Patent Publication Number: US-2021181766-A1

Title: Return flight control method and device, and unmanned aerial vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/CN2018/101958, filed on Aug. 23, 2018, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of control technology and, more specifically, to a return flight control method and device, and an unmanned aerial vehicle (UAV). 
     BACKGROUND 
     UAVs that use smart batteries have the function of return flight with smart power. However, due to the technical constraints and/or environmental factors, the power calculated by the UAV is prone to errors that make it difficult to operate the return flight successfully. In view of this problem, the conventional technical solution is to increase the power reserved for the return flight. However, it is difficult to control the amount of power with the method of increasing the return flight power reserved. If there is too much power reserved, the user experience can be affected. If the reserved power is insufficient, the UAV cannot operate the return flight successfully, and the UAV can be easily lost. Therefore, effectively controlling the return flight of the UAV is of greater importance. 
     SUMMARY 
     One aspect of the present disclosure provides a method for controlling a return flight of an unmanned aerial vehicle (UVA). The method includes controlling the UAV to fly to a predetermined cruising altitude, and controlling the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value when determining that a remaining power of the UVA is less than or equal to a predetermined return flight power threshold; and controlling the UAV to perform a forced landing and the return flight based on the first predetermined horizontal speed control value and a predetermined descent speed control value when determining that the remaining power of the UAV is less than or equal to a predetermined descent power threshold in the process of the horizontal return at the predetermined cruising altitude. 
     Another aspect of the present disclosure provides A device for controlling a return flight of an UAV. The device includes a processor; and a memory storing program instructions that, when being executed by the processor, cause the processor to: control the UAV to fly to a predetermined cruising altitude, and control the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value when determining that a remaining power of the UVA is less than or equal to a predetermined return flight power threshold; and control the UAV to perform a forced landing and the return flight based on the first predetermined horizontal speed control value and a predetermined descent speed control value when determining that the remaining power of the UAV is less than or equal to a predetermined descent power threshold in the process of the horizontal return at the predetermined cruising altitude. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to illustrate the technical solutions in accordance with the embodiments of the present disclosure more clearly, the accompanying drawings to be used for describing the embodiments are introduced briefly in the following. It is apparent that the accompanying drawings in the following description are only some embodiments of the present disclosure. Persons of ordinary skill in the art can obtain other accompanying drawings in accordance with the accompanying drawings without any creative efforts. 
         FIG. 1  is a schematic structural diagram of a UAV return flight control system according to an embodiment of the present disclosure. 
         FIG. 2A  is a schematic diagram of a conventional UAV return flight method. 
         FIG. 2B  is a schematic diagram of a return flight power estimation method in conventional technology when the power is insufficient. 
         FIG. 2C  is a schematic diagram of a UAV forced landing and return flight method according to an embodiment of the present disclosure. 
         FIG. 3  is a flowchart of a UAV return flight control method according to an embodiment of the present disclosure. 
         FIG. 4A  is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure. 
         FIG. 4B  is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure. 
         FIG. 4C  is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure. 
         FIG. 4D  is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure. 
         FIG. 5  is a flowchart of a UAV return flight power estimation method according to an embodiment of the present disclosure. 
         FIG. 6  is a flowchart of a method for establishing a UAV power consumption model per unit of time according to an embodiment of the present disclosure. 
         FIG. 7A  is an effective diagram of an estimated power consumption per unit of time at a predetermined cruising altitude according to an embodiment of the present disclosure. 
         FIG. 7B  is an effective diagram of an estimated power consumption per unit of time during a forced landing and return flight according to an embodiment of the present disclosure. 
         FIG. 8  is a schematic structural diagram of a UAV return flight control device according to an embodiment of the present disclosure. 
         FIG. 9  is a schematic structural diagram of a structure of a return flight power estimation device for a UAV according to an embodiment of the present disclosure. 
         FIG. 10  is a schematic structural diagram of a device for establishing a UAV power consumption model per unit of time according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Technical solutions of the present disclosure will be described in detail with reference to the drawings. It will be appreciated that the described embodiments represent some, rather than all, of the embodiments of the present disclosure. Other embodiments conceived or derived by those having ordinary skills in the art based on the described embodiments without inventive efforts should fall within the scope of the present disclosure. 
     Exemplary embodiments will be described with reference to the accompanying drawings. In the case where there is no conflict between the exemplary embodiments, the features of the following embodiments and examples may be combined with each other. 
     The UAV return flight control method provided in the embodiments of the present disclosure can be executed by a UAV return flight control system, and the UAV return flight control system and the UAV can perform two-way communication. The UAV return flight control system may include a UAV return flight control device and the UAV. In some embodiments, the UAV return flight control device can be disposed on the UAV. In some embodiments, the UAV return flight control device can be spatially independent from the UAV. In some embodiments, the UAV return flight control device can be a component of the UAV, that is, the UAV may include the UAV return flight control device. In other embodiments, the UAV return flight control method can also be applied to other movable devices, such as robots capable of autonomous movement, unmanned vehicles, unmanned ships, and other movable devices. 
     The UAV return flight control device in the UAV return flight control system can obtain the UAV&#39;s remaining power in real time during the movement of the UAV. When it is determined that the remaining power of the UAV is less than or equal to a predetermined return flight power threshold, the UAV return flight control device can control the UAV to fly to a predetermined cruising altitude and control the UAV to return flight horizontally at a return flight altitude based on a first predetermined horizontal speed control value. When the UAV returns horizontally at the predetermined cruising altitude, if the UAV return flight control device determines that the UAV&#39;s remaining power is less than or equal to a predetermined descent power threshold, the UAV can be controlled to perform a forced landing and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. By using this method, the descent time of the UAV can be reduced, the possibility of the UAV returning when the battery is in sufficient can be improved, the probability of losing the UAV can be reduced, and the accuracy and flight safety of the UAV&#39;s return flight can be improved. The following is a description of the UAV return flight control system provided in the embodiments of the present disclosure. 
     Referring to  FIG. 1 , which is a schematic structural diagram of a UAV return flight control system according to an embodiment of the present disclosure. The UAV return flight control system includes a UAV return flight control device  11  and a UAV  12 . In some embodiments, the UAV  12  and the UAV return flight control device  11  may establish a communication connection through a wireless communication connection. In some specific scenarios, a communication connection between the UAV  12  and the UAV return flight control device  11  may also be established through a wired communication connection. In some embodiments, the UAV return flight control device  11  may be a flight controller. The UAV  12  may be a rotary-wing aircraft, such as a quad-rotor aircraft, a hexa-rotor aircraft, an eight-rotor aircraft, or a fixed-wing aircraft. The UAV  12  includes a power system  121 , and the power system  121  can be used to provide power for the UAV  12  to fly. 
     In this embodiment, the UAV return flight control device  11  may obtain the remaining power of the UAV  12  in real time, and when it is determined that the remaining power of the UAV  12  is less than or equal to the predetermined return flight power threshold, the UAV  12  can be controlled to fly to the predetermined cruising altitude, thereby controlling the UAV  12  to return horizontally at the predetermined cruising altitude based on the first predetermined horizontal speed control value. When the UAV  12  is returning horizontally at the predetermined cruising altitude, when the UAV return flight control device  11  determines that the remaining power of the UAV  12  is less than or equal to the predetermined descent power threshold, the UAV return flight control device  11  can control the UAV  12  to perform a forced landing and return the flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. 
     In one embodiment, the UAV  12  may obtain the current position of the UAV  12  in real time during the flight, and calculate the return flight power needed for the UAV  12  to return from the current position to a home point, that is, the return flight power amount, and determine a predetermined return flight power threshold based on the return flight power amount. In some embodiments, the return flight power can be calculated by a return flight power estimation method provided in the later part of the present disclosure, and the UAV return flight control device  11  can perform the return flight power estimation method described later in the present disclosure. In some embodiments, the UAV  12  may obtain the current altitude of the UAV  12  in real time, calculate the amount of power that the UAV  12  needs to descend from the current altitude to the ground, that is, the descent power, and determine the predetermined descent power threshold based on the descent power. In some embodiments, both the predetermined return flight power threshold and the predetermined descent threshold may include a safety margin. 
     In one embodiment, when it is determined that the remaining power of the UAV  12  is less or equal to the predetermined return flight power threshold, the UAV  12  can be trigger to perform the return flight. The UAV  12  can be controlled to fly to the predetermined cruising altitude, and the UAV  12  can be controlled to return horizontally at the predetermined cruising altitude based on the first predetermined horizontal speed control value. 
     In one embodiment, when the UAV  12  is returning horizontally at the predetermined cruising altitude, when the return flight control device  11  of the UAV  12  determines that the remaining power of the UAV  12  is less or equal to the predetermined descent power threshold, the UAV return flight control device  11  may control the UAV  12  to perform a forced landing and return the flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. 
     In one embodiment, when the UAV is performing the forced landing and return flight, the downward speed component, that is, the predetermined descent speed control value, may be added to the first predetermined horizontal speed control value, such that the UAV  12  can perform the return flight while descending horizontally to reduce the descend time. When the UAV  12  descends to a predetermined safe altitude, it may stop the descent, and the UAV  12  may return the flight horizontally at the predetermined safe altitude to prevent to the UAV from hitting the ground and improving the safety of the UAV. When the UAV  12  returns horizontally at the predetermined safe altitude, if the remaining power of the UAV  12  is less than or equal to a predetermined landing power threshold, the UAV can be controlled to land, thereby further improving the safety of the UAV. In some embodiments, the UAV  12  may obtain the current altitude of the UAV  12  in real time, calculate the landing power needed for the UAV  12  to land from the current altitude to the ground, that is, the landing power, and determined the predetermined landing power threshold based on the landing power. In some embodiments, the value of the predetermined landing power threshold may include a small margin. 
     In some embodiments, the embodiments of the present disclosure may be based on the conventional return flight method in the conventional technology shown in  FIG. 2A  and  FIG. 2B . The return flight method provided by the embodiments of the present disclosure will be described in comparison with the return flight method as shown in  FIG. 2C  provided by an embodiment of the present disclosure. 
       FIG. 2A  is a schematic diagram of a conventional UAV return flight method.  FIG. 2A  includes a return flight starting point  201 , a cruising altitude point  202 , a horizontal return flight route  203 , a descent point  204 , and a return flight point  205 . Then conventional UVA return flight method generally adopts a straight return flight, and then descends after reaching the return flight point. As shown in  FIG. 2A , the UAV ascends to the cruising altitude point  202  at the return flight starting point  201 , and returns horizontally along the horizontal return flight route  203  to the descent point  204 . In some embodiments, the descent point  204  may be positioned directly above the return flight point  205 , and the UAV may begin to descend at the descent point  204  and land at the return flight point  205 , where the return flight point  205  may be set on the ground. This return flight method is achieved by setting the predetermined return flight power threshold to a larger power threshold. This return flight method needs a higher amount of the remaining power of the UAV, that is, the UAV needs to have more remaining power when the UAV enters the return flight mode, which will reduce the amount of power of the UAV takes to perform tasks and affect user experience. 
       FIG. 2B  is a schematic diagram of a return flight power estimation method in conventional technology when the power is insufficient.  FIG. 2B  includes a return flight starting point  211 , a cruising altitude point  212 , a horizontal return flight route  213 , a descent point  214 , and a return flight point  215 . As shown in  FIG. 2B , the UAV ascends to the cruising altitude point  212  at the return flight starting point  211 , and returns horizontally along the horizontal return flight route  213 . When the UAV returns horizontally to the descent point  214 , the remaining power may be less than the predetermined descent power threshold, and the UAV may begin to descend at the descent point  214  and land at the return flight point  215 , where the return flight point  215  may be in front of a return flight point  216 . This return flight method estimates the amount of return flight power based on the conventional return flight power estimation method, such that the estimated return flight power may be insufficient, and the predetermined return flight power threshold may be set to a relatively small power threshold. Therefore, when the UAV enters the return flight mode, the remaining power may be insufficient, such that the UAV may land before flying to the return flight point, which may easily cause the UAV to be lost. 
       FIG. 2C  is a schematic diagram of a UAV forced landing and return flight method according to an embodiment of the present disclosure.  FIG. 2C  includes a return flight starting point  221 , a cruising altitude point  222 , a horizontal return flight route  223 , a descent point  224 , a safe altitude point  225 , a landing point  226 , and a return flight point  227 . In view of the situations described above, an embodiment of the present disclosure provides a UAV return flight control method shown in  FIG. 2C . This method can control the UAV to increase the downward speed component, that is, the predetermined descent speed control value, based on the horizontal return flight when the UAV, such that the UAV can perform a forced land while returning the flight, thereby saving descent time and improving the flight safety and user experience of the UAV. 
     As shown in  FIG. 2C , the UAV flies from the return flight starting point  221  to the cruising altitude point  222 , and controls the UAV to return on the horizontal return flight route  223 . If the remaining power of the UAV when flying to the descent point  224  is less than or equal to the predetermined descent power threshold, the UAV may be controlled to perform a forced landing and return the flight in the horizontal direction and the downward perpendicular direction to the horizontal direction. When the UAV descends to the safe altitude point  224 , the UAV can be controlled to return horizontally, and when the horizontal return reaches the landing point  226 , it will land on the return flight point  227 . 
     The following is a description of the UAV return flight control method in conjunction with the accompanying drawing. 
     Referring to  FIG. 3 , which is a flowchart of a UAV return flight control method according to an embodiment of the present disclosure. The method may be executed by the UAV return flight control device, where the specific explanation of the UAV return flight control device is as described above. The UAV return flight control method of the embodiments of the present disclosure will be described in detail below. 
     S 301 , controlling the UAV to fly to a predetermined cruising altitude and controlling the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value when it is determined that the remaining power of the UAV is less than or equal to a predetermined return flight power threshold. 
     In the embodiments of the present disclosure, the UAV return flight control device may obtain the UAV&#39;s remaining power in real time. When it is determined that the UAV&#39;s remaining power is less than or equal to the predetermined return flight power threshold, the UAV return flight control device can control the UAV to fly to the predetermined cruising altitude and control the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value. 
     S 302 , in the process of returning horizontally at the cruising altitude, controlling the UAV to perform a forced landing and a return flight based on the first predetermined horizontal speed control value and a predetermined descent speed control value when it is determined that the remaining power of the UAV is less than or equal to a predetermined descent power threshold. 
     In the embodiments of the present disclosure, when the UAV returns horizontally at the cruising altitude, if the UAV return flight control device determines that the UAV&#39;s remaining power is less than or equal to the predetermined descent power threshold, the UAV can be controlled to perform a forced landing and return the flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. 
     A specific example can be illustrated in  FIG. 4A , which is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure.  FIG. 4A  includes a UAV  40 , a cruising altitude point  401 , a descent point  402 , a safe altitude point  403 , a landing point  404 , and a return flight point  405 , where the cruising altitude point  401  corresponds to the predetermined cruising altitude, and the safe altitude point  403  corresponds to the predetermined safe altitude. Assume the first predetermined horizontal speed control value is V 1 , when the UAV returns from the cruising altitude point  401  to the descent point  402  along the predetermined cruising altitude level with the first predetermined horizontal speed control value V 1 , if the UAV return flight control device determines that the remaining power of the UAV  40  is less than or equal to the predetermined descent power threshold, then the UAV can be controlled to perform the forced landing and return flight based on the first predetermined horizontal speed control value V 1  and a predetermined descent speed control value Vx. 
     In one embodiment, in the process of performing the forced landing and return flight, if the UAV return flight control device determines that the UAV&#39;s altitude has dropped to the predetermined safe altitude, then the UAV may be controlled to return horizontally at the predetermined safe altitude based on a second predetermined horizontal speed control value. In some embodiments, the first predetermined horizontal speed control value may be the same as the second predetermined horizontal speed control value. In other embodiments, the first predetermined horizontal speed control value may also be different from the second predetermined horizontal speed control value, which is not limited in the embodiments of the present disclosure. 
     A specific example can be illustrated in  FIG. 4B , which is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure.  FIG. 4B  includes a UAV  41 , a cruising altitude point  411 , a descent point  412 , a safe altitude point  413 , a landing point  414 , and a return flight point  415 , where the cruising altitude point  411  corresponds to the predetermined cruising altitude, and the safe altitude point  413  corresponds to the predetermined safe altitude. Assume the second predetermined horizontal speed control value is V 2 , when the UAV  41  performs the forced landing and return flight from the descent point  412 , if the UAV return flight control device determines that the altitude of the UAV  41  has dropped to a safe altitude point  413 , then the UAV  41  can be controlled to perform the return flight at the predetermined safe altitude starting from the safe altitude point  413  based on the second predetermined horizontal speed control value V 2 . 
     In one embodiment, when the UAV returns horizontally at the predetermined safe altitude, if the UAV return flight control device determines that the remaining power of the UAV is less than or equal to the predetermined landing power threshold, then the UAV can be controlled to land. In some embodiments, the position point where the remaining power of the UAV is less than or equal to the predetermined landing power threshold may be any position point on the horizontal route at the predetermined safe altitude. 
     Take  FIG. 4B  as an example, when the UAV  41  returns horizontally from the safe altitude point  413  along the predetermined safe altitude with the second predetermined horizontal speed control value V 2 , if the UAV return flight control device determines at the landing point  414  that the remaining power of the UAV  41  is less than or equal to the predetermined landing power threshold, then the UAV can be controlled to land from the landing point  414 . 
     In one embodiment, when the UAV returns horizontally at the predetermined safe altitude, if the UAV return flight control device determines that the UAV reaches above the return flight point, it may control the UAV to land to the return flight point. 
     Take  FIG. 4B  as an example, when the UAV  41  returns horizontally from the safe altitude point  413  along the predetermined safe altitude with the second predetermined horizontal speed control value V 2 , if the UAV return flight control device determines that the UAV  41  has reached the landing point  416  above the return flight point  415 , then the UAV  41  can be controlled to land form the landing point  416  to the return flight point  415 . 
     In one embodiment, when the UAV is performing the forced landing and return flight, if the UAV return flight control device determines that the UAV has reached above the return flight point, it can control the UAV to land on the return flight point. In some embodiments, when the UAV is performing the forced landing and return flight, if the UAV return flight control device determines that the has reached above the return flight point when it descends to the predetermined safe altitude, it can control the UAV to land on the return flight point. 
     A specific example can be illustrated in  FIG. 4C , which is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure.  FIG. 4C  includes a UAV  42 , a cruising altitude point  421 , a descent point  422 , a landing point  423 , and a return flight point  424 , where the cruising altitude point  421  corresponds to the predetermined cruising altitude, and the landing point  423  is positioned at the predetermined safe altitude above the return flight point. When the UAV  42  descends from the descent point  422 , if the UAV return flight control device determines that the UAV has descended to the landing point  423  of the predetermined safe altitude, it can control the UAV  42  to land on the return flight point  424 . 
     In one embodiment, when the UAV performs the forced landing and return flight, if the UAV return flight control device determines that the UAV&#39;s remaining power is less than or equal to the predetermined landing power threshold, then the UAV can be controlled to land. 
     A specific example can be illustrated in  FIG. 4D , which is a schematic diagram of another UAV forced landing and return flight method according to an embodiment of the present disclosure.  FIG. 4D  includes a UAV  43 , a cruising altitude point  431 , a descent point  432 , a landing point  433 , and a return flight point  434 . When the UAV  43  descends from the descent point  432  to perform the return flight, if the UAV return flight control device determines that the remaining power of the UAV is less than or equal to the predetermined landing power threshold, then the UAV  43  can be controlled to start landing from the landing point  433 . 
     In the embodiments of the present disclosure, the UAV return flight control device can control the UAV to fly to the predetermined cruising altitude when it determines that the remaining power of the UAV is less than or equal to the predetermined return flight power threshold, and control the UAV to return horizontally at the predetermined cruising altitude based on the first predetermined horizontal speed control value. During the horizontal return at the predetermined cruising altitude, when it is determined that the remaining power of the UAV is less than or equal to the predetermined descent power threshold, the UAV can be controlled to perform the forced landing and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. By using this method, the probability of losing the UAV is can be reduced, the descent time can be reduced, and the accuracy and the flight safety of the UAV return flight can be improved. 
     Referring to  FIG. 5 , which is a flowchart of a UAV return flight power estimation method according to an embodiment of the present disclosure. The UAV return flight power estimation method can be executed by a UAV return flight power estimation device. A two-way communication may be established between the UAV return flight power estimation device and the UAV, and the UAV return flight power estimation device may be disposed on the UAV. In some embodiments, the UAV return flight power estimation device can be spatially independent from the UAV. In some embodiments, the UAV return flight power estimation device can be a component of the UAV, that is, the UAV may include the UAV return flight power estimation device, and the UAV return flight power estimation device may be the flight controller of the UAV. In other embodiments, the UAV return flight power estimation method can also be applied to other movable devices, such as robots capable of autonomous movement, unmanned vehicles, unmanned ships, and other movable devices, which are not specifically limited in the embodiments of the present disclosure. The UAV return flight power estimation method will be described in detail below. 
     S 501 , determining movement state information of the UAV during the return flight process. 
     In the embodiments of the present disclosure, the UAV return flight power estimation device needs to estimate the UAV return flight power in real time during the flight of the UAV, and the return flight power may be the power needed for the UAV to return from the current position to the return flight point. The UAV return flight power estimation device may determine the movement state information of the UAV during the return flight process. Specifically, during the flight of the UAV, the UAV return flight power estimation device may determine the movement state information of the UAV in the return flight process form the current position to the return flight point in real time. In some embodiments, the movement state information may include at least one of the horizontal flight speed, vertical flight speed, and altitude information of the UAV, where the altitude information of the UAV may include the altitude of the UAV or the height of the UAV relative to the ground. In some embodiments, the return flight process may be the process of the UAV returning from the current position to the return flight point. Take  FIG. 2C  as an example, assume the current position of the UAV is the return flight starting point  221 , the return flight process is the process in which the UAV  40  returns from the return flight starting point  221  to the return flight point  227 . 
     S 502 , estimating the amount of return flight power based on the determined movement state information. 
     In the embodiments of the present disclosure, the UAV return flight power estimation device may estimate the return flight power based on the determined movement state information. 
     The conventional return flight power estimations generally use the power consumption per unit of time obtained based on experience multiplied by the time needed for the return flight. Since the conventional return flight power estimations do not consider the UAV&#39;s movement state information during the return flight process, it cannot accurately reflect the impact of the power consumption and cannot cover various flight scenarios. In some scenarios, the estimation result can deviate from the actual situation and the accuracy is poor, especially when the flight distance is long, the difference between the actual return flight power consumption and the estimated return flight power consumption is more obvious. In the embodiments of the present disclosure, the return flight power can be estimated based on the movement state information determined by the UAV during the return flight process, which can truly reflect the impact of the UAV&#39;s movement state information on the power consumption during the return flight process, and can accurately estimate the return flight power consumption. 
     In one embodiment, when the UAV return flight power estimation device estimates the return flight power based on the determined movement state information, the power consumption per unit of time of the UAV during the return flight process can be determined based on the determined movement state information, and the amount of return flight power can be estimated based on the power consumption per unit of time. 
     More specifically, since the UAV may have different movement state information at different times during the return flight process of the UAV, the UAV may determine the power consumption per unit of time of the UAV based on the movement state information. It can be understood that, since the movement state information of the UAV may be different at different times, the power consumption per unit of time of the UAV may be different at different times. After determining the power consumption per unit of time of the UAV during the return flight process, the return flight power consumption can be determined based on the power consumption per unit of time. For example, the power consumption per unit of time can be accumulated during the return flight process, and the power consumption during the entire return flight process can be estimated based on the cumulative calculation, that is, the amount of return flight power. 
     In one embodiment, the return flight point may substitute the determined movement state information into the UAV&#39;s power consumption model per unit of time to determine the power consumption per unit of time. In some embodiments, the power consumption mode per unit of time of the UAV may be as follow. 
       Δ bat   resume   =R 1+ R 2 V   vert   +R 3 h+R 4 V   horz 7
 
     where V vert , h, and V horz  represent the vertical flight speed, altitude, and horizontal flight speed, respectively. R 1 , R 2 , R 3 , and R 4  are model coefficients, where the model coefficients are parameters other than independent variables in the power consumption model per unit of time of the UAV, and Δbat resume  is the power consumption per unit of time. In some embodiments, for the method of establishing the power consumption model per unit of time of the UAV, reference may be made to the later part of the present disclosure, and the UAV return flight power estimation device may be configured to execute the method of establishing the power consumption model per unit of time of the UAV described in later in the present disclosure. 
     In the embodiments of the present disclosure, the UAV return flight power estimation device can determine the movement state information of the UAV during the return flight process, and estimate the return flight power based on the determined movement state information, By using this method to estimate the return flight power, the error in power estimation can be reduced, and the flight safety and user experience of the UAV can be improved. 
     Referring to  FIG. 6 , which a flowchart of a method for establishing a UAV power consumption model per unit of time according to an embodiment of the present disclosure. The method for establishing a UAV power consumption model per unit of time can be executed by a device that can establish a power consumption model per unit of time of the UAV. The device for establishing the power consumption model per unit of time of the UAV may carry out a two-way communication with the UAV, and the device for establishing the power consumption model per unit of time of the UAV may be disposed on the UAV. In some embodiments, the device for establishing the power consumption model per unit of time of the UAV can be spatially independent from the UAV. In some embodiments, the device for establishing the power consumption model per unit of time of the UAV can be a component of the UAV, that is, the UAV may include the device for establishing the power consumption model per unit of time of the UAV, and the device for establishing the power consumption model per unit of time of the UAV may be the flight controller of the UAV. In other embodiments, the method for establishing the power consumption model per unit of time of the UAV can also be applied to other movable devices, such as robots capable of autonomous movement, unmanned vehicles, unmanned ships, and other movable devices, which are not specifically limited in the embodiments of the present disclosure. In some embodiments, the device for establishing the power consumption model per unit of time of the UAV may be a terminal device, where the terminal device may include at least one of a smart phone, a tablet computer, a laptop computer, and a desktop computer. The method for establishing the power consumption model per unit of time of the UAV will be described in detail below. 
     S 601 , obtaining the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information. 
     In the embodiments of the present disclosure, the device for establishing the power consumption model per unit of time of the UAV may obtain the movement state information of the UAV during the flight, and obtain the actual power consumption per unit of time corresponding to the movement state information, that is, samples of the movement state information and samples of the power consumption per unit of time. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight states. In some embodiments, the plurality of different flight states may include at least two of hovering, uniform flight, accelerated flight, and decelerated flight. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight environments. In some embodiments, the plurality of different flight environments may include any one or more of a plurality of different positions, a plurality of different flying altitudes, a plurality of different temperature environments, a plurality of different wind speed environments, and the like. 
     In some embodiments, the movement state information may include a degree of dispersion, and the degree of dispersion of the movement state information may be greater than or equal to a predetermined degree of dispersion threshold. In some embodiments, the movement state information of the UAV may include at least one of the horizontal flight speed, the vertical flight speed, and the altitude information of the UAV. 
     In some embodiments, the sample of the movement state information and the sample of the power consumption per unit of time can be obtained based on a large amount of sample data, where the device for estimating the UAV return flight power may determine the validity of the sample data before collecting the sample data. In one embodiment, the device for estimating the UAV return flight power may detect whether the flight state of the UAV for which the sample data is obtained is normal. If it is detected that there is no obvious failure in the flight state of the UAV, the flight state of the UAV may be determined as normal. In one embodiment, the device for estimating the UAV return flight power may detect whether the UAV&#39;s flight state is maintaining a stable hover, horizontal uniform flight, or vertical uniform flight. If the detection result is positive, the fight state of the UAV can be determined as normal. In one embodiment, after detecting that the flight state of the UAV is normal, the device for estimating the UAV return flight power may start to collect the sample data. 
     S 602 , substituting the movement state information into the power consumption per unit of time model to obtain an expected power consumption per unit of time of the UAV. 
     In the embodiments of the present disclosure, the power consumption per unit of time model may include one or more model coefficients to be determined. After one or more model coefficients to be determined are determined, the power consumption per unit of time model has been successfully established, and the independent variable of the power consumption per unit of time model may be the independent variable of the movement state information. The device for establishing the power consumption per unit of time model of the UAV may substituted the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time model of the UAV. 
     In one embodiment, the power consumption per unit of time Δbat resume  described above, for the entire UAV return flight process, the device for establishing the power consumption per unit of time model of the UAV can obtain the power needed for the return of the UAV based on the current altitude and the position of the set safe return flight point, the predetermined cruising altitude, the cruising speed, the descent speed, and other return flight information integrated to calculate the return flight time. 
     S 603 , running a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and updating the power consumption per unit of time model by using the determined model coefficients. 
     In the embodiments of the present disclosure, the device for establishing the power consumption per unit of time model of the UAV can obtain a plurality of pieces of movement state information, such as the movement state information of the UAV at a plurality of different times during flight, and obtain a plurality of expected power consumptions per unit of time based on the aforementioned method by substituting the plurality of pieces of movement state information into the power consumption per unit of time model including the model coefficients to be determined. The device for establishing the power consumption per unit of time model of the UAV can obtain a plurality of actual power consumptions per unit of time corresponding to the plurality of pieces of movement state information, run a minimization fitting algorithm based on the plurality of actual power consumptions per unit of time and the plurality of expected power consumptions per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. In some embodiments, the actual power consumption per unit of time may be obtained based on a predetermined unit of time. The embodiments of the present disclosure do not specifically limit the type of the minimization fitting algorithm, and those skilled in the art can select the minimization fitting algorithm based on needs, such as a linear fitting algorithms, a laser square fitting algorithm, etc. After the one or more model coefficients to be determined are determined, the determined model coefficients can be used to update the power consumption per unit of time model of the UAV to successfully establish the power consumption per unit of time model. 
     In one embodiment, the device for establishing the power consumption per unit of time model of the UAV can obtain the vertical flight speed, the altitude, and the horizontal flight speed, and obtain the actual power consumption per unit of time corresponding to the vertical flight speed, the altitude h, and the horizontal flight speed. The vertical flight speed, the altitude, and the horizontal flight speed can be substituted into the power consumption per unit of time model Δbat resume =R 1 +R 2 V vert +R 3   h +R 4 V horz  to calculate the expected power consumption per unit of time Δbat resume  Finally, as described in the above method, a minimization fitting algorithm can be run based on the expected power consumption per unit of time Δbat resume  and the actual power consumption per unit of time to determine the one or more model coefficients R 1 , R 2 , R 3 , and R 4  to be determined, and use the determined model R 1 , R 2 , R 3 , and R 4  to update the power consumption per unit of time model. 
     In one embodiment, when estimating the UAV return flight power based on the determined movement state information, the device for estimating the return flight power of the UAV may substitute the determined movement state information at the predetermined cruising altitude into the power consumption per unit of time model of the UAV to estimate the power consumption per unit of time of the UAV at the predetermined cruising altitude. As shown in  FIG. 7A , which is an effective diagram of an estimated power consumption per unit of time at a predetermined cruising altitude according to an embodiment of the present disclosure.  FIG. 7A  includes an original model power consumption  71  and an actual power consumption  72 . 
     In one embodiment, when estimating the UAV return flight power based on the determined movement state information, the device for estimating the return flight power of the UAV may substitute the determined movement state information of the forced landing and return flight into the power consumption per unit of time model of the UAV to estimate the power consumption per unit of time of the UAV at the predetermined cruising altitude. As shown in  FIG. 7B , which is an effective diagram of an estimated power consumption per unit of time during a forced landing and return flight according to an embodiment of the present disclosure.  FIG. 7B  includes an original model power consumption  73  and an actual power consumption  74 . As can be seen from  FIG. 7A  and  FIG. 7B , the power consumption per unit of time model of the UAV provided by the embodiments of the present disclosure is more accurate than the conventional model, which shows that the accuracy of the return flight power estimated by the power consumption per unit of time model of the UAV provided by the embodiments of the present disclosure is higher. 
     In the embodiments of the present disclosure, the device for establishing the power consumption per unit of time model of the UAV can obtain the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information, and substitute the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time of the UAV. Further, the device for establishing the power consumption per unit of time model of the UAV can run a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. By using this method, the error in estimating the return flight power can be reduced, the accuracy of the model can be improved, and the flight safety and user experience of the UAV can be improved. 
     Referring to  FIG. 8 , which is a schematic structural diagram of a UAV return flight control device according to an embodiment of the present disclosure. More specifically, the UAV return flight control device includes a memory  801 , a processor  802 , and a data interface  803 . 
     The data interface  803  can be used to transfer data of between the UAV return flight control device and the UAV. 
     The memory  801  may include a volatile memory. The memory  801  may also include a non-volatile memory. The memory  801  may further include a combination of the foregoing types of memories. The processor  802  may be a central processing unit (CPU). The processor  802  may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), or any combination thereof. 
     The memory  801  can be configured to store program instructions. The processor  802  can be configured to execute the program instructions stored in the memory  801 . When executed by the processor  802 , the program instructions can cause the processor  802  to control the UAV to fly to a predetermined cruising altitude and controlling the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value when it is determined that the remaining power of the UAV is less than or equal to a predetermined return flight power threshold; and during the horizontal return flight at the predetermined cruising altitude, control the UAV to perform forced landing and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value when determining the remaining power of the UAV is less than or equal to the predetermined landing power threshold. 
     In some embodiments, the target waypoint that satisfies the predetermined position relationship with the position of the UVA may be the target waypoint that is closest to the position of the UAV. 
     In some embodiments, when executed by the processor  802 , the program instructions can further cause the processor  802  to control the UAV to return horizontally at the predetermined safe altitude based on the second predetermined horizontal speed control value when determining that the altitude of the UAV has dropped to the predetermined safe altitude in the process of forced landing and return flight. 
     In some embodiments, when executed by the processor  802 , the program instructions can further cause the processor  802  to control the UAV to land when determining that the remaining power of the UAV is less than or equal to the predetermined landing power threshold in the process of horizontal return at the predetermined safe altitude. 
     In some embodiments, when executed by the processor  802 , the program instructions can further cause the processor  802  to control the UAV to land on the return flight point when determining that the UAV has reached above the return flight point in the process of horizontal return at the predetermined safe altitude. 
     In some embodiments, when executed by the processor  802 , the program instructions can further cause the processor  802  to control the UAV to land on the return flight point when determining that the UAV has reached above the return flight point in the process of forced landing and return flight. 
     In some embodiments, when executed by the processor  802 , the program instructions can further cause the processor  802  to control the UAV to land when determining that the remaining power of the UAV is less than or equal to the predetermined landing power threshold in the process of forced landing and return flight. 
     In the embodiments of the present disclosure, the UAV return flight control device can control the UAV to fly to a predetermined cruising altitude when it determines that the remaining power of the UAV is less than or equal to the predetermined return flight power threshold, and control the UAV to return horizontally at the predetermined cruising altitude based on the first predetermined horizontal speed control value. In the process of horizontal return at the predetermined cruising altitude, when it is determined that the remaining power of the UAV is less than or equal to the predetermined descent power threshold, the UAV can be controlled to perform the forced land and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. By using this method, the probability of losing the UAV can be reduced, the descent time can be reduced, and the flight safety of the UAV can be improved. 
     Referring to  FIG. 9 , which is a schematic structural diagram of a structure of a return flight power estimation device for a UAV according to an embodiment of the present disclosure. More specifically, the return flight power estimation device for the UAV includes a memory  901 , a processor  902 , and a data interface  903 . 
     The data interface  903  can be used to transfer data of between the UAV return flight control device and the UAV. 
     The memory  901  may include a volatile memory. The memory  901  may also include a non-volatile memory. The memory  901  may further include a combination of the foregoing types of memories. The processor  902  may be a central processing unit (CPU). The processor  902  may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), or any combination thereof. 
     The memory  901  can be configured to store program instructions. The processor  902  can be configured to execute the program instructions stored in the memory  901 . When executed by the processor  902 , the program instructions can cause the processor  902  to determine the movement state information of the UAV in the process of the return flight, where the process of the return flight may be the process of returning the UAV from the current position to the return flight point; and determining the return flight power based on the determined movement state information. 
     In some embodiments, the processor  902  executing the program instructions stored in the memory  901  to estimate the return flight power based on the determined movement state information may include determining the power consumption per unit of time of the UAV during the return flight process based on the determined movement state information; and estimating the return flight power based on the power consumption per unit of time. 
     In some embodiments, the processor  902  executing the program instructions stored in the memory  901  to determine the power consumption per unit of time based on the determined movement state information may include substituting the determined movement state information into the power consumption per unit of time model of the UAV to determine the power consumption per unit of time. 
     In some embodiments, the movement state information may include at the least one of the horizontal flight speed, the vertical flight speed, and the altitude information of the UAV. 
     In the embodiments of the present disclosure, the UAV return flight power estimation device can determine the movement state information of the UAV during the return flight process, and estimate the return flight power based on the determined movement state information. By using this method to estimate the return flight power, the error in estimation can be reduced, and the flight safety and user experience of the UAV can be improved. 
     Referring to  FIG. 10 , which is a schematic structural diagram of a device for establishing a UAV power consumption model per unit of time according to an embodiment of the present disclosure. More specifically, the device for establishing the power consumption per unit of time model includes a memory  1001 , a processor  1002 , and a data interface  1003 . 
     The data interface  1003  can be used to transfer data of between the UAV return flight control device and the UAV. 
     The memory  1001  may include a volatile memory. The memory  1001  may also include a non-volatile memory. The memory  1001  may further include a combination of the foregoing types of memories. The processor  1002  may be a central processing unit (CPU). The processor  1002  may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), or any combination thereof. 
     The memory  1001  can be configured to store program instructions. The processor  1002  can be configured to execute the program instructions stored in the memory  1001 . When executed by the processor  1002 , the program instructions can cause the processor  1002  to obtain the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information; substitute the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time of the UAV, where the power consumption per unit of time model may include one or more model coefficients to be determined; and run a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight states. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight environments. 
     In some embodiments, the degree of dispersion of the movement state information may be greater than or equal to the predetermined degree of dispersion threshold. 
     In some embodiments, the movement state information may include at least one of the horizontal flight speed, the vertical flight speed, and the altitude information of the UAV. 
     In the embodiments of the present disclosure, the device for establishing the power consumption per unit of time model of the UAV can obtain the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information, and substitute the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time of the UAV. Further, the device for establishing the power consumption per unit of time model of the UAV can run a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. By using this method, the error in estimating the return flight power can be reduced, the accuracy of the model can be improved, and the flight safety and user experience of the UAV can be improved. 
     An embodiment of the present disclosure further provides a UAV. The UAV may include a body, a power system disposed on the body to provide power for the UAV to move, and a processor configured to control the UAV to fly to a predetermined cruising altitude and controlling the UAV to return horizontally at the predetermined cruising altitude based on a first predetermined horizontal speed control value when it is determined that the remaining power of the UAV is less than or equal to a predetermined return flight power threshold; and during the horizontal return flight at the predetermined cruising altitude, control the UAV to perform forced landing and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value when determining the remaining power of the UAV is less than or equal to the predetermined landing power threshold. 
     In some embodiments, the processor may be further configured to control the UAV to return horizontally at the predetermined safe altitude based on the second predetermined horizontal speed control value when determining that the altitude of the UAV has dropped to the predetermined safe altitude in the process of forced landing and return flight. 
     In some embodiments, the processor may be further configured to control the UAV to land when determining that the remaining power of the UAV is less than or equal to the predetermined landing power threshold in the process of horizontal return at the predetermined safe altitude. 
     In some embodiments, the processor may be further configured to control the UAV to land on the return flight point when determining that the UAV has reached above the return flight point in the process of horizontal return at the predetermined safe altitude. 
     In some embodiments, the processor may be further configured to control the UAV to land on the return flight point when determining that the UAV has reached above the return flight point in the process of forced landing and return flight. 
     In some embodiments, the processor may be further configured to control the UAV to land when determining that the remaining power of the UAV is less than or equal to the predetermined landing power threshold in the process of forced landing and return flight. 
     In the embodiments of the present disclosure, the UAV return flight control device can control the UAV to fly to a predetermined cruising altitude when it determines that the remaining power of the UAV is less than or equal to the predetermined return flight power threshold, and control the UAV to return horizontally at the predetermined cruising altitude based on the first predetermined horizontal speed control value. In the process of horizontal return at the predetermined cruising altitude, when it is determined that the remaining power of the UAV is less than or equal to the predetermined descent power threshold, the UAV can be controlled to perform the forced land and return flight based on the first predetermined horizontal speed control value and the predetermined descent speed control value. By using this method, the probability of losing the UAV can be reduced, the descent time can be reduced, and the flight safety of the UAV can be improved. 
     An embodiment of the present disclosure further provides another UAV. The UAV may include a body, a power system disposed on the body to provide power for the UAV to move, and a processor configured to determine the movement state information of the UAV in the process of the return flight, where the process of the return flight may be the process of returning the UAV from the current position to the return flight point; and determining the return flight power based on the determined movement state information. 
     In some embodiments, the processor estimating the return flight power based on the determined movement state information may include determining the power consumption per unit of time of the UAV during the return flight process based on the determined movement state information; and estimating the return flight power based on the power consumption per unit of time. 
     In some embodiments, the processor determining the power consumption per unit of time based on the determined movement state information may include substituting the determined movement state information into the power consumption per unit of time model of the UAV to determine the power consumption per unit of time. 
     Further, the movement state information may include at the least one of the horizontal flight speed, the vertical flight speed, and the altitude information of the UAV. 
     In the embodiments of the present disclosure, the UAV return flight power estimation device can determine the movement state information of the UAV during the return flight process, and estimate the return flight power based on the determined movement state information. By using this method to estimate the return flight power, the error in estimation can be reduced, and the flight safety and user experience of the UAV can be improved 
     An embodiment of the present disclosure further provides another UAV. The UAV may include a body, a power system disposed on the body to provide power for the UAV to move, and a processor configured to obtain the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information; substitute the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time of the UAV, where the power consumption per unit of time model may include one or more model coefficients to be determined; and run a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight states. 
     In some embodiments, the movement state information may include the movement state information of the UAV in a plurality of different flight environments. 
     In some embodiments, the degree of dispersion of the movement state information may be greater than or equal to the predetermined degree of dispersion threshold. 
     In some embodiments, the movement state information may include at least one of the horizontal flight speed, the vertical flight speed, and the altitude information of the UAV. 
     In the embodiments of the present disclosure, the device for establishing the power consumption per unit of time model of the UAV can obtain the movement state information of the UAV during the flight and the actual power consumption per unit of time corresponding to the movement state information, and substitute the movement state information into the power consumption per unit of time model to obtain the expected power consumption per unit of time of the UAV. Further, the device for establishing the power consumption per unit of time model of the UAV can run a minimization fitting algorithm based on the actual power consumption per unit of time and the expected power consumption per unit of time to determine the one or more model coefficients to be determined, and update the power consumption per unit of time model by using the determined model coefficients. By using this method, the error in estimating the return flight power can be reduced, the accuracy of the model can be improved, and the flight safety and user experience of the UAV can be improved. 
     A computer-readable storage medium is also provided in the embodiments of the present disclosure. The computer-readable storage medium stores a computer program, and the computer program is executed by a processor to implement the methods in the embodiments corresponding to  FIG. 1 ,  FIG. 3 ,  FIG. 5 , or  FIG. 6 . The computer-readable storage medium can also implement the devices according to the embodiments of the present disclosure as shown in  FIG. 8 ,  FIG. 9 , or  FIG. 10 , and details are not described herein again. 
     The computer-readable storage medium may be an internal storage unit of the device according to any one of the foregoing embodiments, such as a hard disk or a memory of the device. The computer-readable storage medium may also be an external storage device of the device, such as a plug-in hard disk, a smart media card (SMC), and a secure digital (SD) card, a flash card, etc., provided in the device. Further, the computer-readable storage medium may further include both an internal storage unit of the above device and an external storage device. The computer-readable storage medium is configured to store the computer program and other programs and data required by the terminal. The computer-readable storage medium may also be configured to temporarily store data that has been or will be output. 
     The above embodiments are only the preferred embodiments of the present disclosure, and of course, and do not limit the claimed scope of the present disclosure. Therefore, equivalent changes made according to the claims of the present disclosure are within the scope of the present disclosure.