A method for online inertia identification of AC servo drives

Abstract

The invention discloses an online inertia identification method for an AC servo driver. The method comprises the following steps: based on a motor motion equation, by real-time acquisition of motor output torque and speed data, utilizing the symmetry of acceleration and deceleration stages, combining segmented mean calculation and integral difference, dynamically calculating the actual rotational inertia of the system; to ensure the stability of system operation, the identified rotational inertia is processed by first-order low-pass filtering and then smoothly output; the invention does not require forced acceleration and deceleration process symmetry, has flexible data acquisition, and has a simple calculation process with strong real-time performance, effectively improving the control response speed and stability of the servo driver under load inertia variation conditions, and simplifying the on-site parameter setting process, and is suitable for high-response and high-precision control applications.

Description

Technical Field

[0001] The present invention relates to the fields of motor control technology and inertia identification technology, and in particular to an online inertia identification method for an AC servo driver. Background Art

[0002] In AC servo control systems, motors and their loads often need to perform high-speed reciprocating motion. In actual applications, the load carried by the system during operation may change significantly due to workpiece weight, shape changes, or posture changes. These changes directly cause the overall moment of inertia of the system to fluctuate, thereby affecting the servo performance of the system.

[0003] In existing methods, AC servo drives are usually controlled based on fixed moment of inertia parameters. However, when the load inertia changes, the pre-set speed control parameters will be difficult to match the actual needs of the system. This mismatch will cause the following problems: First, the system control performance is reduced: the speed response is slow, the position accuracy is reduced, and the production quality is affected. Second, the processing accuracy is impaired: in the high-precision processing process, the uncertainty of the moment of inertia may cause the finished product processing error to exceed the standard. Third, system oscillation and error reporting: when the load inertia changes greatly, the system is prone to vibration or even error reporting, resulting in production interruption.

[0004] Therefore, in order to solve the impact of dynamic changes in load inertia on the performance of AC servo control systems, an online inertia identification method is urgently needed. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed. Therefore, the present invention provides an online inertia identification method for an AC servo drive to solve the problems mentioned in the background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: an online inertia identification method for an AC servo drive, comprising:

[0008] Collecting motor data in an AC servo drive in real time, obtaining a motion equation of the motor in the AC servo drive without a friction coefficient from the motor data in the AC servo drive, and calculating the moment of inertia of the AC servo control system based on the motion equation of the motor in the AC servo drive without a friction coefficient;

[0009] Considering the effectiveness of the real-time acquisition of motor data in the AC servo drive, the rotational inertia of the AC servo control system supported by the effectiveness is calculated, and the rotational inertia of the AC servo control system supported by the effectiveness is used to replace the rotational inertia of the AC servo control system;

[0010] The replacement process is smoothed by a first-order low-pass filter to eliminate the jitter caused by the rotational inertia of the AC servo control system supported by the effectiveness after the replacement, thereby achieving rapid identification of the load inertia of the AC servo drive.

[0011] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, the real-time acquisition of motor data in the AC servo drive includes:

[0012] Motor torque, load torque, friction coefficient, and motor speed.

[0013] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, the motion equation of the motor in the AC servo drive without friction coefficient is obtained from the motor data in the AC servo drive, including:

[0014] The motion equation of the motor in the AC servo drive is expressed as:

[0015]

[0016] Among them, Te represents the motor torque, Tl represents the load torque, B represents the friction coefficient, w represents the motor speed, and J represents the moment of inertia of the servo control system. is the differential term of the motor speed;

[0017] When the friction coefficient B=0, the motion equation of the motor in the AC servo drive without friction coefficient is obtained:

[0018]

[0019] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, the moment of inertia of the servo control system is calculated based on the motion equation of the motor in the AC servo drive without the friction coefficient, including:

[0020] The differential term of the motor speed is discretized and approximated and rewritten in the form of speed difference:

[0021]

[0022] Among them, Δw is the change in motor speed, and Δt is the corresponding time interval;

[0023] Will Replace with get:

[0024]

[0025] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, it also includes:

[0026] Set the t1~t2 period as the motor acceleration state. Integrating both sides yields:

[0027]

[0028] Set the t3~t4 section as the motor deceleration running state. Integrating both sides yields:

[0029]

[0030] Considering the acceleration and deceleration running states of the AC servo control system, if the load conditions remain consistent and do not change, the load torque Tl is set equal in the two running states. At the same time, the data intervals with equal time lengths are selected in the acceleration and deceleration running states, that is, the following conditions are met:

[0031] t2-t1=t4-t3=Δt

[0032] Then we get:

[0033]

[0034] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, wherein: considering the effectiveness of the real-time acquisition of the motor data in the AC servo drive, the rotational inertia of the AC servo control system supported by the effectiveness is calculated, and the rotational inertia of the AC servo control system supported by the effectiveness is used to replace the rotational inertia of the AC servo control system, including:

[0035] The validity of real-time acquisition of motor data in AC servo drives is determined as follows:

[0036] The Te and w data are sampled at Δt, the sampling period is T, and N = Δt / T data are collected within Δt;

[0037] The acquisition process of the motor speed w is divided into two sections, each of which collects N / 2 data and calculates the average as follows:

[0038] wa=(w0+w1+…+w(N / 2-1)) / (N / 2)

[0039] wb=(w(N / 2)+w(N / 2+1)…+w(N)) / (N / 2)

[0040] Among them, wa and wb are the data means of the first acquisition process and the data means of the second acquisition process respectively;

[0041] Subtract the obtained wa and wb to get:

[0042] Δw=wa-wb

[0043] If Δw is greater than ±wTh, it is considered to be an effective motor speed change and is recorded. When Δw>0, it is an acceleration state, and when Δw<0, it is a deceleration state.

[0044] Wherein, wTh represents the judgment threshold of the effective motor speed change;

[0045] For each Δt, the last four data points of the collected motor torque and motor speed data are averaged as the valid data of the Δt.

[0046] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, it also includes:

[0047] When valid data is collected, the valid data is brought into The rotational inertia of the AC servo control system is obtained under effective support, thereby replacing the rotational inertia of the original AC servo control system.

[0048] As a preferred solution of the online inertia identification method of the AC servo drive of the present invention, the replacement process is smoothed by a first-order low-pass filter to eliminate the jitter caused by the rotational inertia of the AC servo control system supported by the effectiveness after the replacement, including:

[0049] The formula for smoothing by the first-order low-pass filter is expressed as:

[0050] Jout=Jout+2πf(J-Jout)

[0051] Wherein, f is the cutoff frequency of the filter, and Jout is the moment of inertia of the AC servo control system after smoothing.

[0052] Compared with the prior art, the invention has the following beneficial effects:

[0053] 1. By adding the online inertia identification function, the change of the moment of inertia can be obtained in real time, and the moment of inertia can be corrected in time to ensure that the servo system can continue to guarantee the servo performance of the system when the moment of inertia changes, thereby improving the reliability of the servo. At the same time, during on-site debugging, this function can also be used to achieve rapid control parameter setting, simplifying the tedious process of adjusting PI parameters and improving efficiency.

[0054] 2. By collecting data in real time and analyzing the status of the data during operation, there is no need to force the data to be symmetrical during the addition and subtraction process, which increases the flexibility of data collection and makes the data suitable for online real-time inertia identification. At the same time, a first-order low-pass filter is added for data smoothing, which ensures the rapidity of identification and the stability of the method during application. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0056] Figure 1 The overall flow chart of the online inertia identification method of the AC servo drive according to one embodiment of the present invention;

[0057] Figure 2 The present invention is a flowchart of determining the validity of motor data in an AC servo drive of an online inertia identification method for an AC servo drive according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0059] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0060] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0061] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0062] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0063] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] Example 1

[0065] Reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, provides an online inertia identification method for an AC servo drive, comprising:

[0066] S1. Real-time acquisition of motor data in the AC servo drive, obtaining the motion equation of the motor in the AC servo drive without a friction coefficient from the motor data in the AC servo drive, and calculating the rotational inertia of the AC servo control system based on the motion equation of the motor in the AC servo drive without a friction coefficient;

[0067] Specifically, the motor data collected in the AC servo drive in real time includes motor torque, load torque, friction coefficient and motor speed;

[0068] Furthermore, the motion equation of the motor in the AC servo drive is expressed as:

[0069]

[0070] Among them, Te represents the motor torque, Tl represents the load torque, B represents the friction coefficient, w represents the motor speed, and J represents the moment of inertia of the servo control system. is the differential term of the motor speed;

[0071] Furthermore, by setting the friction coefficient B = 0, we can obtain the motion equation of the motor in the AC servo drive without friction coefficient:

[0072]

[0073] It should be noted that the friction coefficient B = 0 is because the friction coefficient B of machinery in actual industry is generally very small, so it can be ignored;

[0074] Furthermore, the differential term of the motor speed is discretized and approximated, and rewritten in the form of speed difference to obtain:

[0075]

[0076] Among them, Δw is the change in motor speed, and Δt is the corresponding time interval;

[0077] Furthermore, applying formula (3), Replace with get:

[0078]

[0079] Furthermore, the t1~t2 period is set as the motor acceleration state. Integrating both sides yields:

[0080]

[0081] Furthermore, set the t3~t4 section as the motor deceleration running state. Integrating both sides yields:

[0082]

[0083] Furthermore, if the load condition remains the same and does not change during the acceleration and deceleration operation of the AC servo control system, the load torque Tl is set equal in the two operation states. At the same time, data intervals with equal time lengths are selected in the acceleration and deceleration operation states, that is, the following conditions are met:

[0084] t2-t1=t4-t3=Δt (7)

[0085] Simplifying formula (5) and formula (6), we get:

[0086]

[0087] S2, considering the effectiveness of real-time acquisition of motor data in the AC servo drive, calculating the moment of inertia of the AC servo control system supported by the effectiveness, and replacing the moment of inertia of the AC servo control system with the moment of inertia of the AC servo control system supported by the effectiveness;

[0088] It should be explained that although the moment of inertia of the servo control system is calculated by formula (8), a key problem will be encountered during the entire operation process, that is, the acquisition of torque and speed. Because the acceleration and deceleration process, the uniform speed process and the shutdown process during the operation are uncertain and are all dynamically changing factors, it is necessary to judge the validity of the motor data collected in the real-time AC servo drive, that is, to extract valid data and discard invalid data;

[0089] For further reference, Figure 2 , to judge the validity of the real-time acquisition of motor data in the AC servo drive, the process is as follows:

[0090] S201, sampling Te and w data in Δt, with a sampling period of T, collecting N = Δt / T data within Δt;

[0091] S202, the acquisition process of the motor speed w is divided into two sections, wherein each section acquires N / 2 data and calculates the average value as follows:

[0092] wa=(w0+w1+…+w(N / 2-1)) / (N / 2) (9)

[0093] wb=(w(N / 2)+w(N / 2+1)…+w(N)) / (N / 2) (10)

[0094] Among them, wa and wb are the data means of the first acquisition process and the data means of the second acquisition process respectively;

[0095] S203, subtract wa obtained by formula (9) from wb obtained by formula (10) to obtain:

[0096] Δw=wa-wb (11)

[0097] If Δw is greater than ±wTh, it is considered to be an effective motor speed change and is recorded. When Δw>0, it is an acceleration operation state, and Δw<0 is a deceleration operation state. wTh represents the judgment threshold of the effective motor speed change, which is initially greater than 10rpm or is set according to the actual situation.

[0098] It should be explained that in the process of data sampling, since the torque Te and speed w may be affected by noise, fluctuation or nonlinear factors, directly using the data of a single sampling point may lead to inaccurate or unstable calculation results. In order to obtain more stable data that is closer to the actual situation, it is necessary to take the average value of the data points;

[0099] S204, for each Δt, taking the average of the last four data points in the collected motor torque and motor speed data as the valid data of the Δt;

[0100] Furthermore, after valid data is collected, the valid data is substituted into formula (8) to obtain the rotational inertia of the AC servo control system supported by validity, thereby replacing the rotational inertia of the original AC servo control system;

[0101] It should be noted that, according to S201 to S204, obtaining Te and w of the acceleration and deceleration process usually only requires one operation cycle, and the rotational inertia of the load can be identified based on the rotational inertia (actual rotational inertia) of the AC servo control system supported by effectiveness;

[0102] S3. The replacement process is smoothed by a first-order low-pass filter to eliminate the jitter caused by the rotational inertia of the AC servo control system supported by the effectiveness after the replacement, thereby realizing the rapid identification of the online inertia of the AC servo drive;

[0103] It should be explained that, given that the load moment of inertia may differ greatly from the actual moment of inertia, when the identified moment of inertia directly replaces the actual moment of inertia, operational jitter may occur. Therefore, after the moment of inertia is identified, smoothing processing is required to ensure a smooth transition of system operation.

[0104] Furthermore, a first-order low-pass filter is used for smoothing, and the formula is expressed as:

[0105] Jout=Jout+2πf(J-Jout) (12)

[0106] Wherein, f is the cutoff frequency of the filter, and Jout is the moment of inertia of the AC servo control system after smoothing.

[0107] Those skilled in the art will appreciate that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program codes. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0108] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0109] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0110] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0111] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0112] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. An online inertia identification method for an AC servo drive, characterized in that: include: Collecting motor data in an AC servo drive in real time, obtaining a motion equation of the motor in the AC servo drive without a friction coefficient from the motor data in the AC servo drive, and calculating the moment of inertia of the AC servo control system based on the motion equation of the motor in the AC servo drive without a friction coefficient; Considering the effectiveness of the real-time acquisition of the motor data in the AC servo drive, the rotational inertia of the AC servo control system supported by the effectiveness is calculated, and the rotational inertia of the AC servo control system supported by the effectiveness is used to replace the rotational inertia of the AC servo control system; The replacement process is smoothed by a first-order low-pass filter to eliminate the jitter caused by the rotational inertia of the AC servo control system supported by the effectiveness after the replacement, thereby achieving rapid identification of the load inertia of the AC servo drive.

2. The online inertia identification method of an AC servo drive according to claim 1, characterized in that: Real-time acquisition of motor data in AC servo drives, including: Motor torque, load torque, friction coefficient, and motor speed.

3. The online inertia identification method of the AC servo drive according to claim 2, characterized in that: Based on the motor data in the AC servo drive, the motion equation of the motor in the AC servo drive without friction coefficient is obtained, including: The motion equation of the motor in the AC servo drive is expressed as: Among them, Te represents the motor torque, Tl represents the load torque, B represents the friction coefficient, w represents the motor speed, and J represents the moment of inertia of the servo control system. is the differential term of the motor speed; When the friction coefficient B=0, the motion equation of the motor in the AC servo drive without friction coefficient is obtained:

4. The online inertia identification method of the AC servo drive according to claim 3, characterized in that: Based on the motion equation of the motor in the AC servo drive without the friction coefficient, the moment of inertia of the servo control system is calculated, including: The differential term of the motor speed is discretized and approximated and rewritten in the form of speed difference: Among them, Δw is the change in motor speed, and Δt is the corresponding time interval; Will Replace with get:

5. The online inertia identification method of the AC servo drive according to claim 4, characterized in that: Also includes: Set the t1~t2 period as the motor acceleration state. Integrating both sides yields: Set the t3~t4 section as the motor deceleration running state. Integrating both sides yields: Considering the acceleration and deceleration running states of the AC servo control system, if the load conditions remain consistent and do not change, the load torque Tl is set equal in the two running states. At the same time, the data intervals with equal time lengths are selected in the acceleration and deceleration running states, that is, the following conditions are met: t2-t1=t4-t3=Δt Then we get:

6. The method for online inertia identification of an AC servo drive according to claim 2 or 5, characterized in that: Considering the effectiveness of the real-time acquisition of the motor data in the AC servo drive, the rotational inertia of the AC servo control system supported by the effectiveness is calculated, and the rotational inertia of the AC servo control system supported by the effectiveness is used to replace the rotational inertia of the AC servo control system, including: The validity of real-time acquisition of motor data in AC servo drives is determined as follows: The Te and w data are sampled at Δt, the sampling period is T, and N = Δt / T data are collected within Δt; The acquisition process of the motor speed w is divided into two sections, each of which collects N / 2 data and calculates the average as follows: wa=(w0+w1+…+w(N / 2-1)) / (N / 2) wb=(w(N / 2)+w(N / 2+1)…+w(N)) / (N / 2) Among them, wa and wb are the data means of the first acquisition process and the data means of the second acquisition process respectively; Subtract the obtained wa and wb to get: Δw=wa-wb If Δw is greater than ±wTh, it is considered to be an effective motor speed change and is recorded. When Δw>0, it is an acceleration state, and when Δw<0, it is a deceleration state. Wherein, wTh represents the judgment threshold of the effective motor speed change; For each Δt, the last four data points of the collected motor torque and motor speed data are averaged as the valid data of the Δt.

7. The online inertia identification method of the AC servo drive according to claim 6, characterized in that: Also includes: When valid data is collected, the valid data is brought into The rotational inertia of the AC servo control system is obtained under effective support, thereby replacing the rotational inertia of the original AC servo control system.

8. The method for online inertia identification of an AC servo drive according to claim 7, characterized in that: The replacement process is smoothed by a first-order low-pass filter to eliminate the jitter caused by the rotational inertia of the AC servo control system supported by the effectiveness after the replacement, including: The formula for smoothing by the first-order low-pass filter is expressed as: Jout=Jout+2πf(J-Jout) Wherein, f is the cutoff frequency of the filter, and Jout is the moment of inertia of the AC servo control system after smoothing.

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