Research on signature detection system in collating machine

One of the production processes of printed matter is to bind and shape the single-page printed sheets printed by the printing press, and the key to its success or failure is the matching process.

In order to avoid phenomena such as heavy posts, few posts, and random posts that occur in manual page layout, two main solutions are currently used: First, the principle of photoelectric diffusion and reflection is adopted, and the red LED is used as a light source to illuminate the signature, according to the inspection area. Reflected light intensity to distinguish. The program is sensitive to the surrounding light, and has a greater dependence on the paper's finish, reflective performance, and printing density. In particular, for large color changes, the inspection accuracy is low, and the desired effect is not achieved; the second is to use Optical image recognition technology for image recognition of part of the contents of the signature. However, the signature discrimination rate is not high due to the placement shift or the relative position shift or twist occurring during the work process.

At present, barcodes have been widely used as a timely, accurate, reliable, and economical data input method. Therefore, the use of bar code identification technology to apply it to the printing product binding production site is a simple and effective signature detection system. The starting point of this project design is based on this.

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Figure 1 System composition

System structure and working principle

A signature detection system based on barcode recognition consists of the following components: (1) items to be detected with a barcode, (2) a barcode reader, (3) an embedded control system, and (4) a computer in an enterprise LAN.

Its composition is shown in Figure 1.

First, a bar code is printed on the edge of the layout of the signature as a basis for the subsequent detection of the system. Then, an embedded control system with a barcode reader is used to compare the read barcode information with the set reference barcode information, and according to the set control logic, the external electrical machinery is combined with the read barcode information. The institution completes the operation of this type of signature.

The computer can communicate with the embedded control system through the communication interface, read the bar code content, thereby obtaining the signature information, and then by counting and other operations, the information is written into the database. The computer is in the company LAN. Any computer in any office area can also access the database in the computer in real time to understand the production process and production conditions.

System design and implementation

In the specific system implementation, we use the existing bar code reader to form an embedded control unit with the single-chip microcomputer system. Through the RS485 serial communication port, the control information of the control unit is written into the computer database.

1 Barcode Reader Selection and Modification

The CIPHER 1000 hand-held bar code reader was chosen here. The reader has the following advantages:

● It can identify a variety of common bar code systems.
● With digital keyboard (PS/2), RS232, USB and other digital interfaces.
● Fast reading speed.
● With a variety of reading methods and power saving methods.

We changed the manual contact switch on the reader to start reading the bar code from manual start to automatic control by the embedded system, that is, to simulate the control of the hand by closing and releasing the relay contact controlled by the embedded system. .

2 Embedded Control System

● Hardware design

The embedded control system part contains the digital interface circuit part of the reader and a single-chip microcomputer system and its peripheral interface circuit.

The hardware block diagram is shown in Figure 2.

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Figure 2 detection part of the hardware block diagram

The reset and watchdog chip selects the MAX813, which monitors the operation of the software to prevent the program from running or crashing. In order to more accurately control the communication rate, the 11.592MHz crystal oscillator is selected; the microcontroller is selected from ATMEL Corporation's AT89C51.


● Embedded software section

The use of C51 to write software, software system to achieve the functions shown in Figure 3.

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Figure 3 software function block diagram of the detection part

The software is responsible for capturing the paper feed signal, and then simulating the human hand button, starting the sensor work, judging after reading the bar code information, performing different output according to the judgment result, and communicating with the upper computer at the same time.

In the software working process, in order to capture the input of the request signal in real time, the signal input is read in an interrupt mode. After receiving the signal, the corresponding request event flag is set, and the processing of the request signal is performed outside the interrupt. This can not only effectively capture the request input signal, but also prevent the interrupt program from consuming CPU resources for a long time.

After the main program is powered on and initialized, each event flag is viewed in sequence. If it is found that the event request exists, the event is immediately processed. After the processing is completed, the request flag is cleared. The events to be processed include: capturing the feed timing, receiving data from the computer, checking the comparison after reading the barcode, and processing after the determination. The entire system flow is shown in Figure 4.

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Figure 4 main program flow chart

The feed beat is triggered by an external paper feed mechanism. The software uses external interrupts. Communication events are triggered by the software's serial receive interrupt. Barcode processing events are triggered by high-priority interrupts that receive digital bar code signals.

Set the CIPHER interface board to send the barcode content on the PS/2 keyboard. The timing of the interface signal is shown in Figure 5.

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Figure 5 Barcode Reader Digital Interface Timing

For the other two incidents, the wrong signatures and white paper incidents come from the software's comparison of the barcode information.

1 Processing feed beat signal processing

After detecting a barcode read request-feed signal event, a barcode reader should be activated to read the barcode information. The original manual button on the reader was modified to simulate the electric shock of the relay, and closing the relay can completely realize the purpose of opening the reader.

2 Dealing with Barcode Judgement Events

After the microcontroller receives the complete bar code information, the bar code is set to determine the event. When dealing with a judgment event, the read bar code and the set reference information are first compared. Since barcodes use the keyboard interface to transfer data, the encoding rule for each digit or character is "pass code and break code", that is, each character to be transmitted includes three bytes: "encode + 04F + code". Therefore, when performing the comparison, it is necessary to pay attention to the movement of the reference bar code pointer and the bar code pointer to be determined: the reference pointer moves by 1 byte at a time, and the pointer to be judged moves by 3 bytes.

The state transition after the reading of the barcode is judged as shown in FIG. 6 .

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Figure 6 Bar code judgment state diagram

In the case of signature error, the SCM will output the alarm indication signal according to the set software, and output the drive control signal to the signature eliminator, and remove the wrong signature; if only one signature removal device is installed at the end of the pipeline, the MCU The number of feeds will be counted. After the error signature passes, the microcontroller sends a signal to the signature rejection device. The reject device removes the signature set including the incorrect signature.

3 Computer Communication Section

On the assembly line, each page station equipped with a signature must be equipped with a reader and an embedded control system. All of the signature detection equipment can also be connected to the computer via a bus, and the book can be further completed by the computer. Statistics, query and other functions.

In the physical layer design, a mature RS485 serial communication bus is used to connect to different detection devices and computers; in the link layer design, in addition to the checksum, there are data frames in order to ensure reliable data frame transmission and reception. Special frame header bytes and end-of-frame bytes prevent interference on the link.

4 Database section

The computer uses VC++6.0 to write a user-friendly operation interface and uses ADO (ActiveX Data Object) to manage the database. Obtain the result record set to be obtained by executing the SQL command during operation.

to sum up

The system can be used in any article detection system with a bar code, for different application requirements, as long as the different electrical and mechanical mechanisms are connected to the output terminals of the system according to the site conditions, that is, according to the required control logic automatic detection.