FR2716318A1 - Electrical signal transmission between relatively rotating parts e.g. for armoured vehicle with turret - Google Patents

Abstract

The system includes a rotating joint (10) located on a pivotal axis (X-X) between two parts (3,5). Electrical conducting tracks and sliding contact brush conductors assure the transmission of electrical power signals between the parts. An infra-red link passes across the joint and consists of an emitter (E) and receiver (R) positioned between the two parts on the pivotal axis. It is used for transmission of low power signals. The emitter has an input such as an electro-acoustic transducer leading to an amplifier, a LPF, a modulator and an LED emitter powered by a Darlington pair output stage. The receiver is an infra-red photodiode followed by an amplifier, a LPF, a regeneration circuit and a demodulator. A third LPF reconstitutes the original signal which passes to a speaker output stage.

Description

SYSTEM FOR TRANSMITTING ELECTRIC SIGNALS BETWEEN TWO
STRUCTURES OF WHICH ONE IS ROTATING ROTARY IN RELATION TO
THE OTHER
The invention relates to a system for transmitting electrical signals between two structures, one of which is rotatably mounted relative to the other about a pivot axis, these structures being for example those of a chassis of an armored vehicle. and a turret pivotally mounted on this chassis, the transmission system comprising a rotating joint located on the pivot axis between the two structures and equipped with electrically conductive tracks, on the one hand, and conductive brushes in contact sliding with said tracks, on the other hand, to ensure in particular the transmission of electrical power signals between the two structures.

 In general, the transmission of electrical signals between the chassis of an armored vehicle and the turret it supports is effected by a rotating joint which may include several dozen tracks and associated brushes. I1 results in a rotating joint of complex structure, delicate to produce and of high cost. In addition, signal transmission can be affected by disturbances that are inherent in a mechanical mode of transmission or that result from hostility from the surrounding environment. Finally, any modification aimed in particular at adding a signal transmission is not without posing problems with the installation of this transmission in the rotary joint.

 The main object of the invention is to overcome the aforementioned drawbacks, and for this purpose it proposes a transmission system which uses a rotary joint to ensure in particular the transmission of electrical power signals, and which is characterized in that it comprises also at least one non-guided optical link, of the infrared type, passing through the rotating joint and consisting of a transmitting device and a receiving device supported by the two structures and located on the pivot axis for transmitting signals in particular electrical power between the two structures.

 According to another characteristic of the invention, the transmission system comprises at least a first unguided optical link for transmitting low power electrical signals in analog form, these signals being for example signals of the intercom type.

In a first embodiment, the device emitting this first unguided optical link comprises
- an input stage constituted by an electro-acoustic transducer for example,
- an amplifier circuit to amplify the signals delivered at the output of the transducer,
- a filtering circuit or low-pass filter to eliminate the frequencies higher than the audio frequency spectrum 0-3400 Hz in the signals delivered at the output of the amplifier circuit,
a modulator circuit for frequency modulation of the signals delivered at the output of the filtering circuit, and
- an output stage consisting of a diode emitting infrared radiation for transmitting the frequency modulated signals delivered at the output of the modulator circuit.

 According to a characteristic of this first embodiment, the modulator comprises a variable frequency oscillator controlled by the voltage of the signals delivered at the output of the filtering circuit, the quiescent frequency of the oscillator being for example 20 kHz with an excursion of frequency of the order of 10 kHz.

In this first embodiment, the receiving device comprises
- an input stage constituted by a photodiode sensitive to infrared radiation emitted by the diode of the emitting device,
- an amplifier circuit for amplifying the signals delivered at the output of the input stage,
- a filtering circuit or second-order low-filter to eliminate frequencies above 30 kHz in the signals delivered at the output of the amplifier circuit,
a fitness circuit constituted by a comparator whose tilting threshold is predetermined, for reshaping the signals delivered at the output of the filtering circuit,
- a demodulator circuit of the frequency modulated signals delivered at the output of the fitness circuit,
a second filtering or low-filter circuit with a cut-off frequency greater than the audio frequency spectrum to reconstruct at output the signals delivered by the electro-acoustic transducer of the transmitting device, and
- an output stage constituted by a speaker for example.

 According to a characteristic of the receiving device, the photodiode is reverse biased to behave like a variable resistor as a function of the intensity of the light flux received, the input stage also comprises a current-voltage converter-inverter circuit which delivers in output a voltage signal proportional to the photonic current induced in the photodiode, and the demodulator comprises a phase-controlled oscillator and a phase comparator circuit of the EXCLUSIVE OR type.

 According to another characteristic of the invention, the transmission system also comprises at least one second non-guided optical link of the infrared type for transmitting low power electrical signals in digital form, these signals being for example signals of the gyrometer type relating to angular speeds of the pivoting structure.

According to a second embodiment, the device emitting this second optical link comprises
an input stage receiving the digital signals to be transmitted, these signals being able to result from analog signals converted into digital,
a frequency displacement type FSK modulator circuit for modulating the digital signals delivered at the output of the input stage, and
- an output stage consisting of a diode emitting infrared radiation to transmit the output signals from the modulator circuit.

The device for receiving this second optical link comprises
- an input stage consisting of a photodiode sensitive to infrared radiation emitted by the diode of the emitting device,
- an amplifier circuit to amplify the signals at the output of the input stage,
- a filtering circuit,
- a demodulator circuit of the FSK type, and
- an output stage constituted by a display device for example.

 According to an important advantage of the invention, the optical connections can be made over a few tens of centimeters without being subject to disturbances, in particular of the electromagnetic type.

 According to another advantage of the invention, the transmission system can be easily adapted to add or delete a transmission channel without modifying the structure of the transmitter and receiver devices.

Other advantages, characteristics and details will emerge from the explanatory description which follows, given with reference to the appended drawings, given solely by way of example and in which
FIG. 1 is a schematic view illustrating the principle of a transmission system according to the invention,
FIG. 2 illustrates in the form of a schemabloc the principle of the system according to the invention in the case of a transmission of analog signals,
FIG. 3 illustrates an embodiment of a transmitter device for implementing the transmission principle of FIG. 2,
FIG. 4 illustrates an embodiment of the receiving device for implementing the transmission principle of FIG. 2,
FIG. 5 illustrates in the form of a block diagram the principle of the system according to the invention in the case of a transmission of digital signals,
FIG. 6 illustrates an embodiment of a transmitting device for implementing the transmission principle of FIG. 5, and
FIG. 7 illustrates an embodiment of the receiving device for implementing the transmission principle of FIG. 5.

 Figure 1 schematically illustrates the principle of the transmission system according to the invention.

 This system 1 is for example mounted between a chassis 3, such as that of an armored vehicle, and a basket 4 of a turret 5 rotatably mounted on the chassis 3 around a pivot axis X-X.

 The transmission system 1 comprises a rotary joint 10, known per se, mounted on the axis XX and consisting of two blocks 10a and 10b respectively supported by the chassis 3 and the turret basket 4. The block 10a of the rotary joint 10 is for example equipped with rings or tracks that conduct electricity, while the block 10b of the rotary joint 10 is equipped with conductive brushes in sliding contact with the rings. For reasons of simplification, only contacts between rings and brushes have been indicated in FIG. 1 by the general reference 12.

 The rotary joint 10 is used for the transmission of high power electrical signals to supply the energy necessary for the operation of the equipment of the turret 5, for example.

The rotary joint 10 comprises a central opening 14 which will advantageously be used to provide non-guided optical connections, of the infrared type, between the chassis 3 and the turret basket 4. An optical connection is constituted by an emitting device E and a device receiver R which are respectively supported by the chassis 3 and the turret basket 4, on the one hand, and located on the pivot axis
XX, on the other hand.

 The transmission system 1 which will be described below comprises two unguided optical links for ensuring transmission of low power electrical signals, a first link for transmitting analog signals and a second link for transmitting digital signals.

 The block diagram of FIG. 2 illustrates the principle of the transmission of an analog signal by the aforementioned first optical link. On transmission, the analog signal S1 is frequency modulated and transmitted by an emission device El in the form of infrared radiation. On reception, this infrared radiation is picked up by a reception device R1 and the resulting signal is demodulated to reconstitute the original analog signal S1. This transmission principle is implemented according to the embodiment illustrated in FIGS. 3 and 4, and applied to the case of the transmission of intercom signals between the chassis 3 and the turret 5, or vice versa.

 The transmitter device E of FIG. 3 comprises a source 20 of analog signals, an amplifier circuit A1, a filtering circuit F1, a modulator circuit M1 and a device El for emitting infrared radiation.

 The source 20 of analog signals is for example constituted by an electroacoustic transducer, such as a microphone, which delivers at the output signals of an amplitude of the order of 0 to 100 mV. These signals are amplified by the amplifier circuit A1 which is constituted by an operational amplifier CI1 whose gain is adjusted from a potentiometer P'1 to obtain output signals of the order of 0 to 15 V, for example.

The operational amplifier CI1 is for example that sold by the National Society
Semiconductor Corporation under the reference LM318.

 In general, the frequency spectrum of the audio signals delivered by the electro-acoustic transducer extends from 0 to 3400 Hz approximately. To avoid any distortion problem on reception, the frequencies above 3400 Hz of the analog signals delivered at the output of the amplifier circuit Al are filtered by means of a filtering circuit F1 consisting of a low-pass filter whose resistance values RO and CO capacitors are calculated accordingly.

 The signals at the output of the filtering circuit F1 are frequency modulated by a modulator circuit M1 comprising a variable frequency oscillator controlled by the voltage of the signals delivered at the output of the filtering circuit F1. The rest frequency of the oscillator is by example of 20 kHz with a maximum frequency deviation of the order of 10 kHz, which corresponds to a frequency range f min. from 10 kHz to f max. 30 kHz, which is adjusted by potentiometer P1.

The modulator circuit M1 is for example an integrated circuit CI2, such as that sold by the
RTC company under reference 4046.

 The emission device El consists of a diode D1 emitting infrared radiation. More specifically, the signals from the modulator circuit M1 are transmitted to a power stage of the Darlington type comprising two transistors T1 and T2, the diode D1 being mounted in the collector of the transistor T2. The diode D1 has for example a power of the order of 30 mW, which is sufficient to ensure a good unguided connection over a distance of a few tens of centimeters, a distance which is compatible with the dimensions of the rotary joint 10 used for the transmission of electrical power signals.

The receiver device R illustrated in FIG. 4 comprises an input stage or reception stage R1, an amplifier circuit A2, a first filtering circuit
F2, a fitness circuit SC, a demodulator circuit DM2, a second filtering circuit F3 and an output stage 30.

 The reception stage comprises a photodiode D2 operating in photoconductive mode, that is to say that it is polarized under a reverse voltage by a Zener Z diode to behave like a variable resistance according to the intensity of the emitted infrared radiation. by diode D1. This operating mode allows a quick response time and good linearity. The photo-diode D2 is associated with a current-voltage inverter converter circuit C which outputs a signal proportional to the photonic intensity induced in the photo-diode D2. The proportionality coefficient is determined by the value of the resistor R9 which is advantageously of a low value to maintain good bandwidth.

The converter C is for example an integrated circuit CI3, such as that marketed by the Company
National Semiconductor Corporation under reference
LM118.

 The signal delivered at the output of converter C has a voltage level of the order of 0 to 80 mV, so that it is necessary to amplify this signal by the amplifier circuit A2, mounted as an inverter and whose gain is adjusted so as to obtain at the output signals having an amplitude of the order of 0 to 5 V. The gain adjustment is obtained by adjusting the value of the resistor R10 and of the potentiometer P2.

 The amplifier A2 is for example an integrated circuit CI4 of the same type as that used to make the converter C.

 Since the receiving device R can possibly pick up spurious signals coming from other transmitters for example, the signals delivered at the output of the amplifier circuit A2 are filtered by the filtering circuit F2 which is constituted by a low-pass filter of the second order to eliminate frequencies above 30 kHz, i.e. frequencies outside the range f min. - f max. of the modulator circuit M1 of the emitting device E. The cut-off frequency of the filter is adjusted from the values of resistors R13 and R14.

 The filtering circuit F2 also uses an integrated circuit CI5 of the same type as those used to make the converter C and the amplifier A2.

 The signals delivered at the output of the filtering circuit F2 are reshaped by the circuit SC which is constituted by a comparator of good speed and having a high input impedance. The switchover threshold of the comparator is adjusted using resistors R15, R16 and potentiometer P3.

The SC fitness circuit consists of an integrated circuit CI6, such as that marketed by the National Semiconductor Company
Corporation under reference Lu3032
The signals delivered to the output of the fitness circuit SC are then demodulated by the demodulator circuit DM2 which comprises a phase-controlled oscillator, that is to say an oscillator controlled in voltage and whose output signal is applied to a phase comparator constituted by an EXCLUSIVE OR circuit. The comparator allows the phase lock loop to remain locked despite any noises present in the input signal.

 The demodulator circuit DM2 is for example constituted by an integrated circuit DI7, such as that sold by the company RTC under the reference 4046B.

The comparator of this demodulator circuit DM2 receives as input the reference signals, of rectangular shape, delivered at the output of the fitness circuit SC on the one hand, and the output signals, also of rectangular shape, delivered at the output on the other hand. These input signals are phase shifted, and the comparator delivers at the output signals, of square shape, which are applied to a low-pass filter R18-C2 mounted at the output of the comparator. This filter outputs triangular shaped signals which are applied to the input of the oscillator circuit.

Concretely, the frequency variations in the reference signals cause a variation in the average value of the triangular signal applied to the input of the oscillator of the demodulator circuit DM2.

 The demodulator circuit DM2 is followed by a second filtering circuit F3 to recover the average value of the input voltage of the oscillator of the demodulator circuit DM2 and to reform at its output the intercom signals transmitted by the transmitter circuit E.

The cut-off frequency of the filtering circuit F3 is therefore chosen to be greater than 3400 Hz by setting the values of the resistors R19, R20 and the capacitors C20, C21.

This second filtering circuit F3 is therefore similar to the integrated circuit CI5 of the filtering circuit F2 mounted at the output of the amplifier circuit A2.

 The output stage 30 is for example constituted by a loudspeaker HP which audibly reproduces the analog signals which it receives.

The block diagram of FIG. 5 illustrates the principle of transmission of digital signals between the chassis 3 and the turret 5, or vice versa. These signals can be analog signals S2 which are then converted to digital by an analog / digital converter CAN or digital signals S3 of the all or nothing type. These signals S2 and S3 are modulated according to a modulation of the FSK type and transmitted by a device El for emitting infrared radiation. On reception, the infrared radiation is picked up by a reception device and the resulting signals are demodulated to reconstruct the original signals S2 and
S3, the signals corresponding to the signals S2 being previously converted into analog by a digital / analog converter DAC. The signals S2 are for example of the gyrometer type, that is to say that they give information relating to the angular speeds of the turret 5 relative to the chassis 3, while the signals S3 give information on the open position or closed with doors or hatches.

 FIG. 6 illustrates an exemplary embodiment of the transmitter device E for implementing the transmission principle of FIG. 5.

 The emitting device E comprises an input stage 20 which delivers digital signals, a modulator circuit M1 and a device El for emitting infrared radiation.

 The modulator circuit M1 is a frequency displacement type FSK modulator, which includes an oscillator which provides a low frequency fL to code a logic level 1 and a high frequency fH to code a logic level 0. The central frequency of this oscillator is for example 100 kHz, the low frequency fL of 75 kHz and the high frequency fH of 125 kHz.

The setting of these frequencies is obtained by the resistors Ra, Rc and the potentiometers Pa and Pc. The output signal of the modulator circuit M1 is therefore a frequency signal fL or fH with a duty cycle equal to 50%.

The modulator circuit M1 is for example constituted by an integrated circuit CI8 sold by the
EXAR company under the reference XR2206.

 The device E1 for emitting infrared radiation is constituted by a diode D1 with the interposition of a power stage of the Darlington type consisting of two transistors T1 and T2.

 To limit the heat dissipation of the diode D1, the duty cycle can possibly be reduced by inserting a monostable circuit between the modulator circuit M1 and the power stage associated with the diode D1.

 As in the case of the embodiment of FIGS. 3 and 4, the power of the diode D1 is of the order of 30 mW.

 The receiver device R illustrated in FIG. 7 comprises an input or reception stage R1 of the infrared radiation emitted by the diode D1, an amplifier circuit A2, a fitness circuit SC, a demodulator circuit DM2 and an output stage .

 The input or reception stage R1 comprises a photo-diode D2 operating in photoconductive mode, that is to say that the photo-diode D2 is biased under a reverse voltage by a Zener Z diode to behave like a variable resistance as a function of the intensity of the infrared radiation emitted by the diode D1.

 The photo-diode D2 is associated with a current-voltage converter circuit C, of the non-inverting type, which outputs a signal proportional to the photonic intensity induced in the photo-diode D2. The proportionality coefficient is determined by the value of the resistor R29 which will advantageously be low to maintain good bandwidth.

 The converter C is for example constituted by an integrated circuit CI3 of the same type as that used in the reception circuit of the previous embodiment.

 The amplifier circuit A2 amplifies the signals delivered at the output of the converter C. These signals are then reshaped by the circuit SC consisting of a comparator whose tilting threshold is determined by the values of the resistors R31, R32 and the potentiometer P5 .

 The amplifier A2 and the fitness circuit SC are of the same type as those used in the reception circuit of the previous embodiment.

 The signals delivered to the output of the fitness circuit SC are demodulated by the demodulator circuit DM2 which comprises a voltage controlled oscillator.

The DM2 demodulator circuit is for example constituted by an integrated circuit CI9, such as that marketed by the company EXAR under the reference
XR2211, which also includes a voltage-controlled oscillator whose center frequency is the same as that of the DM1 modulator circuit, i.e. 100 kHz.

 The signals delivered by the demodulator circuit DM1 are then transmitted to an output stage 30 which restores the original digital signals or the original analog signals after conversion by a digital / analog converter DAC, as illustrated in FIG. 5. L 'output stage 30 can be equipped with a display device to materialize the signals transmitted, these signals controlling for example the lighting of an indicator light.

 In general, the transmitter E and receiver R devices are connected by electrical conductors 1 to the associated circuits or devices which equip the chassis 3 and the turret 5.

 In the embodiments described above, we have considered a transmitter device E located at the level of the chassis 3 and a receiver device R located at the level of the turret 5. Of course, this arrangement can be reversed, and two systems can also be provided. transceiver to provide a bidirectional link between chassis 3 and turret 5.

Claims (15)

 1. System for transmitting electrical signals between two structures, one of which is rotatably mounted with respect to the other about a pivot axis, these structures being, for example, those of a chassis (3) of an armored vehicle and a turret (5) pivotally mounted on the chassis (3), this transmission system comprising a rotating joint (10) located on the pivot axis (XX) between the two structures (3, 5) and equipped with electrically conductive tracks, on the one hand, and conductive brushes in sliding contact with said tracks, on the other hand, in particular for ensuring the transmission of electrical power signals between the two structures (3, 5), characterized in that that it also comprises at least one non-guided optical link of the infrared type passing through the rotary joint (10) and consisting of a transmitting device (E) and a receiving device (R) supported by the two structures (3 , 5) and located on the pivot axis (X X), in particular for transmitting low power electrical signals between the two structures (3, 5).  2. Transmission system according to claim 1, characterized in that it comprises at least a first unguided optical link for transmitting low power electrical signals in analog form, these signals being for example signals of the intercom type.  3. Transmission system according to claim 2, characterized in that the emitting device (E) of the first unguided optical link comprises  an input stage (20) constituted by an electro-acoustic transducer for example,  - an amplifier device (A1) for amplifying the signals delivered at the output of the transducer,  - a filtering circuit (F1) or low filter to eliminate the frequencies higher than the audio frequency spectrum 0-3400 Hz in the signals delivered at the output of the amplifier circuit (Al),  a modulator circuit (M1) for frequency modulating the signals delivered at the output of the filtering circuit (F1) and  - an emission circuit (El) consisting of a diode (D1) emitting infrared radiation.  4. Transmission system according to claim 3, characterized in that the modulator circuit (M1) comprises a variable frequency oscillator controlled by the voltage of the signals delivered at the output of the filtering circuit (F1), the rest frequency of l oscillator being for example 20 kHz with a frequency excursion of 10 kHz.  5. Transmission system according to claim 3, characterized in that the output stage also comprises a power circuit (T1, T2) interposed between the modulator circuit (M1) and the diode (D1) emitting infrared radiation .  6. Transmission system according to claim 5, characterized in that the power circuit (T1, T2) is constituted by two transistors mounted in a Darlington arrangement.  7. Transmission system according to claim 3, characterized in that the receiving device (R) comprises  - an input or reception stage (R1) comprising a photo-diode (D2) sensitive to the infrared radiation emitted by the emission diode (D1),  - an amplifier circuit (A2) to amplify the signals delivered at the output of the reception stage (R1), a filtering circuit (F2) or low-pass filter of the second order to eliminate the frequencies higher than 30 kHz in the signals delivered at the output of the amplifier circuit (A2),  a fitness circuit (SC) constituted by a comparator whose tilting threshold is predetermined, for reshaping the signals delivered at the output of the filtering circuit (F2),  - a demodulator circuit (DM2) for demodulating in frequency the signals delivered at the output of the fitness circuit (SC),  a second filtering circuit (F3) or low-pass filter with cutoff frequency greater than the audio frequency spectrum to reconstruct the output of the original signals transmitted by the transmitter device (E) and  - An output stage (20) constituted by a loudspeaker for example.  8. Transmission system according to claim 7, characterized in that the photo-diode (D2) of the reception stage (R1) is reverse biased to behave like a variable resistance according to the intensity of the infrared radiation emitted by the emission diode (D1).  9. Transmission system according to claim 8, characterized in that the reception stage (R1) also comprises a circuit (C) current-voltage inverter converter for outputting a voltage signal proportional to the photon current induced in the photo -diode (D2).  10. Transmission system according to claim 7, characterized in that the demodulator circuit (DM2) comprises a phase-controlled oscillator and a phase comparator circuit of the OR type. EXCLUSIVE.  11. Transmission system according to claim 10, characterized in that the voltage of the output signal of the demodulator circuit (DM2) corresponds to the average value of the input voltage of the oscillator.  12. Transmission system according to claim 1, characterized in that it comprises at least one second non-guided optical link of the infrared type for transmitting low power electrical signals in digital form, these signals being for example signals of the gyrometer type relating to the positioning of the pivoting structure (5).  13. Transmission system according to claim 12, characterized in that the transmitter device (E) comprises  - a source (10) of digital signals,  a modulator circuit (M1) of the FSK type with frequency displacement and the input of which is connected to the output of the source (10) and  - an emission circuit (El) constituted by a diode (D1) emitting infrared radiation to transmit the signals delivered at the output of the modulator circuit (M).  14. Transmission system according to claim 13, characterized in that the receiving device (R) comprises  - an input or reception stage (R1) comprising a photo-diode (D2) sensitive to the infrared radiation emitted by the diode (D1) of the emitter circuit (E),  - an amplifier circuit (A2) for amplifying the signals delivered at the output of the reception stage (R1),  - a circuit (SC) for reshaping the signals delivered at the output of the amplifier circuit (A2),  - a demodulator circuit (DM2) of the FSK type, and  - An output stage (20) constituted by a display device for example.  15. Transmission system according to claim 14, characterized in that the reception stage (R1) also comprises a circuit (C) current-voltage converter proportional to the photonic current induced in the photodiode (D2).