DE2651819C1 - Method and device for the approximate determination of the length of a ship, in particular for controlling the ignition release of sea mines - Google Patents

Description

The invention relates to a method for approximation Determination of the length of a ship.

The invention particularly relates to the problem to release the ignition of a sea mine only if that ship passing over it has a certain minimum size. On this is intended to ignite the sea mine by small Vehicles are avoided.

The invention is characterized by the following Process steps:

• (a) Measurement of the passage of time through the ship at one fixed place on the seabed caused pressure change until their first zero crossing,
• (b) Determining the time interval T between the first and the second zero crossing of the pressure change from the time course up to the first zero crossing, this time interval T being a measure of the ratio from ship length L and ship speed,
• (c) determining the ship's speed U from the bearing of the ship from said fixed location and
• (d) Determining the length of the ship by multiplication the ratio value obtained from the pressure curve with the speed value obtained from the bearing.

According to the invention is by means of a pressure sensor on the seabed, the z. B. can be installed in a sea mine, the pressure curve is tracked as the ship passes over it. The pressure change or pressure deviation from the static mean value resulting from the water depth initially shows an increase when the bow of the ship approaches the location of the pressure sensor. Then the pressure drops below the static mean value, ie the pressure deviation shows a first zero crossing and becomes negative when the hull of the ship passes over the pressure sensor. Finally, after the tail has passed, the pressure temporarily rises again above the static mean. The pressure deviation shows a second zero crossing and becomes positive and then finally decays back to zero. The time interval between the first and the second zero crossing is equal to the time it takes for the ship to travel over the entire length of the pressure sensor. This time interval T is thus where L is the length and U is the speed of the ship.

But it’s not enough to just measure this interval, since then at the end of the measurement at the second zero crossing the ship is already completely over the pressure sensor and thus ran over the sea mine and an ignition of the Sea mine would then no longer make sense. That's why this one Time interval from the time course up to the first zero crossing won by some kind of extrapolation. It stands then the ratio of length to speed of the Ship at the time of the first zero crossing, So while the ship is over the pressure sensor and the sea mine drives away, available.

The time interval T only provides the ratio of length and speed, so it does not yet allow a distinction between a slow, small and a fast, large ship. There is therefore a bearing of the ship from the location of the mine from the invention, which z. B. by means of known acoustic direction finders. The speed U of the ship can be determined from this bearing. Multiplying the time interval T by the speed U gives an estimate of the length L of the ship. If this length exceeds a certain value, the ignition of the sea mine can be released.

A device for performing the aforementioned method is marked by:

• (a) a pressure sensor ( 12 ) for generating a water pressure signal reflecting the water pressure at the location of the device,
• (b) a filter assembly on which the water pressure signal is activated and which to generate a pressure deviation signal is set up, which is the deviation of the water pressure from his Represents mean,
• (c) a transmitter arrangement for generating directional cosine signals which represent the directional cosine from the device to the ship, ie the cosine of the angles ϕ _x , ϕ _y and ϕ _z between a target direction and the axes of an earth-fixed Cartesian coordinate system x, y, z , where the z axis is vertical and the x and y axes are horizontal,
• (d) first computer means ( 30 ), which are acted upon by the pressure deviation signals and are set up to form a time interval signal from the time course up to the first zero crossing, which represents the time interval T between the first and second zero crossing of the pressure deviation signal,
• (e) second computing means, which are acted upon by the direction cosine signals and a depth signal reflecting the depth of the device below the water surface and set up to form coordinate signals therefrom which reflect the horizontal coordinates x, y of the ship in said earth-fixed coordinate system ,
• (f) third computer means which are acted upon by the coordinate signals and which are set up to form a speed signal representing the speed U of the ship, and
• (g) one of the outputs of the first and third Computer means applied multiplier circuit for  Generation of the product of the interval signal and the length signal representing the speed signal is set up, this length signal is an estimate of the length of the ship.

Further refinements of the invention are the subject of Subclaims.

The invention is illustrated below using an exemplary embodiment with reference to the accompanying drawings explained.

Fig. 1 illustrates the passage of a ship over a pressure sensor;

Fig. 2 shows the course of the pressure occurring deviation from the resulting from the static water depth mean;

Fig. 3 is a schematic perspective view and shows the position of the earth-fixed coordinate system used to the idealized, ie assumed as a horizontal plane water surface, the position of the device according to the invention and the ship and its course and the angles resulting from the bearing;

Fig. 4 is a block diagram of an apparatus according to the invention;

FIG. 5 illustrates the course of the coordinate signals occurring in the device according to FIG. 4;

FIG. 6 illustrates in the form of a block diagram a model for the temporal change of the ship position in the coordinate system of FIG. 3;

Fig. 7 shows computer means in the form of a Kalman filter for determining the speed U of the vessel from the coordinate signals;

Fig. 8 schematically shows computer means for "extrapolation" of the time interval T between the zero crossings of the pressure deviation Δ _p in FIG. 1.

InFig. 1 is shown as on the ocean floor10th  a pressure sensor12 at a water depthH is arranged. A ship14 runs over this pressure sensor. The water depthH requires a certain static pressurep, caused by wave movements of the water surface16 something fluctuates, but a constant mean  results. The ship14 causes a change in pressureΔ _p  towards this static mean , and the time course of this Pressure changeΔ _p  is inFig. 2 shown.

How outFig. 2 can be seen, causes the ship14 at Approaching the position of the pressure sensor12 with his Bug first an increase in pressurep, so a positive one Pressure deviationΔ _p . Then when the fuselage of the Ship14 via the pressure sensor12 runs away, sinks the pressurep below the static mean  from that Pressure deviationΔ _p  shows a first zero crossing in Pointt₀ and then becomes negative. If the stern of the ship via the pressure sensor12 runs away, shows the pressure deviation Δ _p  a second zero crossing in pointt₁ and then becomes temporarily positive, eventually returning to sink to zero. The time intervalT between the first zero crossing att₀ and the second zero crossing att₁ indicates what time the ship14 necessary for via the pressure sensor12 drive away. So it is  where, as I said,L the length of the ship14 andU  its speed is. To get a reading forT beautiful before the passage of the ship14 will getT  from the passage of time fromΔ p up to the first zero crossing int₀ "extrapolated" from empirically obtained data. The surface can do thisF₁ under theΔ pCurve that in Fig. 2 is shown hatched, in connection with the riseS the pressure deviationΔ p at the timet₀ of the first zero crossing can be used. If assumes the areaF₁ under the positive course of Pressure deviationΔ p in a certain relationship to the areaF₂ over the negative course of the pressure deviationΔ p  stands and this negative course is similar to a parabola, an assumption that works well with empirical observations matches, then canT for example predicted as follows will: in whichα an empirically determined, dimensionless factor is. However, it is more comfortable under the same conditions for "extrapolation" instead of the surfaceF₁ that first maximumΔ p _Max  to take the pressure deviation into account andT from the relationship to determine whereβ again an empirically to be determined dimensionless factor.

FIG. 3 shows the position of the device 18 , which also contains the pressure sensor 12 (not shown in FIG. 3), on the seabed. The device 18 contains a direction sensor 20 known per se, which supplies three “direction cosine” signals cos ϕ _x , cos ϕ y, cos ϕ _z corresponding to the cosine of the angles ϕ _x , ϕ _y , ϕ _z , which give a target direction R from the device 18 to the ship 14 with the three coordinate axes x ' , y' , z 'forms an earth-fixed coordinate system. For the sake of simplicity, it is first assumed in FIG. 3 that the device 18 is aligned directly according to a predetermined coordinate system. The origin of the coordinate system x ' , y' , z ' lies in the device 18 , ie on the seabed, the coordinate axis z' being directed vertically upwards and the coordinate axes x ' and y' lying in a horizontal plane representing the idealized seabed 10 . In Fig. 3 a second coordinate system x , y , z is shown, the origin of which is perpendicular to the device 18 on the water surface and the x and y axes parallel to the x ' and y' axes of the other coordinate system in the horizontal plane representing the idealized water surface 16 .

The ship 14 moves along the dashed line 22 at the speed U. The relationship between T and L / U explained above also applies in this case. H denotes the water depth in FIG. 3 as in FIG. 1.

Fig. 4 shows in a block diagram, as seen from the pressure signals p of the pressure sensor 12 and the direction cosine signals of the direction sensor 20 is obtained a measured value for the length of the vessel 14 and accordingly, the ignition release takes place for the mine.

The signalp of the pressure sensor12 is on a filter24th  given. The filter24th delivers at an exit26 in  known an output signal which is the mean of water pressurep corresponds and practically that the water depthH resulting hydrostatic pressure. The filter24th continues to deliver at an output28  a pressure deviation signalΔ pwhich is the deviation of the Water pressurep, possibly adjusted for fluctuations due to swell, from the mean  reproduces.

The pressure error signal Δ p, which has approximately the time course shown in Fig. 2 as it approaches a ship, is fed to computing means 30 which at an output 32 the maximum value Δ p _max of the pressure deviation signal Δ p (see. Fig. 2) and an output 34 supplies the value S , ie the value of at the time t ₀ of the first zero crossing. These two signals are connected to a quotient 36 whose output signal by means of a circuit 38 , for. B. a potentiometer in analog signal processing, is multiplied by a factor β . A time interval signal thus appears at an output 40 , which represents the expected time interval T between the zero crossings and is thus a measure of the ratio of length and speed of the ship 14 .

To determine the speed U of the ship 14 , a direction meter 20 , that is, a transmitter for the direction cosine cos ϕ _x '', cos ϕ _y '' and cos ϕ _z '' of the target direction R from the device 18 to the ship 14 , is provided. These direction cosines are related to a device-fixed coordinate system x '' , y '' , z '' , which generally deviates from the specified earth-fixed coordinate system x ' , y' , z ' ( Fig. 3). It is therefore provided in the device 18, a position reference device 42 , which delivers at the outputs 44, 46, 48 position reference signals ε ₁, ε ₂ and ε ₃, which the angle between the corresponding coordinate axes x '' , y '' , and z '' or x ′ , y ′ , and z ′ of the coordinate system and the earth-fixed coordinate system.

The direction cosine signals cos ϕ _x '', cos ϕ _y '' and cos ϕ _z '' of the direction sensor 20 and the position reference signals ε ₁, ε ₂, ε ₃ of the position reference device 42 are connected to a coordinate transformation circuit - 50 , which for Formation of direction cosine signals cos ϕ _x ′, cos ϕ _y ′ and cos ϕ _z ′ is set up, which are related to the earth-fixed coordinate system x ′ , y ′ , z ′ and appear at outputs 52, 54 and 56 , respectively.

The direction cosine signals cos ϕ _x 'and cos ϕ _y ' are connected to the counter input of a quotient 58 and 60 , respectively. The direction cosine signal cos ϕ _z 'is connected to the denominator input of each quotient. A signal then appears at the output 62 of the quotient former 58

A signal appears at the output 64 of the quotient former 60

The signal  at the exit26 of the filter24th is in one circuit66 with the calibration factork multiplied, so that at an exit68 this circuit66 a signal appears which is the water depthH reproduces. This Signal acts on two multiplier circuits in parallel70  and72. The multiplier circuit70 also receives that Output signal62, and the multiplier circuit72 receives  also the signal at the output64. At the exit74 the Multiplier circuit70 a coordinate signal then appears x _m that thex-Coordinate of the ship14 by doing Coordinate systemx ′,y ′,z ′ orx,y,e.g. (Fig. 3) represents as they are from the direction sensor and pressure sensor signals results. At the exit76 appears a Coordinate signaly _m that in the same way they-Coordinate of the ship14 in the coordinate systemx ′,y ′,z ′  orx,y,e.g. reproduces. These coordinate signalsx _m  and y _m who are very noisy are in forFig. 3rd indicated route of the ship14 in dependence of of time inFig. 5 shown.

The coordinate signalsx _m  andy _m  are on computer means78  switched, which next to smoothed "calculated" coordinate signals _s , _s  at exits80, 82 further signals _s , _s   at the exits of the ship14 correspond. These speed component signals _s , _s  are on a circuit88  to form the root of the sum of squares activated. The exit90 this circuit88 delivers then a signal representing the amountU the speed of the Ship14 reproduces.

This signal U , together with the signal T at the output 40 , is fed to a multiplier 92 which, at an output 94, generates a length signal which represents the length L of the ship 14 .

This length signal L is compared in a comparator 96 with a fixed value L ₀; if

L L ₀

is released for the sea mine.

The computing means 78 are a so-called Kalman filter. Fig. 7 is a block diagram of the computing means 78 , and Fig. 6 is for explanation.

If the position and speed of the ship 14 is known at a certain point in time t ₀, then the position can be determined at any later point in time with a constant course and constant speed

x _s  =x _{s 0} + _{s 0} (tt₀)
y _s  =y _{s 0} + _{s 0} (tt₀)

win. That can be done with the inFig. 6 model shown can be simulated. It is - for reasons that are still recognizable are - in the general representation ofFig. 6 two Integrators98, 100 for thex-Coordinate and two integrators 102, 104 for they-Coordinate provided. The Arrows from above symbolize the specification of the initial values, d. H. the values of the integrator output at the timet =t₀, namely _{s 0} and _{s 0}. The entrance of the Integrators98 and102 is constantly zero, so that _s  = _{s 0}  and _s  = _{s 0} remains. These values are determined by the integrators 100 respectively.104 integrated, which the above given relationships. A prediction of the Position through this model is only correct, if bothx _{s 0},y _{s 0} as well as _{s 0}, _{s 0} assumed to be known can be. But this is not the case here. Therefore, according toFig. 7 the respective forecast for the Position as well as for the speed components with the help of the pressure sensor and the direction sensor  20th measured coordinatesx _m  andy _m  compared and corrected the prediction accordingly. This happens in such a way that the difference between measurement and Prediction formed, this difference weighted and used Correction of the prediction of both location and Speed components is used.

InFig. 7 is for thexComponent a channel106 and for them yComponent a channel108 provided that in their construction match and therefore only the channel106 described is. The channel106 contains an entrance110, the with the exit74 is connected and to which the coordinate signal x _m  is turned on, and an output80 for the calculated (or predicted) coordinate signal _s . The channel106 also contains a first and a second Integration level112 respectively.114. At the entrance of the first Integration level112 becomes the difference of the coordinate signal x _m  and the calculated coordinate signal _s   weighted with a changeable first factork₁ activated. This difference is in one point116 educated. At the entrance of the second integration stage114 is the Sum of the output of the first integration level112 and the said, with a changeable second factork₂ applied differencex _m  - _s  activated. The sum becomes at a summation point118 educated. The exit of the second level of integration114 is on said exit for the calculated coordinate signal ₂ switched. The Speed component signal _s  is before the summation point 118 at the exit of the first integration stage112  tapped that with the exit84 (Fig. 4) is connected.

If _s  at the exit80 always the samex _m  then it is Difference at the input of the integration level112 zero. The Integration level112 provides a constant output  correspondingx _{s 0} fromFig. 6. This output will also turn on the summation point118 no longer corrected. It results an output signal that changes linearly with time on the integrator114 like in the model ofFig. 6.

If butx _m  from the predicted or calculated _s   deviates, the difference causes a change in the Output of the integration level112 (Estimate of) and at the same time (with the factorx₂) over the summation point118  a direct change in the output of the integration level114  (Estimate ofx). This correction is carried out as long as until on average the difference fromx _m  and _s  back to has become zero.

Besides the smoothed coordinate signals also the speed component signals of interest here receive.

FIG. 8 shows details of the computing means 30 of FIG. 4.

The pressure deviation signal Δ p is present at an input 120 of a gate circuit 122 . The pressure deviation signal Δ p is also fed to a differentiator 124 , which supplies a signal in accordance with, ie the time derivative of Δ p . This signal acts once on a zero detector 126 , which switches through the gate circuit 122 via an input 128 if = 0. The maximum value Δ p _{max of} the pressure deviation signal Δ p is therefore switched through and stored in a memory 130 .

The output signal of the differentiating element 124 also acts on an input 132 of a gate circuit 134 . The pressure deviation signal Δ p itself is applied to a zero detector 136 , which switches through the gate circuit 134 via an input 138 when Δ p = 0. The signal is thereby switched to a memory 140 at the zero crossing, which stores the value S (see FIG. 2). The outputs 32 and 34 of the memories 130 and 140 are connected to the quotient generator 36 , as has already been described in connection with FIG. 4.

The various operations can be done with analog signals be performed. Preferably the signals however digitize and with digital computing means process in the manner described.

Claims (16)

1. Method for the approximate determination of the length of a ship, characterized by the following method steps:

• (a) measurement of the time course of the pressure change caused by the ship at a fixed location on the sea floor up to its first zero crossing,
• (b) Determining the time interval T between the first and the second zero crossing of the pressure change from the time course up to the first zero crossing, this time interval T being a measure of the ratio from ship length L and ship speed,
• (c) determining the ship's speed U from the bearing of the ship from said fixed location and
• (d) Determining the length of the ship by multiplying the ratio value obtained from the pressure curve by the speed value obtained from the bearing.

2. The method according to claim 1, characterized in that said time interval T from the maximum value Δ P _{max of} the pressure change and the slope S of the pressure change curve at the time of the zero crossing according to the relationship is determined. 3. Apparatus for performing the method according to claim 1, characterized by:

• (a) a pressure sensor ( 12 ) for generating a water pressure signal representing the water pressure (p) at the location of the device ( 18 ),
• (b) a filter assembly (24) to which the water pressure signal (p) is switched and which is adapted to generate a pressure difference signal (Δ p), which represents the deviation of the water pressure (p) from its mean value (),
• (c) a transmitter arrangement ( 20, 42, 50 ) for generating directional cosine signals which represent the directional cosine from the device ( 18 ) to the ship ( 14 ), ie the cosine of the angles ϕ _x , ϕ _y and ϕ _z between a target direction (R) and the axes (x ′, y ′, z ′) of an earth-fixed Cartesian coordinate system (x ′, y ′, z ′) , the z ′ axis being vertical and the x ′ - and y ′ - Axes are horizontal,
• (d) first computer means ( 30 ), which are acted upon by the pressure deviation signals and are set up to form a time interval signal from the time course up to the first zero crossing, which represents the time interval T between the first and second zero crossing of the pressure deviation signal ( Δ p) ,
• (e) second computer means ( 58, 60, 70, 72 ), which are acted upon and set up by the direction cosine signals and a depth signal representing the depth (H) of the device ( 18 ) below the water surface ( 16 ), and coordinate signals therefrom (x _m , y _m ) , which represent the horizontal coordinates x ′, y ′ of the ship in said earth-fixed coordinate system,
• (f) third computer means ( 78, 88 ), which are acted upon by the coordinate signals (x _m , y _m ) and are set up to form a speed signal representing the speed U of the ship, and
• (g) a multiplier circuit ( 92 ) which is acted upon by the outputs of the first and third computer means and which is set up to generate a length signal (L) which represents the product of the time interval signal T and the speed signal U , this length signal being proportional to the length of the ship.

4. Apparatus according to claim 3, characterized in that the filter arrangement ( 24 ) contains a filter for generating a signal representing the mean value () of the water pressure, which acts on the second computer means with a factor (k) as a depth signal. 5. Apparatus according to claim 4, characterized in that the second computer means two quotient formers ( 58, 60 ) for forming quotient signals, which are the quotients of the two direction cosines cos ϕ _x and cos ϕ _y relating to the horizontal coordinate axes to the direction cosine relating to the vertical axis, and also have two multiplier circuits ( 70, 72 ) by means of which the coordinate signals as a product of one of the quotient signals and the depth signal (H) can be generated. 6. Apparatus according to claim 5, characterized in that the third computer means contain a Kalman filter ( 78 ). 7. Apparatus according to claim 5, characterized in that the third computer means one channel each (106, 108) with a Entrance (110) for one of the said coordinate signals and an exit (80) for a calculated coordinate signal ( _s , _s ) exhibit, that each channel ( 106, 108 ) contains a first and a second integration stage ( 112, 114 ), that upon receipt of the first integration level (112) each channel (106, 108) the difference of the associated Coordinate signal(x _m ,y _m ) and the associated calculated Coordinate signal( _s , _s ) with a changeable first factor(k₁) is activated, that the sum of the output of the first integration stage ( 112 ) and said difference, which is applied with a variable second factor (k ₂), is applied to the input of the second integration stage ( 114 ), that the output of the second integration stage (114) on the said output (80 respectively.82) for the calculated coordinate signal ( _s , _s ) is switched and that speed component signals( _s , _s ) to the Outputs of the first integration levels (112) tapped and on a circuit (88) to form the root of the Sum of squares of the speed component signals applied are, the output signal thus obtained this circuit (88) said speed signal (U) forms.   8. Device according to one of claims 3 to 7, characterized in that the transmitter arrangement contains the following components:

• (a) a measuring sensor ( 20 ) for the direction cosine in a coordinate system fixed to the device,
• (b) position reference means ( 42 ) for generating position reference signals, which are the angles ( ε ₁, ε ₂, ε ₃) between corresponding coordinate axes of the coordinate system fixed to the device (x ′ ′, y ′ ′, z ′ ′) and the earth-fixed coordinate system (x ′, y ′, z ′) reproduced, and
• (c) a coordinate transformation circuit ( 50 ) to which the position reference signals and the direction cosine signals of the transmitter ( 20 ) are connected and which is set up to form the direction cosine signals relating to the earth-fixed coordinate system.

9. Device according to one of claims 3 to 8, characterized in that the first computer means ( 30 ) means ( 124, 126, 122 ) for determining the maximum Δ p _{max of} the pressure deviation signal and means ( 124, 136, 134 ) for determining the Incline of the course of this pressure deviation signal ( Δ p) at the time (t ₀) from its zero crossing and a quotient ( 36 ) to form the quotient of said maximum ( Δ p _max ) and said slope (S) . 10. Device according to one of claims 3 to 9, characterized by a comparison stage ( 96 ) for comparing the length signal (L) and a reference value (L ₀) and for triggering a control command if the length signal (L) is greater or not less than that Reference value (L ₀) is. 11. Apparatus according to claim 10, characterized in that the Control command represents the ignition release for a sea mine.