output bearing angle θ, the cotangent is now calculated in block 22 and assigned to the bearing times t. The result is the curve b in Fig. 3 which, assuming that the torpedo starts at approximately constant speed, which is generally the case, is approximately a straight line. In block 23, the rate of change of the cotangent, so its temporal differential is formed, which is compared after passing through a filter 24 for smoothing fluctuations due to the pendulum motion of the torpedo in the wake of the surface ship 10 in block 25 with a default value or a threshold. If the smoothed cotangent change rate exceeds the default value, a warning alarm trigger signal is applied to a logical AND gate 26.

The level maxima P _max are smoothed (filter 27) and fed to a threshold (block 28). If the filtered level maximum signal exceeds the threshold value specified in block 28, then a gate signal is generated and sent to the logical AND gate 26 laid. In the logic AND gate 26, the trigger signal coming from the block 25 and the gate signal coming from the block 28 are linked together, so that at the output of the logical AND gate 26, a logic signal occurs, which activates a warning alarm. The warning alarm is in Fig. 2 symbolically represented by a warning signal lamp 29. In block 30 it is checked whether the logic signal which activates the warning alarm occurs at a bearing angle θ which is in the range between 80 ° and 120 °. If this is the case, then the logic signal is switched through in block 30 and outputs an additional alarm. The additional alarm is indicated, for example, by blinking the signal lamp row of three warning signal lamps 31. At the same time, the link signal through which the block 30 is connected can be used to automatically disconnect a torpedo-combating effector. The additional alarm signals that the torpedo has overrun the towed antenna 13 to its center, so that the distance of the torpedo is based on the length of the tow 14 and the towed antenna 13 can be determined very accurately.

To detect the aft-starting, keel-water-borne torpedo as early as possible, so that sufficient preparation time for the use of the effectors at the time of the overflow of the torpedo on the towed antenna 13 remains, in addition to the so-called. Overflow detection described above, a so-called. Endfire detection is performed , In this endfire detection, the reception levels in the most aft-directional directional characteristics 19, ie in the directional characteristics 19 with the maximum directional angles Θ ( Fig. 1 ), which extend to aft monitors. In these aft-directional characteristics 19, in turn, the maximum of the reception level is monitored as a function of time. In this case, the occurrence of a steep increase in level is sensed and, on the other hand, another continuously increasing level is checked. If the steep level increase exceeds a threshold value, a pre-alarm is output. For this purpose, the time profile of the reception level maximum on the one hand via a low-pass filter 32 with predefinable cutoff frequency to a threshold (block 33) and on the other hand via a low pass 34 with the opposite lower cutoff frequency to another threshold (block 35). If the threshold value specified in block 33 is exceeded, the pre-alarm is output, which in Fig. 2 symbolized by the warning signal lamp 37. If the threshold value specified in block 35 is exceeded, a pre-alarm confirmation is output, which results in Fig. 2 symbolized by the warning signal lamp 38. The warning signal lamps 29, 31, 37 and 38 preferably generate a differently colored display in a display on which the torpedo track is visualized. For example, a newly emerging torpedo is visualized by lighting the warning signal lamp 37 in blue, a confirmation of the newly emerging torpedo by lighting the warning signal lamp 38 in green, an overflow of the torpedo by lighting the warning signal lamp 29 in red and a maximum alarm by flashing lights of the three warning signal lamps 31 ,

In a supplementary embodiment of the method, the normalized received signals can be displayed on a screen, a so-called BTR display. The alarm messages described are then also displayed in the screen. This allows an operator to in addition to verify the alarm messages and thus reduce the false alarm rate.

In general, the parallel active operation of the active sonar 11 interferes with the passive operation of the towing sonar. Therefore, it is advantageous to hide interference by transmission during passive reception. This can be done in such a way that the transmission process is detected by a majority threshold crossing of the level of the received signals (before their normalization in block 20) and the old level value is maintained as long as the threshold crossing persists.

Claims (10)

1. Method for production of a danger warning against a torpedo which is attacking a watercraft (10) from astern, in particular a wake-homing torpedo in which the bearing of the approaching torpedo is found continuously, with the bearing angle and the bearing time being output, by means of a sonar having an underwater antenna which is towed by the watercraft (10), characterized in that the cotangent of the bearing angle is calculated and is associated with the bearing times, in that the rate of change of the cotangent is compared with a preset value, at least in a central bearing angle range, and in that an initiation signal for a warning alarm is emitted if the preset value is exceeded.
2. Method according to Claim 1, characterized in that the central bearing angle range is defined by a lower bearing angle limit of 10°, preferably 40°, and an upper bearing angle limit of 170°, preferably 140°, with the longitudinal axis of the underwater antenna forming the reference line for the bearing angle.
3. Method according to Claim 1 or 2, characterized in that the rate of change of the cotangent is smoothed before comparison with the preset value.
4. Method according to one of Claims 1 to 3, characterized in that the angle, preferably related to the longitudinal axis of the underwater antenna, of a receiving direction with the maximum reception level is emitted as the bearing angle, in that the preferably smoothed maximum reception level is compared continuously with a threshold value and in that a gate signal is generated if the threshold value is exceeded, and is linked to the initiation signal such that a link signal is produced when the gate signal and the initiation signal occur together, and in that the warning alarm is activated by the linking signal.
5. Method according to Claim 4, characterized in that a check is carried out as to the bearing angle at which the linking signal occurs, and in that an additional alarm is emitted when the linking signal occurs for a bearing angle in the region around 90°.
6. Method according to Claim 5, characterized in that the bearing angle range for initiation of an additional alarm is defined by the limit bearing angles 80° and 120°.
7. Method according to one of Claims 1 to 6, characterized in that the underwater antenna has a multiplicity of hydrophones (16) or hydrophone groups which are arranged one behind the other in the towing direction, in that a fan of mutually adjacent directional characteristics (19) with each of which one direction angle is uniquely associated, is spread out on both sides of the underwater antenna (13) by means of direction formation from the electrical output signals of the hydrophones (16) or hydrophone groups, in that the received signals obtained from the directional characteristics (19) are normalized, wherein a normalization window for the received signals is selected roughly from the directional characteristics (19) which point furthest astern in comparison to the normalization window for the received signals from the other directional characteristics (19), and in that the maximum reception level in the normalized received signals is determined, and the direction angle of the directional characteristic (19) with the maximum reception level is emitted as the bearing angle.
8. Method according to Claim 7, characterized in that the reception levels in the directional characteristics (19) which are furthest astern are monitored continuously, and in that an initial alarm is emitted on the occurrence of a steep level rise which exceeds a threshold value.
9. Method according to Claim 8, characterized in that an initial alarm confirmation is emitted if the level continues to become greater.
10. Method according to Claim 8 or 9, characterized in that the reception level monitoring is carried out using the level maximum of the received signals from the directional characteristics (19) which are furthest astern.

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