CN-121985298-A - Single unmanned aerial vehicle assisted LoRa terminal positioning method

CN121985298ACN 121985298 ACN121985298 ACN 121985298ACN-121985298-A

Abstract

The invention relates to the technical field of unmanned aerial vehicle positioning, and discloses a single unmanned aerial vehicle assisted LoRa terminal positioning method, which utilizes an unmanned aerial vehicle as a mobile base station to receive signals sent by a LoRa terminal, extracts received signal strength indication and establishes a ranging model; the method comprises the steps of performing recursive estimation on terminal positions by adopting extended Kalman filtering, establishing an accuracy estimation model based on distance dependence CRLB for a fixed terminal scene, optimizing the unmanned aerial vehicle path by taking the maximum of a Fisher information matrix determinant as a criterion, reconstructing FIM for a mobile terminal scene, optimizing CRLB by utilizing a Minkowski inequality, and performing path planning by taking the maximum of the FIM incremental determinant as a criterion. According to the invention, a large number of fixed base stations are not required to be deployed, and the high-precision positioning of the terminals of the Internet of things with low power consumption and a large range is realized within limited energy consumption and time.

Inventors

JIA BING
HUANG BAOQI
Qiao Wenling
Bi Rigege
TIAN YU

Assignees

内蒙古大学

Dates

Publication Date: 20260505
Application Date: 20260323

Claims (10)

1. The single unmanned aerial vehicle assisted LoRa terminal positioning method is characterized by comprising the following steps of: Constructing a LoRa network, and completing the design of a LoRa terminal node and a LoRa gateway; establishing a LoRa ranging model by adopting a ranging method based on RSSI, and selecting a matched LoRa signal propagation model; The unmanned aerial vehicle with the LoRa gateway receives a signal packet sent by a LoRa terminal in the flight process, analyzes the signal packet and extracts RSSI information, and simultaneously acquires three-dimensional coordinate position information at the current moment through a positioning module carried by the unmanned aerial vehicle; Aiming at a fixed LoRa terminal scene or a mobile LoRa terminal scene, acquiring a terminal position by adopting an EKF-based LoRa terminal position information acquisition method; if the fixed LoRa terminal scene is adopted, a single UAV path optimization method based on CRLB is adopted to optimize the flight path, and if the fixed LoRa terminal scene is adopted, a single UAV path optimization method based on FIM increment and Minkowski inequality is adopted to optimize the flight path; The unmanned aerial vehicle flies according to the optimized flight path, whether the return condition is met or not is judged in real time in the flight process, if the return condition is met, the unmanned aerial vehicle is controlled to return to the initial position along the return path, the current position information of the unmanned aerial vehicle is continuously acquired in the return process, a LoRa signal is received, the terminal positioning is executed, and if the return condition is not met, the unmanned aerial vehicle continues to fly according to the optimized path; Judging whether the total positioning time is reached, if the total positioning time is not reached and the unmanned aerial vehicle does not enter a return state, continuously acquiring the current position information of the unmanned aerial vehicle, receiving the LoRa signal, executing terminal positioning and path optimization, and if the total positioning time is reached or the unmanned aerial vehicle has completed return, outputting a flight path and a positioning result.
2. The single unmanned aerial vehicle assisted positioning method of the loRa terminal according to claim 1 is characterized in that the loRa network comprises a terminal device with a loRa chip, a loRa base station and a server, the loRa terminal node comprises a loRa module, a sensor and an MCU microcontroller, the loRa gateway comprises the loRa module and the MCU microcontroller, the loRa gateway is mounted on an unmanned aerial vehicle, and the unmanned aerial vehicle is used as a mobile base station for positioning the loRa.
3. The single unmanned aerial vehicle assisted positioning method of claim 1, wherein the establishing a LoRa ranging model by using an RSSI-based ranging method specifically comprises: A positioning model is established by adopting a distance measurement method based on RSSI, and the relation between the signal strength and the propagation distance is expressed as follows: ; Wherein, the In order to receive the power of the power source, For the transmit power of the signal to be transmitted, For the gain of the transmitter antenna, For the gain of the receiver antenna, For transmitting signal wavelength, d represents the distance between the receiving end and the transmitting end; Describing a LoRa signal propagation process by adopting a lognormal shadow model, wherein the LoRa ranging model is as follows: ; Wherein, the Representing the distance between the jth receiving point and the transmitting source, Is shown at a distance from the emission source The power of the signal received at the receiver, Representing the average path loss at the reference point, For the reference distance to be a reference distance, As a path loss factor (pathloss factor), Representing the random term caused by the shadow effect.
4. The single unmanned aerial vehicle assisted positioning method of claim 1, wherein for a fixed LoRa terminal scene, the obtaining the terminal position by using the EKF-based LoRa terminal position information obtaining method specifically comprises: the unknown node coordinates are used as a state vector of a positioning system: ; Wherein, the In order to locate the state vector of the system, For node coordinates, T represents a transpose; The state equation for the fixed LoRa terminal is: ; Wherein, the The number of times of positioning is indicated, Represent the first The state vector of the secondary position fix, Represent the first A state vector of +1 fixes, In the form of a state transition matrix, Is process noise; taking RSSI received by the LoRa terminal node as an observation value, and the measurement equation is as follows: ; Wherein, the Is the first The RSSI measurements of the secondary locations are used, As a nonlinear measurement function consisting of RSSI and terminal position, For measuring noise; and carrying out linearization processing on the measurement equation by adopting an EKF, and obtaining a position estimation value of the fixed LoRa terminal through a prediction and update process.
5. The single unmanned aerial vehicle assisted positioning method of claim 1, wherein the obtaining the terminal position by using the EKF-based method for obtaining the position information of the LoRa terminal for the mobile LoRa terminal scene specifically comprises: The state vector of the node to be positioned is: ; Wherein, the As the coordinates of the nodes of the system, In order for the node speed to be the same, For the direction of motion of the LoRa end node, T represents the transpose. Describing the motion of the mobile LoRa terminal by adopting a random walk model, wherein a node motion model of the mobile LoRa terminal is as follows: ; Wherein, the 、 And The position at the current moment in time is indicated, 、 And The position at the next moment in time is indicated, Representing the time interval between the current time and the next time, Indicating the speed of movement at the next moment, Indicating the direction angle of movement at the next moment, Random noise representing a change in the driving speed, Random noise representing the change in driving direction angle; And taking RSSI as an observed quantity, and carrying out dynamic position estimation on the mobile LoRa terminal by adopting an EKF recurrence process to obtain a position estimation value of the mobile LoRa terminal.
6. The single unmanned aerial vehicle assisted positioning method of claim 1, wherein if the single unmanned aerial vehicle assisted positioning method is a fixed LoRa terminal scene, a single UAV path optimization method based on CRLB is adopted to optimize a flight path, and the method specifically comprises: The estimated coordinate covariance matrix of the node to be positioned meets the following conditions: ; Wherein, the A covariance matrix representing the position estimate of the node to be located, Representation and UAV flight path A related FIM; And (3) carrying out path optimization by adopting a D optimal criterion, wherein an objective function of the path optimization is as follows: ; Wherein, the Representing UAV at the first The direction angle of the moment of time, Representing UAV at the first The pitch angle of the moment in time, Representing the corresponding FIM at the next time after the UAV moves in accordance with the candidate flight direction, Representing matrix determinant operations.
7. The single unmanned aerial vehicle assisted positioning method according to claim 1, wherein if the single unmanned aerial vehicle assisted positioning method is a mobile LoRa terminal scene, a single UAV path optimization method based on FIM increment and Minkowski inequality is adopted to optimize the flight path, and the method specifically comprises: reconstructing the FIM and calculating CRLB; according to the Minkowski inequality of the positive definite matrix, the path optimization problem is converted into the problem of optimizing the FIM increment at the next moment, and the objective function of path optimization is as follows: ; Wherein, the Representing UAV at the first The direction angle of the moment of time, Representing UAV at the first The pitch angle of the moment in time, Representing the FIM delta brought by the UAV from the current time to the next time, The path of the flight is represented by a path of the flight, Representing matrix determinant operations.
8. The single unmanned aerial vehicle assisted LoRa terminal positioning method according to claim 6 or 7, wherein in the path optimization process, the objective function needs to satisfy the following constraint conditions: starting position constraint: ; Wherein, the Is the initial position of the UAV; terminating the position constraint: ; Wherein, the A mission termination location for the UAV; and (3) returning constraint: ; Wherein, the Representing the position of the UAV at the current time, Representing the speed of flight of the UAV, The total task duration is indicated and, Representing a single-step time of flight, And The number of times of positioning and the number of times of transmitting signals by the LoRa terminal node measured before the UAV is not positioned are respectively represented; Lower limit constraint of fly height: ; upper limit constraint of flight altitude: ; Wherein, the To UAV at the first The flying height at the moment of time, And A minimum height and a maximum height, respectively, that allow flight; Pitch angle change constraint: ; Wherein, the The maximum pitch angle variation allowed for adjacent moments of the UAV; Azimuth angle change constraint: ; Wherein, the The maximum azimuth angle variation allowed for adjacent moments of the UAV.
9. The single unmanned aerial vehicle assisted LoRa terminal positioning method of claim 1, wherein the single unmanned aerial vehicle assisted LoRa terminal positioning method is applicable to multiple LoRa terminal scenarios including fixed multiple LoRa terminal scenarios and mobile multiple LoRa terminal scenarios.
10. The single unmanned aerial vehicle assisted positioning method of claim 9, wherein for a fixed multi-LoRa terminal scenario, the overall FIM is constructed as a block diagonal array, the path optimization target is the product of all terminal FIM determinant is maximum, and for a mobile multi-LoRa terminal scenario, the cumulative FIM increment of multiple targets is calculated, and the path optimization target is the product of multi-target FIM increment determinant is maximum.

Description

Single unmanned aerial vehicle assisted LoRa terminal positioning method Technical Field The invention relates to the technical field of unmanned aerial vehicle positioning, in particular to a single unmanned aerial vehicle assisted LoRa terminal positioning method. Background With the development of the internet of things technology, the positioning requirements of large-scale low-power terminals are continuously increased. In application scenarios such as environmental monitoring, smart agriculture, logistics tracking, animal behavior monitoring, etc., it is often necessary to locate a large number of terminal devices with long term and low power consumption. However, the existing positioning technology still has certain limitations in a wide range of low-power consumption scenes. Currently, common positioning technologies mainly include global positioning system (Global Positioning System, GPS), radio frequency identification positioning (Radio Frequency Identification, RFID), and wireless signal positioning. GPS positioning accuracy is higher, but terminal power consumption is higher, and equipment cost is higher, is difficult to satisfy the long-term operation demand of low-power consumption thing networking terminal. RFID technology is generally suitable for short range positioning, and has a limited positioning range, which is difficult to apply in large-scale outdoor scenes. In recent years, long Range radio (LoRa) communication technology based on low power wide area networks (Low Power Wide Area Network, LPWAN) is increasingly applied to the internet of things positioning scenario. The LoRa has the characteristics of long communication distance, low power consumption, low cost and the like, and is suitable for communication and data acquisition of large-scale terminal equipment. By analyzing the RSSI (RECEIVED SIGNAL STRENGTH Indicator of received signal strength) of the LoRa signal, the distance estimation between the terminal and the receiving node can be realized, thereby realizing the terminal positioning. In existing LoRa positioning studies, it is often necessary to deploy multiple fixed base stations to achieve positioning. However, in remote areas, complex environments or temporary monitoring scenarios, deployment costs of a large number of fixed base stations are high, and system maintenance difficulties are also increased. In order to reduce the deployment of fixed infrastructure, there have been proposals in the prior art to utilize Unmanned aerial vehicles (un-managed AERIAL VEHICLE, UAV) as mobile base stations for positioning. The unmanned plane has the characteristics of strong maneuverability and flexible deployment, and can collect terminal signals in a larger range, thereby realizing the positioning function. However, in a single unmanned aerial vehicle positioning system, the flight path design has an important impact on positioning accuracy. If the unmanned aerial vehicle flight path is unreasonable in design, measurement information is insufficient, and therefore positioning accuracy is reduced. In addition, in practical applications, the positioning terminal may be a stationary target or a moving target. For example in a pasture monitoring scenario, it is desirable to locate moving livestock. Therefore, how to design an effective unmanned aerial vehicle flight path under different terminal motion states so as to improve positioning accuracy is an important problem to be solved at present. Accordingly, the prior art is still in need of improvement and development. Disclosure of Invention The invention mainly aims to provide a single unmanned aerial vehicle assisted LoRa terminal positioning method, and aims to solve the problem that in a single unmanned aerial vehicle LoRa positioning system in the prior art, a flight path lacks adaptive optimization aiming at a terminal motion state, so that high-precision positioning requirements on a stationary terminal and a mobile terminal are difficult to consider in a limited endurance time. In order to achieve the above purpose, the invention provides a single unmanned aerial vehicle assisted LoRa terminal positioning method, which comprises the following steps: Constructing a LoRa network, and completing the design of a LoRa terminal node and a LoRa gateway; establishing a LoRa ranging model by adopting a ranging method based on RSSI, and selecting a matched LoRa signal propagation model; The unmanned aerial vehicle with the LoRa gateway receives a signal packet sent by a LoRa terminal in the flight process, analyzes the signal packet and extracts RSSI information, and simultaneously acquires three-dimensional coordinate position information at the current moment through a positioning module carried by the unmanned aerial vehicle; Aiming at a fixed LoRa terminal scene or a mobile LoRa terminal scene, acquiring a terminal position by adopting an EKF-based LoRa terminal position information acquisition method; if the fixed LoRa terminal