ROTARY FLYING VEHICLE

CROSS-REFERENCE TO RELATED CASES

This application claims priority to, and the benefit of Provisional U.S. Patent Application Serial No. 61/012,175, filed December 7, 2007, and also Provisional U.S. Patent Application Serial No. 61/106,703, filed October 20, 2008. The entire contents of each of the above-referenced applications are incorporated herein by reference.

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to flying vehicles in general, and to methods and systems for controlling a flying vehicle, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE Methods and systems for constructing remote controlled flying toy vehicles are known in the art. Such a flying toy vehicle generally includes a digital processor, which controls a plurality of propulsion devices attached to a plurality of blades of the toy flying vehicle, according to control signals received from a remote control, to maneuver the flying toy vehicle to a desired location in space.

US Patent No. 6,811 ,460 B1 issued to Tilbor et al., and entitled "Flying Toy Vehicle", is directed to a rotary aircraft configured as a self propelled remotely controlled toy disk. The aircraft includes a hub, a plurality of blade assemblies, a plurality of propulsion devices, a controller, and an energy reservoir. The blade assemblies are connected to the hub. Each propulsion device is mounted to a separate blade assembly. Two or more propulsion devices are provided, so that the propulsion devices are located symmetrically on the aircraft, to develop uniform torque and uniform lift in an upward direction. The controller detects signals

generated by a portable ground control transmitter, and varies the electric power supplied by the energy reservoir to each of the propulsion devices, individually. Alternatively, the controller can simply turn the power to the propulsion devices, on and off. US Patent No. 6,422,509 B1 issued to Yim and entitled

"Tracking Device", is directed to a tracking device. The tracking device includes a top propeller, a bottom propeller, a motor, two fins, a weight, two target sensors, a controller, and a power supply. The top propeller is connected to a stator of the motor, and the bottom propeller is connected to a rotor of the motor. The fins are connected to the tips of the top propeller. The weight is connected to one of the fins. One of the target sensors is connected to the top propeller, and the other is connected to the bottom propeller. The target sensors sense any phenomenon, such as light, sound, electromagnetic radiation, heat, and nuclear radiation. The controller controls the motor to modulate a speed differential between the top propeller and the bottom propeller, in response to the differential between the signals provided by the target sensors. An increase in the speed differential causes the tracking device to accelerate toward a target, by precession of a spinning axis of the tracking device, caused by the weight. A decrease in the speed differential causes the tracking device to decelerate.

US Patent No. 5,297,759 issued to Tilbor et al., and entitled "Rotary Aircraft Passively Stable in Hover", is directed to a rotary aircraft configured as a planar, unmanned, radio controlled, flying disk. The aircraft includes a hub, a plurality of blade assemblies, a plurality of propulsion devices, a controller, and an energy reservoir. The blade assemblies are connected to the hub. Each propulsion device is mounted to a separate blade assembly. Two or more propulsion devices are provided, so that the propulsion devices are located symmetrically on the aircraft, to develop uniform torque around a central axis of the aircraft, and

uniform lift in an upward direction along the central axis. The controller detects signals generated by a portable ground control transmitter, and varies the electric power supplied by the energy reservoir to each of the propulsion devices, individually. Alternatively, the controller can simply turn the power to the propulsion devices, on and off.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

Figure 1 is a schematic illustration of a rotary flying vehicle, constructed and operative in accordance with an embodiment of the disclosed technique;

Figure 2A is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in a first rotation position;

Figure 2B is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in an intermediate rotation position;

Figure 2C is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in a second rotation position; Figure 3 is a schematic illustration of a rotary flying vehicle system, according to a further embodiment of the disclosed technique;

Figure 4A is a schematic illustration of a top-view of a rotary flying vehicle, in a first rotation position, according to another embodiment of the disclosed technique; Figure 4B is a schematic illustration of the rotary flying vehicle of

Figure 4A, in a second rotation position;

Figure 4C is a schematic illustration of the rotary flying vehicle of Figure 4A, in a third rotation position;

Figure 4D is a schematic illustration of the rotary flying vehicle of Figure 4A, in a fourth rotation position;

Figure 5 is a schematic illustration of a time scheme, for operating the propellers of the flying vehicle of Figures 4A, 4B, 4C and 4D;

Figure 6 is a schematic illustration of a rotary flying vehicle, constructed and operative according to a further embodiment of the disclosed technique;

Figure 7 is a schematic illustration of a method for operating a rotary flying vehicle, operative according to another embodiment of the disclosed technique; and Figure 8 is a schematic illustration of a rotary flying vehicle, constructed and operative according to a further embodiment of the disclosed technique.

Figure 9 is a schematic illustration of a rotary flying vehicle, constructed and operative according to a further embodiment of the disclosed technique.

Figure 10A is a schematic illustration of a rotary flying vehicle, constructed and operative according to a further embodiment of the disclosed technique.

Figure 10B is a schematic illustration of the rotary flying vehicle of Figure 10A, in which the aerodynamic fin is horizontally moveable.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by providing a rotary flying vehicle coupled with a light detector, the direction of flight of the flying vehicle being controlled from a remote control, according to the response of the light detector to a respective light source.

Reference is now made to Figure 1 , which is a schematic illustration of a rotary flying vehicle, generally referenced 100, constructed and operative in accordance with an embodiment of the disclosed

technique. Rotary flying vehicle 100 includes a hub 102, a first airfoil 104, a second airfoil 106, a first beam 1Oe ₁ , a second beam 108 ₂ , a first propeller 110i and a second propeller 11O ₂ . Flying vehicle 100 also includes a power source 112, a light detector 114, a light responsive controller 116 and a clearance beacon 122. Hub 102 is coupled with first airfoil 104, second airfoil 106, first beam 108i, second beam 108 ₂ , and with light detector 114.

First airfoil 104, second airfoil 106, first beam 108i and second beam 108 ₂ , are arranged substantially symmetrically relative to hub 102, extending outward there from. First airfoil 104 and second airfoil 106 are located opposite each other, each extending from an opposite side of hub 102. First beam 108i and second beam 108 ₂ are located opposite each other. Beams 108i and 108 ₂ can be located substantially perpendicular to airfoils 104 and 106, or offset from a right angle (e.g., the angle between first beam 108i and airfoil 104 may equal approximately 70°), each extending from an opposite side of hub 102. First beam 108i and second beam 108 ₂ are coupled with hub 102 at the first ends thereof. First propeller 1 10i is coupled with first beam 108i, at the second end thereof. Second propeller 11O ₂ is coupled with second beam 108 ₂ , at the second thereof. Propellers 110i and 11O ₂ are further coupled with power source 112 and with controller 116, for example, through wires running along beams 108i and 108 ₂ , respectively. Controller 116 is further coupled with light detector 114.

In the present embodiment, power source 1 12 and controller 116 are depicted in dotted lines, as being located within hub 102, for minimizing the aerodynamic affect thereof on the flight of flying vehicle 100. However, power source 112 and controller 1 16 may be located at other locations on flying vehicle 100. Clearance beacon 122 is externally coupled with hub 102, at the top section thereof, and coupled with

controller 116. It is noted that clearance beacon 122 is optional, and may be omitted from rotary flying vehicle 100.

Power source 112 may be an electrical power source (e.g., battery), a fuel tank, a compressed air tank, and the like. Propellers 110i and 11O ₂ may be propelled by an electrical engine, a combustion engine, and the like. Alternatively, each of propellers 110i and 1 1O ₂ may be replaced with a rocket motor or jet motor propellers (not shown).

Power source 112 provides electrical power to propellers 110i and 11O ₂ , which rotate and produce thrust, causing flying vehicle 100 to rotate about a substantially vertical axis 121 , passing through the center of hub 102. When each of propellers 110i and 11O ₂ rotates, it generates a respective thrust force, perpendicular to the plane of rotation of the propeller. This aspect will be further elaborated with reference to figures 4A-4D, herein below. Wind curved lines 127 illustrate the rotation of propellers 110i and 11O ₂ . Wind curved lines 125 illustrate the rotation of flying vehicle 100. When airfoils 104 and 106 rotate, they produce vertical lift, causing flying vehicle 100 to ascend (i.e., move in the direction indicated by arrow 131 ). The produced lift is proportional to the rate of rotation of airfoils 104 and 106 (i.e., to the angular frequency of flying vehicle 100), for a given Angle of Attack (AOA) of airfoils 104 and 106. The AOA of an airfoil is the angle between the plane of the airfoil and the horizontal plane, in which flying vehicle 100 rotates. When an airfoil is inclined by a greater AOA, it generates more lift than an airfoil inclined by a smaller AOA. Airfoils 104 and 106 may be pivotally coupled with hub 102, allowing changing of the AOA of airfoils 104 and 106. In this manner, one can change the lift generated by airfoils 104 and 106, by changing their AOA of airfoils 104 and 106, instead of changing the rate of rotation thereof.

A remote control 118 is located in the vicinity of flying vehicle 100. Remote control 118 includes a light source 120, which constantly

emits light waves 123 toward flying vehicle 100. Light detector 114 is configured to detect light emitted from light source 120. When light detector 1 14 detects light from light source 120, light detector 114 is considered to be in a "receiving" state. When light detector 1 14 detects substantially no light from light source 120, it is considered to be in a "non-receiving" state. During the rotation of flying vehicle 100, the state of light detector 1 14 alternately changes between receiving and non-receiving, according to the rotation position of flying vehicle 100 relatively to remote control 118. Remote control 118 is employed to control the direction of flight of flying vehicle 100 in a horizontal plane (not shown), substantially perpendicular to vertical axis 121. Remote control 118 may further include a user interface (not shown), for receiving certain commands from a user of remote control 1 18, to be delivered as control signals to flying vehicle 100. The user interface may be, for example, in the form of command buttons, a touch-screen panel, a joystick, and the like. When a user of remote control 118 provides a command for a change in the direction of flight of flying vehicle 100, light responsive controller 116 directs power source 112 to change the power provided to either one of propellers 110i or 1 1O ₂ , during a certain rotation position of flying vehicle 100. Due to the different power provided to either one of propellers 110i and 11O ₂ , flying vehicle 100 changes its direction of flight in the horizontal plane. This aspect of the disclosed technique will be elaborated herein after, with reference to Figures 4A, 4B, 4C and 4D. Clearance beacon 122 includes a radiation emitter and a radiation detector (both not shown). The radiation emitter emits radiation 129 in a general upward direction. An obstacle (e.g., a ceiling, not shown) located above flying vehicle 100 reflects radiation 129. The radiation detector of clearance beacon 122 detects this reflected radiation. Radiation 129 of clearance beacon 122 may be, for example, IR radiation,

UV radiation, sound waves, and the like. Controller 116 determines the distance between clearance beacon 122 and the obstacle, according to the time elapsed between the emission and the detection of radiation 129. When the distance between clearance beacon 122 and the obstacle is smaller than a predetermined value, controller 116 directs power source 112 to reduce the power provided to propellers 110i and 11O ₂ . When propellers 1 10i and 11O ₂ are provided with reduced power, they rotate at a slower rate. Therefore, airfoils 104 and 106 rotate at a slower rate, thereby reducing the produced lift until flying vehicle stops ascending. Thus, controller 116 prevents flying vehicle 100 from colliding with the obstacle. Clearance beacon 122 renders flying vehicle 100 suitable for indoor use.

Reference is now made to Figures 2A, 2B and 2C. Figure 2A is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in a first rotation position. Figure 2B is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in an intermediate rotation position. Figure 2C is a schematic illustration top-view of the rotary flying vehicle of Figure 1 , in a second rotation position.

Flying vehicle 100 rotates about hub 102, in the direction indicated by arrows 126 and 128, at a substantially constant angular frequency f. In the first rotation position, light detector 114 is directed toward remote control 118, detecting light emitted from light source 120. Light detector 114 is in a receiving state, when flying vehicle 100 is in the first rotation position. In the intermediate rotation (Figure 2B) position, light detector 114 is directed away from remote control 118, and detects substantially no light emitted from light source 120. Light detector 114 is in a non-receiving state, when flying vehicle 100 is in the intermediate rotation position. In the second rotation position (Figure 2C), light detector 114 is located at the opposite side of flying vehicle 100, relative to remote control 1 18, and detects substantially no light emitted from light source

120. Light detector 1 14 is in a non-receiving state, when flying vehicle 100 is in the second rotation position. Flying vehicle 100 returns to the first rotation position, after completing a full rotation, lasting a time period

T, where T = - .

Light responsive controller 116 determines the rotation position

(i.e., first rotation position, intermediate rotation position, second rotation position, as elaborated herein above) of flying vehicle 100 relative to remote control 118, according to the state of light detector 114 (i.e., receiving or non-receiving). Light detector 114 may be in a receiving state for an ongoing time fraction of the period T, as long as it detects light emitted from light source 120. When light detector 114 begins to detect light from light source 20, controller 116 determines that light detector 114 has entered a receiving state and that flying vehicle 100 is in the first rotation position. When light detector 114 enters a receiving state for the next time (i.e., after flying vehicle 100 has completed a full rotation), controller 116 determines the rotation time period T and thereby angular frequency f. For example, if light detector 1 14 enters a receiving state once every 20 milliseconds, then controller 116 determines that the angular frequency f of flying vehicle 100 equals 50 rotations per second (i.e.: f = 50 rot/sec. It is noted, that light detector 114 may be in a receiving state during a quarter of the rotation of flying vehicle 100, i.e., during a time fraction of approximately 5 msec.

Once controller 116 has determined the rotation time period T of flying vehicle 100, it may determine the rotation position of flying vehicle 100 at any given moment, relative to remote control 1 18. Controller 116 may thus control the power provided to either one of propellers 110i and 11O ₂ at a specific rotation position, in order to change the direction of flight of flying vehicle 100, according to a command received from remote control 118.

Reference is now made to Figure 3, which is a schematic illustration of a rotary flying vehicle system, generally referenced 150, according to a further embodiment of the disclosed technique. Rotary flying vehicle system 150 includes a rotary flying vehicle 168 and a remote control 162. Remote control 162 includes a light source 164 and a command interface 166. Rotary flying vehicle 168 is similar to flying vehicle 100 of Figure 1 , and remote control 162 is similar to remote control 1 18 of Figure 1. Rotary flying vehicle 168 includes a plurality of propulsion devices 152^ 152 ₂ and 152 _N , a power supply 154, a light responsive controller 156, a plurality of light detectors 160- ₁ , 16O ₂ and 16O _N , and a clearance beacon 170. Clearance beacon 170 includes a radiation emitter 172 and a radiation detector 174. Controller 156 is coupled with power supply 154, light detectors 16O ₁ , 16O ₂ and 16O _N and with clearance beacon 170. Power supply 154 is further coupled with propulsion devices 152- ₁ , 152 ₂ and 152 _N .

Power source 154 provides electrical power to propulsion devices 152- ₁ , 152 ₂ and 152 _N , which rotate and produce thrust. Light source 164 constantly emits light toward flying vehicle 168. Light detectors 160i, 16O ₂ and 16O _N are configured to detect light emitted from light source 164. When each one of light detectors 160- ₁ , 16O ₂ and 16O _N detects light from light source 164, that light detector is considered to be in a "receiving" state. When each one of light detectors 160i, 16O ₂ and 16O _N detects substantially no light from light source 164, that light detector is considered to be in a "non-receiving" state. During the rotation of flying vehicle 168, the state of each one of light detectors 160i, 16O ₂ and 16O _N alternately changes between receiving and non-receiving, according to the location of remote control 162 relatively to flying vehicle 168.

Remote control 162 is employed to control the horizontal direction of flight of flying vehicle 168. Command interface 166 is employed for receiving certain commands from a user, to be delivered as

control signals to flying vehicle 168. Command interface 166 may be, for example, in the form of command buttons, a touch-screen panel, a joystick, and the like. When a user of remote control 162 provides a command for a change in the direction of flight of flying vehicle 168, light responsive controller 116 directs power supply 154 to change the power provided to a selected one of propulsion devices 152^ 152 ₂ and 152 _N , during a certain period of time. Due to the different power provided to either one of propulsion devices 152- ₁ , 152 ₂ and 152 _N , flying vehicle 168 changes its direction of flight. Radiation emitter 172 of clearance beacon 170 emits radiation in a general upward direction. An obstacle 171 (e.g., a ceiling) located above flying vehicle 168 reflects this radiation, which is then detected by radiation detector 174 of clearance beacon 170. The radiation of clearance beacon 170 may be, for example, IR radiation, UV radiation, sound waves, and the like. Controller 156 determines the distance between clearance beacon 170 and the ceiling, according to the time elapsed between the emission and the detection of the radiation. When the distance between clearance beacon 170 and obstacle 171 is smaller than a predetermined value, controller 156 may direct power supply 154 to reduce the power provided to propulsion devices 152- ₁ , 152 ₂ and 152 _N , to reduce the thrust produced there from. When propulsion devices 152- ₁ , 152 ₂ and 152 _N are provided with reduced power, they rotate at a slower rate, reducing the lift in the airfoils, thereby stopping the ascending of flying vehicle 168, and preventing flying vehicle 168 from colliding with obstacle 171.

Reference is now made to Figures 4A, 4B, 4C, 4D and 5. Figure 4A is a schematic illustration of a top-view of a rotary flying vehicle, generally referenced 200, in a first rotation position, according to another embodiment of the disclosed technique. Figure 4B is a schematic illustration of the rotary flying vehicle of Figure 4A, in a second rotation

position. Figure 4C is a schematic illustration of the rotary flying vehicle of Figure 4A, in a third rotation position. Figure 4D is a schematic illustration of the rotary flying vehicle of Figure 4A, in a fourth rotation position. Figure 5 is a schematic illustration of a time scheme, for operating the propellers of the flying vehicle of Figures 4A, 4B, 4C and 4D.

Rotary flying vehicle 200 includes a hub 202, a first airfoil 204, a second airfoil 206, a first beam 208i, a second beam 208 ₂ , a first propeller 210i and a second propeller 21O ₂ . Flying vehicle 200 also includes a light detector 214, a power source and a light responsive controller (both not shown). Hub 202 is coupled with first airfoil 204, second airfoil 206, first beam 208i, second beam 208 ₂ , and with light detector 214.

First airfoil 204, second airfoil 206, first beam 208i and second beam 208 ₂ , are arranged substantially symmetrically relative to hub 202, extending outward there from. First airfoil 204 and second airfoil 206 are located opposite each other, each extending from an opposite side of hub 202. First beam 208i and second beam 208 ₂ are located opposite each other. Beams 208i and 208 ₂ can be located substantially perpendicular to airfoils 204 and 206, or offset from a right angle (e.g., the angle between first beam 108i and airfoil 104 may equal approximately 70°), each extending from an opposite side of hub 202. First beam 208i and second beam 208 ₂ are coupled with hub 202 at the first ends thereof. First propeller 210i is coupled with first beam 208i, at the second end thereof. Second propeller 21O ₂ is coupled with second beam 208 ₂ , at the second thereof. Propellers 21 Oi and 21O ₂ are further coupled with the power source and with the controller, for example, through wires running along beams 208i and 208 ₂ , respectively. The controller is further coupled with light detector 214. Rotary flying vehicle 200 is substantially similar to rotary flying vehicle 100 of Figures 1 , 2A, 2B and 2C.

A remote control 218 is located in the vicinity of flying vehicle 200. Remote control 218 includes a light source 220. Light source 220

constantly emits light 225 toward flying vehicle 200. Light detector 214 is configured to detect light 225 emitted from light source 220. When light detector 214 detects light from light source 220, light detector 214 is considered to be in a "receiving" state. When light detector 214 detects substantially no light from light source 220, it is considered to be in a "non-receiving" state. During the rotation of flying vehicle 200, the state of light detector 214 alternately changes between receiving and non-receiving, according to the location of remote control 218 relatively to flying vehicle 200. The controller determines the rotation position of flying vehicle 200 relative to remote control 218, according to the state of light detector 214 (i.e., receiving or non-receiving), as described herein above with reference to Figures 2A, 2B and 2C.

Remote control 218 is employed to control the direction of flight of flying vehicle 200, along a horizontal plane, substantially perpendicular to the axis of rotation of flying vehicle 200. Remote control 218 may include a user interface (not shown), for receiving certain commands from a user, to be delivered as control signals to flying vehicle 200. The user interface may be, for example, in the form of command buttons, a touchscreen panel, a joystick, and the like. A user of remote control 218 provides a command for flying vehicle 200 to move away from remote control 218, in a direction indicated by arrow 240.

When propeller 21O ₁ (or 21 O ₂ ) rotates, it produces a thrust force, proportional to the rate of rotation thereof, which is determined by the mean power delivered to propeller 21 Oi (or 21O ₂ ) by the power source. By changing the mean power provided to propeller 21 Oi (or 21 O ₂ ), one can control the produced thrust force. The thrust force is perpendicular to the plane of rotation of propeller 21 Oi (or 21O ₂ ), causing airfoils 204 and 206 to rotate about hub 202. When both propellers 21O ₁ and 21 O ₂ are provided with the same mean power by the power source, flying vehicle 200 remains in the same location along the horizontal plane. However, if

the mean power provided to propeller 21O ₁ is higher than the power provided to propeller 21O ₂ , then the force produced in propeller 21O ₁ would be greater than in propeller 21O ₂ . Flying vehicle 200 would then be forced to move in the direction of the greater thrust force, along the horizontal plane.

With reference to Figure 4A, when flying vehicle 200 is the first rotation position, the thrust force F _{1 , A} produced from propeller 21O ₁ is greater than the thrust force F _2,A produced from propeller 21O ₂ (i.e., F _{1 , A} > F _2,A ). AS depicted in Figure 5, during the first quarter of rotation of flying vehicle 200, i.e., between T _A and T _B , the mean power (P _H ) provided to propeller 21O ₁ is greater than the mean power (P _L ) provided to propeller

21O ₂ (i.e., P _L < P _H ). Thus, during the first quarter of rotation, flying vehicle

200 is forced to move in the direction indicated by arrow 240 (Figure 4A).

With reference to Figure 4B, when flying vehicle 200 is the second rotation position, the thrust force F _{1, B} produced from propeller 21O ₁ is substantially the same as the thrust force F _{2 B} produced from propeller 21O ₂ (i.e., F ₁₃ = F _2,B ). AS depicted in Figure 5, during the second quarter of rotation of flying vehicle 200, i.e., between T _B and T ₀ , the mean power (P _L ) provided to propeller 21O ₁ is substantially the same as the mean power (P _L ) provided to propeller 21O ₂ . It is noted, that the power provided to propellers 21O ₁ and 21O ₂ should be substantially the same during the second rotation position, regardless of the value of the power. Thus, during the second quarter of rotation, flying vehicle 200 is not forced to move in any direction, and remains substantially in the same spatial position.

With reference to Figure 4C, when flying vehicle 200 is the third rotation position, the thrust force F _{1 , c} produced from propeller 21O ₁ is smaller than the thrust force F _{2 C} produced from propeller 21 O ₂ (i.e., F _{1 ,} c ^< F _2, c). As depicted in Figure 5, during the third quarter of rotation of flying vehicle 200, i.e., between T ₀ and T _D , the mean power (P _L ) provided

to propeller 210i is smaller than the mean power (P _H ) provided to propeller 21O ₂ (i.e., P _L < P _H ). Thus, during the third quarter of rotation, flying vehicle 200 is forced to move in the direction indicated by arrow 240. With reference to Figure 4D, when flying vehicle 200 is the fourth rotation position, the thrust force F _{1, D} produced from propeller 21 Oi is equal to the thrust force F _2,D produced from propeller 21O ₂ (i.e., Fi _1D = F ₂ , _D ). AS depicted in Figure 5, during the fourth quarter of rotation of flying vehicle 200, i.e., between T _D and 7>, the mean power (P _L ) provided to propeller 21 Oi is substantially the same as the mean power (P _L ) provided to propeller 21O ₂ . Thus, during the fourth quarter of rotation, flying vehicle 200 is not forced to move in any direction, and remains in the same spatial position. After completing a full rotation, flying vehicle starts another rotation, such that 7> is in effect T _A of the following rotation. It is noted, that in the present description the mean power provided to propellers 210-i and 21O ₂ remains constant throughout every quarter of rotation of flying vehicle 200. However, the mean power may change during the quarter of rotation. For example, the mean power provided to propeller 210i during the first quarter of rotation may be greater only for a portion of the quarter of rotation, instead of the whole quarter. If flying vehicle 200 completes a full rotation every 20 msec, then the first quarter of rotation lasts 5 msec. In this case, the mean power provided to propeller 210-i during the first quarter may be greater than the power provided to propeller 21O ₂ for the first 2 msec of the first quarter of rotation.

It is further noted, that the mean power provided to the propellers of the flying vehicle may change by varying a defined duty cycle of constant voltage. Instead of changing the value of voltage provided to the propeller by the power source, during a predetermined rotation position, one may employ a Pulse Width Modulation (PWM) technique.

According to PWM, a constant voltage is provided to the propeller, but for a varying period of time during a single duty cycle of that propeller. For example, when the first propeller is to be provided with greater mean power, the period of time during the duty cycle of the first propeller, in which voltage is provided to that propeller, is prolonged. Similarly, when the second propeller is to be provided with smaller mean power, the period of time during the duty cycle of the second propeller, in which voltage is provided to that propeller, is shortened.

Reference is now made to Figure 6, which is a schematic illustration of a rotary flying vehicle, generally referenced 260, constructed and operative according to a further embodiment of the disclosed technique. Rotary flying vehicle 260 is similar to flying vehicle 100 of Figure 1. Rotary flying vehicle 260 includes a hub 262, a first airfoil 264, a second airfoil 266, a first beam 268^ a second beam 268 ₂ , a first propeller 270i and a second propeller 27O ₂ . Flying vehicle 260 also includes a power source (not shown), a light detector 274 and a light responsive controller (not shown). Hub 262 is coupled with first airfoil 264, second airfoil 266, first beam 268i, second beam 268 ₂ , and with light detector 274. First airfoil 264 includes a firm section 278 and a folding section 276. Second airfoil 266 includes a firm section 284 and a folding section 282.

First airfoil 264, second airfoil 266, first beam 268i and second beam 268 ₂ , are arranged substantially symmetrically relative to hub 262, extending outward there from. First beam 268i and second beam 268 ₂ are coupled with hub 262 at the first ends thereof. First propeller 270i is coupled with first beam 268i, at the second end thereof. Second propeller 27O ₂ is coupled with second beam 268 ₂ , at the second end thereof. Propellers 270i and 27O ₂ are further coupled with the power source and with the controller. The controller is further coupled with light detector 274. Firm section 278 of first airfoil 264 is firmly coupled with hub 262 at the one end thereof. Folding section 276 of first airfoil 264 is coupled with

firm section 278, at the other end thereof, through a folding hinge 280. Folding section 282 of second airfoil 266 is coupled with firm section 284, at the other end thereof, through a folding hinge 286.

The power source provides electrical power to propellers 270i and 27O ₂ , which rotate and produce thrust, causing flying vehicle 260 to rotate about hub 262. The rotation of propellers 270i and 27O ₂ is illustrated by wind curved lines 287. The rotation of flying vehicle 100 is illustrated by wind curved lines 285. When airfoils 264 and 266 rotate, they produce vertical lift, causing flying vehicle 260 to ascend. The amount of produced lift is proportional to the rate of rotation of airfoils 264 and 266 (i.e., to the angular frequency of flying vehicle 260). Each of first airfoil 264 and second airfoil 266 is movable between an outstretched position (depicted in dotted lines), and a folded position. When flying vehicle rotates at a sufficiently high angular frequency f _high , a sufficient outward centrifugal force (F ce _n t _r i _f uga _l ) operates on airfoils 264 and 266, maintaining them in the outstretched position. The centrifugal force is proportional to the square of the angular frequency of flying vehicle 260: F ce _n t _r i _f uga _l ~ ?■ In the outstretched position, folding sections 276 and 282 and folding hinges 280 and 286 are stretched out, as depicted in dotted lines.

When the angular frequency of flying vehicle 260 is relatively low, the centrifugal force is also relatively small, and may be insufficient for maintaining airfoils 264 and 266 in the outstretched position. If airfoils 264 and 266 were to stay in the outstretched position, flying vehicle would not have sufficient lift and may collapse to the ground. To prevent this from happening, airfoils 264 and 266 move to the folded position, in which folding hinges 280 and 286 are folded, such that folding sections 276 and 282 point substantially upward instead of outward. The folded position requires less lift in order for flying vehicle 260 to stay at a substantially horizontal rotational position. The folded position also provides more

stability to flying vehicle 260, so that it may continue rotating without collapsing, even at a relatively low angular frequency.

Reference is now made to Figure 7, which is a schematic illustration of a method for operating a rotary flying vehicle, operative according to another embodiment of the disclosed technique. For example, the method depicted in Figure 7 may be employed to operate the rotary flying vehicle of Figures 1 and 4.

In procedure 300, a rotation position of a flying vehicle is determined, during rotation of the flying vehicle about a substantially vertical axis thereof, according to a light detection state of a light detector coupled with the flying vehicle. With reference to Figures 1 , 2A, 2B and 2C, light responsive controller 116 determines the rotation position of flying vehicle 100 relative to remote control 1 18, according to the state of light detector 114 (i.e., receiving or non-receiving). Once controller 116 has determined the rotation time period T of flying vehicle 100, it may determine the rotation position of flying vehicle 100 at any given moment.

In procedure 302, at least a selected one of a plurality of propulsion devices coupled with the flying vehicle is directed to produce a thrust of a first value, when the flying vehicle is at a predetermined rotation position, in order to move the flying vehicle in a desired direction along a horizontal plane, substantially perpendicular to the substantially vertical axis. The value of thrust produced by each of the propulsion devices is proportional to the mean power provided thereto. By changing the mean power provided to each of the propulsion devices, one can control the produced thrust force there from. With reference to Figures 4A, in order for flying vehicle 200 to move in the direction indicated by arrow 240, the power provided to first propeller 21 Oi during the first rotation position is greater than the mean power provided to second propeller 21O ₂ . Thus, first propeller 21O ₁ produces a greater thrust force than second propeller 21O ₂ . With reference to Figures 4C, the power

provided to second propeller 21O ₂ during the third rotation position is greater than the mean power provided to first propeller 210-|. Second propeller 21O ₂ thus produces a greater thrust force than first propeller 21O ₁ . In procedure 304, each of the propulsion devices is directed to produce a thrust of substantially the same value, when the flying vehicle is at another predetermined rotation position. With reference to Figures 4B and 4D, when flying vehicle 200 is the second and fourth rotation positions, the thrust force produced from propeller 21 Oi is substantially the same as the thrust force produced from propeller 21 O ₂ (i.e., F ₁₃ = F ₂₃ , and Fi _1D = F _2iD ). It is noted, that after procedure 304 is performed, the method depicted in Figure 7 may return to procedure 302, in order to further control the direction of flight of the flying vehicle along the horizontal plane. Alternatively, the method depicted in Figure 7 may return to procedure 300, to first determine the rotation position of the flying vehicle once again, before performing procedure 302 again.

In procedure 306, the distance between the flying vehicle and an obstacle is determined. With reference to Figure 1 , an obstacle (e.g., a ceiling, not shown) located above flying vehicle 100 reflects the radiation of clearance beacon 122, which is then detected by the radiation detector thereof. Controller 116 determines the distance between clearance beacon 122 and the ceiling, according to the time elapsed between the emission and the detection of the radiation.

In procedure 308, each of the propulsion devices are directed to produce reduced thrust, when the distance between the flying vehicle and the obstacle is smaller than a predetermined value, for preventing the flying vehicle from crashing with the obstacle. With reference to Figure 1 , when the distance between clearance beacon 122 and the ceiling is smaller than a predetermined value, controller 116 may direct power source 112 to reduce the power provided to propellers 11O ₁ and 11 O ₂ .

When propellers 110i and 11O ₂ are provided with reduced power, they rotate at a slower rate, causing airfoils 104 and 106 to rotate at a slower rate, thereby reducing the amount of produced lift. Controller 116 thus stops the ascending of flying vehicle 100, and prevents flying vehicle 100 from crashing with the ceiling. Clearance beacon 122 renders flying vehicle 100 suitable for indoor use. It is noted that procedures 306 and 308 are optional and the method depicted in Figure 7 may proceed from procedure 300 only to procedure 302 and 304.

Reference is now made to Figure 8, which is a schematic illustration of a rotary flying vehicle, generally referenced 320, constructed and operative according to a further embodiment of the disclosed technique. Rotary flying vehicle 320 includes a hub 322, a first airfoil 326, a second airfoil 328, a first propeller 330 and a second propeller 332. Flying vehicle 320 also includes a light detector 324, a power source and a light responsive controller (both not shown). Hub 322 is coupled with first airfoil 326, second airfoil 328, and with light detector 324.

First airfoil 326 and second airfoil 328 are arranged substantially symmetrically relative to hub 322, extending outward there from. Each of first airfoil 326 and second airfoil 328 is coupled with hub 322 at a first end thereof. First propeller 330 is coupled with first airfoil 326 at the other end thereof. Second propeller 332 is coupled with second airfoil 328 at the other end thereof. Propellers 330 and 332 are further coupled with the power source and with the controller, for example, through wires running along airfoils 326 and 328, respectively. The controller is further coupled with light detector 324.

Rotary flying vehicle 320 operates substantially similar to rotary flying vehicle 100 of Figures 1 , 2A, 2B and 2C. The power source provides electrical power to propellers 330 and 332, which rotate and produce thrust, causing flying vehicle 320 to rotate about a substantially vertical axis 334, passing through the center of hub 322. The rotation of

propellers 330 and 332 is illustrated by wind curved lines 327. The rotation of flying vehicle 320 is illustrated by wind curved lines 325. When airfoils 326 and 328 rotate, they produce vertical lift, causing flying vehicle 320 to ascend. The amount of produced lift is proportional to the rate of rotation of airfoils 326 and 328.

A remote control 336 is located in the vicinity of flying vehicle 320. Remote control 336 includes a light source 338. Light source 338 constantly emits light toward flying vehicle 320. Light detector 324 is configured to detect light emitted from light source 338. When light detector 324 detects light from light source 338, light detector 324 is considered to be in a "receiving" state. When light detector 324 detects substantially no light from light source 338, it is considered to be in a "non-receiving" state. During the rotation of flying vehicle 320, the state of light detector 324 alternately changes between receiving and non-receiving, according to the location of remote control 336 relatively to flying vehicle 320. The controller determines the rotation position of flying vehicle 320 relative to remote control 336, according to the state of light detector 324 (i.e., receiving or non-receiving), as described herein above with reference to Figures 2A, 2B and 2C. Remote control 336 is employed to control the direction of flight of flying vehicle 320, along a horizontal plane, substantially perpendicular to axis of rotation 334 of flying vehicle 320, as described herein above with reference to Figures 4A, 4B, 4C and 4D.

According to yet another embodiment of the disclosed technique, the flying vehicle includes only one propeller and a contra weight, for balancing the weight of the propeller on the opposite beam of the vehicle. Reference is now made to Figure 9, which is a schematic illustration of a rotary flying vehicle, generally referenced 350, constructed and operative in accordance with another embodiment of the disclosed technique. Rotary flying vehicle 350 includes a hub 352, a first airfoil 354,

a second airfoil 356, a first beam 35S ₁ , a second beam 358 ₂ , a propeller 360 and a weight 383. Flying vehicle 350 also includes a power source 362, a light detector 364, a light responsive controller 366 and a clearance beacon 372. Hub 352 is coupled with first airfoil 354, second airfoil 356, first beam 358i, second beam 358 ₂ , and with light detector 364.

First airfoil 354, second airfoil 356, first beam 358i and second beam 358 ₂ , are arranged substantially symmetrically relative to hub 352, extending outward there from. First airfoil 354 and second airfoil 356 are located opposite each other, each extending from an opposite side of hub 352. First beam 35S ₁ and second beam 358 ₂ are located opposite each other. Beams 358i and 358 ₂ can be located substantially perpendicular to airfoils 354 and 356, or offset from a right angle (e.g., the angle between first beam 35S ₁ and airfoil 354 may equal approximately 70°), each extending from an opposite side of hub 352. First beam 358i and second beam 358 ₂ are coupled with hub 352 at the first ends thereof. Propeller 360 is coupled with first beam 358i, at the second end thereof. Contra weight 383 is coupled with second beam 358 ₂ , at the second thereof. Propeller 360 is further coupled with power source 362 and with controller 366, for example, through wires running along first beam 358i. Controller 366 is further coupled with light detector 364.

In the present embodiment, power source 362 and controller 366 are depicted in dotted lines, as being located within hub 352, for minimizing the aerodynamic affect thereof on the flight of flying vehicle 350. However, power source 362 and controller 366 may be located at other locations on flying vehicle 350. Clearance beacon 372 is externally coupled with hub 352, at the top section thereof, and coupled with controller 366. It is noted that clearance beacon 372 is optional, and may be omitted from rotary flying vehicle 350.

Power source 362 may be an electrical power source (e.g., battery), a fuel tank, a compressed air tank, and the like. Propeller 360

may be propelled by an electrical engine, a combustion engine, and the like. Alternatively, propeller 360 may be replaced with a rocket motor or jet motor propellers (not shown).

Power source 362 provides power to propeller 360, which rotates and produces thrust, causing flying vehicle 350 to rotate about a substantially vertical axis 371 , passing through the center of hub 352. When propeller 360 rotates, it generates a respective thrust force, perpendicular to the plane of rotation of the propeller. This aspect of the disclosed techniques was elaborated above with reference to figures 4A-4D. Wind curved lines 377 illustrate the rotation of propeller 360. Wind curved lines 375 illustrate the rotation of flying vehicle 350. Contra weight 383 balances the weight of propeller 360, as weight 383 and propeller 360 are coupled at opposite ends of beams 35S ₁ and 358 ₂ . In this manner, flying vehicle 350 is prevented from collapsing to one side, when propeller 360 rotates, causing airfoils 354 and 356 to rotate.

When airfoils 354 and 356 rotate, they produce vertical lift, causing flying vehicle 350 to ascend (i.e., move in the direction indicated by arrow 381 ). The produced lift is proportional to the rate of rotation of airfoils 354 and 356 (i.e., to the angular frequency of flying vehicle 350), for a given Angle of Attack (AOA) of airfoils 354 and 356. The AOA of an airfoil is the angle between the plane of the airfoil and the horizontal plane, in which flying vehicle 350 rotates. When an airfoil is inclined by a greater AOA, it generates more lift than an airfoil inclined by a smaller AOA. Airfoils 354 and 356 may be pivotally coupled with hub 352, allowing changing of the AOA of airfoils 354 and 356. In this manner, one can change the lift generated by airfoils 354 and 356, by changing their AOA of airfoils 354 and 356, instead of changing the rate of rotation thereof.

A remote control 368 is located in the vicinity of flying vehicle 350. Remote control 368 includes a light source 370, which constantly

emits light waves 373 toward flying vehicle 350. Light detector 364 is configured to detect light emitted from light source 370. When light detector 364 detects light from light source 370, light detector 364 is considered to be in a "receiving" state. When light detector 364 detects substantially no light from light source 370, it is considered to be in a "non-receiving" state. During the rotation of flying vehicle 350, the state of light detector 364 alternately changes between receiving and non-receiving, according to the rotation position of flying vehicle 350 relatively to remote control 368. Remote control 368 is employed to control the direction of flight of flying vehicle 350 in a horizontal plane (not shown), substantially perpendicular to vertical axis 371. Remote control 368 may further include a user interface (not shown), for receiving certain commands from a user of remote control 368, to be delivered as control signals to flying vehicle 350. The user interface may be, for example, in the form of command buttons, a touch-screen panel, a joystick, and the like. When a user of remote control 368 provides a command for a change in the direction of flight of flying vehicle 350, light responsive controller 366 directs power source 362 to change the power provided to propeller 360, during a certain rotation position of flying vehicle 350. Due to the different power provided to propeller 360, flying vehicle 350 changes its direction of flight in the horizontal plane. This aspect of the disclosed technique was elaborated above, with reference to Figures 4A, 4B, 4C and 4D. It is noted, that although in Figures 4A, 4B, 4C and 4D the flying vehicle includes two propellers, and according to the present embodiment the flying vehicle includes only one propeller and a contra weight, the control of the single propeller is similar to the control of the propeller of Figures 4A, 4B, 4C and 4D.

According to yet a further embodiment of the disclosed technique, the flying vehicle includes only one propeller and an

aerodynamic fin, on the opposite beam of the vehicle. Reference is now made to Figures 1 OA and 1OB. Figure 10A is a schematic illustration of a rotary flying vehicle, generally referenced 400, constructed and operative in accordance with a further embodiment of the disclosed technique, in which the aerodynamic fin is vertically moveable. Figure 10B is a schematic illustration of the rotary flying vehicle of Figure 10A, in which the aerodynamic fin is horizontally moveable. Rotary flying vehicle 400 is similar in operation to rotary flying vehicle 100 of Figure 1.

Rotary flying vehicle 400 includes a hub 402, a first airfoil 404, a second airfoil 406, a first beam 4Oe ₁ , a second beam 408 ₂ , a propeller 410 and an aerodynamic fin 433A. Flying vehicle 400 also includes a power source 412, a light detector 414, a light responsive controller 416 and a clearance beacon 422. Hub 402 is coupled with first airfoil 404, second airfoil 406, first beam 408i, second beam 408 ₂ , and with light detector 414.

First airfoil 404, second airfoil 406, first beam 408i and second beam 408 ₂ , are arranged substantially symmetrically relative to hub 402, extending outward there from. First airfoil 404 and second airfoil 406 are located opposite each other, each extending from an opposite side of hub 402. First beam 408i and second beam 408 ₂ are located opposite each other, each coupled with hub 402 at the first end thereof. Propeller 410 is coupled with first beam 408i, at the second end thereof. Aerodynamic fin 433A is pivotally coupled with second beam 408 ₂ , at the second thereof, such that aerodynamic fin 433A is vertically moveable in an up-down manner. Propeller 410 and aerodynamic fin 433A are further coupled with power source 412 and with controller 416, for example, through wires running along beams 408i and 408 ₂ . Controller 416 is further coupled with light detector 414. In Figure 10B, aerodynamic fin 433A is replaced by an aerodynamic fin 433B, which is horizontally moveable in a sideways manner. Therefore, in the present embodiment, each reference to

aerodynamic fin 433A may be replaced with aerodynamic fin 433B, respectively.

Power source 412 provides power to propeller 410, which rotates and produces thrust, causing flying vehicle 400 to rotate about a substantially vertical axis 421 , passing through the center of hub 402. When propeller 410 rotates, it generates a respective thrust force, perpendicular to the plane of rotation of the propeller. This aspect of the disclosed techniques was elaborated above with reference to figures 4A-4D. Wind curved lines 427 illustrate the rotation of propeller 410. Wind curved lines 425 illustrate the rotation of flying vehicle 400.

Aerodynamic fin 433A (or 433B) provides further balance to flying vehicle 400, by stabilizing it when it rotates. Furthermore, controller 416 may instruct aerodynamic fin 433A (or 433B) to move up and down (or sideways) according to the rotational position of flying vehicle 400. In other words, aerodynamic fins 433A and 433B may be used to replace the second propeller of Figure 1 , by employing the aerodynamic fin to enhance the rotation of the flying vehicle in certain rotational positions, as elaborated with reference to Figures 4A-4D.

When airfoils 404 and 406 rotate, they produce vertical lift, causing flying vehicle 400 to ascend (i.e., move in the direction indicated by arrow 431 ). The produced lift is proportional to the rate of rotation of airfoils 404 and 406 (i.e., to the angular frequency of flying vehicle 400), for a given Angle of Attack (AOA) of airfoils 404 and 406. The AOA of an airfoil is the angle between the plane of the airfoil and the horizontal plane, in which flying vehicle 400 rotates. When an airfoil is inclined by a greater AOA, it generates more lift than an airfoil inclined by a smaller AOA. Airfoils 404 and 406 may be pivotally coupled with hub 402, allowing changing of the AOA of airfoils 404 and 406. In this manner, one can change the lift generated by airfoils 404 and 406, by changing their

AOA of airfoils 404 and 406, instead of changing the rate of rotation thereof.

A remote control 418 is located in the vicinity of flying vehicle 400. Remote control 418 includes a light source 420, which constantly emits light waves 423 toward flying vehicle 400. Light detector 414 is configured to detect light emitted from light source 420. When light detector 414 detects light from light source 420, light detector 414 is considered to be in a "receiving" state. When light detector 414 detects substantially no light from light source 420, it is considered to be in a "non-receiving" state. During the rotation of flying vehicle 400, the state of light detector 414 alternately changes between receiving and non-receiving, according to the rotation position of flying vehicle 400 relatively to remote control 418.

Remote control 418 is employed to control the direction of flight of flying vehicle 400 in a horizontal plane (not shown), substantially perpendicular to vertical axis 421. Remote control 418 may further include a user interface (not shown), for receiving certain commands from a user of remote control 418, to be delivered as control signals to flying vehicle 400. The user interface may be, for example, in the form of command buttons, a touch-screen panel, a joystick, and the like. When a user of remote control 418 provides a command for a change in the direction of flight of flying vehicle 400, light responsive controller 416 directs power source 412 to change the power provided to propeller 410 (or change the position of aerodynamic fins 433A and 433B), during a certain rotation position of flying vehicle 400. Due to the different power provided to propeller 410, flying vehicle 400 changes its direction of flight in the horizontal plane. This aspect of the disclosed technique is elaborated above, with reference to Figures 4A, 4B, 4C and 4D. It is noted, that although in Figures 4A, 4B, 4C and 4D the flying vehicle includes two propellers, and according to the present embodiment the

flying vehicle includes only one propeller and an aerodynamic fin, the control of the flying vehicle is similar to the control of the flying vehicle of Figures 4A, 4B, 4C and 4D.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.