阅读说明：本技术 一种基于超宽带技术的室内无源实时定位方法 (Indoor passive real-time positioning method based on ultra wide band technology ) 是由 王伟 张家宁 李欣 黄平 薛冰 于 2021-09-10 设计创作，主要内容包括：一种基于超宽带技术的室内无源实时定位方法,涉及超宽带测距领域和室内定位技术领域,针对现有技术中不同设备的时间分辨率不同进而导致测距误差大的问题,本申请提出了一种基于超宽带技术的室内无源实时定位方法。测距方面,利用定位过程中动态估计的时间分辨率以及必要的时间戳来完成测距信息的获取,不仅能提高设备时间戳的利用率,还能为定位系统简化距离差或距离的求解方法以及其信号交流机制,从而以无源的方式准确的获取距离差；定位方面,利用CHAN-最小二乘算法克服非线性迭代初值计算的问题。将两者结合从而形成一套完整的无源定位系统。(An indoor passive real-time positioning method based on an ultra wide band technology relates to the field of ultra wide band ranging and the technical field of indoor positioning, and aims to solve the problem that in the prior art, the ranging error is large due to the fact that time resolutions of different devices are different. In the aspect of distance measurement, the time resolution of dynamic estimation in the positioning process and a necessary timestamp are used for completing the acquisition of distance measurement information, so that the utilization rate of the timestamp of equipment can be improved, and the distance difference or a distance solving method and a signal exchange mechanism thereof can be simplified for a positioning system, so that the distance difference can be accurately acquired in a passive mode; in the aspect of positioning, a CHAN-least square algorithm is used for overcoming the problem of nonlinear iteration initial value calculation. The two are combined to form a complete passive positioning system.)

1. An indoor passive real-time positioning method based on an ultra-wideband technology is characterized by comprising the following steps:

the method comprises the following steps: acquiring initial position information of a main base station and each slave base station, wherein the number of the slave base stations is at least three;

step two: inquiring and responding the master base station and each slave base station respectively, wherein a tag only receives signals of the master base station or the slave base stations in the inquiring and responding processes so as to obtain time difference information, wherein the tag is a user base station;

step three: respectively obtaining the reciprocal of the working frequency of a system time counter of the master base station, each slave base station and the label, namely time resolution;

step four: firstly, obtaining the distance between a main base station and each slave base station according to the obtained time resolution and time difference information, and then obtaining the difference value between the distance from a label to the main base station and the distance from the label to each slave base station by using the time resolution, the time difference information and the obtained distance between the main base station and each slave base station;

step five: obtaining rough label initial position information by using a CHAN-least square algorithm according to the obtained distance difference, then taking the rough label initial position information as the label initial position information in a nonlinear iterative positioning algorithm, and obtaining label positioning information by combining the distance difference;

step six: and repeating the first step to the fourth step to obtain a new distance difference value, then using the label positioning information as label initial position information in a nonlinear iterative positioning algorithm, and carrying out real-time positioning by combining the new distance difference value.

2. An indoor passive positioning method based on ultra-wideband technology according to claim 1, characterized in that the time resolution in the step three is expressed as:

wherein the content of the first and second substances,indicating the time resolution, k, of the master base station using the time resolution ratio of the master base station to the slave base station x^SSxIndicating the time resolution of the slave base station x obtained using the time resolution ratio of the master base station to the slave base station x,indicating the difference in the system time counter of the master base station over the period of two consecutive transmissions to the slave base station x, the TimeSlot_SSxRepresents the difference of the system time counter of the slave base station x in the period of time during which the signal transmitted by the master base station is received twice in succession,indicating the time resolution, k, of the master base station using the time resolution ratio of the master base station to the tags^TIndicating the time resolution of the tag using the time resolution ratio of the master base station to the tag,indicating the difference in the system time counter of the primary base station over the period of time during which the signal is transmitted to the tag twice in succession, the Timeslot_TA system time counter representing the tag is a difference value of counters in a period of time during which a signal transmitted from the main base station is received two consecutive times,representing the nominal temporal resolution.

3. The indoor passive positioning method based on ultra wide band technology of claim 2, characterized in that the distance between the master base station and each slave base station in the fourth step is represented as:

wherein the content of the first and second substances,denotes the distance between the master base station and the slave base station x, c denotes the speed of light, T_roundThe system time counter representing the master base station counts the number of times, T, elapsed from the time of sending the inquiry signal to the slave base station x to the time of receiving the response signal from the slave base station x_replyIndicating the count value of the system time counter of the slave base station x elapsed from the time of receiving the inquiry signal from the master base station to the time of transmitting the response signal.

4. The indoor passive positioning method based on ultra-wideband technology as claimed in claim 3, wherein the difference between the distance of the tag to the master base station and the distance of the tag to each slave base station is represented as:

wherein, T_receiveThe system time counter representing the tag passes the count value from the reception of the inquiry signal issued from the main base station to the reception of the response signal issued from the base station x.

5. The indoor passive positioning method based on ultra wide band technology as claimed in claim 4, wherein the tag initial position information is expressed as:

X＝inv(H^TH)H^TZ

wherein H represents a measurement matrix, Z represents a system measurement value, X represents a system state vector,

wherein x and y represent the horizontal and vertical coordinates of the label, x_SS2And y_SS2Denotes the abscissa and ordinate, x, of the slave base station 2_SS3And_SS3denotes the abscissa and ordinate, x, of the slave base station 3_SSnAnd y_SSnDenotes the abscissa and ordinate, x, of the slave base station n_MSAnd y_MSDenotes the abscissa and ordinate, W, of the main base station_SS2Denotes the sum of squares of the abscissa and ordinate, W, from the base station 2_SS3Denotes the sum of squares of the abscissa and ordinate, W, from the base station 3_SSnDenotes the sum of squares of the abscissa and ordinate, D, from the base station n_MSRepresenting the geometric distance, D, of the master base station from the tag_SS2Representing the geometrical distance, D, from the base station 2 to the tag_SS2,MSRepresenting the difference in distance between the tag to the slave base station 2 and the master base station, i.e. D_SS2,MS＝D_SS2-D_MS；D_SS3Representing the geometrical distance, D, from the base station 3 to the tag_SS3,MSRepresenting the difference in distance between the tag to the slave base station 3 and the master base station, i.e. D_SS3,MS＝D_SS3-D_MS；D_SSnRepresenting the geometric distance, D, from the base station n to the tag_SSn,MSRepresenting the difference in distance between the tag to the slave base station n and the master base station, i.e. D_SSn,MS＝D_SSn-D_MS。

6. The indoor passive positioning method based on the ultra-wideband technology as claimed in claim 5, wherein the nonlinear iterative positioning algorithm in the sixth step is represented as:

whereinAndare respectively a state vector X_newThe (k + 1) th iteration and the (k) th iteration, the operator de (x) represents the error to solve the Jacobian matrix of the system state, V_kRepresenting the amount of state change for the kth iteration.

7. The indoor passive positioning method based on the ultra-wideband technology as claimed in claim 6, wherein the termination condition of the iteration equation of the nonlinear iterative positioning algorithm is that the number of iterations reaches 10 or the sum of squares of errors of two adjacent moments in the iteration process is less than 10cm x cm.

Technical Field

The invention relates to the field of ultra-wideband ranging and the technical field of indoor positioning, in particular to an indoor passive real-time positioning method based on an ultra-wideband technology.

Background

The ultra-wideband wireless communication technology is widely applied to indoor high-precision positioning by virtue of the advantages of high time resolution, multipath interference resistance, low power consumption and the like. In order to fully exploit the advantages of the ultra-wideband technology, a positioning system usually obtains a distance difference or a distance by using the flight time of a signal in the air in a ranging stage, and ranging methods can be divided into two categories: time Difference of Arrival (TDOA) and Time of Arrival (TOA). TDOA is a method for directly obtaining the distance difference between a tag and two different base stations, but strict clock synchronization is required between base station equipment to reduce the distance measurement error caused by different time resolutions; although TOAs based on One-Way Ranging (OWR) also require strict time synchronization, TOAs based on Two-Way Ranging (TWR) can generally reduce the problem of clock asynchronization between different devices by increasing the number of communications and improving the computation method, for example: symmetric Double-Sided Two-Way Ranging (SDS-TWR), Asymmetric Double-Sided Two-Way Ranging (ADS-TWR), Alternative Double-Sided Two-Way Ranging (AltDS-TWR), and the like. In the above ranging method, the AltDS-TWR algorithm has high accuracy and is relatively simple, so it is widely used in ranging of the ultra-wideband positioning system. However, the AltDS-TWR algorithm has a low utilization rate of the time stamp, and when a plurality of base stations perform ranging, the number of times of signal transmission is increased, thereby causing a decrease in reliability of the positioning information given to the tag by the positioning system.

In recent years, in order to reduce the ranging error caused by the different time resolutions of different devices, some ultra-wideband ranging algorithms that change the ranging communication mechanism or utilize the functions of the hardware devices themselves have been researched and proposed. The document (Gu Y, Yang b. clock Compensation Two-Way Communication [ C ]//2018 eigenh International Conference on Instrumentation & Measurement, Computer, Communication and Control (IMCCC).2018.) proposes to use CC-TWR (clock correction Two-Way Ranging) algorithm to calculate the clock error ratio of Two devices, so as to compensate the clock error between the devices, but it has the disadvantage that each device needs to transmit and receive twice, wherein one time calculates the clock error ratio and the other time measures, so as to increase the complexity of device signal Communication during Ranging, and the utilization degree of timestamp is low; the literature (Sidorenko J, Schatz V, Scherer-Negenborn N, et al. error corrections for ultra-wideband ranging [ J ]. IEEE Transactions on Instrumentation and Measurement,2020, PP (99):1-1.) first analyzes all current TOA and TDOA-based ranging algorithms, which consider that the AltDS-TWR algorithm can effectively suppress signal power or device delay, and then generalizes the AltDS-TWR algorithm from TOA to TDOA, which has the disadvantage that although higher accuracy can be achieved, the expression for calculating the air time of flight of the signal is more cumbersome; the literature (autumn park, coma, ultra wide band indoor ranging of TDOA/SDS-TWR combination [ J ] electronic measurement technique, 2021,44(04):75-79.) proposes TDOA/SDS-TWR algorithm whose signal communication is essential in that one TWR is completed between two devices, the other device receives information all the way, the paper simulates the effect of two variables of response time and clock offset on ranging error, and as a result, when the response time is incremented from 0.02 ms, 0.1 ms, 0.2 ms and 0.3 ms, the slope of the error with clock offset increases faster, considering that when the delayed transmission function is actually used for responding, in order to guarantee the transmission distance and reduce the influence of non-line of sight as much as possible, the data modulation and demodulation rate is usually chosen to be 110kbps, and only the Preamble, SFD (frame of timer) part of the transmitted frame needs to be more than 1.2 ms, this may make the ranging error change faster with clock skew when the algorithm is actually used, thereby causing a greater impact on the ranging effect; the literature (high-key, terrestrial, leiqing, satellite, TOF and TDOA joint positioning algorithm using three-way communication [ J ]. electronic measurement and instrumentation, 2020,34(03):66-73.) proposes to use clock drift proportionality coefficient and electromagnetic wave transmission time between master base station and slave base station to calculate TDOA value, and its disadvantage is that the tags need to transmit signals during the whole communication process, thus there is a certain limit to the number of tags, and when the number of tags is increased, the communication mechanism of the whole positioning system needs to be changed.

Disclosure of Invention

The purpose of the invention is: aiming at the problem that the distance measurement error is large due to different time resolutions of different devices in the prior art, an indoor passive real-time positioning method based on the ultra-wideband technology is provided.

The technical scheme adopted by the invention to solve the technical problems is as follows:

an indoor passive real-time positioning method based on an ultra-wideband technology comprises the following steps:

the method comprises the following steps: acquiring initial position information of a main base station and each slave base station, wherein the number of the slave base stations is at least three;

step two: inquiring and responding the master base station and each slave base station respectively, wherein a tag only receives signals of the master base station or the slave base stations in the inquiring and responding processes so as to obtain time difference information, wherein the tag is a user base station;

step three: respectively obtaining the reciprocal of the working frequency of a system time counter of the master base station, each slave base station and the label, namely time resolution;

step four: firstly, obtaining the distance between a main base station and each slave base station according to the obtained time resolution and time difference information, and then obtaining the difference value between the distance from a label to the main base station and the distance from the label to each slave base station by using the time resolution, the time difference information and the obtained distance between the main base station and each slave base station;

step five: obtaining rough label initial position information by using a CHAN-least square algorithm according to the obtained distance difference, then taking the rough label initial position information as the label initial position information in a nonlinear iterative positioning algorithm, and obtaining label positioning information by combining the distance difference;

step six: and repeating the first step to the fourth step to obtain a new distance difference value, then using the label positioning information as label initial position information in a nonlinear iterative positioning algorithm, and carrying out real-time positioning by combining the new distance difference value.

Further, the time resolution in step three is expressed as:

wherein the content of the first and second substances,indicating the time resolution, k, of the master base station using the time resolution ratio of the master base station to the slave base station x^SSxIndicating the time resolution of the slave base station x obtained using the time resolution ratio of the master base station to the slave base station x,indicating the difference in the system time counter of the master base station over the period of two consecutive transmissions to the slave base station x, the TimeSlot_SSxRepresents the difference of the system time counter of the slave base station x in the period of time during which the signal transmitted by the master base station is received twice in succession,indicating the time resolution, k, of the master base station using the time resolution ratio of the master base station to the tags^TIndicating the time resolution of the tag using the time resolution ratio of the master base station to the tag,system time counter indicating main base station transmitting signal to main base station in two successive timesThe difference in the counter over the time period of the tag, TimeSlot_TA system time counter representing the tag is a difference value of counters in a period of time during which a signal transmitted from the main base station is received two consecutive times,representing the nominal temporal resolution.

Further, the distance between the master base station and each slave base station in the fourth step is represented as:

wherein the content of the first and second substances,denotes the distance between the master base station and the slave base station x, c denotes the speed of light, T_roundThe system time counter representing the master base station counts the number of times, T, elapsed from the time of sending the inquiry signal to the slave base station x to the time of receiving the response signal from the slave base station x_replyIndicating the count value of the system time counter of the slave base station x elapsed from the time of receiving the inquiry signal from the master base station to the time of transmitting the response signal.

Further, the difference between the distance from the tag to the master base station and the distance from the tag to each slave base station is represented as:

wherein, T_receiveThe system time counter representing the tag passes the count value from the reception of the inquiry signal issued from the main base station to the reception of the response signal issued from the base station x.

Further, the tag initial position information is expressed as:

X＝inv(H^TH)H^TZ

wherein H represents a measurement matrix, Z represents a system measurement value, X represents a system state vector,

wherein x and y represent the horizontal and vertical coordinates of the label, x_SS2And y_SS2Denotes the abscissa and ordinate, x, of the slave base station 2_SS3And_SS3denotes the abscissa and ordinate, x, of the slave base station 3_SSnAnd y_SSnDenotes the abscissa and ordinate, x, of the slave base station n_MSAnd y_MSDenotes the abscissa and ordinate, W, of the main base station_SS2Denotes the sum of squares of the abscissa and ordinate, W, from the base station 2_SS3Denotes the sum of squares of the abscissa and ordinate, W, from the base station 3_SSnDenotes the sum of squares of the abscissa and ordinate, D, from the base station n_MSRepresenting the geometric distance, D, of the master base station from the tag_SS2Representing the geometrical distance, D, from the base station 2 to the tag_SS2,MSRepresenting the difference in distance between the tag to the slave base station 2 and the master base station, i.e. D_SS2,MS＝D_SS2-D_MS；D_SS3Representing the geometrical distance, D, from the base station 3 to the tag_SS3,MSRepresenting the difference in distance between the tag to the slave base station 3 and the master base station, i.e. D_SS3,MS＝D_SS3-D_MS；D_SSnRepresenting the geometric distance, D, from the base station n to the tag_SSn,MSRepresenting the difference in distance between the tag to the slave base station n and the master base station, i.e. D_SSn,MS＝D_SSn-D_MS。

Further, the nonlinear iterative positioning algorithm in the sixth step is represented as:

whereinAndare respectively a state vector X_newThe (k + 1) th iteration and the (k) th iteration, the operator de (x) represents the error to solve the Jacobian matrix of the system state, V_kRepresenting the amount of state change for the kth iteration.

Further, the termination condition of the iteration equation of the nonlinear iterative positioning algorithm is that the iteration number reaches 10 times or the sum of squares of errors of two adjacent moments in the iteration process is less than 10cm x cm.

The invention has the beneficial effects that:

the application provides an indoor passive real-time positioning method based on an ultra wide band technology. In the aspect of distance measurement, the time resolution of dynamic estimation in the positioning process and a necessary timestamp are used for completing the acquisition of distance measurement information, so that the utilization rate of the timestamp of equipment can be improved, and the distance difference or a distance solving method and a signal exchange mechanism thereof can be simplified for a positioning system, so that the distance difference can be accurately acquired in a passive mode; in the aspect of positioning, a CHAN-least square algorithm is used for overcoming the problem of nonlinear iteration initial value calculation. The two are combined to form a complete passive positioning system.

Drawings

FIG. 1 is a signal communication mechanism for a positioning system to obtain primary position information;

FIG. 2 is a ranging error profile for the AltDS-TWR ranging algorithm under the same conditions as the ranging algorithm described herein;

FIG. 3 is an error distribution of range differences measured by the ranging algorithm described herein;

FIG. 4 is a circle of turns in a room of 11.46m 11.60 m;

FIG. 5 is a plot of the selected position in a room of 11.46m 11.60 m;

fig. 6 is an error distribution of the fixed-point sampling result in fig. 5.

Detailed Description

It should be noted that, in the present invention, the embodiments disclosed in the present application may be combined with each other without conflict.

The first embodiment is as follows: specifically, referring to fig. 1, the present embodiment is described, and an indoor passive real-time positioning method based on the ultra-wideband technology in the present embodiment includes the following steps:

the method comprises the following steps: the method comprises the steps that a label obtains initial position information of a main base station and each slave base station, wherein the number of the slave base stations is at least three, and the label is a user base station;

step two: the master base station inquires and responds to each slave base station respectively, and the tag only receives signals of the master base station or the slave base stations in the inquiring and responding processes so as to obtain time difference information;

step three: respectively obtaining the reciprocal of the working frequency of a system time counter of the master base station, each slave base station and the label, namely time resolution;

step four: according to the obtained time resolution and the time difference information, firstly, the distance between the main base station and each slave base station is calculated, and then the difference value between the distance from the label to the main base station and the distance from the label to each slave base station is obtained by utilizing the time resolution, the time difference information and the calculated distance between the main base station and each slave base station;

step five: and obtaining rough label initial position information by using a CHAN-least square algorithm according to the obtained distance difference, then taking the rough label initial position information as the label initial position information in a nonlinear iterative positioning algorithm, and obtaining label positioning information by combining the distance difference.

Step six: and repeating the first step to the fourth step to obtain a new distance difference value, then using the label positioning information as label initial position information in a nonlinear iterative positioning algorithm, and carrying out real-time positioning by combining the new distance difference value.

In step three, the estimation criterion of the time resolution is as follows:

it is assumed that device a and device B communicate signals in an exchange mechanism provided by the AltDS-TWR protocol. Device A sends out inquiry signal to device B, device B receives inquiry signal and passes count value T in system time counter of device B_reply1Then, a response signal is sent to the device A, and the device A receives the response signal and counts the system time counter of the device AValue T_reply2After that, an end signal is sent to the device B. The system time counter of device a passes the count value T from the sending of the inquiry signal to the receipt of the reply signal_round1. When the device B receives the end signal, the system time counter of the device B passes through the counting value T from the sending of the response signal to the receiving of the end signal_round2. The formula for estimating the device counter value corresponding to the signal flight time by means of the counter difference values is as follows:

wherein the content of the first and second substances,the subscript indicates that the value is a counter value, and Λ represents the estimated value. To obtain the time of flight of the signal, it is usually necessary toPre-multiplying nominal time resolutionNamely, it is¹/(499.2MHz × 128) in seconds. Considering the inter-device variability, it is assumed that the time resolution of device A is k^AThe time resolution of the device B is k^BTwo time resolutions are substituted into the formula for AltDS-TWR estimated signal time of flight:

there is a proportional relationship between the time resolution of both device a and device B. The relationship can be established when device a transmits a signal to device B twice. To describe this relationship, assume now that device A is at time point T₁、T₃Transmitting a signal, device B at a point in time T₂、T₄And receiving signals, wherein the time points are real time and are not reference time corresponding to the devices respectively. The following equation can thus be established:

T₃-T₁＝T₄-T₂

the system time counter of the known device a is at the point in time T₁To T₃The difference between the counters of the time periods is TimeSlot_ASystem time counter of device B at time point T₂To T₄The difference between the counters of the time periods is TimeSlot_BThen, based on the time resolution of devices a and B, the following relationship can be established:

k^A×TimeSlot_A＝k^B×TimeSlot_B

an analogy in the AltDS-TWR AC mechanism is:

k^A×(T_round1+T_reply2)＝k^B(T_round2+T_reply1)

thus, the derivation prior to synthesis can be:

k^Bthe same is true. A careful observation of the above formula reveals that the AltDS-TWR methodEstimation criterion in terms of temporal resolutionConsider the sum of the time resolutions of device a and device B to be approximately equal to twice the nominal time resolution:

in step three, the time resolution is calculated as follows:

for simplicity of description, a typical segment of the communication between the master base station and the slave base station x (x is a positive integer equal to or greater than two) is extracted as an example.

Suppose that the master base station is at time point T₁Time-of-flight transmission of a first signal from base station x at a point in time T₂Time-of-day reception of signals, main base station at time point T₃Time-of-flight transmitting a second signal from base station x at time point T₄A second signal from the primary base station is received. System of main base stationTime counter at time point T₁To T₃The difference between the counters of the time periods is TimeSlot_MS. From the system time counter of base station x at point in time T₂To T₄The difference between the counters of the time periods is TimeSlot_SSx. Then using these time stamps, the master base station can be related to the slave base station x time resolution as follows:

wherein the content of the first and second substances,the time resolution of the master base station calculated by using the time resolution relationship of the master base station and the slave base station x is shown, the physical meaning of the time resolution is the time spent by increasing one time by a DW1000 chip system time counter in the hardware equipment of the master base station, and the same principle is that k^SSxWhich represents the time resolution of the slave base station x calculated using the time resolution relationship of the two devices, the master base station and the slave base station x.

Combining the nominal time resolution given in the DW1000 chip user manualWith the evaluation criterion of claim 2, it is obtained:

it should be noted that this estimation method is an estimation between pairs, which reflects the time resolution relationship between two devices, and the fundamental reason is that the device operating frequencies (frequencies after clock frequency multiplication) cannot be completely consistent, and this proportional relationship does not change much in a short time (tens of milliseconds), but in order to prevent clock drift caused by long-time use of the devices, the time resolution between the two device frequencies needs to be estimated continuously.

In step four, the distance between the master base station and each slave base station is calculated as follows:

for simplicity of description, a typical segment of the communication between the master base station and the slave base station x (x is a positive integer equal to or greater than two) is extracted as an example.

The time resolution of the known main base station isTime resolution k from base station x^SSxWhen the main base station is T at the time point₁Sending an inquiry signal, the slave base station x being T at a time point₂Time-of-reception signal and the count value T of system time counter from base station x_replyThen, at a time point of T₃Sending out a response signal when the time point of the main base station is T₄The signal is received. The system time counter of the main base station passes through the count value T from the sending of the inquiry signal to the receiving of the response signal_round. The distance between the master base station and the slave base station x can then be expressed as:

wherein the content of the first and second substances,denotes the distance between the master base station and the slave base station x, and c denotes the speed of light.

It should be noted that the distance between the master base station and the slave base station can be theoretically obtained through the initial positions of the master base station and the slave base station, but in general, different deviations occur in the final positioning result due to the placement of the antenna positions of the base stations in different directions, the distance between the master base station and the slave base station is calculated by using time resolution and time difference information, and more, whether the antenna positions of the base stations are correctly placed is checked, so that the situation that large-amplitude movement does not occur is ensured.

In step four, the distance difference between the tag and the base station is calculated as follows:

for simplicity of description, a typical segment of the communication between the master base station and the slave base station x (x is a positive integer equal to or greater than two) is extracted as an example.

As in the example process of fig. 4, the master base station sends out an inquiry signal, and the slave base station x sends out a response signal after receiving the inquiry signal. In this process, the system time counter of the tag passes through the count value T from the reception of the inquiry signal transmitted from the main base station to the reception of the response signal transmitted from the base station x_receive。

And the tag knows the time resolution of the master base station and the slave base station through the third step, and then obtains the distance relationship between the master base station and the slave base station:

wherein the content of the first and second substances,respectively indicating the distance between the master base station and the tag, the distance between the slave base station x and the tag, and the distance between the master base station and the slave base station x;k^Tthe time resolution of the main base station and the time resolution of the tag are calculated by utilizing the time resolution relation of the main base station and the tag; t is_roundAnd c is as defined in claim 4.

Combining the distance between the master base station and the slave base station x calculated in 4, a final distance difference expression can be obtained:

note that in the expression of the distance differenceIt is also possible to obtain initial position information by the master base station and the slave base station.

And step five, calculating the initial positioning point of the label according to the CHAN-least square algorithm in the following steps:

first, assume that the distance between point a and point B is expressed as follows:

wherein x is_A，y_ADenotes the abscissa, x, of the point A_B，y_BRepresents the abscissa and ordinate of the point B, and

let D_MSIndicating the distance of the master base station from the tag, D_SSxIndicating the distance from the base station to the tag. The difference in distance between the tag to the slave base station x (x is a positive integer greater than or equal to two) and the master base station is D_SSx，MSI.e. D_SSx，MS＝D_SSx-D_MSThen there is

In the above formula, x_SSx，y_SSxDenotes the abscissa, x, from the base station x_MS，y_MSDenotes the abscissa and ordinate of the main base station, x, y denote the abscissa and ordinate of the tag, and

the principle of simplification is

When the number of the slave base stations is n-1(n is more than 3), the slave base stations are written into a matrix form

Wherein x is_SS2，y_SS2、x_SS3，y_SS3、x_SSn，y_SSn、x_MS，y_MSHorizontal and vertical coordinates of the slave base station 2, the slave base station 3, the slave base station n and the master base station are respectively shown; d_SS2，MSIs the difference in distance between the tag to the slave base station 2 and the master base station, D_SS3，MSFor the difference in distance between the tag from the base station 3 and the master base station, D_SSn，MSIs the distance difference between the tag to the slave base station n and the master base station;

for the above equation, the initial values can be obtained by using the least squares method as follows:

X＝inv(H^TH)H^TZ

wherein H represents a measurement matrix, Z represents a system measurement value, and X represents a system state vector

Example (b):

step 1: acquiring initial position information of a master base station and each slave base station, wherein the number of the slave base stations is at least three, and the labels are user base stations;

step 2: the master base station inquires and responds to each slave base station respectively, and the tag only receives signals of the master base station or the slave base stations in the inquiring and responding processes so as to obtain time difference information;

step 2.1: the positioning system completes the communication process of one positioning as shown in the attached figure 1.

Best shown in FIG. 1The solid line on the left side is a main base station equipment time line, the solid line in the middle is a slave base station equipment time line (the number of slave base stations is n-1, n is more than 3), and the dotted line on the right side is a tag equipment time line. Symbol on the left side of two solid lines(where x in SSx is a positive integer greater than 2 and indicates the number of the slave base station; y is 1, 2, 3, 4 indicates the event node for transmission or reception, where 1 and 3 are transmission event nodes and 2 and 4 are reception event nodes) indicates the counter value of the device system time counter of the master base station or the slave base station corresponding to the transmission event or the reception event node, the superscript of which indicates the slave base station object of the current round of communication, and the subscript of which indicates the recorded event number. Symbol on the right of the dotted line(where x in SSx is a positive integer greater than 2 and indicates the number of the slave base station; y in Ty is 1, and 3 indicates the receiving event node when the master base station or the slave base station receives the signal) indicates the counter value of the device system time counter of the tag corresponding to the receiving event node when the master base station or the slave base station receives the signal transmitted from the master base station, and the superscript indicates the slave base station number that the master base station is exchanging, and the subscript indicates which event number is received.

And step 3: respectively obtaining the reciprocal of the working frequency of a system time counter of the master base station, each slave base station and the label, namely time resolution;

step 3.1: according to(x is a positive integer greater than 2 and represents the number of the slave base station) the proportional relationship of the master base station to the slave base station x time resolution is calculated:

whereinIndicating in the next round of positioningI.e., a transmission event in which the master base station transmits a signal to the slave base station x, a second subsequent transmission event,indicating in the next round of positioningReceiving a receiving event of a signal sent by a main base station from a base station x, and then receiving the event for the second time;indicating the time resolution, k, of the master base station calculated using the time resolution proportional relationship between the master base station and the slave base station x^SSxIndicating the time resolution of the slave base station x calculated using the time resolution proportional relationship between the master base station and the slave base station x.

The time resolution of the master base station and the slave base station x is limited:

wherein the content of the first and second substances,for nominal time resolution, it is therefore possible to obtain:

step 3.2: according to(x is a positive integer greater than 2 and represents the number of the slave base station) calculating the time resolution ratio relationship of the master base station to the tag:

whereinX +1 in the superscript denotes the next slave base station to slave base station x,the same applies to the superscript of (1).Indicating the time resolution, k, of the main base station calculated using the proportional relationship between the main base station and the tag^TIndicating the tag time resolution calculated using the proportional relationship between the master base station and the tag.

The time resolution of the master base station and the tag is limited:

thus, it is possible to obtain:

and 4, step 4: according to the obtained time resolution and the time difference information, firstly, the distance between the main base station and each slave base station is obtained, and then the difference value between the distance from the label to the main base station and the distance from the label to each slave base station is obtained by utilizing the time resolution, the time difference information and the distance between the main base station and each slave base station;

step 4.1: according to the time resolution calculated in step three, the distance between the master base station and the slave base station x can be expressed as:

whereinDenotes the distance between the master base station and the slave base station x, and c denotes the speed of light.

Step 4.2: according to the time resolution calculated in the step (3), the following relationship can be obtained:

whereinThe distance between the master base station and the tag, the distance between the slave base station x and the tag, and the distance between the master base station and the slave base station x are shown, respectively.

According to step 4.1The expression of (A) can be known:

and 5: obtaining rough label initial position information by using a CHAN-least square algorithm according to the obtained distance difference, then taking the rough label initial position information as the label initial position information in a nonlinear iterative positioning algorithm, and obtaining label positioning information by combining the distance difference;

step 5.1: linearizing the coordinate solution according to the CHAN algorithm:

wherein

X in the above expression_T，y_T、x_MS，y_MS、x_SSx，y_SSxRespectively, the horizontal and vertical coordinates D of the tag, the master base station and the slave base station x_MSIndicating the distance of the master base station from the tag, D_SSxDenotes the distance, D, from base station x to the tag_SSx，MSRepresenting the distance from base station x to the tag minus the distance from the main base station to the tag, i.e. D_SSx，MS＝D_SSx-D_MS

Converting the linearized formula into a matrix form:

the complete solution initial point matrix is:

the above equation can be solved using the least squares method:

X＝(H^TH)^-1H^TZ

wherein H represents a measurement matrix, Z represents a system measurement value, and X represents a system state vector

D_MSRepresenting the geometric distance, D, of the master base station from the tag_SS2Representing the geometrical distance, D, from the base station 2 to the tag_SS2，MSIndicating the tag to the slave base station 2 and to the master base stationThe difference in distance between, i.e. D_SS2，MS＝D_SS2-D_MS；D_SS3Representing the geometrical distance, D, from the base station 3 to the tag_SS3，MSRepresenting the difference in distance between the tag to the slave base station 3 and the master base station, i.e. D_SS3，MS＝D_SS3-D_MS；D_SSnRepresenting the geometric distance, D, from the base station n to the tag_SSn，MSRepresenting the difference in distance between the tag to the slave base station n and the master base station, i.e. D_SSn，MS＝D_SSn-D_MS。

Step 5.2: and 5.1, taking the initial value calculated in the step 5.1 as the initial value of the nonlinear iterative algorithm. State vector X of nonlinear iterative algorithm positioning system_newAs the abscissa x of the label_T，y_TI.e. by

X_new＝[x_T y_T]^T

The measurement output of the positioning system is:

Z_new＝[z₂ z₃ … z_n]^T

wherein z is_nDifference between distance of tag actually output by positioning system to main base station and distance of tag to slave base station

Theoretical output of the system

Wherein f is₂(x_T y_T)、f₃(x_T y_T)、f_n(x_T y_T) The difference between the distance from the tag to the master base station and the distance from the tag to the slave base station 2, the difference between the distance from the tag to the master base station and the distance from the slave base station 3, the difference between the distance from the tag to the master base station and the distance from the slave base station n, which are expressed by geometrical relations with the abscissa and the ordinate of the tag as unknowns, respectively

The error between the actual output and the theoretical output of the positioning system is

Estimating states based on minimum Mean Square Error (MSE) criterion

W is a weighting array, and a unit array can be taken. The gradient of the formula is zero, and the nonlinear equation set is solved by using a multivariate Newton iteration method, so that the update equation of the nonlinear iteration algorithm is as follows:

whereinAndare respectively a state vector X_newAnd (4) iterating the k +1 step and the k step, and calculating a Jacobian matrix of the error to the system state by using an operator De (x). V_kRepresenting the state change of the kth iteration; x₀The calculation result in the step five. Two termination conditions of the iteration equation are set, the iteration times and the state variable quantity threshold value are respectively set to 10 times and 10 times (the square sum of errors of two adjacent moments in the iteration process is less than 10 cm).

Step 6: and repeating the first step to the fourth step to obtain a new distance difference value, then using the label positioning information as label initial position information in a nonlinear iterative positioning algorithm, and carrying out real-time positioning by combining the new distance difference value.

Fig. 1 is a signal communication mechanism for a positioning system to obtain primary position information.

Fig. 2 is a ranging error distribution diagram of the AltDS-TWR ranging algorithm under the same condition as the ranging algorithm mentioned herein, and it can be observed that the distribution of the two algorithms is substantially consistent and can be considered as a normal distribution. And the error of more than 99% of all samples (total number of samples 15259) is distributed within 0.06m (3 times standard deviation).

Fig. 3 is an error distribution of the range differences measured by the ranging algorithm presented herein, from which it can be seen that the errors substantially follow a normal distribution, and that more than 99% of the errors of all samples (total number of samples 21225) are distributed within 0.15m (3 times standard deviation).

Fig. 4 is a diagram of a circle in a room of 11.46m × 11.60m, the circle being a square with 6 tiles of 1.10m on a side, i.e. 6.60 m. The five-pointed star in the figure is the four corners of the square to be moved, the coordinates of the lower left corner are (2.66m, 2.70m), the coordinates of the lower right corner are (9.26m, 2.70m), the coordinates of the upper left corner are (2.66m, 9.30m), and the coordinates of the upper right corner are (9.26m, 9.30 m). It can be seen that the five-pointed star point at the upper right corner is denser than other points, and the point is also the starting point of the circle, and then returns to the starting point along the counterclockwise direction. Taking into account the distance that the arm extends out and the shaking of the body when walking, the following graphically plots the sampling points on the four sides of the square.

Fig. 5 shows that a fixed point (6.00m ) is selected for sampling in a room of 11.46m × 11.60m (total sample amount is 11288), and the data is processed by removing the field value and eliminating the deviation, considering that the acquisition process is long and people in the room move to cause the influence of non-line-of-sight of the positioning system.

Fig. 6 is an error distribution of the fixed point sampling result in fig. 5, and it can be seen that the error distance between the sampling point and the real point (6.00m ) is distributed within 20 cm. The research content of the invention is an indoor positioning system based on the ultra-wideband technology. The acquisition of the positioning information needs to be completed by combining a ranging algorithm and a positioning algorithm. The existing distance measurement algorithm usually achieves the purpose of improving the precision by improving a solving expression of signal flight time, but the essential reason of the distance measurement error is the inconsistency of the working frequencies of system time counters of different equipment caused by the clock error of hardware equipment; the nonlinear iteration method in the existing positioning algorithm can approach the global optimal solution by an iteration mode through giving a proper initial value, but the initial value cannot be changed after being written into a chip, so that the flexibility of the positioning algorithm is reduced.

In order to solve the technical problems to be solved by the application, firstly, a distance measurement algorithm for indirectly estimating time resolution is provided, and the algorithm can update the working frequency of a device system time counter in real time in the positioning process, so that the algorithm simplifies the solving expression of signal flight time under the condition of improving the distance measurement precision; then, the problem that the initial value of the nonlinear iterative positioning algorithm is selected is solved by using the CHAN-least square algorithm, and based on the method, a user can obtain positioning information in real time when starting a label at any position in a room.

Based on the two proposed algorithms, the invention integrates a set of passive real-time positioning scheme, and the scheme can provide effective positioning information through verification, and the positioning error of the scheme is less than 20 centimeters.

Starting from the root cause of the ranging error, the distance information with the precision basically consistent with that of an AltDS-TWR algorithm is obtained by using the estimated time resolution of the equipment and the necessary timestamp information; then, a method for solving the problem of initial value selection of the nonlinear iterative algorithm by using CHAN-least squares is combined with a distance measurement method, so that a whole set of passive positioning scheme is formed.

TABLE 1

It should be noted that the detailed description is only for explaining and explaining the technical solution of the present invention, and the scope of protection of the claims is not limited thereby. It is intended that all such modifications and variations be included within the scope of the invention as defined in the following claims and the description.