CN108921253B

CN108921253B - Wireless positioning method

Info

Publication number: CN108921253B
Application number: CN201810840780.9A
Authority: CN
Inventors: 周宏亮; 朱卓敏
Original assignee: Shanghai Powershare Information Technology Co ltd
Current assignee: Shanghai Powershare Information Technology Co ltd
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2022-02-25
Anticipated expiration: 2038-07-27
Also published as: CN108921253A

Abstract

The invention relates to a wireless positioning method, which is used for positioning the relative position of an object in a plane positioning area, and relates to an RFID tag array, RFID tag reading equipment and an embedded module containing a positioning algorithm, wherein the specific method comprises the following steps: arranging a plurality of RFID labels written with corresponding position codes in advance in a plane positioning area to form a label array, and installing reading equipment of the RFID labels on an object to be positioned; and when the object is positioned in the space corresponding to the plane positioning area, reading the RFID label through an RFID reading device, and determining the position of the object in the area according to the read position information of the RFID label. In the positioning algorithm, the number of times of reading the RFID tag and the signal strength (RSSI) are mainly used as the basis of the algorithm, so as to obtain the relative position of the RFID reading device with respect to the RFID tag. The invention can quickly and accurately position the position of an object in the area, and is simple and easy to use.

Description

Wireless positioning method

Technical Field

The invention belongs to the technical field of wireless positioning, and is applied to occasions such as wireless charging of new energy automobiles and the like.

Background

There are many occasions in daily life where it is necessary to locate the position of an object in an area.

For example, with the rapid development of new energy vehicles, people have higher and higher requirements for convenience of charging. Compared with the situation that a charging interface for wired charging is easy to generate heat and damage under the condition of high current, the wireless charging interface is not in physical contact, and the high-power charging function is easier to realize. In addition, since wireless charging has greater flexibility in use, more and more companies are added to the design and development of wireless charging products.

However, wireless charging has its own problems, one of which is the matching problem of the transceiver coil position. Generally, the wireless transceiver coil can work well within 10 cm of position deviation, and the power transmission efficiency is greatly influenced when the distance is exceeded. In addition, in the use process, the transceiver coil is generally arranged at the bottom of the automobile, so that the driver is difficult to align the automobile, and therefore clear position indication is needed. Therefore, how to quickly and accurately position the position of the automobile in the recharging area is an urgent problem to be solved.

Disclosure of Invention

The invention aims to provide a method capable of quickly and accurately positioning the projection position of an object in a plane area.

In order to achieve the purpose, the invention adopts the technical scheme that:

a wireless positioning method is used for positioning the projection position of an object in a plane positioning area, firstly, RFID tags are arranged in the plane positioning area to enable the RFID tags to form a plane RFID array, unique position codes are written into the RFID tags, then RFID reading equipment used for reading the RFID tags is installed on the object to be positioned, when the object is positioned on the plane positioning area, the RFID reading equipment reads the RFID tags, the position codes of the RFID tags read by the RFID reading equipment are sent to a computing unit to be computed, and finally the projection position of the object on the plane positioning area is obtained.

The position code of each RFID label in the planar RFID array represents the relative position of the RFID label in the planar RFID array, the calculating unit stores the position code of the RFID label in the planar positioning area and the corresponding rule of the relative position in advance, and calculates the relative position of the projection of the object in the planar positioning area according to the position code.

The RFID reading device reads a plurality of RFID labels in the reading range of the RFID reading device at the same time, or reads a plurality of RFID labels in the reading range of the RFID reading device in a scanning mode, the reading range of the RFID reading device in the plane positioning area is continuous, the reading range is smaller than one third of the area enclosed by all the RFID labels, and the number of the RFID labels which can be read by the RFID reading device in the plane positioning area is 3-20.

The arrangement interval of the RFID tags is 3-20cm, and the reading and writing distance of the RFID tag reading equipment is larger than the maximum interval distance between the RFID tags.

The calculation unit takes the reading times of the same RFID tag as a first weight of the RFID tag for average calculation, takes the RSSI value of each RFID tag as a second weight for average calculation to obtain a position value obtained by one-time preliminary calculation, and averages the position value obtained by the current-time preliminary calculation with the position value obtained by the latest 2-10 calculation to obtain the position value calculated this time.

And if the deviation between the position value obtained by the preliminary calculation and the position value obtained by the last calculation is within the range of 3 adjacent RFID tags, continuing to calculate the position.

Drawings

Fig. 1 is a schematic diagram of a wireless location system of the present invention.

Fig. 2 is a schematic diagram of the distribution of RFID tags in an area in the wireless location system of the present invention.

Detailed Description

The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.

Example (b): as shown in fig. 1, a wireless positioning system for positioning a projection position of an object in a planar positioning area includes a plurality of RFID tags, an RFID reading device capable of reading the plurality of RFID tags simultaneously, and a computing unit for implementing a data processing algorithm, where the computing unit may employ an embedded module, and communicates with the RFID reading device, so as to obtain information read by the RFID reading device. The RFID tags are arranged in the plane positioning area, so that a plane RFID array is formed, and the arrangement interval of the RFID tags is 3-20cm, or one RFID tag is arranged every 3-20 cm. In this embodiment, the plane positioning area is above a ground primary coil of the new energy vehicle, where the physical size of the ground primary coil is 600mm × 600mm, 11 × 11 RFID tags arranged in a vertical and horizontal grid are covered on a plane parallel to the ground in the primary coil, the area of the plane surrounded by the planar RFID arrays is 590mm × 590mm, and the center distance between the RFID tags is 50 mm. After implementation of the protocol a localization area of 750 x 750mm was created. The RFID reading device is installed at the center of a secondary side coil on the new energy automobile, the distance between the RFID reading device and the ground is 20cm, the RFID reading device is provided with a reading range, the reading range of the RFID reading device in the plane positioning area is continuous, and the RFID reading device can simultaneously read a plurality of RFID labels in the reading range or read the plurality of RFID labels in the reading range in a scanning mode. The reading range of the RFID reading equipment is less than one third of the area enclosed by all the RFID tags, and the number of the RFID tags which can be read by the RFID reading equipment in the plane positioning area is 3-20.

In the present embodiment, the planar positioning area is a square, and the RFID tag using the central symmetric pattern is selected, and the characteristics of the central symmetric tag in each direction are also shown to be central symmetric. The RFID labels are uniformly arranged in rows and columns, and the distances among the RFID labels are equal. After the arrangement of the RFID tags is determined, a corresponding position code is written in each RFID tag in sequence, the position code of each RFID is unique, and the position code is used for representing the relative position of the RFID tags in the planar RFID array. In this embodiment, each RFID tag is numbered regularly, and the number can represent the position information of the corresponding RFID tag, and the RFID tag distribution diagram similar to that shown in fig. 2 can be obtained by writing the number representing the position information into the corresponding RFID tag. In fig. 2, the number corresponding to each RFID tag is two, the first bit from the left represents the row where the RFID tag is located, and the second bit from the left represents the column where the RFID tag is located, so that the xy RFID tag is located in the x-th row and the y-th column. Establishing a coordinate system in the positioning area, wherein each RFID tag has coordinates in the coordinate system to represent an actual position of the RFID tag, and the actual position corresponds to the number of the RFID tag, so that the actual position of the RFID tag can be calculated in the following way: the center-to-center distance between the RFID tags is 50mm, and if the center position coordinates of the RFID tag numbered 11 at the upper left corner are (100 ), the coordinates of the actual position of the RFID tag numbered 43 are ((4-1) × 50+100, (3-1) × 50+100), i.e., (250, 200). This allows the number of the RFID tag to be correlated to its actual location.

In this embodiment, the secondary side coil carrying the RFID tag reading device is installed at the bottom of the new energy vehicle, and when the vehicle enters the charging area, the reading device can read the RFID tag in the primary side coil installed on the ground, and then the read-write device sends the read RFID data to the embedded module in charge of the location algorithm for calculation processing. In fig. 2, each square with characters represents an RFID tag, and the gray squares represent RFID tags read by an RFID reading device.

When the calculating unit determines the position, the calculating unit mainly calculates the average number of times of reading the same RFID tag as the first weight of the RFID tag according to a parameter of the number of times of reading different RFID tags by the RFID reading device within a set time. Since the position code of each RFID tag corresponds to one position, when the number of readings is averaged as a weight value of the position, the larger the weight is, the closer the position value finally calculated is to the position represented by the RFID.

Further, the present embodiment uses the RSSI values (i.e. signal values) of the different read RFID tags to assist in determining the location of the object, i.e. the RSSI value of each read RFID tag is used as a second weight to perform average calculation, because the closer the distance is, the larger the RSSI value is. Therefore, the relative distance between the identification device and each RFID tag can be determined according to the RSSI value of each RFID tag read. For example, in fig. 2, if the RSSI value read to the RFID tag of number 37 is smaller than the RSSI value read to the RFID tag of number 57, this indicates that the identification device is located closer to the RFID tag of number 57 among the RFID tags of

numbers

37 and 57. In the position algorithm, the difference between the RSSI and the set bias is averaged as the weight of the data.

Therefore, the calculated number of times of reading the RFID tag and the RSSI value of each RFID tag can be used to obtain a position value obtained by a single preliminary calculation. And then averaging the position value obtained by the current primary calculation and the position value obtained by the latest 2-10 calculation, thereby obtaining the position value calculated this time. In the calculation process, if the deviation between the position value obtained by the preliminary calculation and the position value obtained by the last calculation is within 3 adjacent RFID label ranges, the position is continuously calculated, otherwise, the position value obtained by the preliminary calculation is adjusted to be within 3 adjacent RFID label ranges.

The above algorithm is expressed as the following formula:

identifying location coordinates of a device

Wherein, px (i), py (i) are actual coordinates of the ith RFID tag read, rssi (i) is a weight value set for the ith RFID tag according to the number of reading times, and n is a total number of reading times of each RFID tag, which may be a value between 20 and 50.

Wherein, the weight calculation formula of Rssi (i) is: RSSI, which is a representation of the strength of the signal for reading the RFID tag, is a value between about-80 and-30 (dBm), and Offset, which is an Offset value for making RSSI (i) positive, and is approximately in the range of 80-200.

In addition, the latest received position data is compared with the current position, and if the deviation between the received position data and the current position is larger than the size of k RFID tags, the received position data is modified to be within the size of k RFID tags (wherein k takes the floating point number between 1 and 3). And averaging the position value obtained by final calculation and the position values obtained in the previous times to finally obtain the position value of the positioning.

In this example, since the wireless charging employs 85kHz frequency, in order to avoid signal interference, a 900MHz frequency band RFID reader is employed.

Because the reading range of the RFID reading and writing equipment on the plane where the RFID tag is located needs to be controlled, the transmitting power and the transmitting direction of the RFID reading and writing equipment need to be adjusted to ensure that the reading range meets the requirements.

Because the deviation of general electric automobile wireless charging coil permission on the horizontal direction is more than 10 centimetres, can ensure the efficiency of wireless transmission electric energy at 10 centimetres scope, and the positioning accuracy of this scheme can reach centimetre level, consequently is particularly suitable for this scene of wireless charging of electric automobile.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A wireless positioning method for positioning a projection position of an object in a planar positioning area, characterized by: arranging RFID tags in the plane positioning area to enable the RFID tags to form a plane RFID array, writing a unique position code into each RFID tag, installing RFID reading equipment for reading the RFID tags on an object to be positioned, reading the RFID tags by the RFID reading equipment when the object is positioned on the plane positioning area, sending the position codes of the RFID tags read by the RFID reading equipment to a computing unit for computing, and finally obtaining the projection position of the object on the plane positioning area; the calculation unit takes the reading times of the same RFID tag as a first weight of the RFID tag for average calculation, takes the RSSI value of each RFID tag as a second weight for average calculation to obtain a position value obtained by one-time preliminary calculation, and averages the position value obtained by the current-time preliminary calculation and the position value obtained by the latest 2-10 calculation to obtain the position value calculated this time; the RFID reading device reads a plurality of RFID labels in the reading range of the RFID reading device at the same time, or reads a plurality of RFID labels in the reading range of the RFID reading device in a scanning mode, the reading range of the RFID reading device in the plane positioning area is continuous, the reading range is smaller than one third of the area enclosed by all the RFID labels, and the number of the RFID labels which can be read by the RFID reading device in the plane positioning area is 3-20.

2. The wireless location method of claim 1, wherein: the position code of each RFID label in the planar RFID array represents the relative position of the RFID label in the planar RFID array, the calculating unit stores the position code of the RFID label in the planar positioning area and the corresponding rule of the relative position in advance, and calculates the relative position of the projection of the object in the planar positioning area according to the position code.

3. The wireless location method of claim 1, wherein: the arrangement interval of the RFID tags is 3-20cm, and the reading and writing distance of the RFID tag reading equipment is larger than the maximum interval distance between the RFID tags.

4. The wireless location method of claim 1, wherein: and if the deviation between the position value obtained by the preliminary calculation and the position value obtained by the last calculation is within the range of 3 adjacent RFID tags, continuing to calculate the position.