KR100379780B1 - System and methode for automatically tuning of laser scanner - Google Patents

Abstract

The present invention relates to an automatic tuning apparatus and method for a laser scanner that enables a more precise tuning while simultaneously performing a tuning process in a laser scanning system instead of a user's manual operation. The mirror according to a predetermined position command signal is provided. An automatic tuning apparatus for a laser scanner for controlling a motor to which a laser beam is attached to irradiate a laser beam to a predetermined position of the workpiece, the position detecting unit detecting a position of the motor corresponding to the angle of the mirror and generating a position detection signal corresponding thereto. ; An error signal generator for generating an error signal based on a difference between the reference position command signal and the position detection signal; A PID control unit including a proportional operation unit, an integration operation unit, and a derivative operation unit, wherein the PID control unit variably sets the gain of each operation unit based on the gain control signal and generates a PID control signal based on the variable set gain; A voltage / current conversion amplifier for converting and amplifying the PID control signal into a motor driving signal capable of driving the motor; The microprocessor unit includes a microprocessor unit that generates a gain control signal so that an error signal is horizontal, is included in an error tolerance range of the laser scanner, and the gain of each operation unit is varied so that its peak error is horizontal. Therefore, according to the present invention, a laser scanner capable of automatically performing a more precise tuning process can be implemented, and the user can reduce the equipment operation cost due to periodic replacement of the scanner head.

Description

Automatic tuning device and method of laser scanner {SYSTEM AND METHODE FOR AUTOMATICALLY TUNING OF LASER SCANNER}

The present invention relates to an automatic tuning apparatus and method of a laser scanner, and more particularly, a laser capable of automatically performing optimal tuning in response to minute fluctuations in an optimum tuning value generated during manufacturing or operation of a laser scanner system. An automatic tuning apparatus and method for a scanner.

As is well known, a laser scanning system is a device for displaying letters, symbols, etc. by irradiating a laser beam onto a surface of a scanning object, i.

1 is a block diagram showing the overall configuration of a conventional laser scanning system, which includes a position signal generator 10, a laser generator 50, first and second optical systems 60 and 60 'and a scanning head unit. (90). The scanning head portion 90 here consists of a position controller 20, first and second motors 30 and 30 ′, first mirror and second mirror 40 and 40 ′, and typically in a hermetically sealed form. The device is mounted on a laser scanning system.

Referring to FIG. 1, a conventional laser scanning system will be described. First, the position signal generator 10 generates a position signal for irradiating a laser beam output from the scanning head unit 90 to a predetermined position of an object to be processed. The position signal is transmitted to the position control unit 20 in the scanning head unit 90.

The position controller 20 generates a position command signal for controlling the driving of the first and second motors 30 and 30 'based on the position signal provided from the position signal generator 10, and the first and the first The two motors 30 and 30 'are driven on the X and Y axes based on this position command signal. The first and second motors 30 and 30 'are attached to the first and second mirrors 40 and 40' as shown in the same drawing. Each of the mirrors 40 and 40 'will be described later. It serves as a reflector reflecting the laser beam generated from the laser generating device 50, the reflection angle is adjusted by the driving of the first and second motors 30, 30 'described above.

Accordingly, the laser beam generated from the laser generator 50 is reflected at a predetermined angle by the first and second mirrors 40 and 40 'via the first optical system 60, and the reflected laser beam is again made. The light is irradiated to a predetermined position of the object to be processed, that is, a position corresponding to the position signal generated from the position signal generator 10 via the two optical systems 60 '.

In such a laser scanning system, it is determined that the laser beam is irradiated exactly at a desired position depends on the performance of the overall system, which is controlled by the position controller 20 which drives the respective motors 30 and 30 'based on the position signal. Associated with precision.

FIG. 2 is a view illustrating the laser scanning system shown in FIG. 1 in more detail, centering on the position control unit 20. In the same drawing, the optical systems 60 and 60 'and the laser generating device 50, and FIG. 2 motor 30 'and the 2nd mirror 40' are abbreviate | omitted and shown.

Referring to FIG. 2, the D / A converter 210 in the position controller 20 performs an analog position command signal through a predetermined signal processing process from a digital position signal provided from the position signal generator 10. Generate and print (S).

The error signal generator 220 compares the position command signal S from the D / A converter 210 with the current position value P of the mirror 40 provided through the position detector 280 described later. The error signal E corresponding thereto is generated and output. The error signal E is provided to each of the calculation units 232, 234, and 236 in the PID control unit 230.

Meanwhile, the PID controller 230 is a conventional analog PID controller for processing an analog input signal, and includes a proportional calculator 232, an integral calculator 234, and a derivative calculator 236, as shown in the drawing. Each of the calculators 232, 234, and 236 outputs the error signal E provided from the error signal generator 220 through a predetermined signal processing.

First, the proportional calculation unit 232 in the PID control unit 230 is a means for adjusting the proportional gain to be an appropriate value, and the error that the magnitude of the error signal E is required by the laser scanning system within a predetermined range. It adjusts the gain to be within the allowable range and outputs it. In addition, the integral calculating unit 234 adjusts and outputs a gain such that the vertex error of the error signal E becomes horizontal, and the derivative calculating unit 236 adjusts and outputs the gain so that the error signal E becomes horizontal. Function. This will be described in detail later with reference to FIG. 3.

The error signal E output through each of the operation units 232, 234, and 236 is synthesized into one PID control signal through the signal synthesis unit 238, and provided to the filter unit 260, and the filter unit 260. ) Filters and removes frequency components that cause the motor to oscillate from this PID control signal.

The filtered PID control signal is transmitted to the voltage / current conversion amplifier 270, and the voltage / current conversion amplifier 270 converts the current into a corresponding current in proportion to the voltage of the filtered PID control signal. It is amplified to a predetermined size and applied to the motor 30 again. Accordingly, the motor is driven in response to the current applied from the voltage / current conversion amplifier 270 to adjust the angle of the mirror 40.

As a result, in the conventional general laser scanning system, the tuning is performed by adjusting the gain of the error signal E through the operation units 232, 234, and 236 included in the PID control unit 230 described above. The motor 30 is controlled so that the laser beam can be irradiated at the correct position corresponding to S). Typically, each of these calculators 232, 234, 236 includes a variable resistor 233, 235, 237 which is operated manually.

On the other hand, in order to perform the tuning process of the PID control unit 230 included in the conventional laser scanning system, the user inputs a predetermined position signal as a reference through a function generator, an input waveform, an output waveform, and an oscilloscope. By visually checking the error waveform accordingly, tuning is performed by manually adjusting the variable resistors 233, 235, and 237 constituting the operation units 232, 234, and 236.

3 is a diagram exemplarily illustrating an input waveform, an output waveform output therefrom, and an error waveform according to the tuning process of a general laser scanning system.

The waveform shown by the solid line at the top of FIG. 3 means the waveform of the input signal S, and the waveform shown by the dotted line means the waveform of the output signal, that is, the position detection signal P, and the waveform shown by the solid line at the bottom. Denotes a waveform of the error signal E generated by the difference between the input signal S and the output signal P. FIG. That is, when the position signal generated from the function generator is input to the PID controller 230 in the form of an input signal S of the form shown in the drawing, and the output signal P of the form shown in the drawing is output, The error signal E at this time has a shape as shown by the solid line at the bottom of the same drawing.

Accordingly, the user manually tunes and adjusts the variable resistors 233, 235, and 237 constituting the operation units 232, 234, and 236 so that the input signal S and the output signal P coincide with each other. If the correct tuning is performed, the error signal E appearing in the oscilloscope has a trapezoidal shape as shown in FIG. 3, and the magnitude of the error signal E is within the error tolerance range, and the top of the trapezoid is horizontal and at the same time vertex error. The section (section 1 to section 4) is also horizontal to the X axis. Here, the proportional calculation unit 232 adjusts the gain so that the error signal E exists within a predetermined error tolerance range, and the integral calculation unit 234 adjusts the peak error (section 1 to section 4) of the error signal E. The gain is adjusted to be horizontal, and the derivative calculator 236 adjusts and outputs the gain such that the upper portion of the trapezoidal error signal E is horizontal to the X axis.

The tuning process of the PID control unit 230 is typically performed at the time of fabrication of the initial laser scanning system to set an optimum PID control (gain) value, and a user who uses it may perform this tuning process if necessary. have.

However, in the conventional laser scanning system, even if the PID control (gain) value is initially set correctly, there is a problem that a tuning error occurs frequently during driving due to the change of state of the motor and the PID control circuit over the driving time. In this case, the user has to disassemble the scanning head 90 mounted in a sealed form every time and perform retuning using a function generator and an oscilloscope. There is a problem of deterioration. In addition, there is a problem that it is practically impossible for the user to perform precise tuning on the PID control circuit.

Accordingly, the present invention is to solve the above-mentioned problems of the prior art and to automatically perform the tuning process in the laser scanning system rather than the manual operation of the user at the same time more precise tuning of the laser scanner and The purpose is to provide a method.

The present invention according to one aspect for achieving the above object is an apparatus for automatically fine tuning the laser scanner for irradiating a laser beam to a predetermined position of the workpiece by controlling a motor with a mirror in accordance with a position command signal A position command signal generator for generating a reference position command signal including a rising section, a falling section, and a constant value maintaining section; A position detector for detecting a position of the motor corresponding to the angle of the mirror and generating a position detection signal corresponding thereto; An error signal generator for generating an error signal based on a difference between the reference position command signal and the position detection signal; A PID control unit including a proportional operation unit, an integration operation unit, and a derivative operation unit, wherein the PID control unit variably sets the gain of each operation unit based on a gain control signal and generates a PID control signal based on the variable set gain; A voltage / current conversion amplifier configured to convert and amplify the PID control signal into the motor driving signal capable of driving the motor; The gain control signal may be generated to be at least a portion of an upper side of a trapezoidal waveform among the error signals detected in the rising section, the falling section, and the constant value maintaining section of the reference position command signal, and at least part of the error signal except for the trapezoidal waveform. And a microprocessor unit for varying the gain of each computing unit so that the waveforms of the vertex errors are horizontal and each has a magnitude within a predetermined tolerance range required by the laser scanner.

According to another aspect of the present invention, there is provided a method of automatically performing a tuning process of a laser scanner for irradiating a laser beam to a predetermined position of a workpiece, wherein the laser scanner provides the laser beam to the predetermined position. A motor for adjusting the position of the mirror reflected to a position, a position command signal generator for generating a position command signal corresponding to a predetermined position of the motor, and a position for detecting an actual position of the motor corresponding to the angle of the mirror A detection unit, an error signal generation unit for detecting an error based on a difference between the reference position command signal and the position detection signal, and performing a PID control to vary the gain of the error signal to provide the variable signal to the motor. And a PID controller configured to set the variable gain of the PID controller to a preset initial value. Setting step; Generating a reference position command signal including a rising section, a falling section, and a constant value holding section and detecting a position signal corresponding to an actual position of the motor in response thereto; Generating an error signal by comparing the reference position command signal with the position signal; The upper edge of the trapezoidal waveform among the error signals detected in the rising section, the falling section, and the constant value holding section of the reference position command signal, and the waveform of the vertex error which is at least a part of the error signal except for the trapezoidal waveform are horizontal, respectively. And a gain adjusting step of varying and adjusting the gain of the PID controller so as to have a size within a predetermined tolerance range required by the laser scanner.

1 is a block diagram showing the overall configuration of a conventional general laser scanner.

2 is a block diagram showing a detailed configuration of a position control unit included in the conventional laser scanner shown in FIG.

3 is a waveform diagram showing input / output waveforms in a general laser scanner tuning apparatus.

Figure 4 is a block diagram showing the configuration of a laser scanner including an automatic tuning device according to a preferred embodiment of the present invention.

FIG. 5 is a flowchart illustrating a tuning process using the laser scanner automatic tuning device shown in FIG. 4. FIG.

<Explanation of symbols for the main parts of the drawings>

10: position signal generator 20: position control

30, 30 ': motor 40, 40': mirror

50: laser generator 60, 60 ': optical system

205: microprocessor unit 210: D / A conversion unit

220: error signal generator 230, 240: PID controller

232, 242: proportional calculation unit 234, 244: integral calculation unit

236, 246: derivative operation unit 238: signal synthesis unit

260: filter unit 270: voltage / current conversion amplifier

280: position detection unit

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

4 is a block diagram showing an overall configuration of a laser scanner including an automatic tuning device according to a preferred embodiment of the present invention, wherein the position signal generator 10, the position controller 20, the motor 30, and the mirror ( 40). The position controller 20 may include a microprocessor unit 205, a D / A converter 210, an error signal generator 220, a PID controller 240, an A / D converter 255, and a filter unit ( 260, a voltage / current conversion amplifier 270, and a position detector 280.

First, in FIG. 4, the configuration of the position control unit 20 is illustrated, and the general construction means as shown in FIG. 1, that is, the laser generating device 50, the optical systems 60 and 60 ′, and the like are omitted. In addition, in FIG. 4, unlike FIG. 1, only one motor 30 and the mirror 40 are illustrated. However, the other motor and the mirror (30 'and 40' in FIG. 1), which are not shown, are illustrated in FIG. 30) and the mirror 40 is controlled in the same manner, so it is omitted for convenience of description.

Referring to FIG. 4, the function of each constituent means will be described in detail. The position signal generator 10 allows the laser beam generated from the laser generator 50 to be irradiated to a predetermined position of the object to be processed, as shown in FIG. 1. The predetermined position signal is generated and transmitted to the microprocessor unit 205 in the position control unit 20. At this time, the position signal generated from the position signal generator 10 is a digital signal.

The microprocessor unit 205 transfers the position signal provided from the position signal generator 10 to the D / A converter 210, and the D / A converter 210 transmits the digital position signal to a predetermined signal processing process. After converting the signal into an analog signal, the reference position command signal S is generated from the analog position signal and transmitted to the error signal generator 220.

The error signal generator 220 may generate a reference position command signal S from the D / A converter 210 and a current position value P of the mirror 40 provided through the position detector 280 described later. The comparison is received from (30), and the error signal E is generated and output accordingly. Here, the error signal E is provided to each of the calculation units 242, 244, 246 and the A / D converter 255 in the PID control unit 240.

The A / D converter 255 converts the error signal E into a digital signal and transmits the error signal E to the microprocessor unit 205 described above, and the microprocessor unit 205 responds to the error signal E. The gain control signal is provided to each operation unit 242, 244, and 246 included in the PID control unit 240.

Meanwhile, the PID controller 240 includes a proportional calculator 242, an integral calculator 244, and a derivative calculator 246, as shown in the same drawing, and each of the calculators 242, 244, and 246 is a microcomputer. And digital resistors 243, 245, and 247 that are variable based on a gain control signal provided from the processor 250. That is, each calculation unit 242, 244, 246 is configured in the form of a hybrid circuit in which the analog signal processing means and the digital element coexist.

Referring to each operation unit 242, 244, 246, the proportional operation unit 242 first obtains a gain (gain) so that the error signal (E) is within a predetermined predetermined tolerance range as shown in FIG. As a means for adjusting and outputting, the gain for the error signal is controlled by varying the digital resistor 243 based on the gain control signal provided from the microprocessor unit 205.

Also, the integral calculating unit 244 also varies the internal digital resistor 245 based on the gain control signal provided from the microprocessor unit 205, thereby showing the peak error (section) of the error signal E as shown in FIG. The gain is adjusted so that 1 to 4 are horizontal.

Similarly, the derivative calculator 246 also varies the digital resistor 247 based on the gain control signal of the microprocessor unit 205 so that the upper portion of the trapezoidal error signal E is horizontal to the X axis as shown in FIG. Adjust the gain as much as possible to output.

As a result, the microprocessor unit 205 generates a control signal corresponding to the error signal E provided through the A / D converter 255 to control the gains of the calculation units 242, 244, and 246. .

The error signal E whose gain is adjusted through each of the operation units 242, 244, and 246 is synthesized into a PID control signal through the signal synthesis unit 238, and then provided to the filter unit 260. The filter unit 260 filters and removes the frequency component causing the oscillation of the motor 30 from the PID control signal, and transmits the filtered PID control signal to the voltage / current conversion amplifier 270.

The voltage / current conversion amplifier 270 converts and amplifies the filtered PID control signal into a predetermined current capable of driving the motor 30, and applies the same to the motor 30. Drive, and the angle of the mirror 40 is adjusted accordingly.

At this time, the position detector 280 detects the position of the mirror 40 according to the driving angle of the motor 30 as described above, and feeds the position detection signal P corresponding thereto to the error signal generator 220. The reference position command signal S and the position detection signal P converge as a result of the PID control process as described above. In the state where the reference position command signal S and the position detection signal P converge through the above process, as shown in FIG. 3, the error signal E has a trapezoidal shape, and the error signal E Is within the predetermined error tolerance range, the upper part of the trapezoid of the error signal E is horizontal, and the vertex error section (section 1 to section 4) is also horizontal to the X axis.

FIG. 5 is a flowchart illustrating a tuning process performed through the automatic tuning apparatus of the laser scanner as shown in FIG. 4. Referring to FIG. 5, a series of processes will be described in detail with reference to the accompanying drawings.

First, in the initial tuning process, the microprocessor unit 205 obtains the gains of the calculation units 242, 244, and 246 constituting the PID control unit 240 and the reference position command signal S output from the D / A converter 210. ) Are all set to '0' (step S10), and then the gain of the proportional calculation unit 242 is incrementally increased within a predetermined range to check whether oscillation occurs (step S20). When the gain level Kp of the proportional calculation unit 242 in which oscillation occurs while repeatedly performing this process is detected, a predetermined margin value a is applied to the gain level Kp and the proportional calculating unit is applied. The threshold gain level Kp x a is set at 242 (step S30).

These steps S20 and S30 are processes for setting the threshold of the proportional calculation unit 242, and are intended to limit the gain adjustment range of the proportional calculation unit 242 to a range where oscillation does not occur.

On the other hand, when the threshold gain level Kp of the proportional calculation unit 242 is set through this process, the microprocessor unit 205 generates the predetermined reference position command signal S through the D / A converter 210. The error signal generator 220 compares the reference position command signal S with the position detection signal P according to the current position of the mirror 40 from the position detection unit 280, and thereby the error signal E accordingly. (Step S40).

At this time, the signal generated from the error signal generator 220 is provided back to the microprocessor unit 205 through the A / D conversion unit 255, the microprocessor unit 205 is a predetermined error signal (E) 3, that is, the error signal E has a trapezoidal shape, as shown in FIG. 3, the magnitude of the error signal E is within a predetermined error tolerance range, and the upper portion of the trapezoid of the error signal E is horizontal. At the same time, it is determined whether the vertex error section (section 1 to section 4) is also a signal parallel to the X axis, and generates a gain control signal for controlling the gain of each of the calculation units 242, 244, and 246 according to the determination result. (Step S50).

In detail, first, the microprocessor unit 205 generates a control signal to the digital variable resistor 243 provided in the proportional calculator 242 to adjust the gain of the proportional calculator 242 (step S510). In addition, a control signal is generated to the digital variable resistor 247 provided in the derivative calculator 246 to adjust the gain of the derivative calculator 246 (step S520).

In this state, the gains of the proportional calculating unit 242 and the derivative calculating unit 246 are adjusted, and the microprocessor unit 205 again has an error signal E provided from the A / D converter 255 being horizontal. It is determined whether it is a signal. That is, as shown in FIG. 3, it is determined whether the trapezoidal upper part of the error signal E is a horizontal signal. If the horizontal signal is not made, the digital variable resistor 247 of the derivative calculator 246 is again controlled to gain. Adjust

When the trapezoidal upper part of the error signal E provided from the A / D converter 255 is determined to be a horizontal signal through the above process (step S530), the microprocessor unit 205 receives the error signal E at this time. It is determined whether or not the size of?) Is appropriate (step S540). In other words, it is determined whether the magnitude of the error signal E is within a preset error tolerance range.

If, as a result of the determination, it is determined that the magnitude of the error signal E is not appropriate, the process returns to step S510 described above, and the digital variable resistor 243 of the proportional calculation unit 242 is changed again to change the error signal E. By adjusting the size of the control unit, the upper end of the ladder bone of the error signal E is horizontally controlled at the same time and the appropriate size signal is controlled.

When the size of the error signal E is determined to be the proper size in step S540, the microprocessor unit 205 generates a control signal to generate the digital variable resistor 245 of the integration calculator 244. ) By adjusting the gain of the integral calculating unit 244 (step S550), and then determining whether the vertex error of the error signal E is horizontal with the X axis, and again integrating the calculating unit ( The gain of step 244 is adjusted (step S560).

When the gain adjustment process of each operation unit 242, 244, 246 is completed through each of these processes, the microprocessor unit 205 finally determines whether the error signal E is the error signal of the above-described predetermined type ( Step S570). That is, as shown in FIG. 3, each section (section 1 to section 4) of the error signal E is horizontal with the X axis, and the trapezoidal upper part of the error signal E is horizontal, and the magnitude of the error signal E is preliminary. Determine whether it exists within the set tolerance range. The tuning process of the laser scanning system is terminated by repeating the process after the above-described step S510 such that the error signal E of this type is obtained.

Meanwhile, in the above-described embodiment, the preset error tolerance may be appropriately set by the system designer as an error tolerance required according to the characteristics of the laser scanning system, and the calculation units 242 and 244 may be performed within the above-described step S50. The order of the gain adjustment process and the error signal determination process of FIG. 246 is not limited to the order shown in FIG. 5 and may be changed according to the needs of the system designer.

As a result, through each of these processes, the laser scanning system performs tuning by adjusting the gain of the PID control unit 240, and this tuning process is performed even when the laser scanning system is mounted on the production line without shutting down the production line. You can always do it as needed.

As described above, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the present invention, in the tuning of the laser scanner system, unlike the conventional method by the manual operation of a user using additional equipment such as a function generator and an oscilloscope, tuning is performed automatically in the system. At the same time, there is an effect to implement a laser scanning system that can be more precise tuning. In addition, the user side can increase the operation rate of the equipment and at the same time can significantly reduce the equipment operating costs due to the periodic replacement of the scanner head portion.

Claims (9)

An apparatus for automatically fine tuning a laser scanner for controlling a motor with a mirror in accordance with a position command signal to irradiate a laser beam to a predetermined position of a workpiece. A position command signal generator for generating a reference position command signal including a rising section, a falling section, and a constant value holding section; A position detector for detecting a position of the motor corresponding to the angle of the mirror and generating a position detection signal corresponding thereto; An error signal generator for generating an error signal based on a difference between the reference position command signal and the position detection signal; A PID control unit including a proportional operation unit, an integration operation unit, and a derivative operation unit, wherein the PID control unit variably sets the gain of each operation unit based on a gain control signal and generates a PID control signal based on the variable set gain; A voltage / current conversion amplifier configured to convert and amplify the PID control signal into the motor driving signal capable of driving the motor; The gain control signal may be generated to be at least a portion of an upper side of a trapezoidal waveform among the error signals detected in the rising section, the falling section, and the constant value maintaining section of the reference position command signal, and at least part of the error signal except for the trapezoidal waveform. And a microprocessor unit for varying the gain of each calculation unit so that the waveforms of the vertex errors are horizontal and have a magnitude within a predetermined tolerance range required by the laser scanner. The method of claim 1, The automatic tuning device of the laser scanner, And a filter unit disposed between the PID control unit and the voltage / current conversion amplifying unit and removing a frequency component causing an oscillation of the motor from the PID control signal. The method according to claim 1 or 2, Each of the proportional calculator, the integral calculator, and the derivative calculator, And a digital resistor for varying the gain by varying the gain control signal. The method according to claim 1 or 2, The position command signal generator, A position signal generator for generating a digital position signal corresponding to the predetermined position; And a D / A converting unit converting the digital position signal into an analog signal and generating the reference position command signal corresponding to the converted position signal and providing the reference position command signal to the error signal generator. Device. The method according to claim 1 or 2, The PID control unit, And a signal synthesizing unit for synthesizing the gains of the calculating units to generate the PID control signal. In the method for automatically performing the tuning process of the laser scanner for irradiating the laser beam to a predetermined position of the workpiece, The laser scanner, A motor for adjusting the position of the mirror reflecting the laser beam to the predetermined position, a position command signal generator for generating a position command signal corresponding to the predetermined position of the motor, and a motor corresponding to the angle of the mirror. A position detecting unit detecting an actual position, an error signal generating unit detecting an error based on a difference between the reference position command signal and the position detecting signal, and performing a PID control to vary a gain of the error signal A PID controller for providing a signal to the motor, The method is: An initial setting step of setting a variable gain of the PID control unit to a preset initial value; Generating a reference position command signal including a rising section, a falling section, and a constant value holding section and detecting a position signal corresponding to an actual position of the motor in response thereto; Generating an error signal by comparing the reference position command signal with the position signal; The upper edge of the trapezoidal waveform among the error signals detected in the rising section, the falling section, and the constant value holding section of the reference position command signal, and the waveform of the vertex error which is at least a part of the error signal except for the trapezoidal waveform are horizontal, respectively. And a gain adjusting step of varying and adjusting a gain of the PID control unit to have a size within a predetermined tolerance range required by the laser scanner. The method of claim 6, The PID control unit includes a proportional operation unit, an integral operation unit, and a derivative operation unit, The initial setting step, A maximum gain detection process of gradually increasing a gain of the proportional calculation unit to calculate a maximum gain value in which oscillation is not detected; And And setting a gain adjustment range of the proportional calculation unit by setting a predetermined margin to the maximum gain value. The method of claim 7, wherein The gain adjustment step, A proportional gain adjustment process of adjusting a gain of the proportional calculation unit within the set gain adjustment range so that the magnitude of the error signal is within an error tolerance range required by the laser scanner; A differential gain adjustment process of adjusting a gain of the differential calculation unit so that the error signal is horizontal; And And an integral gain adjusting step of adjusting a gain of the integral calculating part so that the vertex error of the error signal is horizontal. The method of claim 8, The proportional calculating unit, the integral calculating unit and the derivative calculating unit each include a digital resistor, And said proportional gain adjustment process, said differential gain adjustment process and said integral gain adjustment process are performed by varying said respective digital resistors.