US3802365A

US3802365A - Vehicular control system

Info

Publication number: US3802365A
Application number: US00217399A
Authority: US
Inventors: F Reeser
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1972-01-12
Filing date: 1972-01-12
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09

Abstract

A depth responsive override system for correcting torpedo command signals directing the torpedo beyond a preselected depth, including a depth sensor and an adjustable depth signal source combined in a first differential amplifier to produce a difference signal indicative of the difference of the actual depth minus the preselected depth. A function generator is connected to receive the depth difference signal and the torpedo command signal for producing an override output signal during the times when the pitch command signal is greater than the difference signal. A second differential amplifier is connected to receive the pitch command signal and the function generator output signal for producing an output signal to control the torpedo elevators.

Description

United States Patent Reeser Apr. 9, 1974 VEHICULAR CONTROL SYSTEM Primary ExaminerSarnuel Feinberg Assistant ExaminerThomas H. Webb [75] Inventor. Floyd H. Reeser, Centre Hall, Pa. Attorney Agent, or Firm R S sciascia; Henry Ham [73] Assignee: The United States of America as sen; l. M. Bak-Boychuk represented by the Secretary of the Navy, Washington, DC. [57] ABSTRACT [22] Filed: Jan. 12, 1972 A depth responsive override system for correcting torpedo command signals directing the torpedo beyond a 1 P" N04 2172399 preselected depth, including a depth sensor and an adjustable depth signal source combined in a first differ- [521 US. Cl. 114/25, 114/23 emial amplifier to Preduee a difference Signal indica- 5 Int. C| F41g 7 04 421;, 19 04 42 19/01 tive of the difference of the actual depth minus the [58] Field of Search 114/23, 24, 25; 244/314, preselected p A function generator is eermeeted 244/315, 3.16 3 17 to receive the depth difference signal and the torpedo command signal for producing an override output sig- 5 1 References Ci nal during the times when the pitch command signal is UNITED STATES PATENTS greater than the difference signal. A second differential amplifier is connected to receive the pitch comg g: mand signal and the function generator output signal for producing an output signal to control the torpedo elevators.

8 Claims, 3 Drawing Figures RATE 3| GYRO 32 POSITION GYRO MENTEBAPR 9 I974 8 If ow 2 i o 6 b wm VEll-IICULAR CONTROL SYSTEM STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates to override control systems, and more particularly to depth limiting control systems for underwater vehicles.

Generally in controlled underwater vehicles, and in particular in vehicles which are controlled to home in on a particular target, such as homing torpedoes, the possibility of encountering false signals which would direct the torpedo below a safe depth or which would drive the torpedo to broach the surface of the ocean is always encountered and various techniques have been devised in the prior art to preclude following such signals. Such techniques typically were either highly complex processing systems for distinguishing false from real signals or more simple depth limit controls which override the homing commands and return the torpedo to a predetermined depth. Of those techniques the latter is generally preferred since it involves minimal components, is low in cost and is relatively reliable. In the past, depth override control of the latter type was typically accomplished by disabling the homing signal and substituting therefor a hard-over signal to drive the torpedo back into a safe depth limit. This type of hard- I over control, although relatively simple, is characteristically not efficient since, as soon as the torpedo is within the depth constraint, the homing signal is reactivated and the torpedo is driven back towards the limit. Accordingly, large amounts of propulsive energy are expended in hard-over maneuvers, shortening the effective range of the torpedo. Furthermore, the most typical false signals are signals reflected either from the ocean bottom, from thermal strata within the ocean, or from the ocean surface. Characteristically such signals are laterally accurate and the lateral controls of the torpedo can be maintained bringing the torpedo to the vicinity of the target where the probability of false signals is low. Thus, if the torpedo is guided by hard-over signals in the vertical plane the periodic attitudes of the torpedo often exceed the limits of the lateral sensors with the possibility of complete loss of the lateral signal. Furthermore, such large oscillations consume propellant, greatly reducing the range and the chase speed of the torpedo.

SUMMARY OF THE INVENTION Accordingly, it is the general purpose and object of the present invention to provide a vehicular control system with override control in which the vertical and override control paramenters are combined in a predetermined relationship as a function of elevation during transition. Other objects of the invention are to provide an override control system which will proportionally flare-in to a limit depth without large overshoots.

Briefly these and other objects are provided within the present invention by subtracting a measured depth signal from a preselected limit depth signal and subtracting this difference signal from the pitch command signals of a torpedo. The output signal, corresponding to the difference between the pitch command signal and the depth difference signal, is fed to a function generator or a nonlinear amplifier shaped to pass negative signals only where the output of the nonlinear amplifier is subtracted from the commanded signal going to the control surfaces of the torpedo. In this manner the nonlinear amplifier proportionally augments or partially cancels those pitch command signals that are directing the torpedo to the depth limit, the augmentation signal being functionally dependent on the distance to the limit. As the submarine approaches the depth, limit signals directing further motion of the submarine towards the limit are reduced by the difference between the commanded signal and the depth difference signal while signals directed away from the depth limit are passed unaugmented by the function generator. Thus continuous control can be achieved without disrupting the homing pattern but which in an asymptotic manner approach a preselected depth limit.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of a homing control system constructed according to the present invention;

FIG. 2 is an illustration of a homing path of a torpedo towards a target according to the present invention; and

FIG. 3 graphically illustrates the response function of a typical function generator of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 a torpedo homing system receives incoming signals A, which can be either echo signals from a target such as sonar signals or signals originated by the target, at a pair of hydrophones 11 vertically displaced relative to each other in the pitch plane of the torpedo. The output signals of hydrophones 11 are combined in a conventional resolver 12 which, by wellknown means, produces an output signal 0 indicative of the phase angle 1; relative to the longitudinal axis A thereof. Signal 0,. is connected to a conventional amplifier 14 which raises the signal by a predetermined gain K as required by the control constraints of the torpedo homing system. Also mounted on the torpedo is a depth sensor 15, which could be any kind known in the art, such as a strain gage depth measurement means or sensor, producing an output signal 2,, corresponding to the submerged depth thereof. Signal Z is fed to the positive side of a first differential amplifier 17 which also receives a fixed signal Z, generated by a manually adjustable signal generator 16 preset by conventional means prior to launch of the torpedo. Amplifier 17 produces an output signal Z, Z, corresponding to the difference between the actual depth and the preselected depth limit. Furthermore amplifier 17 amplifies by a gain factor K the Z Z, signal difference, the output signal thereof being connected to a variable coefficient 19. The output signal of amplifier 14 is connected to a variable coefficient l8 and at the same time to a second differential amplifier 25. The respective output signals of

coefficients

18 and 19 are subtracted in a third differential amplifier 20 the output thereof being connected to a function generator 21. Function generator 21 passes negative signals from amplifier 20 only according to a predetermined function as further described hereinbelow. Function generator 21 at the output thereof produces a corrective signal 0 which, subtracted from the amplifier 14 output signal K O produces an output signal 6 out of amplifier connected to the input side of a servo amplifier 30. Servo amplifier is also connected to receive the output signals from a rate gyro 31 and a position gyro 32 comprising a conventional homing loop. The sum of the signals 0 6, and 6, are combined in amplifier 30 to produce a resulting output signal 6, which, in turn, drives a conventional servo motor connected to the pitch control surfaces or elevators 40, deflecting the elevators to a corresponding control angle 8.

FIG. 2 more clearly illustrates a specific case where the torpedo is homing in on a signal beam, reflected from below a safe depth signal Z originating at a virtual target T,. The true target T is in a safe operating depth, above depth corresponding to signal 2,, the direct signal therefrom being attenuated. Accordingly as the torpedo approaches the vertical location of the virtual target T, the commanded pitch signal 6, approaches 90 and the forward velocity degrades to a low value. Thus by canceling or overriding such pitch command signals a flared approach to depth 2, is described during which the lateral controls are operative. The homing path as described by depth signal Z, follows a typical oscillatory pattern of a second order system around the reflected signal A (from the virtual target T until such time when the signal difference 2,, Z, is less than the downward command signal 0,. When signal bl is greater than signal 2,, Z, the homing pattern flares in to a depth corresponding to signal Z Once the torpedo crosses the point of reflection or target T proceeding along the depth limit Z and maintaining lateral control, a direct signal from the target T is picked up and full control is resumed as long as it is away from the limit 2,.

As shown in FIG. 3 the gain function or output signal of function generator 21, corresponding to the vertical axis, follows a negative quadratic in the -V,-, quadrant where the smaller differences or values of -V,,, are passed at much lower gains proportionally than the higher differences. This particular gain function has been selected for purposes of illustration only and does not necessarily produce the most optimum results. This function assures a quicker response to pitch command signal 6, of the torpedo which would result in large overshoots of the limit 2,, the nonlinear character of the function generally corresponding to the nonlinear character of the motion.

The operation of the present invention will now be described with reference to FIGS. 1, 2 and 3. The homing signal A is received by sensors 1] and is converted to a pitch command signal 0,. by resolver 12. At the same time the depth sensor 15 registers a depth signal Z which is combined with a preselected signal Z, in amplifier 17 to produce an output signal K (Z,, 2,), where K is the amplifier gain. Signal 6,. is also amplified at a gain K, through amplifier 14, forming an output signal K,0 Amplifier l4 gain K is selected for homing accuracy and dynamics according to wellknown techniques in the art. Signals K6,. and K (Z,, 2,.) are respectively connected to variable dropping coefficients l8 and 19 which are preset to form an output signal V from amplifier 20 as follows:

(I) where P and P are the respective dropping values of coefficients l8 and 19. Thus, for all values of signal K,P 0 greater than signal K P (Z,, Z,,) a negative output signal V, is produced by amplifier 20. Signal V,-,, is passed to function generator 21 which produces an output signal ,u according to the following relationships and where the signal u is subtracted from signal K0,. in amplifier 25. Thus when signal (Z, Z approaches zero, or when the torpedo approaches the limit corresponding to signal Z signal p. approaches -(K,P,l9,.) canceling signal K 6 when l r 1E 9 0 Accordingly the depth limit 2, is approached asymptot ically limiting at an approach function Conversely for positive values of signal 6 the output of function generator 21 is zero and the signal K 0 is passed unaugmented by amplifier 25. The output signal 6 of amplifier 25 is combined in servo amplifier 30 with signals 9, and 5, corresponding to the outputs of a rate and position gyro, completing conventional stabilization loops as required. The specific values of gains K, and K are selected according to well-known techniques where the respective dropping values P and P are selected for optimum signal mixing in amplifier 20.

Some of the many advantages of the present invention should now be apparent in the light of the above teachings. As described the present invention provides continuous control towards the target which flares in with minimum overshoot, and therefore minimum expenditure of excess energy, to a preselected depth limit and continues along that depth limit until such time as a new signal from a target is picked up which will drive the torpedo back and away from the limit. Furthermore the override system is both adjustable in gain and in damping such that the most optimum energy curve can be picked for most torpedo configurations.

Obviously many modifications and variations of the present invention are possible in view of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A vehicular control system for controlling the vertical excursions of a vehicle comprising, in combination:

guidance means for producing a vertical command signal;

depth measurement means for producing an elevation signal indicative of the vertical displacement of the vehicle; signal generating means for producing a reference signal indicative of a preselected limit elevation;

first comparison means connected to receive the elevation signal and the reference signal for producing a first difference signal indicative of the difference therebetween;

second comparison means connected to receive the vertical command signal and the first difference signal for producing a second difference signal indicative of the difference therebetween; function generating means connected to receive the second difference signal for producing a corrective signal as a predetermined function of the second difference signal; stabilizing means for producing stability augmentation signals indicative of the angular rate and orientation of the vehicle; and surface control means connected to receive the command signal, the corrective signal and the augmentation signals for producing control surface deflections corresponding to a combination thereof. 2. A vehicular control system according to claim 1, further comprising:

said function generating means including means for producing the corrective signal as substantially equal to the negative of the square of the second difference signal for all values thereof less than zero and substantially equal to zero for all values greater than or equal to zero. 3. A vehicular control system according to claim 2, further comprising:

said surface control means including servo amplifying means connected to receive the vertical command signal, the corrective signal and the stability augmentation signals for producing an output signal indicative of a combination thereof, a servo motor connected to receive the servo amplifying means output signal, and control surfaces drivingly connected to said servo motor for controlling the vertical motions of the vehicle. 4. A vehicular control system according to claim 3, further comprising:

said servo amplifying means including a third comparison means connected to receive the vertical command signal and the function generating means output signal for producing a third difference signal indicative of the difference therebetween, and a servo amplifier connected to receive the third difference signal and the stability augmentation signals for producing an output signal indicative of the sum thereof. 5. A vehicular control system according to claim 1, further comprising:

said first, second and third comparison means each including a differential amplifier. 6. A vehicular control system according to claim 5,

g 6 further comprising:

said guidance means including a plurality of sensors vertically disposed relative to each other for receiving signals radiated by a target and producing output signals indicative thereof and a resolver connected to receive respective ones of the sensor output signals for producing a vertical command signal corresponding to the angle of the radiated signals relative said sensors. 7. In a vehicular control system including sensors formed to receive radiated signals from a target, resolvers connected to receive the sensor signals for producing a vertical command signal corresponding to the angle of the radiated signals and servo loops connected to receive the command signal for controlling the vertical motion of the vehicle, the improvement comprising:

signal generating means for producing a reference signal indicative of a preselected elevation of the vehicle;

depth measurement means for producing an elevation signal indicative of the vertical displacement of the vehicle;

comparison means connected to receive said reference and said elevation signals and adapted to receive the vertical command signal for producing an output signal indicative of the difference between the vertical command signal and a signal difference between said reference and elevation signals;

function generating means connected to receive said comparison means output signal for producing an output signal functional therewith when the vertical command signal is greater than the signal difference between said reference and elevation signals; and

combining means adapted to receive the vertical command signal and connected to receive said function generating means output signal for producing an output signal indicative of the difference therebetween.

8. A vehicular control system according to claim 7,

further comprising:

said function generating means including means for producing the output signal as substantially equal to the negative of the square of the comparison means output signal for all values thereof less than zero and. substantially equal to zero for all values greater than or equal to zero.

Claims

1. A vehicular control system for controlling the vertical excursions of a vehicle comprising, in combination: guidance means for producing a vertical command signal; depth measurement means for producing an elevation signal indicative of the vertical displacement of the vehicle; signal generating means for producing a reference signal indicative of a preselected limit elevation; first comparison means connected to receive the elevation signal and the reference signal for producing a first difference signal indicative of the difference therebetween; second comparison means connected to receive the vertical command signal and the first difference signal for producing a second difference signal indicative of the difference therebetween; function generating means connected to receive the second difference signal for producing a corrective signal as a predetermined function of the second difference signal; stabilizing means for producing stability augmentation signals indicative of the angular rate and orientation of the vehicle; and surface control means connected to receive the command signal, the corrective signal and the aUgmentation signals for producing control surface deflections corresponding to a combination thereof.

2. A vehicular control system according to claim 1, further comprising: said function generating means including means for producing the corrective signal as substantially equal to the negative of the square of the second difference signal for all values thereof less than zero and substantially equal to zero for all values greater than or equal to zero.

3. A vehicular control system according to claim 2, further comprising: said surface control means including servo amplifying means connected to receive the vertical command signal, the corrective signal and the stability augmentation signals for producing an output signal indicative of a combination thereof, a servo motor connected to receive the servo amplifying means output signal, and control surfaces drivingly connected to said servo motor for controlling the vertical motions of the vehicle.

4. A vehicular control system according to claim 3, further comprising: said servo amplifying means including a third comparison means connected to receive the vertical command signal and the function generating means output signal for producing a third difference signal indicative of the difference therebetween, and a servo amplifier connected to receive the third difference signal and the stability augmentation signals for producing an output signal indicative of the sum thereof.

5. A vehicular control system according to claim 1, further comprising: said first, second and third comparison means each including a differential amplifier.

6. A vehicular control system according to claim 5, further comprising: said guidance means including a plurality of sensors vertically disposed relative to each other for receiving signals radiated by a target and producing output signals indicative thereof and a resolver connected to receive respective ones of the sensor output signals for producing a vertical command signal corresponding to the angle of the radiated signals relative said sensors.

7. In a vehicular control system including sensors formed to receive radiated signals from a target, resolvers connected to receive the sensor signals for producing a vertical command signal corresponding to the angle of the radiated signals and servo loops connected to receive the command signal for controlling the vertical motion of the vehicle, the improvement comprising: signal generating means for producing a reference signal indicative of a preselected elevation of the vehicle; depth measurement means for producing an elevation signal indicative of the vertical displacement of the vehicle; comparison means connected to receive said reference and said elevation signals and adapted to receive the vertical command signal for producing an output signal indicative of the difference between the vertical command signal and a signal difference between said reference and elevation signals; function generating means connected to receive said comparison means output signal for producing an output signal functional therewith when the vertical command signal is greater than the signal difference between said reference and elevation signals; and combining means adapted to receive the vertical command signal and connected to receive said function generating means output signal for producing an output signal indicative of the difference therebetween.

8. A vehicular control system according to claim 7, further comprising: said function generating means including means for producing the output signal as substantially equal to the negative of the square of the comparison means output signal for all values thereof less than zero and substantially equal to zero for all values greater than or equal to zero.