DEVICE FOR SUPPLYING POWER TO A WIRED DRONE

Abstract

The present invention relates to a device for supplying electrical power to a wired system for a drone (1). The device according to the invention includes at least one power converter (4) on the ground and one power converter (2) at the level of the drone (1), regulation at the level of the converter on the ground ensures that the output voltage of the power converter (4) on the ground increases when the output current of the power converter (4) on the ground increases. The method according to the invention is intended for all wired drones, the wire (3) of which is used to supply electrical power to the drone (1).

Claims

1. A device for supplying power to a wired drone, including at least: a power converter on the ground, a power converter at the level of the drone, a wire connecting the power converters and, the device being characterized in that a regulation of the power converter on the ground ensures that the voltage U.sub.B delivered by the power converter on the ground increases when the current I.sub.B delivered by the power converter on the ground increases, and this over the power range of normal use of the drone.

2. The device according to claim 1, characterized in that the regulation compensates at least partially the voltage drop between the output of the power converter on the ground and the input of the power converter at the level of the drone, due to the resistance R.sub.F of the wire.

3. The device according to claim 1, characterized in that the regulation ensures a voltage U.sub.D at the input of the power converter at the level of the drone, close to the optimal operating voltage of the power converter at the level of the drone.

4. The device according to claim 1, characterized in that the voltage U.sub.B delivered by the power converter on the ground increases linearly with the current, according to an affine law of the type U.sub.B=U.sub.0+R.sub.BI.sub.B where U.sub.0 designates a constant voltage, close to the optimal power supply voltage of the power converter at the level of the drone, and R.sub.B designates a constant approximately equal to the resistance R.sub.F of the wire.

5. The device according to claim 4, characterized in that the constant U.sub.0 is replaced by a function U.sub.0(I.sub.B), such that this function is close to the function that describes the optimal power supply voltage of the power converter at the level of the drone as a function of the power supply current.

6. The device according to claim 1, characterized in that the variation of the resistance R.sub.F of the power supply strands of the wire with temperature is taken into account, for example by measuring the temperature of the wire in one or several location(s), or measuring the ambient temperature, or both.

7. The device according to claim 1, characterized in that the resistance R.sub.F of the wire is reevaluated regularly using the measurements of U.sub.B, U.sub.D, I.sub.B and Ohm's law, U.sub.D being the voltage at the input of the power converter at the level of the drone.

8. The device according to claim 1, characterized in that the regulation is based on a servo-control of the first-order servo-controls class or allowing not obtaining oscillations of the voltage, even following a sudden variation of the power consumed by the drone.

9. The device according to claim 1, characterized in that a circuit on the drone, interposed between the wire and the power converter at the level of the drone, includes at least one capacitive-type element and absorbs the voltage variations during a sudden variation in the power consumed by the drone.

10. The device according to claim 1, characterized in that the power converter at the level of the drone has a fixed ratio.

11. The device according to claim 1, characterized in that U.sub.B is servo-controlled directly to the measurement of the voltage U.sub.D at the input of the power converter at the level of the drone, the value of U.sub.D being transmitted via the wire.

12. The device according to claim 1, characterized in that the regulation maximizes the ratio P.sub.M/T.sub.F or, which is equivalent, the ratio P.sub.M/I.sub.B, P.sub.M designating the power available for the motors of the drone, and T.sub.F the temperature of the wire.

13. The device according to claim 2, characterized in that the regulation ensures a voltage U.sub.D at the input of the power converter at the level of the drone, close to the optimal operating voltage of the power converter at the level of the drone.

14. The device according to claim 2, characterized in that the voltage U.sub.B delivered by the power converter on the ground increases linearly with the current, according to an affine law of the type U.sub.B=U.sub.0+R.sub.BI.sub.B where U.sub.0 designates a constant voltage, close to the optimal power supply voltage of the power converter at the level of the drone, and R.sub.B designates a constant approximately equal to the resistance R.sub.F of the wire.

15. The device according to claim 3, characterized in that the voltage U.sub.B delivered by the power converter on the ground increases linearly with the current, according to an affine law of the type U.sub.B=U.sub.0+R.sub.BI.sub.B where U.sub.0 designates a constant voltage, close to the optimal power supply voltage of the power converter at the level of the drone, and R.sub.B designates a constant approximately equal to the resistance R.sub.F of the wire.

16. The device according to claim 13, characterized in that the voltage U.sub.B delivered by the power converter on the ground increases linearly with the current, according to an affine law of the type U.sub.B=U.sub.0+R.sub.BI.sub.B where U.sub.0 designates a constant voltage, close to the optimal power supply voltage of the power converter at the level of the drone, and R.sub.B designates a constant approximately equal to the resistance R.sub.F of the wire.

17. The device according to claim 16, characterized in that the constant U.sub.0 is replaced by a function U.sub.0(I.sub.B), such that this function is close to the function that describes the optimal power supply voltage of the power converter at the level of the drone as a function of the power supply current.

18. The device according to claim 17, characterized in that the variation of the resistance R.sub.F of the power supply strands of the wire with temperature is taken into account, for example by measuring the temperature of the wire in one or several location(s), or measuring the ambient temperature, or both.

19. The device according to claim 18, characterized in that the resistance R.sub.F of the wire is reevaluated regularly using the measurements of U.sub.B, U.sub.D, I.sub.B and Ohm's law, U.sub.D being the voltage at the input of the power converter at the level of the drone.

20. The device according to claim 19, characterized in that the regulation is based on a servo-control of the first-order servo-controls class or allowing not obtaining oscillations of the voltage, even following a sudden variation of the power consumed by the drone.

Description

SUMMARY DESCRIPTION OF THE FIGURES

[0035] FIG. 1 represents a drone (1) provided with a power converter (2) connected by a wire (3) to a ground base (5) provided with a power converter (4) connected to the mains grid (6).

[0036] FIG. 2 allows comparing the voltages U.sub.B and U.sub.D as a function of the current I.sub.B for a conventional power supply device (FIG. 2a) and a power supply device according to a particular embodiment of the invention (FIG. 2b). In full line, the voltage U.sub.B in Volt is represented as a function of the current I.sub.B in Ampere, in dotted line the voltage U.sub.D in Volt as a function of the current I.sub.B in Ampere. It can be seen that the voltage U.sub.D available for the drone (1) drops with the power demanded for a conventional power supply device, whereas the voltage U.sub.D available for the drone (1) remains constant regardless of the power demanded for the power supply device according to a particular embodiment of the invention.

[0037] FIG. 3 illustrates the reaction of different power supply devices according to the invention when the power of the drone (1) increases suddenly.

[0038] FIG. 3a represents the current I.sub.B in Ampere as a function of time in seconds. This current doubles suddenly at an instant called t.

[0039] FIGS. 3b, 3c, 3d represent the reactions as a function of time of three different power supply devices according to the principle illustrated in FIG. 2b. For these three figures, we find in full line the voltage U.sub.B as a function of time in seconds and in dotted line the voltage U.sub.D as a function of time in seconds.

[0040] FIG. 3b corresponds to a device whose servo-control corresponds to a second-order system. It can be seen that the voltage U.sub.D varies strongly just after the instant t, which could lead to a major malfunction, either by overvoltage or under-voltage.

[0041] FIG. 3c corresponds to a device whose servo-control corresponds to a first-order system. It can be seen that the voltage U.sub.D also varies strongly just after the instant t but there is no oscillation. The only possible malfunction is under-voltage.

[0042] FIG. 3d corresponds to the same device as in FIG. 3c but was added immediately upstream of the power converter (2) of the drone (1) a small capacity to cope with voltage variations and to smoothen U.sub.D.

[0043] FIG. 4 illustrates the reaction of different devices according to the invention when the power of the drone (1) decreases suddenly.

[0044] FIG. 4a represents the current I.sub.B in Ampere as a function of time in seconds. This current is suddenly divided by 2 at an instant called t.

[0045] FIGS. 4b and 4c represent the reactions as a function of time of two different power supply devices according to the principle illustrated in FIG. 2b. For these two figures, we find in full line the voltage U.sub.B as a function of time in seconds and in dotted line the voltage U.sub.D as a function of time in seconds.

[0046] FIG. 4b corresponds to the same device as that of FIG. 3c, and FIG. 4c corresponds to the same device as that of FIG. 3d.

[0047] It can thus be seen that the device of FIG. 3d or 4c is optimal for the operation of the system.

[0048] FIG. 5a represents, in dotted line, the power supply voltage U.sub.D which ensures a maximum efficiency of a power converter (2) located on the drone (1) as a function of the current I.sub.B which traverses the wire (3). It can be seen here that the optimal voltage U.sub.D varies considerably with the input current I.sub.B.

[0049] FIG. 5b represents in full line the voltage U.sub.B delivered by a power supply device according to the invention which allows obtaining the optimal voltage U.sub.D to offer the drone (1) a maximum power as a function of the current I.sub.B.

DETAILED DESCRIPTION

[0050] The ways of achieving the invention and their variants which follow illustrate precisely the invention and are not limiting other ways of achieving the power supply device according to the invention.

[0051] An optimal embodiment of the power supply device according to the invention is achieved as follows.

[0052] A drone (1) with a maximum power of 2600 W supplied with 25V direct voltage is used. This drone (1) has a power converter (2) with a 1/16 fixed ratio connected to a wire. This wire, 100 m length, is constituted by two electric strands, an aramid strand, all in a plastic sheath. The resistance of the used electric strands is 0.06 ohm per meter. This wire (3) is connected to a power converter (4) in a ground base (5). The converter of the ground base (5) is supplied by the mains grid (6) with 230V alternating voltage. The ground base (5) includes a winding drum of the wire, a motor connected to the winding drum of the wire (3) for winding or unwinding the wire (3). A fan cools the winding drum of the wire (3). A temperature sensor is present on the winding drum of the wire (3) to prevent the user from possible overheating of the wound wire (3).

[0053] The drone (1) has various on-board instruments and communicates in real-time with the ground base (5) through the technique called Power-Line Communication, well known to those skilled in the art. The information therefore passes via the power supply strands.

[0054] The power converter (2) at the level of the drone (1) has its maximum efficiency point at about 400V, requires not exceeding 410V at the input, otherwise it stops operating, and also requires never being supplied at more than 480V under penalty of irreparable damage. This power converter (2) being with a 1/16 fixed ratio, it outputs a 25V voltage for an input voltage equal to 400V.

[0055] The power converter (4) at the level of the ground base (5) uses the so-called Power Factor Correction technique, well known to those skilled in the art. The power controller is modified so that the output voltage U.sub.B follows the law expressed in Volt U.sub.B=min (400+R.sub.BI.sub.B, 480) where I.sub.B is the output current of the power converter (4) expressed in Ampere, and R.sub.B a constant expressed in Ohm, in our case equal to 12, which one has been selected equal to R.sub.F the resistance of the wire. To obtain such a law, the modification of the power controller requires simple electronic components such as diodes, resistors, current sensors at the output of the converter, analog multipliers. Particular care is taken to ensure that the components are adjusted in such a way that the regulation, in case of sudden power variations, ensures that the voltage does not undergo oscillations. Thus, the voltage at the level of the power converter (2) of the drone (1) does not exceed 410V which would cause the converter of the drone (1) to stop and the drone (1) to fall. The selection and the way in which the components are adjusted are known to those skilled in the electronics industry and do not require further explanation.

[0056] At the input of the power converter (2) of the drone (1), the voltage U.sub.D is equal to U.sub.B minus the ohmic losses in the wire (3) namely min (400+R.sub.BI.sub.B, 480)R.sub.FI.sub.B Volts. Thus, as long as I.sub.B does not exceed 80/12=6.7 A, the voltage U.sub.D is almost constant and equal to 400V.

[0057] Based on the heat-up of the wires at the level of the ground base (5), it is estimated that the current flowing in the wires should not exceed 6.7 A in continuous operation mode. The maximum power available for the drone (1) in continuous operation mode is therefore equal to 400*6.7=2700 W at the input of the power converter (2) of the drone (1), and the maximum power at the output of the power converter (2) of the drone (1) is equal to about 2600 W. With a conventional 400V fixed voltage power supply at the level of the ground base (5), the maximum available power would be only 320*6.7=2150 W at the input of the power converter (2) of the drone (1), and only 1800 W at the output of the power converter (2) because the efficiency is not optimal at 320V.

[0058] With our device according to the invention, a gain in power of 45% is thus obtained on the maximum power supplied to the drone (1) in continuous operation mode compared to a conventional system, and especially with equal heat-up of the wires.

[0059] In the embodiment of the device according to the preceding invention, the variation of the resistance R.sub.F of the power supply strands with temperature is not taken into account. The power supply strands of this first embodiment are made of copper, and the resistivity of copper varies with temperature: the resistivity increases by about 50% between 20 degrees Celsius and 70 degrees Celsius. To take into account the change of resistance R.sub.F of the wire (3) as a function of the temperature, two variations of the embodiment are possible.

[0060] The first variation of the first embodiment according to the invention consists in using the information of the temperature sensor on the winding drum of the wire. The temperature measured by this sensor is called T.sub.F. In addition, a revolution counter on the winding drum of the wire (3) allows knowing the length I of the wire (3) still wound on the drum. Finally, a temperature sensor on the ground base (5) allows estimating the temperature T.sub.A of the ambient air. We notice then that the resistance RE of the wire (3) is a function f of T.sub.A, T.sub.F, and I: R.sub.F=f (T.sub.A, T.sub.F, I), a function that has been determined theoretically and experimentally verified. The output law of the power converter (4) is then replaced by the law U.sub.B=min (U.sub.Bf(T.sub.A, T.sub.F, I) I.sub.B, 480).

[0061] The second variation of the embodiment according to the invention consists in measuring regularly, every minute, U.sub.D the voltage at the input of the power converter (2) located on the drone (1), U.sub.B the voltage at the output of the power converter (4) of the ground base (5), and I.sub.B the current flowing in the wire. The measurement of U.sub.D is sent to the ground base (5) via the power-line communication technique. The resistance R.sub.F of the power supply strands of the wire (3) is then reevaluated by the Ohm law, by dividing the difference U.sub.BU.sub.D by I.sub.B, and the regulation regulates according to the law min(400+R.sub.FI, 400).

[0062] Another variation of the embodiment of the invention consists in carrying out a software-type rather than electronic voltage regulation of U.sub.B as previously described.

[0063] A third variation of the embodiment according to the invention consists in regulating U.sub.B directly on the measured value of U.sub.D, this then requires a measurement of U.sub.D at high frequency, very significantly higher than one Herz, preferably in the range of a dozen kilohertz.

[0064] The ways of achieving the invention and their variants disclosed in the foregoing illustrate precisely the invention and are not limiting other ways of achieving the power supply device according to the invention.

POSSIBILITIES OF INDUSTRIAL APPLICATIONS

[0065] The power supply system according to the invention is capable of supplying power to all wired drones to the extent that it allows increasing the range and the payload compared to existing power supply systems.