System for measuring the flying height of a hydrofoil boat

Abstract

The invention relates to a system for measuring the flying height of a boat, the hull of which is provided with at least one hydrofoil-type submerged bearing surface, enabling the hull to fly over the water. The system includes: - a radar for measuring the flying height of the hull of the boat with respect to the water; - an inertial unit including at least inertial sensors of linear acceleration and speed of rotation about three axes; - a GPS-type geolocation device; - an inertial navigation unit provided with a unit for processing the electronic signals coming from the radar, sensors of the inertial unit and of the geolocation device, including means for processing the electronic signals with a view to obtaining, at each instant, at least one item of information on the height of the hull with respect to the water.

Description

Description Title of the invention: System for measuring the flight height of a foil boat

[0001] [The present invention relates to the field of foil boats, or more generally boats whose hull is equipped with a submerged foil-type lifting surface. These are boats which have wing-shaped appendages submerged under the hull of the boat, which generate lift when the boat moves at high speed, in reaction to the circulation of the water around them. The invention also applies to surface drones and in particular to unmanned naval surface drones (USV).

[0002] The lift generated by the foil causes the hull to gradually lift off the water. This lift increases with speed until the hull is lifted off the water, correspondingly increasing the efficiency and speed of the boat, because the mere immersion of the foils results in a considerable reduction in water resistance, allowing the boat to glide over the water's surface with much less friction. The presence of the foils actually reduces drag to a minimum. Once the boat is sufficiently lifted off the water, it is in a sense "flying" above the liquid surface. To maintain control, particularly over the vessel's trajectory, it is then necessary to maintain stability in flight.

[0003] In short, foil boats fly just above the water's surface, with the hull in the air and the foils in the water. In other words, the physical interface between the medium in which the hull moves and the medium in which the foil(s) move is the water surface. However, this water surface is likely to vary quite considerably and very frequently in its shape, in relation to many parameters that depend on conditions affecting both environments, for example meteorological factors (notably the wind): thus, when waves appear and the boat flies at a certain speed out of the water, the constantly variable nature of the water surface and the height of the hull in relation to it is very likely to impact its balance, which can quickly become unstable.

[0004] The flight height of flying boats, the measurement of which is the main object of the invention, obviously depends on the flight conditions of the boat, but also on the state of the sea. Measuring the flight height is essential to ensure continuity of flight and balance of the boat, preventing the boat from falling into the water in an uncontrolled and sudden manner. Thus, if the height of the hull relative to the continuously changing surface is poorly assessed, or estimated too late, the boat may climb too high, with the risk of the foils stalling because they come out of the water, or on the contrary, nosing straight towards the sea or into a wave.

[0005] It is therefore very important to be able to correctly measure - that is to say, in this case at all times and continuously during the boat's movements - the height of the boat in relation to this irregular and constantly moving surface interface that is the sea surface. In the piloting process, the speed of the boat is also an important parameter. In fact, it is necessary to constantly keep the hull in flight as horizontal - "flat" - as possible above the water, because the very interest of this type of foiling boat lies in the possibility of them being able to fly flat without being "shaken" by waves or swell.

[0006] Until now, to measure flight height, so-called "flying" boats have used either mechanical systems (rods and floats) as is the case for foiling moths, or electronic altitude sensors using ultrasound to measure the distance between the sensor and the water surface. The current choice, in most electronic height measurements of foiling boats, of ultrasonic sensors also results from their relative simplicity of implementation and their proven robustness. These sensors can measure distances compatible with the flight height of the boats, ranging from a few centimeters to a few meters. They are also easy to find, with numerous manufacturers, and relatively affordable.

[0007] As for racing sailboats used in competitions, they generally simply use an inertial unit with an altitude sensor to adjust the flight parameters, knowing that in this particular environment, pure speed is paramount and the regattas in which they participate take place on fairly sheltered and therefore fairly flat waters. The constraints are therefore less. These boats are also subject to class rules which are sometimes very restrictive in terms of what the onboard system can or cannot do. In most cases, particularly in the context of the famous America's Cup, the steering systems cannot be fully automated.

[0008] The mechanical or ultrasonic systems mentioned above are not very accurate for measuring the flight height of a boat or a flying machine above the water, especially in unprotected environments where the water surface is very changeable and sometimes in significant amplitudes. The signal restitution capacity of the control system is impacted and is often poor, leading to this mentioned insufficiency in the precision of the measurement obtained. As a result, the flight control of the hull of the ship on its foil(s) is not very fine, and potentially causes instability.

[0009] The present invention overcomes these shortcomings and proposes an innovative configuration allowing precise and frequent measurement of the flight height of a boat or a flying machine above the water, with, in addition, a better signal restitution capacity. The precision obtained is notably much higher than that offered, for example, by the mechanical or ultrasonic systems mentioned.

[0010] Thus, according to the invention, the system for measuring the flight height of a boat whose hull is equipped with at least one submerged foil-type bearing surface allowing said hull to fly above the water, is such that it comprises:

[0011] - a radar for measuring the flight height of the boat's hull in relation to the water;

[0012] - an inertial unit comprising at least inertial sensors for linear acceleration and rotation speed on three axes;

[0013] - a GPS-type geopositioning device;

[0014] - an inertial navigation unit equipped with a unit for processing electronic signals from the radar, the inertial navigation unit sensors and the geopositioning device, comprising means for processing said electronic signals in order to obtain at least one piece of information at each moment on the height of the hull relative to the water.

[0015] In short, the measuring system of the invention behaves like a sensor specifically dedicated to flying boats, namely craft navigating on a fluid surface in more or less erratic motion because randomly affected by chop, waves, swell, wakes, etc., themselves having a speed of several km / h to several tens of km / h. The movements of said surface obviously take place in particular but not only in a vertical direction which is of interest for measuring the height of the hull above the water.The inertial navigation unit uses data from the sensors of the inertial navigation unit, which has no data processing capacity, as well as data emitted by the radar and the GPS, using algorithms which integrate in particular the data from the inertial sensors and result in data which can be used for controlling the boat, primarily and within the framework set by the invention, data on the height of the hull relative to the fluid and perpetually moving surface of the water.

[0016] Preferably, according to the invention, the radar is a pulsed Doppler radar, more particularly efficient for measuring the relative speed of moving objects with respect to the radar itself, and which is therefore well suited to the changing environment provided by the surface of moving water. The pulsed Doppler radar emits pulses, generally radiofrequency waves, which propagate to the target, i.e. a portion of the moving surface of the water, where they are reflected. When the radar signals are reflected by the moving water, the frequency of the reflected signals is modified in particular as a function of the relative speed of said portion of the target surface with respect to the radar.The radar detects the change in frequency of the reflected signals and measures the speed of the said targeted portion in the radial (the speed component in the direction of the radar) and tangent (the speed component in a direction normal to that of the radar) directions. This allows the system to have instantaneous information on the moving profile of the water surface at a frequency that will be imposed high (see below). In fact, the system allows not only the measurement of the height of the hull above the water by the. radar sensor, but also to process data relating to the liquid surface independently of the attitude of the boat.

[0017] The speed of height measurement is much faster with the radar system of the invention than with an ultrasonic sensor, said system also making it possible to obtain a better quality and more robust signal, then sent to a computer of the measurement system or for real-time display. The measurement speed and sensitivity are essential for operation on agitated surfaces, knowing that this type of signal has only been used until now for water level measurements in reservoirs and canals where the surface is little disturbed, unlike the context of the invention where it is necessary to measure a surface in perpetual motion from a mobile device itself in motion (horizontal and vertical) evolving on this surface.With the radar, GPS and inertial unit, the measurement system of the invention actually integrates all the sensors necessary for autonomy, so that the measurement performed is independent of the physical model of the ship and does not require calibration or specific parameterization dedicated to this ship.

[0018] In practice, according to the invention, the radar can have an acquisition frequency greater than or equal to 100 Hz.

[0019] According to the invention, the radar can be capable of measuring a height between the hull and the water between 0.2 and 10 m, preferably between 0.2 and 2 m.

[0020] It should also be noted that the measurement system of the invention may comprise a printed circuit comprising the radar, the inertial unit, the GPS-type geopositioning device, the signal processing unit, and at least one communication interface, in which the inertial unit is a 6-axis inertial unit and in which the signal processing unit is a microprocessor.

[0021] Such integration on a single printed circuit board makes it possible to reduce as much as possible the latency of transmission of signals from the radar, the inertial unit and the GPS-type geo-positioning device to the microprocessor.

[0022] Moreover, unlike a solution using different off-the-shelf devices, such integration on a single printed circuit board guarantees the transmission of raw signals. In other words, this allows no filter to be applied before transmission to the microprocessor.

[0023] This transmission of raw signals with reduced latency allows the signal processing unit to generate data relating to the state of the boat equipped with a system according to the invention more quickly and more accurately. In particular, this allows data relating to the height of the boat hull relative to the water to be generated more quickly and more accurately. By way of non-limiting examples, in addition to the data relating to the height of the hull relative to the water, the signal processing unit can generate data relating to the speed of the boat, the acceleration, the position of the boat, its orientation, its altitude, etc.

[0024] This is made possible by the use of a radar which allows for an acquisition frequency higher than state-of-the-art flight height measurement solutions.

[0025] By way of non-limiting example, the signal processing unit can implement a calculation model applying an extended Kalman filter to all of the raw signals received in order to obtain at least one piece of data relating to the height of the hull relative to the water.

[0026] Furthermore, the circuit according to the invention may further comprise a 3-axis magnetometer.

[0027] The magnetometer is used for orientation detection (like a kind of electronic compass) by measuring the magnetic component of the Earth's field. This also allows for redundancy of information to be made available to the signal processing unit.

[0028] In addition, according to one embodiment of the system according to the invention, the printed circuit can be housed in a waterproof housing incorporating a radome. The radome can in particular protect the radar antenna.

[0029] The invention also relates to a boat whose hull is provided with at least one submerged foil-type bearing surface allowing said hull to fly above the water, and which comprises at least one measuring system according to the characteristics stated above.

[0030] Several measuring systems can also be positioned in different places on the boat, allowing for a certain redundancy of measurements, which provides a much higher level of security in the event of failure of one of the systems.

[0031] Other advantages and characteristics will appear on examining the detailed description of a non-limiting embodiment, and the attached drawings in which:

[0032] FIGURE 1 is a very schematic representation of a non-limiting example of a measuring system according to the invention;

[0033] FIGURE 2 is a very schematic representation of a non-limiting example of a measuring system according to the invention associated with a boat control system; and

[0034] FIGURE 3 is an isometric and schematic representation of a non-limiting example of a boat according to the invention.

[0035] It is understood that the embodiments which will be described below are in no way limiting. In particular, it is possible to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one characteristic, preferably functional, without structural details, or with only a part of the structural details if this part is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0036] In the FIGURES, the elements common to several FIGURES retain the same reference.

[0037] As seen in FIGURE 1, the system 100 for measuring the flight height of a boat comprises a radar 102 for measuring the flight height of the hull of a boat relative to the water. The radar 102 makes it possible to measure the distance between the radar, preferably located under the hull of the boat, and the surface of the water. The radar also makes it possible to measure the speed at which the surface of the water moves closer to or further away from the radar. According to preferred embodiments, the radar 102 is a pulsed Doppler radar having an acquisition frequency greater than or equal to 100 Hz.

[0038] The system further comprises an inertial unit 104 comprising at least inertial sensors for linear acceleration (preferably three sensors with one sensor per axis) and rotational speed on three axes. This inertial unit 104 is therefore capable of measuring linear accelerations as well as rotational speed around three axes relative to the boat (preferably corresponding to the roll, pitch and yaw speed).

[0039] The system 100 further comprises a GPS-type geopositioning device 106 (hereinafter referred to as the GPS device). The GPS device 106 is capable of measuring data relating to the position of the boat (longitude, latitude and altitude) as well as data relating to the speed of the boat.

[0040] Furthermore, the system 100 comprises an inertial navigation unit 108 provided with a unit for processing electronic signals from the radar 102, sensors of the inertial unit 104 and the GPS device 106 and comprising means for processing said electronic signals in order to obtain at each instant at least one piece of information on the height of the hull relative to the water.

[0041] In the example illustrated in FIGURE 1, the radar 102, the inertial unit 104 and the GPS device 106 are each connected to an inertial navigation unit 108 so as to enable signal transmission.

[0042] Information relating to the height can obviously be deduced by the inertial navigation unit 108 solely from the signal coming from the radar 102. However, the system 100 according to the invention is capable of taking into account other signals coming from the inertial unit 104 and the device 106 to refine and / or validate the information on the height of the hull relative to the water. It is for example possible to identify and reject possible measurement errors of the radar 102. Alternatively or in addition, it is for example possible to create a so-called damping adjustment making it possible to smooth the information on the height of the hull relative to the water over time as a function of the signals coming from the sensors of the inertial unit 104 and the GPS device 106.

[0043] More particularly, the signal from the GPS device 106 includes data relating to the altitude of the boat allowing redundancy of information relating to the height of the hull relative to the water. Similarly, the evolution of the altitude of the boat over time can be deduced from the signals from the inertial unit 104.

[0044] Preferably, the signals transmitted by the radar 102, the inertial unit 104 and the GPS device 106 are so-called raw signals to which no filter has been applied before transmission to the inertial navigation unit 108. By way of non-limiting example, the signal processing unit of the inertial navigation unit 108 can implement a calculation model applying an extended Kalman filter to all of the raw signals received in order to obtain at each instant data relating to the height of the hull relative to the water.

[0045] In addition to the data relating to the height of the hull relative to the water, a calculation model applying an extended Kalman filter to all of the raw signals received by the inertial navigation unit 108 can generate other data relating to the state of the boat equipped with a system according to the invention. By way of non-limiting examples, in addition to the data relating to the height of the hull relative to the water, the signal processing unit can generate data relating to the speed of the boat, the acceleration, the position of the boat, its orientation, its altitude, etc.

[0046] FIGURE 2 is a very schematic representation of a measurement system 200 according to the invention associated with a control system for a boat whose hull is provided with at least one foil-type bearing surface.

[0047] The measurement system 200 illustrated in FIGURE 2 includes all of the elements of the measurement system 100 described in relation to FIGURE 1.

[0048] The system 200 further comprises a printed circuit 202, said printed circuit 202 comprising the radar 102, the inertial unit 104, the GPS device 106 and the inertial navigation unit 108. In this embodiment, the signal processing unit 204 of the inertial unit 108 is a microprocessor.

[0049] The printed circuit 202 further comprises a three-axis magnetometer 206. The magnetometer 206 is connected to the inertial navigation unit 108 so as to enable signal transmission. The magnetometer 206 makes it possible to measure then to transmit to the signal processing unit 204 of the inertial unit 108 at least one measurement relating to the Earth's magnetic field and / or the boat's magnetic field. Preferably, the signals transmitted by the magnetometer 206 are so-called raw signals to which no filter has been applied before transmission to the inertial navigation unit 108. The use of a magnetometer 206 allows the inertial unit to have additional information redundancy to establish boat status data.

[0050] The integration of these different elements on the same printed circuit 202 makes it possible to reduce as much as possible the latency of transmission of signals from the radar 102, the inertial unit 104, the GPS device 106 and the magnetometer 206 to the microprocessor 204. This reduced latency facilitates the implementation of a calculation model applying an extended Kalman filter.

[0051] The printed circuit 202 may further comprise a power supply means (not shown), such as a battery or a power connector for connecting the printed circuit 202 to a power source of the boat.

[0052] The printed circuit 202 further comprises at least one communication interface 208 (a single interface is illustrated in FIGURE 2). This communication interface may for example be a CAN BUS using the CANopen protocol.

[0053] In FIGURE 2 the communication interface 208 allows the measurement system 200 to communicate with a system 210 for controlling a boat whose hull is equipped with at least one foil-type bearing surface. The measurement system 200 can thus transmit at any time any data relating to the state of the boat which has been generated by the microprocessor 204, in particular the data relating to the height of the hull relative to the water.

[0054] The system 210 comprises a unit 212 for calculating pilot instructions. This instruction calculation unit is capable of calculating the servo-control instructions for electromechanical actuators 214 acting on the angle of incidence of each of the “Flaps” 216 (or ailerons) equipping at least one foil-type lifting surface.

[0055] This calculation unit 212 can calculate instructions based on:

[0056] - signals from control means operable by a boat pilot,

[0057] - pre-informed safety and / or user comfort constraints (for example, the boat's roll angle can be limited depending on the boat's speed in order to increase passenger comfort),

[0058] - boat state data. The data regarding the height of the hull relative to the water is transmitted at all times and necessarily comes from the measuring system 200. Preferably, the measuring system 200 according to the invention can further provide at all times data regarding the speed of the boat, regarding the acceleration, regarding the position of the boat, regarding its orientation, regarding the altitude of the boat. Alternatively, at least one of the data regarding the boat state other than the height of the hull relative to the water can be provided by another system or device. This other system can for example be another measuring system according to the invention.

[0059] Figure 3 is an isometric and schematic representation of a non - limiting example of a boat according to the invention.

[0060] FIGURE 3 illustrates the underside of a boat 300 whose hull 302 is provided with a plurality of foil-type bearing surfaces 304. Each bearing surface 304 is equipped with a “Flap” 306 (or fin) as well as at least one electromechanical actuator (not shown) acting on the angle of incidence of the “Flap” 306. Each bearing surface 304 is connected to the lower surface of the hull 302 of the boat by a vertical leg 308 (or pillar).

[0061] The boat 302 comprises another waterproof housing 310 integrating a radome 312 arranged at a so-called front end of the boat 300, under the hull 302. A measuring system according to the invention (not visible in FIGURE 3) is housed in said housing 310.

[0062] The examples mentioned are obviously not exhaustive of the invention, which encompasses differences in structure / geometry, dimensions, etc. which may affect the measuring system or the vessel.]

Claims

Claims

1. [System (100;200) for measuring the flight height of a boat (300) whose hull (302) is provided with at least one submerged foil-type bearing surface (304) allowing said hull (302) to fly above the water, characterized in that it comprises: - a radar (102) for measuring the flight height of the hull (302) of the boat (304) relative to the water; - an inertial unit (104) comprising at least inertial sensors for linear acceleration and rotation speed on three axes; - a GPS-type geopositioning device (106); - an inertial navigation unit (108) equipped with a unit for processing the electronic signals from the radar (104), the sensors of the inertial unit (104) and the geo-positioning device (106), comprising means for processing said electronic signals in order to obtain at each instant at least one piece of information on the height of the hull (302) relative to the water.

2. System (100;200) for measuring the flight height of a boat (300) according to the preceding claim, characterized in that the radar (102) is a pulsed Doppler radar.

3. System (100; 200) for measuring the flight height of a boat according to one of the preceding claims, characterized in that the radar (102) has an acquisition frequency greater than or equal to 100 Hz.

4. System (100;200) for measuring the flight height of a boat (300) according to one of the preceding claims, characterized in that the radar (102) is capable of measuring a height between the hull (302) and the water of between 0.2 and 2m.

5. System (200) for measuring the flight height of a boat (300) according to one of the preceding claims, characterized in that it comprises a printed circuit (202) comprising the radar (102), the inertial unit (104), the GPS type geo-positioning device (106), the signal processing unit (204) and at least one communication interface (208), in which the inertial unit (104) is a 6-axis inertial unit and in which the signal processing unit (204) is a microprocessor.

6. System (200) for measuring the flight height of a boat (300) according to the preceding claim, characterized in that said printed circuit (202) comprises a 3-axis magnetometer (206).

7. System (200) for measuring the flight height of a boat (300) according to the preceding claim, characterized in that said printed circuit (202) is housed in a sealed housing (310) integrating a radome (312).

8. Boat (300) whose hull (302) is provided with at least one submerged foil-type bearing surface (304) allowing said hull (302) to fly above the water, comprising at least one measuring system (100; 200) according to one of the preceding claims.

9. Boat according to the preceding claim, characterized in that several measuring systems are positioned in different places on the boat.

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