A magnetic suspension radial bearing magnetic force parameter online identification method

Abstract

The application discloses a kind of magnetic suspension radial bearing magnetic force parameter online identification method, comprising the following steps: respectively obtaining magnetic suspension radial bearing magnetic force under zero displacement control mode and zero current control mode;Based on the magnetic suspension radial bearing magnetic force under zero displacement control mode, obtain first vibration force and control current;Based on the magnetic suspension radial bearing magnetic force under zero current control mode, obtain second vibration force and rotor radial displacement;Parameter identification is carried out to the first vibration force, second vibration force, control current and rotor radial displacement, and the magnetic suspension radial bearing magnetic force parameter is estimated.The method of the application is simple, easy to implement, and the identification method is widely used, which can effectively be used for the running state and fault diagnosis of magnetic suspension bearing control system.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation bearing technology, and in particular relates to an online identification method for magnetic force parameters of magnetic levitation radial bearings. Background Technology

[0002] Magnetic levitation bearings can stably levitate a rotor using magnetic force, enabling the rotor to rotate without mechanical contact at speeds of up to hundreds of thousands of revolutions per minute. They require no lubrication, do not pollute the working environment, and can achieve active vibration control by adjusting stiffness and damping. They are now widely used in industrial and other fields, so the reliability and safety of the system are receiving increasing attention.

[0003] To ensure the long-term stable and safe operation of the magnetic levitation bearing system, it is necessary to accurately identify the parameters of the magnetic force of the magnetic levitation bearing. Magnetic levitation bearings control the coil current based on rotor displacement deviation, thereby generating magnetic force to maintain stable rotor levitation. Therefore, the relevant magnetic force parameters are current stiffness and displacement stiffness.

[0004] Currently, the acquisition of magnetic parameters mainly relies on static testing, such as the patent "Radial Magnetic Bearing Stiffness Testing Device." This device uses force sensors to measure current stiffness and displacement stiffness by changing current and displacement values. However, magnetic parameters change with factors such as current, displacement, and temperature, necessitating dynamic testing. For example, the patent "A Method for Measuring Current Stiffness and Displacement of a Magnetic Suspension Bearing" considers current and displacement stiffness under operating conditions, but requires three trial weights and four acceleration / deceleration cycles, making the operation cumbersome. Therefore, there is an urgent need for a simple and efficient online identification method for the magnetic parameters of magnetically levitated radial bearings. Summary of the Invention

[0005] The purpose of this invention is to provide an online identification method for magnetic parameters of a magnetically levitated radial bearing. This method is simple, efficient, and versatile, and can be effectively used for the operation status and fault diagnosis of magnetically levitated bearing control systems, thereby solving the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides an online identification method for magnetic force parameters of a magnetically levitated radial bearing, comprising the following steps:

[0007] The magnetic force of the radial bearing for magnetic levitation is obtained under zero displacement control mode and zero current control mode, respectively.

[0008] Based on the magnetic force of the radial bearing in the zero-displacement control mode, the first vibration force and control current are obtained;

[0009] Based on the magnetic force of the magnetically levitated radial bearing in zero-current control mode, a second vibration force and rotor radial displacement are obtained.

[0010] The parameters of the first vibration force, the second vibration force, the control current, and the rotor radial displacement are identified, and the magnetic force parameters of the magnetic levitation radial bearing are estimated.

[0011] Optionally, the process of obtaining the magnetic force of the magnetically levitated radial bearing in the zero-displacement control mode and the zero-current control mode includes: obtaining the expression of the magnetic force of the magnetically levitated radial bearing at the equilibrium position; in the zero-displacement control mode, setting the rotor radial displacement of the magnetic bearing in the x and y directions to zero, thus obtaining the magnetic force of the magnetically levitated radial bearing in the zero-displacement control mode; in the zero-current control mode, setting the control current of the magnetic bearing in the x and y directions to zero, thus obtaining the magnetic force of the magnetically levitated radial bearing in the zero-current control mode.

[0012] Optionally, the magnetic force expression for the magnetically levitated radial bearing at the equilibrium position is:

[0013]

[0014] Among them, F ax F ay F represents the magnetic force of the first magnetic bearing in the x and y directions, respectively, indicating the radial bearing magnetic force of the magnetic levitation bearing. bx F by Let k represent the magnetic levitation radial bearing magnetic forces of the second magnetic bearing in the x and y directions, respectively. ai k represents the current stiffness of the first magnetic bearing. bi k represents the current stiffness of the second magnetic bearing. ax k represents the displacement stiffness of the first magnetic bearing. bx Indicates the displacement stiffness of the second magnetic bearing, i ax i represents the control current of the first magnetic bearing in the x-direction. ay i represents the control current of the first magnetic bearing in the y direction. bx i represents the control current of the second magnetic bearing in the x-direction. by This represents the control current of the second magnetic bearing in the y-direction, x ax x ay These represent the rotor radial displacements of the first magnetic bearing in the x and y directions, respectively. bx x by These represent the rotor radial displacements of the second magnetic bearing in the x and y directions, respectively.

[0015] Optionally, the process of obtaining the first vibration force includes: in the zero-displacement control mode, obtaining the vibration force in the x-direction of the zero-displacement control mode based on the magnetic force of the first magnetic bearing in the x-direction and the magnetic force of the second magnetic bearing in the x-direction; obtaining the vibration force in the y-direction of the zero-displacement control mode based on the magnetic force of the first magnetic bearing in the y-direction and the magnetic force of the second magnetic bearing in the y-direction; and obtaining the first vibration force based on the vibration forces in the x-direction and y-direction of the zero-displacement control mode.

[0016] Optionally, the process of obtaining the second vibration force includes: in the zero-current control mode, obtaining the vibration force in the x-direction under the zero-current control mode based on the magnetic force of the first magnetic bearing in the x-direction and the magnetic force of the second magnetic bearing in the x-direction; obtaining the vibration force in the y-direction under the zero-current control mode based on the magnetic force of the first magnetic bearing in the y-direction and the magnetic force of the second magnetic bearing in the y-direction; and obtaining the second vibration force based on the vibration forces in the x-direction and y-direction under the zero-current control mode.

[0017] Optionally, the process of estimating the magnetic force parameters of the magnetically levitated radial bearing includes: pre-setting an estimation matrix of the current stiffness and displacement stiffness of the magnetically levitated radial bearing; obtaining a cost function of the first vibration force based on the pre-set current stiffness estimation matrix and the control current under zero-displacement control mode; obtaining a cost function of the second vibration force based on the pre-set displacement stiffness estimation matrix and the rotor radial displacement under zero-current control mode; obtaining an estimated value of the current stiffness of the magnetically levitated radial bearing using the steepest descent method based on the pre-set current stiffness estimation matrix and the cost function of the first vibration force; and obtaining an estimated value of the displacement stiffness of the magnetically levitated radial bearing using the steepest descent method based on the pre-set displacement stiffness estimation matrix and the cost function of the second vibration force.

[0018] Optionally, in the zero-displacement control mode, the amplitude of the control current is less than 1 / 3 of the rated control current amplitude.

[0019] Optionally, in the zero-current control mode, the amplitude of the rotor radial displacement is less than 1 / 5 of the protection gap.

[0020] The technical effects of this invention are as follows:

[0021] (1) This invention was carried out under the normal working condition of the magnetic levitation bearing, so the obtained magnetic force parameters are more accurate;

[0022] (2) This invention can be used to measure at any speed within the rated speed range of magnetically levitated rotating machinery without affecting normal operation;

[0023] (3) The present invention obtains vibration force using only two force sensors, without the need for acceleration or deceleration, and the method is simple and easy to implement;

[0024] (4) The method of the present invention is simple and easy to implement, and this identification method is highly versatile and can be effectively used for the operation status and fault diagnosis of magnetic levitation bearing control system. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 This is a schematic diagram of the magnetic levitation rotating mechanical structure in an embodiment of the present invention;

[0027] Figure 2 This is a block diagram of the magnetic levitation radial bearing control system in an embodiment of the present invention;

[0028] Figure 3 This is a flowchart of the identification method in an embodiment of the present invention;

[0029] Figure 4 The diagram shows the identification results of the magnetic force parameters of the magnetic levitation radial bearing in the embodiment of the present invention. (a) is a schematic diagram of the identification results of the current stiffness of magnetic bearing A, (b) is a schematic diagram of the identification results of the current stiffness of magnetic bearing B, (c) is a schematic diagram of the identification results of the displacement stiffness of magnetic bearing A, and (d) is a schematic diagram of the identification results of the displacement stiffness of magnetic bearing B. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0032] Example 1

[0033] like Figure 1 The diagram shown is a schematic diagram of the magnetic levitation rotating mechanical structure involved in this embodiment. The magnetic levitation rotating mechanical structure includes a shell, a rotor, a first magnetic bearing (i.e., magnetic bearing A), a second magnetic bearing (i.e., magnetic bearing B), a displacement sensor A, and a displacement sensor B. The diagram only shows the magnetic bearing and displacement sensor in the x-direction; the same components are also present in the y-direction.

[0034] like Figure 2 The diagram shown is a block diagram of the magnetic levitation radial control system described in this embodiment. The basic controller outputs a control quantity based on the difference between the reference position and the rotor displacement detected by the displacement sensor. This control quantity is then output to the magnetic bearing via the power amplifier board. The magnetic bearing generates magnetic force, causing the rotor to levitate stably at the reference position. Depending on the control method, a "zero displacement" controller or a "zero current" controller can be connected in series with the basic controller to achieve the "zero displacement" control mode and the "zero current" control mode, respectively.

[0035] The flowchart of this embodiment is as follows: Figure 3 As shown, an online identification method for the magnetic force parameters of a magnetically levitated radial bearing first establishes independent expressions for the magnetic force, control current, and rotor displacement under both "zero displacement" and "zero current" control modes, based on the linearized equation of the magnetic force of the radial bearing at its equilibrium position. Then, two force sensors are installed on the housing of the magnetically levitated rotating machinery to measure vibration force; their output value is equal to the sum of the magnetic forces of the two radial bearings. Next, the rotor is accelerated to a fixed speed, and the control current and vibration force are recorded under the "zero displacement" control mode. Maintaining this fixed speed, the "zero displacement" control mode is canceled, and the "zero current" control mode is used to record the rotor radial displacement and vibration force. Finally, the magnetic force parameters of the magnetically levitated radial bearing are estimated and identified online using the control current, rotor displacement, and vibration force recorded under both control modes.

[0036] A method for online identification of magnetic force parameters of a magnetically levitated radial bearing includes the following steps:

[0037] (1) Establish the relationship expression of the magnetic force of the radial bearing of magnetic suspension under the two control modes of "zero displacement" and "zero current";

[0038] For a magnetically levitated rotor system, the magnetic force of the radial bearing at the equilibrium position can be approximated as linear as:

[0039]

[0040] Among them, the magnetic force of the radial bearing for magnetic levitation in the x and y directions of magnetic bearing A is F. ax F ay The magnetic levitation radial bearing force of magnetic bearing B in the x and y directions is F. bx F by The current stiffness of magnetic bearing A is expressed in k. ai The current stiffness of magnetic bearing B is expressed in k. bi The displacement stiffness of magnetic bearing A is represented by k. ax The displacement stiffness of magnetic bearing B is represented by k. bx This indicates that the control currents of magnetic bearing A in the x and y directions are represented by i. ax and iay This indicates that the control currents of magnetic bearing B in the x and y directions are represented by i. bx and i by Indicates that x ax x ay These represent the rotor radial displacements of magnetic bearing A in the x and y directions, respectively. bx x by These represent the rotor radial displacements of magnetic bearing B in the x and y directions, respectively.

[0041] Since the effects of multiple harmonics are negligible, a "zero displacement" control mode is adopted during rotor rotation, meaning the rotor rotates around its geometric axis with zero radial displacement. In this mode, the magnetic force of the magnetically levitated radial bearing can be expressed as:

[0042]

[0043] During rotor rotation, a "zero current" control mode is adopted, meaning the magnetic bearing control current is 0. At this time, the magnetic force of the magnetically levitated radial bearing can be expressed as:

[0044]

[0045] (2) Two force sensors are installed on the shell of the magnetically levitated rotating machine along the positive x-axis and positive y-axis. The installation position is on the cross section where the rotor's center of mass is located. Since the rotor's gravity acts axially, the vibration force F measured by the two force sensors is... x and F y These are respectively equal to the sum of the magnetic forces of the two radial magnetic levitation bearings:

[0046]

[0047] (3) Make the rotor float stably at the reference position, then accelerate the rotor to a certain fixed speed, adopt the "zero displacement" control mode, and after stabilization, record the control current of the radial four channels and the vibration force F measured by the force sensor at this time. x1 and F y1 Thus, the first vibrational force is obtained:

[0048]

[0049] As a specific implementation, the rotor is stably suspended at a reference position, and then accelerated to 100Hz. A general-purpose frequency selector is used to achieve the "zero displacement" control mode. After the rotor stably rotates around the geometric axis, the control current of the radial four channels and the vibration force F measured by the force sensor at this time are recorded. x1 and F y1 :

[0050]

[0051] In (3), the amplitude of the control current should be less than 1 / 3 of the rated control current amplitude.

[0052] (4) Maintain the fixed rotational speed of step (3), cancel the "zero displacement" control mode, adopt the "zero current" control mode, and after stabilization, record the rotor radial displacement and the vibration force F measured by the force sensor at this time. x2 and F y2 Thus, a second vibrational force is obtained:

[0053]

[0054] As a specific implementation, the fixed rotational speed in step (3) is maintained, the "zero displacement" control mode is canceled, and the LMS adaptive algorithm is used to implement the "zero current" control mode. After the rotor rotates stably, the radial displacement of the rotor and the vibration force F measured by the force sensor at this time are recorded. x2 and F y2 :

[0055]

[0056] In (4), the amplitude of the rotor displacement should be less than 1 / 5 of the protection gap.

[0057] (5) Identify the magnetic parameters of the magnetic levitation bearing based on the recorded control current, rotor radial displacement, and vibration force:

[0058] Define two cost functions J1 and J2 respectively

[0059]

[0060] in and k ai k bi k ax k bx The estimated value.

[0061] Let the estimated matrix of the current stiffness and displacement stiffness of the magnetically levitated radial bearing be:

[0062] and

[0063] The estimated values ​​of the current stiffness and displacement stiffness of the magnetic levitation radial bearing can then be obtained using the steepest descent method, as expressed in the following expressions:

[0064]

[0065] in:

[0066]

[0067] The constants ε1 and ε2 are convergence factors and are positive numbers, which can adjust the convergence speed of the estimated values ​​of the current stiffness and displacement stiffness of the magnetic levitation radial bearing.

[0068] As a specific example:

[0069] The magnetic parameters of the magnetic levitation bearing were identified based on the recorded control current, rotor radial displacement, and vibration force.

[0070] Define two cost functions J1 and J2 as follows:

[0071]

[0072] in and k ai k bi k ax k bx The estimated value.

[0073] Let the estimated matrix of the current stiffness and displacement stiffness of the magnetically levitated radial bearing be:

[0074] and

[0075] The estimated values ​​of the current stiffness and displacement stiffness of the magnetic levitation radial bearing can then be obtained using the steepest descent method, as expressed in the following expressions:

[0076]

[0077] in:

[0078]

[0079] The constants ε1 and ε2 are convergence factors and are positive numbers. They can adjust the convergence speed of the estimated values ​​of the magnetic levitation radial bearing current stiffness and displacement stiffness. Here, the values ​​are taken as 0.01 and 0.02.

[0080] Then the identification results of the magnetic force parameters of the magnetic levitation radial bearing can be obtained as follows: Figure 4 As shown, the current stiffness of magnetic bearing A is 0.39 N / mA and the displacement stiffness is 1.52 N / μm, while the current stiffness of magnetic bearing B is 0.116 N / mA and the displacement stiffness is 0.38 N / μm.

[0081] The basic principle of this embodiment is as follows: Based on the linearized equation of the magnetic force of the magnetically levitated radial bearing at the equilibrium position, independent expressions for the magnetic force, control current, and rotor displacement of the magnetically levitated radial bearing are established under both "zero displacement" and "zero current" control modes. Simultaneously, two force sensors are installed on the magnetically levitated rotating machinery to measure vibration force; their output value is equal to the sum of the magnetic forces of the two radial bearings. When the rotor accelerates to a certain fixed speed, both "zero displacement" and "zero current" control modes are used. By collecting the control current, rotor displacement, and vibration force under both control modes, the magnetic force parameters of the magnetically levitated radial bearing can be estimated online.

[0082] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for online identification of magnetic force parameters of a magnetically levitated radial bearing, characterized in that, Includes the following steps: The magnetic force of the radial bearing for magnetic levitation is obtained under zero displacement control mode and zero current control mode, respectively. Based on the magnetic force of the radial bearing in the zero-displacement control mode, the first vibration force and control current are obtained; Based on the magnetic force of the magnetically levitated radial bearing in zero-current control mode, a second vibration force and rotor radial displacement are obtained. The parameters of the first vibration force, the second vibration force, the control current, and the rotor radial displacement are identified, and the magnetic force parameters of the magnetic levitation radial bearing are estimated. The process of obtaining the first vibration force includes: in the zero-displacement control mode, obtaining the vibration force in the x-direction of the zero-displacement control mode based on the magnetic force of the first magnetic bearing in the x-direction and the magnetic force of the second magnetic bearing in the x-direction; obtaining the vibration force in the y-direction of the zero-displacement control mode based on the magnetic force of the first magnetic bearing in the y-direction and the magnetic force of the second magnetic bearing in the y-direction; and obtaining the first vibration force based on the vibration forces in the x-direction and y-direction of the zero-displacement control mode.

2. The method for online identification of magnetic parameters of a magnetically levitated radial bearing according to claim 1, characterized in that, The process of obtaining the magnetic force of the magnetically levitated radial bearing in zero-displacement control mode and zero-current control mode includes: obtaining the expression for the magnetic force of the magnetically levitated radial bearing at the equilibrium position; and in zero-displacement control mode, causing the magnetic bearing to... x direction and y When the rotor's radial displacement in the direction is zero, the magnetic force of the magnetically levitated radial bearing is obtained in the zero-displacement control mode; in the zero-current control mode, the magnetic bearing is made to... x direction and y If the control current in the direction is zero, then the magnetic force of the magnetically levitated radial bearing in the zero-current control mode is obtained.

3. The online identification method for magnetic force parameters of a magnetically levitated radial bearing according to claim 2, characterized in that, The magnetic force expression for the radial bearing with magnetic levitation at the equilibrium position is: in, F ax , F ay These represent the first magnetic bearing in x direction and y Magnetic force of radial bearing for magnetic levitation in the direction of direction. F bx , F by These respectively represent the second magnetic bearing in x direction and y Magnetic force of radial bearing for magnetic levitation in the direction of direction. k ai This indicates the current stiffness of the first magnetic bearing. k bi This indicates the current stiffness of the second magnetic bearing. k ax This indicates the displacement stiffness of the first magnetic bearing. k bx This indicates the displacement stiffness of the second magnetic bearing. i ax Indicates the first magnetic bearing in x Directional control current, i ay Indicates the first magnetic bearing in y Directional control current, i bx Indicates the second magnetic bearing in x Directional control current, i by Indicates the second magnetic bearing in y Directional control current, x ax , x ay These respectively represent the first magnetic bearing in x direction and y The radial displacement of the rotor in the direction of rotation. x bx , x by These respectively represent the second magnetic bearing in x direction and y The radial displacement of the rotor in the direction.

4. The online identification method for magnetic force parameters of a magnetically levitated radial bearing according to claim 3, characterized in that, The process of obtaining the second vibration force includes: in zero-current control mode, based on the first magnetic bearing... x The magnetic force of the radial bearing and the second magnetic bearing in the direction of magnetic levitation. x The magnetic force of the radial bearing in the direction of magnetic levitation achieves zero-current control mode. x Vibrational force in the direction; based on the first magnetic bearing in y The magnetic force of the radial bearing and the second magnetic bearing in the direction of magnetic levitation. y The magnetic force of the radial bearing in the direction of magnetic levitation achieves zero-current control mode. y Vibration force in the direction; based on zero current control mode x direction and y The vibration force in the direction of the vibration force is used to obtain the second vibration force.

5. The method for online identification of magnetic force parameters of a magnetically levitated radial bearing according to claim 1, characterized in that, The process of estimating the magnetic force parameters of the magnetically levitated radial bearing includes: pre-setting the estimation matrices of the current stiffness and displacement stiffness of the magnetically levitated radial bearing; obtaining the cost function of the first vibration force based on the pre-set current stiffness estimation matrix and the control current under zero-displacement control mode; obtaining the cost function of the second vibration force based on the pre-set displacement stiffness estimation matrix and the rotor radial displacement under zero-current control mode; obtaining the estimated value of the current stiffness of the magnetically levitated radial bearing using the steepest descent method based on the pre-set current stiffness estimation matrix and the cost function of the first vibration force; and obtaining the estimated value of the displacement stiffness of the magnetically levitated radial bearing using the steepest descent method based on the pre-set displacement stiffness estimation matrix and the cost function of the second vibration force.

6. The method for online identification of magnetic parameters of a magnetically levitated radial bearing according to claim 1, characterized in that, In the zero-displacement control mode, the amplitude of the control current is less than 1 / 3 of the rated control current amplitude.

7. The method for online identification of magnetic force parameters of a magnetically levitated radial bearing according to claim 1, characterized in that, In the zero-current control mode, the amplitude of the rotor radial displacement is less than 1 / 5 of the protection gap.

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