CN111432335A - Control method of international trade port system - Google Patents

Control method of international trade port system Download PDF

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CN111432335A
CN111432335A CN202010248602.4A CN202010248602A CN111432335A CN 111432335 A CN111432335 A CN 111432335A CN 202010248602 A CN202010248602 A CN 202010248602A CN 111432335 A CN111432335 A CN 111432335A
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communication unit
transfer
signal
signal tower
trolley
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CN111432335B (en
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王芳
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Jilin Teachers Institute of Engineering and Technology
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Jilin Teachers Institute of Engineering and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H04W4/023—Services making use of location information using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]

Abstract

The invention relates to a control method of a system for an international trade port, which comprises a control unit, a signal tower, a transfer crane, a signal tower communication unit, a transfer crane communication unit, a transfer vehicle and a transfer vehicle label, wherein the signal tower is arranged on the signal tower; the control unit determines the position of the transfer crane, so that a mobile reader attached to the transfer crane can communicate with a reader of a signal tower, the control unit utilizes all read information from a fixed reader and the mobile reader, and based on a matrix least square fitting method, obtains real-time arrival angle estimation by adopting a frequency domain one-dimensional matrix algorithm, utilizes orthogonal frequency division multiplexing technology high-resolution estimation to carry out modeling, utilizes the characteristic of phase difference of adjacent subcarriers to improve estimation performance, inputs the estimation value into a weighted least square estimator to realize high-precision real-time positioning, can avoid the interference of a container stack to a trolley label, and improves the accuracy of the estimation of the position of the trolley.

Description

Control method of international trade port system
Technical Field
The invention relates to the field of trade logistics, in particular to a control method of a system for an international trade port.
Background
In recent years, with the increase of international trade throughput, the throughput of logistics terminals has become an important issue. Port terminals are the connection points for ground transportation and other vessels, and all containers are stored in the cargo yard as part of the logistics process. In container yards, port equipment such as transfer cranes and yard transfer trucks are used for shipping, unloading and transporting containers. The container cargo is usually temporarily stored in the port, and the container is collectively managed by the port. Cargo throughput is an important factor in evaluating logistics terminals. Therefore, it is very important to effectively manage the harbor containers. Real-time cargo tracking information is a basic element for logistics terminal management.
Existing wireless communication-based asset tracking systems estimate the location of a target in real-time by measuring the distance between a receiving device and a target transmitting device. The tracking system is composed of a tracking tag, a reader for receiving wireless signals and a tracking estimation control unit. The tag is attached to the transfer vehicle and a position estimate is generated by communication with the reader of the communication unit. The tracking estimation control unit calculates the position of the target or information received from the transmitting marker device. In port environments, most tags are attached to the tractor in the yard and therefore difficult to communicate with a sufficient number of readers.
In addition, the transfer trolley tracking system adopts 2.4GHz radio frequency wireless communication, and the communication range exceeds 300 m. The system is suitable for a port termination environment because a communication bandwidth is wide, but a method of determining a distance based on a signal arrival time has a large measurement error value when a wireless signal is reflected and scattered by a metal material. Furthermore, when the wireless tag cannot communicate with other readers, it cannot provide sufficient information to the server; in addition, because a large number of containers are stacked in the logistics terminal, the containers are often made of metal materials, and transmission of communication signals is affected, so that the tracking accuracy is greatly reduced.
Disclosure of Invention
The invention provides a control method for an international trade port, which solves the problems that in the prior art, port goods yards are difficult to communicate with a sufficient number of readers due to the low-density layout of signal towers and the obstacles of container piles, transfer car labels and the like.
The invention discloses a control method of a system for an international trade port, wherein the system comprises a control unit, a signal tower, a transfer crane, a signal tower communication unit, a transfer crane communication unit, a transfer vehicle and a transfer vehicle label;
the signal tower communication unit is arranged at the top of the signal tower, and the signal tower is fixedly arranged at a specific position of a port goods yard;
the transfer crane communication unit is arranged at the top of the transfer crane, and the transfer crane moves the transfer container in a port freight yard;
the transfer trolley moves back and forth between container piles in a port freight yard, and the transfer trolley label is arranged on the transfer trolley;
the signal tower communication unit transmits data with the transfer crane communication unit through a transmission path R1; the signal tower communication unit and the transfer crane communication unit transmit data between the transfer trolley label and the transfer trolley label through a transmission path R2;
the control method comprises the following steps:
s1: the control unit sends information to the signal tower communication unit and determines the position coordinate of the signal tower communication unit;
s2: the transfer crane communication unit sends a beacon message to the signal tower communication unit, and then the signal tower communication unit sends a confirmation message to the transfer crane communication unit;
s3: the transfer crane communication unit carries out ranging, measures the distance between the transfer crane communication unit and the signal tower communication unit, and then sends the distance information to the control unit;
s4: the control unit calculates the position coordinates of the transfer crane communication unit by using the distance information and the position coordinates of the signal tower communication unit;
s5: the transfer car label sends beacon messages to the signal tower communication unit and the transfer crane communication unit respectively; the signal tower communication unit and the transfer crane communication unit send confirmation messages to the transfer trolley label;
step S6: the transfer trolley tag carries out distance measurement, measures the distances from the transfer trolley tag to the signal tower communication unit and the transfer crane communication unit respectively, and determines the position of the transfer trolley;
step S7: the trolley tag transmits the measured position information of the trolley to the control unit.
Since the trolley tag provided on the trolley is difficult to communicate with the fixed signal tower communication unit, but the crane communication unit can realize the communication with the trolley tag, the real-time position of the trolley can be estimated by means of the crane communication unit even when the trolley and the signal tower are shielded by the container stack.
Preferably, code readers are arranged in the signal tower communication unit and the transfer crane communication unit to realize communication with the transfer trolley label.
Preferably, the number of the signal towers is more than 4, and the number of the transfer cranes is more than 2. This is due to the fact that the trilateration method for locating the position of the trolley requires communication with the code readers of at least three communication units to estimate the position of the trolley tag. Trilateration requires the use of at least three readers and at least three distances between the cart tag and the readers to calculate position. The control unit continues to use the location of the tags to track port cargo.
In step S6, in order to measure the distance between the tag and the reader, the signal arrival time T needs to be measuredOASum signal angle of arrival AOA. When the label sends a wireless signal to the code reader, and the code reader receives the signal, the propagation speed value of the signal and the arrival time T of the signal are usedOASum signal angle of arrival AOAThe distance is calculated.
D＝VRF*f(TOA，AOA) (1)
Wherein, f (T)OA，AOA) For signal arrival time TOASum signal angle of arrival AOAA function of the composition.
Preferably, the reader and the transfer car tag communicate wirelessly based on IEEE 802.15.4 a. The propagation speed of the signal is equal to the speed of light, and the signal can be transmitted within a distance of 1 meter within 33 nanoseconds. Therefore, in order to obtain an accurate distance value, it is necessary to perform accurate measurement of the signal. The accurate propagation time is measured by applying the IEEE 802.15.4a physical layer to the device. The IEEE 802.15.4a standard uses a chirp spread spectrum technique to minimize the multipath signal problem that causes the ranging error.
The control method of the system for international trade port of the present invention increases the possibility of the tag reader receiving information by using an additional reader attached to a transfer crane, which has mobility, and the control unit estimates the position of the transfer crane before estimating the tag position, since the transfer crane must straddle the top of the container stack, the transfer crane can communicate with the cell tower reader without interference above the stack of containers, the control unit determines the position of the transfer crane, so that a mobile reader attached to the transfer crane can communicate with the reader of the beacon, the control unit estimates the position of the trolley tag hierarchically using all the read information from the fixed reader and the mobile reader, avoiding the interference of the trolley tag by the stack of containers; in addition, based on a matrix least square method fitting method, a frequency domain one-dimensional matrix algorithm is adopted to obtain real-time arrival angle estimation, modeling is carried out by utilizing high-resolution estimation of an orthogonal frequency division multiplexing technology, estimation performance is improved by utilizing the characteristic of phase difference of adjacent subcarriers, high-precision real-time positioning is realized by inputting an estimation value into a weighted least square estimator, and the accuracy of position estimation of a transfer trolley is improved.
Drawings
Fig. 1 is a flowchart of a control method of a system for an international trade port according to the present invention.
Fig. 2 is a schematic diagram of a system for an international trade port of the present invention.
Fig. 3 is a schematic diagram of a linear array receiver of the transfer vehicle of the present invention receiving multipath signals.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
As shown in fig. 1, the control method of the system for the international trade port of the present invention, wherein the system comprises a control unit, a signal tower 1, a transfer crane 2, a signal tower communication unit 3, a transfer crane communication unit 4, a transfer car 5, a transfer car tag 6;
the signal tower communication unit 3 is arranged at the top of the signal tower, and the signal tower 1 is fixedly arranged at a specific position of a port freight yard;
the transfer crane communication unit 4 is arranged at the top of the transfer crane 2, and the transfer crane 2 moves the transfer container in the port freight yard;
the transfer trolley 5 moves back and forth between container piles 7 in a port freight yard, and a transfer trolley label 6 is arranged on the transfer trolley 5;
wherein, the signal tower communication unit 3 transmits data with the transfer crane communication unit 4 through a transmission path R1; the signal tower communication unit 3 and the transfer crane communication unit 4 transmit data to and from the transfer car tag 6 through the transmission path R2.
As shown in fig. 2, wherein the control method comprises the following steps:
s1: the control unit sends information to the signal tower communication unit 3 and determines the position coordinates of the signal tower communication unit 3;
s2: the transfer crane communication unit 4 sends a beacon message to the signal tower communication unit 3, and then the signal tower communication unit 3 sends a confirmation message to the transfer crane communication unit 4;
s3: the transfer crane communication unit 4 carries out ranging, measures the distance between the transfer crane communication unit 4 and the signal tower communication unit 3, and then the transfer crane communication unit 4 sends the distance information to the control unit;
s4: the control unit calculates the position coordinates of the transfer crane communication unit 4 using the distance information and the position coordinates of the signal tower communication unit 3;
s5: the transfer car label 6 sends a beacon message to the signal tower communication unit 3 and the transfer crane communication unit 4 respectively; the signal tower communication unit 3 and the transfer crane communication unit 4 send confirmation messages to the transfer trolley label 6;
step S6: the transfer trolley tag carries out distance measurement, measures the distances from the transfer trolley tag to the signal tower communication unit and the transfer crane communication unit respectively, and determines the position of the transfer trolley;
step S7: the trolley tag transmits the measured position information of the trolley to the control unit.
Fig. 1 shows how the trolley number tag 6 communicates with the signal tower communication unit 3 and the transfer crane communication unit 4, and the trolley number tag 6 provided on the trolley 5 is difficult to communicate with the fixed signal tower communication unit 3, whereas the crane communication unit 4 can perform communication with the trolley number tag 6, so that the real-time position of the trolley 5 can be estimated by means of the crane communication unit 4 even when the space between the trolley and the signal tower is hidden by the stack of containers.
Preferably, code readers are arranged in the signal tower communication unit 3 and the transfer crane communication unit 4 to realize communication with the transfer trolley tag 6.
Preferably, the number of the signal towers 1 is more than 4, and the number of the transfer cranes 2 is more than 2. This is due to the fact that the trilateration method for locating the position of the trolley 5 requires communication with the code readers of at least three communication units to estimate the position of the trolley tag 6. Trilateration requires the use of at least three readers and at least three distances between the cart tag and the readers to calculate position. The control unit continues to use the location of the tags to track port cargo.
Preferably, the reader and the transfer car tag communicate wirelessly based on IEEE 802.15.4 a. The propagation speed of the signal is equal to the speed of light, and the signal can be transmitted within a distance of 1 meter within 33 nanoseconds. Therefore, in order to obtain an accurate distance value, it is necessary to perform accurate measurement of the signal. The accurate propagation time is measured by applying the IEEE 802.15.4a physical layer to the device. The IEEE 802.15.4a standard uses a chirp spread spectrum technique to minimize the multipath signal problem that causes the ranging error.
In step S6, in order to measure the distance between the tag and the reader, the signal arrival time T needs to be measuredOASum signal angle of arrival AOA. When the label sends a wireless signal to the code reader, and the code reader receives the signal, the propagation speed value of the signal and the arrival time T of the signal are usedOASum signal angle of arrival AOAThe distance is calculated.
D＝VRF*f(TOA，AOA) (1)
Wherein, f (T)OA，AOA) For signal arrival time TOASum signal angle of arrival AOAA function of the composition.
As shown in fig. 3, the transfer car 5 is equipped with a uniform linear array receiver of M antenna elements for receiving multipath signals. The transfer trolley 5 is provided with a uniform linear array receiver (the array direction is orthogonal to the motion direction of the vehicle) of M antenna array elements for receiving beacon data sent by the signal tower communication unit 3 and the transfer crane communication unit 4 and estimating the signal arrival time T of a transmission channelOASum signal angle of arrival AOAAnd (4) parameters. Meanwhile, the transfer trolley 5 is also provided with an inertia sensing device, so that the self speed information including the amplitude and the direction of the speed can be acquired in real time.
Further, step S6 includes:
step S61: least squares estimation of channel frequency response:
due to the influence of obstacle reflection and the like, P transmission paths are shared among the signal tower communication unit 3, the transfer crane communication unit 4 and the transfer car 5, one path with the strongest energy is a line-of-sight transmission propagation path, and the rest paths are non-line-of-sight transmission propagation paths. Using the preamble of the frame in the ofdm technique in the received beacon data to measure the transmission channel information, the least squares estimate of the channel frequency response on the kth ofdm sub-carrier and the mth array receiver element can be expressed as:
Figure RE-GDA0002486293620000061
wherein, γp，τpAnd thetapRespectively representing the transmission gain, the propagation delay and the arrival angle on the p path; p ═1，2，···，P；
Figure BDA0002432967470000062
Representing the array response at the mth antenna element, M-0, 1, ·, M-1; tau ism(θp)＝mτ(θp)＝mdsinθpC represents the difference of the propagation delay of the p path between the m antenna array element and the reference array element; the parameter d is the distance between adjacent array elements; c is the propagation velocity of the electric wave; f. ofkRepresents the carrier frequency of the k-th subcarrier; w is am，kMeans mean zero and variance
Figure BDA0002432967470000063
White additive gaussian noise. In general, gamma of different pathspAre considered to be independent of each other, but when the frequency spacing between adjacent subcarriers is greater than the coherence bandwidth, the attenuation between subcarriers is also independent of each other, and can therefore be represented by gammak，pTo replace gammap. Considering that in antenna design, the spacing d between elements is usually equal to half the wavelength of the incident signal, so that d is c/(2 f)c) Thus, therefore, it is
Figure BDA0002432967470000064
Can be simplified into
Figure BDA0002432967470000071
Meanwhile, because the interval of the antenna array elements is far smaller than the length of the propagation path, and the influence of the propagation delay among the array elements on the channel frequency response is far smaller than the influence of the propagation delay of the path, the channel frequency response estimation of the receiving end can be further simplified as follows:
Figure BDA0002432967470000072
step S62: signal arrival angle A by using matrix algorithmOAEstimating:
in order to apply high resolution estimation, the channel frequency response estimation matrix expression (3) measured at the receiving end is first described as X ═ X0，x1，…，xK-1]The k-th column of the matrix is represented as
Figure BDA0002432967470000073
Figure BDA0002432967470000074
Written in vector form:
xk＝Vak+wk(4)
wherein the content of the first and second substances,
Figure BDA0002432967470000075
and wk＝[w0，k，w1，k，…，wM-1，k]TRespectively representing a received signal and a noise vector, V ═ V (θ)1)，v(θ2)，…，v(θP)]Is a steering vector of an array, and has
Figure BDA0002432967470000076
Sampling covariance matrix
Figure BDA0002432967470000077
Expressed as:
Figure BDA0002432967470000078
to pair
Figure BDA0002432967470000079
And (3) carrying out characteristic value decomposition, namely:
Figure BDA00024329674700000710
wherein, ∑s＝diag(λ0，λ1，…，λP-1) Is composed of
Figure BDA00024329674700000711
Middle P larger feature values, remaining featuresThe value is ∑n＝diag(λP，λP+1，…，λM-1) And (4) showing. U shapes＝[u0，u1，…，uP-1]To correspond to ∑sForming a matrix by a matrix composed of eigenvectors of P larger eigenvalues
Figure BDA00024329674700000712
The signal subspace of (1). The subspace dimension P may be given by some estimation algorithm based on information theoretic criteria.
Un＝[uP，uP+1，…，uM-1]A noise subspace is formed for a matrix consisting of eigenvectors corresponding to the other M-P eigenvalues. Let U1And U2The matrix obtained after deleting the last row and the 1 st row of elements in U (n), respectively, so the matrix in the spatial dimension can be expressed as U2-ξU1Angle of arrival A of the multipath signalOAInformation may be represented by a matrix
Figure BDA0002432967470000081
The generalized eigenvalue decomposition and extraction is shown as formula (7):
Figure BDA0002432967470000082
wherein the content of the first and second substances,
Figure BDA0002432967470000083
is represented as being located in
Figure BDA0002432967470000084
A feature vector of null space, corresponding to a feature value of
Figure BDA0002432967470000085
So that the multipath signal arrival angle A can be obtainedOAThe estimation of (d) is:
Figure BDA0002432967470000086
where arg (·) represents an operation of calculating a phase angle.
Step S63: signal arrival time T using curve fittingOAEstimating:
after obtaining the signal arrival angle AOAAfter estimation, the channel frequency response matrix is transformed into a path information matrix of one frequency domain [ a [ ]0，a1，…，aK-1]Therefore, the arrival time T of the signal with low complexity and high resolution can be realized by frequency diversity characteristic and curve fitting technologyOAEstimate. multipath pole ξ has been obtained previouslypIgnoring the noise term, the kth column of the channel frequency response can be written as:
Figure BDA0002432967470000087
where equation (9) can be derived from the previous equation, in equation (9), the path vector a is obtained by a complex least squares solutionk＝[αk，1，αk，2，…，αk，P]TIs estimated, wherein
Figure BDA0002432967470000088
As shown in the following equation (10):
Figure BDA0002432967470000089
wherein, akEach element of (a) contains a complex path fading component yk，pAnd phase component
Figure BDA0002432967470000091
The path fading expression is rewritten as: gamma rayk，p＝ρp(4πfkτp)-1Where ρ ispRepresenting the environmental factor of the p-th path. Thus, akElement α corresponding to the p-th path and the k-th subcarrierk，pCan be expressed as:
Figure BDA0002432967470000092
where ρ ispAnd τpAre all unknown parameters to be estimated αk，pAnd the estimated parameters in equation (10)
Figure BDA0002432967470000093
Fitting is performed according to a least squares method, whereupon the signal arrival time TOAThe estimation can be modeled as a curve fitting problem with an objective function defined as:
Figure BDA0002432967470000094
wherein q is (ρ)1，…，ρP，τ1，…，τP) Is a set of unknown parameters, muk(q) represents the independent fitting error on each subcarrier, and the expression is:
Figure BDA0002432967470000095
wherein, bk，p＝2πfkτpP is 1, 2, …, P, and solving the fitting function to obtain the required multipath signal arrival time TOAEstimated value
Figure BDA0002432967470000096
In equation (13), the phase difference between adjacent subcarrier path information is used as the input to the fitting function to ensure αk，pInput phase of
Figure BDA0002432967470000097
The phases of (a) and (b) are kept consistent. Therefore, equation (13) is modified as:
Figure BDA0002432967470000098
wherein d ═ (τ)1，τ2，…，τP) To include the desired signal arrival time TOAAn unknown vector of parameters. The objective function of the fitting problem is then rewritten as:
Figure BDA0002432967470000101
wherein the overdetermined condition is also changed to K ≧ P + 1. Output of curve fitting d*I.e. the multipath signal arrival time TOAEstimation of information to locate the signal arrival time T of the desired line-of-sight pathOAEstimating
Figure BDA0002432967470000102
Is then d*Minimum value of (1).
Step S64: and (3) estimating the position of the transfer trolley by using a weighted least square method:
signal arrival time T at which line-of-sight path is obtainedOASum signal angle of arrival AOAAfter estimating the value, another pR＝[xR，yR]TRepresenting the known position vectors of the signal tower communication unit 3 and the transfer crane communication unit 4. The current position vector p of the transfer vehicle 5 is x, y]TCan be expressed as:
Figure BDA0002432967470000103
wherein the content of the first and second substances,
Figure BDA0002432967470000104
the included angle between the incident wave and the positive direction of the x axis is expressed, and the% is the operation of solving the modulus.
Figure BDA0002432967470000105
And
Figure BDA0002432967470000106
respectively representing the angle of arrival A of the signalOAAn estimated value of (c) and a heading angle of the vehicle movement. Let [ v ]x，vy]TRepresenting the velocity vector of the vehicle, the heading angle can be described as:
Figure BDA0002432967470000107
in order to further improve the positioning performance, the motion model and the speed information of the fused vehicle are considered, and a weighted least square estimator is adopted to process the position estimation obtained by the formula (16). Let { tkI k |, 0, 1, … } represents the time when the beacon data transmitted by the signal tower communication unit 3 and the transfer crane communication unit 4 reaches the receiving-end array antenna of the transfer vehicle 5. By using
Figure BDA0002432967470000108
And
Figure BDA0002432967470000109
respectively, the transfer trolley 5 at t0And tkThe location of the time of day. While assuming that the speed of the target vehicle remains constant during each time interval, let [ vx(tk)，vy(tk)]TIs represented by [ tk，tk+1) The velocity vector of the trolley 5 over the time period, then a kinematic model can be obtained as (18):
Figure BDA0002432967470000111
where Δ t represents the length of the time interval.
When calculating the position of the transport vehicle 5 at any time, the position vector p (t) at the initial time is known, since the speed information is known0) Is unknown, can be calculated by an estimate of equation (18):
Figure BDA0002432967470000112
wherein the content of the first and second substances,
Figure BDA0002432967470000113
is tiThe time of day is estimated by the step 1 weighted least squares method to obtain a coarse position estimate, p (t)i) (ii) a Is a position vector calculated by equation (18).
Figure BDA0002432967470000114
Is represented at tiThe signal-to-noise ratio measured from the received signal at that time. Finally, the unknown vector can be solved by the least square method:
Figure BDA0002432967470000115
in summary, a method for controlling a system for an international trade port according to the present invention increases the possibility of a tag reader receiving information by using an additional reader attached to a transfer crane, which has mobility, the control unit estimates the position of the transfer crane before estimating the tag position, since the transfer crane must straddle the top of a stack of containers, the transfer crane can communicate with the signal tower reader without interference above the stack of containers, the control unit determines the position of the transfer crane, so that a mobile reader attached to the transfer crane can communicate with the reader of the beacon, the control unit estimates the position of the trolley tag hierarchically using all the read information from the fixed reader and the mobile reader, avoiding the interference of the trolley tag by the stack of containers; in addition, based on a matrix least square method fitting method, a frequency domain one-dimensional matrix algorithm is adopted to obtain real-time arrival angle estimation, an orthogonal frequency division multiplexing technology is used for high-resolution estimation to build a model, the characteristic of phase difference of adjacent subcarriers is used for improving the estimation performance, the estimation value is input into a weighted minimum two-times estimator to realize high-precision real-time positioning, and the accuracy of the position estimation of the transfer trolley is improved.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims (4)

1. A control method of a system for an international trade port is disclosed, wherein the system comprises a control unit, a signal tower (1), a transfer crane (2), a signal tower communication unit (3), a transfer crane communication unit (4), a transfer trolley (5) and a transfer trolley label (6); the method is characterized in that:
the signal tower communication unit (3) is arranged at the top of the signal tower, and the signal tower (1) is fixedly arranged at a specific position of a port goods yard; the transfer crane communication unit (4) is arranged at the top of the transfer crane (2), and the transfer crane (2) moves the transfer container in the port freight yard; the transfer trolley (5) moves in a shuttling way among container piles (7) in a port freight yard, and the transfer trolley label (6) is arranged on the transfer trolley (5); wherein, the signal tower communication unit (3) transmits data with the transfer crane communication unit 4 through a transmission path (R1); the signal tower communication unit (3) and the transfer crane communication unit (4) transmit data between the transfer trolley label (6) and the transfer trolley label (R2) through a transmission path; the control method comprises the following steps:
step S1: the control unit sends information to the signal tower communication unit (3) and determines the position coordinate of the signal tower communication unit (3);
step S2: the transfer crane communication unit (4) sends a beacon message to the signal tower communication unit (3), and then the signal tower communication unit (3) sends a confirmation message to the transfer crane communication unit (4);
step S3: the transfer crane communication unit (4) carries out ranging, measures the distance between the transfer crane communication unit and the signal tower communication unit (3), and then the transfer crane communication unit (4) sends the distance information to the control unit;
step S4: the control unit calculates the position coordinates of the transfer crane communication unit (4) by using the distance information and the position coordinates of the signal tower communication unit (3);
step S5: the transfer car label (6) sends beacon messages to the signal tower communication unit (3) and the transfer crane communication unit (4) respectively; the signal tower communication unit (3) and the transfer crane communication unit (4) send confirmation messages to the transfer trolley label (6);
step S6: the transfer trolley tag (6) carries out ranging, measures the distances from the transfer trolley tag (6) to the signal tower communication unit (3) and the transfer crane communication unit (4) respectively, and determines the position of the transfer trolley (5);
step S7: the transfer trolley label (6) sends the measured position information of the transfer trolley (5) to the control unit;
wherein step S6 uses the propagation velocity value of the signal and the signal arrival time TOASum signal angle of arrival AOATo calculate the distance;
D＝VRF*f(TOA，AOA) (1)
wherein, f (T)OA，AOA) For signal arrival time TOASum signal angle of arrival AOAA function of composition; step S6 specifically includes:
step S61: least squares estimation of channel frequency response:
using the preamble of the frame in the ofdm technique in the received beacon data to measure the transmission channel information, the least squares estimate of the channel frequency response on the kth ofdm sub-carrier and the mth array receiver element can be expressed as:
Figure FDA0002432967460000021
wherein, γp，τpAnd thetapRespectively representing the transmission gain, the propagation delay and the arrival angle on the p path;
Figure FDA0002432967460000022
representing the array response at the m-th antenna element, τm(θp)＝mτ(θp)＝md sinθpC represents the difference of the propagation delay of the p path between the m antenna element and the reference element; the parameter d is the distance between adjacent array elements; c is the propagation velocity of the electric wave; f. ofkRepresents the carrier frequency of the k-th subcarrier; w is am，kMeans mean zero and variance
Figure FDA0002432967460000023
Additive white gaussian noise of (1);
step S62: using matrix algorithmsAngle of arrival a of a line signalOAEstimating:
multipath signal angle of arrival aOAInformation may be represented by a matrix
Figure FDA0002432967460000024
The generalized eigenvalue decomposition and extraction is shown as formula (7):
Figure FDA0002432967460000025
wherein the content of the first and second substances,
Figure FDA0002432967460000026
is represented as being located in
Figure FDA0002432967460000027
A feature vector of null space, corresponding to a feature value of
Figure FDA0002432967460000028
So that the multipath signal arrival angle A can be obtainedOAThe estimation of (d) is:
Figure FDA0002432967460000029
wherein arg (·) represents an operation of calculating a phase angle;
step S63: signal arrival time T using curve fittingOAEstimating:
Figure FDA0002432967460000031
wherein the content of the first and second substances,
Figure FDA0002432967460000038
to include the desired signal arrival time TOAAn unknown vector of parameters; the objective function of the fitting problem is:
Figure FDA0002432967460000032
wherein, the overdetermined condition is also changed to K is more than or equal to P + 1; output of curve fitting d*I.e. the multipath signal arrival time TOAEstimation of information to locate the signal arrival time T of the desired line-of-sight pathOAEstimating
Figure FDA0002432967460000033
Is then d*Minimum value of (1);
step S64: and (3) estimating the position of the transfer trolley by using a weighted least square method:
from the velocity vector of the trolley 5, a kinematic model is obtained as shown in equation (17):
Figure FDA0002432967460000034
wherein Δ t represents the length of the time interval;
calculating the position of the trolley (5) at any time, by estimation of equation (18):
Figure FDA0002432967460000035
wherein the content of the first and second substances,
Figure FDA0002432967460000036
is tiThe time of day is estimated by the step 1 weighted least squares method to obtain a coarse position estimate, p (t)i) Is a position vector calculated by equation (18);
Figure FDA0002432967460000037
is represented at tiSignal-to-noise ratio measured from the received signal at the moment; the position of the transfer trolley (5) at any moment is solved by a least square method to obtain:
Figure FDA0002432967460000041
Figure FDA0002432967460000042
2. a control method of a system for international trade port according to claim 1, characterized in that code readers are provided in the signal tower communication unit (3) and the transfer crane communication unit (4) to communicate with the transfer car tag (6).
3. A method of controlling a system for international port of trade according to claims 1-2, characterized in that the reader and the trolley tag (6) are based on IEEE 802.15.4a wireless communication.
4. A control method of a system for international trade port according to claims 1-4, characterized in that the uniform linear array receiver equipped with M antenna elements of the transfer car (5) receives the beacon data transmitted by the signal tower communication unit (3) and the transfer crane communication unit (4) for estimating the signal arrival time T of the transmission channelOASum signal angle of arrival AOAAnd (4) parameters.
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