FORM-2
THE PATENT ACT,1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
(As Amended)
COMPLETE SPECIFICATION (See section 10;rule 13)
" AN UNMANNED AERIAL VEHICLE"
Tata Sons Limited, a corporation organized and existing under the laws of India, of Bombay House, 24 Homi Mody Street, Mumbai 400 001, Maharashtra, India.

FIELD OF INVENTION
[001] The present disclosure relates to an unmanned aerial vehicle with
improved flight characteristics and a method providing such behaviour.
BACKGROUND OF THE INVENTION
[002] Unmanned aerial vehicles or drones are used for several commercial,
military and recreational purposes. Unmanned aerial vehicles generally include helicopters and multi-copters such as quad-copters, hex-copters and octo-copters. As is known, multi-copters comprise a plurality of propellers or blades. Further, throughout this disclosure, the word propeller will be used. Typically, each propeller is driven by an electric motor. It is also possible that an electric motor drives more than one propeller. It is known that the efficiency of an electric motor (DC motor or brushless DC motor or any other suitable motor) is at a maximum at a specified load. The use of a plurality of electric motors, each at a different angular velocity and hence different loads, improves stability and maneuverability but at the cost of overall efficiency of the unmanned aerial vehicle. As a result, the maximum flight time of the unmanned aerial vehicle, on a fully charged on-board battery, for example, is reduced. Various factors relating to the performance of a UAV based on the overall mission requirements. For instance, applications involving payloads sensitive to sudden movement may emphasize the stability requirements, whereas other applications may call for maximum flight endurance. Such mission requirements may even change during the implementation of the mission, such as in response to changed user requirements or altered weather conditions. A suitable arrangement is required in order to provide optimal implementation of such diverse requirements.
[003] United States patent application 20160272310 discloses an aircraft
which is selectively reconfigurable to modify flight characteristics. The aircraft comprises a set of rotors. The position of at least one rotor relative to the base can be modified by at least one of translation of the rotor relative to the boom, pivoting of the boom relative to the base, and translation of the boom relative to the base; so that flight characteristics can be modified by configuration of position

of at least one rotor relative to the base. A method of configuring an aircraft having a set of rotors on a mission to carry a payload comprises the steps of determining properties of the payload including at least mass properties, determining the manner in which the payload will be coupled to the aircraft, determining configuration for each of the rotors in the set of rotors at least partially in consideration of the properties of the payload, and positioning the set of rotors in the configuration for the aircraft to perform the mission. This approach is limited in its ability to optimize flight characteristics on the basis of defined mission parameters.
[004] It is an objective of this disclosure to provide a multi-rotor UAV, and a
method of controlling such a UAV that provides optimal implementation of diverse and dynamically changing mission requirements.
BRIEF SUMMARY OF THE INVENTION
[005] This summary is provided to introduce a selection of concepts in a simple
manner that is further described in the detailed description of the disclosure. This
summary is not intended to identify key or essential inventive concepts of the
subject matter nor is it intended for determining the scope of the disclosure.
[006] The objective of this disclosure is achieved by partitioning the available
number of rotors on the basis of the desired mission requirements into a plurality
of independently controlled sets of rotors each such set being dedicated to
controlling a corresponding operating parameter group comprising one or more of
said operating parameters, measuring each of the operating parameters in each
group, and controlling each rotor in each said set to regulate operating parameter
group corresponding to the set, so as to meet said mission requirements optimally.
[007] The partitioning of the rotors results in a separation of functions
performed by each rotor or set of rotors. For instance, the separation of controlling the vertical thrust component and the horizontal thrust components may enable the operation of the one or more motors at the maximum efficiency possible for the required flight parameters. Further, this method may also provide the advantage of reducing the computational load on the controller. This may result

from the fact that the controller is not required to calculate the angular velocities of each of the motors in the first set all the time during a flight. The computational load may also be reduced by the reduction in the number of motors whose angular velocities are required to be controlled.
[008] The portioning can be extended to any desired number of sets
depending on specific mission requirements and could also be implemented dynamically. Specific embodiments may relate to two or three sets of rotors but the disclosure is not limited to such embodiments.
[009] A system for controlling a flight of an unmanned aerial vehicle
comprising a plurality of motors is disclosed. The system comprises a first memory, first group of one or more sensors, and a first processor communicatively coupled to the first memory and the first group of sensors, the first processor configured for measuring one or more operating parameters of the unmanned aerial vehicle in flight. The first processor further retrieves one or more mission data from the first memory. The first processor further selects a first set of one or more motors out of the plurality of motors for operating substantially for providing the unmanned aerial vehicle with a vertical thrust component for controlling an altitude of the unmanned aerial vehicle. The first processor further selects a second set of one or more motors for operating substantially for moving the unmanned aerial vehicle in a chosen direction along a horizontal plane at a chosen speed. The first processor further controls an angular velocity of each of the motors selected for substantially controlling the altitude of the unmanned aerial vehicle and an angular velocity of each of the motors for substantially controlling the direction of flight and the speed of flight of the unmanned aerial vehicle. The altitude and the chosen direction and speed are each based on one or more mission data and the electric motor characteristics. Herein, electric motor characteristics means the data regarding the relationships between at least the angular velocity, electric motor current, and torque of the electric motors. The first processor further sets all the motors other than the first set of one or more motors and the second set of one or more motors in a de-energized state. Further, it is to be understood that the controller controls the angular velocity of the electric motor

by issuing an appropriate command to the power controller or drive delivering the
electrical energy to the electric motor. The drive, in turn, delivers power at the
appropriate voltage, frequency, and current in a known way, in the field of electric
motor controllers, to achieve the commanded angular velocity of the motor. In
case of a DC motor, the frequency mentioned above is understood to be zero.
[0010] Thus, a system for controlling a flight of an unmanned aerial vehicle
comprising a plurality of motors is disclosed wherein the system comprises, a first memory, and a first processor coupled to the first memory configured for measuring one or more operating parameter of the unmanned aerial vehicle in flight, retrieving one or more mission data, selecting a first one or more motors from the of the plurality of motors for operating substantially for providing the unmanned aerial vehicle with a vertical thrust component for controlling an altitude of the unmanned aerial vehicle, selecting a second one or more motors for operating substantially for moving the unmanned aerial vehicle in a chosen direction on a horizontal plane, controlling an angular velocity of each of the motors selected for controlling the altitude of the unmanned aerial vehicle and controlling the direction of flight of the unmanned aerial vehicle, wherein the altitude and the chosen direction are each based on one or more mission data, and setting the motors other than the first one or more motors and the second one or more motors in an un-energized state.
[0011] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. The disclosure describes and explains the disclosed method and system with additional specificity and detail along with the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES
[0012] The disclosure will be described and explained with additional specificity
and detail with the accompanying figures in which:
[0013] FIGS. 1A and 1B illustrates an unmanned aerial vehicle in accordance
with one exemplary embodiment of the present disclosure;
[0014] FIG. 1C illustrates an environment of the unmanned aerial vehicle, in
accordance with one embodiment of the present disclosure;
[0015] FIG. 1D illustrates a ground station, in accordance with one
embodiment of the present disclosure;
[0016] FIGS. 2A, 2B, 2C and 2D illustrate operation of motors of the
unmanned aerial vehicle, in accordance with one exemplary embodiment of the
present disclosure.
[0017] FIG. 3 illustrates a method for controlling a flight of an unmanned
aerial vehicle, in accordance with one embodiment of the present disclosure.
[0018] Further, persons skilled in the art to which this disclosure belongs will
appreciate that elements in the figures are illustrated for simplicity and may not
have been necessarily been drawn to scale. Furthermore, in terms of the
construction of the device, one or more components of the device may have been
represented in the figures by conventional symbols, and the figures may show
only those specific details that are pertinent to understanding the embodiments of
the present disclosure so as not to obscure the figures with details that will be
readily apparent to those of ordinary skill in the art having benefit of the
description herein.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present disclosure relates to a method for controlling the flight of
an unmanned aerial vehicle. The unmanned aerial vehicle comprises a plurality of motors. The angular velocity of each of the motors may be controlled dynamically during flight, based on a plurality of operational parameters and mission data. Each of the motors are set to one of a passive state (that is, the first set), an active

state (that is, the second set), or an off state (that is, un-energized set). Upon setting, the angular velocities of the motors are controlled to control the flight of the unmanned aerial vehicle for maximizing an electrical efficiency of the unmanned aerial vehicle or for maximizing an agility of the unmanned aerial vehicle or both. In addition, the configuration of the motors in one of an active state, a passive state or an off state also improves the stability of the unmanned aerial vehicle during flight.
[0020] For the purpose of promoting an understanding of the principles of the
disclosure, reference will now be made to embodiments illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications to the disclosure, and such further applications of the principles of the disclosure as described herein being contemplated as would normally occur to one skilled in the art to which the disclosure relates are deemed to be a part of this disclosure.
[0021] It will be understood by those skilled in the art that the foregoing
general description and the following detailed description are exemplary and
explanatory of the disclosure and are not intended to be restrictive thereof.
[0022] The terms "comprises", "comprising", or any other variations thereof,
are intended to cover a non-exclusive inclusion, such that a process or method that
comprises a list of steps does not include only those steps but may include other
steps not expressly listed or inherent to such a process or a method. Similarly, one
or more devices or sub-systems or elements or structures or components preceded
by "comprises... a" does not, without more constraints, preclude the existence of
other devices, other sub-systems, other elements, other structures, other
components, additional devices, additional sub-systems, additional elements,
additional structures, or additional components. Appearances of the phrase “in an
embodiment”, “in another embodiment” and similar language throughout this
specification may, but do not necessarily, all refer to the same embodiment.
[0023] Unless otherwise defined, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary skill in the

art to which this disclosure belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
[0024] Embodiments of the present disclosure will be described below in detail
with reference to the accompanying figures.
[0025] Referring to FIGS. 1A and 1B, an unmanned aerial vehicle 100 is
shown, in accordance with one exemplary embodiment of the present disclosure. The unmanned aerial vehicle 100 comprises a platform 105. The platform 105 may house the components of the unmanned aerial vehicle 100. The unmanned aerial vehicle 100 further comprises a plurality of motors 110-1, 110-2…110-m (henceforth called rotor 110) structurally supported by the platform 105. In one embodiment, the unmanned aerial vehicle 100 is a rotary wing unmanned aerial vehicle having a number of motors, for example, 18, 16, 8, 6 or 4 motors. Each of the motors 110-1, 110-2…110-m is mechanically coupled to a propeller. In one example, the electric motor may be a brushless DC motor. Further, the platform of the unmanned aerial vehicle may be configured for changing a radial position of each of the rotors 110 around an axis of the unmanned aerial vehicle. This change is to aid a control mechanism in achieving stability. In other words, the position, as described above, of each of the rotors 110 may be changed to aid the control algorithm.
[0026] The unmanned aerial vehicle 100 further comprises a control unit 115.
The control unit 115 may be housed on the platform 105. In one embodiment, the control unit 115 may comprise at least one first processor 120, a first Input/output (I/O) Interface 125 and a first memory 130. In one implementation, the processor 120, the first I/O interface 125 and the first memory 130 may be accommodated in the platform 105. The at least one first processor 120 may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, or any device that manipulates signals based on operational instructions or any suitable combination thereof. Among other capabilities, the at least one first processor 120 is configured to fetch and execute computer-readable instructions stored in the first memory 130.

[0027] The first I/O interface 125 may include a variety of software and
hardware interfaces. The first I/O interface 125 may allow the platform 105 to interact with a ground station (as shown in FIG. 1C) or with other unmanned aerial vehicles. The first I/O interface 125 may facilitate multiple communications within a wide variety of wireless networks and protocol types including wired networks, for example, LAN, cable, etc., and wireless networks, such as WLAN, cellular, radio, or satellite. The wireless protocols may include WLAN, cellular, or satellite based networks.
[0028] The first memory 130 may include any computer-readable medium
known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), or non-volatile memory, such as read only memory (ROM), erasable programmable ROM and flash memories or any suitable combination thereof.
[0029] The unmanned aerial vehicle 100 may further comprise a plurality of
sensors 132-1, 132-2, 132-3. . . 132-p (henceforth called sensors 132). The sensors 132 include, but are not limited to, load sensors, level sensors, gyroscopes, accelerometers, anemometers, magnetic compass, magnetometers, wind vanes, inertial measurement units (IMU), cameras, proximity sensors and Global Positioning System (GPS). In one example, the load sensors or the level sensors or both may be used by the first processor 120 to determine a mass or quantity of the payload. The gyroscopes, accelerometers, IMU, magnetic compass or magnetometers may be used by the first processor 120 to determine the speed and direction of flight of the unmanned aerial vehicle 100. The proximity sensors may be used by the first processor 120 to determine the height of the unmanned aerial vehicle 100 from the ground or objects on the ground or both, during flight. In addition, the proximity sensors may also be employed by the first processor 120 to detect obstructions in the path of the unmanned aerial vehicle 100. The proximity sensors may employ one or more of a SONAR, LIDAR, or any other suitable technology. Further, wind vanes along with anemometers may be used by the first processor 120 to determine the absolute or relative velocity and direction of wind. The outputs from the sensors 132 are further processed by the first processor 120

to measure operating parameters of the unmanned aerial vehicle 100. The operating parameter may include, but not limited to, yaw, roll, pitch, speed, acceleration, along with the direction of each of them, and climb rate and altitude of the unmanned aerial vehicle 100, mass or quantity of payload carried by the unmanned aerial vehicle 100, velocity of wind and direction of wind. Other parameters such as relative humidity and air temperature and any other parameter that may affect the flight and performance of the unmanned aerial vehicle 100 may also be thought of and are to be considered a part of the parameters just mentioned.
[0030] The unmanned aerial vehicle 100 may further comprise a plurality of
payloads 135-1, 135-2…135-n. Further, each of the payloads 135-1, 135-2 . . . 135-n may be mechanically attached, detachably or otherwise, and also communicatively coupled to the first processor 120. In other words, the first processor 120 may communicate or operate one or more of the payloads 135-1, 135-2…135-n during flight.
[0031] In one embodiment, the first processor 120 of the unmanned aerial
vehicle 100 may be based on a Field Programmable Gate Array (FPGA) platform. The FPGA platform may comprise a plurality of embedded processors. Further, the FPGA platform may be dynamically reconfigured at run-time depending on the requirements of the mission and the payload being activated for real-time requirements. For example, consider that the unmanned aerial vehicle 100 is used for farming applications in a field. The unmanned aerial vehicle 100 may have two missions: spraying of pesticides, and monitoring of crops. The unmanned aerial vehicle 100 may comprise an aerial pesticide sprayer (payload 135-1) for spraying of pesticides. The aerial pesticide sprayer may be manually filled by a user, with pesticide of desired concentration prior to flight. Further, the unmanned aerial vehicle 100 may spray the pesticide over the field during flight using a suitable spraying mechanism. The unmanned aerial vehicle 100 may further comprise a camera (payload 135-2) for monitoring of crops. The images captured by the camera may be processed by an image processor, for example by the first processor 120, to determine the health of the crops or infestation. The unmanned

aerial vehicle 100 may, actuate the aerial pesticide sprayer or the camera during flight based on the mission.
[0032] The unmanned aerial vehicle 100 may further comprise a power source
(not shown) for electrically powering the components of the unmanned aerial
vehicle 100. In one example, the power source may be a Lithium Polymer (LiPo)
battery. It may also be any other type of suitable battery or electrical energy
storage device. The components include the first processor 120, the sensors 132, a
sprayer, electric motors and the motor controllers and any such components.
[0033] Referring to FIG. 1C in conjunction with FIGS. 1A and 1B, an
environment of an unmanned aerial vehicle 100 is shown, in accordance with one embodiment of the present disclosure. The unmanned aerial vehicle 100 is configured for being in communication with a ground station 140.
[0034] In one embodiment, the ground station 140 may comprise at least one
second processor 145, a second I/O interface 150 and a second memory 155 as shown in FIG. 1D. The at least one second processor 145 may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, any device that manipulate signals based on operational instructions or any suitable combination thereof. Among other capabilities, the at least one second processor 145 is configured to fetch and execute computer-readable instructions stored in the second memory 155.
[0035] The second I/O interface 150 may include a variety of software and
hardware interfaces, for example, a web interface, a graphical user interface, and the like. The second I/O interface 150 may allow the ground station to interact with the unmanned aerial vehicle 100. The second I/O interface 150 may facilitate multiple communications within a wide variety of networks and protocol types, including wired networks, for example, LAN, cable, etc., and wireless networks, such as WLAN, cellular, or satellite. In one implementation, the ground station 140 may communicate with the unmanned aerial vehicle 100 over a wireless telemetry link.

[0036] The second memory 155 may include any computer-readable medium
known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes.
[0037] The ground station 140 may comprise, but not limited to, a personal
computer, a mobile phone and a remote control unit. Further, the ground station 140 may be installed with an application that enables the ground station 140 to communicate with the unmanned aerial vehicle 100. In one implementation, the ground station 140 receives operational parameters measured by the sensors 132 from the unmanned aerial vehicle 100. Based on the operational parameters and a mission data, the ground station 140 may generate control signals that may be transmitted to the unmanned aerial vehicle 100 for controlling the rotors. The mission data may include, but not limited to, trajectory, altitude, mission time, speed, distance to be covered and direction of flight. In one example, the ground station 140 may determine the mission data based on inputs provided by the user. For example, during a stormy weather, the user may want the unmanned aerial vehicle 100 to maintain a certain altitude for example 10 meters above ground. The user may provide inputs to the ground station 140 to maintain the unmanned aerial vehicle 100 at the altitude at 10 meters. In another example, the ground station 140 may determine the mission data based on a previous mission carried out by the unmanned aerial vehicle 100.
[0038] In another implementation, the mission data may be stored in the first
memory 130 of the unmanned aerial vehicle 100. More specifically, the unmanned aerial vehicle 100 is set up by a user, to store in the first memory 130, the mission data, prior to flight. The first memory 130 is further configured to store the electric motor characteristics, organized to be in a machine readable form. Further, the control unit of the unmanned aerial vehicle 100 may generate the control signals for controlling the motors based on the mission data, the motor characteristics, and the operational parameters measured by the sensors. The

process of controlling the motors based on mission data and the operational parameters is explained with reference to FIG. 2A and FIG. 2B.
[0039] Referring to FIG. 2A and FIG. 2B, an unmanned aerial vehicle 200 is
shown in accordance with one exemplary embodiment of the present disclosure. Consider that the unmanned aerial vehicle 200 is used for a farming application. Further, consider that the unmanned aerial vehicle 200 has eight rotors 210-1, 210-2, 210-3…210-8 (henceforth called rotors 210). The unmanned aerial vehicle 200 may have two missions: spraying of pesticides and monitoring of crops in a farmland. The unmanned aerial vehicle 200 may comprise an aerial pesticide sprayer detachably attached to it or otherwise, for spraying of pesticides and a camera for monitoring of crops. Based on the outputs from the sensors on board the unmanned aerial vehicle 200, a first processor (for example, first processor 120) measures at least one operating parameter associated with the unmanned aerial vehicle 200. Based on the at least one operating parameter measured the first processor determines at least one operating parameter.
[0040] In one example, the operating parameter may be a mass of payload
carried by the unmanned aerial vehicle 200. Now, consider that the mission is spraying of pesticides. The aerial pesticide sprayer may be filled with pesticide of desired concentration. As the unmanned aerial vehicle 200 flies over the farmland, pesticide may be dispensed from the aerial pesticide sprayer. Consequently, the quantity of pesticide in the aerial pesticide sprayer decreases. In other words, the mass of the payload decreases. Upon determining the change in the operating parameter, the first processor may retrieve at least one mission data associated with the mission from a ground station (for example, ground station 140) or a first memory (for example, first memory 130) of the unmanned aerial vehicle 200. As already explained, the mission data may include, but is not limited to, trajectory, altitude, mission time, speed, distance to be covered and direction of flight. Based on the mission data retrieved and the operating parameter, the first processor determines a state for each of the motors 210. The state of each of the motors 210 may be one of an active state, a passive, and an off state. In the active state, the rotor, for example, rotor 210-1, is configured to move the unmanned aerial vehicle

200 in a chosen direction in a horizontal plane. In other words, the motors in active state assist in navigation of the unmanned aerial vehicle 200 in the chosen direction by providing substantially a horizontal thrust component. Further, the motors in active state also ensure the stability of the unmanned aerial vehicle 200 during flight. In one embodiment the orientation of the motors may also be changed to alter the horizontal thrust component, upon changing to active state. In the passive state, the angular velocity of the rotor, for example, rotor 210-2, is controlled for providing substantially a vertical thrust component for manipulating an altitude of the unmanned aerial vehicle 200. In other words, the motors in passive state control the height of the unmanned aerial vehicle 200 from ground level. Further, the motors that are not set in either the passive state or the active state are set to an off state by de-energizing them. In other words, the first processor sets or configures a first set of one or more motors in the passive state, a second set of one or more motors in the active state and the remaining motors to off state.
[0041] Further, the unmanned aerial vehicle is configured for an exchange of
operating parameters such as the number of motors in the active state, the number of motors in the passive state, the number of motors in the off state, the loads and angular velocities of each of the motors, the positions of the motors in each of the states with respect to a predetermined reference point on the platform of the unmanned aerial vehicle. This data, so exchanged, is for controlling the angular velocities of each of the motors for achieving mission requirements as specified in the mission data and for achieving and maintaining stability of the unmanned aerial vehicle.
[0042] Consider that the unmanned aerial vehicle 200 is taking off from
ground level. In order to take off, each of the motors 210-1, 210-2…210-8 are set at the same angular velocity. Consequently, the unmanned aerial vehicle 200 starts ascending and hovering. Upon hovering, the first processor sets the motors 210-1, 210-8, 210-5 and 210-4 to active state while the motors 210-2, 210-3, 210-6 and 210-7 are set to passive state (assuming that the motors 210-1 and 210-8 are on the front end and the motors 210-4 and 210-5 are on the rear end of the

unmanned aerial vehicle 200 with respect to the direction of flight). Further, the angular velocities of the motors 210-1 and 210-8 are set lower than the angular velocities of the motors 210-4 and 210-5. Consequently, the rear end of the unmanned aerial vehicle 200 is lifted upwards causing the unmanned aerial vehicle 200 to tilt at an angle Ø as shown in FIG. 2C. Now, the motors in active state, that is, the motors 210-1, 210-8, 210-5 and 210-4 contribute to controlling the horizontal thrust component for propelling the unmanned aerial vehicle 200 in a forward direction. This is because, when the angular velocities of the motors 210-1 and 210-8 are lower than the angular velocities of the motors 210-4 and 210-5, a force F (thrust) is generated. More specifically, the force F is perpendicular to the direction of rotation of the motors 210-8, 210-1, 210-4 and 210-5. Further, the force F may be resolved into two components: a vertical thrust component FcosƟ, where Ɵ = 90º- Ø, and a horizontal thrust component FsinƟ. The vertical thrust component FcosƟ propels the unmanned aerial vehicle 200 in a vertical direction. In other words, the vertical thrust component FcosƟ controls the altitude of the unmanned aerial vehicle 200. The horizontal thrust component FsinƟ propels the unmanned aerial vehicle 200 in a horizontal direction. In other words, the horizontal thrust component FsinƟ controls the direction of flight of the unmanned aerial vehicle 200. More specifically, the horizontal thrust component FsinƟ is produced due to the difference in angular velocities of the front and rear rotors. As the difference in angular velocities of the front and rear motors increases, the horizontal thrust component FsinƟ increases, that is, the speed of the unmanned aerial vehicle 200 in the forward direction increases. Further, the angular velocities of each of the motors 210-8, 210-1, 210-4 and 210-5 are controlled by the first processor for manipulating the direction of flight of the unmanned aerial vehicle 200 in the horizontal plane. In one embodiment, the positions of the rotors may also be changed to alter the horizontal thrust component such that active motors can operate at or close to peak efficiency while still maintaining the desired mission profile.
[0043] In order to keep the unmanned aerial vehicle 200 afloat, a vertical thrust component is generated substantially by the motors 210-2, 210-3, 210-6 and 210-

7 in the passive state. In other words, the motors 210-2, 210-3, 210-6 and 210-7 are used for controlling the altitude of the unmanned aerial vehicle 200. In one implementation, the motors 210-2, 210-3, 210-6 and 210-7 may be configured to have the same angular velocity, that is, all the motors in passive motors may contribute an equal amount of vertical thrust component. In one embodiment the position of the motors may also be changed to alter the vertical thrust component such that passive motors can operate at or close to peak efficiency while still maintaining the desired mission profile. Further, the vertical thrust component produced by each of the motors in the active and passive states contribute to a total thrust. The total thrust may be manipulated by controlling the angular velocities of each of the rotors. More specifically, the first processor may ensure stability of the unmanned aerial vehicle 200 by controlling the angular velocities of the motors in active and passive states such that, the total thrust is balanced against a total take-off weight, in other words weight of unmanned aerial vehicle combined with payload weight.
[0044] In the present example, the unmanned aerial vehicle 200 performs
similar to a quad-copter. This is because, the direction of flight and the stability of the unmanned aerial vehicle 200 are manipulated by controlling only the four motors 210-8, 210-1, 210-4 and 210-5 in active state out of the total eight rotors. Consequently, the control algorithm required is simpler.
[0045] It may be understood from the above description that the setting of
motors in passive state and active state enables decoupling of controls for actively controlling the vertical thrust component from the navigation and stability. More specifically, the motors in passive state primarily control the vertical thrust component and the motors in active state primarily control the navigation and stability while also contributing to the vertical thrust component. As a result, the electrical efficiency and the agility of the unmanned aerial vehicle 200 may be improved. In order to explain improvement in electrical efficiency, consider an example where payload is constant and UAV is required to operate within a range of speed values. Accordingly, all motors in the active state are configured to operate at angular velocities which are required for UAV to achieve speed and

payload capacity specified by mission data while all motors in the passive state are configured to operate at a constant angular velocity, from within the peak efficiency zone of motors, which is sufficient to achieve payload capacity and altitude specified by mission data. In one embodiment the positions of both active and passive motors may also be changed to alter the horizontal and vertical thrust components such that both sets of motors can operate at or close to peak efficiency while still maintaining the desired mission profile. As a result, the electrical efficiency at which the motors are operated is improved.
[0046] Similarly, one or more of the motors in passive state may be de-
energized during descent of the unmanned aerial vehicle 200 for reducing the vertical thrust component. Upon reducing the vertical thrust component, the altitude of the unmanned aerial vehicle 200 is reduced. Further, as the motors in passive state are de-energized, the electrical efficiency of the unmanned aerial vehicle 200 is improved.
[0047] In case the unmanned aerial vehicle 200 is carrying reducing
(increasing) payload, the two independent control algorithms continuously monitor the mission data (altitude), thrust required for carrying the changing payload, and motor performance levels. The control algorithm for motors in the passive state computes the operating parameters of motors in the passive state based on the motor characteristics of both passive and active rotors. Refreshed operating parameters may include de-energizing one or more motors in the passive state for reducing or the vertical thrust component or energizing one or more motors in the off state for increasing the vertical thrust component. Refreshed operating parameters are also sent to the controller of motors set to the active state for implementation.
[0048] It may be understood from the above explanation that de-energizing of
the motors in passive state does not have any impact on the control algorithm and the direction of flight, as the controls for motors in the passive and active states are separated. As a result, the stability of the unmanned aerial vehicle 200 is not affected.

[0049] The improvement in agility of the unmanned aerial vehicle 200 is
explained using FIG. 2D.
[0050] Referring to FIG. 2D in conjunction with FIG. 2A, FIG. 2B, and FIG.
2C, a path of the unmanned aerial vehicle 200 while spraying pesticides over crops is shown. The crops may be planted in rows R1, R2, and R3 as shown. Initially, the unmanned aerial vehicle 200 may traverse the row R1 in the direction shown by setting the motors 210-8, 210-1, 210-4, and 210-5 in active state and the motors 210-2, 210-3, 210-6, and 210-7 in passive state. Further, the angular velocities of the motors 210-1 and 210-8 may be set lower than the angular velocities of the motors 210-4 and 210-5, in order to propel the unmanned aerial vehicle 200 in the forward direction. Furthermore, the angular velocities of the motors 210-2, 210-3, 210-6, and 210-7 may be controlled to control the altitude of the unmanned aerial vehicle 200.
[0051] Upon reaching the end of row R1, the unmanned aerial vehicle 200 may
change the direction of flight by 90 degrees towards right, by setting the motors 210-2, 210-3, 210-6, and 210-7 to active state and the motors 210-8, 210-1, 210-4, and 210-5 to passive state. Further, the angular velocities of the motors 210-2 and 210-3 are set lower than the angular velocities of the motors 210-6 and 210-7. Furthermore, the unmanned aerial vehicle 200 may be propelled towards the row R2 by controlling the angular velocities of the motors 210-2, 210-3, 210-6, and 210-7 while the motors 210-8, 210-1, 210-4, and 210-5 control the altitude of the unmanned aerial vehicle 200.
[0052] Upon reaching row R2, the motors 210-8, 210-1, 210-4, and 210-5 are
set to active state and the motors 210-2, 210-3, 210-6, and 210-7 are set to passive state. Further, the angular velocities of the motors 210-4 and 210-5 are set lower than the angular velocities of the motors 210-1 and 210-8. Furthermore, the angular velocities of the motors 210-8, 210-1, 210-4, and 210-5 are controlled to propel the unmanned aerial vehicle 200 along the row R2, while the motors 210-2, 210-3, 210-6, and 210-7 control the altitude of the unmanned aerial vehicle 200. Upon reaching the end of row R2, the motors 210-2, 210-3, 210-6, and 210-7 are set to active state and the motors 210-8, 210-1, 210-5, and 210-4 are set to passive

state and the angular velocities are controlled as explained above. Similarly, the
unmanned aerial vehicle 200 may be maneuvered in any direction along the
horizontal plane by changing the states of the motors 210 and by controlling the
angular velocities of the motors 210. From the present example, it may be
understood that the direction of flight of the unmanned aerial vehicle 200 is
changed by reassigning or swapping of states for each of the motors 210-1, 210-
2…210-8. In other words, the unmanned aerial vehicle 200 changes the trajectory,
that is - the direction of flight, without any physical transformation or
reorientation of the platform. Consequently, the agility of the flight is improved.
[0053] It is possible that in one embodiment of an unmanned aerial vehicle,
disclosed herein, comprises motors having two or more characteristics.
[0054] Referring to FIG. 3, a method 300 of controlling flight of an unmanned
aerial vehicle comprising a plurality of motors is shown, in accordance with one
embodiment of the present disclosure.
[0055] The method begins at step 305.
[0056] At step 310, the available number of rotors are partitioned on the basis
of the mission requirements into a plurality of independently controlled sets of rotors each such set being dedicated at least to controlling a corresponding group of operating parameter of the UAV
[0057] At step 320, one or more operating parameters of the unmanned aerial
vehicle in flight are measured.
[0058] At step 330, each rotor in each set is controlled to regulate the operating
parameters of the group corresponding to the set, so as to meet the mission requirements optimally.
[0059] The method ends at step 340.
[0060] In one implementation of the method, in a further step, the controllers
retrieves the electric motor characteristics stored in the memory, say the first memory 130 or the second memory 155, and computes the selection of the motors to be set in the active state and the motors to be set in a passive state and the motors to be set in the off state and along with it the angular velocities of the

motors in the passives state and the motors in the passive state so as to achieve a
maximum possible electrical efficiency of the unmanned aerial vehicle.
[0061] The method 300 has been described in the general context of computer
executable instructions. Generally, computer executable instructions may include routines, programs, objects, components, data structures, procedures, modules, functions, etc., that perform particular functions or implement particular abstract data types. The method 300 may also be practiced in a distributed computing environment where functions are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, computer executable instructions may be located in both local and remote computer storage media, including memory storage devices.
[0062] The order in which the method 300 is described and is not intended to
be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method 300 or alternate methods. Additionally, individual blocks may be deleted from the method 300 without departing from the spirit and scope of the disclosure described herein. Furthermore, the method may be implemented in any suitable hardware, software, firmware, or combination thereof. However, for ease of explanation, in the embodiments described above, the method 300 may be implemented in the above-described unmanned aerial vehicle 100.
[0063] While specific language has been used to describe the disclosure, any
limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.
[0064] The figures and the foregoing description give examples of
embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need

not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.
[0065] The method of controlling the unmanned aerial vehicle disclosed herein
helps in maximizing electrical efficiency of the unmanned aerial vehicle. As a result, the unmanned aerial vehicle may fly for longer durations without recharging of the power source. Further, as the configuration for the motors is determined by the first processor of the unmanned aerial vehicle, the computational load on the ground station is reduced. Furthermore, the method does not require mechanical transformations in the motors of the unmanned aerial vehicle. As a result, the mechanical wear and tear is reduced. In addition, the method also improves agility and stability of flight of the unmanned aerial vehicle. As a result, the risk of endangering the mission and/or damaging the payload are reduced. More specifically, the unmanned aerial vehicle disclosed herein is better suited for industrial applications where bigger platforms are employed and stability is of prime importance.

We claim:
1. A method for optimizing the performance of a multi-rotor unmanned aerial
vehicle (UAV) on the basis of mission requirements, the method comprising
the steps of:
- partitioning the available number of rotors on the basis of said mission requirements into a plurality of independently controlled sets of rotors each such set being dedicated at least to controlling a corresponding group of operating parameter of the UAV;
- measuring the operating parameters of each group; and
- controlling each rotor in each said set to regulate the operating parameters of the group corresponding to the set, so as to meet said mission requirements optimally.

2. A method as claimed in claim 1 wherein said partitioning is modified dynamically on the basis of either alteration in mission requirements or changes in measured operating parameters or both.
3. A method as claimed in claim 1 or in claim 2 wherein said controlling comprises the adjustment of the angular velocity of the rotor.
4. A method as claimed in any of the preceding claims wherein said partitioning comprises three sets of rotors in which a first set of rotors is dedicated to controlling the altitude of the UAV, a second set of rotors is dedicated to controlling the characteristics of flight, and the third set of rotors are deactivated.
5. A method as claimed in any of the preceding claims wherein said mission requirements comprise maximizing an electrical efficiency of the unmanned aerial vehicle based on electric motor characteristics.

6. A method as claimed in any of the preceding claims wherein said mission requirements comprise maximizing an agility of the unmanned aerial vehicle.
7. A multi-rotor Unmanned Aerial Vehicle (UAV) comprising:

- one or more controllers configured to drive each of its rotors in accordance with mission requirements;
- one or more operating parameters sensors coupled to the inputs of said controllers; and
- one or more grouping mechanisms controlled by said controllers for selectively grouping the rotors into a plurality of sets in which each set of rotors is dedicated to the control of a corresponding operating parameter group on the basis of said mission requirements.

8. A multi-rotor UAV as claimed in claim 7 wherein said grouping mechanism is embedded in said controllers.
9. A multi-rotor Unmanned Aerial Vehicle (UAV) comprising:

- means for controlling each of its rotors in accordance with mission requirements;
- means for sensing one or more operating parameters and providing as input to said means for controlling said rotors; and
- means for selectively grouping the rotors into a plurality of sets under the command of said means for controlling said rotors in which each set of rotors is dedicated to the control of a corresponding operating parameter group on the basis of mission requirements.