Field of the invention

The present invention relates to an aerodynamic assembly, comprising a wing body having an aerodynamic profile and a plurality of thrust assemblies. In a further aspect the present invention relates to a wind power generation system utilizing an aerodynamic assembly.

Background art

The internet publication of Wingcopter, www.wingcopter.com, shows an aerodynamic wing body provided with a plurality of actively controlled, pivotally connected thrust propellers. Further known aerodynamic assemblies typically comprise a wing body having a plurality of integrated thrust propellers. In all of these prior art systems, an active actuated connection is present between the wing and thrust propellers, necessitating a control loop, which makes these systems inherently slow (as there will always be delays between control inputs and response from the actuators involved).

Summary of the invention

The present invention seeks to provide an aerodynamic assembly comprising a wing body having an aerodynamic profile and a plurality of thrust assemblies, wherein the aerodynamic assembly has an improved control, especially in adverse conditions.

According to the present invention, an aerodynamic assembly of the type defined in the preamble above is provided comprising a wing body having an aerodynamic profile with a major chord along a flight direction of the wing body, the aerodynamic assembly further comprising at least two thrust assemblies positioned symmetric with respect to a center of gravity of the wing body, each of the at least two thrust assemblies comprising a forward thrust propeller positioned forward of the wing body and an aft thrust propeller positioned aft of the wing body, wherein each thrust assembly of the at least two thrust assemblies comprises an attachment part fixedly attaching the thrust assembly to the wing body, and a linking mechanism, the linking mechanism being connected to the respective forward and aft thrust propellers for synchronizing a thrust vector of both the forward thrust propeller and the aft thrust propeller in a thrust control plane perpendicular to a wing body surface plane and parallel to the major chord, the linking mechanism comprising a pivoting connection to the attachment part, allowing free pivoting of the linking mechanism around a pivot axis perpendicular to the thrust control plane.

According to the present invention embodiments, the linking mechanism pivotally connects the forward thrust and the aft thrust propeller of each thrust assembly, allowing synchronous pitch rotation of the forward thrust propeller and the aft thrust propellers independent from pitch rotation of the wing body. Furthermore, the free pivoting of the linking mechanism allows for fast response times of the thrust assemblies, as no (mechanical) actuation links and control loops are involved. The synchronous pitch motion of the forward thrust and the aft thrust propellers provides improved control of the aerodynamic assembly during windy take-off and landing conditions but also during winged flight.

Short description of drawings

The present invention will be discussed in more detail below, with reference to the attached drawings, in which

Figure 1 shows a top view of an aerodynamic assembly according to an embodiment of the present invention;

Figures 2A-2H each show a side view of an aerodynamic assembly with linking mechanism according to an embodiment of the present invention;

Fig. 3A-C each show a schematic view of an operating mode of a wind power generation system utilizing an aerodynamic assembly according to an embodiment of the present invention;

Figure 5A-5B each show a schematic view of a gearbox of a wind power generation system according to an embodiment of the present invention;

Figures 6-8 each show a side view of a combination of a bridle system and a wing body according to embodiment of the present invention.

Description of embodiments

With reference to Figures 1 and 2A to 2H, showing various views of embodiments of an aerodynamic assembly 1 according to the presenting invention. The depicted aerodynamic assembly 1 comprises a wing body 2 (e.g. a Horten type wing) having an aerodynamic profile with a major chord along a flight direction of the wing body 2. At least two thrust assemblies 4, 6 are positioned symmetric with respect to a center of gravity "CG" of the wing body 2, and each of the at least two thrust assemblies 4, 6 comprise a forward thrust propeller 8, 10 positioned forward of the wing body 2 and an aft thrust propeller 12, 14 positioned aft of the wing body 2. It is noted that in the exemplary embodiments described herein, the thrust assemblies 4, 6 comprise thrust propellers, however, it is noted that alternative thrust devices with a well controllable thrust direction may also be used, such as ducted fans, variable pitch propellers, etc.

Each thrust assembly of the at least two thrust assemblies 4, 6 comprises an attachment part 16, 18 fixedly attaching the thrust assembly 4, 6 to the wing body 2, and a linking mechanism 20. The linking mechanism 20 is connected to the respective forward thrust propellers 8, 10 and aft thrust propellers 12, 14 and is configured to synchronize pitch motion of a forward thrust propeller 8 with an aft thrust propeller 12 of corresponding thrust assembly 6, such that the forward thrust propeller 8 and the aft thrust propeller 12 pitch in unison in forward and backward fashion. This synchronized pitch motion may also be described as parallel motion of rotation axes of the forward and aft thrust propellers 8,12, which is clearly shown in Figures 2A-2H. This allows accurate control of a thrust vector of both the forward thrust propeller 8, 10 and the aft thrust propeller 12, 14 in a thrust control plane perpendicular to a wing body surface plane and parallel to the major chord. Advantageously, the linking mechanism 20 comprises a pivoting connection 22 to the attachment part 16,18, allowing free pivoting of the linking mechanism 20 around a pivot axis perpendicular to the thrust control plane. This allows full control of the aerodynamic assembly 1 using the thrust assemblies 4, 6 only, independent from the wing body 2 orientation and control inputs. The thrust assemblies 4, 6, are provided with (differential) thrust magnitude control, allowing e.g. a stable hover operation. By properly managing the thrust magnitude of the thrust assemblies 4, 6, yaw, pitch and roll inputs can be obtained (as in a conventional quadcopter system) with a very high response rate.

This present invention provides a solution for a kite or wing assembly, i.e. aerodynamic assembly 1 , of a wind power generation system with integrated quad-copter 8, 10, 12, 14 for launch and landing of the aerodynamic assembly 1 in rough wind (i.e. strong and gusty) conditions. By means of the present aerodynamic assembly 1 , a pitch angle of the forward and aft thrust propellers 8, 12 can be controlled independently from a wing pitch angle controlled by control surfaces (not shown in the figures) of the wing body 2. The aerodynamic assembly 1 can be envisaged as a special tilt-rotor construction with one forward thrust propeller 8 in front of a wing neutral point and an aft thrust propeller 12 located aft of the wing neutral point. A mechanical interconnection is provided by the linking mechanism 20 such that the forward thrust propeller 8 and aft thrust propeller 12 pivot simultaneously in unison around their respective pitch axis fully independent from the wing pitch angle.

Various embodiments of the aerodynamic assembly are conceivable and advantageous in many situations, and allow to control the aerodynamic assembly 1 using (mainly) the thrust assemblies 4, 6, as if it were hanging on a number of strings, which is especially advantageous in strong and gusty conditions where normal 'quadcopter' type of control is insufficient, and would often result in an uncontrolled crash of the aerodynamic assembly 1 .

In an embodiment, the linking mechanism 20 is further arranged to allow rotation of the thrust vector in the thrust control plane in a control range including a first thrust vector direction perpendicular to the major wing surface plane, e.g. 0 degrees "hover mode", a second thrust vector direction aligned with the major chord, e.g. +90 degrees "propulsion mode/generator mode", and a third thrust vector direction in a rearward direction opposite to the flight direction of the wing body 2, e.g. -90 degrees. Therefore, in view of Figures 2A-2H, both the forward and aft thrust propellers 8, 12 connected to the mechanism 20 are able to pitch both counter clockwise, "forward", as well clockwise, "backward". In an embodiment, the control range of the thrust vector spans more than 90 degrees.

In an embodiment, the linking mechanism 20 comprises a pivoting attachment member 24, wherein the forward and aft thrust propellers 8, 10, 12, 14 are attached to respective ends of the pivoting attachment member 24. In this way the forward and aft thrust propellers can rotate independently from the wing body 2.

In a further embodiment, the pivoting connection 22 comprises two pivoting points, and the pivoting attachment member 24 comprises a mechanical rod offset from the two pivoting points, as shown in Figure 2A, 2B. In a further embodiment, the pivoting connection 22 comprises two rotating members with an endless loop member connecting the two rotating members, as shown in Figure 2C, 2D. The endless loop may be a chain, a belt, or the like.

In a further embodiment the pivoting attachment member 24 comprises a bevel gear mechanism, as shown in Figure 2E, 2F.

In a further embodiment, the pivoting attachment member 24 comprises a T-shaped body, journaled to the wing body, as shown in Figure 2G, 2H.

In a further embodiment, each of the at least two thrust assemblies 4, 6 comprise a thrust control unit connected to the forward thrust propeller 8, 10 and aft thrust propeller 12, 14. The thrust control unit can be arranged to control thrust magnitude of each thrust propeller, and then allows differential control and/or integrated stability control of the aerodynamic assembly 1 , independent from the actual orientation and/or control inputs of the wing body 2.

With reference to Figure 4, in an embodiment the at least two thrust assemblies 4, 6 comprise at least one pair of thrust assemblies 4, 4a, 4b, 6, 6a, 6b positioned laterally symmetric with respect to the center of gravity CG of the wing body 2. In this embodiment each side of the wing body 2 is provided with a plurality of thrust assemblies 4, 4a, 4b, 6, 6a, 6b, each if which, in turn, comprise a corresponding forward thrust propeller 8, 8a, 8b, 10, 10a, 10b and corresponding aft thrust propellers 12, 12a, 12b, 14, 14a, 14b.

In a further embodiment the thrust control unit of different pairs of thrust assemblies 4, 4a, 4b, 6, 6a, 6b are arranged to provide control over a roll axis of the wing body 2.

In another embodiment the different pairs of thrust assemblies 4, 4a, 4b, 6, 6a, 6b are positioned at different distances from the center of gravity (CG) in the longitudinal direction of the wing body.

Furthermore, as an alternative or additional embodiment compared to the embodiments described above, the thrust control units of different pairs of thrust assemblies 4, 4a, 4b, 6, 6a, 6b are arranged to provide control over a pitch axis of the wing body 2.

In an even further embodiment, the at least two thrust assemblies 4, 6 comprise a central thrust assembly (not shown in the figures) which is positioned along a centreline of the wing body, thereby balancing the central thrust assemblies with respect to the wing body 2.

In order to provide full and safe manoeuvrability of the aerodynamic assembly 1 , in an embodiment a combined thrust of the at least two thrust assemblies 4, 6 is sufficient to carry the total weight of the aerodynamic assembly 1.

The wing body 2 of the aerodynamic assembly may be further arranged to e.g. adjust lift distribution along the wing body 2, so that wing stall is prevented. To that end an embodiment is provided wherein the wing body 2 comprises a twisted wing profile, whereby the twisted wing profile allows an outer part of the wing body to remain in non-stall mode as long as possible, which is advantageous in strong wind conditions. The twisted wing profile e.g. comprises a twist angle of 8 degrees, or even more.

In a further aspect the present invention relates to a wind power generation system 1 utilizing an a aerodynamic assembly according to one of the embodiments described herein. Reference is made to Figure 3A-3C, each showing a schematic view of an operating mode of a wind power generation system 1 utilizing an aerodynamic assembly 1 according to an embodiment of the present invention. Further reference is made to Figure 5A-5B each showing a schematic view of a gearbox of the a wind power generation system 1 according to an embodiment of the present invention.

Figure 3A-C show the various operational situations where the present invention embodiments are particularly useful, that is during stages of reel-out or reel-in of the aerodynamic assembly 1 close to a ground station 32.

Figure 3A shows a situation wherein the thrust assemblies 4, 6, are in a hover mode, i.e. wherein the thrust of the thrust assemblies 4, 6, is directed upward (the first thrust vector direction as described above). The wing body 2, which is attached to the ground station via a traction (or tether) cable 38 is being pulled towards the ground station 32, but in itself still has a positive angle of attack allowing sufficient control of the wing body 2 orientation in this particular stage.

In the situation shown in Fig. 3B, due to a pull down action via the traction cable 38, or e.g. aerodynamic forces on the wing body (gust, turbulence), the wing body 2 has gotten in a pitch down orientation. Due to the free pivoting of the linking mechanism 20 of the thrust assemblies 4, 6 around a pivot axis perpendicular to the thrust control plane, the thrust assemblies 4, 6 can still be held in a hover mode of operation, allowing to maintain full control of the aerodynamic assembly 1 . In this situation, the thrust assemblies 4, 6 are in the third thrust vector direction as described above.

The situation shown in Fig. 3C shows a further operational situation where the present invention embodiments are advantageous, wherein the propellers of the thrust assemblies 4, 6 are held in a forward motion, delivering propulsion thrust the aerodynamic assembly 1 (i.e. the second thrust vector direction as described above).

In the embodiments shown, the wind power generation system 30 comprising a ground station 32 with an electrical energy generator 34 connected to a cable pulley 36 and an aerodynamic assembly 1 with a wing body 2. The wing body 2 is connected to the cable pulley 36 via a traction cable 38. The wind power generation system 30 further comprises a gear box 40 connected between the electrical energy generator 34 and the cable pulley 36, wherein the gear box 40 has a first gear ratio in a first rotation direction of the cable pulley 36 for a launch/power direction (reel- out). The gear box 40 further has a second gear ratio in a second rotation direction for a retraction/landing direction (reel-in) of the cable pulley 36 opposite to the first direction. The first gear ratio is higher than the second gear ratio.

The wind power generation system 30 is able to change the gear reaction based on the first and second direction. That is, during reel-out power can be generated through the first gear ratio, providing a speed adaptation from the cable pulley 36 to the electrical energy generator 34. For example, during reel-out, see Figure 5A, cable pulley 36 is connected to the electrical energy generator 34 through the gears D and C by a first clutch C1 . Conversely, for reel-in, see Figure 5B the aerodynamic assembly 1 can be retracted through the second gear ratio connecting the electrical energy generator 34 to the cable pulley 36 through gears B end A. Depending on sizes of each of the gears A, B, C, D, a speed increase or decrease can be provided by the first and second gear ratio.

In an exemplary embodiment, the first gear ratio is at least three, i.e. 3:1 , and second gear ratio is one, i.e. 1 :1 , providing improved kinetic energy to electricity energy conversion during reel- out of the traction cable 38.

In an embodiment, the first gear ratio and second gear ratio may be selected to allow operation of the electrical energy generator 34 over its full operational range.

In a further embodiment, the electrical energy generator 34 comprises a permanent magnet type of generator.

In a further embodiment the gear box 40 comprises a first set of gears and a second set of gears, of which only one is connected between the cable pulley 36 and electrical energy generator 34 at any given time. This embodiment allows for independent first and second gear ratios for the first and second rotation directions.

In an advantageous embodiment, the gear box 40 comprises a first shaft with a first one- way clutch C1 associated with the first set of gears, and a second shaft with a second one-way clutch C2 associated with the second set of gears. This embodiment is able to change between the first and second gear ratios associated with the first and second rotation directions.

In a specific embodiment, the gear box 40 comprises n shafts and n sets of gears.

From the above the wind power generation system 30 can be seen to provide a solution for a gearbox 40 of the ground station 32 enabling different gear ratios (first and second) for different operational modes Launch/Power ("reel-out") and Retraction/Landing ("reel-in"). For kite power application for example, an exemplary difference in gear ratio is 3:1 . A gear box solution would normally require a mechanical or electrical driven gear selection/clutch mechanism. However, the wind power generation system 30 allows for one set of gears to be active and selected by rotational/torque direction of the electrical energy generator 34 or cable pulley 36 through (oneway) clutches C1 , C2, thereby allowing for two different connecting paths between the cable pulley 36 and the electrical energy generator 34. The first and second gear ratio between electrical energy generator 34 and the cable pulley 36 can be optimized for both operational modes independent from each other while the electrical energy generator 34 is only used in its 0-100% speed range. This allows the use of standard of-the-shelve (low cost) generator solutions.

In an even further aspect the present invention relates to a bridle system 50 for a wing body 2, and in particular to a combination thereof. Reference is made to Figure 6 to 9, each showing a side view of a combination of a bridle system 50 and a wing body 2 according to embodiments of the present invention.

In the depicted combination of a bridle system 50 and a wing body 2, the bridle system 50 comprises a tether attachment point 52, a port wing body attachment point 54, a starboard wing body attachment point 56 and an attachment line 58 connected between the port wing attachment point 54, the starboard wing attachment point 56 and the tether attachment point 52 via at least one pulley. The combination allows for a differential bridle system, allowing rotation of the wing body 2 over a longitudinal axis (roll axis). The wing body 2 may but need not be part of an aerodynamic assembly 1 as outlined above. Also, the wing body 2 may be connectable to a wind power generation system 30 by a traction cable 38 connected to the bridle system 50.

In an embodiment, the tether attachment point 52, in operation, is located at a first distance

L along a line perpendicular from a wing body 2 lower surface, and the port and starboard wing body attachment points 54, 56 in operation, are located at a second distance A along a line perpendicular from the wing body lower surface and at a third distance B along a line perpendicular to a plane formed by a roll axis and a yaw axis of the wing body. A length of the attachment line 58 is selected such that a ratio of the second distance A and the third distance B is substantially equal to a ratio of the third distance B and the difference between the first distance L and second distance A.

In a further embodiment, the at least one pulley 60 comprises a single pulley fixedly attached to the tether attachment point 52, and the attachment line is fixedly attached to the port and starboard attachment points. See e.g. the embodiments as shown in Figure 6 and 7. In this embodiment the wing body 2 is able to roll as the attachment line 58 rolls over the pulley 60 at the tether attachment point 52.

In a further embodiment, the at least one pulley 60 comprises two wing pulleys 60a, 60b fixedly attached to the port and starboard attachment points 54, 56, and the attachment line 58 is fixedly attached to the tether attachment point 52. In this embodiment the wing body 2 is able to roll as the attachment line 58 rolls over both wing pulleys 60a, 60b. See e.g. the embodiments as shown in Figure 8.

With reference to Figure 9, in a further embodiment of the combination, the bridle system 50 comprises multiple combinations of a tether attachment point 52, port and starboard wing body attachment points 54, 55, 56, 57, attachment lines 58, 59 and at least one pulley 60. In this way different ratios can be given to the first distance L, second distance A and third distance B.

In a further embodiment, the port and starboard wing body attachment point 54, 56 are held at the second distance using a secondary bridle system, e.g. utilizing restraint ropes/beams/etc.

In a further embodiment, the bridle system 50 comprises a reel-in guiding system for the attachment line.

In view of the exemplary embodiments shown in Figures 6-9, the present invention is a solution for supporting the span load of a tethered aircraft or kite wing body 2 with a plurality of lines 58, 59 without restricting roll/bank movements of the wing body 2. Such a tethered wing body 2 can be used for airborne wind energy systems that produce electricity utilizing such a wing body 2 connected to the ground via a traction cable 38 as described for the wind power generation system 30.

When the wing body 2 is supported at multiple locations or bridle connection points, see the Figures 6-9 showing further embodiments of the port and starboard wing body attachment points 54, 55, 56, 57, each having a plurality of auxiliary bridle lines 54a, 55a, 56a, 57a connected to the wing body 2. The plurality of these auxiliary bridle lines 54a, 55a, 56a, 57a are advantageously attached to the wing body 2 in distributed fashion latterly along the wind body 2. This allows for a structurally lighter wing body 2 that can withstand higher wing loads, which, in turn, allows the wing body 2 to be used in a more efficient wind power generation system 30.

Note that a conventional rigid bridle or plurality of tether attachment points would be able to distribute the tether connection forces over a wing span of an aircraft but would, however, limit the aircrafts ability to roll. When an aircraft would be required to roll for making a turn, it would need a larger aerodynamic steering input provided by aileron deflection, dihedral differential effects and the like causing more drag and a lower flight efficiency.

The combination of a differential bridle system 50 and wing body 2 according to the present invention allows for aircraft attachment lines 58, 59 and one or more pulleys 60, 60a, 60b, 61 a, 61 b, that enable such attachment lines 58, 59 supporting a port side of an aircraft wing body 2 to communicate with such attachment lines 58, 59 supporting a starboard side of the aircraft wing body 2, such that when port side attachment lines are getting longer, starboard side attachment lines are getting shorter and vice versa.

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.