CN116618855A

CN116618855A - Automatic control method and system for laser cutting unit

Info

Publication number: CN116618855A
Application number: CN202310726259.3A
Authority: CN
Inventors: 陈跃华; 徐永斌; 赵菁; 郭利华; 熊金猛
Original assignee: Wisdri Engineering and Research Incorporation Ltd
Current assignee: Wisdri Engineering and Research Incorporation Ltd
Priority date: 2023-06-16
Filing date: 2023-06-16
Publication date: 2023-08-22

Abstract

The invention discloses an automatic control method and a system of a laser cutting unit, wherein a driving roller encoder is used for calculating the calculated distance between the head of a to-be-cut object and a cutting position; the length grating is matched with the X-axis servo motor to realize the accurate positioning of the object to be cut; controlling the Y-axis servo motor to cut, and performing automatic zero correction of the Y-axis servo motor after cutting is completed; calibrating a distance sensor of the laser head, and controlling a Z-axis servo motor in the whole cutting process to keep the cutting height stable; according to the installed photoelectric switch, the transmission roller way is segmented, the middle roller way segment operates at the highest speed as possible, and the transmission speed conversion is stably realized on the end roller way segment. The invention realizes full automation and intellectualization of the whole laser cutting process, realizes high-precision cutting and positioning of the steel plate, solves the control problem of cutting height in the cutting process, considers the production efficiency and the safety of the roller way transmission process, and realizes stable transition with the next working procedure.

Description

Automatic control method and system for laser cutting unit

Technical Field

The invention relates to the technical field of electrical control, in particular to an automatic control method and system of a laser cutting unit.

Background

With the rapid development of the processing industry, the laser cutting machine is widely applied, and can realize rapid, accurate and efficient cutting of metal materials such as stainless steel, carbon steel, aluminum plates, galvanized plates, iron plates and the like.

In a laser cutting unit, the positioning requirements for the shaft in each direction are very high.

In the length direction of the cut steel sheet, it is necessary to reach 0.05% of the cut length, and if 6m long objects to be cut are cut, the positioning accuracy of the cut length is within 3 mm.

The servo motor in the cutting direction (width direction of the steel plate) converts the rotation of the motor into the displacement on the linear guide rail through the gear and screw rod device, a gap exists inevitably when the gear and the screw rod are meshed, and when the cutting is carried out once, the measurement reading of the absolute value encoder has a tiny offset, and a large error is accumulated for a plurality of times, so that the automatic correction is carried out once after each cutting, and the accumulated error is eliminated.

If the fluctuation of the cutting height is large, the cutting effect can be greatly affected, slag and knots on the cutting surface are caused, and even the cutting is continuous. The precision requirement on the cutting height is very high in the cutting process, and the positioning precision requirement is within 0.05 mm. The thickness of the metal sheet in the width direction often has a certain fluctuation, and in order to keep the stability of the cutting height, the laser head of the current mainstream is equipped with a non-contact distance sensor, so that the distance between the laser head and the surface of the metal sheet can be measured. For example, the measuring range of a distance sensor of a laser head of a certain brand is 0.0-10.0 mm, and the corresponding output is 0-10V. The proportional relation between the measured output voltage and the corresponding distance value is stored in the height adjuster of the laser head and can be influenced by the measured material.

Because of certain errors in the width data of the cutting plate, in order to ensure that the cutting plate can be completely cut, laser and cooling gas need to be started in advance before a laser head reaches the edge of the cutting plate; similarly, after the cutting plate is cut, the laser head has already been out of the edge of the other side of the cutting plate, and still needs to keep the laser and cooling gas on for a short period of time. Thus, the process that the laser head enters the edge of the cutting plate once in the cutting process and the process that the laser head exits from the edge of the cutting plate once can be realized. The laser head follow-up function is enabled in both processes, and the sensing distance of the laser head is out of range outside the range of the cutting board. And the sensing distance will have a transition time of about two sampling periods, depending on the actual observation. Taking the laser head as an example, when the laser head goes out from the edge of the cutting plate, the sensing distance is changed from the vicinity of the cutting height to a larger value within one measuring range, then the next sampling period reaches the vicinity of the measuring range, and then the next sampling period exceeds the measuring range.

The cut steel plates are conveyed to the next working procedure through a conveying roller way, and the next working procedure can be directly stacked, packed and conveyed away or further processed. Generally, the processing speed of the next process is low, and the steel plate is transported as fast as possible to improve the production efficiency. However, in actual production, the accident that two steel plates collide together due to too high speed for a plurality of times is summarized, the experience that the two steel plates should keep a certain safety distance, run at a high speed when the distance is large, and automatically slow down or stop when the distance is smaller than the safety distance. This puts high demands on the real-time positioning and tracking of the heads and the tails of the steel plates.

Disclosure of Invention

The invention mainly aims at: the automatic control method and the system for the laser cutting unit can improve the positioning accuracy of the whole laser cutting process.

The technical scheme adopted by the invention is as follows: an automatic control method of a laser cutting unit, the laser cutting unit comprises: the conveying mechanism is arranged on the cutter frame on the conveying mechanism along the width direction of the object to be cut, and is used for driving the servo motor unit for moving the cutter frame, and a length grating extending to the conveying end point of the conveying mechanism is arranged at the downstream position of the cutter frame; the transmission mechanism comprises driving rollers which are sequentially arranged along the transmission direction, the transmission mechanism is provided with a cutting start position and a cutting position, a start photoelectric switch and a first driving roller are arranged at the cutting start position, a driving roller encoder is arranged on the first driving roller, a second driving roller and a third driving roller are sequentially arranged at the downstream of the first driving roller, and the cutting position is positioned between the second driving roller and the third driving roller; the cutting machine frame is arranged above the cutting position, two ends of the cutting machine frame are driven to move along the transmission direction through a first X-axis servo motor and a second X-axis servo motor respectively, the first X-axis servo motor is provided with an X-axis absolute value encoder, a laser head is arranged on the cutting machine frame, the laser head moves along the width direction of an object to be cut through a Y-axis servo motor, the Y-axis servo motor is provided with a Y-axis absolute value encoder, the laser head moves along the height direction of the object to be cut through a Z-axis servo motor, the Z-axis servo motor is provided with a Z-axis absolute value encoder, a laser head nozzle is arranged on the laser head, and a distance sensor for judging the distance between the laser head nozzle and the object to be cut is arranged on the laser head nozzle;

The method comprises the following steps:

p1, accurately positioning the object to be cut:

p101, starting when the head of the object to be cut reaches the starting photoelectric switch, calculating the calculated distance between the head of the object to be cut and the cutting position according to the value of the driving roller encoder;

p102, after the head of the object to be cut enters the measuring area of the length grating, compensating the calculated distance between the head of the object to be cut and the cutting position by using the first effective measuring value of the length grating; controlling the speed of the driving roller according to the calculated distance between the compensated head of the object to be cut and the cutting position;

p103, stopping transmission when the calculated distance between the head of the object to be cut and the cutting position reaches the designated length, delaying for a short period of preset time, waiting for the length grating measurement value to be stable, calculating the positioning error of the object to be cut according to the length grating measurement value, and compensating the positioning error of the object to be cut by using an X-axis servo motor so as to adjust the laser head to reach the accurate cutting position;

p2, cutting:

p201, recording the reading of an X-axis absolute value encoder when in cutting position, setting the position limiting of a laser head in the X-axis direction, and controlling a first X-axis servo motor and a second X-axis servo motor to finish cutting positioning;

P202, controlling a Y-axis servo motor to enable a laser head to move to a cutting starting point positioned at the edge of the object to be cut, starting laser and cutting gas, enabling the laser head to move along the Y-axis at a designated cutting speed at a constant speed to cut the object to be cut, and when the laser head moves to a cutting ending point positioned at the other edge of the object to be cut, finishing cutting and closing the laser and the cutting gas;

p203, after cutting is completed, the laser head returns to the cutting starting point at a change speed of first quick and then slow in the Y axis, a zero limit switch is arranged at the cutting starting point, and when a rising edge signal appears on the zero limit switch, automatic zero correction of the laser head in the Y axis direction is performed;

p3, calibrating a distance sensor:

p301, adjusting the focal length of the laser head to a zero position, checking a laser head state signal, and setting a calibration characteristic curve according to a cutting height range; the calibration characteristic curve consists of a plurality of characteristic points in a measuring range; when setting a calibration characteristic curve, setting denser characteristic points in a cutting height range of a laser cutting machine, and setting sparser characteristic points outside the cutting height range; the dense and sparse are relative concepts;

p302, controlling a Y-axis servo motor to initially displace the laser head to the upper part of the object to be cut, and then controlling a Z-axis servo motor to descend until a laser head nozzle contacts the object to be cut; controlling a Z-axis servo motor to sequentially move the laser head to each characteristic point on the calibration characteristic curve for calibration;

P303, after calibration is completed, controlling the Y, Z axis servo motor to return to an initial position, and performing filtering processing on the measured value of the distance sensor;

p304, if a fault occurs in the calibration process, processing the fault and restarting the calibration;

p4, speed control:

p401, segmenting a transmission mechanism along the transmission direction of the object to be cut according to the installed photoelectric switches, wherein a roller way segment is arranged between two adjacent photoelectric switches, the head and tail positions of the transmitted object to be cut are calculated in each roller way segment, and head and tail occupation signals are respectively generated; the last roller way section is a last roller way section, and the other roller way sections are middle roller ways;

p402, setting the safe distance between objects to be cut, and setting the speed of each roller way section according to the head and tail occupation signals and the actual distance between the objects to be cut when the objects to be cut are conveyed on the middle roller way;

p403, setting a speed change position interval in a last-stage roller way, after the head of the object to be cut reaches the speed change position interval, carrying out speed change adjustment on the last-stage roller way according to a roller way advance allowing signal of the next process and a signal that the object to be cut is entering the next process, monitoring whether the object to be cut is clamped, and stopping the whole line when the object to be cut is clamped.

According to the above scheme, the P101 specifically includes:

when the head of the object to be cut reaches the starting photoelectric switch, firstly calculating the length of the object to be cut at each sampling moment according to the value of the driving roller encoder;

the distance between the starting photoelectric switch and the cutting position is measured and is recorded as S _S，Cut The method comprises the steps of carrying out a first treatment on the surface of the Starting from starting the calculation of the transport length of the object to be cut, accumulating the length S passed at each sampling instant _Inc Obtaining the total length value of the head of the object to be cut from the starting photoelectric switch, and recording as S _Accum The method comprises the steps of carrying out a first treatment on the surface of the The calculated distance S between the head of the object to be cut and the cutting position _Head，Cal Is S _Accum -S _S，Cut 。

According to the above scheme, the P102 specifically includes:

p102.1, distance compensation:

the distance from the cutting bit to the length grating start point is recorded as S _Cut，Opt Will S _Cut，Opt As a starting value for the length grating measurement, in this wayThe length grating measures the distance between the head of the object to be cut and the cutting position; after the object to be cut enters the length grating measuring range, if the length grating measuring value is greater than S at a certain sampling time _Cut，Opt Judging that the measured value at the moment is valid;

after the head of the object to be cut enters the grating measuring area, judging effective sampling time when a grating measured value appears for the first time, and marking the effective sampling time as m time; grating measurement S at m time _Optical (m), and a calculated distance S between the head of the object to be cut and the cutting position _Head，Cal (m) the error between them is recorded as the compensation value S _Com ：

S _Com ＝S _Optical (m)-S _Head，cal (m)

The length calculated value of the compensated object to be cut is set as S _Head，F Then:

S _Head，F ＝S _Head，cal +S _Com

p102.2, calculating a deceleration distance according to the highest speed and the deceleration of the driving roller:

wherein V is _Max For maximum linear speed of driving roller A _Dec For deceleration of the driving roller S _Dec Namely the distance that the driving roller needs to walk when the driving roller is decelerated from the highest speed to zero;

p102.3, setting the speed of a driving roller:

let the cutting length of the object to be cut be L _Cut The distance that needs to be transmitted is also:

S _Left ＝L _Cut -S _Head，F

according to the distance to be transmitted, setting a transmission speed set value as follows:

wherein t is _Dec Is from S _Left ＝S _Dec A deceleration time calculated from the moment; when the distance to be transmitted is larger than the deceleration distance, the driving roller runs at the maximum speed, and when the distance to be transmitted is smaller than or equal to the deceleration distance, the driving roller runs at the deceleration A _Dec Deceleration to zero.

According to the above scheme, the P103 specifically includes:

p103.1, calculating a positioning error:

after the constant driving roller is decelerated to zero, delaying for a short period of time to wait for the length grating measurement value to be stable, reading the grating measurement value at the current moment, calculating the positioning error of the object to be cut, and using the grating measurement value S _Optical Calculating the positioning error S of the object to be cut _Error ：

S _Error ＝L _Cut -S _Optical

In which L _Cut The cutting length of the object to be cut;

p103.2, calculating the position of the laser head in the transmission direction of the object to be cut:

taking the advancing direction of the object to be cut as the forward direction, and the position P when the laser head moves to the cutting position along the X axis _Cut The position P of the laser head in the conveying direction of the object to be cut _X，Set The method comprises the following steps:

P _X，Set ＝P _Cut -S _Error

controlling the servo motor group to enable the laser head to move to P _X，Set Accurate positioning is realized.

According to the above scheme, the P201 specifically includes:

determining the position relation between the cutting position and the driving roller for conveying the object to be cut, controlling the laser head to move to the cutting position along the X axis by the X-axis servo motor, and then recording the position value of the X-axis absolute value encoder as the cutting position value, namely P _X，Cut ；

According to the distance between the driving rollers and the roller diameter value, calculating the movable range of the laser head in the front and back of the cutting position along the X axis, and reserving a preset allowance, thereby obtaining the X axis direction position limiting value; if the calculated position set value of the cutting position exceeds the position limiting value in the X-axis direction, alarming and stopping the cutting step;

a length grating for collecting the distance from the head of the object to be cut to the cutting position is arranged at the outlet of the cutting machine, and the position set value of the cutting position is calculated and recorded as P according to the length of the transmission material collected by the length grating _X，Set Presetting an X-axis small range value P _A，X As in-place range, note P _X，Act To cut the actual position of bit, when |P _X，Set -P _X，Act |≤P _A，X When the X-axis servo motor is in place, the X-axis servo motor stops acting; if |P _X，Set -P _X，Act |>P _A，X The set value of the moving speed of the X-axis servo motor is calculated by using the proportional controller, and the limiting is carried out, wherein the following formula is adopted:

V _ServoX，Set ＝LIM _X [K _P，X ×(P _X，Set -P _X，Act )]

wherein V is _ServoX，Set LIM is set for the moving speed of the X-axis servo motors at two sides _X A limiting link representing X-axis speed, K _P，X Is the proportionality coefficient of the X-axis proportional controller.

According to the above scheme, in the step P202, the Y-axis servo motor is controlled to move the laser head to the cutting start point of the edge of the object to be cut, specifically:

subtracting a maximum value of 2 times of width error on the basis of the position of the edge of the object to be cut calculated according to the width data from a set position value of the cutting starting point in the process that the laser head moves to the edge of the object to be cut along the Y axis;

presetting a Y-axis small range value P _A，Y As the in-place range, when the difference between the actual position value of the laser head on the Y axis and the set position of the cutting start point is out of the in-place range, the speed set value at the time of the first positioning of the Y axis is calculated as follows:

V _{ServoY，Set1} ＝LIM _Y [K _P，Y ×(P _Y，Set1 -P _Y，Act )]

in LIM _Y Limiting link representing Y-axis speed, K _P，Y For the proportionality coefficient of the Y axis, P _Y，Act Is excited byActual position value of optical head on Y-axis, P _Y，Set1 The set position value of the cutting start point is used for the first positioning of the laser head.

According to the above scheme, the P401 specifically performs the segmentation of the conveying roller table of the object to be cut in the following manner:

a photoelectric switch is arranged on a conveying roller way of the object to be cut at intervals along the conveying direction of the object to be cut, and when the object to be cut passes through the position of the photoelectric switch, an identification signal is sent;

dividing the driving rollers between two adjacent photoelectric switches into a group, so as to divide the whole conveying roller way of the object to be cut into a plurality of sections, wherein the driving speed of the driving rollers in each roller way section is changed together;

taking the position of an initial photoelectric switch of a conveying roller way of an object to be cut as a starting point, and measuring the position values of all the photoelectric switches at the back relative to the starting point as known values;

the real-time position of the transmitted head of the object to be cut is calculated in the following way, and a head occupation signal is generated:

the position of the photoelectric switch at the starting position of a certain roller way segment X is set as P _X，Start The position of the photoelectric switch at the end position of the roller way segment X is P _X，End The method comprises the steps of carrying out a first treatment on the surface of the When the head of the object to be cut reaches P _X，Start ，P _X，Start The photoelectric switch at the position sends out an identification signal and takes up a position signal Occupy of the head of the object to be cut in the roller way section X _X，Head Set to 1; when the head of the object to be cut reaches P _X，End ，P _X，End The photoelectric switch at the position sends out an identification signal and takes up a position signal Occupy of the head of the object to be cut in the roller way section X _X，Head Resetting to 0;

on-head occupancy signal Occupy _X，Head In the time of 1, according to the transmission speed of the roller way section X, accumulating the transmission distance of the object to be cut in the roller way section X once at each sampling moment to obtain the real-time position of the head of the object to be cut;

the real-time position of the tail of the transmitted object to be cut and the acquisition mode of the tail occupying signal are the same as the real-time position of the head of the transmitted object to be cut and the head occupying signal.

According to the above scheme, the P402 specifically includes:

marking the roller way segments along the conveying direction of the object to be cut;

1) If the head occupation signals of the objects to be cut on the roller way section X are 0 and the tail occupation signals on the roller way sections X+1 and X+2 are 0, the roller way section X takes up the highest speed V _Max Operating;

2) If the head occupation signal of the object to be cut on the roller way segment X is 0, the tail occupation signal on the X+1 roller way segment is 1, the distance Dis between two objects to be cut is calculated according to the following formula _X，X+2 ：

Dis _X，X+2 ＝P _X+2，Tail -P _X，Head

P _X+2，Tail P for the tail position of the steel plate on the roller way segment X+2 _X，Head The head position of the object to be cut is positioned on the roller way section X;

if Dis _X，X+2 >D _Safe The roller way segment X is at the highest speed V _Max Operating; d (D) _Safe Is a safe distance;

if Dis _X，X+2 <D _Safe The transmission speed of the roller way section X+2 is 0.0, and the speed of the roller way section X is set to be 0.0;

if Dis _X，X+2 <D _Safe And the transmission speed of the roller way segment X+2 is a preset low speed V _Low Setting the speed of the roller way section X as V _LOw ；

3) If the head occupation signal of the object to be cut is on the roller way section X and the tail occupation signal on the roller way section X+1 is 1, the speed of the roller way section X is set to be 0.0.

According to the above scheme, in the above P403, the speed change adjustment specifically includes:

1) If the head of the object to be cut does not reach the speed change position, the steel plate is entering the next working procedure signal Switch _Next 0, the final roller way is at the highest speed V _Max Operating;

2) The head of the object to be cut enters a gear shifting interval, if the steel plate is entering the next workerSequence signal Switch _Next =0, and the allowed roller way advance signal Allow for the next process _Next =1, the last stage roller bed is at the next process speed V _Next Operating; if Switch is _Next =0 and alloy _Next When=0, the speed of the last roller way is set to 0.0, and the alloy is waited for _Next After the speed of the roller way at the end section is changed into 1, the speed of the roller way at the end section is set as V _Next ；

3) When the head of the object to be cut enters the gear shifting interval, if the Switch _Next =1, then the speed of the last roller way is set to 0.0;

whether the cardboard is monitored, all-line parking is specifically:

starting a timer when the signal of the next working procedure is changed from 0 to 1, and resetting the timer when the signal of the next working procedure is changed from 1 to 0 to obtain the timing T of the timer _Next ；

Calculating theoretical transmission time T _Trans ：T _Trans ＝L _Plate /V _next Wherein L is _Plate For the length of the object to be cut, V _Next The next working procedure speed;

if T _Next >T _Trans And +T1, wherein T1 is a preset time interval, a full-line stop signal is immediately triggered, all roller ways are immediately stopped, and an operator waits for processing faults.

The automatic control system of the laser cutting machine set comprises a control unit and a frequency converter, wherein the control unit is used for executing the automatic control method of the laser cutting machine set, sending a speed set value of each roller way section to the frequency converter, and sending the speed set value to a driving roller of each roller way section by the frequency converter.

The invention has the beneficial effects that: the full automation and the intellectualization of the whole laser cutting process are realized, the accurate positioning and the high-precision cutting positioning of objects to be cut are realized, the problem that the Y-axis servo motor generates accumulated errors is solved, the difficulty in controlling the cutting height in the cutting process is solved, the production efficiency and the safety of the roller way transmission process are both considered, the smooth transition with the next process is realized, the labor intensity of staff is reduced, and the production efficiency is improved.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a flow chart of a method according to an embodiment of the present invention.

Fig. 2 is a schematic top view of a laser cutting unit according to an embodiment of the invention.

Fig. 3 is a schematic left view of a laser cutting unit according to an embodiment of the present invention.

In the figure: 1-PLC controller, 2-servo amplifier, 3-converter, 4-driving roller encoder, 5-first X axle servo motor, 6-X axle absolute value encoder, 7-first X axle servo motor operation track, 8-first driving roller, 9-to-be-cut thing, 10-second driving roller, 11-third driving roller, 12-cutter frame, 13-Y axle servo motor operation track, 14-initial photoelectric switch, 15-laser head, 16-Y axle servo motor, 17-Y axle absolute value encoder, 18-length grating, 19-Y axle zero limit switch, 20-second X axle servo motor, 21-second X axle servo motor operation track, 22-Z axle servo motor operation track, 23-laser, 24-height adjuster, 25-Z axle servo motor, 26-Z axle absolute value encoder, 27-laser head nozzle, 28-distance sensor.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The object to be cut according to the present embodiment is a steel plate, but may be other plate-like materials that need to be cut, such as a metal plate.

As shown in fig. 2 and 3, the laser cutting unit includes: a conveying mechanism, a cutter frame 12 arranged on the conveying mechanism along the width direction of the object 9 to be cut, a servo motor group for driving the cutter frame 12 to move, and a length grating 18 extending to the conveying end point of the conveying mechanism at a position downstream of the cutter frame 12; the transmission mechanism comprises driving rollers sequentially arranged along the transmission direction, the transmission mechanism is provided with a cutting start position and a cutting position, a start photoelectric switch 14 and a first driving roller 8 are arranged at the cutting start position, a driving roller encoder 4 is arranged on the first driving roller 8, a second driving roller 10 and a third driving roller 11 are sequentially arranged at the downstream of the first driving roller 8, and the cutting position is positioned between the second driving roller 10 and the third driving roller 11; the cutting machine frame 12 set up in the cutting position top, the both ends of cutting machine frame 12 are equipped with X axle absolute value encoder 6 through first X axle servo motor 5 and the drive of second X axle servo motor 20 respectively on the first X axle servo motor 5, be equipped with laser head 15 on the cutting machine frame 12, laser head 15 is equipped with Y axle absolute value encoder 17 along waiting to cut the wide 9 degree direction of thing through Y axle servo motor 16 to remove, Y axle servo motor 16 is equipped with Y axle absolute value encoder 17, laser head 15 is equipped with Z axle absolute value encoder 26 along waiting to cut the high direction of thing 9 through Z axle servo motor 25, be equipped with laser head nozzle 27 on the laser head 15, be equipped with the distance sensor 28 that is used for judging the distance between laser head nozzle 17 and the waiting to cut the thing 9 on the laser head nozzle 27. Wherein, first X axle servo motor 5 and second X axle servo motor 20 move along first X axle servo motor operation track 7 and second X axle servo motor operation track 21 respectively, and Y axle servo motor 16 moves along Y axle servo motor operation track 13, and Z axle servo motor 25 moves along Z axle servo motor operation track 22, and Y axle zero point limit switch 19 is used for the zero point correction of Y axle servo motor 16. The laser head is also provided with a height adjuster 24.

The invention provides an automatic control system of a laser cutting machine set, which comprises a control unit and a frequency converter 3, wherein the control unit is used for executing the automatic control method of the laser cutting machine set, sending a speed set value of each roller way section to the frequency converter 3, and sending the speed set value to a driving roller of each roller way section by the frequency converter 3. In this embodiment, the control unit is a PLC controller 1, and when the servo motors are controlled, the PLC controller 1 is connected to each servo motor through a servo amplifier 2.

The invention provides an automatic control method of a laser cutting unit, which is shown in figure 1 and comprises the following parts:

p1, accurately positioning the object 9 to be cut:

p101, starting when the head of the object 9 to be cut reaches the starting photoelectric switch 14, calculating the calculated distance between the head of the object 9 to be cut and the cutting position according to the value of the driving roller encoder 4; p101 is specifically:

when the head of the object 9 to be cut reaches the position of the initial photoelectric switch 14, firstly calculating the length of the object 9 to be cut at each sampling moment according to the value of the driving roller encoder 4; the method comprises the following steps:

when the head of the object 9 reaches the start photoelectric switch 14, a rising edge signal of the start photoelectric switch 14 is received and denoted as P _Start The method comprises the steps of starting the calculation of the walking length of the object 9 to be cut;

according to the reading of the driving roller encoder 4 at the starting point of the cutting area, calculating the length of the object 9 to be cut at each sampling moment;

if P _Encoder (n)>P _Encoder (n-1), then:

S _Inc (n)＝π×D _drv ×[P _Encoder (n)-P _Encoder (n-1)]/P _Max

if P _Encoder (n)<P _Encoder (n-1), then:

S _Inc (n)＝π×D _drv ×[P _Encoder (n)+P _Max -P _Encoder (n-1)]/P _Max

wherein S is _Inc (n) represents the length of travel of the object 9 to be cut at the present time, D _drv For diameter of driving roller, P _Encoder (n) and P _Encoder (n-1) represents the readings of the driving roller encoder 4 at the present time and the last sampling time, respectively, P _Max The amount of change in the reading of the driving roller encoder 4 for one rotation of the driving roller.

The distance between the start photoelectric switch 14 and the cutting position is measured and is recorded as S _S，Cut The method comprises the steps of carrying out a first treatment on the surface of the Starting from the start of the calculation of the transport length of the object 9 to be cut, the length S travelled at each sampling instant is accumulated _Inc Obtain the total length value of the head of the object 9 to be cut from the starting photoelectric switch 14, and record as S _Accum The method comprises the steps of carrying out a first treatment on the surface of the The calculated distance S between the head of the object 9 to be cut and the cutting position _Head，Cal Is S _Accum -S _S，Cut 。

The cutting position is arranged in the middle of the nearest upstream and downstream driving rollers, and the distance between the starting photoelectric switch 14 and the cutting position is measured and is marked as S _S，Cut The method comprises the steps of carrying out a first treatment on the surface of the Starting from the start of the calculation of the transport length of the object 9 to be cut, the length S travelled at each sampling instant is accumulated _Inc Obtain the total length value of the head of the object 9 to be cut from the starting photoelectric switch 14, and record as S _Accum The method comprises the steps of carrying out a first treatment on the surface of the The calculated distance S between the head of the object 9 to be cut and the cutting position _Head，cal Is S _Accum -S _S，Cut 。

P102, after the head of the object to be cut enters the measuring area of the length grating, compensating the calculated distance between the head of the object to be cut and the cutting position by using the first effective measuring value of the length grating; and controlling the speed of the driving roller according to the calculated distance between the compensated head of the object to be cut and the cutting position. The method comprises the following steps:

p102.1, distance compensation:

the distance from the cutting bit to the length grating start point is recorded as S _Cut，Opt Will S _Cut，Opt As a starting value for the length grating measurement, the distance between the head of the object to be cut and the cutting position is measured by the length grating; after the object to be cut enters the length grating measuring range, if the length grating measuring value is greater than S at a certain sampling time _Cut，Opt Judging that the measured value at the moment is valid;

after the head of the object to be cut enters the grating measuring area, judging effective sampling time when a grating measured value appears for the first time, and marking the effective sampling time as m time; grating measurement S at m time _Optical (m), and a calculated distance S between the head of the object 9 to be cut and the cutting position _Head，Cal (m) the error between them is recorded as the compensation value S _Com ：

S _Com ＝S _Optical (m)-S _Head，Cal (m)

The length calculated value of the object 9 to be cut after compensation is set as S _Head，F， Then:

S _Head，F ＝S _Head，cal +S _Com

p102.3, setting the speed of a driving roller:

S _Left ＝L _Cut -S _Head，F

And P103, stopping transmission when the calculated distance between the head of the object to be cut and the cutting position reaches the designated length, delaying for a short period of preset time, waiting for the length grating measurement value to be stable, calculating the positioning error of the object to be cut according to the length grating measurement value, and compensating the positioning error of the object to be cut by using the X-axis servo motor so as to adjust the laser head to reach the accurate cutting position. The method comprises the following steps:

p103.1, calculating a positioning error:

after the constant driving roller is decelerated to zero, the measured value of the grating 18 is stabilized after a small period of time delay, the measured value of the grating at the current moment is read, the error of positioning the object to be cut is calculated, and light is used Gate measurement S _Optical Calculating the positioning error S of the object to be cut _Error ：

S _Error ＝L _Cut -S _Optical

In which L _Cut Is the cutting length of the object 9 to be cut;

p103.2, calculating the position of the laser head 15 in the direction of transport of the object to be cut:

the forward direction of the object 9 to be cut is taken as the forward direction, and the position when the laser head 15 moves to the cutting position along the X axis is P _Cut The position P of the laser head 15 in the conveying direction of the object 9 to be cut _X，Set The method comprises the following steps:

P _X，Set ＝P _Cut -S _Error

P2, cutting:

p201, recording the reading of an X-axis absolute value encoder when cutting the position, setting the position limiting of the laser head in the X-axis direction, and controlling the first and second X-axis servo motors to finish cutting positioning. The specific P201 is:

According to the distance between the driving rollers and the roller diameter value, calculating the movable range of the laser head in the front and back of the cutting position along the X axis, and reserving a preset allowance, thereby obtaining the X axis direction position limiting value; and if the calculated position set value of the cutting position exceeds the position limiting value in the X-axis direction, alarming and stopping the cutting step.

In this embodiment, the distance between the front driving roller 7 and the rear driving roller 8 is 550mm, the roller diameter is 180mm, and the cutting position is located at the position right in between, so that the cutting position can only move within the range of 185mm along the X axis, and if the laser exceeds the range, the driving roller is cut, so that the equipment is damaged. Taking a certain margin into consideration, finally setting XThe movable shaft is positioned in the range P _X，Cut Within 130 mm.

V _ServoX，Set ＝LIM _X [K _P，X ×(P _X，Set -P _X，Act )]

In the embodiment, the speed limiting range of the X-axis servo motor is 0.0-50.0 mm/s, and the proportion coefficient K _P，X =1.15. If |P _X，Set -P _X，Act And if the I is large, the action speed is an upper limit value, and the speed gradually slows down when approaching to the set position until the X-axis servo motor enters the in-place range, and the X-axis servo motor stops.

P202, controlling a Y-axis servo motor to enable a laser head to move to a cutting starting point positioned at the edge of the object to be cut, starting laser and cutting gas, enabling the laser head to move along the Y-axis at a specified cutting speed at a constant speed to cut the object to be cut, and when the laser head moves to a cutting ending point positioned at the other edge of the object to be cut, finishing cutting and closing the laser and the cutting gas. In P202, the Y-axis servo motor is controlled to enable the laser head to move to a cutting start point of the edge of the object to be cut, specifically:

the position of the edge of the object 9 to be cut calculated from the width data may not be in line with the actual situation due to a certain error in the width data of the steel plate. For the sake of completenessAnd cutting the object 9 to be cut, wherein in the process that the laser head moves to the edge of the object 9 to be cut along the Y axis, the set position value of the cutting starting point subtracts the maximum value of the 2 times width error on the basis of the position of the edge of the object 9 to be cut calculated according to the width data. In the present embodiment, the position of the operation side edge portion of the object 9 to be cut calculated from the width data is set to P _Y，OS The maximum error value of the width data is 40.0mm, and then the first positioning set value of the Y axis is P _Y，Set1 ＝P _Y，OS -80.0mm。

V _{ServoY，Set1} ＝LIM _Y [K _P，Y ×(P _Y，Set1 -P _Y，Act )]

in LIM _Y Limiting link representing Y-axis speed, K _P，Y For the proportionality coefficient of the Y axis, P _Y，Act For the actual position value of the laser head on the Y axis, P _Y，Set1 The set position value of the cutting start point is used for the first positioning of the laser head. In this embodiment, the Y-axis is in the range of P _A，Y The speed limiting range of the Y-axis servo motor is 0.0-250.0 mm/s, and the proportion coefficient is K _P，Y ＝2.0。

Before cutting, the laser related devices such as a laser, a water cooler, a laser head and the like are required to be powered on, a valve of a cutting gas cylinder is also required to be opened, and the laser reaches the working temperature range until all the laser related devices are completely started, so that preparation is made for laser light emission, and the cutting step can be started. After all laser related equipment is ready and the laser head has been in place for the first time in the Y-axis (P is reached _Y，Set1 ) Firstly, cutting gas is started (the cutting gas plays a role of cooling a laser head and assisting in cutting), after the cutting gas is started for 1s, laser is started to emit light, and the laser is emitted from a laser head nozzle to start cutting the object 9 to be cut.

While the cutting gas is started, the Y-axis servo motor is started at a specified cutting speed V _Cutting Operated from the object 9 to be cutSide-to-side movement is performed, namely:

V _{ServoY，set2} ＝V _Cutting

wherein V is _{ServoY，Set2} The speed setting for the Y-axis uniform motion (cutting) is set. The position of the transmission side edge of the object 9 to be cut calculated according to the width data is set as P _Y，DS The position setting value of the completion of the Y-axis cutting is P _Y，DS Plus a width error maximum of 2 times. In the present embodiment, the position setting value of the cutting process along the Y-axis is P _Y，Set2 ＝P _Y，DS +80.0mm. And when the actual position of the laser head on the Y axis reaches a set value, decelerating to zero, closing the laser at the same time, and closing the cutting gas after the laser is closed for 1 s.

And P203, after cutting is finished, the laser head returns to the cutting starting point at the Y-axis at a change speed of first fast and then slow, the cutting starting point is provided with a Y-axis zero limit switch 19, and when the zero limit switch generates a rising edge signal, the automatic zero correction of the laser head in the Y-axis direction is performed. The actual position of the laser head on the Y axis is measured by a Y axis absolute value encoder, the zero limit switch on the operation side is taken as a cutting starting point, the laser head moves towards the transmission side, and the position value is gradually increased. After the cutting is completed, the Y-axis needs to return to the starting point of the cutting from the transmission side to wait for the next cutting.

The method comprises the following steps:

after cutting is completed, the Y-axis servo motor is controlled to move towards a cutting starting point at a preset high speed, and meanwhile, the acceleration is set to be a preset higher value; specifically, in the present embodiment, when the actual position of the laser head in the Y axis is 200.0mm or more, V is set _{ServoY，Set3} ＝250mm/s，A _Acc ＝A _Dec ＝500mm/s ² . Wherein A is _Acc For the acceleration set value, A _Dec Is the deceleration set point.

When the laser head moves close to the cutting start point, the running speed is reduced, the deceleration is set to a preset lower value, and the laser head runs at a medium speed. Specifically, in the present embodiment, when the actual position of the laser head in the Y-axis is 20.0mm to 200.0mm, V _{ServoY，Set3} ＝80mm/s，A _Acc ＝A _Dec ＝300mm/s ² 。

When the laser head moves to a certain small range of the cutting starting point, the laser head moves to the cutting starting point at a preset slow speed. For example, in the present embodiment, when the actual position of the Y axis is less than 20.0mm, V is set _{ServoY，Set3} ＝10mm/s，A _Acc ＝A _Dec ＝500mm/s ² 。

When a rising edge signal appears on the zero limit switch, indicating that the laser head has moved to a cutting starting point, recording the reading of the Y-axis absolute value encoder at the current moment, and taking the reading as a new cutting starting point position value; and simultaneously, setting the speed of the Y-axis servo motor to be zero, and setting the deceleration to a preset higher value so as to stop the Y-axis servo motor as soon as possible. Specifically, set V _{ServoY，Set3} ＝0.0mm/s，A _Acc ＝A _Dec ＝500mm/s ² . Therefore, the Y-axis returns to the zero position after each cutting is completed and is automatically corrected once, so that accumulated errors are not generated.

P3, calibrating a distance sensor:

p301, adjusting the focal length of the laser head to a zero position, checking a laser head state signal, and setting a calibration characteristic curve according to a cutting height range; the calibration characteristic curve consists of a plurality of characteristic points in a measuring range; when setting a calibration characteristic curve, setting denser characteristic points in a cutting height range of a laser cutting machine, and setting sparser characteristic points outside the cutting height range; the dense and sparse are relative concepts.

Before the distance sensor is calibrated, the focal length of the laser head is adjusted to zero so as to avoid calibration deviation. In this embodiment, an automatic focusing laser head is adopted, and the focusing can be completed only by setting the focal length to be zero and then giving a focusing instruction. If the laser head is focused manually, the focal length of the laser head needs to be adjusted to the zero position manually.

Calibration can only be performed if the laser head is functioning properly, and various status signals of the laser head are checked in the PLC, which are sent to the PLC by hard wiring or by communication. In this embodiment, the laser head status signal is transmitted to the PLC by hard wiring, specifically, the following signals need to be checked: the laser head nozzle is not contacted with the steel plate; the side surface of the laser head is not contacted with the steel plate; the focal length of the laser head is at the zero position; the laser head nozzle can detect; the wiring of the laser head is normal; the distance between the laser head and the steel plate is larger than the measuring range. Only if all of the above conditions are satisfied, the calibration operation can be performed.

In this embodiment, the measuring range of the distance sensor is 0.0 to 10.0mm. In order to realize high-precision calibration, a calibration mode of 16 characteristic points is adopted in a measurement range, and the 16 characteristic points form a characteristic curve. Considering that the cutting height of the laser cutting machine is usually within 2.0mm, more characteristic points are arranged below 2.0mm, and the characteristic points in the range of 2.0 mm-10.0 mm are distributed sparsely. In this embodiment, the feature points selected are:

[0.2，0.5，0.7，1.0，1.2，1.5，1.8，2.0，2.5，3.0，4.0，5.0，6.0，7.0，8.0，10.0]mm

p302, controlling a Y-axis servo motor to initially displace the laser head to the upper part of the object to be cut, and then controlling a Z-axis servo motor to descend until a laser head nozzle contacts the object to be cut; and controlling the Z-axis servo motor to sequentially move the laser head to each characteristic point on the calibration characteristic curve for calibration.

Since different steel grades affect the sensing distance value, the calibration of the distance sensor is mainly used for adapting to different steel grades, and the laser head needs to be arranged on the upper part of the steel plate when the calibration is required, so that the laser head is firstly moved to the upper part of the steel plate. Then, a zero value of the sensing distance needs to be determined, so that the Z-axis servo motor is controlled to contact the laser head nozzle with the steel plate. And then controlling the Z-axis servo motor to move to each characteristic point on the calibration characteristic curve.

P302.1, controlling a Y-axis servo motor to move the laser head to the upper part of the steel plate;

and controlling the Y-axis servo motor to move the laser head from the initial position to a position with a certain distance inside the edge of the steel plate. Let the middle position of the roller way be Y _Center The width of the steel plate is S _width To ensure the laser head is on the steel plateA portion further moving inward by a certain distance D at the edge of the steel plate _in . In the present embodiment, this distance is set to D _in =150.0mm, then the position setting for the Y-axis servo motor is:

the Y-axis servo motor is moved to a set position, so that the laser head can be positioned on the upper portion of the steel plate.

And P302.2, controlling the Z-axis servo motor to descend until the nozzle of the laser head contacts the steel plate.

And adjusting the Z-axis servo motor to quickly descend the laser head from the initial position to the measuring range of the distance sensor. In this embodiment, the measuring range of the distance sensor is 0.0-10.0 mm, and in order to ensure that the laser head descends into the measuring range, the target position of the Z-axis servo motor is set at a position 8.0mm away from the steel plate. The Z-axis descent speed was set to 10.0mm/s.

The Z-axis continues to descend at a slow rate after the position is reached so as not to damage the laser head nozzle, for example, set to 0.5mm/s, until the laser head return nozzle comes into contact with the steel sheet signal to stop. The laser head height adjuster records the induction voltage value at the moment as a zero value of the induction distance.

And P302.3, controlling a Z-axis servo motor to sequentially move the laser head to each characteristic point on the calibration characteristic curve.

And controlling the Z-axis servo motor to lift the laser head to the characteristic point with the maximum distance from the steel plate, namely to the position 10.0mm away from the steel plate, wherein the characteristic point is the first characteristic point for calibration, and delaying for 2s after the calibration is in place, waiting for the recording position of the height regulator and the corresponding voltage value. And then controlling the Z-axis servo motor to sequentially reach all the characteristic points from high to low according to the calibration characteristic curve, and delaying for 2s after reaching the specified distance of the characteristic points each time to wait for the recorded position of the height regulator and the corresponding voltage value until all the characteristic points on the calibration characteristic curve are completed.

And P303, after the calibration is finished, controlling the Y, Z axis servo motor to return to an initial position, and performing filtering processing on the measured value of the distance sensor.

After the calibration of all the characteristic points is completed, the Y-axis servo motor and the Z-axis servo motor need to be controlled to return to initial positions, wherein the initial positions are generally defined as zero positions of Y-axis absolute value encoders and Z-axis absolute value encoders, the initial positions need to be operated at high speed for saving time, and the speed needs to be gradually reduced after the initial positions are approached so as to accurately stop at the initial positions. In order to reduce the influence of external disturbances on the measured value of the distance sensor, the measured value needs to be subjected to a filtering process.

P303.1, controlling the Y-axis servo motor and the Z-axis servo motor to return to initial positions by using a proportional controller;

calculating the speed set value of the Y-axis servo motor and the Z-axis servo motor returning to zero positions by using a proportional controller:

S _Y，SP ＝Lim(K _Y ×Y _Act )

S _Z，SP ＝Lim(K _Z ×Z _Act )

wherein S is _Y，SP And S is _Z，SP Speed set values of zero position return of Y axis and Z axis respectively, K _Y And K _Z Proportional coefficients of the Y-axis proportional controller and the Z-axis proportional controller respectively, Y _Act And Z _Act And the actual values of the positions measured by the Y-axis absolute value encoder and the Z-axis absolute value encoder are respectively, and Lim represents a limiting link, namely limiting the speed set value to be within a given maximum value range. In this embodiment, the maximum speed of the Y axis is set to 250mm/s and the maximum speed of the Z axis is set to 35mm/s. Thus, the Y axis and the Z axis can run at the maximum speed until approaching zero in the initial stage of returning to zero, the speed gradually decreases after approaching zero, and finally, the Y axis and the Z axis can stop at zero accurately and stably.

And P303.2, filtering the measured value of the distance sensor.

After the calibration of all the characteristic points is finished, the distance sensor can output an induction distance value, but in actual use, the distance sensor can be influenced by interference factors such as on-site dust, mist and the like, in order to reduce the influence of interference, the induction distance value needs to be filtered, a common filtering link comprises a first-order smooth filtering link and a multi-point average filtering link, and a filtering method can be selected to filter the induction distance value and then output. In this embodiment, multipoint average filtering is adopted, that is, several adjacent sampling values are selected for averaging and then output.

And P304, if a fault occurs in the calibration process, processing the fault and restarting the calibration.

During the actual calibration, some faults will inevitably occur, and when a fault occurs, corresponding processing needs to be performed and the calibration needs to be restarted.

P304.1, processing when a calibration long-time non-start-up failure occurs.

If the servo motor does not act for a long time after a calibration command is sent, the calibration failure is obtained. This failure is generally caused by the calibration requirement not being satisfied, and therefore it is necessary to check whether the calibration requirement is satisfied, specifically, in the present embodiment, it is necessary to check the following conditions: the laser head nozzle is not contacted with the steel plate; the side surface of the laser head is not contacted with the steel plate; the laser head nozzle can detect; the wiring of the laser head is normal; the distance between the laser head and the steel plate is larger than the measuring range.

After all the above conditions are met, calibration is started again.

P304.2, processing when no touch signal failure occurs.

After calibration begins, the zero point of the distance sensor needs to be determined, at the moment, the laser head nozzle is contacted with the steel plate, the PLC receives a signal of the steel plate when the nozzle is contacted with the steel plate under normal conditions, and the Z-axis servo motor stops and does not descend. However, in practice, a failure occurs in which the nozzle has been in contact with the steel plate but the PLC has not received the touch signal, and at this time, it is necessary to check whether the nozzle, ceramic body, protective lens of the laser head are stained, and if there is a problem, to replace the fitting with a new one, and then to perform calibration again.

P304.3, processing when a touch plate fault in calibration occurs.

In the calibration process, the laser head gradually approaches the steel plate from the largest characteristic point of the steel plate, and the last two characteristic points are usually very close to the steel plate, so that touch plate faults are likely to occur. I.e. a signal that the nozzle touches the steel plate occurs at the last two feature points of the calibration, at which time the calibration is aborted and misreported. If such a failure occurs occasionally, the Z-axis servo motor may be manually lifted up until the laser head is more than 10mm from the steel plate, and then calibration may be started again. If such a fault occurs frequently, it is necessary to reduce the descent speed of the Z-axis servomotor during calibration, and then start the calibration again.

And adjusting the Y-axis servo motor and the Z-axis servo motor according to the steps, moving the laser head to each characteristic point on the calibration characteristic curve, returning to an initial position, and processing the fault respectively, thereby completing the calibration method of the distance sensor of the laser head.

In summary, the distance sensor is calibrated by firstly adjusting the focal length of the laser head to zero, checking the state signal of the laser head, and setting a proper calibration characteristic curve according to the cutting height range; then, a Y-axis servo motor is adjusted to move the laser head to the upper part of the steel plate, and then a Z-axis servo motor is adjusted to contact the laser head nozzle with the steel plate and then move to each characteristic point on the calibration characteristic curve; and then the Y-axis servo motor and the Z-axis servo motor are moved back to the initial positions by using the proportional controller, and the measured distance values are subjected to filtering processing. Finally, a processing method when faults occur in the calibration process is provided. Thus, the calibration method of the distance sensor of the laser head is completed.

P4, speed control:

p401, segmenting a transmission mechanism along the transmission direction of the object to be cut according to the installed photoelectric switches, wherein a roller way segment is arranged between two adjacent photoelectric switches, the head and tail positions of the transmitted object to be cut are calculated in each roller way segment, and head and tail occupation signals are respectively generated; the last roller way section is a last roller way section, and the other roller way sections are middle roller ways. The P401 specifically performs segmentation of the conveying roller table of the object to be cut in the following manner:

and measuring the position values of all the photoelectric switches at the back relative to the starting point to serve as known values by taking the starting photoelectric switch position of the object to be cut conveying roller way as the starting point.

In this embodiment, when the head of the object to be cut reaches the position of the photoelectric switch, a rising edge signal is sent, and the steel plate always maintains a high level when passing through until the tail of the object to be cut reaches the position of the photoelectric switch, a falling edge signal is sent, and then the steel plate always maintains a low level when no steel plate passes through.

the position of the photoelectric switch at the starting position of a certain roller way segment X is set as P _X，Start The position of the photoelectric switch at the end position of the roller way segment X is P _X，End The method comprises the steps of carrying out a first treatment on the surface of the When the head of the object to be cut reaches P _X，Start ，P _X，Start The photoelectric switch at the position sends out an identification signal (in the embodiment, the photoelectric switch at the position sends out a rising edge signal), and the head of the object to be cut is positioned in the roller way section X and is occupied with a signal Occupy _X，Head Set to 1; when the head of the object to be cut reaches P _X，End ，P _X，End The photoelectric switch at the position sends out an identification signal (in the embodiment, the photoelectric switch at the position sends out a rising edge signal) and a occupation signal Occupy of the head of the object to be cut in the roller way section X _X，Head Resetting to 0;

in a certain roller way section X, the actual rotation speed of the driving roller is N _X，acr The fluctuation of the rotating speed value is large due to the interference of the field environment, so that the influence of the interference is reduced by adopting a dynamic average method. The transmission speed of the roller way section X is obtained by adopting the following modes: the roller path is arranged in the roller way section X and is Dia _X The average value of the rotation speeds of the driving rollers at a plurality of adjacent sampling moments is calculatedThe actual rotational speed of the driving roller at the current moment is converted into the transmission speed of the roller way segment X. In this embodiment, an average of 5 adjacent sampling instants is used.

N _X (n)＝[N _X，act (n)+N _X，act (n-1)+N _X，act (n-2)+N _X，act (n-3)+N _X，act (n-4)]/5

Where n represents the current time, n-1 represents the previous time, and so on.

The calculation formula of the real-time position of the head of the object to be cut is as follows:

P _X，Head ＝P _X，Start +∑N _X ·π·Dia _X ·T _S /G _X

wherein P is _X，Head For the real-time position of the head of the object to be cut, N _X For average rotation speed of driving roller, dia _X Is the roller diameter of the driving roller, T _S For sampling period of PLC, G _X The reduction ratio of the motor is driven by the driving roller.

The real-time position of the tail of the transmitted object to be cut and the acquisition mode of the tail occupying signal are the same as the real-time position of the head of the transmitted object to be cut and the head occupying signal. Specific:

the position of the photoelectric switch at the starting position of a certain roller way segment X is set as P _X，Start The position of the photoelectric switch at the end position of the roller way segment X is P _X，End The method comprises the steps of carrying out a first treatment on the surface of the When the tail of the object to be cut reaches P _X，Start ，P _X，Start The photoelectric switch at the position sends out an identification signal (in the embodiment, the photoelectric switch at the position sends out a falling edge signal), and the tail part of the object to be cut is positioned in the occupied signal Occupy of the roller way section X _X，Head Set to 1; when the tail of the object to be cut reaches P _X，End ，P _X，End The photoelectric switch at the position sends out an identification signal (in the embodiment, the photoelectric switch at the position sends out a falling edge signal) and takes up a position signal Occupy of the tail part of the object to be cut in the roller way section X _X，Head Resetting to 0;

on-tail occupancy signal Occupy _X，Head For a time of 1, according to the transport speed of the roller table segment X, eachAnd accumulating the distance of the object to be cut transmitted in the roller way section X once at the sampling moment to obtain the real-time position of the tail of the object to be cut.

P402, setting the safe distance between objects to be cut, and setting the speed of each roller way section according to the head and tail occupation signals and the actual distance between the objects to be cut when the objects to be cut are conveyed on the middle roller way; in order to prevent two objects to be cut on the roller way from collision, a certain distance needs to be kept between two adjacent objects to be cut, and the distance is a safe distance. If the safety distance is too large, the production efficiency can be affected, and if the safety distance is too small, potential safety hazards exist. The safe distance is only required to be slightly longer than the length of a segment of the segment roller way, and if the segment lengths are inconsistent, the safe distance is required to be slightly longer than the length of the longest segment roller way. In this embodiment, the longest segment roller way has a length of 4.95m, and thus a safety distance D is set _Safe =5.0m. The method specifically comprises the following steps:

marking the roller way segments along the conveying direction of the object to be cut; when the objects to be cut run on the conveying roller way, the distance between the two objects to be cut can be calculated according to the occupying signals and the head and tail positions, and the speed of the roller way of the section can be adjusted according to the distance.

1) If the head occupation signals of the objects to be cut on the roller way segment X are 0 and the tail occupation signals on the roller way segments X+1 and X+2 are 0, which means that the interval between two objects to be cut is too large, the roller way segment X takes the highest speed V _Max Operating;

Dis _X，X+2 ＝P _X+2，Tail -P _X，Head

if Dis _X，x +2<D _Safe And the transmission speed of the roller way segment X+2 is a preset low speed V _Low Setting the speed of the roller way section X as V _Low ；

P403, setting a speed change position interval in a last-stage roller way, after the head of the object to be cut reaches the speed change position interval, carrying out speed change adjustment on the last-stage roller way according to a roller way advance allowing signal of the next process and a signal that the object to be cut is entering the next process, monitoring whether the object to be cut is clamped, and stopping the whole line when the object to be cut is clamped. The last-stage roller way is used for conveying the steel plate to the next working procedure, and the processing speed of the next working procedure is generally lower than the highest conveying speed of the roller way. In the last-stage roller way, a gear position needs to be determined, and when the head of the object to be cut reaches the vicinity of the gear position, the speed V of the next process is changed _Next Or stopped. The gear position P is comprehensively considered _change Is set at a safe distance (5.0 m) from the starting position of the next working procedure and is set at P _change The + -0.2 m is used as a speed change position interval, so that a buffer interval for speed change of the object to be cut is reserved.

The next procedure mainly has two signals influencing the roller way transmission, one is to Allow the roller way to advance by a signal alloy _Next When the signal is 1, the roller way is allowed to convey the steel plate to the next working procedure; a signal is also provided that the steel sheet is going to the next process, which is determined by the entrance photoelectric Switch of the next process, and is denoted as Switch _Next . When the signal is 1, the object to be cut is transmitted to the next procedure, the signal has a falling edge (the moment from 1 to 0) which indicates that the tail of the object to be cut has passed through the entrance photoelectric switch of the next procedure, one blockAnd (5) finishing conveying the objects to be cut.

When the head of the object to be cut enters the end section roller way, the speed set value of the end section roller way needs to be determined according to the two signals, and the three conditions are divided:

1) If the head of the object to be cut does not reach the speed change position, the steel plate is entering the next working procedure signal Switch _Next 0 (indicating that there has been no object to be cut before), the last roller way is at the highest speed V _Max Operating;

2) The head of the object to be cut enters a gear shifting interval, if the steel plate is entering the next working procedure signal Switch _Next =0, and the allowed roller way advance signal Allow for the next process _Next =1 (indicating that no object has been cut before and that it is allowed to be transported to the next process), the last stage roller bed is operated at the next process speed V _Next Operating; if Switch is _Next =0 and alloy _Next =0 (indicating that no steel sheet has been previously provided but transport to the next process is not allowed), the speed of the last stage roller table is set to 0.0, and the alloy is waited for _Next After the speed of the roller way at the end section is changed into 1, the speed of the roller way at the end section is set as V _Next ；

whether the cardboard is monitored, all-line parking is specifically:

at the moment when the signal of the object to be cut is changed from 0 to 1 in the next process (Switch _Next A rising edge occurs on the signal), a timer is started, and the timer is reset (Switch) at the moment when the object to be cut is entering the next process signal from 1 to 0 _Next Signal falling edge) to obtain the timing T of the timer _Next 。

Calculating theoretical transmission time T _Trans ：T _Trans ＝L _Plate /V _next Wherein L is _Plate For the length of the object to be cut, V _Next The next process speed.

If T _Next >T _Trans The +T1, T1 is a predetermined time interval, which may take a value of 8-12s, in this example 10s. Triggering the full-line stop signal immediately, and stopping all roller tables immediatelyAnd waiting for the operator to handle the fault.

The automatic control function of all the laser cutting units is programmed and realized in the PLC controller 1.

According to the automatic control method and the automatic control system for the laser cutting machine set, firstly, cutting and positioning of the steel plate are performed, the high-precision length grating is used for measuring the transmission length of the steel plate, and the calculated length is compensated for the first time when the grating measured value is effective for the first time, so that the final positioning error can be reduced to a greater extent; and then, the high-precision X-axis servo motor is adopted to compensate the positioning error, so that the accurate cutting and positioning of the steel plate are completed. Controlling a Y-axis servo motor to be positioned near the edge of the operation side of the steel plate, starting cutting gas and laser in advance, running the steel plate at a constant speed to the outer side of the edge of the transmission side of the steel plate, and closing the cutting gas and the laser in a delayed manner so as to ensure that the steel plate is completely cut; and after the cutting is finished, the Y-axis servo motor returns to the zero position at a variable speed, and the correction is automatically performed at the zero position limit switch. When cutting the steel plate, comparing the sensing distance with a cutting height set value to obtain a position difference value, and calculating the speed and acceleration and deceleration of the Z-axis servo motor in the middle process of cutting according to the position difference value by the PLC; finally, a calculation method of the speed and the acceleration and deceleration of the Z-axis servo motor when the laser head enters the edge of the steel plate and exits from the edge of the steel plate is provided, so that the cutting height can be kept stable during cutting. And after cutting, conveying the steel plate to the next working procedure by using a conveying roller way, tracking the steel plate on each section of roller way, and calculating the head-tail position value of the steel plate and the head-tail occupying signals of the sectional roller way in real time. The steel plates are conveyed on the middle roller way, a safe distance is set, and the speed of the sectional roller way is set according to the occupying signal and the distance between two adjacent steel plates. And setting a speed change position in the last-stage roller way, setting the speed of the last-stage roller way according to signals of the next process after the head of the steel plate reaches the speed change position interval, monitoring whether the steel plate is clamped when being conveyed to the next process, and stopping the steel plate in a full line if the clamping plate appears. Thus, the process of cutting the steel sheet is automatically completed. The method realizes high-precision steel plate cutting and positioning, realizes accurate positioning of four servo motors, solves the problem that the Y-axis servo motors generate accumulated errors, solves the difficult problem of controlling the cutting height in the cutting process, gives consideration to the production efficiency and the safety of the roller way transmission process, and realizes stable transition with the next process, thereby realizing full automation and intellectualization of the whole laser cutting process, reducing the labor intensity of workers and improving the production efficiency.

It will be understood that modifications and variations will be apparent to those skilled in the art from the foregoing description, and it is intended that all such modifications and variations be included within the scope of the following claims.

Claims

1. An automatic control method of a laser cutting unit is characterized in that the laser cutting unit comprises: the conveying mechanism is arranged on the cutter frame on the conveying mechanism along the width direction of the object to be cut, and is used for driving the servo motor unit for moving the cutter frame, and a length grating extending to the conveying end point of the conveying mechanism is arranged at the downstream position of the cutter frame; the transmission mechanism comprises driving rollers which are sequentially arranged along the transmission direction, the transmission mechanism is provided with a cutting start position and a cutting position, a start photoelectric switch and a first driving roller are arranged at the cutting start position, a driving roller encoder is arranged on the first driving roller, a second driving roller and a third driving roller are sequentially arranged at the downstream of the first driving roller, and the cutting position is positioned between the second driving roller and the third driving roller; the cutting machine frame is arranged above the cutting position, two ends of the cutting machine frame are driven to move along the transmission direction through a first X-axis servo motor and a second X-axis servo motor respectively, the first X-axis servo motor is provided with an X-axis absolute value encoder, a laser head is arranged on the cutting machine frame, the laser head moves along the width direction of an object to be cut through a Y-axis servo motor, the Y-axis servo motor is provided with a Y-axis absolute value encoder, the laser head moves along the height direction of the object to be cut through a Z-axis servo motor, the Z-axis servo motor is provided with a Z-axis absolute value encoder, a laser head nozzle is arranged on the laser head, and a distance sensor for judging the distance between the laser head nozzle and the object to be cut is arranged on the laser head nozzle;

The method comprises the following steps:

p1, accurately positioning the object to be cut:

p2, cutting:

p3, calibrating a distance sensor:

p4, speed control:

2. The automatic control method of a laser cutting machine set according to claim 1, wherein the P101 specifically is:

3. The automatic control method of a laser cutting unit according to claim 1, wherein the P102 specifically is:

p102.1, distance compensation:

S _Com ＝S _Optical (m)-S _Head，Cal (m)

S _Head，F ＝S _Head，Cal +S _Com

p102.3, setting the speed of a driving roller:

S _Left ＝L _Cut -S _Head，F

4. The automatic control method of a laser cutting machine set according to claim 1, wherein the P103 specifically is:

P103.1, calculating a positioning error:

S _Error ＝L _Cut -S _Optical

In which L _Cut The cutting length of the object to be cut;

P _X，Set ＝P _Cut -S _Error

5. The automatic control method of a laser cutting machine set according to claim 1, wherein the P201 specifically comprises:

V _Servox，Set ＝LIM _X [K _P，X ×(P _X，Set -P _X，Act )]

6. The automatic control method of a laser cutting machine set according to claim 1, wherein in the P202, the Y-axis servo motor is controlled to move the laser head to a cutting start point of the edge of the object to be cut, specifically:

V _{ServoY，Set1} ＝LIM _Y [K _P，Y ×(P _Y，Set1 -P _Y，Act )]

In LIM _Y Limiting link representing Y-axis speed, K _P，Y For the proportionality coefficient of the Y axis, P _Y，Act For the actual position value of the laser head on the Y axis, P _Y，Set1 The set position value of the cutting start point is used for the first positioning of the laser head.

7. The automatic control method of a laser cutting machine set according to claim 1, wherein the P401 specifically performs the segmentation of the conveying roller table of the object to be cut in the following manner:

8. The automatic control method of a laser cutting machine set according to claim 1, wherein the P402 specifically is:

2) If the head space occupying signal of the object to be cut is arranged on the roller way section X, the tail space occupying signal on the X+1 roller way section is 0 and the tail space occupying signal on the X+2 roller way sectionIf the tail space occupying signal of (2) is 1, calculating the distance Dis between two objects to be cut according to the following formula _X，X+2 ：

Dis _X，X+2 ＝P _X+2，Tail -P _X，Head

9. The automatic control method of a laser cutting machine set according to claim 1, wherein in the P403, the variable speed adjustment is specifically:

2) The head of the object to be cut enters a gear shifting interval, if the steel plate is entering the next working procedure signal Switch _Next =0, and the allowed roller way advance signal Allow for the next process _Next =1, the last stage roller bed is at the next process speed V _Next Operating; if Switch is _Next =0 and alloy _Next When=0, the speed of the last roller way is set to 0.0, and the alloy is waited for _Next After the speed of the roller way at the end section is changed into 1, the speed of the roller way at the end section is set as V _Next ；

3) The head of the object to be cut enters a speed change position sectionAt the time of Switch _Next =1, then the speed of the last roller way is set to 0.0;

whether the cardboard is monitored, all-line parking is specifically:

starting a timer when the signal of the next process is changed from 0 to 1, and resetting the timer when the signal of the next process is changed from 1 to 0 to obtain the timing T of the timer _Next ；

10. An automatic control system of a laser cutting unit, which is characterized in that: the system comprises a control unit and a frequency converter, wherein the control unit is used for executing the automatic control method of the laser cutting unit according to any one of claims 1 to 9, sending the speed set value of each roller way section to the frequency converter, and sending the speed set value to the driving roller of each roller way section by the frequency converter.