UAV NEVIGATION CALIBRATION METHOD, NON-TRANSITORY COMPUTER-READABLE STORAGE MEDIUM AND UAV IMPLEMENTING THE SAME

FIELD OF THE INVENTION

This application relates to the field of unmanned aerial vehicle (UAV) navigation sensors, and more specifically, to a calibration method for navigation of an unmanned aerial vehicle (UAV), a non-transitory computer-readable storage medium and a UAV implementing the same.

BACKGROUND OF THE INVENTION

During a flight of a UAV, to provide precise navigation paths, various types of vector sensor are required to measure headings and postures of the UAV in real time. A vector sensor can provide a direction and a size of a to-be-measured physical quantity. For example, a three-axis magnetoresistive vector sensor capable of measuring the direction of the earth magnetic field is used to manufacture a compass to achieve azimuth measurement. For another example, a three-axis acceleration vector sensor capable of measuring the gravity acceleration of the earth provides an angle of inclination relative to a horizontal plane. However, when the to-be-measured physical quantity is zero, data output of a vector sensor is often not zero, that is, a zero-point error exists, accuracy of UAV navigation is affected.

SUMMARY OF THE INVENTION

According to the first aspect of the present invention, an unmanned aerial vehicle (UAV) is provided. The UAV comprises a vector sensor for measuring headings and postures of the UAV; and one or more processors configured to: collect, during a flight of the UAV, a current correction value E_kand current data during a current measurement performed by the vector sensor; acquire previous data during a previous measurement performed by the vector sensor; acquire an adjustment quantity W_kaccording to the current data and the previous data; acquire a next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k, and acquire next original data R_k+1during a next measurement performed by the vector sensor, and acquire next valid data V_k+1according to the next original data R_k+1and the next correction value E_k+1; and control headings and postures of the UAV according to the next valid data V_k+1. The current data comprises current original data R_kand the previous data comprises previous original data R_k−1. The one or more processors are further configured to: acquire a weight D_kand an estimated quantity M_kaccording to the current original data R_kand the previous original data R_k−1; and acquire the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

According to the second aspect of the present invention, a calibration method for navigation of an unmanned aerial vehicle (UAV) is provided. The UAV includes a vector sensor for measuring headings and postures of the UAV The calibration method comprises: collecting, during a flight of the UAV, a current correction value E_kand current data during a current measurement performed by the vector sensor; acquiring previous data during a previous measurement performed by the vector sensor; acquiring an adjustment quantity W_kaccording to the current data and the previous data; acquiring a next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k, and acquiring next original data R_k+1during a next measurement performed by the vector sensor, and acquiring next valid data V_k+1according to the next original data R_k+1and the next correction value E_k+1; and controlling headings and postures of the UAV according to the next valid data V_k+1. The current data comprises current original data R_k, the previous data comprises previous original data R_k−1. The acquiring the adjustment quantity W_kaccording to the current data and the previous data comprises: acquiring a weight D_kand an estimated quantity M_kaccording to the current original data R_kand the previous original data R_k−1; and acquiring the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

According to the third aspect of the present invention, a non-transitory computer-readable storage medium storing a computer program is provided. When the computer program is executed by one or more processors, the calibration method for navigation of an unmanned aerial vehicle (UAV) is implemented.

According to the calibration method for navigation of an unmanned aerial vehicle (UAV) in the implementations of this application, the adjustment quantity W_kmay be acquired according to the current data collected during a flight of the UAV and the previous data, and the next correction value E_k+1may be acquired according to the current correction value E_kand the adjustment quantity W_k, to acquire a more accurate correction value, so as to perform zero-point error calibration on the next original data R_k+1according to the next correction value E_k+1during a next measurement to acquire next valid data V_k+1more closely approximating to a true value. Headings and postures of the UAV can be controlled according to the next valid data V_k+1. Therefore, accuracy of UAV navigation is improved. Moreover, the entire calibration process is carried out in flight state of the UAV without manual intervention, and the calibration method is efficient and convenient.

Additional aspects and advantages of the implementations of this application is provided in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or additional aspects and advantages of this application will become apparent and comprehensible from the descriptions of the implementations below with reference to the accompanying drawings.

FIG. 1 is a schematic flowchart of a calibration method for navigation of an unmanned aerial vehicle (UAV) according to some implementations of this application.

FIG. 2 is a schematic structural diagram of an UAV according to some implementations of this application.

FIG. 3 is a schematic diagram of a scenario in which a vector sensor acquires original data R_kand valid data V_kaccording to some implementations of this application.

FIG. 4 is a schematic diagram of a scenario in which a vector sensor acquires original data R_kand valid data V_kaccording to some implementations of this application.

FIG. 5 is a schematic diagram of a zero-point calibration scenario of a vector sensor according to some implementations of this application.

FIG. 6 is a schematic diagram of a scenario of different postures of the vector sensor according to some implementations of this application.

FIG. 7 is a schematic flowchart of a calibration method according to some implementations of this application.

FIG. 8 is a schematic diagram of a scenario in which the vector sensor measures a vector at different postures according to some implementations of this application.

FIG. 9 is a schematic diagram of a scenario of acquiring a direction of a zero-point offset Mo according to some implementations of this application.

FIG. 10 is a schematic diagram of a scenario of acquiring a direction of a zero-point offset Mo according to some implementations of this application.

FIG. 11 is a schematic diagram of a zero-point calibration scenario of a vector sensor according to some implementations of this application.

FIG. 12 is a schematic flowchart of a calibration method according to some implementations of this application.

FIG. 13 is a schematic flowchart of a calibration method according to some implementations of this application.

FIG. 14 is a schematic flowchart of a calibration method according to some implementations of this application.

FIG. 15 is a schematic diagram of a scenario of acquiring a direction of a zero-point offset M₀according to some implementations of this application.

FIG. 16 is a schematic diagram of a connection status between a computer-readable storage medium and a processor according to some implementations of this application.

FIG. 17 is a schematic flowchart of a calibration method according to some implementations of this application.

DETAILED DESCRIPTION

The following describes embodiments of this application in detail. Examples of the embodiments are shown in the accompanying drawings, and same or similar reference numerals throughout the accompanying drawings indicate same or similar components or components having same or similar functions. The following embodiments described with reference to the accompanying drawings are exemplary, aim to explain this application, and shall not be understood as limiting this application.

Referring to FIG. 1 and FIG. 2, an implementation of this application provides a calibration method for navigation of an UAV 100 including a vector sensor 40. The vector sensor 40 is configured for measuring headings and postures of the UAV 100. The calibration method includes the following steps:

01: Collecting, during a flight of the UAV 100, a current correction value E_kand current data during a current measurement performed by the vector sensor 40.

02: Acquiring previous data during a previous measurement performed by the vector sensor 40.

03: Acquiring an adjustment quantity W_kaccording to the current data and the previous data.

04: Acquiring a next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k.

05: Acquiring next original data R_kduring a next measurement performed by the vector sensor 40, and acquiring next valid data V_k+1according to the next original data R_k+1and the next correction value E_k+1.

06: Controlling headings and postures of the UAV 100 according to the next valid data V_k+1.

Referring to FIG. 2, an implementation of this application further provides an UAV 100. The UAV 100 includes one or more vector sensors 40, a processor 30, a memory 10, one or more electric motors 50 and one or more electronic speed controllers (ESCs) 60. Each ESC 60 acts as interface between the processor 30 and a corresponding electric motor 50. The processor 30 acts as a master and the vector sensors 40 act as slaves. Each of the vector sensors 40 may include a serial clock (SCL) pin and a serial data (SDA) pin corresponding respectively to a serial clock line and a serial data line over a I2C bus used communicate with the processor 30.

When the SCL pin is at a high level, the processor 30 determines a binary value of a corresponding bit by detecting a level on the SDA pin, so as to collect original heading data and original posture data measured by the vector sensor 40. Then the original heading data and the original posture data are calibrated to obtain target heading data and target posture data. The processor 30 generates a control command according to the calibrated target heading data and target posture data and transmits it to the ESC 60. The ESC 60 is configured to control the electric motor 50 to rotate at a speed according to the control command generated by the processor 30 to drive flying motion parts (such as propellers) of the UAV 100, so as to translate or rotate the UAV 100, and adjust to the target heading and posture to achieve navigation calibration. That is to say, the processor 30 may be configured to: collect, during a flight of the UAV, the current correction value E_kand the current data during the current measurement performed by the vector sensor 40; acquire the previous data during the previous measurement performed by the vector sensor 40;

acquire the adjustment quantity W_kaccording to the current data and the previous data; acquire the next correction value E_k+1 according to the current correction value E_kand the adjustment quantity W_k; and acquire the next original data R_k+1during the next measurement performed by the vector sensor 40, acquire the next valid data V_k+1according to the next original data R_k+1and the next correction value E_k+1, and control headings and postures of the UAV according to the next valid data V_k+1.

In this implementation, UAV refers to any types of unmanned aerial vehicle which may be used in various fields such as aerial photography, surveillance, agriculture, plant protection, courier transportation, disaster rescue, observation of wild animals, surveying and mapping, and news reporting. For example, in home surveillance, UAVs can refer to indoor flying security cameras that fly along a customized flight path to see what is happening in the home no matter where the user is. In the field of plant protection, UAVs can refer to plant protection drones, which are used to perform spraying operations according to set flight routes, such as the spraying of pesticides. Due to external electronic equipment, magnetic field interference and other reasons, navigation system of UAV often has errors which affect the flight path planning and flight safety of the UAV. Therefore, calibration of navigation of the UAV is needed to be carried out, that is to calibrate the heading and posture of the UAV.

The vector sensor 40 may be a vector sensor 40 having two or more two axes, for example, a two-axis sensor, a three-axis sensor, a six-axis sensor, or a multi-axis sensor, which is not enumerated herein. Depending on a type of a to-be-measured vector, the vector sensor 40 may selectively be a geomagnetic sensor, a gravity acceleration sensor, an angular velocity sensor, an acceleration sensor, or the like, which is not enumerated herein. In some implementations, the vector sensor 40 may be a micro-electro-mechanical system (MEMS) sensor. The MEMS sensor may be configured to measure one or more types of vectors. For example, the MEMS sensor includes six axes, and can have functions of both a three-axis acceleration sensor and a three-axis geomagnetic sensor. The specific type of the MEMS sensor is not limited thereto, and is not enumerated herein.

In this implementation, the vector sensor 40 may be a combination sensor of a three-axis geomagnetic sensor and a three-axis acceleration sensor, for example. Since the three-axis geomagnetic sensor is a sensor for measuring heading, and the three-axis acceleration sensor is a sensor for measuring posture, Therefore, the processor 30 can collect the heading data and posture data of the UAV at any time through the combined sensor. Specifically, current original data R_kmay include current original heading data and current original posture data, previous original data R_k−1may include previous original heading data and previous original posture data, next original data R_k+1may include next original heading data and next original posture data; current valid data V_kmay include current target heading data and current target posture data, previous valid data V_k−1may include previous target heading data and previous target posture data, next valid data V_k+1may include next target heading data and next target posture data. During current calibration, the processor 30 may determine the UAV's current target heading and current target posture according to the current valid data V_k, and then control the UAV to translate or rotate, so that the UAV is adjusted to have the current target heading and current target posture. Similarly, during next calibration, the processor 30 may determine the UAV's next target heading and next target posture according to the next valid data V_k+1, and then control the UAV to translate or rotate, so that the UAV is adjusted to have the next target heading and next target posture. As such, calibration of heading and posture of the UAV is realized. During the flight of the UAV, through the calibration of the headings and postures of the UAV, the accuracy of UAV navigation is improved. Moreover, the entire calibration process is carried out in flight state of the UAV, no manual intervention is required, thus efficiency and convenience of the calibration can be enhanced.

Referring to FIG. 2, in an embodiment, the processor 30 and the vector sensor 40 are integrally disposed. In another embodiment, the processor 30 and the vector sensor 40 are independently disposed. The vector sensor 40 may transmit the measurement data to the processor 30. The processor 30 acquires the next correction value E_k+1according to data measured by the vector sensor 40, and transmits the next correction value E_k+1to the vector sensor 40, so that the vector sensor 40 acquires the next valid data V_kbased on the next correction value E_k+1. Alternatively, the processor 30 side acquires the next valid data V_k+1according to the next correction value E_k+1and the next original data R_k+1acquired by the vector sensor 40.

Referring to FIG. 3, Generally, a zero-point offset Mo exists between a theoretical zero-point position P₀of the vector sensor 40 and a measurement zero-point position Pe adopted during the measurement performed by the vector sensor 40. Specifically, the vector sensor 40 can still acquire non-zero data when the to-be-measured vector is zero. A vector difference between the vector data acquired by the vector sensor 40 and zero is the zero-point offset M₀of the vector sensor 40. If the vector sensor 40 adopts the theoretical zero-point position during measurement, the vector data acquired by the vector sensor 40 is zero when the to-be-measured vector is zero. That is to say, the vector data acquired by the vector sensor 40 can represent the real to-be-measured vector.

Since the zero-point offset M₀is the vector difference between the theoretical zero-point position P₀and the measurement zero-point position Pe, and the original data R_kacquired based on the measurement zero-point position Pe can reflect the zero-point position Pe, the theoretical zero-point position P₀can be determined by using the zero-point offset M₀based on the original data R_kacquired by the vector sensor 40 if the zero-point offset M₀can be determined, thereby acquiring the accurate valid data V_k. The valid data V_kis data acquired based on an actual zero-point position of the vector sensor 40, that is, data acquired after a zero-point error is eliminated.

Specifically, referring to FIG. 2 and FIG. 3, the original data R_kmeasured by the two-axis vector sensor 40 based on the measurement zero-point position Pe is used as an example. In a coordinate system of the two-axis vector sensor 40, P₀is the theoretical zero-point position, Pe is the measurement zero-point position, the zero-point offset M₀is the vector difference between the theoretical zero-point position P₀and the measurement zero-point position Pe, and V_kis theoretical vector data that can be acquired based on the theoretical zero-point position P₀, which is a theoretical vector after the zero-point error of {right arrow over (R_k)} is eliminated. It can be learned that, P₀=Pe+{right arrow over (M₀)}, {right arrow over (V_k)}={right arrow over (R_k)}−{right arrow over (M₀)}. Therefore, the zero-point error of the original data {right arrow over (R_k)} can be eliminated to obtain the vector data {right arrow over (V_k)} if the zero-point offset {right arrow over (M₀)} can be determined, and the vector data {right arrow over (V_k)} is outputted as at the valid data to acquire an accurate measurement vector.

Referring to FIG. 4, according to the calibration method in the implementations of this application, the current correction value {right arrow over (E_k)} and the current data may be obtained, and the current data may include current original data {right arrow over (R_k)} obtained by the vector sensor 40 during a current measurement. The current correction value {right arrow over (E_k)} is an estimated value of the zero-point offset {right arrow over (M₀)} , and the correction value {right arrow over (E_k)} represents the vector difference between the measurement zero-point position Pe and an estimated zero-point position P_k. During actual measurement, it is usually difficult to directly acquire an accurate zero-point offset {right arrow over (M₀)}. Therefore, it is necessary to estimate a zero-point position by using the current correction value {right arrow over (E_k)}. The current valid data {right arrow over (V_k)} may be acquired based on the estimated zero-point position P_k, the current correction value {right arrow over (E_k)}, and the current original data {right arrow over (R_k)}. The current valid data {right arrow over (V_k)} is vector data acquired by performing zero-point error calibration on the current original data {right arrow over (R_k)}, which more closely approximates to an actual value of the to-be-measured vector.

Referring to FIG. 3 and FIG. 4, if the current correction value {right arrow over (E_k)} coincides with the zero-point offset {right arrow over (M₀)}, that is, the current correction value {right arrow over (E_k)} is completely accurate, the estimated zero-point position P_kdetermined according to the current correction value {right arrow over (E_k)} coincides with the theoretical zero-point position P₀. In this case, the theoretical zero-point position P₀can be determined according to only the current correction value {right arrow over (E_k)}. That is to say, after the zero-point error calibration is performed on the current original data {right arrow over (R_k)} by using the current correction value {right arrow over (E_k)}, a zero-point error of the current original data {right arrow over (R_k)} can be completely eliminated to obtain the current valid data {right arrow over (V_k)}. The current valid data {right arrow over (V_k)} can reflect an actual value of a current measurement result. Similarly, when the next correction value {right arrow over (E_k+1)} more closely approximates to the zero-point offset {right arrow over (M₀)}, it indicates that the next correction value {right arrow over (E_k+1)} is more accurate, and therefore the next valid data {right arrow over (V_k+1)} acquired based on the next original data {right arrow over (R_k+1)} and the next correction value {right arrow over (E_k+1)} acquired during the next measurement is more accurate, which more closely approximates to an actual value of a next measurement result.

Further, Referring to FIG. 5, according to the calibration method in the implementations of this application, the next correction value E_k+1may be acquired according to the current correction value E_kand the adjustment quantity W_k, and the adjustment quantity W_kis used to adjust the current correction value E_kto obtain the next correction value E_k+1. The correction value obtained after the adjustment more closely approximates to the zero-point offset M₀. As shown in FIG. 5, the adjustment quantity W_krepresents a vector difference between the estimated zero-point position P_kand an estimated zero-point position P_k+1, and the next correction value {right arrow over (E_k+1)} is a vector difference between the estimated zero-point position P_k+1and the measurement zero-point position Pe. It may be learned that, after the adjustment, the estimated zero-point position P_k+1determined according to the next correction value {right arrow over (E_k+1)} more closely approximates to the theoretical zero-point position P₀than the estimated zero-point position P_kdetermined based on the current correction value {right arrow over (E_k)}, and the next correction value {right arrow over (E_k+1)} more closely approximates to the zero-point offset {right arrow over (M₀)}. As the measurement number k increases, the correction value is continuously adjusted, so that the newly acquired correction value increasingly approximates the zero-point offset {right arrow over (M₀)}, that is, the zero-point calibration is becoming more accurate.

According to the calibration method and the UAV 100 in the implementations of this application, the adjustment quantity W_kmay be acquired according to the current data and the previous data, and the next correction value E_k+1may be acquired according to the current correction value E_kand the adjustment quantity W_k, to acquire a more accurate correction value, so as to perform zero-point error calibration on the next original data R_k+1according to the next correction value E_k+1during a next measurement to acquire next valid data V_k+1more closely approximating to a true value. In addition, the zero-point calibration process of the vector sensor 40 is performed while the vector sensor 40 normally outputs data, and therefore does not affect the normal use of the vector sensor 40.

This application is further described below with reference to the accompanying drawings.

Refer to FIG. 1. Method 01: Collecting, during the flight of the UAV, the current correction value E_kand the current data during the current measurement performed by the vector sensor 40. Method 02: Acquiring the previous data during the previous measurement performed by the vector sensor 40. k is a natural number greater than 0, that is, a minimum value of k is 1. k represents a number of measurements. For example, when k=2, a current correction value E₂represents a correction value corresponding to a second measurement, and the adjustment quantity W_krepresents an adjustment quantity corresponding to the second measurement.

The correction value may be a preset value. For example, the current correction value E_kis a correction value determined according to a plurality of measurements performed in advance or a correction value determined according to experience. This is not limited herein.

The correction value may alternatively be determined based on an adjustment quantity corresponding to a previous measurement performed by the vector sensor 40. For example, for a next measurement, the current measurement is a previous measurement of the next measurement. Therefore, a next correction value E_k+1may be determined according to the current correction value E_kand an adjustment quantity W_kcorresponding to the current measurement. In another example, the current correction value E_kmay be determined according to a previous correction value E_k−1and an adjustment quantity W_k−1corresponding to the previous measurement. Specifically, for example, when k=2, the correction value E₂may be determined according to a correction value E₁and an adjustment quantity W₁existing when k=1. In particular, when k=1, the current measurement is a first measurement. Since a correction value E₀and an adjustment quantity W₀corresponding to the previous measurement do not exist, the correction value E₁is a preset value.

In some implementations, a posture of the vector sensor 40 during the previous measurement is different from a posture of the vector sensor 40 during the current measurement.

Referring to FIG. 6, specifically, different postures mean postures corresponding to different angles of the reference vector in a preset coordinate system relative to the vector sensor 40. For example, the vector sensor 40 is moved or rotated from a first posture to a second posture relative to a fixed reference vector. For example, the reference vector is an acceleration of gravity, and a direction of the acceleration of gravity is constant. In this case, the vector sensor 40 is moved or rotated relative to the direction of the acceleration of gravity to change the posture. In another example, the vector sensor 40 is not moved or rotated, but the reference vector is moved or rotated relative to the vector sensor 40. For example, the reference vector is an electromagnetic field vector, the vector sensor 40 is placed in a horizontal plane and kept still, and an electromagnetic field source is moved or rotated relative to the vector sensor 40. In this case, an angle of the electromagnetic field vector is changed relative to a coordinate axis of the vector sensor 40. Therefore, it is also considered that the vector sensor 40 is changed relative to the posture of the reference vector. In another example, at least one of the vector sensor 40 or the reference vector is moved or rotated relative to the other. For example, the vector sensor 40 is fixed, and the reference vector is movable, or the vector sensor 40 is movable, and the reference vector is fixed, or the vector sensor 40 and the reference vector are both movable. In all of the above cases, it is considered that the posture of the vector sensor 40 is changed relative to the reference vector.

Referring to FIG. 7, in some implementations, the current data includes current original data R_k, and the previous data includes the previous original data R_k−1. 03 of acquiring the adjustment quantity W_kaccording to the current data and the previous data includes the following steps:

031: Acquiring a weight D_kand an estimated quantity M_kaccording to the current original data R_kand the previous original data R_k−1.

032: Acquiring the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

Referring to FIG. 2, in some implementations, the processor 30 may be further configured to perform the methods in 031 and 032. That is to say, the processor 30 may be further configured to acquire the weight D_kand the estimated quantity M_kaccording to the current original data R_kand the previous original data R_k−1, and acquire the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

Referring to FIG. 5, the adjustment quantity W_kis a vector difference between the next correction value E_k+1and the current correction value E_k. Specifically, E_k+1=E_k+W_k. According to the implementations of this application, the adjustment quantity W_kmay be acquired according to the weight D_kand the estimated quantity M_k.

Specifically, referring to FIG. 8, for example, the two-axis vector sensor 40 measures a vector {right arrow over (Me)} at different postures and acquires the previous original data {right arrow over (R_k−1)} and the current original data {right arrow over (R_k)}. Vector values |Me| of the vector {right arrow over (Me)} during the previous measurement and the current measurement are the same. Referring to FIG. 6, directions of the vector {right arrow over (Me)} relative to the coordinate system of the vector sensor 40 during the previous measurement and the current measurement are different. For the vector sensor 40, if the zero-point error does not exist, the vector data measured by the vector sensor 40 is a vector pointing to a circumference of a circle C from the theoretical zero-point position P₀. The circle C is a circle having P₀as a center and |Me| as a radius. For example, when the zero-point error does not exist, vector data measured by the vector sensor 40 during the previous measurement is A₁·{right arrow over (Me)}, and vector data measured during the current measurement is A₂·{right arrow over (Me)}. A1 is an external parameter matrix corresponding to the coordinate system of the vector sensor 40 at the posture during the previous measurement, and A2 is an external parameter matrix corresponding to the coordinate system of the vector sensor 40 at the posture during the current measurement. A₁·{right arrow over (Me)} and A₂·{right arrow over (Me)} illustrate a posture changing process of the vector sensor 40 relative to the to-be-measured vector. The previous original data {right arrow over (R_k−1)} and the current original data {right arrow over (R_k)} are vectors measured based on the measurement zero-point position Pe. {right arrow over (R_k−1)} and {right arrow over (R_k)} point to the circumference of the circle C from the zero-point position Pe.

Specifically, referring to FIG. 8, A₁·{right arrow over (Me)} and A₂·{right arrow over (Me)} have the following relationship:

A
₁·{right arrow over (Me)}={right arrow over (R_k−1)}−{right arrow over (M₀)}; Formula I

A
₂·{right arrow over (Me)}={right arrow over (R_k)}−{right arrow over (M₀)}. Formula II

Formula III is obtained by squaring both sides of the equation of Formula I.

|Me|²=|{right arrow over (R_k−1)}|²−2({right arrow over (R_k−1)}·{right arrow over (M₀)})+|M₀|². Formula III

Formula IV is obtained by squaring both sides of the equation of Formula II.

|Me|²=|{right arrow over (R_k)}|²−2({right arrow over (R_k)}·{right arrow over (M₀)})+|M₀|². Formula IV

Formula V is obtained by using differences between both sides of each of the equations of Formula III and Formula IV.

|{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|²=2({right arrow over (R_k)}−{right arrow over (R_k−1)})·{right arrow over (M₀)}. Formula V

Let {right arrow over (M_k)}={right arrow over (R_k)}−{right arrow over (R_k−1)}, and D_k=|{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|². In this case, Formula V may be revised to Formula VI: D_k=2({right arrow over (M_k)}·{right arrow over (M₀)}). D_kis the weight, and {right arrow over (M_k)} is the estimated amount.

According to Formula VI, if D_k>0, that is, {right arrow over (M_k)}·{right arrow over (M₀)}>0, it indicates that {right arrow over (M_k)} and {right arrow over (M₀)} are in a same direction, or if D_k<0, that is, {right arrow over (M_k)}·{right arrow over (M₀)}<0, it indicates that {right arrow over (M_k)} and {right arrow over (M₀)} are in different directions. Referring to FIG. 9, a normal plane S_kof the vector {right arrow over (M_k)} segments a space into two parts: a side T_kin a same direction as {right arrow over (M_k)} and a side F_kin a direction opposite to that of {right arrow over (M_k)}. When {right arrow over (M_k)}·{right arrow over (M₀)}>0, it may be determined that the direction of {right arrow over (M₀)} is on the T_kside. When {right arrow over (M_k)}·{right arrow over (M₀)}<0, it may be determined that the direction of {right arrow over (M₀)} is on the F_kside.

Referring to FIG. 10, similarly, after the (k+1)^thmeasurement, the vector sensor 40 acquires data {right arrow over (R_k+1)}. Therefore, {right arrow over (M_k+1)} and D_k+1may be acquired according to {right arrow over (R_k)} and {right arrow over (R_k+1)}, where D_k+1=2({right arrow over (M_k+1)}·{right arrow over (M₀)}). It may be determined according to a sign (i.e., +or −) of D_k+1whether the direction of {right arrow over (M₀)} is on a T_k+1side or an F_k+1side of the normal plane S_k+1of {right arrow over (M_k+1)}. In the example of FIG. 10, D_kand D_k+1are both <0, and it may be determined according to signs of D_kand D_k+1that the direction of {right arrow over (M₀)} is in a range of δ. As the measurement number k increases, a plurality of directional relationships between the estimated quantity {right arrow over (M_k)} and the zero-point offset {right arrow over (M₀)} may be determined. That is to say, it may be determined that {right arrow over (M₀)} is located on which side of a plurality of half-spaces segmented by the normal plane S_kof {right arrow over (M_k)}, thereby further determining a range of {right arrow over (M₀)} in the space, that is, reducing the range of δ. An intersection of the distributions of {right arrow over (M₀)} in the space is acquired to determine a relatively small spatial range, which can reflect the direction of the zero-point offset {right arrow over (M₀)}.

Referring to FIG. 11, the adjustment quantity W_kis used to adjust the correction value E_kto obtain the adjusted correction value E_k+1. Therefore, the estimated zero-point position P_k+1obtained after the correction of the correction value E_{k +1}for the measurement zero-point position Pe more closely approximates to the theoretical zero-point position P₀. That is to say, a more accurate direction and magnitude of the obtained correction value E_k+1leads to more accurate zero-point calibration. The correction value E_k+1=E_k+W_k. Therefore, a more accurate direction and magnitude of the adjustment quantity W_kleads to a more accurate direction and magnitude of the obtained correction value E_k+1and thereby leads to more accurate zero-point calibration.

The direction of the adjustment quantity W_kdepends on a vector direction of the estimated quantity M_kand a sign of the weight D_k. Referring to FIG. 9 and FIG. 10, if D_k<0, the direction of the adjustment quantity W_kis same as the vector direction of the estimated quantity M_k, and the adjustment quantity and the zero-point offset {right arrow over (M₀)} are both in a direction toward the T_kside of the normal plane S_kof M_k. If D_k>0, the direction of the adjustment quantity W_kis opposite to the vector direction of the estimated quantity M_k, and the adjustment quantity and the zero-point offset {right arrow over (M₀)} are both in a direction toward the F_kside of the normal plane S_kof M_k. It may be learned that the direction of the adjustment quantity W_kand the direction of the zero-point offset {right arrow over (M₀)} face the same side of the half space defined by the normal plane S_kof M_k. Therefore, the direction of the zero-point offset {right arrow over (M₀)} may be estimated by using the adjustment quantity W_k, that is, a direction of the correction value E_kis adjusted by using the adjustment quantity W_k, so that the adjusted direction of the correction value E_k+1more closely approximates to the direction of the zero-point offset {right arrow over (M₀)}. As the measurement number k increases, the range of the zero-point offset {right arrow over (M₀)} in the space that can be determined is becoming more accurate, and the adjusted direction of the correction value E_k+1more closely approximates to the true direction of the zero-point offset {right arrow over (M₀)}.

The magnitude of the adjustment quantity W_kdepends on the magnitude of the estimated quantity M_kand the weight D_k. Specifically, |{right arrow over (W_k)}|=α|D_k||{right arrow over (M_k)}. α is a preset empirical factor used to avoid an excessively large value of |{right arrow over (W_k)}| and avoid an excessively large value of the correction value E_k+1, and thereby avoid divergence of the estimated zero-point position P_k+1and improve a peed of convergence of the zero-point position P_k+1to the theoretical zero-point position P₀. When the convergence speed is not required, a value of α is 1. |D_k| can reflect a degree of change in the posture of the vector sensor 40 from the previous measurement to the current measurement. |{right arrow over (M_k)}|=|{right arrow over (R_k)}−{right arrow over (R_k−1)}| is a differential process. Due to the impact of noise, during actual measurement, |{right arrow over (M_k)}|=|{right arrow over (R_k)}−{right arrow over (R_k−1)}|+Z, where Z is a noise value. If the degree of change in the posture of the vector sensor 40 from the previous measurement to the current measurement is relatively small, values of |{right arrow over (R_k)}| and |{right arrow over (R_k−1)}| are relatively close, |{right arrow over (R_k)}−{right arrow over (R_k−1)}| is relatively small, and the noise value Z has a relatively large impact on a difference result of |{right arrow over (M_k)}|, which is likely to cause divergence of the estimated zero-point position Pp_k+1. When the degree of change in the posture of the vector sensor 40 from the previous measurement to the current measurement is relatively large, the noise value Z has a relatively small impact on the difference result of |{right arrow over (M_k)}|, so that the estimated zero-point position P_k+1can converge to the theoretical zero-point position P₀. Therefore, in order to avoid the divergence of the estimated zero-point position P_k+1, it is necessary to use the adjustment quantity W_kto obtain the correction value E_k+1to determine the convergent estimated zero-point position P_k+1when the degree of change in the posture of the vector sensor 40 is relatively large. |D_k| is positively correlated with the degree of change in the posture of the vector sensor 40. A larger value of |D_k| indicates a larger degree of change in the posture of the vector sensor 40, and a smaller value of |D_k| indicates a smaller degree of change in the posture of the vector sensor 40. |{right arrow over (D_k)}||{right arrow over (M_k)}| represents a degree of utilization of |{right arrow over (M_k)}|. A larger |D_k| indicates a larger degree of utilization of |{right arrow over (M_k)}| to the value of |{right arrow over (W_k)}|, and thereby indicates a larger degree of adjustment of the correction value E_kby the adjustment quantity W_kand a larger distance between the determined estimated zero-point position P_k+1and the previous estimated zero-point position P_k. A smaller |D_k| indicates a smaller degree of utilization of |{right arrow over (M_k)}| to the value of |{right arrow over (W_k)}|, and thereby indicates a smaller degree of adjustment of the correction value E_kby the adjustment quantity W_kand a smaller distance between the determined estimated zero-point position P_k+1and the previous estimated zero-point position P_k.

Further, in some embodiments, when |Dk| is greater than the preset threshold, the correction value E_kmay be adjusted by using the adjustment quantity W_kto obtain the correction value E_k+1. When |Dk| is less than or equal to the preset threshold, it may be considered that the correction value E_kdoes not require correction. The adjustment quantity W_kmay be set to zero to cause E_k+1E_k+0=E_k, or E_k+1=E_kmay be directly set. In this case, zero-point calibration is not required. When |D_k+n| is greater than the preset threshold, the correction value E_k+nis acquired by using the adjustment quantity W_k+n.

Specifically, referring to FIG. 12, in some implementations, the method 03 of acquiring the adjustment quantity W_kaccording to the current data and the previous data includes the following steps:

033: Acquiring a weight D_kand an estimated quantity M_kaccording to the current data and the previous data.

034: When the weight D_kis greater than a preset threshold, acquiring the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

035: When the weight D_kis less than or equal to the preset threshold, setting the adjustment quantity W_kto zero.

Referring to FIG. 2, in some implementations, the processor 30 may be further configured to perform the methods in 033, 034 and 035. That is to say, the processor 30 may be further configured to: acquire the weight D_kand the estimated quantity M_kaccording to the current data and the previous data; when the weight D_kis greater than the preset threshold, acquire the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k; and when the weight D_kis less than or equal to the preset threshold, set the adjustment quantity W_kto zero.

In this way, it can be ensured that the estimated zero-point position P_k+1determined after the zero-point calibration converges to the theoretical zero-point position P₀, thereby improving the accuracy of the acquired valid data.

Similarly, when the vector sensor 40 is a vector sensor 40 having more than two axes, the adjustment quantity W_kcan still be acquired by using the calibration method in the implementations of this application, and the next correction value E_k+1can be acquired according to the adjustment quantity W_kand the current correction value E_k. Details are not described herein.

Refer to Formula VI: D_k=2({right arrow over (M_k)}·{right arrow over (M₀)}). In some implementations, the current data includes the current original data R_kand the current valid data V_k, and the previous data includes the previous valid data V_k−1. The weight D_kand the estimated quantity M_kmay be acquired according to the current valid data V_kand the previous valid data V_k−1.

Specifically, referring to FIG. 13, in some implementations, the method 01 of collecting the current correction value E_kand the current data during the current measurement performed by the vector sensor 40 includes the following steps:

011: Acquiring current valid data V_kaccording to the current original data R_kand the current correction value E_k.

Referring to FIG. 2, in some implementations, the processor 30 may be further configured to perform the method in 011. That is to say, the processor 30 may be further configured to: acquire the current valid data V_kaccording to the current original data R_kand the current correction value E_k.

Specifically, referring to FIG. 4, {right arrow over (V_k)}={right arrow over (R_k)}−{right arrow over (E_k)}, which represents a vector pointing to the circumference of the circle C from the estimated zero-point position P_k. Similarly, the previous valid data {right arrow over (V_k−1)}={right arrow over (R_k−1)}−{right arrow over (E_k−1)}, which represents a vector pointing to the circumference of the circle C from the estimated zero-point position P_k−1.

Referring to FIG. 14, in some implementations, the method 03 of acquiring the adjustment quantity W_kaccording to the current data and the previous data includes the following steps:

036: Acquiring a weight D_kand an estimated quantity M_kaccording to the current valid data V_kand the previous valid data V_k−1.

037: Acquiring the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

Referring to FIG. 2, in some implementations, the processor 30 may be further configured to perform the methods in 036 and 037. That is to say, the processor 30 may be further configured to: acquire the weight D_kand the estimated quantity M_kaccording to the current valid data V_kand the previous valid data V_k−1, and acquire the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

With reference to FIG. 8, Formula V, and Formula VI, in Formula V, |{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|²=2 ({right arrow over (R_k)}−{right arrow over (R_k−1)}){right arrow over (M₀)}, {right arrow over (R_k)} and {right arrow over (R_k−1)} may be acquired by the vector sensor 40 by measuring any vector. Therefore, a vector obtained by {right arrow over (R_k)}−{right arrow over (R_k−1)} may be any vector in the space. That is to say{right arrow over (, M_k)}={right arrow over (R_k)}−{right arrow over (R_k−1)} in Formula VI substantially means representing, by using M_k, any vector obtained by {right arrow over (R_k)}−{right arrow over (R_k−1)}. In Formula V, |{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|²=2({right arrow over (R_k)}−{right arrow over (R_k−1)}) {right arrow over (M₀)}, |{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|²reflects a degree of change in the posture of the vector sensor 40 during two measurements. That is to say, in Formula VI, D_k=|{right arrow over (R_k)}|²−|{right arrow over (R_k−1)}|²substantially means representing, by using D_k, the degree of change in the posture of the vector sensor 40 during the two measurements. If {right arrow over (V_k)}−{right arrow over (V_k−1)} is used to represent any vector in the space, and |{right arrow over (V_k)}|−|{right arrow over (V_k−1)}| is used to represent the degree of change in the posture of the vector sensor 40 during the two measurements, that is, {right arrow over (M_k)}={right arrow over (V_k)}−{right arrow over (V_k−1)}, and D_k=|{right arrow over (V_k)}|−|{right arrow over (V_k−1)}, Formula VII: {right arrow over (V_k)}−{right arrow over (V_k−1)}=U(|{right arrow over (V_k)}−|{right arrow over (V_k−1)}|) {right arrow over (M₀)} may be obtained from Formula VI, where U is a non-zero constant, {right arrow over (V_k)}−{right arrow over (V_k−1)}={right arrow over (M_k)}, and |{right arrow over (V_k)}−|{right arrow over (V_k−1)}=D_k.

Referring to FIG. 15 and FIG. 9, when {right arrow over (M_k)}={right arrow over (V_k)}−{right arrow over (V_k−1)}, and D_k=|{right arrow over (V_k)}|−|{right arrow over (V_k−1)}|, a direction of {right arrow over (M_k)} relative to the zero-point offset {right arrow over (M₀)} can still be determined according to the sign of D_k, that is, a side, in the half-spaces segmented by the normal plane S_kof {right arrow over (M_k)}, on which the direction of the zero-point offset {right arrow over (M₀)} is located is determined. A detailed process is not described herein. In this way, when {right arrow over (M_k)}={right arrow over (V_k)}−{right arrow over (V_k−1)}, and D_k=|{right arrow over (V_k)}|−|{right arrow over (V_k−1)}|, the direction of {right arrow over (W_k)} can still be determined by using the sign of D_kand the direction of {right arrow over (M_k)}, and the magnitude of {right arrow over (W_k)} can still be determined by using |{right arrow over (W_k)}|=α|D_k||{right arrow over (M_k)}|. A detailed process is not described herein.

Referring to FIG. 8, in addition to the degree of change in the posture of the vector sensor 40 during the two measurements, D_k=|{right arrow over (V_k)}|−|{right arrow over (V_k−1)}| may further represent a degree of calibration of the zero-point error. For example, if the zero-point error does not exist, the estimated zero-point position P_k−1, the estimated zero-point position P_k, and theoretical zero-point position P₀in FIG. 8 coincide, {right arrow over (V_k−1)}=A₁·{right arrow over (Me)}, and {right arrow over (V_k)}=A₂·{right arrow over (Me)}. Therefore, D_k=|{right arrow over (V_k)}|−|{right arrow over (V_k−1)}|=0. If the zero-point error exists, the estimated zero-point position P_k−1and the estimated zero-point position P_kare closer to the theoretical zero-point position P₀, which indicates a higher degree of calibration of the zero-point error. In this case, the value of |{right arrow over (V_k)}|−|{right arrow over (V_k−1)}| is smaller, and D_kis smaller. If the zero-point position P_k−1and the estimated zero-point position P_kare farther from the theoretical zero-point position P₀, which indicates a lower degree of calibration of the zero-point error, the value of |{right arrow over (V_k)}|−|{right arrow over (V_k−1)}| is larger, and D_kis larger. Method 035: When the weight D_kis less than or equal to the preset threshold, the adjustment quantity W_kis set to zero, that is to say, the current correction value E_kis not adjusted when the degree of calibration of the zero-point error is relatively high, and it is considered that the calibration of the zero-point error satisfies the requirements. Method 034: When the weight D_kis greater than the preset threshold, the adjustment quantity W_kis obtained according to the weight D_kand the estimated quantity M_k, to acquire the next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k, which is used to perform zero-point calibration during the next ((k+1)^th) ranging.

Refer to Formula VI: D_k=2 ({right arrow over (M_k)}·{right arrow over (M₀)}). The weight D_krepresents the degree of change in the posture of the vector sensor 40 during the two measurements. In some implementations, the weight D_kmay be determined according to the posture data. The posture data is data measured by other sensors that can represent the degree of change in the posture of the vector sensor 40 during the two measurements. In an embodiment, the posture data may be a first angular velocity and a second angular velocity measured by the angular velocity sensor during the two measurements performed by the vector sensor 40. A larger difference between the first angular velocity and the second angular velocity indicates a larger degree of change in the posture of the vector sensor 40 during the two measurements, and thereby indicates a larger determined weight D_k. A type of the posture data is not limited to a rate of change in the angular velocity of the vector sensor 40 during the two measurements, and is not limited herein.

Specifically, referring to FIG. 17, in some implementations, the method 03 of acquiring the adjustment quantity W_kaccording to the current data and the previous data includes the following steps:

038: Acquiring posture data.

039: Acquiring the adjustment quantity W_kaccording to the current data, the previous data, and the posture data.

Referring to FIG. 2, in some implementations, the processor 30 may be further configured to perform the methods in 038 and 039. That is to say, the processor 30 may be further configured to acquire the posture data, and acquire the adjustment quantity W_kaccording to the current data, the previous data, and the posture data.

Specifically, the adjustment quantity W_kdepends on the weight D_kand the estimated quantity M_k, the weight D_kdepends on the posture data, and the estimated quantity M_kdepends on the current data and the previous data. Based on the above, if the current data and the previous data are respectively the current original data {right arrow over (R_k)} and the previous original data {right arrow over (R_k−1)}, {right arrow over (M_k)}={right arrow over (R_k)}−{right arrow over (R_k−1)}. If the current data and the previous data are respectively the current valid data V_kand the previous valid data V_k−1, {right arrow over (M_k)}={right arrow over (V_k)}−{right arrow over (V_k−1)}.

In conclusion, according to the calibration method and the UAV 100 in the implementations of this application, the adjustment quantity W_kmay be acquired according to the current data and the previous data, and the next correction value E_k+1may be acquired according to the current correction value E_kand the adjustment quantity W_k, to acquire a more accurate correction value, so as to perform zero-point error calibration on the next original data R_k+1according to the next correction value E_k+1during a next measurement to acquire next valid data V_k+1more closely approximating to a true value.

According to the calibration method and the UAV 100 in the implementations of this application, zero-point calibration may be performed during output of the valid data. Specifically, zero-point calibration may be performed during any k^thmeasurement, so as to dynamically complete zero-point calibration during the use of the vector sensor 40, thereby maintaining the accuracy of the valid data.

Referring to FIG. 16, an implementation of this application further provides a non-transitory computer-readable storage medium 400 including a computer program 401. When the computer program 401 is executed by one or more processors 30, the one or more processors 30 are caused to perform the calibration method described in any of the above implementations. The non-transitory computer-readable storage medium 400 may be disposed in the UAV 100, or may be disposed in a cloud server or other apparatuses. In this case, the UAV 100 can communicate with the cloud server or the other apparatuses to acquire the corresponding computer program 401.

Referring to FIG. 2, for example, when the computer program 401 is executed by one or more processors 30, the one or more processors 30 are caused to perform the methods in 01, 02, 03, 04, 05, 06, 011, 031, 032, 033, 034, 035, 036, 037, 038, and 039. For example, the following application calibration method is performed.

01: Collecting, during a flight of the UAV 100, a current correction value E_kand current data during a current measurement performed by the vector sensor 40.

02: Acquiring previous data during a previous measurement performed by the vector sensor 40.

03: Acquiring an adjustment quantity W_kaccording to the current data and the previous data.

04: Acquiring a next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k.

05: Acquiring next original data R_k+1during a next measurement performed by the vector sensor 40, and acquiring next valid data V_k+1according to the next original data R_k+1and the next correction value E_k+1.

06: Controlling headings and postures of the UAV 100 according to the next valid data V_k+1.

In another example, when the computer program 401 is executed by one or more processors 30, the one or more processors 30 are caused to perform the following calibration method.

01: Collecting, during a flight of the UAV 100, a current correction value E_kand current data during a current measurement performed by the vector sensor 40.

02: Acquiring previous data during a previous measurement performed by the vector sensor 40.

031: Acquiring a weight D_kand an estimated quantity M_kaccording to the current original data R_kand the previous original data R_k−1.

032: Acquiring an adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k;

034: When the weight D_kis greater than a preset threshold, acquiring the adjustment quantity W_kaccording to the weight D_kand the estimated quantity M_k.

035: When the weight D_kis less than or equal to the preset threshold, setting the adjustment quantity W_kto zero.

04: Acquiring a next correction value E_k+1according to the current correction value E_kand the adjustment quantity W_k.

06: Controlling headings and postures of the UAV 100 according to the next valid data V_k+1.

In the descriptions of this specification, descriptions of reference terms such as “some implementations”, “in one example”, or “exemplarily” mean that specific characteristics, structures, materials, or features described with reference to the implementation or example are included in at least one implementation or example of this application. In this specification, schematic descriptions of the foregoing terms are not necessarily with respect to the same implementation or example. Further, the described specific characteristics, structures, materials, or features may be combined in a proper manner in any one or more implementations or examples. In addition, different embodiments or examples described in this specification, as well as features of different embodiments or examples, may be integrated and combined by a person skilled in the art without contradicting each other.

Any process or method in the flowcharts or described herein in another manner may be understood as indicating a module, a segment, or a part including code of one or more executable instructions for implementing a particular logical function or process step. In addition, the scopes of preferred embodiments of this application include other implementations which do not follow the order shown or discussed, including performing, according to involved functions, the functions basically simultaneously or in a reverse order, which should be understood by a person skilled in the art to which the embodiments of this application belong.

Although the embodiments of this application are shown and described above, it may be understood that the foregoing embodiments are exemplary, and cannot be understood as a limitation to this application. A person of ordinary skill in the art may make changes, modifications, replacements, and variations to the foregoing embodiments without departing from the scope of this application.

	Number	Date	Country
Parent	17585505	Jan 2022	US
Child	17940015		US

UAV NEVIGATION CALIBRATION METHOD, NON-TRANSITORY COMPUTER-READABLE STORAGE MEDIUM AND UAV IMPLEMENTING THE SAME

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