A control system for gear shaft drilling cutting force

Abstract

The application relates to the technical field of gear shaft machining, and discloses a gear shaft drilling and cutting force control system which comprises a data acquisition module, a first identification module, a second identification module, a control strategy module and a control instruction module; wherein: the data acquisition module is used for continuously acquiring the cutting force of a drill bit and the working parameters of a machine tool; the first identification module is used for constructing a rhythm offset chain of the cutting force and identifying the fluctuation abnormality of the cutting force based on the rhythm offset chain; the second identification module is used for calculating a lag index between the cutting force and the working parameters and identifying the response abnormality of the cutting force based on the lag index; the control strategy module formulates a control strategy of the cutting force based on the fluctuation abnormality and the response abnormality; and the control instruction module is used for executing the control strategy and controlling the cutting force of the drill bit. The application realizes accurate identification of the cutting force abnormality and improves the cutting force control precision and stability in the gear shaft drilling process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of gear shaft machining, and in particular to a gear shaft drilling and cutting force control system. BACKGROUND

[0002] In the machining process of a gear shaft, drilling is a key process, and the machining quality will affect the subsequent transmission performance and assembly accuracy. The cutting force generated during drilling reflects the workpiece material state, tool wear condition, chip discharge condition and other factors, and is one of the core parameters affecting the stability of hole machining and the service life of the tool. Abnormal changes in the cutting force are not always sudden events, but show a certain evolution trend. Existing systems mostly rely on threshold triggering mechanisms, which are difficult to identify early features of abnormal evolution in a timely manner, leading to misjudgment, missed judgment or delayed intervention. Existing control systems mainly focus on data threshold judgment based on a single time point, and lack continuous identification and analysis of the rhythm change trend in the cutting process. This judgment method is difficult to identify early potential abnormalities.

[0003] In addition, the compensation control mechanism of the existing scheme for abnormal working conditions is still rough. In most cases, even if the system detects abnormal fluctuations or response delays, it often uses a unified speed reduction process, and fails to intervene based on the severity and type of abnormal trends, making it difficult to balance response speed and control accuracy, and prone to problems such as reaction lag or excessive intervention, resulting in unstable cutting force control or ineffective intervention.

[0004] A metal shell dangerous goods drilling method is disclosed in a Chinese patent with the authorization announcement number CN103752895B. The metal shell dangerous goods drilling system used in the method includes an anti-explosion chamber, a drilling main machine located in the anti-explosion chamber, a control chamber, and a control system located in the control chamber. The drilling main machine is provided with an axial feed drill bit. The control chamber is isolated from the anti-explosion chamber. The control system is connected to control the drilling main machine, and the control system includes a controller and a detection device that detects the axial force of the drill bit in real time. When the detection device detects a sharp drop in the axial force of the drill bit, the controller controls the drill bit to stop drilling. This scheme controls the entire drilling process by real-time monitoring of the axial force of the drill bit, making the drilling more accurate and improving the degree of automation.

[0005] A drilling method and drilling system based on ultrasonic assisted thermoplastic are disclosed in a Chinese patent application with the publication number CN116197434A. The method includes: controlling the drilling system to rotate at a preset speed and ultrasonic vibrate at a preset amplitude; and controlling the drilling system to move towards a workpiece to drill the workpiece. This scheme can reduce the machining force of the drilling system, facilitate chip removal during hole formation, and prolong the service life of the thermoplastic drill of the drilling system.

[0006] The above prior art all have the problem of the background art: it is difficult to identify early potential abnormalities in the drilling process.

[0007] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general context of the application. It should not be taken as an acknowledgement or any form of suggestion that this information forms part of the prior art. SUMMARY

[0008] The technical problem to be solved by the present application is to overcome the defects of the prior art, and to provide a gear shaft drilling cutting force control system that can accurately identify cutting force abnormalities and improve the cutting force control accuracy and stability during the gear shaft drilling process.

[0009] To solve the above technical problems, the present application provides the following technical solutions:

[0010] A gear shaft drilling cutting force control system, comprising a data acquisition module, a first identification module, a second identification module, a control strategy module, and a control instruction module; wherein:

[0011] The data acquisition module is used to continuously acquire the cutting force of the drill bit and the working parameters of the machine tool;

[0012] The first identification module is used to construct a rhythm shift chain of the cutting force and identify cutting force fluctuation abnormalities based on the rhythm shift chain;

[0013] The second identification module is used to calculate a lag index between the cutting force and the working parameters and identify cutting force response abnormalities based on the lag index;

[0014] The control strategy module formulates a cutting force control strategy based on the cutting force fluctuation abnormalities and response abnormalities;

[0015] The control instruction module is used to execute the control strategy and control the cutting force of the drill bit by adjusting the feed speed and rotational speed of the drill bit.

[0016] As a preferred solution of the gear shaft drilling cutting force control system described in the present application, the first identification module comprises a rhythm detection unit; the rhythm detection unit is used to construct a rhythm shift chain of the cutting force, specifically including:

[0017] Continuously acquire the cutting force; construct and real-time update the time series of the cutting force;

[0018] Divide the time series of the cutting force into consecutive time windows; each time window contains the cutting force at M time points; M is a positive integer;

[0019] Calculate the time sequence characteristics of the cutting force in each time window respectively; arrange each time sequence characteristic of the cutting force in each time window as a feature vector of each time window;

[0020] Mark the time window containing the latest M moments of the cutting force as a target time window; mark the two time windows closest to the target time window as a first reference time window and a second reference time window respectively; wherein the first reference time window is adjacent to the target time window;

[0021] Update or reconstruct the rhythm offset chain based on the feature vectors of the target time window, the first reference time window and the second reference time window.

[0022] As a preferred scheme of the control system of the gear shaft drilling cutting force described in the present application, wherein: the update or reconstruction of the rhythm offset chain comprises:

[0023] Determine whether the cutting force of the target time window has rhythm offset based on the feature vector;

[0024] If the cutting force of the target time window has rhythm offset, create a rhythm offset point based on the target time window, comprising: mark the moment corresponding to the latest collected cutting force in the target time window as the time stamp of the rhythm offset point; calculate the rhythm difference value of the rhythm offset point; the rhythm difference value is the similarity between the feature vector of the target time window and the feature vector of the reference time window; the reference time window is the time window closest to the target time window among the time windows before the target time window and not having rhythm offset;

[0025] Update or reconstruct the rhythm offset chain based on the rhythm offset point corresponding to the target time window.

[0026] As a preferred scheme of the control system of the gear shaft drilling cutting force described in the present application, wherein: the determination of whether the cutting force of the target time window has rhythm offset based on the feature vector specifically comprises:

[0027] Select a time sequence characteristic from the feature vector as a target time sequence characteristic; calculate the change direction of the target time sequence characteristic between the target time window and the first reference time window as a first change direction; calculate the change direction of the target time sequence characteristic between the first reference time window and the second reference time window as a second change direction;

[0028] Calculate the similarity between the feature vector of the target time window and the feature vector of the first reference time window as a first change amplitude; calculate the similarity between the feature vector of the first reference time window and the feature vector of the second reference time window as a second change amplitude;

[0029] If the first change direction and the second change direction are opposite, or the first change amplitude is greater than the second change amplitude, the cutting force of the target time window has rhythm offset.

[0030] As a preferred scheme of the gear shaft drilling cutting force control system, the first identification module further comprises a first identification unit.

[0031] The first identification unit is configured with a first identification strategy, which is used to identify the fluctuation anomaly of the cutting force, and specifically comprises:

[0032] If the number of rhythm offset points contained in the rhythm offset chain is greater than the preset offset point threshold, the rhythm difference value of each rhythm offset point is sorted into a rhythm difference value sequence according to the arrangement order of the rhythm offset point in the rhythm offset chain.

[0033] The rhythm difference value sequence is linearly fitted to obtain a fitting slope; if the fitting slope is greater than a preset fluctuation increasing threshold, the cutting force has a fluctuation anomaly.

[0034] As a preferred scheme of the gear shaft drilling cutting force control system, the working parameter is any one of the spindle current and the motor torque; the second identification module comprises a lag calculation unit and a second identification unit.

[0035] The lag calculation unit is used to calculate a lag index between the cutting force and the working parameter.

[0036] The second identification unit is configured with a second identification strategy, which is used to identify the response anomaly of the cutting force, and specifically comprises: if the lag index is greater than a preset lag index threshold, the response anomaly of the cutting force.

[0037] As a preferred scheme of the gear shaft drilling cutting force control system, the lag calculation unit calculates a lag index between the cutting force and the working parameter, and specifically comprises:

[0038] The working parameter is continuously collected; a time sequence of the working parameter is constructed and updated in real time; the time sequence of the cutting force is time-aligned with the time sequence of the working parameter.

[0039] A cutting force sequence segment is intercepted from the time sequence of the cutting force; a working parameter sequence segment corresponding to the cutting force sequence segment in time is intercepted from the time sequence of the working parameter.

[0040] The change rate of the cutting force at each time in the cutting force sequence segment is calculated; the change rate of the working parameter at each time in the working parameter sequence segment is calculated.

[0041] The starting point of the change rate of the cutting force in the cutting force sequence segment, which continuously increases, is detected as the change trend starting point; the starting point of the change rate of the working parameter in the working parameter sequence segment, which continuously increases, is detected as the response trend starting point.

[0042] The time difference between the response trend starting point and the change trend starting point is calculated as a hysteresis index between the cutting force and the working parameter.

[0043] As a preferred solution of the control system of the gear shaft drilling cutting force described in the present application, wherein: the control strategy module comprises a first control unit; the control strategy comprises a first control strategy;

[0044] The first control strategy is used to control the feed speed of the drill bit; the first control unit formulates the first control strategy based on the fluctuation anomaly of the cutting force, specifically including:

[0045] If there is a fluctuation anomaly in the cutting force, the increase amplitude of the rhythm difference value between any two adjacent rhythm offset points in the rhythm difference value sequence is calculated; that is, the rhythm difference value of the rhythm offset point with the later timestamp is subtracted from the rhythm difference value of the rhythm offset point with the earlier timestamp to obtain the increase amplitude of the rhythm difference value;

[0046] The average increase amplitude of the rhythm difference value is calculated; the average increase amplitude is the average of the increase amplitudes of the rhythm difference values between all adjacent rhythm offset points in the rhythm difference value sequence;

[0047] The value range of the feed speed adjustment amount is set; the feed speed adjustment amount is assigned within the value range of the feed speed adjustment amount based on the average increase amplitude of the rhythm difference value, and the greater the average increase amplitude, the greater the feed speed adjustment amount.

[0048] As a preferred solution of the control system of the gear shaft drilling cutting force described in the present application, wherein: the control strategy module further comprises a second control unit; the control strategy further comprises a second control strategy; the second control strategy is used to control the rotational speed of the drill bit; the second control unit formulates the second control strategy based on the response anomaly of the cutting force, specifically including:

[0049] If there is a response anomaly in the cutting force, the difference between the hysteresis index between the cutting force and the working parameter and the hysteresis index threshold value is calculated as a response degradation index;

[0050] The value range of the spindle speed adjustment amount is set; the spindle speed adjustment amount is assigned within the value range of the spindle speed adjustment amount based on the response degradation index, and the greater the response degradation index, the greater the spindle speed adjustment amount.

[0051] As a preferred solution of the control system of the gear shaft drilling cutting force described in the present application, wherein: the control strategy module further comprises a third control unit; the control strategy further comprises a control compensation strategy; the control compensation strategy is used to compensate and adjust the first control strategy and the second control strategy; the third control unit is used to formulate the control compensation strategy, specifically including:

[0052] If the cutting force has both fluctuation abnormality and response abnormality, the real-time feed speed is obtained, and the adjusted feed speed is pre-calculated based on the feed speed adjustment amount as the target feed speed; the real-time spindle speed is obtained, and the adjusted spindle speed is pre-calculated based on the spindle speed adjustment amount as the target spindle speed;

[0053] The coupling ratio of the drilling processing speed is calculated; the coupling ratio is the ratio of the target feed speed to the target spindle speed;

[0054] The effective value range of the coupling ratio is set; if the coupling ratio is not located within the effective value range, the feed speed adjustment amount or the spindle speed adjustment amount is adjusted and the coupling ratio is recalculated until the coupling ratio is located within the effective value range.

[0055] Compared with the prior art, the application has the following beneficial effects:

[0056] By constructing the rhythm offset chain and monitoring the hysteresis index of the cutting force and the working parameter, the time sequence change trend of the cutting force and the system response can be continuously monitored, the traditional abnormality monitoring mode depending on the instantaneous threshold is broken through, the process of the evolution of the cutting force from the steady state to the abnormality is identified, and the dynamic abnormality trend distinguishing ability is achieved.

[0057] The feed speed and the spindle speed are dynamically adjusted according to the abnormality trend, and the linkage control relationship between the two is coordinated, so that the over-regulation or the steady state imbalance of different parameter adjustments is avoided, the stability of the cutting force regulation action is ensured, and the processing quality of the gear shaft drilling is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0059] Figure 1 A structural schematic diagram of a gear shaft drilling cutting force control system provided by the application;

[0060] Figure 2 A functional schematic diagram of a gear shaft drilling cutting force control system provided by the application. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solutions of the present application, but not limitations of the technical solutions of the present application. In the case of no conflict, the technical features in the embodiments and the embodiments can be combined with each other.

[0062] The present embodiment introduces a control system for drilling and cutting force of gear shaft, referring to Figure 1 The system comprises a data acquisition module, a first identification module, a second identification module, a control strategy module and a control instruction module.

[0063] The functions of each module are shown in Figure 2 , wherein:

[0064] The data acquisition module is used for continuously acquiring the cutting force of the drill bit and the working parameters of the machine tool.

[0065] The data acquisition module comprises a first detection unit and a second detection unit.

[0066] The first detection unit is used for acquiring the cutting force of the drill bit. The cutting force is the cutting resistance of the drill bit to the contact area of the drill bit and the gear shaft workpiece.

[0067] The second detection unit is used for acquiring the working parameters of the machine tool. The working parameters are any one of the spindle current and the motor torque.

[0068] The first identification module is used for constructing the rhythm offset chain of the cutting force, and identifying the fluctuation anomaly of the cutting force based on the rhythm offset chain.

[0069] The first identification module comprises a rhythm detection unit and a first identification unit.

[0070] The rhythm detection unit is used for constructing the rhythm offset chain of the cutting force, specifically comprising:

[0071] Continuously acquiring the cutting force; constructing and real-time updating the time sequence of the cutting force;

[0072] Dividing the time sequence of the cutting force into continuous time windows; each time window contains the cutting force at M time points; M is a positive integer;

[0073] Calculating the time sequence features of the cutting force in each time window respectively; arranging each time sequence feature of the cutting force in each time window into a feature vector of each time window.

[0074] Optionally, the time sequence characteristics of the cutting force in any time window include the mean, range, standard deviation, skewness, kurtosis of the cutting force in the time window. These time sequence characteristics reflect the magnitude and variation of the cutting force in each time window, for example, the range and standard deviation reflect the fluctuation of the cutting force; the skewness reflects the trend direction of the cutting force; and the kurtosis reflects the extreme degree of the cutting force.

[0075] The time window containing the latest M moments of the cutting force is marked as a target time window; the two time windows closest to the target time window are marked as a first reference time window and a second reference time window, respectively; wherein the first reference time window is adjacent to the target time window;

[0076] In this embodiment, the target time window, the first reference time window and the second reference time window are three consecutive time windows in the time sequence of the cutting force; the second reference time window appears earliest in the time sequence, i.e. the cutting force contained corresponds to the earliest moment; the first reference time window is located in the middle of the other two; and the target time window contains the latest M cutting forces.

[0077] The rhythm shift chain is updated or reconstructed based on the feature vectors of the target time window, the first reference time window and the second reference time window; specifically including:

[0078] Based on the feature vector, it is determined whether the cutting force of the target time window has a rhythm shift; specifically including:

[0079] From the feature vector, a time sequence characteristic is selected as a target time sequence characteristic; the change direction of the target time sequence characteristic between the target time window and the first reference time window is calculated as a first change direction; and the change direction of the target time sequence characteristic between the first reference time window and the second reference time window is calculated as a second change direction.

[0080] The similarity between the feature vector of the target time window and the feature vector of the first reference time window is calculated as a first change amplitude; and the similarity between the feature vector of the first reference time window and the feature vector of the second reference time window is calculated as a second change amplitude.

[0081] If the first change direction and the second change direction are opposite, or the first change amplitude is greater than the second change amplitude, the cutting force of the target time window has a rhythm shift.

[0082] For example, if the first change direction of the selected target time sequence feature is increasing (i.e., the target time sequence feature increases compared with the first reference time window), and the second change direction is decreasing, the change trend of the target time sequence feature changes, and the time sequence feature in the target time window is offset compared with the previous time window. Alternatively, the first change direction and the second change direction of each time sequence feature are calculated, and if the first change direction and the second change direction of at least N time sequence features are opposite, the cutting force of the target time window has a rhythm offset. Alternatively, the cosine similarity between the feature vectors is calculated as the similarity; if the first change amplitude is greater than the second change amplitude, it indicates that the fluctuation trend of the feature vector in the target time window is more significant compared with the previous time window, and the cutting force of the target time window has a rhythm offset.

[0083] If the cutting force of the target time window has a rhythm offset, a rhythm offset point is created based on the target time window, including: marking the time corresponding to the latest collected cutting force in the target time window as the timestamp of the rhythm offset point; calculating the rhythm difference value of the rhythm offset point; the rhythm difference value is the similarity between the feature vector of the target time window and the feature vector of the reference time window; the reference time window is the time window closest to the target time window among the time windows before the target time window and not having a rhythm offset.

[0084] The rhythm offset chain is updated or reconstructed based on the rhythm offset point corresponding to the target time window. Alternatively, the method for updating or reconstructing the rhythm offset chain is as follows:

[0085] If the current rhythm offset chain exists, the time difference between the rhythm offset point corresponding to the target time window and the last rhythm offset point in the rhythm offset chain is calculated based on the timestamp; if the time difference is less than a preset time difference threshold, the rhythm offset point corresponding to the target time window is added to the rhythm offset chain; otherwise, the current rhythm offset chain is deleted, a new rhythm offset chain is created, and the rhythm offset point corresponding to the target time window is taken as the first rhythm offset point in the rhythm offset chain. The rhythm offset chain is an ordered sequence of rhythm offset points that appear continuously or close in time order in the drilling process; those skilled in the art can set the time difference threshold according to experience or actual needs, for example, the time difference threshold is set to 3 times the length of the time window; when the time difference between two rhythm offset points is large, it is considered that the rhythm offset of the cutting force has not been sustained, and the comparison value between the old rhythm offset point and the newly established rhythm offset point is not great, and the original rhythm offset chain is interrupted.

[0086] The first identification unit is configured with a first identification strategy; the first identification strategy is used to identify the fluctuation anomaly of the cutting force, and specifically includes:

[0087] If the number of rhythm offset points included in the rhythm offset chain is greater than the preset offset point threshold, the rhythm difference value of each rhythm offset point is sorted into a rhythm difference value sequence according to the arrangement order of the rhythm offset point in the rhythm offset chain.

[0088] The rhythm difference value sequence is linearly fitted to obtain a fitting slope; if the fitting slope is greater than a preset fluctuation increasing threshold, the cutting force has abnormal fluctuation.

[0089] When the length of the rhythm offset chain is long, that is, the number of rhythm offset points included is greater than the offset point threshold, it is detected that the rhythm difference value of the rhythm offset point has a significant increasing trend, and the cutting force has a sustained abnormal fluctuation, and the abnormal fluctuation has a deterioration trend. By constructing the rhythm offset chain, potential abnormal trends such as material hard points, chip accumulation or drill wear caused by abnormal fluctuations can be detected to intervene and adjust in time.

[0090] The second identification module is used to calculate a hysteresis index between the cutting force and the working parameter, and identify a response abnormality of the cutting force based on the hysteresis index;

[0091] The second identification module includes a hysteresis calculation unit and a second identification unit.

[0092] The hysteresis calculation unit is used to calculate a hysteresis index between the cutting force and the working parameter; specifically including:

[0093] The working parameter is continuously collected; a time sequence of the working parameter is constructed and updated in real time; the time sequence of the cutting force is time-aligned with the time sequence of the working parameter;

[0094] A cutting force sequence segment is intercepted from the time sequence of the cutting force; a working parameter sequence segment corresponding to the cutting force sequence segment in time is intercepted from the time sequence of the working parameter; optionally, the cutting force sequence segment includes the cutting force at the last m time points, and the time points of the working parameters in the working parameter sequence segment correspond to the time points of the cutting forces in the cutting force sequence segment one by one. m is a positive integer.

[0095] The change rate of the cutting force at each time point in the cutting force sequence segment is calculated; the change rate of the working parameter at each time point in the working parameter sequence segment is calculated;

[0096] The starting point of the continuously increasing rate of change of the cutting force in the cutting force sequence segment is detected as the change trend starting point; the starting point of the continuously increasing rate of change of the working parameter in the working parameter sequence segment is detected as the response trend starting point; optionally, if the rate of change of the cutting force or the working parameter at at least n consecutive time points continuously increases, the first time point in the n consecutive time points is marked as the corresponding change trend starting point or response trend starting point. n is a positive integer. Before detecting the rate of change, the cutting force sequence segment and the working parameter sequence segment are filtered and denoised.

[0097] The time difference between the response trend starting point and the change trend starting point is calculated as the lag index between the cutting force and the working parameter.

[0098] The second identification unit is configured with a second identification strategy; the second identification strategy is used to identify the response anomaly of the cutting force, specifically including: if the lag index is greater than a preset lag index threshold, the response anomaly of the cutting force.

[0099] Optionally, the cutting force and the working parameter are synchronously collected under normal working conditions, and the lag index is calculated multiple times to obtain the value range of the lag index under normal working conditions, and then the lag index threshold is set. When the lag index is greater than the lag index threshold, the working parameter fails to respond to the rise of the cutting force in time, that is, the lag response phenomenon caused by heat accumulation, chip blockage or drill wear, etc. When there are heat accumulation, chip blockage or drill wear, etc. Abnormal, the efficiency of the servo drive system used for drilling processing in automatically sensing and responding to load changes is affected, which is manifested as the abnormal increase of the lag time of the cutting force and the working parameters such as spindle current and motor torque.

[0100] In actual production, the diameter of the hole corresponding to the hydraulic or lubricating oil circuit is less than 1.5mm; when machining such holes, the precision requirement is not high, but the drill is easy to break; the broken drill is not easy to take out from the part, which leads to the failure to continue processing, resulting in waste parts. The first identification strategy and the second identification strategy can identify the abnormal situation of the cutting force in the early stage of the development of the abnormal situation of the drill such as chip extrusion, drill blade collapse, drill wear, etc., so as to take timely intervention measures, effectively prevent the drill from breaking, and reduce the scrap rate.

[0101] For the machining of holes with high machining precision requirements and low drill breakage risk, the control strategy module of the present application scheme can also control the abnormal situation of the cutting force through the control strategy formulated by the control strategy module to automatically restore the cutting force to normal, so as to ensure the machining precision.

[0102] The control strategy module formulates the control strategy of the cutting force based on the fluctuation anomaly and the response anomaly of the cutting force;

[0103] The control strategy module comprises a first control unit, a second control unit and a third control unit;

[0104] The control strategy comprises a first control strategy, a second control strategy and a control compensation strategy.

[0105] The first control strategy is used to control the feed speed of the drill bit; the first control unit formulates the first control strategy based on fluctuation abnormalities of the cutting force, and specifically comprises:

[0106] If there are fluctuation abnormalities of the cutting force, the increase of the rhythm difference value between any two adjacent rhythm offset points in the rhythm difference value sequence is calculated; that is, the rhythm difference value of the rhythm offset point with the later timestamp is subtracted from the rhythm difference value of the rhythm offset point with the earlier timestamp to obtain the increase of the rhythm difference value.

[0107] The average increase of the rhythm difference value is calculated; the average increase is the average of the increases of the rhythm difference values between all adjacent rhythm offset points in the rhythm difference value sequence.

[0108] The value range of the feed speed adjustment amount is set; the feed speed adjustment amount is assigned within the value range of the feed speed adjustment amount based on the average increase of the rhythm difference value, and the greater the average increase, the greater the feed speed adjustment amount.

[0109] The value range of the feed speed adjustment amount is set through industry experience, so that when the feed speed adjustment amount is assigned within its value range and the feed speed of the drill bit is further adjusted, the fluctuation abnormalities of the cutting force can be inhibited without over-adjustment. The greater the average increase of the rhythm difference value, the more significant the fluctuation abnormalities of the cutting force, and the greater the feed speed adjustment amount.

[0110] The fluctuation abnormalities of the cutting force are manifested as frequent and dramatic changes in the cutting load during the drilling process. Multiple mutations of the drill bit stress can easily cause local cutting force peak value to rise, drill bit to vibrate and thermal expansion to intensify, and wear to accelerate, etc. Through the regulation and control of the first control strategy, the present application appropriately reduces the feed speed, prolongs the processing time of the unit feed distance, makes the cutting process more stable, reduces the cutting disturbance intensity per unit time, and thus inhibits the drilling processing abnormalities.

[0111] The second control strategy is used to control the rotation speed of the drill bit; the second control unit formulates the second control strategy based on response abnormalities of the cutting force, and specifically comprises:

[0112] If there are response abnormalities of the cutting force, the difference between the hysteresis index between the cutting force and the working parameter and the hysteresis index threshold value is calculated as a response degradation index.

[0113] set a value range of the spindle speed adjustment amount; based on the response deterioration index, the spindle speed adjustment amount is assigned within the value range of the spindle speed adjustment amount, and the greater the response deterioration index, the greater the spindle speed adjustment amount.

[0114] The value range of the spindle speed adjustment amount is set through industry experience, so that when the spindle speed adjustment amount is assigned within its value range and used to adjust the spindle speed, the final speed of the drill bit is adjusted, which can suppress the response abnormality of the cutting force and not over-adjust. The greater the response deterioration index, the more significant the response abnormality of the cutting force, and the greater the spindle speed adjustment amount.

[0115] When the response abnormality of the cutting force is caused by heat accumulation, material hard points, mechanical hysteresis, etc., the response of the servo drive system to the load change of the drill bit becomes slower, which easily causes the error inertia to increase, causing the automatic control of the servo drive system to fail. Through the control of the second control strategy, the spindle speed is appropriately increased, the speed of the drill bit is increased, and the cutting frequency per unit time is increased, which can improve the response sensitivity of the system to load changes and improve the heat dissipation speed, and suppress the error amplification caused by response lag.

[0116] The control compensation strategy is used to compensate and adjust the first control strategy and the second control strategy; the third control unit is used to formulate the control compensation strategy, specifically including:

[0117] If the cutting force has both fluctuation abnormality and response abnormality, the real-time feed speed is obtained, and the adjusted feed speed is pre-calculated based on the feed speed adjustment amount as the target feed speed; the real-time spindle speed is obtained, and the adjusted spindle speed is pre-calculated based on the spindle speed adjustment amount as the target spindle speed;

[0118] Calculate the coupling ratio of the drilling speed; the coupling ratio is the ratio of the target feed speed to the target spindle speed;

[0119] Set the effective value range of the coupling ratio; if the coupling ratio is not within the effective value range, adjust the feed speed adjustment amount or the spindle speed adjustment amount and recalculate the coupling ratio until the coupling ratio is within the effective value range.

[0120] According to the industry experience, the effective value range of the coupling ratio is set to avoid over-adjustment of the feed speed or the spindle speed, imbalance between the cutting trajectory line speed of the drill bit and the feed step, and unstable local cutting state. Optionally, the severity of the cutting force fluctuation anomaly and the response anomaly is measured based on the mean amplitude of the rhythm difference value and the size of the response degradation index; for example, the mean amplitude of the rhythm difference value and the response degradation index are normalized and dimensionless, respectively; if the mean amplitude of the rhythm difference value is greater than λ times the response degradation index, it is considered that the fluctuation anomaly is more serious, the feed speed adjustment amount in the first control strategy is kept unchanged, and the spindle speed adjustment amount is adjusted until the coupling ratio falls within the effective value range. λ is an empirical adjustment factor, and its value is determined by a person skilled in the art based on experience or a large number of experiments.

[0121] The control instruction module is configured to execute the control strategy to control the cutting force of the drill bit by adjusting the feed speed and the rotation speed of the drill bit, and specifically includes: generating a first control instruction containing a feed speed adjustment amount based on the first control strategy; generating a second control instruction containing a spindle speed adjustment amount based on the second control strategy; sending the first control instruction and the second control instruction to the execution mechanism of the machine tool; and the execution mechanism of the machine tool executes the first control instruction and the second control instruction to adjust the feed speed and the spindle speed of the drill bit, thereby realizing the control of the cutting force of the drill bit and eliminating the fluctuation anomaly and the response anomaly, and keeping the cutting force within a reasonable range. The execution mechanism of the machine tool includes a feed mechanism, such as a lead screw and a servo motor, which can control the feed speed of the drill bit; the execution mechanism also includes a spindle mechanism, such as a motor and a transmission device, which can adjust the rotation speed of the drill bit by controlling the spindle speed.

[0122] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0123] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above-described specific embodiments, which are only illustrative and not limiting. Those skilled in the art can make many forms without departing from the purpose and scope of the present application under the inspiration of the present application, and these are all within the protection of the present application.

Claims

1. A system for controlling the drilling force of a gear shaft, characterized by: The system comprises a data acquisition module, a first identification module, a second identification module, a control strategy module, and a control instruction module. The data acquisition module is configured to continuously acquire the cutting force of the drill bit and the working parameters of the machine tool. The first identification module is configured to construct a rhythm deviation chain of the cutting force and identify fluctuation abnormalities of the cutting force based on the rhythm deviation chain. The first identification module comprises a rhythm detection unit configured to construct the rhythm deviation chain, specifically comprising: continuously acquiring the cutting force, constructing and updating a time series of the cutting force in real time; dividing the time series of the cutting force into continuous time windows, each time window containing the cutting force at M time points, M being a positive integer; calculating the time sequence features of the cutting force in each time window respectively, and arranging each time sequence feature of the cutting force in each time window into a feature vector of each time window; marking the time window containing the cutting force at the latest M time points as a target time window, and marking the two time windows closest to the target time window as a first reference time window and a second reference time window respectively, wherein the first reference time window is adjacent to the target time window; updating or reconstructing the rhythm deviation chain based on the feature vectors of the target time window, the first reference time window, and the second reference time window; The second identification module is configured to calculate a lag index between the cutting force and the working parameters, and identify response abnormalities of the cutting force based on the lag index. The control strategy module formulates a control strategy for the cutting force based on the fluctuation abnormalities and the response abnormalities of the cutting force. The control instruction module is configured to execute the control strategy by adjusting the feed rate and rotational speed of the drill bit to control the cutting force of the drill bit.

2. A system for controlling the cutting forces of a gear shaft drilling according to claim 1, characterized in that: The updating or reconstructing of the rhythm deviation chain comprises: determining whether the cutting force of the target time window has a rhythm deviation based on the feature vectors; if the cutting force of the target time window has a rhythm deviation, creating a rhythm deviation point based on the target time window, including: marking the time point corresponding to the latest acquired cutting force in the target time window as the time stamp of the rhythm deviation point; calculating the rhythm difference value of the rhythm deviation point; the rhythm difference value is the similarity between the feature vector of the target time window and the feature vector of a reference time window; the reference time window is the time window closest to the target time window among the time windows before the target time window and not having a rhythm deviation; updating or reconstructing the rhythm deviation chain based on the rhythm deviation point corresponding to the target time window.

3. A system for controlling the cutting forces of a gear shaft drilling according to claim 2, characterized in that: The determination of whether the cutting force of the target time window has a rhythm deviation based on the feature vectors specifically comprises: selecting a time sequence feature from the feature vectors as a target time sequence feature; calculating the change direction of the target time sequence feature between the target time window and the first reference time window as a first change direction; calculating the change direction of the target time sequence feature between the first reference time window and the second reference time window as a second change direction; calculating the similarity between the feature vector of the target time window and the feature vector of the first reference time window as a first change amplitude; calculating the similarity between the feature vector of the first reference time window and the feature vector of the second reference time window as a second change amplitude; If the first change direction is opposite to the second change direction, or the first change amplitude is greater than the second change amplitude, the cutting force of the target time window exists rhythm deviation.

4. A system for controlling the cutting forces of a gear shaft drilling according to claim 3, characterized in that: The first identification module further includes a first identification unit; The first identification unit is configured with a first identification strategy; the first identification strategy is used to identify the fluctuation anomaly of the cutting force, and specifically includes: If the number of rhythm deviation points contained in the rhythm deviation chain is greater than a preset deviation point threshold, the rhythm difference values of each rhythm deviation point are arranged into a rhythm difference value sequence according to the arrangement order of the rhythm deviation points in the rhythm deviation chain; The rhythm difference value sequence is linearly fitted to obtain a fitting slope; if the fitting slope is greater than a preset fluctuation increasing threshold, the cutting force has a fluctuation anomaly.

5. A system for controlling the cutting forces of a gear shaft drilling according to claim 4, characterized in that: The working parameter is any one of the spindle current and the motor torque; the second identification module includes a lag calculation unit and a second identification unit; The lag calculation unit is used to calculate a lag index between the cutting force and the working parameter; The second identification unit is configured with a second identification strategy; The second identification strategy is used to identify the response anomaly of the cutting force, and specifically includes: if the lag index is greater than a preset lag index threshold, the response anomaly of the cutting force.

6. A system for controlling the cutting forces of a gear shaft drilling operation as set forth in claim 5, characterized in that: The lag calculation unit calculates a lag index between the cutting force and the working parameter, and specifically includes: The working parameter is continuously collected; a time sequence of the working parameter is constructed and updated in real time; the time sequence of the cutting force is time-aligned with the time sequence of the working parameter; A cutting force sequence segment is intercepted from the time sequence of the cutting force; a working parameter sequence segment corresponding to the cutting force sequence segment in time is intercepted from the time sequence of the working parameter; The change rate of the cutting force at each time in the cutting force sequence segment is calculated; the change rate of the working parameter at each time in the working parameter sequence segment is calculated; The starting point of the change rate of the cutting force in the cutting force sequence segment, at which the change rate continuously increases, is detected as a change trend starting point; the starting point of the change rate of the working parameter in the working parameter sequence segment, at which the change rate continuously increases, is detected as a response trend starting point; The time difference between the response trend starting point and the change trend starting point is calculated as the lag index between the cutting force and the working parameter.

7. A system for controlling the cutting forces of a gear shaft drilling according to claim 6, characterized in that: The control strategy module includes a first control unit; the control strategy includes a first control strategy; The first control strategy is used to control the feed speed of the drill bit; The first control unit formulates the first control strategy based on the fluctuation anomaly of the cutting force, and specifically includes: If the cutting force has a fluctuation anomaly, the amplitude of the rhythm difference value of any two adjacent rhythm deviation points in the rhythm difference value sequence is calculated; that is, the rhythm difference value of the rhythm deviation point with the later time stamp is subtracted from the rhythm difference value of the rhythm deviation point with the earlier time stamp to obtain the amplitude of the rhythm difference value; The mean amplitude of the rhythm difference value is calculated; the mean amplitude is the mean of the amplitudes of the rhythm difference values between all adjacent rhythm deviation points in the rhythm difference value sequence; A value range of the feed speed adjustment amount is set; the feed speed adjustment amount is valued within the value range of the feed speed adjustment amount based on the mean amplitude of the rhythm difference value, and the greater the mean amplitude, the greater the feed speed adjustment amount.

8. A system for controlling the cutting forces of a gear shaft drilling according to claim 7, characterized in that: The control strategy module further comprises a second control unit; the control strategy further comprises a second control strategy; the second control strategy is used for controlling the rotating speed of the drill bit; the second control unit formulates the second control strategy based on the response abnormality of the cutting force, and specifically comprises: If the cutting force has the response abnormality, a difference between a hysteresis index between the cutting force and the working parameter and the hysteresis index threshold value is calculated as a response degradation index; A value range of the spindle rotating speed adjustment amount is set; the spindle rotating speed adjustment amount is valued within the value range of the spindle rotating speed adjustment amount based on the response degradation index, and the greater the response degradation index is, the greater the spindle rotating speed adjustment amount is.

9. A system for controlling the cutting forces of a gear shaft drilling according to claim 8, characterized in that: The control strategy module further comprises a third control unit; the control strategy further comprises a control compensation strategy; the control compensation strategy is used for compensating and adjusting the first control strategy and the second control strategy; the third control unit is used for formulating the control compensation strategy, and specifically comprises: If the cutting force has the fluctuation abnormality and the response abnormality simultaneously, a real-time feed speed is obtained, and a pre-calculated adjusted feed speed based on the feed speed adjustment amount is obtained as a target feed speed; a real-time spindle rotating speed is obtained, and a pre-calculated adjusted spindle rotating speed based on the spindle rotating speed adjustment amount is obtained as a target spindle rotating speed; A coupling ratio of the drilling processing speed is calculated; the coupling ratio is a ratio of the target feed speed to the target spindle rotating speed; An effective value range of the coupling ratio is set; if the coupling ratio is not located within the effective value range, the feed speed adjustment amount or the spindle rotating speed adjustment amount is adjusted, and the coupling ratio is recalculated until the coupling ratio is located within the effective value range.

Images