CN110133584A - One kind being based on passive reflective signal high precision hand-written trajectory track method in real time - Google Patents
One kind being based on passive reflective signal high precision hand-written trajectory track method in real time Download PDFInfo
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Abstract
The invention discloses one kind to be based on passive reflective signal high precision hand-written trajectory track method in real time, for including a passive backscatter tag, first deployment passive reflective tracking scene of the receiving end of the transmitting terminal and two signals of one signal and including a passive backscatter tag, in second deployment passive reflective tracking scene of the receiving end of the transmitting terminal and three signals of one signal, the following steps are included: step a, confirm that the passive reflective tracking scene is that the first deployment passive reflective tracks scene, or the second deployment passive reflective tracks scene, scene is tracked if the first deployment passive reflective, then carry out step b, scene is tracked if the second deployment passive reflective, then carry out step c；Step b carries out processing by the first tracing model and tracks real-time handwriting tracks；Step c carries out processing by the second tracing model and tracks real-time handwriting tracks.The method for tracing can realize the high-precision trajectory track of grade with low cost and single system.
Description
Technical Field
The invention relates to the field of track tracking of wireless sensing, in particular to a high-precision real-time handwriting track tracking method based on passive reflection signals.
Background
Video-based approaches, such as those of Kinect and Leap motion, often require specialized equipment and are susceptible to relationship conditions and indoor layout. Electronic blackboards or other similar technologies are often very expensive and maintenance overhead is large. While the inertial sensor based system is low in overhead and easy to deploy, it is very error, e.g. its cumulative error over 6s may be as high as 60cm, clearly not usable in accurate tracking positioning. Recently, some sound-based systems have been proposed, such as Vernier's solution, which can achieve trace-tracking accuracy on the millimeter level, but unfortunately, there are many practical problems with using sound signals, such as: the low-frequency sound signals are easily interfered by environmental noise, the high precision cannot be achieved in practical application scenes, the high-frequency ultrasonic signals have strong directivity and are possibly harmful to animals (the hearing range of a dog is 15-50000 Hz, and the hearing range of a cat is 60-65000 Hz).
With more and more wireless devices deployed in home and work environments, a recent trend is to use Radio Frequency (Radio Frequency) signals for tracking the movement trajectory. RFID-based systems, such as those proposed by Tagoram, Tadar, RF-finger, etc., are generally limited in sampling rate and cannot track objects moving at high speed with high accuracy. Even with the tag array, the error is on the order of centimeters. Meanwhile, existing WiFi-based trajectory tracking systems typically require multiple antennas and errors on the order of decimeters, such as: the WiDraw solution uses 25-antenna Angle-of-arrival (aoa) technology to implement a tracking system with 5cm error, while the WiTag solution uses only 2 APs but may have an error exceeding 1 m. Other rf-based systems, such as those utilizing 60GHz wireless technology, suffer from fast signal attenuation, high overhead, and hardware platform limitations. The solution proposed by WiTrack uses a dedicated FMCW (Frequency-Modulated Continuous-Wave)1.79GHz bandwidth radar to track body movements behind the wall, but with errors up to 20 cm. Therefore, the current handwriting trace tracking scheme has the problem that special equipment is needed, so that the system is complex or has large errors.
Disclosure of Invention
Based on the problems in the prior art, the invention aims to provide a high-precision real-time handwriting track tracking method based on passive reflection signals, which can realize quick and precise handwriting track tracking at lower cost.
The purpose of the invention is realized by the following technical scheme:
the embodiment of the invention provides a high-precision real-time handwriting trajectory tracking method based on a passive reflection signal, which is used in a first deployed passive reflection tracking scene comprising a passive backscatter tag, a signal sending end and two signal receiving ends and a second deployed passive reflection tracking scene comprising a passive backscatter tag, a signal sending end and three signal receiving ends, and comprises the following steps:
step a, confirming whether the passive reflection tracking scene is a first deployment passive reflection tracking scene or a second deployment passive reflection tracking scene, if the passive reflection tracking scene is the first deployment passive reflection tracking scene, performing step b, and if the passive reflection tracking scene is the second deployment passive reflection tracking scene, performing step c;
b, in the first deployment passive reflection tracking scene, a signal sending end is positioned on a connecting line of two signal receiving ends, and after the two receiving ends receive reflection signals of the sending end reflected by the passive backscatter tag, a real-time handwriting track is processed and tracked through a first tracking model;
and c, in the second deployment passive reflection tracking scene, the signal sending end is positioned at any position in the connecting area of the three signal receiving ends, and after the three signal receiving devices receive the reflection signals of the passive reflection labels, the real-time handwriting track is processed and tracked through a second tracking model.
According to the technical scheme provided by the invention, the high-precision real-time handwriting track tracking method based on the passive reflection signal has the beneficial effects that:
the tracking method utilizes the working mode of wireless reflection, removes the constraint of a communication protocol and communication overhead, can effectively improve the sampling rate and realize millimeter-grade high-precision track tracking; moreover, no learning and training process is needed; the tracking of high-speed moving objects is supported, and the tracking of any track is supported; if the system can be deployed more widely, the application prospect in the Internet of things can be effectively expanded.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flowchart of a high-precision real-time handwriting trajectory tracking method based on passive reflected signals according to an embodiment of the present invention;
fig. 2 is a schematic view of an application scenario of the trajectory tracking method according to the embodiment of the present invention;
fig. 3 is a schematic view of an application scenario of the trajectory tracking method according to the embodiment of the present invention;
fig. 4 is a schematic view of an application scenario of the trajectory tracking method according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the specific contents of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention. Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art.
As shown in fig. 1, an embodiment of the present invention provides a passive reflection signal-based high-precision real-time handwriting trajectory tracking method, which is used in a first deployed passive reflection tracking scenario including a passive backscatter tag, a signal transmitting end, and two signal receiving ends, and a second deployed passive reflection tracking scenario including a passive backscatter tag, a signal transmitting end, and three signal receiving ends, and includes the following steps:
step a, confirming whether the passive reflection tracking scene is a first deployment passive reflection tracking scene or a second deployment passive reflection tracking scene, if the passive reflection tracking scene is the first deployment passive reflection tracking scene, performing step b, and if the passive reflection tracking scene is the second deployment passive reflection tracking scene, performing step c;
b, in the first deployment passive reflection tracking scene, a signal sending end is positioned on a connecting line of two signal receiving ends, and after the two receiving ends receive reflection signals of the sending end reflected by the passive backscatter tag, a real-time handwriting track is processed and tracked through a first tracking model;
and c, in the second deployment passive reflection tracking scene, the signal sending end is positioned at any position in the connecting area of the three signal receiving ends, and after the three signal receiving devices receive the reflection signals of the passive reflection labels, the real-time handwriting track is processed and tracked through a second tracking model.
In step b of the method, a processing manner of the first tracking model (which may be referred to as a PDI-C model, and a label position estimation method is performed by using a phase difference iterative model (PDI-C) with a limited transmitting end position) includes:
a is used for single-tone sinusoidal signals transmitted by a transmitting end in the air0sin(ω0t+θ0) Is shown in phase with
Establishing a plane rectangular coordinate system, wherein A, B and 0 are used for respectively representing the position of the first receiving end, the position of the second receiving end and the position of the transmitting end; setting the position 0 of a transmitting end as a coordinate origin, and setting the coordinates of A and B as (-R,0) and (R,0), wherein R represents the linear distance from the transmitting end to one of receiving ends;
in the rectangular plane coordinate system, P is usedt(xt，yt) and Pt+1(xt+1，yt+1) To respectively represent the positions of the passive reflective tags at two adjacent times t and t + 1;
by dA、dB and dORespectively represent PtDistance from point A, B, O, d'A、d′B and d′ORespectively represent Pt+1Distance from point A, B, O;
by usingRespectively, passive backscatter tags from PtMove to Pt+1Distance traveled in time A, B, O;
the following equations are set forth in terms of the above parameters:
let ∠ Pt+1AO is α at Δ Pt+1The calculation of the AO by the cosine theorem is as follows:
at Δ PtAB and ΔPt+1And AB, calculating by using a median theorem to obtain:
by combining the above equations (2) and (3), the following equation (4) is obtained:
from the ith receiving end RxiFormula of acquired phase value
The phase of the received signal of the first receiving end is obtained as follows:
expand the above formula (5) The phase of (2) eliminates the influence of 2 pi radian period, wherein delta t represents the time interval of two adjacent sampling points, and the difference of angular frequency, namely omega is eliminated by synchronizing all receiving ends1＝ω2＝ω′；
Subtracting the upper and lower equations in equation (5) to obtain the phase differencePost-differencing cancellation device difference term θc；
Calculating the received signal phases of other receiving ends according to the same steps;
if specified, specifyAnd combining the results of equation (2) above, the result of the difference is rewritten as follows:
wherein By combining the above equations (4) and (6), a quadratic equation can be obtained as follows:
wherein ,dA、dB and dOThe above-mentioned definitions in equation (2), all of which are known quantities, can be solved
Finally, d 'is calculated by equations (2) and (6) above'AThe position of the passive backscatter tag at the time t +1 is obtained as follows:
wherein ,setting y to be less than or equal to 0; under the condition that the initial position p (0) is known, the position of the passive backscatter tag is obtained through iterative computation according to p (t +1) ═ f (p (t)), namely the real-time tracing of the handwriting track is completed.
Among the above methods, DAH (see Lei Yang, Yekui Chen, Xiang-Yang Li, Chaoweixiao, Mo Li, and Yunhao Liu.2014. tagoram: Real-time Tracking of Mobile RFID tag high-precision Using COTS devices in Proceedings of the20th and nuclear coherence on Mobile computing and networking ACM, 237-.
In step C of the method, a processing method of the second tracking model (which may be referred to as a PDI-a model, and a label position estimation method is performed by using a phase difference iterative model (PDI-C) at an arbitrary transmitting end position) includes:
a is used for single-tone sinusoidal signals transmitted by a transmitting end in the air0sin(ω0t+θ0) Is shown in phase with
Establishing a plane rectangular coordinate system, wherein A, B and 0 are used for respectively representing the position of the first receiving end, the position of the second receiving end and the position of the third receiving end; setting the position of a transmitting end as a coordinate origin, setting the coordinates of A and B as (-R,0) and (R,0), wherein R represents the linear distance from a third receiving end to the other two receiving ends, and the position of the transmitting end is arbitrarily arranged in the plane rectangular coordinate system;
in the rectangular plane coordinate system, P is usedt(xt，yt) and Pt+1(xt+1，yt+1) Respectively representing the positions of the passive reflection label at two adjacent moments t and t + 1;
by dA、dB and dORespectively represent PtDistance from point A, B, O, d'A、d′B and d′ORespectively represent Pt+1Distance from point A, B, O; wherein d isORepresenting a distance between the passive backscatter tag and a third receiving end;
by usingRespectively, passive backscatter tags from PtMove to Pt+1Distance traveled in time A, B, O;
by dTIndicating the distance between the position of the transmitting end and the passive backscatter tag;
the following equations are set forth in terms of the above parameters:
wherein ,θc1，θc2，θc3Representing the equipment difference item, and calculating to obtain:
wherein
Expressed by the third expression of the above equation (9)Obtaining:
by combining the above equations (9) and (10), the following equation (11) is obtained:
the simultaneous establishment of the above equations (11) and (10) yieldsLinear form solution of (c):
d 'is calculated by the above equations (8) and (9)'AThe position of the passive backscatter tag at the time t +1 is obtained as follows:
wherein ,setting y to be less than or equal to 0; under the condition that the initial position p (0) is known, the position of the passive backscatter tag is obtained through iterative computation according to p (t +1) ═ f (p (t)), namely the real-time tracing of the handwriting track is completed.
In the above method, the initial position of the passive backscatter tag may be calculated using a DAH or MOWI method.
The embodiments of the present invention are described in further detail below.
The embodiment of the invention provides a track tracking method, which is used for positioning a tag to realize track tracking by capturing the existing signal in the passive tag reflection space. The system applied by the method has 3 parts of deployment, as shown in figure 2,
wherein, TX represents a transmitting end, that is, a signal transmitter as a signal source, which is an energy source and may be a WiFi signal, a bluetooth signal, a TV broadcast signal, etc. widely existing in the space at present. Tx transmits a single tone sinusoidal signal over the air, with A0sin(ω0t+θ0) Is shown in phase with
The Tag is a passive backscatter Tag (hereinafter, referred to as a passive Tag for convenience of description), and may be composed of an antenna and a microcontroller, and the microcontroller can control an on (or off) state of the antenna, so that the antenna of the Tag switches back and forth between a reflective state and a non-reflective state, thereby generating a reflected signal of two frequency bands (a process of moving a frequency spectrum).
The energy of the reflected signal of the passive tag can be expressed as follows:
wherein Ptx and GtxRepresenting transmission energy and antenna gain at the transmitting end, d represents the distance between Tx and Tag, ΔΓShows the change in RCS (Radar Cross section) as follows:
wherein λ represents the wavelength of the signal, GtagRepresenting the antenna gain, Γ, of tag*The reflection coefficient is expressed, which is specifically expressed as follows:
wherein Za＝Ra+jXaIs the complex impedance of the antenna, and the impedance jumps between two values by controlling the on-off of the antenna, so as to generate a reflected signal, and the frequency of the impedance jump determines the cheap frequency of the reflected signal.
RX denotes the receiving end, and if Δ f denotes the frequency of the antenna on-off hopping, the frequency of the reflected signal is f + Δ f and f- Δ f (spectrum shifting). The receiving end can select one of the two frequencies to receive.
The signal generation utilizes the existing signal in the space, only needs an inexpensive passive reflection device to generate a new signal, and the reflected signal has weak energy and short working range, but can reduce the interference between systems in the space domain and can also control the offset frequency to avoid or reduce the interference of other channels in the frequency spectrum domain through controllable delta f.
The signal propagation model of the system is shown in FIG. 2, when the signal comes from Tx to reach Tag (distance is d)0Presentation), the phase of the signal will occurIn which λ iscRepresenting the carrier frequency. The signal is then backscattered by Tag to the receiver Rxi(distance d)iRepresents); due to spectral shift, the phase shift is expressed asIn addition to the phase shift of the rf signal due to propagation, the hardware circuitry (including all Tx, Tag, and Rx) introduces an additional phase shift, denoted as θTx，θTag and θRx(ii) a Thus the final receiving end RxiThe obtained phase value is wherein In addition, if clocks of a transmitting end and a receiving end cannot be synchronized, frequency offset is inevitably introduced; thus, at the receiving end RxiNeed to use omegaiTo replace omega0. Finally, the following is obtainedExpression (c):
wherein θciRepresenting a device difference term that is related to a hardware characteristic. Where the phase is a function of the period 2 pi. The phase value has a device diversity constant at different receiving endsFurther, the initial phase θ0Phase shift θ caused by the transmitting endTxTag induced phase shift θTagThe tracking method is an unknown parameter, the unknown parameter has great influence on the tracking and positioning result, and how to eliminate the influence is the key for ensuring the tracking accuracy and precision.
The existing traditional methods, such as ellipse-based and hyperbola-based models, face a plurality of problems in such systems, cannot eliminate the influence caused by equipment diversity, and are difficult to realize real-time calculation. Considering calculation and deployment costs, the invention provides two efficient Phase difference iterative algorithms (Phase Differential iterative scheme-PDI scheme), and deduces the position of the next moment by using the position and geometric information of the previous moment; the two schemes are called PDI-C (phase Differential Iterative Scheme with Constrained Locations of Transmitter) and PDI-A (phase Differential Iterative Scheme with ArbitraryLocations of Transmitter), respectively; the position of the transmitting end Tx in the PDI-C model is constrained, only two Rx are needed, and the position of the transmitting end Tx in the PDI-A model can be arbitrary, but three Rx are needed for realization. The application scenarios of the PDI-C model and the PDI-A model are shown in FIGS. 3 and 4, respectively.
The following specific descriptions of the processing procedures of the PDI-C model and the PDI-A model are as follows:
(A) the PDI-C model (Phase Differential induced Scheme with constrained locations of Transmitter) is specifically (i.e., the first tracking model):
in this model, Tx is placed on the line connecting two receiving ends Rx (constrained), as shown in fig. 3, Tx is placed at the midpoint of the two receiving ends to illustrate the operation principle, and then expanded to a more general case.
As shown in fig. 3, a planar rectangular coordinate system is established, where a, B, and 0 respectively represent a receiving end Rx1 position, a receiving end Rx2 position, and a transmitting end Tx position, the Tx position is designated as an origin of coordinates, and coordinates of a and B are (-R,0) and (R,0), where R represents a linear distance from the transmitting end to one of the receiving ends; at the same time, with Pt(xt，yt) and Pt+1(xt+1，yt+1) Respectively represents the position of 'Tag' at two adjacent times t and t + 1; dA，dB，dORespectively represent PtAnd the distance between points A, B, O, d'A，d′B，d′ORespectively represent Pt+1And the distance between points a, B, O.Denotes the 'Tag' from PtMove to Pt+1The distance of the movement to the direction of a,the same is true. Following these definitions, the following equations can be listed:
let ∠ Pt+1AO is α at Δ Pt+1The cosine theorem in AO can be used to obtain:
at Δ PtAB and ΔPt+1In AB, using the Apollonius theorem (median theorem) one can obtain:
simultaneous equations (2), (3) can yield:
from equation (1), the receiver' Rx can be obtained1The received signal phase of' is:
the phase is expanded to eliminate the influence of 2 pi radian period, delta t represents the time interval of two adjacent sampling points, and the angular frequency difference is eliminated by synchronizing all receiving ends, wherein the angular frequency difference is omega1＝ω2ω'. Subtracting the two equations above and below in equation (5) (i.e. performing phase difference) can obtain(to the receiving end' Rx)2The same applies to the calculation of'). The equipment difference item theta can be found by the difference methodcIs well eliminated. If specified, specifyAnd in conjunction with the results of equation (2), the results of the difference can be rewritten as follows:
wherein Simultaneous equations (4) and (6) can yield a twoThe equation of the order is as follows:
dA，dB，dOdefined in equation (2), are all known quantities, since equation (7) is with respect toCan be easily solved by the quadratic equation of one elementFinally, d 'can be calculated'ABy equations (2) and (6), the position of Tag at time t +1 is obtained as follows:
cos α has been defined above, where y is assumed to be ≦ 0. in fact, this process is an iterative process, with p (t +1) ≦ f (p (t)), where the position of Tag can be iteratively derived as long as the initial position p (0) is known, and is a linear time complexity.
(B) The PDI-A model (Phase Differential induced Scheme with ArbitraryLocations of Transmitter) (i.e. the second tracking model) is specifically:
the PDI-C model described above presents a simple and efficient Tag location tracking method, but if in most practical scenarios the location of Tx may not be controllable, it is expected that it can be arbitrarily placed/deployed, and thus the PDI-A model is further developed. In this model, a new receiver Rx is introduced at the origin, as shown in fig. 43To release Tx. In this model, most of the definitions in PDI-C, d, can be multiplexedA，dBHas no change in the meaning of (a), dOShown are Tag and Rx3R denotes the receiving end Rx3To two other receiving ends (Rx)1/Rx2) The distance of (c). At the same time, an additional variable d is introducedTIt represents the distance from Tx (at any position) to Tag. The same is as follows:
wherein ,θc1，θc2，θc3Representing the equipment difference term, similar to the analysis of equation (6) above, one can obtain:
wherein Compared with a PDI-C model, the method has one more new variableIt can be expressed by the third equation of equation (9), which yields:
in PDI-A, equation (4) is still true, and simultaneous equations (4) and (10) can be obtainedLinear form solution of (c):
the subsequent procedures are consistent with those of PDI-C, and are not described herein, it is noted that
The component omega' delta related to the time angular frequency and the sampling interval is eliminated by using a mode of twice differencetThis is very significant, in some extreme conditions, the angular frequency ω' and the sampling interval ΔtMay not be constant and their effect may be neglected. Furthermore, the processing of the PDI-C model remains linear and is lighter weight than the PDI-C model becauseHere a linear solution. The algorithm pseudo code corresponding to the PDI-A model processing process is as follows:
(C) and (4) other treatment:
(C1) kalman filtering:
in order to further remove noise and improve the track precision, the invention adopts a Kalman filtering model (see L.Wang, K.Sun, H.Dai, A.X.Liu, and X.Wang, WiTrace: center-Level Passive testing Using WiFi, IEEE SECON, 2018) based on 2D Continuous Wiener ProcessAccelaction (CWPA), and can process the condition that the acceleration of an object is disturbed by Gaussian noise. After the addition of the traditional kalman filtering step, the computational complexity is still linear.
(C2) Doppler effect:
the formula for the Doppler effect can be expressed as wherein voRepresenting the speed of movement, v, of the observersRepresenting the moving speed of the signal source, and f' representing the transmit frequency and the observation frequency, respectively. As shown in fig. 2, in the system of the present invention, the signal propagation is divided into two parts: tx → Tag and Tag → Rx. Taking Tag → Rx as an example (Tx → Tag the same way), v represents the propagation velocity of electromagnetic wave in air, and is about 3 × 108m/s，vsDenotes the speed of 'Tag' relative to Rx, voSince Rx is stationary in the present design. Thus, the effect of the Doppler effect can be expressed asDue to vsC, i.e.So f' ≈ f, where the effect of the doppler effect on the tracking accuracy is neglected.
(D) Generalizing to more general deployments:
the method of the invention supports a more liberal deployment in the application scenario of the device, in fig. 3, if Rx1 and Rx2Are respectively (-R)A0) and (0, R)5) At Δ Pt+1AO and ΔPt+1The cosine theorem for α in AB can be obtained:
finishing to obtain:
RBd′A 2+RAd′B 2＝(RA+RB)(d′O 2+RA*RB)；
it can be found that when R isA＝RBWhen R, this form is consistent with equation (3) (another equation can be derived by subtracting Δ PtAO and ΔPtAB middle pair ∠ PtAO using cosine theorem). Further, Tx is at Rx1Left, or Rx2The same relationship can be obtained on the right. Therefore, in the PDI-C model, the positional constraint on Tx is that it needs to be placed on the line between the two receivers, which can be considered a semi-free deployment. In PDI-a, Tx can be arbitrarily placed (mainly in the signal receiving range), and 3 receivers are placed on a single line, theoretically without distance limitation.
The tracking method of the invention utilizes the working mode of wireless reflection, removes the constraint of communication protocol and communication overhead, can effectively improve the sampling rate and can realize millimeter-grade high-precision track tracking; moreover, no learning and training process is needed; the tracking of high-speed moving objects is supported, and the tracking of any track is supported; if the system can be deployed more widely, the application prospect in the Internet of things can be effectively expanded.
Example (b):
the used devices in the step a are 1 passive reflection tag, 1 signal generator and a plurality of signal receiving devices. The number of signal receiving devices is 2 or 3 depending on the scene. If the position of the signal generator can be controlled, only 2 receiving devices are needed, and if the position of the signal generator is not controllable (arbitrary), 3 receiving devices are needed, and the arrangement mode is shown in fig. 3 and 4. If the position of the sending end is controllable, only 1 sending end and 2 receiving ends need to be deployed on one connecting line, and if the position of the sending end is not controllable, 3 receiving ends need to be deployed on one connecting line.
B, after the signal transceiver is deployed, the transmitting end generates a constant single-tone sinusoidal signal, the carrier frequency is f, the object with the tag is moved only by attaching the tag to the object with the tracking function (the object can be a hand, a commodity, a cargo and the like), meanwhile, the receiving end receives the signal, the frequency of the received signal is f + delta f or f-delta f, the delta f is the antenna impedance change frequency of the tag, and the frequency is controllable and can be set according to actual conditions. Multiple receiving devices require clock synchronization.
And C, after receiving the signal of the receiving end, processing the signal through the corresponding PDI-A model or PDI-C model to obtain the motion track of the label, thereby realizing track tracking.
Those of ordinary skill in the art will understand that: all or part of the processes of the methods for implementing the embodiments may be implemented by a program, which may be stored in a computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods as described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. A high-precision real-time handwriting trajectory tracking method based on passive reflection signals is characterized by being used in a first deployed passive reflection tracking scene comprising a passive backscatter tag, a signal sending end and two signal receiving ends and a second deployed passive reflection tracking scene comprising a passive backscatter tag, a signal sending end and three signal receiving ends, and comprising the following steps of:
step a, confirming whether the passive reflection tracking scene is a first deployment passive reflection tracking scene or a second deployment passive reflection tracking scene, if the passive reflection tracking scene is the first deployment passive reflection tracking scene, performing step b, and if the passive reflection tracking scene is the second deployment passive reflection tracking scene, performing step c;
b, in the first deployment passive reflection tracking scene, a signal sending end is positioned on a connecting line of two signal receiving ends, and after the two receiving ends receive reflection signals of the sending end reflected by the passive backscatter tag, a real-time handwriting track is processed and tracked through a first tracking model;
and c, in the second deployment passive reflection tracking scene, the signal sending end is positioned at any position in the connecting area of the three signal receiving ends, and after the three signal receiving devices receive the reflection signals of the passive reflection labels, the real-time handwriting track is processed and tracked through a second tracking model.
2. The passive reflected signal based high-precision real-time handwriting trajectory tracking method according to claim 1, wherein in step b of said method, the processing mode of the first tracking model comprises:
a is used for single-tone sinusoidal signals transmitted by a transmitting end in the air0sin(ω0t+θ0) Is shown in phase with
Establishing a plane rectangular coordinate system, wherein A, B and O are used for respectively representing the position of the first receiving end, the position of the second receiving end and the position of the transmitting end; setting the position O of a transmitting end as a coordinate origin, and coordinates of A and B as (-R,0) and (R,0), wherein R represents the linear distance from the transmitting end to one of receiving ends;
in the rectangular plane coordinate system, P is usedt(xt，yt) and Pt+1(xt+1，yt+1) To respectively represent the positions of the passive reflective tags at two adjacent times t and t + 1;
by dA、dB and dORespectively represent PtDistance from point A, B, O, d'A、d′B and d′ORespectively represent Pt+1Distance from point A, B, O;
by usingRespectively, passive backscatter tags from PtMove to Pt+1Distance traveled in time A, B, O;
the following equations are set forth in terms of the above parameters:
let ∠ Pt+1AO is α at Δ Pt+1The calculation of the AO by the cosine theorem is as follows:
at Δ PtAB and ΔPt+1And AB, calculating by using a median theorem to obtain:
by combining the above equations (2) and (3), the following equation (4) is obtained:
from the ith receiving end RxiFormula of acquired phase valueThe phase of the received signal of the first receiving end is obtained as follows:
the phase developed by the above equation (5) eliminates the influence of the2 π radian period, where Δ t represents the adjacencyThe time interval of two sampling points, by synchronizing all receivers, eliminates the difference in angular frequency, i.e. ω1＝ω2＝ω′；
Subtracting the upper and lower equations in equation (5) to obtain the phase difference
Post-differencing cancellation device difference term θc；
Calculating the received signal phases of other receiving ends according to the same steps;
if specified, specifyAnd combining the results of equation (2) above, the result of the difference is rewritten as follows:
wherein By combining the above equations (4) and (6), a quadratic equation can be obtained as follows:
wherein ,dA、dB and doThe above-mentioned definitions in equation (2), all of which are known quantities, can be solved
Finally, d 'is calculated by equations (2) and (6) above'AThe position of the passive backscatter tag at the time t +1 is obtained as follows:
wherein ,setting y to be less than or equal to 0; under the condition that the initial position p (0) is known, the position of the passive backscatter tag is obtained through iterative computation according to p (t +1) ═ f (p (t)), namely the real-time tracing of the handwriting track is completed.
3. The passive reflected signal-based high-precision real-time handwriting trajectory tracking method according to claim 2, characterized in that in said method, DAH or MOWI method is used to calculate initial position of passive backscatter tag, and Fast Fourier Transform (FFT) is used to estimate angular frequency ω'.
4. The passive reflected signal based high-precision real-time handwriting trajectory tracking method according to any one of claims 1 to 3, wherein in step c of said method, the second tracking model is processed in a manner that includes:
a is used for single-tone sinusoidal signals transmitted by a transmitting end in the air0sin(ω0t+θ0) Is shown in phase with
Establishing a plane rectangular coordinate system, wherein A, B and O respectively represent the position of the first receiving end, the position of the second receiving end and the position of the third receiving end; setting the position of a transmitting end as a coordinate origin, setting the coordinates of A and B as (-R,0) and (R,0), wherein R represents the linear distance from a third receiving end to the other two receiving ends, and the position of the transmitting end is arbitrarily arranged in the plane rectangular coordinate system;
in the rectangular plane coordinate system, P is usedt(xt，yt) and Pt+1(xt+1，yt+1) Respectively representing the positions of the passive reflection label at two adjacent moments t and t + 1;
by dA、dB and dOIndividual watchShow PtDistance from point A, B, O, d'A、d′B and d′ORespectively represent Pt+1Distance from point A, B, O; wherein d isORepresenting a distance between the passive backscatter tag and a third receiving end;
by usingRespectively, passive backscatter tags from PtMove to Pt+1Distance traveled in time A, B, O;
by dTIndicating the distance between the position of the transmitting end and the passive backscatter tag;
the following equations are set forth in terms of the above parameters:
wherein ,θc1，θc2，θc3Representing the equipment difference item, and calculating to obtain:
wherein
Expressed by the third expression of the above equation (9)Obtaining:
by combining the above equations (9) and (10), the following equation (11) is obtained:
the simultaneous establishment of the above equations (11) and (10) yieldsLinear form solution of (c):
d 'is calculated by the above equations (8) and (9)'AThe position of the passive backscatter tag at the time t +1 is obtained as follows:
wherein ,setting y to be less than or equal to 0; under the condition that the initial position p (0) is known, the position of the passive backscatter tag is obtained through iterative computation according to p (t +1) ═ f (p (t)), namely the real-time tracing of the handwriting track is completed.
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