Magnetic platform for drones

Abstract

The subject of the present invention is a platform for retaining a drone (1) comprising: at least one position sensor (3), a switching actuator (5), a control unit (4) in data exchange with the sensor (3) and with the actuator (5), and a switchable magnet, comprising a permanent magnet (6) and at least one pair of pole expansions, switchable by means of the actuator (5) between two positions in which the first position corresponds to a docking position and the second to a release position.

Description

DescriptionTitle of Invention: “MAGNETIC PLATFORM FOR DRONES”Technical Field

[0001] The present invention relates to a magnetic platform for the docking and releasing of a drone through a switchable magnet.

[0002] STATE OF THE ART

[0003] Magnetic platforms use magnets to promote the landing of a drone. The main difference between the various magnetic platforms is the nature of the magnet used. Indeed, there are different solutions that allow docking a drone.

[0004] Examples of possible solutions are:

[0005] a. Use of permanent magnets,

[0006] b. Use of electromagnets,

[0007] c. Use of a magnet coupled with an electric winding, and

[0008] d. Use of a permanent magnet coupled with a magnetic coil.

[0009] The different examples will now be discussed in greater detail.

[0010] Example a: The docking system uses a permanent magnet, which allows keeping the drone anchored without energy consumption. For the release, a motorized mechanism is used to mechanically move the anchor away from the magnet, overcoming the entire retaining force provided by the magnet, until the attractive force becomes negligible and the drone can move freely.

[0011] The main advantage is that, during docking, the system does not consume energy. However, the disadvantage is that the release mechanism must counteract the attraction force of the magnet on the ferromagnetic anchor: a higher attraction force during docking results in greater energy expenditure during release. A further disadvantage is that the attraction force is always present, so during the docking phase, the drone might couple in an incorrect and / or unstable position.

[0012] Example b: The docking system uses an electromagnet that can be activated or deactivated by controlling the supply electric current. The main advantage is the simplicity of the release: it is sufficient to interrupt the power supply to the electromagnet. However, the disadvantage is that the electromagnet consumes a considerable amount of electric energy for the entire duration the drone remains docked.

[0013] Example c: The docking system uses a magnet that can be demagnetized and remagnetized depending on the current flowing through a winding. The main advantage is that during docking it does not consume energy. However, the disadvantage is that high currents and electric powers are necessary to demagnetize and remagnetize the magnet. To facilitate this process, low coercivity materialsare used, such as AlNiCo alloys, which however reduce the system’s performance. Moreover, the current pulse necessary for magnetization generates a high-intensity magnetic field, which may cause EMI (electromagnetic interference) problems and interference with onboard instrumentation.

[0014] Example d: The docking system uses a permanent magnet flanked by a magnetic coil. During docking, the coil is off. During release, the coil is activated to cancel the magnetic field of the permanent magnet. The advantage is that the coil consumes electric energy only during release.

[0015] However, there are disadvantages:

[0016] Two magnetic elements are required (permanent magnet and coil) instead of one.

[0017] During release, the current pulse in the coil can cause electromagnetic interference (EMI) with the onboard instrumentation.

[0018] The attraction force is always present, so during the docking phase, the drone might docke in an incorrect or unstable position, unless the release winding is kept continuously powered, causing large energy losses and heating.

[0019] Considering the state of the art, the need emerges for a technology capable of docking and releasing the drone in a safe manner, i.e., without electromagnetic interference, economically and energy-efficiently.SUMMARY OF THE INVENTION

[0020] The above-mentioned problems are solved through the platform claimed in the present claim 1.

[0021] Therefore, the object of the present invention is a magnetic platform comprising:

[0022] at least one position sensor,

[0023] a switching actuator,

[0024] a control unit in data exchange with the sensor and the actuator,

[0025] a permanent magnet switchable between two positions, preferably angular positions, wherein the first position corresponds to a docking position and the second to a release position.

[0026] In particular, the docking position corresponds to a first angular position in which the magnetic flux is maximized through the landing surface; this allows capturing the element carrying the small anchor, preferably a drone. Conversely, the release position of the permanent magnet corresponds to a second angular position in which the magnetic flux crossing the landing surface of the platform is minimized. This allows the ferromagnetic small anchor no longer to be constrained on the platform, and thus to remove the element carrying the small anchor.

[0027] According to an alternative embodiment, the permanent magnet is switchable between two positions through a translation between a first position, corresponding to a docking position, and a second release position.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention is described below based on non-limiting examples illustrated for illustrative purposes in the following figures, which refer respectively to:

[0029] - Figure 1: schematic representation according to the present invention.

[0030] - Figure 2: schematic representation of the magnetic field lines of the magnet in the docking (a) and release (b) positions;

[0031] - Figure 3: further schematic representation of the magnetic field lines of the magnet in the docking (a) and release (b) positions.

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] Figure 1 shows a non-limiting exemplary embodiment of the present invention, namely a platform for docking and releasing an object with a ferromagnetic portion, preferably a drone 1, through a switchable magnet. According to the present invention, “drone” means an unmanned vehicle or aircraft. Drone 1 can therefore be an unmanned ground vehicle (UGV), an unmanned air vehicle (UAV), an unmanned sea vehicle (USV), an unmanned underwater vehicle (UUV), or a combination thereof. The drone can move on land, on water, or underwater, it can fly with fixed-wing or rotary-wing, or a combination of both. The drone can be radio-controlled or autonomously guided. For the purposes of this invention, the weight of drone 1 is relevant, including the empty weight and any payload.

[0034] The non-limiting exemplary embodiment of the present invention comprises a switchable magnet 6, a switching actuator 5, at least one position sensor 3, and a control unit 4. Furthermore, drone 1 must have a ferromagnetic portion, or, if absent, can be equipped with a ferromagnetic small anchor 2. The ferromagnetic anchor 2 can be positioned on the lower part of drone 1, or indifferently on the upper or side part depending on the application's needs.

[0035] The mechanism underlying the present invention is based on the orientation in space of the permanent magnet 6. In fact, magnet 6 is configured to be switchable between two positions. In particular, it is possible to switch from a first position to a second position through a rotation (see Figure 2). The rotation occurs around an axis belonging to the permanent magnet 6, preferably around the axis perpendicular to the magnetic axis of the permanent magnet 6 (passing through the north and south poles).

[0036] In the first position, magnet 6 generates a first magnetic force through the landing surface of the platform, while in the second position it generates a second magnetic force through the landing surface. The first magnetic force depends mainly on thecharacteristics of the permanent magnet 6 and can be as strong as desired, compatible with the technology of magnet 6 itself and the structure of the magnetic circuit that includes the pole expansions and the ferromagnetic anchor. The second magnetic force depends on the shape of the pole expansions surrounding permanent magnet 6 and can be as small as desired, ideally null. In particular, the first magnetic force is greater than the second.

[0037] In the first position, i.e., the docking position, the magnetic induction flux of permanent magnet 6 concatenates with the magnetic small anchor 2 carried by drone 1, that is, it applies an attractive force on the small anchor, so that below a threshold distance the element carrying the small anchor gets docked. In an exemplary embodiment where the switchable magnet has a surface of 50x50 mm, the threshold distance is 10 mm. Conversely, in the second position, i.e., the release position, the flux closes within the pole expansions of the switchable magnet and the force generated on the small anchor 2 is smaller and in particular smaller than the take-off force exerted by drone 1, that is: in the second position drone 1 is free to take off.

[0038] This occurs because the switchable magnet is engaged in a stator equipped with at least one pair of pole expansions made of ferromagnetic material. In general terms, the stator defines a first contact zone and a second contact zone for the drone 1, wherein the first and second contact zones are spaced apart by a non-ferromagnetic material, e.g., air, aluminium, polymeric material, and wherein in the docking position, the permanent magnet 6 is arranged to polarize the first contact zone oppositely to the second contact zone so that the drone 1 is docked when it contacts both the first and the second contact zones through a portion of ferromagnetic material, thus completing the magnetic circuit.

[0039] In the release position, the permanent magnet 6 is rotated so that the flux lines close within the ferromagnetic material of the pole expansions, which in this position create a path of minimal reluctance, effectively excluding the magnetic keeper from the magnetic circuit, thereby minimizing the magnetic flux concatenated with it and thus the resulting attraction force.

[0040] The switching between the docking position and the release position is carried out by a switching actuator 5. In one embodiment, this is any motor capable of exerting sufficient torque to rotate the permanent magnet 6 and overcome mechanical friction in the system, e.g., an electromechanical or pneumatic actuator or technical equivalents.

[0041] The switching actuator 5 is in data communication with a control unit 4 and is actuated following a signal sent by the latter. Moreover, the control unit 4 can be based on any programmable electronic system, e.g., microcontroller, microprocessor, digital signal processor (DSP), field programmable gate array (FPGA), or a combinationthereof. The control of the switching actuator 5 involves such a reduced complexity that it can be managed with any programmable digital electronic device.

[0042] According to an alternative embodiment, the permanent magnet 6 is configured to translate along an axis so that it is possible to switch from the first to the second position by translating the permanent magnet 6 itself. By way of example but not limitation, the attached Figure 3 shows a platform where the permanent magnet 6 translates from a first position (see Figure 3a), docking position, to a second position (see Figure 3b), release position.

[0043] Similarly to what has been described concerning the previous embodiment, in the release position, the permanent magnet 6 is translated so that the flux lines close within the ferromagnetic material of the pole expansions, which in this position create a path of minimal reluctance, effectively excluding the magnetic keeper 2 from the magnetic circuit, thereby minimizing the magnetic flux concatenated with it and thus the resulting attraction force.

[0044] According to this embodiment, the switching between the docking position and the release position is carried out by a switching actuator 5, configured to exert a pushing or pulling action sufficient to translate the permanent magnet 6 and overcome mechanical friction in the system, e.g., an electromechanical or pneumatic actuator or technical equivalents.

[0045] The control unit 4 is further in data communication with at least one position sensor3 that detects the presence of the drone 1. The logic for using the position sensor3 can be hard or soft. With a hard or threshold logic, the position sensor 3 detects when the drone 1 is within a portion of space suitable for docking, for example, at a distance of less than 2 cm from the landing platform, and then, the switching actuator 5 is actuated. With a soft logic, the position sensor 3 continuously measures and / or estimates the relative position of the drone 1 concerning the landing platform. The switching actuator 5 is controlled in a closed-loop (or feedback) manner based on the position measurement and / or estimation. The position sensor 3 can be a time-of-flight sensor or an ultrasonic sensor or a microwave radar or a lidar or a combination thereof.

[0046] The present invention may optionally have other types of sensors such as speed sensors, e.g., radar, or sensors to monitor the drone's orientation, e.g., position sensors or cameras operating in the visible or infrared spectrum. The type and technology of sensors used do not affect the architecture of the switchable magnet but may require particular characteristics in the control unit 4. For example, if time-of-flight sensors or ultrasonic sensors are used, the control unit 4 can be based on simple and inexpensive microcontrollers and microprocessors. If radars, lidars, or cameras are used, which entail a high computational load, it may be necessary to use high-performance microprocessors, DSPs, or FPGAs, or a combination thereof, to process the information.

[0047] In use, when the drone 1 with a ferromagnetic portion or a drone carrying a ferromagnetic keeper 2 is at a distance less than a predefined threshold value, the sensor 3 carried by the platform signals the presence of the drone 1. The control unit 4 receives as input the signal from the position sensor 3 and sends as output a signal to the switching actuator 5. In response to the signal sent by the control unit, the switching actuator 5 is actuated. Following the action of the actuator, the magnet 6 carried by the platform in a stator moves to the first position, i.e., the docking position. In this position, the magnetic flux crosses the landing surface of the platform and captures the drone 1 (Figure 2a).

[0048] Alternative embodiments of the previously discussed docking mechanism do not deviate from the inventive concept but are implementations for improvement purposes. In particular, if orientation sensors are present, it is possible to monitor the landing angle between the base of the drone and the platform, preferably the landing angle is between +3 and -3 degrees. According to a further embodiment, the control unit 4 can be connected to a remote unit via wired or wireless technology, so that the docking and release system can be controlled remotely. According to another embodiment, the platform may comprise a plurality of switchable magnets, thus allowing for greater control over the orientation of the drone during the docking phase and multiplying the docking force.

[0049] The release phase is a mirror image of the docking phase. A signal is sent to the control unit 4, which actuates the position switch 5. The release signal can be generated by a human operator, for example, via a toggle switch or a button, or it can be generated by another system / machine, for example, an autonomous mobile rover deciding to release a drone to collect data on the surrounding area for its navigation purposes. The actuator 5 switches the magnet 6 from the docking position to the release position. In this position, the magnetic flux through the landing surface is minimized, detaching the drone 1 (Figure 2b) and allowing it to take off. Operationally, the drone 1 can be started before the signal is sent to the control unit, so that the drone's motor(s) are running and can promptly take off when the magnetic flux through the surface is null, i.e., when the magnet 6 is in the second position, i.e., the release position.

[0050] It should be noted that if the force of the magnet 6 in the docking position is greater than the force exerted by the drone's 1 propellers, it becomes possible to perform a rapid takeoff maneuver called quick takeoff. In particular, the drone 1 can be released after the propellers are started and with the motors already at full throttle, allowing itto take off with full thrust from the very moment of detachment and thus quickly move away from the takeoff surface, for example, to avoid collisions.

[0051] Advantageously, the switching mechanism consumes a minimal amount of energy, corresponding to the energy required to switch the magnet 6; therefore, the power supply of the platform can also be provided by a battery. The battery can be rechargeable, for example a lithium-ion or lead-acid battery, or non-rechargeable, for example lithium thionyl chloride batteries or alkaline batteries. Given the limited energy consumption of the proposed invention, the energy source may optionally be a supercapacitor (or supercap). According to this embodiment, the present invention can be integrated into systems already on the market as a third-party component comprising the platform and a magnetic anchor or any ferromagnetic body associable with drone 1 or element to be constrained. The anchor can be fixed in various ways, some non-limiting examples of the fixing method being: screws, glue, interlocks, etc.

[0052] With reference to the previous embodiment, the present invention can be used not only with a drone 1 but as an optional apparatus for different systems having as a technical problem the need to dock and release an element onto a constrained body, e.g., a luggage rack on a car or a capsule on an airplane.

[0053] It should also be noted that variants of the present invention in which the magnet is not unique but it is possible to have a plurality of switchable magnets are still within the scope of protection of the present invention. Furthermore, embodiments in which the magnet has a number of pole pairs greater than one, and consequently the stator comprises a number of pole expansions greater than two, are also within the scope of the present invention.

Claims

Claims

1. Platform for retaining a drone (1) with a ferromagnetic portion comprising: at least one position sensor (3), a switching actuator (5), a control unit (4) in data exchange with the sensor and with the actuator, a switchable magnet, comprising a permanent magnet (6) and at least one pair of pole expansions, switchable by means of the switching actuator (5) between two positions in which the first position corresponds to a docking position such that, in use, the magnetic field flux of the magnet concatenates with the drone (1) or with a ferromagnetic anchor (2) fixed to the object to generate a first force that retains it in contact with the platform, and the second to a release position in which the concatenation of the magnetic field flux with the drone (1) or with the ferromagnetic anchor (2) generates a second force lower than the first force, wherein, when a control parameter, e.g., a distance parameter, associated with a drone (1) carrying a ferromagnetic portion (2), is below a threshold value, the sensor detects the presence of the object and the control unit in data exchange activates the switching actuator (5), switching the permanent magnet (6) into the docking position such that the object is captured by the platform, wherein said permanent magnet (6) is configured to rotate around an axis such that it is possible to switch from the first to the second position by means of a rotation of the permanent magnet (6), or wherein said permanent magnet (6) is configured to translate along an axis such that it is possible to switch from the first to the second position by means of a translation of the permanent magnet (6).

2. Platform according to claim 1, comprising a ferromagnetic stator defining a first contact area and a second contact area for the drone (1), wherein the first and second contact areas are spaced by a non-ferromagnetic material, e.g., air, aluminum, plastic material, and wherein, in the docking position, the permanent magnet (6) is arranged to polarize the first contact area oppositely to the second contact area such that the drone (1) is docked when it contactsboth the first and the second contact area through a portion of ferromagnetic material.

3. Platform according to claims 1 or 2, wherein the permanent magnet (6) is configured to roto-translate relative to an axis such that it is possible to switch from the first to the second position by means of a roto-translation of the permanent magnet (6).

4. Platform according to claim 1 or 2, wherein the docking force of the platform's magnet is greater than the thrust force exerted by the drone (1) to take off, so as to achieve a quick takeoff, in which the drone (1) takes off with full thrust from the detachment and thus moves away more quickly.

5. Platform according to claims 1-2, wherein, in addition to the docking position and the release position, the magnet (6) can be configured in a third position between said two positions.

6. Platform according to claims 1 or 2, 3 and / or 4, wherein the platform is equipped with a plurality of switchable magnets.

7. Platform according to any of the preceding claims, wherein the permanent magnet (6) has a number of pole pairs greater than one, and wherein the number of pole expansions is greater than two.

8. Method comprising: providing a platform for retaining a drone according to any of claims 1 to 7 ; wherein, after the drone (1) is detected by the sensors, the angular position or translation of the magnet (6) is progressively controlled to increase the attraction force as the distance of the drone (1) from the platform decreases.

9. Method according to claim 8, wherein, after the drone (1) is detected by the sensors, the position of the permanent magnet (6) is progressively controlled along a translation axis to increase the attraction force as the distance of the drone from the platform decreases.

10. Method according to claim 8 or 9, wherein the force is calculated as a function of the sensor signal.

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