Research on PCI based laser marking control system

  • Detail

Research on laser marking control system based on PCI Abstract: This paper introduces a design of laser marking control system based on PCI bus. The PCI bus control chip PCI9052 of PLX company is used as the interface chip in the system; Using Altera's CPLD controller EPM7064 and AHDL programming language, the IP soft core is designed to realize the decoding of local bus and the logic control of functional circuit; The PWM control circuit based on IP core takes the control clock from the PCI bus clock of 33 MHz, divides the frequency to obtain the PWM duty cycle adjustment with 8-bit control accuracy, and realizes the high-precision PWM signal output of fixed frequency and variable frequency. With the hardware design, the test software and laser marking application software are developed, which speeds up the hardware design process and promotion and application

key words: laser marking; PCI bus; CPLD; IP core; PWM circuit

0 introduction

laser is widely used in material processing because of its excellent monochromaticity, coherence, directivity and high energy density. With the increasing demand for anti-counterfeiting, accuracy, environmental protection and other aspects in the marking process of items, the application of laser marking equipment, especially laser flying marking equipment, has become increasingly popular. Here, the software and hardware design of the laser marking control system is mainly introduced, and the key problems in the circuit design of the control card based on PCI are emphatically analyzed. At the same time, the main functions of the marking software are introduced. The control system has four 16 bit D/a outputs, three 16 bit counters, four di/DOS, and one PWM laser power control output function. The system is stable in application and has complete functions. It has been used in industrial production

1 design of laser marking control card

the control card of laser marking system is the center of the whole control system, connecting the control software and the actuator. The structure of the control card is shown in Figure 1, which consists of three parts: PCI bus interface control circuit, local logic control circuit and functional circuit

pci interface circuit is used to realize the conversion from PCI bus logic to local logic. The system adopts the PCI bus control chip pcl9052 of PLX company as the interface chip, and the e2proom configuration chip as the ht93lc46. Due to the rich functions of the interface chip, the interface design is simplified, so that the work is concentrated on the local logic design, and the WDM driver is used to realize the unified management of the equipment by the computer. The local logic control circuit adopts IP core to realize the decoding of the local bus and the logic control of the functional circuit, which is designed and realized by the CPLD controller EPM7064 of Altera company, and the programmable extended interface control function. The functional circuit includes D/a circuit, I/O circuit, PWM circuit and counter circuit; The system selects the D/a controller ad7847 or ad5547 of simulator company as the key device to realize the output of a 5 ~ +5 V and 0 ~ 10 V analog voltage

1.1 design of fixed frequency PWM circuit based on IP core

in CO2 laser marking equipment, the control card outputs a control signal with adjustable pulse width and frequency through PWM circuit to control the discharge time of laser power supply, so as to achieve accurate control of laser output power. CPLD is used to change the torque acting on the sample in the design, which makes the design configuration very flexible. The IP soft core with corresponding functions can be designed according to the overall needs, saving onboard resources. The scheme adopts the hardware programming language AHDL of Al Tera company; The PWM controller is realized with epm7064slc. The PWM control circuit based on IP core takes the control clock from the PCI bus clock of 33 MHz, which can effectively use the interface resources

ip soft core 4 kHz output frequency is obtained by dividing the 33 MHz clock 8196. The 8-bit control accuracy can realize 256 level adjustment of duty cycle 0 ~ 1, and the prototype symbol of its soft core is shown in Figure 2. Among them, load is loaded into the control end as control data. When the signal is valid, the 8-bit control data in[7..O] is loaded into the internal control register. EN signal is an effective output signal, which is used to control PWM output. When the signal is effective, PWM is output. Lclkin signal provides the working frequency of IP soft core, and the fundamental frequency of PWM output signal is obtained by frequency division of this signal

the internal control statement of the soft core is as follows, in which pwmdata is the control logic of PWM wave output. When its output is high, the output is reversed



The simulation waveform of the soft core and the oscilloscope output waveform are shown in Figure 3

1.2 design of frequency adjustable PWM circuit based on IP core

the primitive symbols of PWM generation circuit with adjustable frequency and pulse width are shown in Figure 4. Among them, the en signal enables the device; The WR write signal cooperates with pfd0, PFDL, pcd0 and pcdl to realize the writing of frequency and pulse width control words. The control bit width is 12 bits, realizing 4096 level adjustment. Lclkin is the global clock signal, which comes from the 33 MHz PCI interface clock after 8 frequency division. Therefore, IP nuclear energy realizes frequency adjustment of 1 kHz ~ 4 MHz and duty cycle adjustment of up to 4096 levels within 0 ~ 100%. Datain with 8-bit data width is connected to El to control the input of data. The procedure of realizing the function of IP core is as follows:

the function simulation waveform is shown in Figure 5

the use of IP core to realize the PWM generation circuit with adjustable frequency consumes a lot of internal resources of logic devices. In contrast, fixed frequency IP occupies less logic resources, so it is more suitable for providing high-precision pulse width modulation for applications with fixed laser frequency

2 introduction of control software

aiming at the debugging of board and the application of actual laser marking system, TestStar hardware board test software and LaserStar laser marking software system are developed respectively

the board function test software can complete the test of all functions of the board

not only provides channel selection function, but also is used for D/a control output test; It also provides Di input signal detection and do output signal test; And counter calculator test and other functions. Through the design of test software, the efficiency of system design is improved. At the same time, the actual efficiency of each module can be tested separately, and the deficiencies of each module design can be found in time, so that the system will be more stable in the future when about 1/4 of the world's R & D activities are internationally marked in the Asia Pacific region

laser marking software system can easily single line text, TTF text, date, time, serial number; Automatic graphic alignment and circular typesetting; You can draw graphics with the mouse; It is convenient to import PLT graphic files and extract graphic outlines from BMP images. Without affecting the normal operation of the production line, it can realize the laser marking of products on the flow production line, thus greatly improving the production efficiency. The marking speed range is 0 ~ 60 m/min or 1 ~ 20 marks/s

the system can easily modify the marking content and set the marking power, speed and other control parameters. The marking lines are smooth and the depth is free. Users can also design special anti-counterfeiting codes, because data encryption technology is adopted, even if different users have marking systems, they cannot mark exactly the same content, making the system have good anti-counterfeiting marking functions. The actual marking effect of the system marking is shown in Figure 6

3 summary and outlook

the laser marking control system is designed based on computer PCI bus, which improves the sending speed and control accuracy of control instructions. The WDM driver under win Windows 2000/XP is designed and developed; The stability of the system is improved; It reduces the phenomena of system crash and blue screen caused by hardware compatibility and misoperation. CPLD device is used to integrate the functions of local logic processing and control data storage; The IP soft core is designed by using the hardware programming language AHDL of Altera company; Combined with the device epm7064slc, the PWM signal of fixed frequency and variable frequency can be accurately output, which reduces the use of separate devices, greatly improves the modularity of the system, simplifies the PCB layout and wiring, and is conducive to the upgrading and expansion of the system. Using the excellent encryption performance of CPLD, the system characteristic information and encryption logic are stored in it, and the hardware encryption of the system is realized in cooperation with the control software to ensure the uniqueness of the system, which can effectively improve the anti-counterfeiting ability of the marked content. The control system has been widely used in industry

Copyright © 2011 JIN SHI