GB2292209A

GB2292209A - Remote control system for guiding a moving object onto a target

Info

Publication number: GB2292209A
Application number: GB8518731A
Authority: GB
Inventors: Roland Albert Allezard
Original assignee: Telecommunications Radioelectriques et Telephoniques SA TRT
Current assignee: Telecommunications Radioelectriques et Telephoniques SA TRT
Priority date: 1984-11-27
Filing date: 1985-07-24
Publication date: 1996-02-14
Anticipated expiration: 2005-07-24
Also published as: DE3541061C1; SE8504840L; FR2714495A1; SE8504840D0; NL8503248A; GB8518731D0; GB2292209B; FR2714495B1

Abstract

A transmitter (20) sending at least one beam of radiation (10) and a first coding circuit to modulate the transmitting device in order to transmit position data by varying the pulse separation of the radiation. A receiver 25 attached to the moving object demodulates at 100 the received guidance data intended for a fin control circuit. The demodulated data is compared at 172 with outboard generated coded signals from 170 to validate the received control data. The on board code generator 170 is initialised before launch by a connection 150, 155 between itself and the transmitter coding circuit 70. The system is thereby more resistant to jamming. <IMAGE>

Description

REMOTE CONTROL SYSTEM FOR GUIDING A MOVING OBJECT ONTO A TARGET The present invention relates to a remote control system for guiding a moving object fitted with fins onto a target, the system including on the one hand a transmitter formed from a transmission device for sending towards the moving object at least one beam of radiation and from a first coding circuit acting on the transmission device in order to transmit position data by modulation of the radiation and on the other hand a receiver attached to the moving object formed from a receiving circuit for providing from the detected modulation guidance data intended for a fin control circuit, a linking circuit being provided for connecting the transmitter and receiver before launching the moving object.

Such systems are well known and have important applications in the military field in which the target is an objective to be destroyed and the moving object is a projectile carrying an explosive charge. A problem that arises with this type of system is that due to jamming. This jamming can have at least two causes : a first cause is in the fact that the enemy can transmit a beam of radiation near to the moving object in such a way as to falsify the position data. A second cause is in the fact that several moving objects can be directed onto the same or onto other targets located in the same neighborhood. It is important therefore that the moving objects should receive the correct position data that is intended for them.

The United States of America Patent No 4 102 521 describes a system of this type. In order to eliminate a large amount of the undesirable jammings, a random code word is stored on the one hand in the transmitter in order to code the position data and on the other hand, by means of the linking circuit, in the receiver in order to decode it. The linking circuit must therefore transmit relatively complex data without error in order that the decoding can be carried out in a satisfactory way in the receiver.

The present invention proposes a system of the type quoted in the preamble having good immunity to jamming while avoiding a complex transmission in the linking circuit. In order to do this, such a remote control system for guiding a moving object onto a target is remarkable in that the receiver includes a second coding circuit, a data comparison circuit for comparing the transmitted data with the data produced from the second coding circuit and an enabling circuit for only transmitting guidance data to the fin control circuit if the comparison circuit indicates that the data to be compared are compatible with each other while the linking circuit only transmits initialization data for initializing the second coding circuit on the first coding circuit.

The following description given with reference to the appended drawings, all given as non limiting examples, will give a good understanding of how the invention can be embodied.

Figure 1 represents a guidance system.

Figure 2 represents the appearance of the modulation of the pulses.

Figure 3 represents a remote control system according to the invention.

Figure 4 represents a variant of embodiment of a suitable receiver for a remote control system according to the invention.

In Figure 1, which represents an overall view of the remote control system, the target is referenced 1, and the moving object is referenced 3. This moving object 3 is in this example a rocket which carries an explosive charge and which is fitted with fins 4; the moving object is guided from a firing station 5. In order to guide this moving object a beam of infra-red radiation 10 is used scanning on either side of the target 1; the beam 10 oscillates from an angle X G to an angle α D; if the firing is well directed the target 1 is located on the bisector of the angle X G - XD.

The angle made by the beam with respect to M D is called O((t). In order to define the value of (t), the beam of radiation is pulse modulated; the time which separates two successive pulses Ati gives a value X j(t). Figure 2 shows the appearance of the time distribution of these pulses. Thus the time intervals Ati between two pulses develop from a value AtMIN for α(t) close to y D to a value A tMAX.It can be accepted, in order to facilitate the description, that this law is linear, i.e. that 2 i(t) = k a ti = k( A tj-1 + gt) where k is a constant and # t is a fixed time difference.

This type of law which makes a time interval correspond with an angle value is known particularly from the United States of America Patent No 3 191 175.

Figure 3 shows the remote control system in greater detail. The transmitter referenced 20 in Figure 3 is attached to the firing station 5 (Figure 1) and the receiver 25 is attached to the moving object 3. In this described example the transmission device 45 is formed first of all by a rectilinear set of laser diodes 50 functioning in infra-red - the radiation emitted by this set 50 is reflected by an oscillating mirror 55 in order to form the beam 10. This oscillating movement is such that the beam 10 pivots through angles from y D to b(G.These extreme positions are detected by sensors not represented on the figures and their output signals are combined with references ND and o(G. This mirror 55 is driven by a stepper motor 57; this motor is powered by pulses coming from an "OR" gate 60 provided with two inputs; in order to be able to reverse the direction of rotation of the motor 57 the output of gate 60 has been connected to an inverter 62 of which the invert command is provided by the output signal of a flip-flop 64. This flip-flop is put into the "1" state by the signal OeG and into the "0" state by the signal g D. Thus the motor 57 changes direction as soon as an extreme position of the mirror 55 is detected.

In order to modulate the beam 10 of infra-red radiation a first coding circuit 70 is used which provides pulses at its MOD output for the set 50.

It also provides on its MOT output, via gate 60, the pulses for the motor 57. Circuit 70 is formed first of all by an up-down counter 84 of which the clock CK input is connected to the output MOT connected to the first input of gate 60; thus these inputs receive the same signal and it results that each position of the mirror 55 corresponds with a value contained in the updown counter 84. This up-down counter 84 includes an output TC which provides an active signal as soon as its content reaches an extreme count : maximum or minimum. The active signal changes the state of a flipflop 86. The output signal of this flip-flop acts on the UD control of the up-down counter 84 to set it up as a count up or count down counter. Connected in this way, this up-down counter 84 is set to count up as soon as its content is minimum and is set to count down as soon as its content is maximum. The content of this up-down counter 84 is used to address a read only memory 90. This memory makes each address code correspond with a position code the numerical value of which is proportional to the time interval required.

This position code is Loaded into a count-down counter 92 which is provided with a CK input for clock signals connected to the output of a quartz oscillator 94; it is appropriate to note at this point that for the implementation of the invention a good stability quartz will be chosen. The count-down counter is provided with an output Z; at this output appears a signal which, when active, signifies that the content of the count-down counter 92 is at zero. This Z output is connected to the CK input of the up-down counter 84, to the first input of gate 60 and also to the L input of the count-down counter 92, via an OR gate 95 to load the position code supplied by the memory 90.Thus the active signal appears at the output Z after a time after loading that is proportional to the code contained in the count-down counter 92; a monostable circuit 96 shapes the signal at the Z output which is thus made available at the MOD output of the coding circuit 70 and which finally pulse modulates the set 50.

The receiver 25 is formed by a receiving circuit 100 including a diode 101 that is sensitive to infrared radiation which, in conjunction with an amplifying circuit 105, provides pulses each time that an infrared radiation reaches it. These pulses are supplied to the reset to zero input IZ of a counter 110 and to a first input of an AND gate 112. The purpose of this counter is to measure the time interval that separates the reception of two pulses. Its capacity greatly exceeds the time that separates the longest time interval corresponding to the extreme position data. These excess positions of this counter 110 are processed by an "EXCLUSIVE NOR" gate 115 of which the output is connected to the second input of gate 112.The output of this gate 112 is connected to the load input L of a register 120 of which the parallel inputs are connected to the outputs of the non-excess positions of counter 110. An excess count results in the appearance of at least one "1" in the excess positions and this therefore inhibits gate 112. Thus the register 120 cannot contain data corresponding to suitable position data. The time elapsing between each scan frame when the moving object is no longer in the beam is not taken into account. The content of register 120 is used to address a read only memory 125 programmed to give guidance data, i.e. a code which causes a command to fin 4 in order to correct, if necessary, the trajectory of the moving object.This guidance data is in digital form and can be processed by a digital-analog converter 130 the output of which is connected to the rotation control of a motor 135 that is mechanically coupled to the fins 4.

In addition the remote control system includes a linking circuit 150 which connects, before the launch of the moving object, the transmitter 20 to the receiver 25; this link breaks when the moving object separates from the firing station 5. A connector 155 enables this removable link.

According to the invention, the receiver attached to the moving object 3 includes a second coding circuit 170 (similar therefore to circuit 70), a comparison circuit 172 to compare the guidance data available at the output of the receiving circuit 100 with that provided by the second coding circuit 170 and an enabling circuit formed here by a set 174 of switches for only transmitting fin data to the fin control circuit (here formed by the digital-analog converter 130 and the motor 135) if the comparison circuit 172 indicates that the data being compared are compatible with each other, while the linking circuit transmits only initialization data produced by a push-button 175 coupled to a monostable circuit 176 to initialize the second coding circuit 170 to the first coding circuit.For this initialization the output signal of the monostable circuit 176 is applied on the one hand to the INI inputs which are provided for the coding circuits 70 and 170 and on the other hand to a first input of an "AND" gate 177 having two inputs, the second of which receives the signal D after an inversion obtained by a logic signals inverter 178.

The output of gate 177 is connected to one of the two inputs of an "AND" gate 179 of which the second input receives pulses from a generator 180. The output of gate 179 is connected to the second input of the "OR" gate 60 of which the first input is connected to the MOT output.

The INI input is connected, via gate 95, to the input of the counter 92, to the reset to zero RS input of the flip-flop 86 and to the reset to zero RZ input of the up-down counter 84. On the receiver side this INI input is connected in the same way to the corresponding elements. In the receiver shown in Figure 3 the counter 192 (corresponding to counter 92 in circuit 70) is used as an addressing unit for a memory 185 programmed in a way that is identical to that of memory 125. It will be noted that the clock signals input CK of the counter 110 is connected to the output of a quartz oscillator 194 corresponding with oscillator 94 and forming part of circuit 170.

The remote control system of the invention operates as follows. Before the moving object is launched, we operate push-button 175 which can obviously be coupled with the firing command. The monostable circuit 176 is triggered; its monostable period is a little greater than twice the duration that the rotating mirror takes to make the beam pivot from angle iG to angle s D, the pivoting taking place at the rate of the pulses produced by generator 180. This duration corresponds with the time taken by the mirror to return to angle i D whatever its position may be and whatever the state of flip-flop 64 may be.

The active signal supplied by the monostable circuit 176 opens gates 177 and 179 so that the pulses from the generator 180 are applied to the motor 57; this lasts as long as the 0 < D signal does not become active. When the signal y D becomes active the gate 177 closes causing the closure of gate 179; the mirror 55 is then immobilized. The active signal provided by monostable circuit 176 sets to zero, within circuit 70, the up-down counter 84 and the count-down counter 96 by loading the output code of memory 90 which is addressed by the "0" code produced by the up-down counter 84. The same applies to the corresponding count-down counter and up-down counter of circuit 170; the flip-flops 86 and the corresponding flip-flop (not represented) of circuit 170 are both put to the "O" state.

Once the monostable period of the monostable circuit 176 has elapsed, the signal on its output becomes inactive, the count-down counters 92 and 192 are released, they contain the value of the code coming from memory 90 and from the corresponding memory contained in circuit 170. This code is entered into these memories at the "O" address supplied by the updown counter 84 and the corresponding up-down counter in circuit 170. Starting from this moment the moving object is launched and the linking circuit 150 is broken. As the quartzes 94 and 194 are good stability quartzes, the contents of the count-down counters 92 and 192 will develop practically in sychronism throughout the duration of the firing.Then infrared radiation pulses will be picked up; the counter 110 will provide an indication of the duration of the interval separating them; if this duration is less than the time interval a tX then the content of this counter is transferred into register 120.

This content determines the direction along which the moving object is moving, it is therefore necessary to determine a correction so that the moving object reaches its target; this correction is preset in memory 125. Before being sent to the motor 135, this correction is compared with that provided by memory 185 programmed in the same way as memory 125. This memory 185 is addressed by counter 192 of which the content is, within a few slight differences, identical to that of counter 92. These contents indicate the duration of the time intervals between each pulse such that a time interval measured by counter 110 and transferred into the register must correspond with that indicated by register 192.The comparison circuit 172 determining a coincidence between the data supplied by the memories 125 and 185 closes the set of switches 174 and the correction is thus applied to the fins 4.

It is obvious, without leaving the scope of the invention, that this comparison can be made at different levels. The comparison could have been made at the level of register 120 and counter 192.

Figure 4 shows another way of making this comparison. This is carried out by an AND gate 195 inserted at the output of circuit 105. The purpose of this gate is to allow or prevent the passing of the pulses to the rest of circuit 100. This gate is opened by pulses produced by a monostable circuit 196 corresponding with monostable circuit 96 but with the difference that the pulses provided by this monostable circuit 196 are of large width thus allowing a certain tolerance. The output of memory 125 is connected directly to the converter 130 Thus it is noted that the remote control system is protected by pulses from jamming since only the data sent by the transmitter are decoded by the receiver, previously initialized by it and it is thus possible to have several remote control systems according to the invention in a restricted neighborhood.

Claims

1. Remote control system for guiding a moving object fitted with fins onto a target, the system including on the one hand a transmitter formed from a transmission device for sending towards the moving object at least one beam of radiation and from a first coding circuit acting on the transmission device in order to transmit position data by modulation of the radiation and on the other hand a receiver attached to the moving object formed from a receiving circuit for providing from the detected modulation guidance data intended for a fin control circuit, a linking circuit being provided for connecting the transmitter and receiver before launching the moving object, characterized in that the receiver includes a second coding circuit, a data comparison circuit for comparing the transmitted data with the data produced from the second coding circuit and an enabling circuit for only transmitting guidance data to the fin control circuit if the comparison circuit indicates that the data to be compared are compatible with each other, while the linking circuit only transmits initialization data for initializing the second coding circuit on the first coding circuit.

2. Remote control system according to Claim 1, characterized in that the comparison circuit is designed to make a direct comparison between the guidance data at the output of the receiving circuit and the output data of the second coding circuit.

3. Remote control system according to Claim 1, characterized in that the comparison circuit is designed to make a direct comparison between the position data available in the receiving circuit and the output data of the second coding circuit.

4. Remote control system according to Claim 1, characterized in that the comparison circuit is designed to make a direct comparison between the modulation detected in the receiving circuit and the output data of the second coding circuit.

5. A remote control system for guiding a moving object substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 4 of the accompanying drawings.

Amendments to the claims have been filed as follows

1. Remote control system for guiding a moving object fitted with fins onto a target, the system including on the one hand a transmitter formed from a transmission device for sending towards the moving object at least one beam of radiation and from a first coding circuit acting on the transmission device in order to transmit position data by modulation of the radiation and on the other hand a receiver attached to the moving object formed from a receiving circuit for providing from the detected modulation guidance data intended for a fin control circuit, a linking circuit being provided for connecting the transmitter and receiver before launching the moving object, characterized in that the receiver includes a second coding circuit sinilar to the first coding circuit, a data comparison circuit for comparing the transmitted data ith the data produced frozen the second coding circuit and an enabling circuit for only transmitting uidance data to the fin control circuit if the comparison circuit indicates that the data to be compared are compatible with each other, while the linking circuit only transmits initialization data for initializing the second coding circuit with respect to the first coding circuit.