CN115118322B - Method and device for collaborative flight of unmanned aerial vehicle in indoor complex environment based on event triggering - Google Patents
Method and device for collaborative flight of unmanned aerial vehicle in indoor complex environment based on event triggering Download PDFInfo
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18502—Airborne stations
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- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D1/00—Control of position, course or altitude of land, water, air, or space vehicles, e.g. automatic pilot
- G05D1/10—Simultaneous control of position or course in three dimensions
- G05D1/101—Simultaneous control of position or course in three dimensions specially adapted for aircraft
- G05D1/106—Change initiated in response to external conditions, e.g. avoidance of elevated terrain or of no-fly zones
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
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- G06T7/579—Depth or shape recovery from multiple images from motion
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- H—ELECTRICITY
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- H04L67/00—Network arrangements or protocols for supporting network services or applications
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- H04L67/12—Protocols specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
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Abstract
The invention provides a method and a device for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering, wherein the method comprises the following steps: comprising the following steps: s1, a service end constructs a dense map for a complex environment, and transmits dense map information to each unmanned aerial vehicle; s2, repositioning the unmanned aerial vehicle according to the received dense map information, and acquiring the pose transformation relation of the position point of the unmanned aerial vehicle relative to the repositioning point; s3, the unmanned aerial vehicle packages the position and pose transformation relation of the depth map data acquired by the unmanned aerial vehicle and the depth map matching into a picture position and pose package and transmits the picture position and pose package to the server; s4, the server stores the received picture pose package into a buffer queue Q for asynchronous operation, and a preset control strategy is adopted to control the data transmission rate of the unmanned aerial vehicle; and S5, the server side drawing building thread takes out the picture pose package from the buffer queue Q to carry out integral ESDF drawing building, and carries out path planning and data transmission control on each unmanned aerial vehicle. The invention is helpful for assisting the unmanned aerial vehicle to cooperatively control the flight in a complex indoor environment.
Description
Technical Field
The invention relates to the technical field of unmanned aerial vehicles, in particular to a method and a device for collaborative flight of an unmanned aerial vehicle in an indoor complex environment based on event triggering.
Background
The unmanned plane has the advantages of flexible use, strong adaptability, high cost performance and the like, and the application range of the unmanned plane is continuously expanded under the double promotion of actual demands and technical development. The unmanned aerial vehicle is required to complete large-scale complex tasks in an indoor complex environment, and a dynamic obstacle avoidance strategy is indispensable. In an indoor complex environment, a positioning scheme of the unmanned aerial vehicle generally adopts a laser or visual scheme, the two schemes have higher calculation force requirements on an onboard processor, and the calculation force which is necessarily distributed to a dynamic obstacle avoidance strategy is necessarily insufficient. In the existing scheme, an open-source framework of Teach-Repeat-replay exists, but the computational power required by the framework is high, and an onboard processor at a low end cannot meet the computational power requirement.
In the prior art, the indoor dynamic obstacle avoidance strategy is mainly aimed at a single machine, and the indoor multi-machine cooperative control obstacle avoidance strategy is always a local obstacle avoidance strategy. Secondly, the running of the existing open source framework has high calculation power on the CPU which is depended on the embedded equipment, the performance of the low-end CPU cannot meet the requirements, but the cost of a high-performance processor is high, and the manufacturing cost of the whole system is high.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method and a device for cooperatively flying an unmanned aerial vehicle in a complex indoor environment based on event triggering, which are used for helping the unmanned aerial vehicle cooperatively control the flying in the complex indoor environment.
The aim of the invention is realized by adopting the following technical scheme:
in a first aspect, the invention provides a method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering, which comprises the following steps:
s1, a service end builds a dense map for a complex environment, and transmits dense map information to each unmanned aerial vehicle, wherein the center origin of the dense map is a locating point;
s2, repositioning the unmanned aerial vehicle according to the received dense map information, and acquiring the pose transformation relation of the position point of the unmanned aerial vehicle relative to the repositioning point;
s3, the unmanned aerial vehicle packs the depth map data acquired by the unmanned aerial vehicle and the position and pose transformation relation matched with the depth map into a picture position and pose package and transmits the picture position and pose package to the server, wherein the unmanned aerial vehicle limits data transmission between the unmanned aerial vehicle and the server in a self-adaptive adjustment mode in the process of transmitting the picture position and pose package to the server;
s4, the server stores the received picture pose packets into a buffer queue Q for asynchronous operation, and controls the data transmission rate of the unmanned aerial vehicle by adopting a preset control strategy according to the number of the picture pose packets of the current buffer queue Q;
and S5, the server side drawing building thread takes out the picture pose package from the buffer queue Q to carry out integral ESDF drawing, displays the position of the unmanned aerial vehicle in the ESDF drawing in real time, and carries out path planning and data transmission control on each unmanned aerial vehicle.
In one embodiment, step S1 includes: and processing and modifying the ORB-SLAM2 frame to increase a dense map building part, building a dense map in a small range for a complex environment, and transmitting information of the built dense map to each unmanned aerial vehicle by taking the central origin of the map building at the time as a locating point O point.
In one embodiment, an unmanned aerial vehicle is provided with a board on which only the trace thread in ORB-SLAM2 is run, and a repositioning function.
In one embodiment, step S2 includes: the onboard processor on the unmanned aerial vehicle performs repositioning work according to the established dense map information, finds the pose transformation relation of the self position point relative to the repositioning point O point, and aims at n unmanned aerial vehicles, and the pose transformation relation of each unmanned aerial vehicle relative to the repositioning point O point is T 1 ，T 2 .......T n Is a relationship of (3).
In an implementation manner, in step S3, the unmanned aerial vehicle packages the depth map data acquired by the unmanned aerial vehicle and the pose transformation relationship matched with the depth map into a picture pose package, and transmits the picture pose package to the server, including: each unmanned aerial vehicle is used as a client to be connected with a server, and the unmanned aerial vehicle packages the depth map data of the sensor and the pose transformation relation T matched with the depth map into a picture pose package and transmits the picture pose package to the server.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
1) The speed of data transmission is adjusted according to the running condition of the unmanned aerial vehicle: the acceleration of the unmanned aerial vehicle obtained from the flight control is set as a, the obtained speed of the unmanned aerial vehicle is set as v, and the speed x for transmitting the picture pose package between the single unmanned aerial vehicle and the server can be obtained by the following formula:
and C is the number of picture pose packages transmitted to the server end by the client of the unmanned aerial vehicle per second, and when the flight speed and the acceleration of the unmanned aerial vehicle are fast, the number of the transmitted picture pose packages is increased according to a formula.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
2) And (3) carrying out rate adjustment of transmission data according to the current network operation condition: the method comprises the steps that dynamic adjustment is conducted on the data transmission rate between an unmanned aerial vehicle and a server, firstly, the server detects the rate of the unmanned aerial vehicle transmitted to the server in real time, each time the server receives a picture transmitted by the unmanned aerial vehicle, an Acknowledgement (ACK) is replied, each ACK is provided with a corresponding sequence number, the unmanned aerial vehicle replies to the server with an ACK after receiving the ACK, and if the server does not receive the ACK replied by the unmanned aerial vehicle, the ACK is repeatedly sent continuously; setting a dynamic congestion control threshold value congwin, wherein the congwin represents the upper limit of the number of pictures which are sent to a server at most by an unmanned aerial vehicle per second, and the unmanned aerial vehicle transmits picture pose packets to the server according to the current limit number of the congwin;
under the initial condition, the unmanned aerial vehicle operates in a slow start strategy SS or congestion avoidance strategy CA mode, wherein the congwin increases by 2 times each time under the slow start strategy SS; when under the congestion avoidance policy CA, the congwin increases by 1 each time;
when the unmanned aerial vehicle is under the slow start strategy SS and the ACK which is not received before is received by the service end, the unmanned aerial vehicle is controlled to be switched from the slow start strategy SS to the congestion avoidance strategy CA;
when the unmanned aerial vehicle is under the congestion avoidance policy CA and the ACK which is not received before is received by the service end, controlling the unmanned aerial vehicle to keep the congestion avoidance policy CA;
when the unmanned aerial vehicle is under a slow start strategy SS or a congestion avoidance strategy CA and the unmanned aerial vehicle receives 3 repeated ACK, dividing the current Congwin by 2;
when the unmanned aerial vehicle is under the slow start strategy SS or the congestion avoidance strategy CA and the unmanned aerial vehicle does not receive repeated ACK, the unmanned aerial vehicle is switched to the slow start strategy SS.
In an embodiment, in step S4, a preset control policy is adopted to control a data transmission rate of the unmanned aerial vehicle according to the number of the picture pose packets of the current buffer queue Q, including:
setting a maximum threshold value h1=min { B, H } of a buffer queue, wherein B represents the number of the most capable of transmitting picture pose packets converted according to the total bandwidth capacity of the server, and the size of the B value is determined according to different bandwidths; h represents the number of the largest possible buffered picture pose packets in the set buffer queue;
when the server detects that the number m < h1 of the transmitted picture pose packages is smaller than the preset value, the server increases the data quantity of transmission for the unmanned aerial vehicle with the fastest speed in the current unmanned aerial vehicle, and if the data transmitted by the unmanned aerial vehicle with the fastest speed reaches the upper limit, the unmanned aerial vehicle is pushed backwards in sequence according to the speed, so that the unmanned aerial vehicle is required to increase the speed of transmitting the picture pose packages.
When the server detects that the number m of the picture pose packets is greater than or equal to h1, the server reduces the data volume of transmission for the sending message with the slowest speed in the current unmanned aerial vehicle, and when the speed of the unmanned aerial vehicle for sending the picture pose packets is equal to the lower limit, the picture pose packets are sequentially sent upwards according to the speed increasing direction of the unmanned aerial vehicle.
In one embodiment, step S5 includes: the server side map building thread takes out a picture pose package from the buffer queue Q to carry out integral ESDF map building, the map building mode adopts incremental map building, and the position of the unmanned aerial vehicle in the ESDF map is displayed in real time;
planning a path of a destination to be reached by each unmanned aerial vehicle; and when the unmanned aerial vehicle performs real-time path planning according to the ESDF which is continuously changed. And triggering the event of the data transmission of the unmanned aerial vehicle when the unmanned aerial vehicle is about to reach the vicinity of an obstacle or the boundary of the established ESDF diagram, wherein the event triggering comprises the following steps: setting a threshold h2, wherein h2=0.5, in meters; when the boundary of the ESDF map built by the distance between p unmanned aerial vehicles is smaller than h2, the transmission quantity of the unmanned aerial vehicle picture pose packages of the p unmanned aerial vehicles is increased, and the increased quantity of each unmanned aerial vehicle picture pose package is that
Wherein W is the number of current picture pose packages to be transmitted; if the picture is increased, the speed of the unmanned aerial vehicle is reduced.
In a second aspect, the present invention provides an event-triggered indoor complex environment unmanned aerial vehicle collaborative flight device, where the device is configured to implement a method for event-triggered indoor complex environment unmanned aerial vehicle collaborative flight according to an embodiment of the first aspect.
The beneficial effects of the invention are as follows:
firstly, the invention does not need GPS equipment and the like, can operate in a GPS-free environment, and has stronger application universality.
The invention also discloses a method for controlling the unmanned aerial vehicle by the aid of the multi-frame unmanned aerial vehicle.
Thirdly, the method controls the flow of the data transmitted to the server by the unmanned aerial vehicle in an event triggering mode and a self-adaptive bandwidth adjusting mode, so that the processing of the data transmitted by the unmanned aerial vehicle by the server is improved as much as possible, and the dynamic obstacle avoidance capability of the unmanned aerial vehicle is improved.
Drawings
The invention will be further described with reference to the accompanying drawings, in which embodiments do not constitute any limitation of the invention, and other drawings can be obtained by one of ordinary skill in the art without inventive effort from the following drawings.
FIG. 1 is a schematic diagram of steps of a method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering;
fig. 2 is a schematic flow chart of a method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering.
Detailed Description
The invention is further described in connection with the following application scenario.
Referring to fig. 1, a method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering includes the following steps:
s1, a service end builds a dense map for a complex environment, and transmits dense map information to each unmanned aerial vehicle, wherein the center origin of the dense map is a locating point;
in one embodiment, step S1 includes: and processing and modifying the ORB-SLAM2 frame to increase a dense map building part, building a dense map in a small range for a complex environment, and transmitting information of the built dense map to each unmanned aerial vehicle by taking the central origin of the map building at the time as a locating point O point.
The server comprises a server.
S2, repositioning the unmanned aerial vehicle according to the received dense map information, and acquiring the pose transformation relation of the position point of the unmanned aerial vehicle relative to the repositioning point;
in one embodiment, an unmanned aerial vehicle is provided with a board on which only the trace thread in ORB-SLAM2 is run, and a repositioning function.
In one embodiment, step S2 includes: the onboard processor on the unmanned aerial vehicle performs repositioning work according to the established dense map information, finds the pose transformation relation of the self position point relative to the repositioning point O point, and aims at n unmanned aerial vehicles, and the pose transformation relation of each unmanned aerial vehicle relative to the repositioning point O point is T 1 ，T 2 .......T n Is a relationship of (3).
S3, the unmanned aerial vehicle packs the depth map data acquired by the unmanned aerial vehicle and the position and pose transformation relation matched with the depth map into a picture position and pose package and transmits the picture position and pose package to the server, wherein the unmanned aerial vehicle limits data transmission between the unmanned aerial vehicle and the server in a self-adaptive adjustment mode in the process of transmitting the picture position and pose package to the server;
in an implementation manner, in step S3, the unmanned aerial vehicle packages the depth map data acquired by the unmanned aerial vehicle and the pose transformation relationship matched with the depth map into a picture pose package, and transmits the picture pose package to the server, including: each unmanned aerial vehicle is used as a client to be connected with a server, and the unmanned aerial vehicle packages the depth map data of the sensor and the pose transformation relation T matched with the depth map into a picture pose package and transmits the picture pose package to the server.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
1) The speed of data transmission is adjusted according to the running condition of the unmanned aerial vehicle: the acceleration of the unmanned aerial vehicle obtained from the flight control is set as a, the obtained speed of the unmanned aerial vehicle is set as v, and the speed x for transmitting the picture pose package between the single unmanned aerial vehicle and the server can be obtained by the following formula:
and C is the number of picture pose packages transmitted to the server end by the client of the unmanned aerial vehicle per second, and when the flight speed and the acceleration of the unmanned aerial vehicle are fast, the number of the transmitted picture pose packages is increased according to a formula.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
2) And (3) carrying out rate adjustment of transmission data according to the current network operation condition: the method comprises the steps that data transmission rate between an unmanned aerial vehicle and a server side is dynamically adjusted, firstly, the server side detects the rate of the unmanned aerial vehicle transmitted to the server side in real time, each time the server side receives a picture transmitted by the unmanned aerial vehicle, an Acknowledgement (ACK) is replied, and each ACK is provided with a corresponding sequence number; setting a dynamic congestion control threshold value congwin, wherein the congwin represents the upper limit of the number of pictures which are sent to a server at most by an unmanned aerial vehicle per second, and the unmanned aerial vehicle transmits picture pose packets to the server according to the current limit number of the congwin;
under the initial condition, the unmanned aerial vehicle operates in a slow start strategy SS or congestion avoidance strategy CA mode, wherein the congwin increases by 2 times each time under the slow start strategy SS; when under the congestion avoidance policy CA, the congwin increases by 1 each time;
when the unmanned aerial vehicle is under the slow start strategy SS and the ACK which is not received before is received by the service end, the unmanned aerial vehicle is controlled to be switched from the slow start strategy SS to the congestion avoidance strategy CA;
when the unmanned aerial vehicle is under the congestion avoidance policy CA and the ACK which is not received before is received by the service end, controlling the unmanned aerial vehicle to keep the congestion avoidance policy CA;
when the unmanned aerial vehicle is under a slow start strategy SS or a congestion avoidance strategy CA and receives 3 repeated ACKs, dividing the current Congwin by 2;
when the unmanned aerial vehicle is under the slow start strategy SS or the congestion avoidance strategy CA and does not receive repeated ACK, the unmanned aerial vehicle is switched to the slow start strategy SS.
S4, the server stores the received picture pose packets into a buffer queue Q for asynchronous operation, and controls the data transmission rate of the unmanned aerial vehicle according to a preset control strategy according to the number of the picture pose packets of the current buffer queue Q;
in an embodiment, in step S4, the controlling the data transmission rate of the unmanned aerial vehicle according to the number of the picture pose packets of the current buffer queue Q and a preset control policy includes:
setting a maximum threshold value h1=min { B, H } of a buffer queue, wherein B represents the number of the most capable of transmitting picture pose packets converted according to the total bandwidth capacity of the server, and the size of the B value is determined according to different bandwidths; h represents the number of the largest possible buffered picture pose packets in the set buffer queue;
when the server detects that the number m < h1 of the transmitted picture pose packages is smaller than the preset value, the server increases the data quantity of transmission for the unmanned aerial vehicle with the fastest speed in the current unmanned aerial vehicle, and if the data transmitted by the unmanned aerial vehicle with the fastest speed reaches the upper limit, the unmanned aerial vehicle is pushed backwards in sequence according to the speed, so that the unmanned aerial vehicle is required to increase the speed of transmitting the picture pose packages.
When the server detects that the number m of the picture pose packets is greater than or equal to h1, the server reduces the data volume of transmission for the sending message with the slowest speed in the current unmanned aerial vehicle, and when the speed of the unmanned aerial vehicle for sending the picture pose packets is equal to the lower limit, the picture pose packets are sequentially sent upwards according to the speed increasing direction of the unmanned aerial vehicle.
And S5, the server mapping thread takes out the picture pose package from the buffer queue Q to carry out integral ESDF mapping, displays the position of the unmanned aerial vehicle in the ESDF mapping in real time, and carries out path planning and data transmission control on each unmanned aerial vehicle.
In one embodiment, step S5 includes: the server side map building thread takes out a picture pose package from the buffer queue Q to carry out integral ESDF map building, the map building mode adopts incremental map building, and the position of the unmanned aerial vehicle in the ESDF map is displayed in real time;
planning a path of a destination to be reached by each unmanned aerial vehicle; and when the unmanned aerial vehicle performs real-time path planning according to the ESDF which is continuously changed. And triggering the event of the data transmission of the unmanned aerial vehicle when the unmanned aerial vehicle is about to reach the vicinity of an obstacle or the boundary of the established ESDF diagram, wherein the event triggering comprises the following steps: setting a threshold h2, wherein h2=0.5, in meters; when the boundary of the ESDF map built by the distance between p unmanned aerial vehicles is smaller than h2, the transmission quantity of the unmanned aerial vehicle picture pose packages of the p unmanned aerial vehicles is increased, and the increased quantity of each unmanned aerial vehicle picture pose package is that
Wherein W is the number of current picture pose packages to be transmitted; if the picture is increased, the speed of the unmanned aerial vehicle is reduced.
In one embodiment, an unmanned aerial vehicle is provided with a board on which only the trace thread in ORB-SLAM2 is run, and a repositioning function.
In one embodiment, step S2 includes: the onboard processor on the unmanned aerial vehicle performs repositioning work according to the established dense map information, finds the pose transformation relation of the self position point relative to the repositioning point O point, and aims at n unmanned aerial vehicles, and the pose transformation relation of each unmanned aerial vehicle relative to the repositioning point O point is T 1 ，T 2 .......T n Is a relationship of (3).
In an implementation manner, in step S3, the unmanned aerial vehicle packages the depth map data acquired by the unmanned aerial vehicle and the pose transformation relationship matched with the depth map into a picture pose package, and transmits the picture pose package to the server, and the method includes: each unmanned aerial vehicle is used as a client to be connected with a server, and the unmanned aerial vehicle packages the depth map data of the unmanned aerial vehicle sensor and the position and pose transformation relation T matched with the depth map into a picture position and pose package and transmits the picture position and pose package to the server.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
1) The speed of data transmission is adjusted according to the running condition of the unmanned aerial vehicle: the acceleration of the unmanned aerial vehicle obtained from the flight control is set as a, the obtained speed of the unmanned aerial vehicle is set as v, and the speed x for transmitting the picture pose package between the single unmanned aerial vehicle and the server can be obtained by the following formula:
and C is the number of picture pose packages transmitted to the server end by the client of the unmanned aerial vehicle per second, and when the flight speed and the acceleration of the unmanned aerial vehicle are fast, the number of the transmitted picture pose packages is increased according to a formula.
In an implementation manner, in step S3, in a process that the unmanned aerial vehicle transmits the picture pose package to the server, a self-adaptive adjustment mode is adopted to limit data transmission between the unmanned aerial vehicle and the server, including:
2) And (3) carrying out rate adjustment of transmission data according to the current network operation condition: the method comprises the steps that data transmission rate between an unmanned aerial vehicle and a server side is dynamically adjusted, firstly, the server side detects the rate of the unmanned aerial vehicle transmitted to the server side in real time, each time the server side receives a picture transmitted by the unmanned aerial vehicle, an Acknowledgement (ACK) is replied, and each ACK is provided with a corresponding sequence number; setting a dynamic congestion control threshold value congwin, wherein the congwin represents the upper limit of the number of pictures which are sent to a server at most by an unmanned aerial vehicle per second, and the unmanned aerial vehicle transmits picture pose packets to the server according to the current limit number of the congwin;
under the initial condition, the unmanned aerial vehicle operates in a slow start strategy SS or congestion avoidance strategy CA mode, wherein the congwin increases by 2 times each time under the slow start strategy SS; when under the congestion avoidance policy CA, the congwin increases by 1 each time;
when the unmanned aerial vehicle is under the slow start strategy SS and the ACK which is not received before is received by the service end, the unmanned aerial vehicle is controlled to be switched from the slow start strategy SS to the congestion avoidance strategy CA;
when the unmanned aerial vehicle is under the congestion avoidance policy CA and the ACK which is not received before is received by the service end, controlling the unmanned aerial vehicle to keep the congestion avoidance policy CA;
when the unmanned aerial vehicle is under a slow start strategy SS or a congestion avoidance strategy CA and receives 3 repeated ACKs, dividing the current Congwin by 2;
when the unmanned aerial vehicle is under the slow start strategy SS or the congestion avoidance strategy CA and does not receive repeated ACK, the unmanned aerial vehicle is switched to the slow start strategy SS.
In an embodiment, in step S4, the controlling the data transmission rate of the unmanned aerial vehicle according to the number of the picture pose packets of the current buffer queue Q and a preset control policy includes:
setting a maximum threshold value h1=min { B, H } of a buffer queue, wherein B represents the number of the most capable of transmitting picture pose packets converted according to the total bandwidth capacity of the server, and the size of the B value is determined according to different bandwidths; h represents the number of the largest possible buffered picture pose packets in the set buffer queue;
when the server detects that the number m < h1 of the picture pose packages is smaller than the number m, the server side improves the data quantity of transmission for the unmanned aerial vehicle with the fastest speed in the current unmanned aerial vehicle, and if the data transmitted by the unmanned aerial vehicle with the fastest speed reaches the upper limit, the data are sequentially pushed backwards according to the speed, so that the unmanned aerial vehicle is required to improve the speed of transmitting the picture pose packages.
When the server detects that the number m of the picture pose packets is greater than or equal to h1, the server reduces the data volume of transmission for the sending message with the slowest speed in the current unmanned aerial vehicle, and when the speed of the unmanned aerial vehicle for sending the picture pose packets is equal to the lower limit, the picture pose packets are sequentially sent upwards according to the speed increasing direction of the unmanned aerial vehicle.
In one embodiment, step S5 includes: the server side map building thread takes out a picture pose package from the buffer queue Q to carry out integral ESDF map building, the map building mode adopts incremental map building, and the position of the unmanned aerial vehicle in the ESDF map is displayed in real time;
planning a path of a destination to be reached by each unmanned aerial vehicle; and when the unmanned aerial vehicle performs real-time path planning according to the ESDF which is continuously changed. And triggering the event of the data transmission of the unmanned aerial vehicle when the unmanned aerial vehicle is about to reach the vicinity of an obstacle or the boundary of the established ESDF diagram, wherein the event triggering comprises the following steps: setting a threshold h2, wherein h2=0.5, in meters; when the boundary of the ESDF map built by the distance between p unmanned aerial vehicles is smaller than h2, the transmission quantity of the unmanned aerial vehicle picture pose packages of the p unmanned aerial vehicles is increased, and the increased quantity of each unmanned aerial vehicle picture pose package is that
Wherein W is the number of current picture pose packages to be transmitted; if the picture is increased, the speed of the unmanned aerial vehicle is reduced.
The invention provides a method for collaborative flight of unmanned aerial vehicles in an indoor complex environment based on event triggering, which comprises the steps of 1, adopting a self-adaptive adjustment strategy to adjust the picture rate transmitted to a server by a single unmanned aerial vehicle in real time. 2. By adopting a buffer queue mode, the pictures transmitted from the unmanned aerial vehicle firstly enter the buffer queue, and the impact of a data transmission peak is reduced. 3. And by adopting event triggering, the establishment of the ESDF diagram is prioritized, the priority of the unmanned aerial vehicle which is close to the boundary for transmitting the image information to the server is increased, and the obstacle avoidance precision is improved. 4. And an event triggering bandwidth allocation strategy is adopted, and the server allocates more bandwidth resources to the unmanned aerial vehicle with high speed according to the allowance of the bandwidth, so that the real-time performance of obstacle avoidance is improved. 5. The adoption of the picture transmission congestion avoidance strategy avoids the situation that too many pictures are sent to the server by the unmanned aerial vehicle, so that network congestion is caused, and the processing capacity of the server is exerted to the greatest extent.
Compared with the prior art, the invention has the following advantages that firstly, the invention does not need equipment such as GPS and the like, can operate in a GPS-free environment, and has stronger application universality. The invention also discloses a method for controlling the unmanned aerial vehicle by the aid of the multi-frame unmanned aerial vehicle. Thirdly, the method controls the flow of the data transmitted to the server by the unmanned aerial vehicle in an event triggering mode and a self-adaptive bandwidth adjusting mode, so that the processing of the data transmitted by the unmanned aerial vehicle by the server is improved as much as possible, and the dynamic obstacle avoidance capability of the unmanned aerial vehicle is improved.
Corresponding to the method for cooperatively flying the unmanned aerial vehicle in the indoor complex environment based on the event triggering provided by the invention, the embodiment of the invention also provides a device for cooperatively flying the unmanned aerial vehicle in the indoor complex environment based on the event triggering, wherein the device is used for realizing the method steps of the corresponding embodiments of the method steps in the figures 1 and 1. The present invention is not repeated here.
The complete method for collaborative flight of the unmanned aerial vehicle in the indoor complex environment based on event triggering is shown in fig. 2:
the first step is to process and modify the ORB-SLAM2 frame to increase the dense map building part, build a dense map in a small range for the complex environment, and take the center origin point of the map building as the heavy locating point, namely the O point. And transmitting the information of the established dense map to each unmanned aerial vehicle.
And secondly, modifying the ORB-SLAM2 framework to reduce the calculated amount, only running the tracking thread in the ORB-SLAM2 on the board of the unmanned aerial vehicle, and removing the back-end optimization part in the ORB-SLAM2 by a repositioning function, so that the back-end optimization is not performed any more, and the calculation pressure of a board processor is reduced. And the onboard processor performs repositioning work according to the established dense map information, and finds the pose transformation relation of the self position point relative to the repositioning point O point. The unmanned aerial vehicle is provided with n unmanned aerial vehicles, and the pose transformation relation of each unmanned aerial vehicle relative to the repositioning point O point is T 1 ，T 2 .......T n Is a relationship of (3). Each frame obtains pose transformation information relative to the origin O. In the invention, the depth map and the pose information are collectively called a picture pose package.
And thirdly, each unmanned aerial vehicle is used as a client to be connected with a server, the unmanned aerial vehicle transmits depth map data of a sensor of the unmanned aerial vehicle to the server, and meanwhile, the pose transformation relation T matched with the depth map is transmitted to the server. For example, any one y in the unmanned aerial vehicle in n frames can acquire depth map information of RGBD camera and pose change relation T generated after the machine board processes the depth map y Packaged together to the server side. In the process of image transmission, the occupied bandwidth of the network is relatively large, and the transmission of data between the unmanned aerial vehicle and the server side is limited by adopting self-adaptive adjustment. The following two strategies are mainly used for adjustment: 1. the speed of data transmission is adjusted according to the running condition of the unmanned aerial vehicle: let the acceleration of the unmanned aerial vehicle obtained from the flight control be a and the speed of the unmanned aerial vehicle be v. The rate for transmitting the picture pose package between the single frame unmanned aerial vehicle and the server can be obtained by the following formula.
And C is the number of picture pose packages transmitted to the server end by the client of the unmanned aerial vehicle per second, and when the flight speed and the acceleration of the unmanned aerial vehicle are fast, the number of the transmitted picture pose packages is increased according to a formula.
2. And (3) carrying out rate adjustment of transmission data according to the current network operation condition: the method comprises the steps that data transmission rate between an unmanned aerial vehicle and a server side is dynamically adjusted, firstly, the server side detects the rate of the unmanned aerial vehicle transmitted to the server side in real time (the rate is the number of pictures transmitted to the server side by the unmanned aerial vehicle every second), each time the server side receives a picture transmitted by the unmanned aerial vehicle, the picture replies with a response ACK, each ACK has a serial number, the unmanned aerial vehicle replies with an ACK to the server side after receiving the ACK, and if the server side does not receive the ACK replied by the unmanned aerial vehicle, the ACK is repeatedly sent continuously. In order to avoid the situation that all unmanned aerial vehicles send a large number of pictures to a server at the same time and cause congestion of the server, the following strategy is adopted to avoid the congestion situation. Setting a dynamic congestion control threshold value Congwin (the upper limit of the number of pictures which are sent to the server by the unmanned aerial vehicle at most per second), wherein the Congwin has the function of uniformly controlling the number of the unmanned aerial vehicles sent to the server by all the unmanned aerial vehicles at a certain moment, and the Congwin is an upper limit value. And this value is a dynamic value. There are two kinds of sending picture strategies: policy SS (slow start policy): under this strategy, congwin is incremented by a factor of 2 at a time. Policy CA (congestion avoidance policy): under this strategy, the congwin is incremented by a speed of 1 every time (e.g., every second). The drone dynamically adjusts according to the policies of the following table.
Fourthly, the server receives a picture pose package of the unmanned aerial vehicle; a buffer queue is additionally arranged in the server, and all pictures transmitted to the server firstly enter the buffer queue Q to perform asynchronous operation, so that the real-time processing capacity is improved, and packet loss is prevented. The server receives the total number of the picture pose packages of all unmanned aerial vehicles, and the following two control strategies are provided. 1. The method is characterized in that the method is limited by the capacity B of the total bandwidth of a server (namely, the value congwin obtained by the network strategy), the bandwidth of the B network is converted into the maximum number of picture pose packets capable of being transmitted, the different bandwidths are different by 2, the method is limited by the maximum number H of picture pose packets capable of being buffered in a buffer queue, and the H parameter is set to be 60. And triggering the sampling event for the data transmission. Given a threshold h1=min { B, H }, when the number of transmitted picture pose packets m < H, trigger event a: the server side increases the data quantity of transmission for the unmanned aerial vehicle with the fastest speed in the current unmanned aerial vehicle, if the data transmitted by the unmanned aerial vehicle with the fastest speed reaches the upper limit (the upper limit is C+10 determined by the speed and the acceleration of the current unmanned aerial vehicle), the unmanned aerial vehicle is required to increase the speed of transmitting the picture pose package according to the speed, and the speed is sequentially pushed backwards. When m is greater than or equal to h, triggering event B: and the server reduces the transmitted data quantity for the transmission message with the slowest speed in the current unmanned aerial vehicle, and when the speed of the unmanned aerial vehicle for transmitting the picture pose package is equal to the lower limit (the lower limit is C determined by the speed and the acceleration of the current unmanned aerial vehicle, and the lower limit is C-5), the unmanned aerial vehicle is ranked according to the flying speed of the unmanned aerial vehicle, and the information for reducing the transmitted data quantity is sequentially transmitted to the unmanned aerial vehicle according to the size of the rate ranking until m < h.
And fifthly, the server side map creation thread takes out the picture pose package from the buffer queue Q to carry out integral ESDF map creation, the map creation mode adopts incremental map creation, and the position of the unmanned aerial vehicle in the ESDF map is displayed in real time. And planning a path for each destination to be reached by the unmanned aerial vehicle. And the unmanned aerial vehicle performs path planning according to the established ESDF diagram. And triggering the event of the data transmission of the unmanned aerial vehicle when the unmanned aerial vehicle is about to reach the vicinity of the obstacle or the boundary of the established ESDF diagram. A threshold h2 is given, where h2=0.5, in meters. Triggering event C when the boundary of the ESDF map established by the distance between p unmanned aerial vehicles is smaller than h 2: the transmission quantity of the p frames of unmanned aerial vehicle picture pose packages is increased, and the increased quantity of each frame is that
Wherein the method comprises the steps ofW is the number of current transmitted picture pose packets. If the picture is increased, the speed of the unmanned aerial vehicle is reduced. />
It should be noted that, in each embodiment of the present invention, each functional unit/module may be integrated in one processing unit/module, or each unit/module may exist alone physically, or two or more units/modules may be integrated in one unit/module. The integrated units/modules described above may be implemented either in hardware or in software functional units/modules.
From the description of the embodiments above, it will be apparent to those skilled in the art that the embodiments described herein may be implemented in hardware, software, firmware, middleware, code, or any suitable combination thereof. For a hardware implementation, the processor may be implemented in one or more of the following units: an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), a processor, a controller, a microcontroller, a microprocessor, other electronic units designed to perform the functions described herein, or a combination thereof. For a software implementation, some or all of the flow of an embodiment may be accomplished by a computer program to instruct the associated hardware. When implemented, the above-described programs may be stored in or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. The computer readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (6)
1. The method for cooperatively flying the unmanned aerial vehicle in the indoor complex environment based on event triggering is characterized by comprising the following steps of:
s1, a service end builds a dense map for a complex environment, and transmits dense map information to each unmanned aerial vehicle, wherein the center origin of the dense map is a locating point;
s2, repositioning the unmanned aerial vehicle according to the received dense map information, and acquiring the pose transformation relation of the position point of the unmanned aerial vehicle relative to the repositioning point;
s3, the unmanned aerial vehicle packs the depth map data acquired by the unmanned aerial vehicle and the position and pose transformation relation matched with the depth map into a picture position and pose package and transmits the picture position and pose package to the server, wherein the unmanned aerial vehicle limits data transmission between the unmanned aerial vehicle and the server in a self-adaptive adjustment mode in the process of transmitting the picture position and pose package to the server; comprising the following steps:
1) The speed of data transmission is adjusted according to the running condition of the unmanned aerial vehicle: the acceleration of the unmanned aerial vehicle obtained from the flight control is set as a, the obtained speed of the unmanned aerial vehicle is set as v, and the speed x for transmitting the picture pose package between the single unmanned aerial vehicle and the server can be obtained by the following formula:
c is the number of picture pose packages transmitted to a server by a client of the unmanned aerial vehicle per second, and when the flight speed and the acceleration of the unmanned aerial vehicle are fast, the number of the transmitted picture pose packages is increased;
and/or the number of the groups of groups,
2) And (3) carrying out rate adjustment of transmission data according to the current network operation condition: the method comprises the steps that dynamic adjustment is conducted on the data transmission rate between an unmanned aerial vehicle and a server, firstly, the server detects the rate of the unmanned aerial vehicle transmitted to the server in real time, each time the server receives a picture transmitted by the unmanned aerial vehicle, an Acknowledgement (ACK) is replied, each ACK is provided with a corresponding sequence number, the unmanned aerial vehicle replies to the server with an ACK after receiving the ACK, and if the server does not receive the ACK replied by the unmanned aerial vehicle, the ACK is repeatedly sent continuously; setting a dynamic congestion control threshold value congwin, wherein the congwin represents the upper limit of the number of pictures which are sent to a server at most by an unmanned aerial vehicle per second, and the unmanned aerial vehicle transmits picture pose packets to the server according to the current limit number of the congwin;
under the initial condition, the unmanned aerial vehicle operates in a slow start strategy SS or congestion avoidance strategy CA mode, wherein the congwin increases by 2 times each time under the slow start strategy SS; when under the congestion avoidance policy CA, the congwin increases by 1 each time;
when the unmanned aerial vehicle is under the slow start strategy SS and the ACK which is not received before is received by the service end, the unmanned aerial vehicle is controlled to be switched from the slow start strategy SS to the congestion avoidance strategy CA;
when the unmanned aerial vehicle is under the congestion avoidance policy CA and the ACK which is not received before is received by the service end, controlling the unmanned aerial vehicle to keep the congestion avoidance policy CA;
when the unmanned aerial vehicle is under a slow start strategy SS or a congestion avoidance strategy CA and the unmanned aerial vehicle receives 3 repeated ACK, dividing the current Congwin by 2;
when the unmanned aerial vehicle is under the slow start strategy SS or the congestion avoidance strategy CA and the unmanned aerial vehicle does not receive repeated ACK, the unmanned aerial vehicle is switched to the slow start strategy SS;
each unmanned aerial vehicle is used as a client to be connected with a server, and the unmanned aerial vehicles package the depth map data of the unmanned aerial vehicles and the position and pose transformation relation T matched with the depth map into a picture position and pose package and transmit the picture position and pose package to the server;
s4, the server stores the received picture pose packets into a buffer queue Q for asynchronous operation, and controls the data transmission rate of the unmanned aerial vehicle by adopting a preset control strategy according to the number of the picture pose packets of the current buffer queue Q; comprising the following steps:
setting a maximum threshold value h1= { B, H } of a buffer queue, wherein B represents the number of the most capable of transmitting picture pose packets converted according to the total bandwidth capacity of a server side, and the size of the B value is determined according to different bandwidths; h represents the number of the largest possible buffered picture pose packets in the set buffer queue;
when the server detects that the number m < h1 of the transmitted picture pose packages, the server increases the transmission data quantity for the unmanned aerial vehicle with the highest speed in the current unmanned aerial vehicle, and if the data transmitted by the unmanned aerial vehicle with the highest speed reaches the upper limit, the unmanned aerial vehicle is sequentially pushed backwards according to the speed, so that the unmanned aerial vehicle is required to increase the speed of transmitting the picture pose packages;
when the server detects that the number m of the picture pose packets is greater than or equal to h1, the server reduces the transmitted data quantity for the transmission message with the slowest speed in the current unmanned aerial vehicle, and when the speed of the unmanned aerial vehicle for transmitting the picture pose packets is equal to the lower limit, the picture pose packets are sequentially transmitted upwards according to the speed increasing direction of the unmanned aerial vehicle;
and S5, the server side drawing building thread takes out the picture pose package from the buffer queue Q to carry out integral ESDF drawing, displays the position of the unmanned aerial vehicle in the ESDF drawing in real time, and carries out path planning and data transmission control on each unmanned aerial vehicle.
2. The method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering according to claim 1, wherein step S1 comprises: and processing and modifying the ORB-SLAM2 frame to increase a dense map building part, building a dense map in a small range for a complex environment, and transmitting information of the built dense map to each unmanned aerial vehicle by taking the central origin of the map building at the time as a locating point O point.
3. The method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering according to claim 2, wherein a carrier is provided on the unmanned aerial vehicle, and only a tracking thread in ORB-SLAM2 and a repositioning function are operated on the carrier of the unmanned aerial vehicle.
4. The method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering according to claim 2, wherein step S2 comprises: the onboard processor on the unmanned aerial vehicle performs repositioning work according to the established dense map information, finds the pose transformation relation of the self position point relative to the repositioning point O point, and aims at n unmanned aerial vehicles, and the pose transformation relation of each unmanned aerial vehicle relative to the repositioning point O point is T 1 ，T 2 ....... n Is a relationship of (3).
5. The method for collaborative flight of an indoor complex environment unmanned aerial vehicle based on event triggering according to claim 1, wherein step S5 comprises: the server side map building thread takes out a picture pose package from the buffer queue Q to carry out integral ESDF map building, the map building mode adopts incremental map building, and the position of the unmanned aerial vehicle in the ESDF map is displayed in real time;
planning a path of a destination to be reached by each unmanned aerial vehicle; when the unmanned aerial vehicle performs real-time path planning according to the ESDF which is continuously changed, and the unmanned aerial vehicle is about to reach the vicinity of an obstacle or the boundary of an ESDF diagram is established, the event triggering is performed on the data transmission of the unmanned aerial vehicle, and the method comprises the following steps: setting a threshold h2, wherein h2=0.5, in meters; when the boundary of the ESDF map built by the distance between p unmanned aerial vehicles is smaller than h2, the transmission quantity of the unmanned aerial vehicle picture pose packages of the p unmanned aerial vehicles is increased, and the increased quantity of each unmanned aerial vehicle picture pose package is that
Wherein W is the number of current picture pose packages to be transmitted; if the picture is increased, the speed of the unmanned aerial vehicle is reduced.
6. An event trigger-based device for cooperatively flying an indoor complex environment unmanned aerial vehicle, which is used for realizing the method for cooperatively flying the indoor complex environment unmanned aerial vehicle based on event trigger according to any one of claims 1 to 5.
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