DEVICE AND METHOD FOR AUTOMATIC CHECKING OF THE SERVICE STATUS OF A PARACHUTE SYSTEM OF A DRONE

Description

[0001] The present invention relates to a device and a method for automatically controlling the service status of the parachute system of an autonomous flying drone. The invention also relates to an autonomous flying drone equipped with the preceding device.

[0002] The invention relates more particularly to the field of site surveillance by autonomous aerial drones (UAV for Unmanned aerial vehicle).

[0003] Aerial drones weighing less than 25 kg can pose a risk to people and property flown over in the event of a fall. Indeed, most drones, particularly multi-rotor drones, are not capable of self-sustaining in the event of a loss of propulsion. Thus, in the event of a major drone failure, freefall is inevitable.

[0004] However, the lethal risk of an impact for any individual occurs when the energy released at the point of impact is greater than 69 Joules. This energy can be reached with drones having a mass greater than or equal to 2 kg.

[0005] It is therefore necessary to reduce the impact energy of drones in order to limit the danger of their use and allow them to fly near people. Some countries, such as France, make this type of impact energy limitation device mandatory for flying in certain scenarios, particularly with autonomous drones, i.e., without a pilot and automatically carrying out predefined or non-predefined flight plans.

[0006] The total energy accumulated by a drone is mainly composed of its potential energy and its kinetic energy. The first is mainly a function of the drone's height. The second of its speed. During a free fall, potential energy (altitude) is converted into kinetic energy (fall speed). Since kinetic energy is proportional to mass and to the square of speed, it is understandable that to most effectively reduce the drone's total energy, it is more effective to reduce the fall speed. This is why the most commonly used method in the drone field to reduce the risks associated with a ground impact is the use of one or more parachutes. By significantly increasing the drone's aerodynamic drag, they limit the fall speed to an acceptable threshold.

[0007] The impact energy limitation device is an essential element of drone safety. It must therefore be checked regularly to ensure its proper functioning.

[0008] Document WO20191819989 describes a drone operation control device that cannot be temporarily inactivated to prevent inadvertent deployment.

[0009] Document CN208775024 describes a parachute system for drones without describing the electronic actuation circuit.

[0010] For site surveillance by autonomous drones to be possible and compatible with the absence of manpower, it is necessary for each autonomous drone to be able to automatically check the health of the parachute deployment device. Indeed, for piloted drones, this task usually falls to a human. An autonomous drone implies that there is no longer anyone to carry out this task on a daily basis while being forced to an even higher level of reliability. The parachute must indeed automatically compensate for cases of system malfunction where, normally, a pilot would be able to regain control.

[0011] An objective of the present invention is therefore to propose a device and a method for automatically controlling the service status of the parachute system of an autonomous drone.

[0012] Another objective is to propose a device and a method for automatically controlling the service status of the parachute system of an autonomous drone which is safe, i.e. without risk of untimely triggering of the parachute system.

[0013] This check is carried out at least before the flight of the autonomous drone, but it can advantageously continue during the flight for certain parameters.

[0014] To this end, the present invention provides a device for automatically controlling the service status of a parachute system for a flying drone according to claim 1.

[0015] According to other embodiments, which can be combined with each other: the deployment mechanism may comprise a pyrotechnic ejection charge for the parachute electrically triggerable by the electric actuator; the deployment mechanism may comprise a parachute ejection spring electrically releasable by the electric actuator, the automatic control device further comprising a sensor for the stress position of the ejection spring and a means for comparing the stress position measured by the sensor with a minimum nominal threshold stress position stored in the storage memory; the deployment mechanism may comprise a reserve of parachute ejection gas electrically releasable by the electric actuator, the automatic control device further comprising a sensor for the pressure of the ejection gas reserve and a means for comparing the pressure of the ejection gas reserve with a minimum nominal threshold pressure stored in the storage memory;the actuator switch and the test switch may be electronic switches; the switches may be MOSFET type transistors; the automatic control device may further comprise an electromechanical connector to the electronic deployment circuit, the electromechanical connector comprising a contact which closes an electrical circuit only when the electromechanical connector is correctly connected; the automatic control device may further comprise a temperature and / or humidity sensor placed as close as possible to the parachute, and in which the storage memory comprises minimum and maximum threshold values ​​of nominal temperature and / or humidity as well as temperature and / or humidity values ​​measured over time;and / or the storage memory may contain historical time information of at least one maintenance operation as well as at least one maintenance delay corresponding to a maximum authorized duration between two operations of a given maintenance.;

[0016] The invention also relates to an autonomous flying drone comprising an electronic flight circuit and a parachute system comprising: a parachute; a deployment mechanism, an electronic deployment circuit intended to be connected to the flight electronic circuit and to apply an operating voltage to control the parachute deployment mechanism; and an electrical actuator of the parachute deployment mechanism connected to the electronic deployment circuit, the actuator having a nominal internal resistance, an effective internal resistance and an activation threshold current at the operating voltage, the actuator being connected to electrical ground by an actuator switch controllable by the electronic deployment circuit, characterized in that it comprises a device for automatically controlling the service status of the preceding parachute system.

[0017] The invention also relates to an electronic card for actuating the deployment of a parachute provided with a deployment mechanism for a flying drone, the electronic card comprising an electrical connector intended to be connected to the deployment mechanism, an electrical connector intended to be connected to an electronic circuit for deploying the flying drone capable of applying an operating voltage to control the parachute deployment mechanism, and an electrical actuator of the deployment mechanism having a nominal internal resistance and an activation threshold current at the operating voltage, the electrical actuator being connected to ground by an actuator switch controllable by the electronic deployment circuit, the electronic card being characterized in that it comprises a device for automatically controlling the operating state of a previous parachute system.

[0018] The invention also relates to a parachute kit comprising a parachute provided with a parachute deployment mechanism, characterized in that it comprises a preceding electronic card.

[0019] In a particular embodiment, the parachute kit may further comprise an electronic parachute deployment circuit connected to the electrical actuator of the parachute deployment mechanism, and comprising an electrical connector intended to be connected to an electronic flight circuit of a flying drone.

[0020] The invention also relates to a method for automatically controlling the service status of a parachute system for a flying drone according to claim 14.

[0021] According to other embodiments, which can be combined with each other: the method may further comprise, before each take-off of the drone, a step of checking electrical continuity between the electronic deployment circuit and the automatic control device through the electromechanical connector (90), the drone being prohibited from taking off if no electrical continuity is detected; the method may further comprise, before each take-off of the drone, a step of comparing the temperature and / or humidity values ​​measured over time with nominal minimum and maximum threshold values ​​of temperature and / or humidity stored in memory, the drone being prohibited from taking off if the measured temperature and / or humidity values ​​are outside the nominal minimum and maximum threshold values ​​of temperature and / or humidity stored in memory;and / or the method may further comprise, before each takeoff of the drone and for each maintenance operation, a step of comparing each item of historical time information of maintenance operations with the maintenance deadline, the drone being prohibited from taking off if, for at least one determined maintenance operation, historical time information exceeds the maintenance deadline of said determined maintenance operation.;

[0022] Other characteristics of the invention will be set out in the detailed description below, made with reference to the appended drawings, which represent, respectively: [ Fig. 1 ], a functional diagram of an autonomous flying drone equipped with a device for automatically controlling the service status of a parachute system according to the invention; [ Fig. 2 ], an electrical diagram of an example of an electric actuator of the parachute deployment mechanism provided with a device for automatically controlling the service state of the parachute system according to the invention, in the test position; [ Fig. 3 ], an electrical diagram of the electric actuator of the figure 2 , in the drone's flight position; [ Fig. 4 ], an electrical diagram of the electric actuator of the figure 2 , in parachute trigger position; [ Fig. 5 ], an electrical diagram of a first embodiment of an electric actuator of the parachute deployment mechanism provided with a device for automatically controlling the operating state of the parachute system according to the invention, in the flight position of the drone, and comprising a capacitive energy reserve and a discharge circuit; and [ Fig. 6 ], an electrical diagram of the electric actuator of the figure 5 , equipped with MOSFET switch.

[0023] To ensure the parachute device is working properly, all the elements making up its operating chain should be checked. figure 1 illustrates this chain of operation. As described later, certain elements may be part of different assemblies depending on the embodiments.

[0024] The operating chain 1 essentially comprises flight electronics 10, a storage memory 20, deployment electronics 30 of the parachute 60, an electric actuator 40 of a deployment mechanism 50 of the parachute 60, and a parachute 60. The latter is divided, for automatic control of the service state, into three functional sub-elements: the sail 61, the lines 62 and the line attachments 63 on the drone.

[0025] The flight electronics circuit 10 is responsible for determining whether to deploy the parachute 60 automatically or upon receipt of an order from a ground control module 70 if present. This module 70 allows a ground operator to trigger the parachute in the event of a problem. This module 70 is optional and does not exist in the operating chain of an autonomous drone. Indeed, the latter must be programmed to detect dangerous situations requiring the deployment of the parachute itself.

[0026] The storage memory 20 stores nominal operating data of certain elements of the chain (in particular, but not exclusively, the electric actuator 40, the deployment mechanism 50 and the parachute 60) and operational flight data from certain modules (in particular, but not exclusively, the parachute 60). The storage memory 20 may also include data entered during maintenance of the drone.

[0027] The electronic deployment circuit 30 is responsible for managing the activation of the electric actuator(s) 40 to control the deployment mechanism 50 in order to release the sail 61 from the parachute 60.

[0028] The electronic deployment circuit 30 is connected, in use, to the flight electronic circuit 10 and is programmed to apply a determined operating voltage to control the parachute deployment mechanism and, consequently, the deployment of the parachute.

[0029] There are several types of deployment mechanisms 50: spring ejection mechanism, pressurized gas ejection mechanism using CO2 cartridges, pyrotechnic charge ejection mechanism.

[0030] They all have in common that they are electrically actuated by an electric actuator 40. This may be, depending on the ejection mechanisms, a solenoid, a servomotor, an electromechanical release or a pyrotechnic initiator.

[0031] The automatic control of the service status of the parachute system according to the invention aims primarily to verify the correct operation of the electric actuator 40.

[0032] THE figures 2 à 4 illustrate the electrical assembly of an electric actuator 40 in different configurations: verification of the operating state of the electric actuator 40 ( figure 2 ), normal flight in which the parachute is not triggered ( figure 3 ), activation of the electric actuator 40 to trigger the parachute in the event of a crisis ( figure 4 ).

[0033] Generally speaking, the electric actuator 40 is characterized by a nominal internal resistance R_40 which is a theoretical value corresponding to an ideal electric actuator 40 in perfect working order. In reality, the electric actuator 40 has an effective internal resistance R_41 which depends on the working state of the electric actuator 40. For the electric actuator 40 to be considered to be in working order, the effective internal resistance R_40 must be between two minimum and maximum threshold values ​​R_40min and R_40max stored in the storage memory 20.

[0034] The electric actuator 40 depends on the deployment mechanism 50 of the parachute.

[0035] In a preferred embodiment, the deployment mechanism comprises a pyrotechnic parachute ejection charge that can be electrically triggered by the electric actuator. In this case, the electric actuator 40 is a pyrotechnic initiator that has an internal resistance of the order of 2 ohms. It heats up when an electric current passes through it and ignites the pyrotechnic charge. Ignition occurs with a current of 5A for 10ms or 4A for 15ms, while a current of 10mA allows the internal resistance to be tested without risk as described below.

[0036] Alternatively, the deployment mechanism includes a parachute ejection spring electrically releasable by the electric actuator.

[0037] Alternatively, the deployment mechanism includes a reserve of parachute ejection gas electrically releasable by the electric actuator.

[0038] In both of these variants, the electric actuator can be, for example, a solenoid or an electromechanical release.

[0039] A solenoid consists of an electrical coil that generates a magnetic field that moves a ferromagnetic part in a linear motion. It therefore has internal resistance.

[0040] An electromechanical release is either a motor or a wire that heats up and breaks like a fuse, thus releasing its mechanical function. It therefore has internal resistance.

[0041] The electric actuator 40 is also characterized by an activation threshold current I_40 at the operating voltage U applied by the electronic deployment circuit 30.

[0042] In practice, the electric actuator 40 is connected to the electrical ground M by an actuator switch 42 controllable by the electronic deployment circuit 30. Thus, when the latter commands the closing of the actuator switch 42, and applies the operating voltage U, an activation current I_40 passes through the electric actuator 40 and triggers the parachute deployment mechanism ( figure 4 ).

[0043] To check the proper functioning of an element, it is activated under the conditions of use. However, for the electric actuator, this would lead to ordering the ejection of the parachute, which is unthinkable for reasons of cost, availability (once the parachute is ejected, the drone can no longer fly until a maintenance person has intervened) and danger, in particular for parachutes with a pyrotechnic deployment mechanism which can injure people near the drone.

[0044] The difficulty is to make a measurement that does not accidentally trigger the deployment itself. The invention therefore proposes to measure a physical parameter that attests to the correct operating condition, but without activating the electric actuator 40 itself. The invention proposes to use an intrinsic characteristic of the electric actuator by measuring the effective internal electrical resistance of the actuator. Indeed, the different electric actuators 40 that can be used in the invention all have an internal electrical resistance that induces an actuation current when a potential difference is applied to its terminals.

[0045] To this end, the invention proposes to integrate into the circuit of the electric actuator, a control device 400 comprising a resistive test branch 401 having a test resistor 402 of determined value mounted in series with a test switch 403 controllable by the electronic deployment circuit 30.

[0046] According to the invention, the test branch is connected in parallel with the actuator switch 42, between the electrical ground M and a connection node N1 arranged between the actuator 40 and the actuator switch 42.

[0047] The value R_test of the test resistor 402 is chosen to generate a test current I_test lower than the activation current I_40 of the actuator 40 when the operating voltage U is applied.

[0048] Thus, thanks to the device according to the invention, when carrying out the test, there is no risk that the current I_test generated during the test by the application of the operating voltage U will trigger the parachute. In addition, the test resistor 402 is also chosen so that, if the actuator is short-circuited, the induced test current I_test still remains lower than the activation current I_40.

[0049] The control device 400 according to the invention also comprises a voltage measurement circuit 404 between the terminals of the test resistor 402 and a means for calculating an effective internal resistance of the electric actuator. This calculation means is not illustrated, but it may be, for example, the electronic deployment circuit 30, the electronic flight circuit 10, or an electronic circuit provided with an independent calculation processor located near the electric actuator, for example on the same electronic card.

[0050] Thus, the calculation means is programmed to calculate the effective internal resistance R_41 of the electric actuator 40 as explained below.

[0051] To carry out the check of the service status of the electric actuator 40, the electronic deployment circuit 30 opens (or keeps open) the actuator switch 42 and closes the test switch 403 ( figure 2 ). Then, it applies an operating voltage U in the circuit comprising the electric actuator 40 and the resistive test branch 401, the operating voltage U being equal to the sum of the voltage U_40 at the terminals of the actuator 40 and the voltage U_test at the terminals of the test resistor 402. The application of this operating voltage U generates a test current I_test of intensity lower than the activation intensity of the electric actuator. Thus, during the test, the current I_test passing through the electric actuator 40 is insufficient to trigger said actuator.

[0052] Then the electronic deployment circuit 30 measures the voltage U_test across the test resistor 402 with the voltage measuring circuit 404.

[0053] From the voltage U_test measured across the test resistor 402 and the test resistor 402 of determined value R_test, the electronic deployment circuit 30 calculates with Ohm's law the value of the test current I_test generated by the application of the operating voltage: I_test = U_test / R_test

[0054] Once the calculated value of the test current I_test has been calculated, the electronic deployment circuit 30 can calculate with Ohm's law the effective internal resistance R_41 of the electric actuator 40 with the operating voltage U, the voltage U_test measured across the test resistor 402: Puisque U = U_test + U_40 ,

[0055] Where U_40 is the voltage across the electric actuator 40, then U_40 = U − U_test

[0056] Gold, U_40 = R_41 * I_test

[0057] SO R_41 = U_40 / I_test

[0058] That's to say R_41 = U − U_test / I_test

[0059] The calculated effective internal resistance R_41 of the electric actuator 40 can then be compared with the minimum and maximum threshold values ​​R_40min and R_40max of the nominal internal resistance R_40 of the electric actuator 40 stored in the storage memory 20.

[0060] To this end, the control device 400 according to the invention comprises a means for comparing the calculated effective internal resistance R_41 of the actuator 40 with the minimum and maximum values ​​R_40min and R_40max of nominal internal resistance R_40 of the electric actuator stored in the storage memory 20.

[0061] If the effective internal resistance R_41 of the electric actuator is between the minimum and maximum threshold values ​​R_40min and R_40max of nominal internal resistance, this means that the electric actuator 40 is in working order and the electronic flight circuit 20 can authorize the takeoff of the drone which will be able to trigger the parachute correctly in the event of a problem.

[0062] In this case, during flight, the electronic deployment circuit 30 opens the test switch 403 and the actuator switch 42 ( figure 3 ). If a dangerous situation is detected by the flight electronic circuit 10, the latter controls the deployment electronic circuit 30 which will close the actuator switch 42 ( figure 4 ), which will trigger the parachute to deploy.

[0063] On the contrary, if the effective internal resistance R_41 of the electric actuator is lower than the minimum threshold value R_40min or higher than the maximum threshold value R_40max, this means that the electric actuator 40 is respectively close to short circuit (very low electrical resistance tending towards that of a simple electric wire) or close to breakage (very high electrical resistance tending towards that of an open circuit). In these two cases, the electric actuator 40 is out of order and the electronic flight circuit 20 prohibits the takeoff of the drone which could not correctly trigger the parachute in the event of a problem.

[0064] In a preferred embodiment, the electronic trigger circuit 30 also verifies that the drone has sufficient energy reserves to be able to trigger the parachute in the event of a problem.

[0065] In the case of a parachute with a pyrotechnic deployment mechanism, the electronic trigger circuit 30 only checks the electrical reserve. This is done, for example, by measuring the voltage level of the electrical reserve (from the battery or a dedicated reserve; see below) before each flight and comparing it with a threshold voltage defined in the storage memory 20.

[0066] In the case of a mechanical deployment mechanism (spring / elastic), the electronic trigger circuit 30 at least checks that the electrical reserve is sufficient to actuate the mechanical deployment mechanism.

[0067] Preferably, the automatic control device further comprises an ejection spring stress position sensor and means for comparing the stress position measured by the sensor with a minimum nominal threshold stress position stored in the storage memory.

[0068] This sensor allows the electronic trigger circuit 30 to also check the reserve of mechanical energy necessary for the correct deployment of the parachute, by ensuring that the spring is tensioned beyond a position guaranteeing the correct accumulation of mechanical energy to guarantee the correct deployment of the canopy.

[0069] In the case of a gas deployment mechanism, the electronic trigger circuit 30 at least verifies that the electrical reserve is sufficient to release the ejection gas reserve.

[0070] Preferably, the automatic control device further comprises an ejection gas reserve pressure sensor and means for comparing the ejection gas reserve pressure with a minimum nominal threshold pressure stored in the storage memory.

[0071] This sensor allows the electronic trigger circuit 30 to also check that the pneumatic reserve is sufficient for the deployment of the parachute.

[0072] Alternatively or in combination, in an advantageous embodiment, the automatic control device 400 according to the invention further comprises an independent electrical energy reserve intended to power the electric actuator 40 on command of the electronic deployment circuit 30, independently of the main electrical power supply (the battery) of the drone. The electrical energy reserve thus guarantees a sufficient reserve so that the deployment of the parachute can be carried out in total electrical autonomy.

[0073] In a first variant, the independent electrical energy reserve is constituted by a secondary battery whose correct charge level is checked by the electronic deployment circuit 30 before each flight. If the charge is insufficient, the drone is prohibited from flying.

[0074] In a preferred embodiment, illustrated in figure 5 , the automatic control device 400 according to the invention further comprises a capacitive electrical energy reserve 410 intended to be arranged between an electrical energy source S (the main battery of the drone or, preferably, the electrical power supply of the drone docking station before takeoff) and the electrical actuator 40 to be charged by the energy source S and to be able to power the actuator 40 on command of the electronic deployment circuit 30.

[0075] The capacitive energy reserve comprises capacitors whose number and characteristics are chosen to enable the deployment mechanism to be triggered. For example, when the latter is a pyrotechnic charge, the capacitive energy source is sized to be able to deliver 5A for 10ms or 4A for 15ms in order to enable the charge to be triggered.

[0076] For safety reasons, this capacitive reserve is preferably oversized so that it stores more energy than is necessary to trigger the deployment mechanism.

[0077] In addition to its power and speed, this capacitive electrical energy reserve 410 has the advantage of being able to be discharged to avoid any untimely triggering of the parachute.

[0078] To this end, the automatic control device 400 according to the invention further comprises a discharge circuit 420 for the capacitive energy reserve 410. The discharge circuit 420 is arranged in parallel with the actuator 40, between the electrical ground M and a connection node N2 arranged between the capacitive energy reserve 410 and the actuator 40.

[0079] This circuit includes one or more resistors 421 capable of dissipating sufficient electrical power to discharge the energy stored in the capacitive energy reserve 410 in a discharge time short enough to make the circuit safe after the end of the flight, and before a person takes charge of maintenance.

[0080] For example, the resistor(s) will be sized so that the discharge takes place between 2 and 25 seconds, preferably between 3 and 10 seconds, advantageously between 4 and 6 seconds.

[0081] Thus, to size the discharge circuit 420, it is appropriate to choose one or more resistors that are low enough to allow rapid dissipation of the energy, but capable of withstanding the heat generated by the discharge without being altered.

[0082] Thus, before each takeoff of the drone, the electronic deployment circuit controls the charging of the capacitive energy reserve 410 by an energy source S (the battery of the drone or, preferably, the power supply of the drone docking station before takeoff) to allow the deployment of the parachute in the event of a problem during the flight.

[0083] After each landing, the electronic deployment circuit 30 controls the discharge of the capacitive energy reserve 410 in the discharge circuit 420. For this, the electronic deployment circuit opens or keeps open the actuator switch 42, the switch closes the test switch 403, and closes the discharge switch 422 of the discharge circuit 420.

[0084] Thus, when the drone is on the ground and therefore when the parachute is no longer necessary, the electronic deployment circuit 30 controls the discharge of the energy reserve 410 and then checks that it has been discharged correctly. If the reserve is not discharged correctly, the electronic deployment circuit 30 informs the operator in charge of maintenance of the “armed” state of the parachute (and therefore of its potential accidental triggering) either by a light or sound warning, or by a digital message to a person-machine interface of the flight management system of the autonomous drone.

[0085] In order to allow control of the automatic control device and the discharge circuit according to the invention by the electronic deployment circuit 30, the various switches, and in particular the actuator switch 42, the test switch 403 and the discharge switch 422 are electronic switches, preferably MOSFET type transistors to avoid the effects of premature wear linked to the opening / closing of the electrical electromechanical contacts.

[0086] Some electrical actuators 40 such as pyrotechnic initiators present handling risks which require them to be disconnected before each handling to avoid any risk of explosion. There is therefore a risk that the person in charge of maintaining it forgets to reconnect the electrical actuator 40 or reconnects it incorrectly. This therefore requires checking before each flight that the connector has been reconnected correctly in order to avoid any risk of human handling error.

[0087] For ease of assembly and / or replacement and / or maintenance, the electric actuator 40 of the automatic control device according to the invention can be connected to the electronic deployment circuit 30 via an electromechanical connector 90 allowing them to be easily disconnected.

[0088] Thus, the electromechanical connector 90 includes a contact that closes the electrical circuit only if the electromechanical connector 90 is correctly connected. If it is not correctly connected, electrical continuity is not ensured. The electronic deployment circuit can then test the state of this electrical circuit in order to ensure, before each takeoff, the correct connection of the connector. If it is not correctly connected, takeoff is prohibited.

[0089] Thus, before each takeoff of the drone, the electronic deployment circuit 30 checks for electrical continuity between the electronic deployment circuit 30 and the automatic control device 400 through the electromechanical contact 90, the drone being prohibited from taking off if no electrical continuity is detected.

[0090] Advantageously, the automatic control device according to the invention also comprises a temperature and / or humidity sensor placed as close as possible to the parachute 60. In this case, the storage memory 20 also comprises minimum and maximum threshold values ​​of nominal temperature and / or humidity as well as temperature and / or humidity values ​​measured over time and written to the storage memory by the electronic flight circuit 10 or the electronic deployment circuit 30.

[0091] In this way, if the humidity level, for example, exceeds a threshold value stored in the memory 20, the electronic deployment circuit 30 prohibits the flight and information is sent to the operator to plan a maintenance operation. · The parachute canopy 61, which deploys when activated, has the role of slowing the drone's fall. It must therefore deploy and open correctly in order to provide its full potential. · The lines 62 connect the canopy 61 to the drone. They must withstand the sudden shock of the drone's abrupt deceleration when the canopy opens quickly. · The attachment of the lines 63 to the drone must also withstand the mechanical shock caused by the drone's sudden slowdown.

[0092] The proper functioning of the entire parachute 60 of this chain of functional sub-assemblies 61-62-63 is normally guaranteed by different inspections carried out by an operator at different intervals: before each flight, after each use, when installing the parachute, etc.

[0093] For example, the canopy and lines must be inspected each time the parachute is folded to detect any defects. The parachute must also be unfolded at least once a year to dry the canopy of any moisture it may have accumulated, which tends to "stick" the fabric to itself and thus disrupt its proper opening.

[0094] The storage memory 20, which stores the different threshold levels considered nominal in order to validate the proper functioning of the parachute, can also be updated manually, each time a major maintenance operation is carried out on the parachute. In particular, it is necessary to keep track of the operations of unfolding and drying the canopy and the lines of the parachute for traceability reasons. The memory therefore allows an operator to enter reminder dates. The date in memory is then compared with the UTC universal time known by the drone in order to automatically notify the user when a maintenance operation must be carried out. The device can also prohibit the drone from taking off again if the parachute's use-by date has passed. This avoids any human error concerning compliance with the parachute's use-by dates.

[0095] Thus, before each takeoff of the drone, the electronic deployment circuit 30 compares the temperature and / or humidity values ​​measured over time by the sensor(s) with nominal minimum and maximum temperature and / or humidity threshold values ​​stored in memory 20. The drone is then prohibited from taking off if the measured temperature and / or humidity values ​​are outside the nominal minimum and maximum temperature and / or humidity threshold values ​​stored in memory.

[0096] A first mode of operation of the invention consists of a flying drone, preferably autonomous, comprising an electronic flight circuit and a parachute system comprising a parachute, a deployment mechanism, an electronic deployment circuit connected to the electronic flight circuit and applying an operating voltage to control the parachute deployment mechanism, and an electric actuator of the parachute deployment mechanism connected to the electronic deployment circuit.

[0097] As described previously, the actuator has a nominal internal resistance and an activation threshold current at the operating voltage.

[0098] The electric actuator is connected to ground by an actuator switch controllable by the electronic deployment circuit, and it includes a device for automatically monitoring the service status of the parachute system.

[0099] This automatic control device comprises a resistive test branch 401 comprising a test resistor 402 of determined value connected in series with a test switch 403 controllable by the electronic deployment circuit. The test branch is connected in parallel with the actuator switch 42, between the ground and a connection node N1 arranged between the actuator 40 and the actuator switch 42.

[0100] As described previously, the value R_test of the test resistor 402 is chosen to generate a test current I_test lower than the activation current I_40 of the actuator 40 when the operating voltage U is applied or the actuator is short-circuited.

[0101] The automatic control device also comprises: a voltage measuring circuit 404 between the terminals of the test resistor 402, a means for calculating the effective internal resistance R_41 of the electric actuator, a storage memory 20 comprising at least minimum and maximum threshold values ​​of nominal internal resistance of the electric actuator, and a means for comparing the calculated effective internal resistance of the actuator with the minimum and maximum values ​​of nominal internal resistance of the electric actuator stored in the storage memory 20 (preferably the electronic deployment circuit is programmed for this purpose).

[0102] Another mode of exploitation of the invention may consist in selling separately from the flying drone and the parachute itself an electronic card for deploying the parachute specially adapted to also allow automatic control of the service status of the parachute. In this case, the parachute is provided with its own deployment mechanism, and the flying drone includes an electronic flight circuit.

[0103] The electronic card according to the invention comprises an electrical connector intended to be connected to the deployment mechanism, and an electrical connector intended to be connected to the electronic deployment circuit of the flying drone. Alternatively, the electronic deployment circuit can be carried by the electronic card itself. In this case, it comprises an electrical connector between the electronic deployment circuit of the card and the electronic flight circuit of the drone, the latter being programmed to command the electronic deployment circuit of the card to apply an operating voltage to control the parachute deployment mechanism.

[0104] In both cases, the board also includes an electrical actuator for the deployment mechanism having a nominal internal resistance and an activation threshold current at the operating voltage. The electrical actuator is connected to ground by an actuator switch controllable by the deployment electronics.

[0105] Finally, the electronic card includes a device for automatic control of the electric actuator of the parachute deployment mechanism.

[0106] This automatic control device comprises a resistive test branch 401 comprising a test resistor 402 of determined value connected in series with a test switch 403 controllable by the electronic deployment circuit. The test branch is connected in parallel with the actuator switch 42, between the ground and a connection node N1 arranged between the actuator 40 and the actuator switch 42.

[0107] As described previously, the value R_test of the test resistor 402 is chosen to generate a test current I_test lower than the activation current I_40 of the actuator 40 when the operating voltage U is applied and the actuator is short-circuited.

[0108] The automatic control device also comprises: a voltage measuring circuit 404 between the terminals of the test resistor 402, a means for calculating the effective internal resistance R_41 of the electric actuator, a storage memory 20 comprising at least minimum and maximum threshold values ​​of nominal internal resistance of the electric actuator, and a means for comparing the calculated effective internal resistance of the actuator with the minimum and maximum values ​​of nominal internal resistance of the electric actuator stored in the storage memory 20 (preferably the electronic deployment circuit is programmed for this purpose).

[0109] In an alternative mode of operation, the invention may be operated in the form of a parachute kit comprising a parachute provided with a parachute deployment mechanism, and the preceding electronic card.

[0110] As described above, the electronic board of the parachute kit may further comprise an electronic parachute deployment circuit connected to the electrical actuator of the parachute deployment mechanism, and an electrical connector intended to be connected to a flight electronic circuit of a flying drone.

[0111] In both of the above-mentioned operating modes (electronic card and parachute kit), the electrical connectors are advantageously electromechanical connectors 90 comprising a contact which closes an electrical circuit only when the electromechanical connector 90 is correctly connected.

[0112] Thanks to the device according to the invention, it is possible to check the serviceability of the parachute before takeoff or during the flight.

[0113] The verification sequence can be as follows: When the drone wants to take off, the flight electronic circuit 10 asks the deployment electronic circuit 30 if the parachute device is ready. At the same time, this makes it possible to check the correct communication between the two electronic circuits 10 and 30 of the drone. The deployment electronic circuit 30 refreshes the threshold parameters from the memory. If the electrical energy reserve is dischargeable and in a discharged state, the electronics charge the electrical energy reserve, and measure that it is operational. Then, the deployment electronic circuit 30 checks that the connector(s) is / are properly connected, and validates that the humidity level is consistent with the nominal thresholds in memory. The deployment electronic circuit 30 then validates that the electric actuator 40 is present and / or has the correct effective internal resistance value.· If all tests are satisfactory, the electronic deployment circuit 30 informs the electronic flight circuit 10 that the parachute is fully operational. Flight is then authorized.

[0114] If one of the tests is negative, the electronic deployment circuit 30 informs the electronic flight circuit 10 that the parachute is not operational. Takeoff is then prohibited. An operator is then informed of the need for maintenance.

[0115] If one of the tests is negative and the electrical energy reserve is dischargeable and in a charged state, the electronics discharge the electrical energy reserve and measure that it is indeed discharged in order to secure the system.

[0116] If the drone is part of a drone fleet managed by an automatic system, the latter may decide to automatically command the flight of another available drone from the fleet and located nearby to carry out the mission previously assigned to the drone prohibited from flying.

Claims

1. Device (400) for automatically checking the service state of a parachute system for a flying drone which comprises an electronic flight circuit (10), the parachute system comprising: • a parachute (60); • a deployment mechanism (50); • an electronic deployment circuit (30) intended to be connected to the electronic flight circuit (10) and to apply an operating voltage (U) for controlling the deployment mechanism (50) of the parachute; and • an electric actuator (40) of the deployment mechanism of the parachute connected to the electronic deployment circuit (30), the electric actuator (40) having a nominal internal resistance (R_40), an effective internal resistance (R_41) and an activation threshold current (I_40) at the operating voltage (U), the actuator being connected to electrical earth (M) by an actuator switch (42) controllable by the electronic deployment circuit, the checking device (400) comprising: • a resistive test branch (401) comprising a test resistor (402) of a determined value (R_test) connected in series with a test switch (403) controllable by the electronic deployment circuit (30), the test branch being connected in parallel with the actuator switch (42), between electrical earth (M) and a first connection node (N1) arranged between the electric actuator (40) of the deployment mechanism of the parachute and the actuator switch (42), the value (R_test) of the test resistor (402) being chosen so as to generate a test current (I_test) lower than the activation current (I_40) of the electric actuator (40) when the operating voltage (U) is applied and so that, if the actuator is short-circuited, the induced test current (I_test) remains lower than the activation current (I_40); • a voltage measuring circuit (404) between the terminals of the test resistor; • a means of calculating an effective internal resistance of the electric actuator; • a storage memory (20) comprising at least minimum (R_40min) and maximum (R_40max) threshold values for the nominal internal resistance (R_40) of the electric actuator; and • a means of comparing the calculated effective internal resistance (R_41) of the actuator with the minimum (R_40min) and maximum (R _40max) values for the nominal internal resistance (R_40) of the electric actuator (40) which are stored in the storage memory (20); and further comprising: • a capacitive electrical energy reserve (410) intended to be arranged between an energy source (S) of the drone and the electric actuator (40) so as to be charged by the energy source (S) of the drone and supply power to the actuator (40) on command of the electronic deployment circuit (30), • a discharge circuit (420) of the capacitive electrical energy reserve (410) arranged in parallel with the actuator (40), between electrical earth (M) and a second connection node (N2) arranged between the capacitive electrical energy reserve (410) and the actuator (40).

2. Automatic checking device according to Claim 1, wherein the deployment mechanism (50) comprises a pyrotechnic charge for ejecting the parachute and which is electrically triggerable by the electric actuator.

3. Automatic checking device according to Claim 1, wherein the deployment mechanism (50) comprises a spring for ejecting the parachute and which is electrically releasable by the electric actuator, the automatic checking device further comprising a sensor for sensing the stress position of the ejection spring and a means of comparing the stress position measured by the sensor with a minimum nominal threshold stress position stored in the storage memory.

4. Automatic checking device according to Claim 1, wherein the deployment mechanism (50) comprises a reserve of ejection gas for the parachute and which is electrically releasable by the electric actuator, the automatic checking device further comprising a sensor for sensing the pressure of the reserve of ejection gas and a means of comparing the pressure of the reserve of ejection gas with a minimum nominal threshold pressure stored in the storage memory.

5. Automatic checking device according to any one of Claims 1 to 4, wherein the actuator switch (42) and the test switch (403) are electronic switches.

6. Automatic checking device according to Claim 5, wherein the switches are MOSFET transistors.

7. Automatic checking device according to any one of Claims 1 to 6, further comprising an electromechanical connector (90) to the electronic deployment circuit, the electromechanical connector (90) comprising a contact which closes an electrical circuit only when the electromechanical connector (90) is correctly connected.

8. Automatic checking device according to any one of Claims 1 to 7, further comprising a temperature and / or humidity sensor placed as close as possible to the parachute, and wherein the storage memory comprises minimum and maximum threshold values for nominal temperature and / or humidity as well as temperature and / or humidity values measured over time.

9. Automatic checking device according to any one of Claims 1 to 8, wherein the storage memory (20) contains historical time information relating to at least one operation of a maintenance procedure as well as at least one maintenance time corresponding to a maximum permitted duration between two operations of a determined maintenance procedure.

10. Autonomous flying drone comprising an electronic flight circuit (10) and a parachute system comprising: • a parachute (60); • a deployment mechanism (50); • an electronic deployment circuit (30) intended to be connected to the electronic flight circuit (10) and to apply an operating voltage (U) for controlling the deployment mechanism of the parachute; and • an electric actuator (40) of the deployment mechanism of the parachute connected to the electronic deployment circuit, the actuator having a nominal internal resistance (R_40), an effective internal resistance (R_41) and an activation threshold current (I_40) at the operating voltage (U), the actuator being connected to electrical earth (M) by an actuator switch controllable by the electronic deployment circuit, characterized in that it comprises a device (400) for automatically checking the service state of the parachute system according to any one of Claims 1 to 9.

11. Electronic card for actuating the deployment of a parachute provided with a deployment mechanism for a flying drone, the electronic card comprising an electrical connector intended to be connected to the deployment mechanism (50), an electrical connector intended to be connected to an electronic deployment circuit (30) of the flying drone capable of applying an operating voltage (U) for controlling the deployment mechanism (30) of the parachute (60), and an electric actuator (40) of the deployment mechanism (50) having a nominal internal resistance (R_40), an effective internal resistance (R_41) and an activation threshold current (I_40) at the operating voltage, the electric actuator being connected to earth (M) by an actuator switch (42) controllable by the electronic deployment circuit, the electronic card being characterized in that it comprises a device for automatically checking the service state of a parachute system according to any one of Claims 1 to 9.

12. Parachute kit comprising a parachute (60) provided with a deployment mechanism of the parachute (50), characterized in that it comprises an electronic card according to Claim 11.

13. Parachute kit according to Claim 12, further comprising an electronic deployment circuit (30) of the parachute connected to the electric actuator of the deployment mechanism of the parachute, and comprising an electromechanical connector (90) intended to be connected to an electronic flight circuit (10) of a flying drone.

14. Method for automatically checking the service state of a parachute system for a flying drone which comprises an electronic flight circuit (10), the parachute system comprising: • a parachute (60); • an electronic deployment circuit (30) of the parachute intended to be connected to the electronic flight circuit and • an electric actuator (40) of a deployment mechanism of the parachute (50) having a nominal internal resistance (R_40), an effective internal resistance (R_41) and an activation threshold current (I_40) at the operating voltage, the electric actuator being connected to earth (M) by an actuator switch (42) controllable by the electronic deployment circuit, the drone comprising an automatic checking device according to Claim 1; the checking method comprising the following steps: i) connecting a resistive test branch (401) comprising a test resistor (402) of a determined value (R_test) connected in series with a test switch (403) controllable by the electronic deployment circuit (30), the test branch being connected in parallel with the actuator switch (42), between electrical earth (M) and a first connection node (N1) arranged between the electric actuator (40) of the deployment mechanism of the parachute and the actuator switch (42); ii) opening the actuator switch (42) and closing the test switch (403); iii) applying an operating voltage (U) between a terminal of the actuator and earth, the operating voltage being equal to the sum of the voltage (U_40) across the terminals of the actuator and the voltage (U_test) across the terminals of the test resistor, so as to generate a test current (I_test) having an intensity of less than the activation intensity (I_40); iv) measuring the voltage (U_test) across the terminals of the test resistor; v) calculating, on the basis of the voltage (U_test) measured across the terminals of the test resistor and the determined value (R_test) of the test resistor (402), the value of the test current (I_test) generated by the application of the operating voltage (U) using Ohm's law, vi) calculating, on the basis of the operating voltage (U), the voltage (U_test) measured across the terminals of the test resistor and the calculated value of the test current (I_test), the effective internal resistance (R_41) of the electric actuator (40) using Ohm's law; vii) comparing the calculated effective internal resistance (R_41) of the electric actuator (40) with minimum (R_40min) and maximum (R_40max) threshold values for the nominal internal resistance of the electric actuator stored in a storage memory (20); viii) permitting the drone to take off only if the effective internal resistance (R_41) of the electric actuator is between the minimum (R_40min) and maximum (R_40max) threshold values for nominal internal resistance; the method further comprising, before each take-off of the drone, a step of charging the capacitive energy reserve (410) by an energy source (S), and, after each landing, a step of discharging the capacitive energy reserve (410) into the discharge circuit (420).

15. Method according to Claim 14, wherein the drone comprises an automatic checking device according to Claim 7, the method further comprising, before each take-off of the drone, a step of verifying electrical continuity between the electronic deployment circuit (30) and the automatic checking device through the electromechanical connector (90), the drone being prohibited from taking off if no electrical continuity is detected.

16. Method according to either one of Claims 14 and 15, wherein the drone comprises an automatic checking device according to Claim 9, the method further comprising, before each take-off of the drone, a step of comparing the temperature and / or humidity values measured over time with minimum and maximum nominal threshold values for temperature and / or humidity which are stored in memory, the drone being prohibited from taking off if the measured temperature and / or humidity values are outside the minimum and maximum nominal threshold values for temperature and / or humidity which are stored in memory.

17. Method according to any one of Claims 14 to 16, wherein the drone comprises an automatic checking device according to Claim 9, the method further comprising, before each take-off of the drone and for each maintenance operation, a step of comparing each piece of historical time information relating to maintenance operations with the maintenance time, the drone being prohibited from taking off if, for at least one determined maintenance operation, a piece of historical time information exceeds the maintenance time of said determined maintenance operation.