Aircraft with decoupled degrees of freedom

Abstract

An aircraft (1) comprises a main frame (3) and a plurality of operable multirotor aircraft units (2a-2d). Each multirotor aircraft unit has a plurality of propulsion units (5). The propulsion units (5) are attached to the corresponding multirotor aircraft units (2a-2d) at a fixed roll angle, a fixed pitch angle and a fixed yaw angle. The plurality of operable multirotor aircraft units (2a-2d) are attached to the main frame (3) by insertion of corresponding joints (4) and rotate independently of each other relative to the main frame (3). At least one of the joints (4) has at least one degree of freedom, so that the main frame (3) has at least the same or more number of controllable degrees of freedom compared to the total number of degrees of freedom of the main frame (3).

Description

Technical Field

[0001] The present invention relates to the field of manned and unmanned aerial vehicles, and more particularly to an aerial vehicle with decoupled degrees of freedom (DOF), the aerial vehicle being formed by a plurality of multirotor aircraft connected to a central body, wherein the performance of the plurality of multirotor aircraft provides an aerial vehicle with decoupled DOF. Background Art

[0002] An unmanned aerial vehicle (UAV) is an aircraft without a human pilot. A manned aircraft is an aircraft with a human pilot who manages at least some of the aircraft's functions. A drone may be a manned or unmanned aircraft and may be remotely controlled by a remote controller using, for example, radio signals, or may be an autonomous drone implementing an onboard computer system. An example of a drone is a multicopter.

[0003] As used herein, a multirotor aircraft may refer to any aircraft that flies using more than one propulsion unit (e.g., propellers, rotors, turboprop engines, jet engines, etc.), whether manned or unmanned and remotely or autonomously controlled. Examples of multirotor aircraft include, but are not limited to, biaxial aircraft (two propulsion units), triaxial aircraft (three propulsion units), quadcopter aircraft (four propulsion units), hexacopter aircraft (six propulsion units), octocopter aircraft (eight propulsion units), etc. The motion of a multirotor aircraft can be controlled by changing the relative thrust generated by each propulsion unit. Specifically, the motion around the three symmetric axes of the multirotor aircraft, called roll (rotation around the front-back axis), pitch (rotation around the lateral axis), and yaw (rotation around the vertical axis), can each be controlled by changing the relative thrust generated by each propulsion unit. For example, roll and pitch can be achieved by increasing the thrust of the propulsion unit on one side and reducing the thrust of the propulsion unit on the other side, while yaw can be achieved by increasing the thrust of the propulsion units positioned diagonally to each other. Horizontal movement can be achieved by tilting the multicopter toward the desired direction of travel, and vertical movement can be achieved by simultaneously increasing the thrust of each propulsion unit (ascent) or by simultaneously reducing the thrust of each propulsion unit (descent).

[0004] The use of multicopters has become increasingly popular over the past few years, and as the technology matures, new applications for multicopters have emerged. For example, using a multicopter to transport large items or people are some of the applications that are beginning to be considered.

[0005] However, applying existing multirotor architectures to new applications leads to new problems that have not yet been solved. One of these problems is that none of the existing multirotor aircraft with fixed propulsion units have the decoupled DOF of the multirotor aircraft (motion in the X, Y and Z planes, yaw, roll and pitch are not decoupled), and therefore these multirotor aircraft are unable to perform certain movements without significantly increasing the number of propulsion units included in the multirotor aircraft and thus significantly increasing the weight and complexity of the multirotor aircraft.

[0006] Aircraft with decoupled DOF provide at least two main advantages, in other words, aircraft with DOF independent of each other provide at least two main advantages. The first advantage is the improvement of the efficiency of the aircraft. By enabling the aircraft to move with decoupled DOF, unnecessary intermediate movements when moving the aircraft from a first point to a second point are avoided, and energy is thus saved. In addition, by being able to guide the aircraft in a direction with less energy loss to seek maximum aerodynamic efficiency, higher flight efficiency is obtained. The second advantage is the improvement of the precision of the movement of the aircraft as well as the control, maneuverability and stability. The improvement in the precision of the movement allows the aircraft with independent DOF to perform tasks that the existing multi-rotor aircraft with interdependent DOF cannot perform, such as precise handling of sensitive loads, precise landing, etc. It also allows to provide the aircraft with extended maneuverability, which may be crucial in missions where flight conditions change (gusty winds, variable or moving payloads) or where such extended maneuverability is necessary for certain maneuvers or complex and very demanding flight dynamics.

[0007] In order to provide an aircraft with independent DOF, some existing multirotor aircraft have rotors coupled to the body of the multirotor aircraft through servo actuators to allow the propulsion units to tilt relative to the body. However, using servo actuators to precisely control the tilt of the propulsion units increases the complexity of the architecture, increases the weight of the multirotor aircraft, increases manufacturing and maintenance costs, and reduces safety and reliability. Summary of the invention

[0008] In order to overcome the above disadvantages, the present invention discloses an aircraft with decoupled degrees of freedom and a method for manipulating the aircraft.

[0009] The aircraft may include a main frame and a plurality of operable multirotor aircraft units. Each of the plurality of operable multirotor aircraft units may have a plurality of propulsion units, which may be attached to the multirotor aircraft unit at a fixed yaw angle, a fixed roll angle, and a fixed pitch angle, in other words, the propulsion unit may be fixed to the multirotor aircraft body. The thrust applied by each of the propulsion units may be different from each other. Therefore, the plurality of propulsion units of the multirotor aircraft unit may be configured to apply thrust in the same direction but with different thrust magnitudes. Examples of propulsion units may include, but are not limited to, propellers, rotors, turboprop engines, jet engines, and the like. The plurality of operable multirotor aircraft units may be attached to the main frame by the insertion of corresponding joints and may rotate independently of each other relative to the main frame. At least one of these joints may have at least one DOF, so that the main frame, i.e., the aircraft, has the same or greater number of controllable degrees of freedom (CDOF) than the total number of DOF of the main frame. Preferably, the joints may have a number of DOF between one and three, although in some embodiments some of the joints may be fixed.

[0010] As used herein, CDOF may refer to the maximum number of directional control variables that may be simultaneously manipulated during flight of an aircraft.

[0011] In three-dimensional space, the maximum number of DOF of a solid rigid part is six. Although solid rigid parts can present configurations with a number of DOF less than six, solid rigid parts with a total of six decoupled DOF provide the highest possible control. Therefore, the number of directional control variables that can be manipulated simultaneously in the aircraft with decoupled DOF disclosed in this article can be equal to or greater than the six DOF of the main frame (and therefore equal to or greater than the six DOF of the aircraft as a whole). The six DOF of the main frame are longitudinal movement in the X, Y and Z directions and rotational movement of yaw, roll and pitch. Then, the main frame (and therefore the aircraft) will have the same or more number of CDOFs compared to the total number of DOFs of the rigid entity to be moved (the aircraft). In this way, each DOF of the aircraft can move independently.

[0012] Depending on the architecture of the aircraft (number of multirotor units, number of propulsion units in each multirotor unit, and number of DOFs of joints), the aircraft can have more or less CDOFs. When the number of CDOFs is equal to the total number of DOFs of solid rigid parts, the aircraft has a complete architecture, and when the number of CDOFs is greater than the total number of DOFs of rigid entities, the aircraft has a redundant architecture. In these redundant architectures, the redundant CDOFs, i.e., those additional CDOFs above the total number of DOFs of rigid entities, can be changed without changing any of the other CDOFs of the aircraft. Redundant CDOFs increase safety, provide fail-safe modes, provide operating modes that conventional drones cannot provide, etc.

[0013] The additional CDOF of the aircraft described herein (compared to conventional drones that have only 4 CDOF to produce a total of six DOF in their primary structure) allows to deploy different set points (different tilt angles and thrusts) for each of the multirotor units, thus developing dynamic operating modes that are not currently available in existing drones, such as a stable mode where the modules are placed at a certain tilt angle and the reaction forces against gusts give stability to the aircraft or a mode where the coordinated movement of all modules results in movement in the X or Y direction without changing any of the other DOFs. It also allows to have the necessary redundancy so that even if some propulsion units fail, the aircraft can maintain a minimum of six CDOF to produce six DOF in its primary structure.

[0014] For example, for an aircraft architecture with a center of gravity that is symmetrically arranged relative to the forces generated by the multirotor units, the basic modes of forward, backward, left and right movement can be generated by simply generating the same force in each of the multirotor units, because each multirotor unit will be positioned at the same tilt angle so that the same thrust is applied. The aircraft will move according to the thrust generated and the tilt angle at which the multirotor is operated.

[0015] In some examples, all multirotor units may be attached to the main frame via one joint with at least one DOF. However, in some other examples, some of the plurality of multirotor units may be fixed to the main frame, i.e., fixed to the main frame by inserting joints with no DOF relative to the main frame. In some other examples, the number of DOF of each of the plurality of joints in the aircraft may be different from each other.

[0016] In some examples, the joints can have up to three DOF. For example, the joints with three DOF can be ball joints. These ball joints that connect each multirotor unit to the main frame can allow up to 3 degrees of rotational freedom (rotation about the X axis, rotation about the Y axis, and rotation about the Z axis) and enable each of the modules to be precisely positioned relative to the main frame, allowing the aircraft to perform movements that existing drones cannot currently perform (e.g., movement along the X axis without modifying roll and pitch or other precise maneuvers).

[0017] In some examples, the main frame may have a plurality of arms extending radially from the main frame, and each operable multirotor unit may be attached to a corresponding arm of the plurality of arms. Thus, the joint may be located near the free end of the arm so that the multirotor unit is coupled to the frame via the respective free end of the arm.

[0018] In some examples, the joint may include a quick release system such that the plurality of operable multirotor units are releasably attached to the main frame. For example, the joint may have an upper portion that is attached to the multirotor units and a lower portion that is attached to the main frame such that the quick release system may allow the upper portion to be released from the lower portion of the joint. Releasably attaching the multirotor units to the main frame facilitates maintenance operations of the aircraft and allows for expandability of the aircraft, as currently operating multirotor units may be easily and quickly replaced with different multirotor units.

[0019] In some examples, the joint can include a locking mechanism configured to limit the movement of the joint in at least one DOF. These joints with limited DOF may be useful for specific applications where not all DOFs need to be decoupled or specific DOFs are not required.

[0020] In some examples, the joint may include a blocking mechanism configured to temporarily block the joint's motion in at least one DOF. These joints with temporarily blocked DOFs may be useful for cruise modes where it is desirable to ensure that the joint maintains its position without external interference.

[0021] In some examples, the joints may include shock absorbing mechanisms configured to absorb shock pulses generated by the movement of the multicopter units relative to the main frame. These joints with shock absorbing devices can improve stability and accuracy.

[0022] In some examples, the joint capable of moving the angular DOF independently of each other without changing its position in the X-axis, Y-axis, and Z-axis can be selected from the group consisting of a spherical joint, a universal joint, a ball and socket joint, a constant velocity joint, and any combination thereof. In addition, the joint can be a combination of joints with less than three DOF to provide a combined joint with up to three DOF. For example, the joint can be a combination of two or three continuous barrel joints to provide two or three degrees of freedom, respectively.

[0023] In some examples, the plurality of operable multirotor units are positioned equidistantly relative to a center point of the main frame. In this manner, the stability of the aircraft is maximized. In some other examples, and depending on the purpose and specific architecture of the aircraft, the multirotor units may be attached to the main frame in a different distribution.

[0024] In some examples, the aircraft may include a reference processing unit located on the mainframe. The reference processing unit may also be configured to determine the displacement of the mainframe relative to a horizontal plane. Preferably, the reference processing unit may be communicatively coupled to an inertial measurement unit and a plurality of accelerometers and / or gyroscopes located on the mainframe. Reference of the mainframe allows precise control of the flight of the aircraft, as tilting relative to the horizontal plane may enable directional thrust of the aircraft and also allow the flight to be adapted to environmental conditions.

[0025] In some examples, the aircraft may include a controller located in the main frame and configured to operate the plurality of multirotor aircraft units. The controller may be communicatively coupled to a reference processing unit to receive information about the orientation and current direction of travel of the main frame. In this way, a controller having information about the current orientation, current direction of travel, and expected direction of travel of the aircraft is able to operate the multirotor aircraft units to change the direction of travel of the aircraft toward the expected direction of travel. To this end, the controller operates the multirotor aircraft units by changing the thrust of the propulsion units of each multirotor aircraft unit, thereby modifying the orientation of the multirotor aircraft units relative to the main frame via the joints, and thus modifying the direction of travel of the aircraft.

[0026] Preferably, the controller may include an airflow measurement unit for determining airflow information data on the aircraft. The controller may use the airflow information data to determine an operation to be performed on the multirotor aircraft unit.

[0027] In some other examples, the aircraft may include a primary controller located in the main frame and a plurality of secondary controllers, each of which is located in a corresponding multi-rotor aircraft unit. The plurality of secondary controllers may be configured to operate the corresponding multi-rotor aircraft unit, and the primary controller may be configured to manage the plurality of secondary controllers. The primary controller may be communicatively coupled to a reference processing unit to receive information about the orientation of the main frame. The secondary controller may be communicatively coupled to the primary controller. In this way, the primary controller having information about the current orientation, current direction of travel, and expected direction of travel of the aircraft is able to determine the direction to be taken by the aircraft. The primary controller may transmit the direction to be taken by the aircraft to the secondary controllers, so that each secondary controller may operate the corresponding multi-rotor aircraft unit to guide the aircraft in the direction to be taken. For example, each secondary controller may change the thrust of the propulsion unit of the corresponding multi-rotor aircraft unit, thereby modifying the orientation of the multi-rotor aircraft unit relative to the main frame via the corresponding joint and thus modifying the direction of travel of the aircraft.

[0028] In some examples, a method for manipulating an aircraft as previously disclosed is described. The method may include determining, by a reference processing unit, a displacement of the aircraft relative to a horizontal plane. The controller may then determine a set point or thrust vector, i.e., thrust magnitude and tilt angle (yaw, roll, and pitch) of the aircraft based on the determined displacement. The controller may adjust the thrust of each multi-rotor aircraft unit based on the determined thrust. The controller may also adjust the tilt angles, i.e., yaw, roll, and pitch, of the plurality of multi-rotor aircraft units by performing a rotational movement of each multi-rotor aircraft unit relative to the main frame via a corresponding joint, the relative rotational movement being based on the tilt angle determined for the aircraft. The sum of the thrust vectors in the plurality of multi-rotor aircraft units will be equal to the calculated thrust vector of the aircraft to perform a particular maneuver. This example provides centralized management of the aircraft.

[0029] In some examples, an aircraft may have a primary controller attached to a main frame and secondary controllers attached to each multi-rotor aircraft unit. The plurality of secondary controllers may be used to operate the respective multi-rotor aircraft units, and the primary controller may be used to manage the plurality of secondary controllers. After determining the displacement of the aircraft, the primary controller may determine the thrust and tilt angle of the aircraft based on the determined displacement. Each of the secondary controllers, upon receiving the thrust and tilt angle of the aircraft from the primary controller, may determine and adjust the specific thrust of the multi-rotor aircraft unit on which the secondary controller is mounted based on the thrust previously determined for the aircraft. Each secondary controller may also determine and adjust the tilt angle of the respective multi-rotor aircraft unit by performing a rotational movement of the multi-rotor aircraft unit relative to the main frame via a joint, the relative rotational movement being based on the tilt angle previously determined for the aircraft. The sum of the thrust vectors of the plurality of multi-rotor aircraft units will be equal to the calculated thrust vector of the aircraft to perform a particular maneuver. This example provides decentralized management of the aircraft.

[0030] In some examples, the aircraft may have multiple controllers configured to operate any of the multiple multirotor aircraft units. Then, one of the controllers may determine and define the set point of the aircraft, i.e., the thrust and the tilt angle, based on the previously determined displacement. Afterwards, any of the multiple controllers - the same controller that has determined the set point of the aircraft or any other controller within the aircraft - may determine and adjust the thrust of the multiple multirotor aircraft units based on the thrust of the aircraft. One of the multiple controllers may also determine and adjust the tilt angle of the multiple multirotor aircraft units by performing a rotational movement of the multirotor aircraft unit relative to the main frame via a joint, the relative rotational movement being based on the determined tilt angle. The sum of the thrust vectors of the multiple multirotor aircraft units will be equal to the thrust vector of the aircraft. This example provides distributed management of the aircraft, wherein any of the multiple controllers may control the aircraft in the event of a failure of the controller currently responsible for managing the aircraft. This control redundancy increases the safety and reliability of the aircraft.

[0031] In the following description, for the purpose of explanation, many specific details are set forth to provide a thorough understanding of the present system and method. However, it is apparent to those skilled in the art that the present device, system and method can be practiced without these specific details. Reference to "example" or similar language in the specification means that a particular feature, structure or characteristic described in conjunction with the example is included as described, but may not be included in other examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to complete the description and to provide a better understanding of the present invention, a set of drawings is provided. The drawings form an integral part of the specification and illustrate embodiments of the present invention, which should not be interpreted as limiting the scope of the present invention, but only as examples of how the present invention can be implemented. The drawings include the following figures:

[0033] Figure 1 An example aircraft with decoupled DOF is shown, where four quadcopters are attached to a main frame by insertion of corresponding joints.

[0034] FIG. 2A to FIG. 2C They are shown respectively Figure 1 Front, side, and top views of an example aircraft in which four quadcopters are positioned and operated to cause the aircraft to hover.

[0035] FIG. 3A to FIG. 3C They are shown respectively Figure 1 Front, side, and top views of an example aircraft in which four quadcopters are positioned and operated to cruise the aircraft.

[0036] FIG. 4A to FIG. 4C They are shown respectively Figure 1 Front, side and top views of an example aircraft of FIG. 1 , wherein four quadcopters are positioned and operated to hover the aircraft with downwash directed toward the outside of the aircraft in a stabilized mode.

[0037] FIG. 5A to FIG. 5C They are shown respectively Figure 1 Front, side and top views of an example aircraft in which four quadcopters are positioned and operated to move the aircraft to its right side and with different thrusts in their rotors.

[0038] Fig. 6A Shows Figure 1 Detailed view of one of the quadcopters in the quadcopter, where the quadcopter is pulling the arm of the aircraft (stabilizing balance). Figure 6B Shows Figure 1 Detailed view of one of the quadcopters in the diagram, wherein the quadcopter is pushing the arms of the aircraft (unstable balance).

[0039] Figure 7 Schematic diagrams of different example aircraft architectures with decoupled DOF are shown.

[0040] Figure 8 An example ball joint assembly is shown for attaching a particular quadcopter to an arm of a mainframe of an example aircraft with decoupled DOF.

[0041] Fig. 9 Shown for management Figure 1 An example control system for an aircraft.

[0042] Fig.10 A flow chart of an example method for maneuvering an aircraft with decoupled DOF is shown. DETAILED DESCRIPTION

[0043] Reference Figure 1 , illustrates an example aircraft 1 with decoupled DOF, which has four quadcopters 2a to 2d, which are attached to an elongated main frame 3 by the insertion of a joint 4 with three DOF, such as a ball joint. It should be understood that the example aircraft 1 may include additional components and some of the components described herein may be removed and / or modified without departing from the scope of the example aircraft 1. In addition, the implementation of the example aircraft 1 is not limited to the following. Figure 1 This example is shown.

[0044] The quadcopter 2a to 2d is attached to the main frame 3 by the insertion of joints 4, thereby providing six decoupled DOFs for the main frame 3. Specifically, the main frame 3 has six DOFs and each of the ball joints 4 provides three additional CDOFs, so that the main frame 3 is provided with sixteen CDOFs. Each of the quadcopter 2a to 2d has four fixed propulsion units 5, such as rotor blades, which are attached to corresponding rotor frames 6 in the body 7 of the quadcopter 2a to 2d.

[0045] These operable rotor blades 5 provide aircraft functions for the aircraft 1. Specifically, the rotor blades 5 will provide lift during vertical maneuvers of the aircraft 1 and directional thrust for horizontal displacement. In some examples, the aircraft 1 may include a pair of rotor blades 5 located within a rotor frame 6, the pair of rotor blades 5 being provided as an upper rotor blade and a lower rotor blade for precise thrust control.

[0046] Each quadcopter 2a to 2d includes, in addition to the rotor blades 5, a motor (not shown), such as a brushless motor, associated with the rotor blades 5, and a speed processing unit (not shown) that forwards a signal determining how fast to rotate to the motor in the quadcopter 2a to d. Alternatively, the quadcopter 2a to 2d may include a torque processing unit in place of the speed processing unit to forward a signal determining how fast to rotate to the motor. At any given moment, each of the motors in a particular quadcopter 2, and therefore the corresponding rotor blades 5, may rotate at a different speed to provide a different thrust. Alternatively, the main frame 3 may include a central speed processing unit that communicates with each of the motors of the quadcopter 2a to 2d. This arrangement provides excellent thrust output, thereby achieving the maximum possible lift capability of the aircraft 1. Although in Figure 1 In the drawings, the quadcopters 2a to 2d comprise rotor blades 5 for providing the aircraft functionality, but alternative propulsion units are envisaged, for example using propellers, turboprop engines or adjustable jet engines.

[0047] The aircraft 1 further comprises at least one controller (not shown) to operate the quadcopters 2 based on the intended direction of travel. The at least one controller operates the rotor blades 5 via the speed processing unit by changing the relative speed of the rotor blades 5, so that the position of each of the quadcopters 2 relative to the main frame 3 can be independently changed, and thus the thrust vector generated by each quadcopter can be changed. Therefore, the at least one controller is configured to determine the relative position of each of the quadcopters 2 independently of the relative position of the remaining quadcopters 2 and the main frame 3 in the aircraft 1. In this way, the at least one controller can determine different set points (thrust and bank angle, roll, pitch and yaw) for each of the quadcopters 2, thereby providing the aircraft 1 with additional operating modes in addition to the basic operating modes (these basic operating modes are those movements performed by the aircraft, which have common set points for all its multi-rotor units). Examples of these additional operating modes are: stability mode, in which the multicopter has opposite rotor angles so that the forces generated by the multicopter cancel each other out, thereby improving the stability of the aircraft; precision mode, which results from the improved maneuverability of the aircraft with decoupled DOF; or efficient cruise mode, in which the multicopter units can be positioned in their cruise position but at the same time keeping the cabin in a position that minimizes aerodynamic drag.

[0048] The aircraft also has a fuselage body 8 attached to the main frame 3. In this example, the fuselage body 8 is a cabin for transporting users or passengers, so the cabin 8 includes seats 9 for users. The main frame 3 has four arms 10, which are located in pairs at the two ends of the main frame 3. Each of these arms 10 has a corresponding ball joint 4 near its free end to attach the corresponding quadcopter 2 to the main frame 3. In some examples and according to the geometry of the main frame 3, the arms 10 can extend from the center of the aircraft 1 to a radial point of the main frame 3.

[0049] The main frame 3 and the fuselage body 8 may be releasably attached or may be formed integrally with each other. The fuselage body 8 may also include structures to carry other elements such as batteries, different types of payloads, and the like.

[0050] although Figure 1 An aircraft 1 formed of four quadcopters 2 is shown, but it is apparent that any other suitable aircraft architecture - including any number of multicopter units arranged to a main frame and any number of propulsion units arranged to each multicopter unit - may be used to provide multicopter functionality to the aircraft 1. Figure 1 Four quadcopters 2 are shown coupled to a main frame 3 via ball joints 4, but other types of joints with between one and three DOF may be used. Furthermore, the joints may be different from one another, with different numbers of DOF between the joints. In some implementations, some of the joints may be fixed joints.

[0051] FIG. 2A to FIG. 2C They are shown respectively Figure 1 Front, side, and top views of an example aircraft in which four quadcopters are positioned and operated to cause the aircraft to hover.

[0052] In this example, four quadcopters 2a to 2d are positioned relative to the main frame 3 and operated to allow the aircraft 1 to hover, that is, to stay in the same position while flying in the air. In this example, quadcopters 2a and 2b are positioned in a first common plane, while quadcopters 2c and 2d are positioned in a second common plane different from the first plane. Figure 2BAs shown in more detail, the two planes are substantially horizontal planes parallel to each other, and the distance between the two planes is such that the cabin 8 and therefore the seats 9 are positioned in a substantially vertical position for the passengers. The quadcopters 2a and 2b generate a first thrust vector (thrust magnitude and tilt angle, i.e., yaw, roll and pitch), and the quadcopters 2c and 2d generate a second thrust vector, the first thrust magnitude being different from the second thrust magnitude, and the sum of the thrust vectors generated by the four quadcopters 2a to 2d is the thrust vector required to keep the aircraft 1 balanced and the passengers in the same position. In this example, the center of gravity is placed at the center of the aircraft 1, and therefore the thrust is completely vertical. This position of the quadcopters 2a to 2d relative to each other can also be used for ascent operations when the rotor thrust of all rotors 5 of the aircraft 1 increases by the same magnitude, and can be used for descent operations when the rotor thrust of all rotors 5 of the aircraft 1 decreases by the same magnitude.

[0053] FIG. 3A to FIG. 3C They are shown respectively Figure 1 Front, side, and top views of an example aircraft in which four quadcopters are positioned and operated to cruise the aircraft.

[0054] In this example, four quadcopters 2a to 2d are positioned relative to the main frame 3 and operated so that the aircraft 1 cruises, that is, moves in a specific direction (see Figure 3B The controller operates all the quadcopters 2a to 2d to rotate relative to their corresponding ball joints 4 so that the thrust vectors (thrust magnitude and tilt angle) of the quadcopters 2a to 2d relative to the main frame 3 are the same. Ultimately, the thrust generated by the rotor 5 can be changed according to the required cruising speed. In some other examples, the quadcopters 2a to 2d can be rotated at different tilt angles relative to the main frame 3 via their corresponding ball joints so that the direction of travel can be different, for example, the quadcopters 2a to 2d can be rotated to the left at the same angle and the same thrust relative to the main frame 3 to guide the aircraft 1 in that direction.

[0055] FIG. 4A to FIG. 4C They are shown respectively Figure 1 1 shows a front view, a side view and a top view of an example aircraft, wherein four quadcopters 2a to 2d are positioned and operated to hover the aircraft 1 and wherein the downwash is directed toward the outside of the aircraft 1 in a stabilized mode.

[0056] In this example, the quadcopters 2a to 2d are all tilted at the same angle toward the center of the main frame 3. Therefore, each quadcopter 2a to 2d is positioned in a different plane, but tilted at the same angle relative to the horizontal plane. The controller operates all quadcopters 2a to 2d to rotate relative to their corresponding ball joints 4 so that the thrust magnitudes of the quadcopters 2a to 2d are the same and the tilt angles relative to the horizontal plane are the same, but wherein the quadcopters 2a and 2b are oriented opposite to each other from the quadcopters 2c and 2d. In some other examples, the controller may operate the quadcopters 2a to 2d to be rotated relative to their corresponding ball joints to form an angle complementary to the angle shown in FIG. 4, so that the quadcopters 2a to 2d are all tilted away from the center of the main frame 3. In some other examples, the four quadcopters 2a to 2d may also be positioned and operated to hover the aircraft 1, but wherein the downwash is directed toward the interior of the aircraft 1.

[0057] FIG. 5A to FIG. 5C They are shown respectively Figure 1 Front, side and top views of an example aircraft in which four quadcopters are positioned and operated to move the aircraft toward its right side and in which the thrust in the rotors of the four quadcopters is different.

[0058] In this example, quadcopters 2a and 2c have a first thrust vector inclined at a first angle relative to the horizontal plane, and quadcopters 2b and 2d have a second thrust vector inclined at a second angle relative to the horizontal plane, the first angle being smaller than the second angle. Thus, all quadcopters 2a to 2d are positioned in different planes, but are all facing the same direction, in particular, towards the right (see Figure 5A The controller tilts the quadcopters 2a to 2d relative to their respective ball joints 4 at the aforementioned tilt angles relative to the horizontal plane. The thrust of the quadcopters 2a and 2c is the same and different from the thrust of the quadcopters 2b and 2d.

[0059] Fig. 6A Shows Figure 1 Detailed view of one of the quadcopters of FIG. 1 , wherein the quadcopter pulls the arm of the aircraft (stabilizing balance). In this example, the quadcopter 2a is positioned in the upper plane of the arm 10 relative to the main frame 3, so that the arm 10 is pulled via the ball joint 4. Therefore, the thrust generated by the quadcopter 2a (upward arrow) pulls the aircraft vertically and upward, while gravity (downward arrow) pushes the aircraft 1 downward. Figure 6B Shows Figure 1Detailed view of one of the quadcopters of FIG. 1 , wherein the quadcopter pushes the arm of the aircraft (unstable balance). In this example, the quadcopter 2a is positioned in the lower plane of the arm 10 relative to the main frame 3, so that the arm 10 is pushed via the ball joint 4. Therefore, the thrust generated by the quadcopter 2a (upward arrow) pushes the aircraft 1 vertically and upward, while the gravity (downward arrow) pushes the aircraft 1 downward.

[0060] although Fig. 6A and Figure 6B A quadcopter 2a is shown connected to a main frame 3 by the insertion of a ball joint 4, but any joint with a maximum of three DOF relative to a given point of rotation (e.g., a spherical joint) and a minimum of one DOF relative to a given point of rotation (e.g., a hinge joint) may be used, wherein the joint is in its pulling configuration or pushing configuration, i.e., wherein the joint pulls the quadcopter or wherein the joint is pushed by the quadcopter. The pulling configuration is the more stable configuration because the balance of forces (thrust and weight) is in a stable equilibrium, while the pushing configuration is the least stable because the balance of forces is in an unstable equilibrium.

[0061] Figure 7 Schematic diagrams of different example aircraft architectures are shown. Five different architectures are shown in the schematic diagram. It should be understood that the example aircraft architecture may include additional components and some of the components described herein may be removed and / or modified without departing from the scope of the example aircraft architecture. In addition, the implementation of the example aircraft architecture is not limited to the following. Figure 7 The example shown.

[0062] Many combinations of the number of multirotor aircraft and the number of propulsion units (e.g., motors, turboprop engines, jet engines, etc.) arranged on each multirotor aircraft unit will be possible. Therefore, different aircraft architectures can be combined according to the following formula, which gives the total number of propulsion units in a multirotor unmanned aerial vehicle:

[0063] Np=N×A

[0064] Where "Np" is the number of propulsion units, "N" is the number of multirotor units attached to the main frame of the aircraft (at least two multirotor units), and "A" is the number of propulsion units each multirotor has (at least two propulsion units). For example, when N=4 and A7=4, the aircraft is a quadcopter (main frame has four multirotor units) formed by quadcopters (each multirotor unit has four propulsion units attached to it), and when N=3 and A=4, the aircraft is a tricopter (main frame has three multirotor units) formed by quadcopters (each multirotor unit has four propulsion units attached to it).

[0065] The first architecture a) corresponds to a biaxial aircraft (N=2 and A=2) formed by biaxial aircraft. Thus, the aircraft 11 is formed by two biaxial aircraft 12 attached to a main frame 13 by the insertion of a ball joint. In this architecture, the main frame 13 may be an elongated body, with two biaxial aircraft 12 attached near the respective ends of the main frame 13. Each biaxial aircraft 12 has a tree-like propulsion unit 14 attached to its respective body 15.

[0066] The second architecture b) corresponds to a biaxial aircraft (N=2 and A=3) formed by tricopters. Thus, the aircraft 16 is formed by two tricopters 17 attached to a main frame 18 by the insertion of a ball joint. In this architecture, the main frame 18 may be an elongated body, with the two tricopters 17 attached near the respective ends of the main frame 18. Each tricopter 17 has a tree-like propulsion unit 19 attached to its respective body 20.

[0067] The third architecture c) corresponds to a tricopter formed of tricopters (N=3 and A=3). Thus, the vehicle 21 is formed by three tricopters 22 attached to a main frame 23 by the insertion of ball joints. In this architecture, the main frame 23 may be a substantially triangular body, with three tricopters 22 attached near the corners of the main frame 23. Each tricopter 22 has a tree-like propulsion unit 24 attached to its respective body 25.

[0068] The fourth architecture d) corresponds to a quadcopter formed by quadcopters (N=4 and A=4). Thus, the vehicle 26 is formed by four quadcopters 27 attached to a main frame 28 by the insertion of ball joints. In this architecture, the main frame 28 may be a substantially quadrangular body, with four quadcopters 27 attached near the corners of the main frame 28. Each quadcopter 27 has four propulsion units 24 attached to its respective body 30.

[0069] The fifth architecture e) corresponds to a quadcopter formed by tricopters (N=4 and A=3). Thus, the vehicle 31 is formed by four tricopters 32 attached to a main frame 33 by the insertion of ball joints. In this architecture, the main frame 33 may be a substantially quadrangular body, with four tricopters 32 attached near respective corners of the main frame 33. Each tricopter 32 has a tree-like propulsion unit 34 attached to its respective body 35.

[0070] In this example, all architectures may include ball joints or spherical joints with three DOF to provide redundant CDOF for the aircraft. Other architectures and geometries of the aircraft are contemplated. However, the architectures described in this example are merely indicative example multi-axis unmanned aerial vehicle architectures, and other alternative architectures and geometries may be considered.

[0071] Figure 8 An example ball joint assembly 40 is shown for attaching a particular quadcopter 48 to an arm 46 of a mainframe of an example aircraft with decoupled DOF. As used herein, a ball joint may refer to any joint that allows free rotation in two planes simultaneously while preventing translation in any direction. It should be understood that the example ball joint assembly 40 may include additional components and that some of the components described herein may be removed and / or modified without departing from the scope of the example ball joint assembly 40. Furthermore, implementations of the example ball joint assembly 40 are not limited to the following. Figure 8 The example shown.

[0072] In this example, the ball joint assembly 40 is a ball-and-socket joint assembly formed by a ball stud 41 and a housing 42. The housing 42 has an open hole into which the ball stud 41 is inserted. The ball stud 41 has a rod portion 43 and a ball head portion 44. The ball head portion 44 has a hemispherical shape and is received in the open hole of the housing 42 so that the rod portion 43 protrudes from the open hole. The rod portion 43 is attached to a protrusion 45 of an arm 46 of a main frame of the aircraft.

[0073] The housing 42 is formed in a socket portion 47 of the ball joint assembly 40. The socket portion 47 is coupled to the body of the quadcopter 48. For example, the socket portion may be attached to the body of the quadcopter 48 using screws.

[0074] The ball joint assembly 40 allows for movement that will be determined by the sum of the forces generated by the quadcopters 48 attached to the ball joint assembly 40. The ball joint assembly allows the relative positions of the quadcopters to be changed and, therefore, provides additional mobility and independent DOF to the aircraft by combining the different forces generated by multiple multicopters attached to the main frame via ball joints.

[0075] In some examples, the ball joint may include a mechanism to limit one or more DOF. For example, in an aircraft that transports people, it may not be necessary to have all the DOF of the ball joint, such as an operating mode that does not require moving the aircraft backward at maximum speed. In this case, the ball joint can have a mechanical system, such as a bolt or latch, to limit backward tilt. The joint can also include a remote control system to enable a mechanical system for limiting specific DOF. These limiting mechanisms can also be useful in operating modes that require higher controllability or safety (such as during landing). For example, during an emergency landing, some of the DOF of the ball joint can be blocked to keep the ball joint perpendicular to the ground.

[0076] The ball joint may also have additional elements to provide additional functionality, such as shock absorbing mechanisms to variably damp the forces exerted on the joint during motion of the vehicle, force generating mechanisms to generate opposing and variable forces in the knee of the joint when in motion, and force generating mechanisms to generate variable forces to the joint when the joint reaches its mechanical limit (crash stop), etc.

[0077] Thus, attaching a multirotor unit to a mainframe using a joint having at least one DOF provides independent DOF without adding servo actuators to the architecture. Furthermore, the weight and electronics associated with servo actuators are avoided while reducing energy consumption.

[0078] Fig. 9 Shown for management Figure 1 It should be understood that the example control system 50 may include additional components and some of the components described herein may be removed and / or modified without departing from the scope of the example control system 50. In addition, the implementation of the example control system 50 is not limited to the following. Fig. 9 The example shown.

[0079] In this example, the control system 50 includes a controller 51 that is communicatively coupled to a reference processing unit 52 that determines the displacement of the main frame 3 relative to a horizontal plane. The reference processing unit 52 may be communicatively coupled to an inertial measurement unit 53. In turn, the inertial measurement unit 53 is also communicatively coupled to a plurality of accelerometers 54 and / or gyroscopes 55 positioned at different locations on the main frame 3 to measure parameters such as acceleration, orientation, angular velocity, etc. As used herein, the reference processing unit 52 may be any combination of software and hardware configured to perform the described functions of the reference processing unit.

[0080] If the aircraft 1 is remotely controlled, the controller 51 may be further communicatively coupled to a transceiver configured to receive instructions from the remote controller to fly the aircraft. Alternatively, if the aircraft 1 is an autonomous aircraft, the controller may be coupled to an autopilot processing unit including software and hardware to perform autonomous flight.

[0081] The controller 51 is configured to receive the current orientation of the main frame 3 from the reference processing unit 52. Based on the current orientation of the main frame 3, the current thrust and the expected thrust, and the direction of travel, the primary controller determines the thrust magnitude of each of the motors 56 associated with the propulsion units (e.g., rotors). The controller 52 sends the calculated thrust to the speed processing unit 57. The speed processing unit 57, which communicates with each of the motors 56 of the quadcopters 2a to 2d, sends a corresponding forwarding signal to the corresponding motor in the quadcopters 2a to 2d that will determine the speed of its rotor. By changing the thrust magnitude of the different propulsion units, the position of the quadcopters 2a to 2d relative to the main frame 3 will be changed.

[0082] In some other examples, the control system may include a primary controller located in the main frame and a plurality of secondary controllers, each of which is located in a corresponding multi-rotor aircraft unit. In addition, each multi-rotor aircraft unit may have its own speed processing unit. Through this control system architecture, the secondary controller may be configured to operate the corresponding multi-rotor aircraft unit and the primary controller may be configured to manage a plurality of secondary controllers. The primary controller may be communicatively coupled to the reference processing unit to receive information about the orientation of the main frame, and the secondary controller may be communicatively coupled to the primary controller. In this way, the primary controller having information about the current direction, the current direction of travel, and the expected direction of travel of the aircraft is able to determine the direction to be taken by the aircraft. The primary controller may transmit the direction to be taken, i.e., the thrust vector of the aircraft, to the secondary controller so that each secondary controller may operate the corresponding multi-rotor aircraft unit to guide the aircraft in the direction to be taken. Each secondary controller may send the thrust calculated for the particular quadcopter to the corresponding speed processing unit. The speed processing unit may send a corresponding forwarding signal to the corresponding motor in the quadcopter that will determine its rotor speed.

[0083] Fig.10 A flow chart of an example method for maneuvering an aircraft with decoupled DOF is shown.

[0084] At step 61 of method 60, an aircraft with decoupled DOF as previously disclosed is provided. The aircraft comprises a main frame, a plurality of multirotor aircraft units attached to the main frame by insertion of corresponding joints, wherein at least one joint has a minimum of one degree of freedom, so that the main frame has the same or more number of CDOF as the total number of DOF of the main frame.

[0085] At step 62 of the method, a reference processing unit of the aircraft determines the displacement of the aircraft relative to a horizontal plane. Preferably, the reference processing unit may be communicatively coupled to an inertial measurement unit and a plurality of accelerometers and / or gyroscopes positioned on the main frame.

[0086] At step 63 of method 60, the controller of the aircraft determines a global thrust vector or set point (thrust+bank angle, yaw, roll and pitch) for the entire aircraft based on the determined displacements. The controller then calculates a thrust vector (thrust and bank angle) for each of the plurality of multirotor aircraft units based on the previously calculated global thrust vector.

[0087] At step 64 of method 60 , the controller adjusts the thrust of each propulsion unit of the plurality of multirotor units based on the determined thrust.

[0088] At step 65 of method 60 , the controller adjusts the tilt angles of the plurality of multicopter units by performing a rotational movement of each multicopter unit relative to the main frame via a joint, the relative rotational movement being based on the determined tilt angles.

[0089] The aircraft with decoupled DOF as described herein can be used to provide an expandable aircraft architecture based on minimal propulsion modules connected to a common structure via joints with at least one DOF and up to three rotational DOFs. These joints connecting each multirotor aircraft unit to the main aircraft structure can allow up to 3 rotational degrees of freedom (rotation about the X axis, rotation about the Y axis, and rotation about the Z axis) and enable each of the multirotor aircraft units to be precisely positioned relative to the main aircraft structure. All of these advantages enable the aircraft to perform movements that existing aircraft with fixed propulsion units are currently unable to perform.

[0090] In this document, the term “comprise” and its derivatives (eg, “comprising”, etc.) should not be interpreted in an exclusive sense, that is, these terms should not be interpreted as excluding the possibility that the described and defined contents may include more elements.

[0091] The invention is obviously not limited to the specific embodiments described herein, but also covers any variant that a person skilled in the art may consider within the general scope of the invention as defined by the claims.

Claims

1. An aircraft, comprising: Main frame; a plurality of operable multirotor units, each multirotor unit having four propulsion units, wherein the plurality of propulsion units are attached to the multirotor units at a fixed yaw angle, a fixed roll angle, and a fixed pitch angle; and wherein the plurality of operable multirotor units are attached to the main frame by the insertion of respective joints and rotate independently of each other relative to the main frame, each joint being located at the center of a corresponding multirotor unit, and wherein all joints have at least one degree of freedom such that the main frame has the same number of controllable degrees of freedom as the total number of degrees of freedom of the main frame, the main frame having a plurality of arms extending radially from the main frame, and each operable multirotor unit is attached to a corresponding arm of the plurality of arms; The aircraft includes a reference processing unit located on the main frame and configured to determine a displacement of the main frame relative to a horizontal plane.

2. The aircraft according to claim 1, wherein: The joint has a maximum of three degrees of freedom.

3. The aircraft according to claim 1, wherein: The joint includes a release system that enables the plurality of operable multirotor units to be releasably attached to the main frame.

4. The aircraft according to claim 1, wherein: The joint includes a locking device configured to restrict movement of the joint in at least one degree of freedom.

5. The aircraft according to claim 1, wherein: The joint includes a blocking device configured to temporarily block movement of the joint in at least one degree of freedom.

6. The aircraft according to claim 1, wherein: The joint includes a shock absorbing device configured to absorb shock pulses generated by movement of the multicopter unit relative to the main frame.

7. The aircraft according to claim 1, wherein: The joint is selected from the group consisting of a spherical joint, a universal joint, a ball and socket joint, a constant velocity joint, and any combination thereof.

8. The aircraft according to claim 1, wherein: The plurality of operable multirotor units are equidistantly positioned relative to a center point of the main frame.

9. The aircraft of claim 1, comprising a controller located in the main frame, the controller configured to operate the plurality of multirotor aircraft units.

10. An aircraft according to any one of the preceding claims, comprising: a main controller, the main controller being located in the main chassis; as well as a plurality of secondary controllers, each secondary controller being located in a corresponding multirotor unit, Wherein, the plurality of secondary controllers are configured to operate corresponding multirotor aircraft units, and the primary controller is configured to manage the plurality of secondary controllers.

11. A method for maneuvering an aircraft, the method comprising: Providing an aircraft according to claim 1; Determining, by the reference processing unit, a displacement of the aircraft relative to a horizontal plane; determining, by a controller of the aircraft, a thrust and a tilt angle of the aircraft based on the determined displacement; adjusting, by the controller, the thrust of each of the plurality of multirotor units based on the determined thrust; as well as The tilt angle of each multicopter unit of the plurality of multicopter units is adjusted by the controller by performing a rotational movement of each multicopter unit relative to the main frame via the joint, the relative rotational movement being based on the determined tilt angle.

12. The method according to claim 11, wherein: The aircraft has a primary controller attached to the main frame and secondary controllers attached to each multirotor unit, wherein the plurality of secondary controllers are used to operate the respective multirotor units and the primary controller is used to manage the plurality of secondary controllers, the method comprising: determining, by the primary controller, thrust and a tilt angle of the vehicle based on the determined displacement; adjusting, by each secondary controller, the thrust of a corresponding multirotor unit based on the determined thrust; and The tilt angle of the respective multicopter unit is adjusted by each secondary controller by performing a rotational movement of the multicopter unit relative to the main frame via the joint, the relative rotational movement being based on the determined tilt angle.

13. The method according to claim 11, wherein: The aircraft has a plurality of controllers configured to operate the plurality of multirotor aircraft units, the method comprising: determining, by any one of the plurality of controllers, a thrust and a tilt angle of the aircraft based on the determined displacement; adjusting, by any of the plurality of controllers, thrust of the plurality of multirotor units based on the determined thrust; and The tilt angle of the plurality of multicopter units is adjusted by any of the plurality of controllers by performing a rotational movement of the multicopter unit relative to the main frame via the joint, the relative rotational movement being based on the determined tilt angle.

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