Patent Application
20240217652
The disclosed invention relates to a VTOL (vertical take-off and landing) box-wing aerial vehicle, and more specifically to the configuration of the box-wing airframe with multiple rotors for VTOL flight and fixed push rotor for forward flight.
The helicopter is an essential modern air transportation vehicle. Technically, helicopter with rotary wing is also referred as “rotorcraft” or “rotary wing vehicle”. The rotary wing is commonly referred as “rotor”. Rotary wing positioned in the center of a shroud is called “ducted fan”. In general, rotary wing comprising of a plurality of blades rotating on the same axis. The rotary movement of the blades generates thrust by moving air. The rotary wing permits the helicopter to land and take-off vertically without the presence of a long run way. Disadvantageously, helicopter with fossil fuel engine is associated with expensive operational cost, undesirable high level of noise and carbon emission.
As the traffic is increasing heavy in the global urban area, an affordable electrical VTOL vehicle is a solution to avoid the congestion on the road. Without traffic delay, an electrical VTOL vehicle can also operate as law enforcement vehicle, ambulance and medical cargo transporter. A new term UAM (urban air mobility) is adopted for this new type of aerial transportation.
The arrival of distributed electrical propulsion system allows modern VTOL multirotor vehicle to substitute the traditional helicopter. The VTOL multirotor rotorcraft is advantageous for safety redundancy, in comparison to a single large rotor helicopter. The electrical propulsion system contains multiple independent smaller rotors to provide lift, propulsion and steering control. Quad-rotorcraft is a popular design for electrical multirotor vehicle, a simple design comprises of four moving rotors. The fixed pitch smaller rotor has low inertia, which allows the speed of the rotating blade to be decreased or increased rapidly. The modulation of the power setting on the rotors provides agile lift, propulsion and steering control. The disadvantage of the four rotors propulsion is that the rotor is smaller in diameter. Based on the momentum theory, small diameter rotor has low thrust lift efficient, due to the high disc loading.
Advantageously, modern electrical VTOL vehicle also has the capability to transition to airplane mode for forward flight. The energy required for VTOL flight is significantly higher than the energy required for a fix wing airplane flight to maintain forward flight. The VTOL vehicle can experience the following three types of flight mode: thrust borne, partial wing borne and wing borne. The vehicle is thrust borne in VTOL flight, which means the flight is made possible by vertical rotor thrust. Partial borne means the flight is made possible by the combination of vertical rotor thrust and wing lift. The vehicle is wing borne in airplane flight, which means the flight is made possible by lift generated by the wing. Furthermore, the forward propulsive movement in the airplane mode is generated by at least one push rotor. The main challenge of the transitional capability is the rapid hand over from thrust borne flight to wing borne flight. The desirable solution is to design the vehicle with partial wing borne flight capability between the transition of thrust borne flight to wing borne flight.
Traditional fixed wing aircraft suffers from significant loses of lift efficiency at the tip of the wings, due to the occurrence of vortex. As a result, winglet, sharklet and box-wing design is introduced to improve lift efficiency.
In one embodiment of the invention of a box-wing multirotor vehicle with both VTOL and airplane forward flight capability is provided, comprising a detachable cabin, a fuselage base having a longitudinal axis, fixed wings having a biplane arrangement, a pylon secured to the fixed wings at the tip, a pair of rudder, a pair of rotor boom, a pair of forward contra-rotating lift rotor, a pair of rear contra-rotating lift rotor, a main landing gear pad or wheel, a horizontal and vertical stabilizer, a push rotor, and a nose landing gear pad or wheel. Also in one embodiment the detachable cabin is separable from the box-wing multirotor vehicle for ground transportation.
In another embodiment of the invention of a box-wing multirotor vehicle with both VTOL and airplane forward flight capability is provided, comprising a detachable cabin, a fuselage base having a longitudinal axis, fixed wings having a biplane arrangement, a pylon secured to the fixed wings at the tip, a pair of rudder, a pair of rotor boom, pivotable rotor booms, a pair of forward lift rotor mounted on the rotor boom, a pair of forward lift rotor mounted on the pivotable rotor boom, a pair of rear lift rotor mounted on the rotor boom, a pair of rear lift rotor mounted on the pivotable rotor boom, a main landing gear pad or wheel, a horizontal and vertical stabilizer, a push rotor, and a nose landing gear pad or wheel.
Regarding the invention disclosure, the feature and advantage of the invention are particularly pointed and distinctly claimed in the claims. Detailed description and methods are given to provide further comprehension of the functionality of the invention. It should be observed that three mutual orthogonal directions X, Y, and Z are shown in some of the FIGURES. The first direction X is said to be “longitudinal”, and the forward side is referenced to be positive. Rotational movement around the longitudinal axis is said to be “roll”. The second direction Y is said to be “transverse”, and the port side is referenced to be positive. And the Y plane is referenced as centerline of the vehicle. Rotational movement around the transverse axis is said to be “pitch”. Finally, the third direction Z is said to be “vertical”, and the up side is referenced to be positive. Rotational movement around the vertical axis is said to be “yaw”. Furthermore, the direction of motion is shown in dash arrow and axis of rotation is shown in dot dash line.
Advantageously, VTOL (vertical take-off and landing) vehicle can operate without a long runway. However, VTOL flight requires significantly higher energy than the energy required for a fixed wing aircraft to maintain forward flight. Therefore, the usefulness of VTOL vehicle is limited to short range flight. Modern VTOL is commonly designed with electrical power plant. In order to reduce the weight of electrical energy storage, an efficient VTOL vehicle can convert to airplane configuration for long range forward fight. In the disclosure of the invention, the technical term rotary wing is referred as “rotor”, and a rotary wing dedicated to generate lift is referred as “lift rotor”.
As shown in
The operation of the box-wing multirotor vehicle 100 is described in the following sections. Advantageously, the box-wing multirotor vehicle 100 has four dedicated contra-rotating lift rotors to operate in VTOL flight (thrust borne flight). Naturally, the quad contra-rotating lift rotors provide the thrust vector during VTOL flight for taking-off, landing, hovering, and flying vertically. Moreover, the torque effect of the rotors assists the vehicle to change yaw heading. In order to transition from VTOL flight (thrust borne flight) to airplane flight (wing borne flight), the push rotor 111 propels the vehicle forward. Upon reaching a desired cruise speed, lift rotors 109, 110, 114 and 115 becomes unpowered. As a result, undisturbed air flow interacts with the wings 103 and 104 to generate airfoil lift. Finally, the flight is fully transition to airplane flight when the airborne lift force is fully provided by the wings 103 and 104. During airplane flight, the blade of the lift rotor 109, 110, 114 and 115 are stowed in parallel with the longitudinal axis to reduce aerodynamic drag. Furthermore, the rudder 106, elevator 117 and aileron 118 provide the flight control capability to steer the vehicle in the pitch, roll and yaw axis. Moreover, horizontal and vertical stabilizer 112 provides directional stability during airplane flight and might have hinged trim tabs to tune the heading, levelling, speed and attitude of the vehicle.
As shown in
The VTOL flight (thrust borne flight) of the box-wing multirotor vehicle 600 is described in the following sections. As shown in
The transitional flight from VTOL flight (thrust borne flight) to airplane flight (wing borne flight) of the box-wing multirotor vehicle 600 is described in the following section. Firstly, the push rotor 611 is powered to propel the vehicle forward. Secondly, at given forward speed, lift rotors 609 and 614 become unpowered, and stowed in parallel with the longitudinal axis of the fuselage to reduce aerodynamic drag. Consequently, undisturbed air flow interacts with the wing 603 and 604 to generate airfoil lift. As a result, the sum of airborne lift force is contributed by the wings 603, 604 and lift rotors 610, 615. The vehicle is known to be in partial wing borne flight. Consequently, wing lift force increases and lift rotor lift decreases, as the forward speed accelerates to the desired cruise speed. Finally, upon reaching the desired cruise speed, the flight is fully transition to airplane flight when all the airborne lift force is provided by the wings 603, 604. Moreover, lift rotors 610 and 615 become unpowered and the blade of the lift rotors 610 and 615 are stowed in parallel with the longitudinal axis to reduce aerodynamic drag. During cruise, the forward pivotable rotor boom 607a and rear pivotable rotor boom 607b retract to the stowed position as shown in
Naturally, there are numerous variations, modifications and configurations which may be made hereto without departing from the scope of the disclosure invention. It should be understood that the embodiments are for illustrative and explanatory purpose and it is not conceivable to identify exhaustively all possible embodiments. In particular, it is important to observe that the invention as described relates in particular to an aerial multirotor vehicle with specific positioning of lift rotors secured to the box-wing. The design of the box-wing benefits from an improvement of structural strength, fatigue strength and load carrying strength. The box-wing permits the lift rotors to be secured to the upper portion of the vehicle, which prevents the rotating blade from striking a person or object near the ground. Finally, the box-wing with a plurality of main wings design permits the wing span to be reduced in the transverse direction. Nevertheless, the invention is applicable to any multirotor vehicle of arbitrary weight, such as a light drone to a large tonnage vehicle.
