A sensor node positioning method based on path planning and transmission power control

Abstract

The present invention discloses a sensor node positioning method based on path planning and transmission power control, which belongs to the technical field of wireless sensor network nodes, and designs a new mobile path, transmission power control scheme and obstacle handling mechanism for mobile anchor nodes. The purpose is to reduce the path length and the number of beacon points of the mobile anchor node, thereby reducing energy consumption and reducing positioning time; to achieve full coverage of the monitoring area by the mobile anchor node, reduce the number of collinear beacon points, and ensure the success rate of positioning; to control the transmission power of the mobile anchor node, reduce the number of transmissions of unnecessary beacon points, so as to further reduce energy consumption and improve positioning accuracy; the obstacle handling mechanism reduces the impact of obstacles on positioning, and ensures the positioning of all unknown nodes as much as possible.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless sensor network nodes, and in particular relates to a sensor node positioning method based on path planning and transmission power control. Background Art

[0002] Nowadays, with the continuous advancement of Internet of Things (IoT) technology, humans can connect and interact with the real world on the Internet. Wireless Sensor Networks (WSNs), as an important part of IoT, have been applied to many fields in human life, such as fire monitoring and target tracking. By locating the sensor nodes in WSNs, the specific location of the event can be quickly determined to reduce the impact and loss caused by unforeseen events.

[0003] Sensor node localization is a key issue in WSNs. Nodes with unknown locations (unknown nodes) are located by using a portion of nodes with known locations (anchor nodes) in combination with a localization algorithm. Existing research mainly uses the distance vector-hop (DV-Hop) algorithm or mobile anchor nodes based on path planning for localization. The error of distance estimation can be reduced by optimizing the hop count calculation of DV-Hop; the localization accuracy can be improved by performing secondary localization on the localization results or using optimization algorithms (such as genetic algorithms); and the localization performance of mobile anchor nodes can be improved by improving the moving paths of mobile anchor nodes.

[0004] The existing node positioning methods have the following problems: it is difficult to achieve a balance between positioning accuracy and positioning energy consumption, and the improvement of positioning accuracy often increases positioning energy consumption; positioning energy consumption is not fully considered; the real-time positioning is not effectively solved; the impact of obstacles on node positioning is not solved; the positioning accuracy is reduced when the anchor nodes are unevenly distributed or the network is irregular. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention proposes a sensor node positioning method based on path planning and transmission power control, which has a reasonable design, solves the shortcomings of the prior art and has good effects.

[0006] A sensor node positioning method based on path planning and transmission power control comprises the following steps:

[0007] S1. Determine the monitoring area, determine the division level and divide the area according to the area size and positioning accuracy requirements, and randomly place the unknown nodes used for monitoring in the monitoring area or manually place them at the locations that need to be monitored;

[0008] S2, using a mobile car or robot as a mobile anchor node, equipped with a GPS module to obtain the location at any time, equipped with an ultrasonic or infrared module to detect obstacles, and equipped with a wireless communication module for communication;

[0009] S3. Design a transmission power control method and obstacle handling mechanism, place the mobile anchor node at the starting point of the monitoring area, make it traverse the entire monitoring area at a certain speed along the designed path, and send a message to the unknown node at the beacon point of the path. The message includes the message number, the current position of the anchor node, and the signal strength;

[0010] S4. The unknown node receives the message sent by the mobile anchor node at any time, distinguishes the message by judging the received information number, and determines its own position after receiving three or more non-collinear messages.

[0011] Furthermore, in S1, the monitoring area is divided horizontally into small squares of equal size. If the area is an irregular shape, it will be circumscribed into a square area; , the required division level is determined according to the area size and positioning accuracy requirements. The higher the level, The larger the value, the more beacon points there are in the path, the more location information the anchor node will send, and the higher the positioning accuracy will be. The side length of the divided small square is called the resolution of the trajectory, which is set to , the resolution is used to realize the designed path, and the designed path is the VL trajectory;

[0012] The unknown node is an embedded device based on stm32, equipped with a wireless communication module for communication and ranging. The distance between the unknown node and the anchor node is obtained through the signal strength value in the anchor node message. The three-sided positioning algorithm is implanted in the unknown node to calculate its own position based on the received information.

[0013] Furthermore, the mobile anchor node The movement process under the trajectory is as follows:

[0014] (1) The starting position is the small square in the lower left corner of the monitoring area. The anchor node is moved from the starting position along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex above two adjacent small squares in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the left and connect the center of each side of the small square in turn; After the axis moves to the left, the anchor node moves along the center of the upper side of the small square on the left. Axis upward movement ; then along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex below the two adjacent small squares in turn. After the axis moves rightward to the center of the rightmost small square, go to process (3);

[0015] (2) Move the anchor node along Move along the left axis in a V-shaped trajectory, connecting the center of each small square and the common vertex above the common vertices of two adjacent small squares in sequence; After the axis moves to the center of the leftmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the right and connect the centers of the upper sides of each small square in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement ; then along The axis moves to the left in a V-shaped trajectory, connecting the center of each small square and the common vertex below the common vertex of two adjacent small squares in sequence; After the axis moves left to the center of the leftmost small square, go to process (3);

[0016] (3) Determine whether the mobile anchor node has traversed the entire monitoring area. If it has traversed the entire area, the movement process ends; if it has not traversed the entire area, determine whether the mobile anchor node is in the middle of the small square on the far left of the network or in the middle of the small square on the far right of the network; if it is in the center of the small square on the far left of the network, the mobile anchor node moves along Axis upward movement Go to process (1). If the node is at the center of the small square on the far right of the network, move the anchor node along Axis upward movement And go to process (2).

[0017] Furthermore, in S3, the transmission power control method of the mobile anchor node is as follows:

[0018] There are four different transmission states for mobile anchor nodes. Each state corresponds to a transmission power. The mobile anchor node uses the following formula to determine the transmission power according to the required transmission distance: , thereby controlling the transmission power of the mobile anchor node;

[0019] (1);

[0020] in, is the signal-to-noise ratio, is the reference distance The power loss at is the path loss exponent, is the standard deviation of a Gaussian-distributed random variable, is the noise floor, which depends on the radio and the environment, is the transmission distance, which depends on the transmission state;

[0021] Different transmission powers correspond to different transmission distances and energy consumption. The transmission distance only needs to be sufficient to enable all unknown nodes to receive the location information of at least three anchor nodes.

[0022] Furthermore, the first transmission state is specifically: the first beacon point is located at the center of the two small squares on the leftmost side and the two small squares on the rightmost side under the V-shaped track; assuming that the first beacon point located on the outside The small square is , the first beacon point located inside The small square is ,set up yes Medium distance The farthest sensor, if Can receive mobile anchor node The beacon message sent at All sensors in adjacent small squares can receive the mobile anchor node's ; therefore, the beacon message at and All sensors in adjacent small squares can also receive the mobile anchor node's Beacon message sent at

[0023] set up and The distance between , For anchor nodes The communication radius at , then:

[0024] (2);

[0025] (3);

[0026] Therefore, when the communication range of the anchor node at the first beacon point When the first beacon point is located in the small square where the sensor and the first beacon point in the small square adjacent to the small square can receive the beacon message sent by the anchor node, so the transmission power of the first transmission state should ensure that the transmission distance of the anchor node is not less than .

[0027] Furthermore, the second transmission state is specifically: the second beacon point is located under the V-shaped track, except for the center of the small square containing the first beacon point, and one of the second beacon points is set to The small square is , in the small square In It is the distance The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0028] set up and The distance between , For anchor nodes The communication radius at , then:

[0029] (4);

[0030] (5);

[0031] When the communication range of the anchor node at the second beacon point When the second beacon point is located, all sensors in the small square where the second beacon point is located can receive the beacon message sent by the anchor node at these beacon points, so the transmission power of the second transmission state should ensure that the transmission distance of the anchor node is not less than .

[0032] Furthermore, the third transmission state is specifically: the third beacon point is located under the V-shaped track, at the common vertex above and below two adjacent small squares, and one of the third beacon points is set The four adjacent small squares are ,and The distance between these four small squares The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0033] set up and The distance between , For anchor nodes The communication radius at , then:

[0034] (6);

[0035] (7);

[0036] When the anchor node is within the communication range of the third beacon point When , all sensors in the four small squares adjacent to the third beacon point can receive the beacon message sent by the anchor node, so the transmission power of the third transmission state should ensure that the transmission distance of the anchor node is not less than .

[0037] Furthermore, the fourth transmission state is specifically: the fourth beacon point is located under the straight track in the VL track, at the center of the common side of two small squares adjacent to each other. is one of the fourth beacons Two adjacent small squares Middle distance The farthest sensor, if Can receive anchor node The beacon message sent at All sensors in the Beacon message sent at

[0038] set up and The distance between , For anchor nodes The communication radius at , then:

[0039] (8);

[0040] (9);

[0041] When the anchor node is within the communication range of the fourth beacon point When , all sensors in the two small squares adjacent to the fourth beacon point can receive the beacon message sent by the anchor node, so the transmission power of the fourth transmission state should ensure that the transmission distance of the anchor node is not less than .

[0042] Furthermore, in S3, the obstacle handling mechanism is as follows: when no obstacle is encountered, the anchor node travels along the designed normal path and transmits a beacon message at the beacon point with a corresponding transmission power; when encountering an obstacle, the anchor node enters the obstacle bypass mode, and sends beacon messages at the location where the obstacle is encountered, the location where the obstacle is left, and the turning point during the bypass, and the same transmission power as the second transmission state is maintained in the bypass mode; when traveling along a V-shaped trajectory, the anchor node decides whether to bypass the obstacle from the left or right based on whether the anchor node is going to turn left or right at the last beacon point before encountering the obstacle; when traveling along a straight trajectory, the anchor node decides whether to bypass the obstacle from the left or right based on whether it turns left or right to enter the straight trajectory; after bypassing the obstacle, the anchor node continues to travel along the normal path; when the path is realized, the obstacle is monitored through an infrared or ultrasonic module and the obstacle handling mode is entered.

[0043] Beneficial technical effects brought by the present invention:

[0044] The present invention reduces the path length and the number of beacon points of the mobile anchor node, reduces energy consumption and shortens the positioning time; reduces the number of collinear beacon points and ensures the positioning success rate; controls the transmission power of the mobile anchor node and reduces the number of transmissions of unnecessary beacon points, further reduces energy consumption and improves positioning accuracy; and the obstacle handling mechanism reduces the impact of obstacles on positioning and ensures the positioning of all unknown nodes to the greatest extent possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of the sensor node positioning method proposed in the present invention.

[0046] Figure 2 Schematic diagram of the moving path of the mobile anchor node when n=3.

[0047] Figure 3 Schematic diagram of obstacle handling for mobile anchor nodes. DETAILED DESCRIPTION

[0048] The specific implementation of the present invention is further described below in conjunction with specific embodiments:

[0049] A sensor node localization method based on path planning and transmission power control, such as Figure 1 As shown, the following steps are included:

[0050] S1. Determine the monitoring area, determine the division level and divide the area according to the area size and positioning accuracy requirements, and randomly place the unknown nodes used for monitoring in the monitoring area or manually place them at the locations that need to be monitored;

[0051] S2, using a mobile car or robot as a mobile anchor node, equipped with a GPS module to obtain the location at any time, equipped with an ultrasonic or infrared module to detect obstacles, and equipped with a wireless communication module for communication;

[0052] S3. Design a transmission power control method and obstacle handling mechanism, place the mobile anchor node at the starting point of the monitoring area, make it traverse the entire monitoring area at a certain speed along the designed path, and send a message to the unknown node at the beacon point of the path. The message includes the message number, the current position of the anchor node, and the signal strength;

[0053] S4. The unknown node receives the message sent by the mobile anchor node at any time, distinguishes the message by judging the received information number, and determines its own position after receiving three or more non-collinear messages.

[0054] In step S1, the monitoring area is divided into small squares of equal size. If the area is an irregular shape, it will be circumscribed into a square area; , the required division level is determined according to the area size and positioning accuracy requirements. The higher the level, The larger the value, the more beacon points there are in the path, the more location information the anchor node will send, and the higher the positioning accuracy will be. The side length of the divided small square is called the resolution of the trajectory, which is set to , the resolution is used to realize the designed path, and the designed path is the VL trajectory;

[0055] The unknown node is an embedded device based on stm32, equipped with a wireless communication module for communication and ranging. The distance between the unknown node and the anchor node is obtained through the signal strength value in the anchor node message. The unknown node is implanted with a three-sided positioning algorithm or an improved dung beetle optimization algorithm to calculate its own position based on the received information.

[0056] The improved dung beetle optimization algorithm is as follows:

[0057] (1) The Logistic-Tent chaotic mapping is used to generate a more random initial position for the population than the original algorithm. The formula principle is as follows:

[0058] (1);

[0059] Use Logistic-Tent mapping to initialize the initial position of the population and enhance the search capability of the dung beetle optimization algorithm;

[0060] (2) The foraging behavior of dung beetles in the dung beetle optimization algorithm is disturbed by adaptive t distribution:

[0061] The distribution is expressed as , which has a degree of freedom parameter, when hour, The distribution converges to the standard normal distribution when hour, The distribution is basically equivalent to the Cauchy distribution; the Cauchy mutation gives the algorithm a strong global search capability. The Gaussian mutation gives the algorithm a strong local development capability, ensuring the convergence speed of the algorithm in the later stage. The number of iterations used As The degrees of freedom parameter of the distribution is then used The distribution perturbs the foraging behavior of the dung beetle during the foraging stage; this method enables the dung beetle optimization algorithm to have better global development capabilities in the early stage of its iteration, better local exploration capabilities in the later stage of its iteration, and improves its convergence speed. The degree of freedom parameter is given by the following formula:

[0062] (2);

[0063] in, is the current number of iterations, T is the maximum number of iterations; the updated position of the foraging behavior after disturbance is as follows:

[0064] (3);

[0065] in is the updated position, is the current global optimal position. Distributed perturbation enhances the algorithm's ability to escape from local optimality and ensures the algorithm's convergence speed.

[0066] When the improved dung beetle optimization algorithm is used to calculate the coordinates of unknown nodes, the position of each particle in the algorithm population corresponds to the coordinates of the unknown node, the particle dimension is 2, and the two components of the position vector correspond to the coordinates of the unknown node. Coordinates and Coordinates. Each iteration of the algorithm will get a more accurate position. When calculating the coordinates of unknown nodes, the following fitness function is used to calculate the unknown node position:

[0067] (4);

[0068] in, is the number of anchor node information received, is the estimated position of the unknown node, is the coordinate of the anchor node, is the distance between the unknown node and the anchor node.

[0069] In order to verify the effectiveness of the present invention, some data are presented, and the data are obtained through simulation:

[0070] Table 1 Comparison of positioning accuracy between the three-sided positioning algorithm and the improved dung beetle optimization algorithm;

[0071] ;

[0072] It can be seen from Table 1 that when the division level is 3, the three-sided positioning algorithm provides a higher positioning accuracy with an error of less than 1 meter. Compared with the three-sided positioning algorithm, the improved dung beetle optimization algorithm provides a higher positioning accuracy. If the division level is increased, the positioning accuracy can be even higher.

[0073] The specific method for determining the path is as follows:

[0074] When the level When the mobile anchor node is The movement process under the trajectory is as follows:

[0075] (1) The starting position is the small square in the lower left corner of the monitoring area. The anchor node moves from the starting position along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex above two adjacent small squares in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the left and connect the center of each side of the small square in turn; After the axis moves to the left, the anchor node moves along the center of the upper side of the small square on the left. Axis upward movement ; then along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex below the two adjacent small squares in turn. After the axis moves rightward to the center of the rightmost small square, go to process (3);

[0076] (2) Move the anchor node along Move along the left axis in a V-shaped trajectory, connecting the center of each small square and the common vertex above the common vertices of two adjacent small squares in sequence; After the axis moves to the center of the leftmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the right and connect the centers of the upper sides of each small square in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement ; then along The axis moves to the left in a V-shaped trajectory, connecting the center of each small square and the common vertex below the common vertex of two adjacent small squares in sequence; After the axis moves left to the center of the leftmost small square, go to process (3);

[0077] (3) Determine whether the mobile anchor node has traversed the entire monitoring area. If it has traversed the entire area, the movement process ends; if it has not traversed the entire area, determine whether the mobile anchor node is in the middle of the small square on the far left of the network or in the middle of the small square on the far right of the network; if it is in the center of the small square on the far left of the network, the mobile anchor node moves along Axis upward movement Go to process (1). If the node is at the center of the small square on the far right of the network, move the anchor node along Axis upward movement And go to process (2).

[0078] In S3, the transmission power control method of the mobile anchor node is as follows:

[0079] There are four different transmission states for mobile anchor nodes. Each state corresponds to a transmission power. The mobile anchor node uses the following formula to determine the transmission power according to the required transmission distance: , thereby controlling the transmission power of the mobile anchor node;

[0080] (5);

[0081] in, is the signal-to-noise ratio, is the reference distance The power loss at is the path loss exponent, is the standard deviation of a Gaussian-distributed random variable, is the noise floor, which depends on the radio and the environment, is the transmission distance, which depends on the transmission state;

[0082] Different transmission powers correspond to different transmission distances and energy consumption. The transmission distance only needs to be sufficient to enable all unknown nodes to receive the location information of at least three anchor nodes, which can save energy consumption and improve positioning accuracy.

[0083] The first transmission state is specifically: the first beacon point is located at the center of the two small squares on the left and the two small squares on the right under the V-shaped track; let the first beacon point located on the outside The small square is , the first beacon point located inside The small square is ,set up yes Medium distance The farthest sensor, if Can receive mobile anchor node The beacon message sent at All sensors in adjacent small squares can receive the mobile anchor node's ; therefore, the beacon message at and All sensors in adjacent small squares can also receive the mobile anchor node's Beacon message sent at

[0084] set up and The distance between , For anchor nodes The communication radius at , then:

[0085] (6);

[0086] (7);

[0087] Therefore, when the communication range of the anchor node at the first beacon point is When the first beacon point is located in the small square where the sensor and the first beacon point in the small square adjacent to the small square can receive the beacon message sent by the anchor node, so the transmission power of the first transmission state should ensure the transmission distance of the anchor node. .

[0088] The second transmission state is specifically: the second beacon point is located under the V-shaped track, except for the center of the small square containing the first beacon point, and one of the second beacon points is set The small square is , in the small square In It is the distance The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0089] set up and The distance between , For anchor nodes The communication radius at , then:

[0090] (8);

[0091] (9);

[0092] When the communication range of the anchor node at the second beacon point When the second beacon point is located, all sensors in the small square where the second beacon point is located can receive the beacon message sent by the anchor node at these beacon points, so the transmission power of the second transmission state should ensure the transmission distance of the anchor node. .

[0093] The third transmission state is specifically: the third beacon point is located under the V-shaped track, at the common vertex above and below two adjacent small squares, and one of the third beacon points is set The four adjacent small squares are ,and The distance between these four small squares The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0094] set up and The distance between , For anchor nodes The communication radius at , then:

[0095] (10);

[0096] (11);

[0097] When the anchor node is within the communication range of the third beacon point When , all sensors in the four small squares adjacent to the third beacon point can receive the beacon message sent by the anchor node, so the transmission power of the third transmission state should ensure the transmission distance of the anchor node. .

[0098] The fourth transmission state is specifically: the fourth beacon point is located under the straight line track in the VL track, at the center of the common side of two small squares adjacent to each other. is one of the fourth beacons Two adjacent small squares Middle distance The farthest sensor, if Can receive anchor node The beacon message sent at All sensors in the Beacon message sent at

[0099] set up and The distance between , For anchor nodes The communication radius at , then:

[0100] (12);

[0101] (13);

[0102] When the anchor node is within the communication range of the fourth beacon point When the fourth beacon point is connected to the two small squares, all sensors in the two small squares adjacent to the fourth beacon point can receive the beacon message sent by the anchor node, so the transmission power of the fourth transmission state should ensure the transmission distance of the anchor node. .

[0103] The obstacle handling mechanism is as follows: when no obstacle is encountered, the anchor node moves along the designed normal path and transmits a beacon message at the beacon point with the corresponding transmission power; when encountering an obstacle, it enters the obstacle bypass mode, and sends beacon messages at the location where the obstacle is encountered, the location where the obstacle is left, and the turning point during the bypass. In the bypass mode, the same transmission power as the second transmission state is maintained; when moving along a curve (V-shaped trajectory), the anchor node decides whether to bypass the obstacle from the left or right based on whether the anchor node will turn left or right at the last beacon point before encountering the obstacle; when moving along a straight trajectory, the anchor node decides whether to bypass the obstacle from the left or right based on whether it turns left or right to enter the straight trajectory; after bypassing the obstacle, the anchor node continues to move along the normal path; when implementing the path with code, obstacles are monitored through infrared or ultrasonic modules and the obstacle handling mode is entered.

[0104] Example 1, for fire monitoring in campus greening areas, the monitored greening area has a side length of 100m, and n=3, 4^3=64, divided into 64 small squares. Since 64=8×8, d=100 / 8=12.5 is obtained;

[0105] Place the mobile anchor node at the starting point of the monitored green area, and make it traverse the entire monitored area along the designed path at a certain speed. The trajectory is shown in the attached figure. Figure 2 As shown, the transmission distance of the anchor node is determined as follows:

[0106] (1) First transmission state: as attached Figure 2 As shown in the figure, the first beacon point is a yellow beacon point, which is located in the center of the two small squares on the left and the two small squares on the right under the V-shaped track. Taking the two small squares on the left as an example, the first beacon point on the outside The small square is , the first beacon point located inside The small square is , yes Medium distance The farthest sensor, if Can receive mobile anchor node The beacon message sent at All sensors within can receive the beacon message because and are isomorphic, so All sensors in the area can receive the mobile anchor node's The beacon message sent at All sensors in the area can receive the mobile anchor node's Similarly, All sensors in the area can receive the mobile anchor node's Beacon message sent from .

[0107] but:

[0108] (14);

[0109] The above formula is applicable to all yellow beacon points. When the communication range of the anchor node at these beacon points is When , the sensors in the small square where the beacon point is located and all the sensors in the small squares adjacent to the small square where the beacon point is located can receive the beacon message sent by the anchor node.

[0110] (2) Second transmission state: as attached Figure 2 As shown, the second beacon point is a purple beacon point located under the V-shaped track. The second beacon point is the center of the small square except for the first beacon point. For example, The small square is , in the small square In It is the distance The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0111] but:

[0112] (15);

[0113] The above formula is applicable to all purple beacon points. When the communication range of the anchor node at the purple beacon point is At this time, all sensors in the small squares where the purple beacon points are located can receive the beacon messages sent by the anchor nodes at these beacon points.

[0114] (3) The third transmission state: as attached Figure 2 As shown, the third beacon point is a red beacon point, located under the V-shaped track, at the common vertex above and below two adjacent small squares. For example, with The four adjacent small squares are ,and The distance between these four small squares The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at

[0115] but:

[0116] (16);

[0117] The above formula is applicable to all red beacon points. When the communication range of the anchor node at the red beacon point is When , all sensors in the four small squares adjacent to the red beacon point can receive the beacon message sent by the anchor node.

[0118] (4) Fourth transmission state: as attached Figure 2 As shown, the fourth beacon point is a black beacon point located under the straight track in the VL track, at the center of the common side of two small squares adjacent to each other. For example, is with Two adjacent small squares Middle distance The farthest sensor, if Can receive anchor node The beacon message sent at All sensors in the Beacon message sent at

[0119] but:

[0120] (17);

[0121] The above formula is applicable to all black beacon points. When the communication range of the anchor node at the black beacon point is When , all sensors in the two small squares adjacent to the black beacon point can receive the beacon message sent by the anchor node.

[0122] The mobile anchor node broadcasts its current position to unknown nodes at the beacon point on the path. When the mobile anchor node encounters an obstacle (such as a stone or a small mound), it enters the obstacle handling mode to bypass the obstacle and broadcasts its current position at the corner of the bypass. After the bypass, it returns to the normal position. Figure 3 As shown, Figure 3 Several boxes in the figure are obstacles. Take the first small square in the lower left corner as an example. The anchor node is located at the beacon point in the center of the small square. When moving left along the V-shaped trajectory, it encounters an obstacle, so it turns left into a straight line to bypass the obstacle. After bypassing the obstacle, it moves along the normal path.

[0123] The unknown node receives the message sent by the mobile anchor node at any time and determines its own position after receiving three or more position information.

[0124] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A sensor node positioning method based on path planning and transmission power control, characterized in that: The following steps are involved: S1. Determine the monitoring area, determine the division level and divide the area according to the area size and positioning accuracy requirements, and randomly place the unknown nodes used for monitoring in the monitoring area or manually place them at the locations that need to be monitored; S2, using a mobile car or robot as a mobile anchor node, equipped with a GPS module to obtain the location at any time, equipped with an ultrasonic or infrared module to detect obstacles, and equipped with a wireless communication module for communication; S3. Design a transmission power control method and obstacle handling mechanism, place the mobile anchor node at the starting point of the monitoring area, make the mobile anchor node traverse the entire monitoring area according to the designed path, and send a message to the unknown node at the beacon point of the path. The message includes the message number, the current position of the anchor node and the signal strength; S4, the unknown node receives the message sent by the mobile anchor node at any time, distinguishes the message by judging the received message number, and determines its own position after receiving three or more non-collinear messages; In S1, the monitoring area is divided into small squares of equal size. If the area is an irregular shape, it will be circumscribed into a square area; , the required division level is determined according to the area size and positioning accuracy requirements. The higher the level, The larger the value, the more beacon points there are in the path, the more location information the anchor node will send, and the higher the positioning accuracy will be. The side length of the divided small square is called the resolution of the trajectory, which is set to ; In S3, the transmission power control method of the mobile anchor node is as follows: There are four different transmission states for mobile anchor nodes. Each state corresponds to a transmission power. The mobile anchor node uses the following formula to determine the transmission power according to the required transmission distance: , thereby controlling the transmission power of the mobile anchor node; (1)； in, is the signal-to-noise ratio, is the reference distance The power loss at is the path loss exponent, is the standard deviation of a Gaussian-distributed random variable, is the noise floor, which depends on the radio and the environment, is the transmission distance, which depends on the transmission state; Different transmission powers correspond to different transmission distances and different energy consumption. The transmission distance only needs to be sufficient to allow all unknown nodes to receive the location information of at least three anchor nodes. The first transmission state is specifically: the first beacon point is located at the center of the two small squares on the left and the two small squares on the right under the V-shaped track. The transmission power of the first transmission state should ensure that the transmission distance of the anchor node is not less than ; The second transmission state is specifically: the second beacon point is located under the V-shaped track, in the center of the small square other than the first beacon point, and the transmission power of the second transmission state should ensure that the transmission distance of the anchor node is not less than ; The third transmission state is specifically: the third beacon point is located under the V-shaped track, at the common vertex above and below two adjacent small squares. The transmission power of the third transmission state should ensure that the transmission distance of the anchor node is not less than ; The fourth transmission state is specifically: the fourth beacon point is located under the straight line track in the VL track, at the center of the common side of two small squares adjacent to each other. The transmission power of the fourth transmission state should ensure that the transmission distance of the anchor node is not less than .

2. A sensor node positioning method based on path planning and transmission power control according to claim 1, characterized in that: In S1, the monitoring area is divided into small squares of equal size. If the area is an irregular shape, it will be circumscribed into a square area; , the required division level is determined according to the area size and positioning accuracy requirements. The higher the level, The larger the value, the more beacon points there are in the path, the more location information the anchor node will send, and the higher the positioning accuracy will be. The side length of the divided small square is called the resolution of the trajectory, which is set to , the resolution is used to realize the designed path, and the designed path is the VL trajectory; The unknown node is an embedded device based on stm32, equipped with a wireless communication module for communication and ranging. The distance between the unknown node and the anchor node is obtained through the signal strength value in the anchor node message. The three-sided positioning algorithm is implanted in the unknown node to calculate its own position based on the received information.

3. A sensor node positioning method based on path planning and transmission power control according to claim 2, characterized in that: Mobile anchor node The movement process under the trajectory is as follows: (1) The starting position is the small square in the lower left corner of the monitoring area. The anchor node is moved from the starting position along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex above two adjacent small squares in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the left and connect the center of each side of the small square in turn; After the axis moves to the left, the anchor node moves along the center of the upper side of the small square on the left. Axis upward movement ; then along The axis moves to the right in a V-shaped trajectory, connecting the center of each small square and the common vertex below the two adjacent small squares in turn. After the axis moves rightward to the center of the rightmost small square, go to process (3); (2) Move the anchor node along Move along the left axis in a V-shaped trajectory, connecting the center of each small square and the common vertex above the common vertices of two adjacent small squares in sequence; After the axis moves to the center of the leftmost small square, the anchor node moves along Axis upward movement , then along Move the axis to the right and connect the centers of the upper sides of each small square in turn; After the axis moves right to the center of the rightmost small square, the anchor node moves along Axis upward movement ; then along The axis moves to the left in a V-shaped trajectory, connecting the center of each small square and the common vertex below the common vertex of two adjacent small squares in sequence; After the axis moves left to the center of the leftmost small square, go to process (3); (3) Determine whether the mobile anchor node has traversed the entire monitoring area. If it has traversed the entire area, the movement process ends; if it has not traversed the entire area, determine whether the mobile anchor node is in the middle of the small square on the far left of the network or in the middle of the small square on the far right of the network; if it is in the center of the small square on the far left of the network, the mobile anchor node moves along Axis upward movement Go to process (1). If the node is at the center of the small square on the far right of the network, move the anchor node along Axis upward movement And go to process (2).

4. A sensor node positioning method based on path planning and transmission power control according to claim 3, characterized in that: The first transmission state is specifically: the first beacon point is located at the center of the two small squares on the left and the two small squares on the right under the V-shaped track; let the first beacon point located on the outside The small square where , the first beacon point located inside The small square where ,set up yes Medium distance The farthest sensor, if Can receive mobile anchor nodes The beacon message sent at All sensors in adjacent small squares can receive the mobile anchor node's ; therefore, the beacon message at and All sensors in adjacent small squares can also receive the mobile anchor node's Beacon message sent at set up and The distance between , For anchor nodes The communication radius at , then: (2)； (3)； Therefore, when the communication range of the anchor node at the first beacon point When the first beacon point is located in the small square where the sensor and the first beacon point in the small square adjacent to the small square can receive the beacon message sent by the anchor node, so the transmission power of the first transmission state should ensure that the transmission distance of the anchor node is not less than .

5. A sensor node positioning method based on path planning and transmission power control according to claim 4, characterized in that: The second transmission state is specifically: the second beacon point is located under the V-shaped track, except for the center of the small square containing the first beacon point, and one of the second beacon points is set The small square where , in the small square In It is the distance The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at set up and The distance between , For anchor nodes The communication radius at , then: (4)； (5)； When the communication range of the anchor node at the second beacon point When the second beacon point is located, all sensors in the small square where the second beacon point is located can receive the beacon message sent by the anchor node at these beacon points, so the transmission power of the second transmission state should ensure that the transmission distance of the anchor node is not less than .

6. A sensor node positioning method based on path planning and transmission power control according to claim 5, characterized in that: The third transmission state is specifically: the third beacon point is located under the V-shaped track, at the common vertex above and below two adjacent small squares, and one of the third beacon points is set The four adjacent small squares are ,and The distance between these four small squares The farthest sensor; if Can receive anchor node The beacon message sent from the small square All sensors in the Beacon message sent at set up and The distance between , For anchor nodes The communication radius at , then: (6)； (7)； When the anchor node is within the communication range of the third beacon point When , all sensors in the four small squares adjacent to the third beacon point can receive the beacon message sent by the anchor node, so the transmission power of the third transmission state should ensure that the transmission distance of the anchor node is not less than .

7. A sensor node positioning method based on path planning and transmission power control according to claim 6, characterized in that: The fourth transmission state is specifically: the fourth beacon point is located under the straight line track in the VL track, at the center of the common side of two small squares adjacent to each other. is one of the fourth beacons Two adjacent small squares Middle distance The farthest sensor, if Can receive anchor node The beacon message sent at All sensors in the Beacon message sent at set up and The distance between , For anchor nodes The communication radius at , then: (8)； (9)； When the anchor node is within the communication range of the fourth beacon point When , all sensors in the two small squares adjacent to the fourth beacon point can receive the beacon message sent by the anchor node, so the transmission power of the fourth transmission state should ensure that the transmission distance of the anchor node is not less than .

8. A sensor node positioning method based on path planning and transmission power control according to claim 7, characterized in that: In S3, the obstacle handling mechanism is as follows: when no obstacle is encountered, the anchor node moves along the designed normal path and transmits a beacon message at the beacon point with a corresponding transmission power; when encountering an obstacle, the obstacle bypass mode is entered, and beacon messages are sent at the location where the obstacle is encountered, the location where the obstacle is left, and the turning point during the bypass, and the same transmission power as the second transmission state is maintained in the bypass mode; when moving along a V-shaped trajectory, the anchor node is determined to bypass the obstacle from the left or right according to whether the anchor node is going to turn left or right at the last beacon point before encountering the obstacle; when moving along a straight trajectory, the anchor node is determined to bypass the obstacle from the left or right according to whether it turns left or right to enter the straight trajectory; after bypassing the obstacle, the anchor node continues to move along the normal path; when the path is realized, the obstacle is monitored through an infrared or ultrasonic module and the obstacle handling mode is entered.

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