1 Introduction
With the rapid development of photonics technology, laser processing technology in a more extensive range of machining
accuracy have become increasingly demanding. Reflect the level of development of laser material processing three factors:
first, the laser technology used in laser materials processing, laser device technology; second is laser equipment and
processing machinery, control systems, laser processing equipment; second The laser processing technology. Because the laser
technology has been very mature technology, so the possibility of laser equipment for effective control and laser technology
level laser processing technology application bottlenecks.
At present, many domestic manufacturers specializing in the production of laser processing equipment, compete with them
by the laser technology to the effective control of the laser equipment and processing technology, can effectively solve the
following problems, multi-axis of three-dimensional graphics, high-speed laser scanning and rapid advance caused synchronous
scanning of the vibration, scan format size and scanning accuracy, laser and reciprocating scanning dislocation, complex
algorithms and rules of graphic interpolation problems, has become the key to competition.
2 based on the OSP and FPGA design
In response to these problems, we designed the FPGA and DSP-based motion control card, laser engraving debugging solve
the above problems.
2.1 control card circuit design
Control card main DSP chip of FPGA two functions, extends around the DSP FLASH and SRAM to store programs and data, each
of the two FLASH and SRAM can share a chip select signal CS, composed of high and low double word 32 data bus read and write,
you can increase the communication speed of the DSP and MEMORY, an EPROM to store the downloaded program for the FPGA
configuration. Connect the DSP local bus and the PCI interface chip is a PCI bus controller (PCI bridge), which contains a
128KBit dual port shared memory, DSP local bus and PCI bus for data exchange, in addition to configure an EEPROM to store
data. DSP and FPGA mentioned in this article are low-power, low voltage operation, the I / O signal voltage is 3.3V, core
voltage I.8V, so the configuration while the output voltage of 3.3V and 1.8V voltage adjustment device.
FPGA resources, cost-effective, can the scene be repeated several times to program specific requirements for different
low-volume customers the flexibility to modify the design. DSP has the ability of high-speed floating-point operations, the
S-curve motion in the process of data and some interpolation algorithm for computing processing, to get rid of the dependence
of the PC, and processing data in real-time communication with the FPGA. The PCI interface is relatively common, the bus is
rich in resources, communication speed, the addressing space. USB door to work offline, do not have to configure a PC for
each boards, industrial site is easy to use, low cost, in line with the trend of the times.
2.2 the implementation of various functions
As the program has identified properly, the four-axis functions in an FPGA chip can be identical but independent of each
other\\ s operations, enabling multi-axis, flat-screen graphics and 3D graphics processing, you can use two and three-axis
linkage. Scanning opened KAM zone bitmap pixel control, not only to solve the large-format graphics processing, but also
achieved a synchronous scan, improve the accuracy of the scanning to ensure that the image quality of the carving.
(1) S-curve to a smooth high-speed movement and rapid advance.
To promote the process of high-speed reciprocating movement and fast line, without the technical processing, such as
ladder diagrams shown in the great acceleration of high-speed movement of towels, vibration, shock, the graphics will appear
irregular dislocation, severe will appear similar to the deformation of the corrugated. If the acceleration is reduced, the
growth time (t2-t1) processing zones, high-speed segment (F uniform above), thus resulting in efficient processing format
decreases. To solve this problem, S-curve in the variable motion, allows movement in a very short period of time, from low to
high-speed or mountain high speed to low speed gentle transition. The scene repeated the experiment on the same device, can
greatly improve the efficiency of processing and graphics quality.
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(2) the use of bitmap pixel control, to ensure the simultaneous scanning and scanning accuracy.
Order to store large amounts of scan data and to synchronize scanning purposes, the use of the FPGA built-in 2MBit block
RAM resources to store each line of image data. If each scan pixel. 1mm, maximum scanning accuracy, in theory, scan format
can reach 1.6m. Scan from low address to high address from each line of low to high in turn. Pulse of each scan, the stepper
motor driver before the laser head, a graphical data is read from the RAM area, and in accordance with the read data \\ 1 \\ or
\\ 0\\ state to decide whether to switch the light. DSP time to time in the FPGA RAM area to write a single line of graphics
data 512 X 32Bit during these 16KBit data processing, DSP, without further FPGA write data. Not only greatly increased the
efficiency of the laser equipment, but also to ensure the synchronization of the scan back and forth to scan the overall
dislocation, reverse compensation software also provides feasibility.
Synchronous scan, in order to improve the accuracy of scanning to improve image quality, an increase of eight laser
control register LCR set of LCR size (0 to 255), to improve the scanning accuracy, see the following analysis:
(3) the problems of image pixel control laser switches
For example analysis: assume that the bitmap data for 1010, the spot diameter Φ0. 1mm, single-pixel pulse number 5,
pulse and laser scanning are as follows:
Analysis can be seen from the above graphic: solely on the basis of the bitmap pixel control of the laser pulse width
determined for the number of single-pixel pulse width; due to the existence of the laser spot diameter, in theory, open the
laser spot position \"over cut\" phenomenon pixels \\ 1 \\ eat the next pixel is \\ 0\\ point.
Laser open, off delay:
If the laser on delay, off delay equal to the actual carving of the graph will pan;
â'¡ If the laser on delay> Off delay (on the light slowly off light) to \"gouge\" will decrease;
â'¢ If the laser on delay
(4) control of the laser pulse width.
In order to reduce or eliminate the phenomenon of \"over cut\" above the bitmap pixels \\ 1 \\ . Should send a shortest
possible laser pulse. The laser pulse width of the laser-driven power and laser tube open, off nature. Able to accurately
give the developers of the laser switch delay data is not, you can use the test method to determine the width of the laser
pulse. Reference: pixels \\ 1 \\ the first step pulse falling edge to trigger the laser ON, the counter delay T, (Mountain Laser
control register LCR 8 settings), the laser turn-off (OFF) . Such laser pulse width can be adjusted, rather than a single
pixel width of the pulse number. In this way, through the control of the laser pulse width, in pixels \\ 1 \\ send a laser spot
(rather than a segment), you can reduce the above-mentioned\\ gouge \\ , to improve the quality of laser engraving.
2.3 system, anti-jamming measures
The interference phenomenon is inevitable on the industry site and the practical application of the anti-interference
performance of the system is an important symbol of the system reliability. The printed circuit board devices, signal lines,
power lines, a high degree of aggregation of its design is good or bad a great influence on the anti-jamming capability. In
this design, mainly using the following anti-jamming measures:
(1) the number of analog circuits separately: the curse of the ordinary optical coupling or high-speed optical isolation,
separate power and ground in the middle of the internal circuit and external mechanical input signal.
(2) configuration to curse the capacitor: configuration to disaster capacitance in key areas, such as power input
termination 0.1 ~ 47uF SMD capacitors, filter out the interference of different frequency bands, power and ground side of
each component are configured O.1uF chip capacitors.
(3) digital filter configuration: For a few signals of the FPGA chip, reset, alarm, back to zero, can cause a system
reset or stop, in order to increase system reliability, plus a digital filter, this can be implemented in software, these
signals with VHDL language after several stages of D flip-flop (series, as the case may be), then the signal at all levels of
logical and or logical or.
3 Conclusion
With the continuous development of photonics technology and LSI, laser engraving will get a wider range of applications,
thus promoting the DSP and FPGA in related fields should Sichuan and development. In the foreseeable future. DSP technology
and FPGA is bound to get a wider range of applications in the aerospace, communications, laser engraving, and many other
areas, thereby promoting the progress and development of this technology.
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