An accurate calibration control method and system for a laser head distance sensor

Abstract

The present invention discloses an accurate calibration control method for a laser head distance sensor, which adjusts the laser head focal length to the zero position and checks the laser head status signal, and sets a calibration characteristic curve according to the cutting height range; the calibration characteristic curve is composed of several characteristic points within the measurement range; denser characteristic points are set within the cutting height range of the laser cutting machine, while sparser characteristic points are set outside the cutting height range; the Y-axis servo motor is controlled to move the laser head from the initial position to the upper part of the steel plate, and then the Z-axis servo motor is controlled to descend until the laser head nozzle touches the steel plate; the Z-axis servo motor is controlled to move the laser head to each characteristic point on the calibration characteristic curve in turn for calibration; after calibration is completed, the Y-axis and Z-axis servo motors are controlled to return to the initial position, and the measured value of the distance sensor is filtered; if a fault occurs during the calibration process, the fault is processed and the calibration is restarted. The present invention can ensure the measurement accuracy of the distance sensor near the working point.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial automation, and particularly to an accurate calibration control method and system for a laser head distance sensor. Background Art

[0002] With the rapid development of the processing industry, laser cutting machines have been more and more widely used. Whether it is for metal materials such as stainless steel, carbon steel, aluminum plates, galvanized plates, or iron plates, rapid, accurate, and high-efficiency cutting can be achieved.

[0003] In order to achieve good cutting effects, it is required that all process parameters be maintained at the set optimized values during the laser cutting process. Among them, the cutting height is a relatively important process parameter. If the parameter setting is unreasonable, it will greatly affect the cutting effect, causing slag hanging and nodulation on the cutting surface, or even unable to cut through. Therefore, it is very important to keep the cutting height stable during the laser cutting process.

[0004] The thickness of metal sheets often fluctuates in the width direction. In order to keep the cutting height stable, currently mainstream laser heads are equipped with non-contact distance sensors, which can measure the distance between the laser head and the surface of the metal sheet. The accuracy of cutting height control directly depends on the measurement accuracy of the laser head distance sensor. For example, the measurement range of the distance sensor of a certain brand of laser head is 0.0 - 10.0 mm, and the corresponding output is 0 - 10 V voltage. The proportional relationship between the measured output voltage and the corresponding distance value is stored in the height adjuster of the laser head. This proportional relationship is affected by the measured material. Therefore, calibration must be carried out after the initial measurement or when replacing steel plates of different specifications and steel grades. When calibrating, the laser head will contact the steel plate. At this time, the height adjuster of the laser head will send a touch plate signal. If the laser head is relatively far from the steel plate, exceeding the measurement range of 10.0 mm, the height adjuster of the laser head will send a signal of exceeding the measurement range. Summary of the Invention

[0005] The main purpose of the present invention is to provide an accurate calibration control method and system for a laser head distance sensor to improve the measurement accuracy.

[0006] The technical solution adopted by the present invention is as follows: An accurate calibration control method for a laser head distance sensor, which is used for a laser cutting device. The laser cutting device includes a controller, a servo amplifier, a height adjuster, a laser head, a Y-axis servo motor, a Z-axis servo motor, a Y-axis track, and a Z-axis track. The Y-axis servo motor and the Z-axis servo motor are used to move the laser head on the Y-axis track and the Z-axis track. The Y-axis servo motor and the Z-axis servo motor are respectively equipped with absolute encoders for measuring the actual positions of the Y-axis servo motor and the Z-axis servo motor. The laser head is equipped with a distance sensor for sensing the distance between the laser nozzle at the bottom of the laser head and the steel plate to be cut. The distance sensor is connected to the height adjuster. The controller reads the sensed distance measurement value from the height adjuster, and the absolute encoder readings are input into the controller. The controller sends instructions to the servo amplifier, and the servo amplifier controls the movement of the Y-axis and Z-axis servo motors. The Y-axis is the axis of movement in the cutting direction, and the Z-axis is the axis of movement in the height direction.

[0007] This method includes the following steps:

[0008] S1. Adjust the laser head focal length to zero and check the laser head status signal, and set the calibration characteristic curve according to the cutting height range. The calibration characteristic curve is composed of several characteristic points within the measurement range. When setting the calibration characteristic curve, denser characteristic points are set within the cutting height range of the laser cutting machine, and sparser characteristic points are set outside the cutting height range. The terms "dense" and "sparse" are relative concepts.

[0009] S2. Control the Y-axis servo motor to move the laser head from the initial position to the upper part of the steel plate, and then control the Z-axis servo motor to descend until the laser head nozzle touches the steel plate. Control the Z-axis servo motor to move the laser head to each characteristic point on the calibration characteristic curve in turn for calibration.

[0010] S3. After calibration is completed, control the Y-axis and Z-axis servo motors to return to the initial position, and perform filtering processing on the distance sensor measurement value.

[0011] S4. If a fault occurs during the calibration process, handle the fault and start the calibration again.

[0012] According to the above method, in step S1, the method of adjusting the laser head focal length to zero and checking the laser head status signal is as follows:

[0013] Automatically or manually adjust or set the laser head focal length to zero.

[0014] Check various status signals of the laser head in the controller. These status signals are sent to the controller by hard wiring or through communication.

[0015] The state signals described above include: the laser head nozzle not touching the steel plate; the side of the laser head not touching the steel plate; the laser head focal length at zero; the laser head nozzle being detectable; the laser head wiring being normal; the distance between the laser head and the steel plate being greater than the measurement range;

[0016] When all of the above state signals are satisfied, a calibration operation is performed.

[0017] According to the above method, in S1, the number of the feature points is 16.

[0018] According to the above method, in S2, the method for controlling the Y-axis servo motor to move the laser head from the initial position to the upper part of the steel plate is as follows:

[0019] Control the Y-axis servo motor to move the laser head from the initial position to a certain distance inside the inner side of the edge of the steel plate; set the cutting position at the middle position Y of the roller table Center with the width of the steel plate being S Width To ensure that the laser head is above the steel plate, it is also necessary to move a certain distance D further inside from the edge of the steel plate in That is, the position set value Y of the Y-axis servo motor Set is:

[0020]

[0021] Move the Y-axis servo motor to the position set value to ensure that the laser head is above the steel plate.

[0022] According to the above method, in S2, the method for controlling the Z-axis servo motor to lower until the laser head nozzle touches the steel plate is as follows:

[0023] Adjust the Z-axis servo motor to quickly lower the laser head from the initial position to within the measurement range of the inductor; after reaching the position, the Z-axis continues to lower at a very slow speed to avoid damaging the laser head nozzle until the laser head returns the signal that the nozzle touches the steel plate and stops; the height adjuster records the induced voltage value at this time as the zero value of the induction distance.

[0024] According to the above method, in S2, the method for controlling the Z-axis servo motor to move the laser head to each feature point on the calibration feature curve in sequence for calibration is as follows:

[0025] Control the Z-axis servo motor to lift the laser head to the feature point at the maximum distance from the steel plate, which is the first feature point for calibration. After reaching the position, delay for a preset short period of time to wait for the height adjuster to record the position and the corresponding voltage value; then control the Z-axis servo motor to reach each feature point from high to low in sequence according to the calibration feature curve. After reaching the specified distance of each feature point, delay for a preset short period of time to wait for the height adjuster to record the position and the corresponding voltage value until all the feature points on the calibration feature curve are completed.

[0026] According to the above method, in step S3, the specific method for controlling the Y-axis and Z-axis servo motors to return to the initial position is as follows:

[0027] Use a proportional controller to calculate the speed set values for the Y-axis and Z-axis servo motors to return to the zero position:

[0028] S Y，SP =Lim(K Y ×Y Act )

[0029] S Z，SP =Lim(K Z ×Z Act )

[0030] In the formula, S Y，SP and S Z，SP are the speed set values for the Y-axis and Z-axis to return to the zero position respectively, K Y and K Z are the proportionality coefficients of the proportional controllers for the Y-axis and Z-axis respectively, Y Act and Z Act are the actual position values measured by the absolute value encoders of the Y-axis and Z-axis respectively. Lim represents a limiting link, that is, limiting the speed set value within the given maximum value range; in this way, the Y-axis and Z-axis will run at the maximum speed in the initial stage of returning to the zero position until approaching the preset position near the zero position, and then the speed will gradually decrease and finally stop at the zero position.

[0031] According to the above method, in step S4, the method for handling the long-time unstarted calibration fault is as follows: If the servo motor does not move for a long time after the calibration command is issued, it is a calibration unstarted fault. At this time, check whether the necessary conditions for calibration are met;

[0032] The method for handling the no-touch plate signal fault is as follows: Check whether the nozzle, ceramic body, and protective lens of the laser head are damaged. If there is a problem, replace the new parts and then perform calibration again;

[0033] The method for handling the touch plate fault during calibration is as follows: If the number of occurrences or frequency is less than the preset value, manually lift the Z-axis servo motor until the maximum measurement range of the distance sensor between the laser head and the steel plate, and then start calibration again; if the number of occurrences or frequency is greater than or equal to the preset value, reduce the descending speed of the Z-axis servo motor during calibration, and then start calibration again.

[0034] An accurate calibration control system for a laser head distance sensor, including a laser cutting device, which includes a controller, a servo amplifier, a height adjuster, a laser head, a Y-axis servo motor and a Z-axis servo motor, a Y-axis track and a Z-axis track; the Y-axis servo motor and the Z-axis servo motor are used to move the laser head on the Y-axis track and the Z-axis track, and absolute encoders are respectively installed on the Y-axis servo motor and the Z-axis servo motor for measuring the actual positions of the Y-axis servo motor and the Z-axis servo motor. The laser head is equipped with a distance sensor for sensing the distance between the laser nozzle at the bottom of the laser head and the steel plate to be cut; the distance sensor is connected to the height adjuster, the controller reads the sensed distance measurement value from the height adjuster, the readings of the absolute encoders are input into the controller, and the controller sends instructions to the servo amplifier, which controls the movement of the Y-axis and Z-axis servo motors; the Y-axis is the axis of movement in the cutting direction, and the Z-axis is the axis of movement in the height direction;

[0035] The controller is used to implement the accurate calibration control method of the laser head distance sensor.

[0036] According to the above system, the controller is a PLC controller.

[0037] The beneficial effects produced by the present invention are:

[0038] 1. Denser feature points are set in the common cutting height range of the laser cutting machine, and a calibration feature curve with multiple feature points is set within the entire measurement range, so as to ensure the measurement accuracy of the distance sensor near the working point.

[0039] 2. The moving speed of the servo motor is adjusted during the calibration process and after the calibration is completed. It runs at a high speed initially to save time and drops to a low speed when approaching the target value to ensure positioning accuracy and protect the safety of the equipment; after the calibration is completed, a multi-point average filtering method is adopted to reduce the influence of external interference on the measurement value of the distance sensor.

[0040] 3. Multiple processing methods for calibration failures are set, thus solving the problem that it is difficult to accurately calibrate the laser head distance sensor. Description of the Drawings

[0041] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0042] Figure 1 is the method flow chart of an embodiment of the present invention.

[0043] Figure 2 is the device structure schematic diagram of an embodiment of the present invention.

[0044] In the figure: 1 - Y-axis track, 2 - Y-axis servo motor, 3 - Y-axis absolute encoder, 4 - Z-axis track, 5 - servo amplifier, 6 - controller, 7 - laser head, 8 - distance sensor, 9 - laser nozzle, 10 - Z-axis servo motor, 11 - Z-axis absolute encoder, 12 - height adjuster, 13 - steel plate, 14 - transfer roller table. Detailed implementation

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] As Figure 2 shown, the present invention provides a precise calibration control system for a laser head distance sensor, including a laser cutting device. The laser cutting device includes a controller 6, a servo amplifier 5, a height adjuster 12, a laser head 7, a Y-axis servo motor 2 and a Z-axis servo motor 10, a Y-axis track 1 and a Z-axis track 4; the Y-axis servo motor 2 and the Z-axis servo motor 10 are used to move the laser head 7 on the Y-axis track 1 and the Z-axis track 4. The Y-axis servo motor 2 and the Z-axis servo motor 10 are also respectively equipped with a Y-axis absolute encoder 3 and a Z-axis absolute encoder 11, which are used to measure the actual positions of the Y-axis servo motor 2 and the Z-axis servo motor 10. The laser head 7 is equipped with a distance sensor 8, which is used to sense the distance between the laser nozzle 9 at the bottom of the laser head and the steel plate 13 to be cut. The steel plate 13 is transported on the transfer roller table 14; the distance sensor 8 is connected to the height adjuster 12. The controller 6 reads the sensed distance measurement value from the height adjuster 12, and the absolute encoder readings are input into the controller 6. The controller 6 sends instructions to the servo amplifier 5, and the servo amplifier 5 controls the movement of the Y-axis and Z-axis servo motors 2 and 10; the Y-axis is the axis of movement in the cutting direction, and the Z-axis is the axis of movement in the height direction. In this embodiment, the controller 6 is a PLC controller.

[0047] The controller is used to implement the precise calibration control method of the laser head distance sensor. As Figure 1 shown, this method specifically includes the following steps:

[0048] S1. Adjust the laser head focal length to zero and check the laser head status signal, and set the calibration characteristic curve according to the cutting height range; the calibration characteristic curve is composed of several characteristic points within the measurement range; when setting the calibration characteristic curve, relatively dense characteristic points are set within the cutting height range of the laser cutting machine, and relatively sparse characteristic points are set outside the cutting height range; the dense and sparse are relative concepts.

[0049] Before calibrating the distance sensor with the laser head, the focal length of the laser head needs to be adjusted to zero first to avoid calibration deviation. In this embodiment, an autofocus laser head is used, and it can be completed by simply setting the focal length to zero and then giving a focusing command. For a manually focused laser head, the focal length of the laser head needs to be adjusted manually to zero.

[0050] Calibration can only be performed when the laser head is functioning properly. Check various status signals of the laser head in the PLC. These status signals are sent to the PLC through hard wiring or communication. In this embodiment, the laser head status signals are transmitted to the PLC through hard wiring. Specifically, the following signals need to be checked: the laser head nozzle does not touch the steel plate; the side of the laser head does not touch the steel plate; the focal length of the laser head is at zero; the laser head nozzle can be detected; the laser head wiring is normal; the distance between the laser head and the steel plate is greater than the measurement range. Calibration operations can only be carried out when all the above conditions are met.

[0051] In this embodiment, the measurement range of the distance sensor is 0.0 - 10.0 mm. To achieve high-precision calibration, a calibration method with 16 characteristic points is adopted within the measurement range, and these 16 characteristic points form a characteristic curve. Considering that the cutting height of the laser cutting machine is usually within 2.0 mm, more characteristic points are set below 2.0 mm, and the characteristic points in the range of 2.0 mm - 10.0 mm are relatively sparse. In this embodiment, the selected characteristic points are:

[0052] [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

[0053] S2. Control the Y-axis servo motor to move the laser head from the initial position to the upper part of the steel plate, and then control the Z-axis servo motor to descend until the laser head nozzle touches the steel plate; control the Z-axis servo motor to move the laser head to each characteristic point on the calibration characteristic curve for calibration.

[0054] Since different steel grades will affect the induction distance value, the calibration of the distance sensor is mainly used to adapt to different steel grades, which requires the laser head to be above the steel plate during calibration. Therefore, the laser head needs to be moved to the upper part of the steel plate first. Then, the zero value of the induction distance needs to be determined, so the Z-axis servo motor needs to be controlled to make the laser head nozzle contact the steel plate. Then control the Z-axis servo motor to move to each characteristic point on the calibration characteristic curve.

[0055] S201. Control the Y-axis servo motor to move the laser head to the upper part of the steel plate;

[0056] Control the Y-axis servo motor to move the laser head from the initial position to a certain distance inside the edge of the steel plate. Let the middle position of the roller table be Y Center and the width of the steel plate be S Width . To ensure that the laser head is above the steel plate, it is necessary to move a certain distance D further inside from the edge of the steel plate in . In this embodiment, this distance is set to D in = 150.0, then the position setting value of the Y-axis servo motor is:

[0057]

[0058] Moving the Y-axis servo motor to the set position can ensure that the laser head is above the steel plate

[0059] S202. Control the Z-axis servo motor to descend until the laser head nozzle touches the steel plate

[0060] Adjust the Z-axis servo motor to quickly lower the laser head from the initial position to within the measurement range of the distance sensor. In this embodiment, the measurement range of the distance sensor is 0.0 - 10.0 mm. To ensure that the laser head descends to within the measurement range, set the target position of the Z-axis servo motor to a position 8.0 mm away from the steel plate. The descending speed of the Z-axis is set to 10.0 mm / s

[0061] After reaching the position, the Z-axis continues to descend at a very slow speed to avoid damaging the laser head nozzle, for example, set to 0.5 mm / s, until the signal that the laser head returns and the nozzle touches the steel plate stops. The laser head height adjuster will record the induced voltage value at this time as the zero value of the sensing distance

[0062] S203. Control the Z-axis servo motor to move the laser head to each feature point on the calibration characteristic curve in sequence

[0063] Control the Z-axis servo motor to lift the laser head to the feature point at the maximum distance from the steel plate, that is, 10.0 mm from the steel plate. This is the first feature point for calibration. After reaching the position, delay for 2 s to wait for the height adjuster to record the position and the corresponding voltage value. Then, control the Z-axis servo motor to reach each feature point from high to low according to the calibration characteristic curve. After reaching the specified distance of each feature point, delay for 2 s to wait for the height adjuster to record the position and the corresponding voltage value until all the feature points on the calibration characteristic curve are completed

[0064] S3. After calibration is completed, control the Y- and Z-axis servo motors to return to the initial position and perform filtering processing on the measurement value of the distance sensor

[0065] After calibrating all the feature points, it is necessary to control the Y-axis and Z-axis servo motors to return to their initial positions. The initial positions are generally defined as the zero positions of the absolute encoders of the Y-axis and Z-axis. To save time, they should run at high speed initially, and then gradually reduce the speed as they approach the initial positions to accurately stop at the initial positions. To reduce the influence of external interference on the measured values of the distance sensor, it is necessary to filter the measured values.

[0066] S301. Use a proportional controller to control the Y-axis and Z-axis servo motors to return to their initial positions;

[0067] Use a proportional controller to calculate the speed set values for the Y-axis and Z-axis servo motors to return to the zero positions:

[0068] S Y，Sp = Lim(K Y ×Y Act )

[0069] S Z，SP = Lim(K Z ×Z Act )

[0070] In the formula, S Y，SP and S Z，SP are the speed set values for the Y-axis and Z-axis to return to the zero positions respectively, K Y and K Z are the proportional coefficients of the proportional controllers for the Y-axis and Z-axis respectively, Y Act and Z Act are the actual position values measured by the absolute encoders of the Y-axis and Z-axis respectively. Lim represents a limiting link, that is, limiting the speed set value within the given maximum value range. In this embodiment, the maximum speed of the Y-axis is set to 250 mm / s, and the maximum speed of the Z-axis is set to 35 mm / s. In this way, the Y-axis and Z-axis will run at the maximum speed in the initial stage of returning to the zero positions until they approach the zero positions. After approaching the zero positions, the speed will gradually decrease, and finally they can accurately and smoothly stop at the zero positions.

[0071] S302. Filter the measured values of the distance sensor.

[0072] After calibrating all the feature points, the distance sensor can output the sensed distance values. However, in actual use, the distance sensor will be affected by interference factors such as dust and fog at the site. To reduce the influence of the interference, it is necessary to filter the sensed distance values. Commonly used filtering links include a first-order smoothing filtering link and multi-point averaging filtering. One of the filtering methods can be selected to filter the sensed distance values and then output them. In this embodiment, multi-point averaging filtering is adopted, that is, several adjacent sampling values are selected and averaged before output.

[0073] S4. If a fault occurs during the calibration process, handle the fault and restart the calibration.

[0074] During the actual calibration process, some faults will inevitably occur. When a fault occurs, corresponding handling is required and the calibration needs to be restarted.

[0075] S401. Handle the fault when the calibration has not been started for a long time.

[0076] If the servo motor does not move for a long time after the calibration command is issued, it is a fault that the calibration has not been started. This fault is generally caused by the failure to meet the necessary conditions for calibration. Therefore, it is necessary to check whether the necessary conditions for calibration are met. Specifically, in this embodiment, the following conditions need to be checked: the nozzle of the laser head does not touch the steel plate; the side of the laser head does not touch the steel plate; the nozzle of the laser head can be detected; the wiring of the laser head is normal; the distance between the laser head and the steel plate is greater than the measurement range.

[0077] After all the above conditions are met, start the calibration again.

[0078] S402. Handle the fault when there is no touch plate signal.

[0079] After the calibration starts, it is first necessary to determine the zero point of the distance sensor. At this time, the nozzle of the laser head will contact the steel plate. Normally, when the nozzle touches the steel plate, the PLC will receive the touch plate signal and the Z-axis servo motor will stop descending. However, in fact, there has been a fault that the nozzle has touched the steel plate but the PLC cannot receive the touch plate signal. At this time, it is necessary to check whether the nozzle, ceramic body, and protective lens of the laser head are damaged. If there is a problem, replace the new parts and then perform the calibration again.

[0080] S403. Handle the fault when there is a touch plate fault during calibration.

[0081] During the calibration process, the laser head gradually approaches the steel plate from the feature point with the maximum distance from the steel plate. Generally, the last two feature points are very close to the steel plate, and at this time, a touch plate fault may occur. That is, a signal that the nozzle touches the steel plate appears at the last two feature points of the calibration, and at this time, the calibration will be aborted and an error will be reported. If this fault occurs occasionally, the Z-axis servo motor can be manually lifted until the laser head is more than 10 mm away from the steel plate, and then the calibration can be started again. If this fault occurs frequently, it is necessary to reduce the descending speed of the Z-axis servo motor during the calibration process, and then start the calibration again.

[0082] Adjust the Y-axis and Z-axis servo motors according to the above steps, move the laser head to each feature point on the calibration feature curve, and then return to the initial position. When a fault occurs, handle it separately, and then this calibration method for the laser head distance sensor can be completed.

[0083] The calibration control method of the laser head distance sensor provided by the embodiment of the present invention first adjusts the laser head focal length to the zero position and checks the laser head status signal, and sets a suitable calibration characteristic curve according to the cutting height range; then adjusts the Y-axis servo motor to move the laser head to the upper part of the steel plate, and then adjusts the Z-axis servo motor to first contact the laser head nozzle with the steel plate and then move to each feature point on the calibration characteristic curve; then uses a proportional controller to move the Y-axis and Z-axis servo motors back to the initial position and filters the measured distance value. Finally, a processing method for faults occurring during the calibration process is given. In this way, the calibration method of this laser head distance sensor is completed.

[0084] In summary, the precise calibration control method and system of the laser head distance sensor provided by the embodiment of the present invention realizes the precise calibration of the laser head distance sensor automatically. Denser feature points are set in the commonly used cutting height range of the laser cutting machine, and a calibration characteristic curve with 16 feature points is set within the entire measurement range, so as to ensure the measurement accuracy of the distance sensor near the working point; during the calibration process, the moving speed of the servo motor is adjusted, running at a high speed initially to save time and dropping to a low speed when approaching the target value to ensure the positioning accuracy and protect the safety of the equipment; after calibration, a multi-point average filtering method is adopted to reduce the influence of external interference on the measured value of the distance sensor; finally, a processing method for faults occurring during calibration is given, thus solving the problem that it is difficult to precisely calibrate the laser head distance sensor.

[0085] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. An accurate calibration control method for a laser head distance sensor, characterized in that For a laser cutting device, the laser cutting device includes a controller, a servo amplifier, a height adjuster, a laser head, a Y-axis servo motor and a Z-axis servo motor, a Y-axis track and a Z-axis track; the Y-axis servo motor and the Z-axis servo motor are used to move the laser head on the Y-axis track and the Z-axis track, and absolute encoders are respectively installed on the Y-axis servo motor and the Z-axis servo motor for measuring the actual position values of the Y-axis servo motor and the Z-axis servo motor. The laser head is equipped with a distance sensor for sensing the distance between the laser nozzle at the bottom of the laser head and the steel plate to be cut; the distance sensor is connected to the height adjuster, the controller reads the sensed distance measurement value from the height adjuster, the readings of the absolute encoders are input into the controller, and the controller sends instructions to the servo amplifier to control the movement of the Y-axis and Z-axis servo motors; the Y-axis is the axis for cutting direction movement, and the Z-axis is the axis for height direction movement; This method includes the following steps: S1. Adjust the laser head focal length to zero and check the laser head status signal, and set the calibration characteristic curve according to the cutting height range; the calibration characteristic curve is composed of several characteristic points within the measurement range; when setting the calibration characteristic curve, denser characteristic points are set within the cutting height range of the laser cutting machine, and sparser characteristic points are set outside the cutting height range; the dense and sparse are relative concepts; S2. Control the Y-axis servo motor to move the laser head from the initial position to the upper part of the steel plate, and then control the Z-axis servo motor to descend until the laser head nozzle touches the steel plate; control the Z-axis servo motor to move the laser head to each characteristic point on the calibration characteristic curve in turn for calibration; S3. After calibration is completed, control the Y-axis and Z-axis servo motors to return to the initial position and filter the measurement value of the distance sensor; S4. If a fault occurs during the calibration process, handle the fault and start the calibration again.

2. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that, In the above S1, the method of adjusting the laser head focal length to zero and checking the laser head status signal is as follows: Automatically or manually adjust or set the laser head focal length to zero; Check various status signals of the laser head in the controller, and these status signals are sent to the controller by hard wiring or through communication; The status signals include: the laser head nozzle does not touch the steel plate; the side of the laser head does not touch the steel plate; the laser head focal length is at zero; the laser head nozzle can be detected; the laser head wiring is normal; the distance between the laser head and the steel plate is greater than the measurement range; When all the above status signals are satisfied, the calibration operation is performed.

3. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that In the above S1, the number of the characteristic points is 16.

4. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that In the above S2, the method of controlling the Y-axis servo motor to move the laser head from the initial position to the upper part of the steel plate is as follows: Control the Y-axis servo motor to move the laser head from the initial position to a certain distance inside the edge of the steel plate; set the cutting position at the middle position Y of the roller table Center , the width of the steel plate is S Width , to ensure that the laser head is above the steel plate, it is also necessary to move a certain distance D further inside from the edge of the steel plate in , that is, the position set value Y of the Y-axis servo motor Set is: Move the Y-axis servo motor to the position set value to ensure that the laser head is located above the steel plate.

5. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that In the above S2, the method of controlling the Z-axis servo motor to descend until the laser head nozzle touches the steel plate is as follows: Adjust the Z-axis servo motor to quickly lower the laser head from the initial position to within the measurement range of the sensor; after reaching the position, the Z-axis continues to lower at a very slow speed to avoid damaging the nozzle of the laser head until the signal that the laser head returns to contact the steel plate stops; the height adjuster records the induced voltage value at this time as the zero value of the sensing distance.

6. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that In the S2, the method of controlling the Z-axis servo motor to move the laser head to each feature point on the calibration characteristic curve in sequence for calibration is as follows: Control the Z-axis servo motor to lift the laser head to the feature point at the maximum distance from the steel plate, which is the first feature point for calibration. After reaching the position, delay for a preset short period of time to wait for the height adjuster to record the position and the corresponding voltage value; then control the Z-axis servo motor to reach each feature point from high to low in sequence according to the calibration characteristic curve. Each time after reaching the specified distance of the feature point, delay for a preset short period of time to wait for the height adjuster to record the position and the corresponding voltage value until all the feature points on the calibration characteristic curve are completed.

7. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that In the S3, the specific method of controlling the Y-axis and Z-axis servo motors to return to the initial position is as follows: Use a proportional controller to calculate the speed set values for the Y-axis and Z-axis servo motors to return to the zero position: S Y，SP = Lim(k Y × Y Act ) S Z，SP = Lim(K Z ×Z Act ) Wherein, S Y,SP and S Z,SP are respectively the speed setting values for returning to the zero position of the Y-axis and the Z-axis, K Y and K Z are respectively the proportionality coefficients of the proportional controllers for the Y-axis and the Z-axis, Y Act and Z Act are respectively the actual position values measured by the absolute encoders of the Y-axis and the Z-axis. Lim represents a limiting link, that is, limiting the speed setting value within a given maximum value range; in this way, the Y-axis and the Z-axis will run at the maximum speed in the initial stage of returning to the zero position until approaching the preset position near the zero position, then the speed will gradually decrease and finally stop at the zero position.

8. The precise calibration control method of the laser head distance sensor according to claim 1, characterized in that, In the S4, the method of handling the failure that calibration has not been started for a long time is as follows: If the servo motor does not move for a long time after the calibration command is issued, it is a calibration not started failure. At this time, check whether the necessary conditions for calibration are met; The method of handling the failure of no touch plate signal is as follows: Check whether the nozzle, ceramic body, and protective lens of the laser head are damaged. If there are problems, replace with new accessories, and then perform calibration again; The method of handling the touch plate failure during calibration is as follows: If the occurrence times or frequency are less than the preset value, manually lift the Z-axis servo motor until it reaches the maximum measurement range of the distance sensor between the laser head and the steel plate, and then start calibration again; if the occurrence times or frequency are greater than or equal to the preset value, reduce the lowering speed of the Z-axis servo motor during calibration, and then start calibration again.

9. An accurate calibration control system for a laser head distance sensor, characterized in that, It includes a laser cutting device, which includes a controller, a servo amplifier, a height adjuster, a laser head, a Y-axis servo motor and a Z-axis servo motor, a Y-axis track and a Z-axis track; the Y-axis servo motor and the Z-axis servo motor are used to move the laser head on the Y-axis track and the Z-axis track. The Y-axis servo motor and the Z-axis servo motor are also respectively equipped with absolute encoders for measuring the actual position values of the Y-axis servo motor and the Z-axis servo motor. The laser head is equipped with a distance sensor for sensing the distance between the laser nozzle at the bottom of the laser head and the steel plate to be cut; the distance sensor is connected to the height adjuster. The controller reads the sensed distance measurement value from the height adjuster, and the absolute encoder readings are input into the controller. The controller sends instructions to the servo amplifier, and the servo amplifier controls the movement of the Y-axis and Z-axis servo motors; the Y-axis is the axis for cutting direction movement, and the Z-axis is the axis for height direction movement; The controller is used to implement the precise calibration control method of the laser head distance sensor described in any one of claims 1-8.

10. The precise calibration control system of the laser head distance sensor according to claim 9, characterized in that, The controller is a PLC controller.

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