Passive positioning method for port carriage

Abstract

The invention discloses a passive positioning method for a port pallet, and the method comprises the steps: enabling a GPS positioning module and an RFID reader-writer to be disposed on a pallet head of a first pallet truck, and enabling an RFID electronic tag to be disposed on a pallet of a second pallet truck; acquiring a dragging head coordinate value through the RFDI reader-writer; reading tag information of the RFID electronic tag based on the drag head coordinate value, and receiving a signal intensity value sent by the RFID reader-writer through the RFID electronic tag; acquiring an actual distance between the mop head and the RFID electronic tag based on the signal intensity value; and calculating the coordinate value of the RFID electronic tag by using the actual distance, and obtaining the actual position of the carriage. According to the method provided by the invention, the passive port carriage can be accurately positioned, and the maintenance cost of the passive port carriage is reduced.

Description

Technical Field

[0001] The invention relates to the field of passive positioning, and in particular to a passive positioning method for a port trailer. Background Art

[0002] Ports are the gathering points and hubs of land and water transportation with relatively low density of communication base stations. There are a large number of pallet trucks that need to participate in production operations. For the pallets on these pallet trucks, it is necessary to establish a very high operating order and obtain accurate operating positions, otherwise the loading efficiency will be low or even accidents will occur during the loading process. How to stably and accurately position the pallets on the pallet trucks at the centimeter level has become an urgent problem that major ports need to solve.

[0003] Normally, sub-meter GPS positioning modules are generally used to locate movable objects in ports, but the moving range of the located objects needs to be relatively large; LoRa technology can locate movable objects more accurately, with long positioning distance and low power consumption, but it requires multi-point positioning of movable objects, which has unavoidable shortcomings in terms of complexity of use and equipment maintenance; more importantly, the above technologies are only applicable to objects with continuous power supply. If you want to locate a pallet truck without continuous power supply, you can only use a low-power Bluetooth (BLE) module with its own battery, and use the ibeacon function or passive RFID tags to locate the pallet. Among them, the Bluetooth modules widely used for positioning are mainly Bluetooth beacons, which can be used in UWB (Ultra Wide Band) scenarios. However, the disadvantage of Bluetooth beacons is that they need to set up multiple base stations with dense spacing, and Bluetooth beacons need to be powered by batteries. Although the batteries can be used for about two years, the maintenance cost of the batteries is high because the pallet trucks are often outdoors when in use and have a high distribution range. In addition, since most pallet trucks are made of all-metal bodies, they have a great impact on the signals of Bluetooth beacons, so it is likely to cause the effective distance of signal transmission to become smaller, or even shortened to half of the normal distance. Therefore, a positioning method is needed to perform passive positioning of port pallets. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a passive positioning method for a port trailer, characterized by comprising:

[0005] A GPS positioning module and an RFID reader are installed on the tractor head of the first tractor, and an RFID electronic tag is installed on the tractor of the second tractor;

[0006] Acquire the coordinate value of the tractor head through the RFDI reader;

[0007] Reading the tag information of the RFID electronic tag based on the tractor coordinate value, and receiving the signal strength value sent by the RFID reader / writer through the RFID electronic tag;

[0008] Acquire the actual distance between the tractor and the RFID electronic tag based on the signal strength value;

[0009] The actual distance is used to calculate the coordinate value of the RFID electronic tag to obtain the actual position of the carriage.

[0010] Preferably, the GPS positioning module has an RTK function and is provided with an inertial guidance system. When the coordinate value of the tughead is obtained through the RFDI reader / writer, the GPS positioning module first compensates the coordinate value of the tughead through the RTK function, and then obtains the 6-axis acceleration of the tughead during operation through the MEMS gyroscope in the inertial guidance system and calculates the running trajectory of the tughead. Based on the running trajectory of the tughead and the coordinate value of the tughead after the coordinate value compensation is completed through the RTK function, the position of the tughead is further corrected.

[0011] Preferably, the formula for obtaining the actual distance between the tractor and the RFID electronic tag based on the RSSI signal value is:

[0012] D=200 (SIV-A) / 10n

[0013] Wherein, D is the actual distance; SIV is the signal strength value sent by the RFID reader when the RFID electronic tag receives it; A is the absolute value of the signal strength when the distance between the tractor and the towing board is 1 meter, and the value range is -15 to 25; n is the environmental attenuation factor, and the value range is 3.25 to 4.5.

[0014] Preferably, the tughead coordinate value is a coordinate value obtained by reading the RFDI reader once every time period when the tughead is in a moving state, including an initial longitude and latitude coordinate value, a secondary longitude and latitude coordinate value, and a tertiary longitude and latitude coordinate value; the signal strength value includes a first signal strength value, a second signal strength value, and a third signal strength value; the actual distance includes a first distance, a second distance, and a third distance.

[0015] Preferably, using the actual distance to calculate the coordinate value of the RFID electronic tag includes: using the initial longitude and latitude, secondary longitude and latitude, and tertiary longitude and latitude as basic coordinates, combining the first distance, the second distance, and the third distance to establish an RFID signal radiation model, and calculating the coordinate value of the RFID electronic tag according to the RFID signal radiation model.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention installs a GPS positioning module, an RFID reader and an RFID electronic tag on the tractor and the trailer respectively, obtains the RSSI value and the running track of the tractor, and indirectly determines the position information of the trailer by performing corresponding calculations on the running track, thereby providing an effective and accurate method for passive object position monitoring and reducing the cost of maintaining passive port trailers.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic flow chart of a passive positioning method for a port trailer provided in an embodiment of the present invention.

[0022] Figure 2 A schematic diagram of a tug structure of a passive positioning method for a port tug provided in an embodiment of the present invention.

[0023] Figure 3 A schematic diagram of a carriage structure of a passive positioning method for a port carriage provided by an embodiment of the present invention.

[0024] Figure 4 A schematic diagram of a tug moving trajectory of a passive positioning method for a port tug provided in an embodiment of the present invention.

[0025] Figure 5 Another schematic diagram of the moving track of a tughead in a passive positioning method for a port tug provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] To facilitate understanding of this embodiment, Figure 1 A passive positioning method for a port trailer disclosed in an embodiment of the present invention is introduced in detail.

[0028] Embodiment 1:

[0029] S1: Install a GPS positioning module and an RFID reader / writer on the tractor head of a first tractor, and install an RFID tag on the tractor of a second tractor.

[0030] In this embodiment, the GPS positioning module and the RFID reader are arranged on the tractor of the first tractor as shown in the structural diagram. Figure 2 The schematic diagram of the structure of setting the RFID tag on the second pallet truck is as shown in Figure 3 shown.

[0031] S2: Get the coordinate value of the tractor head through the RFDI reader.

[0032] Preferably, the GPS positioning module has an RTK function and is provided with an inertial guidance system. When the coordinate value of the tughead is obtained through the RFDI reader, the GPS positioning module first compensates the coordinate value of the tughead through the RTK function, and then obtains the 6-axis acceleration of the tughead during operation through the MEMS gyroscope in the inertial guidance system and calculates the running trajectory of the tughead. Based on the running trajectory of the tughead and the coordinate value of the tughead after the coordinate value compensation is completed through the RTK function, the position of the tughead is further corrected.

[0033] S3: Read the tag information of the RFID electronic tag based on the coordinate value of the tractor, and receive the signal strength value sent by the RFID reader through the RFID electronic tag.

[0034] The tag information includes the ID number of the RFID electronic tag, wherein the ID number is used to distinguish the identity of the carriage.

[0035] S4: Obtaining the actual distance between the tractor and the RFID electronic tag based on the signal strength value.

[0036] When the actual distance between the tractor and the RFID electronic tag is obtained based on the RSSI signal value, the tractor is in a moving state and the carriage is in a stationary state.

[0037] Preferably, the formula for obtaining the actual distance between the tractor and the RFID electronic tag based on the RSSI signal value is:

[0038] D=200 (SIV-A) / 10n

[0039] Where D is the actual distance; SIV is the signal strength value sent by the RFID reader when the RFID electronic tag receives it; A is the absolute value of the signal strength when the distance between the tractor and the towing board is 1 meter, and the value range is -15 to 25; n is the environmental attenuation factor, and the value range is 3.25 to 4.5.

[0040] In this embodiment, the unit of the actual distance is meter, and the unit of A is dBm; the RSSI signal value is a negative value, and n needs to be corrected through testing.

[0041] S5: Calculate the coordinate value of the RFID electronic tag using the actual distance to obtain the actual position of the carriage.

[0042] Preferably, the tughead coordinate value is the coordinate value obtained by reading the RFDI reader once every time period when the tughead is in a moving state, including the initial longitude and latitude coordinate value, the secondary longitude and latitude coordinate value, and the tertiary longitude and latitude coordinate value; the signal strength value includes the first signal strength value, the second signal strength value, and the third signal strength value; the actual distance includes the first distance, the second distance, and the third distance.

[0043] In this embodiment, the time period is 3 seconds.

[0044] Combination Figure 4 , wherein the coordinate value of the tractor corresponds to the coordinate value when the tractor is in a moving state, and the coordinates include initial longitude and latitude, secondary longitude and latitude, and tertiary longitude and latitude, which correspond to the first coordinate value, the second coordinate value, and the third coordinate value respectively; the distances between the initial longitude and latitude coordinates, the secondary longitude and latitude coordinates, and the tertiary longitude and latitude coordinates and the tractor correspond to the first distance, the second distance, and the third distance respectively.

[0045] Furthermore, using the actual distance to calculate the RFID electronic tag coordinate value includes: using the initial longitude and latitude, secondary longitude and latitude, and tertiary longitude and latitude as basic coordinates, combining the first distance, the second distance, and the third distance to establish an RFID signal radiation model, and calculating the RFID electronic tag coordinate value according to the RFID signal radiation model.

[0046] In this embodiment, the schematic diagram of the RFID signal radiation model is as follows: Figure 5 As shown in the figure, the RFID signal radiation model includes: firstly, a relative coordinate system is established with the initial longitude and latitude as the origin, and then the initial longitude and latitude (x a ,y a ), secondary longitude and latitude (x b ,yb ), third-level longitude and latitude (x c ,y c ) are respectively used as the first circle center a, the second circle center b, and the third circle center c, and the signal is transmitted outward through the RFID reader, and the first distance SIV 1, the second distance SIV 2, and the third distance SIV 3 are respectively used as the radius of the above-mentioned circle center, including the first radius R a , the second radius R b , the third radius R c Draw circles to obtain a first circular trajectory, a second circular trajectory, and a third circular trajectory;

[0047] Furthermore, the moving trajectory ab of the first tughead is the distance between the initial longitude and latitude and the secondary longitude and latitude, and the moving trajectory bc of the second tughead is the distance between the secondary longitude and latitude and the tertiary longitude and latitude; point A and point B are the intersection points of the first circular trajectory and the second circular trajectory, AB is the distance between intersection A and intersection B, Aa is the distance between intersection A and the initial longitude and latitude, and Bb is the distance between intersection B and the secondary longitude and latitude; point O is the intersection point of ab and AB, AO, BO, aO, and bO are the distances between point O and point A, point B, the first circle center a, and the first circle center b, respectively.

[0048] Obviously, when two circular trajectories intersect, they will be tangent at one tangent point or intersect at two intersection points; when three circular trajectories intersect, they will inevitably intersect at only one intersection point. Therefore, taking the distance between the tractor and the RFID electronic tag as the radius, the intersection point between the three circular trajectories can be obtained. Therefore, in this embodiment, the initial longitude and latitude, the secondary longitude and latitude, and the tertiary longitude and latitude are used as basic coordinates, and the RFID signal radiation model is established in combination with the first distance, the second distance, and the third distance. The RFID electronic tag coordinate value calculated according to the RFID signal radiation model includes:

[0049] S101: Calculate the moving trajectory ab of the first tractor by combining the following formulas:

[0050]

[0051] S102: Calculate the first distance SIV 1 and the second distance SIV 2 by combining the following formulas to obtain the value of AO:

[0052] ab=aO+bO

[0053] SIV 1 2 =R a 2 =aO 2 +AO 2

[0054] SIV 2 2 =R b2 =bO 2 +AO 2

[0055] aO=(SIV 2 2 -SIV 1 2 -ab 2 ) / -2ab

[0056] =(R b 2 -R a 2 -ab 2 ) / -2ab

[0057] S103: By obtaining x O ,y O The value of O is obtained by O ,y O ), including the following formula:

[0058] x O =x a +((x b -x a )*aO) / ab

[0059] y O =y a +((y b -y a )*aO) / ab

[0060] S104: Obtain the slopes K of ab and AB respectively according to the coordinates of point O ab and K AB , including the following formula:

[0061] K ab =(y b -y a ) / (x b -x a )

[0062] K AB =-1 / k ab

[0063] S105: Calculate the angle ∠ABX between AB and the x-axis, and obtain the coordinates of point A (x A ,y A ) and the coordinates of point B (x B ,y B ), including the following formula:

[0064] ∠ABX=atan(K AB )

[0065] xA =x O +AO*cos(∠ABX)

[0066] y A =y O +AO*sin(∠ABX)

[0067] x B =x O -AO*cos(∠ABX)

[0068] y B =y O -AO*sin(∠ABX)

[0069] Based on the method provided in this embodiment, 23 tractors equipped with GPS positioning modules with RTK and inertial guidance functions and RFID electronic tag reading function equipment and 173 tractors equipped with RFID electronic tags are used as sample experimental objects, where the effective reading distance of the RFID electronic tag is 20 meters, and the readback data contains the RSSI signal value, and the RSSI accuracy is 2000 / 200=12.5 cm. Under the condition of correcting the environmental attenuation factor through actual measurement data, the positioning accuracy error of the tractor finally obtained is 20 cm, and the time delay of the output result after data acquisition and background calculation is 80ms, which preliminarily meets the real-time requirements of the actual operation of port production.

[0070] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A passive positioning method for port trailers, characterized in that: include: A GPS positioning module and an RFID reader are installed on the tractor head of the first tractor, and an RFID electronic tag is installed on the tractor of the second tractor; Acquire the coordinate value of the tractor head through the RFDI reader; Reading the tag information of the RFID electronic tag based on the tractor coordinate value, and receiving the signal strength value sent by the RFID reader / writer through the RFID electronic tag; Acquire the actual distance between the tractor and the RFID electronic tag based on the signal strength value; The actual distance is used to calculate the coordinate value of the RFID electronic tag to obtain the actual position of the carriage.

2. A passive positioning method for port trailers according to claim 1, characterized in that: The GPS positioning module has an RTK function and is provided with an inertial guidance system. When the coordinate value of the tughead is obtained through the RFDI reader, the GPS positioning module first compensates the coordinate value of the tughead through the RTK function, and then obtains the 6-axis acceleration of the tughead during operation through the MEMS gyroscope in the inertial guidance system and calculates the running trajectory of the tughead. Based on the running trajectory of the tughead and the coordinate value of the tughead after the coordinate value compensation is completed through the RTK function, the position of the tughead is further corrected.

3. A passive positioning method for port trailers according to claim 1, characterized in that: The formula for obtaining the actual distance between the tractor and the RFID electronic tag based on the RSSI signal value is: D＝200 (SIV-A) / 10n Wherein, D is the actual distance; SIV is the signal strength value sent by the RFID reader when the RFID electronic tag receives it; A is the absolute value of the signal strength when the distance between the tractor and the towing board is 1 meter, and the value range is -15 to 25; n is the environmental attenuation factor, and the value range is 3.25 to 4.

5.

4. A passive positioning method for port trailers according to claim 1, characterized in that: The tughead coordinate value is the coordinate value obtained by reading the RFDI reader once every time period when the tughead is in a moving state, including the initial longitude and latitude coordinate value, the secondary longitude and latitude coordinate value, and the tertiary longitude and latitude coordinate value; the signal strength value includes the first signal strength value, the second signal strength value, and the third signal strength value; the actual distance includes the first distance, the second distance, and the third distance.

5. A passive positioning method for a port trailer according to claim 4, characterized in that: Using the actual distance to calculate the coordinate value of the RFID electronic tag includes: using the initial longitude and latitude, secondary longitude and latitude, and tertiary longitude and latitude as basic coordinates, combining the first distance, the second distance, and the third distance to establish an RFID signal radiation model, and calculating the coordinate value of the RFID electronic tag according to the RFID signal radiation model.

Images