Patent Publication Number: US-2021188426-A1

Title: Multi-rotor aerial vehicle and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/CN2018/101110, filed on Aug. 17, 2018, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of aircraft and, more specifically, to a multi-rotor aerial vehicle and a control method thereof. 
     BACKGROUND 
     Ordinary aerial vehicles adopt multi-rotor flight system with equal size and equal wing shape, and the excitation frequency of each rotor is basically the same when hovering. However, in order to achieve all direction flight and provide horizontal component moment, the rotation speed of each rotor motor needs to be different, resulting in a change in the excitation frequency of each rotor. For the entire multi-rotor aerial vehicle, the vibration frequency band during flight is significantly wider than hovering, and the width of this frequency band becomes wider with the increase of the motor speed difference, which can increase the probability of coupling between the excitation frequency and the natural frequency of the multi-rotor aerial vehicle, causing additional vibration. The vibration will cause the imaging quality of the imaging device on the multi-rotor aerial vehicle to be poor. 
     SUMMARY 
     One aspect of the present disclosure provides a multi-rotor aerial vehicle. The multi-rotor aerial vehicle includes a body, the body including a first side and a second side opposite to each other; a first rotor connected to the first side of the body; and a second rotor connected to the second side of the body, a torque coefficient of the second rotor being different from a torque coefficient of the first rotor. When the multi-rotor aerial vehicle flies in a direction from the second side toward the first side or from the first side toward the second side, the first rotor rotates at a first rotational speed, the second rotor rotates at a second rotational speed, and an absolute value of a difference between the first rotational speed and the second rotational speed is less than a predetermined value. 
     Another aspect of the present disclosure provides a multi-rotor aerial vehicle control method. The method includes controlling a first rotor connected to a first side of a body of the multi-rotor aerial vehicle to rotate at a first rotational speed; and controlling a second rotor to connected to a second side of the body of the multi-rotor aerial vehicle to rotate at a second rotational speed when the multi-rotor aerial vehicle flying from the second side toward the first side or from the first side toward the second side, the first side being opposite to the second side, a torque coefficient of the second rotor being different from a torque coefficient of the first rotor. An absolute value of a difference between the first rotational speed and the second rotational speed is less than a predetermined value. 
     Another aspect of the present disclosure provides a multi-rotor aerial vehicle. The vehicle includes a body, the body including a first side and a second side opposite to each other; a first rotor connected to the first side of the body; a second rotor connected to the second side of the body, a torque coefficient of the second rotor being different from a torque coefficient of the first rotor; and a flight control system. When the multi-rotor aerial vehicle flies in a direction from the second side toward the first side or from the first side toward the second side, the flight control system is configured to control the first rotor to rotate at a first rotational speed; and control the second rotor to rotate at a second rotational speed, an absolute value of a difference between the first rotational speed and the second rotational speed being less than a predetermined value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or additional aspects and advantages of the present disclosure will become obvious and easy to understand from the description of embodiments in conjunction with the following drawings. 
         FIG. 1  is a schematic structural diagram of a multi-rotor aerial vehicle according to an embodiment of the present disclosure. 
         FIG. 2  is a schematic side view of the multi-rotor aerial vehicle during a fixed-direction flight according to an embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram of an excitation force frequency band of a multi-rotor aerial vehicle during a fixed-direction flight in conventional technology. 
         FIG. 4  is a schematic diagram of the excitation force frequency band of the multi-rotor aerial vehicle during a fixed-direction flight according to an embodiment of the present disclosure. 
         FIG. 5  is a schematic side view of the multi-rotor aerial vehicle when hovering according to an embodiment of the present disclosure. 
         FIG. 6  is a schematic flowchart of a multi-rotor aerial vehicle control method according to an embodiment of the present disclosure. 
         FIG. 7  is a schematic flowchart of the multi-rotor aerial vehicle control method according to an embodiment of the present disclosure. 
         FIG. 8  is a schematic flowchart of the multi-rotor aerial vehicle control method according to an embodiment of the present disclosure. 
         FIG. 9  is a schematic structural diagram of the multi-rotor aerial vehicle including a flight control system according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings, in which the same or similar reference numbers throughout the drawings represent the same or similar elements or elements having same or similar functions. Embodiments described below with reference to drawings are merely exemplary and used for explaining the present disclosure, and should not be understood as limitation to the present disclosure. 
     In the description of the present disclosure, it should be understood that the terms “first,”, “second,” etc. are only used to indicate different components, but do not indicate or imply the order, the relative importance, or the number of the components. Further, in the description of the present disclosure, unless otherwise specified, the term “first,” or “second” preceding a feature explicitly or implicitly indicates one or more of such feature 
     In the present disclosure, unless specified or limited otherwise, the terms “mounted,” “connected,” “coupled,” “fixed” and the like are used broadly, and may be, for example, fixed connections, detachable connections, or integral connections; may also be mechanical or electrical connections; may also be direct connections or indirect connections via intervening structures; may also be inner communications of two elements or interactions of two elements, which can be understood by those skilled in the art according to specific situations. 
     Referring to  FIG. 1 , a multi-rotor aerial vehicle  100  of an embodiment of the present disclosure includes a body  10 , a first rotor  20 , and a second rotor  30 . The body  10  includes a first side  11  and a second side  12  opposite to each other. The first rotor  20  may be connected to the first side  11  of the body  10 . The second rotor  30  may be connected to the second side  12  of the body  10 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . When the multi-rotor aerial vehicle  100  is flying in a direction from the second side  12  toward to the first side  11  or flying in a direction from the first side  11  toward to the second side  12 , the first rotor  20  may rotate at a first rotational speed, and the second rotor  30  may rotate at a second rotational speed. The absolute value of the difference between the first rotational speed and the second rotational speed may be less than a predetermined value N. 
     More specifically, the multi-rotor aerial vehicle  100  of the embodiments of the present disclosure may be a quad-rotor aerial vehicle, a hexa-rotor aerial vehicle, or an octo-rotor aerial vehicle, etc., which is not limited here. Referring to both  FIG. 1  and  FIG. 2 , the multi-rotor aerial vehicle  100  of this embodiment takes a quad-rotor aerial vehicle as an example, which can be equipped with an imaging device  200 . The imaging device  200  can be used to capture images or videos when the multi-rotor aerial vehicle  100  is flying or hovering. The imaging device  200  may be mounted on a gimbal  300 , and the gimbal  300  may be fixedly connected to the body  10 . The gimbal  300  can provide a suitable imaging angle for the imaging device  200 . When the body  10  of the multi-rotor aerial vehicle  100  vibrates greatly, the imaging device  200  also vibrates greatly, and the imaging quality of the imaging device  200  is poor. Especially for a high-power optical zoom lens, a slight vibration of the body  10  may cause significant shaking of the captured image, which affects the quality of the imaging. 
     Both the first rotor  20  and the second rotor  30  may be connected to the body  10  through an arm  50 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . The torque coefficient may refer to the magnitude of the interaction between the rotor and the air. The smaller the torque coefficient, the smaller the interaction between the rotor and the air. For example, the torque coefficient of the first rotor  20  is smaller than the torque coefficient of the second rotor  30  indicates that the interaction of the first rotor  20  with the air is smaller than the interaction of the second rotor  30  with the air. 
     The multi-rotor aerial vehicle  100  may also include a drive assembly (not shown in FIGS.) disposed on the arm  50 . The drive assembly can be used to apply an exciting force to the first rotor  20  and the second rotor  30  to drive the first rotor  20  and the second rotor  30  to rotate. The drive assembly may include a plurality of driving motors. The plurality of driving motors may be fixedly connected to the first rotor  20  and the second rotor  30 , respectively. Driven by the drive assembly, the first rotor  20  may rotate at a certain speed, and the second rotor  30  may rotate at a certain speed. In the present embodiment, when the multi-rotor aerial vehicle  100  flies toward a direction from the second side  12  toward to the first side  11 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  flies toward a direction from the first side  11  toward to the second side  12 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. The propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be respectively equal to the excitation force frequency of the corresponding drive motor. The greater the rotational speed of the drive motor, the greater the rotational speed of the corresponding rotor, and the greater the rotor frequency. 
     The multi-rotor aerial vehicle  100  needs to have the effect of the horizontal component moment to fly in a fixed-direction flight. Referring to  FIG. 3 , in the conventional multi-rotor aerial vehicle, since the torque coefficients of the multiple rotors are equal, when the multi-rotor aerial vehicle is flying, e.g., flying forward, the absolute value of the difference between the rotational speed of the rotor on the nose side and the rotational speed of the rotor on the tail side may be large. The frequency band between the propeller frequency of the rotor on the nose side and the propeller frequency of the rotor on the tail side may be relatively wide, resulting in a higher probability of coupling between the excitation force band frequency band and neutral frequency of the body, and a higher probability of resonance between the body and the rotor. Therefore, in the present embodiment, the torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . For example, the torque coefficient of the second rotor  30  may be greater than the torque coefficient of the first rotor  20 , or the torque coefficient of the second rotor  30  may be less than the torque coefficient of the first rotor  20 . Referring to  FIG. 2  and  FIG. 4 , when the multi-rotor aerial vehicle  100  is flying from the second side  12  toward the first side  11  (the X direction as shown in  FIG. 2 ), since the absolute value of the difference between the first rotational speed and the second rotational speed is less than the predetermined value N, therefore, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow, and the smaller the predetermined value, the narrower the frequency band between the two propeller frequencies. At this time, the probability of the excitation force frequency band coupling with the natural frequency of the body  10  may be low, and the probability of the body  10  resonating with the rotor may be low. In the present embodiment, the predetermined value N may be adjusted based on a parameter condition of the rotor of the multi-rotor aerial vehicle  100 . For example, the predetermined value N may be less than or equal to 50, 100, 150 revolutions per minutes (RPM), etc., then the absolute value of the difference between the first rotational speed and the second rotational speed may be any value in [ 0 , N]. For example, when N=50 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 1, 10, 30, 45, 48, 50 RPM, etc. In another example, when N=100 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 30, 50, 70, 90, 95 RPM, etc. In another example, when N=150 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 25, 50, 100, 120, 140 RPM, etc. In this way, the vibration can be relatively small when the multi-rotor aerial vehicle  100  flies with the first rotor  20  and the second rotor  30  having the same or similar rotational speed and in a direction from the second side  12  toward the first side  11  or in a direction from the first side  11  toward the second side  12 , and the imaging quality of the imaging device  200  can be relatively high. In addition, the predetermined value N may be close to zero. It can be understood that may also be set based on actual needs, such as less than or equal to 20 revolution per second (RPS), less than 30 RPS, etc., which is not limited in this embodiment. 
     Referring to  FIG. 1 , in this embodiment, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is in the forward flight state (as shown in  FIG. 2 ). At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering (shown in  FIG. 5 ), the first rotor  20  may rotate at a third rotational speed, the second rotor  30  may rotate at a fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering. The probability of the body  10  and the rotor resonating may be lower, thereby reducing the probability of the body  10  and the rotor resonating and causing poor imaging effect. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the backward flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is the left flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies left, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the right flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies right, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     Of course, in addition to the first side  11  and the second side  12  of the multi-rotor aerial vehicle  100  being a fixed side of the body  10 , during the flight of the multi-rotor aerial vehicle  100 , the first side  11  and the second side  12  may also change based on the flight state of the multi-rotor aerial vehicle  100 . For example, the multi-rotor aerial vehicle  100  may change from one flight state to another flight state, or the multi-rotor aerial vehicle  100  may change from one flight to another flight state, and then change to another flight state. Regardless of type of flight state change, the first rotor  20  and the second rotor  30  may also change, correspondingly, the original torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also change. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another, for example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight. A detailed description will be provided below by taking the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight as an example. At the initial moment, the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  may be flying forward. The torque coefficient K 1  of the rotor on the tail side may be greater than the torque coefficient K 2  of the rotor on the nose side. At this time, the first rotor  20  may rotate at the first rotational speed of the forward flight, the second rotor  30  may rotate at the second rotational speed of the forward flight, and the absolute value of the difference between the first rotational speed of the forward flight and the second rotational speed of the forward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. When the multi-rotor aerial vehicle  100  changes from forward flight to left flight, the first rotor  20  may change from a rotor on the nose side to a rotor on the left side of the body, the second rotor  30  may change from a rotor on the tail side to a rotor on the right side of the body, and the torque coefficient K 3  of the rotor on the right side of the body may be greater than the torque coefficient K 4  of the rotor on the left side of the body. At this time, the first rotor  20  may rotate at the first rotational speed of the left flight, the second rotor  30  may rotate at the second rotational speed of the left flight, and the absolute value of the difference between the first rotational speed of the left flight and the second rotational speed of the left flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  flies left, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. In this way, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow in both the forward flight and the left flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In one example, the first rotational speed of the forward flight may be equal to the first rotational speed of the left flight, and the second rotational speed of the forward flight may be equal to the second rotational speed of the left flight. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to other flight states. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the backward flight, the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, which will not be repeated here. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then change from the left flight to the backward flight. A detailed description will be provided by taking the case where the /10 is changing from the forward flight to the left flight, and then from the left flight to the backward flight as an example. For the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight, reference may be made to the embodiment described above, and no further description will be provided here. When the multi-rotor aerial vehicle  100  has changed from the forward flight to the left flight, and needs to change from the left flight to the backward flight, the first rotor  20  may change from a rotor on the left side of the body to a rotor on the nose side, the second rotor  30  may change from a rotor on the right side of the body to a rotor on the tail side, and the torque coefficient K 5  of the rotor on the nose side may be greater than the torque coefficient K 6  of the rotor on the tail side. At this time, the first rotor  20  may rotate at the first rotational speed of the backward flight, the second rotor  30  may rotate at the second rotational speed of the backward flight, and the absolute value of the difference between the first rotational speed of the backward flight and the second rotational speed of the backward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, the frequency band of the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  can still be relatively narrow. As such, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow during the forward flight, the left flight, and the backward flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, and then change to the backward flight; the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then to the left flight; the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, and then to the forward flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, and then from the left flight to the backward flight, which will not be repeated here. 
     In this embodiment, the number of the first rotor  20  can be more than one, and the number of the second rotor  30  can be more than one. In the embodiment shown in  FIG. 1 , when the multi-rotor aerial vehicle  100  is an X-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) of the body  10 ; alternatively, the second rotor  30  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the first rotor  20  may be the two rotors disposed at the rear side (the tail side) of the body  10 . In another example, when the multi-rotor aerial vehicle  100  of the present disclosure is a cross-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) and the left side of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) and the right side of the body  10 . Of course, the number and mounting method of the first rotor  20  and the second rotor  30  are not limited to the above discussion, and can be adjusted based on actual needs, which is not limited here. In addition, when the number of the first rotors  20  is more than one and the number of the second rotor  30  is also more than one, both the first rotational speed and the third rotational speed may be the average rotational speed of the multiple first rotors  20 , and both the second rotational speed and the fourth rotational speed may be the average rotational speed of the multiple second rotors  30 . 
     In this embodiment, the torque coefficient of each rotor may be determined by any one or more of the dimensions of the rotor and the wing shape parameters of the rotor. In other words, each of the size of the rotor and the wing shape parameters of the rotor may affect the torque coefficient of the rotor. More specifically, under the condition of other parameters being the same, if the first rotor  20  and the second rotor  30  are only different in size, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the first rotor  20  and the second rotor  30  only have different wing shape parameters, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the size and wing shape parameters of the first rotor  20  and the second rotor  30  are different, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different. In this way, the multi-rotor aerial vehicle  100  can adopt different rotor sizes and/or wing shape parameters to mount the first rotor  20  and the second rotor  30  with suitable torque coefficients (for example, the aerial vehicle  100  may adopt different rotor sizes and/or wing shape parameters to realize the torque coefficient of the second rotor  30  being different from the torque coefficient of the first rotor  20 ). 
     In the embodiment shown in  FIG. 1 , the size of the first rotor  20  and the second rotor  30  are different, where the size of the rotor includes the diameter of the rotor. The larger the diameter of the rotor, the greater the torque coefficient of the rotor; and the smaller the diameter of the rotor, the smaller the torque coefficient of the rotor. The diameter of the second rotor  30  may be greater than the diameter of the first rotor  20 , and the interaction of the second rotor  30  with air may be greater than the interaction of the first rotor  20  with the air. Therefore, the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger diameter toward the rotor with the smaller diameter, that is, when the multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . In other embodiments, when the first side refers to the left side of the body, the second side refers to the right side of the body, the first rotor is the tow rotors on the left, and the second rotor is the two rotors on the right, the size of the second rotor being larger than the size of the first rotor can also realize the torque coefficient of the second rotor being greater than the torque coefficient of the first rotor. As such, when the aerial vehicle flies in a fixed-direction flight (the left flight), the absolute value of the difference between the first rotational speed of the first rotor and the second rotational speed of the second rotor may be relatively small, and the excitation force frequency band may be relatively narrow, thereby reducing the possibility of the body resonating with the first rotor or the second rotor, and improving the imaging quality of the imaging device carried by the body. 
     In other embodiments, the wing shape parameters of the first rotor  20  and the second rotor  30  may be different, where the wing shape parameters of the rotor may include one or more of the angle of attack, pitch, and chord length. The difference in the wing shape parameters of the first rotor  20  and the second rotor  30  may include one or more of the parameters being different. Take the angle of attack as an example, the larger the angle of attack of the rotor, the larger the windward area of the rotor, and the greater the interaction with the air, the greater the torque coefficient of the rotor; and the smaller the angle of attack of the rotor, the smaller the windward area of the rotor, and the smaller the interaction with the air, the smaller the torque coefficient of the rotor. In one example, the angle of attack of the second rotor  30  may be larger than the angle of attack of the first rotor  20 , and the interaction of the second rotor  30  with the air may be greater than the interaction of the first rotor  20  with the air. Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with larger angle of attack toward the rotor with small angle of attack, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the pitch as an example. The larger the pitch of the rotor, the greater the torque coefficient of the rotor; and the smaller the pitch of the rotor, the smaller the torque coefficient of the rotor. In another example, the pitch of the second rotor  30  may be larger than the pitch of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger pitch toward the rotor with the smaller pitch, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the chord length as an example. The longer the chord length of the rotor, under the same diameter, the larger the cross-section area of the rotor and the greater the interaction with the air; and the shorter the chord length of the rotor, under the same diameter, the smaller the cross-section area of the rotor and the smaller the interaction with the air. In another example, the chord length of the second rotor  30  may be longer than the chord length of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the longer chord length toward the rotor with the shorter chord length, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . 
     In this embodiment, the torque coefficient of the rotor may be determined at the factory, or it may be further adjusted during use. More specifically, the torque coefficient of the first rotor  20  may be adjustable, the torque coefficient of the second rotor  30  may be adjustable, or both the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may be adjustable. For example, a rotor pitch changing device may be disposed on the rotor. The multi-rotor aerial vehicle  100  may use the pitch changing device to change the angle of attack of the first rotor  20  or the second rotor  30  to change the pitch of the first rotor  20  or the  30 , thereby adjusting the torque coefficient of the first rotor  20  or the second rotor  30 . In the foregoing embodiments, when the multi-rotor aerial vehicle  100  changes its flight state, the original torque coefficient of the first rotor  20  and the original torque coefficient of the second rotor  30  may be changed by using the pitch changing device. A detailed description of how to adjust the torque coefficient of the rotor is provided by taking the quadrotor aerial vehicle changing from the forward flight to the left flight as an example. When the quadrotor aerial vehicle is flying forward, the torque coefficient of the two rotors on the tail side (the second rotor  30 ) may be K 1 , the torque coefficient of the two rotors on the nose side (the first rotor  20 ) may be K 2 , and K 1  may be greater than K 2 . When the quadrotor aerial vehicle changes to the left flight, the pitch of all the rotors may change such that the torque coefficients of all the rotors may change. More specifically, the pitch of the first rotor  20  originally on the right may change, and the torque coefficient may change to K 3 , the pitch of the second rotor  30  originally on the right may change, and the torque coefficient may change to K 3 ; and the pitch of the first rotor  20  originally on the left may change, and the torque coefficient may change to K 4 , the pitch of the second rotor  30  originally on the left may change, and the torque coefficient may change to K 4 . Therefore, the torque coefficients of the two rotors on the right side of the body may both be K 3 , the torque coefficients of the two rotors on the left side of the body may both be K 4 , and K 3  may be greater than K 4 . In one example, K 1  can be equal to K 3 , K 2  can be equal to K 4 , and the pitch of the first rotor  20  originally on the left can remain unchanged. The torque coefficient can still be K 1 , the pitch of the first rotor  20  can increase, and the torque coefficient can change to K 4 . 
     In summary, the multi-rotor aerial vehicle  100  of the embodiments of the present disclosure can adopt the first rotor  20  and the second rotor  30  with different torque coefficients. When the multi-rotor aerial vehicle  100  is in the fixed-direction flight, the first rotor  20  can rotate at a first rotational speed, the second rotor  30  can rotate at a second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed can be relatively small and the excitation force frequency band can be relatively narrow, thereby reducing the probability of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improving the imaging quality of the imaging device  200  carried by the body  10 . 
     Referring to  FIG. 1  and  FIG. 6 , an embodiment of the present disclosure provides a multi-rotor aerial vehicle  100  control method. The multi-rotor aerial vehicle  100  of an embodiment of the present disclosure includes a body  10 , a first rotor  20 , and a second rotor  30 . The body  10  includes a first side  11  and a second side  12  opposite to each other. The first rotor  20  may be connected to the first side  11  of the body  10 . The second rotor  30  may be connected to the second side  12  of the body  10 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . When the multi-rotor aerial vehicle  100  is flying in a direction from the second side  12  toward to the first side  11  or flying in a direction from the first side  11  toward to the second side  12 , the control method of an embodiment of the present disclosure includes the following steps. 
     S 1 , controlling the first rotor  20  to rotate at a first rotational speed. 
     S 2 , controlling the second rotor  30  to rotate at a second rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed is less than a predetermined value N. 
     More specifically, the multi-rotor aerial vehicle  100  of the embodiments of the present disclosure may be a quad-rotor aerial vehicle, a hexa-rotor aerial vehicle, or an octo-rotor aerial vehicle, etc., which is not limited here. Referring to both  FIG. 1  and  FIG. 2 , the multi-rotor aerial vehicle  100  of this embodiment takes a quad-rotor aerial vehicle as an example, which can be equipped with an imaging device  200 . The imaging device  200  can be used to capture images or videos when the multi-rotor aerial vehicle  100  is flying or hovering. The imaging device  200  may be mounted on a gimbal  300 , and the gimbal  300  may be fixedly connected to the body  10 . The gimbal  300  can provide a suitable imaging angle for the imaging device  200 . When the body  10  of the multi-rotor aerial vehicle  100  vibrates greatly, the imaging device  200  also vibrates greatly, and the imaging quality of the imaging device  200  is poor. Especially for a high-power optical zoom lens, a slight vibration of the body  10  may cause significant shaking of the captured image, which affects the quality of the imaging. 
     Both the first rotor  20  and the second rotor  30  may be connected to the body  10  through an arm  50 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . The torque coefficient may refer to the magnitude of the interaction between the rotor and the air. The smaller the torque coefficient, the smaller the interaction between the rotor and the air. For example, the torque coefficient of the first rotor  20  is smaller than the torque coefficient of the second rotor  30  indicates that the interaction of the first rotor  20  with the air is smaller than the interaction of the second rotor  30  with the air. 
     The multi-rotor aerial vehicle  100  may also include a drive assembly (not shown in FIGS.) disposed on the arm  50 . The drive assembly can be used to apply an exciting force to the first rotor  20  and the second rotor  30  to drive the first rotor  20  and the second rotor  30  to rotate. The drive assembly may include a plurality of driving motors. The plurality of driving motors may be fixedly connected to the first rotor  20  and the second rotor  30 , respectively. Driven by the drive assembly, the first rotor  20  may rotate at a certain speed, and the second rotor  30  may rotate at a certain speed. In the present embodiment, when the multi-rotor aerial vehicle  100  flies toward a direction from the second side  12  toward to the first side  11 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  flies toward a direction from the first side  11  toward to the second side  12 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. The propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be respectively equal to the excitation force frequency of the corresponding drive motor. The greater the rotational speed of the drive motor, the greater the rotational speed of the corresponding rotor, and the greater the rotor frequency. 
     The multi-rotor aerial vehicle  100  needs to have the effect of the horizontal component moment to fly in a fixed-direction flight. Referring to  FIG. 3 , in the conventional multi-rotor aerial vehicle, since the torque coefficients of the multiple rotors are equal, when the multi-rotor aerial vehicle is flying, e.g., flying forward, the absolute value of the difference between the rotational speed of the rotor on the nose side and the rotational speed of the rotor on the tail side may be large. The frequency band between the propeller frequency of the rotor on the nose side and the propeller frequency of the rotor on the tail side may be relatively wide, resulting in a higher probability of coupling between the excitation force band frequency band and neutral frequency of the body, and a higher probability of resonance between the body and the rotor. Therefore, in the present embodiment, the torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . For example, the torque coefficient of the second rotor  30  may be greater than the torque coefficient of the first rotor  20 , or the torque coefficient of the second rotor  30  may be less than the torque coefficient of the first rotor  20 . Referring to  FIG. 2  and  FIG. 4 , when the multi-rotor aerial vehicle  100  is flying from the second side  12  toward the first side  11  (the X direction as shown in  FIG. 2 ), since the absolute value of the difference between the first rotational speed and the second rotational speed is less than the predetermined value N, therefore, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow, and the smaller the predetermined value, the narrower the frequency band between the two propeller frequencies. At this time, the probability of the excitation force frequency band coupling with the natural frequency of the body  10  may be low, and the probability of the body  10  resonating with the rotor may be low. In the present embodiment, the predetermined value N may be adjusted based on a parameter condition of the rotor of the multi-rotor aerial vehicle  100 . For example, the predetermined value N may be less than or equal to 50, 100, 150 revolutions per minutes (RPM), etc., then the absolute value of the difference between the first rotational speed and the second rotational speed may be any value in [0, N]. For example, when N=50 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 1, 10, 30, 45, 48, 50 RPM, etc. In another example, when N=100 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 30, 50, 70, 90, 95 RPM, etc. In another example, when N=150 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 25, 50, 100, 120, 140 RPM, etc. In this way, the vibration can be relatively small when the multi-rotor aerial vehicle  100  flies with the first rotor  20  and the second rotor  30  having the same or similar rotational speed and in a direction from the second side  12  toward the first side  11  or in a direction from the first side  11  toward the second side  12 , and the imaging quality of the imaging device  200  can be relatively high. In addition, the predetermined value N may be close to zero. It can be understood that may also be set based on actual needs, such as less than or equal to 20 revolution per second (RPS), less than 30 RPS, etc., which is not limited in this embodiment. 
     Referring to  FIG. 5  and  FIG. 7 , in this embodiment, when the multi-rotor aerial vehicle  100  is hovering, the multi-rotor aerial vehicle  100  control method further includes the following steps. 
     S 3 , controlling the first rotor  20  to rotate at a third rotational speed. 
     S 4 , controlling the second rotor  30  to rotate at a fourth rotational speed, where the absolute value of the different between the first rotational speed and the second rotational speed is less than the absolute value of the difference between the third rotational speed and the fourth rotational speed. 
     Since the torque coefficient of the first rotor  20  may be less than the torque coefficient of the second rotor  30 , the interaction of the first rotor  20  with the air may be less than the interaction of the second rotor  30  with the air. Driven by the same power of the driving motor, when the first rotor  20  rotates at the third rotational speed, the second rotor  30  rotates at the fourth rotational speed, and the third rotational speed is greater than the fourth rotational speed, the pulling force generated by the first rotor  20  can be ensured to equal to the pulling force generated by the second rotor  30 . In this way, the body  10  can be balanced and the multi-rotor aerial vehicle  100  can hover. 
     Referring to  FIG. 1 , in this embodiment, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is in the forward flight state (as shown in  FIG. 2 ). At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering (shown in  FIG. 5 ), the first rotor  20  may rotate at a third rotational speed, the second rotor  30  may rotate at a fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering. The probability of the body  10  and the rotor resonating may be lower, thereby reducing the probability of the body  10  and the rotor resonating and causing poor imaging effect. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the backward flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is the left flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies left, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the right flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies right, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     Of course, in addition to the first side  11  and the second side  12  of the multi-rotor aerial vehicle  100  being a fixed side of the body  10 , during the flight of the multi-rotor aerial vehicle  100 , the first side  11  and the second side  12  may also change based on the flight state of the multi-rotor aerial vehicle  100 . For example, the multi-rotor aerial vehicle  100  may change from one flight state to another flight state, or the multi-rotor aerial vehicle  100  may change from one flight to another flight state, and then change to another flight state. Regardless of type of flight state change, the first rotor  20  and the second rotor  30  may also change, correspondingly, the original torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also change. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another, for example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight. A detailed description will be provided below by taking the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight as an example. At the initial moment, the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  may be flying forward. The torque coefficient K 1  of the rotor on the tail side may be greater than the torque coefficient K 2  of the rotor on the nose side. At this time, the first rotor  20  may rotate at the first rotational speed of the forward flight, the second rotor  30  may rotate at the second rotational speed of the forward flight, and the absolute value of the difference between the first rotational speed of the forward flight and the second rotational speed of the forward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. When the multi-rotor aerial vehicle  100  changes from forward flight to left flight, the first rotor  20  may change from a rotor on the nose side to a rotor on the left side of the body, the second rotor  30  may change from a rotor on the tail side to a rotor on the right side of the body, and the torque coefficient K 3  of the rotor on the right side of the body may be greater than the torque coefficient K 4  of the rotor on the left side of the body. At this time, the first rotor  20  may rotate at the first rotational speed of the left flight, the second rotor  30  may rotate at the second rotational speed of the left flight, and the absolute value of the difference between the first rotational speed of the left flight and the second rotational speed of the left flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  flies left, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. In this way, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow in both the forward flight and the left flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In one example, the first rotational speed of the forward flight may be equal to the first rotational speed of the left flight, and the second rotational speed of the forward flight may be equal to the second rotational speed of the left flight. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to other flight states. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the backward flight, the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, which will not be repeated here. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then change from the left flight to the backward flight. A detailed description will be provided by taking the case where the /10 is changing from the forward flight to the left flight, and then from the left flight to the backward flight as an example. For the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight, reference may be made to the embodiment described above, and no further description will be provided here. When the multi-rotor aerial vehicle  100  has changed from the forward flight to the left flight, and needs to change from the left flight to the backward flight, the first rotor  20  may change from a rotor on the left side of the body to a rotor on the nose side, the second rotor  30  may change from a rotor on the right side of the body to a rotor on the tail side, and the torque coefficient K 5  of the rotor on the nose side may be greater than the torque coefficient K 6  of the rotor on the tail side. At this time, the first rotor  20  may rotate at the first rotational speed of the backward flight, the second rotor  30  may rotate at the second rotational speed of the backward flight, and the absolute value of the difference between the first rotational speed of the backward flight and the second rotational speed of the backward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, the frequency band of the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  can still be relatively narrow. As such, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow during the forward flight, the left flight, and the backward flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, and then change to the backward flight; the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then to the left flight; the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, and then to the forward flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, and then from the left flight to the backward flight, which will not be repeated here. 
     In this embodiment, the number of the first rotor  20  can be more than one, and the number of the second rotor  30  can be more than one. In the embodiment shown in  FIG. 1 , when the multi-rotor aerial vehicle  100  is an X-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) of the body  10 ; alternatively, the second rotor  30  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the first rotor  20  may be the two rotors disposed at the rear side (the tail side) of the body  10 . In another example, when the multi-rotor aerial vehicle  100  of the present disclosure is a cross-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) and the left side of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) and the right side of the body  10 . Of course, the number and mounting method of the first rotor  20  and the second rotor  30  are not limited to the above discussion, and can be adjusted based on actual needs, which is not limited here. In addition, when the number of the first rotors  20  is more than one and the number of the second rotor  30  is also more than one, both the first rotational speed and the third rotational speed may be the average rotational speed of the multiple first rotors  20 , and both the second rotational speed and the fourth rotational speed may be the average rotational speed of the multiple second rotors  30 . 
     In this embodiment, the torque coefficient of each rotor may be determined by any one or more of the dimensions of the rotor and the wing shape parameters of the rotor. In other words, each of the size of the rotor and the wing shape parameters of the rotor may affect the torque coefficient of the rotor. More specifically, under the condition of other parameters being the same, if the first rotor  20  and the second rotor  30  are only different in size, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the first rotor  20  and the second rotor  30  only have different wing shape parameters, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the size and wing shape parameters of the first rotor  20  and the second rotor  30  are different, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different. In this way, the multi-rotor aerial vehicle  100  can adopt different rotor sizes and/or wing shape parameters to mount the first rotor  20  and the second rotor  30  with suitable torque coefficients (for example, the aerial vehicle  100  may adopt different rotor sizes and/or wing shape parameters to realize the torque coefficient of the second rotor  30  being different from the torque coefficient of the first rotor  20 ). 
     In the embodiment shown in  FIG. 1 , the size of the first rotor  20  and the second rotor  30  are different, where the size of the rotor includes the diameter of the rotor. The larger the diameter of the rotor, the greater the torque coefficient of the rotor; and the smaller the diameter of the rotor, the smaller the torque coefficient of the rotor. The diameter of the second rotor  30  may be greater than the diameter of the first rotor  20 , and the interaction of the second rotor  30  with air may be greater than the interaction of the first rotor  20  with the air. Therefore, the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger diameter toward the rotor with the smaller diameter, that is, when the multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . In other embodiments, when the first side refers to the left side of the body, the second side refers to the right side of the body, the first rotor is the tow rotors on the left, and the second rotor is the two rotors on the right, the size of the second rotor being larger than the size of the first rotor can also realize the torque coefficient of the second rotor being greater than the torque coefficient of the first rotor. As such, when the aerial vehicle flies in a fixed-direction flight (the left flight), the absolute value of the difference between the first rotational speed of the first rotor and the second rotational speed of the second rotor may be relatively small, and the excitation force frequency band may be relatively narrow, thereby reducing the possibility of the body resonating with the first rotor or the second rotor, and improving the imaging quality of the imaging device carried by the body. 
     In other embodiments, the wing shape parameters of the first rotor  20  and the second rotor  30  may be different, where the wing shape parameters of the rotor may include one or more of the angle of attack, pitch, and chord length. The difference in the wing shape parameters of the first rotor  20  and the second rotor  30  may include one or more of the parameters being different. Take the angle of attack as an example, the larger the angle of attack of the rotor, the larger the windward area of the rotor, and the greater the interaction with the air, the greater the torque coefficient of the rotor; and the smaller the angle of attack of the rotor, the smaller the windward area of the rotor, and the smaller the interaction with the air, the smaller the torque coefficient of the rotor. In one example, the angle of attack of the second rotor  30  may be larger than the angle of attack of the first rotor  20 , and the interaction of the second rotor  30  with the air may be greater than the interaction of the first rotor  20  with the air. Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with larger angle of attack toward the rotor with small angle of attack, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the pitch as an example. The larger the pitch of the rotor, the greater the torque coefficient of the rotor; and the smaller the pitch of the rotor, the smaller the torque coefficient of the rotor. In another example, the pitch of the second rotor  30  may be larger than the pitch of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger pitch toward the rotor with the smaller pitch, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the chord length as an example. The longer the chord length of the rotor, under the same diameter, the larger the cross-section area of the rotor and the greater the interaction with the air; and the shorter the chord length of the rotor, under the same diameter, the smaller the cross-section area of the rotor and the smaller the interaction with the air. In another example, the chord length of the second rotor  30  may be longer than the chord length of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the longer chord length toward the rotor with the shorter chord length, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . 
     In this embodiment, the torque coefficient of the rotor may be determined at the factory, or it may be further adjusted during use. More specifically, the torque coefficient of the first rotor  20  may be adjustable, the torque coefficient of the second rotor  30  may be adjustable, or both the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may be adjustable. For example, a rotor pitch changing device may be disposed on the rotor. The multi-rotor aerial vehicle  100  may use the pitch changing device to change the angle of attack of the first rotor  20  or the second rotor  30  to change the pitch of the first rotor  20  or the  30 , thereby adjusting the torque coefficient of the first rotor  20  or the second rotor  30 . In the foregoing embodiments, when the multi-rotor aerial vehicle  100  changes its flight state, the original torque coefficient of the first rotor  20  and the original torque coefficient of the second rotor  30  may be changed by using the pitch changing device. A detailed description of how to adjust the torque coefficient of the rotor is provided by taking the quadrotor aerial vehicle changing from the forward flight to the left flight as an example. When the quadrotor aerial vehicle is flying forward, the torque coefficient of the two rotors on the tail side (the second rotor  30 ) may be K 1 , the torque coefficient of the two rotors on the nose side (the first rotor  20 ) may be K 2 , and K 1  may be greater than K 2 . When the quadrotor aerial vehicle changes to the left flight, the pitch of all the rotors may change such that the torque coefficients of all the rotors may change. More specifically, the pitch of the first rotor  20  originally on the right may change, and the torque coefficient may change to K 3 , the pitch of the second rotor  30  originally on the right may change, and the torque coefficient may change to K 3 ; and the pitch of the first rotor  20  originally on the left may change, and the torque coefficient may change to K 4 , the pitch of the second rotor  30  originally on the left may change, and the torque coefficient may change to K 4 . Therefore, the torque coefficients of the two rotors on the right side of the body may both be K 3 , the torque coefficients of the two rotors on the left side of the body may both be K 4 , and K 3  may be greater than K 4 . In one example, K 1  can be equal to K 3 , K 2  can be equal to K 4 , and the pitch of the first rotor  20  originally on the left can remain unchanged. The torque coefficient can still be K 1 , the pitch of the first rotor  20  can increase, and the torque coefficient can change to K 4 . 
     Referring to  FIG. 1  and  FIG. 8 , the control method of the multi-rotor aerial vehicle  100  according to an embodiment of the present disclosure further includes the following steps. 
     S 5 , controlling the third rotational speed of the first rotor  20  to change to the first rotational speed. 
     S 6 , controlling the fourth rotational speed of the second rotor  30  to change to the second rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed is less than the absolute value of the difference between the third rotational speed and the fourth rotational speed to cause the multi-rotor aerial vehicle  100  to change from hovering to flying from the second side toward the first side. 
     More specifically, when the multi-rotor aerial vehicle  100  is hovering, since the absolute value of the difference between the third rotational speed and the third rotational speed is relatively large, the third rotational speed and the fourth rotational speed may need to be adjusted. By controlling the speed of the driving motor connected to the first rotor  20  to reduce to reduce the speed of the first rotor  20  and controlling the speed of the driving motor connected to the second rotor  30  to increase to increase the speed of the second rotor  30 , the third rotational speed of the first rotor  20  can change to the first rotational speed, the fourth rotational speed can change to the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed can be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed when hovering. In addition, when hovering, the pulling of the first rotor  20  may be similar to the pulling force of the second rotor  30 . After adjusting the third rotational speed and the fourth rotational speed, the pulling force of the first rotor  20  may decrease, and the pulling force of the second rotor  30  may increase. As a result, the multi-rotor aerial vehicle  100  is subjected to the horizontal component moment of the second rotor  30  pointing toward the first rotor  20 , such that the multi-rotor aerial vehicle  100  can from the second side  12  toward the first side  11 . In this way, the multi-rotor aerial vehicle  100  can change from the hovering state to the fixed-direction flight state. 
     Further, when the absolute value of the difference between the first rotational speed and the second rotational speed is still greater than the predetermined value, continue controlling the speed of the driving motor connected to the first rotor  20  to reduce to reduce the speed of the first rotor  20  and controlling the speed of the driving motor connected to the second rotor  30  to increase to increase the speed of the second rotor  30 , until the absolute value of the difference between the first rotational speed and second rotational speed is less than the predetermined value. In this embodiment, the predetermined value may be set to a relatively small value, such that the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  of the multi-rotor aerial vehicle  100  in the fixed-direction flight may be similar, the excitation force frequency may be relatively narrow, thereby reducing the probability of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improving the imaging quality of the imaging device  200 . 
     In summary, in the control method of the multi-rotor aerial vehicle  100  according to an embodiment of the present disclosure, the first rotor  20  and the second rotor  30  can have different torque coefficients. During the fixed-direction flight of the multi-rotor aerial vehicle  100 , the first rotor  20  can be controlled to rotate at the first rotational speed, the second rotor  30  can be controlled to rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed can be relatively small, the excitation force frequency may be relatively narrow, thereby reducing the probability of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improving the imaging quality of the imaging device  200  carried by the body  10 . 
     Referring to  FIG. 6  and  FIG. 9 , an embodiment of the present disclosure further provides a multi-rotor aerial vehicle  100  including a flight control system  40 . The multi-rotor aerial vehicle  100  includes a body  10 , a first rotor  20 , a second rotor  30 , and a flight control system  40 . The body  10  includes a first side  11  and a second side  12  opposite to each other. The first rotor  20  may be connected to the first side  11  of the body  10 . The second rotor  30  may be connected to the second side  12  of the body  10 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . When the multi-rotor aerial vehicle  100  is flying in a direction from the second side  12  toward to the first side  11  or flying in a direction from the first side  11  toward to the second side  12 , the flight control system  40  may be used to control the first rotor  20  to rotate at a first rotational speed, control the second rotor  30  to rotate at a second rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than a predetermined value N. That is, the flight control system  40  can be used to implement the processes at S 1  and S 2 . 
     More specifically, the multi-rotor aerial vehicle  100  of the embodiments of the present disclosure may be a quad-rotor aerial vehicle, a hexa-rotor aerial vehicle, or an octo-rotor aerial vehicle, etc., which is not limited here. Referring to both  FIG. 1  and  FIG. 2 , the multi-rotor aerial vehicle  100  of this embodiment takes a quad-rotor aerial vehicle as an example, which can be equipped with an imaging device  200 . The imaging device  200  can be used to capture images or videos when the multi-rotor aerial vehicle  100  is flying or hovering. The imaging device  200  may be mounted on a gimbal  300 , and the gimbal  300  may be fixedly connected to the body  10 . The gimbal  300  can provide a suitable imaging angle for the imaging device  200 . When the body  10  of the multi-rotor aerial vehicle  100  vibrates greatly, the imaging device  200  also vibrates greatly, and the imaging quality of the imaging device  200  is poor. Especially for a high-power optical zoom lens, a slight vibration of the body  10  may cause significant shaking of the captured image, which affects the quality of the imaging. 
     Both the first rotor  20  and the second rotor  30  may be connected to the body  10  through an arm  50 . The torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . The torque coefficient may refer to the magnitude of the interaction between the rotor and the air. The smaller the torque coefficient, the smaller the interaction between the rotor and the air. For example, the torque coefficient of the first rotor  20  is smaller than the torque coefficient of the second rotor  30  indicates that the interaction of the first rotor  20  with the air is smaller than the interaction of the second rotor  30  with the air. 
     The multi-rotor aerial vehicle  100  may also include a drive assembly (not shown in FIGS.) disposed on the arm  50 . The drive assembly can be used to apply an exciting force to the first rotor  20  and the second rotor  30  to drive the first rotor  20  and the second rotor  30  to rotate. The drive assembly may include a plurality of driving motors. The plurality of driving motors may be fixedly connected to the first rotor  20  and the second rotor  30 , respectively. Driven by the drive assembly, the first rotor  20  may rotate at a certain speed, and the second rotor  30  may rotate at a certain speed. In the present embodiment, when the multi-rotor aerial vehicle  100  flies toward a direction from the second side  12  toward to the first side  11 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  flies toward a direction from the first side  11  toward to the second side  12 , the first rotor  20  may rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. The propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be respectively equal to the excitation force frequency of the corresponding drive motor. The greater the rotational speed of the drive motor, the greater the rotational speed of the corresponding rotor, and the greater the rotor frequency. 
     The multi-rotor aerial vehicle  100  needs to have the effect of the horizontal component moment to fly in a fixed-direction flight. Referring to  FIG. 3 , in the conventional multi-rotor aerial vehicle, since the torque coefficients of the multiple rotors are equal, when the multi-rotor aerial vehicle is flying, e.g., flying forward, the absolute value of the difference between the rotational speed of the rotor on the nose side and the rotational speed of the rotor on the tail side may be large. The frequency band between the propeller frequency of the rotor on the nose side and the propeller frequency of the rotor on the tail side may be relatively wide, resulting in a higher probability of coupling between the excitation force band frequency band and neutral frequency of the body, and a higher probability of resonance between the body and the rotor. Therefore, in the present embodiment, the torque coefficient of the second rotor  30  may be different from the torque coefficient of the first rotor  20 . For example, the torque coefficient of the second rotor  30  may be greater than the torque coefficient of the first rotor  20 , or the torque coefficient of the second rotor  30  may be less than the torque coefficient of the first rotor  20 . Referring to  FIG. 2  and  FIG. 4 , when the multi-rotor aerial vehicle  100  is flying from the second side  12  toward the first side  11  (the X direction as shown in  FIG. 2 ), since the absolute value of the difference between the first rotational speed and the second rotational speed is less than the predetermined value N, therefore, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow, and the smaller the predetermined value, the narrower the frequency band between the two propeller frequencies. At this time, the probability of the excitation force frequency band coupling with the natural frequency of the body  10  may be low, and the probability of the body  10  resonating with the rotor may be low. In the present embodiment, the predetermined value N may be adjusted based on a parameter condition of the rotor of the multi-rotor aerial vehicle  100 . For example, the predetermined value N may be less than or equal to 50, 100, 150 revolutions per minutes (RPM), etc., then the absolute value of the difference between the first rotational speed and the second rotational speed may be any value in [ 0 , N]. For example, when N=50 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 1, 10, 30, 45, 48, 50 RPM, etc. In another example, when N=100 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 30, 50, 70, 90, 95 RPM, etc. In another example, when N=150 RPM, the absolute value of the difference between the first rotational speed and the second rotational speed may be any value such as 0, 25, 50, 100, 120, 140 RPM, etc. In this way, the vibration can be relatively small when the multi-rotor aerial vehicle  100  flies with the first rotor  20  and the second rotor  30  having the same or similar rotational speed and in a direction from the second side  12  toward the first side  11  or in a direction from the first side  11  toward the second side  12 , and the imaging quality of the imaging device  200  can be relatively high. In addition, the predetermined value N may be close to zero. It can be understood that may also be set based on actual needs, such as less than or equal to 20 revolution per second (RPS), less than 30 RPS, etc., which is not limited in this embodiment. 
     Referring to  FIG. 7  and  FIG. 9 , in this embodiment, when the multi-rotor aerial vehicle  100  is hovering, the flight control system  40  of the multi-rotor aerial vehicle  100  can also be used to control the first rotor  20  to rotate at a third rotational speed; control the second rotor  30  to rotate at a fourth rotational speed, where the absolute value of the different between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed. That is, the flight control system  40  can also be used to implement the processes at S 3  and S 4 . 
     Since the torque coefficient of the first rotor  20  may be less than the torque coefficient of the second rotor  30 , the interaction of the first rotor  20  with the air may be less than the interaction of the second rotor  30  with the air. Driven by the same power of the driving motor, when the first rotor  20  rotates at the third rotational speed, the second rotor  30  rotates at the fourth rotational speed, and the third rotational speed is greater than the fourth rotational speed, the pulling force generated by the first rotor  20  can be ensured to equal to the pulling force generated by the second rotor  30 . In this way, the body  10  can be balanced and the multi-rotor aerial vehicle  100  can hover. 
     Referring to  FIG. 9 , in this embodiment, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is in the forward flight state (as shown in  FIG. 2 ). At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering (shown in  FIG. 5 ), the first rotor  20  may rotate at a third rotational speed, the second rotor  30  may rotate at a fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering. The probability of the body  10  and the rotor resonating may be lower, thereby reducing the probability of the body  10  and the rotor resonating and causing poor imaging effect. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the backward flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is greater than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the second side  12  toward the first side  11  may indicate that the multi-rotor aerial vehicle  100  is the left flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies left, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     In other embodiments, when the torque coefficient of the second rotor  30  is less than the torque coefficient of the first rotor  20 , the first side  11  may be the left side of the body  10 , the second side  12  may be the right side of the body  10 , and the multi-rotor aerial vehicle  100  flying in the direction from the first side  11  toward the second side  12  may indicate that the multi-rotor aerial vehicle  100  is the right flight state. At this time, the first rotor  20  mat rotate at the first rotational speed, the second rotor  30  may rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the predetermined value N. When the multi-rotor aerial vehicle  100  is hovering, the first rotor  20  may rotate at the third rotational speed, the second rotor  30  may rotate at the fourth rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the difference between the third rotational speed and the fourth rotational speed. Therefore, when the multi-rotor aerial vehicle  100  flies right, since the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be narrower than when hovering and the probability of the body  10  and the rotor resonating may be lower. 
     Of course, in addition to the first side  11  and the second side  12  of the multi-rotor aerial vehicle  100  being a fixed side of the body  10 , during the flight of the multi-rotor aerial vehicle  100 , the first side  11  and the second side  12  may also change based on the flight state of the multi-rotor aerial vehicle  100 . For example, the multi-rotor aerial vehicle  100  may change from one flight state to another flight state, or the multi-rotor aerial vehicle  100  may change from one flight to another flight state, and then change to another flight state. Regardless of type of flight state change, the first rotor  20  and the second rotor  30  may also change, correspondingly, the original torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also change. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another, for example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight. A detailed description will be provided below by taking the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight as an example. At the initial moment, the first side  11  may be the nose side of the body  10 , the second side  12  may be the tail side of the body  10 , and the multi-rotor aerial vehicle  100  may be flying forward. The torque coefficient K 1  of the rotor on the tail side may be greater than the torque coefficient K 2  of the rotor on the nose side. At this time, the first rotor  20  may rotate at the first rotational speed of the forward flight, the second rotor  30  may rotate at the second rotational speed of the forward flight, and the absolute value of the difference between the first rotational speed of the forward flight and the second rotational speed of the forward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying forward, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. When the multi-rotor aerial vehicle  100  changes from forward flight to left flight, the first rotor  20  may change from a rotor on the nose side to a rotor on the left side of the body, the second rotor  30  may change from a rotor on the tail side to a rotor on the right side of the body, and the torque coefficient K 3  of the rotor on the right side of the body may be greater than the torque coefficient K 4  of the rotor on the left side of the body. At this time, the first rotor  20  may rotate at the first rotational speed of the left flight, the second rotor  30  may rotate at the second rotational speed of the left flight, and the absolute value of the difference between the first rotational speed of the left flight and the second rotational speed of the left flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  flies left, the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  may be relatively narrow. In this way, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow in both the forward flight and the left flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In one example, the first rotational speed of the forward flight may be equal to the first rotational speed of the left flight, and the second rotational speed of the forward flight may be equal to the second rotational speed of the left flight. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to other flight states. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the backward flight, the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, which will not be repeated here. 
     The multi-rotor aerial vehicle  100  may change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then change from the left flight to the backward flight. A detailed description will be provided by taking the case where the /10 is changing from the forward flight to the left flight, and then from the left flight to the backward flight as an example. For the multi-rotor aerial vehicle  100  changing from the forward flight to the left flight, reference may be made to the embodiment described above, and no further description will be provided here. When the multi-rotor aerial vehicle  100  has changed from the forward flight to the left flight, and needs to change from the left flight to the backward flight, the first rotor  20  may change from a rotor on the left side of the body to a rotor on the nose side, the second rotor  30  may change from a rotor on the right side of the body to a rotor on the tail side, and the torque coefficient K 5  of the rotor on the nose side may be greater than the torque coefficient K 6  of the rotor on the tail side. At this time, the first rotor  20  may rotate at the first rotational speed of the backward flight, the second rotor  30  may rotate at the second rotational speed of the backward flight, and the absolute value of the difference between the first rotational speed of the backward flight and the second rotational speed of the backward flight may be less than the predetermined value N. Therefore, when the multi-rotor aerial vehicle  100  is flying backward, the frequency band of the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  can still be relatively narrow. As such, by changing the torque coefficients of the rotors on the first side  11  and the second side  12 , the multi-rotor aerial vehicle  100  can ensure that the frequency band between the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  is relatively narrow during the forward flight, the left flight, and the backward flight. As such, the probability of resonance between the body  10  and the rotor can be relatively low, and the imaging quality of the imaging device  200  can be relatively high. In addition, the multi-rotor aerial vehicle  100  can change from one flight state to another flight state, and then change to another flight state. For example, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, the multi-rotor aerial vehicle  100  may change from the forward flight to the right flight, and then change to the backward flight; the multi-rotor aerial vehicle  100  may change from the forward flight to the left flight, and then to the left flight; the multi-rotor aerial vehicle  100  may change from the left flight to the right flight, and then to the forward flight, etc., all of which can be operated with reference to the foregoing embodiment of changing from the forward flight to the left flight, and then from the left flight to the backward flight, which will not be repeated here. 
     In this embodiment, the number of the first rotor  20  can be more than one, and the number of the second rotor  30  can be more than one. In the embodiment shown in  FIG. 9 , when the multi-rotor aerial vehicle  100  is an X-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) of the body  10 ; alternatively, the second rotor  30  may be the two rotors disposed at the front side (the nose side) of the body  10 , and the first rotor  20  may be the two rotors disposed at the rear side (the tail side) of the body  10 . In another example, when the multi-rotor aerial vehicle  100  of the present disclosure is a cross-shaped quadrotor, the first rotor  20  may be the two rotors disposed at the front side (the nose side) and the left side of the body  10 , and the second rotor  30  may be the two rotors disposed at the rear side (the tail side) and the right side of the body  10 . Of course, the number and mounting method of the first rotor  20  and the second rotor  30  are not limited to the above discussion, and can be adjusted based on actual needs, which is not limited here. In addition, when the number of the first rotors  20  is more than one and the number of the second rotor  30  is also more than one, both the first rotational speed and the third rotational speed may be the average rotational speed of the multiple first rotors  20 , and both the second rotational speed and the fourth rotational speed may be the average rotational speed of the multiple second rotors  30 . 
     In this embodiment, the torque coefficient of each rotor may be determined by any one or more of the dimensions of the rotor and the wing shape parameters of the rotor. In other words, each of the size of the rotor and the wing shape parameters of the rotor may affect the torque coefficient of the rotor. More specifically, under the condition of other parameters being the same, if the first rotor  20  and the second rotor  30  are only different in size, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the first rotor  20  and the second rotor  30  only have different wing shape parameters, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different; or, if the size and wing shape parameters of the first rotor  20  and the second rotor  30  are different, the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may also be different. In this way, the multi-rotor aerial vehicle  100  can adopt different rotor sizes and/or wing shape parameters to mount the first rotor  20  and the second rotor  30  with suitable torque coefficients (for example, the aerial vehicle  100  may adopt different rotor sizes and/or wing shape parameters to realize the torque coefficient of the second rotor  30  being different from the torque coefficient of the first rotor  20 ). 
     In the embodiment shown in  FIG. 9 , the size of the first rotor  20  and the second rotor  30  are different, where the size of the rotor includes the diameter of the rotor. The larger the diameter of the rotor, the greater the torque coefficient of the rotor; and the smaller the diameter of the rotor, the smaller the torque coefficient of the rotor. The diameter of the second rotor  30  may be greater than the diameter of the first rotor  20 , and the interaction of the second rotor  30  with air may be greater than the interaction of the first rotor  20  with the air. Therefore, the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger diameter toward the rotor with the smaller diameter, that is, when the multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . In other embodiments, when the first side refers to the left side of the body, the second side refers to the right side of the body, the first rotor is the tow rotors on the left, and the second rotor is the two rotors on the right, the size of the second rotor being larger than the size of the first rotor can also realize the torque coefficient of the second rotor being greater than the torque coefficient of the first rotor. As such, when the aerial vehicle flies in a fixed-direction flight (the left flight), the absolute value of the difference between the first rotational speed of the first rotor and the second rotational speed of the second rotor may be relatively small, and the excitation force frequency band may be relatively narrow, thereby reducing the possibility of the body resonating with the first rotor or the second rotor, and improving the imaging quality of the imaging device carried by the body. 
     In other embodiments, the wing shape parameters of the first rotor  20  and the second rotor  30  may be different, where the wing shape parameters of the rotor may include one or more of the angle of attack, pitch, and chord length. The difference in the wing shape parameters of the first rotor  20  and the second rotor  30  may include one or more of the parameters being different. Take the angle of attack as an example, the larger the angle of attack of the rotor, the larger the windward area of the rotor, and the greater the interaction with the air, the greater the torque coefficient of the rotor; and the smaller the angle of attack of the rotor, the smaller the windward area of the rotor, and the smaller the interaction with the air, the smaller the torque coefficient of the rotor. In one example, the angle of attack of the second rotor  30  may be larger than the angle of attack of the first rotor  20 , and the interaction of the second rotor  30  with the air may be greater than the interaction of the first rotor  20  with the air. Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with larger angle of attack toward the rotor with small angle of attack, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the pitch as an example. The larger the pitch of the rotor, the greater the torque coefficient of the rotor; and the smaller the pitch of the rotor, the smaller the torque coefficient of the rotor. In another example, the pitch of the second rotor  30  may be larger than the pitch of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the larger pitch toward the rotor with the smaller pitch, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . Next, take the chord length as an example. The longer the chord length of the rotor, under the same diameter, the larger the cross-section area of the rotor and the greater the interaction with the air; and the shorter the chord length of the rotor, under the same diameter, the smaller the cross-section area of the rotor and the smaller the interaction with the air. In another example, the chord length of the second rotor  30  may be longer than the chord length of the first rotor  20 . Therefore, when the multi-rotor aerial vehicle  100  flies in the direction from the rotor with the longer chord length toward the rotor with the shorter chord length, that is, multi-rotor aerial vehicle  100  flies in the direction from the second side  12  toward the first side  11  or from the first side  11  toward the second side  12 , the excitation force frequency band of the multi-rotor aerial vehicle  100  may be narrower than the excitation force frequency band when hovering. This can reduce the possibility of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improve the imaging quality of the imaging device  200  carried by the body  10 . 
     In this embodiment, the torque coefficient of the rotor may be determined at the factory, or it may be further adjusted during use. More specifically, the torque coefficient of the first rotor  20  may be adjustable, the torque coefficient of the second rotor  30  may be adjustable, or both the torque coefficient of the first rotor  20  and the torque coefficient of the second rotor  30  may be adjustable. For example, a rotor pitch changing device may be disposed on the rotor. The multi-rotor aerial vehicle  100  may use the pitch changing device to change the angle of attack of the first rotor  20  or the second rotor  30  to change the pitch of the first rotor  20  or the  30 , thereby adjusting the torque coefficient of the first rotor  20  or the second rotor  30 . In the foregoing embodiments, when the multi-rotor aerial vehicle  100  changes its flight state, the original torque coefficient of the first rotor  20  and the original torque coefficient of the second rotor  30  may be changed by using the pitch changing device. A detailed description of how to adjust the torque coefficient of the rotor is provided by taking the quadrotor aerial vehicle changing from the forward flight to the left flight as an example. When the quadrotor aerial vehicle is flying forward, the torque coefficient of the two rotors on the tail side (the second rotor  30 ) may be K 1 , the torque coefficient of the two rotors on the nose side (the first rotor  20 ) may be K 2 , and K 1  may be greater than K 2 . When the quadrotor aerial vehicle changes to the left flight, the pitch of all the rotors may change such that the torque coefficients of all the rotors may change. More specifically, the pitch of the first rotor  20  originally on the right may change, and the torque coefficient may change to K 3 , the pitch of the second rotor  30  originally on the right may change, and the torque coefficient may change to K 3 ; and the pitch of the first rotor  20  originally on the left may change, and the torque coefficient may change to K 4 , the pitch of the second rotor  30  originally on the left may change, and the torque coefficient may change to K 4 . Therefore, the torque coefficients of the two rotors on the right side of the body may both be K 3 , the torque coefficients of the two rotors on the left side of the body may both be K 4 , and K 3  may be greater than K 4 . In one example, K 1  can be equal to K 3 , K 2  can be equal to K 4 , and the pitch of the first rotor  20  originally on the left can remain unchanged. The torque coefficient can still be K 1 , the pitch of the first rotor  20  can increase, and the torque coefficient can change to K 4 . 
     Referring to  FIG. 8  and  FIG. 9 , the flight control system  40  of the multi-rotor aerial vehicle  100  according to an embodiment of the present disclosure can also be used to control the third rotational speed of the first rotor  20  to change to the first rotational speed; and control the fourth rotational speed of the second rotor  30  to change to the second rotational speed, where the absolute value of the difference between the first rotational speed and the second rotational speed may be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed to cause the multi-rotor aerial vehicle  100  to change from hovering to flying from the second side toward the first side. That is, the flight control system  40  can be used to implement the processes at S 5  and S 6 . 
     More specifically, the flight control system  40  can first determine the current state of the multi-rotor aerial vehicle  100 . When it is determined that the multi-rotor aerial vehicle  100  is hovering, since the absolute value of the difference between the third rotational speed and the third rotational speed is relatively large, therefore, the flight control system  40  may need to adjust the third rotational speed and the fourth rotational speed. The flight control system  40  may control the speed of the driving motor connected to the first rotor  20  to reduce to reduce the speed of the first rotor  20  and control the speed of the driving motor connected to the second rotor  30  to increase to increase the speed of the second rotor  30 , such that the third rotational speed of the first rotor  20  can change to the first rotational speed, the fourth rotational speed can change to the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed can be less than the absolute value of the difference between the third rotational speed and the fourth rotational speed when hovering. In addition, when hovering, the pulling of the first rotor  20  may be similar to the pulling force of the second rotor  30 . After the flight control system  40  adjusts the third rotational speed and the fourth rotational speed, the pulling force of the first rotor  20  may decrease, and the pulling force of the second rotor  30  may increase. As a result, the multi-rotor aerial vehicle  100  is subjected to the horizontal component moment of the second rotor  30  pointing toward the first rotor  20 , such that the multi-rotor aerial vehicle  100  can from the second side  12  toward the first side  11 . In this way, the multi-rotor aerial vehicle  100  can change from the hovering state to the fixed-direction flight state. 
     Further, the flight control system  40  may further determine whether the absolute value of the difference between the first rotational speed and the second rotational speed is less than the predetermined value N. If the absolute value of the difference between the first rotational speed and the second rotational speed is still greater than the predetermined value, the flight control system  40  may continue controlling the speed of the driving motor connected to the first rotor  20  to reduce to reduce the speed of the first rotor  20  and controlling the speed of the driving motor connected to the second rotor  30  to increase to increase the speed of the second rotor  30 , until the absolute value of the difference between the first rotational speed and second rotational speed is less than the predetermined value. In this embodiment, the predetermined value may be set to a relatively small value, such that the propeller frequency of the first rotor  20  and the propeller frequency of the second rotor  30  of the multi-rotor aerial vehicle  100  in the fixed-direction flight may be similar, the excitation force frequency may be relatively narrow, thereby reducing the probability of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improving the imaging quality of the imaging device  200 . 
     In summary, in the multi-rotor aerial vehicle  100  provided in an embodiment of the present disclosure, the first rotor  20  and the second rotor  30  can have different torque coefficients. During the fixed-direction flight of the multi-rotor aerial vehicle  100 , the flight control system  40  may control the first rotor  20  to rotate at the first rotational speed, control the second rotor  30  to rotate at the second rotational speed, and the absolute value of the difference between the first rotational speed and the second rotational speed can be relatively small, the excitation force frequency may be relatively narrow, thereby reducing the probability of the body  10  resonating with the first rotor  20  or the second rotor  30 , and improving the imaging quality of the imaging device  200  carried by the body  10 . 
     In the present description, descriptions of reference terms such as “an embodiment,” “some embodiments,” “illustrative embodiment,” “example,” “specific example,” or “some examples,” mean that characteristics, structures, materials, or features described in relation to the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present description, illustrative expression of the above terms does not necessarily mean the same embodiment or example. Further, specific characteristics, structures, materials, or features may be combined in one or multiple embodiments or examples in a suitable manner. 
     Processes or methods described in the flow charts or described in other manners may be understood as including one or more code modules, segments, or portions of executable instructions configured to execute specific logic functions or steps of a process. The scope of the preferred embodiments of the present disclosure may include other executions. Executions may not need follow the illustrated or described sequence or order. The functions may be executed in a substantially simultaneous manner or in a reversed order. These should be understood by a person having ordinary skills in the technical field of the embodiments of the present disclosure. 
     Logics and/or steps of illustrated in the flowchart or described in other manners may be regarded as a fixed-order sequence list of executable instructions configured to execute the logic functions. The logics and/or steps may be executed in any suitable non-transitory computer-readable medium, and may be used by instruction-execution systems, apparatuses, or devices (e.g., computer-based systems, systems having processors, or other systems that can retrieve instructions from the instruction-execution systems, apparatuses, or devices and execute the instructions), or may be used in combination with the instruction-execution systems, apparatuses, or devices. In the present specification, a “computer-readable medium” may include any device that can include, store, communicate, broadcast, or transfer programs to be used by instruction-execution systems, apparatuses, or devices. Examples of the computer-readable medium may include, but not be limited to, the following: an electrical connector (e.g., an electrical device) having one or multiple wirings, a portable computer disk (e.g., a magnetic device), a random access memory (“RAM”), a read only memory (“ROM”), an erasable programmable read only memory (“EPROM”) or a flash memory, an optical device, or a portable compact disc read only memory (“CDROM”). In some embodiments, the computer-readable medium may be paper on which the programs may be printed or other suitable medium, because the paper or other medium may be optically scanned. The scanned copy may be edited, interpreted, or if necessary processed using other suitable method to obtain the programs in an electrical manner. The programs can then be stored in a computer storage device. 
     A person having ordinary skills in the art can appreciate that various parts of the present disclosure may be implemented using related hardware, computer software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods may be executed by software or firmware stored in the computer-readable storage medium and executable by a suitable instruction-executing system. For example, if the present disclosure is executed by hardware, the hardware may include any of the following technologies known in the art or any combination thereof: a discreet logic circuit of a logic gate circuit configured to perform logic functions for digital signals, an application specific integrated circuit having suitable combinations of logic gate circuits, a programmable gate array (“PGA”), a field programmable gate array (“FPGA”), etc. 
     A person having ordinary skills in the art can understand that some or all of the steps of the above embodiments of the disclosed method may be implemented by a program instructing relevant hardware. The program may be stored in a computer-readable medium. When executed, the program may include one of the steps or a combination of the steps of the disclosed method. Various functional units may be integrated in a single processing module, or may exist as separate physical units. In some embodiments, two or more units may be integrated in a single module. The integrated module may be executed by hardware or by software functional modules. If the integrated module is executed by software functional modules and sold or used as an independent product, the integrated module may also be stored in a computer-readable storage medium. The storage medium mentioned above may be a read only storage device (e.g., memory), a magnetic disk, or an optical disk, etc. 
     Although the above has shown and described the embodiments of the present disclosure, it should be understood that the above embodiments are illustrative, and cannot be understood as limiting the present disclosure. A person having ordinary skills in the art can modify, edit, replace, and vary the embodiments within the scope of the present disclosure.