Unmanned aerial vehicle hovering control method and system based on laser scanning reference

Abstract

The invention discloses an unmanned aerial vehicle hovering control method and system based on a laser scanning reference, and belongs to the field of unmanned aerial vehicle control. The control method comprises the following steps: when a laser receiver receives a laser signal generated by a swinger through scanning at an elevation benchmark, obtaining the relative height of the laser receiver and an elevation datum plane according to the laser signal, and setting the target hovering height of the current unmanned aerial vehicle according to the relative height, in each control period, the following steps are executed: acquiring position information through the RTK module, and acquiring attitude data through the inertial measurement unit; three height data are obtained according to the real-time laser signal, the position information change and the attitude data change, the height feedback quantity in the gravitational acceleration direction is obtained after the height data are preprocessed and filtered, and real-time hovering control is conducted on the unmanned aerial vehicle according to the height feedback quantity. And the gravity acceleration direction parameter change information of the laser receiver, the inertial measurement unit and the RTK module is fused to realize high-precision position control.

Description

Technical Field

[0001] The present invention belongs to the field of unmanned aerial vehicle (UAV) control, and more specifically, relates to a UAV hovering control method and system based on a laser leveling reference. Background Art

[0002] With the rapid development of UAV technology and the increasing demand for high-precision measurement, UAVs have gradually become important tools in fields such as elevation measurement, building construction, industrial inspection, and agricultural monitoring; UAVs have high flexibility and versatility, can adapt to diverse application scenarios, especially in elevation measurement, and can quickly obtain accurate measurement data in complex environments; through the application of UAVs, the measurement process has not only been simplified, but also the response speed has been improved, meeting the requirements of the engineering and industrial fields for efficient measurement; its high efficiency and accuracy have shown great application potential in industries such as engineering and inspection; in the application of elevation measurement, the height stability of UAV hovering directly affects the accuracy and reliability of data collection; therefore, precisely controlling the UAV to hover within a specific height range is of great significance for improving the quality of elevation measurement control and supporting engineering monitoring.

[0003] With the continuous improvement of measurement application requirements, UAVs face higher requirements in hovering position control and height stability, especially in complex environments such as low light, weak signals, or no GPS signals; existing hovering control technologies are difficult to achieve precise height positioning and difficult to meet the measurement accuracy requirements in some key scenarios; in addition, external interference factors such as wind speed changes and air flow disturbances affect the stability of UAVs, further increasing the error of measurement data.

[0004] Traditional hovering control methods have many deficiencies in height control in the direction of gravitational acceleration, such as insufficient sensor accuracy and susceptibility to external interference, resulting in difficulty in maintaining stable accuracy of measurement data in the direction of gravitational acceleration; although existing measurement systems can basically meet conventional application scenarios, they show deficiencies in complex environments and high-precision requirements. Summary of the Invention

[0005] Aiming at the deficiencies of related technologies, the purpose of the present invention is to provide a UAV hovering control method and system based on a laser leveling reference, aiming to solve the problem that existing UAV hovering control methods have insufficient sensor accuracy and are susceptible to external interference in height control in the direction of gravitational acceleration, resulting in difficulty in maintaining precise height control in the direction of gravitational acceleration.

[0006] To achieve the above object, in the first aspect, the present invention provides a UAV hovering control method based on a laser leveling reference, which is characterized by including:

[0007] When the laser receiver installed on the UAV receives the laser signal generated by the leveling instrument scanning the elevation benchmark, the relative height of the laser receiver and the elevation reference surface is obtained based on the laser signal, and the current target hovering height of the UAV is set based on the relative height. The following steps are performed in each control cycle:

[0008] S1. Obtain the position information of the UAV through the RTK module and the attitude data of the UAV through the inertial measurement unit; calculate the first height data h1 based on the relative height corresponding to the real-time laser signal and the target hovering height, calculate the second height data h2 based on the change in the position information, and calculate the third height data h3 based on the change in the attitude data;

[0009] S2. Perform Kalman filtering on the three altitude data to obtain altitude feedback in the direction of gravity acceleration;

[0010] S3. Performing real-time hovering control on the UAV according to the height feedback;

[0011] The scanning plane of the leveling instrument at the elevation level point constitutes an elevation reference plane.

[0012] Optionally, the target hovering height of the current UAV is dynamically set according to the wide-area reception characteristics of the laser receiver;

[0013] When it is detected that the elevation reference plane is located in the first measurement area of the laser receiver, the fixed height H0 is reduced from the current height to serve as the target hovering height at this time;

[0014] When the elevation reference plane is located in the second measurement area of the laser receiver, the current altitude is used as the target hovering altitude;

[0015] When the elevation reference plane is located in the third measurement area of the laser receiver, a fixed height H0 is added to the current height as the target hovering height at this time.

[0016] Optionally, the three altitude data are processed by Kalman filtering to obtain altitude feedback in the direction of gravity acceleration, including: estimating the noise variance of the laser receiver, RTK module and inertial measurement unit in real time through exponentially weighted moving average And according to the noise variance of the sensor Update the measurement covariance R of the Kalman filter at time k k :

[0017] μ i,k =αμ i,k-1 +(1-α)h i,k

[0018]

[0019] where α ∈ (0, 1) is the smoothing coefficient, and μ i,k is the mean estimate of sensor i at time k, representing the laser receiver, RTK module, and inertial measurement unit in sequence;

[0020] Allocate measurement covariance weights according to the sensor noise variance and calculate the credibility of the sensor Normalize the credibility and update the weights:

[0021] w i = clip(w i,min + c i ′(w i,max - w i,min ), w i,min , w i,max )

[0022] where w i is the measurement covariance weight coefficient of sensor i after normalization, representing the laser receiver, RTK module, and inertial measurement unit in sequence. w1 is greater than w2, w2 is greater than w3, and w1 + w2 + w3 = 1; clip(x, a, b) means restricting x within the interval [a, b];

[0023] Recalculate the measurement covariance R in the Kalman filter at time k according to the updated allocated weights k :

[0024]

[0025] where ∈ takes a non - zero value, represents the noise variance of the laser receiver at time k, represents the noise variance of the RTK module at time k, represents the noise variance of the inertial measurement unit at time k.

[0026] Optionally, adopt the active disturbance rejection control algorithm to perform real - time hovering control on the UAV according to the height control feedback quantity.

[0027] Optionally, while executing S3, it further includes:

[0028] Within a control period, calculate the first horizontal position feedback quantity according to the change of position information, calculate the second horizontal position feedback quantity according to the change of attitude data, and perform real - time horizontal hovering control on the UAV according to the first horizontal position feedback quantity and the second horizontal position feedback quantity.

[0029] Optionally, while executing S3, it further includes: performing real - time attitude compensation on the UAV through the attitude data.

[0030] In a second aspect, the present invention further provides a UAV hovering control system based on a laser leveling reference, including: a laser receiver, an RTK module, an inertial measurement unit, and a flight controller disposed on the UAV;

[0031] The laser receiver is configured to receive the laser signal corresponding to the elevation reference plane scanned by the level at the elevation benchmark point;

[0032] The RTK module is configured to obtain the position information of the UAV;

[0033] The inertial measurement unit is configured to obtain the attitude data of the UAV;

[0034] The flight controller is connected to the laser receiver, the RTK module, and the inertial measurement unit, and is configured to execute the UAV hovering control method based on the laser leveling reference according to any one of the first aspects.

[0035] Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

[0036] 1. The present invention provides a UAV hovering control method based on a laser leveling reference. By using a laser level to establish a stable elevation reference plane in space, after the laser receiver detects the horizontal laser beam, the relative height between the laser receiver and the elevation reference plane is obtained, and the target hovering height of the UAV at this moment is set according to this relative height; at the same time, the change information of the gravity acceleration direction parameters of the inertial measurement unit and the RTK module is fused to adjust the height of the UAV in real time; Kalman filtering utilizes the data advantages of different sensors to achieve more stable and accurate height feedback, thereby realizing high-precision hovering control.

[0037] 2. The present invention provides a UAV hovering control method based on a laser leveling reference. The UAV can utilize the optimal sensor feedback mechanism in different directions respectively, significantly improving the hovering accuracy and response speed. In the direction of gravity acceleration, by using the high-precision real-time relative height provided by the laser receiver as the dominant feedback, the UAV can quickly adjust the thrust to maintain above the specified height, enhancing the stability and accuracy of the UAV in the direction of gravity acceleration; in the horizontal direction, the data fused by the inertial measurement unit and the RTK is fully utilized to ensure the stability and anti-interference ability of the UAV at the target position; separating the control in the direction of gravity acceleration and the horizontal direction can significantly improve the positioning accuracy and continuous stability of the measurement point, ensuring that the UAV hovers at the specified position for high-precision elevation measurement; this method is not only applicable to high-precision elevation measurement, but also can be extended to other application scenarios that require precise position maintenance, providing a solid technical guarantee for diversified measurement tasks. Description of the Drawings

[0038] Figure 1 It is a schematic flow chart of a method for controlling a drone to hover based on a laser leveling reference provided by the present invention;

[0039] Figure 2 It is a schematic diagram of a control system for a drone to hover based on a laser leveling reference provided by the present invention;

[0040] Figure 3 It is a schematic diagram for dynamically setting the target height of a drone;

[0041] Figure 4 It is a schematic flow chart for preprocessing and filtering altitude data.

[0042] In the above-mentioned drawings, the reference numerals are:

[0043] 1. Laser receiver, 2. Flight controller, 3. RTK module, 4. Laser leveler. Specific implementation manners

[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention; in addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] The following describes the content involved in the above embodiments with reference to a preferred embodiment.

[0046] Embodiment 1

[0047] The present invention provides a method for controlling a drone to hover based on a laser leveling reference, which is characterized in that it includes:

[0048] When the laser receiver installed on the drone receives the laser signal generated by the leveler scanning at the elevation benchmark point, the relative height between the laser receiver and the elevation reference plane is obtained according to the laser signal, and the target hovering height of the current drone is set according to the relative height. The following steps are executed in each control cycle:

[0049] S1. Obtain the position information of the drone through the RTK module, and obtain the attitude data of the drone through the inertial measurement unit; calculate the first altitude data h1 according to the relative height corresponding to the real-time laser signal and the target hovering height, calculate the second altitude data h2 according to the change of the position information, and calculate the third altitude data h3 according to the change of the attitude data;

[0050] S2. Perform Kalman filtering on the three altitude data to obtain the altitude feedback quantity in the direction of gravitational acceleration;

[0051] S3. Perform real-time hovering control on the UAV according to the altitude feedback quantity;

[0052] Wherein, the scanning plane of the level at the elevation benchmark point constitutes the elevation reference plane.

[0053] In view of the deficiencies of the prior art, the present invention proposes a UAV hovering control method based on a laser leveling reference. The laser plane signal received by the laser receiver is used as the feedback parameter of the UAV control system to provide a reliable altitude reference for the UAV and achieve high-precision measurement in complex environments; referring to Figure 2 , place the laser level at the elevation benchmark point, and use the laser level to establish a stable elevation reference plane in space. The laser level emits horizontal laser by rotation to form a unified reference altitude; the laser receiver installed on the UAV receives the signal from the laser level, quantifies the relative altitude data through internal calculation, and obtains the altitude information of the UAV relative to the laser reference plane. The UAV flight control system receives the relative altitude information between the UAV and the laser reference plane, generates the real-time target hovering altitude at the current measurement point; the UAV flight control system takes the real-time generated target hovering altitude as the reference, compares the altitude data collected by the subsequent laser receiver with this target altitude to calculate the altitude error; at the same time, the UAV flight control system collects the altitude data of the on-board RTK module and inertial measurement unit in real time. After performing Kalman filtering on the three altitude data, the altitude error (altitude feedback quantity) for feedback adjustment is obtained; according to this error, the system can adopt algorithms such as PID control, adaptive control, sliding mode control or active disturbance rejection control to adjust the altitude of the UAV in real time, so as to achieve high-precision hovering control.

[0054] In this embodiment, before the laser receiver receives the laser signal, the flight control is mainly realized by the joint participation of the inertial measurement unit and RTK module on the UAV; in this stage, the inertial measurement unit is responsible for providing attitude data such as acceleration and angular velocity, while the RTK module provides accurate positioning coordinates to ensure that the UAV always maintains the correct attitude and position during the process of flying to the target point; when the laser receiver receives the signal from the laser level, its control strategy is further refined and split into two parts to optimize the control effect in different directions. One part is the control in the horizontal direction, which is realized by the data changes of the inertial measurement unit and RTK module as the feedback quantity, and the other part is the control in the direction of gravitational acceleration, which is dominated by the change of the relative position information collected by the laser receiver as the feedback quantity, and at the same time integrates the change information of the gravitational acceleration direction parameters of the inertial measurement unit and RTK module.

[0055] In the elevation measurement scenario, improve the hovering accuracy in the direction of the acceleration due to gravity; use a laser receiver to collect data in the direction of the acceleration due to gravity, and use the relative position data of the laser plane collected by the laser receiver as the main feedback quantity of the UAV in the direction of the acceleration due to gravity. At the same time, fuse the information on the change of the acceleration due to gravity direction parameters of the inertial measurement unit and the RTK module; with the precise relative position data provided by the laser receiver as the main factor, the UAV can respond to the height change requirements in real time; the inertial measurement unit and RTK provide additional supplementary data to enhance the stability and anti-interference ability of the system in a dynamic environment, so as to achieve higher-precision vertical position control.

[0056] When performing Kalman filtering, the noise variances during the measurement processes of the laser receiver, the RTK module, and the inertial measurement unit are estimated in real time through exponentially weighted moving average. And according to the noise variances of the sensors Update the measurement covariance R in the Kalman filter k ; Since the accuracies of the three sensors are different, the weights of the three sensors in the calculation of the measurement covariance during the Kalman filtering process are different. The first height data h1 calculated from the relative position information collected by the laser receiver and the target hovering height, the calculated weight w1 ranges from 0.5 to 0.7; the second height data h2 calculated from the position information in the direction of the acceleration due to gravity obtained by the RTK module, the calculated weight w2 ranges from 0.2 to 0.3; the third height data h3 calculated by the inertial measurement unit for the height in the direction of the acceleration due to gravity, the calculated weight w3 ranges from 0.1 to 0.2; the height feedback quantity obtained after Kalman filtering can reflect the height error jointly affected by the three height data for feedback adjustment, ensuring the height stability of the UAV in the direction of the acceleration due to gravity.

[0057] Furthermore, the elevation reference plane established by the laser level in the present invention can not only serve as an accurate reference point for the UAV to hover, but also provide a reliable elevation reference for elevation data measurement in the elevation measurement scenario. At the same time, in the elevation measurement scenario, the function of the laser receiver is not limited to receiving the reference plane information to stabilize the hovering height of the UAV, but can also obtain height information by analyzing the received laser signal, so as to directly measure the relative height data between the UAV at different positions and the elevation reference plane.

[0058] Such as Figure 3 shown, optionally, the target hovering height of the current UAV is dynamically set according to the wide-area reception characteristics of the laser receiver;

[0059] When it is detected that the elevation reference plane is located in the first measurement area of the laser receiver, the current height is reduced by a fixed height H0 as the target hovering height at this time;

[0060] When the elevation reference plane is located in the second measurement area of the laser receiver, the current height is used as the target hovering height;

[0061] When the elevation reference plane is located in the third measurement area of the laser receiver, a fixed height H0 is added to the current height as the target hovering height at this time.

[0062] In this embodiment, a fixed hovering target height is not set, but the dynamic target height hovering control is realized according to the wide-area receiving characteristics of the laser receiver; in the actual elevation measurement scenario, the laser receiver is fixed at the bottom of the unmanned aerial vehicle, and the receiving direction is perpendicular to the body of the unmanned aerial vehicle to ensure that the beam emitted by the laser level can be received within its flight range; after the laser receiver of the unmanned aerial vehicle receives the laser, the unmanned aerial vehicle enters the vicinity of the stable elevation reference plane established by the laser level in space at this time; once the laser receiver detects the laser signal, it will immediately measure and calculate the relative height of the unmanned aerial vehicle relative to the laser reference plane, and generate the real-time target hovering height at the current measurement point.

[0063] The dynamic setting of the target hovering height includes three cases. Exemplarily, when it is detected that the elevation reference plane is within 1.2 cm of the upper edge of the laser receiver, that is, Figure 3 in the first measurement area, a fixed height H0 (1.2 cm) is subtracted from the current height as the target hovering height at this time; when the elevation reference plane is within the area between 1.2 cm from the upper edge and the lower edge of the laser receiver, that is, Figure 3 in the second measurement area, the current relative height is used as the target hovering height; when the elevation reference plane is within 1.2 cm of the lower edge of the laser receiver, that is, Figure 3 in the third measurement area, a fixed height H0 (1.2 cm) is added to the current height as the target hovering height at this time.

[0064] At this time, the unmanned aerial vehicle control system will use the real-time generated target hovering height as the reference, and continuously adjust the flight attitude and height through the feedback control mechanism to make the unmanned aerial vehicle hover precisely at this position; this method of dynamically generating the target height and performing real-time feedback control ensures that the unmanned aerial vehicle can automatically adapt to the environment at different measurement points and maintain high-precision hovering, thus greatly improving the efficiency and accuracy in the elevation measurement and fine measurement scenarios.

[0065] After receiving the laser signal, the height control in the direction of the gravitational acceleration of the UAV takes the change in the relative position information collected by the laser receiver as the main feedback quantity, and at the same time fuses the change information of the gravitational acceleration direction parameters of the inertial measurement unit and the RTK module; specifically, after the laser receiver detects the horizontal laser beam, the UAV measures the relative height between the current laser receiver and the elevation reference plane, and sets the target hovering height of the UAV at this moment according to this relative height; subsequently, the height data of the laser receiver, the RTK module and the inertial measurement unit are subjected to Kalman filtering to obtain the height feedback quantity, and it is input into the active disturbance rejection controller in the direction of the gravitational acceleration to adjust the thrust in real time so that the UAV can accurately maintain at the target hovering height; the Kalman filtering of the sensor height data specifically includes the following steps:

[0066] (1) Data preprocessing

[0067] Data preprocessing of the laser receiver: The laser receiver provides relative height information as the main feedback quantity; in order to smooth the relative height data, moving average filtering is used:

[0068]

[0069] Among them, h1[n] is the relative height data measured by the laser receiver, and N is the size of the filtering window.

[0070] The RTK module and the inertial measurement unit provide auxiliary feedback height information for compensating and correcting the laser receiver data, and a first-order low-pass filter is used to process this data:

[0071] h 2,filtered [n] = α2h2[n] + (1 - α2)h 2,filtered [n - 1]

[0072] h 3,filtered [n] = α3h2[n] + (1 - α3)h 3,filtered [n - 1]

[0073] h2[n] and h3[n] are the height data measured by the RTK module and the inertial measurement respectively, α2 ∈ (0, 1) is the first-order low-pass filtering coefficient of the RTK module height data, and α3 ∈ (0, 1) is the first-order low-pass filtering coefficient of the inertial measurement unit height data.

[0074] (2) Kalman filtering

[0075] The purpose of Kalman filtering is to utilize the data advantages of different sensors to achieve more stable and accurate height feedback; the height data of the laser receiver, the RTK module and the inertial measurement unit are used as the measurement input for Kalman filtering, and the main contents are as follows:

[0076] State vector h k represents the height data at time k, representing the rate of change of height at time k;

[0077] The state transition model x k = Ax k-1 + w k , where w k is the process noise, a random noise with a mean of zero and a covariance of Q,

[0078] State prediction:

[0079] Covariance prediction: P k|k-1 = AP k-1|k-1 A T + Q

[0080] Observation vector where h 1,k , h 2,k , h 3,k respectively represent the observed height data of the laser receiver, RTK module, and inertial measurement unit at time k;;

[0081] Observation equation z k = Hx k + v k , where the observation matrix z k is the observed height data at time k, x k is the height data at time k, v k is the measurement noise, a random noise with a mean of zero and a covariance of R.

[0082] Estimate the noise variances during the measurement processes of the laser receiver, RTK module, and inertial measurement unit through exponentially weighted moving average and update the measurement covariance R of the Kalman filter according to the noise variances of the sensors : k :

[0083] μ i,k = αμ i,k-1 + (1 - α)h i,k

[0084]

[0085] where α ∈ (0, 1) is the smoothing coefficient, μ i,k is the mean estimate of sensor i at time k, representing the laser receiver, RTK module, and inertial measurement unit in sequence;

[0086] According to the sensor noise variance Allocate measurement covariance weights and calculate the credibility of the sensor Normalize the credibility And update the weights:

[0087] w i = clip(w i,min + c i ′(w i,max - w i,min ), w i,min , w i,max )

[0088] where ∈ takes a non - zero value, w i is the measurement covariance weight coefficient of sensor i after normalization, representing the laser receiver, RTK module, and inertial measurement unit in sequence. w1 is greater than w2, w2 is greater than w3, and w1 + w2 + w3 = 1; clip(x, a, b) means restricting x within the interval [a, b];

[0089] Recalculate the measurement covariance R in the Kalman filter at time k according to the updated allocation weights k :

[0090]

[0091] where, represents the noise variance of the laser receiver at time k, represents the noise variance of the RTK module at time k, represents the noise variance of the inertial measurement unit at time k.

[0092] Obtain the observation data z at time k k After that, use the dynamically updated R k to enter the measurement update step.

[0093] Calculate the Kalman gain: K k = P k|k-1 H T (HP k|k-1 H T + R k I3) -1 , where I3 represents a 3×3 identity matrix;

[0094] Height feedback quantity update:

[0095] Covariance update: P k|k = (I - K k H)P k|k-1 , where I is the identity matrix;

[0096] Perform Kalman filtering on the altitude data of the laser receiver, RTK module, and inertial measurement unit to obtain the altitude feedback quantity. Further, adopt the active disturbance rejection control algorithm to perform real-time hovering control on the UAV according to the altitude control feedback quantity.

[0097] Use an active disturbance rejection controller to handle the disturbances of the system, ensuring that the UAV can stably hover at the target hovering altitude in the direction of gravitational acceleration; the active disturbance rejection altitude control realizes the precise hovering of the UAV by estimating and compensating the comprehensive disturbances inside and outside the system in real time; first, the tracking differentiator smooths the UAV target hovering altitude command, generates a non-overshooting transition signal and extracts its differential value to avoid oscillations caused by sudden changes in the set value; subsequently, the extended state observer unifies the uncertain factors such as model errors and external wind disturbances in the UAV dynamics as the total disturbance, expands it into a new state variable through a non-linear feedback mechanism for real-time observation, and synchronously outputs the estimated values of altitude and vertical velocity; the controller dynamically adjusts the proportional and differential gains using a non-linear function according to the command signal of the tracking differentiator and the state deviation estimated by the observer, generates a preliminary control quantity and deducts the observed total disturbance compensation term, and finally calculates the actual thrust command in combination with the control input gain; the control quantity output by the active disturbance rejection controller will be directly used to adjust the power of the UAV motor to maintain altitude stability under strong anti-interference ability.

[0098] Optionally, while executing S3, it further includes:

[0099] Within one control period, calculate the first horizontal position feedback quantity according to the change in position information, calculate the second horizontal position feedback quantity according to the change in attitude data, and perform real-time hovering control on the UAV in the horizontal direction according to the first horizontal position feedback quantity and the second horizontal position feedback quantity.

[0100] Further, optionally, while executing S3, it further includes: performing real-time attitude compensation on the UAV through the attitude data.

[0101] At this time, the stability and precise position control of the drone in the horizontal direction are achieved through the cooperation of the inertial measurement unit and the RTK module; the inertial measurement unit provides real-time attitude angles, angular velocities, and acceleration information to help the drone continuously maintain horizontal stability; the RTK module ensures that the drone does not deviate from the horizontal target point through high-precision position information feedback; the data of the inertial measurement unit and the RTK module are filtered by Kalman filter to remove noise and improve the reliability and accuracy of the signal; combined with the PID controller, the drone can efficiently achieve precise maintenance of the horizontal position and avoid lateral drift caused by external disturbances such as wind; the PID controller uses the feedback data after Kalman filtering to instantly calculate the required adjustment instructions to ensure that the drone can quickly return to the target position under external disturbances and achieve precise hovering; this control process greatly improves the anti-disturbance ability and position maintenance performance of the drone in complex environments and effectively meets the requirements of high-precision hovering.

[0102] When the drone is in a hovering state, the drone's inertia, according to the measurement unit, provides real-time attitude angles, angular velocities, and acceleration information, and continuously detects small changes in the pitch angle and roll angle, and performs attitude compensation through motor power adjustment; for example, if the pitch angle changes due to wind, the drone immediately identifies the tilt and compensates by adjusting the thrust of the front and rear motors to bring its own pitch angle back to the target angle; similarly, an offset in the roll angle will also trigger a corresponding compensation operation. For example, when there is a small offset in the roll angle, the system corrects it in the opposite direction by adjusting the thrust of the left and right motors to ensure that the drone always maintains a horizontal attitude; the entire compensation process is completed within milliseconds to ensure that the drone maintains an accurate hovering state and is not affected by environmental micro-disturbances.

[0103] The advantage of the above-mentioned separate control strategy is that the drone can utilize the optimal sensor feedback mechanism in different directions respectively, significantly improving the hovering accuracy and response speed; in the direction of gravitational acceleration, by using the high-precision real-time relative height provided by the laser receiver as the main feedback, the drone can quickly adjust the thrust to maintain above the specified height; this precise feedback method based on laser overcomes the errors generated by the inertial measurement unit and the RTK system in height detection and improves the stability and accuracy of the drone in the direction of gravitational acceleration; in the horizontal direction, make full use of the data after the fusion of the inertial measurement unit and the RTK to ensure the stability and anti-disturbance ability of the drone at the target position; the angle, angular velocity, and acceleration information output by the inertial measurement unit in real time, combined with the high-precision position information of the RTK, provides a strong suppression of the lateral drift of the drone, enabling it to effectively resist the influence of environmental disturbances such as wind.

[0104] In the embodiments of the present invention, a stable elevation reference plane is established in space by using a laser level. After the laser receiver detects the horizontal laser beam, the relative height between the laser receiver and the elevation reference plane is obtained, and the target hovering height of the UAV at this moment is set according to this relative height; the relative position data measured by the laser receiver is used as the main feedback quantity in the direction of the gravitational acceleration of the UAV, and at the same time, the change information of the gravitational acceleration direction parameters of the inertial measurement unit and the RTK module is fused to adjust the height of the UAV in real time; this solves the problem that the existing UAV hovering control method has insufficient sensor accuracy and is vulnerable to external interference in the height control in the direction of the gravitational acceleration, resulting in difficulty in maintaining precise height control in the direction of the gravitational acceleration; data fusion utilizes the data advantages of different sensors to achieve more stable and accurate height feedback, thereby realizing high-precision hovering control.

[0105] This dual feedback mechanism in the direction of the gravitational acceleration and the horizontal direction endows the UAV with height control accuracy and dynamic stability in three-dimensional space, enabling it to cope with the changing external environment and achieve more accurate hovering positioning.

[0106] Furthermore, in the elevation measurement task, this separation control strategy can significantly improve the positioning accuracy and continuous stability of the measurement points, ensuring that the UAV hovers at the specified position for high-precision elevation measurement; in this way, on the basis of maintaining high-precision stable hovering, the UAV system can further collect data of the on-board sensors, finely measure the elevation information of the position to be measured, and achieve high-precision acquisition of the elevation data of each measurement point in the measurement area; with the support of this dual feedback mechanism, the UAV shows higher reliability and measurement accuracy in the elevation measurement task; this control architecture is not only applicable to high-precision elevation measurement, but also can be extended to other application scenarios that require precise position maintenance, providing a solid technical guarantee for diverse measurement tasks.

[0107] Embodiment 2

[0108] The present invention also provides a UAV hovering control system based on a laser-swept reference, including: a laser receiver, an RTK module, an inertial measurement unit, and a flight controller arranged on the UAV;

[0109] The laser receiver is used to receive the laser signal corresponding to the elevation reference plane scanned by the level at the elevation benchmark point;

[0110] The RTK module is used to obtain the position information of the UAV;

[0111] The inertial measurement unit is used to obtain the attitude data of the UAV;

[0112] The flight controller is connected to the laser receiver, the RTK module and the inertial measurement unit, and is configured to execute the UAV hovering control method based on the laser leveling reference as described in any one of Embodiment 1.

[0113] A UAV hovering control system based on the laser leveling reference provided in this embodiment is used to execute the UAV hovering control method based on the laser leveling reference, and has the same beneficial effects.

[0114] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for controlling the hovering of an unmanned aerial vehicle based on a laser leveling reference, characterized in that Including: When a laser receiver disposed on the unmanned aerial vehicle (UAV) receives a laser signal generated by the laser level scanner scanning at the elevation benchmark point, the relative height between the laser receiver and the elevation reference plane is obtained according to the laser signal, and the target hovering height of the current UAV is set according to the relative height. In each control period, the following steps are executed: S1. Obtain the position information of the UAV through the RTK module, and obtain the attitude data of the UAV through the inertial measurement unit; calculate the first height data h1 according to the relative height corresponding to the real-time laser signal and the target hovering height, calculate the second height data h2 according to the change of the position information, and calculate the third height data h3 according to the change of the attitude data; S2. Perform Kalman filtering on the three height data to obtain the height feedback amount in the direction of the gravitational acceleration; S3. Perform real-time hovering control on the UAV according to the height feedback amount; Wherein, the scanning plane of the laser level scanner at the elevation benchmark point constitutes the elevation reference plane.

2. The method according to claim 1, wherein The target hovering height of the current UAV is dynamically set according to the wide-area reception characteristics of the laser receiver; When it is detected that the elevation reference plane is located in the first measurement area of the laser receiver, the current height is reduced by a fixed height H0 as the target hovering height at this time; When the elevation reference plane is located in the second measurement area of the laser receiver, the current height is used as the target hovering height; When the elevation reference plane is located in the third measurement area of the laser receiver, the current height is increased by a fixed height H0 as the target hovering height at this time.

3. The method according to claim 1, characterized in that, Perform Kalman filtering on the three height data to obtain the height feedback in the direction of gravitational acceleration, including: real-time estimating the noise variances during the measurement processes of the laser receiver, RTK module, and inertial measurement unit through exponentially weighted moving average And based on the noise variances of the sensors Update the measurement covariance R of the Kalman filter at time k k : μ i,k = αμ i,k-1 + (1 - α)h i,k where α ∈ (0, 1) is the smoothing coefficient, and μ ,k is the mean estimation of sensor i at time k, representing the laser receiver, RTK module, and inertial measurement unit in sequence; According to the sensor noise variance Allocate measurement covariance weights and calculate the credibility of the sensor Normalize the credibility And update the weights: w i = clip(w i,min + c i ′(w i,max - w i,min ), w i,min , w i,max ) where ∈ takes a non - zero value, w i is the measurement covariance weight coefficient of the normalized sensor i, representing the laser receiver, RTK module, and inertial measurement unit in sequence, w1 takes a value greater than w2, w2 takes a value greater than w3, and w1 + w2 + w3 = 1; clip(x, a, b) represents restricting x within the interval [a, b]; Recalculate the measurement covariance R in the Kalman filter at time k according to the updated allocation weights k : Among them, represents the noise variance of the laser receiver at time k, represents the noise variance of the RTK module at time k, represents the noise variance of the inertial measurement unit at time k.

4. The method according to claim 1, wherein Adopt an active disturbance rejection control algorithm to perform real-time hovering control on the UAV according to the height control feedback amount.

5. The method according to claim 1, wherein While executing S3, it also includes: In a control period, calculate the first horizontal position feedback amount according to the change of the position information, calculate the second horizontal position feedback amount according to the change of the attitude data, and perform real-time hovering control on the UAV in the horizontal direction according to the first horizontal position feedback amount and the second horizontal position feedback amount.

6. The method according to claim 1, wherein While executing S3, it also includes: performing real-time attitude compensation on the UAV through the attitude data.

7. A drone hovering control system based on a laser leveling reference, characterized in that, Including: A laser receiver, an RTK module, an inertial measurement unit and a flight controller disposed on the UAV; The laser receiver is used to receive the laser signal corresponding to the elevation reference plane generated by the laser level scanner scanning at the elevation benchmark point; The RTK module is used to obtain the position information of the UAV; The inertial measurement unit is used to obtain the attitude data of the UAV; The flight controller is connected to the laser receiver, the RTK module and the inertial measurement unit, and is used to execute the UAV hovering control method based on the laser leveling benchmark according to any one of claims 1-6.

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