GB2250719A

GB2250719A - Torpedo guidance systems

Info

Publication number: GB2250719A
Application number: GB8603971A
Authority: GB
Inventors: Uwe Krogmann
Original assignee: Bodenseewerk Geratetechnik GmbH
Current assignee: Bodenseewerk Geratetechnik GmbH
Priority date: 1985-02-26
Filing date: 1986-02-18
Publication date: 1992-06-17
Anticipated expiration: 2006-02-18
Also published as: DE3506683C1; GB2250719B; FR2673460B1; NO860707L; FR2673460A1; NL8600435A

Description

Guidance and Stabilizing Device for Torpedos Technical Field The invention relates to a guidance and stabilizing device for torpedos.

Background Art German patent 2,922,415 describes a navigational instrument for land vehicles, wherein heading and attitude signals are derived from angular rate signals which are provided by vehicle-fixed inertial sensor means. A speed sensor provides a speed signal. From the heading signal and the attitude signals, signals are obtained which represent the components of the vehicle speed in an earth-fixed coordinate system. A position computer provides the position of the vehicle by integration of the speed components.

In order to aid the heading angle, vehicle fixed magnetic sensors are provided which respond to components of the magnetic field of the earth in a vehicle-fixed coordinate system. A transformation circuit, to which attitude informations in the form of elements of the coordinate transformation matrix are applied, provides from the signals of the magnetic sensors a heading angle signal derived from the magnetic field of the earth.

This hedging angle signal together with angular rate signals and attitude informations again in the form of elements of the coordinate transformation -matrix is applied to estimator means, which provide optimal estimated values of the heading drift and the trigonometric functions of the heading angle.

These functions serve to form the components of the vehicle speed in an earth-fixed coordinate system for the calculation of position.

The attitude informations are obtained in a filter circuit from the angular rate signals provided by the inertial sensors as well as from the signals of two vehicle-fixed accelerometers responding to longitudinal and transverse accelerations and of the speed sensor. The angular rates in linear combination with matrix elements of the coordinate transformation matrix provides the time derivatives of such matrix elements. The matrix elements required for the linear combination are, in turn, obtained by integration of these time derivatives with respect to time.The attitude information thus obtained is aided by comparison of the "inertial speed" obtained by integration of the longitudinal acceleration with the speed provided by the speed sensor, the longitudinal acceleration being derived from the signal of the accelerometer responding to the longitudinal acceleration, corrected for an amount which is formed by one of the matrix elements and the acceleration due to gravity. This latter amount is equal to the component of the acceleration due to gravity acting in longitudinal direction. A corresponding procedure is applied to the transverse axis of the vehicle. Thus the filter provides attitude informations and an "inertial" speed signal which is obtained by integration of the longitudinal acceleration.

A filter to which the "inertial" speed signals and the speed signal from the speed sensor are applied, provides an estimated value of the error of the speed sensor. The signal of the speed sensor is corrected for this estimated value.

In German patent 2,922,415 the inertial sensors are a two-axis rate gyro, the spin axis of which, with the mode of operation as heading-attitude reference unit, is parallel to the longitudinal axis of the vehicle, as well as an angular acceleration meter 'responding to angular accelerations about the longitudinal axis of the vehicle. For the initialisation, i.e. for the determination of North direction prior to starting on the mission, the spin axis is rotated towards the vehicle vertical axis whereby the rate gyro responds to components of the angular rate of the earth.

A similar arrangement is shown in German patent application 2,922,414.

German patent application 1,549,614 describes a guidance computer for an unmanned missile provided with an inertial navigation system and an autopilot and steered along a preselected, programmed path.

Such a guidance computer, in particular, is intended for guidance of a reconaissance missile equipped with an aerial camera along a flight path composed of polygonal lines. A memory for the coordinates of starting point and end point of a straight section of the path in an earth-fixed coordinate system is provided. A four-terminal coordinate transformer (resolver) is rotatable about the desired heading angle by a servomotor controlled by the memory. The actual coordinates of the missile in an earth-fixed coordinate system from the inertial navigation system and the coordinates of the end point from the memory are applied to this resolver. Then the outputs of the resolver provide the 1 ateral deviation from the desired path and the distance from the end point.

The deviation signal from the resolver is applied to the outopilot as steering signal. Thus the missile is held on the desired path.

The memory contains all corner point coordinates of the polygonal path to be flown along. Starting point and end point of each path section determine also the respective desired heading angle of this path section. Correspondingly the servomotor is controlled by servomotor control means as a function of two pairs of consecutive corner point coordinates which determine the starting point and the end point of a path section. When the respective end point has been reached, the servomotor control means are switched automatically to the coordinates of the starting and end points of the next following path section.

A similar guidance computer is shown in German patent application 1,774,129.

Furthermore it is known to locate the position of a target object, for example of a ship, acoustically.

To this end sonic pulses are emitted which are reflected by the target object. By evaluating the reflected sound waves with regard to propagation time and direction, the distance and direction of the target object can be detected.

When using conventional torpedos, a submarine has to approach rather closely a target object to be attacked. Then the target object is observed through the periscope. In accordance with this observation a lead angle is fixed which takes the speed of the target object into account. With this method the submarine itself is endangered to a large degree. Also the risk of failures is relatively high.

Disclosure of Invention It is an object of the invention to provide a guidance and stabilizing device for torpedos which allows a torpedo to be launched from a large distance - as compared with the prior art - and which reduces the danger for the torpedo carrier, for example a submarine, itself.

According to the invention this object is achieved by (a) autonomous initial phase steering means for guiding the torpedo to near a target ob-ject and (b) end phase steering means responding to the target object for homing the torpedo to the target object.

Thereby it becomes possible to launch the torpedo at a large distance from the target object. The torpedo is guided to near the target object by the initial phase steering means, without the torpedo carrier itself having to advance into dangerous proximity of the target object. Near the target object the end phase steering means responding to the target object and preferably equipped with sonar undertake to guide the torpedo to the target.

The initial phase steering means may also be used to select one out of a plurality of target objects, for example a certain ship.

An advantageous embodiment consists in that the initial phase steering means comprise (a) a memory for storing trajectory points and (b) guidance means for guiding the torpedo along a polygonal path defined by the stored trajectory points.

In this way the torpedo can be guided along a path on which it avoids electronic countermeasures (ECM) of the target object.

Modifications of the invention are subject matter of the further sub-claims.

An embodiment of the invention is described in greater detail hereinbelow with reference to the accompanying drawings: Brief Description of Drawings Fig. 1 shows a block diagram of the total system of a guidance and stabilizing device for torpedos.

Fig. 2 shows a block diagram of the system portion of "navigation".

Fig. 3 shows a block diagram of the stabilizing system.

Fig. 4 is a schematic illustration of the guidance means by which the torpedo is guided along a polygonal path.

Fig. 5 is a schematic illustration and shows the geometry of the guidance of the torpedo along a selected path section by the guidance means.

Fig. 6 illustrates the inertial sensor means for the navigation.

Fig. 7 illustrates a filter for an attitude parameter, used in the system portion of "navigation".

Fig. 8 shows a filter, used in the system portion of "navigation", for providing an optimal estimated value of the longitudinal speed of the torpedo.

Fig. 9 is a schematic illustration .and shows the geometry of the acoustic locating of a target object (ship) by the end phase steering means (sonar).

Fig. 10 shows an arrangement for providing signals for the correction of the guidance of the torpedo during the initial phase steering by short-time acoustic locating of the target object.

Description of a Preferred Embodiment The torpedo contains inertial sensor means 10 (Fig.l), which are arranged 'torpedo-fixed and provide signals p.q.r indicative of the angular rates about three torpedo-fixed axes. Magnetic field sensors 12 are also arranged torpedo-fixed and provide signals indicative of the components Gx ,G y ,G of the magnetic field of the earth in the direction of the said axes. Eventually accelerometer means 16 are provided which respond to accelerations AXF in the direction of the longitudinal axis xF of the torpedo and A F in the y direction of the transverse axis of the torpedo.

The axes mentioned are the longitudinal axis xF of the torpedo, the transverse axis yF of the torpedo and the vertical axis F of the torpedo, which are all mutually orthogonal. A depth sensor 18 provides the depth of the torpedo in the water. A speed sensor 20 provides a speed signal proportional to the torpedo speed vFx in the direction of the longitudinal axis of the torpedo, this signal being derived from the rotary speed of the propeller. The signals provided by these sensors are applied to a navigational computer 22.The navigational computer 22 provides the following output signals: x R a first position coordinate in an earth-fixed coordinate system, y R a second position coordinate in the earth-fixed coordinate system, R v x the component of the speed of the torpedo in the direction of the coordinate axis of the first position coordinate, R v y the component of the speed of the torpedo in the direction of the coordinate axis of the second position coordinate, + the heading angle of the torpedo and H the depth of the torpedo.

These signals are applied to a guidance computer 24. The guidance computer 24 provides the following output signals: ss H the depth deviation from a predetermined desired depth H 1 H , L the lateral deviation from a predetermined desired path, L the time derivative of this lateral deviation, and the heading error.

Furthermore the guidance computer 24, at an output 26 thereof provides a signal which causes changing-over from the autonomous initial phase steering to the end phase steering. These signals are applied to the stabilizing system 28 of the torpedo. Furthermore this stabilizing system 28 receives the following signals directly from the navigational computer 22: the time derivative of the heading angle and C31 ,C32 attitude parameters in the form of matrix elements of the transformation matrix for a coordinate transformation from a torpedo-fixed coordi nat,e system into an earth-fixed coordinate system, and C31 ,C32 the time derivations of these attitude parameters.

Eventually the stabilizing system 28 receives also the angular rates q and r from the inertial sensor means. The stabilizing system 28, at outputs 30 and 32, provides output signals for actuators 34 and 36, respectively, for the actuation of the elevator and rudder, respectively.

Fig.2 shows the setup of the navigational computer 22, i.e. of the system portion of "navigation".

Here the inertial sensor means are illustrated as three sensors 38,40,42. These sensors may be three rate gyros, the input axes of which are mutually orthogonal. However the sensors may also comprise an arrangement of the type shown in Fig.5, which will be described in greater detail hereinbelow.

The accelerometer means 16 are illustrated as two accelerometers 44,46 the input axes of which extend in the directions of the longitudinal axis x F of the torpedo and the transverse axis yF of the torpedo respectively.

The signals # F = p, # F = q and # F = r are, on one x y z hand, applied to a circuit arrangement 48 which from (1) C 31 = C 32 # F - C 33 # F z y (2) C 32 = C 33 #F - C 31 # F x z provides time derivative of the attitude parameters 31 and C 32 These time derivatives C31 and C32 are applied to a C 31-filter 50 and a C32 -filter 52 of identical construction. Furthermore the C -filter 50 receives an acceleration signal AF from the accelerometer 44 and a speed signal #x from the speed sensor 20. The C 32 -filter receives an acceleration signal AF from the accelerometer 46.

y The construction of the filters 50 and 52 is described in greater detail hereinbelow with reference to Fig.6. The filter 50 provides an A optimal estimated value C 31 of the attitude parameter C31 and an "inertial" speed signal #IX, i.e. a speed signal derived from the acceleration measurement. Correspondingly the filter 52 provides an optimal estimated value C 32 of the attitude parameter C 32 and an "inertial" transverse speed signal vF .The estimated values C and C32as well Iy A 31 32 as an estimated value C 33 derived therefrom are applied, in a manner not illustrated, to the circuit arrangement 48 and are linearly combined with the angular rates oF F and oF in x y z accordance with equations (1) and (2).

The inertial speed signals vF and v F from the Ix Iy filters 50 and 52, respectively, are applied to a vF -filter 54 together with the speed signal vxF F from the speed sensor. The v x -filter 54 provides an optimal estimated value OF of the torpedo speed in the longitudinal direction of the torpedo. The F -filter is of the type illustrated in Fig.7 and x will be described in detail hereinbelow.

The angular rate signal #Fx = p and #Fy = q together A A y with the estimated values C31and C32of the attitude parameters from filters 50 and 52, respectively, are applied to computer means 56 which provide a signal

which represents the time derivative of the heading angle. This signal + is integrated by an integrator 58 and provides an estimated value #I of the heading angle determined from the signals of the inertial sensor means 10.

The signals G GY ,G z from the magnetic sensors 12 are applied to computer means 60. The computer means 60 have stored therein the influences of soft iron effects and systematic sensor errors which are caused by constant addit-ive field components. The reading-in of these influences is indicated by the inputs 62 and 64, respectively. The influence of the soft iron effects is also dependent on heading and attitude. Therefore the estimated values "C31and C 32 of the attitude parameters are applied to the computer means 60 through inputs 66 and 68. Then the computer means provide a magnetic heading signal which represents a "magnetic heading" + M.

The magnetic heading signal is applied to a heading filter 70 together with the "inertial" heading signal +1 The heading filter 70 makes use of the fact that magnetic he hiding and inertial heading have different types of errors: The magnetic heading has a fixed declination but no drift. The inertial heading has no declination but has drift. An estimated value Dz of the drift of the inertial heading can be derived from these two heading signals by means of the heading filter.

A This estimated value D of the drift is superposed to the + -signal at a summation point 72 at the input of the integrator. Thus the time derivative of the heading angle is corrected for the drift, A whereby a drift-corrected estimated value ÇI of the heading angle is obtained.

The following signals are applied to transformation means 74: the estimated value of the "inertial" heading angle, A A C31,C32 the estimated values of the attitude parameters, vFx the estimated value of the speed in the direction of the longitudinal axis of the torpedo, and H the depth signal from the depth sensor 18.

The transformation means 74 provide the first and second position coordinates xR and y R respectively, in the earth-fixed coordinate system, the speed components vR and vR , the depth zR = H x y and the heading + . In addition, of course, p,q and r from the inertial sensor means 10 as well as C A . 31 and C32 from the filters 50 and 52, and C 31 and C32 from the circuit arrangement 48 are available. This corresponds to the outputs of the navigational computer 22 of Fig.l.

Fig.3 shows a block diagram of the stabilizing system 28 of Fig.l. The stabilizing system 28 stabilizes the torpedo in a predetermined attitude.

In addition it receives steering commands from the guidance means 24 by which the torpedo is kept on a predetermined path.

The stabilizing system 28 comprises means 76 for generating output signals in accordance with predetermined control laws to be explained hereinbelow. The output signal generating means 76 receive the following signals: the time derivative of the heading angle, q,r the angular rates about torpedo-fixed axes,

and

the time integrals of these angular rates, which time integrals are provided by integrating means 78, the pitch angle, which is obtained from the estimated angle of the A attitude parameter C31 through an arc sine function generator 80, the time derivative of the pitch angle {k , which is obtained by division of the time derivative of the attitude parameter C31 by cos this division being represented by block 82, the roll angle which is obtained from the estimated value of the attitude parameter C 32 by divison by cos # , represented by block 84, and through an arc sine function generator, the time derivative of the roll angle, which is obtained from the time derivatives C31 and C 32 of the attitude parameters by multiplying C by tanb , as represented by block 88, and by adding this product C31tanb to C 32 at a summing point 90, and eventually by dividing the sum by cos g , which is indicated by block 92. (Because of the roll stabilization cos ? can be assumed to be approximately "1".) Furthermore, the output signal generating means 76 receive from the guidance computer as. steering signals the heading error e , the lateral deviation L, the time derivative L of the lateral deviation, and the depth deviation A H. At inputs 94 and 96, the output signal generating means 76 receive steering commands for pitch and yaw movements from end phase steering means which are formed by an acoustic locating means.At an input 98, the output signal generating means 76 receive a change-over command from the guidance computer 24, this command initiating change-over from the initial phase steering to the end phase steering Output signals for the actuation of elevator and rudder appear at outputs 100 and 102 of the output signal generating means. The output signals are applied to servo amplifiers 104 and 106, respectively. Each of the servo amplifiers feeds an associated actuator 34 and 36, respectively, (see Fig.l) ) for the elevator and the rudder of the torpedo. There is a conventional position feedback from the actuators 34 and 36, respectively, to the inputs of the servoamplifiers 104 and 106, respectively.

Fig.4 illustrates schematically the mode of operation of the guidance computer 24. The guidance computer 24 is illustrated in Fig.4 with analog signal processing, because analog signal processing permits best to recognize the functions. However signal processing may also be made digitally in a manner readily apparent to a person skilled in the art.

Two potentiometers 112 and 114 having a plurality of taps serve as memory for the corner point coordinates xl .. x and y1 .yof a polygonal path 1 x1 .. x an along which the torpedo is to be guided. A third potentiometer 116 having a corresponding number of taps stores desired depths H1 .. H . Numeral 118 n designates a selector switch having six decks 118A,118B,118C,118D,118E and 118F. Each of the decks has n contacts corresponding to the number of the corner points of the polygonal path. The selector switch 118 is arranged to be advanced stepwise from the stationary contacts "1" to the stationary contacts "n". The taps of the potentiometer 112 are connected to one of the stationary contacts "l"..."n" each of the decks 118B and 118C.The movable contact arms of the decks 118E and 118C lag by one step relative to the contact arms of the remaining decks. The taps of the potentiometer 116 are connected to one of the stationary contacts "l"..."n" . . " n " each of the deck 118A. The stationary contacts "1"... "n" of the deck are connected to one contact of a contact pair 122.1...122.n each. The other contacts of these contact pairs 122.1..122.n are together connected to an output 124. The deck 118F has an additional stationary contact 126 following contact "n", which additional contact is connected with an output 130 through a relay contact 128. The operational voltage is applied to the movable contact arm of the deck 118F. The output 130 is connected with the input of the output signal generating means 76 (Fig.3).When the switch contacts "1" to "n" have been scanned consecutively, and the corner points of the polygonal path have been passed accordingly, the contact arm of deck 118F moves onto the stationary contact 126 and applies voltage to the output 130 whereby steering of the torpedo is changed over from the guidance computer 24 to the end phase steering means.

A plurality of resolves 132,134 and 136 and a synchro 138 are provided, the rotors of which are interconnected and are rotatable in unison by a servomotor 140. The movable contact arms of the decks 118B and 118C are connected to one input terminal each of a differential amplifier 142. The output of the differential amplifier 142 is connected to one input 144 of thte resolver 132. The movable contact arms of the decks 118D and 118E are connected to one input terminal each of a differential amplifier 146. The output of the differential amplifier 146 is connected to an input 148 of the resolver 132. The motor 140 is arranged to be energized by an output 150 of the resolver 132 through a servoamplifier.

Thus signals corresponding to Yi - 1 and x. -x; 1, respectively, are connected to the two inputs 144 and 148 of the resolver 132, xi ,yj being the end point and xi, yi-1 being the start point of the respective path section. If Y r | designates the angle of rotation of the rotor of the resolver 132, a signal (4) (x. - x.-1) sin Y - (Yj ~ Yj-l ) cos Y will appear at the output 150 of the resolver 132.

This signal energizes the servomotor 140. This servomotor 140 rotates the rotor of the resolver 132 until the signal becomes zero. This is the case when (5) tan r = Yj will Xj It will be noticed that the rotor of the resolver rotates to an angular position y which is equal to the desired heading of the respective path section.

Also the rotors of the resolvers 134 and 136 and of the synchro 138 are set to this angular position.

The voltage from the movable contact arm of the R deck 118D and the position coordiante x from the navigational computer 22 are applied to the two input terminals of a differential amplifier 154.

The output of the differential amplifier, which thus represents (xi xR), is applied to an input 156 of the resolver 134. The voltage from the movable contact arm of the deck 118B and the position coordinate yR from the navigational computer 22 are applied to the two input terminals of a differential amplifier 158. The output of the differential amplifier 158, which thus represents (y.yR), is applied to an input 160 of the resolver 134. A signal (6) D = (x. - x R ) cos Y - (y. - y) sin γ 1 1 appears at an output 162 of the resolver 134.

As can be verified from Fig.5 this signal represents the distance - measured in the direction of the path section - of the torpedo from the end point (xi,Yi) of the respective path section. This signal D is applied to a zero indicator 164 which supplies a switching pulse to the relay 120, when the signal D passes through zero. This relay 120 advances the selector switch 118 by one step.

Thereby guidance of the torpedo along the next stored path section is initiated. The switching pulse also energizes a relay 166 which closes the relay contact 128.

A signal (7) L = (x - x R ) sin γ - (y; y R ) cos r appears at an output 168 of the resolver 134. as can be verified from Fig.5, this signal represents the lateral deviation of the torpedo from the predetermined path section. It sis s applied to the stabilizing system 28 as steering signal.

R The speed component v x from the navigational computer 22 is applied to an input 170 of the R resolver 136. The speed component vy is applied to another input 172. Then the time derivative L of the lateral deviation, namely the transverse speed, and the time derivative 6 of the distance from the end point, namely the the speed component in the direction of the path section are obtained at the outputs 174 and 176, respectively, of the resolver 136. The latter signal can be used to control the speed of the torpedo and/or to control the change-over from one path section to the next.

The stator of the synchro 138 is supplied with a three-phase a.c. current the phase of which represents the azimuth angle + . Then, because of the rotation of its rotor to the desired heading positionrthe synchro 138 will provide the heading error r The voltage from the movable contact arm of the deck 118A and the depth signal H from the depth sensor 18 are applied to the two input terminals of a differential amplifier 178. Then the depth deviation AH will appear at the output of the differential amplifier 178.

As has been mentioned before, the operational voltage is applied to the contact arm of deck 118F and thus is applied to one contact of the contact pairs 122.1...122 n in each swtch position. The contacts of individual contact pairs 122.1...122.n can be interconnected by bridges 180. Then a signal at the output 124 is provided on the respective path section and causes the end phase steering means to be switched on for a short period.

In Fig.6, an example of the construction of the inertial sensor means 10 is illustrated. The inertial sensor means 10 comprise a two-axis, electrically restrained rate gyro 182, the spin axis of which extends in the direction of the longitudinal axis xF of the torpedo and the two input axes of which extend parallel to the transverse axis yF and the vertical axis zF respectively, of the torpedo. This rate gyro 182 F F provides the angular rates yF and o F . An angular acceleration meter 184 with an integrator 186 connected to the output thereof is provided for F measuring the angular rate o x about the F longitudinal axis x of the torpedo.

Fig.7 shows the structure of the C31 -filter 50 of Fig.2.

The acceleration signal AxF from the accelerometer 44 as well as a first and a second correction signal illustrated by the arrows 190 and 192, respectively, are superposed in a summing. point 118. The sum signal thus obtained is integrated, as indicated by block 194, whereby an "inertial" speed F signal vIxis obtained. This intertial speed signal F Ix is output, as can be seen from Fig.2.

speed the inertial speed signal v Furthermore, the inertial speed signal F F1x is compared to the speed signal ,Vx from the speed sensor 20 at a summing point lS6. The difference obtained is, on one hand, multiplied by a time-dependent factor Kv , illustrated by block 198, and thus forms the first correction signal illustrated by arrow 190 and applied to summing point 188. On the other hand the difference is multiplied by a time-dependent factor Kc illustrated by block 200. The difference thus multiplied is added, at a summing point 202, to a signal C31 which is provided by the circuit arrangement 48 in accordance with equation (1). The signal thus obtained at the summing point 202 is integrated with respect to time, as illustrated by block 204. This integration provides an estimated value C31 of the attitude parameter C 31 . This estimated attitude parameter C31 is multiplied by the acceleration due to gravity g, as illustrated by block 206. This provides the second correction signal at the summing point 188, which signal is illustrated by the arrow 192.

Fig.8 illustrates the structure of the V Fx -filter 54 in Fig.2.

The difference of the inertial speed signal vFIx F for the longitudinal axis xF of the torpedo and of the speed signal vF from the speed sensor 20 is formed at a summing point 208. The inertial speed signal F is obtained from the C 31 -filter 50.

Correspondingly the C -filter 52 provides an inertial speed signal v Iy . This speed signal vF can be compared with a transverse speed signal at a summing point 210, said latter signal being assumed, however, to be zero in the present case.

The signals from the summing points 208 and 210 are applied to a filter 212 which prbvides an estimated value of the error A GX of the speed signal v . The measured speed value is corrected for this optimally estimated value at a summing point 214.

The vFx -filter 212 may be substantially of the type illustrated in Fig.6 of German patent 2,922,415.

Fig.9 is a schematic illustration and shows the geometry of the acoustic locating of a ship 216 by means of a sonar provided on the torpedo 218. The torpedo-fixed coordinate system is designated by F F d F x ,y and z . The torpedo is at a depth below the surface of the sea 220. A coordinate system the coordinate origin 0' of which is located on the surface of the sea vertically above the torpedo and the coordinate axes of which extend parallel to those of the torpedo-fixed coordinate system is designated by x',y' and z'. The sonar "sees" or "hears" the ship 216 at an azimuth angle A relative to the y F -axis and at an elevation angle E F F relative to the x -y -plane. The distance of the ship 216 from the torpedo is R. Numeral 222 designates the path of the ship 216.

During the end phase steering, steering commands are generated from the azimuth and elevation signals and are applied to the inputs 94 and 96 of the output signal generating means.

The acoustic locating means, i.e. the sonar, are switched on for a short period by a signal at the output 124 (Fig.4) during the operation of the initial phase steering means. The azimuth and elevation signals A and E then obtained are applied to coordinate transformation means 224, as shown in Fig.10. The coordinate transformation means 224 have position and attitude signals applied thereto (in a manner not shown) and provide position signals indicative of the position of the target object, i.e. of the ship, in an earth-fixed coordinate system. The position signals are applied to an optimal filter 226. The optimal filter is a second order optimal filter with a model of the kinematics of the movements of the ship.At the input of the optimal filter estimated values I:s and ys of the position coordinates of the ship are subtracted, at summing points 228,230, from the position coordinates x s ,y s of the ship derived from the azimuth and elevation signals. The optimal filter contains a model of the kinematics of the movement of the ship.Apart from the estimated A A values of the position coordinates x s, y s, it provides also the time derivations thereof x5 ,y5 These estimated values xs ,ys ,x s and y s are applied to a computer for calculating the shortest distance R mi n between torpedo and target object 216 which can be achieved by means of the initial phase steering means, the time T* required, until this distance will be reached, and the heading of the target object 216. The initial phase steering means are arranged to be corrected by the output signals of this computer 232.

The described guidance and stabilizing device for torpedos operates as follows: The navigational computer 22 provides position and attitude signals of the torpedo from the signals of the sensors 10,12,16,18 and 20. During the initial phase the guidance computer 24 gives a polygonal path determined by its corner points and provides steering signals in the form of the lateral deviation L and its time derivative L and the heading error e from the position signals and the given path coordinates.The output signal generating means 76 provide output signals from the steering signals, these output signals having the form: roll output signal: Ux = A1 cp + A29 pitch output signal u = Blå H + B 2 + B3 yaw output signal: Uz = Cl . E + C2 . ç + C3 L + C4 L There is stabilization about the roll axis, whereby the transverse axis of the torpedo is always kept horizontal. When the depth deviation A H = 0, the torpedo is also stabilized about its pitch axis.

Its longitudinal axis is kept horizontal. A depth deviation A H causes inclination of the torpedo in a sense to correct this depth deviation. The steering signals L,L and a enter into the yaw signal Uz and cause a corresponding change of the heading +, in oder to correct for the lateral deviation or heading error.

The path sections are given by the stored corner points. When the distance D of the torpedo from the respective end point becomes zero, the selector switch 118 is advanced by one step and thus the next path section is given. At the end of the path given by the initial phase steering means output 130 (Fig.4) causes change-over to the end phase steering means, i.e. the sonar.

In the end phase the output signal generating means 76 provide the following output signals for stabilization: roll output signal: pitch output signal: yaw output signal:

These stabilizing output signals are aided by steering commands from the end phase steering means. The roll output signal is stabilized as a function of the roll angle g . This is important, as an unambiguous roll attitude of the torpedo is required for the unambiguity of the azimuth and elevation signals of the sonar. The stabilization about the pitch and yaw axes is effected by means of the angular rate signals q,r and the time integrals thereof.

Navigation is effected autonomously after the method of dead reckoning making use of angular rate sensors 10, of accelerometers 16 and of a speed sensor 20 responding to the rotary speed of the propeller. The signals are combined in optimal filters such that they aid each other. Attitude informations result from the angular rates aided by the signals of the accelerometers, which are exposed to acceleration due to gravity, if they are not arranged horizontally. Discrimination between acceleration due to gravity and Newtonian acceleration, in turn, is permitted by comparison of the "inertial" - speed signal obtained by integration of the acceleration with the signal from the speed sensor. Thus the signal from the speed sensor aids the attitude angles. Comparison of the inertial speed signal with the signal of the speed sensor permits estimating an error of the latter signal and to correct this signal accordingly. The inertially measured heading is aided by a magnetic heading derived from the magnetic field of the earth.

Claims

1. Guidance and stabilizing device for torpedos, characterized by (a) autonomous initial phase steering means for guiding the torpedo to near a target object and (b) end phase steering means responding to the target object for homing the torpedo to the target object.

2. Device as claimed in claim 1, characterized in that the initial phase steering means comprise (a) a memory (112,114) for storing trajectory points and (b) guidance means for guiding the torpedo along a polygonal path path defined by the stored trajectory points.

3. Device as claimed in claim 2, characterized in that the guidance means comprise (a) inertial sensor means (10) for determining the heading and attitude of the torpedo, (b) speed sensor means (20) for determining the speed of the torpedo, and (c) position computer means (74) to which the signals from the inertial sensor means (10) and the signals from the speed sensor means are applied and which provide therefrom position signals after the method of dead reckoning.

4. Device as claimed in claim 3, characterized in that the inertial sensor means (10) are arranged in strapdown configuration.

5. Device as claimed in claim 4, characterized in that the inertial sensor means (10) are aided by magnetic sensors (12) which respond to the magnetic field of the earth.

6. Device as claimed in claim 3, characterized in that the speed sensor means comprise (a) means (20) for providing a signal proportinal to the rotary speed of the driving propeller, said signal representing a first speed signal, (b) an accelerometer (16) responding to the longitudinal acceleration of the torpedo to provide a longitudinal acceleration signal, (c) integrator means for integration of the longitudinal acceleration signal to provide an inertial speed signal, and (d) a Kalman filter (54) to which the speed signal derived from the rotary speed and the inertial signal are applied and which provides an estimated value of speed which is optimal taking into account the speed signal derived from the rotary speed and the inertial signal, and which is applied to the position computer means.

7. Device as claimed in claim 1, characterized in that the end phase steering means responding to the target object (216) comprise an acoustic locating device (for example sonar), which provide azimuth and elevation of the target object in a torpedo-fixed coordinate system in the form of azimuth and elevation signals.

8. Device as claimed in claim 7, characterized in that (a) the acoustic locating device is arranged to be switched on for a short time during operation of the initial phase steering means, (b) the azimuth and elevation signals obtained thereby are applied to coordinate transformation means , which have position and attitude signals applied thereto and provide position signals indicative of the position of the target object ; -. in an earth-fixed coordinate system, (c) the position signals are applied to an optimal filter which is- designed as a model of the kinematics of the movement of the target object and which provides estimated values of the position coordinates and the time derivatives thereof in the earth-fixed coordinate system, (d) the said estimated values are applied to a computer for computing the shortest distance between torpedo and target object to be achieved by the initial phase steering means and/or the time required to reach this distance and/or the heading of the target object, and (e) the initial phase steering means are arranged to be corrected by output signals from this computer in a sense to improve the approach to the target object

8. Device as claimed in claim 7, characterized in that (a) the acoustic locating device is arranged to be switched on for a short time during operation of the initial phase steering means, (b) the azimuth and elevation signals obtained thereby are applied to coordinate transformation means (224), which have position and attitude signals applied therto and provide position signals indicative of the position of the target object (216) in an earth-fixed coordinate system, (c) the position signals are applied to an optimal filter (226) which is designed as a model of the kinematics of the movement of the target objects and which provides estimated values of the position coordinates and the time derivatives thereof in the earth-fixed coordinate system, (d) the said estimated values are applied to a computer (232) for computing the shortest distance between torpedo and target object to be achieved by the initial phase steering means and/or the time required to reach this distance and/or the heading of the target object, and (e) the initial phase steering means are arranged to be corrected by output signals from this computer (232) in a sense to improve the approach to the target object (216).

Amendments to the claims have been filed as follows

1. Guidance and stabilizing device for torpedos, comprising in combination (a) autonomous initial phase steering means including means for storing a selected position near a target object and autonomous navigation means for steering the torpedo to said position, and (b) end phase steering means responding to the target object for homing the torpedo to the target object, and means for activating said end phase steering means when the torpedo has reached said selected position.

2. Device as claimed in claim 1, characterized in that the initial phase steering means comprise (a) a memory for storing trajectory points, and (b) guidance means for guiding the torpedo along a polygonal path defined by the stored trajectory points.

3. Device as claimed in claim 2, characterized in that the guidance means comprise (a) inertial sensor means for determining the heading and attitude of the torpedo, (b) speed sensor means for detennining the speed of the torpedo, and ~~~~~~~~ (c) position computer means to which the signals from the inertial sensor means and the signals from the speed sensor means are applied and which provide therefrom position signals after the method of dead reckoning.

4. Device as claimed in claim 3, characterized in that the inertial sensor means are arranged in strapdown configuration.

5. Device as claimed in claim 4, characterized in that the inertial sensor means are aided by magnetic sensors which respond to the magnetic field of the earth.

6. Device as claimed in claim 3, characterized in that the speed sensor means comprise (a) means for providing a signal proportional to the rotary speed of the driving propeller, said signal representing a first speed signal, -(b) an accelerometer responding to the longitudinal acceleration of the torpedo to provide a longitudinal acceleration signal, (c) integrator means for integration of the longitudinal acceleration signal to provide an inertial speed signal, and (d) a Kalman filter to which the speed signal derived from the rotary speed and the inertial speed signal are applied and which provides an estimated value of speed which is optimal taking into account the speed signal derived from the rotary speed and the inertial speed signal, and which is applied to the position computer means 7.Device as claimed in claim 1, characterized in that the end phase steering means responding to the target object comprise an acoustic locating device (for example a sonar), which provides azimuth and elevation of the target object in a torpedo-fixed coordinate system in the form of azimuth and elevation signals.