NL2016130B1

NL2016130B1 - Multiple pairs of flapping wings for attitude control.

Info

Publication number: NL2016130B1
Application number: NL2016130A
Authority: NL
Inventors: De Wagter Christophe
Original assignee: Univ Delft Tech
Priority date: 2016-01-21
Filing date: 2016-01-21
Publication date: 2017-07-25
Also published as: WO2017126964A1

Abstract

The present invention is in the field of flapping wing micro air vehicles, combining a multicopter and a flapping micro air vehicle in one device. Micro air vehicle is defined as a pow- ered aerial vehicle that does not carry a human operator and uses aerodynamic forces to provide vehicle lift.

Description

Multiple pairs of flapping wings for attitude control

FIELD OF THE INVENTION

The present invention is in the field of micro air vehicles having flapping wings.

BACKGROUND OF THE INVENTION

The present invention is in the field of micro air vehicles (MAVs) having flapping wings, which combines a multicopter technology and a flapping micro air vehicle in one device .

An MAV commonly known as drone relates to a powered aerial vehicle that does not carry a human operator and uses aerodynamic forces to provide vehicle lift. MAVs can fly autonomously by computers and by piloted remotely. MAVs are used in several applications, such as for intelligence, in military and non-military security work, and in toy industry. MAVs can fly outdoors, or enter a doorway to investigate indoor environments.

Three types of MAVs exist, fixed wing (airplane type), rotatory wing (helicopter type) and flapping wing vehicles (ornithopters). These are more attractive compared to the other two types. Although fixed wing MAVs have a high efficiency and a long flight, they cannot hover. Rotary wings on the other hand can hover but have a shorter flight. A multicopter is a type of rotary wing craft with more than two rotors. In this respect, the term "oligocopter" may be a better term. Multicopters can achieve stable hovering by balancing the forces produced by the multiple number of rotors.

Flapping wings offer potential advantages in manoeuvrability and energy saving. They have a combined function of providing both lift and thrust simultaneously by twisting the wings throughout the flapping stoke. Lift is the force that keeps the MAV airborne, and thrust is the force that propels the MAV forward.

Especially for the smaller vehicles, flapping wings are interesting, if and only if they have sufficient attitude control. Especially in confined areas, such as small indoor areas, there is a problem with manoeuvrability and tight radius turns of MAVs, due to lack of attitude control.

Attitude control is controlling the orientation of the vehicle with respect to its centre of mass. Attitude control in flight dynamics is defined by three critical flight dynamics parameters, known as "roll", "pitch" and "yaw". Roll is rotation of the vehicle around the longitudinal axis (such as front-to-back) (figure 3, 16), pitch is rotation around the lateral axis (such as wingtip-to-wingtip) (figure 3, 17), and yaw is rotation around the vertical axis (such as top-to-bottom) (figure 3, 15) .

Various flapping wing MAVs are on the market. An example thereof is a tailed MAV. Tailed MAVs have stabilizing aerodynamic horizontal and vertical tail sections, typically with control surfaces or propellers to make the vehicle stable. A problem with tailed MAVs is their non-linear behaviour due to changing flow over the tail. For instance, when a MAV descends, the airflow over the tail reverses (parallel to a flight orientation) which means that in that regime, there is improper attitude control.

Another class of MAVs relates to tailless vehicles. Tailless MAVs have more potential to be more manoeuvrable compared e.g. to the tailed MAVs. However, they use heavy and complex mechanical systems to change forces on the wing during a flapping motion. This typically heavy mechanism is driven by actuators, which must be fast, strong and light. This combination is very difficult and typically, only two of the three are met: they are either fast and light but weak, or strong and fast but heavy, or fast and light but not strong. Solutions that meet all three relatively well are extremely expensive. This directly means that the vehicle is not well controllable or extremely heavy.

In addition to the above problems, when two opposing wings do not flap in phase and/or may have a different frequency (rpm), unwanted vibrations occur. This causes further instabilities .

The present invention therefore relates to an apparatus for flying with sophisticated attitude control, which solves one or more of the above problems and drawbacks of the prior art, providing reliable results, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

In a first aspect the present invention relates to a mini flapping wing device for flying according to claim 1.

According to the present invention there is provided a mini flapping device, which has an improved maneuverability, reduced complexity, reduced weight and increased strength, and is more efficient compared to the prior art concepts. The invention uses pairs of wings (also called "wing arrangement" (3) comprising a first and second wing). At least three wing arrangements can be used in this invention, in which preferably at least three egual driving mechanisms are attached on each wing arrangement. In case of three wing arrangements, yaw and roll are close-coupled, meaning that the aircraft cannot yaw without rolling and the aircraft cannot roll without yawing. This yaw-roll coupling can be used in toy industry, e.g. in drone racing competitions. In case of three wing arrangement, to obtain non-coupled yaw-roll an extra servomotor is required.

The present controller is for independently adopting thrust vectors of the wing arrangements. Therewith full and very quick attitude control is provided.

Each wing arrangement extends outwards at a side of the device; seen from above, a first pair of wings may for example extend at a left top side of the device, a second pair at a left bottom side, and similar two pairs at a right side. Or a pair may extend at a front side, and two pairs may extend at a right and left bottom side, respectively.

Each of the thrust vectors (see fig.l, 5), (adjusted by wing arrangements), is independently controllable to allow full attitude control. In addition, less vibration is achieved due to use of wing arrangements. In fact high-speed high-resolution recordings did not show any problematic vibration. A mini flapping wing device relates to a flapping flight vehicle which is less than 200 cm in size. The size is the largest cross sectional dimension. The present vehicles could be as small as 0.1 mm size, but typically are 1-15 cm in size, such as 2-10 cm, e.g. 25 mm.

The flapping motion in the present invention may use a traditional crank rocker flapping mechanism (1), which con sists of a fixed link, a crank, and a rocker. In the crank rocker flapping mechanism, the rocker, which is connected to the fixed link, oscillates, while the crank can fully rotate (360 degree). The rocker crank mechanism provides a way to transform the 360-degree rotation of the motor shaft (which drives the crank) to a flapping motion (by connecting the wing to the rocker). The rocker is driven by a driver. In other words, the crank rocker flapping mechanism converts rotational motion to translational motions. A controller is connected to each drive engine, and it controls the driving means.

One cycle in the flight of a flapping wing vehicle consists of a down stroke and an upstroke, which produce both thrust and lift components of the aerodynamic force.

The flapping wings may be in a more horizontal configuration (trailing edge to leading edge vector points forward) during a horizontal flight mode, and in a vertical configuration (trailing edge to leading edge vector points upward) for a hover mode.

During fast forward flight, the lift (for staying in the air) is typically not provided by the thrust anymore, such as in multicopters, but instead is provided by the airflow over the flapping wings; this results in much more efficient (estimated to attribute to 20-50% in terms of energy) forward flight.

The present flapping wings can also achieve 30% higher lift coefficients (=lift per unit of surface) than fixed wing craft as estimated. A wing arrangement (3) is used to minimize vibrations by operating in phase while allowing independent force control. The wings can be thin, bendable and of any shape. Each wing comprise a wing area, and a leading edge (see fig. 1).

The front of the wing is called leading edge. Each leading edge is rigid (e.g. having a flexural strength of > 50 MPa, preferably > 100 MPa (measured according to ASTM D790) and each wing area is resilient. Suitable materials for the leading edge are lightweight metals, such as aluminum, polymers, such as thermo-hardened polymers, epoxy comprising materials, and composites, such as an epoxy comprising carbon fibres, and combinations thereof. Suitable materials for the wing area are thin foils (1-100 pm) of elastomeric polymers. Both wings can be in a first position, wherein both leading edges and both wing areas are close to one and another, such as substantially parallel and adjoining (γ=0), (4.B), and a second position wherein both leading edges and both wing areas are positioned at a larger angle (γ e.g. e[5,180]) and form a V-shape (4.A).

In order to keep the device flying, an electrical power source (14), such as a battery, is required. In an example approximately 1W is required for a device with four wing arrangements .

Thereby the present invention provides a solution to one or more of the above-mentioned problems.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

In an exemplary embodiment of the present flapping wing device, at least one wing arrangement is rotatably mounted on the mini flapping wing device via a single pivot point for both wings for attitude control, specifically yaw control. In other words, with respect to a fuselage at least one pair of wings is rotated, or two pairs of wings are rotated at a same time, etc. in view of an intended attitude control. A "tri-flapper" is an example of such a device, wherein one pair may rotate in order to provide yaw.

The present invention can have multiple wing arrangements, and each wing arrangements can flap independently. Flapping motion is regarded as a movement of wings, such as up and down or back and forth, i.e. a flight is bird like. In other words, when one wing of the pair moves one way, the other moves the other way at the same speed to balance the moments. The wings can be connected to a fuselage (7) (see fig. 1-2) of the mini flapping device through various mechanical points. A fuselage (6) is considered to be the main body of the aircraft. In principle, a fuselage (7) can be customized to accommodate any number of wing arrangements. A suitable stabilization electronics for the present device with four wing arrangements is for instance the same as for the CX10 multicopter of Cheerson; said multicopter provides a less preferred example of a fuselage to which the present wing arran gements could be attached, albeit with some further modifications . A pivot point is regarded as an apparent virtual center of rotation of the flapping wing arrangement. In an example, the pivot point is an interface to attach two wings. The pivot points can be customized, for instance, two wings of a wing arrangement are mounted on the same plane, or one wing of a wing arrangement is shifted up with respect to the other wing of the wing arrangement, or there is a horizontal distance between first wing and the second wing.

Pitch and roll controls are done by changing thrust vectors to provide a difference between these vectors, e.g. from left and right, and front to back, respectively. In other words, more thrust to one wing arrangement and/or less thrust to its opposite wing arrangement can be applied. Yaw control can be obtained by mounting diagonally opposing wings at an angle (11, ±a) and increasing thrust from one diagonal compared to the other. Yaw control relates to changing the direction of which the flapping wing device is oriented. The present device can change direction, i.e. a 90-degree rotation, within a few hundred millisecond, and possibly within 50 msec. To adjust the thrust, an amplitude of a flapping motion of the wings can be adjusted (for a same frequency). For instance, to produce a higher thrust, the amplitude of the flapping motion can be increased. To produce a lesser amount of thrust, the amplitude of the flapping motion can be decreased. Likewise, the frequency can be increased, in case of a same amplitude.

In an exemplary embodiment of the present flapping wing device, at least two wing arrangements are arranged in a wing arrangement pair (e.g. 12.1 and 12.2 of fig. 2, respectively) , comprising a first wing arrangement mounted at one side of the flying apparatus and a second wing arrangement mounted at an opposite side of the flying apparatus, wherein configuration angles (11, a) of both wing arrangements are equal and opposing. A configuration angle (11, a) is considered to be the angle between a flapping axis (8) and the fuselage (7). In an example of such a device multiple "biplanar" wings are provided.

In an exemplary embodiment the present flapping wing device comprises at least two wing arrangement pairs (WAP)(12) and wherein the device has a two-fold symmetry axis (10) and optionally also a mirror plane (9) (fig. 2). At least two wing arrangements are located at each of the opposite extremities of the fuselage (7), and the two flapping wings of each wing arrangement are arranged with respect to the rotational symmetry (two-fold symmetry axis (10)) of the center of the mass of the aircraft. This arrangement will result in non-aligned thrust vectors in view of yaw. In an example of such a device a rotatably mounted wing arrangement (or wing pair) is controllable and adaptable.

In an exemplary embodiment, at least one configuration angle (11, a) in the present flapping wing device is adjustable during flight, such as by using a servomotor.

In an exemplary embodiment, the present flapping wing device comprises a drive engine (2) drivingly connected to each wing arrangement independently. Here brushed or brushless electric motors can be used which are widely available. In an example of such a device each pair of wings is controlled independently and a position of the wing arrangement is controlled and adaptable.

By independently varying the speed of each drive engine, it is possible to generate a desired lift and have a full attitude control. Each wing arrangement can flap at desired frequency, amplitude and angle. A supplementary drive engine can be included, which controls the frequency and amplitude of two sets of wings, i.e. wing arrangement pair (12).

In an exemplary embodiment, the present flapping wing device comprises at least one of a gyroscope (13) and an accelerometer. A Gyroscope and an accelerometer can be used for stabilization of the device. The present invention can also include a GPS module. A Gyroscope can sense rotation, whereas the accelerometer cannot. At present the capabilities of the gyroscope are preferred as information can be processed quickly and therefore control is almost instantly. In an example of such a device each a position of the wing arrangement is therewith controlled and adaptable.

In an exemplary embodiment, the controller is con- nected to each drive engine and a sensor, where-in said controller is arranged to control the driving means using attitude data obtained from the sensor. The control system can control the orientation of the flapping wing device, by means of attitude data received from the sensor. In an example of such a device a position thereof is controlled independently and a position of the wing arrangement is controlled and adaptable.

In a second aspect, the invention relates to a device with a wing arrangement comprising a first and a second wing, which are pivotal relative to each other, wherein both wings comprise a wing area, and a leading edge, wherein driving means can provide movement of both wings relative to each other, characterized in that each leading edge is rigid and each wing area is resilient, wherein both wings can be in a first position, wherein both leading edges and both wing areas are substantially parallel and adjoining, and a second position wherein both leading edges and both wing areas are positioned at an angle (6,γ) and form a V-shape; and wherein both wings are movable between the first and second position in anti-phase. The V-shape configuration makes sure that four wings are not exactly perpendicular.

In an exemplary embodiment, the present device comprises a wing arrangement wherein the angle between the first and second wing in the second position is controllable. In an example the angle of the second position may be varied from 10-120 degrees.

In an exemplary embodiment, the present device comprises a wing arrangement wherein the angular velocity of the first and second wing is controllable. It is noted that the term "angular velocity" at least partly overlaps in a functio-nal/physical aspect with the term "flapping frequency" used in scientific literature. The control system can control angular velocity of the first and second wing of an arrangement independently. In an example thereof a first wing arrangement may have a first angular velocity, whereas, at a same moment in time, a second wing arrangement may have a second, and different from the first, angular velocity. In an example therewith differential thrust between left and right, or likewise front and back, and combinations thereof, is provided.

The present device may further comprise at least one of a sensor, such as a chemical sensor, such as a sensor for detecting smoke, CO, a chemical species, a remote control, a memory, the memory comprising flight information, such as for performing a navigation loop, for flying in an "autonomous mode", an optical camera, an infrared camera, etc. As such the present device may perform various tasks, such as inspection of a specific location.

The invention is further detailed by the accompanying figures, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying exemplary embodiments and figures.

SUMMARY OF THE FIGURES

Fig. la-d show a schematic layout of the present pairs of flapping wings.

Fig. 2 shows a schematic top view of the present device

Fig. 3 shows attitude parameters. Figure 3 is copied from DIY, Arduino, Quadrirotor, http ://theboredengineers. com/2012/05/the-quadcopter-basics/.

DETAILED DESCRIPTION OF THE FIGURES

The figures have been detailed throughout the description .

In the figures: 1 Traditional crank rocker flapping mechanism 2 Electric motor (1 per pair) 3 Wing arrangement 4 Flapping motions 4.A both leading edges and both wing areas are po sitioned at an angle and form a V-shape 4.B both leading edges and both wing areas are substantially parallel and adjoining 5 Several independent thrust vectors 6 V-shape angle 7 Fuselage 8 Flapping axis 9 Mirror 10 Two fold symmetry axis 11 Configuration angle (a) 12 Wing pair arrangement (WPA) 12.1 WPA1 12.2 WPA2 13 Gyroscope or accelerometer 14 Power source 15 Yaw 16 Roll 17 Pitch

Fig. lb shows a side view of a configuration with three wing arrangements, of which one is rotatably mounted.

Fig. lc provides a side view of figure la. The central arrows indicate that the thrust vectors provided by the wing arrangements are slightly out of plane (10-20 degrees).

Fig. Id provides a top view of figure la. The arrows indicate that the thrust vectors provided by the wing arrangements are slightly out of plane (10-20 degrees), of which two are pointing upwards and two are pointing downwards. As such e.g. yaw control is provided.

It should be appreciated that for commercial application it may be preferable to use one or more variations of the present system, which would similar be to the ones disclosed in the present application and are within the spirit of the invention.

The following section is added to support searching of the prior art of the patent. 1. A mini flapping wing device for flying, comprising a driver, and a connection for a power source (14), characterized in that it comprises at least three wing arrangements, preferably at least four wing arrangements, each wing arrangement extending outwards at a side of the device, the wing arrangement comprising a first and a second wing which are pivotal relative to each other, wherein both wings comprise a wing area, and a leading edge; wherein the driver provides movement of both wings relative to each other, wherein each leading edge is rigid and each wing area is resilient, wherein both wings can be in a first position, wherein both leading edges and both wing areas are close to one and another, such as substantially parallel and adjoining, and a second position wherein both leading edges and both wing areas are positioned at a larger angle (γ, 6) and form a ν'-shape; wherein both wings are movable between the first and second position in anti-phase, and a controller for independently adopting thrust vectors of the wing arrangements. 2. A mini flapping wing device for flying according to claim 1, characterized in that at least one wing arrangement is rotatably mounted on the mini flapping wing device via a single pivot point for both wings or via a pivot point for each wing, for attitude control, specifically yaw control. 3. A mini flapping wing device for flying according to claim 1 or 2, characterized in that at least two wing arrangements are arranged in a wing arrangement pair, comprising a first wing arrangement mounted at one side of the flying apparatus and a second wing arrangement mounted at an opposite side of the flying apparatus, wherein configuration angles (10) of both wing arrangements are equal and opposing. 4. A mini flapping wing device for flying according to any one of claims 1-3, characterized in that it comprises at least two wing arrangement pairs and wherein the device has a two-fold symmetry axis (9)and optionally also a mirror plane (8) . 5. A mini flapping wing device for flying according any one of claims 1-4, characterized in that at least one configuration angle (10) is adjustable during flight. 6. A mini flapping wing device for flying according to any one of claims 1-5, characterized in that it comprises a drive engine drivingly connected to each wing arrangement independently. 7. A mini flapping wing device for flying according to any one of claims 1-6, characterized in that it comprises at least one of a gyroscope and an accelerometer. 8. A mini flapping wing device for flying according to any one of claims 1-7, characterized in that it comprises a controller connected to each drive engine and a sensor, wherein said controller is arranged to control the driving means using attitude data obtained from the sensor. 9. A wing arrangement for a mini flapping wing device for flying comprising a first and a second wing which are pivotal relative to each other, wherein both wings comprise a wing area, and a leading edge; wherein driving means can provide movement of both wings relative to each other, characterized in that each leading edge is rigid and each wing area is resilient, wherein both wings can be in a first position, wherein both leading edges and both wing areas are close to one and another, such as substantially parallel and adjoining, and a second position wherein both leading edges and both wing areas are positioned at a larger angle and form a V-shape; and wherein both wings are movable between the first and second position in anti-phase. 10. A wing arrangement according to claim 9, characterized in that the angle between the first and second wing in the second position is controllable. 11. A wing arrangement according to claim 9 or 10, characterized in that the angular velocity of the first and second wing is controllable.

Claims

A mini flapping wing device for flying, comprising a control, and a connection for a power source (14), characterized in that it comprises at least three wing assemblies, preferably at least four wing assemblies, each wing assembly extending outward on one side of the device, wherein the wing assembly comprises a first and a second wing which are relative to each other about a spindle, wherein both wings comprise a wing surface, and a leading edge; wherein the control provides movement of both wings relative to each other, with each leading edge being stiff and each wing surface resilient, with both wings being in a first position, in which both leading edges and both wing surfaces are close to each other, such as substantially parallel and adjacent, and a second position in which both front edges and both wing surfaces are positioned at a larger angle (γ, 6) and form a V shape; wherein both wings are movable in counter-phase between the first and second position, and a controller for independent adjustment of thrust vectors of the wing assemblies.

A mini flapping wing device for flying according to claim 1, characterized in that at least one wing assembly is rotatably mounted on the mini flapping wing device by means of a single pivot point for both wings or by means of a pivot point for each wing, for attitude control, in particular pivot control.

A mini flapping wing device for flying according to claim 1 or 2, characterized in that at least two wing assemblies are arranged in a wing assembly pair, comprising a first wing assembly on one side of the flying device and a second wing assembly arranged on an opposite side of the flying device, wherein configuration angles (10) of both wing assemblies are identical and opposite.

A mini flapping wing device for flying according to any one of claims 1-3, characterized in that it comprises at least two wing assemblies, the device having a dual axis of symmetry (9) and optionally also a mirror surface (8).

A mini flapping wing device for flying according to any one of claims 1-4, characterized in that at least one configuration angle (10) is adjustable during a flight.

A mini flapping wing device for flying according to any one of claims 1-5, characterized in that it comprises a drive motor drivably independently connected to each wing assembly.

7. A mini flapping wing device for flying as claimed in any of the claims 1-6, characterized in that it comprises at least one of a gyroscope and an accelerometer.

A mini flapping wing device for flying according to any one of claims 1-7, characterized in that it comprises a controller connected to each drive and a sensor, the controller being adapted to control the control using attitude data obtained from the sensor.

A wing assembly for a mini flapping wing assembly for flies, comprising a first and a second wing which are relative to each other about a spindle, wherein both wings comprise a wing surface and a leading edge; wherein drive means can provide a movement of both wings relative to each other, characterized in that each front edge is stiff and each wing surface is resilient, wherein both wings can be in a first position, in which both front edges and both wing surface falcons are close to each other, such as in substantially parallel and adjacent, and a second position in which both front edges and both wing incidents are positioned at a larger angle and form a V shape; and wherein both wings are movable in counter-phase between the first and second position.

A wing assembly according to claim 9, characterized in that the angle between the first wing and second wing is adjustable in the second position.

A wing assembly as claimed in claim 9 or 10, characterized in that the angular speed of the first and second wing is adjustable.