WO2003006248A1 - System and method for automatically tuning of laser scanner - Google Patents

System and method for automatically tuning of laser scanner

Info

Publication number
WO2003006248A1
WO2003006248A1 PCT/KR2002/001203 KR0201203W WO03006248A1 WO 2003006248 A1 WO2003006248 A1 WO 2003006248A1 KR 0201203 W KR0201203 W KR 0201203W WO 03006248 A1 WO03006248 A1 WO 03006248A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
gain
calculator
error
pid control
Prior art date
Application number
PCT/KR2002/001203
Other languages
French (fr)
Inventor
Kyoung Cheol Park
Myung Won Lee
Original Assignee
O.I.S. Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by O.I.S. Inc filed Critical O.I.S. Inc
Publication of WO2003006248A1 publication Critical patent/WO2003006248A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/435—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material
    • B41J2/447—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources
    • B41J2/455—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources using laser arrays, the laser array being smaller than the medium to be recorded
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K15/00—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers
    • G06K15/02—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers
    • G06K15/12—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by photographic printing, e.g. by laser printers
    • G06K15/1204—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by photographic printing, e.g. by laser printers involving the fast moving of an optical beam in the main scanning direction
    • G06K15/1219—Detection, control or error compensation of scanning velocity or position, e.g. synchronisation

Definitions

  • the present invention relates to a system an d a method for automatically tuning of a laser scanner, and more particularly, to a system and a method for automatically tuning of a laser scanner that can perform an optimal tuning against a minute change of an optimal tuning value occurring while manufacturing or operating a laser scanner system.
  • FIG. 1 is a block diagram showing an overall construction of a general laser scanning system, which includes a position signal generation part 10, a laser-generating device 50, a first and a second optical systems 60 and 60' , and a scanning head part 90.
  • the scanning head part 90 is comprised of a position control part 20, a first and a second motors 30 and 30', and a first and a second mirrors 40 and 40', and is generally installed on the laser scanning system as a single sealed device.
  • the position signal generation part 10 is a means for generating a position signal to project the laser beam output from the scanning head part 90 on a predetermined position of the object to be processed, and the position signal is transmitted to the position control part 20 in the scanning head part 90.
  • the position control part 20 generates a position command signal for controlling the operation of the first and the second motors 30 and 30' on the basis of the position signal provided by the position signal generation part 10, and the first and the second motors 30 and 30' are driven along X-axis and Y-axis according to the position command signal.
  • the first and the second motors 30 and 30' are installed with the first and the second mirrors 40 and 40' as shown in the figure, where the respective mirrors 40 and 40' function as a reflecting mirror for reflecting the laser beam generated by a laser- generating device 50 described later, and the reflection angles thereof are regulated by the driving of the aforementioned first and the second motors 30 and 30' .
  • the laser beam generated from the laser- generating device 50 is reflected at a predetermined angle by the first and the second mirrors 40 and 40' via the first optical system 60, and the reflected laser beam is projected on a predetermined position, i.e., a position corresponding to the position signal generated by the position signal generation part 10, of the object to be processed, via the second optical system 60' .
  • the performance of the entire system depends on the exactness of the projection of the laser beam on a desired position, which has the close relation with the exactness of the control of the control part 20 that drives the respective motors 30 and 30' in accordance with the position signal.
  • FIG. 2 shows the laser scanning system, especially the control part 20 therein, shown in FIG. 1 in greater detail, in which the optical systems 60 and 60' , the laser-generating device 50, the second motor 30' and the second mirror 40' are omitted for the convenience of illustration.
  • the D/A conversion part 210 in the position control part 20 generates and outputs an analog type position command signal S through a predetermined signal processing of a digital type position signal provided from the position signal generation part 10.
  • the error signal generation part 220 compares the position command signal S from the D/A conversion part 210 with the present position value P of the mirror 40 provided through a position detection part 280 which will be described later, to generate and output an error signal E corresponding thereto. And, the error signal E is provided to the respective calculators 232, 234 and 236 in the PID control part 230.
  • the PID control part 230 is a general analog PID controller for processing the analog input signal, which is comprised of a proportional calculator 232, an integral calculator 234 and a derivative calculator 236 as shown in the figure, and the respective calculators 232, 234 and 236 output the error signal E provided from the aforementioned error signal generation part 220 after performing a predetermined signal processing.
  • the proportional calculator 232 in the PID control part 230 is a means for regulating a proportional gain thereof to a proper value, which functions to regulate and then output the magnitude of the error signal E to be included in an allowable error range required by the laser scanning system within a preset range.
  • the integral calculator 234 functions to regulate and then output a gain thereof so that the peak error of the error signal E becomes horizontal
  • the derivative calculator 236 functions to regulate and then output a gain thereof so that the error signal E becomes horizontal. This will be described later in greater detail with reference to FIG. 3.
  • the error signal E output through the respective calculators 232, 234 and 236 is synthesized by a signal synthesizing part 238 into a single control signal and then is provided to the filter part 260, and the filter part 260 filters to remove the frequency component causing the oscillation of the motor from the PID control signal.
  • the filtered PID control signal is transmitted to the voltage/current converting amplifier part 270, and the voltage/current converting amplifier part 270 converts the voltage of the filtered PID control signal to the corresponding current, and then amplifies it to a predetermined magnitude and applies it to the motor 30. Accordingly, the motor controls the angle of the mirror 40 by driving it according to the current applied from the voltage/current converting amplifier part 270.
  • the conventional general laser scanning system performs the tuning by controlling the gains of the error signal E through the respective calculators 232, 234 and 236 included in the aforementioned PID control part 230, whereby the motor 30 is controlled to project the laser beam on the exact position corresponding to the position command signal S.
  • the calculators 232, 234 and 236 are generally comprised of variable resistors 233, 235 and 237 that can be regulated manually.
  • a user inputs a reference position signal through a function generator, confirms the input waveform, the output waveform, and the error waveform corresponding thereto with his own visual sense using an oscilloscope, and then operates manually the variable resistors 233, 235 and 237 of the calculators 232, 234 and 236, in order to perform tuning.
  • FIG. 3 shows the examples of the waveforms input and output during the tuning of the general laser scanning system, and the corresponding error waveform.
  • the waveform shown by the solid line on the upper part of FIG. 3 is the waveform of the input signal S
  • the waveform shown by the dotted line is the waveform of the position detection signal P
  • the waveform shown by the solid line on the lower part thereof is the waveform of the error signal E generated by the difference of the input signal S and the output signal P.
  • the error signal E becomes the shape as shown on the lower part of the figure with a solid line.
  • the user tunes the variable resistors 233, 235 and 237 composing the respective calculators 232, 234 and 236 by a manual operation so that the input signal S and the output signal P are identical to each other, and in such a situation, if the tuning has been performed exactly, the error signal E displayed on the oscilloscope becomes the trapezoidal shape as shown in FIG. 3, and the magnitude of the error signal E is included in the allowable error range, the upper side of the trapezoid becomes horizontal, and the peak error sections (section 1 through section 4) becomes parallel with X-axis.
  • the proportional calculator 232 controls the gain thereof so that the error signal E can exist within the predetermined allowable error range
  • the integral calculator 234 controls the gain thereof so that the peak error (section 1 through section 4) of the error signal E becomes horizontal
  • the derivative calculator 236 controls the gain thereof so that the upper side of the trapezoidal error signal E becomes parallel with X-axis.
  • the tuning process of the PID control part 230 is generally performed while the laser scanning system is manufactured initially to set an optimal PID control (gain) value, and also the user thereof can perform the tuning process as required.
  • the tuning error during the operation may occur frequently due to the change of state of the motor and the PID control circuit as the operating time lapses, and in such a situation, the user has to disassemble the sealedly- installed scanning head part 90 and then perform re-tuning with the function generator and the oscilloscope, which may cause the deterioration of productivity by the cessation of the operation of the laser scanner. Furthermore, it is impossible in fact for the user to perform the exact tuning of the PID control circuit.
  • the present invention has been proposed to overcome such a problem of the above conventional art, and it is the object of the present invention to provide a automatic tuning system and method for a laser scanner that the tuning process of the laser scanner system can be performed not by the manual operation of a user but automatically, and it is possible to perform the tuning with greater exactness.
  • an automatic tuning system for a laser scanner that projects a laser beam on a predetermined position of an object to be processed by controlling a motor according to a predetermined position command signal, the motor to which a mirror is assembled, the automatic tuning system comprising: a position detection part for detecting a position of the motor corresponding to an angle of the mirror, and generating a position detection signal corresponding to the detected position; an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal; a PID control part having a proportional calculator, an integral calculator and a derivative calculator, the PID control part for changeably setting gains of the respective calculators based on a gain control signal, and generating a PID control signal based on the gains; a voltage/current converting amplifier part for converting/amplifying the PID control signal to a motor driving signal capable of driving the motor; and a microprocessor part for generating the gain control signal to change the gains of
  • an automatic tuning method of a laser scanner that projects a laser beam on a predetermined position of an object to be processed
  • the laser scanner comprises a motor for controlling a position of a mirror that reflects the laser beam on the predetermined position, a position command signal generation part for generating a position command signal corresponding to the predetermined position, a position detection part for detecting a position of the motor corresponding to an angle of the mirror, an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal, and a PID control part for changing a gain of the error signal by performing a PID control to provide the changed signal to the motor
  • the method comprising the steps of: setting a changeable variable gain of the PID control part as a predetermined initial value; generating the position command signal and detecting a position signal corresponding to the position of the motor; generating an error signal by comparing the position command signal with the position signal; and regulating the gain of
  • FIG. 1 is a block diagram showing an overall construction of a conventional general laser scanner
  • FIG. 2 is block diagram showing a detailed construction of a position control part included in the conventional laser scanner shown in FIG. 1;
  • FIG. 3 is a waveform diagram showing input/output waveforms of a general laser scanner tuning system
  • FIG. 4 is a block diagram showing the construction of a laser scanner including an automatic tuning system according to the preferred embodiment of the present invention.
  • FIG. 5 is a flow chart showing a tuning process performed by the laser scanner automatic tuning system shown in FIG. 4.
  • D/A conversion part 220 error signal generation part
  • FIG. 4 is a block diagram showing an overall construction of a laser scanning system according to the preferred embodiment of the present invention, which includes a position signal generation part 10, a position control part 20, a motor 30, and a mirror 40.
  • the position control part 20 is comprised of a microprocessor part 205, a D/A conversion part 210, an error signal generation part 220, a PID control part 240, an A/D conversion part 255, a filter part 260, a voltage/current converting amplifier part 270, and a position detection part 280.
  • FIG. 4 mainly shows the construction of the control part 20, and the general elements shown in FIG. 1, i.e., the laser- generating device 50, optical systems 60 and 60', etc. are omitted in the figure. Further, only a single motor 30 and a single mirror 40 are shown in FIG. 4 differently from FIG. 1, however, as the omitted motor and mirror (which correspond to 30' ad 40' of FIG. 1) are controlled identically to the motor 30 and the mirror 40 in FIG. 4, they are omitted for the convenience of illustration. Describing the functions of the respective elements in detail with reference FIG. 4, the position signal generation part 10 generates a position signal to project the laser beam output from the laser-generating device 50 as shown in FIG. 1 on a predetermined position of the object to be processed, and transmits the position signal to the microprocessor part 205 in the position control part 20.
  • the position signal generation part 10 generates a position signal to project the laser beam output from the laser-generating device 50 as shown in FIG. 1 on a predetermined position of the object
  • the microprocessor part 205 transmits the position signal provided from the position signal generation part 10 to the D/A conversion part 210, and the D/A conversion part 210 converts the digital position signal to an analog signal through a predetermined signal processing, and generates the position command digital S from the analog position signal and then transmits the position command signal S to the error signal generation part 220.
  • the error signal generation part 220 compares the position command signal S from the D/A conversion part 210 with the present position value P of the mirror 40 provided from the motor 30 through the position detection part 280 which will be described later, and then outputs the error signal E according to the comparison result.
  • the error signal E is provided to the respective calculators 242, 244 and 246 in the PID control part 240 and the A/D conversion part 255.
  • the A/D conversion part 255 converts the error signal E to a digital signal and then transmits to the aforementioned microprocessor part 205 again, and the microprocessor part 205 provides the gain control signals to the respective calculators 242, 244 and 246 included in the PID control part 240 in accordance with the error signal E.
  • the PID control part 240 is comprised of the proportional calculator 242, the integral calculator 244 and the derivative calculator 246 as shown in the figure, and the respective calculators 242, 244 and 246 are comprised of digital resistors 243, 245 and 247 respectively which are changed according to the gain control signals provided from the aforementioned microprocessor part 250. That is, the respective calculators 242, 244 and 246 are constructed as a hybrid circuit that the analog signal processing means and digital devices exist together.
  • the proportional calculator 242 is a means for controlling and outputting a gain thereof within a predetermined allowable error range as shown in FIG. 3, which controls the gain with respect to the error signal by changing the digital resistor 243 therein in accordance with the gain control signal provided from the microprocessor part 205.
  • the integral calculator 244 controls and outputs a gain thereof so that the peak error (section 1 thorough section 4) of the error signal E becomes horizontal as shown in FIG. 3 by changing the digital resistor 245 therein in accordance with the gain control signal provided from the microprocessor part 205.
  • the derivative calculator 246 also controls and outputs a gain thereof so that the upper side of the trapezoidal error signal E becomes parallel with X-axis as shown in FIG. 3 by changing the digital resistor 247 therein in accordance with the gain control signal provided from the microprocessor part 205.
  • the microprocessor part 205 generates the control signals corresponding to the error signal E provided through the A/D conversion part 255, so as to control the gains of the respective calculators 242, 244 and 246.
  • the error signal E of which gain has been controlled through the respective calculators 242, 244 and 246 is synthesized by the signal synthesizing part 238 into a PID control signal, and then is provided into the filter part 260. And, the filter part 260 filters to remove the frequency component causing the oscillation of the motor 30 from the PID control signal, and then transmits the filtered PID control signal to the voltage/current converting amplifier part 270.
  • the voltage/current converting amplifier part 270 converts and amplifies the filtered PID control signal to a current capable of driving the motor 30, and then applies the it to the motor 30, whereby the motor 30 is operated as much as the applied current and the angle of the mirror 40 is controlled accordingly.
  • the position detection part 280 detects the position of the mirror 40 according to the driving angle of the motor 30 and feed-back the corresponding position detection signal P to the error signal generation part 220, and the position command signal S and the position detection signal P are converged consequently through the PID control process as described above. And, in such a status that the position command signal S and the position detection signal P have converged according to such a process, as shown in FIG. 3, the error signal E has a trapezoidal shape, the magnitude of the error signal E is included in the predetermined allowable error range, the upper side of the trapezoidal error signal E becomes horizontal, and simultaneously, the peak error sections (section 1 through section 4) become parallel with X-axis.
  • FIG. 5 is a flow chart showing a tuning process performed by the laser scanner automatic tuning system shown in FIG. 4, and the overall process is described below in detail with reference to the figure.
  • the microprocessor part 205 sets all of the gains of the respective calculators 242, 244 and 246 of the PID control part 240 and the position command signal S output from the D/A conversion part 210 to zero (step S10) , and then increases the gain of the proportional calculator 242 gradually within a predetermined range while checking the occurrence of the oscillation (step S20) . And, as the gain level Kp of the proportional calculator 242 that the oscillation occurs is detected during the repetition of the above process, a predetermined margin value a is applied to the gain level Kp to set the critical gain level
  • the steps S20 and S30 are steps for setting the critical value of the proportional calculator 242 so that the control range of the proportional calculator 242 is confined within a range that the oscillation does not occur. Meanwhile, as the critical gain level Kp of the proportional calculator 242 is set according to such a process, the microprocessor part 205 generates a position command signal S through the D/A conversion part 210, and the error signal generation part 220 generates the error signal E according to the comparison of the position command signal S with the position detection signal P corresponding to the present position of the mirror 40 from the position detection part 280 (step S40) .
  • the signal generated by the error signal generation part 220 is provided again to the microprocessor part 205 through the A/D conversion part 255, and the microprocessor part 205 judges whether the error signal E has a predetermined shape, i.e., the trapezoidal shape as shown in FIG. 3, whether the magnitude of the error signal E is included in the predetermined allowable error range, and whether the upper side of the error signal is horizontal and the error sections (section 1 through section 4) are parallel with X-axis, and according to the judged result, the microprocessor part 205 generates the gain control signals for controlling the gains of the respective calculators 242, 244 and 246 (step S50) .
  • a predetermined shape i.e., the trapezoidal shape as shown in FIG. 3, whether the magnitude of the error signal E is included in the predetermined allowable error range, and whether the upper side of the error signal is horizontal and the error sections (section 1 through section 4) are parallel with X-axis
  • the microprocessor 205 generates the control signal to the digital variable resistor 243 equipped in the proportional calculator
  • step S510 and then generates the control signal to the digital variable resistor 247 equipped in the derivative calculator 246 to control the gain of the derivative calculator 246 (step S520)
  • the microprocessor 205 judges whether the error signal E provided from the A/D conversion part 255 is a horizontal signal. In other words, it is determined whether the upper side of the trapezoidal error signal E is horizontal as shown in FIG. 3, and if it is determined not to be horizontal signal, the digital variable resistor 247 in the derivative calculator 246 is controlled to change the gain thereof.
  • the microprocessor 205 determines whether the magnitude of the error signal E in that situation is proper (step S540) . In other words, it is determined whether the magnitude of the error signal E is within the predetermined allowable error range.
  • step S510 is performed again to change the digital variable resistor 243 in the proportional calculator 242 again to regulate the magnitude of the error signal E, whereby the upper side of the trapezoidal error signal E becomes horizontal and the error signal E has the proper magnitude, consequently.
  • the microprocessor part 205 generates the control signal to change the digital variable resistor 245 in the integral calculator 244 to regulate the gain of the integral calculator 244 (step S550) , and after that, determines whether the peak error of the error signal E is parallel with X-axis, and controls the gain of the integral calculator 244 again so that the peak error becomes parallel with X-axis (step S560) .
  • the gain control of the respective calculators 242, 244 and 246 has been completed, and then the microprocessor part 205 finally determines whether the error signal E is a signal having the aforementioned predetermined shape (step S570) .
  • the respective sections section 1 through section 4
  • the steps following the above step S510 are repeated to achieve the error signal E having the above shape, and then the tuning process of the laser scanning system is completed.
  • the predetermined allowable error range in the above embodiment is the allowable error range required by the laser scanning system that depends on the characteristics thereof, which can be set properly by a system designer, and the order of the steps in the above step S50, that is, the steps for the gain control of the respective calculators 242, 244 and 246, is not limited to the order shown in FIG. 5, and it can be changed by the system designer as needed.
  • the laser scanning system regulates the gain of the PID control part 240 to perform the tuning, and such a tuning process can be performed whenever required while the laser scanning system is being installed on a manufacturing line without any stoppage of the operation of the manufacturing line.
  • the present invention differently from the conventional manual tuning method of the laser scanner system using additional apparatuses such as a function generator and an oscilloscope, it is possible to realize a laser scanning system capable of performing an automatic tuning in the system and providing the tuning of greater exactness. Furthermore, for the user of the same, there are provided effects that the rate of operation of the equipment can be increased, and the maintenance costs of the equipment due to the periodic exchange of the scanner head part can be reduced substantially.

Abstract

The present invention relates to automatic tuning system and method for a laser scanner that the tuning process of the laser scanner system can be performed automatically, and it is possible to perform the tuning with greater exactness, which includes a position detection part for detecting a position of the motor corresponding to an angle of the mirror; an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal; a PID control part; a voltage/current converting amplifier part; and a microprocessor part for generating the gain control signal to change the gains of the respective calculators so that the error signal has a horizontal shape and has a magnitude within an allowable error range required by the laser scanner; and a peak error becomes horizontal.

Description

SPECIFICATION
TITLE OF THE INVENTION
SYSTEM AND METHOD FOR AUTOMATICALLY TUNING OF LASER SCANNER
TECHINICAL FIELD
The present invention relates to a system an d a method for automatically tuning of a laser scanner, and more particularly, to a system and a method for automatically tuning of a laser scanner that can perform an optimal tuning against a minute change of an optimal tuning value occurring while manufacturing or operating a laser scanner system.
BACKGROUND OF THE INVENTION
As known well, a laser scanning system is an apparatus for scanning characters or symbols by projecting a laser beam on the surface of a scanning object, i.e., object to be processed, to heat in an instant. FIG. 1 is a block diagram showing an overall construction of a general laser scanning system, which includes a position signal generation part 10, a laser-generating device 50, a first and a second optical systems 60 and 60' , and a scanning head part 90. Here, the scanning head part 90 is comprised of a position control part 20, a first and a second motors 30 and 30', and a first and a second mirrors 40 and 40', and is generally installed on the laser scanning system as a single sealed device.
Describing the conventional general laser system with reference to FIG. 1, the position signal generation part 10 is a means for generating a position signal to project the laser beam output from the scanning head part 90 on a predetermined position of the object to be processed, and the position signal is transmitted to the position control part 20 in the scanning head part 90.
The position control part 20 generates a position command signal for controlling the operation of the first and the second motors 30 and 30' on the basis of the position signal provided by the position signal generation part 10, and the first and the second motors 30 and 30' are driven along X-axis and Y-axis according to the position command signal. The first and the second motors 30 and 30' are installed with the first and the second mirrors 40 and 40' as shown in the figure, where the respective mirrors 40 and 40' function as a reflecting mirror for reflecting the laser beam generated by a laser- generating device 50 described later, and the reflection angles thereof are regulated by the driving of the aforementioned first and the second motors 30 and 30' .
Therefore, the laser beam generated from the laser- generating device 50 is reflected at a predetermined angle by the first and the second mirrors 40 and 40' via the first optical system 60, and the reflected laser beam is projected on a predetermined position, i.e., a position corresponding to the position signal generated by the position signal generation part 10, of the object to be processed, via the second optical system 60' .
In such a laser scanning system, the performance of the entire system depends on the exactness of the projection of the laser beam on a desired position, which has the close relation with the exactness of the control of the control part 20 that drives the respective motors 30 and 30' in accordance with the position signal.
FIG. 2 shows the laser scanning system, especially the control part 20 therein, shown in FIG. 1 in greater detail, in which the optical systems 60 and 60' , the laser-generating device 50, the second motor 30' and the second mirror 40' are omitted for the convenience of illustration.
Referring to FIG. 2, the D/A conversion part 210 in the position control part 20 generates and outputs an analog type position command signal S through a predetermined signal processing of a digital type position signal provided from the position signal generation part 10.
The error signal generation part 220 compares the position command signal S from the D/A conversion part 210 with the present position value P of the mirror 40 provided through a position detection part 280 which will be described later, to generate and output an error signal E corresponding thereto. And, the error signal E is provided to the respective calculators 232, 234 and 236 in the PID control part 230.
Meanwhile, the PID control part 230 is a general analog PID controller for processing the analog input signal, which is comprised of a proportional calculator 232, an integral calculator 234 and a derivative calculator 236 as shown in the figure, and the respective calculators 232, 234 and 236 output the error signal E provided from the aforementioned error signal generation part 220 after performing a predetermined signal processing.
At first, the proportional calculator 232 in the PID control part 230 is a means for regulating a proportional gain thereof to a proper value, which functions to regulate and then output the magnitude of the error signal E to be included in an allowable error range required by the laser scanning system within a preset range. And, the integral calculator 234 functions to regulate and then output a gain thereof so that the peak error of the error signal E becomes horizontal, and the derivative calculator 236 functions to regulate and then output a gain thereof so that the error signal E becomes horizontal. This will be described later in greater detail with reference to FIG. 3.
The error signal E output through the respective calculators 232, 234 and 236 is synthesized by a signal synthesizing part 238 into a single control signal and then is provided to the filter part 260, and the filter part 260 filters to remove the frequency component causing the oscillation of the motor from the PID control signal.
Then, the filtered PID control signal is transmitted to the voltage/current converting amplifier part 270, and the voltage/current converting amplifier part 270 converts the voltage of the filtered PID control signal to the corresponding current, and then amplifies it to a predetermined magnitude and applies it to the motor 30. Accordingly, the motor controls the angle of the mirror 40 by driving it according to the current applied from the voltage/current converting amplifier part 270.
Consequently, the conventional general laser scanning system performs the tuning by controlling the gains of the error signal E through the respective calculators 232, 234 and 236 included in the aforementioned PID control part 230, whereby the motor 30 is controlled to project the laser beam on the exact position corresponding to the position command signal S. And, the calculators 232, 234 and 236 are generally comprised of variable resistors 233, 235 and 237 that can be regulated manually.
Meanwhile, in order to perform the tuning process of the PID control part 230 included in such a conventional laser scanning system, a user inputs a reference position signal through a function generator, confirms the input waveform, the output waveform, and the error waveform corresponding thereto with his own visual sense using an oscilloscope, and then operates manually the variable resistors 233, 235 and 237 of the calculators 232, 234 and 236, in order to perform tuning.
FIG. 3 shows the examples of the waveforms input and output during the tuning of the general laser scanning system, and the corresponding error waveform.
The waveform shown by the solid line on the upper part of FIG. 3 is the waveform of the input signal S, and the waveform shown by the dotted line is the waveform of the position detection signal P, and the waveform shown by the solid line on the lower part thereof is the waveform of the error signal E generated by the difference of the input signal S and the output signal P. In other words, as the position signal generated by the function generator is input to the PID control part 230 as the input signal S as shown in the figure, and accordingly as the output signal P as shown in the figure is output, the error signal E becomes the shape as shown on the lower part of the figure with a solid line.
Accordingly, the user tunes the variable resistors 233, 235 and 237 composing the respective calculators 232, 234 and 236 by a manual operation so that the input signal S and the output signal P are identical to each other, and in such a situation, if the tuning has been performed exactly, the error signal E displayed on the oscilloscope becomes the trapezoidal shape as shown in FIG. 3, and the magnitude of the error signal E is included in the allowable error range, the upper side of the trapezoid becomes horizontal, and the peak error sections (section 1 through section 4) becomes parallel with X-axis. In that situation, the proportional calculator 232 controls the gain thereof so that the error signal E can exist within the predetermined allowable error range, the integral calculator 234 controls the gain thereof so that the peak error (section 1 through section 4) of the error signal E becomes horizontal, and the derivative calculator 236 controls the gain thereof so that the upper side of the trapezoidal error signal E becomes parallel with X-axis.
The tuning process of the PID control part 230 is generally performed while the laser scanning system is manufactured initially to set an optimal PID control (gain) value, and also the user thereof can perform the tuning process as required.
However, in the conventional general laser scanning system, even though the initial PID control (gain) value has been set exactly, the tuning error during the operation may occur frequently due to the change of state of the motor and the PID control circuit as the operating time lapses, and in such a situation, the user has to disassemble the sealedly- installed scanning head part 90 and then perform re-tuning with the function generator and the oscilloscope, which may cause the deterioration of productivity by the cessation of the operation of the laser scanner. Furthermore, it is impossible in fact for the user to perform the exact tuning of the PID control circuit.
DETAILED DESCRIPTION OF THE INVENTION
The present invention has been proposed to overcome such a problem of the above conventional art, and it is the object of the present invention to provide a automatic tuning system and method for a laser scanner that the tuning process of the laser scanner system can be performed not by the manual operation of a user but automatically, and it is possible to perform the tuning with greater exactness.
According to one aspect of the present invention to achieve the above object, there is provided an automatic tuning system for a laser scanner that projects a laser beam on a predetermined position of an object to be processed by controlling a motor according to a predetermined position command signal, the motor to which a mirror is assembled, the automatic tuning system comprising: a position detection part for detecting a position of the motor corresponding to an angle of the mirror, and generating a position detection signal corresponding to the detected position; an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal; a PID control part having a proportional calculator, an integral calculator and a derivative calculator, the PID control part for changeably setting gains of the respective calculators based on a gain control signal, and generating a PID control signal based on the gains; a voltage/current converting amplifier part for converting/amplifying the PID control signal to a motor driving signal capable of driving the motor; and a microprocessor part for generating the gain control signal to change the gains of the respective calculators so that the error signal has a horizontal shape and has a magnitude within an allowable error range required by the laser scanner, and a peak error becomes horizontal .
According to another aspect of the present invention to achieve the above object, there is provided an automatic tuning method of a laser scanner that projects a laser beam on a predetermined position of an object to be processed, wherein the laser scanner comprises a motor for controlling a position of a mirror that reflects the laser beam on the predetermined position, a position command signal generation part for generating a position command signal corresponding to the predetermined position, a position detection part for detecting a position of the motor corresponding to an angle of the mirror, an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal, and a PID control part for changing a gain of the error signal by performing a PID control to provide the changed signal to the motor, the method comprising the steps of: setting a changeable variable gain of the PID control part as a predetermined initial value; generating the position command signal and detecting a position signal corresponding to the position of the motor; generating an error signal by comparing the position command signal with the position signal; and regulating the gain of the PID control part so that the error signal has a horizontal shape and has a magnitude within an allowable error range required by the laser scanner, and a peak error thereof becomes horizontal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing an overall construction of a conventional general laser scanner;
FIG. 2 is block diagram showing a detailed construction of a position control part included in the conventional laser scanner shown in FIG. 1;
FIG. 3 is a waveform diagram showing input/output waveforms of a general laser scanner tuning system;
FIG. 4 is a block diagram showing the construction of a laser scanner including an automatic tuning system according to the preferred embodiment of the present invention; and
FIG. 5 is a flow chart showing a tuning process performed by the laser scanner automatic tuning system shown in FIG. 4.
<Description of the Reference Numerals of the main parts in the Drawings>
10 : position signal generation part
20 : position control part
30 and 30' : motors 40 and 40' : mirrors
50 : laser-generating device
60 and 60' : optical systems
205 : microprocessor part
210 : D/A conversion part 220 : error signal generation part
230 and 240 : PID control parts
232 and 242 : proportional calculators
234 and 244 : integral calculators
236 and 246 : derivative calculators 238 : signal synthesizing part
260 : filter part
270 : voltage/current converting amplifier
280 : position detection part
DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinbelow the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings . FIG. 4 is a block diagram showing an overall construction of a laser scanning system according to the preferred embodiment of the present invention, which includes a position signal generation part 10, a position control part 20, a motor 30, and a mirror 40. And, the position control part 20 is comprised of a microprocessor part 205, a D/A conversion part 210, an error signal generation part 220, a PID control part 240, an A/D conversion part 255, a filter part 260, a voltage/current converting amplifier part 270, and a position detection part 280.
FIG. 4 mainly shows the construction of the control part 20, and the general elements shown in FIG. 1, i.e., the laser- generating device 50, optical systems 60 and 60', etc. are omitted in the figure. Further, only a single motor 30 and a single mirror 40 are shown in FIG. 4 differently from FIG. 1, however, as the omitted motor and mirror (which correspond to 30' ad 40' of FIG. 1) are controlled identically to the motor 30 and the mirror 40 in FIG. 4, they are omitted for the convenience of illustration. Describing the functions of the respective elements in detail with reference FIG. 4, the position signal generation part 10 generates a position signal to project the laser beam output from the laser-generating device 50 as shown in FIG. 1 on a predetermined position of the object to be processed, and transmits the position signal to the microprocessor part 205 in the position control part 20.
The microprocessor part 205 transmits the position signal provided from the position signal generation part 10 to the D/A conversion part 210, and the D/A conversion part 210 converts the digital position signal to an analog signal through a predetermined signal processing, and generates the position command digital S from the analog position signal and then transmits the position command signal S to the error signal generation part 220.
The error signal generation part 220 compares the position command signal S from the D/A conversion part 210 with the present position value P of the mirror 40 provided from the motor 30 through the position detection part 280 which will be described later, and then outputs the error signal E according to the comparison result. Here, the error signal E is provided to the respective calculators 242, 244 and 246 in the PID control part 240 and the A/D conversion part 255. The A/D conversion part 255 converts the error signal E to a digital signal and then transmits to the aforementioned microprocessor part 205 again, and the microprocessor part 205 provides the gain control signals to the respective calculators 242, 244 and 246 included in the PID control part 240 in accordance with the error signal E.
Meanwhile, the PID control part 240 is comprised of the proportional calculator 242, the integral calculator 244 and the derivative calculator 246 as shown in the figure, and the respective calculators 242, 244 and 246 are comprised of digital resistors 243, 245 and 247 respectively which are changed according to the gain control signals provided from the aforementioned microprocessor part 250. That is, the respective calculators 242, 244 and 246 are constructed as a hybrid circuit that the analog signal processing means and digital devices exist together.
Describing the respective calculators 242, 244 and 246 in detail, the proportional calculator 242 is a means for controlling and outputting a gain thereof within a predetermined allowable error range as shown in FIG. 3, which controls the gain with respect to the error signal by changing the digital resistor 243 therein in accordance with the gain control signal provided from the microprocessor part 205. And, the integral calculator 244 controls and outputs a gain thereof so that the peak error (section 1 thorough section 4) of the error signal E becomes horizontal as shown in FIG. 3 by changing the digital resistor 245 therein in accordance with the gain control signal provided from the microprocessor part 205.
Similarly, the derivative calculator 246 also controls and outputs a gain thereof so that the upper side of the trapezoidal error signal E becomes parallel with X-axis as shown in FIG. 3 by changing the digital resistor 247 therein in accordance with the gain control signal provided from the microprocessor part 205.
Consequently, the microprocessor part 205 generates the control signals corresponding to the error signal E provided through the A/D conversion part 255, so as to control the gains of the respective calculators 242, 244 and 246.
The error signal E of which gain has been controlled through the respective calculators 242, 244 and 246 is synthesized by the signal synthesizing part 238 into a PID control signal, and then is provided into the filter part 260. And, the filter part 260 filters to remove the frequency component causing the oscillation of the motor 30 from the PID control signal, and then transmits the filtered PID control signal to the voltage/current converting amplifier part 270.
The voltage/current converting amplifier part 270 converts and amplifies the filtered PID control signal to a current capable of driving the motor 30, and then applies the it to the motor 30, whereby the motor 30 is operated as much as the applied current and the angle of the mirror 40 is controlled accordingly.
In such a situation, the position detection part 280 detects the position of the mirror 40 according to the driving angle of the motor 30 and feed-back the corresponding position detection signal P to the error signal generation part 220, and the position command signal S and the position detection signal P are converged consequently through the PID control process as described above. And, in such a status that the position command signal S and the position detection signal P have converged according to such a process, as shown in FIG. 3, the error signal E has a trapezoidal shape, the magnitude of the error signal E is included in the predetermined allowable error range, the upper side of the trapezoidal error signal E becomes horizontal, and simultaneously, the peak error sections (section 1 through section 4) become parallel with X-axis.
FIG. 5 is a flow chart showing a tuning process performed by the laser scanner automatic tuning system shown in FIG. 4, and the overall process is described below in detail with reference to the figure.
At first, in the initial tuning process, the microprocessor part 205 sets all of the gains of the respective calculators 242, 244 and 246 of the PID control part 240 and the position command signal S output from the D/A conversion part 210 to zero (step S10) , and then increases the gain of the proportional calculator 242 gradually within a predetermined range while checking the occurrence of the oscillation (step S20) . And, as the gain level Kp of the proportional calculator 242 that the oscillation occurs is detected during the repetition of the above process, a predetermined margin value a is applied to the gain level Kp to set the critical gain level
KpXa of the proportional calculator 242 (step S30) .
The steps S20 and S30 are steps for setting the critical value of the proportional calculator 242 so that the control range of the proportional calculator 242 is confined within a range that the oscillation does not occur. Meanwhile, as the critical gain level Kp of the proportional calculator 242 is set according to such a process, the microprocessor part 205 generates a position command signal S through the D/A conversion part 210, and the error signal generation part 220 generates the error signal E according to the comparison of the position command signal S with the position detection signal P corresponding to the present position of the mirror 40 from the position detection part 280 (step S40) . In that situation, the signal generated by the error signal generation part 220 is provided again to the microprocessor part 205 through the A/D conversion part 255, and the microprocessor part 205 judges whether the error signal E has a predetermined shape, i.e., the trapezoidal shape as shown in FIG. 3, whether the magnitude of the error signal E is included in the predetermined allowable error range, and whether the upper side of the error signal is horizontal and the error sections (section 1 through section 4) are parallel with X-axis, and according to the judged result, the microprocessor part 205 generates the gain control signals for controlling the gains of the respective calculators 242, 244 and 246 (step S50) .
Describing the above in greater detail, at first, the microprocessor 205 generates the control signal to the digital variable resistor 243 equipped in the proportional calculator
242 to control the gain of the proportional calculator 242
(step S510) , and then generates the control signal to the digital variable resistor 247 equipped in the derivative calculator 246 to control the gain of the derivative calculator 246 (step S520)
After the gains of the proportional calculator 242 and the derivative calculator 246 have been regulated according to such a process, the microprocessor 205 judges whether the error signal E provided from the A/D conversion part 255 is a horizontal signal. In other words, it is determined whether the upper side of the trapezoidal error signal E is horizontal as shown in FIG. 3, and if it is determined not to be horizontal signal, the digital variable resistor 247 in the derivative calculator 246 is controlled to change the gain thereof.
And, if the upper side of the trapezoidal error signal E provided from the A/D conversion part 255 is determined to be the horizontal signal according to such a process (step S530) , the microprocessor 205 determines whether the magnitude of the error signal E in that situation is proper (step S540) . In other words, it is determined whether the magnitude of the error signal E is within the predetermined allowable error range.
If the magnitude of the error signal E is determined to be improper, the above step S510 is performed again to change the digital variable resistor 243 in the proportional calculator 242 again to regulate the magnitude of the error signal E, whereby the upper side of the trapezoidal error signal E becomes horizontal and the error signal E has the proper magnitude, consequently.
And, if the magnitude of the error signal E is determined to be proper according to such a process, the microprocessor part 205 generates the control signal to change the digital variable resistor 245 in the integral calculator 244 to regulate the gain of the integral calculator 244 (step S550) , and after that, determines whether the peak error of the error signal E is parallel with X-axis, and controls the gain of the integral calculator 244 again so that the peak error becomes parallel with X-axis (step S560) .
According to respective steps, the gain control of the respective calculators 242, 244 and 246 has been completed, and then the microprocessor part 205 finally determines whether the error signal E is a signal having the aforementioned predetermined shape (step S570) . In other words, it is determined whether the respective sections (section 1 through section 4) is parallel with X-axis and simultaneously the upper side of the trapezoidal error signal E is horizontal, and whether the magnitude of the error signal E is within the predetermined allowable error range. And, the steps following the above step S510 are repeated to achieve the error signal E having the above shape, and then the tuning process of the laser scanning system is completed.
Meanwhile, the predetermined allowable error range in the above embodiment is the allowable error range required by the laser scanning system that depends on the characteristics thereof, which can be set properly by a system designer, and the order of the steps in the above step S50, that is, the steps for the gain control of the respective calculators 242, 244 and 246, is not limited to the order shown in FIG. 5, and it can be changed by the system designer as needed.
Consequently, according to the respective steps, the laser scanning system regulates the gain of the PID control part 240 to perform the tuning, and such a tuning process can be performed whenever required while the laser scanning system is being installed on a manufacturing line without any stoppage of the operation of the manufacturing line.
Although the preferred embodiment of the present invention has been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiment, but various changes and modifications can be made within the spirit and the scope of the present invention. Accordingly, the scope of the present invention is not limited within the described range but the following claims.
INDUSTRIAL APPLICABILITY
As described above, according to the present invention, differently from the conventional manual tuning method of the laser scanner system using additional apparatuses such as a function generator and an oscilloscope, it is possible to realize a laser scanning system capable of performing an automatic tuning in the system and providing the tuning of greater exactness. Furthermore, for the user of the same, there are provided effects that the rate of operation of the equipment can be increased, and the maintenance costs of the equipment due to the periodic exchange of the scanner head part can be reduced substantially.

Claims

What is claimed is:
1. Automatic tuning system for a laser scanner that projects a laser beam on a predetermined position of an object to be processed by controlling a motor according to a predetermined position command signal, the motor to which a mirror is assembled, the automatic tuning system comprising: a position detection part for detecting a position of the motor corresponding to an angle of the mirror, and generating a position detection signal corresponding to the detected position; an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal; a PID control part having a proportional calculator, an integral calculator and a derivative calculator, the PID control part for changeably setting gains of the respective calculators based on a gain control signal, and generating a
PID control signal based on the gains; a voltage/current converting amplifier part for converting/amplifying the PID control signal to a motor driving signal capable of driving the motor; and a microprocessor part for generating the gain control signal to change the gains of the respective calculators so that the error signal has a horizontal shape and has a magnitude within an allowable error range required by the laser scanner, and a peak error becomes horizontal.
2. The automatic tuning system according to claim 1, further comprising a filter part disposed between the PID control part and the voltage/current converting amplifier part, the filter part for removing a frequency component causing an oscillation of the motor from the PID control signal.
3. The automatic tuning system according to any one of claims 1 and 2, wherein each of the proportional calculator, the integral calculator and the derivative calculator comprises a digital resistor of which value is changed according to the gain control signal so as to change the gains.
4. The automatic tuning system according to any one of claims 1 and 2, wherein the position command signal generation part comprises: a position signal generation part for generating a digital position signal corresponding to the predetermined position; and a D/A conversion part for converting the digital position signal to an analog signal, and generating the position command signal corresponding to the converted position signal to provide the position command signal to the error signal generation part.
5. The automatic tuning system according to any one of claims 1 and 2, wherein the PID control part comprises a signal synthesizing part for synthesizing the gains of the respective calculators to generate the PID control signal.
6. An automatic tuning method of a laser scanner that projects a laser beam on a predetermined position of an object to be processed, wherein the laser scanner comprises a motor for controlling a position of a mirror that reflects the laser beam on the predetermined position, a position command signal generation part for generating a position command signal corresponding to the predetermined position, a position detection part for detecting a position of the motor corresponding to an angle of the mirror, an error signal generation part for generating an error signal based on a difference between the position command signal and the position detection signal, and a PID control part for changing a gain of the error signal by performing a PID control to provide the changed signal to the motor, the method comprising the steps of: setting a changeable variable gain of the PID control part as a predetermined initial value; generating the position command signal and detecting a position signal corresponding to the position of the motor; generating an error signal by comparing the position command signal with the position signal; and regulating the gain of the PID control part so that the error signal has a horizontal shape and has a magnitude within an allowable error range required by the -laser scanner, and a peak error thereof becomes horizontal.
7. The automatic tuning method according to claim 6, wherein the PID control part comprises a proportional calculator, an integral calculator and a derivative calculator, and the setting step comprises the steps of: detecting a maximum gain by which an oscillation is not detected ' while a proportional gain of the proportional calculator is gradually increased; and setting a range for regulating the gain of the proportional calculator by setting a predetermined margin on the maximum gain.
8. The automatic tuning method according to claim 7, the step of regulating the gain comprises the steps of: regulating the proportional gain of the proportional calculator within a preset gain control range so that the magnitude of the error signal is included in the allowable error range required by the laser scanner; regulating a derivative gain of the derivative calculator so that the error signal becomes horizontal; and regulating an integral gain of the integral calculator so that the peak error of the error signal becomes horizontal.
9. The automatic tuning method according to claim 8, wherein each of the proportional calculator, the integral calculator and the derivative calculator comprises a digital resistor, and the steps of regulating the proportional gain, the derivative gain and the integral gain are performed by changing the respective digital resistors.
PCT/KR2002/001203 2001-06-28 2002-06-25 System and method for automatically tuning of laser scanner WO2003006248A1 (en)

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