JPH03210834A - Method for discriminating position of travelling object in travelling object communication - Google Patents

Abstract

PURPOSE:To attain effective data feed in a short time by utilizing a time between transmission and reception of a usual data between a fixed station and a mobile station so as to discriminate a current position of the travelling object. CONSTITUTION:When radio waves of different frequencies f1, f2, f3 are sent sequentially from radio equipments 9A-9C of each fixed station side, a data terminal equipment 3 of a fork lift 1B identifies respectively a received electric field strength of a radio wave received sequentially by a radio equipment 2 and specifies the frequency giving the highest reception electric field strength. The data terminal equipment 3 of the fork lift 1B sends the specified frequency from the radio equipment 2 as a position data by means of a radio wave. Thus, a host computer 14 discriminates it that the current position of the fork lift 1B is a position close to the radio equipment 9B of the fixed station side based on the position data of the radio wave sent from the fork lift 1B.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to wireless LAN (Local Area
The present invention relates to a method for determining the position of a mobile object in mobile communication using a network.

[Prior Art] In recent years, wireless LANs have been used to enable the movement of data terminals by exchanging desired data via radio waves. Since data terminals are mobile, their wireless LANs are used in logistics systems, for example, logistics systems that use cargo handling vehicles as moving objects.

That is, a cargo handling vehicle is equipped with a wireless device and a data terminal to serve as a mobile station, and multiple wireless devices distributed at appropriate locations within the premises are used as multiple fixed stations, and the desired data to be transmitted to the mobile station is transmitted. is output from the host computer in the office to the radio equipment at each fixed station and transmitted via radio waves. In addition, since the radio waves emitted are limited to weak radio waves according to the provisions of the Radio Law, in order to effectively exchange data between fixed stations and mobile stations over a wide range of premises, stations are distributed throughout the premises. The communicable ranges of the wireless devices at each fixed station are expanded by overlapping each other.

In the above-mentioned logistics system, when sending normal cargo handling data to the data terminal of a specific cargo handling vehicle moving within the premises, the radio equipment at each fixed station is activated in sequence to transmit radio waves containing the cargo handling data. Send messages in sequence. Furthermore, among the radio waves emitted from the radio equipment on each fixed station side, the radio equipment on the mobile station side can reliably process the radio waves emitted from the nearest fixed station and processed as cargo handling data by the data terminal. As soon as a radio wave is received that exceeds the received field strength of the predetermined level,
Sends a reception confirmation radio wave to the fixed station wireless device. In other words, when sending cargo handling data to a data terminal of a specific cargo handling vehicle, so-called polling has been performed.

[Problems to be Solved by the Invention] However, in the conventional logistics system, polling is performed every time desired data is sent to the data terminal of a specific cargo handling vehicle, so there is a problem that it takes time to send the data. there were. This is because the location of the cargo handling vehicle is not known at any given time.If the location of the cargo handling vehicle at the destination is known at the time the desired data is sent, the radio equipment at the nearest fixed station can be used. It was possible to specify and activate the data, and data could be sent reliably and in a short time.

This invention was made in view of the above-mentioned circumstances, and its purpose is to reliably and quickly send data from a plurality of arbitrarily distributed fixed stations to a mobile station mounted on a mobile body. Therefore, it is an object of the present invention to provide a method for determining the position of a mobile body in mobile communication, which allows the current position of the mobile body to be known at all times.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a plurality of fixed stations that are centrally controlled by a central control unit and that are arbitrarily distributed and installed on a mobile body. In mobile communications in which desired data is exchanged via radio waves with mobile stations, each fixed station simultaneously transmits radio waves having different frequencies assigned in advance to each fixed station.

Then, the transmitted radio waves are sequentially received by the mobile station without being tuned, and the received electric field strength is determined for each frequency.

Subsequently, when transmissions from all fixed stations are completed, the received field strengths corresponding to each frequency determined by the mobile station are compared with each other, and the frequency with the highest received field strength is identified. Next, the identified frequency is used as position data of the mobile body, and the current position of the mobile body is determined based on the position data.

[Operation] According to the above configuration, by determining the current position of the mobile object using the interval between normal data exchange between the fixed station and the mobile station, the mobile object can be moved at the time of sending normal data. Body position is always known.

Therefore, when transmitting normal data, radio waves can be transmitted from the fixed station closest to the mobile object, and effective data transmission can be performed in a short time.

Furthermore, in order to determine the position of each mobile object, radio waves are simultaneously transmitted from each fixed station, leading to a reduction in the time required for position determination.

[Embodiment] Hereinafter, an embodiment in which the present invention is applied to a wireless LAN in a logistics system using forklifts will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a wireless LAN. There are multiple (four in this case) manned forklifts IA, IB, and IC as moving vehicles on the premises.

ID is in operation.

Each forklift IA-ID is equipped with a wireless device 2, a data terminal 3, and a printer 4, which constitute a mobile station as shown in FIG. The wireless device 2 on the mobile station side is a device that transmits and receives radio waves containing desired data, and modulates and demodulates signals for the transmission and reception. This wireless device 2 is connected to a data terminal 3 via a coaxial cable 5, and data is exchanged between the two. The data terminal 3 includes a keyboard 6 for inputting data by an operator and a display 7 for displaying data. The data terminal 3 also has a control function for controlling the operation of the wireless device 2. Further, the data terminal 3 is connected to a printer 4 via a coaxial cable 8, so that the data input manually to the data terminal 3 can be output and printed by the printer 4.

On the other hand, a plurality of (three in this case) wireless devices 9A, 9B, and 9C constituting a fixed station are distributed at appropriate positions near the ceiling of the premises. Here, the wireless devices 9A to 9C on the fixed station side transmit and receive radio waves containing desired data, and also modulate and demodulate signals for the transmission and reception.

Furthermore, since the radio waves to be transmitted from each of the wireless devices 9A to 9C are limited to weak radio waves in accordance with the provisions of the Radio Law, communication between the fixed station side and the mobile station side can be performed throughout the wide premises. In order to enable wireless devices 9A to 9C on each fixed station side,
The communicable ranges of the two are overlapped with each other and extended throughout the campus.

The wireless devices 9A to 9C on each fixed station side are connected to a wireless controller 2 via a coaxial cable IO, and the wireless controller 11 is connected to a host computer 14 installed in a command office 13 via a coaxial cable 12. It is connected to the. The wireless controller 11 and the host computer 14 constitute a general control section, and the host computer 14 is connected to each forklift truck IA to IA.
Manage the desired data to be sent to the data terminal 3 of D,
The wireless controller 11 controls the operation of the wireless devices 9A to 9C at each fixed station in order to transmit the data via radio waves.

Next, regarding the operation of the wireless system configured as above,
This will be explained according to the flowcharts shown in FIGS. 3 and 4.

FIG. 3 is a flowchart illustrating the processing operations of the host computer 14 in the office 13.

In this embodiment, the processing operation for determining the position of each forklift IA-ID is performed using the interval in which normal cargo handling data is exchanged between each forklift IA-ID and the office 13.

Once the normal processing for exchanging cargo handling data is completed, the processing moves to the routine of this flowchart.

First, in step 101, in order to inform each forklift IA-ID that position determination is to be started, the wireless devices 9A to 9C at each fixed station are activated simultaneously to transmit a command radio wave to start position determination.

Next, in step 102, radio waves having different frequencies assigned in advance to the radio devices 98 to 9C on the fixed station side are simultaneously transmitted for a predetermined time from each of the radio devices 9A to 9C.

That is, radio waves of different frequencies are transmitted all at once from the radio device 9A, the radio device 9B, and the radio device 9C.

Subsequently, in step 103, each wireless device 9A is used to notify each forklift truck IA to ID that the wireless devices 9A to 9C on the fixed station side have finished transmitting radio waves.
~ 9C are activated all at once to send out a radio wave notifying the end of the call.

Thereafter, in step 104, each forklift) I
Wait for reception of radio waves from the mobile station side wireless device 2 installed in A~ID, and when the radio waves are received, step 105
In step 105, radio waves containing position data from each mobile station's wireless device 2 are sequentially received and input. Here, the position data is data transmitted from the wireless device 2 of each mobile station as the position data of each forklift IA-ID at the current time.

Next, in step 106, the current position of each forklift truck IA to IO is determined based on each input position data, and the data of the current position is sequentially stored in the internal memory.

Subsequently, in step 107, it is determined whether or not storage of current position data for all forklifts LA-ID has been completed. If the memorization is not completed, jump to step 105,
The processing of steps 105 to 107 is repeated. Further, when the storage is completed, the subsequent processing is temporarily ended.

On the other hand, FIG. 4 is a flowchart illustrating the processing operation of the data terminal 3 of each forklift truck IA to ID.

In this embodiment, when a command radio wave to start position determination is received from the wireless devices 9A to 9C of each fixed station during a period of normal exchange of cargo handling data, the process shifts to the routine of this flowchart.

That is, in step 201, the process waits for a command radio wave to start position determination from the wireless devices 9A to 9C on the fixed station side, and when the radio wave is received, the process moves to step 202.

In step 202, each fixed station side wireless device 9A
Radio waves of different frequencies transmitted simultaneously from ~9C are sequentially received while being synchronized. In other words, it sequentially receives radio waves of different frequencies while scanning them.

Next, in step 203, the received electric field strength corresponding to each frequency of each received radio wave is determined, and then in step 204, the received electric field strength corresponding to each frequency is stored in an internal memory.

For example, the received electric field strength is determined for the first frequency tuned, and the received electric field strength corresponding to that frequency is stored in the internal memory.

Then, in step 205, it is determined whether a notification radio wave indicating the end of transmission has been received from the wireless devices 9A to 9C on the fixed station side. Here, if the notification radio wave is not received, step 202 hedge jumps and step 202~
The process of 205 is repeated. If the notification radio wave is received, the process moves to step 206.

Then, in step 206, the received electric field strengths corresponding to the wireless devices 9A to 9C on the fixed station side stored in the internal memory are compared with each other, and the frequency having the highest received electric field strength is specified.

Subsequently, in step 207, the identified frequency is used as position data of the forklift I A-I D,
A radio wave containing the same location data is transmitted from the wireless device 2 on the mobile station side, and the subsequent processing is temporarily terminated.

Here, to explain the position determination for the forklift IB in FIG. 1 as an example, the wireless device 9A on each fixed station side
-9C to different frequencies fl, f2. When the radio waves of f3 are simultaneously transmitted, the data terminal 3 of the forklift IB calculates the received field strength of each of the radio waves sequentially received while being synchronized by the wireless device 2, and specifies the frequency with the highest received field strength. In this case, the receiving field strength is the closest to the wireless device 9.
The data terminal 3 of the forklift IB transmits the specified frequency as position data from the wireless device 2 via radio waves.

Therefore, the host computer 14 determines that the current position of the forklift IB is close to the wireless device 9B on the fixed station side based on the position data of the radio waves transmitted from the forklift IB, that is, based on the pre-assigned frequency f2. Determine.

As described above, in this embodiment, the wireless device 9 on each fixed station side
Radio waves of different frequencies simultaneously transmitted from 8 to 9C are sequentially received by the wireless devices 2 of each forklift IA to ID, and based on each received radio wave, the radio waves having different frequencies are received by each forklift IA to ID, and based on the received radio waves, the radio waves having different frequencies are transmitted simultaneously from the forklifts IA to ID. It is possible to specify the frequency that is the received electric field strength, and to know the current position of each forklift truck IA to ID based on the specified frequency. In addition, in this embodiment, in order to determine the position of each forklift IA-ID, radio waves are simultaneously transmitted from the wireless devices 9A to 9C at each fixed station, compared to a case where radio waves are transmitted sequentially. The time for position determination can be shortened.

Moreover, in this embodiment, each forklift I A-L
The process for knowing the current position of D is carried out during the regular exchange of cargo handling data between each forklift IA-I D and office 13, so normal cargo handling data is sent. Each forklift IA~ID at the time
You can always know the location of

Therefore, unlike the case where polling is performed to send normal cargo handling data as in the conventional example, in this embodiment, normal cargo handling data is sent to a specific forklift I A-I D.
Since the current position of each forklift LA-ID can be grasped at any time, the wireless devices 9A to 9 on the fixed station side closest to each forklift IA to ID can be sent to
C can be identified and radio waves containing cargo handling data can be transmitted from the wireless devices 9A to 9C, and normal cargo handling data can be sent reliably and in a short time.

Further, in this embodiment, since the current position of each forklift truck 1A-1D can be grasped in the host computer 14, cargo handling operations can be managed efficiently.

Note that this invention is not limited to the above embodiments (
The present invention can be implemented as follows by changing a part of the structure as appropriate without departing from the spirit of the invention.

(1) In the above embodiment, three wireless devices 9A to 9C are provided as fixed stations, and four forklifts IA-ID are provided as mobile units, and each has a mobile station side wireless device 2 and a data terminal. However, the number of wireless devices and forklifts on the fixed station side may be other than the above. In other words, the scale of a logistics system using a wireless LAN can be expanded or reduced as appropriate. Particularly when the scale of the logistics system is expanded, the effectiveness of determining the position of each forklift can be further enhanced.

(2) In the above embodiment, in the data terminal device 3 of each forklift truck IA to ID, each fixed station side wireless device 9A to 9
The received field strengths corresponding to C were compared and the wireless devices 9A to 9C with the highest received field strength were identified.
The received field strength data corresponding to the wireless devices 9A to 9C on the fixed station side is once sent from the wireless device 2 on the mobile station side to the wireless devices 9A to 9C on the fixed station side via radio waves, and then sent to the host computer 14. The wireless devices 9A to 9C having the highest received field strength may be identified.

(3) In the embodiments described above, a wireless LAN is implemented in a logistics system, but it may also be implemented in a case other than a logistics system where data is simply exchanged between a fixed station and a mobile station.

(4) In the above embodiment, the manned forklift IA~
Although the present invention has been embodied in a logistics system using ID, it may also be embodied in a logistics system using automatically operated unmanned forklifts or automated guided vehicles.

[Effects of the Invention] As detailed above, according to the present invention, data can be reliably and quickly sent from a plurality of arbitrarily distributed fixed stations to a mobile station mounted on a mobile body. This has the excellent effect of being able to always know the current location of a moving object.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic configuration diagram showing a wireless LAN in an embodiment embodying the present invention, FIG. 2 is a diagram showing the configuration of a mobile station mounted on each forklift, and FIG. FIG. 3 is a flowchart explaining the processing operation of the host computer, and FIG. 4 is a flowchart explaining the processing operation of the data terminal. In the figure, lA to ID are forklifts as moving objects, 2
3 is a wireless device, 3 is a data terminal (2, 3, etc. constitute a mobile station), 9A to 9C are wireless devices that constitute a fixed station, 11 is a wireless controller, 14 is a host computer (11, 14 are (forming the general control unit).

Claims (1)

[Claims] 1. Exchange of desired data via radio waves between a plurality of fixed stations that are centrally controlled by a central control unit and are arbitrarily distributed and a mobile station installed in a mobile body. In mobile communication, radio waves consisting of different frequencies assigned in advance to each of the fixed stations are simultaneously transmitted from each of the fixed stations, and the transmitted radio waves are sequentially received by the mobile station while being synchronized. The received electric field strength is determined for each frequency by the mobile station, and when transmission from all fixed stations is completed, the received electric field strength corresponding to each frequency determined by the mobile station is compared with each other, and the received electric field strength is determined to be the highest. specifying a frequency that is the electric field strength, and using the specified frequency as position data of the mobile object;
A method for determining the position of a mobile body in mobile communication, wherein the current position of the mobile body is determined based on the position data.