A feedforward method and device for a feeding system considering system delay

Abstract

The present invention belongs to the technical field related to numerical control technology, and discloses a feedforward method and device for a feed system taking into account system delay, comprising the following steps: (1) inputting a position command signal containing a uniform speed change section and a reverse section to a machine tool; (2) collecting and recording position tracking error data e1 of the uniform speed change section at this time; (3) adjusting a speed feedforward time offset parameter according to the phase difference between a speed feedforward and a speed feedback quantity in a delay link existing in the system, and collecting and recording position tracking error data e2 of the current uniform speed change section; (4) comparing e1 and e2, and determining whether the position tracking error data e2 is close to 0; if so, ending the process and obtaining an optimal speed feedforward time offset parameter that makes the uniform speed tracking error close to 0; otherwise, continuing to adjust the speed feedforward time offset parameter according to the obtained comparison result until the uniform speed tracking error is close to 0. The present invention improves the level of position tracking error control.

Description

Technical Field

[0001] The present invention belongs to the technical field related to numerical control technology, and more specifically, relates to a feedforward method and device for a feeding system taking system delay into consideration. Background Art

[0002] CNC machine tools are highly efficient, high-precision, and highly automated processing equipment, widely used in major technological fields such as aerospace, automotive, medical equipment, and engineering machinery. With the development of modern manufacturing and the increasing sophistication of industrial design, the precision requirements for component processing are constantly increasing. This places stringent demands on CNC machine tools in terms of position tracking error control and dynamic response performance improvement.

[0003] Feedforward control is currently widely used in the field of CNC machine tools. Feedforward control is a control strategy that compensates for system errors based on predictions of the system model. By applying feedforward control to the drive control link, it can proactively compensate for system errors before they occur, reducing position tracking errors in machine tool feed motions, thereby improving the machine tool's dynamic performance and enhancing machining accuracy, efficiency, and stability.

[0004] Currently, ball screw drive type machine tools are the most widely used. For this type of machine tools, the commonly used feedforward control methods are instruction-based speed feedforward and acceleration feedforward methods: by applying speed feedforward in the speed loop, the position tracking error of the machine tool in the steady speed section can be effectively reduced; by applying inertia force feedforward in the current loop, the position tracking error of the machine tool in the variable speed section can be improved.

[0005] The feed system of a CNC machine tool consists of a CNC system, a servo control system, and a mechanical transmission system. The CNC system is responsible for trajectory planning and command output; the servo control system is responsible for motion control and signal generation; and the mechanical transmission system is responsible for completing the motion. To complete the entire control process, data transmission and communication are also required between these systems. Specifically, the CNC system outputs position commands and feedforward instructions, which are transmitted via a bus to the servo drive. The servo drive executes control to drive the mechanical system. Simultaneously, signals from measuring devices such as the motor encoder and position grating scale are fed back to the servo drive to participate in closed-loop control. This feedback signal is also transmitted via the bus to the CNC system for analysis and calculation.

[0006] The above-mentioned data transmission process will inevitably lead to timing deviations between different control signals. At the micron-level tracking precision control level, the deviation of signal timing will significantly affect the accuracy of feedforward control, resulting in poor effect in reducing position tracking errors. Summary of the Invention

[0007] In response to the above defects or improvement needs of the prior art, the present invention provides a feedforward method and device for a feed system taking into account system delay, which aims to solve the problem that the deviation of signal timing significantly affects the accuracy of feedforward control and leads to poor tracking error reduction effect.

[0008] To achieve the above object, according to one aspect of the present invention, a feedforward method for a feed system taking into account system delay is provided, the method comprising the following steps:

[0009] (1) Inputting a position command signal containing a uniform speed change section and a reverse section to the machine tool;

[0010] (2) Turn on the velocity acceleration feedforward function, collect and record the position tracking error data e1 of the uniform speed change section at this time;

[0011] (3) Adjust the time offset parameter of the speed feedforward according to the phase difference between the speed feedforward and the speed feedback caused by the delay link in the system, and collect and record the position tracking error data e2 of the current uniform speed change section;

[0012] (4) Compare the position tracking error data e1 and the position tracking error data e2, and determine whether the position tracking error data e2 is close to 0. If so, end the process and obtain the optimal speed feedforward time offset parameter that makes the uniform speed tracking error close to 0; otherwise, continue to adjust the speed feedforward time offset parameter according to the comparison result until the uniform speed tracking error is close to 0.

[0013] Furthermore, the speed feedforward time offset parameter is adjusted to a positive value. The speed feedforward time offset parameter debugging range starts from 1 and increases sequentially. The increased range is determined according to the position tracking error of the uniform speed change section.

[0014] Furthermore, when the position tracking error data e2 is closer to 0 than the position tracking error data e1, but still not near 0, it is necessary to further increase the velocity feedforward time offset parameter.

[0015] Furthermore, when the position tracking error data e2 moves away from the zero position in the reverse direction, the value of the velocity feedforward time offset parameter is reduced.

[0016] Furthermore, a delay link is added to the speed feedback loop, which is approximated as a first-order inertia link. At this time, the transfer function of the control system is:

[0017]

[0018] The position tracking error transfer function of the system is the difference between the current transfer function and 1, that is, 1-G(s):

[0019]

[0020] Furthermore, based on the position tracking error transfer function of the system, the steady-state error expression caused by time lag during machine tool motion is obtained. The position instructions of the system under uniform speed motion and variable speed motion are respectively:

[0021]

[0022] Performing Laplace transform on the input signal yields:

[0023]

[0024] According to the final value theorem of Laplace transform, the steady-state error expression caused by time lag in uniform motion and variable speed motion is obtained:

[0025]

[0026] The tracking error of the speed change section is proportional to the lag time τ and acceleration a.

[0027] Furthermore, when there is a delay link in both the system feedback path and the feedforward path, the speed feedforward path also adds a first-order inertia link. The position tracking error expression when there are delay links in both the feedforward path and the feedback loop is obtained:

[0028]

[0029] Where, τ v ,τ are the lag times of the feedforward path and the feedback loop respectively.

[0030] Furthermore, when there is a time lag in both the system feedforward loop and the feedback loop, it has no effect on the tracking error in the uniform speed section, and the tracking error in the variable speed section is proportional to τ v ,τ,a, when τ v =τ, the speed change tracking error is also not affected by time lag.

[0031] The present invention also provides a feed forward system that takes into account system delay. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the feed forward method for the feed system that takes into account system delay as described above.

[0032] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the feedforward method of the feeding system considering the system delay as described above.

[0033] In general, compared with the prior art, the above technical solutions conceived by the present invention provide a feed forward method and device for a feed system taking into account system delay, which has the following beneficial effects:

[0034] 1. This method reduces the influence of the timing of each link in the feedforward control on the position tracking error by compensating for the delay link. On the basis of the traditional feedforward method, it further reduces the position tracking error of the machine tool feed system and achieves a position tracking error control level of micron level (within 5μm).

[0035] 2. The present invention analyzes the situation where there is a delay link in the control loop, explores the impact of the delay link in the system feedback loop and the feedforward path on the system tracking error under different speed conditions (uniform motion, uniformly variable speed motion), and proposes a compensation scheme for the simple delay link in the control system, which can effectively compensate for the impact of timing deviation on position tracking error.

[0036] 3. The present invention improves the accuracy of feedforward control by compensating the transfer function and performing time-series processing on the velocity feedforward amount. Compared with the traditional velocity acceleration feedforward method, it further improves the dynamic response performance of the machine tool feed system, further reduces the position tracking error of the machine tool feed, and improves the machining accuracy of the machine tool.

[0037] 4. The present invention involves fewer parameters, is simpler to operate, and has stronger real-time performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of a feed forward method for a feed system taking into account system delay provided by the present invention;

[0039] Figure 2 (a) and (b) are schematic diagrams comparing the effects of the pure delay link and the first-order inertia link in the simulation environment;

[0040] Figure 3 This is the control system block diagram of the single inertia motor control model considering the speed feedback loop delay;

[0041] Figure 4 This is the servo control block diagram of the single inertia motor control model considering the feedback loop filter;

[0042] Figure 5 (a) and (b) are schematic diagrams of the implementation principle of the feedforward method of the feeding system considering the system delay in the example of the present invention;

[0043] Figure 6 This is a comparison chart of the tracking error reduction effect of the present invention and the traditional velocity acceleration feedforward method;

[0044] Figure 7 (a), (b), and (c) are schematic diagrams of command signals required for debugging the speed feedforward time offset parameter in an embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram of the tracking error when a certain position command signal is input and there is a signal timing deviation in the system, corresponding to the X-axis tracking position and X-axis command speed respectively;

[0046] Figure 9 This is a schematic diagram of the effect of different speed feedforward time offset parameters on the following error when a certain position command signal is input, corresponding to the X-axis tracking position and X-axis command speed respectively. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0048] See also Figure 1 The present invention provides a feedforward method for a feeding system taking into account system delay. This method analyzes the influence of the delay link on the feedforward effect through simulation, and performs feedforward control based on the analysis results.

[0049] Among them, the simple definition of the delay link is that the delay link only exists in the speed feedback loop, that is, there are fewer filters in the speed feedback loop, such as only one low-pass filter. According to the derivation of the formula, for this simple delay situation, it is sufficient to add a corresponding filter to the feedforward path. The complex definition of the delay link is the situation where there are multiple filters in the entire system, such as the notch filter that exists between the command speed and the command current, and the low-pass filter and the anti-oscillation filter that appear in the speed feedback loop. This situation of multiple filters is very complicated to derive from the formula, and it is difficult to achieve real-time compensation in the feedforward loop. The time offset parameter of the speed feedforward is adjusted according to the phase difference between the speed feedforward and the speed feedback according to the delay link existing in the system. Because the delay links of different systems are different, the time offset parameters are also different.

[0050] The time lag in the control system will reduce the closed-loop stability of the system and deteriorate the dynamic performance. The input-output relationship of the pure delay link in the time domain is: y(t) = r(t-τ), and the transfer function in the complex frequency domain is: e -τs , where τ is the system delay time.

[0051] However, the above transfer function analysis is more difficult. When the delay time τ is small, Taylor expansion is performed on it, and the high-order terms are ignored, which can be approximated as a first-order inertia link. The control frequency of the machine tool feed system is relatively high. The interpolation and communication cycle of the CNC system is generally 1ms, while the inner loop control cycle of the driver is generally 1 / 8ms or even lower. Therefore, the delay link e -τs It is approximately a first-order inertia link. Figure 2 As shown in the figure, when the delay is 1 / 8ms, the first-order inertia link has a better approximation effect.

[0052] By adding a delay link to the control loop, the impact of the delay link on the system transfer function and the position tracking error transfer function is explored. Specifically, a delay link is added to the velocity feedback loop, and this delay link is approximated as a first-order inertia link.

[0053] Considering the influence of the timing of the speed loop feedback loop and the feedforward path on the position tracking error, taking the single inertia motor control model as an example, the control system block diagram considering the delay is as follows Figure 3 shown.

[0054] Add a first-order inertia link to the speed loop feedback loop. The transfer function of the control system is:

[0055]

[0056] From the above equation, we can see that after adding the delay link, the system's transfer function G(s) ≠ 1. In this control system, the system's input and output are the command position and the machine tool's actual position, respectively. The transfer function is equal to the ratio of output to input, that is, the ratio of actual position to command position. A ratio not equal to 1 indicates that the actual position cannot track the command position well, and feedforward control will no longer meet the full error compensation condition.

[0057] The position tracking error transfer function of the system is the difference between the current transfer function and 1, that is, 1-G(s):

[0058]

[0059] Through the position tracking error transfer function of the system, we explore the impact of the delay link in the system feedback path on the system tracking error under different speed conditions (uniform speed motion, variable speed motion):

[0060] According to the position tracking error transfer function of the above system, the steady-state error expression caused by time lag when the machine tool moves can be obtained.

[0061] The position instructions of the system under uniform motion and variable speed motion are:

[0062]

[0063] Performing Laplace transform on the input signal yields:

[0064]

[0065] According to the final value theorem of Laplace transform, the steady-state error expression caused by time lag in uniform motion and variable speed motion can be obtained:

[0066]

[0067] According to the above calculation results, when there is a time lag in the system feedback path, it has no effect on the tracking error of the uniform speed section, but will increase the tracking error of the variable speed section. The tracking error of the variable speed section is proportional to the lag time τ and the acceleration a.

[0068] Through the position tracking error transfer function of the system, the influence of the system tracking error under different speed conditions (uniform motion, variable speed motion) when there are delay links in the system feedback path and feedforward path is explored.

[0069] In order to explore the impact of hysteresis on tracking error when both the feedforward path and the feedback path exist, a first-order inertia link is added to the velocity feedforward path. The position tracking error expression can be obtained by the same logic as above when there are delay links in both the feedforward path and the feedback loop:

[0070]

[0071] Where, τ v ,τ are the lag times of the feedforward path and feedback loop respectively. According to the above calculation results, when there is a time lag in both the system feedforward loop and the feedback loop, it has no effect on the tracking error in the uniform speed section, and the tracking error in the variable speed section is related to τ v ,τ,a, when τ v =τ, the speed change tracking error is also not affected by time lag.

[0072] When the delay link in the servo control loop is known and simple, the tracking error caused by the delay link can be compensated by correcting the transfer function:

[0073] In the actual machine tool servo control system, the feedback loop generally has a low-pass filter to filter the speed feedback value. When the servo control system, the feedback loop delay link is relatively simple, such as Figure 4 As shown in Figure 2, only one low-pass filter in the speed feedback loop is considered. According to the above formula (6), to compensate for the speed change tracking error caused by time lag, it is necessary to add the same filter in the feedforward path.

[0074] LPF1 and LPF2 are two low-pass filters. The transfer function of this control system is:

[0075]

[0076] The transfer function of this control system is the ratio of the actual position to the command position. When the transfer function equals 1, the actual position can theoretically completely follow the command position, achieving a tracking error of 0. Analysis of the transfer function reveals that when LPF1 and LPF2 are equal, the transfer function is 1, and the position tracking error is unaffected by the delay element.

[0077] In the case of complex delay links in the servo control loop, the speed feedforward is offset: In the actual machine tool servo control system, the delay link is relatively complex. If the delay link is compensated by the above method, the operation is complicated. The present invention proposes a feedforward method for the feed system considering the system delay, which offsets the speed feedforward to compensate for the tracking error caused by the delay link of the feedback loop. The speed feedforward time offset processing is shown in the figure below. Figure 5 As shown in the figure, the interpolated position increment (i.e., command velocity) and the synchronously calculated velocity feedforward are buffered for one cycle within the CNC system. During the current interpolation cycle, the command velocity sequence is issued normally, while the velocity feedforward sequence is time-shifted before the newly calculated velocity feedforward is issued, completing the timing adjustment of the feedforward path within the current cycle.

[0078] The calculation formula of the speed feedforward sequence after time offset is:

[0079]

[0080] Where ΔT is the system control period, and Δt is the system delay time. Δt>0 indicates that the speed feedforward is lagging, and Δt<0 indicates that the speed feedforward is advancing. FF(k-1), FF(k), and FF(k+1) are the normal speed feedforward sequence, and FF'(k) is the calculated offset speed feedforward sequence. The speed feedforward is adjusted in time by the above method. According to the derivation of formula (6), when the time adjustment is completed, the position tracking error of the uniform speed change section will also be compensated and approach 0. That is, this method can compensate for the position tracking error caused by the delay link of the feedback loop.

[0081] The lag link of the feedback loop is added to the simulation model to simulate the time lag of the feedback loop in the actual servo control process. The effect of the timing adjustment method is verified, and the specific impact of the time offset of the velocity feedforward on the tracking error is analyzed. The simulation results are as follows:

[0082] Table 1 Simulation results of tracking error before and after time offset of velocity feedforward

[0083]

[0084] The tracking error curve before and after the speed feedforward time offset is as follows: Figure 6 shown.

[0085] From the above results, it can be seen that there is a time lag in the feedback loop of the simulation model, which leads to a timing deviation between the feedforward path and the feedback path, causing a significant increase in the tracking error of the speed change section and the reverse section, and the tracking error waveform is consistent with the acceleration curve; by using this method, after time offset processing of the velocity feedforward, the position tracking error of the speed change section and the reverse section can be further reduced, achieving near-zero tracking error control in the uniform speed section and micron-level (within 5μm) tracking error control in the speed change section.

[0086] The feedforward method mainly includes the following steps:

[0087] (1) Input a position command signal containing a uniform speed change section and a reverse section to the machine tool.

[0088] (2) Turn on the velocity acceleration feedforward function, collect and record the position tracking error data e1 of the uniform speed change section at this time.

[0089] (3) The time offset parameter of the speed feedforward is adjusted according to the phase difference between the speed feedforward and the speed feedback caused by the delay link in the system, and the position tracking error data e2 of the current uniform speed change section is collected and recorded.

[0090] Adjust the time offset parameter of the speed feedforward. Since the delay link in the system generally causes signal timing deviation, the position tracking error reduction effect is poor. In order to compensate for the timing deviation caused by the delay link, the time offset parameter of the speed feedforward is generally adjusted to a positive value. According to formula (8), when Δt is a positive value, it is equivalent to delaying the speed feedforward, compensating for the error caused by the signal timing deviation. The debugging range of the speed feedforward time offset parameter generally starts from 1 and increases in sequence. The increase range is determined by the position tracking error of the uniform speed change section. After adjusting to the appropriate speed feedforward time offset parameter, collect and record the position tracking error data e2.

[0091] (4) Compare the position tracking error data e1 and the position tracking error data e2, and determine whether the position tracking error data e2 is close to 0. If so, end the process and obtain the optimal speed feedforward time offset parameter that makes the uniform speed tracking error close to 0; otherwise, continue to adjust the speed feedforward time offset parameter according to the comparison result until the uniform speed tracking error is close to 0.

[0092] The present invention is further described in detail below with reference to specific embodiments. The steps of the specific embodiments are as follows:

[0093] (1) Input the position command signal with uniform speed change section and reverse section to the machine tool. The command signal is as follows: Figure 7 The command signal is designed to have both a uniform speed segment and a uniformly variable speed segment, which can be compared with a good one to demonstrate the effect of this method on timing compensation.

[0094] (2) Enable the velocity and acceleration feedforward function, collect and record position tracking error data, ensure that the velocity and acceleration feedforward is effective, and save this data for comparison with the data from the subsequent feedforward solution that takes system delay into account. When there is a time lag in the system feedback path, it has no effect on the tracking error in the uniform speed section, but it will increase the tracking error in the variable speed section. The tracking error in the variable speed section is proportional to the lag time and acceleration. Figure 8 When the position command signal is input, the system has tracking error when the signal timing deviation occurs. Figure 8 As shown in the figure, during the uniform speed change process from -24000 mm / min to 0 and from 0 to 24000 mm / min, the tracking error is not near 0, but due to the influence of timing deviation, the tracking error in the uniform speed change section is increased.

[0095] (3) The speed feedforward time offset parameter is set in the range of -64 to 64 on the machine tool, representing -1ms to 1ms. To adjust the speed feedforward time offset parameter, in order to compensate for the timing deviation caused by the delay link, the speed feedforward time offset parameter is generally adjusted to a positive value. According to formula (8), when Δt is a positive value, it is equivalent to delaying the speed feedforward, compensating for the error caused by the signal timing deviation. The speed feedforward time offset parameter debugging range generally starts from 1 and increases in sequence. The increase range is determined by the tracking error of the uniform speed change section in the subsequent steps. After adjusting to the appropriate speed feedforward time offset parameter, collect and record the position tracking error data. Use the sampling tool SSTT to collect and record the position tracking error data.

[0096] (4) Analyze the position tracking error data collected in step (3). According to formula (6), when the speed feedforward offset time is set in place, the speed change section tracking error should be near 0. Therefore, the setting of the offset parameter is determined based on this criterion. If the tracking error of the uniform speed change section in step (3) is closer to 0 than that in step (2), but is still not near 0, it is necessary to further increase the speed feedforward time offset parameter and repeat steps (3)-(4). If the tracking error of the uniform speed change section in step (3) has moved away from the 0 position in the reverse direction, it means that the speed feedforward time offset parameter is too large and does not meet the requirements. It is necessary to return to step (3) to reduce the value of the speed feedforward time offset parameter and repeat steps (3)-(4). The specific effect of the speed feedforward time offset parameter on the tracking error is as follows. Figure 9As shown in the figure, the speed feedforward time is Δt = 1 / 8ms, 2 / 8ms, 3 / 8ms, and 4 / 8ms respectively. In the figure, as the speed feedforward offset time increases, the tracking error of the uniform speed section approaches the 0 line, and after reaching near zero, it increases in the opposite direction. When a situation similar to Δt = 1 / 8ms appears in the figure during debugging, that is, it is closer to the 0 line than when no timing compensation is performed, but still has not reached the 0 line, it is necessary to return to step 3, increase the speed feedforward time offset parameter, and repeat step 4. When a situation similar to Δt = 4 / 8ms appears in the figure during debugging, that is, it deviates from the 0 line in the opposite direction compared to when no timing compensation is performed, it means that the speed feedforward offset parameter is too large, and it is necessary to return to step (3), reduce the speed feedforward time offset parameter, and repeat step (4). When a situation similar to Δt = 2 / 8ms appears in the figure during debugging, that is, it is closer to the 0 line than when no timing compensation is performed, and is near the 0 line, it means that the speed feedforward offset parameter is appropriate, and you can also perform step (3) to fine-tune the parameters and save them. At this point, the speed feedforward time offset parameter debugging is completed.

[0097] The present invention also provides a feed forward system that takes into account system delay. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the feed forward method for the feed system that takes into account system delay as described above.

[0098] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the feedforward method of the feeding system considering the system delay as described above.

[0099] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A feedforward method for a feeding system taking into account system delay, characterized by: The method comprises the following steps: (1) Inputting a position command signal containing a uniform speed change section and a reverse section to the machine tool; (2) Turn on the velocity acceleration feedforward function, collect and record the position tracking error data e1 of the uniform speed change section at this time; (3) Adjust the time offset parameter of the speed feedforward according to the phase difference between the speed feedforward and the speed feedback caused by the delay link in the system, and collect and record the position tracking error data e2 of the current uniform speed change section; (4) Compare the position tracking error data e1 and the position tracking error data e2, and determine whether the position tracking error data e2 is close to 0. If so, end the process and obtain the optimal speed feedforward time offset parameter that makes the uniform speed tracking error close to 0; otherwise, continue to adjust the speed feedforward time offset parameter according to the comparison result until the uniform speed tracking error is close to 0.

2. The feedforward method for a feed system taking into account system delay as claimed in claim 1, characterized in that: Adjust the speed feedforward time offset parameter to a positive value. The speed feedforward time offset parameter debugging range starts from 1 and increases in sequence. The increase range is determined according to the position tracking error of the uniform speed change section.

3. The feedforward method for a feed system taking into account system delay as claimed in claim 1, characterized in that: When the position tracking error data e2 is closer to 0 than the position tracking error data e1, but still not near 0, it is necessary to further increase the velocity feedforward time offset parameter.

4. The feedforward method for a feed system taking into account system delay as claimed in claim 1, characterized in that: When the position tracking error data e2 moves away from the 0 position in the opposite direction, the value of the speed feedforward time offset parameter is reduced.

5. The feedforward method for a feed system taking into account system delay as claimed in claim 1, characterized in that: Adding a delay link to the speed feedback loop, the delay link is approximated as a first-order inertia link; at this time, the transfer function of the control system is: The position tracking error transfer function of the system is the difference between the current transfer function and 1, that is, 1-G(s):

6. The feedforward method for a feed system taking into account system delay as claimed in claim 5, characterized in that: According to the position tracking error transfer function of the system, the steady-state error expression caused by time lag when the machine tool is moving is obtained. The position instructions of the system under uniform speed motion and variable speed motion are respectively: Performing Laplace transform on the input signal yields: According to the final value theorem of Laplace transform, the steady-state error expression caused by time lag in uniform motion and variable speed motion is obtained: The tracking error of the speed change section is proportional to the lag time τ and acceleration a.

7. The feedforward method for a feed system taking into account system delay as claimed in claim 1, characterized in that: When there are delay links in both the system feedback path and the feedforward path, the speed feedforward path also adds a first-order inertia link. The position tracking error expression when there are delay links in both the feedforward path and the feedback loop is obtained: Where, τ v ,τ are the lag times of the feedforward path and the feedback loop respectively.

8. The feedforward method for a feeding system taking into account system delay as claimed in claim 7, characterized in that: When there is a time lag in both the system feedforward loop and the feedback loop, it has no effect on the tracking error in the uniform speed section, and the tracking error in the variable speed section is related to τ v ,τ,a, when τ v =τ, the speed change tracking error is also not affected by time lag.

9. A feedforward system for a feeding system taking into account system delay, characterized by: The system includes a memory and a processor, the memory stores a computer program, and the processor executes the feedforward method for a feeding system considering system delay according to any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores machine-executable instructions. When the machine-executable instructions are called and executed by the processor, the machine-executable instructions prompt the processor to implement the feedforward method for a feeding system considering system delay according to any one of claims 1 to 8.

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