FR2712563A1 - Bidirectional optical signal transmission device for optical cable guided missile - Google Patents

Abstract

The device is mounted aboard a missile (1), guided through an optical cable (19) from a control post (2), and includes a reel on which the cable is wound (11) and a dynamometer (13e) with a spring. A motor (12) actuates the reel. The cable is made of glass fibre and pulled by a system of pulleys (13a,b,c). The dynamometer generates a signal which indicates the traction effort in the cable. An optical coupler (17) is mounted on the reel. A cable (17c) makes the connection from the coupler to various equipment aboard the missile. An image separator is attached to the extremity of the optical cable. AN LED generates a light beam which is transmitted to a phototransistor. Signals generated are then sent to a microprocessor (20) with EPROM.

Description

"Equipment of a flying machine controlled by wire from a control station, for bidirectional transmission of
signals by the wire "
The invention relates to on-board equipment of a flying machine controlled by wire from a control station, for bidirectional transmission of signals by wire, the latter being reusable, equipment where a store containing a reserve of wire is provided to deliver an adequate length of wire unwound from the machine to the control station.

 Many flying machines or missiles guided by wire are planned to be destroyed at the end of the trajectory, this moreover representing as short a journey as possible between the departure near the command post, and the arrival at the end of path. The guide wire, or connecting conductor, is also normally lost, and is used practically only to send to the machine, from the control station, the signals necessary for the adaptation of the trajectory. The wire is then wound on a reel and located at the rear of the machine, so as to unwind at zero speed relative to the ground, and to land gradually without the risk of catching an obstacle.

This avoids the risk of accidental breakage of the connecting conductor which would exist, if the wire were pulled over the ground at the speed of movement of the machine.

 Another application of remotely controlled flying machines consists of observation machines, equipped with a camera. The link conductor then allows an exchange of signals between the machine and the control station, the machine receiving signals for controlling the flight parameters and orientation of the camera, and transmitting image signals. We can limit the on-board weight to that which is strictly necessary for piloting, the orientation of the camera and the transmission of image signals, and use vehicles of reduced size and of limited weight, omitting all that, in conventional aircraft, relates to the information, comfort and safety of a crew.

 In this type of application, the use of a link conductor overcomes certain constraints of radio transmissions with a high information rate, namely the need for directional directional aerials, the risks of interference and 'indiscretions, and the weight of the on-board transmitters. This type of device has the advantage of being recoverable, since the return of the device to its starting base does not lead to an overload due to the necessary equipment.

 Even if we do not request flying machines for observing cruising speeds of the same order as that of wire-guided missiles, the flight times must be incomparably longer (for example 1/4 hour at 25 m / s ), so that the distance traveled during a flight (22,500 m according to the previous example) is almost an order of magnitude greater than that of conventional wire-guided devices.

 There is therefore no question of carrying a length of connecting conductor corresponding to the distance traveled in flight. I1 is also not question either unwind from the control station the wire attached to the machine which should have a substantially straight path and would not be recoverable. Finally, losses in a conductor of this length would prohibit broadband transmission.

 As an observation machine guided by wire will normally remain in a limited area of action, it has been proposed to limit the length of the unrolled connecting conductor and, when this length is unrolled, to make the machine evolve in looped paths such as the connecting conductor is permanently subjected to a traction lower than a mechanical tension value capable of causing the rupture of the conductor, but nevertheless sufficient for the slope of the conductor to always be positive when leaving the control station, so that the driver does not hold on to an obstacle. It will be noted that the aerodynamic reactions on the driver driven by the machine have the effect of separating the connecting driver from the vertical plane which contains the control station and the machine.

 It has been shown experimentally that there are trajectories for which, with a fixed length of connecting conductor, the mechanical tension of the conductor is maintained between a maximum value chosen, with a safety factor, to avoid a risk of breakage of the conductor, and a minimum value where the conductor slope is always positive, starting from the control station.

 It will be noted that, due to the low linear density of the connecting conductor, and the limited acceleration capacities of flying machines combining the necessary carrying capacity and the desirable hardiness, it may be considered that the conductor is in stationary conditions, and that its mechanical tension is substantially constant over the entire length.

 The trajectories which maintain the mechanical tension at an intermediate value between the maximum and minimum values mentioned above, while keeping fixed the unrolled length of the connecting conductor, are made up of linked loops, which make it possible to maintain the machine in an observation area limited useful. However, these trajectories are relatively rigid, and require trained personnel to follow them. They may prove to be inadequate, either because the scenes to be observed are located outside the overflown area, or because the meteorological circumstances (gusts of wind, for example) bring unacceptable disturbances to the trajectories.

 Finally, the recovery of the flying machine can be made difficult because of the excess length of the unrolled driver compared to the distance between the control station and the landing area. If the device itself can be recovered, the link driver will not be. However, it goes without saying that, if one chooses a conductor which simultaneously presents a diameter and a low linear density, an excellent tenacity, and a wide bandwidth, its price will exclude that it is lost with each flight a few thousand of meters.

 It has been proposed (French patent application No. 92,02030 of February 23, 1993 not yet published, and filed by the same Applicant with the same inventor as the present application), to ensure better coverage of the area overflown and allow recovery of both the flying object that of the connecting conductor, to have at the control station a reel carrying the conductor's reserve turns equipped with a reeling-reeling means coupled to a motor, a mechanical tension detector inserted on a path of the conductor at the output of the drum and delivering a voltage image signal, and a servo control device controlling the motor in one direction which adjusts the voltage signal to a setpoint signal.

 This arrangement makes it possible to reduce the on-board equipment to a minimum, which, a priori, would allow a reduction in size and short of the flying machine, and would not result in any limitation of the length of wire in reserve, and therefore of radius d action of the machine.

 However, in practice, the dimensions and cost of the flying machine itself are determined in the first place by the observation and measurement equipment to be carried, as well as by the flight duration capacity requested. The reduction in weight provided by the driver store layout is often secondary.

 Furthermore, when the link conductor magazine is arranged at the control station, this conductor, during the flight of the machine, moves with respect to the environment at the speed of reeling-reeling, as a first approximation in the direction of the machine store and at the radial speed thereof relative to the location of the store. However, if at altitude the longitudinal displacement of the conductor or connecting wire in the air generates, by drag, only a negligible additional tension, near the store located at the control station, the conductor or connecting wire can hold on to obstacles that arise, such as trees and shrubs, various pylons, hedges or artificial hedges, constructions and others. If the signal conductor wire gets caught, it risks breaking when the machine moves away from the control station, without the servo-control of the reeling-reeling device intervening, and of taking up slack when the machine gets closer, which increases the risk of snagging.

 It is therefore necessary that, at the start of the control station, the conductive wire has a rising slope towards the machine sufficient to escape close obstacles.

 However, as we know, a wire of uniform linear weight held at its two ends takes the form called chain (hyperbolic cosine) with a parameter which is the ratio of the tension to the linear weight, homogeneous to a length. For a given traction or tension, such as that which corresponds to the setpoint of the servo-control, the shape taken by the conducting wire is entirely determined by the differences in coordinates between the ends, namely the horizontal distance and the relative altitude of l 'machine in relation to the command post. It is understood that, with fixed traction, the positive slope condition at the control station limits the radius of action and therefore the maximum length of wire to be unwound.

 To allow the range of action of the machine to be increased, the invention provides on-board equipment for a flying machine controlled by wire from a control station for the bidirectional transmission of signals by wire, that -this being reusable, equipment where a store containing a reserve of wire is provided to deliver an adequate length of wire unwound from the machine to the control station, characterized in that the store comprises a drum where the reserve is wound, provided with '' a reeling-reeling mechanism driven by a reversible motor, a dynamometric means interposed between the reeling-reeling mechanism and a die through which the thread leaves the machine, producing a signal representative of the traction exerted on the thread, and servo means sensitive to this representative traction signal to control the motor in unwinding-winding so as to maintain traction on the wire between a maximum and a minimum.

 Since at the start of the control station the connecting wire is immobile with respect to the environment, the constraints linked to obstacles on the ground near the control station are very reduced, and the critical slope at the control station can be reduced and even occasionally canceled without drawbacks so that the length of unwound wire can be increased, as well as the radius of action. In addition, an attachment of the connecting wire does not cause an abrupt increase in traction on the wire, since the latter was already stationary relative to the obstacle, and moreover the dynamometric means remains sensitive to traction on the wire despite hanging. We can thus accept to adjust the traction maintained by the servo-control to a value closer to the breaking limit, the safety factor being taken lower without increasing the risks of breaking.

 According to a preferred arrangement of the invention, the equipment comprises a navigation device determining, in a geodetic tracking system, the position coordinates of the machine connected to those of the control station, a means, coupled to the mechanism of reeling-reeling, measuring the unwound length of wire, and calculation means adapted to determine, from the position coordinates of the machine and the control station, the horizontal and vertical distances between them and to deduce therefrom given the unwound length of the wire, the slope at the station of the chain closed by the wire1, the servo means being further adapted to control the motor so as to maintain the chain slope between two prefixed values, maintaining traction exercised on the wire below the maximum, however, having priority.

 It is understood that, thanks to this arrangement, the traction on the wire is modulated by maintaining the slope of the wire at the start of the control station between the prefixed values, which are chosen such that the wire is not likely to catch on to local obstacles without exaggerating this slope, while the maximum traction limit persists and provides additional security.

 In addition, it will often be the case that outsourced missions require precise knowledge of the coordinates of the machine in a geodetic tracking system, and for example the use of a "GPS" (Global Positioning System) receiver in connection with a network. of geodetic satellites. Under these conditions, the data from the navigation device and transmitted to the control station will be used directly on board the machine, for determining the unwound length of wire. In addition, the calculation means which use the data received from the satellites can, at the cost of small additions to the calculation program, execute the calculations relating to the configuration of the wire.

Other secondary characteristics and advantages of the invention will emerge from the description which follows, by way of example, with reference to the appended drawings in which
Figure 1 is an organizational diagram of equipment according to the invention
Figure 2 is a general representation of the piloting of a flying machine equipped according to the invention.

 According to the embodiment of the invention chosen and shown in the figures, the equipment shown schematically in Figure 1 is on board a flying machine 1 in Figure 2, controlled by wire 19 from a station control 2 as a whole, here shown on the ground. The wire 19 is here a glass fiber of 0.2 mm in diameter, through which pass in particular from the control station 2 to the flying machine 1 the piloting orders coming from the cockpit 2a, and from the machine 1 at the control station 2, the data collected by the flying machine, such as video signals supplied by an on-board video camera, which result in data processing devices shown diagrammatically here by a display screen 2b.

The glass fiber 19 is fixed, at the control station, at the head of an elastic material 2d, similar to a tip, supported by the central unit 2c of the control station 2.

 As shown in FIG. 1, the wire 19 enters the machine through a trumpet-shaped die 18 to limit the curvature of the fiberglass wire when entering the machine. The wire comprises a reserve 10, wound on a drum 11, driven in rotation about an axis 11a by a motor 12. The wire is wound with contiguous turns on the drum 11 by means of a cutting carriage 13 moved parallel to the axis 11a by a cutting ramp consisting of a lead screw 14, driven in rotation by a set of gears 15 forming an inverter, with a drive pinion 15a wedged on the shaft 11a.

 On the cutting trolley 13, the wire leaving the reserve passes over a first pulley 13a forming a wire guide and returns to around 900, turning idly on an axis secured to the carriage 13, then on a second pulley 13k also turning mad on a axis fixed to the carriage 13, beyond which the wire goes towards the die 18.

Between the pulleys 13a and 13b, the wire passes over a pulley 13c turning madly on an axis located at the end of a lever 13d pivoting on the axis of a dynamometer 13e which comprises a spring which urges the pulley 13c to s '' between the pulleys 13a and 13b. It is understood that the angular position of the lever 13d is an image of the traction exerted on the wire. The dynamometer 13e emits a signal which is a function of the angular position of the lever 13d, and therefore representative of the traction exerted on the wire 19.

 At the center of the face of the drum 11 opposite the motor 12, the wire ends at a rotating optical coupler 17, bidirectional, and composed of a part 17a secured to the drum, and a part 17k secured to the machine, from which a cable 17c for the differentiated link to the signal transmitting apparatuses, and the receiving apparatuses, in particular the flight controls. Part 17a comprises an image separator at the end of an optical fiber, with an input optic which receives the light emitted by an electro-optical transducer such as a light-emitting diode, and an output optic which directs the light onto a opto-electronic transducer, such as a phototransistor. It will be understood that the electro-optical and opto-electronic transducers included in part 17b of the optical seal 17 have sufficient bandwidth for the transmission of the necessary data.

 In addition, the microprocessor is supplied with data coming from the control station 2 via the wire 19, the rotary joint 17 and the connection cable 17c through an input 20a.

 On the axis lla of the drum 11 is set a counter up-down counter 16. A microprocessor 20, equipped with an electrically programmable read-only memory (EPROM) 21, and a random access memory 22 receives the data from the dynamometer 13e and the counter - down counter 16, and sends commands to a pair of power amplifiers 23, 24 which supply the motor 12 to control the rotation of the drum 11, and the unwinding-reeling of the wire 19 on this drum under various conditions.

 In addition, the equipment comprises a "GPS" receiver 25 which receives by an aerial 25b signals from a network of satellites of a geodetic tracking system. This “GPS” receiver 25 coupled to the microprocessor 20 translates the signals from the satellites into three-dimensional geodetic coordinates, with a relative precision of less than a meter. By using a receiver analogous to the control station and sending by the wire 19 of the geodetic coordinates of the control station, the microprocessor keeps in RAM the horizontal and vertical relative distances of the flying machine 1 at the control station 2.

The microprocessor 20, here of the type
Intel N 80 C 196 kB commonly used in "GPS" receivers, processes the control signals of amplifiers 23, 24 according to two processes.

 From the dynamometer 13e, it determines the traction exerted on the wire, and compares it to two threshold values, a maximum corresponding to the traction which must not be exceeded so as not to risk a break, and a minimum below from which the wire takes an indeterminate form. If the traction reaches the maximum, the motor 12 is controlled in reeling, and if the traction is reduced to the minimum, the motor 12 is controlled in reeling. These commands have priority.

 Furthermore, the microprocessor 20 develops the controls for the motor 12 to optimize the shape of the wire 19 between the flying machine 1 and the control station 2.

 We know that a wire without stiffness and of constant linear mass, held at its two ends takes the form of a hyperbolic chain or cosine.

 In reduced coordinates, x and z of the current point.

z = chx - 1 (1)
taking as its origin the lowest point of the chain.

The reduced coordinates are linked to the actual coordinates altitude A and horizontal distance R of the current point at the origin by the relations
x = 1R and z = 1A (2)
oo
where 1o is a reference length such that the weight of the wire which it comprises is equal to the traction exerted on the wire in the form of a chain.

From Equation 1, we deduce the slope of the wire at the current point
tga = shx (3)
as well as the length of wire between the flying machine 1 of coordinates xl and zl and the control station 2 of coordinates x2, Z2
1 = lo (six1 - shx2) (4)
It will be observed that there remains an arbitrary magnitude for passing from the system reported at the origin R = 0, A = o, and the system comprising the relative positions of the flying machine 1 and of the control station 2, the traction on the wire and the reference length being indeterminate.

 But if we set the slope of the tga2 wire from the control station, the indeterminacy disappears and we have a system of equation which can be solved by microprocessor 20 by effecting the change of coordinates corresponding to the positions of the control station 2 and the flying machine 1.

 Furthermore, the length of wire unwound between the control station 2 and the flying machine 1 is a one-to-one function of the number of turns in unwinding the drum 11, the account of which is kept by the microprocessor 20 from the up-down counter 16 , as soon as the wire is wound regularly on the drum 11, this function having as parameters the diameter of the wire 19, the length and the bare diameter of the drum 11.

If D is the bare diameter of the drum, m the length of the drum and d the diameter of the wire, and N the number of turns of the wire in reserve, the length 1 'in reserve is given by
1 '= n <ND + N2d2> (5)
m
from where it is easy to deduce the unwound length, knowing the total length of wire.

 The microprocessor 20 periodically compares the length of the wire actually unwound, with the calculated length corresponding to the fixed slope tga2 from the control station, taking account of the horizontal and vertical distances between the control station 2 and the flying machine 1, and will control the reeling or reeling of the drum 11 to adjust the length actually unrolled over the calculated length, to bring the slope of the wire from the control station to the fixed value.

 In fact, the controls will be adjusted so that this tga2 slope at the start of the control station remains between two limit values.

 It will be understood that thus the trajectories described by the flying object 1 are practically no longer subjected to constraints linked to the presence of the connecting wire.

 To fix orders of magnitude, the wire 19 could consist of a silica fiber coated with a polymer, with an external diameter of 0.2 mm, which has a linear mass of 90 g per kilometer (90 tex), and can withstand without risk of breakage a traction of at least 6 Newtons (the reference length reaches approximately 7 km). In addition, a drum 11 having a length between cheeks of 50 mm, and a bare diameter, or core diameter of 50 mm can accommodate approximately 3.9 km of optical fiber of 0.2 mm in diameter, the diameter of the winding reaching 80 mm, and the number of turns on the full drum being 18,750 turns.

 Of course, the invention is not limited to the example described, but embraces all of the variant embodiments thereof.

 In particular, the description made reference to a ground control station. However, the control station could be mobile, such as a vehicle on land, a boat on a body of water, or even an aircraft at a speed compatible with that of the flying machine, the equipment of the control station with a receiver "GPS" enabling the coordinates of the control station 2 to be refreshed in the microprocessor, and keeping the horizontal and vertical distances of the machine 1 up to date with respect to the control station 2.

Claims (8)

 1. On-board equipment of a flying machine (1) controlled by wire (19) from a control station (2) for the bidirectional transmission of signals by wire, the latter being reusable, equipment where a store containing a reserve of wire (10) is provided for delivering an adequate length of wire unwound from the machine (1) to the control station (2), characterized in that the magazine comprises a drum (11) where the reserve is wound up (10), provided with a reeling-reeling mechanism (13) driven by a reversible motor (12), a dynamometric means (13q, 13e) interposed between the reeling-reeling mechanism (13) and a die (18) by which the wire (19) leaves the machine (1), producing a signal representative of the traction exerted on the wire, and control means (20, 23, 24) sensitive to this representative signal of traction for controlling the motor (12) in unwinding-winding so as to maintain the traction on the wire (19) between a maximum and a min imum.  2. Equipment according to claim 1, characterized in that it comprises a navigation device (25) determining, in a geodetic tracking system, the position coordinates of the machine (1) connected to those of the control station ( 2), a means (16), coupled to the unwinding-reeling mechanism, measuring the unwound length of wire, and calculation means (21) adapted to determine, from the position coordinates of the machine (1) and from the control station (2), the horizontal and vertical distances between them, and to deduce therefrom, taking into account the unwound length of wire (19), the slope (tga2) at the control station of the chain formed by the wire, the servo means (20) being further adapted to control the motor (12) so as to maintain the slope (tga2) between two prefixed values, maintaining the traction of the wire below the maximum is however a priority.  3. Equipment according to claim 2, characterized in that the navigation device is of the so-called "GPS" receiver type (25) in connection with a network of geodetic satellites.  4. Equipment according to any one of claims 1 to 3, characterized in that the drum (11) is rotatably mounted about an axis (they) driven by the motor (12), the reel-feed mechanism (13) further comprising a cutting ramp (14) with a wire guide (13a) suitable for ensuring a regular winding of the wire (19) on the drum (11).  5. Equipment according to claim 4, characterized in that the cutting ramp (14) is adapted to a winding with contiguous turns on the drum.  6. Equipment according to one of claims 4 and 5, characterized in that the end of the reserve wire ends, in the axis of the drum, at a rotating coupler (17) ensuring the passage of signals in both directions.  7. Equipment according to claim 6, characterized in that the rotary coupler (17) comprises optical couplers.  8. Equipment according to any one of claims 1 to 7, characterized in that the wire (19) is an optical fiber.