Numerical control machine tool parameter optimization method and related device and program

Abstract

The embodiment of the invention provides a numerical control machine tool parameter optimization method, a related device and a program, and the method comprises the steps: obtaining a position instruction at a current moment, and the position instruction at least comprises a feeding speed; setting a following error alarm threshold value at the current moment at least according to the feeding speed at the current moment; and calculating the position following error of the current moment according to the position instruction of the current moment and the actual position, fed back by the machine tool, of the previous moment, and when the position following error of the current moment is larger than a following error alarm threshold value, enabling the machine tool to give an alarm and stop machining. As the following error alarm threshold value is set according to the feeding speed at the current moment, the machine tool cannot give an alarm when the following error is larger than the following error alarm threshold value due to the fact that the feeding speed is too high or too low, the machining continuity of the numerical control machine tool can be improved, and normal operation of the machine tool is guaranteed.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of CNC machine tools, and specifically to a CNC machine tool parameter optimization method and related devices and programs. Background Art

[0002] In the field of CNC machine tools, the servo drive system is an important functional component of CNC machine tools, and its control performance directly affects the processing performance of CNC machine tools. The servo control system is a closed-loop control system that achieves precise control of position, speed and torque through feedback control. The servo control system usually has a multi-control loop structure. The servo control system in CNC machine tools widely uses the three-closed-loop control technology of current loop, speed loop and position loop.

[0003] In a servo control system, for the control of the position loop, the position following error is the difference between the actual position and the set position. A large following error will cause the system to be unable to accurately track the set trajectory, affecting the accuracy of processing or motion. When the following error is greater than the following error threshold, the machine tool will alarm and stop processing. However, the existing CNC machine tool parameter adjustment method may cause the following error alarm to be frequently triggered, interfering with the normal operation of the machine tool. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a device and program related to a CNC machine tool parameter optimization method.

[0005] In a first aspect, the present application provides a method for optimizing parameters of a CNC machine tool, comprising: obtaining a position instruction at a current moment, wherein the position instruction includes at least a feed speed; setting a following error alarm threshold at a current moment at least according to the feed speed at a current moment; calculating a position following error at a current moment according to the position instruction at a current moment and an actual position at a previous moment fed back by the machine tool, and when the position following error at a current moment is greater than the following error alarm threshold, causing the machine tool to alarm and stop processing.

[0006] In the second aspect, the present application also provides a CNC machine tool parameter optimization device, including: a position instruction acquisition module, used to obtain the position instruction at the current moment, the position instruction at least includes a feed speed; an alarm threshold setting module, the alarm threshold setting module sets the following error alarm threshold at the current moment at least according to the feed speed at the current moment; a following error alarm module, the following error alarm module calculates the position following error at the current moment based on the position instruction at the current moment and the actual position at the previous moment feedback from the machine tool, and when the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing.

[0007] In a third aspect, the present application further provides a CNC machine tool control system, the parameters of which are optimized according to the CNC machine tool parameter optimization method described in the first aspect.

[0008] In a fourth aspect, the present application also provides a computer-readable storage medium, wherein the storage medium stores one or more computer instructions, and when the one or more computer instructions are executed, they are used to implement the steps of the CNC machine tool parameter optimization method as described in the first aspect.

[0009] In a fifth aspect, the present application further provides a computer program product, comprising a computer program, which, when executed, implements the steps of the CNC machine tool parameter optimization method as described in the first aspect.

[0010] The CNC machine tool parameter optimization method provided in the present application first obtains the position instruction at the current moment, wherein the position instruction includes at least the feed speed. After obtaining the feed speed at the current moment, a following error alarm threshold is set at least according to the feed speed at the current moment to avoid frequent alarms of the machine tool; the position following error at the current moment is calculated according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool, and when the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing. Since the following error alarm threshold is set according to the feed speed at the current moment, the machine tool alarms when the following error is greater than the following error alarm threshold due to the feed speed being too high or too low, thereby improving the continuity of CNC machine tool processing and ensuring the normal operation of the machine tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0012] Figure 1 It is a dynamic control system structure diagram of a numerical control system.

[0013] Figure 2 It is a schematic diagram of a machine tool control system provided by this application.

[0014] Figure 3 It is a flow chart of the CNC machine tool parameter optimization method provided by this application.

[0015] Figure 4 It is a schematic diagram of the relationship between the following error alarm threshold and the feed speed provided in this application.

[0016] Figure 5This is a test result diagram of the CNC machine tool parameter optimization method provided in an embodiment of the present application.

[0017] Figure 6 This is another test result diagram of the CNC machine tool parameter optimization method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0018] The processing of CNC machine tools is carried out under the control of the CNC system. The structure diagram of a dynamic control system of a CNC system is as follows: Figure 1 As shown. In the CNC system, the computer numerical control system (CNC, Computer Numerical Control) sends control instructions to the servo driver through the interface. After receiving these instructions, the servo driver drives the servo motor to perform corresponding movements. The servo motor is equipped with speed and position sensors, which serve as feedback links to monitor the operating status of the motor in real time and feed this information back to the CNC system. In this way, the CNC system can adjust the control instructions according to the feedback information, ensure the precise movement and positioning of the machine tool, and achieve precise control of the processing process.

[0019] As described in the background technology, the servo control system in CNC machine tools widely adopts the three-loop control technology of current loop, speed loop and position loop. For the control of the position loop, the position following error is the difference between the actual position and the set position. A large following error will cause the system to be unable to accurately track the set trajectory, affecting the accuracy of processing or movement. Therefore, during the processing of CNC machine tools, when the position following error is greater than the following error threshold, the machine tool will alarm and stop processing.

[0020] There are two reasons for the generation of following error. One is caused by the mechanical structure. For example, machine tool factors such as poor machine tool rigidity, low guide rail guidance accuracy, poor transmission pair transmission accuracy, etc. will affect the following accuracy of the CNC system. The other is caused by the system. Due to the delay of the CNC system interpolation cycle, there will inevitably be a following error. Following error is unavoidable.

[0021] In existing CNC machine tool control systems, since the following error is directly related to the position loop, and the position loop is usually adjusted using the PID algorithm (Proportional-Integral-Derivative), the adjustment of the following error threshold is usually more complicated. If the following error threshold is not set properly, the following error alarm may be triggered frequently, resulting in frequent interruptions of the machine tool's processing process and interfering with the normal operation of the machine tool.

[0022] A schematic diagram of a machine tool control system provided in this application is as follows Figure 2 As shown, the input position command X(S) is divided into two paths, one of which is the feedforward coefficient K fMultiply, and then pass through the integrator s, and compare with the position feedback signal of the previous cycle collected in the current cycle to obtain the error signal, which is compared with the position gain K p After multiplication, it is added to the signal passing through the proportional differential controller in the adder, and the sum is passed through an integrator 1 / s to obtain the output Y(s).

[0023] right Figure 2 The specific analysis of the model shown is as follows:

[0024] According to the model, the transfer function G(s) of the system is derived as follows:

[0025]

[0026] Let the position command function be X(t)=F·t, and its Laplace transform X(S) in the frequency domain is:

[0027]

[0028] The error ξ(S) = X(S) - Y(S) can be derived from the following formula:

[0029]

[0030] Performing inverse Laplace transform on the error in the time domain, the end point error ξ(t) is obtained as:

[0031]

[0032] When the system is in a steady state, that is, t tends to ∞, and K P >1, the following error ξ(t) is:

[0033]

[0034] It can be seen that at the position gain K P >1, the following error ξ(t) is proportional to the feed speed F. Therefore, the alarm caused by the servo control system when the following error is too large needs to take into account the speed of the system at that time. That is to say, the following error alarm threshold should increase with the increase of the feed speed F.

[0035] Therefore, an embodiment of the present application provides a method for optimizing CNC machine tool parameters to improve the continuity of CNC machine tool processing and ensure the normal operation of the machine tool. Figure 3 This is a flow chart of the CNC machine tool parameter optimization method provided by this application, refer to Figure 3 , the parameter optimization method comprises:

[0036] Step S10: Obtain the current position instruction, which at least includes the feed speed.

[0037] In CNC machining, especially the machining of complex shapes, the machine needs to move at a specific speed and trajectory to achieve precise machining. In the CNC machine tool parameter optimization method provided in the present application, the position instruction at least includes a feed speed, and the feed speed is the speed of the tool relative to the workpiece in the feed direction. The position instruction is the input of the position loop in the CNC machine tool. The command pulse sequence issued by the machine tool control system is processed by interpolation and the like to form the position instruction, and the position instruction can ensure that the tool moves to the correct position according to the predetermined path. After obtaining the position instruction, continue to execute step S20.

[0038] Step S20: Setting a following error alarm threshold at the current moment at least according to the current feed speed.

[0039] According to the deduction of a machine tool control system provided by the present application, it can be concluded that the following error alarm threshold should increase with the increase of the feed speed F. Therefore, setting the following error alarm threshold at the current moment according to the feed speed at the current moment can meet the processing accuracy of the CNC machine tool while avoiding frequent alarms of the machine tool that affect the continuity of the machine tool processing.

[0040] Specifically, if the feed speed at the current moment is less than or equal to the feed speed threshold, the following error alarm threshold at the current moment is set to the first alarm threshold; if the feed speed at the current moment is greater than the feed speed threshold, the following error alarm threshold at the current moment is set to the sum of the first alarm threshold and the second alarm threshold, wherein the second alarm threshold is proportional to the difference between the feed speed at the current moment and the feed speed threshold.

[0041] The feeding speed threshold is used to determine the feeding speed at the current moment. Figure 4 This is a schematic diagram of the relationship between the following error alarm threshold and the feed speed provided by this application, refer to Figure 4 When the feed speed at the current moment is less than or equal to the feed speed threshold, the following error alarm threshold at the current moment is set to the first alarm threshold, and the first alarm threshold is a fixed value, which can ensure the processing accuracy and processing continuity of the machine tool when the feed speed is low; when the feed speed at the current moment is greater than the feed speed threshold, the following error alarm threshold at the current moment is set to the sum of the first alarm threshold and the second alarm threshold, wherein the second alarm threshold is proportional to the difference between the feed speed at the current moment and the feed speed threshold. That is to say, when the feed speed is high, since the following error alarm threshold should increase with the increase of the feed speed F, it is necessary to increase the following error alarm threshold at the current moment with the increase of the feed speed at the current moment, so as to avoid frequent alarms of the machine tool affecting the continuity of the machine tool processing.

[0042] For example, the feed speed threshold is set to 40mm / s and the first alarm threshold is set to 1mm. If the feed speed at the current moment is 10mm / s, the following error alarm threshold is the first alarm threshold of 1mm. If the feed speed at the current moment is 80mm / s, the following error alarm threshold is the sum of the first alarm threshold and the second alarm threshold. The second alarm threshold is proportional to the difference between the feed speed at the current moment and the feed speed threshold. The difference is 80mm / s-40mm / s=40mm / s. The second alarm threshold is set to 1 / 40 (mm) of the difference, that is, the second alarm threshold at the current moment is 40*1 / 40 (mm)=1mm. The following error alarm threshold at the current moment is the sum of the first alarm threshold and the second alarm threshold, that is, 2mm.

[0043] In some specific embodiments, setting the following error alarm threshold at the current moment at least according to the feed speed at the current moment includes: setting a second alarm threshold according to the feed speed at the current moment and the position loop gain, wherein the second alarm threshold is inversely proportional to the position loop gain.

[0044] According to the conclusion derived from a machine tool control system provided by the present application, the following error ξ(t) is:

[0045]

[0046] It can be seen that the following error ξ(t) is related to the position loop gain K P Inversely proportional, that is, increasing the position loop gain K P It can effectively reduce the following error, but the rigidity of CNC machine tools is limited. Too high a gain will cause the system to lose its steady state and vibrate. Therefore, it is necessary to increase the position loop gain K as much as possible while ensuring that the machine tool does not vibrate. P It can be seen that the position loop gain K also needs to be considered when setting the following error alarm threshold. P Therefore, in some specific implementations, it is necessary to set a second alarm threshold according to the current feed speed and the position loop gain, wherein the second alarm threshold is inversely proportional to the position loop gain. In some specific implementations, the position loop gain is 70% to 80% of the position loop gain critical value, wherein the position loop gain critical value is the position loop gain when the machine tool vibrates.

[0047] Further, the step S20 sets the following error alarm threshold at the current moment according to at least the current feed speed, including: setting the following error alarm threshold at the current moment according to the current feed speed, the position loop gain and the feedforward gain, wherein the second alarm threshold is inversely proportional to the position loop gain. fIt is the coefficient of feedforward compensation in the machine tool control system. Feedforward compensation means to estimate the following error at the current moment and compensate a suitable feedforward value to improve the machining accuracy. However, the feedforward gain K f The setting needs to be cautious. If the feedforward compensation is too large, the entire control system will advance, that is, the position loop will overshoot, resulting in reduced machine tool stability and other problems.

[0048] For example, setting the feedforward gain K f =0, position loop gain K P =80, set the feed speed threshold to 40mm / s. If the current feed speed is 80mm / s, the following error alarm threshold is the second alarm threshold. The second alarm threshold is proportional to the difference between the current feed speed and the feed speed threshold. The difference is 80mm / s-40mm / s=40mm / s. Therefore, the second alarm threshold is set to 1 / 40 (mm) of the difference, that is, the second alarm threshold at the current moment is 40*1 / 40 (mm)=1mm. Because the second alarm threshold is inversely proportional to the position loop gain, when the position loop gain is increased, for example, the position loop gain K is set. P =100, the second alarm threshold at the current moment is 1*80 / 100=0.8mm. Under the above premise, if the feedforward gain K is set f =0.3, the second alarm threshold can be set to 0.8*(1-0.3)=0.56mm.

[0049] Please continue to refer to Figure 3 After setting the following error alarm threshold at the current moment, continue to execute step S30.

[0050] Step S30: Calculate the position following error at the current moment according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool. When the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing.

[0051] The control system will collect the actual position of the tool at the previous moment at each current moment. However, due to factors such as delay caused by interpolation of the CNC machine tool control system, the actual position at the previous moment is not the same as the position at the current moment in the system, and there is a position following error between the two. Therefore, it is necessary to calculate the position following error at the current moment based on the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool, wherein the position following error at the current moment is the following error between the position of the tool at the current moment and the actual position at the previous moment, specifically, the position difference between the two. For example, when the actual position at the previous moment is 49.99mm and the position at the current moment is 50.04mm, the position following error at the current moment is the position difference between the two of 0.05mm.

[0052] According to the above content, the CNC machine tool parameter optimization method provided by the present application first obtains the position instruction at the current moment, and the position instruction at least includes the feed speed. After obtaining the feed speed at the current moment, a following error alarm threshold is set at least according to the feed speed at the current moment to avoid frequent alarms of the machine tool; the position following error at the current moment is calculated according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool. When the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing. Since the following error alarm threshold is set according to the feed speed at the current moment, the machine tool will not alarm when the following error is greater than the following error alarm threshold due to the feed speed being too high or too low. Therefore, the continuity of CNC machine tool processing can be improved and the normal operation of the machine tool can be ensured.

[0053] Furthermore, in the CNC machine tool parameter optimization method provided in the present application, taking into account the large range of variation of the feed speed, when the feed speed at the current moment is less than or equal to the feed speed threshold, the following error alarm threshold at the current moment is set to a fixed first alarm threshold, so as to ensure the machining accuracy and machining continuity of the machine tool when the feed speed is low; when the feed speed at the current moment is greater than the feed speed threshold, the following error alarm threshold at the current moment is set to the sum of the first alarm threshold and the second alarm threshold, wherein the second alarm threshold is proportional to the difference between the feed speed at the current moment and the feed speed threshold, that is, when the feed speed is high, the following error alarm threshold at the current moment increases with the increase of the feed speed at the current moment, so as to further improve the continuity of the machine tool machining.

[0054] To illustrate the effect of the CNC machine tool parameter optimization method provided in the embodiment of the present application, please refer to Figure 5 and Figure 6 .

[0055] Figure 5 This is a test result diagram of the CNC machine tool parameter optimization method provided in the embodiment of the present application. When testing, the test speed is set to 1000mm / min, and the acceleration is set to 2000mm / s in the parameter setting interface. 2 , s-curve time is 0.003, feedforward gain K f is 0, the position loop gain K P is 80. According to the above CNC machine tool parameter optimization method, the first alarm threshold AXFEMIN is set to 1 mm, and the second alarm threshold AXFEVEL is set to (VEL-40) / 40 (mm), where VEL is the feed speed in mm / s. The test results are as follows: Figure 5As shown, the maximum position following error is 0.949 mm, and the machine tool did not alarm during the test, ensuring the continuity of machine tool processing.

[0056] Figure 6 This is a test result diagram of the CNC machine tool parameter optimization method provided in the embodiment of the present application. When testing, the test speed is set to 1000mm / min, and the acceleration is set to 2000mm / s in the parameter setting interface. 2 , s-curve time is 0.003, feedforward gain K f is 0, the position loop gain K P =100, according to the above CNC machine tool parameter optimization method, the first alarm threshold AXFEMIN = 1mm, the second alarm threshold AXFEVEL = (VEL-40) / 40 (mm), where VEL is the feed speed in mm / s. The test results are as follows Figure 6 As shown, the maximum position following error is 0.433 mm, and the machine tool did not alarm during the test, ensuring the continuity of machine tool processing.

[0057] The present application also provides a CNC machine tool parameter optimization device, including: a position instruction acquisition module, used to obtain the position instruction at the current moment, the position instruction at least includes a feed speed; an alarm threshold setting module, the alarm threshold setting module sets the following error alarm threshold at the current moment according to at least the feed speed at the current moment; a following error alarm module, the following error alarm module calculates the position following error at the current moment according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool, and when the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing.

[0058] The present application also provides a CNC machine tool control system, the parameters of which are optimized according to the CNC machine tool parameter optimization method described in any one of the aforementioned embodiments.

[0059] The present application also provides a computer-readable storage medium, which stores one or more computer instructions. When the one or more computer instructions are executed, they are used to implement the steps of the CNC machine tool parameter optimization method as described in any of the aforementioned embodiments.

[0060] The present application also provides a computer program product, comprising a computer program, which, when executed, implements the steps of the CNC machine tool parameter optimization method as described in any one of the aforementioned embodiments.

[0061] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be subject to the scope defined by the claims.

Claims

1. A method for optimizing parameters of a numerical control machine tool, characterized in that: include: Obtaining a position instruction at a current moment, wherein the position instruction at least includes a feed speed; At least set the following error alarm threshold at the current moment according to the feed speed at the current moment; The position following error at the current moment is calculated according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool. When the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing.

2. The method for optimizing CNC machine tool parameters according to claim 1, characterized in that: The step of setting the following error alarm threshold at the current moment at least according to the feed speed at the current moment comprises: If the current feed speed is less than or equal to the feed speed threshold, the current following error alarm threshold is set as the first alarm threshold; If the current feed speed is greater than the feed speed threshold, the current following error alarm threshold is set to the sum of the first alarm threshold and the second alarm threshold, wherein the second alarm threshold is proportional to the difference between the current feed speed and the feed speed threshold.

3. The method for optimizing parameters of a numerically controlled machine tool according to claim 1, characterized in that: The step of setting the following error alarm threshold at the current moment at least according to the feed speed at the current moment comprises: A second alarm threshold is set according to the current feed speed and the position loop gain, wherein the second alarm threshold is inversely proportional to the position loop gain.

4. The method for optimizing parameters of a numerically controlled machine tool according to claim 1, wherein: The step of setting the following error alarm threshold at the current moment at least according to the feed speed at the current moment comprises: The following error alarm threshold at the current moment is set according to the feed speed at the current moment, the position loop gain and the feedforward gain, wherein the second alarm threshold is inversely proportional to the position loop gain.

5. The method for optimizing CNC machine tool parameters according to any one of claims 3 or 4, characterized in that: The position loop gain is 70% to 80% of a position loop gain critical value, and the position loop gain critical value is the position loop gain when the machine tool vibrates.

6. A CNC machine tool parameter optimization device, characterized in that: include: A position instruction acquisition module, used to acquire the position instruction at the current moment, wherein the position instruction at least includes a feed speed; An alarm threshold setting module, wherein the alarm threshold setting module sets a following error alarm threshold at a current moment at least according to a feed speed at a current moment; A following error alarm module calculates the position following error at the current moment according to the position instruction at the current moment and the actual position at the previous moment fed back by the machine tool. When the position following error at the current moment is greater than the following error alarm threshold, the machine tool alarms and stops processing.

7. The CNC machine tool parameter optimization device according to claim 6, characterized in that: The alarm threshold setting module sets the following error alarm threshold at the current moment at least according to the feed speed at the current moment, including: If the current feed speed is less than or equal to the feed speed threshold, the current following error alarm threshold is set as the first alarm threshold; If the current feed speed is greater than the feed speed threshold, the current following error alarm threshold is set to the sum of the first alarm threshold and the second alarm threshold, wherein the second alarm threshold is proportional to the difference between the current feed speed and the feed speed threshold.

8. A CNC machine tool control system, characterized in that: The parameters of the CNC machine tool control system are optimized according to the CNC machine tool parameter optimization method according to any one of claims 1-5.

9. A computer-readable storage medium, characterized in that: The storage medium stores one or more computer instructions, and when the one or more computer instructions are executed, they are used to implement the steps of the CNC machine tool parameter optimization method as described in any one of claims 1-5.

10. A computer program product, characterized in that It comprises a computer program, which, when executed, implements the steps of the CNC machine tool parameter optimization method as described in any one of claims 1 to 5.

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