CN109946650B - Positioning system and method for wireless synchronous receiving and transmitting separation - Google Patents

Abstract

The invention belongs to the technical field of ultrasonic positioning, and provides a positioning system and method for wireless synchronized transmission and reception separation. This positioning system with separate wireless synchronization transceivers includes: a vehicle body, a transmitting and data processing unit provided on the vehicle body, and multiple beacon units provided within the target positioning range. The transmitting and data processing unit includes: an ultrasonic signal generator , data processing module one, wireless communication module one, directional rotation device, rotary encoder, the beacon unit includes an ultrasonic signal receiver, wireless communication module two, and data processing module two. This kind of positioning system that separates wireless synchronous transceivers and receivers shortens the ultrasonic positioning calibration time, extends the maintenance cycle of the beacon unit, and saves costs.

Description

A positioning system and method for wireless synchronized transmission and reception separation

Technical field

The present invention relates to the technical field of ultrasonic positioning, and in particular to a positioning system and method for wireless synchronized transmission and reception separation.

Background technique

Ultrasonic positioning technology is mainly used indoors, in situations where higher positioning accuracy is required, satellite positioning signals cannot be used, or satellite positioning accuracy cannot meet the requirements. Representative ultrasonic positioning methods and systems include ActiveBat and Cricket. In addition, wireless sensors are also used to develop ultrasonic ranging methods and systems that integrate two-way sending and receiving.

The ActiveBat positioning system performs positioning based on the time of arrival (TOA) positioning method, and uses a maximum likelihood estimation algorithm to improve positioning accuracy. The positioning terminal is equipped with an ActiveBat tag. The controller sends a radio frequency signal as a time synchronization signal. The signal transmitter (Bat tag) receives the time synchronization signal and immediately sends an ultrasonic wave signal. The positioning beacon (AP) on the roof is used to receive the signal sent by the controller. The radio frequency signal and the ultrasonic signal sent by the Bat tag are calculated, and the arrival time difference t is calculated, and the distance information between the Bat tag and the beacon node is measured. The central unit collects individual distance measurements and performs positioning calculations.

The Cricket positioning system performs positioning based on the time difference of arrival (TDOA) positioning algorithm. It consists of a positioning terminal, a beacon node fixed on the ceiling of the house, and a central controller. The beacon node allocates radio frequency channels through carrier monitoring. When the radio frequency signal channel is idle, the beacon node transmits ultrasonic signals and radio frequency signals at the same time; the positioning terminal is used to receive and extract the arrival time difference of the two signals, and then calculate the difference between the positioning terminal and the beacon The distance between nodes, and finally the positioning operation is performed.

Ultrasonic ranging method and system based on two-way transceiver integration of wireless sensors. After synchronizing each node in the system through the wireless network, the sending node sends the ultrasonic signal, the receiving node receives the ultrasonic signal and times, and uses the time of arrival (TOA) method for ranging. and positioning.

The main flaw of the ActiveBat positioning system and Cricket positioning system is that the system layout is complex. In order to prevent obstacles from affecting the ultrasonic signal, all positioning beacons (AP) need to be installed on the ceiling of the room; when the beacon fails or the power is insufficient, Maintenance is more difficult when there is a problem; due to the installation location, these two positioning systems cannot be used outdoors. In addition, the ActiveBat positioning system is not suitable for system expansion, so it is not suitable for large-scale indoor positioning. The Cricket positioning system positioning terminal consumes a lot of energy and has a slow response time.

The shortcomings of the ultrasonic ranging method and system based on the two-way integrated transceiver of wireless sensors are that each node requires more than 8 ultrasonic modules, which is large in size, complex in system structure, and high in cost. Since each node has to perform ultrasonic transmission and reception operations and perform data processing, it consumes a lot of energy, which is not conducive to the long-term maintenance-free use of the positioning system.

Therefore, there is an urgent need for a positioning method with low energy consumption, short response time, wide adaptability, and easy maintenance.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a positioning system and method with low energy consumption, short response time, multiple application scenarios, and easy maintenance.

In order to achieve the above-mentioned object of the invention, the present invention provides a positioning system with separate wireless synchronization transceivers and receivers, which adopts the following technical solutions:

A positioning system with separate wireless synchronous transceivers, including a vehicle body, a transmitting and data processing unit provided on the vehicle body, and a plurality of beacon units provided within the target positioning range. The transmitting and data processing unit includes: ultrasonic signals Generator, data processing module one, wireless communication module one, directional rotation device, rotary encoder, the beacon unit includes an ultrasonic signal receiver, wireless communication module two, and data processing module two,

The rotary encoder records the information of the vehicle body movement and sends the information to the data processing module one,

The data processing module receives the rotary encoder information and controls the operation of the directional rotation device and the ultrasonic signal generator,

The directional rotation device controls the emission direction of the ultrasonic signal generator,

The ultrasonic signal generator generates and transmits ultrasonic signals,

The ultrasonic signal receiver receives ultrasonic signals

The second data processing module controls the operation of the ultrasonic signal receiver and receives the information received by the ultrasonic signal receiver,

Information is transmitted between the data processing module one and the data processing module two through the wireless communication module one and the wireless communication module two.

The data processing module 1 can calculate the incremental position of the moving object based on the received information from the rotary encoder.

It can be seen from the above technical solution that the invention provides a positioning system with separate wireless synchronous transceivers. The transmitting and data processing unit only transmits ultrasonic waves but does not receive ultrasonic signals. The beacon unit only receives ultrasonic signals but does not transmit ultrasonic signals. This shortens the The ultrasonic positioning time also reduces the energy consumption of the beacon unit and extends the beacon usage time; the data processing module determines the positional relationship between the incremental position and the preset beacon unit, and controls the directional rotation device to convert the ultrasonic signal The generator faces the preset beacon unit, which reduces the number of ultrasonic transmitting modules and beacon units. At least one ultrasonic transmitting module and two beacon units are needed to complete positioning calibration, saving costs.

Optionally, the vehicle body adopts a tricycle or a four-wheel vehicle with differential steering of two driving wheels and the remaining wheels are universal wheel structures. The rotary encoder adopts a direct connection method or an indirect connection method such as gears and synchronous toothed belts. Connected to the drive wheel axle.

Optionally, the beacon unit is arranged on the pole. The stakes can be placed directly or inserted into the ground surface, making it easy to install the beacon unit in the target positioning area, avoiding the trouble of array installation on the ceiling, and reducing beacon and deployment costs.

Optionally, the beacon unit is provided with two ultrasonic signal receivers, and adjacent ultrasonic signal receivers are installed at an angle of 15° along the central axis. Expand the signal receiving fan angle and reduce the blind area of ultrasonic signal receiving.

The present invention also provides a positioning method using the above-mentioned wireless synchronization transceiver separation positioning system, specifically adopting the following technical solutions:

A positioning method that separates wireless synchronization and reception, including the following steps:

S1. In the preparation stage, according to the requirements of the usage scenario, install the beacon unit within the positioning area, align the beacon unit signal receiving direction with the movement range of the positioned object, measure and calibrate the position data information (coordinates) input of the beacon unit Transmission and data processing unit;

S2. In the initialization stage, the vehicle body is reset at the origin to obtain the initial position coordinates and initial direction;

S3. Measurement of incremental position, the car body moves freely within the positioning range, the data processing module obtains the rotation angle data through the rotary encoder connected to the motion axis, and the speed ratio relationship between the rotary encoder and the wheel and the connected wheel radius, etc. The data is converted into moving distance data and direction;

S4. Calibration of positioning coordinates:

S4.1 The car body stops at the positioning point. The data processing module 1 calculates and judges based on the incremental position and direction of the car body and the coordinate position data of the beacon unit, and issues a fixed-angle rotation command to the directional rotation device to generate an ultrasonic signal. Aim the beacon unit in the corresponding direction;

S4.2 The transmitting and data processing unit sends a handshake signal to the wireless communication module 2 of the corresponding beacon unit through the wireless communication module 1. After the handshake is successful, the beacon unit is awakened, and the transmitting and data processing unit performs time base synchronization operation with the beacon unit;

S4.3 is controlled by data processing module one and data processing module two. In the synchronized clock pulse sequence, a rising edge or falling edge of the clock signal is taken at the same time. The transmitting and data processing unit triggers the ultrasonic transmitting action, and the beacon unit triggers at the same time. timing;

S4.4 After receiving the ultrasonic signal, the beacon unit stops timing and sends the timing value to the transmitting and data processing unit through the communication module;

After the S4.5 transmitting and data processing unit receives the timing data from the beacon unit, it converts it into distance data between the transmitting and data processing unit and the beacon unit through a formula combined with correction coefficients such as temperature, humidity, and system time loss. ;

S4.6 selects another beacon unit, repeats the S4.1~S4.5 process, and obtains the distance data between the transmitting and data processing unit and the other beacon unit;

S4.7 Data processing module 1 can obtain the positions of two points based on the obtained distance to the two beacon units through the two-point positioning method, and use the current incremental position data to determine the position data of one of the points. That is, the absolute position of the car body is obtained;

S4.8 uses this absolute position to correct the incremental position, that is, to obtain accurate positioning coordinates and eliminate the cumulative error caused by the rotary encoder measurement.

Optionally, in step S1, set the device address and number of the beacon unit so that each beacon unit has an independent address and number, and establish an ordered beacon array for all beacon units, that is, Network the beacon unit. During operation, the beacon unit is in the wireless signal listening state, and other parts are in the sleep state until it is awakened by the handshake signal of the transmitting and data processing unit. During positioning, the transmitting and data processing unit selectively wakes up according to the incremental position and direction. Beacon units that need to receive ultrasonic signals can greatly save the average energy consumption of the beacon unit and extend the use time of the beacon unit with the same battery life.

Optionally, in step S4.3, there is a delay time before data processing module one and data processing module two take the rising edge or falling edge of a clock signal at the same time. Allow preparation time for the operation of the ultrasonic signal generator and ultrasonic signal receiver.

Optionally, in step S4.5, when calculating the distance data between the transmitting and data processing unit and the beacon unit, the TOA (time of arrival) method is used for calculation. It can reduce time errors caused by circuit jitter, delay and other problems, and further improve positioning accuracy.

Optionally, in step S4.5, the correction coefficient is obtained based on the pre-measured external temperature and humidity data and input into the data processing module one, or a temperature and humidity sensor is installed on the vehicle body, and based on the pre-made data table, the correction coefficient is Processing module 1 calculates the correction coefficient. The correction coefficient is used to compensate for ultrasonic measurement errors and further improve positioning accuracy.

It can be seen from the above technical solution that the ultrasonic calibration and positioning method for wireless synchronized transmission and reception separation provided by the present invention has the following beneficial effects:

1. Energy saving, the transmitting unit with large energy consumption is installed on the car body and is powered by the rechargeable power supply of the car body. It can be easily returned to the charging station for charging. The beacon unit is arranged on the boundary of the movement range of the moving object, with a large number. , the distance is relatively long, and generally powered by mobile power sources such as dry batteries or lithium batteries. The beacon unit only receives ultrasonic signals, which can reduce energy consumption, greatly extend battery life, and reduce the difficulty of system maintenance and usage costs.

2. High efficiency. The present invention adopts the method of separation of ultrasonic transmission and reception for positioning. The ultrasonic wave only runs one way. Compared with the ordinary two-way ultrasonic transmission and reception positioning method, it effectively shortens the time consumption and improves the positioning efficiency.

3. Good adaptability, using directional rotation device and more than two beacon units to reduce the possibility of signal failure due to small fan angle of ultrasonic signal, using incremental position to obtain the current position and direction of the vehicle body, and through directional rotation The device aims the ultrasonic signal generator at the beacon unit. The beacon unit uses more than two ultrasonic signal receivers installed at an angle of 15° along the central axis, which reduces the possibility that the beacon cannot receive the signal.

4. Good scalability. Networking beacon units can easily upgrade the positioning system and provide positioning services for multiple vehicles at the same time. Each transmitting and data unit and beacon unit are equipped with independent addresses, so new transmitting and data units can be easily added to the network, and the positioning data of each transmitting and data processing unit can be obtained through sub-address operation.

5. The structure is simple and the cost is low. Each beacon unit uses no more than 2 ultrasonic signal receivers. The structure is simple and the volume is small. The beacon unit is set on the pole and can be placed directly or inserted into the ground surface to facilitate the signal transmission. The beacon unit is installed in the target positioning area, avoiding the trouble of array installation on the ceiling and reducing beacon unit costs and deployment costs.

Description of the drawings

In order to more clearly explain the specific embodiments of the present invention or the technical solutions in the prior art, the drawings that need to be used in the description of the specific implementations or the prior art will be briefly introduced below. Throughout the drawings, similar elements or portions are generally identified by similar reference numerals. In the drawings, elements or parts are not necessarily drawn to actual scale.

Figure 1 is a structural block diagram of the transmitting and data processing unit and the beacon unit;

Figure 2 is a schematic structural diagram of the vehicle body and the transmitting and data processing unit;

Figure 3 is a schematic structural diagram of the beacon unit;

Figure 4 is a schematic diagram of the rotation angle of the ultrasonic transmitter;

Figure 5 is a flow chart of time base synchronization and signal transmission and reception;

Figure 6 is a schematic diagram of linear incremental displacement;

Figure 7 is a schematic diagram of the relationship between turning positions;

Figure 8 is a schematic diagram of two-point positioning.

In Figure 2 and Figure 3, 1 car body, 11 driving wheels, 21 data processing module one, 22 ultrasonic signal generator, 23 wireless communication module one, 24 directional rotation device, 25 rotary encoder, 31 data processing module two, 32 Ultrasonic signal receiver, 33 wireless communication module two, 4 poles.

Detailed ways

The embodiments of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, and are therefore only used as examples and cannot be used to limit the protection scope of the present invention. Unless otherwise specifically stated, the components and steps described in these examples are not Relative steps, numerical expressions and numerical values do not limit the scope of the invention.

It should be noted that, unless otherwise stated, the technical terms or scientific terms used in this application should have the usual meanings understood by those skilled in the art to which this invention belongs.

As shown in Figure 1-3, a positioning system with separate wireless synchronous transmission and reception includes: a vehicle body 1, a transmitting and data processing unit provided on the vehicle body, and more than two beacon units provided within the target positioning range. , the car body adopts two drive wheels 11 for differential steering, and the remaining wheels are tricycles or four-wheeled vehicles with a universal wheel structure. The car body motor uses a GP36 high-power planetary deceleration DC motor. The launch and data processing unit includes: Data processing module 1 21 , ultrasonic signal generator 22, wireless communication module 23, directional rotation device 24, and rotary encoder 25. The corresponding STM32 main development board, US-020 ultrasonic sensor, esp8266 WiFi module, SG90 steering gear, and 500-line rotary encoder are respectively used. The ultrasonic signal generator generates and emits ultrasonic signals. The directional rotation device controls the emission direction of the ultrasonic signal generator. The rotary encoder is connected to the driving wheel of the car body through a synchronous gear. The rotary encoder records the information of the car body movement and sends the information to Data processing module one. The data processing module one calculates the incremental position of the moving object based on the received rotary encoder information and controls the work of the directional rotation device and the ultrasonic signal generator. The data processing module one transmits information to the outside world through the wireless communication module one. , the beacon unit includes a data processing module 31, an ultrasonic signal receiver 32, and a wireless communication module 33. The corresponding STM32 control board, US-020 ultrasonic sensor, and esp8266 WiFi module are used respectively. The ultrasonic signal receiver receives the ultrasonic signal, and the data processing module Two controls the operation of the ultrasonic signal receiver and receives the information received by the ultrasonic signal receiver. The data processing module two transmits information to the outside world through the wireless communication module two. The data processing module one and the data processing module two communicate through the wireless communication module one and the wireless communication module two. The communication module 2 transmits information. The beacon unit is installed on the pole 4. The beacon unit is equipped with two ultrasonic signal receivers. The central axes of the two ultrasonic signal receivers are at an included angle of 15°.

The implementation principles and technical effects of the device provided by the embodiments of the present invention are the same as those of the following method embodiments. For a brief description, for parts not mentioned in the device embodiments, please refer to the corresponding content in the following method embodiments.

A positioning method using the above-mentioned wireless synchronous transceiver separation positioning system, including the following steps:

S1. In the preparation phase, according to the requirements of the usage scenario, install beacon units AP ₁ , AP ₂ ,... AP _n within the positioning area, and align the beacon unit signal receiving direction with the motion range of the positioned object, and manually measure and calibrate The position of each beacon unit, and input the measurement data as coordinate position data into the data processing module 1 of the transmitting and data processing unit;

S2. In the initialization stage, the vehicle body is reset to the origin, and the data processing module obtains the initial position coordinates and initial direction;

S3. Measurement of incremental position. The car body moves freely within the positioning range. The rotation angle data is obtained through the rotary encoder connected to the motion axis. The movement is converted through the speed ratio relationship between the rotary encoder and the wheel and the connected wheel radius. Distance data and direction are accumulated to obtain incremental position and direction;

S4. Calibration of positioning coordinates:

S4.1 As shown in Figure 4, the car body runs to the positioning point P _j+1 and stops. The data processing module 1 records the displacement coordinate P _j+1 (x _j+1 ,y _{j+ 1} ) Calculate and judge the direction angle ∑a _j+1 and the coordinate position data of the beacon unit, and issue a fixed-angle rotation command to the directional rotation device to align the ultrasonic signal generator with the rotation angles of the beacon units AP ₁ and AP ₂ respectively. are β and γ,

S4.2 As shown in Figure 5, the transmitting and data processing unit sends a handshake signal to the wireless communication module 2 of the corresponding beacon unit through the wireless communication module 1. After the handshake is successful, the beacon unit is awakened, and the transmitting and data processing unit communicates with the beacon unit Perform time base synchronization operations;

S4.3 is shown in Figure 5. It is controlled by data processing module one and data processing module two. In the synchronized clock pulse sequence, after a delay of a period of time t, a rising edge of the clock signal is taken at the same time, and the transmitting and data processing unit triggers Ultrasonic emission action, beacon unit triggers timing at the same time;

S4.4 As shown in Figure 5, after the beacon unit receives the ultrasonic signal, it stops timing and sends the timing value T to the wireless communication module 1 of the transmitting and data processing unit through the wireless communication module 2;

After the data processing module of the S4.5 transmitting and data processing unit receives the timing value T from the wireless communication module, it uses the formula and combines the temperature, humidity, system time loss and other correction coefficients to convert using the TOA (time of arrival) method. distance data between the transmitting and data processing unit and the beacon unit;

S4.6 selects another beacon unit, repeats the S4.1~S4.5 process, and obtains the distance data between the transmitting and data processing unit and the other beacon unit;

S4.7 Data processing module 1 can obtain the positions of two points based on the obtained distance to the two beacon units through the two-point positioning method, and use the current incremental position data to determine the position data of one of the points. That is, the absolute position of the car body is obtained;

S4.8 When the absolute position is judged to be within a reasonable tolerance range, the incremental position data is replaced and used as the actual positioning coordinate data of the vehicle body to eliminate the cumulative error caused by the rotary encoder measurement.

The specific working principle of the present invention:

1. Incremental displacement measurement principle:

1.1 Linear incremental displacement:

As shown in Figure 6, the linear incremental displacement Δx _j+1 and Δy _j+1 are calculated as follows:

Δx _j+1 =iθ _j+1 r·sin(∑a _j )

Δy _j+1 =iθ _j+1 r·cos(∑a _j )

L _j+1 =iθ _j+1 r, where L _j+1 is the linear incremental displacement length of the j+1th segment, i is the gear set speed ratio connecting the driving wheel and the rotary encoder, θ _j+1 is the The rotation angle of the j+1 segment rotary encoder, r is the radius of the drive wheel, and ∑a _j is the angle between the displacement direction of this straight line segment and the Y-axis of the coordinate system.

1.2 Direction deflection angle:

By default, this system moves in a plane, and the direction deflection angle represents the attitude of the vehicle body.

As shown in Figure 7, when the rotation speed of the two left and right driving wheels ω ₁ ≠ ω ₂ , the vehicle body will turn. α _j+1 is the direction deflection angle,

Among them: H is the wheel spacing; Δl is the arc length difference between the inner and outer drive wheels; i is the gear set speed ratio connecting the drive wheel to the rotary encoder; θ ₁ is the inner drive wheel angle, obtained by the left rotary encoder; θ ₂ is the outer drive The wheel rotation angle is obtained by the right rotating encoder; r is the driving wheel radius,

Among them: L _c is the chord length corresponding to the deflection arc,

β is the angle between the vehicle body deflection direction vector and the y-axis with the starting point of the arc as the origin of the coordinate system and the chord length as the modulus, indicating the deflection direction of this turn.

1.3 Turn incremental position coordinates:

Among them, k is the deflection direction selection coefficient. When the vehicle body turns left, k=2 is taken; when the vehicle body turns right, k=1 is taken.

1.4 Incremental position recursion formula:

∑a _j+1 =∑a _j +a _j+1 ,

Among them, s is the selection coefficient. When the running trajectory of the vehicle body is a straight segment, s=1, and when the vehicle body turns, s=0.

2Principle of ultrasonic positioning:

2.1 Ultrasonic ranging:

The ultrasonic speed formula C=C ₀ +0.607T, where: C is the ultrasonic speed at the current temperature, C ₀ is the sound wave speed at zero degrees 331.5m/s, and T is the actual temperature (℃);

The ultrasonic ranging formula L=Ct, where L is the distance between the ultrasonic wave from the transmitter to the receiver, and t is the propagation time of the ultrasonic wave from the transmitter to the receiver.

2.2 Two-point positioning principle:

Ultrasonic positioning generally uses two-point positioning or three-point positioning. In most cases, the car body runs in a flat area. In this case, the two-point positioning method can be simplified.

As shown in Figure 8, the coordinate positions of beacons AP ₁ and AP ₂ have been measured and calibrated in advance. The ultrasonic transmitter is loaded on the vehicle body and aims at the beacons in order to transmit ultrasonic signals. Using the TOA (time of arrival) method, the beacon unit starts timing when the ultrasonic signal is transmitted, and stops timing when the ultrasonic signal is received. The ultrasonic propagation time is obtained, and then the distances L ₁ and L ₂ between the vehicle body and the two beacons are obtained. , draw circles with beacons AP ₁ and AP ₂ as centers and L ₁ and L ₂ as radii respectively, and obtain two intersection points G ₁ and G ₂ . The intersection points can be calculated through the following set of equations:

Among them, (X, Y) is the coordinate value of the intersection point G ₁ and G _2. By comparing with the incremental coordinate, the group with the smaller difference between G ₁ and G ₂ is selected as the current vehicle body position coordinate, as shown in Figure 8 Select point G ₁ to complete ultrasonic positioning.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention. scope, they should be covered by the claims and the scope of the description of the present invention.

Claims (8)

1. A positioning method of a positioning system with wireless synchronous receiving and transmitting separation is characterized by comprising the following steps: the positioning system comprises: the device comprises a vehicle body, a transmitting and data processing unit arranged on the vehicle body and a plurality of beacon units arranged in a target positioning range, wherein the transmitting and data processing unit comprises: the beacon unit comprises an ultrasonic signal receiver, a wireless communication module II and a data processing module II, wherein the rotary encoder records information of vehicle body movement and sends the information to the data processing module I, the data processing module I receives the information of the rotary encoder and controls the directional rotation device and the ultrasonic signal generator to work, the directional rotation device controls the transmitting direction of the ultrasonic signal generator, the ultrasonic signal generator generates and transmits an ultrasonic signal, the ultrasonic signal receiver receives the ultrasonic signal, the data processing module II receives the information transmitted by the ultrasonic signal receiver, and the data processing module I and the data processing module II transmit information through the wireless communication module I and the wireless communication module II; the positioning method comprises the following steps:

s1, in the preparation stage, a beacon unit is installed in the range of a target positioning domain according to a use field Jing Xuqiu, and coordinate data of the beacon unit are measured and calibrated, and are input into a transmitting and data processing unit;

s2, in an initialization stage, the vehicle body is reset at the original point to obtain initial position coordinates and an initial direction;

s3, measuring the increment position, wherein the data processing module I receives information of the rotary encoder and calculates the increment position and direction of the vehicle body;

s4, calibrating positioning coordinates:

s4.1, stopping the vehicle body at a positioning point, calculating and judging by a data processing module I according to the increment position and the direction of the vehicle body and the coordinate position data of the beacon unit, and sending a fixed angle rotation instruction to the directional rotation device to enable the ultrasonic signal generator to be aligned to the direction of the corresponding beacon unit;

s4.2, the transmitting and data processing unit transmits a handshake signal to the wireless communication module II of the corresponding beacon unit through the wireless communication module, and after handshake is successful, the transmitting and data processing unit and the beacon unit perform time base synchronization operation;

s4.3, the first data processing module and the second data processing module control the transmitting and data processing unit to trigger the ultrasonic wave transmitting action, and the beacon unit triggers timing at the same time;

s4.4, after the beacon unit receives the ultrasonic signal, stopping timing, and sending the timing value to the transmitting and data processing unit through the wireless communication module II;

s4.5, after the transmitting and data processing unit receives the timing data, converting the timing data into distance data between the transmitting and data processing unit and the beacon unit through a formula and combining a correction coefficient;

s4.6, selecting another beacon unit, repeating the processes of S4.1-S4.5, and obtaining distance data between the transmitting and data processing unit and the other beacon unit;

s4.7, the data processing module firstly obtains two point positions by a two-point positioning method according to the obtained distance between the two beacon units, and judges and obtains one position data by using the current increment position data to obtain the absolute position of the vehicle body;

s4.8, correcting the increment position by the data processing module through the absolute position to obtain accurate positioning coordinates, and eliminating accumulated errors caused by measurement of the rotary encoder.

2. The positioning method according to claim 1, wherein: the tricycle body adopts differential steering of two driving wheels and has universal wheel structure, and the rotary encoder is connected to the driving wheel shaft of the tricycle body.

3. The positioning method according to claim 1, wherein: the beacon unit is provided with two ultrasonic signal receivers, and adjacent ultrasonic signal receivers are distributed and installed according to the central axis at an included angle of 15 degrees.

4. The positioning method according to claim 1, wherein: the beacon unit is arranged on the pile rod.

5. The positioning method according to claim 1, wherein: in the step S1, the beacon units are set with device addresses and numbered, so that each beacon unit has an independent address and number, and an ordered beacon array is established for all beacon units.

6. The positioning method according to claim 1, wherein: in the step S4.3, a delay time is left between the first data processing module and the second data processing module before a rising edge or a falling edge of a clock signal is taken at the same time.

7. The positioning method according to claim 1, wherein: the correction coefficient in the step S4.5 is obtained according to the external temperature and humidity data which are measured in advance and is input into the first data processing module in advance.

8. The positioning method according to claim 1, wherein: in the step S4.5, the correction coefficient is obtained by installing temperature and humidity sensors on the vehicle body in advance, and the temperature and humidity sensors transmit the acquired data to the data processing module one, which calculates according to a prefabricated data table.