Closed-loop and open-loop hybrid position control method for two-phase hybrid stepping motor

Abstract

Aiming at the control problem of two-phase hybrid stepping motor in the frequent start-stop position positioning control condition, the application provides a two-phase hybrid stepping motor closed-loop and open-loop mixed position control method which selects closed-loop or open-loop control according to position tracking error, namely, when the absolute value of motor position tracking error is greater than a threshold value, the system is two-phase hybrid stepping motor closed-loop position control; when the absolute value of motor position tracking error is less than or equal to the threshold value, the system is two-phase hybrid stepping motor open-loop position control. The two-phase hybrid stepping motor closed-loop and open-loop mixed position control method can overcome the problems of stepping motor out of step and frequent start-stop positioning oscillation caused by load mutation, too large and unreasonable motion speed planning curve, and has small calculation amount and easy engineering implementation.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, and particularly relates to a closed-loop and open-loop hybrid position control method for a two-phase hybrid stepper motor. Background Technology

[0002] Existing two-phase hybrid stepper motor position control methods include closed-loop control based on position sensors and open-loop control based on speed planning curves. Open-loop control suffers from poor response and load fluctuation resistance. Sudden or excessive load changes, or an unreasonable speed planning curve, can lead to increased stepper motor pulsation, oscillation, and even step loss. Closed-loop position control, which borrows from servo motor vector control, requires comparing and processing position angle information with the position sensor encoding each time. Overshoot can cause delays and oscillations, resulting in poorer position tracking control characteristics compared to open-loop stepper motor position control due to frequent start-stop cycles. Summary of the Invention

[0003] To address the control problem of two-phase hybrid stepper motors under frequent start-stop positioning control conditions, this invention proposes a hybrid closed-loop / open-loop position control method for two-phase hybrid stepper motors, which selects between closed-loop and open-loop control based on the position tracking error. Specifically, when the absolute value of the motor position tracking error is greater than a threshold, the system uses closed-loop position control; when the absolute value of the motor position tracking error is less than or equal to the threshold, the system uses open-loop position control. This hybrid closed-loop / open-loop position control method overcomes problems such as stepper motor step loss and frequent start-stop positioning oscillations caused by sudden load changes, excessive load, and unreasonable motion speed planning curves. Furthermore, it requires less computation and is easy to implement in engineering.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A hybrid closed-loop and open-loop position control method for a two-phase hybrid stepper motor is characterized in that: when the absolute value of the motor position tracking error is greater than a threshold, the system is a closed-loop position control for the two-phase hybrid stepper motor; when the absolute value of the motor position tracking error is less than or equal to the threshold, the system is an open-loop position control for the two-phase hybrid stepper motor.

[0006] Furthermore, it specifically includes the following steps:

[0007] Step S1: Set the open-loop control holding torque current amplitude I dout Initialize the closed-loop control PID controller parameters and controller output saturation value:

[0008] Step S2: Based on the position command signal θ * Based on the position information detected by the stepper motor position sensor, calculate e = (θ) *-θ), determine the absolute value of e: if it is greater than 0.5π / Z r Proceed to step S3; if it is less than or equal to 0.5π / Z r Proceed to step S4;

[0009] Step S3: Set e = (θ) * -θ) I is calculated by the closed-loop control PID controller. qout , and I out =|I qout |, according to I qout The sign selection control method: if it is greater than zero, then the AB phase current is i a =I out cos(Z r θ+0.5π), i b =I out sin(Z r The electromagnetic torque is calculated as KI (θ+0.5π). out If it is less than or equal to zero, then the AB phase current is i a =I out cos(Z r θ-0.5π), i b =I out sin(Z r Calculated using θ-0.5π, the electromagnetic torque is -KI out After completion, proceed to step S2;

[0010] Step S4: Open-loop control, making I q =|I qout |, calculation The output current of phase AB is i a =I out cos(Z r θ * ), i b =I out sin(Z r θ * Calculate; after completion, proceed to step S2;

[0011] In the above steps:

[0012] θ is the mechanical angle of the stepper motor, Z r Where K is the number of motor stage pairs, and K is the torque coefficient.

[0013] Compared with the prior art, the two-phase hybrid stepper motor closed-loop and open-loop composite position control method proposed by this invention and its preferred embodiment has smooth phase amplitude of the A-phase and B-phase current curves. In the closed-loop control stage, it can overcome the stepper motor step loss problem caused by sudden load changes, excessive load, and unreasonable motion speed planning curve. In the open-loop stage, it can quickly position the motor with small oscillations. Moreover, the closed-loop and open-loop transition algorithm is simple and smooth, with low computational load and easy engineering implementation. Attached Figure Description

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0015] Figure 1 This is a schematic diagram of a two-phase hybrid stepper motor position closed-loop hybrid position control method according to an embodiment of the present invention. Detailed Implementation

[0016] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation:

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] The following embodiment provides a more detailed description of the present invention:

[0020] The two-phase hybrid stepper motor position control method designed in this invention is as follows: Figure 1 As shown.

[0021] The principles and specific design processes underlying the aforementioned technical problems include:

[0022] In this embodiment, to facilitate analysis by establishing a mathematical model of the electromagnetic torque of a two-phase hybrid stepper motor, some minor factors are ignored, and the following assumptions are made:

[0023] (1) The effects of core saturation are ignored and the effects of higher harmonics in the main magnetic permeation are neglected;

[0024] (2) The self-inductance of the stator coil is constant. Ignoring the internal magnetic circuit of the rotor magnet, the self-inductance of the rotor coil is constant and does not change with the rotation angle.

[0025] At this time, the torque vector generated by phases A and B is divided into two parts, one of which is electromagnetic torque:

[0026]

[0027] The other part is the holding torque, which is aligned with the direction of the rotor's magnetic centerline.

[0028]

[0029] In the formula: T aq T bq T is the electromagnetic torque generated by phases AB. ad T bd The holding torque generated by phases AB; K is the torque coefficient; i a i b θ is the AB phase current; θ is the stepper motor mechanical angle, Z r Let be the number of motor stage pairs. From the above formula, it can be seen that its moment-angle characteristic is a sine curve.

[0030] This leads to the open-loop and closed-loop control methods for stepper motors:

[0031] (1) Closed-loop vector control of stepper motor, namely the rotor position signal θ detected by the position sensor and the current amplitude I calculated by PID. qout After passing through cosine and sine waves, the current is used as the given control current for phases A and B. The formula for calculating the phase AB current is as follows:

[0032]

[0033] The corresponding electromagnetic torques of phases AB are:

[0034] T aq +T bq =-KI qout cos(Z r θ+0.5π)sin(Z r θ)+KI qout sin(Z r θ+0.5π)cos(Z r θ)=KI qout (4) The holding torque is:

[0035] T ad +T bd =KI qout cos(Z r θ+0.5π)cos(Z r θ)+KIqout sin(Z r θ+0.5π)sin(Z r θ)=0 (5)

[0036] (2) Stepper motor open-loop microstepping control, that is, when the given position signal θ * And set the current amplitude I according to the holding torque dout After passing through cosine and sine waves, the current is used as the given control current for phases A and B. The formula for calculating the phase AB current is as follows:

[0037]

[0038] The corresponding electromagnetic torques of phases AB are:

[0039] T aq +T bq =-KI dout cos(Z r θ * sin(Z) r θ)+KI dout sin(Z r θ * cos(Z) r θ)=KI dout sin(Z r (θ * -θ)) (7)

[0040] The holding torque is:

[0041] T ad +T bd =KI dout cos(Z r θ * cos(Z) r θ)+KI dout sin(Z r θ * sin(Z) r θ)=KI dout cos(Z r (θ * -θ))(8)

[0042] Based on the above analysis, under frequent start-stop position positioning control conditions, the two-phase hybrid stepper motor can be positioned according to the position tracking error Z. r (θ * -θ) Whether the absolute value is greater than the threshold 0.5π switches between closed-loop and open-loop control to achieve closed-loop and open-loop composite position control of a two-phase hybrid stepper motor, that is:

[0043] (1) When the error e = (θ) between the motor rotor and the set position... *-θ) The absolute value is greater than 0.5π / Z r At that time, the output current of phases A and B is given by formula (3), I qout The amplitude is calculated by PID control, generating the maximum electromagnetic torque component while maintaining zero torque. At this point, the two-phase hybrid stepper motor uses vector position closed-loop control, which can overcome the problem of step loss due to large starting loads and sudden load changes, while ensuring smooth starting.

[0044] (2) When the error e = (θ) between the motor rotor and the set position... * The absolute value of -θ) is less than or equal to 0.5π / Z r At that time, the current output of phases A and B is given by formula (6), and the cosine and sine curves of phases A and B are given by the phase angle Z. r Smoothly switch to Z with θ+0.5π r θ * At this time, the two-phase hybrid stepper motor is in open-loop control, which can ensure that the position control system has no step loss problem and no position control delay or oscillation within the electrical angle error range of 0.5π, and the transition between closed-loop and open-loop is smooth;

[0045] (3) The amplitude switching of the cosine curve of phase AB is smoothed in both closed-loop and open-loop control. The transition point is based on the absolute value of the error, 0.5π / Z. r Flow amplitude value I q =|I qout The error of the open-loop control changes linearly to the set position, and the open-loop control holds the torque current amplitude I. dout ,Right now

[0046]

[0047] In summary, the specific implementation steps of the algorithm finally formed in this embodiment are as follows:

[0048] Step 1: Set the open-loop control holding torque current amplitude I dout Initialize the closed-loop control PID controller parameters and controller output saturation value:

[0049] Step 2: Based on the position command signal θ * Based on the position information detected by the stepper motor position sensor, calculate e = (θ) * -θ), determine the absolute value of e: if it is greater than 0.5π / Z r Proceed to step 3; if it is less than or equal to 0.5π / Z r Proceed to step 4;

[0050] Step 3: Set e = (θ) * -θ) I is calculated by the closed-loop control PID controller. qout , and I out =|I qout |, according to Iqout The sign selection control method: if it is greater than zero, then the AB phase current is i a =I out cos(Z r θ+0.5π), i b =I out sin(Z r The electromagnetic torque is calculated as KI (θ+0.5π). out If it is less than or equal to zero, then the AB phase current is i a =I out cos(Z r θ-0.5π), i b =I out sin(Z r Calculated using θ-0.5π, the electromagnetic torque is -KI out Proceed to step 2;

[0051] Step 4: Open-loop control, making I q =|I qout |, calculation The output current of phase AB is i a =I out cos(Z r θ * ), i b =I out sin(Z r θ * Calculate and proceed to step 2.

[0052] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0053] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0054] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0055] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0056] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of two-phase hybrid stepper motor closed-loop and open-loop hybrid position control methods under the guidance of this patent. All equivalent changes and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A closed-loop and open-loop hybrid position control method for a two-phase hybrid stepper motor, characterized in that: When the absolute value of the motor position tracking error is greater than the threshold, the system is a closed-loop position control for a two-phase hybrid stepper motor; when the absolute value of the motor position tracking error is less than or equal to the threshold, the system is an open-loop position control for a two-phase hybrid stepper motor. Specifically, the following steps are included: Step S1: Set the open-loop control holding torque current amplitude Initialize the closed-loop control PID controller parameters and controller output saturation value: Step S2: Based on the position command signal Calculate the position information detected by the stepper motor position sensor. ,judge The absolute value: if greater than Proceed to step S3; if less than or equal to Proceed to step S4; Step S3: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Calculation via closed-loop control PID controller ,and ,according to The sign selection control method: if it is greater than zero, then the AB phase current is... , The electromagnetic torque is calculated as follows: If it is less than or equal to zero, then the AB phase current is... , The electromagnetic torque is calculated as follows: After completion, proceed to step S2; Step S4: Open-loop control, making ,calculate The output current of phases AB is as follows: , Calculate; after completion, proceed to step S2; In the above steps: For the mechanical angle of the stepper motor, For the number of motor stages, This is the torque coefficient.

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