Omnidirectional multi-rotor aerial vehicle

Abstract

Described herein is an omnidirectional multi-rotor aerial vehicle system. The system includes a main body and a plurality of arms. The system includes a plurality of propellers. Each of the plurality of propellers are coupled to an end of a respective arm of the plurality of arms and are configured to generate a force and a moment. The system includes a plurality of motors, each communicatively coupled to a respective propeller and configured to rotate the respective propeller. The system includes a controller communicatively coupled to the plurality of motors. The controller includes one or more processors to compute a propeller action for each propeller. The propeller action is computed based upon a desired position of the system and a weight of the system.

Description

Atty. Dkt. No.: 046434-0967OMNIDIRECTIONAL MULTI-ROTOR AERIAL VEHICLECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U. S. Provisional Patent App. No.63 / 730,877 filed on December 11, 2024, the disclosure of which is incorporated herein by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates generally to systems for an omnidirectional multirotor aerial vehicle.BACKGROUND

[0003] The use of multi-rotor aerial vehicles (MRAVs) spans a variety of uses and applications, including photography, surveying, and aerial-physical interaction, leveraging an expansive workspace provided by MRAVs when compared to ground vehicles.

[0004] MRAVs can reach any location in three-dimensional space. However, the most commonly used multi-rotor aerial vehicles have a coupling between their orientation and their position change and are inherently underactuated necessitating tilting maneuvers for lateral movement. Several modifications to overcome these limitations focus on decoupling the multi-rotor aerial vehicle's orientation and position change, leading to the development of fully actuated platforms. However, most MRAVs still show a restricted operational workspace and are limited to hovering within a narrow range of orientations where the MRAV’s vertical axis remains approximately upright. Of these solutions, very few MRAVs can provide non-tethered flight while relying on fixed propellers (i.e. propellers that are not actuated via servomotors) that can rotate in one direction and provide corresponding unidirectional thrust, hereby referred to as uni-directional thrusters.

[0005] Unmanned aerial vehicles (UAVs) have been introduced to address these limitations.From these solutions, one solution, M. Hamandi, K. Sawant, M. Tognon and A. Franchi, “Omni -Plus-Seven (07+): An Omnidirectional Aerial Prototype with a Minimal Number of Unidirectional Thrusters,” 2020 International Conference on Unmanned Aircraft Systems (ICUAS) (2020), incorporated by reference herein, demonstrated a working prototype.14911-2423-5130Atty. Dkt. No.: 046434-0967However, the design required an external power source, and external computation. Another solution equipped with a manipulator system was introduced, where the manipulator can reach any orientation and position and apply arbitrary force and moments solely through the use of the multi-rotor aerial vehicle's propeller-induced forces and moments; however, this solution was demonstrated in simulation only. Additionally, the aforementioned solutions require a maximum lift-to-weight ratio much higher than what current motors / propellers could achieve for classically sized multi-rotor aerial vehicles, where the lift-to-weight ratio is defined here as the maximum thrust any motor has to provide to lift the platform's weight in any arbitrary orientation.

[0006] Therefore, there is a need for multi-rotor aerial vehicle solutions that could be equipped with a gripper, or any other attachment that could benefit from the omnidirectional workspace, and that can operate via batteries, do not have coupling between their orientation and position change, can position and orient the attached gripper to any desired position and orientation, and apply arbitrary forces and moments along the gripper while relying only on the forces and moments generated by the propellers. Additionally, there remains a need for such solutions with an efficient maximum lift-to-weight ratio.SUMMARY

[0007] At least one embodiment relates to a system for omnidirectional flight. The system includes a main body and a plurality of arms. Each of the plurality of arms are coupled to the main body at a first end and each of the plurality of arms include a main tube that has a tube length. The system includes a plurality of propellers. Each of the plurality of propellers are coupled to a second end of a respective arm of the plurality of arms. Each of the plurality of propellers are configured to generate a force and a moment. The system includes a plurality of motors, each communicatively coupled to a respective propeller and configured to rotate the respective propeller. The system includes a controller communicatively coupled to the plurality of motors. The controller includes one or more processors to compute a propeller action for each propeller. The propeller action is computed based upon a desired position and orientation of the system and a weight of the system.

[0008] At least one embodiment relates to a system for omnidirectional flight. The system includes a main body, an arm coupled to the main body at a first end and a propeller coupled to a second end of the arm. The arm includes a main tube that has a tube length. The propeller24911-2423-5130Atty. Dkt. No.: 046434-0967is configured to generate a force and a moment. The system includes a motor communicatively coupled to the propeller and configured to rotate the propeller. The system includes a controller communicatively coupled to the motor. The controller includes one or more processors to perform operations including receiving a current status of the system including a current position and a current orientation of the system, receiving an input including a desired position and a desired orientation of the system, and determining, based on the input and the current status, a propeller action. The propeller action includes at least one of a computed force or a computed moment. The operations include sending a signal related to the propeller action to the motor to cause rotation of the propeller. A position and an orientation of the propeller position and orientation is determined such that an air funnel generated based on the rotation of the propeller is at a distance away from the main body and at a distance away from a second air funnel generated by a second propeller of the system.

[0009] At least one embodiment relates to a system for omnidirectional flight. The system includes a main body, a first arm coupled to the main body, and a first propeller coupled to the first arm at an end distal from the main body. The first propeller is configured to rotate in a first direction to generate a first force and a force moment. The system includes a second arm coupled to the main body and a second propeller coupled to the second arm at an end distal from the main body. The second propeller is configured to rotate in a second direction opposite the first direction to generate a second force and a second moment. The first propeller generates a first air funnel and the second propeller generates a second air funnel. The first air funnel and the second air funnel are configured to not interact with each other and the main body. The system is configured to move in a linear direction and a rotational direction, and the linear direction and the rotational direction are decoupled.

[0010] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein.BRIEF DESCRIPTION OF THE FIGURES

[0011] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the34911-2423-5130Atty. Dkt. No.: 046434-0967accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

[0012] FIG. 1 shows a schematic perspective view of a multi-rotor aerial vehicle, according to an example embodiment.

[0013] FIG. 2 shows a schematic perspective view of arms of the vehicle of FIG. 1, according to an example embodiment.

[0014] FIG. 3 shows views of an arm -base connector of the vehicle of FIG. 1, according to an example embodiment.

[0015] FIG. 4A shows a schematic perspective view of arms of the vehicle of FIG. 1, according to an example embodiment. FIG. 4B shows views of a propeller-arm connector of the vehicle of FIG. 1, according to an example embodiment.

[0016] FIG. 5 shows a schematic perspective view of a 3 -link gripper of the vehicle of FIG. 1, according to an example embodiment.

[0017] FIG. 6 shows a perspective view of a multi-rotor aerial vehicle, according to an example embodiment.

[0018] FIG. 7 shows a testing configuration for propeller aerodynamic funnel identification.

[0019] FIG. 8 shows normalized measured forces and moments for varying distances and angles between propellers.

[0020] FIG. 9 shows normalized forces and moments while varying a distance between a propeller and a surface.

[0021] FIG. 10 shows flight performance of a multi-rotor aerial vehicle while hovering horizontally, rotating, translating, and rotating back to a horizontal orientation.44911-2423-5130Atty. Dkt. No.: 046434-0967

[0022] FIG. 11 shows flight performance of the multi-rotor aerial vehicle of FIG. 10 while hovering horizontally, rotating while simultaneously translating, and then rotating back to a horizontal orientation and landing.

[0023] FIG. 12 shows snapshots of the multi-rotor aerial vehicle of FIG. 10 performing a full flip, where each of the subfigures shows the hovering at different roll angles; a) 0g = 0°, b) 0 = 90°, c) 0g = 180°, d) 0g = 270°.

[0024] FIG. 13 shows flight performance of the multi-rotor aerial vehicle of FIG. 10 while performing the full flip of FIG. 12.

[0025] Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.DETAILED DESCRIPTION

[0026] Embodiments described herein relate generally to systems for an omnidirectional multi-rotor aerial vehicle. The system can use a number of propellers to lift itself in any orientation, utilizing computing and power sources available on the system without the need for an external power source. In some embodiments, one or more of the propellers are fixed pitch propellers. In some embodiments, the number of propellers is greater than or equal to 7. The system includes a main body 102 and propeller pair is attached via an arm, which may be, for example, a carbon fiber rod. The arms may be square tubes. The sizes of each of the arms and shape and size of each of the corresponding connectors are deduced from the positions and orientations of the propellers generated by the proposed optimization algorithm.

[0027] Some embodiments relate to a multi-rotor aerial vehicle. FIG. 1 is a schematic perspective view of an omnidirectional multi-rotor aerial vehicle (e.g., a vehicle system),54911-2423-5130Atty. Dkt. No.: 046434-0967herein referred to as vehicle 100. The vehicle 100 includes a main body 102. The main body 102 houses a majority of components of the vehicle 100.

[0028] The vehicle 100 includes a number of arms 104 and propellers. While one embodiment of the vehicle 100 includes eight propellers, the vehicle 100 may have any number of propellers greater than or equal to seven. An increase in the number of propellers results in a lower value of a maximum thrust-to-weight ratio. However, an increase in the number of propellers requires an addition of weight to the vehicle 100 as added components (e.g., motors, arms, electronics) are necessary. For some embodiments, eight propellers were found to be an optimal number with the maximum thrust-to-weight-ratio and the weight of the vehicle 100. Examples discussed herein focus on the vehicle 100 with eight propellers; however, vehicles with different number of propellers could be conceptualized and constructed in a similar manner as discussed.

[0029] As shown in FIG. 2, each of the arms 104 include a main tube 124. The main tube 124 has a tube length L. The tube length L can be a different value or a same value for each main tube 124. In various embodiments, the tube length L for at least one of the main tubes 124 may be adjustable. For example, a user of the vehicle 100 may manually adjust the tube length L. In another example, the tube length L may be electronically adjustable (e.g., via a controller, controller 107). The main tube 124 may have a cylindrical, rectangular, triangular, square, or other polygonal cross section. Further, the main tube 124 may have different cross-sectional shapes. For example, the main tube 124 may have a different cross-sectional shape at one or more ends than in a middle portion of the main tube 124, such as to facilitate connection to a connector (e.g., arm-base connector 114).

[0030] With further reference to FIG. 2, each of the arms 104 also includes a connector, shown as an arm-base connector 114 that connects the main tube 124 to the main body 102. FIG. 3 shows the arm-base connector 114. In one embodiment, the arm-base connector 114 includes a base portion 116 that is coupled onto the main body 102. In various embodiments, the base portion 116 is positioned flat on the main body 102. In various embodiments, the base portion 116 includes holes that correspond with holes on the main body 102 to securely couple the arm-base connector 114 to the main body 102. The arm-base connector 114 also includes an elevated portion 118 that is coupled to the main tube 124. In various embodiments, the elevated portion 118 includes holes that correspond with holes on the main tube 124 to securely couple the arm-base connector 114 to the main tube 124. The angles64911-2423-5130Atty. Dkt. No.: 046434-0967between the base portion 116 and the elevated portion 118 in a first view and a second view are labelled as α₁₄ and β₁₄, respectively. The first view is a 90° rotation along an axis from the second view. The first view may be a right view of the arm -base connector 114 and the second view may be a front view of the arm-base connector 114.

[0031] As shown in FIG. 4A, among others, each of the arms 104 also include a propellerarm connector 134 that is attached at the end of the corresponding main tube 124. In various embodiments, the propeller-arm connector 134 is made of rigid plastic. A motor 108 (e.g., a brushless DC motor) is attached to the corresponding propeller-arm connector 134. In some embodiments, the plurality of motors 108 of the vehicle 100 includes seven or more motors. Although a brushless DC motor is used in this embodiment, it can be appreciated by those skilled in the art that different types of motors may be used. FIG. 4B shows the propeller-arm connector 134 of the vehicle 100 in detail. The propeller-arm connector 134 can be manufactured as a single part. In some embodiments, the propeller-arm connector 134 includes a base part 135 that is coupled to the main tube 124.

[0032] The vehicle 100 includes a plurality of propellers 144. Each of the propellers 144 is coupled to one of the arms 104. The propeller 144 is coupled to an end of the arm 104 distal from the main body 102. The propeller 144 is configured to provide thrust generation when rotated in a direction. In some embodiments, at least one of the propellers 144 is a fixed pitch propeller. In some embodiments, at least one of the propellers 144 is a variable pitch propeller or a constant speed propeller.

[0033] Each propeller 144, in some embodiments, is associated with one of the plurality of motors 108 to facilitate independent operation. As shown in FIG. 2, a propeller 144 is associated with an adjacent motor 108. The paired propeller 144 and motor 108 are positioned a distance from the main body 102 by the arms 104. As further described below, the propellers 144 and the motors 108 are coupled to the main body 102 based on the required position and orientation of the propellers 144 to achieve desired system capabilities.

[0034] The motor 108 of the respective arm 104 may supply power to cause movement of the respective propeller 144. The movement of the propeller 144 can occur along an axis of the propeller 144. In various embodiments, the direction is a clockwise orientation. In various embodiments, the direction is a counterclockwise orientation. The vehicle 100 may be configured such that alternating propellers 144 rotate in the counterclockwise orientation74911-2423-5130Atty. Dkt. No.: 046434-0967and the remaining propellers 144 rotate in the clockwise orientation. In other words, the propellers 144 positioned adjacent a first propeller may rotate in a direction different than a direction the first propeller rotates. As a result, approximately half (or at least half) of the propellers 144 may generate thrust via rotation in a clockwise direction and the remaining propellers 144 may generate thrust via rotation in a counterclockwise direction, and vice versa.

[0035] The vehicle 100 also includes a controller 107 configured to control operation of the vehicle 100. The controller 107 is coupled to the main body 102. The controller 107 includes one or more processors and memory to perform operations allowing for the computation of required controls to operate the vehicle 100. The controller 107 may be configured to interpret data given from a user or controls. Additionally, the controller 107 may be communicably coupled to the motors 108. The controller 107 can send control signals to at least one of the motors 108 to control operation of the motor 108 and the respective propeller 144 for the motor 108. The controller 107 may also store data to estimate a state of the vehicle 100 when estimation is necessary for control of the vehicle 100. For example, as described herein, the controller 107 may store information related to the position and thrust direction of at least one of the propellers 144. In various embodiments, the data includes information from sensors for estimation. The sensors may be positioned on any part of the vehicle 100. The sensors may include accelerometers, gyroscopes, GPS, and magnetometer, or any combination thereof. The sensors could be extended or replaced to include any sensor used for the localization of the orbital angular momentum (OAM) of the vehicle 100.

[0036] The controller 107 may be communicably coupled to a user device. The vehicle 100 may be remotely controlled with the user device. The user device is communicably connected to the vehicle 100 via the controller 107 and is configured to allow a user to remotely adjust the vehicle 100. For example, the user may use the user device to turn the vehicle 100 on. In another example, the user may use the user device to input a desired movement of the vehicle 100. The user device may be an electronic device, such as a remote control, a smartphone, etc. Additionally, the user device may be an application installed onto an electronic device.

[0037] In various embodiments, the vehicle 100 (e.g., the controller 107, the motor 108) is powered by at least one battery 109. As shown in FIG. 1, the vehicle 100 includes batteries 109. The batteries 109 may be positioned below the main body 102. The batteries 109 may84911-2423-5130Atty. Dkt. No.: 046434-0967be replaceable by the user. In other embodiments, the vehicle 100 may utilize a wired connection to provide electrical supply to power the controller 107 and the motor 108. In other embodiments, the vehicle 100 can be powered by an external power source. For example, the vehicle 100 can be powered through a tethered cable. The vehicle 100 may also be powered through a combination of at least one battery 109 and one or more external power sources.

[0038] In various embodiments, as is shown in FIG. 1, the vehicle 100 includes a landing gear 300. The main body 102 is coupled to the landing gear 300. The landing gear 300 is configured to aid in landing the vehicle 100. For example, the landing gear 300 may help in cushioning landing of the vehicle 100. As is shown in FIG. 1, the landing gear 300 includes tubes 302 and connectors 322, with the connectors 322 being coupled to an end of the tubes 302. The connectors 322 are coupled to the main body 102 The landing gear 300 also includes a landing pad 312 coupled to an end of the tubes 302 opposite the end that the connectors 322 are coupled to. The landing pad 312 aids in softening an impact of landing the vehicle 100.

[0039] As shown in FIGS. 1 and 5, the vehicle 100 may include a gripper 200. The gripper 200 is positioned below the main body 102. In one embodiment, the gripper 200 includes at least one gripper end 202 to couple the gripper 200 to a portion of the vehicle 100. The gripper ends 202 may couple to a portion of the main body 102 and / or the vehicle 100 (e.g., tubes 302). The gripper 200 includes at least one gripper support arms 206 that extends from the gripper ends 202. In various embodiments, the clasping and / or gripping portion of the gripper 200 (e.g., two articulated links 212, fixed link 232) is positioned between the gripper support arms 206. The gripper support arms 206 may be plastic, steel, or carbon fiber rods.

[0040] The gripper 200 includes at least one articulated link 212 or arm to selective clasping or engagement with an object (e.g., an object external to the vehicle 100). In one embodiment, the gripper 200 also includes a fixed link 232 and two articulated links 212. In one embodiment, each of the articulated links 212 and the fixed link 232 are padded with a soft surface 208, such as a rubber or thermoplastic. The two articulated links 212 may be articulated with servomotors 204. In some embodiments, a side of the servomotor 204 is coupled (e.g., attached) to one of the gripper support arms 206. In some embodiments, the gripper 200 includes an additional structure or part to couple the articulated links 212 and / or the fixed link 232 to the gripper support arms 206.94911-2423-5130Atty. Dkt. No.: 046434-0967

[0041] The gripper 200 is configured to couple (e.g., latch, etc.) onto an external object. For example, the gripper 200 can open and close around the external object to apply an arbitrary force to the external object. For example, the gripper 200 can apply the arbitrary force to the object to grip the object. The external object may be a circular object, such as a tube or a light bulb. In various embodiments, the at least one articulated links 212 moves (e.g., via the servomotors 204) to grasp the external object. In some embodiments, the gripper 200 is positionable in a two- or three-dimensional space relative to the main body 102. For example, the gripper 200 may having two or more degrees of articulation such as to enable grasping or holding an object. The gripper 200 may be positioned and oriented using the controller 107. In various embodiments, the modeling and computation described below with reference to the propeller 144 may be used to apply arbitrary forces and moments the gripper 200. For example, the gripper 200 may apply a gripper force and a gripper moment onto the external object that corresponds to the force and moment applied by the propeller. Although shown as a gripper, the gripper 200 may be another attachment, such as a cutting device, a bending device, etc.

[0042] In various embodiments, the vehicle 100 includes an imaging device, such as a camera, configured to capture image and / or video data. In various embodiments, the camera is a configured to capture color images. Additionally, the camera may be a depth camera (e.g., an RGB-D camera). The camera can be used for capturing image and / or video data related to an environment of the vehicle 100 during landing, target identification, object grasping, and localization. Further, the camera may be used for obstacle avoidance. The camera may be communicatively coupled to the controller 107 to communicate information. For example, the camera may capture an image or video of the environment of the vehicle 100 including an obstacle and the controller 107 may receive the image or video and send a signal to control movement of the vehicle 100.Modeling

[0043] As is shown in FIG. 1, a geometric center of the vehicle 100 is defined by axes x-x, y-y, and z-z. Specifically the geometric center lies on an origin of the axes. Movement of the vehicle 100 is governed by inertial parameters and mass of the vehicle 100 and force and moment generated by each propeller 144. Modeling the governance of relationship of the parameters is important for determining optimization parameters of the vehicle 100.104911-2423-5130Atty. Dkt. No.: 046434-0967

[0044] As described herein, an optimization formulation may be used with the vehicle 100 to find the required position and orientation of the propellers in a fixed frame defined at the geometric center of the vehicle 100 (e.g., the main body 102). An optimization-based design ensures the decoupling between the orientation of the vehicle 100 and its ability to change its position. The movement of the vehicle 100 (e.g., along the axes of the vehicle 100) and the orientation movement (e.g., rotation, roll, etc.) of the vehicle 100 are decoupled. The optimization-based design ensures the vehicle 100 can carry its weight in any arbitrary orientation and is balanced in terms of sharing the required forces and moments required to lift its weight in different orientations among all propellers. The optimization also ensures the air funnels generated by different propellers do not interact. In various embodiments, a size and / or length of each of the main tube 124 and shape and size of each of the corresponding arm -base connector 114 are determined from the positions and orientations of the corresponding propeller 144 generated by the proposed optimization algorithm.

[0045] The mass of the vehicle 100 is denoted by mis E R>o. The inertial parameters of the vehicle 100 was denoted as a matrix JB E IR|O3. The number of propellers 144 was denoted as N E R, with z = 1,..., N. The position and thrust direction of the z-th propeller 144 are denoted as d / E R3and v / E R3, respectively. FIG. 6 shows a schematic of the vehicle 100 with these labelled parameters. A world frame is represented by xw, yw, and zw. Force and moment generated by each propeller 144 can be modeled as:ft = VtXi.mi = + [di + rCoM]x)v Eq. 1£A£

[0046] In Eq. 1, CT and Cf are a drag coefficient and a lift coefficient of the propeller 144, respectively. Thrust generated by all of the propellers 144 can be concatenated into a vector 2 = [21(A / v]T. An allocation matrix F is defined as a map from the thrust of the propellers 144 to total force and moment applied on the vehicle 100 at the geometric center. Specifically,FA = Eq.2lXim£.

[0047] Static hovering is defined at an orientationw / ?g as an ability of the vehicle 100 to lift its weight such that the orientation along the zw axis (w / ? zw) is parallel to the z-z axis and zero moment is applied, similar to E. Baskaya, M. Hamandi, M. Bronz, and A. Franchi,114911-2423-5130Atty. Dkt. No.: 046434-0967“A novel robust hexarotor capable of static hovering in presence of propeller failure,” IEEE Robotics and Automation Letters (2021), incorporated by reference herein. To achieve static hovering at the orientationw / ?g, the vehicle 100 is required to apply a thrust:W'pdnfiz7WZ + yB Eq.3O3y = argmin||yB|| Eq. 4

[0048] In Eq. 3-4, g is the gravitational constant,is the Moore-Penrose pseudo inverse of the allocation matrix F, and B is the null space basis of F.

[0049] The vehicle 100 is an omnidirectional platform meaning that the vehicle 100 can lift its weight in any orientation. A maximum thrust required by any propeller 144 to lift the vehicle 100 in any orientation is defined as:E>i-5

[0050] R is a group of all possible flight orientations represented in body frame. In some embodiments, R includes all possible orientations in three-dimensional space (e.g., a full rotation group). In other embodiments, R is any set of orientations that includes at least one complete rotation about a body-fixed axis that is perpendicular to the z-z axis of the vehicle 100. Similar to what is described in M. Hamandi, A. M. Ali, N. Evangeliou, D. Chaikalis, A. Tzes, K. Kyriakopoulos, and F. Khorrami, “Mechatronic Design of an Omnidirectional Octorotor UAV,” in 10th International Conference on Automation, Robotics and Applications (ICARA) (2024), incorporated by reference herein, a funnel generated by each propeller 144 is modeled as a series of overlapping spheres identified through computer vision techniques followed by injection of smoke into the propeller 144. Each funnel is restricted with m-overlapping spheres. For the z-th propeller 144, each sphere is denoted by a ball (c;, B / ,s), s = 1,..., m, where c / ,s (B;) is a center of the corresponding sphere.Optimization

[0051] An optimization formulation is used to find the required position and orientation of the propellers 144 in a fixed frame defined at the center of the main body 102. An optimization-based design ensures the decoupling between the orientation of the vehicle 100124911-2423-5130Atty. Dkt. No.: 046434-0967and its ability to change its position. The optimization-based design ensures the vehicle 100 can carry its weight in any arbitrary orientation and is balanced in terms of sharing the required forces and moments required to lift its weight in different orientations among all propellers. The optimization also ensures the air funnels generated by different propellers 144 do not interact. As described herein, in various embodiments, each motor 108 and propeller 144 pair is attached via an arm 104. The sizes of each of the arms 104 and shape and size of each of the corresponding connectors (e.g., arm-base connector 114, propeller-arm connector 134) are deduced from the positions and orientations of the propellers 144 generated by the proposed optimization algorithm.

[0052] The thrust and moment of the propellers 144 are expected to be affected by any blockage or disturbance to a flow of the propellers 144. Two main cases of blockage / disturbance are: 1) propeller flow disrupted by flow of another propeller 144 and 2) propeller flow blocked by a fixed object (e.g., the main body 102 of the vehicle 100).

[0053] FIG. 7 shows a testing configuration for the case of propeller flow disrupted by flow of another propeller 144. Each motor 108 and propeller 144 are mounted on a forcetorque sensor attached to an aluminum support structure. Additional electronics are connected to the motor 108 and the force-torque sensor to send angular velocity commands to the motors 108 and to capture data from the force-torque sensors. The configuration of the test set up is mobile and thus allows for ease of placement of the two motors 108 away from obstructions, and at different distances and angles. In this experiment, the direction of thrust was reversed compared to the usual UAV configuration to avoid interference from the supporting structure and electronics with the airflow.

[0054] As is shown in FIG. 7, a distance between the position d / and an intersection between the thrust direction vi for each of the two propellers 144 is denoted by daero. ( / >aero is defined as an angle between the thrust direction v / and a line between the positions di and d2, assuming that the v;and d / are co-planar. For clarity of data, the two propellers 144 are placed at the comers of an isosceles triangle, such that daero and ero are the same for both propellers 144 as shown in FIG. 7.

[0055] During the experiment, each propeller 144 is rotated at its nominal angular fvelocity (in rpm) required for flight. FIG. 8 shows normalized forces fz / fzand normalized fmoments mzlvzalong thrust directions v for various daero and ( / )aero. When < / > aero 0°, vi and134911-2423-5130Atty. Dkt. No.: 046434-0967V2 are collinear, and one propeller 144 is downstream of another. To account for this, at <j)aero = 0°, data is reported separately for the upstream 0upropeller 144 and the downstream 0dpropeller 144.

[0056] FIG. 8 shows a significant loss in force and moment at ro = 0° for the downstream propeller 144, and a less significant loss for the upstream propeller. This loss of the downstream propeller decreases as the distance between the two propellers 144 increases (e.g., daero increases). However, the loss is significant even at daero = 200 centimeters (cm). While the upstream propeller 144 is subject to a less significant loss of force and moment, it endures a loss of moment that increases with the distance between the two propellers 144. When (j)aero is greater than 0, the loss of force and moment is insignificant as shown in FIG.8.

[0057] The aerodynamic interaction between the propeller 144 and a surface was also assessed experimentally for the case of propeller flow blocked by a fixed object. This was done by measuring the force generated by the propeller 144 while a surface is placed in its downstream, with the surface being perpendicular to the thrust direction v. FIG. 9 shows the normalized force and moment along the thrust direction v for various distances dpiate between the surface and the propeller 144. As seen in the figure, the loss of force is present only for dpiate less than or equal to 60 cm. It can be seen that the maximum change in moment corresponds to approximately 2% of the total applied moment (at a distance of approximately 60 cm), with the corresponding change dropping to less than 1% for dpiate values that are greater than 60 cm.

[0058] FIGS. 8 and 9 show an importance in avoiding placing the propellers 144 such that aero 0°. Additionally, it may be advantageous to avoid a propeller’s funnel from interacting with the main body 102 within a distance dpiate < 60 cm. The first few spheres fitted to the funnel is denoted by k < m such that He / ,* - cull + Bk > 60 cm. To avoid aerodynamic interaction between the propellers 144 and between the propellers 144 and obstacles, the following constraints are necessary for the vehicle 100: 1) the funnel from any propeller 144 should not interact with inflow from another propeller and 2) the first few spheres in the funnel should not interact with a sphere centered around a surface denoted by (cP, Bp). The first constraint can be achieved by ensuring that || c£ s— Cj - I > Bs+ Blti,j E144911-2423-5130Atty. Dkt. No.: 046434-09671,..., N, s e l,..., m. The second constraint can be achieved by ensuring that ||QS— cp|| > Bs+ Bv, i e 1,..., N, s e 1,..., k.

[0059] In order to optimize the vehicle 100 such that the vehicle 100 can achieve omnidirectional hovering while satisfying additional construction requirements as noted f hereafter, problems were addressed. Given the propeller parameters (cf, cT, X), weight mBof fixed parts of the vehicle 100, and arm density p, the propeller positions and orientations (d, v) that minimize the weight of the vehicle 100 and the maximum thrust required from each motor 108 to achieve omnidirectional hovering was found based on the parameters.

[0060] Reducing the weight of the vehicle 100 can be achieved by reducing parts of the vehicle 100 that are variable, such as sum of the tube lengths L. To ensure proper operation of the vehicle 100 and avoid aerodynamic interaction, the funnels generated by different propellers 144 must not interact at nominal operation. Additional construction requirements are enforced as follows: 1) propellers 144 are placed in an upper hemisphere of the vehicle 100 (i.e., the• z — z > OVi G {1,..., A}, where a lower hemisphere is kept empty for ease of aerial manipulation and ease of landing. 2) Maximum and minimum tube length L is restricted such that Lmin < L;< Lmax due to space requirements and to allocate space for the main body 102 of the vehicle 100. 3) The elevation of each propeller 144 is minimized as higher elevations require more material to ensure structural integrity of the vehicle 100. 4) To ensure the propellers 144 are uniformly distributed, each propeller is restricted to be placed in its own octant (for N=8 example), i.e., < ^. 5) For similar reasoning as 4), thedifference in the tube length L between the arms 104 are minimized. 6) A shift in the Center of Mass (CoM) rcoM is minimized to achieve a more balanced design of the vehicle 100.

[0061] The vehicle 100 can apply independent forces and moments in all directions in order to achieve omnidirectional hovering. The vehicle 100 (e.g., the controller 107) can compute a propeller action for each of the propellers 144 to achieve a desired position and / or a desired orientation of the vehicle 100. The propeller action may be based on a number of factors, as described herein, including a weight of the vehicle 100, the current status of the vehicle 100, the desired trajectory of the vehicle 100, etc. The propeller action may include a computed thrust, a computed force, and / or a computed moment. Since the propellers 144 can generate thrust in a single direction, this can be achieved by ensuring that the allocation matrix F has full rank and has a null space, which ensures we can have 6 degrees of freedom. To154911-2423-5130Atty. Dkt. No.: 046434-0967ensure a balanced omnidirectional design, a vector of all ones is enforced to be in the null space of the allocation matrix F, such that Fl = 0. Additionally, the propellers 144 are configured to generate uni-directional thrust. For any force applied, the computed thrusts in an optimal way will have at least one of the thrusts negative (e.g., for hovering in an upwards direction, any propeller 144 pointing in a downwards direction will need to generate negative thrust). The null space corrects for negative thrust. In addition, omnidirectionality is achieved by ensuring a maximum thrust, given the weight of the vehicle 100, to hover is less than the maximum thrust allowed by any propeller 144. With the aforementioned, the design of the vehicle 100 can be formulated in accordance to the following optimization.(d,v) = argmin (ft + ft + ft + ft + ft \ iii-BMOLmax °YmaxDp7' v,LLma "x"' ^fmi.nJ / Eq. 6rrank(F) = 6Fl = 0 Lmin — — Lmax (i-l)n in < N ~1~ N > Vi e {1,...,1V} Eq. 70 < ipi < Ipmax ||ci,s_ cj,i || > Bs+ B±+ e, j G 1,...,1V, s e l,...,m< 11 Q,s Cp 11 — Bs+ Bp + €, s E 1,..., k >

[0062] Eq. 6 is subject to Eq. 7. C E TRNxNis a matrix with a zero entry in the first row, ones along the diagonal for the other rows, and -1 on the left columns of each 1 entry. CL is a vector with a zero entry in the first row, and (L;- L / .y) in the other rows. i / Jmaxis equal to 90°, and e is a safety factor that accommodates for any deflections due to static deformation of the arms 104.are weighting factors such that £?; = 1, and the highest weight is allocated forto advantage choosing an efficient omnidirectional design. Eq. 6 is nonlinear and non-smooth due to the computationof and rank} / 7). Eq. 6 is nonconvex, and each starting configuration results in a different final solution. The design of the vehicle 100 with the lowestw / mBg is chosen after computation of multiple designs.

[0063] The controller 107 is configured to steer the vehicle 100 towards a desired position ^PBCF) and a desired orientationKFg(T). T is a desired time to reach the desired position and the desired time. A smooth trajectory from a current status of the vehicle 100 (e.g., a164911-2423-5130Atty. Dkt. No.: 046434-0967current position and a current orientation of the vehicle 100) to the desired one is assumed. A virtual input for the controller 107 that steers the vehicle 100 towards the desired position and the desired orientation at time t is similar to M. Tognon and A. Franchi, “Omnidirectional aerial vehicles with unidirectional thrusters: Theory, optimal design, and control,” IEEE Robotics and Automation Letters, vol. 3, no. 3, pp. 2277-2282 (2018), incorporated by reference herein, and is:j r t gmBzw+ vg + Kpep+ Kvev+ KipJQeprt Eq. 8x JBMB + KRGR + Kwew+ KiRJQeR

[0064] Kp, Kv, Ki,p, KR, KW, Ki,RG R3 3are matrices with tunable control gains along the diagonal of each matrix. ep=wpB(t) —wpB, ev=wvB(t) —wvB, ew=w)B(t) —w<nB. Rotation error is calculated from the rotation matrix such that eR= | RBT(t)wRB—wRWR*(t.

[0065] In some embodiments, the desired virtual input is applied by the vehicle 100 by commanding Xcto the motors as follows:011Lc= FfWRB Vp + yl. 0 I3-

[0066] Af > 0 V i E {1,...,1V}. yl G null(F), since 1 6 null(F) due to constraints in Eq.

[0067] In some embodiments, the desired virtual input is applied by the vehicle 100 by commanding Xcto the motors as follows:Ac= FfWRB or1Vp + nF Eq.10. 0 h-174911-2423-5130Atty. Dkt. No.: 046434-0967

[0068] Such that 0 < A <maxV i 6 {1,..., / V], nF E null(F), andmaxis the maximum allowed propeller thrust.Experimental Studies

[0069] Using preliminary results from M. Hamandi, et. al., N (the number of propellers) was set to be 8. The positions and orientations of the propellers 144 were computed using Eq.6. The shape of the funnel was identified similar to M. Hamandi, et. al., with m = 13. The corresponding sphere positions and radii are shown below in Table I.Ci,s0 7.6 23 38 54 69 84 99 114 130 147 165 183 [cm]Bi,s11.3 9.1 10.4 11.5 12 13 14 14.6 15.6 16.3 16.8 17.3 18.3 [cm]Table I

[0070] In this experiment the arms 104 are made from 12 mm carbon fiber rods, with brushless motors 108 mounted at the ends using 3D-printed polyamide- 12 parts, fabricated via SLS techniques. The vehicle 100 includes eight propellers 144. The propellers 144 have an 8 inch diameter and 4° pitch. Each propeller 144 is capable of producing up to 40 N of thrust with the selected motor 108 combination. The landing gear 300 is installed below the main body 102 of the vehicle 100 and is made of tubes (e.g., carbon fiber and / or square tubes) with soft endings. In various embodiments, the soft endings are 3D printed.

[0071] The controller 107 is positioned at the geometric center of the main body 102 and communicates via a serial connection. In various embodiments, the serial connection is with a Raspberry Pi 5 onboard computer running a Robot Operating System (ROS) middleware. The controller 107 is connected to a remotely controlled cut-off circuit for protection purposes.

[0072] Communication in both directions occurs at 500 hertz (Hz) using the Multiwii Serial Protocol (MSP). The controller 107 runs a modified version of the INAV firmware, which estimates the position and orientation of the vehicle 100 by fusing data from the onboard MPU6000 Inertial Measurement Unit (IMU) at 500 Hz with external position and orientation data from a Vicon-based motion capture system at 120 Hz when operated indoors,184911-2423-5130Atty. Dkt. No.: 046434-0967and from a GPS, a magnetometer sensor, and a barometer sensor when operated outdoors. A controller running inside the onboard computer calculates PWM outputs, which are then sent to motor controllers of the controller 107.

[0073] An experiment was conducted to demonstrate the omnidirectional ability of the vehicle 100. FIG. 10 shows the ability of the vehicle 100 to track a desired trajectory while being oriented at 90° roll. FIG. 10 shows the vehicle 100 taking off horizontally from ground in the first 7.6 seconds (s), which is shown by the change in ZB (z-position of the vehicle 100). As shown in FIG. 10, the desired movement in the z-direction, z, closely aligns to the actual change in the z-direction, ZB. Once, the vehicle 100 is hovering, the vehicle 100 is rotated to a desired orientation, which includes a desired roll 0B= 90°. The rotation of the vehicle 100 is shown as 0B. Once rotated, the vehicle 100 is subsequently moved primarily laterally along the yB direction with some movement in the XB direction (e.g., in the positive direction of xw and yw), while maintaining its orientation. As shown in FIG. 10, during lateral movement of the vehicle 100, the actual orientation (e.g., the rotation of the vehicle 100) of the vehicle 100 remains similar to the desired orientation. Finally, the vehicle 100 rotates back to its horizontal attitude between 30.3 and 37.9 s and is landed after 37.9 s. The experiment shown in FIG. 10 shows that the vehicle 100 is able to follow a trajectory opposite to the direction of the z-z axis (e.g., after being rotated), where in this case z-z axis is equal to -yw.

[0074] FIG. 11 shows the ability of the vehicle 100 to simultaneously change its orientation and position in opposite directions. FIG. 11 shows the vehicle 100 taking off horizontally from ground in the first 7.5 seconds (s), which is shown by the change in ZB. The vehicle 100 is shown to hover until approximately 15.1 s. As shown from 15.1-30.1 s, the vehicle 100 is linearly moved along the XB and the yB direction, while maintain a same ZB position. Simultaneously, during the linear change in position, the vehicle 100 is moved to a desired orientation, which includes a rotation to a desired roll 0B= 60°. During linear movement of the vehicle 100, the rotation of the vehicle 100, shown as 0B, remains similar to the desired roll. Additionally, the position of the vehicle 100, shown as XB, yB, and ZB, remain similar to the desired positions, shown as xB, yB, and z, respectively. This shows that the simultaneous change in orientation and position is achieved as both the linear movement and the rotation occurs substantially as desired. Finally, the vehicle 100 rotates back as the vehicle 100 is landed, shown by the change in ZB direction and the change in the roll direction at a same time period. The linear movement of the vehicle 100 and the194911-2423-5130Atty. Dkt. No.: 046434-0967orientation movement (e.g., angular motion, rotation, roll) are decoupled, allowing for both to happen simultaneously as desired.

[0075] In addition to being a fully actuated platform, the vehicle 100 can lift its weight in all orientations in order to be omnidirectional. FIGS. 12 and 13 show the ability of the vehicle 100 to make a full rotation about yw while maintaining its position and orientation about the other axes fixed. FIG. 12 shows snapshots of the full flip, where each sub-image shows the vehicle 100 hovering at a different angle. While rotating about yw, the vehicle 100 has to continuously change the direction of the applied force to counteract the direction of gravity. Additionally, FIG. 13 shows the thrust of each propeller 144 throughout the flight. It can be seen from this figure that the propellers 144 applying significant thrust change throughout the flight depending on its orientation, while always having one propeller generating near-zero thrust, and all the desired thrusts of each propeller 144 being positive. Advantageously, the determination (by the controller 107) of the positions and orientations of the propeller 144 to achieve a desired thrust allows for an omnidirectional design and control of the vehicle 100.Definitions.

[0076] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “a member” is intended to mean a single member or a combination of members, “a material” is intended to mean one or more materials, or a combination thereof.

[0077] As used herein, the terms “about” and “approximately” generally mean plus or minus 10% of the stated value. For example, about 0.5 would include 0.45 and 0.55, about 10 would include 9 to 11, about 1000 would include 900 to 1100.

[0078] It should be noted that the term “exemplary” as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and / or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

[0079] As used herein, the terms “coupled,” “connected,” and the like mean the joining of two additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.204911-2423-5130Atty. Dkt. No.: 046434-0967

[0080] It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

[0081] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.214911-2423-5130

Claims

Atty. Dkt. No.: 046434-0967WHAT IS CLAIMED IS:

1. A system for omnidirectional flight comprising:a main body;a plurality of arms, each of the plurality of arms coupled to the main body at a first end, each of the plurality of arms including a main tube that has a tube length;a plurality of propellers, each of the plurality of propellers coupled to a second end of a respective arm of the plurality of arms, each of the plurality of propellers configured to generate a force and a moment;a plurality of motors, each of the plurality of motors communicatively coupled to a respective propeller and configured to rotate the respective propeller; anda controller communicatively coupled to the plurality of motors, the controller comprising one or more processors to compute a propeller action for each propeller;wherein the propeller action is computed based upon a desired position of the system and a weight of the system.

2. The system of claim 1, wherein at least one of the plurality of propellers is configured to rotate in an alternating direction compared to an adjacent propeller of the plurality of propellers.

3. The system of claim 1, wherein the force and the moment of one of the plurality of propellers is different than the force and the moment for at least one other propeller of plurality of propellers.

4. The system of claim 1, wherein the tube length of one of the main tubes is different than the tube length for at least one other main tube.

5. The system of claim 1, further comprising a gripper coupled to the main body, the gripper configured to couple onto an external object.

6. The system of claim 5, wherein the gripper can reach any position and orientation in a three-dimensional space of the system using the propeller actions.

7. The system of claim 1, further comprising a camera communicatively coupled to the controller, the camera configured to send image data related to an environment of the system to the controller.224911-2423-5130Atty. Dkt. No.: 046434-09678. The system of claim 1, wherein a number of the plurality of propellers is at least 7.

9. The system of claim 1, wherein:each propeller is positioned along a respective axis and configured to generate positive thrust along their respective axis; andat least half of the propellers are configured to rotate in a first direction, the first direction being a clockwise direction or a counterclockwise direction.

10. The system of claim 1, wherein the system has a direction of linear movement and a direction of orientational movement, the direction of linear movement and the direction of orientational movement decoupled.

11. The system of claim 1, wherein the system is configured to lift the weight of the system while oriented in any direction.

12. The system of claim 1, wherein a first propeller of the plurality of propellers generates a first air funnel and a second propeller of the plurality of propellers generates a second air funnel, the first air funnel and the second air funnel not interacting with each other.

13. The system of claim 1, wherein the plurality of propellers are positioned on an upper hemisphere of the system.

14. The system of claim 1, wherein computing a position and an orientation for at least one of the plurality of propellers comprises optimization in accordance with:(d, v) = argmin (ft;^- + ft + ft + ft + ft \l,iByOLmaxOlrmaxDp7'({Ltma "x"fLmi.n) A / 15. A system for omnidirectional flight, comprising:a main body;an arm coupled to the main body at a first end, the arm including a main tube that has a tube length;a propeller coupled to a second end of the arm, the propeller configured to generate a force and a moment;a motor communicatively coupled to the propeller and configured to rotate the propeller; and234911-2423-5130Atty. Dkt. No.: 046434-0967a controller communicatively coupled to the motor, the controller comprising one or more processors to perform operations including:receiving a current status of the system, the current status including a current position and a current orientation of the system;receiving an input including a desired position and a desired orientation of the system;determining, based on the input and the current status, a propeller action, the propeller action including at least one of a computed force or a computed moment; and sending a signal related to the propeller action to the motor to cause rotation of the propeller;wherein a position and an orientation of the propeller is determined such that an air funnel generated based on the rotation of the propeller is at a distance away from the main body and at a distance away from a second air funnel generated by a second propeller of the system.

16. The system of claim 15, wherein the propeller action is continuously determined as the current status of the system changes.

17. The system of claim 15, wherein:the operations further include determining a maximum thrust of the system to hover based on a weight of the system; andthe propeller action is determined such that the maximum thrust of the system is less than a maximum thrust generated by the propeller.

18. The system of claim 15, wherein the input further includes a desired time and the controller is configured to determine a trajectory from the current status to the desired position and the desired orientation within the desired time, the propeller action further based on the trajectory.

19. The system of claim 15, wherein determining a position and an orientation for the propeller comprises optimization in accordance with:(d, v) = argmin (ft + ft + ft + ft + ft \l,iByOLmaxOlrmaxDp, '{(LLma "x"'Lfmi.n) J / 244911-2423-5130Atty. Dkt. No.: 046434-096720. A system for omnidirectional flight, comprising:a main body;a first arm coupled to the main body;a first propeller coupled to the first arm at an end distal from the main body, the first propeller configured to rotate in a first direction to generate a first force and a force moment;a second arm coupled to the main body; anda second propeller coupled to the second arm at an end distal from the main body, the second propeller configured to rotate in a second direction opposite the first direction to generate a second force and a second moment;wherein the first propeller generates a first air funnel and the second propeller generates a second air funnel, the first air funnel and the second air funnel not interacting with each other and the main body; andwherein the system is configured to move in a linear direction and a rotational direction, the linear direction and the rotational direction decoupled.254911-2423-5130

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