Object tracking and management system and method using radio-frequency identification tags

System and method for tracking and managing objects using radio frequency identification tags

Other objectives and advantages of the present invention can be understood by reading the following detailed description of the specific embodiment and by referring to the drawings, among which:

Figure 1 illustrates an embodiment of the present invention, in which an RFID tag is attached to both the object and the location;

Figures 2(a), 2(b) and 2(c) illustrate one of the monitor displays on a panel of the interrogator at different stages of completing a load reconfiguration operation;

Figure 3 illustrates another embodiment of the present invention, in which a barcode label is attached to an object, and an RFID label is arranged at the position;

Figure 4 illustrates one of the principles of using RFID tags to determine location and movement;

Figure 5 illustrates an embodiment of the present invention, in which two RFID tags close to each other are arranged for the relevant position of the transport vehicle;

Figure 6 illustrates that the present invention is basically similar to one of the embodiments shown in Figure 5, but with a fixed interrogator and a mobile RFID tag for determining the relative position of the object to which the RFID tag is attached;

Figure 7 illustrates an embodiment of the present invention, in which an RFID interrogator is constructed and configured to detect only the RFID tag closest to the interrogator;

Figure 8 illustrates a concept of the present invention to identify a processor that is closest to an RFID tag of an interrogator; and

FIG. 9 illustrates a visual display of a trust phase in the RFID tag identification provided by the embodiment shown in FIG. 7;

Figure 10 illustrates an embodiment of the present invention in which an RFID tag is used to identify an object and a magnetic tape is used to identify a location.

Figure 11 illustrates an embodiment of the present invention in which a height sensor is used to identify a specific slot in a storage rack marked by an RFID tag.

Technical category

The present invention generally relates to a system and method for tracking and managing objects, and in particular, such a system and method using a combination of mobile and/or fixed radio frequency identification tags to identify and monitor the location and movement of objects.

Background of the invention

In order to complete high-efficiency warehouse operations, it is necessary to accurately track the configuration and/or transfer of different locations in the warehouse, such as storage locations, storage locations, grading areas, and loading docks to transport them by pallet loading and the movement of other objects. In a conventional warehouse management operation, the operator of a transport vehicle, such as a forklift truck, stretch truck, crane truck, or pallet truck, receives a set of printed inventory or pick-up instructions, usually generated by a computer, and by Visually recognize loading and location, and carry out instructions for transporting and loading back and forth at the location specified on the instructions. In this system, especially in large warehouses with a large number of locations and loads to handle, there are many opportunities for errors.

Some warehouse management operations use barcodes that are attached to the load or its marking refers to the configuration location. In the general example of this system, the operator uses a hand-held barcode scanner to read on the load, and in some cases, read it on the inventory location. Barcode. Although this system is an improvement over pure visual procedures, it may be partly due to the need for a straight line for the horizon, termination of approach, and difficulty in performing proper procedures between the scanner and the barcode, and it also requires the operator to participate. Load the recognition program. In some cases, the operator can leave the transport vehicle to manually scan the bar code, slowing down warehouse operations. Clear locations, such as high storage racks and loading docks, are usually particularly difficult to use for barcodes because of the need to terminate the access between the code and the reader. Therefore, the loading in the areas is usually replaced by visual recognition.

A radio frequency identification ("RFID") tag system has been proposed for use in inventory tracking. In this system, an RFID tag belongs to an object or location and includes a non-volatile memory used to store information to identify the object or location The body and an electronic circuit for interrogator interaction. RFID tags can be passive or active. In the case of a passive RFID tag, the tag includes a circuit for converting at least a part of the RF signal into electronic power required by the tag for signal processing and transmission. In a common conventional system, the RFID tag contains information about the characteristics of the tracked inventory item belonging to the inventory item. An RFID interrogator is used to detect the appearance of an RFID tag and read identification information from the tag. A general RFID interrogator includes an RF transceiver for transmitting the interrogation signal to the RFID tag and receiving the response signal from the RFID tag. One or more antennas are connected to the transceiver, and related encoders and decoders are used for receiving and transmitting respectively. Read and write coding information in the RF signal. The interrogator can be a portable device that can carry it close to tag reading, or it can be a fixed device that reads tags such as carrying them to the interrogator, such as returning a marked library book until it meets an interrogation One of the devices reports the situation of the platform. It is also possible to attach an RFID tag close to a location such as a location marker. After detecting both a tag belonging to an inventory item and a location mark tag, a program unit related to the interrogator can determine the location where the inventory item is close to the mark. When these conventional object tracking systems can keep a record of inventory items and sometimes their locations, they are not effectively used to track and/or manage the movement of inventory items.

There is also a warehouse inventory tracking system that includes fixed RFID interrogators in different locations when the RFID-marked item is close to the location where the interrogator is deployed. For example, there are warehouses equipped with RFID interrogators at or near the loading dock gates. This system can track the arrival of items marked at different locations, but cannot detect errors from remote locations to those locations. For example, if a forklift truck picks up an incorrect device because it drives the truck to an incorrect pickup position, the error will not be detected until the load has reached the gate. This delayed error detection negatively impacts the overall efficiency of warehouse operations. In addition, it is not an effective cost to have an interrogator for each gate equipped with a large number of loading dock gates.

It is necessary to provide a system that provides automatic procedures for object identification, movement and tracking throughout a warehouse or other similar environments, and it needs to be suitable for all wide and different warehouse operations, such as storage locations, storage locations, and floor passages. And the system used in the location of the shipping dock. It also needs to operate a related central data repository to point to and track the movement of all objects throughout the warehouse.

The present invention refers to eliminating one or more of the aforementioned problems and satisfying one or more of the above-defined requirements.

Summary of the invention

The present invention is used to provide an automatic object and location identification system, which is preferably used in warehouse management operations, and does not require a large number of locations to be equipped with fixed RFID interrogators. In an embodiment of the present invention, a transportation vehicle, such as a forklift truck or an extension truck, has an RFID interrogator installed on it. RFID tags are attached to objects (such as pallets and loading) and locations (such as a storage location, passing location, or loading dock). In the case of a carriage, the information sent from the tag may include identification of the weight of the carriage, the carriage, and one of the characteristics of the items on the carriage. In the case of a location, the information is a description of the location, such as a location code or coordinates. The RFID interrogator transmits the interrogation signal to the RFID tag. Each RFID tag transmits a signal that is equipped with the information code of the tag in response to the interrogation signal, especially when the vehicle is sufficiently close to the tag, although it does not need to be in the line of vision.

The operation linking a processor to the RFID interrogator is used to process the signal received from the tag by the interrogator and determine the characteristics of the loading and location of the RFID tag for the detection location. The processor can be configured on the panel of the vehicle, at a remote station, or in a combination of the two.

It is preferable to use RFID tags on both the object and the location. In addition, when RFID tags are used in one or more locations, an identification tag such as a code tag may be attached to the object. In this case, the interrogator on the transportation vehicle also includes a barcode scanner for reading the information stored in the barcode label. Similarly, when barcode labels are used in locations, such as next to a loading dock door, RFID tags can be used on objects.

Preferably, the processor is provided with characteristics related to the object, wherein feedback information of the position of the configured object and the position of the moving object therein is provided to the operator through a user interface. For example, the processor can send an audible signal (such as a beep) or a visual signal (such as red or green light or a graphic display on a monitor) to the operator to notify the operator whether the correct object has been picked up Or whether the object has been placed in the correct position. The processor can be further constructed to send instructions to the operator about the operations performed, or the processor can instruct the interrogator to send information, such as the movement history of an object to the RFID tag of the object. RFID tags store information, which can be read later, for example, by an RFID interrogator at another station. Similarly, the processor can instruct the interrogator to send information to an RFID tag at a location, and then store it by the location tag.

In another embodiment of the invention, the interrogator can recognize and therefore only read information from the tag that is in the distance closest to the interrogator. This is accomplished by dynamically attenuating the power in the interrogation signal until only the RFID tag responds in the distance closest to the interrogator. This reduces the possibility of misidentifying a location or object.

In the embodiment of the present invention, the processor can generate a signal that can be seen by the operator, which is an indication of the minimum interrogation signal strength required to detect the RFID tag (target RFID tag) seen by the interrogator. It can represent the minimum interrogator signal strength as a trust stage (the lower the minimum signal strength, the higher the trust stage) or the approximate distance between the tag and the interrogator (the lower the minimum signal strength, the shorter the distance).

In another embodiment of the present invention, a passing position, such as a loading dock gate or a truck parked at the loading dock gate, is marked by an RFID combination having two RFID tags close to each other. Configure an RF shield, such as a metal plate or a metal curtain between the two tags. When the interrogator is attached to one side of the shelter, only the label on the same side of the shelter as the interrogator responds to the interrogation signal. Therefore, this configuration method enables the system to determine the moving direction of an object with respect to the passing position. For example, the system can determine whether a vehicle carrying objects has been moved from the inside of the warehouse to the loading dock or entering the warehouse from the loading dock through the gate.

In another embodiment of the present invention, an RFID interrogator for object identification and for location identification operations is equipped with a transportation vehicle. Equipped with RFID tags to mark objects and possible locations. In addition, the warehouse floor is equipped with a magnetic strip line segment that provides a magnetic signal indicating the location of the line segment. Equipped with a magnetic signal reader for detecting magnetic signals from the belt. Vehicles are also provided. The processor on the vehicle panel is operatively connected to both the RFID interrogator and the magnetic signal reader for determining the characteristics of the object and the arbitrary position of the signal received from the interrogator, and the position of the signal from the tape reader .

In another embodiment of the present invention, the transportation vehicle is equipped with an "arrival tracking" type of lifting device that can arrange an object at multiple heights. It is further equipped with a height sensor for generating a signal indicating the height of the configured object by the lifting device, which is linked to the vehicle equipped with the lifting device. The height signal can be electronic, visual, audible, magnetic, electromagnetic or any type of signal. The embodiments of the present invention are particularly useful when loading or unloading items from one of the warehouse slots in a vertical row. In this embodiment, it only needs to connect a single position tag with the row, and the system can use the height sensor to identify the correct slot in the row.

Therefore, in one of the concepts of the present invention, a system for arranging an object in a plurality of positions includes: (a) a transport vehicle moves the object back and forth in any of the plurality of positions; (b) an object related to the object The tag stores information describing the characteristics of the object; (c) a plurality of location tags, each tag is arranged in one of the plurality of locations and stores information describing the location of the tag; (d) an interrogator, including a radio frequency transmitter And a receiver configured on the transportation vehicle to receive information describing the characteristics of the object from the object tag and receiving information describing the location of the tag from the location tag; and (e) a processor, operatively connected to the interrogator. The processor determines the characteristics of the object from the information describing the characteristics of the object, and determines the position of at least one position label and the spatial relationship between the object and the position from the information describing the position of the label. For example, the simplest format for determining the spatial relationship is to determine when the RFID tag of the object and position is detected after the same clock, the object is placed close to or the position of a mark.

Preferably, the processor can also provide instructions to the operator through a user interface to pay attention to the movement of the object. These instructions can include (a) a feedback such as whether a required object has been detected; (b) a direction to a required location; (c) a feedback such as whether the object has been carried to a required location.

In the above system, the transmitter of the interrogator is preferably capable of transmitting a signal equipped with information codes, such as the movement history of the object or the storage history of the location, and the storage code information of the object and location tags.

The system preferably also includes a signal generator operatively connected to the processor to provide a signal to the operator of the vehicle through a user interface, such as a visual display or computer monitor display that can hear a beep or light, in the interrogator The description of the position of one of the plural positions when receiving the information describing the position of the label from the position label.

In another concept of the present invention, the RFID interrogator is constructed and arranged to read information only from the RFID tag closest to the interrogator. This is preferably done by dynamically attenuating the output power of the interrogation signal until only the RFID tag closest to the interrogator responds to the interrogation signal. Preferably, a target trust indicator is included to provide visual feedback of the tracking process.

In another concept of the present invention, at least one location tag defines a flat panel, and the tag transmits a first signal indicating that the interrogator is arranged on one side of the flat panel and transmits a second signal indicating a second signal different from the first signal on the flat panel. Configure the interrogator on the other side. The location tag can include two RFID tags separated by a shield, such as a metal plate or a screen usually arranged in the plate, where only the RFID tag arranged on the same side of the plate as the interrogator responds to the response from the interrogator Signal.

Another concept of the present invention is a system for tracking an object at a plurality of positions configurable on the surface of a passing bearing. The system includes a transport vehicle to move objects between locations, an object tag of the object stores information describing the characteristics of the object, and an interrogator arranged on the vehicle to receive the information describing the characteristics of the object from the object tag. The system further includes a magnetic tape attached to the surface of the passing bearing. The magnetic tape contains a plurality of line segments. Each line segment is provided with information codes describing the position of the line segment, and a magnetic signal is generated with an information code describing the position of the line segment. The vehicle is equipped with a magnetic signal reader for sensing the signal generated by the magnetic band. A processor is operatively connected to the interrogator and the magnetic signal reader to determine the characteristics of the object from the information describing the characteristics of the object, the position of the line segment of at least one magnetic tape, and the spatial relationship between the object and the position.

Another concept of the present invention is a transportation vehicle for moving an object with a radio frequency identification tag attached to it at a specific height position back and forth. The vehicle includes: (a) a radio frequency identification interrogator to receive a signal from the tag; (b) a crane that can arrange objects at multiple heights; (c) a height sensor to generate a signal indicating the height of the arranged object (D) A device for generating a signal indicating the horizontal position of the vehicle; and (e) A processor is operatively connected to the interrogator, height sensor and signal generating device. The signal received by the processor from the tag determines the characteristics of the object, the signal received from the height sensor determines the height of the object, and the signal generating device determines the horizontal position of the vehicle.

Another concept of the present invention is a method of managing the movement of an object between locations in an environment. A first RFID tag is attached to a location and stored in it, and can transmit a signal with an information code describing the characteristics of the object. A second RFID tag is attached to a location and has been stored in it and can transmit a signal with an information code indicating the location of the second tag. Equipped with an RFID interrogator equipped with a means of transportation, it can receive the signal from the tag and determine the information stored in a tag. The method includes the steps: (a) use an interrogator to receive information describing the characteristics of the object; (b) determine the proposed position of a moving object; (c) use a vehicle to move the object to a position; (d) use the interrogator To receive location information; and (e) when the location indicated by the information received in step (d) matches the proposed location, the object is placed at the location.

Another concept of the present invention is a method of using an RFID interrogator equipped with an adjustable power output stage to find a target RFID tag among a plurality of RFID tags. Each tag is constructed and configured to transmit an identification signal in response to an interrogation signal from the interrogator. The method includes the following steps: (a) transmit the interrogation signal in a power output stage; (b) determine whether the target tag has been detected by the interrogator; (c) if the detected target tag reduces the power output stage; (d) repeat Steps (a)-(c), each use the power output stage reached in the previous repeated step (c), such as the power output stage in step (a) until the target tag is no longer detected; and (e) The termination of the repetition immediately transmits an interrogation signal at the power output stage that arrived before the most recent repetition in (d).

Schematic description

Other objectives and advantages of the present invention can be understood by reading the following detailed description of the specific embodiment and by referring to the drawings, among which:

Figure 1 illustrates an embodiment of the present invention, in which an RFID tag is attached to both the object and the location;

Figures 2(a), 2(b) and 2(c) illustrate one of the monitor displays on a panel of the interrogator at different stages of completing a load reconfiguration operation;

Figure 3 illustrates another embodiment of the present invention, in which a barcode label is attached to an object, and an RFID label is arranged at the position;

Figure 4 illustrates one of the principles of using RFID tags to determine location and movement;

Figure 5 illustrates an embodiment of the present invention, in which two RFID tags close to each other are arranged for the relevant position of the transport vehicle;

Figure 6 illustrates that the present invention is basically similar to one of the embodiments shown in Figure 5, but with a fixed interrogator and a mobile RFID tag for determining the relative position of the object to which the RFID tag is attached;

Figure 7 illustrates an embodiment of the present invention, in which an RFID interrogator is constructed and configured to detect only the RFID tag closest to the interrogator;

Figure 8 illustrates a concept of the present invention to identify a processor that is closest to an RFID tag of an interrogator; and

FIG. 9 illustrates a visual display of a trust phase in the RFID tag identification provided by the embodiment shown in FIG. 7;

Figure 10 illustrates an embodiment of the present invention in which an RFID tag is used to identify an object and a magnetic tape is used to identify a location.

Figure 11 illustrates an embodiment of the present invention in which a height sensor is used to identify a specific slot in a storage rack marked by an RFID tag.

Detailed description of the invention

1, the object tracking and warehouse management system 100 is used to track an object 132 such as a load or pallet, and includes a transportation vehicle 110 such as a pallet truck, forklift truck, or stretch truck. Configure an interrogator 120 such as an RFID interrogator linked to a processor on the vehicle 110, which may belong to it and includes a central processing unit (CPU) 160, a display 170 and an input device 180, such as a keypad, The format of a pointing device and/or a computer that touches the panel display. The system further includes some tags, such as RFID tags 130, 140, and 150. An object tag is, for example, an RFID tag 130 attached to an object 132; other tags, such as RFID tags 140 and 150, serve as location tags and are arranged in different locations such as a storage location (warehouse slot) 142 and a loading dock 152. The processor on the vehicle can also be linked to a remote host computer 190 through an RF link or other suitable communication system that provides a continuous link between the vehicle and the host computer. The main computer 190 can also be linked to RFID interrogators and processors on other transportation vehicles. The host computer 190 and processor can also be part of a larger computer network.

RFID tags 130, 140 and 150 can receive, store and transmit information and can be of any type suitable for this purpose. The tag can include an antenna, a circuit for processing RF signals, a microprocessor, and digital memory. They can be passive devices that only transmit signals based on receiving an interrogation signal and rely on the power contained in the incoming RF wave. They can be active devices that continuously or periodically transmit signals and include their unique power sources. Examples of commercially available RFID tags include Intellitag available from Intermec Technologies Corporation, Everett, WA ^ RFID tags.

Tags can store wide and different information about objects and locations. For example, the tag 130 may store a code, such as a loading number or a carriage number, to describe the characteristics of the object. It can also store information about the movement history of the object or the weight of the object. The tags 140 and 150 can store information indicating the location, such as a loading dock number, warehouse slot number, and trailer identification number. The location tag can also store other information about the location, such as the history of objects stored in the location, information about the types of objects stored in the location, or restrictions or warnings about the location.

The RFID interrogator 120 can be any type commonly used for receiving signals, and it can be an RF receiver; it can also include a transmitter for providing an interrogation signal to a passive RFID tag. The RFID interrogator 120 can further transmit information stored in an RFID tag. Therefore, the interrogator can provide updated information about the movement history of an object or the storage history of a warehouse location. As another example, in a situation where this information can be stored on the label and/or the comparison of the information already stored on the label is provided, a weight sensor that determines the weight of the object can be equipped with a vehicle.

The processor can include any suitable processor, including general or special purpose computers. The processor preferably has a robust design suitable for use on a mobile vehicle. The display 170 may include a monitor, light, or a horn or buzzer. The processor can be programmed to provide operator interaction through a graphical user interface. An input device 180 may include a keypad, any suitable pointing device, and/or a voice recognition device. In the case where the input device 180 is part of a monitor, the display 170 may also be a touch screen monitor.

The remote computer 190 can be of any applicable type, including general or special purpose computers. It can also contain a database for warehouse management, storing this information such as load movement history, configuration, characteristics, announcement records, personal records and customer records. It can sometimes be provided with query results from the interrogator, manual input by the operator through the processor on the panel, and information from the host computer through the remote link to update the content of the database.

It can also be equipped with a transport vehicle 110 to inquire about the RFID tags placed at different positions (such as height) of the vehicle 110 and/or at a different frequency (for example, the tags used for characteristic items can use a frequency different from those used for the location). ) The label of communication. This flexibility can be achieved by connecting multiple antennas with different orientations to one of the interrogators, or configuring multiple RFID interrogators with each interrogator with its own unique frequency.

In an illustrative application of the present invention, consider a warehouse, where items arriving at the warehouse at different locations are moved along a main conveyor belt and then transferred to a branch line, where pallets are assembled at its terminal. The operator of the transportation vehicle 110 reads the instructions from the remote computer 190 from the display 170 and picks up a carriage 132 at the terminal of a specific branch line 142. Refer to Figure 2(a). The operator drives the vehicle 110 to a specific warehouse location 142 and approaches a pallet. The interrogator 120 interrogates the tag 140 which transmits a signal provided with a position information code. The interrogator detects the signal and transmits it to the processor to determine whether the vehicle 110 is close to the correct position. When the processor confirms that the position is correct, the processor then uses the interrogator 120 to interrogate the tag 130 to identify the carriage 132. The tag 130 transmits a signal with a carriage number code. The signal received by the interrogator 120 is processed by the processor. If the carriage number is correct, the operator picks up the carriage 132. The processor then instructs the operator to move the pallet to the loading dock 152 (Figure 2(b)). At the loading dock 152, a position confirmation procedure similar to that used for the start position 142 is performed. If the vehicle has arrived at the correct loading dock, the operator receives a confirmation that the vehicle has arrived at the correct loading dock (Figure 2(c)). If the operator has taken the carriage to an error position, the program will send a message to the display 170 to indicate the error. The processor can additionally display a map and/or a set of directions to instruct the operator how to reach the correct location. Therefore, the use of RFID tags and related computer systems is easier and is mainly used for immediate identification and confirmation of loading and location. Immediately identify any operator errors corresponding to the characteristics, positions, and movements of the load, and can immediately take corrective actions. Therefore, the opportunity for errors related to visual inspection is greatly reduced.

During or termination of the above sampling procedure, the processor on the vehicle 110 can send the status of the object and other related information to the host computer 190. The processor can also write the updated movement history and/or the status of the carriage 132 to the RFID tag 130. For example, this information can then be used by a tracking system at the target location. The information can be generated by a processor, and received from a host computer or manually input by an operator through the input device 180.

A modification management system 200 is disclosed in FIG. 3, which is similar to the system 100 shown in FIG. The difference between the barcode scanner 220 of the barcode. The location is still identified by RFID tags 140 and 150. The use of different types of identification tags for objects and locations provides additional flexibility in accommodating a wide variety of warehouse configurations and operations, including accommodating bar code trays with unmarked RFID tags. Of course, there is no need to use barcodes to replace all RFID tags used for loading. The combination of a code and RFID tags can be used for loading identification purposes, thereby further increasing the range of objects that the system can handle.

Movement and direction determination

In a specific application, in addition to knowing the location of a load, it needs to know whether and in the direction in which a load has moved through a specific point. For example, when a forklift truck transfers a pallet to a trailer, it is often not enough to know that the pallet has reached the loading dock; often it is better to know whether the pallet has passed the gate of the trailer from the side of the loading dock. In principle, as shown in FIG. 4, it is allowed to use two RFID tags 320 and 330 on both sides of a board and determine the direction of movement of the interrogator according to the first detected tag. But in order to achieve any reasonable accuracy in this decision, two tags must be placed far away. That is, the distance between the two tags is large enough so that the intensity of the interrogation signal at that distance decreases from clearly above the detection threshold to clearly below the detection threshold. This distance is often larger than the allowable size of the platform (such as the warehouse trailer door). In addition, in this configuration, most of the movement is accurately determined when the pallet truck system arrives at the point 310 from a distance, rather than when it only passes through the point 310. Therefore, the measurement will not reflect the true state of the device.

To solve this problem, FIG. 5 illustrates a preferred configuration of a position label 400 corresponding to a concept of the present invention that can detect the movement of an object. It includes two tags 420 and 430 separated by a short distance. An RF shield 410, such as a metal plate, metal screen, or other RF reflective or absorbing material is arranged between the tags. Preferably, the shield 410 is arranged at an angle (for example, 45 degrees) with respect to the moving direction of the load. A gap 450, preferably approximately one inch (2.5 cm), is defined between the label 420 and the cover to preserve the sensitivity of the label. It is preferable to arrange a second metal plate 440 after the second label, and define a second gap of 460° close to 1/2 inch (1.25cm). The plate 440 can better reduce the maximum reading distance of the label 430 to facilitate further Ensure that only one label can be read at any given position. All combinations can be enclosed in an RF transparent accessory (not shown).

Because the RF shield prevents all subsequent interrogation signals from the tag 2430 when the transport vehicle carries the RFID interrogator and is loaded on the same side of the RF shield 410 as the tag 1420, the interrogator will not detect the tag 2. Similarly, when the interrogator is attached to the same side of the RF shield 410 as the tag 2430, the tag 1420 will not be detected. It divides the two tags detected by the interrogator only when the interrogator transmits through a short range close to the board. Therefore, by detecting the time sequence judgment of the tags 1420 and 2430, the direction of the board movement defined by the RF shield 410 can be accurately determined.

The same principle can be used in one of the slightly different configurations shown in Figure 6. In this case, a mobile tag 400 moves through a fixed interrogator antenna 510. The precise timing of when the RF shield passes through the antenna can be determined by detecting the time sequence of the two tags in the tag 400.

Distinguish most FRID tags

In a state where most RFID tags are within the detectable range of an interrogator, the difficulty can increase if more than one RFID tag responds to the interrogation signal. For example, suppose a vehicle approaches a target location marked by an RFID tag, but no other location tags are within the detection range of the interrogator and they also respond to the interrogation signal. Because the interrogator receives more than one response signal, if the target tag is closest to the vehicle, the operator of the vehicle may not be able to decide. One solution would be to retain the low-power RF interrogation signal, thereby reducing the possibility of having many tags in the detection range. But it also mainly reduces the detection range of the interrogator, thereby reducing many of the advantages of using RFID tags.

This difficulty can be overcome by the so-called dynamic attenuation of the interrogation signal corresponding to a concept of the present invention, by using a high RF power stage interrogation signal to start the interrogation and reduce the power stage until the target RFID tag responds to the criticality of the interrogation signal stage. As illustrated in FIG. 7, a system includes an interrogator 120, a processor 660, an antenna 122, and an attenuator 640. Preferably, the attenuator of a digital device transmits a stronger interrogation signal when the tag 620 is further away than when the tag 620 is closer. For an interrogator that can change the output power, construct an attenuator in the interrogator; for an interrogator with a fixed output power, you can connect a digital control attenuator between the output of the interrogator and the antenna. As illustrated in FIG. 8, the interrogator (810) is started by transmitting the interrogation signal at full power and determines whether the target tag has been detected. If the target tag (820) is detected, other tags may be prepared together, and the power of the interrogation signal (830) is reduced by a predetermined coefficient or increment. If the target tag is still being detected, the procedure is repeated starting with a larger power reduction factor or a larger power reduction increment until the target label is no longer detected (840). Once the target tag is no longer detected, increase the power of the interrogation signal and return to the stage of the previous step (850). A power reduction factor or increment is prepared, and the procedure is repeated from step 840. Preferably, the coefficient or increment can be determined empirically based on the expected minimum space between adjacent tags when the system is installed.

The network effect of this procedure is to continue to reduce the RF power stage of the interrogation signal as long as the detection distance is greater than the distance between the interrogator and the target tag, and continue as long as the detection distance is less than the distance between the interrogator and the target tag Increase the power stage of the interrogation signal. Therefore, if the distance between the interrogator and the target tag changes, adjust the power stage of the interrogation signal to the "search" for the best stage so that the detection distance matches the distance.

One of the results of the dynamic attenuation system described in the article is that the optimal RF power stage of the interrogation signal is directly linked to the stage where the interrogator is placed close to the trust of the target tag: a low RF power stage means a smaller detection range and therefore a comparison Approaching target tag and higher trust stage. Conversely, a high RF power stage means a larger detection range and therefore a farther target tag and a lower trust stage.

This feature can be used to provide a signal indicating the distance between the interrogator and the target tag. For example, the output of a digital attenuator can be used to represent a function of the distance. In addition, in a variable power interrogator, the output power can be set by a variable voltage at one of the control points in the interrogator. This voltage can be used as a signal indicating distance. The signal indicating the distance can be used in turn to generate a visual aid to the operator for approaching a target tag through a user interface. For example, a graphic bar 700 shown in FIG. 9 can be displayed on the panel computer display 170 to represent the trust phase. The length of the programmable bar 710 is changed between a minimum position 720 corresponding to one of the highest RF power settings, and a maximum position 730 corresponding to one of the lowest RF power settings. In addition, a stylized bar can indicate the distance to the target label. Then the length of the bar in this case is increased with the RF power stage. Some other possibilities exist. The size from the digital display in the trust stage of the distance to the dot type indicates the distance to the label.

In addition, the trust stage indicator can be programmed to display a moving average calculated from the ratio between the count of the detected target tag and the total count of all tags that are successfully read.

Another dynamic attenuation system includes the same components as the system described above, but is constructed and configured to repeatedly transmit the interrogation signal but continue to reduce the power stage of the interrogation signal as long as most RFID tags are detected, until only one RFID tag responds to the interrogation signal. Because of the distance to reduce the interrogation signal strength, the single response RFID tag is then the closest to the interrogator among most RFID tags.

Additional/additional location recognition

An example of other control and/or guidance systems combined with RFID tag-based system systems can be provided to complete the required functions. For example, a magnetic tape applied to aisles and warehouse floors for vehicle guidance can be used for location determination such as an additional or additional device for RFID location tags. Applicable magnetic tapes are known in the art. The US Patent Application Serial No. 08/341,369 filed by Dahlin and others on November 17, 1994, titled "Recognizable Magnetic Items for Use on the Surface of Transport Bearings", was disclosed in WO96/16231. Instance. In a system using this magnetic belt, the belt is arranged on a transport bearing surface. A magnetic sensor arranged on the transportation vehicle detects the magnetic signal when the sensor passes over a part of the belt. Further, the tape can be magnetized ("encoded" or "written") along the type of position along the tape, so as to allow the determination of the vehicle position based on the coded information read by the sensor on the vehicle. This guidance system can be used in a combination equipped with an RFID system to achieve an equivalent greater operating efficiency.

An example of this system is shown in FIG. 10, in which carriages are stored in separate passages on the floor of a warehouse, and one magnetic tape 540 can be arranged along each passage. A vehicle 510 is equipped with an RFID interrogator (disclosure of its integration into the processor 52) and a magnetic signal reader 530. In this way, the position of the coded belt can be determined along the belt by the belt reader on the vehicle. For example, it is possible to read the magnetic type such as a numeric code of a line segment of a tape next to a storage location, and the processor recognizes it as a description corresponding to the location number of the storage location, such as a floor location. The processor receives the position information from the belt through the belt reader 530 and the carriage characteristic information from the RFID tag (such as the tag 560) through the interrogator and the antenna 550. The processor also sends instructions to the vehicle to complete the work, including the pallet pick-up coordination, the pallet number, and the pallet target coordination.

As shown in FIG. 11, another example of the allowed operation of the present invention is the movement of the pallet, not only about the horizontal vehicle movement but also the vertical movement of the pallet back and forth between the slots in the warehouse shelf. In this system, the warehouse shelf can be marked by the RFID tag 790 as described above. As in the previous embodiment, there is an interrogator 760 and an antenna 770 that can be used to read the tag 790 in order to identify a warehouse shelf that is required to be equipped with a vehicle 750. In order to avoid the need to have a separate position label to mark each slot in each warehouse shelf, it may need to be equipped with a vehicle 750, which in this embodiment is equipped with a height sensor 780 to extend the truck. The vertical movement of the fork of the extended truck is monitored by the height sensor, which sends a height signal to the processor or remote host computer. The height sensor is preferably a counter connected to the driving device of the fork, but can be any other suitable device for measuring height, such as a linear moving device, a laser rangefinder, etc. The processor can instruct the operator to raise the fork to a predetermined height for storage or retrieval from a shelf. The operator can manually control the fork to rise to the height, or can program the crane truck to automatically stop at the required height. Equipped with this system, it can effectively and accurately control the movement of inventory items in all three dimensions. In addition, the use of a height sensor on the stacker eliminates the need to configure RFID sensors for each storage stage (slot) in a vertically extending warehouse shelf. A single RFID tag can be used to identify each column of the slot. Position, equipped with a height indicator to identify individual slots in that field.

The specific embodiment described above provides a fully automated system for identifying, moving, and tracking objects throughout a warehouse or other similar environment. The system provides immediate feedback to operators operating throughout the warehouse, thus minimizing the possibility of errors. The system is suitable for use in a wide range of locations with all the operations related to the warehouse, such as storage locations, storage shelves, floor passages, and shipping docks. Because the system can be operated in relation to a central data container, the system can point to and track all movement of objects throughout the warehouse. By using the present invention, errors in inventory management can be greatly reduced, thereby increasing productivity.

The specific embodiments disclosed above are for illustration only, and those skilled in the art will understand that the present invention can be modified and implemented in different but equivalent devices, with the advantages of instruction therein. Moreover, there are no plans for the details of the configuration or the design shown therein, except for the limitations as described in the scope of the patent application below. Therefore, it is obvious that the specific embodiments disclosed above can be changed or modified, and all such changes are considered within the scope and spirit of the present invention. Therefore, the protection of search is proposed in the scope of patent application below.