Computing apparatus for tracking moving objects

Claim 2

Computing apparatus for tracking moving objects, the apparatus comprising: input circuit means for receiving temporally-spaced input positional signals each of which is indicative of a position of at least one moving object and may be subject to error; means for producing from said input signals a plurality of temporally-spaced pairs of digital positional signals x, y, each of which pairs of signals is representative in cartesian co-ordinate form of a position of said at least one object; digital signal storage means connected to receive said pairs of signals and arranged to store a predetermined number of the most recently produced thereof; digital filter means arranged to receive the stored signals, said digital filter means including digital multiplier means for multiplying each of said stored signals x by a respective one of a first set of predetermined coefficients and each of said stored signals y by a respective one of a second set of predetermined coefficients, and means for summing the products of x thus formed and for summing the products of y thus formed, so as to produce respective digital signals representative of the time derivatives dmx/dtm and dmy/dtm (m 0, 1, 2, . . . ) at at least one preselected common point in time on respective hypothetical functions x f1(t) and y f2(t) which substantially fit the values represented by x and y, both of said hypothetical functions being selected from the group of functions comprising polynomial functions of at least the second order and spline functions; and means for producing output signals which are dependent upon said time derivative digital signals.

Claim 3

Computing apparatus as claimed in claim 1, wherein said predetermined coefficients are selected on the basis that saId hypothetical functions are both third order polynomial functions.

Claim 4

Computing apparatus as claimed in claim 1, wherein said predetermined coefficients are selected on the basis that said hypothetical functions are both a least squares fit with the values represented by x and y.

Claim 5

Computing apparatus as claimed in claim 1, wherein the digital signals produced by said digital filter means are representative of the first time derivaties dx/dt and dy/dt.

Claim 6

Computing apparatus as claimed in claim 4, wherein the preselelcted common point in time is in the region of the time represented by the most recent stored pair of signals, and the multiplying means is further arranged to multiply each of said stored signals x by a respective one of a third set of predetermined coefficients and each of said stored signals y by a respective one of a fourth set of predetermined coefficients, and the summing means is arranged to sum the products of x thus formed and to sum the products of y thus formed, so as to produce further time derivative digital signals respectively representative of the time derivatives (dx/dt)mid and (dy/dt)mid at a second preselected common point in time on said hypothetical functions, said second preselected common point in time lying nearer to the middle of the time interval between the respective times represented by the most recent and the oldest stored pairs of signals, the output signal producing means being arranged to produce said output signals in dependence upon both the firstmentioned time derivative digital signals and the further time derivative digital signals.

Claim 7

Computing apparatus as claimed in claim 1, wherein the digital filter means includes further storage means for storing said predetermined coefficients.

Claim 8

Computing apparatus as claimed in claim 6, wherein the further storage means comprises a read only memory (ROM).

Claim 9

Computing apparatus as claimed in claim 1, wherein the first-mentioned storage means comprises a random access memory (RAM).

Claim 10

Computing apparatus as claimed in claim 1, wherein the input circuit is adapted to receive said input positional signals in polar co-ordinate form.

Claim 11

Computing apparatus as claimed in claim 9, wherein the means for producing said pairs of positional signals includes cordic polar co-ordinate to cartesian co-ordinate conversion means.

Claim 12

Computing apparatus as claimed in claim 9, wherein the input circuit means includes gating means connected to receive the input positional signals, and enabling means for enabling the gating means to transmit those input positional signals indicative of an object whose range and bearing fall within respective predetermined ranges of values.

Claim 13

Computing apparatus as claimed in claim 11, wherein there is provided control means connected between the digital filter means and the enabling means, the control means being arranged to adjust the respective predetermined ranges over which the enabling means is operative in accordance with said time derivative digital signals, whereby the area defined by said predetermined ranges of values moves in substantially the same direction and at substantially the same speed as said at least one object.

Claim 14

Computing apparatus as claimed in claim 12, wherein the control means includes at least one cordic cartesian co-ordinate to polar co-ordinate conversion means.

Claim 15

Computing apparatus as claimed in claim 1, said apparatus being adapted for use with radar or sonar apparatus carried by a moving vehicle such as a ship, and including means for receiving input signals indicative of the speed and direction of movement of the vehicle, and calculating means for calculating from these input signals the position of the vehicle with respect to a substantially stationary origin at predetermined intervals of time, and for producing signals representative in cartesian co-ordinate form of these calculated positions.

Claim 16

Computing apparatus as claimed in claim 14, wherein the means for producing said pairs of digital positional signals is connected to receive said calculated position signals and arranged to combine them with said input positional signals, whereby said digital positional signals are representative of positions with respect to said substantially stationary origin.

Claim 17

Computing apparatus as claimed in claim 14, wherein the means for receiving the input signals indicative of the speed and direction of movement of the vehicle include switching means whereby trial input signals indicative of trial speeds and/or directions may be manually selected.

Claim 18

Computing apparatus as claimed in claim 14, wherein the calculating means is additionally arranged to calculate from its input signals the speed of the vehicle in the x and y directions with respect to said substantially stationary origin and to produce further signals representative of these speeds.

Claim 19

Computing apparatus as claimed in claim 17, wherein there is provided further calculating means, which is connected to receive the firstmentioned and further signals produced by the firstmentioned calculating means, and which is arranged to calculate linearly the respective predicted future tracks of the vehicle from said firstmentioned and further signals.

Claim 20

Computing apparatus as claimed in claim 18, wherein the further calculating means is additionally connected to receive the most recent stored pair of positional signals from the storage means and the output signals from the output signal producing means, and is arranged to calculate linearly the predicted future track of the object from said positional signals and said output signals.

Claim 21

Computing apparatus as claimed in claim 19, wherein the further calculating means is also adapted to calculate the time and/or distance of closest approach of the object to the vehicle as the latter moves along any one of said predicted future tracks.

Claim 22

Computing apparatus as claimed in claim 20, wherein there is provided alarm means for operating a visible and/or audible alarm if the time and/or distance of closest approach falls below a predetermined value.

Claim 23

Computing apparatus as claimed in claim 14, wherein there is provided means for storing a predetermined number of the most recent calculated position signals.

Claim 24

Computing apparatus as claimed in claim 1, wherein there is provided display means, and first signal forming means connected to receive said stored digital signals and arranged to produce a first display signal for causing said display means to display the past track of said at least one object.

Claim 25

Computing apparatus as claimed in claim 23, wherein the first signal forming means comprises a digital-to-analogue converter connected to sequentially scan the stored digital signals, so as to produce an analogue output which varies with the values of the stored digital signals, and smoothing means for smoothing said analogue output to produce said display signal.

Claim 26

Computing apparatus as claimed in claim 23, wherein there is provided second signal forming means connected to said digital filter means and arranged to produce a second display signal for causing said display means to display a predicted future track of said at least one object, the direction and length of said predicted track being determined in dependence on said time derivative digital signals.

Claim 27

Computing apparatus as claimed in claim 22, wherein there is provided third signal forming means, which is connected to receive the stored calculated position signals and arranged to produce a third display signal for causing said display means to display the past track of the vehicle.

Claim 28

Computing apparatus as claimed in claim 19, wherein there is provided fourth signal forming means connected to said further calculating means and arranged to produce a fourth display signal for causing the display means to display any one of said predicted future tracks of the vehicle.

Claim 29

ComPuting apparatus for tracking moving objects, the apparatus comprising: input circuit means for receiving temporally spaced input positional signals each of which is indicative of a position of at least one moving object and may be subject to error; means for producing from said input signals a plurality of temporally spaced pairs of digital positional signals x, y, each of which pairs of signals is representative in cartesian co-ordinate form of a position of said at least one object; digital signal storage means connected to receive said pairs of signals and arranged to store a predetermined number of the most recently produced thereof; digital filter means arranged to receive the stored signals; said digital filter means including digital multiplier means for multiplying each of said stored signals x by a respective one of a first set of predetermined coefficients and each of said stored signals y by a respective one of a second set of predetermined coefficients, and means for summing the products of x thus formed and for summing the products of y thus formed, so as to produce first and second digital signals respectively representative of the time derivatives xr and yr at at least one preselected common point in time on respective hypothetical functions x f1(t) and y f2(t) which substantially fit the values represented by x and y, both of said hypothetical functions being selected from the group of functions comprising polynomial functions of at least the second order and spline functions, said preselected common point in time being in the region of the time represented by the most recent stored pair of signals; said multiplier means being further arranged to multiply each of said stored signals x by a respective one of a third set of predetermined coefficients and each of said stored signals y by a respective one of a fourth set of predetermined coefficients, and the summing means is arranged to sum the products of x thus formed and to sum the products of y thus formed, so as to produce third and forth time derivatives digital signals respectively representative of the time derivatives xm and ym at a second preselected common point in time on said hypothetical functions, said second preselected common point in time lying nearer to the middle of the time interval between the respective times represented by the most recent and the oldest stored pair of signals; tangent circuit means for producing digital output signals in the form Alpha B tan 1 yr/xr representative of the course of said object at said first, recent, preselected common point in time; and squaring, adding and square rooting circuit means for producing digital output signals in the form vB Square Root xm2 + ym2 representative of the speed of said object at said second preselected common point in time lying nearer to the middle of the time interval between the respective times represented by the most recent and the oldest stored pairs of signals.

Claim 30

ComPuting apparatus for tracking moving objects, the apparatus comprising: input circuit means for receiving temporally spaced input positional signals each of which is indicative of a position of at least one moving object and may be subject to error; means for producing from said input signals a plurality of temporally spaced pairs of digital positional signals x, y, each of which pairs of signals is representative in cartesian co-ordinate form of a position of said at least one object; digital signal storage means connected to receive said pairs of signals and arranged to store a predetermined number of the most recently produced thereof; digital filter means arranged to receive the stored signals; said digital filter means including digital multiplier means for multiplying each of said stored signals x by a respective one of a first set of predetermined coefficients and each of said stored signals y by a respective one of a second set of predetermined coefficients, and means for summing the products of x thus formed and for summing the products of y thus formed, so as to produce first and second digital signals respectively representative of the time derivatives xr and yr at at least one preselected common point in time on respective hypothetical functions x f1(t) and y f2(t) which substantially fit the values represented by x and y, both of said hypothetical functions being selected from the group of functions comprising polynomial functions of at least the second order and spline functions, said preselected common point in time being in the region of the time represented by the most recent stored pair of signals; said multiplier means being further arranged to multiply each of said stored signals x by a respective one of a third set of predetermined coefficients and each of said stored signals y by a respective one of a fourth set of predetermined coefficients, and the summing means is arranged to sum the products of x thus formed and to sum the products of y thus formed, so as to produce third and forth time derivatives digital signals respectively representative of the time derivatives xm and ym at a second preselected common point in time on said hypothetical functions, said second preselected common point in time lying nearer to the middle of the time interval between the respective times represented by the most recent and the oldest stored pair of signals; tangent circuit means for producing digital output signals in the form Alpha B tan 1 yr/xr representative of the course of said object at said first, recent, preselected common point in time; and squaring, adding and square rooting circuit means for producing digital output signals in the form vB Square Root xm2 + ym2 representative of the speed of said object at said second preselected common point in time lying nearer to the middle of the time interval between the respective times represented by the most recent and the oldest stored pairs of signals.