Abstract:
Embodiments described herein relate to multicopters with separate engines to power each rotor, wherein the multicopters also include with unique controls to guide the multicopter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims a benefit of priority under 35 U.S.C. §119 to Provisional Application No. 62/184,837 filed on Jun. 25, 2015, which is fully incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments disclose systems and methods associated with a rideable multicopter. Specifically, embodiments are directed towards a multicopter with separate engines to rotate corresponding propellers, wherein the multicopter includes with unique controls to guide the multicopter. 
       BACKGROUND 
       [0003]    Multicopters are devices that are lifted and propelled by vertically oriented propellers. By varying the speed at which each propeller rotates, the multicopter may be controlled. Some experimental multicopters are comprised of two propellers to create the lift and use thrust vectoring to steer the vehicle. 
         [0004]    However, said experimental multicopters are typically unstable. Furthermore, multicopters that use electrical motors may be light, but they require a large battery. Current battery technology only allows multicopters to fly for a limited amount of time. 
         [0005]    Additionally, controls for conventional multicopters involve the use of two joysticks. The first joystick may control movement along a horizontal plane, and the second joystick may control altitude thrust and yawing. Yet, it is an arduous task to yaw on a single joystick without affecting altitude. 
         [0006]    Accordingly, needs exist for a multicopter with independent, combustion engine powered rotors with a control interface that separates yawing and altitude control. 
       SUMMARY 
       [0007]    Embodiments described herein relate to multicopters with separate engines to power each propeller, wherein the multicopters also include with unique controls to guide the multicopter. Embodiments of a multicopter utilize combustion engines, which will allow the multicopter to take advantage of the higher energy density of fossil fuels to have a much longer flight time. Additionally, each propeller of the multicopter may have a mechanically independent engine. This may allow the multicopter to maintain altitude control and perform user controlled emergency descents in the event of a single engine failure. 
         [0008]    Embodiments may also utilize a control interface that includes a first joystick to control horizontal plane movement, a second joystick to control altitudinal movement and braking, and a handle bar steering column to control yawing. 
         [0009]    These, and other, aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. The following description, while indicating various embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many substitutions, modifications, additions, or rearrangements may be made within the scope of the invention. The invention includes all such substitutions, modifications, additions or rearrangements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0011]      FIG. 1  depicts a perspective view of a multicopter, according to an embodiment. 
           [0012]      FIG. 2  depicts a top view of a multicopter, according to an embodiment. 
           [0013]      FIG. 3  depicts a side view of a multicopter, according to an embodiment. 
           [0014]      FIG. 4  depicts a front view of a control interface, according to an embodiment. 
           [0015]      FIG. 5  depicts a perspective view of a handle bar, according to an embodiment. 
           [0016]      FIG. 6  depicts a network topology of the computing systems of a multicopter, according to an embodiment. 
           [0017]      FIG. 7  depicts a propeller unit, according to an embodiment. 
           [0018]      FIG. 8  illustrates a method for a multicopter performing a braking operation or decelerating utilizing a position tracking system, according to an embodiment. 
           [0019]      FIG. 9  illustrates a method for a controlling a multicopter, according to an embodiment. 
       
    
    
       [0020]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present disclosure. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure. 
       DETAILED DESCRIPTION 
       [0021]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention. 
         [0022]      FIG. 1  depicts a perspective view of multicopter  100 , according to an embodiment. Multicopter  100  may include a frame  110 , landing rails  115 , gas tank  120 , first propeller unit  125 , second propeller unit  130 , third propeller unit  135 , fourth propeller unit  140 , and control interface  145 . 
         [0023]    Frame  110  may be a structural system that supports other components of multicopter  100 . Frame  110  may be comprised of a first beam that extends along a major axis of multicopter  110 , and second and third beams that extend along a minor axis of multicopter  110 . The beams may be assembled into an “H” shape. 
         [0024]    The first beam may have a longer length than the second and third beams, and be positioned perpendicular to the second and third beams. In use, a pilot of multicopter  110  may be positioned over first beam  110 . 
         [0025]    The second beam may be positioned at a distal end of the first beam, and the third beam may be positioned at a proximal end of the first beam, wherein the second beam and the third beam are in parallel to each other. The lower surfaces of second and third beams may be positioned above upper surfaces of the propeller units  125 ,  130 ,  135 ,  140 . In embodiments, the ends of the second beam may be positioned over centers of propeller units  125  and  130 , and the ends of the third beam may be positioned over centers of propeller units  135  and  140 . 
         [0026]    Landing rails  115  may be landing gear that is utilized to stabilize multicopter  100  during takeoff and landing. Additionally, landing rails may support a pilot&#39;s feet while in use. Landing rails  115  may be tubular landing skids that are positioned lower than the bottom of other elements of multicopter  100 . In embodiments, a distal end of landing rails  115  may be positioned underneath propeller units  125  and  130 , and a proximal end of landing rails  115  may be positioned underneath propeller units  135  and  140 . 
         [0027]    Gas tank  120  may be a device that is a safe container for flammable fluids. Fuel stored within gas tank  120  may be utilized to power propeller units  125 ,  130 ,  135 , and  140 . In embodiments, gas tank  120  may be positioned behind a pilot. However, gas tank  120  may be positioned at any desired location within or on multicopter  100 . 
         [0028]    Propeller units  125 ,  130 ,  135 ,  140  may each be engine subsystems configured to move multicopter  100 . Each propeller unit  125 ,  130 ,  135 , and  140  may include an engine, a propeller, a tachometer, a protection cage, and a position controlled motor. 
         [0029]    Each engine may be a combustion engine that is configured to generate mechanical power by combustion of fuel. Each engine may be configured to independently receive fuel from gas tank  120  via a fuel line. Additionally, each engine may be configured to independently power a corresponding propeller. Therefore, in the event of a single engine failure for a propeller unit, the engines of the other propeller units may still function. 
         [0030]    Each propeller may be a type of fan that transmits power by converting a rotational motion into thrust. A pressure difference is produced between the upper and lower surfaces of the propeller. In embodiments, each of the propellers may be configured to rotate around a fixed axis, which may be positioned under an end of second or third beams. The fixed axis of rotation for each propeller may allow the propellers to a have a direction of rotation that is in parallel with a ground surface when multicopter  100  is positioned on a flat, planar surface. 
         [0031]    Furthermore, propellers positioned diagonally across from each other may rotate in the same direction, while adjacent propellers may rotate in the opposite direction. For example, propeller units  125  and  135  may rotate in a clockwise direction, while propeller units  130  and  140  may rotate in a counter clockwise direction. A first pair of propeller units  125  and  135  and a second pair of propeller units  130  and  140  may operate together to exert a net yaw torque as desired. 
         [0032]    The tachometers may be an instrument configured to measure the rotation speed of a corresponding propeller. The tachometers may be configured to measure the rotation speed of the propellers in revolutions per interval of time. 
         [0033]    The protection cages may be configured to encompass the propellers to protect the propellers and exterior objects from the propellers. The protection cages may be comprised of a tube frame that allows the propellers to move air, while limiting objects coming in direct contact with the propellers. 
         [0034]    The position controlled electronic motors are configured to control the throttle of its corresponding propeller engine. In embodiments, the position controlled motors may be controlled by a control computer utilizing a position feedback loop via an electronic motor position encoder. The position encoder may communicate position data associated with a throttle position of a propeller engine to a processor linked with the position control motor. The tachometer will transmit propeller engine speed data to the computer. The computer may analyze the throttle position data and the tachometer data to determine an appropriate desired throttle position to command each electronic motor with and dynamically change the rotation rate of the corresponding propeller engine to achieve a desired propeller speed 
         [0035]    Control interface  145  may be a device configured to control the positioning of multicopter  100  based on receiving commands from a pilot. Control interface  145  may include a computer. 
         [0036]    The computer may be configured to transmit real-time commands to the individual engine subsystems, and receive real-time data from the individual engine subsystems and the control interface  145 . In embodiments, the commands may be based on a control algorithm to determine a desired rotational speed of each propeller. The control algorithm may be a closed feedback loop that is based on orientation data and acceleration data from the inertial measurement unit. 
         [0037]    The control interface may be configured to allow the pilot to control the yaw, pitch forward and back (i.e. accelerate forward and backward), roll left and right (i.e. accelerate left and right), and ascend and descend. In embodiments, the control interface may include a steering column and two handle bars. 
         [0038]    The steering column may be positioned between the two handle bars, and the steering column may be configured to turn axially. Responsive to the steering column being turned, the steering column may transmit yaw command data to the computer. The steering column yaw data may indicate a desired magnitude of the yawing angular velocity of the vehicle that is proportional the angle offset of the handlebars. The steering column may be coupled to an electric motor, wherein the motor is configured to constantly center the steering column in a straight, upright position with slight torque. This upright position may indicate a zero offset of the steering column. This slight torque received by the steering column from the electric motor may provide the pilot with a haptic sensation that is the equivalent of that of a virtual torsional spring on the steering column so that the handle bars return to the zero offset in the event the pilot disengages with the handle bars. 
         [0039]    The handle bars may be configured to receive the arms of the pilot and receive force from the pilot. Responsive to the pilot applying force to the handle bars the steering column may turn. Additionally, the two handle bars may each include a two axis thumb stick and a trigger. 
         [0040]    A first handle bar may be configured to control horizontal plane motion. Responsive to the thumb stick on the first handle bar being moved or the trigger being pressed, corresponding acceleration command data may be transmitted to the computer. In embodiment, the first handle bar may be the right handle bar or the left handle bar. 
         [0041]    In embodiments, the transmitted acceleration command data may correspond to an angle or direction at which the thumb stick is pressed, and the transmitted acceleration command data may also be proportional to the angle at which the thumb stick is pressed. For example, when a first thumb stick is moved forward or backward, fine forward acceleration or fine backward acceleration command data may be transmitted to the computer, respectively. Furthermore, when the first thumb stick is fully pressed forward, the acceleration data may correspond with a greater forward acceleration rate than a partially forward pressed first thumb stick. 
         [0042]    Additionally, when the first thumb stick is moved left or right, fine strafe left acceleration command data or fine strafe right acceleration command data may be transmitted to the computer, respectively. Fine strafe acceleration data may be configured to provide limited sideways acceleration to the multicopter  100 . 
         [0043]    Responsive to the trigger on the first handle bar being pressed, acceleration command data corresponding to a forward motion may be transmitted to the computer. In embodiments, the acceleration command data associated with a pressed trigger may be associated with a greater maximum acceleration than the acceleration command data associated with an angled thumb stick. When the pilot fully presses the trigger on the first handle bar, the transmitted acceleration data may correspond to a maximum forward acceleration at which the multicopter may move. The trigger may correspond to only forward acceleration to encourage piloting the vehicle at high speeds only in the direction in which the pilot is facing. 
         [0044]    A second handle bar may be configured to control altitude and braking. Responsive to the thumb stick being moved or the trigger being pressed, corresponding altitude control command data and braking command data may be transmitted to the computer, respectively. In embodiments, the second handle bar may be the right handle bar or the left handle bar. 
         [0045]    The altitude control command data may correspond to an angle or direction at which the thumb stick on the second handle bar is pressed, and may also be proportional to the angle at which the thumb stick on the second handle bar is pressed. For example, moving the second thumb stick to the left may transmit vertical movement command data to the computer associated with an ascending acceleration, and moving the second thumb stick to the right may transmit vertical movement data to the computer associated with a descending acceleration. When the second thumb stick is pressed further to the right or to the left, the data may command a greater acceleration. Movements of the second thumb stick forward or backwards may not cause any movement command data to be transmitted. 
         [0046]    In embodiments, the second thumb stick may include a spring or other zeroing mechanism to return the second thumb stick to the center of the left-right axis of the second thumb stick but may not include a spring in the up-down axis. In conventional multicopters, the spring-less axis is used to control altitude acceleration and it may be difficult to maintain a fixed vertical height. To alleviate strain on a pilot&#39;s focus, upon start-up of multicopter  100 , a counter-acceleration to gravity to maintain multicopter  100  at a fixed height may be determined. A pilot may be able to specify this counter-acceleration by using the second joystick to determine an ascending acceleration that will result in multicopter  100  maintaining a constant altitude. Upon moving the second thumb stick to determine the counter acceleration of gravity, this counter-acceleration data may be transmitted and stored on the computer. Then, when the pilot lets go of the second thumb stick, the computer will maintain this counter-acceleration at the thumb stick neutral position to maintain constant altitude. 
         [0047]      FIG. 2  depicts a top view of multicopter  100 , according to an embodiment. Elements depicted in  FIG. 2  may be substantially the same as those described above. Therefore, for the sake of brevity an additional description of these elements is omitted. 
         [0048]    As depicted in  FIG. 2 , each of the propeller units  125 ,  130 ,  135 ,  140  may be set equidistance from a major axis of multicopter  100 , with propeller units  125  and  130  being positioned behind the pilot and propeller units  135  and  140  being positioned in front of the pilot. In embodiments, a distance between propeller units  125  and  130  may be less than a distance between propeller units  125  and  135 . 
         [0049]    As additionally depicted in  FIG. 2 , the ends of landing rails  115  may be positioned between the second beam  220  and the third beam  230 , wherein first beam  210  may be positioned between landing rails  115 . 
         [0050]      FIG. 3  depicts a side view of multicopter  100 , according to an embodiment. Elements depicted in  FIG. 3  may be substantially the same as those described above. Therefore, for the sake of brevity an additional description of these elements is omitted. 
         [0051]    As depicted in  FIG. 3 , the ends of landing rails  115  may be positioned under the corresponding propeller units  125 ,  130 ,  135 ,  140 . Additionally, a front end  310  of landing rails  115  may be angled at an incline. This may allow multicopter  100  to more safely takeoff and land. 
         [0052]      FIG. 4  depicts a front view of control interface  145 , according to an embodiment.  FIG. 5  depicts a perspective view of a handle bar  500 , according to an embodiment. Elements depicted in  FIGS. 4 and 5  may be substantially the same as those described above. Therefore, for the sake of brevity an additional description of these elements is omitted. 
         [0053]    As depicted in  FIG. 4 , control interface  145  may include a computer  410 , a steering column  420 , a first handle bar  430 , and a second handle bar  430 . 
         [0054]    Computer  410  may include a processing device, a communication device, a memory, and a graphical user interface. It may be understood that computer  410  may include a plurality of processing devices, communication devices, memories, and graphical user interfaces. 
         [0055]    The processing devices can include memory, e.g., read only memory (ROM) and random access memory (RAM), storing processor-executable instructions and one or more processors that execute the processor-executable instructions. In embodiments where the processing device includes two or more processors, the processors may operate in a parallel or a distributed manner. The processing devices may execute an operating system of multicopter  100  or software associated with other elements of multicopter  100 . 
         [0056]    The communication device may be a device that allows computer  410  to communicate with other devices associated with multicopter  100 , such as the embedded systems or position tracking system. The communication device may include one or more wireless transceivers for performing wireless communication and/or one or more communication ports for performing wired communication. The communication device may be utilized to communicate data to each of the propeller units to control the angular speed of each propeller based in part on the acceleration data and the vertical offset data. 
         [0057]    The memory device may be a device configured to store data generated or received by computer  410 . The memory device may include, but is not limited to a hard disc drive, an optical disc drive, and/or a flash memory drive. 
         [0058]    The user interface may be a device that allows a user to interact with computer. While one user interface is shown, the term “user interface” may include, but is not limited to being, a touch screen, a physical keyboard, a mouse, a camera, a video camera, a microphone, and/or a speaker. Utilizing the user interface, a pilot may set data associated with multicopter  100 , such as a counter-acceleration to gravity to maintain multicopter  100  at a fixed altitude. 
         [0059]    Steering column  420  may be a device that is physically coupled to an electric motor, first handle bar  440  and second handle bar  430 , and electronically connected to computer  410 . Steering column  420  may be configured to transfer the pilots input torque to the electric motor. The electric motor may be configured to continuously provide gentle torque to reset steering column in a straight, upright position. This gentle torque from the electric motor may provide a haptic sensation of a torsional spring on steering column  420 , such that steering column  420  returns to a zero offset if the pilot provides no force upon steering column  420 . 
         [0060]    Responsive to the steering column  420  being turned via first handle bar  440  and/or second handle bar  430 , yaw data may be transmitted from the steering column  420  to the computer  410 . The yaw data may include direction data and magnitude data associated with the yawing angular velocity that is proportional to the angular offset of first handle bar  440  and second handle bar  430 . In embodiments, the greater the magnitude of the yawing, the greater the rate of rotation of multicopter  100 . 
         [0061]    First handle bar  440  and second handle bar  430  may be positioned at opposite sides of steering column  420 . First handle bar  440  and second handle bar  430  may be inwardly angled. As depicted in  FIG. 5 , first handle bar  430 , which is substantially symmetrical and interchangeable with second handle bar  430 , may include a thumb stick  510  and a trigger  520 . The thumb stick  510  may be tilted in different directions, and the trigger  520  may be depressed. 
         [0062]      FIG. 6  depicts a network topology of the computing systems  600  of multicopter  100 , according to an embodiment. Elements depicted in  FIG. 6  may be substantially the same as those described above. Therefore, for the sake of brevity an additional description of these elements is omitted. 
         [0063]    As depicted in  FIG. 6 , control interface  145  may be coupled with computer  410 . The control interface  145  may be configured to transmit command data to control the movement of multicopter  110  via the propeller units  125 ,  130 ,  135 ,  140 . The inertial measurement unit  610  (IMU) may be configured to determine specific accelerations, geo-directional data, angular velocities and orientation of multicopter  100 . The data determined by inertial measurement unit  610  may be utilized to control the movement of multicopter  100 . 
         [0064]    Responsive to control computer receiving acceleration and yaw command data from control interface  145 , control computer may dynamically determine the desired shaft speed of each propeller based on a control algorithm and a closed loop feedback control structure, which utilizes the yaw command data, acceleration command data, and measurements determined by the inertial measurement unit  610 . 
         [0065]    The propeller units  125 ,  130 ,  135 , and  140  may be configured to receive data from the control computer to dynamically and independently change the rotation speed of each corresponding propellers. Tachometers associated with each of the propeller units  125 ,  130 ,  135 , and  140  may be configured to transmit a determined angular velocity of each corresponding propeller to the control computer. 
         [0066]      FIG. 7  depicts a propeller unit  125 , according to an embodiment. One skilled in the art may appreciate that the other propeller units include similar elements. Elements depicted in  FIG. 7  may be substantially the same as those described above. Therefore, for the sake of brevity an additional description of these elements is omitted. 
         [0067]    As depicted in  FIG. 7 , propeller unit  125  may include a DC motor driver  705 , DC motor  710 , DC motor encoder  715 , carburetor  720 , engine  725 , propeller shaft  730 , tachometer  735 , and propeller  740 . 
         [0068]    DC motor driver  705  may be a device that is configured to receive a throttle position command from computer  410 . DC motor driver  705  may also be configured to receive position data of the DC motor  710  via DC motor encoder  715 . Responsive to receiving the position data, DC motor driver  705  may be configured to determine an appropriate current to send to DC motor  710  to achieve a desired position. 
         [0069]    DC motor  710  may be an electrical machine that converts direct current electrical power into mechanical power. DC motor  705  may be configured to receive the electrical power from DC motor driver  705 , and in return create mechanical power. 
         [0070]    DC motor encoder  715  may be a device that is configured to communicate the actual position of the throttle to DC motor driver  705 . In embodiments, DC motor encoder  715  may be configured to transmit the angular position of the throttle to DC motor driver  705 . 
         [0071]    Carburetor  720  may be a device that blends air and fuel from the throttle for engine  725 . Engine  725  may be an internal combustion engine where the combustion of fuel occurs with an oxidizer, such as air, in a combustion chamber. The amount of air received by engine  725  may be based on the current supplied to DC motor  705 , wherein the amount of air received by engine determines the rotation speed of propeller shaft  730 . Responsive to propeller shaft  730  rotating, propeller  740  may also rotate and tachometer  735  may determine the angular velocity of propeller shaft  730 . Then, tachometer  735  may transmit the angular velocity of propeller shaft  730  to the control computer. 
         [0072]      FIG. 8  illustrates a method  800  for multicopter  100  performing a braking operation or decelerating utilizing position tracking and computed vectors. The operations of method  800  presented below are intended to be illustrative. In some embodiments, method  800  may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of method  800  are illustrated in  FIG. 8  and are described below is not intended to be limiting. 
         [0073]    In some embodiments, method  800  may be implemented in one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method  800  in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of method  800 . 
         [0074]    At operation  810 , a positioning system for determining the location of a multicopter in space may be implemented. The positioning system may include camera based localization systems that allow a computer to determine a multicopters spatial position and velocity vector. In other implementations, other positioning systems such as fiducial tracking motion capture systems or etc. may be utilized. 
         [0075]    At operation  820 , a movement vector associated with the directional movement and magnitude based on the speed of the multicopter may be determined. 
         [0076]    At operation  830 , a trigger associated with a second handle bar may be pressed, wherein the trigger corresponds to a braking operation. 
         [0077]    At operation  840 , acceleration command data associated with the braking operation may be transmitted from the control interface to the computer. 
         [0078]    At operation  850 , the computer may determine a braking vector. The braking vector is based on a vector opposite to the movement vector and the amount of the depression of the trigger. When the trigger is fully pressed, the magnitude of the deceleration vector commanded will be at a maximum safe deceleration vector determined by the control algorithms. 
         [0079]    At operation  860 , the computer may transmit commands to each of the propeller units to perform movements associated with the braking vector. 
         [0080]      FIG. 9  illustrates a method  900  for controlling multicopter  100 . The operations of method  900  presented below are intended to be illustrative. In some embodiments, method  900  may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of method  900  are illustrated in  FIG. 9  and described below is not intended to be limiting. 
         [0081]    In some embodiments, method  900  may be implemented in one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method  900  in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of method  900 . 
         [0082]    At operation  910 , a zero offset for the altitude acceleration data may be determined. The zero offset for the altitude acceleration data may be equal to a counter acceleration of gravity on the multicopter to maintain the multicopter at a fixed vertical height. 
         [0083]    At operation  920 , yaw data may be received that is proportional to the angular offset of a first handle bar and a second handle bar. The yaw data may include direction data and magnitude data. 
         [0084]    At operation  930 , horizontal plane acceleration command data may be received. The horizontal plane acceleration data may be received responsive to a thumb stick on the first handle bar being moved or trigger being pressed, wherein the horizontal plane acceleration data may be utilized to move the multicopter along a horizontal plane. 
         [0085]    At operation  940 , altitude acceleration data may be received. The altitude acceleration data may be received responsive to a thumb stick on the second handle bar being moved, wherein the altitude acceleration angle is proportional to the angle at which the thumb stick on the second handle bar is pressed. 
         [0086]    At operation  950 , a desired shaft speed of each propeller may be determined based on a control algorithm and a closed loop feedback control structure, which utilizes the yaw command data, horizontal plane acceleration data, altitude acceleration data and measurements determined by an inertial measurement unit. 
         [0087]    At operation  960 , the angular velocity of each propeller may be changed independently from the other propellers. 
         [0088]    In the foregoing specification, embodiments have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the invention. 
         [0089]    Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and are thus not restrictive of the invention. The description herein of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein (in particular, the inclusion of any particular embodiment, feature, or function is not intended to limit the scope of the invention to such embodiment, feature, or function). 
         [0090]    Rather, the description is intended to describe illustrative embodiments, features and functions in order to provide a person of ordinary skill in the art context to understand the invention without limiting the invention to any particularly described embodiment, feature, or function. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the invention, as those skilled in the relevant art will recognize and appreciate. 
         [0091]    As indicated, these modifications may be made to the invention in light of the foregoing description of illustrated embodiments of the invention and are to be included within the spirit and scope of the invention. Thus, while the invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes, and substitutions are intended in the foregoing disclosures. It will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the invention. 
         [0092]    Reference throughout this specification to “one embodiment,” “an embodiment,” “a specific embodiment” or similar terminology means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment and may not necessarily be present in all embodiments. Thus, respective appearances of the phrases “in one embodiment,” “in an embodiment,” or “in a specific embodiment” or similar terminology in various places throughout this specification are not necessarily referring to the same embodiment. 
         [0093]    Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the invention. 
         [0094]    In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment may be able to be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the invention. While the invention may be illustrated by using a particular embodiment, this is not and does not limit the invention to any particular embodiment and a person of ordinary skill in the art will recognize that additional embodiments are readily understandable and are a part of this invention. 
         [0095]    It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Additionally, any signal arrows in the drawings/figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. 
         [0096]    Furthermore, the term or as used herein is generally intended to mean “and/or” unless otherwise indicated. As used herein, a term preceded by “a” or an (and the when antecedent basis is “a” or “an”) includes both singular and plural of such term (i.e., that the reference “a” or an clearly indicates only the singular or only the plural). Also, as used in the description herein, the meaning of in includes in and on unless the context clearly dictates otherwise. 
         [0097]    Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component.