A Three-Loop Suspension Control Method for Bearingless Motors Based on Eccentric Compensation

Abstract

The application discloses a three-loop suspension control method of a bearingless motor based on eccentricity compensation. In view of the problem that the rotor of the bearingless motor is prone to oscillation and difficult to be stably suspended, eccentricity compensation is introduced to inhibit positive feedback generated by rotor eccentricity. In view of the problem of large overshoot in the radial displacement adjustment process, a radial velocity loop is introduced on the basis of traditional displacement current double-loop suspension control, so that when the displacement error is zero, the given value and the actual radial velocity are both zero, and the rotor can move to the given position without overshoot and oscillation. By introducing the eccentricity compensation and the radial velocity control, the bearingless motor which is complex and difficult to control can be equivalent to a traditional servo motor, the design difficulty of the controller parameters is reduced, and the stability of the suspension control system is improved.

Description

Technical Field

[0001] This invention relates to the field of bearingless motor control technology, and in particular to a three-ring suspension control method for bearingless motors based on eccentric compensation. Background Technology

[0002] A bearingless motor is a type of motor that integrates the functions of a motor and a magnetic levitation bearing. Because it has no mechanical friction and requires no lubrication, it is widely used in aerospace, semiconductor manufacturing, and life sciences. However, the radial displacement of the rotor in a bearingless motor is prone to oscillation, and achieving high-precision, stable levitation remains a significant challenge.

[0003] The root cause of the difficulty in controlling the radial displacement of a bearingless motor rotor lies in the positive feedback caused by rotor eccentricity. The greater the eccentricity, the more intense the positive feedback, making the suspension control system even more difficult to stabilize. Even if the suspension control system achieves stability, overshoot in the rotor radial displacement will occur during adjustment, reducing the suspension control accuracy. Furthermore, the suspension controller has numerous parameters, which are heavily coupled with variables such as motor current and rotor radial displacement, making parameter design complex. Selecting inappropriate controller parameters may lead to increased radial displacement fluctuations or even instability of the suspension control system.

[0004] Therefore, how to ensure that the rotor of the bearingless motor moves to a given position without overshoot and oscillation, while also reducing the difficulty of designing the suspension controller parameters, has become a research topic. Summary of the Invention

[0005] The embodiments of the present invention provide a three-loop suspension control method for a bearingless motor based on eccentric compensation. The three-loop suspension control method for a bearingless motor that considers eccentric compensation proposed in this invention introduces eccentric compensation control and radial speed control on the basis of the traditional displacement current dual-loop suspension control (currently, the suspension control part of the bearingless motor adopts displacement current dual-loop control).

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] S1. A radial displacement sampling signal x is obtained by sampling through a displacement sensor installed in the bearingless motor. sn Radial displacement given signal x * Subtract x sn Then, the obtained radial displacement error signal is transmitted to the radial displacement controller (APR), and the APR outputs the radial velocity setpoint signal v. x * ;

[0008] S2, according to x sn and displacement sensor gain k sn Obtain the actual radial velocity signal vx ;

[0009] S3, v x * Subtract v x The obtained radial velocity error signal is transmitted to the radial velocity controller (ASR) to obtain the uncompensated suspension force given signal.

[0010] The output of S4 and ASR, i.e., the uncompensated suspension force command signal, is subtracted from the output of the eccentricity compensation controller to obtain the suspension force command signal F. x * ;

[0011] S5, F x * Through mathematical model calculations, the given value i of the levitation current of the bearingless motor can be obtained. x * .

[0012] The bearingless motor three-loop suspension control method based on eccentric compensation provided in this invention addresses the problem of rotor oscillation and difficulty in stable suspension of bearingless motors by introducing eccentric compensation, which can suppress positive feedback caused by rotor eccentricity. To address the issue of large overshoot during radial displacement adjustment, a radial velocity loop is introduced on top of the traditional displacement current dual-loop suspension control. This ensures that when the displacement error is zero, both the radial velocity setpoint and the actual radial velocity are zero, allowing the rotor to move to the given position without overshoot or oscillation. By introducing eccentric compensation and radial velocity control, this invention can transform the complex and difficult-to-control bearingless motor into an equivalent traditional servo motor, reducing the design difficulty of controller parameters and improving the stability of the suspension control system. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 The present invention provides a block diagram of a bearingless motor three-ring suspension control structure considering eccentricity compensation.

[0015] Figure 2 The invention presents the rotor radial displacement, radial velocity, and levitation current waveforms of a bearingless motor under a three-loop suspension control system that considers eccentricity compensation, compared to those under a traditional two-loop control system. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Embodiments of the present invention will be described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in the specification of the present invention means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0017] This invention provides a three-loop suspension control method for a bearingless motor based on eccentric compensation, such as... Figure 1 As shown, eccentricity compensation is introduced to suppress positive feedback caused by rotor eccentricity. Based on the traditional dual-loop displacement current suspension control, a radial velocity loop is introduced, ensuring that when the displacement error is zero, both the radial velocity setpoint and the actual radial velocity are zero. This allows the rotor to move to the given position without overshoot or oscillation. By introducing eccentricity compensation and radial velocity control, this invention can transform the complex and difficult-to-control bearingless motor into a traditional servo motor, reducing the design difficulty of controller parameters and improving the stability of the suspension control system.

[0018] The general flow of the method includes:

[0019] S1. A radial displacement sampling signal x is obtained by sampling through a displacement sensor installed in the bearingless motor. sn Radial displacement given signal x * Subtract x snThen, the obtained radial displacement error signal is transmitted to the radial displacement controller (APR), and the APR outputs the radial velocity setpoint signal v. x * ;

[0020] S2, according to x sn and displacement sensor gain k sn Obtain the actual radial velocity signal v x ;

[0021] S3, v x * Subtract v x The obtained radial velocity error signal is transmitted to the radial velocity controller (ASR) to obtain the uncompensated suspension force given signal.

[0022] The output of S4 and ASR, i.e., the uncompensated suspension force command signal, is subtracted from the output of the eccentricity compensation controller to obtain the suspension force command signal F. x * ;

[0023] S5, F x * Through mathematical model calculations, the given value i of the levitation current of the bearingless motor can be obtained. x * .

[0024] S6, Floating current given signal i x * After the equivalent current loop G i (s), to obtain the actual levitation current i x .

[0025] S7, Actual Floating Current i x When output to a bearingless motor, a controllable levitation force f can be generated. ix Controllable levitation force f ix eccentric force f ex With external force f d Adding them together, we get the net external force F acting on the rotor. x .

[0026] S8, F x Dividing by the rotor mass m and integrating twice, the radial displacement can be obtained.

[0027] Among them, x sn Divide by k sn Then, by differentiating with respect to time, we obtain v. x .

[0028] S4 includes: subtracting the compensation force f from the uncompensated levitation force given signal in the ASR. c The given levitation force signal F is obtained.x * Among them, the eccentricity compensation controller determines the value based on x. sn This generates a compensating force f that is the same in magnitude but opposite in direction to the eccentric force currently acting on the rotor of the bearingless motor. c and f c Introduced to the given levitation force.

[0029] In this embodiment, the transfer function of the eccentricity compensation controller is: k x k is the force displacement coefficient. sn Let be the displacement sensor gain, and s be a complex variable. The eccentricity compensation controller can be a non-physical controller, specifically a compensation method implemented in code.

[0030] In this embodiment, S5 includes:

[0031] F x * Input levitation force model G mm (s), and output the floating current given signal i x * The transfer function of the levitation force model is: k c is the force-current coefficient, used to characterize the levitation force generated per unit levitation current.

[0032] In this embodiment, S6 includes:

[0033] i x * Input equivalent current loop G i (s), to obtain the actual levitation current i x The transfer function of the equivalent current loop is: ω bc This represents the bandwidth of the equivalent current loop.

[0034] In this embodiment, S7 includes:

[0035] F x =f ix +f ex +f d f ix =k c i x f ix =k c i x f ix f represents the controllable levitation force. ex denoted by eccentric force, and x represents the radial displacement of the rotor.

[0036] In this embodiment, APR uses a proportional (P) control algorithm, ASR uses a proportional-integral (PI) control algorithm, and the floating current controller uses a proportional-integral (PI) control algorithm. Figure 2 This invention presents the rotor radial displacement, radial velocity, and levitation current waveforms of a bearingless motor under a three-loop levitation control system with eccentric compensation, compared to a traditional two-loop control system. Under the three-loop levitation control system with eccentric compensation, the rotor's velocity remains constant above or equal to zero as it moves from its initial position (x = -200 μm) to the displacement setpoint (x = 0 μm), preventing reverse movement and eliminating overshoot. Furthermore, under this system, the rotor begins to decelerate before reaching the displacement setpoint, and when it does, the radial velocity decreases to zero, allowing the rotor to stably levitate at the setpoint. The radial displacement controller (APR) employs a proportional (P) control algorithm, the radial velocity controller (ASR) employs a proportional-integral (PI) control algorithm, and the levitation current controller employs a proportional-integral (PI) control algorithm. With the addition of eccentric compensation and radial velocity control, the proportional-integral (PI) parameters in the APR, ASR, and levitation current controllers can be designed using the same parameters as traditional servo motor controllers.

[0037] Compared with the prior art, the main advantages of this embodiment are:

[0038] 1. The control method proposed in this invention enables the rotor of a bearingless motor to move to a given position without overshoot or oscillation.

[0039] 2. The control method proposed in this invention can convert a bearingless motor into a traditional servo motor for control. The parameters in the suspension controller can be designed according to the parameter design process of a traditional servo motor controller, which reduces the difficulty of designing the suspension controller parameters.

[0040] 3. In the control method proposed in this invention, the radial displacement controller can achieve system stability and no steady-state error without integral or derivative control. At the same time, the proportional coefficient of the radial displacement controller is decoupled from parameters such as motor excitation current and rotor radial displacement.

[0041] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A three-ring suspension control method for a bearingless motor based on eccentricity compensation, characterized in that, Comprising: S1, sampling radial displacement sampling signal x by displacement sensor installed in the bearingless motor sn , radial displacement given signal x * Subtract x sn After that, the obtained radial displacement error signal is transmitted to the radial displacement controller (Automatic Position Regulator, APR), and the APR outputs the radial velocity given signal v x * ; S2, according to x sn and displacement sensor gain k sn , acquiring an actual radial velocity signal v x ; S3, v x * Subtracting v x The radial velocity error signal obtained is transmitted to a radial velocity controller (ASR) to obtain a suspension force command signal before compensation. S4, the output result of the ASR, i.e. the suspension force given signal before compensation, is subtracted by the output result of the eccentricity compensation controller, to obtain the suspension force given signal F x * ; S4 comprises: subtracting the compensation force f from the given signal of the non-compensated suspension force c , to obtain the given signal of the suspension force F x * ; wherein the compensation force f same in magnitude and opposite in direction to the current eccentric force suffered by the rotor of the bearingless motor is generated by the eccentricity compensation controller according to x sn c ;​ S5、according to F x * , the suspension current given value i x * ; S5 includes: in the suspension current controller, F x * input suspension force model G mm (s), and output suspension current given signal i x * , the transfer function of the suspension force model is: , k c is the force current coefficient, which is used to represent the suspension force generated by unit suspension current; i x * input equivalent current loop G i (s), get actual suspension current i x , the transfer function of the equivalent current loop is: , ω bc is the bandwidth of the equivalent current loop; actual suspension current i x output to the bearingless motor, the bearingless motor generates controllable suspension force f ix .

2. The method according to claim 1, characterized in that S2 Comprising: x sn divide by k sn post time differentiation gives v x .

3. The method of claim 1, wherein, The transfer function of the eccentricity compensation controller is: , k x is a force displacement coefficient, k sn is a displacement sensor gain, and s is a complex variable.

4. The method according to claim 1, characterized by S5 Comprising: , f ix represents the controllable suspension force, f ex represents the eccentric force, x represents the rotor radial displacement, k x is the force displacement coefficient.

5. The method of claim 1, wherein, The APR employs a proportional (P) control algorithm, the ASR employs a proportional-integral (PI) control algorithm, and the suspension current controller employs a proportional-integral (PI) control algorithm.

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