A heterogeneous multirotor configuration with a single main rotor and partially tilted multiple slave rotors.

Abstract

This invention discloses a heterogeneous multi-rotor layout with a single main rotor and partially tilted multiple slave rotors, relating to the field of unmanned aerial vehicle (UAV) design technology. It includes a large main rotor providing primary lift and n control rotors arranged around it, with some control rotors mounted horizontally and the rest tilted at a fixed angle. During steady-state flight, the anti-torsional torque of the main rotor is statically balanced by the horizontal component torque of the pull force from the tilted slave rotors. Attitude control of the UAV is achieved by differentially adjusting the rotational speeds of the control rotors, including pitch control, roll control, and yaw control. Pitch and roll control are achieved by differentially adjusting the rotational speeds of symmetrically positioned control rotors, while yaw control is achieved by differentially adjusting the rotational speeds between the horizontally mounted and tilted control rotor groups. This invention achieves a fusion of high aerodynamic efficiency and easy operation, effectively improving the UAV's endurance and flight performance.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) design technology, and in particular to a heterogeneous multi-rotor layout with a single main rotor and partially tilted multiple slave rotors. Background Technology

[0002] In recent years, multi-rotor drones have been widely used in numerous fields such as aerial photography, logistics transportation, geographic surveying, and unmanned inspection due to their advantages of simple structure, flexible operation, and low cost, demonstrating significant potential in both civilian and military applications. However, insufficient endurance has consistently constrained their further development. Extensive research on rotor aerodynamics has shown that increasing the rotor diameter and correspondingly reducing the disk load can effectively improve aerodynamic efficiency. Improved propeller efficiency is directly related to flight endurance. Therefore, maximizing the propeller diameter within finite size constraints is crucial for enhancing the endurance of multi-rotor drones.

[0003] Under the same takeoff weight and envelope size constraints, single-rotor helicopters, with their largest rotor diameter, achieve lower disk loads and ultimately exhibit optimal aerodynamic efficiency. However, this configuration typically requires cyclic pitch control of the main rotor for roll and pitch attitude control, and necessitates a tail rotor to balance the main rotor's anti-torque and perform yaw attitude control. This results in a complex overall mechanical structure, difficult maintenance, increased airframe size, reduced flight capability in confined spaces, and a more challenging control system design, leading to poorer handling performance.

[0004] Coaxial twin-rotor helicopters maintain low disk loads and high lift efficiency and handling quality while eliminating the tail rotor system. However, due to the wake interference between the upper and lower rotors, their aerodynamic efficiency is lower than that of single-rotor configurations. In addition, their mechanical structure is more complex and difficult to maintain, which limits their widespread application.

[0005] Conventional multi-rotor drones employ multiple small rotors, achieving attitude control through differential speed. They feature a relatively simple mechanical structure, making manufacturing and maintenance convenient. However, due to the inability to fully utilize envelope size limitations, they suffer from high rotor disk loads and require greater power to generate the same lift, resulting in the lowest aerodynamic efficiency among the three configurations. This also leads to generally insufficient endurance for multi-rotor drones, limiting their application scenarios.

[0006] Based on the above analysis, in order to balance the maneuverability of multi-rotor UAVs with the high aerodynamic efficiency of large-size single-rotor helicopters, an innovative aerodynamic layout scheme is urgently needed to fundamentally solve the contradiction between endurance and maneuverability. Summary of the Invention

[0007] The purpose of this invention is to provide a heterogeneous multi-rotor layout with a single main rotor and partially tilted multiple slave rotors. This layout provides core lift by setting a single large, high-efficiency main rotor in a limited space, and surrounds it with multiple small, fast-response control rotors to achieve full attitude control and anti-torsion balance, thereby achieving performance optimization at the system level.

[0008] To achieve the above objectives, the present invention provides a heterogeneous multirotor configuration with a single main rotor and partially tilted multiple slave rotors, comprising:

[0009] A main rotor located in the middle of the fuselage provides the main lift for the drone;

[0010] n control rotors are arranged around the main rotor, and the control rotors include... A horizontal plane from the rotor and One tilted from the rotor, in which , , The tilt is at a predetermined angle between the rotor's rotation axis and the vertical direction. The installation angle, with a preset tilt angle, is configured to balance the torque generated by the horizontal component of the rotor's thrust from the tilting rotor with the remaining anti-torque torque of the main rotor. for: ,in, The anti-torque of the main rotor, The horizontal torque from the rotor is the reverse torque. The anti-torque torque from the tilting rotor;

[0011] Flight control of the UAV is achieved by coordinating and adjusting the rotational speed of all rotors. Flight control includes altitude control and attitude control.

[0012] Preferably, the expression for the anti-torque of each rotor is as follows:

[0013] ;

[0014] In the formula, This represents the torque coefficient controlling the rotor. Indicates air density, This indicates the proportion of lift provided by the main rotor to the total lift. Indicates the mass of the aircraft. Represents gravitational acceleration. This indicates the thrust coefficient that controls the rotor. This indicates the diameter of the control rotor. This represents the main rotor torque coefficient. Indicates the main rotor thrust coefficient. This indicates the diameter of the main rotor.

[0015] Preferably, a preset tilt angle The expression is as follows:

[0016] ;

[0017] in, It indicates the distance from the rotor center to the aircraft's center of gravity.

[0018] Preferably, the main rotor is a rotor without a periodic pitch mechanism.

[0019] Preferably, the distance between the control rotor and the main rotor is ,in, The radius of the main rotor.

[0020] Preferably, altitude control is achieved by synchronously adjusting the rotational speeds of the main rotor and all control rotors.

[0021] Preferably, attitude control is achieved by differential adjustment of the rotor speed, and attitude control includes pitch attitude control, roll attitude control and yaw attitude control.

[0022] Preferably, pitch attitude control includes pitching up and pitching down. Pitching up is achieved by increasing the speed of the control rotor on the nose side and decreasing the speed of the control rotor on the tail side to generate a pitching torque. Conversely, pitching down is achieved by simultaneously decreasing the speed of the control rotor on the nose side and increasing the speed of the control rotor on the tail side.

[0023] Preferably, the roll attitude control includes left roll motion and right roll motion. By increasing the rotational speed of the right control rotor and decreasing the rotational speed of the left control rotor, a left roll torque is generated, thereby achieving the left roll motion of the UAV. Conversely, by simultaneously decreasing the rotational speed of the right control rotor and increasing the rotational speed of the left control rotor, a right roll torque is generated, thereby achieving the right roll motion of the UAV.

[0024] Preferably, yaw attitude control is achieved by differentially adjusting the rotational speed between the horizontal follower rotor and the tilt follower rotor. By increasing the rotational speed of the tilt follower rotor and decreasing the rotational speed of the horizontal follower rotor while keeping the main rotor rotational speed constant, the UAV can yaw in the same direction as the main rotor rotation. By decreasing the rotational speed of the tilt follower rotor and increasing the rotational speed of the horizontal follower rotor while keeping the main rotor rotational speed constant, the UAV can yaw in the opposite direction to the main rotor rotation.

[0025] Therefore, the present invention adopts the above-mentioned heterogeneous multi-rotor layout of a single main rotor and partially tilted multiple slave rotors, which has the following beneficial effects:

[0026] (1) The large-size main rotor maximizes aerodynamic efficiency within a limited envelope, controls the rotor load to be small, and the overall range is significantly improved compared with the same class of multi-rotor.

[0027] (2) Attitude control can be achieved by controlling the rotor differential speed, eliminating the need for complex mechanical structures such as the main rotor periodic pitch change, greatly reducing the difficulty of aircraft maintenance, improving flight reliability, and reducing aircraft weight.

[0028] (3) By tilting the rotor to balance the anti-torque of the main rotor, there is no need for a complex mechanical structure such as a helicopter tail rotor. The overall structure of the aircraft is compact, the mechanics are simple, and maintenance is easy.

[0029] (4) Multiple control rotors can independently achieve attitude control, avoiding the coupling of altitude and yaw control due to different response speeds of different rotors; in addition, under the constraint of the outer envelope size, this type of UAV can have stronger power and stronger load capacity.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a simplified structural diagram of a heterogeneous multi-rotor layout with a single main rotor and partially tilted multiple slave rotors according to the present invention.

[0032] Figure 2 This is a conceptual design diagram of a UAV with a heterogeneous multi-rotor layout consisting of a single main rotor and partially tilted multiple slave rotors, according to an embodiment of the present invention.

[0033] Reference numerals: 1. Main rotor; 2. Inclined follower rotor; 3. Horizontal follower rotor. Detailed Implementation

[0034] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] Example

[0036] To address the shortcomings of traditional multirotor UAVs in terms of limited endurance and the overly complex mechanical structure of helicopters, this paper proposes a heterogeneous multirotor configuration with a single main rotor and partially tilted multiple slave rotors. A conceptual design diagram of this configuration is shown below. Figure 2 As shown in the diagram, the UAV has 1+n rotors, where n is the number of control rotors. The single main rotor in the center provides the primary lift, while the n surrounding control rotors provide control torque through differential speed, while also generating some lift. Figure 1 As can be seen, this type of UAV layout can achieve the largest possible main rotor diameter within the size envelope constraint, thereby significantly reducing the rotor disk load. Therefore, this layout can greatly reduce the rotor disk load on each rotor, thus improving aerodynamic efficiency. The analysis of rotor aerodynamic efficiency is as follows:

[0037] The model for propeller thrust and torque can be simplified as follows:

[0038] ;

[0039] in and These represent the thrust and torque of a certain rotor, respectively. and These represent the thrust coefficient and torque coefficient of a certain rotor, respectively. Indicates the rotor speed. Indicates the diameter of the rotor. This represents air density. When the rotor generates a thrust of T, the required rotor speed is as follows:

[0040] ;

[0041] The torque of each rotor can be calculated as follows:

[0042] ;

[0043] Power required by the rotor for:

[0044] ;

[0045] Further, force efficiency can be obtained. :

[0046] ;

[0047] This demonstrates that, for the same propeller aerodynamic design, the greater the thrust, the lower the propeller efficiency; conversely, the larger the propeller diameter, the higher the propeller efficiency. Therefore, the UAV layout in this invention maximizes the overall aerodynamic efficiency of the UAV and achieves longer endurance by maximizing the main rotor diameter within the envelope size and ensuring the main rotor provides the majority of lift, while controlling the rotor to provide only a smaller proportion of lift, thus minimizing its disk load.

[0048] A heterogeneous multirotor configuration with a single main rotor and partially tilted multiple slave rotors includes:

[0049] A main rotor 1 located in the middle of the fuselage is used to provide the main lift of the UAV; the main rotor 1 is a rotor without a cyclic pitch mechanism.

[0050] n control rotors are arranged around the main rotor, responsible for attitude control of the multi-rotor UAV. n typically takes values ​​between 3 and 8. The distance between the control rotors and the main rotor is... ,in, The radius of the main rotor, and the control rotors include... A horizontal axis from rotor 3 and One tilted from rotor 2, where , , The tilt is at a predetermined angle between the rotation axis of rotor 2 and the vertical direction. The installation angle of the preset tilt angle is configured to balance the torque generated by the horizontal component of the tilting force from rotor 2 with the remaining anti-torsional torque of main rotor 1.

[0051] The expressions for the anti-torque of each rotor are as follows:

[0052] ;

[0053] In the formula, This represents the torque coefficient controlling the rotor. Indicates air density, This indicates the proportion of lift provided by the main rotor to the total lift. Indicates the mass of the aircraft. Represents gravitational acceleration. This indicates the thrust coefficient that controls the rotor. This indicates the diameter of the control rotor. This represents the main rotor torque coefficient. Indicates the main rotor thrust coefficient. Indicates the diameter of the main rotor;

[0054] Remaining anti-torque of the main rotor for:

[0055] ;

[0056] in, The anti-torque of the main rotor, The horizontal torque from the rotor is the reverse torque. The anti-torque torque from the tilting rotor;

[0057] Next, consider tilting the rotor installation angle to balance the remaining main rotor counter-torque:

[0058] ;

[0059] Where L is the tilt distance from the rotor center to the aircraft's center of gravity;

[0060] Preset tilt angle The expression is as follows:

[0061] .

[0062] The main rotor power system, mounted on top of the fuselage, is located at the center of gravity of the multi-rotor and will not generate roll or pitch torque on the n control rotors arranged around the main rotor. It includes a brushless motor and a large main rotor, with the brushless motor mounted on top of the fuselage to drive the main rotor to rotate. The n control rotors are located below the main rotor to minimize the influence of the main rotor on the control rotors. The n small brushless motors are mounted below the control rotors to provide rotational power to the control rotors. At the same time, the connection between the control rotor arms and the fuselage uses a folding mechanism, which folds them into the fuselage during transportation, effectively reducing the space occupied by the drone.

[0063] Flight control of the UAV is achieved by coordinating and adjusting the rotational speeds of all rotors. Flight control includes altitude control and attitude control. Altitude control is achieved by synchronously adjusting the rotational speeds of the main rotor 1 and all control rotors. Specifically, increasing the rotational speeds of all rotors simultaneously increases the thrust, enabling the UAV to ascend; similarly, decreasing the rotational speeds of all rotors simultaneously decreases the thrust, enabling the UAV to descend. When the desired altitude is reached, the rotational speeds of all rotors are controlled so that the thrust generated by the rotors is equal to the weight of the UAV. Attitude control is achieved by differentially adjusting the rotational speeds of the rotors. Attitude control includes pitch attitude control, roll attitude control, and yaw attitude control.

[0064] Pitch attitude control includes head-up and head-down movements. Specifically, by increasing the speed of the control rotor on the nose side and decreasing the speed of the control rotor on the tail side, a head-up torque is generated to achieve head-up movement of the UAV. Conversely, by simultaneously decreasing the speed of the control rotor on the nose side and increasing the speed of the control rotor on the tail side, the UAV achieves head-down movement. The distribution law of the speed change amplitude is the same as that of conventional n-rotor multi-rotor UAVs.

[0065] Roll attitude control includes left roll motion and right roll motion. Specifically, by increasing the rotational speed of the right control rotor while decreasing the rotational speed of the left control rotor, a left roll torque is generated, thus achieving left roll motion of the UAV. Conversely, by simultaneously decreasing the rotational speed of the right control rotor and increasing the rotational speed of the left control rotor, a right roll torque is generated, thus achieving right roll motion of the UAV.

[0066] Yaw attitude control is achieved by differentially adjusting the rotational speeds of the horizontal follower rotor 3 and the tilt follower rotor 2. Specifically: by increasing the rotational speed of the tilt follower rotor 2 and decreasing the rotational speed of the horizontal follower rotor 3, while keeping the rotational speed of the main rotor 1 constant, the UAV yaws in the same direction as the main rotor 1. By decreasing the rotational speed of the tilt follower rotor 2 and increasing the rotational speed of the horizontal follower rotor 3, while keeping the rotational speed of the main rotor 1 constant, the UAV yaws in the opposite direction to the rotational speed of the main rotor. Taking n=4 as an example, the control allocation logic for the yaw axis is as follows:

[0067] ;

[0068] in Indicates the main rotor speed. This indicates the rotational speed of the four control rotors. This represents the desired yaw control torque.

[0069] Therefore, this invention adopts a heterogeneous multi-rotor layout of a single main rotor and partially tilted multiple slave rotors. It uses a heterogeneous architecture of a large, high-efficiency main rotor and multiple small, fast control rotors. Static balance of main and counter-torque is achieved through the fixed geometry design of the tilted slave rotors. Attitude control of the UAV is achieved by differentially adjusting the rotational speed of the control rotors. Attitude control includes pitch control, roll control, and yaw control. Pitch control and roll control are achieved by differentially adjusting the rotational speed of the control rotors in symmetrical positions, while yaw control is achieved by differentially adjusting the rotational speed between the horizontal and tilted slave rotor groups. This scheme is synergistically optimized from three dimensions: aerodynamics, structure, and control. It achieves a balance of high endurance, ease of operation, and high reliability under limited size constraints.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors, characterized in that, include: A main rotor located in the middle of the fuselage provides the main lift for the drone; n control rotors are arranged around the main rotor, and the control rotors include... A horizontal plane from the rotor and One tilted from the rotor, in which , , The tilt is at a predetermined angle between the rotor's rotation axis and the vertical direction. The installation angle, with a preset tilt angle, is configured to balance the torque generated by the horizontal component of the rotor's thrust from the tilting rotor with the remaining anti-torque torque of the main rotor. for: ,in, The anti-torque of the main rotor, The horizontal torque from the rotor is the reverse torque. The anti-torque torque from the tilting rotor; Flight control of the UAV is achieved by coordinating and adjusting the rotational speed of all rotors. Flight control includes altitude control and attitude control. The expressions for the anti-torque of each rotor are as follows: ； In the formula, This represents the torque coefficient controlling the rotor. Indicates air density, This indicates the proportion of lift provided by the main rotor to the total lift. Indicates the mass of the aircraft. Represents gravitational acceleration. This indicates the thrust coefficient that controls the rotor. This indicates the diameter of the control rotor. This represents the main rotor torque coefficient. Indicates the main rotor thrust coefficient. Indicates the diameter of the main rotor; Preset tilt angle The expression is as follows: ； in, This indicates the distance from the rotor center to the aircraft's center of gravity. Attitude control is achieved by differentially adjusting the rotor speed. Attitude control includes pitch attitude control, roll attitude control and yaw attitude control. Yaw attitude control is achieved by differentially adjusting the rotational speeds of the horizontal follower rotor and the tilt follower rotor. By increasing the rotational speed of the tilt follower rotor and decreasing the rotational speed of the horizontal follower rotor while keeping the main rotor rotational speed constant, the UAV can yaw in the same direction as the main rotor rotation. By decreasing the rotational speed of the tilt follower rotor and increasing the rotational speed of the horizontal follower rotor while keeping the main rotor rotational speed constant, the UAV can yaw in the opposite direction to the main rotor rotation.

2. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors according to claim 1, characterized in that: The main rotor is a rotor with a non-cyclic pitch mechanism.

3. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors according to claim 1, characterized in that: The distance between the control rotor and the main rotor is ,in, The radius of the main rotor.

4. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors according to claim 1, characterized in that: Altitude control is achieved by synchronously adjusting the rotational speeds of the main rotor and all control rotors.

5. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors according to claim 1, characterized in that, Pitch attitude control includes head-up and head-down movements. By increasing the speed of the control rotor on the nose side and decreasing the speed of the control rotor on the tail side, a head-up torque is generated, enabling the UAV to tilt up. Conversely, by simultaneously decreasing the speed of the control rotor on the nose side and increasing the speed of the control rotor on the tail side, the UAV can tilt down.

6. A heterogeneous multirotor with a single main rotor and partially tilted multiple slave rotors according to claim 1, characterized in that: Roll attitude control includes left roll motion and right roll motion. By increasing the speed of the right control rotor and decreasing the speed of the left control rotor, a left roll torque is generated, thus achieving the left roll motion of the UAV. Conversely, by decreasing the speed of the right control rotor and increasing the speed of the left control rotor, a right roll torque is generated, thus achieving the right roll motion of the UAV.

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