ELECTRICAL EQUIPMENT FOR CONNECTION TO A TACHOMETER

Description

[0001] The invention relates to the field of electrical equipment of the calculator or data concentrator type, intended to be connected to tachometers. BACKGROUND OF THE INVENTION

[0002] A tachometer, intended to measure the rotational speed of a wheel of an aircraft landing gear, typically comprises a rotor integral in rotation with the wheel, a stator and a rotational speed sensor. The rotational speed sensor comprises a winding positioned on the stator.

[0003] The winding is connected via a cable to a computer (or any other electrical equipment, for example a data concentrator). The computer then acquires an electrical measurement signal whose voltage and / or frequency are representative of the rotation speed of the wheel.

[0004] Typically, a plurality of cables from a plurality of tachometers are bundled into a harness that runs from the landing gear to inside the aircraft fuselage where the computer is positioned.

[0005] However, it is possible that one of the landing gear wheel tires could burst. Tire debris would then be thrown out and could damage the harness and sever one of the cables.

[0006] It is then necessary to detect the loss of the tachometer connected to the severed cable. Note that a zero voltage of the electrical measurement signal can correspond to a zero rotation speed and therefore to a "normal" and correctly measured rotation speed measurement.

[0007] We also note that it is possible that one of the wheels, which is spinning, has a zero rotation speed while the rotation speed of the other wheels is non-zero.

[0008] The simple detection of zero voltage, even combined with a comparison with the rotation speeds of other wheels, is therefore not sufficient to detect a severed cable.

[0009] For each tachometer, it was considered to make the rotation speed sensor redundant. This redundancy requires doubling the number of computer inputs dedicated to measuring wheel rotation speed, and adds additional mass and bulk to each tachometer. This redundancy also involves using two cables instead of just one between the tachometer and the computer.

[0010] Consideration was also given to redundant only the cable that connects the tachometer to the computer. This redundancy also adds additional ground and creates loops in the electrical circuit formed by the cables and the computer, which is problematic for compliance with electromagnetic compatibility requirements.

[0011] It should be noted that, in the two solutions just described, the loss of the two cables connecting the tachometer to the computer is not detected.

[0012] Finally, it was considered to regularly test the continuity of the cable and the winding by injecting a weak signal into the cable and the winding. However, this implies regularly deactivating the acquisition of the electrical measurement signal, and therefore of the wheel rotation speed, which is not acceptable in a braking system that implements an anti-skid function. Document EP 0 764 829 A1 discloses an approach for detecting a disconnection of a measurement wire in a tachometer device. SUBJECT OF THE INVENTION

[0013] The object of the invention is to detect a break in a cable connecting a tachometer to electrical equipment in a simple, space-saving manner and without deactivating the measurement of the wheel rotation speed. SUMMARY OF THE INVENTION

[0014] To achieve this goal, electrical equipment of the calculator or data concentrator type is proposed, intended to be connected to a tachometer via a cable comprising a measurement wire and a test wire, the electrical equipment comprising a measurement input to which the measurement wire can be connected and a test input to which the test wire can be connected, measurement acquisition components connected to the measurement input and arranged to acquire an electrical measurement signal present on the measurement wire and produced by the tachometer, test acquisition components connected to the test input and arranged to detect whether the test wire is in open circuit or not, and processing components arranged to detect a break in the measurement wire if the test wire is in open circuit.

[0015] A break in the measuring wire is therefore detected by detecting an open circuit in the test wire. This solution is simple to implement and space-saving, since it only requires the addition of the test wire in the cable that includes the measuring wire connected to the tachometer. This solution does not require deactivating the acquisition of the electrical measurement signal, since the test wire, which allows the detection of the break in the measuring wire, is separate from the measuring wire.

[0016] Further provided is a system comprising a tachometer, a cable comprising a measuring wire and a test wire, and electrical equipment such as that just described, the cable comprising a first end connected to the tachometer and a second end connected to the electrical equipment.

[0017] The invention will be better understood in light of the following description of particular non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Reference will be made to the attached drawings, including: there figure 1 represents electrical equipment according to a first embodiment of the invention, a cable and a tachometer; the figure 2 represents test acquisition components of the electrical equipment according to the first embodiment of the invention; the figure 3 represents test acquisition components of electrical equipment according to a second embodiment of the invention; the figure 4 represents electrical equipment according to a third embodiment of the invention, a cable and a tachometer; the figure 5 represents electrical equipment according to a fourth embodiment of the invention, a cable and a tachometer. DETAILED DESCRIPTION OF THE INVENTION

[0019] In reference to the figure 1 , the electrical equipment according to a first embodiment of the invention is here a computer 1. The computer 1 is connected to a tachometer 2 via a cable 3.

[0020] Computer 1 is located in a hold of an aircraft.

[0021] The computer 1 comprises a casing 4 in which measurement acquisition components 7, test acquisition components 8 and processing components 9 are integrated.

[0022] The computer 1 comprises a first measurement input 11 and a second measurement input 12. The first measurement input 11 and the second measurement input 12 are connected to the measurement acquisition components 7.

[0023] The computer 1 also has a test input 14. The test input 14 is a discrete input. The test input 14 is connected to the test acquisition components 8.

[0024] The test acquisition components 8 are visible on the figure 2 . The test acquisition components 8 are here discrete signal acquisition components.

[0025] The test acquisition components 8 comprise a resistor 17 and a resistor 18 connected to the test input 14, a reference voltage source 19 connected via a resistor 21 to a point P located between the resistor 17 and the resistor 18, and a resistor 22 connected between the resistor 18 and an electrical ground 23 of the computer 1. The test acquisition components 8 further comprise a low-pass filter 25 and a hysteresis comparator 26. An input of the low-pass filter 25 is connected to the resistor 18 and to the resistor 22. An output of the low-pass filter 25 is connected to an input of the hysteresis comparator 26.

[0026] Electrical ground 23 is connected to housing 4 of computer 1.

[0027] The tachometer 2 is intended to measure the rotational speed of a wheel of a landing gear of the aircraft. The tachometer 2 comprises a casing 30 in which a rotational speed sensor is integrated. The rotational speed sensor comprises a rotor and a stator which comprises a winding 31.

[0028] Cable 3 is here positioned, over part of its length, in a harness which groups together a plurality of similar cables connected to tachometers. The harness runs from the landing gear to the aircraft's hold.

[0029] The cable 3 has a first end 33 and a second end 34. The first end 33 is connected to the tachometer 2. The second end 34 is connected to the computer 1.

[0030] The cable 3 comprises a first measuring wire 36, a second measuring wire 37 and a test wire 38. The first measuring wire 36, the second measuring wire 37 and the test wire 38 are twisted, i.e. they are wound helically around each other.

[0031] At the first end 33 of the cable 3, the first measuring wire 36 is connected to a first terminal of the stator winding 31. The second measuring wire 37 is connected to a second terminal of the stator winding 31. The test wire 38 is connected to a ground 39 of the tachometer 2 via a shield of the harness or the cable 3, or via a mechanical ground of the tachometer 2 if the casing 30 of the tachometer 2 is referenced to ground.

[0032] At the second end 34 of the cable 3, the first measuring wire 36 is connected to the first measuring input 11 of the computer 1, the second measuring wire 37 is connected to the second measuring input 12, and the test wire 38 is connected to the test input 14.

[0033] The measurement acquisition components 7 of the computer 1 acquire an electrical measurement signal whose voltage and / or frequency are representative of the rotation speed of the wheel.

[0034] The test acquisition components 8, for their part, compare a test voltage Vt at the input of the hysteresis comparator 26 with a detection threshold, in this case a predetermined voltage threshold. The test voltage Vt is representative of the impedance applied to the test input 14.

[0035] If the test voltage Vt is lower than the predetermined voltage threshold, the test acquisition components 8 detect that a discrete ground signal is applied to the test input 14. The grounding corresponds to the connection of the test wire 38 to the ground 39 of the tachometer 2 at the first end 33 of the cable 3.

[0036] The processing components 9 then detect continuity of the test wire 38, and therefore that the test wire 38 is not broken. The processing components 9 therefore do not detect a break in the first measuring wire 36 or the second measuring wire 37. Indeed, due to the proximity between the test wire 38 and the first measuring wire 36 and the second measuring wire 37, a break in the test wire 38, due for example to a tire explosion, would very probably have been accompanied by a break in the first measuring wire 36 or the second measuring wire 37.

[0037] If the test voltage Vt is greater than or equal to the predetermined voltage threshold, the test acquisition components 8 detect that a discrete open circuit signal is applied to the test input 14. The open circuit corresponds to an open circuit of the test wire 38.

[0038] The processing components 9 then detect a break in the test wire 38, and therefore a break in the first measuring wire 36 and / or the second measuring wire 37. The processing components 9 invalidate rotational speed measurements from the electrical measuring signal, deactivate the tachometer 2 and generate a fault message.

[0039] In reference to the figure 3 , the electrical equipment according to a second embodiment of the invention is again a computer. The computer is connected to a tachometer via a cable. The tachometer and the cable are similar to those just described.

[0040] The calculator this time comprises a first test input 101 and a second test input 102. The first test input 101 and the second test input 102 are both discrete inputs. The calculator comprises test acquisition components 103. The test acquisition components 103 are again components for acquiring a discrete signal.

[0041] The test acquisition components 103 include an operational amplifier 104, a low-pass filter 105 and a hysteresis comparator 106.

[0042] A non-inverting input of the operational amplifier 104 is connected to the first test input 101 via a resistor 107. An inverting input of the operational amplifier 104 is connected to the second test input 102 via a resistor 108.

[0043] The test wire is connected to the first test input 101.

[0044] The second test input 102 is connected to an electrical ground 110 of the computer, for example via the computer housing or via the shielding of the harness or cable.

[0045] A first reference current source 111 is connected to the non-inverting input via a resistor 112. A second reference current source 113 is connected to the inverting input via a resistor 114.

[0046] An output of the operational amplifier 104 is connected to an input of the low-pass filter 105. An output of the low-pass filter 105 is connected to an input of the hysteresis comparator 106.

[0047] Again, the test acquisition components 103 compare a test voltage Vt at the input of the hysteresis comparator 106 with a predetermined voltage threshold. The test voltage Vt is representative of the impedance applied between the first test input 101 and the second test input 102.

[0048] If the test voltage Vt is lower than the predetermined voltage threshold, the test acquisition components 103 detect that a discrete ground signal is applied to the first test input 101.

[0049] The processing components then detect continuity of the test wire, and therefore that the test wire is not broken. The processing components therefore do not detect a break in the first measuring wire or the second measuring wire.

[0050] If the test voltage Vt is greater than the predetermined voltage threshold, the test acquisition components 103 detect that a discrete open circuit signal is applied to the first test input 101.

[0051] The processing components then detect a break in the test wire, and therefore a break in the first measuring wire and / or the second measuring wire. The processing components invalidate rotational speed measurements from the electrical measurement signal, deactivate the tachometer and generate a fault message.

[0052] In reference to the figure 4 , the electrical equipment according to a third embodiment of the invention is a computer 201. The computer 201 is connected to a tachometer 202 via a cable 203.

[0053] The tachometer 202 comprises an electrical circuit on which a resistor 204 is mounted. The test wire 205 is connected to the ground 206 of the tachometer 202 via the resistor 204.

[0054] The calculator 201 has a test input 207 connected to the test wire 205. The test acquisition components 208 are this time resistance measurement components.

[0055] The test acquisition components 208 comprise a first input 210 connected to the test input 207 of the computer 201, and a second input 211 connected to an electrical ground of the computer 201.

[0056] The test acquisition components 208 measure a test resistance between the first input 210 and the second input 211, and therefore between the test input 207 and the electrical ground of the computer 201.

[0057] If the test resistance is less than a predetermined resistance threshold, the test acquisition components 208 do not detect that the test wire 205 is open circuited. The processing components 212 detect that the test wire 205 is not broken.

[0058] If the test resistance is greater than or equal to a predetermined resistance threshold, the test acquisition components 208 detect that the test lead 205 is open circuited.

[0059] The processing components 212 then detect a break in the test wire 205, and therefore a break in the first measuring wire and / or the second measuring wire. The processing components 212 invalidate rotational speed measurements from the electrical measuring signal, deactivate the tachometer and generate a fault message.

[0060] In reference to the figure 5 , the electrical equipment according to a fourth embodiment of the invention is a computer 301. The computer 301 is connected to a tachometer 302 via a cable 303.

[0061] In the fourth embodiment of the invention, the cable 303 this time comprises a first test wire 305 and a second test wire 306.

[0062] The first test wire 305 is connected, at a first end 307 of the cable 303, to a first terminal of a resistor 308 of the tachometer 302. The second test wire 306 is connected, at the first end 307 of the cable 303, to a second terminal of the resistor 308.

[0063] The first test wire 305 is connected, at a second end 309 of the cable 303, to a first test input 311 of the computer 301. The second test wire 306 is connected, at the second end 309 of the cable 303, to a second test input 312 of the computer 301.

[0064] The test acquisition components 314 comprise a first input 315 connected to the first test input 311 of the computer 301, and a second input 316 connected to the second test input 312 of the computer 301.

[0065] The 314 test acquisition components are again resistance measurement components.

[0066] The test acquisition components 314 measure a test resistance between the first input 315 and the second input 316, and therefore between the first test input 311 and the second test input 312 of the computer 301.

[0067] If the test resistance is within a valid range of resistance values, the processing components 317 detect that the first test lead 305 and the second test lead 306 are not broken.

[0068] If the test resistance is not within the valid range of resistance values, the processing components 317 detect that the first test lead 305 and / or the second test lead 306 are broken.

[0069] The processing components 317 then detect a break in the first measuring wire 318 and / or the second measuring wire 319. The processing components 317 invalidate rotational speed measurements from the electrical measuring signal, deactivate the tachometer and generate a fault message.

[0070] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0071] Although the electrical equipment described here is a computer, this electrical equipment could be different equipment, for example a data concentrator.

Claims

1. Electrical equipment of the type comprising calculation means or a data concentrator for connecting to a tachometer (2; 202; 302) via a cable (3; 203; 303) that comprises a measurement wire (36, 37; 318, 319) and a test wire (38; 205; 305, 306), the electrical equipment having a measurement input (11, 12) to which the measurement wire can be connected and a test input (14; 101, 102; 207; 311, 312) to which the test wire can be connected, measurement acquisition components (7) connected to the measurement input and arranged to acquire an electrical measurement signal present on the measurement wire and produced by the tachometer, test acquisition components (8; 103; 208; 314) connected to the test input and arranged to detect whether the test wire is or is not open-circuit, and processor components (9; 212; 317) arranged to detect a break of the measurement wire if the test wire is open-circuit.

2. Electrical equipment according to claim 1, wherein the test input (14; 101, 102) is a discrete input, and wherein the test acquisition components (8; 103) are arranged to detect a discrete open-circuit signal or a discrete ground signal.

3. Electrical equipment according to claim 2, the electrical equipment including a first test input (101) and a second test input (102), the first test input being for connecting to the test wire and the second test input being connected to electrical ground of the electrical equipment.

4. Electrical equipment according to claim 1, wherein the test acquisition components are arranged to measure a test resistance.

5. Electrical equipment according to claim 4, wherein the test resistance is a resistance between the test input (207) and electrical ground of the electrical equipment.

6. Electrical equipment according to claim 4, wherein the electrical equipment includes a first test input (311) and a second test input (312), the test resistance being a resistance between the first test input (311) and the second test input (312).

7. A system comprising a tachometer, a cable including a measurement wire and a test wire, and electrical equipment according to any preceding claim, the cable having a first end (33) connected to the tachometer and a second end (34) connected to the electrical equipment.

8. A system according to claim 7, wherein the measurement wire and the test wire are twisted together.

9. A system according to claim 7, wherein the test wire is connected to tachometer ground at the first end of the cable.

10. A system according to claim 7, wherein the tachometer includes an electric circuit having a resistor (204) connected therein, and wherein the test wire (205) is connected to tachometer ground via the resistor.

11. A system according to claim 7, wherein the cable has two test wires (305, 306), wherein the tachometer has an electrical circuit having a resistor (308) connected therein, and wherein each test wire is connected to a distinct terminal of the resistor.