A real-time detection method for laser cutting event interruption

Abstract

The present invention discloses a real-time detection method for laser cutting event interruption. First, a standard laser cutting template of a normal laser cutting process is identified, then an actual laser cutting event is captured, and interruption detection is performed based on the laser cutting event. When the last laser cutting event is captured, it is detected whether there is a matching event to be detected. When there is a matching event to be detected, interruption detection judgment is performed together with the event. The present invention can quickly obtain accurate abnormal interruption judgment results by receiving the laser cutting output current sequence in real time, dividing the laser cutting events and comparing them with the laser cutting template.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent welding and cutting, and in particular relates to a real-time detection method for interruption of laser cutting events. Background Art

[0002] During the laser cutting process, cutting abnormality analysis for laser cutting events is an effective method to monitor the health of the laser cutting process. The prior art generally adopts vision-based image processing methods, time series data analysis and monitoring methods, etc. In the process of processing laser cutting time series data, abnormal interruption of workpiece cutting is a typical cutting abnormality phenomenon and is the focus of real-time monitoring. However, there is currently no method that can obtain the cutting abnormal interruption situation in real time through the processing and analysis of time series data. Summary of the invention

[0003] Purpose of the invention: In view of the problems existing in the above-mentioned background technology, the present invention provides a real-time detection method for laser cutting event interruption, which collects timing current data during the laser cutting operation and identifies the laser cutting template corresponding to a single workpiece. The real-time captured laser cutting event is compared with the laser cutting template to finally determine whether the currently captured laser cutting event is an abnormal interruption.

[0004] Technical solution: A method for real-time detection of laser cutting event interruption, comprising the following steps:

[0005] Step S1, capturing a complete laser cutting event and performing laser cutting template recognition;

[0006] Step S2, capturing the actual laser cutting event in real time, and performing interruption detection based on the laser cutting event;

[0007] Step S3: when capturing the last laser cutting event, detect whether there is a matching event to be detected. When there is a matching event to be detected, repeat the interrupt detection step in step S2.

[0008] Furthermore, the specific method of capturing the laser cutting event in step S1 includes:

[0009] The first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event.

[0010] Furthermore, the specific method of identifying the laser cutting template in step S1 includes:

[0011] Capture laser cutting events. When the laser cutting template is not currently set, store the laser cutting events in pattern_list in sequence, where pattern_list represents a set of candidate events for setting the laser cutting template. When the number of laser cutting events stored in pattern_list is equal to 3, make a judgment on the setting of the laser cutting template:

[0012] When the difference between the maximum cutting time and the minimum cutting time among the three laser cutting events is less than or equal to the preset threshold th2, the laser cutting event with the middle cutting time is selected as the laser cutting template, otherwise the first laser cutting event in pattern_list is removed and a new laser cutting event is added, and the recognition is repeated.

[0013] Furthermore, when performing the laser cutting event interruption detection in step S2, the preset sets last_current_list and pending_current_list are used, wherein last_current_list is used to store the two most recently captured laser cutting events, and pending_current_list is used to store the laser cutting events to be judged; the laser cutting events are captured in real time and the interval time between adjacent events is recorded. When the interval time is equal to the preset threshold interrupt_time, event interruption detection is performed based on the identified laser cutting template.

[0014] Furthermore, event interrupt detection based on the identified laser cutting template specifically includes:

[0015] Step S2.1, when the number of laser cutting events in pending_current_list is equal to 2, calculate the difference between the length of the last laser cutting event in pending_current_list and the length of the laser cutting template; when the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the laser cutting event is not an interrupt sequence; otherwise, splice the two laser cutting events in pending_current_list into a new event merge_current_list, and judge the merge_current_list and the laser cutting template; when the absolute value of the difference between the length of merge_current_list and the length of the laser cutting template is less than or equal to th3 and the absolute value of the difference between the current mean in merge_current_list and the current mean of the laser cutting template is less than or equal to the preset threshold value th5, judge that the two current sequences in pending_current_list are interrupt sequences of the laser cutting template; after the judgment is completed, clear pending_current_list;

[0016] Step S2.2: When the number of laser cutting events in pending_current_list is less than 2, make a judgment based on last_current_list; when the number of laser cutting events in last_current_list is greater than 0 and the length of the last laser cutting event is greater than the preset threshold th4, compare the laser cutting event with the laser cutting template for judgment; specifically,

[0017] Step S2.2.1, calculate the dtw distance between the last laser cutting event in last_current_list and the laser cutting template. When conditions (1) and (2) or conditions (1) and (3) are met at the same time, it means that the laser cutting event is an interrupt sequence of the laser cutting template:

[0018] (1) The ratio of the dtw distance to the length of the laser cutting event is less than a preset threshold value th6;

[0019] (2) The absolute value of the difference between the current mean of the laser cutting event and the laser cutting template is less than or equal to a preset threshold value th7;

[0020] (3) The absolute value of the difference between the effective value rms of the laser cutting event and the laser cutting template is less than or equal to the preset threshold th8;

[0021] Step S2.2.2, when conditions (1)-(3) are not met, calculate the rms difference between the last laser cutting event in the last_current_list and the laser cutting template. When the absolute value of the rms difference is less than or equal to the preset threshold value th7, judge that the laser cutting event is an interruption sequence of the laser cutting template; otherwise, further calculate the difference between the sum of the lengths of the two laser cutting events in the last_current_list and the length of the laser cutting template. When the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the two current sequences in the last_current_list are both interruption sequences of the laser cutting template. Otherwise, store the most recent current sequence in pending_current_list.

[0022] Furthermore, when the user replaces the workpiece and starts cutting, the original laser cutting template is discarded, and the real-time detection method for laser cutting event interruption described in step S1 to step S3 is repeated.

[0023] The interruption detection method based on the laser cutting output current sequence designed by the present invention has the following beneficial effects:

[0024] The present invention captures the laser cutting event in real time and compares it with the identified laser cutting template to monitor in real time whether there is an abnormal interruption in the current laser cutting event. The present invention designs a specific comparison and judgment method, compares the cutting event with the laser cutting template from the dimensions of cutting event length, current mean and effective value, and can obtain the most accurate abnormal interruption judgment result. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the principle of the real-time detection method for laser cutting event interruption provided by the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a real-time detection method for laser cutting event interruption, firstly capturing a complete cutting event and identifying a laser cutting template, then comparing the captured laser cutting timing sequence with the laser cutting template, building a comparison model and providing a detailed comparison judgment method, and judging in real time whether the currently captured laser cutting timing sequence belongs to an interruption sequence in the laser cutting template. The present invention is further explained below in conjunction with the accompanying drawings.

[0027] like Figure 1 As shown, the present invention provides a method for real-time detection of laser cutting event interruption, and the specific steps include:

[0028] Step S1: Capture the complete laser cutting event and perform laser cutting template recognition. Specifically,

[0029] The first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event.

[0030] The laser cutting template identification method is as follows:

[0031] Capture laser cutting events. When the laser cutting template is not currently set, store the laser cutting events in pattern_list in sequence, where pattern_list represents a set of candidate events for setting the laser cutting template. When the number of laser cutting events stored in pattern_list is equal to 3, perform a laser cutting template setting judgment: when the difference between the maximum cutting time and the minimum cutting time among the three laser cutting events is less than or equal to the preset threshold th2, select the laser cutting event with the middle cutting time as the laser cutting template, that is, Figure 1 Otherwise, the first laser cutting event in pattern_list is removed and a new laser cutting event is added, and the recognition is repeated.

[0032] Step S2: Capture the actual laser cutting event in real time and perform laser cutting event interruption detection.

[0033] The preset sets last_current_list and pending_current_list, wherein last_current_list is used to store the two most recently captured laser cutting events, and pending_current_list is used to store the laser cutting events to be judged.

[0034] Capture laser cutting events in real time and record the interval time between adjacent events. When the interval time is equal to the preset threshold interrupt_time, make event interrupt judgment based on the identified laser cutting template.

[0035] Step S2.1, when the number of laser cutting events in pending_current_list is equal to 2, calculate the difference between the length of the last laser cutting event in pending_current_list and the length of the laser cutting template. When the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the laser cutting event is not an interrupt sequence. Otherwise, the two laser cutting events in pending_current_list are spliced ​​into a new event merge_current_list, and merge_current_list is compared with the laser cutting template. When the absolute value of the difference between the length of merge_current_list and the length of the laser cutting template is less than or equal to th3 and the absolute value of the difference between the current mean in merge_current_list and the current mean of the laser cutting template is less than or equal to the preset threshold value th5, it means that merge_current_list is similar to the laser cutting template. At this time, the two laser cutting events in pending_current_list together constitute a complete laser cutting template, and finally judge that the two current sequences in pending_current_list are interrupt sequences of the laser cutting template. After the judgment is completed, clear pending_current_list.

[0036] Step S2.2: When the number of laser cutting events in pending_current_list is less than 2, make a judgment based on last_current_list. When the number of laser cutting events in last_current_list is greater than 0 and the length of the last laser cutting event is greater than the preset threshold th4, compare the laser cutting event with the laser cutting template. Specifically,

[0037] Step S2.2.1, calculate the dtw distance between the last laser cutting event in last_current_list and the laser cutting template. When conditions (1) and (2) or conditions (1) and (3) are met at the same time, it means that the laser cutting event is an interrupt sequence of the laser cutting template:

[0038] (1) The ratio of the dtw distance to the length of the laser cutting event is less than a preset threshold value th6;

[0039] (2) The absolute value of the difference between the current mean of the laser cutting event and the laser cutting template is less than or equal to a preset threshold value th7;

[0040] (3) The absolute value of the difference between the effective value rms of the laser cutting event and the laser cutting template is less than or equal to a preset threshold value th8.

[0041] Step S2.2.2, when the above conditions are not met, calculate the effective value rms difference between the last laser cutting event in last_current_list and the laser cutting template, and when the absolute value of the effective value rms difference is less than or equal to the preset threshold value th7, judge that the laser cutting event is an interruption sequence of the laser cutting template. Otherwise, further calculate the difference between the sum of the lengths of the two laser cutting events in last_current_list and the length of the laser cutting template. When the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the two current sequences in last_current_list are both interruption sequences of the laser cutting template, otherwise store the most recent current sequence in pending_current_list.

[0042] Step S3: When the last laser cutting event is captured, it is necessary to determine whether the cutting is completed normally or interrupted due to other reasons. At this time, it is detected whether there is a laser cutting event to be determined in pending_current_list. If there is a laser cutting event in pending_current_list, the last laser cutting event is stored in pending_current_list, and the laser cutting event interruption detection in step S2 is repeated.

[0043] When there is no laser cutting event in pending_current_list, the current laser cutting event may be a complete cutting event or the first half of two interruption events.

[0044] It should be noted that when the user performs laser cutting to replace parts, the laser cutting template needs to be re-identified, and the detection method of steps S1 to S3 is repeated based on the new laser cutting template.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for real-time detection of laser cutting event interruption, characterized in that: The following steps are involved: Step S1, capturing a complete laser cutting event and performing laser cutting template recognition; Specifically, During the laser cutting operation, the time series current data is collected, the first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event. Capture laser cutting events. When the laser cutting template is not currently set, store the laser cutting events in pattern_list in sequence, where pattern_list represents a set of candidate events for setting the laser cutting template. When the number of laser cutting events stored in pattern_list is equal to 3, make a judgment on the setting of the laser cutting template: When the difference between the maximum cutting time and the minimum cutting time among the three laser cutting events is less than or equal to the preset threshold th2, the laser cutting event with the middle cutting time is selected as the laser cutting template, otherwise the first laser cutting event in pattern_list is removed and a new laser cutting event is added, and the recognition is repeated; Step S2, capturing the actual laser cutting event in real time, and performing interrupt detection based on the laser cutting event; specifically, presetting the sets last_current_list and pending_current_list, wherein last_current_list is used to store the two most recently captured laser cutting events, and pending_current_list is used to store the laser cutting event to be judged; Capture laser cutting events in real time and record the interval time between adjacent events. When the interval time is equal to the preset threshold interrupt_time, perform event interrupt detection based on the identified laser cutting template. The event interrupt detection based on the identified laser cutting template specifically includes: Step S2.1, when the number of laser cutting events in pending_current_list is equal to 2, calculate the difference between the length of the last laser cutting event in pending_current_list and the length of the laser cutting template; when the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the laser cutting event is not an interrupt sequence; otherwise, splice the two laser cutting events in pending_current_list into a new event merge_current_list, and judge the merge_current_list and the laser cutting template; when the absolute value of the difference between the length of merge_current_list and the length of the laser cutting template is less than or equal to th3 and the absolute value of the difference between the current mean in merge_current_list and the current mean of the laser cutting template is less than or equal to the preset threshold value th5, judge that the two current sequences in pending_current_list are interrupt sequences of the laser cutting template; after the judgment is completed, clear pending_current_list; Step S2.2: When the number of laser cutting events in pending_current_list is less than 2, make a judgment based on last_current_list; when the number of laser cutting events in last_current_list is greater than 0 and the length of the last laser cutting event is greater than the preset threshold th4, compare the laser cutting event with the laser cutting template for judgment; specifically, Step S2.2.1, calculate the dtw distance between the last laser cutting event in last_current_list and the laser cutting template. When conditions (1) and (2) or conditions (1) and (3) are met at the same time, it means that the laser cutting event is an interrupt sequence of the laser cutting template: (1) The ratio of the dtw distance to the length of the laser cutting event is less than a preset threshold value th6; (2) The absolute value of the difference between the current mean of the laser cutting event and the laser cutting template is less than or equal to a preset threshold value th7; (3) The absolute value of the difference between the effective value rms of the laser cutting event and the laser cutting template is less than or equal to the preset threshold th8; Step S2.2.2, when conditions (1)-(3) are not met, calculate the effective value rms difference between the last laser cutting event in last_current_list and the laser cutting template, and when the absolute value of the effective value rms difference is less than or equal to the preset threshold value th7, judge that the laser cutting event is an interruption sequence of the laser cutting template; otherwise, further calculate the difference between the sum of the lengths of the two laser cutting events in last_current_list and the length of the laser cutting template, and when the absolute value of the difference is less than or equal to the preset threshold value th3, it means that the two current sequences in last_current_list are both interruption sequences of the laser cutting template, otherwise, store the most recent current sequence in pending_current_list; Step S3: when capturing the last laser cutting event, detect whether there is a matching event to be detected. When there is a matching event to be detected, repeat the interrupt detection step in step S2.

2. A method for real-time detection of laser cutting event interruption according to claim 1, characterized in that: When the user changes the workpiece and starts cutting, the original laser cutting template is discarded and the real-time detection method for laser cutting event interruption described in step S1 to step S3 is repeated.

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