Aircraft and method of stabilizing an aircraft

An aircraft is provided, including: at least one sensor for measuring a wind; actuators (motors, control surfaces, etc.); a data base embedded aboard the aircraft, the data base associating various values of wind measurement with various set points for the attention of the actuators. The aircraft furthermore includes a system of analysis and control, arranged so as, or programmed so as:

BACKGROUND

The present invention relates to an aircraft. It also relates to a method utilized by an aircraft.

Such an aircraft or method makes it possible to stabilize the aircraft that is subjected to wind variations such as gusts or turbulences. The field of the invention is more particularly, but non-limitatively, that of lighter-than-air aircraft.

Flight stability in a turbulent environment (in particular for improving passenger comfort) is a recurring topic in the aeronautical world.

The detection and forecasting of gusts of wind are fundamental elements in keeping to an aircraft flight plan. This is even more important for a lighter-than-air aircraft, given its large windage and its relatively low manoeuvrability due to its inertia.

Several solutions are known from the state of the art for detecting or forecasting such gusts for an aircraft:“piloting” technologies, which are based on an action by the pilot or pilots, following captured information displayed in the cockpit,“warning” technologies, which are based on detecting turbulences so as to be able to warn the passengers of entering a turbulence zone,“absorption” technologies, which are based on mechanical systems (gust absorber) making it possible to stabilize flight.

Several problems arise:reaction time: reaction times can be too long in relation to the sudden onset of squalls or gusts or turbulences (in particular for “piloting” technologies),hovering flight or direction of flight: certain technologies, (in particular that of “absorption”) are generally not effective in hovering flight but only in cruise flight at high speeds, and furthermore their operation only makes stabilization possible in the direction of flight,becoming endangered during hovering flight: during the loading/unloading phases in hovering flight a lighter-than-air aircraft is extremely vulnerable to turbulent wind. The effect of gusts can in fact generate severe instabilities leading in extreme cases to endangering the lighter-than-air aircraft.accuracy of hovering flight: in the event of positioning a load, the accuracy of the hovering flight can be very important. Gusts can cause a significant deterioration in this accuracy, to the detriment of its operational capabilities.

The purpose of the present invention is to solve at least one of the aforementioned problems or disadvantages.

SUMMARY

This objective is achieved with an aircraft comprising:at least one sensor, arranged in order to measure a wind,actuators,an on-board database in the aircraft, the database associating different wind measurement values with different instructions intended for the actuators,analysis and control means, arranged or programmed in order to:receive wind measurement values originating from the at least one sensor,search, within the database, for a match with the wind measurement values originating from the at least one sensor, and determine, as a function of this search, instructions to be sent to the actuators,send these determined instructions to the actuators.

The at least one sensor is preferably arranged in order to measure a wind at a measurement frequency of at least 0.1 Hz, preferably at least 1 Hz. The analysis and control means are preferably arranged or programmed in order to determine instructions to be sent to the actuators at a frequency of at least 0.1 Hz, preferably at least 1 Hz.

The aircraft according to the invention is preferably arranged in order to perform hovering flight.

The aircraft according to the invention preferably consists of a lighter-than-air aircraft.

The at least one sensor is preferably arranged in order to measure the wind remotely.

The wind measurement values can comprise:an amplitude or a variation in amplitude of the wind, and/oran origin or a direction of the wind, or a variation in the origin or direction of the wind.

The analysis and control means can be arranged or programmed in order to send the instructions directly to the actuators, without the need for a validation or approval step by a human operator.

The aircraft according to the invention can also comprise means for measuring the effects, on the position of the aircraft, of the instructions determined then sent to the actuators. In this case, the analysis and control means can also be arranged or programmed in order to modify the database as a function of the measured effects.

The actuators can comprise propulsion means of the aircraft and/or control surfaces of the aircraft.

The at least one sensor is preferably arranged in order to measure winds in several directions or from several origins.

According to yet another aspect of the invention, a method is proposed for stabilizing an aircraft (preferably utilized in an aircraft according to the invention) comprising:measurement of a wind by at least one sensor of the aircraftanalysis and control, by on-board analysis and control means in the aircraft, comprising:receiving wind measurement values originating from the at least one sensor,searching, within an on-board database in the aircraft, which associates different wind measurement values with different instructions intended for actuators of the aircraft, for a match with the wind measurement values originating from the at least one sensor,determining, as a function of this search, instructions to be sent to the actuators,sending these determined instructions to the actuators.

The at least one sensor preferably measures a wind at a measurement frequency of at least 0.1 Hz, preferably at least 1 Hz. The analysis and control means preferably determine instructions to be sent to the actuators at a frequency of at least 0.1 Hz, preferably at least 1 Hz.

During this method according to the invention, the aircraft can perform hovering flight.

The aircraft according to the invention is preferably a lighter-than-air aircraft.

The at least one sensor preferably measures the wind remotely.

The wind measurement values can comprise:an amplitude or a variation in amplitude of the wind, and/oran origin or a direction of the wind, or a variation in the origin or direction of the wind.

The analysis and control means preferably send the instructions directly to the actuators, without a validation or approval step by a human operator.

The method according to the invention can also comprise measuring the effects, on the position of the aircraft, of the instructions determined then sent to the actuators. In this case, the method according to the invention can also comprise modification of the database, by the analysis and control means, as a function of the measured effects.

The actuators can comprise propulsion means of the aircraft and/or control surfaces of the aircraft.

The at least one sensor can measure winds in several directions or from several origins.

DETAILED DESCRIPTION

As these embodiments are in no way limitative, variants of the invention can be considered, comprising only a selection of the characteristics described or shown hereinafter, in isolation from the other characteristics described or shown (even if this selection is isolated within a phrase comprising these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. This selection comprises at least one, preferably functional, characteristic without structural details, and/or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art.

Firstly, a first embodiment of the aircraft1according to the invention will be described, with reference toFIGS. 1a, 1b,2,3and4.

In the present description, the term “aircraft” denotes any means of transport (of persons or goods) capable of movement by flying.

The aircraft1is arranged in order to perform hovering flight. This is understood to mean that the aircraft1is capable (in the absence of wind) of flight in a fixed position with respect to the ground, as is the case for a dirigible or a helicopter.

More particularly, the aircraft1consists of a lighter-than-air aircraft.

In the present description, the term lighter-than-air aircraft is an aircraft the lift of which is provided by buoyancy (unlike a heavier-than-air aircraft) such as for example a balloon with nacelle or a dirigible.

The lighter-than-air aircraft1(a vehicle the lift of which is ensured by a gas that is lighter than the ambient air surrounding it, i.e. a balloon or a dirigible) is a dirigible intended for carrying loads.

In this non-limitative example, the lighter-than-air aircraft1used is a dirigible having a length of 70 m and a volume of 6000 m3of helium. The lighter-than-air aircraft1moves horizontally with the aid of four engines41(electric motors or thermal engines), distributed at intervals of 90° around the circumference of the lighter-than-air aircraft1(preferably in a substantially horizontal plane parallel to the plane ofFIGS. 1a,2and3), including:two front/rear engines41,411that have a reversible direction of propulsion, andtwo lateral engines41,412that are vectorable or orientable (operating both for vertical propulsion upwards or downwards and for horizontal propulsion forwards or backwards) and which also have a reversible direction of propulsion.

The engines41are for example thermal engines having an individual power P=160 kW, SMA reference FR305-230E, equipped with a pair of contra-rotating propellers.

In order to ensure sufficiently accurate positioning of the load carried, the aircraft1is equipped with an active flight stabilization system of the aircraft1(comprising the means2,4,5and6described hereinafter), that is effective in a turbulent environment and in hovering flight. The stabilization system makes it possible, based on a remote sensing wind measurement (speed and intensity), to anticipate the behavioural response of the aircraft1in all directions, and thus to operate the actuators4in order to ensure its stability.

The aircraft1comprises at least one sensor2, arranged in order to measure wind3. By wind3is meant in the present description any air movement (preferably towards the aircraft1), preferably comprising one or more turbulence(s) and/or one or more gust(s) and/or one or more squall(s).

The at least one sensor2is arranged in order to measure the wind3remotely (by transmitting a signal22), i.e. before this wind3comes into contact with the aircraft1. Each sensor2can thus comprise one or more LIDAR (light detection and ranging) device (a remote measurement technology based on analysis of the properties of a light beam reflected back to its emitter) and/or one or more SODAR (sonic detection and ranging) device (a sensor that uses sound waves for measuring wind speed and direction).

The sensors2are arranged together in order to measure winds3in several directions or from several origins. More precisely, the measurement sensors2are placed so as to capture information in all directions around the aircraft1, in order to detect the gusts of wind3.

The at least one sensor2comprises several sensors2(at least four, preferably at least six sensors2). The embodiment shown in the figures comprises six sensors2.

Of these (six) sensors, several (four, cfFIG. 1a) sensors2are distributed in one and the same horizontal plane (a horizontal plane being defined as perpendicular to the vertical, i.e. the direction of attraction of gravity).

Of these (six) sensors, several (four, cfFIG. 1b) sensors2are distributed in one and the same vertical plane.

In the example shown in the figures, the lighter-than-air aircraft1is equipped with several sensors2of the LIDAR type (pulsed laser, wavelength λ=1.54 μm) making it possible to measure the speed of the wind3in all horizontal directions. To this end, measurement lines, for example 24, are positioned on the circumference of the lighter-than-air aircraft1. Each sensor2is arranged in order to measure the speed of the wind3at a distance comprised between 40 m and 400 m from the lighter-than-air aircraft1with a range gate of 10 or 20 m (which corresponds to 10 simultaneous measurements per beam). A vertical wind measurement (from a sensor2equipped with four beams for example) makes it possible to increase the measurement accuracy. Each on-board LIDAR2is for example a Wind Iris. Each sensor2comprises at least two measurement lines making it possible to measure two coordinates of the wind speed. In the present embodiment, each sensor2comprises four measurement lines making it possible to measure a third wind speed coordinate. The aircraft1comprises at least six LIDAR sensors, i.e. at least 24 measurement lines.

The at least one sensor2is arranged in order to measure a wind3at a measurement frequency of at least 0.1 Hz, preferably at least 1 Hz.

The aircraft1comprises actuators4, arranged in order to modify a position of the aircraft1in flight as a function of instructions received by these actuators4.

The actuators4comprise propulsion means (the engines41) and control surfaces42.

This embodiment comprises four engines41and four control surfaces42.

The control surfaces42are moveable devices that make it possible to produce or to control the movements of the aircraft1, for example the angle of attack or the angle of sideslip of the aircraft1.

These actuators4can be dedicated to the stabilization system according to the invention or not.

The aircraft1comprises an on-board computerized and/or electronic database6in the aircraft1. The database6associates different wind measurement values with different instructions intended for the actuators4. These instructions are provided in order to compensate for the effect, on the aircraft1, of the wind3, having measurement values associated with these instructions in the database6.

This database6is constructed:By aerodynamic calculations that simulate the effects of several wind measurement values on the aircraft1, and calculates the theoretical instructions to be sent to the actuators4in order to compensate for these effects, and/orBy empirical data (obtained for example in a wind tunnel on the aircraft1, or by hydrodynamic tests on a mock-up or by tests of the aircraft1in flight, or by digital simulations), obtained by subjecting the aircraft1to different values for wind3and by testing different instructions sent to the actuators4until the effects of this wind3are satisfactorily compensated for.

The database6comprises a computer, and/or a central processing or computing unit, and/or an analogue electronic circuit (preferably dedicated) and/or a digital electronic circuit (preferably dedicated) and/or a microprocessor (preferably dedicated), and/or software means. In the present embodiment, the database6is stored on the flash memory in the calculator5described hereinafter. This database6is typically in the form of a look-up table, for example in a format of the “csv” type.

The aircraft1comprises analysis and control means5(also called “calculator”5).

The analysis and control means5comprise a computer, and/or a central processing or computing unit, and/or an analogue electronic circuit (preferably dedicated) and/or a digital electronic circuit (preferably dedicated) and/or a microprocessor (preferably dedicated), and/or software means.

As will be seen hereinafter, the analysis and control means5are arranged (for example by comprising a dedicated electronic card) and/or more precisely programmed (for example by comprising software means) in order to carry out certain functions or operations or control or calculation, etc.

As will be seen hereinafter, each of the steps of the method according to the invention utilized by the aircraft1is not carried out in a purely abstract or purely intellectual manner, butis performed automatically (excluding all human intervention), andinvolves the use of at least one technical means.

The analysis and control means5are arranged and/or programmed in order to:receive, originating from the at least one sensor2, measurement values of a wind3,search, within the database6, for a match with these wind measurement values originating from the at least one sensor2,determine, as a function of the result of this search, instructions to be sent to the actuators4, andsend these determined instructions to the actuators4(the calculator5sends the instructions that control the engines41and the control surfaces42).

The wind measurement values typically comprise (preferably for each point of several points in space around the aircraft1):at least one amplitude or at least one variation (in the case of a gust of wind3) in the amplitude of the wind3, each amplitude typically being a wind speed or intensity. The at least one (variation in the) amplitude can thus comprise a (variation in the) local speed of the wind3and a (variation in the) approach speed of the wind3towards the aircraft1: it will be understood for example that in the case of a tornado, the local wind speed inside the tornado can be very high but this tornado can have a fixed position (and thus an approach speed of zero) with respect to the aircraft1, andat least one origin (for example a position of wind3with respect to the aircraft1, and/or a number of the sensor2having detected this wind3) and/or a direction of the wind3(or at least one variation in the origin or direction of the wind3). The at least one (variation in the) direction can thus comprise a (variation in the) local direction of the speed vector of the wind3and a (variation in the) approach direction of the wind3towards the aircraft1: it will be understood for example that in the case of a tornado, the local wind speed inside the tornado can have a rotational direction about a centre of the tornado but this tornado can have a fixed position (and thus no approach direction) with respect to the aircraft1;and optionally a distance of this wind3with respect to the aircraft1.

The analysis and control means5are also arranged and/or programmed in order to convert the measurement values originating from the at least one sensor2into a format adopted in (or compatible with) the database6(i.e. convert the measurement information into data that are known or can be used by the database6).

Typically, this transformation (carried out by the calculator5) consists of reconstructing a wind field based on separate measurements from several of the sensors2(for example 24 beams with 10 measurement points i.e. 240 points every second for a measurement at 1 Hz). On each measurement (every second for a measurement at 1 Hz), these points are interpolated in order to reconstruct a three-dimensional vector field representing directions and speeds of the wind3in the space surrounding the aircraft1.

The analysis and control means5are arranged and/or programmed in order to send the instructions directly to the actuators4, without the need for a validation or approval step by a human operator (such as a pilot of the aircraft1for example).

Thus, each sensor2is linked to the on-board calculator5dedicated to the stabilization system. The communication protocol between the sensors2and the calculator5will preferably be based on the CAN (Controller Area Network) system, which is a serial bus system that due to its reliability is suitable for real-time on-board systems. This analyzes the data originating from the sensors2in order to identify the disturbances. It then compares these disturbances to the database6established beforehand. The database6is stored in a memory of the calculator5. The data of the database6define or associate for each “case” (i.e. field of speeds and directions of the wind3), a response strategy, i.e. instructions intended for the actuators4. A certain number of external data items can also, if desired, be taken into account in the choice of the response strategy, such as:flight data, such as for example IAS data (for “Instant Air Speed” or instantaneous speed of air or wind), IGS data (for “Instant Ground Speed” or instantaneous speed of the aircraft1relative to the ground),system data (engines, propellers, . . . ),GPS location data;environmental data such as for example topography around the aircraft, temperature, humidity, etc.

In order to carry out these operations, the calculator5has a computing power typically corresponding to at least that of a Xeon E3-1220 CPU clocked at 3.10 GHz and a storage capacity of at least a 2 Gb memory. The algorithm (which compares the values captured by the sensors2and the data originating from the database6) is for example produced in a LabVIEW environment or in C language.

The analysis and control means5are arranged or programmed in order to determine instructions to be sent to the actuators4at a frequency of at least 0.1 Hz, preferably at least 1 Hz.

The aircraft1also comprises means (not shown) for measuring the effects, on the position of the aircraft1, of the instructions determined and then sent to the actuators4; and the analysis and control means5are also arranged and/or programmed in order to modify, in the database6, the instructions associated with these wind measurement values as a function of the measured effects, so as to improve the compensation for the wind by the instructions contained in the database6.

In order to measure these effects, inertial data are used (obtained with an inertial navigation system) as well as GPS data, all these data being recorded.

Thus, the method utilized by the aircraft1typically comprises:remote measurement of a wind3by the at least one sensor2of the aircraft1(step11inFIG. 4), or preferably several winds in several directions or from several origins (inFIGS. 1aand 1b, several sensors2are placed all around the aircraft1and take measurements all around the aircraft1; inFIG. 2, a gust of wind3is detected by one of the sensors2), thentransformation, by the analysis and control means5, of the measurement values originating from the at least one sensor2into a format adopted in (or compatible with) the database6(i.e. transformation of the measurement information into data that are known or can be used by the database6). Typically, this transformation (carried out by the calculator5) consists of reconstructing a wind field (i.e. a three-dimensional vector field representing directions and speeds of the wind3for several points of a space surrounding the aircraft1) based on separate measurements from several of the sensors2(for example 24 beams with ten measurement points i.e. 240 points every second for a measurement at 1 Hz). On each measurement (every second for a measurement at 1 Hz), these points are interpolated in order to reconstruct this vector fieldanalysis and control, by the analysis and control means5, comprising:receiving, originating from the at least one sensor2, (step12inFIG. 4) measurement values of the wind3, thensearching (step13inFIG. 4), within the on-board database6in the aircraft1, for a match with these wind measurement values originating from the at least one sensor2, thendetermining (step14inFIG. 4), as a function of the result of this search, instructions to be sent to the actuators4, (i.e. the calculator5analyzes the situation by comparing it to the database6and thus determines a response strategy), thensending these determined instructions (step15inFIG. 4) to the actuators4(via a flight control computer8of the aircraft1, also called a Flight Director), the analysis and control means5sending the instructions directly to the actuators4, without a step of validation or approval by a human operator (the measurement values of the wind3are processed by the calculator5andFIG. 3shows that the response strategy is established and that the actuators4are operating so as to generate on the aircraft1a vectored thrust7that counters or compensates for the effects of the gust of the wind3on the aircraft1).

Each of these steps can be utilized when the aircraft1performs a movement or performs (or at least intends to perform) hovering flight.

The at least one sensor2measures a wind3at a measurement frequency of at least 0.1 Hz, preferably at least 1 Hz. The analysis and control means5determine instructions to be sent to the actuators at a control frequency of at least 0.1 Hz, preferably at least 1 Hz.

This method is utilized continuously. To this end, the measurement step is reiterated at the measurement frequency (measurement frequency of 1 Hz for example) in order to follow the change in the wind3. The analysis and control step is reiterated at the control frequency.

The search within the database6for a match with wind measurement values called “measured values” originating from the at least one sensor2is a search within the database6for wind measurement values called “stored values”:that are stored in the database6and that are associated with instructions intended for the actuators4as previously explained, andthat match the “measured” wind measurement values:exactly (the search result matches a single “scenario” orwith a certain margin of error, typically plus or minus 1% of the measured values, or that are the closest possible of all the stored measurement values (the search result matches a single “scenario” or several very similar scenarios).

In cases where the search step13comprises a comparison between a three-dimensional “measured” field (originating from the at least one sensor2) of vectors representing directions and speeds of the wind3in the space surrounding the aircraft1with the set of scenarios (i.e. stored values or stored three-dimensional vector fields representing directions and speeds of the wind3in the space surrounding the aircraft1) stored in the database6, the search result13typically matches different very similar scenarios, and the determination step14will supply a response for each actuator4in the form of a weighted composition of several instructions stored in the database6and associated with these different scenarios (in particular when the measured wind3comprises several gusts in several directions).

This method also comprises:a measurement (not shown inFIG. 4) of the effects, on the position of the aircraft1, of the associated instructions sent to the actuators4, and thenif these effects are not satisfactory (the “satisfactory” character being obtained for example by comparing the measured effects with respect to a position stability threshold of the aircraft1in the case of hovering flight) a correction or modification (not shown inFIG. 4), by the analysis and control means5, of the database6as a function of the measured effects. The system2,4,5and6records all the data, and can therefore carry out the correction or modification:during the flight of the aircraft1(“Online”) during which these data are measured, orafter the flight of the aircraft1(“Offline”) during which these data are measured, so as to propose improvements to the database that will be implemented during maintenance sessions.

Thus, the invention operates by forecasting, i.e. the response of the aircraft1with respect to flight dynamics when facing a given wind3scenario is known beforehand. The resulting system has the advantage of being much more responsive than if the calculations needed to be carried out in real time. Furthermore, the responses can change as a function of the feedback. Each response is analyzed, and if the latter is not satisfactory, then the system2,4,5,6can change its strategy.

Of course, the invention is not limited to the examples that have just been described and numerous amendments can be made to these examples without exceeding the scope of the invention.

For example, in a variant, each one of all or part of the sensors2can be replaced by a sensor (for example Pitot tubes and/or an anemometer) that is not arranged in order to measure the wind remotely, i.e. it is arranged in order to measure a wind only when this wind is in contact with the aircraft1.

Moreover, in a “non-automatic” (less advantageous) variant, it is possible to give the pilot of the aircraft1a map of the aerological environment around the aircraft1(this map being established based on the values measured by the at least one sensor2), thus leaving her free to act accordingly (with for example a recommendation on the choices to be taken).

Of course, the different features, forms, variants and embodiments of the invention can be combined together in various combinations if they are not incompatible or mutually exclusive. In particular, all the variants and embodiments previously described can be combined together.