CN108445448A - A kind of Zigbee difference Precision Orientation Algorithms based on subsurface environment - Google Patents

Abstract

A ZigBee differential precise positioning method based on the underground environment, which belongs to the field of equipment remote monitoring and management. Its outstanding feature is that the system uses differential precise positioning algorithm to locate the mobile node of underground miners. Positioning, and introducing differential variables in the process of trilateral positioning for correction, thereby eliminating the error of the Zigbee mobile node equipment, achieving three-dimensional management of underground miners and ensuring safety.

Description

A Zigbee differential precise positioning algorithm based on downhole environment

technical field

The present invention belongs to the field of equipment remote monitoring and management. Its outstanding feature is that the system adopts a differential precise positioning algorithm to locate underground miners' mobile nodes. The differential variable is corrected to eliminate the error of the equipment of the Zigbee mobile node, so as to achieve the three-dimensional management of underground miners and ensure the safety.

Background technique

The frequent occurrence of mine accidents exposes the drawbacks of the current mine monitoring system: poor flexibility of wired communication, inconvenient wiring, high cost, insufficient coverage, incomplete information, and inability to provide timely information on the underground environment and the location of staff. Accidents occur, and it is difficult to carry out rescue operations. The traditional underground positioning system often cannot provide accurate underground location information. Therefore, once a dangerous situation occurs underground, it is impossible to effectively guide the underground miners and fail to timely feedback the underground situation to the mine management personnel, resulting in slow accident discovery and handling. Therefore, the low-maintenance cost we researched, the Zigbee differential precise positioning algorithm based on the downhole environment has great significance.

Contents of the invention

The reference node is installed and arranged underground, and the Zigbee mobile node integrated on the miner's helmet can perform real-time differential and precise positioning, so that the mine management personnel can grasp the location information of all miners.

A ZigBee differential precise positioning method based on downhole environment at least comprises the following steps:

Step 1: Set reference nodes downhole;

Step 2: Select the distance curve corresponding to the scene;

Step 3: Determine whether the received signals are greater than or equal to 3;

If it is equal to 3, use the trilateral positioning algorithm to perform differential calculation and correction to obtain the coordinates of the mobile node;

If there are more than 3, select the strongest 4 reference nodes, a total of 4 combinations, use the trilateration positioning algorithm to obtain 4 coordinates, perform differential calculation and correction, take the center of gravity of the 4 coordinates, and obtain the coordinates of the mobile node;

If it is less than 3, judge again.

The trilateration algorithm is

Using RSSI to measure the distance of signal strength, the following model is selected:

RSSI=-(10nlog _10d +A) (1)

Among them, the radio frequency parameter A is defined as the received signal strength at the transmitting node 1m expressed in dBm; n is the signal transmission constant, which is related to the signal transmission environment; d is the distance from the transmitting node.

According to the trilateration positioning algorithm, the distance is converted into position coordinates to complete the differential positioning; the formula is as follows:

If equation (3) has a solution, judge which point is the closest to the point, and select this point as point D;

If equation (4) has a solution, judge which point is the closest to the point, and select this point as point F;

If equation (5) has a solution, then judge which point-to-point distance is the shortest, and select this point as point E;

The center of gravity of the triangle DEF is the position of the mobile node we need to locate;

If the equation (3) has no solution, then connect the centers of the two circles, and the center of the two points intersecting the circle is point D;

For the case where equations (4) and (5) have no solutions, the coordinates of points E and F can be obtained in the same way.

The RSSI value has a jump random error in practical applications, so the above model needs to be optimized, and a variable σ is introduced as the RSSI jump error, then (1) formula becomes

RSSI＝-(10nlog _10d +A)+σ (2)

Then σ can be eliminated by two mobile nodes at the same position installed on the miner's hat, that is, a differential positioning operation is performed, which can effectively solve the problem of RSSI jump error and provide accurate ranging information.

The beneficial effect of the present invention is that through Zigbee network communication and differential precise positioning technology, the environment under the mine and the position of miners are effectively monitored, and when an emergency occurs, the speed and efficiency of disposal are improved and losses are reduced.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

The technical scheme that the present invention solves its technical problem adopts is

Firstly, install and arrange reference nodes downhole, and measure the distance curve on the spot according to the corresponding downhole environment.

The Zigbee mobile node integrated on the miner's helmet can send a positioning request signal to the surrounding Zigbee reference nodes in real time, and calculate its position according to the RSSI value returned by the reference node. The uploaded data is uploaded to the host computer via other reference nodes and gateways for display. When a mining disaster occurs, the node where the signal of the Zigbee mobile node disappears can basically be identified as a landslide here, shielding the signal. At this time, the search and rescue work can be carried out through the location of the miners at the last moment, which greatly improves the pertinence and efficiency of search and rescue.

The Zigbee positioning algorithm uses a self-developed differential precise positioning algorithm, and ranging is the basic requirement for positioning. The position of the mobile node can only be determined by obtaining the distances of three or more reference nodes. The range of signal strength can be RSSI. Using RSSI ranging, the following models can be selected:

RSSI=-(10nlog _10d +A) (1)

Among them, the radio frequency parameter A is defined as the received signal strength at the transmitting node 1m expressed in dBm; n is the signal transmission constant, which is related to the signal transmission environment; d is the distance from the transmitting node.

However, in the actual application process, the RSSI value has a jump random error, so the above model needs to be optimized. We introduce a variable σ as the RSSI jump error, and the formula (1) becomes

RSSI＝-(10nlog _10d +A)+σ (2)

Then σ can be eliminated by two mobile nodes at the same position installed on the miner's cap, that is, a differential positioning operation is performed, which can effectively solve the problem of RSSI jump error and provide accurate ranging information. Then, according to the trilateration positioning algorithm, the distance is converted into position coordinates to complete the differential positioning. Carry out differential precise positioning according to accompanying drawing 3, the formula is as follows:

If equation (3) has a solution, judge which point is the closest to the point, and select that point as point D; if equation (4) has a solution, judge which point is the closest to the point, and select that point as point F; If the equation (5) has a solution, then judge which point is the closest to the point, select this point as point E, the center of gravity of triangle DEF is the position of the mobile node we need to locate. If the equation (3) has no solution, then the center connecting the two circle centers and intersecting the two points with the circle is point D; when there is no solution to equation (4) and (5), the same method can be used to obtain point E, The coordinates of F. Therefore, no matter whether the circles intersect or not, we can obtain 3 points D, E, F, and obtain the coordinates of the mobile node by calculating the center of gravity.

Environmental information is obtained through the gas concentration sensor, carbon monoxide concentration sensor, air pressure sensor and temperature and humidity sensor installed on the Zigbee reference node, and is transmitted to the Zigbee gateway node through the Zigbee relay node installed on the roadway wall, and then the gateway node Upload to the host computer management system for real-time monitoring and display. When a certain environmental data exceeds the pre-set warning threshold set by the management personnel, the monitoring software will issue an alarm to warn the management personnel to confirm the warning information in time to eliminate potential safety hazards.

The routing node power supply integrates the hybrid power supply mode of mains power supply and rechargeable battery power supply. Under normal circumstances, the mains power is transformed into 9V AC through a transformer, and a relatively stable DC voltage is obtained through a half-wave rectification and filtering circuit, and then input into a voltage stabilizing chip to obtain a stable 3.3V DC power supply. The battery is a common 7.2V battery on the market, and the rectified and filtered DC voltage needs to pass through the power selection circuit, that is, the diode anti-reverse structure to select the power supply. When the mains power is cut off, it will automatically switch to battery power supply, which greatly reduces battery consumption and maintenance costs.

When a mining disaster occurs, the mine manager can set the mobile node equipped on the safety helmet of the underground staff through the Zigbee network to send an alarm signal, thereby instructing the miners to escape from a safe path. Moreover, in case of a landslide accident, the reference node will be interrupted, so that the mine management personnel can judge the approximate location of the accident from the interrupted node position, so as to facilitate the follow-up rescue work.

The beneficial effect of the present invention is that through the Zigbee network communication and differential precise positioning technology, the environment under the mine and the position of miners are effectively monitored, and when an emergency occurs, the speed and efficiency of disposal are improved and losses are reduced.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is an overall block diagram of the system of the present invention. Terminal is a blind node, that is, a Zigbee terminal integrated on the miner's helmet. Router is the reference node, that is, the Zigbee module installed on the roadway wall. The Coordinator is the gateway, that is, the Zigbee root node responsible for managing the Zigbee network and communicating with the host computer. Computer is the host computer used for system management.

In the embodiment shown in Figure 1, the Zigbee mobile node sends out the location information, and the reference node in the underground roadway locates and transmits the location information to the host computer to realize real-time positioning. In case of danger, the host computer will automatically query the location of the signal interruption and start the search and rescue operation.

Fig. 2 is a flow chart of the positioning algorithm of the present invention. First set the reference node coordinates and select the environment curve. Judging whether the received signals are more than 3, if more than 3, select the 4 signals with the strongest signals for differential positioning. If it is equal to 3, perform differential positioning directly. If the number is less than 3, repeat the signal acquisition until the number of signals greater than or equal to 3 is satisfied.

Figure 3 is a schematic diagram of the Zigbee differential precise positioning algorithm. For 4 positioning situations, the differential precise positioning is performed through the RSSI value of each reference node. In actual operation, it is first necessary to judge how many of the 3 circles intersect, and the method used It can be to combine the equations of the three circles in pairs to judge whether there is a solution. Then according to the situation of the solution, determine the position of the mobile node.

Figure 4 is the appearance diagram of the Zigbee mobile node. 4-1 is the battery box, with two 1.5V batteries installed inside to supply power for blind nodes. 4-2 is the Zigbee communication antenna. 4-3 is the control circuit integrated on the top of the helmet. 4-4 is a low-power OLED display. 4-5 are special searchlights for underground.

Figure 5 is a functional block diagram of Zigbee mobile nodes. 5-1 is the OLED display, 5-2 is the microcontroller of the Zigbee blind node, 5-3 is the battery power supply circuit, 5-4 is the microcontroller of the Zigbee routing node communicating with this node, and 5-5 is the abnormal situation in the well alarm system.

Fig. 6 is a functional block diagram of Zigbee routing node. 6-1 is an alarm circuit, including an alarm bell and an arrow indicator light. 6-2 is a gas concentration sensor, a carbon monoxide concentration sensor, an air pressure sensor and a temperature and humidity sensor. 6-3 is a power management module combining battery and commercial power. 6-4 is the Zigbee reference node microcontroller.

In the embodiment shown in Figure 6, the Zigbee reference node receiving and transmitting module collects the position signal sent by the underground mobile node, and multiple reference nodes determine the specific location of the mobile node through the RSSI ranging model return value and the trilateral differential positioning algorithm. The precise position is transmitted to the ground step by step, and the data is sent to the host computer. When a dangerous situation occurs underground, the host computer will report the location of the last signal interruption in real time, guide the search and rescue personnel to search and rescue, and the alarm will also sound an alarm to warn relevant personnel to leave as soon as possible. At the same time, the mobile node also includes four sensors for gas concentration, carbon monoxide concentration, air pressure, and temperature and humidity to monitor the underground environment in real time to ensure the safety of underground employees.

Claims (3)

1. a ZigBee differential accurate positioning method based on downhole environment, is characterized in that, at least comprises the following steps: Step 1: Set reference nodes downhole; Step 2: Select the distance curve corresponding to the scene; Step 3: Determine whether the received signals are greater than or equal to 3; If it is equal to 3, use the trilateral positioning algorithm to perform differential calculation and correction to obtain the coordinates of the mobile node; If there are more than 3, select the strongest 4 reference nodes, a total of 4 combinations, use the trilateration positioning algorithm to obtain 4 coordinates, perform differential calculation and correction, take the center of gravity of the 4 coordinates, and obtain the coordinates of the mobile node; If it is less than 3, judge again. 2. a kind of ZigBee differential precise positioning method based on downhole environment according to claim 1, is characterized in that: described trilateral positioning algorithm is Using RSSI to measure the distance of signal strength, the following model is selected: RSSI=-(10nlog _10d +A) (1) Among them, the radio frequency parameter A is defined as the received signal strength at the transmitting node 1m expressed in dBm; n is the signal transmission constant, which is related to the signal transmission environment; d is the distance from the transmitting node. According to the trilateration positioning algorithm, the distance is converted into position coordinates to complete the differential positioning; the formula is as follows: If equation (3) has a solution, judge which point is the closest to the point, and select this point as point D; If equation (4) has a solution, judge which point is the closest to the point, and select this point as point F; If equation (5) has a solution, then judge which point-to-point distance is the shortest, and select this point as point E; The center of gravity of the triangle DEF is the position of the mobile node we need to locate; If the equation (3) has no solution, then connect the centers of the two circles, and the center of the two points intersecting the circle is point D; For the case where equations (4) and (5) have no solutions, the coordinates of points E and F can be obtained in the same way. 3. a kind of ZigBee differential precise positioning method based on downhole environment according to claim 2, is characterized in that: described RSSI value has jumping random error in practical application, therefore need to optimize above-mentioned model, introduce a The variable σ is used as the RSSI jump error, then the formula (1) becomes RSSI＝-(10nlog _10d +A)+σ (2) Then σ can be eliminated by two mobile nodes at the same position installed on the miner's cap, that is, a differential positioning operation is performed, which can effectively solve the problem of RSSI jump error and provide accurate ranging information.