Flight control method and system for unmanned aerial vehicle to perform waypoint task based on differential coordinates

Abstract

The application provides a flight control method and system for unmanned aerial vehicle (UAV) to perform waypoint tasks based on differential coordinates, which comprises: north calibration: determining the angle between the self-built coordinate system and the NED coordinate system by capturing a mark line pointing to the north direction from an arbitrary origin, and obtaining the parameters required for coordinate conversion; establishing a conversion relationship between the self-built coordinate system and the NED coordinate system based on the parameters required for coordinate conversion, so that the waypoint coordinates in the UAV waypoint flight task, i.e. the coordinates in the self-built coordinate system, are output as the coordinates in the NED coordinate system, and can completely reflect the relative positions of the coordinate points in the self-built coordinate system, so that the path is completely consistent with the flight path required by the waypoint task; based on the new coordinates in the NED coordinate system after conversion, the UAV can obtain the relative positions of the waypoints, so as to obtain the flight control instructions based on the coordinate differential operation, and perform the fixed-point flight.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of unmanned aerial vehicle navigation and the technical field of Internet of Things application, and particularly relates to an indoor positioning and navigation method for unmanned aerial vehicles. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] With the development of unmanned aerial vehicle technology and Internet of Things technology, the research scope of civil quadcopter applications has gradually expanded, and the traditional GPS-based coordinate navigation system has greatly limited the application of unmanned aerial vehicles in some special environments. For example, in indoor environments or large venues, GPS signals will be significantly affected, and civil quadcopters (taking DJI Mavic2 as an example) usually use the GPS global satellite positioning system combined with their own optical positioning system for precise positioning, thereby controlling the unmanned aerial vehicle to fly to the waypoint. In the absence of GPS signals, only the optical positioning system cannot determine the relative coordinates of the unmanned aerial vehicle itself and the task node, thereby making it impossible to normally perform the waypoint task, which is a technical problem existing in current unmanned aerial vehicle applications.

[0004] In addition, GPS plays an important role in the process of unmanned aerial vehicle hovering at a specific point. Commercial parameters and experiments show that in the absence of GPS signals, only the optical positioning system can achieve a hovering accuracy of 1.5m+-, while in the presence of GPS, the hovering accuracy can be maintained at 0.5m+-, and the inability to accurately position and hover poses many safety hazards.

[0005] In the prior art, to solve the GPS precision problem, some engineering projects use RTK+GPS auxiliary positioning means to improve the GPS positioning accuracy to the decimeter level or even the centimeter level, but this method requires the unmanned aerial vehicle to carry additional loads, which is too complex for civil unmanned aerial vehicles, and also cannot get rid of the dependence on GPS signals. Although larger industrial-grade unmanned aerial vehicles can achieve a certain degree of waypoint flight through ground-based positioning and other methods, general consumer-grade unmanned aerial vehicles have lower loads (or some unmanned aerial vehicles only provide aerial photography functions without additional loads) and smaller battery capacities (with a battery life of less than 20 minutes), which makes it impossible for traditional methods to work on consumer-grade unmanned aerial vehicles, causing application difficulties. SUMMARY

[0006] To overcome the shortcomings of the prior art, the present application provides a flight control method for unmanned aerial vehicles to perform waypoint tasks based on differential coordinates, which realizes the point flight, hovering, and waypoint task of unmanned aerial vehicles in the absence of GPS signals.

[0007] To achieve the above object, one or more embodiments of the present application provide the following technical solutions:

[0008] In a first aspect, a flight control method for a UAV to perform a waypoint task based on differential coordinates is disclosed, comprising:

[0009] North calibration: the angle between the self-built coordinate system and the NED coordinate system is determined by capturing a mark line pointing to the north direction from an arbitrary origin point, and the required parameters for coordinate conversion are obtained;

[0010] Based on the required parameters for coordinate conversion, a conversion relationship is established between the self-built coordinate system and the NED coordinate system, so that the waypoint coordinates in the UAV waypoint flight task, i.e. the coordinates in the self-built coordinate system, are output as coordinates in the NED coordinate system, and can fully reflect the relative positions of each coordinate point in the self-built coordinate system, so that the path is completely consistent with the required flight path of the waypoint task;

[0011] Based on the new coordinates in the NED coordinate system after conversion, the UAV can obtain the relative position of the waypoint, so as to obtain the flight control command based on the coordinate differential operation and perform the point flight.

[0012] As a further technical solution, when performing "north calibration", a motion capture device is used to assist calibration to determine the relative coordinates of the calibration point.

[0013] As a further technical solution, the motion capture device includes a plurality of reflective points and a plurality of camera devices surrounding the flight area;

[0014] With the assistance of the motion capture device, the positions of the reflective points placed in the field are captured, and their x, y, z coordinates are derived according to the coordinate system established by the motion capture device.

[0015] As a further technical solution, the NED coordinate system is a reference coordinate system selected by the UAV for navigation solution according to the needs of the navigation system in operation;

[0016] The coordinate system has three axes, N - the north axis points to the north of the earth; E - the east axis points to the east of the earth; D - the ground axis is perpendicular to the earth's surface and points downward, which is convenient for calculation, and the north axis is defined as the x axis of the coordinate system, the east axis is defined as the y axis, and the ground axis is defined as the z axis;

[0017] The NED coordinate system is used as a kind of world coordinate system of the UAV to control the flight action of the UAV, and the world coordinate system refers to the coordinate system whose coordinate axis direction always remains unchanged, so it is used to determine the absolute heading of the UAV in space.

[0018] As a further technical solution, the specific steps for performing "north calibration" are as follows:

[0019] Determine the north direction;

[0020] Marking the due north direction, using two motion capture devices to mark a ray pointing to the due north direction, one is placed at the starting point, set as the positive calibration point A, and the other is placed at the end point, set as the due north calibration point B;

[0021] Read the coordinates A(x1, y1), B(x2, y2) of points A and B from the motion capture device, and initialize the judgment variable q = 0;

[0022] Calculate the Euclidean distance, sine value and cosine value of A and B;

[0023] Calculate the calibration parameters μ1 = x1*cos + y1*sin, μ2 = -x1*sin + y1*cos;

[0024] Determine the pointing direction of the vector AB. Specifically, in the plane rectangular coordinate system with A as the origin, if B is located in the first and third quadrants, modify the calibration parameters μ1 = x1*sin + y1*cos, and modify the judgment variable q = 1;

[0025] Record the calibration parameter ω1 = μ2;

[0026] Recalculate the calibration parameters based on B, modify μ1 = x2*cos + y2*sin, and μ2 = -x2*sin + y2*cos;

[0027] If the judgment variable q = 1, modify the calibration parameters μ1 = x2*cos - y2*sin, and μ2 = x2*sin + y2*cos;

[0028] Record the calibration parameter ω2 = μ2;

[0029] Initialize the judgment variable p = 0, and modify p = 1 if ω1 > ω2;

[0030] Save the following four parameters: a, b, p, q, where a = sin, b = cos, p and q are the above judgment variables p and q.

[0031] As a further technical solution, the coordinates in the self-built coordinate system are converted into control coordinates in the NED ground coordinate system through coordinate conversion, specifically:

[0032] The "due north calibration" outputs parameters a, b, p, q, and the translation and rotation relationship between the self-built coordinate system and the NED coordinate system is obtained based on the four parameters, so that the task point coordinates in the self-built coordinate system are converted into new coordinates in the NED coordinate system through coordinate transformation, and the unmanned aerial vehicle navigates and searches according to these new coordinates.

[0033] As a further technical solution, the translation and rotation relationship between the self-built coordinate system and the NED coordinate system is obtained based on four parameters, specifically:

[0034] Input parameters a, b, p, q;

[0035] Determine whether all nodes that need to be converted have been converted, if not, enter the coordinate conversion process;

[0036] Input the coordinates to be converted x, y;

[0037] Calculate the calibration parameters μ1=x*b+y*a, μ2=-x*a+y*b;

[0038] If q=1, modify the calibration parameters μ1=x*b-y*a, μ2=x*a+y*b;

[0039] If p=1, the new coordinate system needs to be rotated, at this time modify μ1=-μ1, μ2=-μ2;

[0040] Output the new coordinates μ1, μ2 after conversion for coordinates x, y;

[0041] Store the new coordinates in the answer array, and repeat the above process until there are no more coordinates to be converted;

[0042] Generate a formatted output according to the answer array.

[0043] In a second aspect, a flight control system for unmanned aerial vehicles to perform waypoint tasks based on differential coordinates is disclosed, comprising:

[0044] The north calibration module is configured to determine the angle between the coordinate axes of the self-built coordinate system and the NED coordinate system by capturing a line pointing to the north direction from an arbitrary origin, and to obtain the parameters required for coordinate conversion;

[0045] The coordinate conversion module is configured to establish a conversion relationship between the self-built coordinate system and the NED coordinate system based on the parameters required for coordinate conversion, so that the waypoint coordinates in the unmanned aerial vehicle waypoint flight task, i.e. the coordinates in the self-built coordinate system, are output as coordinates in the NED coordinate system, and can fully reflect the relative positions of each coordinate point in the self-built coordinate system, so that the path is completely consistent with the flight path required by the waypoint task;

[0046] The flight control module is configured to obtain the relative position of the waypoint based on the new coordinates in the NED coordinate system after conversion, so as to obtain the flight control command based on coordinate differential operation, and perform point flight.

[0047] The above one or more technical solutions have the following beneficial effects:

[0048] The technical scheme of the present application is based on a coordinate system rotation translation conversion algorithm, and is assisted by a motion capture system to complete, first, north calibration is performed, an angle between a self-built coordinate system and a NED coordinate system is determined by capturing a mark line pointing to the north direction from an arbitrary origin point, and required parameters are obtained, so that the coordinate conversion can be calculated based on these parameters.

[0049] The embodiment establishes a conversion relationship between the self-built coordinate system and the NED coordinate system, so that the waypoint coordinates in the unmanned aerial vehicle waypoint flight task, that is, the coordinates in the self-built coordinate system, can be output as the coordinates in the NED coordinate system under the assistance of the motion capture system and the conversion of the embodiment, and can fully reflect the relative positions of the coordinate points in the self-built coordinate system, so that the flight path required by the path and waypoint task is completely consistent.

[0050] Based on the new coordinates in the NED coordinate system after conversion, the unmanned aerial vehicle can recognize the relative positions of the waypoints, so as to obtain flight control instructions based on coordinate difference calculation, and realize fixed-point flight, which realizes the goal that the unmanned aerial vehicle can still perform fixed-point flight and waypoint task in the case of GPS signal loss, and provides an algorithm basis for subsequent embodiments.

[0051] The advantages of the additional aspects of the present application will be partially given in the following description, partially will become obvious from the following description, or will be known by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0052] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and their explanations serve to explain the present application, and do not constitute improper limitations on the present application.

[0053] Figure 1 is an algorithm flowchart of "north calibration" in the coordinate system conversion algorithm of the first embodiment of the present application;

[0054] Figure 2 is an algorithm flowchart of "coordinate conversion" in the coordinate system conversion algorithm of the first embodiment of the present application;

[0055] Figure 3 is an algorithm flowchart of the second embodiment of the present application;

[0056] Figure 4 is a software architecture schematic diagram of the third embodiment of the present application. DETAILED DESCRIPTION

[0057] It should be noted that the following detailed description is exemplary, and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0058] It is to be noted that the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit exemplary embodiments according to the present application.

[0059] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0060] Overall concept:

[0061] Based on the assistance of the compass and software tools, the calibration of the NED coordinate axis, also known as "north calibration", is realized with the assistance of the motion capture system, so as to determine the parameters of the coordinate system conversion algorithm; based on the north calibration, the coordinate conversion from the self-built coordinate system to the NED coordinate system is realized; based on the conversion parameters and the coordinates of the task points obtained by the conversion, the coordinates of the task points after the coordinate conversion algorithm derived based on the rotation and translation of the coordinate system are obtained, and the navigation of the unmanned aerial vehicle for fixed-point flight is realized through the flight control steps based on the differential coordinates provided by the present application, so that the unmanned aerial vehicle can complete the waypoint flight task in the self-built coordinate system; based on the above-mentioned coordinate system conversion algorithm and flight control algorithm, an indoor flight experiment platform system of the unmanned aerial vehicle is built, so as to realize the verification of the waypoint flight task of the unmanned aerial vehicle in the case of lack of GPS signal, and provide a basic experiment platform and software platform for other unmanned aerial vehicle pathfinding experiments; the experiment platform built based on the above-mentioned scheme and the related computer equipment.

[0062] Among them, the north calibration process is completed with the assistance of the motion capture system, and the input required by the algorithm is obtained by fixing two rays for marking the direction of the north and obtaining the coordinates of the rays in the self-built coordinate system. The coordinates of the calibration point coordinates in the self-built coordinate system are taken as the input, the target result is obtained through the operation of the rotation angle of the coordinate system, and the four conversion parameters are taken as the output.

[0063] The coordinate conversion algorithm is specifically: based on the four conversion parameters output and the task point coordinates in the self-built coordinate system input, the coordinates in the NED coordinate system after conversion are obtained through the translation and rotation of the coordinate system and the corresponding processing of different conversion conditions, and the coordinates after conversion are taken as the output.

[0064] When flying:

[0065] Based on the coordinate information in any coordinate system input, the waypoint task is generated, the waypoints in the waypoint task, i.e. the task points, are scheduled in sequence, and the flight control signal is generated, the flight control command is sent through the remote controller, and the unmanned aerial vehicle is operated to traverse the waypoints in sequence according to the specified route, so as to execute the waypoint flight task.

[0066] Based on the relative position of the two adjacent nodes in the sequence, the heading and time information required for flight control command is calculated by calculating the angle between the vector and the coordinate axis, the distance and other parameters, thereby completing a sub-task in the waypoint flight task, flying from one task point to another task point.

[0067] The parameters of the flight control command are calculated based on the relative position of the two adjacent nodes in the sequence.

[0068] Embodiment one

[0069] The embodiment discloses a flight control method for unmanned aerial vehicle to perform waypoint task based on differential coordinates, as shown in Figure 2 , 3, specifically comprising the following steps:

[0070] Step one, "north calibration", as shown in Figure 1 .

[0071] Specifically, in the coordinate system conversion, it is necessary to first determine the direction of the north in the self-built coordinate system, so as to determine the direction of the x axis in the NED coordinate system. The main purpose is to adapt to the control of the parameter yaw in the unmanned aerial vehicle flight control signal. This parameter is adapted to the NED coordinate system (navigation coordinate system), and its value uniquely limits the orientation of the unmanned aerial vehicle head, and is pointed and corrected by the compass information of the unmanned aerial vehicle itself. For the coordinate system conversion algorithm shown in embodiment one, the main purpose of "north calibration" is to provide the parameters required for operation, so as to facilitate the coordinate conversion process in step two. The calibration needs to rely on motion capture equipment or other ways to determine the relative coordinates of the calibration point. Here, motion capture equipment is used to assist calibration.

[0072] Specifically, the present embodiment uses an optical motion capture device to assist in the calibration process. The motion capture device includes a number of reflective points, a number of cameras surrounding the flight area, and processing software. The processing software uses Seeker software developed by Nokov Company, which can connect the cameras through a gateway and set and adjust the camera area, resolution, focal length, etc. of a number of cameras. When used in the present example to obtain the task point coordinates, the following steps are used: use a network cable to connect the cameras and the device used for calculation in the same network environment, configure the network IP, and until the software can read the image information of each connected camera; perform software calibration, i.e., L calibration and T calibration, the calibration method is shown in the software manual, and finally the indoor environment is established; the task points are placed in the field as reflective points. Since Seeker cannot read single point coordinates, but needs to set the reflective points as point sets or rigid bodies and then read them respectively, more than 4 task points need to be set as point sets, and then select each point to read the coordinates of the task points in the self-built coordinate system using the calibrated Seeker software. With the assistance of the motion capture device, the positions of the reflective points placed in the field are captured by the cameras, and their x, y, z coordinates are derived according to the coordinate system established by the motion capture device. The origin position and axial position of the coordinate system established by the motion capture device do not need to be considered in this embodiment, because this embodiment is based on relative position for coordinate conversion.

[0073] In the present embodiment, a NOKOV motion capture system or other similar motion capture system is used.

[0074] In the present embodiment, the NED coordinate system refers to the NED (North East Down) coordinate system, i.e., the North East Down coordinate system, also known as the navigation coordinate system, which is a reference coordinate system selected for navigation calculation according to the needs of the navigation system. This coordinate system has three axes, N - the north axis pointing to the north of the earth; E - the east axis pointing to the east of the earth; D - the ground axis perpendicular to the earth's surface and pointing downward, which is convenient for calculation, and the north axis is defined as the x-axis of the coordinate system, the east axis is defined as the y-axis, and the ground axis is defined as the z-axis. For the purpose of precise control of the unmanned aerial vehicle, the NED coordinate system is used as a world coordinate system of the unmanned aerial vehicle to control the flight movement of the unmanned aerial vehicle. The world coordinate system refers to a coordinate system whose coordinate axis direction always remains unchanged, so it is used to determine the absolute heading of the unmanned aerial vehicle in space.

[0075] The bottom layer control of the unmanned aerial vehicle uses its own coordinate system, which is different from the world coordinate system. The origin and coordinate axes of the coordinate system change constantly with the movement, attitude, etc. of the unmanned aerial vehicle, but remain consistent with the direction of the physical structure of the unmanned aerial vehicle, so it is used to determine the relative heading of the unmanned aerial vehicle and represent the change and adjustment of the heading.

[0076] Generally speaking, the NED coordinate system cannot directly navigate the unmanned aerial vehicle as a world coordinate system, and ultimately needs to be converted to the self-coordinate system by the internal algorithm, which provides the bottom control, similar to the manual operation of human beings, but this part of the coordinate conversion has been encapsulated, so that the NED coordinate system can be directly used as the reference coordinate system of the control signal to realize the accurate control of the heading of the unmanned aerial vehicle.

[0077] The embodiment introduces a third coordinate system, i.e., a self-built coordinate system, which aims to solve the defect that the NED coordinate system origin translation can only control the heading and cannot perceive the spatial task point and control the unmanned aerial vehicle to fly to the point.

[0078] In the NED coordinate system, although the coordinate axes remain unchanged, the origin point is consistent with the center of the unmanned aerial vehicle, so the origin point will translate with the movement of the unmanned aerial vehicle, which makes the unmanned aerial vehicle unable to fly to the target point in a certain direction. In the case of GPS intervention, the NED coordinate system will be further converted with the WGS84 earth coordinate system to realize the positioning flight, but in the case of GPS signal loss, this method is no longer possible. In this embodiment, a self-built coordinate system is provided, which is a stable coordinate system, similar to the earth coordinate system, and the coordinate axes and origin point remain unchanged, which makes it possible to obtain the relative position of each point in this coordinate system, thereby enabling the unmanned aerial vehicle to achieve the goal of flying to the point.

[0079] Therefore, the core purpose of this embodiment is to establish the conversion relationship between the self-built coordinate system and the NED coordinate system, so that the self-built coordinate system can replace the earth coordinate system to provide navigation for the unmanned aerial vehicle.

[0080] The calibration process is as follows:

[0081] Step 1-1: Determine the north direction, which can use a compass, and in the "flight control module" of embodiment 3, a function is configured to facilitate calibration, which can make the unmanned aerial vehicle point to the north direction, which is convenient for determining the direction without a compass.

[0082] Step 1-2: Mark the north direction, use two reflective points of the motion capture device to mark a ray pointing to the north direction, one is placed at the starting point and set as the calibration point A, and the other is placed at the ending point and set as the north calibration point B.

[0083] Step 1-3: Read the coordinates of points A and B from the motion capture device A(x1, y1), B(x2, y2), and initialize the judgment variable q = 0;

[0084] Step 1-4: Calculate the Euclidean distance of A and B The sine value sin = abs(x1-x2) / dis, the cosine value cos = abs(y1-y2) / dis, and abs is an absolute value function.

[0085] Step 1-5: Calculate the calibration parameters μ1 = x1*cos + y1*sin, μ2 = -x1*sin + y1*cos.

[0086] Step 1-6: Determine the pointing direction of the vector AB. Specifically, in the plane rectangular coordinate system with A as the origin, if B is located in the first or third quadrant, modify the calibration parameters μ1 = x1*sin + y1*cos, and modify the judgment variable q = 1.

[0087] Step 1-7: Record the calibration parameter ω1 = μ2.

[0088] Step 1-8: Recalculate the calibration parameters according to B, modify μ1 = x2*cos + y2*sin, and μ2 = -x2*sin + y2*cos.

[0089] Step 1-9: If the judgment variable q = 1, modify the calibration parameters μ1 = x2*cos - y2*sin, and μ2 = x2*sin + y2*cos.

[0090] Step 1-10: Record the calibration parameter ω2 = μ2.

[0091] Step 1-11: Initialize the judgment variable p = 0, and if ω1 > ω2, modify p = 1.

[0092] Step 1-12: Save the following four parameters: a, b, p, q, where a = sin, b = cos, p, and q are the judgment variables p and q mentioned above.

[0093] Step 1-13: The algorithm ends.

[0094] After the "north calibration" is completed, the direction information required from the calibration has been included in the saved four parameters, and the four parameters have no actual meaning in the current step and need to be imported into the coordinate conversion algorithm in step two to participate in the algorithm execution process, so that the coordinate conversion algorithm can be executed correctly.

[0095] Step two: Execute the coordinate conversion algorithm, as shown in Figure 2

[0096] ​The "north calibration" of step one outputs parameters a, b, p, q after being correctly executed, and the coordinate conversion algorithm will obtain the translation and rotation relationship between the self-built coordinate system and the NED coordinate system based on the four parameters, so as to convert the coordinates of a plurality of task points in the self-built coordinate system into new coordinates in the NED coordinate system through coordinate transformation, so that the UAV can navigate and pathfind according to the new coordinates. The specific execution process is as follows:

[0097] Step 2-1: The algorithm starts, and the parameters a, b, p, q are input.

[0098] Step 2-2: Determine whether all the nodes that need to be converted have been converted. If not, go to the coordinate conversion process.

[0099] Step 2-3: Input the coordinates x, y to be converted.

[0100] Step 2-4: Calculate the calibration parameters μ1 = x*b + y*a, μ2 = -x*a + y*b.

[0101] Step 2-5: If q = 1, modify the calibration parameters μ1 = x*b - y*a, μ2 = x*a + y*b.

[0102] Step 2-6: If p = 1, the new coordinate system needs to be rotated, so modify μ1 = -μ1, μ2 = -μ2.

[0103] Step 2-7: Output the new coordinates μ1, μ2 after conversion for the coordinates x, y.

[0104] Step 2-8: Store the new coordinates in the answer array, and repeat the above process until there are no more coordinates to be converted.

[0105] Step 2-9: Generate a formatted output based on the answer array for subsequent processing.

[0106] In specific implementation, install and debug the NOKOV motion capture system or other similar motion capture systems, perform the calibration process, and assist in establishing the indoor coordinate system.

[0107] Use the UAV flight control software or compass to perform origin-north calibration to obtain the coordinate axis direction of the NED ground coordinate system.

[0108] Set up a plurality of coordinate nodes on the ground, and obtain their coordinates x, y in the self-built coordinate system through the motion capture system.

[0109] Execute the self-built coordinate system-NED coordinate system coordinate conversion algorithm, input the coordinates x, y, and output the converted NED coordinate system coordinates x', y'.

[0110] Step three: flight control step based on relative position of coordinate points, in this flight control step, the origin position of coordinate system will not be considered, only the relative position of coordinate points in the case of unchanged coordinate axis, i.e. in the NED coordinate system, including distance and heading. Since the origin position is dynamic, the coordinates of the same task point in the self-built coordinate system may be significantly different due to the different origin positions selected when building the system, but since the relative position remains unchanged, the same flight control can still be achieved for the above different coordinates, so that the UAV performs waypoint flight task according to the absolute position of the task point.

[0111] As shown in Figure 3 It is worth noting that the flight control method provided in this embodiment can be used based on the coordinates provided in other coordinate systems, and only the relative position of the coordinates is used for flight control. However, this embodiment does not guarantee the flight control effect of the coordinates obtained based on the coordinate conversion algorithm not using the coordinate system conversion algorithm of embodiment one.

[0112] The specific implementation steps are as follows.

[0113] Step 3-1: initialize the waypoint mission WaypointMission[], which stores a series of coordinate points and forms a waypoint flight mission, and the UAV will fly according to the order of the coordinate points. Initialize the flight control parameters, including the flight speed v, the flight height, etc., the control mode, etc. The flight control parameters may be different according to the UAV model, the controller, the task requirements, etc., and are not part of the embodiment.

[0114] Step 3-2: for the waypoint flight mission WaypointMission, determine whether there are any remaining waypoints to be processed, if there are, continue to execute, if there are no remaining waypoints, the task is completed, return the waypoint task completion signal, and the algorithm ends.

[0115] Step 3-3: set the i-th waypoint to be executed, calculate the Euclidean distance dis between the i-th waypoint and the i+1-th waypoint, i.e. the next waypoint, and the angle θ° between the vector composed of the i-th waypoint and the i+1-th waypoint and the y-axis.

[0116] Step 3-4: if θ>180, set θ as 180-360. This is to adapt to the characteristics of yaw based on positive and negative adjustment. When adjusting yaw, if the heading direction is to the left front or left rear, i.e. 3, 4 quadrants, θ is negative.

[0117] Step 3-5: calculate the flight time t = dis / v.

[0118] Step 3-6: initialize the flight control signal structure, set yaw = θ, pitch = v, and the signal duration is t.

[0119] Step 3-7: Send the control signal according to the required signal frequency.

[0120] Step 3-8: Time delay 2s, clear local variables in the process, and destroy the flight control signal structure generated in step 3-6.

[0121] Step 3-8: Return to step 3-2.

[0122] The embodiment provides a flight control step based on the relative position of the task point, the generated control signal can be continuously executed or distributed according to the experimental requirements, can be dynamically processed or offline processed, and the method can be used for navigation of the absolute coordinate of the fixed-point flight task based on the relative position, and has a higher requirement on the accuracy of the flight of the unmanned aerial vehicle. The embodiment solves the conversion process from the waypoint coordinate to the waypoint task execution, so that the coordinate can be converted into the control signal of the unmanned aerial vehicle and finally complete the goal of the unmanned aerial vehicle completing the waypoint flight task between the task points in the self-built coordinate system, and provides a theoretical basis for solving the engineering problem in embodiment three.

[0123] Embodiment two

[0124] The purpose of the embodiment is to provide a computer device, including a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to realize the steps of the above method.

[0125] Embodiment three

[0126] The purpose of the embodiment is to provide a computer readable storage medium.

[0127] A computer readable storage medium has a computer program stored thereon, and the program is executed by a processor to execute the steps of the above method.

[0128] Embodiment four

[0129] The purpose of the embodiment is to provide an indoor flight experiment system of an unmanned aerial vehicle, which includes the following modules, such as Figure 4 As shown in the figure:

[0130] The experiment front-end module is configured to generate a simulation path image based on user input coordinate information, and store the user input experiment path data in the memory experiment database.

[0131] The coordinate conversion module is configured to output the coordinates in the NED coordinate system based on the user input coordinates in the self-built coordinate system after calculation. The related method in the first embodiment is adopted;

[0132] The flight control module includes an Android APP, which is configured to obtain database path information based on user instructions, and realize the control and navigation of the unmanned aerial vehicle.

[0133] The cloud data module includes an experiment database and a cloud function: for interfacing data access requests between modules and saving experiment data. Among them, the experiment database is defined as a table containing a table for mapping experiment serial numbers and path information, including three attributes: the primary key stores the unique serial number of the experiment and is incremented; the route attribute is used to store a flight path corresponding to the experiment serial number in the form of a point set string, which is easy to read and used for quick error correction; the route_json attribute is used to store the json format string of the path stored in route, which is used for front-end parsing and parsing and execution of the flight control software. The cloud function is defined as a web program written in python, which can be quickly deployed and run on the FaaS platform. The cloud function is used to realize data transfer, including a web interface that can import experiment path data from the outside, a function that stores experiment data into the database, a web interface that reads data from the database according to the experiment serial number of Post and returns it, and an internal function for string processing.

[0134] The path calculation module includes a cloud function, which is configured as: a cloud function based on python, which can be run on the FaaS platform, and functions as an input routing algorithm, calculates the optimized flight path based on waypoint coordinates, and feeds back the calculated optimized path to other modules. Among them, the routing algorithm can be defined as a function used by this module to calculate the flight path, which can be rewritten according to the user's demand to test different routing algorithms, and this module provides a data interface to ensure that data is read into the specified format. As an example, a usable algorithm has been reserved in the path calculation module, which is a path calculation algorithm based on DFS enumeration. This algorithm starts from a given starting point and performs a depth-first search, enumerates possible paths and constantly optimizes path selection according to path length until the optimal path is found. This algorithm is only used as an example and has not been optimized and can be replaced by other routing algorithms for testing. The path calculation module also provides a web interface for outputting the calculated path, which can send data in json format to the cloud data module or the experiment front-end module.

[0135] The program is executed by the processor under the operation of the professional experiment personnel to realize the steps of the flight control method based on differential coordinates to perform waypoint tasks as described above. Specifically, it includes:

[0136] Path reading: read the experiment path information from the remote database and load it into the flight scheduling data structure storage.

[0137] Heading calculation: read coordinate information from the flight scheduling data structure, calculate differential information to get the relative heading of the next waypoint.

[0138] Distance control: according to the heading information and the coordinate difference information, the flight distance is calculated, so as to obtain the speed and time of motor operation.

[0139] Instruction formation: the parameters required by the flight control signal are obtained from the heading calculation result, the format processing is performed, the flight instruction is formed, and the control signal is sent according to the frequency required by the unmanned aerial vehicle.

[0140] In this embodiment, the realization of coordinate conversion is a computer program corresponding to the algorithm in embodiment one, which is a specific implementation of the algorithm in embodiment one. When the program is executed by the processor, the steps of the coordinate system conversion algorithm described in embodiment one are realized.

[0141] In this embodiment, the flight control module is a computer program corresponding to the algorithm in embodiment one, but the algorithm in embodiment one only provides algorithm basis for part of the functions in the flight control module. Therefore, part of the program in the flight control module is a specific implementation of the algorithm in embodiment one. When the part of the program is executed by the processor, the steps of the flight control of the unmanned aerial vehicle based on the differential coordinates to perform the waypoint task described in embodiment one are realized.

[0142] This embodiment provides a solution for building an indoor flight experiment system of an unmanned aerial vehicle. The modules involved in this scheme are connected through data flow or control flow, and the specific flight experiment is completed under the operation of professional experimenters. As an advantage, it has the ability to make the unmanned aerial vehicle complete the complete waypoint task in the self-built coordinate system under the premise of the absence of GPS signal, so that the algorithm in embodiment one can be applied in the actual operation environment, and it also provides a feasible experimental place and software basis for completing other unmanned aerial vehicle path finding experiments.

[0143] The present application provides a kind of unmanned aerial vehicle control coordinate conversion algorithm, it can establish self-built coordinate system and obtain the coordinates of task node in self-built coordinate system under the assistance of motion capture system, then the control coordinates in NED ground coordinate system are converted from the coordinates in self-built coordinate system by coordinate conversion, so as to provide accurate task node coordinates for the flight control of unmanned aerial vehicle in self-built coordinate system, so that unmanned aerial vehicle completes the waypoint flight task in self-built coordinate system becomes possible.

[0144] The present application provides a kind of unmanned aerial vehicle based on the flight control method of differential coordinates to perform waypoint task, on the basis of the coordinates obtained by the above-mentioned coordinate conversion algorithm, the heading information, the rotation speed information and the flight time information required by the flight control of unmanned aerial vehicle are obtained by coordinate difference, so as to calculate the change value of the three variables of roll, yaw and pitch required by the bottom flight control of unmanned aerial vehicle, achieve the flight control of unmanned aerial vehicle based on differential coordinates, and achieve the purpose of completing the waypoint flight task of unmanned aerial vehicle.

[0145] The application provides an experimental platform for verifying properties, and based on the first two technical innovations, an experimental system for testing a route searching algorithm of a UAV is constructed indoors, so that the effects of the above technologies are verified, and simulation experimental verification of other path planning algorithms can be realized through an algorithm interface in a path calculation module.

[0146] The steps and methods involved in the devices of the above embodiments two, three and four correspond to the method embodiment one, and the specific implementation can be understood with reference to the relevant description part of the embodiment one. The term 'computer readable storage medium' should be understood as including a single medium or multiple media of one or more instruction sets; and should also be understood as including any medium capable of storing, encoding or carrying the instruction set for execution by the processor and causing the processor to perform any method in the application.

[0147] Those skilled in the art should understand that the above modules or steps of the application can be realized by a general computer device, and alternatively, they can be realized by program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, or they can be respectively manufactured into integrated circuit modules, or a plurality of modules or steps among them can be manufactured into a single integrated circuit module to realize. The application is not limited to any specific combination of hardware and software.

[0148] Although the specific embodiments of the application are described above in combination with the drawings, the description is not a limitation on the protection scope of the application, and those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the application without creative labor are still within the protection scope of the application.

Claims

1. A flight control method for unmanned aerial vehicles to perform waypoint missions based on differential coordinates, characterized in that, The application comprises: North calibration: the angle between the self-built coordinate system and the NED coordinate system is determined by capturing a reticle pointing to the north direction from an arbitrary origin, and the parameters required for coordinate conversion are obtained; Based on the parameters required for coordinate conversion, the conversion relationship between the self-built coordinate system and the NED coordinate system is established, so that the waypoint coordinates in the UAV waypoint flight task, i.e. the coordinates in the self-built coordinate system, are output as the coordinates in the NED coordinate system, and can fully reflect the relative positions of the coordinate points in the self-built coordinate system, so that the flight path required by the path and waypoint task is completely consistent; Based on the new coordinates in the NED coordinate system after conversion, the UAV can obtain the relative positions of the waypoints, so as to obtain the flight control instructions based on coordinate difference operation and perform point flight; The specific steps of "north calibration" are as follows: Determine the north direction; Mark the north direction, use two reflective points of the motion capture device to mark a ray pointing to the north direction, one is placed at the starting point and is set as the calibration point A, and the other is placed at the ending point and is set as the north calibration point B; Read the coordinates A(x1, y1), B(x2, y2) of points A and B from the motion capture device, and initialize the judgment variable q=0; Calculate the Euclidean distance, sine value and cosine value of A and B; Calculate the calibration parameters μ1=x1*cos+y1*sin, μ2=-x1*sin+y1*cos, dis is the Euclidean distance, sin=abs(x1-x2) / dis, cos=abs(y1-y2) / dis, and abs is the absolute value function; Determine the pointing direction of vector AB, specifically, in the plane rectangular coordinate system with A as the origin, if B is located in the first and third quadrants, modify the calibration parameters μ1=x1*sin+y1*cos, and modify the judgment variable q=1; Record the calibration parameter ω1=μ2; Recalculate the calibration parameters based on B, modify μ1=x2*cos+y2*sin, and μ2=-x2*sin+y2*cos; If the judgment variable q=1, modify the calibration parameters μ1=x2*cos-y2*sin, and μ2=x2*sin+y2*cos; Record the calibration parameter ω2=μ2; Initialize the judgment variable p=0, and modify p=1 if ω1>ω2; Save the following four parameters: a, b, p, q, where a=sin, b=cos, p and q are the above judgment variables p and q; Convert the coordinates in the self-built coordinate system into the control coordinates in the NED ground coordinate system through coordinate conversion, specifically: The north calibration output parameters a, b, p, q are used to obtain the translation and rotation relationship between the self-built coordinate system and the NED coordinate system, so as to convert the task point coordinates in the self-built coordinate system into new coordinates in the NED coordinate system through coordinate transformation, and the UAV can navigate and search the path according to these new coordinates; The translation and rotation relationship between the self-built coordinate system and the NED coordinate system is obtained based on the four parameters, and the specific execution process is as follows: Input parameters a, b, p, q; Determine whether all the nodes to be converted have been converted, if not, enter the coordinate conversion process; Input the coordinate x, y to be converted; Calculate the calibration parameters μ1=x*b+y*a, μ2=-x*a+y*b; If q=1, modify the calibration parameters μ1=x*b-y*a, μ2=x*a+y*b; If p=1, the new coordinate system needs to be rotated, at this time modify μ1=-μ1, μ2=-μ2; Output the new coordinate μ1, μ2 after conversion for the coordinate x, y; Store the new coordinate into the answer array, and repeat the above process until there is no coordinate point to be converted; Generate the formatted output according to the answer array. 2.The flight control method for the UAV to perform a waypoint task based on differential coordinates according to claim 1, wherein, When performing "north calibration", use the motion capture device to assist calibration to determine the relative coordinates of the calibration points. 3.The flight control method of the UAV performing waypoint missions based on differential coordinates according to claim 1, wherein, The motion capture device includes a plurality of reflective points and a plurality of camera devices surrounding the flight area; Under the assistance of the motion capture device, the positions of the reflective points placed in the field are captured, and their x, y, z coordinates are derived according to the coordinate system established by the motion capture device. 4.The flight control method of the UAV performing waypoint tasks based on differential coordinates according to claim 1, wherein, The NED coordinate system is a reference coordinate system selected by the unmanned aerial vehicle for navigation calculation according to the needs of the navigation system in operation; The coordinate system has three axes, N-the north axis points to the north of the earth; E-the east axis points to the east of the earth; D-the ground axis is perpendicular to the earth's surface and points downward, which is convenient for calculation, and the north axis is defined as the x-axis of the coordinate system, the east axis is defined as the y-axis, and the ground axis is defined as the z-axis. The NED coordinate system is used as a kind of world coordinate system of the unmanned aerial vehicle to control the flight action of the unmanned aerial vehicle. The world coordinate system refers to the coordinate axis direction of the coordinate system which always remains unchanged, so it is used to determine the absolute heading of the unmanned aerial vehicle in space.

5. The flight control system of the UAV based on the differential coordinates to perform the waypoint task, which realizes the steps of the method of any one of claims 1-4, characterized in that, It comprises: A north calibration module configured to determine the angle between the self-built coordinate system and the NED coordinate system coordinate axis by capturing a calibration line pointing to the north direction from an arbitrary origin, and obtain the parameters required for coordinate conversion; A coordinate conversion module configured to establish a conversion relationship between the self-built coordinate system and the NED coordinate system based on the parameters required for coordinate conversion, so that the waypoint coordinates in the unmanned aerial vehicle waypoint flight task, i.e. the coordinates in the self-built coordinate system, are output as coordinates in the NED coordinate system, and can fully reflect the relative positions of the coordinate points in the self-built coordinate system, so that the flight path required by the path and waypoint task is completely consistent; A flight control module configured to enable the unmanned aerial vehicle to obtain the relative position of the waypoint based on the new coordinates in the NED coordinate system after conversion, so as to obtain the flight control command based on coordinate difference operation and perform fixed-point flight.

6. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory and loadable on the processor, characterized in that, The processor executes the program to implement the steps of the method of any one of claims 1-4.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The program is executed by the processor to perform the steps of the method of any one of claims 1-4.

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