Steel pipe plasma cutting machine adaptive height control method, system and storage medium

Abstract

The application relates to the technical field of plasma cutting control, in particular to a self-adaptive height control method and system of a steel pipe plasma cutting machine and a storage medium. The method obtains rotation angle and axial position information of a steel pipe to be cut, and establishes a corresponding circumferential geometric baseline of the steel pipe; a cutting track program is analyzed and a process dangerous area is identified; an arc voltage signal is collected in real time during the cutting process, a first height change trend corresponding to the arc voltage signal and a second predicted height change trend corresponding to the geometric baseline are extracted; based on the consistency cross verification result of the two and whether the current position is located in the process dangerous area, credibility gating judgment is performed, height closed-loop control is performed when the arc voltage signal is reliable, and the cutting torch is operated based on the alternative target height control generated by the circumferential geometric baseline of the steel pipe when the arc voltage signal is distorted, so as to balance the height control stability and machining precision in the complex track cutting process.

Description

Technical Field

[0001] This application relates to the field of plasma cutting control technology, and in particular to an adaptive height control method, system and storage medium for a steel pipe plasma cutting machine. Background Technology

[0002] In the field of CNC plasma cutting of steel pipes, to complete the cutting of steel pipe ends, drilling, grooving, intersecting line contour cutting, and local irregular contour processing, it is usually necessary to drive the steel pipe to rotate through the machine tool's rotary axis, and coordinate with the cutting torch to move along the axial, radial, or combined trajectory, so that the plasma arc can continuously travel along different positions on the outer wall of the steel pipe. Due to its advantages such as high cutting speed, wide applicable wall thickness range, and strong adaptability to steel pipe materials, plasma cutting has been widely used in steel pipe processing scenarios.

[0003] In actual processing, steel pipes are often not ideal cylinders. Affected by manufacturing tolerances, transportation and stacking, clamping and positioning, and the weight of the steel pipe itself, the outer wall of the steel pipe usually exhibits a certain degree of out-of-roundness, local runout, longitudinal deflection, clamping eccentricity, or local undulations. Simultaneously, the plasma cutting process involves high heat input, and the steel pipe may experience localized heat accumulation and thermal deformation during continuous cutting. To maintain a relatively stable cutting distance between the torch and the outer wall of the steel pipe during the cutting process, existing steel pipe plasma cutting equipment typically adjusts the torch height in real time based on the arc voltage, i.e., using the arc voltage signal for closed-loop control of the torch height to adapt to changes in the outer wall of the steel pipe.

[0004] However, the inventors discovered through long-term engineering practice that the intersection lines and openings of steel pipes often involve complex local topological morphology, and the height control mechanism relying solely on arc pressure feedback has significant limitations. When the cutting torch travels to complex process areas with holes, existing kerfs, or abrupt changes in local contour curvature, the plasma arc loses its original solid metal support, and the arc shape is prone to stretching or distortion, resulting in abnormal abrupt changes or fluctuations in the arc pressure signal acquired by the control system. When receiving the above-mentioned distorted signals, traditional arc pressure closed-loop control logic is prone to outputting incorrect following instructions, such as controlling the cutting torch to abnormally descend and collide with the pipe wall, or controlling the cutting torch to abnormally rise and cause arc interruption. To address the arc pressure distortion problem in complex morphological regions, the existing conventional approach is to forcibly freeze and maintain the current cutting torch height when cutting into such areas. While the above strategy avoids significant torch descent due to abnormal arc pressure to some extent, it does not solve the problem of accurate height following in complex areas. The reason is that steel pipes commonly exhibit irregular physical undulations during actual processing, such as out-of-roundness, deflection, and thermal deformation. When the cutting torch continues to cross holes, slits, or other complex trajectory sections while in a height-locked state, the fixed height cannot continue to adapt to changes in the actual outer wall of the steel pipe. If this section is also accompanied by local bulges, it may still cause physical interference between the cutting torch and the pipe wall. If this section is also accompanied by local depressions, the increased cutting distance will lead to a decrease in cutting penetration, unstable cut formation, or increased slag buildup. Therefore, there is an urgent need for a height control technology that can balance the accuracy of following irregular morphologies and the stability of the cutting process even when arc voltage distortion is caused by complex topological morphology. Summary of the Invention

[0005] (I) The technical problem to be solved by the present invention is that during the plasma cutting of steel pipes, when the outer wall of the steel pipe has irregular shapes such as out-of-roundness, deflection, clamping deviation or local undulation, and the cutting trajectory passes through complex sections such as openings, intersection lines, cross seams and local contour changes, the existing height control method is difficult to accurately distinguish the signal abnormalities caused by changes in torch height and local process disturbances, resulting in inaccurate height control judgment during the cutting of complex trajectories, and thus it is difficult to balance the stability of the cutting process and the processing accuracy of complex sections.

[0006] (II) Technical Solution To address the aforementioned technical problems, this invention provides an adaptive height control method for a steel pipe plasma cutting machine, comprising the following steps: S10. Obtain the rotation angle and axial position information of the steel pipe to be cut, and obtain or establish the circumferential geometric baseline of the steel pipe corresponding to the rotation angle and axial position information; S20. Analyze the cutting trajectory program to be executed, and identify and mark the process hazard area based on the local contour features corresponding to the cutting trajectory program; S30. During the process of controlling the cutting torch to cut the steel pipe, the arc pressure signal of the plasma arc is collected in real time. S40. Determine the first height change trend based on the arc pressure signal, and simultaneously extract the second predicted height change trend corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position; S50. Based on the consistency cross-validation results of the first height change trend and the second predicted height change trend, and combined with whether the current cutting position is located in the process danger zone, a confidence gating determination is performed: If the current cutting position is not in the process danger zone and the consistency cross-validation result meets the preset conditions, the arc voltage signal is determined to be reliable, and the arc voltage signal is used for closed-loop control of the torch height. If the current cutting position is in the process danger zone or the consistency cross-check result does not meet the preset conditions, the arc pressure signal is determined to be distorted, the height closed-loop control based on the arc pressure signal is exited, an alternative target height is generated based on the circumferential geometric baseline of the steel pipe, and the cutting torch is controlled according to the alternative target height.

[0007] Through the above steps, this invention first establishes a continuous reference to the actual outer wall morphology of the steel pipe using the circumferential geometric baseline. Then, it pre-identifies the process hazard zone based on the cutting trajectory and performs consistency cross-verification between the first height change trend corresponding to the arc pressure signal and the second predicted height change trend corresponding to the geometric baseline. This allows the control logic to first determine the reliability of the current arc pressure signal and then select the appropriate height control method accordingly. In ordinary cutting sections, the system can continue to use the arc pressure closed loop to track the dynamic morphological changes of the steel pipe in real time during the cutting process. However, in complex sections, when the arc pressure signal is distorted due to factors such as holes, cuts, or sudden changes in local contours, it can promptly exit the tracking of the distorted signal and switch to alternative control based on the circumferential geometric baseline of the steel pipe. Therefore, height control can adapt to the irregular undulations of the steel pipe's outer wall while avoiding interference from arc pressure anomalies caused by complex topological morphology, thus balancing control stability and tracking accuracy during complex trajectory cutting.

[0008] Furthermore, the circumferential geometric baseline of the steel pipe is established in the following manner: before arc initiation or in the reference section at the start of cutting, at least two sampling sections are selected along the axial direction of the steel pipe to be cut, and the outer wall of the steel pipe to be cut is circumferentially scanned at each sampling section to obtain the outer wall height data corresponding to different rotation angles and different axial positions. Based on the outer wall height data, the circumferential geometric baseline of the steel pipe corresponding to the rotation angle information and axial position information is established.

[0009] By selecting at least two sampling sections along the axial direction of the steel pipe to be cut and performing circumferential scanning sampling at each section, it is possible to obtain not only the circumferential outer wall undulations of the steel pipe on a single section, but also to simultaneously reflect the axial deflection, eccentricity, and local morphological changes of the steel pipe. This allows the established circumferential geometric baseline of the steel pipe to no longer be limited to local measurement results, but to more realistically characterize the overall outer wall morphology of the steel pipe in its current clamping state. Thus, during subsequent cutting, the system can both identify the actual geometric undulations corresponding to the current position and provide continuous reference for height judgment across different axial sections, thereby reducing height judgment errors caused by the irregular morphology of the steel pipe itself.

[0010] Furthermore, the process hazardous area includes at least one of the following sections: The segment in the interpolation segment corresponding to the cutting trajectory program that has a local contour curvature change rate greater than the first preset threshold. In the interpolation segment corresponding to the cutting trajectory program, the segment in which the ratio of the equivalent aperture or equivalent groove width to the wall thickness of the steel pipe to be cut is less than the second preset threshold. The segment whose span distance from the formed cut is less than the third preset threshold; Cut the transition section at the beginning; The deceleration section before the cutting is terminated.

[0011] By refining the process hazard zone into specific sections such as abrupt changes in local contour curvature, abnormal ratios of hole / groove dimensions to wall thickness, adjacent existing cuts, and transitions between cutting start and end points, quantitative identification criteria can be established for high-risk locations prone to arc pressure anomalies from different physical dimensions, including abrupt changes in local contour, interruption of solid support conditions, cut boundary disturbances, and dynamic instability at the start and end stages. By analyzing the cutting trajectory program to identify and mark these sections in advance, the control system can make targeted spatial state predictions before significant control instability occurs in the hazard zone. This more effectively distinguishes between fluctuations in the actual torch height and arc pressure signal anomalies caused by local process disturbances, providing a reliable preliminary basis for subsequent height control judgments and improving the control accuracy and stability during complex trajectory cutting processes.

[0012] Furthermore, in step S50, the consistency cross-validation result between the first altitude change trend and the second predicted altitude change trend is obtained in the following way: Within a preset time window or preset angle window, the direction of change, rate of change, and phase difference of the first height change trend and the second predicted height change trend are extracted respectively. When at least two of the following conditions are met: the direction of change is consistent, the deviation between the rates of change is less than a first preset threshold, and the phase difference is less than a second preset threshold, the consistency cross-validation result is determined to meet the preset conditions. In step S50, the alternative target height is generated in the following manner: The torch height of the most recent stable section before exiting the height closed-loop control based on the arc voltage signal is extracted as the receiving benchmark, and the height change between the baseline height of the steel pipe circumferential geometric baseline at the current cutting position and the baseline height of the corresponding switching position when exiting the height closed-loop control is superimposed on the receiving benchmark to generate the alternative target height. Step S50 further includes: After the consistency cross-validation result meets the preset conditions again, the torch height closed-loop control based on the arc voltage signal is gradually restored according to the preset transition function.

[0013] By jointly comparing the direction, rate of change, and phase difference of the first height change trend and the second predicted height change trend within a preset time window or angle window, the control system can identify the consistency between the arc pressure signal and the actual undulations of the steel pipe's outer wall from the perspective of dynamic change patterns. This reduces the interference of local abnormal fluctuations on gating decisions and improves the stability of height judgment inside and outside the danger zone. By extracting the torch height of the most recent stable section before exiting closed-loop control as the receiving benchmark and superimposing the relative height change of the corresponding interval of the steel pipe's circumferential geometric baseline to generate a substitute target height, it can continue to reflect the undulations of the steel pipe's outer wall in space while retaining the actual cutting state before entering the danger zone. This avoids the following deviation caused by simply freezing the height or directly applying the absolute baseline height in the danger zone. Furthermore, after the consistency cross-validation result meets the preset conditions again, the arc pressure closed-loop control is gradually restored according to the preset transition function. This reduces abrupt jumps and oscillations when switching control bases, ensuring a relatively smooth following process for the torch both before and after entering the danger zone, thus balancing the following accuracy and overall control stability in complex trajectory cutting.

[0014] Furthermore, when the process danger zone is the transition zone at the start of cutting, within the transition zone after the arc piercing is completed, the central axis of the cutting torch is controlled to form a preset offset angle relative to the normal direction of the current cutting position, and the composite interpolation speed of the machine tool is reduced simultaneously. The height of the cutting torch is controlled based on the circumferential geometric baseline of the steel pipe or the alternative target height. After the torch exits the transition section at the current cutting position and the arc voltage signal stabilizes, the torch is controlled to eliminate the preset offset tilt angle, restore the synthetic interpolation speed, and resume the confidence gating determination of the height control.

[0015] By controlling the torch to form a preset offset angle and simultaneously reducing the machine tool's composite interpolation speed in the transition zone after arc initiation and piercing, a relatively stable spatial relationship can be formed between the arc direction, plasma gas flow direction, and molten metal discharge direction during the initial cutting stage. This reduces the adverse effects of initial splashing and local disturbances on the torch tip. Simultaneously, a lower feed rate helps the arc establish a more stable cutting state during the initial cutting stage, reducing the impact of sudden changes in operating conditions on trajectory tracking and height adjustment. Furthermore, the torch height is still controlled based on the circumferential geometric baseline of the steel pipe or a substitute target height, ensuring that attitude and speed adjustments in the initial transition zone do not deviate from the actual undulations of the steel pipe's outer wall. This avoids the height mismatch problem caused by simply reducing speed or merely changing attitude. After the vehicle exits the transition zone and the arc voltage signal stabilizes, the preset offset tilt angle is eliminated, the synthetic interpolation speed is restored, and the execution reliability gating judgment is resumed. This allows the special control of the initial cutting stage to exit smoothly, reducing the additional disturbances caused by the switching of control modes and motion states, thereby balancing the stability of the initial cutting stage with the following accuracy in the subsequent continuous cutting process.

[0016] Furthermore, the method also includes a collaborative intervention step: When the current cutting position is in the process danger zone and the arc voltage signal does not participate in the torch height closed-loop control, a physical intervention command is output synchronously. The physical intervention command includes adjusting the protective gas parameters for plasma cutting, and includes limiting at least one of limiting the composite interpolation speed of the machine tool and limiting the rotational axis acceleration of the machine tool to maintain arc stability during the cutting process.

[0017] By synchronously outputting physical intervention commands when the current cutting position is in the process hazard zone and the arc voltage signal is not involved in the torch height closed-loop control, height control in the hazard zone can go beyond simply switching control criteria. It can further coordinate the constraints on arc stability from two dimensions: the shielding gas state and the machine tool motion state. Adjusting the shielding gas parameters of plasma cutting helps improve the arc's sustaining ability and concentration under conditions where solid metal support is lost. Limiting at least one of the machine tool's synthetic interpolation speed and rotational axis acceleration helps reduce arc stretching, swaying, and local instability when the torch crosses complex topological sections. Thus, position control and process control work together in the hazard zone, enabling the torch to not only avoid erroneous following under arc voltage distortion conditions but also maintain a relatively stable cutting state in complex sections, thereby improving control stability and continuous cutting consistency during hazard zone passage.

[0018] Furthermore, the step of performing the confidence gating determination also includes kinematic feedforward decoupling processing: Real-time acquisition of the machine tool's composite acceleration and rate of change of velocity; When the combined acceleration is greater than or equal to a first preset motion disturbance threshold, or the rate of change of velocity is greater than or equal to a second preset motion disturbance threshold, in order to suppress the arc voltage disturbance caused by the acceleration and deceleration of the machine tool from triggering the exit of the torch height closed-loop control based on the arc voltage signal, at least one of the following feedforward decoupling operations is performed: Expand the decision threshold corresponding to the consistency cross-validation results; The credibility gating decision is performed with a delay within a preset shielding time window.

[0019] By introducing kinematic feedforward decoupling into the reliability gating decision, normal arc voltage fluctuations caused by drastic acceleration and deceleration of the machine tool can be distinguished from abnormal arc voltage changes caused by process disturbances. During high-dynamic movements such as rapid start-up and shutdown, sharp turns, or significant speed changes, the arc will experience short-term fluctuations due to sudden changes in motion state. If only ordinary gating logic is used for direct judgment, these signal fluctuations caused by machine tool motion can easily be misjudged as actual pipe wall undulations or process distortions, leading to erroneous exits of the highly closed loop. Therefore, by acquiring the synthetic acceleration and rate of change of velocity in real time, and performing feedforward decoupling operations to expand the judgment threshold or mask the delay when the preset motion disturbance threshold is exceeded, the control system possesses the necessary fault tolerance during the dynamic changes of the machine tool, preventing the amplification of short-term mechanical motion disturbances into state switching signals. This not only improves the adaptability of the gating decision to the dynamic working conditions of the machine tool but also helps ensure the control continuity and high-level following stability during complex trajectory acceleration and deceleration switching processes.

[0020] Furthermore, the method also includes a baseline online correction step: When the current cutting position is not in the process danger zone and the consistency cross-validation result meets the preset condition, the cutting current, the arc voltage signal, the cutting duration and the cumulative cutting length in the current cutting process are obtained. Based on the cutting current, the arc voltage signal, the cutting duration, and the cumulative cutting length, the thermal accumulation state value at the current cutting position is determined, and the thermal deformation correction amount of the circumferential geometric baseline of the steel pipe is calculated based on the thermal accumulation state value. The thermal deformation correction amount is corrected based on the deviation between the actual height corresponding to the arc pressure signal and the baseline height corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position. Based on the corrected thermal deformation correction amount, the circumferential geometric baseline of the steel pipe is corrected online according to a preset correction cycle.

[0021] By introducing an online baseline correction step, the circumferential geometric baseline of the steel pipe can be dynamically adjusted according to the thermal state changes during the cutting process. Because plasma cutting involves continuous heat input, the steel pipe gradually accumulates heat during continuous cutting, inducing morphological changes such as local expansion, warping, and stress release. If the static geometric baseline established before arc initiation is used for a long period, the initial reference will gradually deviate from the current true physical morphology of the steel pipe as the cutting process progresses. Therefore, in the stable cutting section outside the process hazard zone, the heat accumulation state value is determined by combining parameters such as cutting current, cutting duration, and cumulative cutting length. The thermal deformation correction amount is then corrected using the deviation between the actual height corresponding to the current arc pressure signal and the baseline height. This allows the geometric baseline to both absorb the overall change trend corresponding to the cumulative heat input and correct the morphological deviation at the current position. Furthermore, updating the geometric baseline online according to a preset correction cycle can gradually adjust the baseline with changes in thermal state while reducing additional fluctuations caused by frequent updates. This reduces the cumulative deviation between the baseline reference and the actual pipe wall morphology in the later stages of cutting, improving the continuous accuracy of subsequent height judgment and position tracking.

[0022] The present invention also provides an adaptive height control system for a steel pipe plasma cutting machine, comprising: The position determination module is used to obtain the rotation angle and axial position information of the steel pipe to be cut, and to determine the current cutting position; The baseline acquisition module is used to acquire or establish the circumferential geometric baseline of the steel pipe corresponding to the rotation angle information and the axial position information; The hazard zone identification module is used to parse the cutting trajectory program to be executed, and identify and mark the process hazard zone based on the local contour features corresponding to the cutting trajectory program; The arc voltage acquisition module is used to acquire the arc voltage signal of the plasma arc in real time during the process of controlling the cutting torch to cut the steel pipe. The trend extraction module is used to determine the first height change trend based on the arc pressure signal, and simultaneously extract the second predicted height change trend corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position; The gating decision module is used to perform a confidence gating decision based on the consistency cross-validation result of the first height change trend and the second predicted height change trend, combined with whether the current cutting position is located in the process danger zone; The height control module is used to perform closed-loop control of the torch height using the arc pressure signal when the closed-loop control based on the arc pressure signal is not exited; and when the closed-loop control of the torch height based on the arc pressure signal is exited, an alternative target height is generated based on the circumferential geometric baseline of the steel pipe, and the torch operation is controlled according to the alternative target height.

[0023] By setting up the aforementioned position determination module, baseline acquisition module, hazard zone identification module, arc pressure acquisition module, trend extraction module, gating judgment module, and height control module, a seamless system control link is formed in the plasma cutting process of steel pipe, encompassing position acquisition, geometric baseline establishment, hazard zone identification, arc pressure signal acquisition, trend extraction, reliability judgment, and height control execution. In this way, each module does not independently perform a single function, but rather coordinates information acquisition, status judgment, and control execution around the unified reference of the current cutting position. This allows the system to continuously follow the actual undulations of the steel pipe's outer wall in ordinary cutting sections, and to promptly switch the height control basis based on gating judgment results in complex sections. This provides clear module support and execution foundation for the aforementioned adaptive height control method and improves the operational stability of the entire control process.

[0024] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the adaptive height control method for a steel pipe plasma cutting machine as described in any of the preceding claims.

[0025] (III) Beneficial effects of the present invention: Compared with the prior art, the present invention obtains the circumferential geometric baseline of the steel pipe corresponding to the rotation angle and axial position information of the steel pipe, and identifies the process danger zone by combining the cutting trajectory. Then, it performs consistency cross-verification on the height change trend corresponding to the arc pressure signal and the predicted height change trend corresponding to the geometric baseline to determine whether the arc pressure signal participates in the closed-loop control of the cutting torch height. In this way, it maintains the dynamic following ability of the irregular shape of the outer wall of the steel pipe in the ordinary section, and suppresses the erroneous following caused by arc pressure distortion in the complex section, so as to achieve a balance between the stability of the cutting torch height control and the processing accuracy during the cutting of complex trajectories. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating an adaptive height control method for a steel pipe plasma cutting machine according to an embodiment of the present invention. Detailed Implementation

[0028] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation

[0029] This embodiment provides an adaptive height control method and system for a steel pipe plasma cutting machine.

[0030] This method is applied to CNC plasma cutting equipment for steel pipes and is suitable for processing scenarios such as end cutting, hole drilling, grooving, intersecting line contour cutting, and continuous cutting across seams. It is particularly suitable for complex processing conditions where the steel pipe has external wall morphology deviations such as out-of-roundness, deflection, local bulges, and clamping eccentricity after clamping, and the cutting trajectory simultaneously includes hole boundaries, existing cuts, local sharp turns, and start-end transition sections. Under such conditions, the cutting torch must maintain a stable cutting distance according to the actual undulations of the steel pipe's external wall, while avoiding mis-following due to abnormal arc pressure fluctuations in local complex sections. Therefore, the entire cutting process involves not only height adjustment but also joint judgment of the actual morphology of the steel pipe, the characteristics of the trajectory section, the arc pressure change state, and the timing of control switching.

[0031] The CNC plasma cutting equipment for steel pipes in this embodiment includes at least a steel pipe clamping and rotation mechanism, an axial traveling mechanism, a torch lifting mechanism, a plasma cutting power supply, an arc voltage acquisition unit, an outer wall measuring device, a protective gas supply and adjustment unit, and a control system. The steel pipe clamping and rotation mechanism clamps the steel pipe to be cut and drives it to rotate around its own axis. The axial traveling mechanism drives the torch to move along the axial direction of the steel pipe. The torch lifting mechanism drives the torch to adjust its height. In some embodiments, a radial adjustment mechanism or a posture adjustment mechanism may also be provided to assist the torch in posture correction during the initial cutting transition stage or in special trajectory sections. The plasma cutting power supply is connected to the torch to provide the cutting arc. The arc voltage acquisition unit is electrically connected to the torch circuit and the cutting power supply to acquire the arc voltage signal of the plasma arc in real time. The outer wall measuring device acquires the outer wall morphology data of the steel pipe before cutting begins or within a reference section. The protective gas supply and adjustment unit provides protective gas, cutting gas, or auxiliary gas to the torch and adjusts the gas flow rate, pressure, or valve opening according to control commands.

[0032] The control system can be deployed in the main control unit of a CNC machine tool, or in an industrial control platform or edge control module that communicates with the CNC machine tool. The control system includes a processor, memory, and a communication interface. The processor executes the control program stored in the memory, and the communication interface interacts with the rotary drive, carriage drive, lifting drive, arc pressure acquisition board, outer wall measuring device, gas path regulating assembly, and plasma power supply for data and control communication. The control program can be directly embedded or loaded into the control system, or it can be stored as a program product in a computer-readable storage medium and executed as described in this embodiment after being called by the processor.

[0033] In this embodiment, the control system includes a position determination module, a baseline acquisition module, a hazard zone identification module, an arc pressure acquisition module, a trend extraction module, a gating judgment module, and a height control module. In some implementations, a collaborative intervention module, a kinematic feedforward decoupling module, and a baseline online correction module may also be included. The position determination module uses the rotation angle detection signal and the axial position feedback signal to determine the current cutting position; the baseline acquisition module uses the outer wall measuring device and the corresponding data processing program to establish the circumferential geometric baseline of the steel pipe; the hazard zone identification module analyzes the cutting trajectory program and marks the process hazard zone; the arc pressure acquisition module receives the real-time arc pressure signal output by the arc pressure acquisition unit; the trend extraction module extracts the corresponding dynamic change trend and predicted change trend based on the arc pressure signal and the circumferential geometric baseline of the steel pipe; the gating judgment module determines whether the current arc pressure signal is reliable based on the current position, the state of the process hazard zone, and the consistency cross-validation result between the two trends; and the height control module outputs corresponding control commands to the torch lifting mechanism, the axial traveling mechanism, the rotary drive, and the gas regulation unit based on the gating judgment result. In this way, the actual outer wall morphology of the steel pipe, the status of the trajectory segment, the arc pressure feedback status, and the actions of the cutting torch are all collected, judged, and executed in the same control link, rather than operating independently.

[0034] Specifically, the steel pipe clamping and rotation mechanism can adopt a chuck-type clamping structure, a roller-type support rotation structure, or other mechanisms that can stably rotate the steel pipe; the rotation angle information can be provided by a rotation shaft encoder, servo drive feedback, or an independent angle detection unit; the axial position information can be provided by a grating ruler, linear encoder, servo feedback, or CNC interpolation position signal. The control system determines the current cutting position based on the rotation angle and axial position information, so that any processing point on the outer wall of the steel pipe can be uniformly represented by "rotation angle + axial position". Subsequent actions, such as calling the circumferential geometric baseline of the steel pipe, marking the process danger zone, and extracting the correspondence between the first height change trend and the second predicted height change trend, all rely on this unified position reference system. The normal direction involved in the attitude adjustment during the initial cutting stage can be calculated based on the local geometric relationship of the outer wall of the steel pipe at the current position and the tangential relationship of the current trajectory, or it can be obtained by looking up a table based on the pre-established outer wall morphology data.

[0035] To obtain the actual outer wall morphology of the steel pipe in its current clamping state, the baseline acquisition module invokes an outer wall measuring device to scan and sample the outer wall of the steel pipe within the reference section before or at the start of cutting. The outer wall measuring device can be a laser rangefinder, a line laser profile sensor, a contact probe, a capacitive displacement sensor, a vision measuring device, or a combination thereof. The control system controls the steel pipe clamping and rotation mechanism to rotate the steel pipe and controls the outer wall measuring device to perform a circumferential scan of the outer wall of the steel pipe along its axial direction at at least two sampling sections, thereby obtaining outer wall height data corresponding to multiple rotation angles and multiple axial positions. The control system further organizes this outer wall height data into a lookup table, discrete dataset, interpolation curve set, surface mapping relationship, or other callable data formats, thus forming the circumferential geometric baseline of the steel pipe. This geometric baseline is not an abstract concept, but rather outer wall morphology reference data that can be directly invoked during subsequent cutting processes based on the current cutting position.

[0036] Meanwhile, the hazard zone identification module receives and parses the cutting trajectory program to be executed. The cutting trajectory program can be CNC code, interpolation instruction sequence, trajectory point set, path segment parameters, or a combination thereof. During the parsing process, the control system can extract process features such as local curvature change rate, equivalent aperture, equivalent groove width, crossing distance with existing cuts, and starting and ending sections, and mark the process hazard zone according to preset rules. The arc pressure acquisition module continuously acquires arc pressure signals during the cutting process, and the trend extraction module extracts the first height change trend based on the arc pressure signal and the second predicted height change trend corresponding to the current cutting position based on the circumferential geometric baseline of the steel pipe. The first height change trend and the second predicted height change trend can be obtained within a preset time window, preset angle window, or preset sampling point window, and can be represented in the form of change direction, change rate, phase difference, etc. The gating judgment module further combines the process hazard zone markings and the consistency cross-validation results between the above two trends to determine whether the current arc pressure signal is reliable.

[0037] Based on this, the height control module executes different control paths according to the gating judgment results. When the arc pressure signal is reliable, the height control module outputs a height closed-loop adjustment command based on the arc pressure signal to the torch lifting mechanism to maintain the real-time following of the torch to the actual outer wall undulations of the steel pipe; when the arc pressure signal is distorted, the height control module exits the height closed-loop control based on the arc pressure signal and outputs a height control command to the torch lifting mechanism according to the circumferential geometric baseline of the steel pipe or the alternative target height. In the process hazard zone, in order to maintain the stability of the cutting process, the control system can also synchronously output protective gas parameter adjustment commands and speed and acceleration constraint commands through the gas regulation unit and motion control interface via the collaborative intervention module; when the machine tool enters the high dynamic motion stage, the kinematic feedforward decoupling module can also perform feedforward correction of the gating judgment threshold or judgment timing according to the synthetic acceleration and the rate of change of speed; in the stable cutting section of the non-hazard zone, the baseline online correction module can also periodically update the circumferential geometric baseline of the steel pipe by combining the relevant parameters of the heat input and the actual height deviation of the current position. Thus, location determination, baseline acquisition, danger zone identification, arc voltage acquisition, trend extraction, gating determination, altitude control, as well as further collaborative intervention, kinematic feedforward decoupling, and online baseline correction together constitute a complete adaptive altitude control system.

[0038] For example, for a steel pipe with axial deflection and a cutting trajectory including a small hole and a seam crossing, during the outer contour cutting stage, the control system can maintain a normal height closed loop based on the current arc pressure signal. As the trajectory gradually approaches the boundary of the small hole or the edge of the existing cut, the danger zone identification module marks the process danger zone in advance based on the characteristics of the cutting trajectory, while the trend extraction module and the gating judgment module further determine whether the arc pressure fluctuation still reflects the actual outer wall undulation. If only the real-time overall arc pressure response is relied upon, abnormal fluctuations formed when the arc loses continuous support locally may be mistaken for changes in pipe wall height, causing the lifting mechanism to output action commands that are inconsistent with the actual shape of the steel pipe. It is in this implementation environment that the control system needs to perform targeted control of the subsequent height control process of the cutting torch based on the current cutting position, the circumferential geometric baseline of the steel pipe, the state of the process danger zone, and the arc pressure change trend.

[0039] Based on the aforementioned hardware, data, and control infrastructure, such as Figure 1 As shown in the figure, the following embodiment will further explain the execution method of the adaptive height control method of the steel pipe plasma cutting machine in conjunction with the specific control process in the complex trajectory cutting process of steel pipe.

[0040] Step S10: Obtain and establish the circumferential geometric baseline of the steel pipe In this embodiment, before the formal arc cutting begins, or within the reference section at the start of cutting, the control system first acquires the rotation angle and axial position information of the steel pipe to be cut, and establishes a correspondence between the outer wall morphology of the steel pipe and its spatial position. Specifically, the control system controls the steel pipe clamping and rotation mechanism to drive the steel pipe to rotate around its own axis, while simultaneously controlling the outer wall measuring device to sequentially reach at least two sampling sections along the axial direction of the steel pipe, and performing circumferential scanning sampling of the outer wall of the steel pipe at each sampling section.

[0041] In a preferred embodiment, the outer wall measuring device employs a laser displacement sensor. The steel pipe rotates at a constant low speed for one revolution, and the displacement sensor samples the outer wall height value at fixed angular intervals. Preferably, the circumferential sampling angle interval can be 1° to 5°, for example, 2°; in this case, a single sampling section can obtain 72 to 360 circumferential sampling points. For steel pipes with larger diameters and more significant roundness errors, the sampling angle interval can be further reduced to 0.5° to 1° to improve the resolution of undulations in the outer wall of the section. The number of sampling sections in the axial direction of the steel pipe can be determined according to the length of the steel pipe, the clamping span, and the distribution of the processing section. In a preferred embodiment, when the length of the steel pipe is no more than 2m, 2 to 3 sampling sections can be set along the axial direction; when the length of the steel pipe is greater than 2m but no more than 6m, 3 to 8 sampling sections can be set; when the length of the steel pipe further increases, additional sections can be added according to a preset axial interval. Preferably, the axial spacing between adjacent sampling sections can be 100mm to 500mm, for example, 200mm or 300mm.

[0042] After completing the circumferential scan at each sampling section, the control system obtains the outer wall height data corresponding to different rotation angles and different axial positions. In one implementation, the outer wall height value at the i-th sampling section Li with a rotation angle of θj is denoted as Hi(θj). The control system can organize the height data of each sampling section into a two-dimensional lookup table or into a discrete point set. For any current cutting position located between two adjacent sampling sections Li and Li+1 with a rotation angle of θx and an axial position of Lx, its corresponding baseline height Hbase(Lx,θx) can be obtained by interpolation. In a preferred embodiment, linear interpolation can be used, specifically: Hbase(Lx,θx)=Hi(θx)+[(Lx-Li) / (Li+1-Li)]×[Hi+1(θx)-Hi(θx)] Where Hi(θx) represents the height value of the i-th sampling section at the rotation angle θx, and Hi+1(θx) represents the height value of the (i+1)-th sampling section at the same rotation angle θx. Thus, when the current cutting position is located between two sampling sections, the control system can calculate the baseline height corresponding to the current position based on the axial proportional relationship between that position and the two sampling sections.

[0043] In another preferred embodiment, to make the baseline smoother in both the axial and circumferential directions, spline interpolation, local polynomial fitting, or surface fitting can be used to establish the mapping relationship of the steel pipe's outer wall morphology. For example, periodic spline fitting can be performed on the circumferential height data of each sampling section first, and then axial spline interpolation can be performed on the points at the same angle between different sampling sections to form a continuous surface. In cases where the controller's computing power is limited, the above fitting results can be pre-discretized and stored as a baseline data table for direct retrieval based on the current location.

[0044] In this embodiment, the circumferential geometric baseline of the steel pipe does not represent the nominal outer diameter under ideal cylindrical conditions, but rather serves as spatial reference data characterizing the actual outer wall morphology of the steel pipe in its current clamping state. By performing circumferential scanning at at least two sampling sections along the axial direction, the control system can not only obtain the circumferential undulations of the steel pipe on a single section, but also simultaneously reflect the overall morphological changes of the steel pipe along the axial direction. For example, when the steel pipe experiences overall movement due to clamping eccentricity, the height distribution at different rotation angle positions will show an overall shift; when the steel pipe undergoes axial deflection due to its own weight or support conditions, the baseline height at the same rotation angle position at different axial coordinates will show a gradual change; when the steel pipe has local weld protrusions, indentations, or local bulges, the outer wall height data at the corresponding sampling point will show a local sudden increase. All of the above morphological information is solidified into the circumferential geometric baseline of the steel pipe, thereby providing a continuous reference for height determination in subsequent complex trajectory cutting.

[0045] In this embodiment, the current cutting position is determined by both the rotation angle information and the axial position information. Based on the established circumferential geometric baseline of the steel pipe, the control system can extract the corresponding baseline height at any current cutting position and further extract the geometric change trend near that position during subsequent cutting operations. For example, a baseline height sequence of several adjacent points can be extracted near the current cutting position according to a preset angle window or axial window, thereby obtaining the local rising trend, falling trend, or rate of change at that position. Therefore, when subsequently judging the height change corresponding to the arc pressure signal, there is a real outer wall morphology reference basis that corresponds one-to-one with the current position.

[0046] Step S20: Identify and mark process hazard areas After the circumferential geometric baseline of the steel pipe is established, the control system further analyzes the cutting trajectory program to be executed to identify process hazard zones that may cause abnormal arc pressure during the cutting process. The cutting trajectory program can be CNC code, interpolation instruction sequence, trajectory point set, path segment parameter set, or a combination thereof. When the control system analyzes the cutting trajectory program segment by segment, it extracts the local contour features corresponding to each interpolation segment and completes the identification and marking of process hazard zones based on these local contour features.

[0047] In this embodiment, the process hazardous area includes at least the following types of sections.

[0048] The first category consists of segments where the rate of change of local contour curvature exceeds a first preset threshold. For this type of segment, the control system can determine the rate of change of local contour curvature based on the directional change relationship between adjacent interpolation segments, the change relationship of local curvature radius, or the tangential change relationship of discrete trajectory points. In a preferred embodiment, for discrete trajectory points Pk-1, Pk, and Pk+1, the angle change Δφk between two adjacent trajectory segments can be calculated first, and then the rate of change of local curvature Gk can be calculated in combination with the arc length spacing Δsk. Specifically, it can be written as: Gk=|Δφk| / Δsk When Gk exceeds a first preset threshold T1, the section near Pk is marked as a process hazard zone. Preferably, the first preset threshold T1 can be pre-calibrated based on the machine tool's dynamic response capability and cutting process requirements, for example, it can be taken as 0.02 rad / mm to 0.20 rad / mm. At the acute angle intersection of complex intersection lines, at extremely small arc transition angles, or in local abrupt turnback sections, Gk usually increases significantly. At this time, the machine tool's motion state and arc state are prone to change in a short period of time, so such sections are marked as process hazard zones.

[0049] The second category comprises sections where the ratio of the equivalent aperture or equivalent slot width to the steel pipe wall thickness is less than a second preset threshold. For hole cutting or slot cutting, the control system can determine the equivalent aperture or equivalent slot width based on the local closed contour dimensions, local opening width, slot envelope width, or minimum envelope rectangle width. For approximately circular holes, the aperture diameter can be directly used as the equivalent aperture diameter; for non-circular holes, the diameter of a circle with an equal area can be used as the equivalent aperture diameter, i.e., calculated based on the opening area A. Deq = 2 × √(A / π) For a groove profile, the minimum opening width or minimum envelope width can be used as the equivalent groove width Weq. The ratio of the equivalent aperture Deq or equivalent groove width Weq to the steel pipe wall thickness t is calculated to obtain R = Deq / t or R = Weq / t. When this ratio is less than a second preset threshold T2, it indicates that the local opening size is relatively small, and the solid metal support conditions of the electric arc in this section are prone to significant changes; therefore, this area is marked as a process hazard zone. Preferably, the second preset threshold T2 can be between 1.2 and 3.0, for example, 1.5, 2.0, or 2.5. For small holes or narrow grooves on thick-walled steel pipes, when this ratio is small, the electric arc is more prone to abnormal fluctuations due to changes in local support conditions and restricted slag discharge.

[0050] The third category consists of sections where the crossing distance from the existing cut is less than a third preset threshold. For this type of section, the control system can determine the crossing distance dcross based on the minimum distance between the current trajectory advancement direction and the existing cut boundary. When dcross is less than the third preset threshold T3, it indicates that the current cutting position is close to the edge of the existing cut, and the electric arc is prone to abnormal fluctuations at this position due to local support interruption and boundary disturbance; therefore, it is marked as a process hazard zone. Preferably, the third preset threshold T3 can be 2mm to 20mm, or it can be set as a multiple of the steel pipe wall thickness, for example, 0.5t to 3t.

[0051] In addition to the sections identified by local contours and kerf relationships, this embodiment also includes the transition section at the start of cutting and the deceleration section before the end of cutting in the process hazard zone. The transition section at the start of cutting can be determined based on a preset travel distance, preset angle range, or preset time range after the completion of arc piercing. For example, in a preferred embodiment, the travel section 5mm to 30mm before the completion of piercing, or the turning section 5° to 20° before the completion of piercing, or the cutting period 50ms to 300ms before the completion of cutting can be defined as the starting transition section. The deceleration section before the end of cutting can be determined based on a preset distance, preset angle range, or deceleration control start point before the end of the trajectory. For example, the section 10mm to 50mm before the end of the trajectory, or the turning section 5° to 15° before the end of the trajectory, can be defined as the ending deceleration section. In this way, the identification of the process hazard zone not only covers high-risk sections caused by local complex topography, but also covers high-risk sections caused by the switching of working conditions at the start and end of cutting.

[0052] In this embodiment, the hazard zone identification result can be stored in association with the cutting trajectory program in the form of segment markers, status flags, hazard category labels, or trajectory attribute fields. As the current position is continuously updated during the cutting process, the control system can directly determine whether the current position has entered the process hazard zone and the type and source of the current process hazard zone. For example, when the small hole boundary segment corresponding to the current position is marked as a hole-groove type hazard zone, the subsequent control logic can prepare in advance for gating processing of arc pressure distortion; when the current position corresponds to the initial transition segment, the subsequent control logic can further call the attitude adjustment and deceleration strategies of the starting cutting stage. Thus, the circumferential geometric baseline of the steel pipe and the process hazard zone marker together constitute the prerequisite for subsequent control: the former is used to provide a reference for the real outer wall morphology corresponding to the current position, and the latter is used to provide process risk status information corresponding to the current position. On this basis, the control system further combines the real-time arc pressure signal to judge and select the height control method for the current position.

[0053] After establishing the circumferential geometric baseline of the steel pipe and identifying the process hazard zone, the control system enters the cutting execution stage. At this time, the control system continuously acquires the real-time status of the plasma arc and, based on the current position, retrieves the data corresponding to the circumferential geometric baseline of the steel pipe. Based on this, it determines whether the current arc pressure signal can continue to be used as a basis for height control. The following describes the specific execution process of real-time arc pressure acquisition, trend extraction, and reliability gating judgment.

[0054] Step S30: Real-time arc voltage signal acquisition and preprocessing In this embodiment, the control system continuously and in real-time acquires the arc voltage signal of the plasma arc while controlling the cutting torch to cut the steel pipe along the cutting trajectory. The arc voltage acquisition unit can extract the voltage signal from the plasma cutting power supply and the cutting torch circuit through a high-frequency isolation voltage divider circuit, and then input it into the control system after analog-to-digital conversion. To ensure the real-time performance of subsequent judgments, the arc voltage acquisition frequency is preferably higher than the height control output frequency. In a preferred embodiment, the arc voltage acquisition frequency can be from 500Hz to 10kHz, for example, 1kHz, 2kHz, or 5kHz; for CNC systems with a control cycle of 5ms to 20ms, multiple arc voltage sample values ​​can be buffered and processed within each control cycle.

[0055] Since power ripple, instantaneous splashing, electromagnetic interference, and local contact state changes may occur simultaneously during the cutting process, in this embodiment, the control system preprocesses the arc voltage sequence after obtaining the original arc voltage sampling values ​​before using it for subsequent trend extraction. In one implementation, moving average filtering, median filtering, amplitude limiting filtering, or a combination thereof can be used to smooth the arc voltage sequence. For example, a moving average can be performed on the most recent n sampling points, where n can be 3 to 20; alternatively, outliers exceeding the current mean ± 3σ range can be removed first, and then the remaining sampling values ​​can be averaged. For individual spikes caused by splashing or temporary arc interruption, an upper limit for instantaneous changes can be set. When the arc voltage difference between two adjacent sampling points exceeds a preset mutation amount, the sampling point is replaced with the previous moment value or the local mean. The arc voltage sequence obtained after preprocessing serves as the input data for subsequent first height change trend extraction.

[0056] In a preferred embodiment, if the control system has pre-established a calibration relationship between arc voltage and equivalent arc length, the arc voltage signal can be converted into an equivalent height signal before trend extraction. For example, calibration can show that the equivalent height Heq and the arc voltage U satisfy an approximately linear relationship. Heq = a × U + b Where a and b are calibration coefficients, and a can be pre-calibrated based on the torch model, cutting current level, nozzle type, and gas parameters. In another embodiment, the arc pressure can be used as a raw signal reflecting the height change trend instead of directly converting the arc pressure to absolute height, and then participating in subsequent calculations. As long as consistent trend extraction and comparison logic is used before and after, the implementation requirements of this embodiment can be met.

[0057] Step S40: Extracting the first and second predicted altitude change trends In this embodiment, after the arc pressure signal is acquired and preprocessed, the control system determines the first height change trend based on the arc pressure signal and simultaneously extracts the second predicted height change trend corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position. Here, "trend" is not limited to the absolute value at a single moment, but rather a set of dynamic characteristics used to characterize the direction, speed, and phase of signal change within the current window.

[0058] Regarding the trend of the first height change, in one implementation, the control system extracts the arc pressure sequence within a preset time window or a preset angle window, denoted as U(1), U(2), ..., U(N). The time window can be set according to a fixed time length, for example, 10ms to 200ms, preferably 20ms to 100ms; the angle window can be set according to the rotation angle of the steel pipe, for example, 2° to 20°, preferably 5° to 10°. When using a time window, the direction of change can be determined according to the arc pressure difference between the beginning and end of the window; when using an angle window, the direction of change can be determined according to the overall increase or decrease trend of the arc pressure sequence within the corresponding angle range. In a preferred implementation, the rate of change k1 within the window can be calculated using the difference between the beginning and end: k1=[U(N)-U(1)] / [(N-1)×Δt] Where Δt is the time interval between adjacent sampling points. To improve noise resistance, a least-squares fitting method can be used to perform a linear fit on the arc pressure sequence within the window, with its slope serving as the rate of change k1. If the aforementioned arc pressure signal has been converted into an equivalent height sequence, the equivalent height sequence can also be used to replace the arc pressure sequence in the above calculations. The corresponding direction of change dir1 can be determined by the sign of k1: when k1>0, it indicates an upward trend; when k1<0, it indicates a downward trend; and when |k1| is less than a preset small change threshold, it indicates a basically stable trend.

[0059] For the second predicted height change trend, the control system extracts the baseline height sequence near the current cutting position from the circumferential geometric baseline of the steel pipe within the position range corresponding to the current time window or angle window, denoted as Hbase(1), Hbase(2), ..., Hbase(M). Here, Hbase(i) represents the baseline height value corresponding to the i-th position point within the window. In one implementation, the method for determining the position points within the window corresponds to the trajectory advancement method: when extracting by time window, the time window can be mapped to the position sequence on the baseline based on the trajectory advancement amount within the current control cycle; when extracting by angle window, the baseline height sequence within the corresponding angle range can be directly extracted based on the change in the rotation angle. The rate of change k2 of the second predicted height change trend can be calculated using the following formula: k2=[Hbase(M)-Hbase(1)] / [(M-1)×Δs] Here, Δs represents the interval length between adjacent points within the window along the trajectory advancement direction; if an angle window is used, Δs can be replaced with the corresponding angle step size. Similarly, k2 can be obtained by fitting the slope. The corresponding direction of change dir2 is determined by the sign of k2.

[0060] In this embodiment, to perform subsequent consistency cross-validation, the control system also extracts the phase relationship between the two trends. The phase difference can be understood as the time or position offset of a significant change in the two trends. In one implementation, the phase difference φ can be obtained by comparing the positional differences of local extrema, zero-crossing points, or slope peaks in the two sequences; in another implementation, the optimal alignment offset corresponding to the two trend sequences can be determined through cross-correlation calculations, and this offset can be used to characterize the phase difference. The smaller φ is, the more synchronized the first height change trend and the second predicted height change trend are within the current window.

[0061] Through the above processing, the control system can obtain the direction, rate of change, and phase relationship of the first altitude change trend and the second predicted altitude change trend in each control judgment cycle, thereby providing direct input for subsequent confidence gating judgment.

[0062] Step S50: Credibility gating determination, alternative target height generation and control recovery In this embodiment, after obtaining the first height change trend and the second predicted height change trend, the control system performs a confidence gating judgment based on the consistency cross-validation result between the two trends and in combination with whether the current cutting position is located in the process danger zone.

[0063] In a preferred embodiment, the control system extracts the change direction, change rate and phase difference of the first height change trend and the second predicted height change trend respectively within a preset time window or a preset angle window, and performs consistency cross-check based on the above. Specifically, the control system sequentially judges the following three conditions: first, whether the change directions are consistent, that is, whether dir1 and dir2 are the same; second, whether the change rate deviation is less than the first preset threshold T11, that is, |k1-k2|<T11; third, whether the phase difference is less than the second preset threshold T12, that is, |φ|<T12. In this embodiment, when at least two of the above three conditions are satisfied, it is determined that the consistency cross-check result meets the preset condition; otherwise, it is determined that the consistency cross-check result does not meet the preset condition.

[0064] The first preset threshold T11 and the second preset threshold T12 can be calibrated according to the response speed of the machine tool, arc voltage sampling resolution, steel pipe size and cutting process requirements. In a preferred embodiment, if k1 and k2 are expressed as change rate per unit time, T11 can be a change rate difference of 5% to 30% under the corresponding calibration scale; if φ is expressed as a time offset, T12 can be 5ms to 50ms; if φ is expressed as an angle offset, T12 can be 1° to 10°. The above values are only examples of preferred embodiments, and those skilled in the art can adjust them according to specific equipment conditions.

[0065] In this embodiment, the credibility gating judgment depends not only on the consistency cross-check result, but also on whether the current position is located in the process dangerous area. When the current position is not in the process dangerous area and the consistency cross-check result meets the preset condition, the control system determines that the current arc voltage signal is credible, and continues to use the arc voltage signal for closed-loop control of the torch height. At this time, the height control module can adopt PID control, fuzzy PID control, incremental closed-loop control or other control methods that can drive the torch lifting mechanism to adjust the height according to the arc voltage deviation, so as to maintain real-time tracking of the real outer wall fluctuation of the steel pipe by the torch.

[0066] When the current position is in the process dangerous area, or the consistency cross-check result does not meet the preset condition, the control system determines that the current arc voltage signal is distorted. At this time, the control system exits the closed-loop height control based on the arc voltage signal, generates an alternative target height based on the circumferential geometric baseline of the steel pipe, and then controls the operation of the torch according to the alternative target height. The term "exit" here does not mean that the torch stops height control, but means that the subsequent height control basis is switched from the real-time arc voltage signal to the alternative control based on the geometric baseline.

[0067] In this embodiment, the alternative target height is generated as follows. The control system first extracts the torch height of the most recent stable section before exiting the arc voltage closed-loop control as the receiving reference Href. Here, "stable section" refers to a section where the current position is not in the process danger zone for several consecutive control cycles, and the consistency cross-check results continuously meet the preset conditions. In a preferred embodiment, the stable section can be defined as a section that meets the above conditions for 5 to 50 consecutive control cycles, preferably 10 to 20 control cycles. When the control system confirms the moment of switching from arc voltage closed-loop to alternative control, it records the corresponding switching position Psw and obtains the baseline height Hbase(sw) corresponding to the switching position. Subsequently, for the current cutting position Pcur, the control system extracts the corresponding baseline height Hbase(cur) from the circumferential geometric baseline of the steel pipe and calculates the change in baseline height ΔHbase of the current position relative to the switching position: ΔHbase = Hbase(cur) - Hbase(sw) The control system then adds this height change to the reference height Href to obtain the alternative target height Hsub: Hsub=Href+ΔHbase The alternative target height generated in this way retains the true cutting height state established in the most recent stable section before cutting into the danger zone, while continuing to follow the actual undulations of the outer wall of the steel pipe in space, thus avoiding the following deviation caused by simply freezing the current height or directly applying the absolute baseline height in the danger zone.

[0068] In this embodiment, when the consistency cross-validation result meets the preset conditions again, the control system does not immediately switch the control basis from the alternative target height back to the arc voltage closed-loop control. Instead, it gradually restores the torch height closed-loop control based on the arc voltage signal according to a preset transition function. The preset transition function can be a linear weighting function, a first-order inertia function, or an exponential smoothing function. In a preferred embodiment, the following linear weighting recovery method can be used: Hcmd(t)=α(t)×Harc(t)+[1-α(t)]×Hsub(t) Where Hcmd(t) represents the target height output to the torch lifting mechanism during the transition phase, Harc(t) represents the closed-loop target height calculated based on the current arc voltage signal, Hsub(t) represents the current alternative target height, and α(t) is a weighting coefficient that gradually increases from 0 to 1 with the transition time. The transition time Tr can be set according to the machine tool response speed and cutting process requirements, preferably from 50ms to 500ms, for example, 100ms, 200ms, or 300ms. Through the above gradual recovery method, abrupt jumps in height commands during control basis switching can be avoided, reducing oscillations caused by control mode switching.

[0069] In this embodiment, to avoid false disturbances to the reliability gating judgment caused by the machine tool's own high dynamic motion, the control system further includes kinematic feedforward decoupling processing when executing step S50. Specifically, the control system acquires the machine tool's composite acceleration and rate of change of speed in real time. The composite acceleration can be calculated based on the change in speed command or position command of each execution axis; in a preferred embodiment, the speed changes of axial motion, rotary motion, and other interpolated execution axes can be combined to obtain the composite acceleration asyn in the current control cycle. The rate of change of speed can be calculated based on the difference in execution speed between the current control cycle and the previous control cycle. The control system compares asyn with a first preset motion disturbance threshold Ta and the rate of change of speed with a second preset motion disturbance threshold Tv, respectively.

[0070] When asyn is greater than or equal to Ta, or the rate of change of speed is greater than or equal to Tv, it indicates that the machine tool is currently in a significant acceleration / deceleration switching phase, and the arc will experience short-term fluctuations due to sudden changes in motion state. To suppress the arc voltage disturbance caused by the machine tool's acceleration / deceleration motion from triggering the exit from the arc voltage closed-loop control, the control system performs at least one of the following feedforward decoupling operations. First, the judgment threshold corresponding to the consistency cross-validation result is expanded. For example, when a high-dynamic motion state is detected, the first preset threshold T11 is expanded to β1×T11, and the second preset threshold T12 is expanded to β2×T12, where β1 and β2 can be taken as 1.2 to 3.0. Second, the confidence gating judgment is delayed within a preset shielding time window. Preferably, the shielding time window can be taken as 10ms to 200ms, for example, 20ms, 50ms, or 100ms. Through the above-mentioned feedforward decoupling process, the control system can retain the necessary fault tolerance during the dynamic change phase of the machine tool, avoid amplifying short-term mechanical motion disturbance errors into state switching signals, thereby improving the adaptability of gating decision to the dynamic working conditions of the machine tool, and maintaining control continuity and high following stability during complex trajectory switching processes.

[0071] Through the continuous execution of steps S30, S40, and S50, the control system can acquire the arc pressure state in real time during the cutting process, establish a prediction of the true outer wall morphology corresponding to the current position, maintain normal closed-loop following when the arc pressure is reliable, switch to alternative control in a timely manner when the arc pressure is distorted, and smoothly switch back to arc pressure closed-loop control after the recovery conditions are met. Therefore, height control during the cutting process no longer relies on a single arc pressure signal, but forms a complete main control closed loop through the combined effects of position reference, trend judgment, gating determination, and control switching.

[0072] During the cyclic execution of steps S30 to S50, the control system also performs cutting transition control, hazardous area coordinated intervention, and baseline online correction based on the current operating condition. Specifically: Control Branch A: Attitude and speed control of the initial cutting transition section In this embodiment, when the current position is identified as the transition zone for the start of cutting, the control system synchronously adjusts the torch posture, machine tool running speed, and height control based on the completion of arc piercing. The completion of arc piercing can be determined based on at least one of the following: a piercing end signal, a penetration detection signal, or a preset piercing duration condition being met. The initial transition zone can be determined based on a preset travel distance, a preset rotation angle range, or a preset duration after piercing. For example, the trajectory segment from 5mm to 30mm after piercing, the rotation segment from 5° to 20°, or the cutting period from 50ms to 300ms after piercing can be defined as the initial transition zone.

[0073] Upon entering this section, the control system first obtains the surface normal vector corresponding to the current position. The surface normal vector can be calculated based on the local surface shape near the current position according to the circumferential geometric baseline of the steel pipe, or it can be obtained by looking up a table based on the local fitted surface corresponding to the current position. In one embodiment, the control system extracts the local height changes in both the circumferential and axial directions near the current position, establishes a local tangent plane, and then obtains the normal vector based on this tangent plane.

[0074] After obtaining the surface normal vector, the control system controls the central axis of the cutting torch to form a preset offset angle with the surface normal vector along a direction opposite to the planned cutting trajectory. The direction opposite to the planned cutting trajectory can be determined based on the trajectory advancement direction and the direction of the cut opening side at the current position, causing molten metal and spatter to be discharged away from the planned trajectory. In one embodiment, the absolute value of the preset offset angle is 5° to 15°; it can be 10° to 15° when the wall thickness is large, and 5° to 10° when the wall thickness is small, for example, 8°, 10°, or 12°.

[0075] Simultaneously, the control system synchronously reduces the machine tool's composite interpolation speed. The composite interpolation speed is the current trajectory execution speed, formed by the combined axial travel speed, rotational speed, and the speeds of other motion axes involved in the interpolation. In one embodiment, after entering the initial transition zone, the control system reduces the composite interpolation speed to 40% to 80% of the normal cutting speed, for example, to 50%, 60%, or 70%.

[0076] Within this transition zone, the torch height is controlled based on the circumferential geometric baseline of the steel pipe or an alternative target height. When the arc voltage signal is still fluctuating significantly, the control system uses the alternative target height to control the torch height; when the arc voltage has not yet participated in the closed loop but the geometric baseline corresponding to the current position can be stably accessed, the control system uses the height corresponding to the geometric baseline to control the torch height.

[0077] Once the current position has exited the initial transition zone and the arc voltage signal has stabilized, the control system controls the cutting torch to eliminate the preset offset angle, restore the synthetic interpolation speed, and resume the reliability gating judgment for height control. Arc voltage signal stability can be determined based on the arc voltage change rate falling within a preset range over several consecutive control cycles, or by consistency cross-checking to re-meet the preset conditions. In one embodiment, the stability criterion can be that the arc voltage change rate is less than a preset threshold for 5 to 20 consecutive control cycles.

[0078] Control Branch B: Coordinated Intervention and Predictive Deceleration Control in Hazardous Areas In this embodiment, when the current location is in a process hazard zone, and the control system exits the height closed-loop control based on the arc voltage signal according to the aforementioned gating determination result, the control system simultaneously outputs a physical intervention command. The physical intervention command includes adjusting the protective gas parameters, and limiting at least one of limiting the synthetic interpolation speed and limiting the rotational shaft acceleration.

[0079] In one implementation, the protective gas parameters include at least one of gas flow rate, pressure, valve opening, and gas distribution ratio. Upon entering the hazardous process zone, the control system can adjust the protective gas flow rate to 1.05 to 1.30 times that of the normal cutting stage, or increase the corresponding valve opening by 5% to 20%. For multi-path cutting equipment, only the protective gas branch can be adjusted, while keeping the main cutting gas path parameters unchanged.

[0080] In addition to adjusting the protective gas parameters, the physical intervention commands also include limiting at least one of the machine tool's composite interpolation speed and limiting the rotary axis acceleration. In one embodiment, when the current position enters the slot boundary, the gap crossing section, or the deceleration termination section, the control system limits the composite interpolation speed to 50% to 90% of the normal execution speed; in another embodiment, only the rotary axis acceleration may be limited, for example, to 50% to 80% of the upper limit of normal acceleration; in a further embodiment, the control system limits both the composite interpolation speed and the rotary axis acceleration simultaneously.

[0081] To ensure that speed constraints take effect before entering the hazardous zone, the control system also pre-reads the trajectory geometry ahead of the current position based on the cutting trajectory program and calculates the maximum permissible composite speed within a preset span. The preset span can be determined by trajectory length, rotation angle, or number of control cycles; for example, a trajectory length of 10mm to 100mm ahead, or a rotation section of 5° to 30° ahead. Within this preset span, the control system analyzes local curvature changes, slot opening size, adjacency with existing cuts, and the state of the upcoming start and end sections, and determines the target deceleration value before entering the hazardous zone.

[0082] In one implementation, the control system calculates the composite velocity constraint value of the current position based on the dynamic constraints of each motion axis of the machine tool. The dynamic constraints include at least one of the following: maximum speed, maximum acceleration, maximum deceleration, drive response time, and allowable trajectory error for each motion axis. If the maximum allowable composite speed within a preset span is denoted as Vallow, the current execution speed as Vcur, the current available deceleration as adec, and the remaining distance from the current position to the entrance of the danger zone as Sremain, then the control system can determine whether early deceleration is necessary using the following formula: Vcur^2-Vallow^2>2×adec×Sremain This determines the composite speed constraint value for the current position. When this composite speed constraint value is less than the current execution speed, the control system pre-processes the machine tool's composite interpolation speed according to a preset acceleration / deceleration curve, ensuring the cutting torch reaches the target deceleration value before entering the process danger zone. The preset acceleration / deceleration curve can be a trapezoidal speed curve, an S-shaped acceleration / deceleration curve, or an exponential smooth deceleration curve; for applications with lower impact requirements, an S-shaped acceleration / deceleration curve can be used.

[0083] Control branch C: Online baseline correction for stable cutting sections In this embodiment, when the current position is not in a hazardous process zone and the consistency cross-validation result meets the preset conditions, the control system performs online baseline correction. At this time, the control system acquires the cutting current, arc voltage signal, cutting duration, and cumulative cutting length during the current cutting process. The cutting duration can be the total cutting time accumulated since the arc ignition moment, or the cutting time accumulated since the most recent baseline correction; the cumulative cutting length can be obtained by integrating the trajectory execution length, or it can be directly output by the path accumulation function of the CNC system.

[0084] In one implementation, the control system determines the thermal accumulation state value Qheat based on the cutting current, arc voltage signal, cutting duration, and cumulative cutting length. For example, it can be calculated using a weighted function: Qheat = w1×I + w2×U + w3×T + w4×L Where I is the current cutting current, U is the average or characteristic value of the current arc voltage signal, T is the cutting duration, L is the cumulative cutting length, and w1, w2, w3, and w4 are preset weighting coefficients. Alternatively, an integral thermal input model can be used, which estimates the cumulative thermal input based on the integral value of the product of current and arc voltage over time, and then normalizes it by combining the path length or the steel pipe wall thickness.

[0085] After obtaining the thermal accumulation state value, the control system calculates the thermal deformation correction amount for the circumferential geometric baseline of the steel pipe based on this value. In one embodiment, the thermal deformation correction amount ΔHthermal can be calculated proportionally: ΔHthermal=kq×Qheat Where kq is the thermal deformation calculation coefficient, which can be obtained based on the steel pipe material, wall thickness, diameter, and process calibration results. Alternatively, a piecewise function, lookup table model, or empirical fitting model can be used to calculate the thermal deformation correction based on Qheat.

[0086] To correct the discrepancy between the theoretical thermal deformation model and the actual state at the current location, the control system further adjusts the thermal deformation correction based on the deviation between the actual height corresponding to the current arc pressure signal and the baseline height corresponding to the geometric baseline at the current location. Let the actual height calculated from the current arc pressure signal be Hreal, and the baseline height corresponding to the current location be Hbase, then the current deviation is: ΔHerror = Hreal - Hbase In one implementation, the control system corrects the thermal deformation correction amount according to the following formula: ΔHcorrect=ΔHthermal+λ×ΔHerror Where λ is the correction coefficient, which can range from 0.1 to 1.0, for example, 0.2, 0.5, or 0.8. The corrected amount is used to update the geometric baseline data of the current location and its neighboring segments.

[0087] In this embodiment, the control system performs online correction of the circumferential geometric baseline of the steel pipe according to a preset correction cycle. The preset correction cycle can be set by time interval, cutting length interval, rotation angle interval, or a combination thereof. In one embodiment, the correction cycle can be 100ms to 1000ms; in another embodiment, correction can be performed once every 5mm to 20mm of cumulative cutting path length; for cutting scenarios dominated by rotational motion, correction can also be performed once every 2° to 10° of cumulative rotation. The control system superimposes the corrected thermal deformation correction amount onto the circumferential geometric baseline of the steel pipe according to the preset correction cycle, updating the baseline data for the current position and subsequent sections.

[0088] In summary, in this embodiment, the control system establishes a circumferential geometric baseline of the steel pipe and identifies the process hazard zone before cutting begins, serving as a prerequisite for subsequent control. During the cutting process, it collects arc pressure signals in real time, extracts the first height change trend and the second predicted height change trend, and performs reliability gating. When the arc pressure signal is reliable, it executes closed-loop height control based on the arc pressure signal; when the arc pressure signal is unreliable, it switches to alternative control based on the circumferential geometric baseline of the steel pipe. Furthermore, based on the current working conditions, it selectively executes attitude and speed control in the transition section, collaborative intervention and pre-reading deceleration control in the hazard zone, and online baseline correction in the stable cutting section. Therefore, those skilled in the art can implement the adaptive height control method for the steel pipe plasma cutting machine in this embodiment based on the above hardware configuration, data organization method, judgment logic, and control flow. It should be understood that the above parameter ranges, calculation methods, and control calibers are preferred examples in this embodiment. Other equivalent methods can be used for substitution or adjustment without departing from the technical concept of this application. All modifications and substitutions that do not depart from the technical concept and substance of this invention should fall within the protection scope of this invention.

Claims

1. An adaptive height control method for a steel pipe plasma cutting machine, characterized in that, Includes the following steps: S10. Obtain the rotation angle and axial position information of the steel pipe to be cut, and obtain or establish the circumferential geometric baseline of the steel pipe corresponding to the rotation angle and axial position information. S20. Analyze the cutting trajectory program to be executed, and identify and mark the process hazard area based on the local contour features corresponding to the cutting trajectory program; S30. During the process of controlling the cutting torch to cut the steel pipe, the arc pressure signal of the plasma arc is collected in real time. S40. Determine the first height change trend based on the arc pressure signal, and simultaneously extract the second predicted height change trend corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position; S50. Based on the consistency cross-validation results of the first height change trend and the second predicted height change trend, and combined with whether the current cutting position is located in the process danger zone, a confidence gating determination is performed: If the current cutting position is not in the process danger zone and the consistency cross-validation result meets the preset conditions, the arc voltage signal is determined to be reliable, and the arc voltage signal is used for closed-loop control of the torch height. If the current cutting position is in the process danger zone or the consistency cross-check result does not meet the preset conditions, the arc pressure signal is determined to be distorted, the height closed-loop control based on the arc pressure signal is exited, an alternative target height is generated based on the circumferential geometric baseline of the steel pipe, and the cutting torch is controlled according to the alternative target height.

2. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, The circumferential geometric baseline of the steel pipe is established in the following manner: before arc initiation or in the reference section at the start of cutting, at least two sampling sections are selected along the axial direction of the steel pipe to be cut, and the outer wall of the steel pipe to be cut is circumferentially scanned at each sampling section to obtain the outer wall height data corresponding to different rotation angles and different axial positions. Based on the outer wall height data, the circumferential geometric baseline of the steel pipe corresponding to the rotation angle information and axial position information is established.

3. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, The process hazardous area includes at least one of the following sections: The segment in the interpolation segment corresponding to the cutting trajectory program that has a local contour curvature change rate greater than the first preset threshold. In the interpolation segment corresponding to the cutting trajectory program, the segment in which the ratio of the equivalent aperture or equivalent groove width to the wall thickness of the steel pipe to be cut is less than the second preset threshold. The segment whose span distance from the formed cut is less than the third preset threshold; Cut the transition section at the beginning; The deceleration section before the cutting is terminated.

4. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, In step S50, the consistency cross-validation result between the first altitude change trend and the second predicted altitude change trend is obtained in the following way: Within a preset time window or preset angle window, the direction of change, rate of change, and phase difference of the first height change trend and the second predicted height change trend are extracted respectively. When at least two of the following conditions are met: the direction of change is consistent, the deviation between the rates of change is less than a first preset threshold, and the phase difference is less than a second preset threshold, the consistency cross-validation result is determined to meet the preset conditions. In step S50, the alternative target height is generated in the following manner: The torch height of the most recent stable section before exiting the height closed-loop control based on the arc voltage signal is extracted as the receiving benchmark, and the height change between the baseline height of the steel pipe circumferential geometric baseline at the current cutting position and the baseline height of the corresponding switching position when exiting the height closed-loop control is superimposed on the receiving benchmark to generate the alternative target height. Step S50 further includes: After the consistency cross-validation result meets the preset conditions again, the torch height closed-loop control based on the arc voltage signal is gradually restored according to the preset transition function.

5. The adaptive height control method for a steel pipe plasma cutting machine according to claim 3, characterized in that, When the process danger zone is the transition zone at the start of cutting, within the transition zone after the arc piercing is completed, the central axis of the cutting torch is controlled to form a preset offset angle relative to the normal direction of the current cutting position, and the composite interpolation speed of the machine tool is reduced simultaneously. The height of the cutting torch is controlled based on the circumferential geometric baseline of the steel pipe or the alternative target height. After the torch exits the transition section at the current cutting position and the arc voltage signal stabilizes, the torch is controlled to eliminate the preset offset tilt angle, restore the synthetic interpolation speed, and resume the confidence gating determination of the height control.

6. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, The method also includes a collaborative intervention step: When the current cutting position is in the process danger zone and the arc voltage signal does not participate in the torch height closed-loop control, a physical intervention command is output synchronously. The physical intervention command includes adjusting the protective gas parameters for plasma cutting, and includes limiting at least one of limiting the composite interpolation speed of the machine tool and limiting the rotational axis acceleration of the machine tool to maintain arc stability during the cutting process.

7. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, The step of performing the confidence gating decision also includes kinematic feedforward decoupling processing: Real-time acquisition of the machine tool's composite acceleration and rate of change of velocity; When the combined acceleration is greater than or equal to a first preset motion disturbance threshold, or the rate of change of velocity is greater than or equal to a second preset motion disturbance threshold, in order to suppress the arc voltage disturbance caused by the acceleration and deceleration of the machine tool from triggering the exit of the torch height closed-loop control based on the arc voltage signal, at least one of the following feedforward decoupling operations is performed: Expand the decision threshold corresponding to the consistency cross-validation results; The credibility gating decision is performed with a delay within a preset shielding time window.

8. The adaptive height control method for a steel pipe plasma cutting machine according to claim 1, characterized in that, The method also includes an online baseline correction step: When the current cutting position is not in the process danger zone and the consistency cross-validation result meets the preset condition, the cutting current, the arc voltage signal, the cutting duration and the cumulative cutting length in the current cutting process are obtained. Based on the cutting current, the arc voltage signal, the cutting duration, and the cumulative cutting length, the thermal accumulation state value at the current cutting position is determined, and the thermal deformation correction amount of the circumferential geometric baseline of the steel pipe is calculated based on the thermal accumulation state value. The thermal deformation correction amount is corrected based on the deviation between the actual height corresponding to the arc pressure signal and the baseline height corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position. Based on the corrected thermal deformation correction amount, the circumferential geometric baseline of the steel pipe is corrected online according to a preset correction cycle.

9. An adaptive height control system for a steel pipe plasma cutting machine, characterized in that, include: The position determination module is used to obtain the rotation angle and axial position information of the steel pipe to be cut, and to determine the current cutting position; The baseline acquisition module is used to acquire or establish the circumferential geometric baseline of the steel pipe corresponding to the rotation angle information and the axial position information; The hazard zone identification module is used to parse the cutting trajectory program to be executed, and identify and mark the process hazard zone based on the local contour features corresponding to the cutting trajectory program; The arc voltage acquisition module is used to acquire the arc voltage signal of the plasma arc in real time during the process of controlling the cutting torch to cut the steel pipe. The trend extraction module is used to determine the first height change trend based on the arc pressure signal, and simultaneously extract the second predicted height change trend corresponding to the circumferential geometric baseline of the steel pipe at the current cutting position; The gating decision module is used to perform a confidence gating decision based on the consistency cross-validation result of the first height change trend and the second predicted height change trend, combined with whether the current cutting position is located in the process danger zone; The height control module is used to perform closed-loop control of the torch height using the arc pressure signal when the closed-loop control based on the arc pressure signal is not exited; and when the closed-loop control of the torch height based on the arc pressure signal is exited, an alternative target height is generated based on the circumferential geometric baseline of the steel pipe, and the torch operation is controlled according to the alternative target height.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the adaptive height control method for a steel pipe plasma cutting machine as described in any one of claims 1 to 8.

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