FR2836991A1 - ELECTRO-PYROTECHNIC SECURITY DEVICE FOR AMMUNITION AND ITS CONTROL METHOD - Google Patents

Abstract

A firing system (1) is arranged to send to an electro-pyrotechnic safety device (2) messages formed of logical function words. The device (2) comprises a device (3) which can be ignited by a current which can only flow through it if the switches (14, 15) located in the device (2) are closed. The closing of the switches (14, 15) is controlled in response to signals produced as a result of the analysis of the logical words contained in the message.

Description

seconded. The present invention relates to a method for controlling a

  electro-pyrotechnic safety device for ammunition, intended to be coupled to a system

  firing, as well as an initiator for such an electropyrotechnic safety device.

  In the context of the present invention, the term “electrical pyrotechnic safety device” means a device formed by a device such as a primer, a detonator, an igniter or the like, and a payload which can be of very different natures, such as a pyrotechnic composition for ignition, ejection or propulsion, an element of decoy cartridges or a dynamite cartridge used for example in the field of civil engineering. At the time of their use, these electro-pyrotechnic wind safety devices couples to a

  firing system which can also be of very different designs.

  In the case of decoy in particular, such an electropyrotechnical safety device can be part of a munition with multiple cartridges fixed on the structure of an aircraft, each of these cartridges being provided with a device. The cartridges are fired successively under the control of a firing system which supplies the ammunition with the cartridge selection signals, the control signals necessary for their firing, and the electrical energy required for their initiation and

  operation of their electrical equipment.

  To ensure the safety of personnel and property, it is necessary to ensure that the ignition of an electro-pyrotechnic device can only take place if certain conditions predetermined according to severe criteria are met. This is of course true for military applications only for

civil engineering applications.

  The document EP O 798 535 describes a system for transmitting information between a weapon (that is to say a firing system) and an ammunition by which the safety conditions are implemented in the weapon using the '' safety switches which are inserted into an electrical circuit of the weapon ensuring the supply of the ammunition and on which wind is transmitted in a bi-directional manner, command and verification signals exchanged between the electronics of the weapon and that ammunition. In this case, the main safety function determining whether or not to light the device is implemented in the tin system. This presents the drawback that an ammunition not coupled to the firing system can be fired by application of the necessary energy without having to go through the safety function. Thus, a hostile entity to which the ammunition must be abandoned, or in the case of civilian use, unskilled or ill-intentioned personnel, can destroy the ammunition by sending the current through

ignition required.

  The object of the invention is to propose a method for controlling an electro-pyrotechnic device, the wind safety conditions of which are improved compared to those provided in the prior art. The subject of the invention is therefore a method for controlling at least one electro-pyrotechnic safety device coupled to a firing system, this device being able to communicate with the firing system in order to circulate therein a current intended to convey information of command control. '' at least one function of the electro-pyrotechnic safety device and an energy pulse for the ignition of a device of this device, method which consists in authorizing the passage of said energy pulse in said device only when 'at least one authorization to circulate this pulse is issued by said firing system, characterized in that it consists of) generating in said firing system a message composed of at least one logical word representative of said function traffic authorization, b) transmitting said logic word to the electro-pyrotechnic safety device, c) analyzing said logic word therein to extract a command signal from said function one of traffic authorization and

  d) to issue the authorization to circulate in said electro-

  safety pyrotechnics in response to said control signal.

  Thanks to these characteristics, the operation of the device can only be possible when an authorization to this effect is given in the electro pyrotechnic safety device itself, the securing of the function being thus ensured as close as possible to the place where this function will be fulfilled. 11 results

  better overall safety of the firing-ammunition system assembly.

  According to other advantageous features of the invention, - said circulation authorization function is doubled in the led to the electro-pyrotechnic safety device, and the method consists in executing operations a), b) and c) for each of said functions, and to issue the authorization to circulate the current pulse in said device only in response to the cumulative appearance of the two control signals produced; the electro-pyrotechnic safety device comprising electronic means of analysis and control and electrical supply means with accumulation to which the current is selectively sent to ensure the supply of energy to said electronic means of analysis and control, said method further consists, at least prior to the execution of said operations a), b) and c), in generating in said firing system a logic power word, and in accumulating the energy represented by the successive bits of this logic supply word in said storage supply means to allow the operation of said analysis and control means; - the logical supply word represents a maximum of possible transitions, such as the code "55" in hexadecimal on the basis of a byte; - The method consists in generating in said firing system at least one other logical word representative of another function to be performed in the electro-pyrotechnic safety device, in transmitting said other logic word to said electro-pyrotechnic safety device, to be analyzed said logic word in said electro-pyrotechnic safety device for generating a control signal for said other function, and for executing said other function in response to said control signal which corresponds to it; - said other function is capable of sterilizing said current flow authorization function; - Said other function is capable of commanding the destruction of at least 20 parts of a part of said electro-pyrotechnic safety device; - The method further consists in generating in said firing system a logical function word representative of a status request to said electro-pyrotechnic safety device, in transmitting said function word to the latter, in generating in said device a reply to said request for status as a function of a determined state of this device, and to send said reply to said firing system; - said response to a status request is coded on a single bit: - the method consists in encrypting at least one part of said message in said firing system, and in decrypting said part of message in said electro-pyrotechnic safety device before d 'execute said function defined in said message; - at least some logical function words in said message include a first group of bits coding for a predetermined functionality to said electro-pyrotechnic safety device and a second group of bits defining the number of bits on which said message is encrypted and said encryption bits wind codes in logical words following the corresponding function word; - in said message each logical function word is preceded and

  followed by logical power words.

  The invention also relates to an electro-pyrotechnic safety device coupled to a firing system, comprising: a device for igniting said ammunition, transmission / reception means for receiving a current for said firing system intended for convey control information of at least one function of the electropyrotechnical safety device and an energy pulse for the ignition of a device of this device, and analysis and control means for interpreting the messages re , cus and generate control signals, this electro-pyrotechnic safety device being characterized in that said device is connected in a current circulation circuit in which is inserted at least one switch which can be closed in response to the production of a signal

  predetermines among said control signals.

  According to other interesting characteristics of this electro pyrotechnic safety device: - it also comprises means for sterilizing said switch in response to the production of another of said control signals; - It also includes means for destroying at least a portion of said electro-pyrotechnic safety device in response to the production of a

another of said control signals.

  Other characteristics and advantages of the present invention will appear

  during the description which follows, given only by way of example and made

  with reference to the accompanying drawings in which: - Figure 1 is a simplified diagram of an electro pyrotechnic safety device according to the invention; - Figure 2 shows an example of a possible form of message that can be exchanged between a firing system and an electro-pyrotechnic security device according to the invention connected to this firing system; - Figure 3 shows an example of a possible form of the words composing the message of Figure 2; - Figure 4 shows a message according to Figure 2 in which is incorporated a firing pulse of the electro-pyrotechnic device

3 5 security.

  In FIG. 1, the block 1 designates a firing system designed to form messages M (FIGS. 2 and 4) and to address these messages to an electro pyrotechnic safety device 2 according to the invention (hereinafter designated by the abbreviation DEP). This DEP is incorporated into a munition which has not been shown in detail. The DEP includes a pyrotechnic device 3 intended to cause the operation of the munition. The DEP 2 is also able to send messages back to the

firing system 1.

  In the example shown, the firing system 1 is connected to the DEP 2 by means of a two-wire link 4 on which the messages comprising the energy pulse necessary for the operation of the device 3 and [can pass through] information that is essential for it to be ordered. This two-wire connection 4 is connected to the DEP 2 by only two terminals 5 and 6, no other connection to

  the exterior is not planned for the DEP 2.

  It should be noted that according to alternative embodiments, the communication between the firing system 1 and the DEP2 can be established by other means. For example, the ignition energy and the control information can be transmitted by inductive, optical or similar flight, with appropriate coupling elements then being

  provided for this purpose between firing system 1 and DEP2.

  The communication flight (in this case the two-wire connection 4 and the terminals 5 and 6) is connected to a transmission / reception block 7 which constitutes an interface capable of routing the incoming and outgoing messages, respectively to the blocks

  DEP2 internal functional units and, if applicable, to the firing system 1.

  Incoming messages appear on a line 8 which is connected to a block

  9 and has a microcontroller 10.

  The power supply unit 9 is designed to generate the supply voltage U on a terminal 11. The latter is connected to supply terminals 12 of all

the other blocks of DEP 2.

  The microcontroller 10 is also connected to the transmit / receive block 7 by the intermediary of a line 13 on which transit the messages which have to leave the

DEP2.

  The pyrotechnic device 3 is connected between the terminals 5 and 6 respectively by the intermediary of control switches 14 and 15 forming with [device 3 an eerie circuit. Consequently, the initiator 3 can only be turned on if the two switches 14 and 15 are closed. Each of the switches 14, 15 can be closed by an actuating circuit 16, respectively 17, which in turn receives control signals from the microcontroller 10. The switches 14 and 15 are preferably produced in the form of semi- conductors drives like transistors

or the like.

  The microcontroller 10 also controls a so-called "sterilization" circuit 18 as well as a so-called "destruction" circuit 19. The sterilization circuit 18 is connected to the actuation circuits 16 and 17 which it can make inoperative in order to prevent the

  operation of switches 14 and 15.

  The destruction circuit is connected not only to the actuation circuits 16 and 17, but also to the transmission / reception block 7. When the 0 microcontroller 10 sends it a control signal, this destruction circuit 19 makes it possible to destroy the blocks to which it is relic and thus prevent any communication from outside with DEP electronics by

through terminals 5 and 6.

  As is known in itself in particular by the precise European patent, the supply circuit 9 comprises an energy storage capacitor 9a which

  when it is charged, allows to temporarily power the DEP 2 circuits, i.e.

  say at least during the time it takes to fire the ammunition at which

the DEP is incorporated.

  To this end, the firing system 1 is arranged to generate messages M

  2 o (FIG. 2) comprising information coded in a series of words m, m2, m3 ......

  themselves forms of a series of bits. In the example described here, the topology of a message M is preferably of the UART type known to specialists comprising eight bits framed by a start bit and an end bit; the information rate can be chosen at 9600 baud, for example. In the case described and as represented in FIG. 3, each word m ', m2, m3 ... of the message M is therefore composed of the bits Bdebu, Bo to B7 and B5'n At least the first word m, of each message M sent to the DEP 2 is intended for the charge of the capacitor 9a of the supply circuit 9. Preferably, the content of this word is that of the example of FIG. 3, because it makes it possible to transfer a maximum of energy to the supply circuit 9 (code "55" in hexadecimal on the

base of a byte).

  Table 1 below lists, by way of example, the functional content that the words that can compose a message M can have, such as that represented in FIG. 2. It should be noted that these words can be followed in order desired by the designer to carry out a sequence of events predetermined in the DEP 2, it being understood that as a function of the capacitance of the capacitor 9a of the supply circuit 9, it is necessary to insert either between two consecutive functional words defining a functionality (hereinafter referred to as "functional moss"), or between several of these mosses, a word known as "supply", the logical composition of which is then represented in FIG. 3. The second column of table 1 indicates the meaning of flow of information which is directed from firing system 1 to DEP 2 for all moss,

  [except for word 8 which implies a reverse flow of information.

Table 1

  N words Meaning Function 1 1 2 Supply the DEP circuits 1 2 Close the switch 14 1 - 2 Close the switch 15 4 1 2 Fire the device 3 1 2 Open the switch 14 1 2 Open the switches 14 and 15 1 2 Request the status at l:) EP 8 2 1 Return the status to the firing system 9 1 2 Sterilize the DEP 1 2 Destroy the electronics of the DEP 1 2 Initialization of the DEP o As already mentioned above, the supply word N 1 code for supplying the DEP 2 circuits. This code (Figure 3) is preferably "55" in hexadecimal to allow the transmission of maximum energy by this word. For example, if the intensity of the current I sent by the firing system 1 to the DEP 2 is 0.1 A, it is possible to transmit 50 J per word N 1. In this case, if the electronic circuits of the DEP 2 consume a total current of 10, uA, its autonomy can be a maximum of 5 seconds with a ga capacitor of suitable capacity. However, it is possible to admit a shorter duration of autonomy, for example only 0.5 seconds, which will make it possible to reduce the size of the capacitor 9a. It should be noted in this regard that one can consider connecting to the capacitor 9a a load resistor 9b which absorbs the energy accumulated in the capacitor if, for a predetermined period (for one second for example), no information is available. has passed from the firing system 1 to the DEP 2. This energy absorption function guarantees increased operational safety of the DEP, the electronics being systematically put on standby by the absence of power supply if the firing system 1 does not ['activate. The function words n 2 year 6 do not require any particular comments, except that when they are sent by the firing system 1, their logical content is sent to the microcontroller 10 which analyzes it and prepares the appropriate command. , then sends a control signal to the corresponding organ or circuit of DEP 2. For example, if the word n 2 is sent, the microcontroller 10 activates the actuation circuit 16 which closes the switch 14. The same process is executed for all other mosses, it being understood that each of these words is

  precede word n 1 for charging the capacitor 9a.

  It will be noted in connection with the activation of device 3 that it requires the cumulative closing of switches 14 and 15, this action having the effect of authorizing the circulation of a current in this device. It is therefore seen that this authorization depends on elements which are located in the DEP, that is to say on elements which are located as close as possible to the device. This characteristic brings in particular the advantage of making it possible, when the ammunition is separated from the firing system 1, to make ignition of the device 3 impossible, an untimely or fraudulent ignition being made impossible without knowledge of the code which the microcontroller must receive 10. As explained below, security in this respect can be further reinforced if the messages intended for microcontroller 10 undergo encryption.

  to make possible the execution of the functions they contain.

  2 5 The word n contains the command to sterilize the DEP 2 through the sterilization circuit 18. This functionality subsequently prevents the closing of the switches 14 and 1S, so that the device 3 can no longer be lit. However, DEP 2 can still answer words n s 7 and 10 provided

  that they are sent by the firing system 1.

  The word n 10 has the effect of activating the destruction circuit 19. By this command, not only the switches 14 and 15 can no longer be closed, but also the transmission / reception circuit 7 being destroyed, no communication can no longer take place with the outside. This characteristic can prove useful, if the ammunition endowed with the DEP according to the invention must be abandoned by force for example,

  a hostile or unauthorized entity then being unable to fire the ammunition.

  Table 2 above presents by way of example a possible coding of the function word n 7 of status request, each code corresponding to a particular status request sent by the firing system 1 to the DEP 2. The request calls a response from the DEP in the form of the word n 8 whose content is representative of a specific state of the DEP. It should be noted that the word n 8 is fa code, special con, since emanating from DEP 2, it should be sent to the firing system 1 in DEP 2 requires only a very low energy consumption . This word n 8 is therefore code of preference

  on only one bit which can take the value "1" or "O".

  The code of the function word n 7 is preferably formed by a four-bit identification part designating the status request followed by a part also with a length of four bits designating the nature of the status requested. at

  DEP. Table 2 lists the meaning of this part of the requested status.

Table 2

  Code Meaning (fexedecimaf) O Not used Functional control by transmission of a "1" 2 Functional control by transmission of a "0" 3 State of switch 14 4 State of switches 14 and 15 State of control of sterilization 18 6 State of the supply circuit 9 7 Voltage lJ> at a predetermined voltage? (4 Volts per

example)

  Firework 3 OK? 9 Deja tir A A Not used DEP 2 identification; Bit 1 C Identification of DEP 2; Bit 2 D Identification of DEP 2; Bit 3 E Identification of DEP 2; Bit 4 DEP identification; Bit 5 As an example, assuming that the firing system 1 must successively check the state of switches 14 and 15 and that of device 3, the message sent by firing system 1 to DEP 2 will be as follows : word n 1 (table 1), word n 7 (table 1) with code n 4 (table 2), message n 8 (bit "1, if the wind switches are closed and bit" 0 "if the switches are open wind ), word n 1, word n 7, but with code n 8, word n 1, word n 8 (with bit a "1" or a "0" depending on the state of

  ['device 3), and finally the code word n 1.

  According to a characteristic particularly favoring the operational safety of the DEP according to the invention, at least certain function words can be accompanied by at least one crypt word in which the code for

  control of the corresponding functionality.

  Like the function word N 7, each other function word in table 1 is composed of a byte whose four most significant bits identify the corresponding functionality. According to the invention, the four low-weight bits of these words can define the length of an encryption message which can be sent in the message M following the function word in Table 1 defining the

functionality considered.

  An encrypted message can be prepared in the firing system 1 and be sent in groups of eight successive bits, each time with the interposition of the supply word n 1 to charge the capacitor 9a. The encryption can be carried out in a known manner using a public or private key encryption algorithm. In this case, the microcontroller 10 will be able to execute a corresponding decryption program loaded in its memory using an inverse algorithm using the same public or private key according to the cast. The four least significant bits of each function word will thus be able to define the length of the encrypted message, ie its number of bits or, more precisely and preferably, quartets (group of four hits). Note that when the four low weight bits of the function word represent the hexadecimal value "0", the entire command code is contained in the single byte of that word and there is then no encryption. For example, if the function consists in closing the switch 14 and this function is considered as not very sensitive from the security point of view, the sequence of words sent by the shooting system 1 to the DEP 2 will be as follows: word n 1 , word n 2 (with the four bits of

low weight at "0", word n 1 .......

  The following sequence of words illustrates by way of example the command with encryption of the closing function of the switch 15, assuming that the four least significant bits of the function word have the value "8" (hexadecimal) meaning that the encryption is performed on eight quartet or 32 bits: word n 1, word n 3 with the code "8" (in hexadecimal), word n 1, word n 3 comprising the first quartet encrypts in addition falble weight, word n 1 , word n 3 with the second crypt quartet, word n 1, word n 3 with the third crypt quartet, word n 1, word N 3 with the fourth

crypt quartet, word n 1, ..........

  It should be noted that the security level of the transmission of messages lo between the firing system 1 and the DEP 2 will be all the higher the greater the number of encrypted bits. Of course, the processing time will also increase with

  an increasing number of cryptic bits.

  Thus, it may be advantageous to encrypt on a large number of bits only the sensitive commands such as for example the simultaneous closing functions of the switches 14 and 15 and to choose for the other functions lower numbers of encrypted bits. One of the important advantages of the invention resides in the large choice of degrees of confidentiality available to the designer.

  to design secure messages.

  The function word 11 of table 1 is only used to initialize the ammunition during manufacture. It can in particular be used to determine the number of bits a

  encrypt for each function word used.

  FIG. 4 illustrates a firing sequence implying by way of example a sequence of four function words, of a period of sending the ignition energy for the device 3 (time T) during which the current I rises to a level ^ 5 comparatively very high compared to the intensity used for the transmission of messages M, and finally several additional words sent after the shooting for

  interrogate the DEP 2 when it has its status.

Claims (15)

  1. Method for controlling at least one electro- device   pyrotechnic security (2) couple to a firing system (1), this device being able to communicate with the firing system (1) to circulate there a current (I) intended to convey information (M) of command of '' at least one function of this device and an energy pulse for the ignition of a device (3) to said device, method which consists in authorizing the passage of said energy pulse in said device (3) when at least one authorization for the circulation of this pulse is delivered by said firing system (1), lo characterized in that it consists of) generating in said firing system (1) a message (M) composed of at least one logical word (m ,, m2, m3) representative of said traffic authorization function, b) to transmit said logical word to the electro-pyrotechnic safety device (2), c) to analyze said logical word in that -this to extract a control signal from said traffic authorization function and d) to issue the authorization circulation in led it electro device   safety pyrotechnics (2) in response to said control signal.   2. Control method according to claim 1, characterized in that said traffic authorization function is doubled in said electro-pyrotechnic safety device (2), in that it consists in executing operations a), b ) and c) for each of said functions, and to deivert the authorization to circulate the current pulse (I) in said device (3) only in response to the cumulative appearance of the two signals order products.   3. Control method according to claim 1, of an electropyrotechnical safety device (2) comprising electronic analysis and control means (10, 16 to 19) and electrical storage means (9) to which the current (I) is selectively sent to supply power to said electronic analysis and control means (10, 16 to 19), said method being further characterized in that it consists, at least beforehand in [ 'execution of said operations a), b) and c), to generate in said firing system (1) a logic power word, and to accumulate the energy represented by the successive bits of this logic power word in said storage means (g) to allow   the operation of said analysis and control means (10, 16 to 19).   4. Control method according to claim 3, characterized in that the logic supply word represents a maximum of possible transitions, such as   than the code "55" in hexadecimal, based on a byte.   5. Control method according to any one of claims 1 a   4, characterized in that it consists in generating in said firing system (1) at least one other logical word representative of another function to be performed in the electro-pyrotechnic safety device (2), in transmitting said other logical word to said audit electro-pyrotechnic security device (2), analyzing said logic word in said electro-pyrotechnic security device (2) to generate a control signal for said other function, and executing said other function in response to said control signal which corresponds to it . 6. Ordering method according to claim 5, characterized in that said other function is capable of steriiizing said authorization function of current flow.   7. Control method according to any one of claims   and 6, characterized in that said other function is capable of controlling the destruction of at least part of said electropyrotechnical safety device 2 5 (2)   8. Control method according to any one of claims 1 a   7, characterized in that it further consists in generating in said firing system (1) a logic function word representative of a status request to said electro-pyrotechnic safety device (2), in transmitting said function word to said electro-pyrotechnic security device, to generate in said electro-pyrotechnic security device (2) a response to said status request as a function of a determined state of this electro-pyrotechnic security device, and   to return said response to said firing system (1).   9. Control method according to claim 8, characterized in that   that said response to a status request is coded on a single bit.   10. Control method according to any one of claims 1 a   9, characterized in that it consists in encrypting at least a portion of said message (M) in said firing system (1), and in decrypting the said portion of message in said electro pyrotechnic security device (2) before to execute said function defined in said 1 0 message.   11. Control method according to claim 10, characterized in that at least certain logical function words in said message (M) comprise a first group of bits coding for a predetermined functionality to said electro-pyrotechnic safety device (2) and a second group of bits defining the number of bits on which said message is encrypted and in that said encryption bits are coded in following logical words the function word match.   12. Control method according to any one of claims 3 a   11, characterizes in that in said message each logical function word is   precede and follow logic feed words.   13. Electro-pyrotechnic safety device coupled to a firing system, comprising: a device (3) for igniting said ammunition, transmission / reception means (7) for receiving at said firing system (1) a 2s current (I) intended to convey information (M) for controlling at least one function of the electro-pyrotechnic safety device and an energy pulse for the ignition of a device (3) of the electro device safety pyrotechnics, analysis and control means (10, 16 to 19) for interpreting rec, us messages and generating control signals, this electro-pyrotechnic safety device being characterized in that said device (3 ) is connected in a current circulation circuit in which is inserted at least one switch (14, 15) which can be closed in response to the   producing a predetermine of said control signals.   14. electro-pyrotechnic safety device according to claim 13, characterized in that it also comprises means (18) for sterilizing said 1errupur Q4, 15) in response to the production of a car of the commando snake desdRs. 15. Oppose Alero-pytechnlque de sAcudtA according to any of the mndlcatlons 13 and 14, Crisp in this quill compound Also means s (1g) for dAtruim in the hands a padie with said device Alem-pyrotecholque