Decoupling method of torque system and suspension system of single-winding magnetic suspension permanent magnet synchronous motor

Abstract

The application discloses a torque system and suspension system decoupling method of single-winding magnetic suspension permanent magnet synchronous motor, the motor adopts a suspension parallel type single-winding structure, realizes torque system decoupling to suspension current, and the permanent magnet adopts an alternating pole, realizing suspension system decoupling to the rotor position angle; for the suspension system current loop, the coupling term of the torque system to the suspension system is regarded as a disturbance, a sliding mode disturbance observer based on an improved super spiral algorithm is designed, the disturbance is observed and compensated, and the decoupling of the suspension system and torque control is realized; for the suspension system displacement / suspension force loop, a sliding mode active disturbance rejection controller is designed, the disturbance of the rotor displacement is observed, the suspension force is compensated, and the decoupling between different suspension degrees of freedom is realized; the remaining coupling factors of the torque system are regarded as system disturbances, a sliding mode-active disturbance rejection composite control method is used, the disturbances are observed and compensated in real time, and the decoupling of the remaining coupling factors is realized. The application realizes the overall decoupling of the torque system and the suspension system.

Description

Technical Field

[0001] This invention relates to the field of motor body design and control technology, specifically to a decoupling method between the torque system and the suspension system of a single-winding magnetic levitation permanent magnet synchronous motor. This method achieves complete decoupling of various coupled variables within the motor system through topology design and control methods. Background Technology

[0002] Magnetic levitation permanent magnet synchronous motors are widely used in high-speed rotating machinery, vacuum environments, and other special environments because they can achieve frictionless rotor levitation without the need for mechanical bearings. However, traditional single-winding magnetic levitation permanent magnet synchronous motors suffer from coupling problems between the torque system and the levitation system. This coupling complicates the design of the control system and affects the performance and stability of the motor.

[0003] Existing decoupling methods typically improve control strategies by adding complex decoupling algorithms to reduce the mutual influence between torque and the suspension system. However, these methods often rely on complex models and control algorithms, making it difficult to achieve ideal results in practical applications. Furthermore, while some methods can achieve a certain degree of decoupling, they fail to adequately consider system coupling issues in the motor topology design, resulting in suboptimal decoupling performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for decoupling the torque system and suspension system of a single-winding magnetic levitation permanent magnet synchronous motor. By optimizing the motor's topology and control strategy, a complete decoupling of the torque system and suspension system in the single-winding magnetic levitation permanent magnet synchronous motor is achieved.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] Methods for decoupling the torque system from the suspension system of a single-winding magnetically levitated permanent magnet synchronous motor:

[0007] The motor adopts a suspended parallel single winding structure to decouple the torque system from the suspended current;

[0008] The permanent magnets employ an alternating pole design to decouple the levitation system from the rotor position angle;

[0009] In the current loop of the levitation system, the voltage at the torque inverter terminal is regarded as a disturbance term, which, together with other disturbance factors affecting the levitation current control, constitutes the system disturbance. A sliding mode disturbance observer is designed to observe the disturbance in real time and compensate the levitation current, thereby decoupling the levitation current control from the torque system.

[0010] In the displacement / levitation force loop of the suspension system, the coupling between different levitation degrees of freedom and other displacement disturbances are all regarded as system disturbances. A sliding mode active disturbance rejection controller is designed to observe and compensate for the levitation force, thereby achieving control decoupling between different levitation degrees of freedom.

[0011] The internal disturbances unknown in the mathematical model of the torque control system, as well as the external disturbances caused by the external environment and operating conditions, are regarded as disturbances affecting the stable operation of the motor torque system. The sliding mode-active disturbance rejection composite control method is used to observe and compensate for the disturbances in real time, so as to achieve high-performance and robust torque system control.

[0012] Furthermore, the motor adopts a floating parallel single-winding structure to decouple the torque system from the floating current. Specifically, each phase torque winding is connected in series, and the torque inverter only provides three-phase torque current i. mA i mB i mC The floating inverter provides the floating current i s and Where i s Including three-phase floating current i sA i sB i sC The i sA i sB i sC Injected from the midpoint of each phase torque winding, the Connect to the torque inverter and inject torque windings.

[0013] Furthermore, the permanent magnet adopts an alternating pole design, specifically: the permanent magnet is of the surface insertion type, and the number of permanent magnet pole pairs is ≥4; the magnetization direction of the permanent magnet is arranged in the same polarity along the rotor surface, and the rotor core portion adjacent to the permanent magnet is magnetized to the opposite polarity.

[0014] Furthermore, in the sliding mode disturbance observer, the designed linear sliding surface s is: Among them, e ix For the observation error of the levitation current, i sx This represents the actual floating current generated by the motor in the x-axis direction. This represents the estimated floating current in the x-axis direction.

[0015] Furthermore, in the sliding mode perturbation observer, the sliding mode reaching law of the improved superspiral algorithm is: Where k1 and k2 are the superspiral sliding mode gains, v is the state variable, ρ1 and ρ2 are the external disturbances, t is time, λ is the exponential gain, and α is a constant.

[0016] Furthermore, the perturbation observation error e diTreating it as a disturbance term, the control law for the sliding mode disturbance observer based on the improved superspiral algorithm is:

[0017] Furthermore, the sliding mode active disturbance rejection controller is:

[0018]

[0019] Where, the sliding surface s = c2e x1 +e x2 intermediate quantity e x1 =x1-z x1 e x2 =x2-z x2 , z x1 z x2 z x3 The output of the sliding mode disturbance observer for the displacement / levitation force loop is given by k3, λ1, and c2, which are constants greater than 0. f0 (t) represents the feedback control law of the sliding mode active disturbance rejection controller. For disturbance compensation, b1 is the system parameter, and f0 represents the disturbance.

[0020] Furthermore, the feedback control law of the sliding mode active disturbance rejection controller satisfies:

[0021]

[0022] Among them, intermediate quantity x represents the displacement of the motor rotor in the positive x-axis direction, and the coefficient k ecc Related to the characteristics of the air gap magnetic field and the air gap permeability, m is the rotor mass.

[0023] Furthermore, the sliding mode-active disturbance rejection composite control method specifically involves: setting the sliding mode control surface s = e ω By selecting parameter k4 and employing the sliding mode control design method, a sliding mode active disturbance rejection controller for the speed loop is designed:

[0024]

[0025] Among them, e ω For speed error, For the control law of the speed loop, Let z1 be the first derivative of the state variable z1.

[0026] Furthermore, the reference torque current calculated by the sliding mode active disturbance rejection controller of the speed loop is compensated using an extended state observer, and the compensated current command i q * for:

[0027]

[0028] Where b2 is the system control gain, and z2 is the state variable. The tracking signal ω represents a given rotational speed. v1 The derivative with respect to time.

[0029] Compared with the prior art, the present invention, by adopting the above technical solution, has the following beneficial effects:

[0030] 1. Effective decoupling of torque and suspension system: This invention effectively decouples the torque system from the suspension system by designing a suspended parallel single winding structure and adopting an alternating pole permanent magnet design. This solves the problem of mutual interference between torque control and suspension control in traditional magnetic levitation permanent magnet synchronous motors, simplifies system design, and improves control performance.

[0031] 2. Improve system stability and control accuracy: This invention uses a sliding mode observer and a sliding mode active disturbance rejection controller based on an improved superhelical algorithm to observe and compensate for disturbances in the system in real time, thereby further enhancing the system's stability and disturbance rejection capability and improving the accuracy of the suspension system and torque control.

[0032] 3. Simplified suspension control system: By decoupling the suspension system from the rotor position angle, the design of the suspension control system is simplified, making the control more intuitive and easier to implement, which helps to improve the reliability and response speed of the motor in practical applications.

[0033] 4. Enhanced robustness of the control system: This invention designs a robust torque operation control strategy that can cope with the remaining coupling factors in the torque system, achieve complete decoupling of torque control, and ensure that the system can still operate stably under complex working conditions, thus exhibiting good robustness.

[0034] 5. Adaptable to various application environments: Since the topology-control cooperative decoupling method of the present invention can achieve efficient torque and suspension decoupling, it is particularly suitable for high-speed rotating machinery, vacuum environments and other special environments with high requirements for accuracy and stability. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the alternating pole magnetic levitation permanent magnet synchronous motor structure described in this invention;

[0036] Figure 2(a) is a schematic diagram of the levitation force generation principle of the alternating pole magnetic levitation permanent magnet synchronous motor when the rotation angle is 0° in this invention;

[0037] Figure 2(b) is a schematic diagram of the levitation force generation principle of the alternating pole magnetic levitation permanent magnet synchronous motor when the rotation angle is 45° in this invention;

[0038] Figure 2(c) is a finite element magnetic flux density simulation diagram when the rotation angle is 0° according to the present invention;

[0039] Figure 2(d) is a finite element magnetic flux density simulation diagram when the rotation angle is 45° according to the present invention;

[0040] Figure 3 This is the single-winding topology diagram described in this invention;

[0041] Figure 4 This is the air gap magnetic permeability distribution diagram described in this invention;

[0042] Figure 5 This is a control block diagram of the suspension system based on sliding mode self-disturbance rejection as described in this invention;

[0043] Figure 6 This is a block diagram of the suspended current sliding mode disturbance observer described in this invention;

[0044] Figure 7 This is a block diagram of the displacement ring sliding mode observer structure described in this invention;

[0045] Figure 8 This is a block diagram of the rotational speed active disturbance rejection control based on magnetic field orientation as described in this invention;

[0046] Figure 9 This is a block diagram illustrating the active disturbance rejection control principle of the rotational speed slip mode described in this invention.

[0047] Figure 10 This is a flowchart of the decoupling method between the torque system and the suspension system of the single-winding magnetic levitation permanent magnet synchronous motor described in this invention. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0049] like Figure 10 As shown, the present invention provides a method for decoupling the torque system and suspension system of a single-winding magnetically levitated permanent magnet synchronous motor:

[0050] In terms of topology design, this invention proposes a suspended parallel single-winding structure, which decouples the torque control from the levitation current when the levitation force varies within a certain range. The permanent magnet of the motor adopts an alternating pole design, utilizing the structural characteristics of an alternating pole permanent magnet synchronous motor to achieve decoupling of the rotor position angle from the levitation system, thereby simplifying the control of the levitation system.

[0051] In terms of control strategy, for the current loop of the suspension system, this invention treats the coupling term of the torque system to the suspension system as a disturbance. By designing a sliding mode disturbance observer based on an improved superhelical algorithm, the disturbance is observed and compensated in real time, thereby achieving decoupling between the motor suspension system and torque control. For the displacement / suspending force loop of the suspension system, this invention designs a sliding mode active disturbance rejection controller. By observing the disturbance of rotor displacement and compensating for the suspending force in real time, control decoupling between different degrees of freedom of suspension is achieved. The remaining coupling factors of the torque system are treated as system disturbances. Using a combined sliding mode-active disturbance rejection control method, the disturbances are observed and compensated in real time, achieving high-performance, robust torque system control and decoupling of the remaining coupling factors.

[0052] Specifically, it includes the following:

[0053] (1) The prototype is designed as a 48-slot, 8-pole alternating pole magnetic levitation permanent magnet synchronous motor. A cross-sectional schematic diagram of the alternating pole permanent magnet synchronous motor structure is shown below. Figure 1 Its stator is the same as that of a traditional permanent magnet synchronous motor. The permanent magnets in the rotor are of the same polarity and are arranged along the rotor surface. The rotor core adjacent to the permanent magnets is magnetized to the opposite polarity. The magnetized part is called the "iron pole".

[0054] Because the permeability of the rotor core is much greater than that of the permanent magnet, the magnetic flux linkage generated by the stator windings almost entirely passes through the rotor core. Therefore, the bias magnetic field for the rotor's levitation force is actually a single-pole magnetic field within the "iron pole." To obtain a stable and controllable levitation force, the number of pole pairs p in the levitation windings is... s The value is 1, and the number of pole pairs of the torque winding no longer must follow p. s =p m The relationship between ±1.

[0055] Figures 2(a) and (b) illustrate the principle of levitation force generation in an alternating pole magnetic levitation permanent magnet synchronous motor. The air gap magnetic field of the alternating pole magnetic levitation permanent magnet synchronous motor is the superposition of the magnetic fields excited by the permanent magnet, torque current, and levitation current. In Figures 2(a) and 2(b), the thin dashed line represents the magnetic flux generated by the permanent magnet, and the dotted line represents the levitation winding N. y The generated magnetic flux. Within one electrical cycle, as the rotor rotates to different positions, the magnetic field generated by the levitation winding and the magnetic field generated by the permanent magnet are superimposed, resulting in an increase in magnetic flux density at air gap 1 and a decrease in magnetic flux density at air gap 2, generating a radial force along the positive y-axis. When a reverse current is applied, a radial force is generated along the negative y-axis. The principle of radial force generation in the x-axis direction is similar to that in the y-axis direction.

[0056] Let p m A represents the number of pole pairs of the permanent magnet (i.e., the number of pole pairs of the torque winding). p A sLet G be the magnetomotive force generated by the permanent magnet and the levitation winding, respectively; G be the air gap length; r be the average air gap radius; l be the rotor core length; μ0 be the free permeability; and θ be the magnetic field strength. m It is the pole arc angle of the permanent magnet in each pair of poles (including the permanent magnet and the rotor core on one side), with a value range of (0, 2π), and includes the pole arc angle of the permanent magnet and the pole arc angle of the iron pole in each pair of poles (θ). i The sum of ) is 2π / p m When p m When ≥4, the expression for the rotor's levitation force can be written as:

[0057]

[0058] As can be seen from equation (1), the levitation force F is independent of the rotor position angle and the rotating magnetic field excited by the torque current. Finite element simulation of Figures 2(a) and (b) yields magnetic density cloud diagrams as shown in Figures 2(c) and (d). When the rotor position is at different angles, the levitation winding can generate a controllable and stable levitation force.

[0059] (2) The single-winding topology of the alternating pole magnetic levitation permanent magnet synchronous motor is as follows: Figure 3 As shown. The motor torque inverter only provides three-phase torque current i mA i mB i mC The torque windings of each phase of the motor are connected in series, similar to a dual-winding motor; the floating inverter provides the floating current i s (including three-phase floating current i) sA i sB i sC )and Where i sA i sB i sC Injected from the midpoint of each phase torque winding, Connect to the torque inverter and inject torque windings.

[0060] From the perspective of a floating inverter, each phase torque winding is divided into two parallel coil groups, with the floating current flowing in opposite directions within each coil group. Taking phase A winding as an example, the currents in the two coil groups are as follows:

[0061]

[0062] The different current excitations in the two coil groups disrupted the air gap magnetic field balance, generating a radial force. Current i sx i sy These are the levitation currents required to generate levitation forces only in the x or y directions, respectively. Adjusting i sx i sy Generate different F x F yThe desired radial force vector F can be obtained. The three-phase floating current can be obtained by conversion from equation (3), where, The initial position angle is the space vector of the suspended current of phase A.

[0063]

[0064] Taking phase A as an example, such as Figure 3 Let the terminal voltage of the torque inverter be v. m Floating inverter terminal voltage v s The voltages of the two coil groups in phase A winding are v1 and v2, respectively. R is the coil group resistance, L is the coil group self-inductance, M is the mutual inductance between coil groups A1 and A2, and i m Let ω be the torque current, ω be the rotor electric angular velocity, and Ψ be the magnetic flux in a coil group, then:

[0065]

[0066] torque inverter terminal v m and the voltage v at the floating inverter terminal s It can be written as:

[0067] v m =v1+v2

[0068]

[0069] Equations (6) and (7) show that the voltage at the motor winding suspension inverter terminal is coupled with the voltage at the torque inverter terminal, and torque decoupling must be considered when controlling the suspension inverter terminal. When the voltage at the torque inverter terminal is decoupled from the suspension inverter terminal, the torque control system is not affected by the suspension control.

[0070] (3) Based on the characteristics of the suspended parallel single winding structure of the designed motor, the mathematical model of the motor is analyzed and established. The following assumptions are made first:

[0071] ① The magnetic permeability of the magnetic material is infinite, and the entire magnetic flux passes radially through the air gap;

[0072] ②The air gap magnetomotive force exhibits a sinusoidal distribution, and higher harmonics are ignored;

[0073] ③ Ignore magnetic saturation;

[0074] ④ Ignore losses such as eddy currents and friction;

[0075] ⑤ The stator surface is smooth, and the cogging effect and winding end effect are ignored.

[0076] 1) Suspension motion model of alternating pole magnetic levitation permanent magnet synchronous motor

[0077] The air gap magnetic field of an alternating pole magnetic levitation permanent magnet synchronous motor is mainly generated by three excitations: permanent magnets, torque current, and levitation current. Assume the applied torque current is i. m The suspending current is i s The magnetomotive force of the magnetic field generated by the three excitations is A. f A m A s The magnetic flux density is denoted as B. f B m B s Therefore, the magnetomotive force of the air gap magnetic field of the motor can be expressed as:

[0078] A(φ,t)=A f +A m cos(p m φ-p m ωt-μ)+A s cos(φ-λ)(8)

[0079] Where φ is the stator spatial position, ωt is the rotor position angle, μ is the angle between the rotating magnetomotive force and the current in phase A winding, and λ is the angle between the levitation magnetomotive force and the current in phase A winding. To ensure a stable levitation force in the alternating pole magnetic levitation permanent magnet synchronous motor, the levitation current is set to DC, therefore A... s It does not contain the ωt term.

[0080] Based on the structure of the alternating pole magnetic levitation permanent magnet synchronous motor, the air gap magnetic permeability per unit area is:

[0081]

[0082] Considering the case of air gap eccentricity, the air gap permeability per unit area is written as:

[0083] Λ(φ,ωt,θ r )=μ0G -1 (φ,ωt,θ r (10)

[0084] Where, θ r The rotor electrical angle.

[0085] Based on the structure of the alternating pole magnetic levitation permanent magnet synchronous motor, the magnetic flux densities of its torque magnetic field and levitation magnetic field are respectively:

[0086]

[0087] B m and B s The fundamental amplitudes are as follows:

[0088]

[0089] Among them, Imm I sm These represent the amplitudes of the torque current winding and the levitation current winding, respectively, k m k s These are the fundamental winding coefficients of the torque winding and the suspension winding, respectively, and N is the number of turns in series per phase of the winding.

[0090] The radial levitation force per unit area on the rotor surface can be obtained by applying Maxwell's tensor method:

[0091]

[0092] Among them, B n For B m and B s The combined magnetic flux density is given by S, where S is the rotor surface area and B is the air gap magnetic flux density of the motor.

[0093] The components of the radial levitation force acting on the rotor in the positive x-axis and y-axis directions are as follows:

[0094]

[0095] Figure 4 The air gap magnetic permeability distribution diagram of the alternating pole magnetic levitation permanent magnet synchronous motor on the stator circumference is given.

[0096] Depend on Figure 4 Write the air gap permeability P(φ) of the motor on the stator circumference in piecewise function form:

[0097]

[0098] Where G is the air gap length at the core, θ m h is the polar arc radius of a permanent magnet within one electrical cycle. m For the thickness of the permanent magnet, μ rPM The relative permeability of the permanent magnet, k = 1, 2, 3…p m .

[0099] The expression for the air gap magnetic flux density of an alternating pole magnetic levitation motor is:

[0100] B(φ)=A(φ)p(φ)(16)

[0101] Substituting equations (15) and (16) into equation (14), integrating over φ and summing the results, we get:

[0102]

[0103] Since we assume the magnetic permeability of the magnetic material is infinite and the magnetic flux passes entirely radially through the air gap, it is known that the magnetic field lines enter and exit the core surface almost perpendicularly. Therefore, the second term in the above two equations can be ignored. The prototype design parameters include: the number of pole pairs p of the torque winding. m=4. Number of pole pairs p of the levitation winding s Substituting 1 into the equation, we get:

[0104]

[0105] From equation (19), it can be seen that the levitation force is independent of the rotor position angle ωt. When the angles between the torque current magnetic field, the levitation current magnetic field vector, and phase A are all 0 (i.e., μ = 0, λ = 0), the levitation force in the x-axis direction can be simplified as:

[0106]

[0107] In equation (20), the suspending current is coupled with the air gap magnetic field generated by the torque current. The torque current is decomposed into i md i mq i md The magnetomotive force that generates the magnetic field and the magnetomotive force that generates the magnetic field of the permanent magnet combine to form A. F i mq The resulting rotating magnetic field magnetomotive force is A q Equation (8) can be rewritten as:

[0108] A(φ,t)=A F +A q sin(p m φ-p m ωt-μ)+A s cos(φ-λ)(21)

[0109] Therefore, equation (19) can be rewritten as:

[0110]

[0111] When μ or λ is zero, F x Only the first term on the right-hand side of the equation is considered. When λ = 0 or μ = λ = 0, the levitation force is written as:

[0112]

[0113] If a levitation current i that only generates levitation force in the y direction is applied y We can obtain:

[0114]

[0115] The motor's levitation force, besides the controllable levitation force generated by the levitation current, also includes the unilateral magnetic pull caused by the imbalance of the air gap magnetic field due to air gap eccentricity. The levitation force in the x-axis direction, taking into account the effect of air gap eccentricity, can be written as:

[0116]

[0117] In the formula, x is the projection of the rotor eccentricity onto the x-axis, and the coefficient k ecc Related to the characteristics of the air gap magnetic field and the air gap permeability, when the motor parameters are constant, the external excitation is given, and the Fourier expansion of the air gap permeability takes a certain number of terms, this coefficient is constant. In addition, the air gap permeability is also related to the rotor eccentricity type. Equation (15) gives the dynamic eccentricity case. When the rotor is statically eccentric, vibratingly eccentric, or mixedly eccentric, the coefficient k is different. ecc The coefficients are all different and their expressions are quite complex. They can be obtained through finite element simulation or experimental testing based on the actual situation of the prototype.

[0118] Therefore, the radial levitation force on the rotor can be written as:

[0119]

[0120] Where, k s The motor current stiffness coefficient is a quantity related to the motor structure.

[0121] Based on formula (26), the levitation motion model of the alternating pole magnetic levitation permanent magnet synchronous motor is as follows:

[0122]

[0123] In the formula, m is the rotor mass, F zx F zy F represents the applied radial loads in the x and y directions, respectively. sx F sy It is the Maxwell force that is proportional to the eccentric displacement.

[0124] The levitation motion model in equation (27) is derived based on the structural characteristics of the motor body. If we consider the power electronic devices, namely the torque inverter and the levitation inverter, then, combined with equation (7), we can see that the levitation current equation of the motor includes both the levitation inverter terminal voltage v. s It also includes the torque inverter terminal voltage v. m Substituting equations (6) and (7) into the levitation force equation (equation (26)), equation (27) can be written as:

[0125]

[0126] It can be seen that there is a torque-current coupling term in the motor suspension control, and the coupling factors also include rotor eccentric displacement and external disturbance force.

[0127] 2) Torque mathematical model of alternating pole magnetic levitation permanent magnet synchronous motor

[0128] a. Voltage equation

[0129] Analyzing the motor's torque operation performance, neglecting magnetic saturation, eddy current losses, and hysteresis losses, the three-phase voltage of the torque inverter can be written as:

[0130]

[0131] In the formula, R s Ψ is the stator winding resistance. mA Ψ is the magnetic flux linkage of the air gap magnetic field excited by the A-phase stator current. mB Ψ is the magnetic flux linkage of the air gap magnetic field excited by the B-phase stator current. mC The flux linkage of the air gap magnetic field excited by the C-phase stator current.

[0132] Analyzing the motor using the dq-axis mathematical model, the voltage equation for the torque inverter can be written as:

[0133]

[0134] In the formula, Ψ md Ψ mq These are the stator flux linkages along the d and q axes, respectively, i md i mq These are the d-axis and q-axis components of the torque current, respectively, u d u q The stator voltage is in a rotating coordinate system.

[0135] b. Magnetic flux linkage equation

[0136] The air gap magnetic flux linkage generated by the three-phase torque current is:

[0137]

[0138] In the formula, Ψ f It is the magnetic flux generated by the permanent magnet, L AA For phase A self-inductance, L AB For A to be mutually inductive with B, L AC For A to be mutually inductive with C, L BA For B to be mutually inductive with A, L BB For phase B self-inductance, L BC For B to be mutually inductive with C, L CA For C to be mutually inductive with A, L CB For C to be mutually inductive with B, L CC The self-inductance is for phase C.

[0139] In a rotating coordinate system, the torque flux linkage equation can be written as:

[0140]

[0141] In the formula, L md L mq Let i be the magnetizing inductance of the d-axis and q-axis coils.f The equivalent excitation current of the permanent magnet can be considered a constant if the effect of temperature on the performance of the permanent magnet is not considered.

[0142] c. Torque equation

[0143] Let β be the spatial angle between the air gap magnetic flux linkage excited by the torque current and the air gap magnetic field generated by the permanent magnet. The electromagnetic torque of the motor can be written as:

[0144]

[0145] In the formula, T em For electromagnetic torque, L d L q The values ​​are the d-axis and q-axis inductance components; the second term in parentheses is the reluctance torque caused by the rotor's salient poles.

[0146] d. Equations of motion

[0147] Record the motor load torque T L Given the moment of inertia J and the coefficient of friction K, the mechanical equation of motion for the motor is:

[0148]

[0149] In the formula, This is the mechanical angular velocity of the motor rotation.

[0150] The establishment of mathematical models for electric motors provides a foundation for the research of electric motor control systems.

[0151] (4) Analysis of coupling characteristics of alternating pole magnetic levitation permanent magnet synchronous motor.

[0152] Analysis of the topology design, operating principle, and mathematical model of the alternating pole magnetic levitation permanent magnet synchronous motor reveals that, from the perspective of the motor's topology, the levitation system and the rotor position angle θ... e Decoupling, floating current i s For the current i that generates torque mq Decoupling; Alternating pole magnetic levitation permanent magnet synchronous motors require a torque inverter and a levitation inverter to drive the motor's torque and levitation operation respectively. From the perspective of the torque inverter, the torque system is decoupled from the levitation current i. s However, looking from the floating inverter end, the floating system includes the torque inverter terminal voltage v. m The coupling term, from the levitation force motion model of the alternating pole magnetic levitation permanent magnet synchronous motor, shows that theoretically there is no coupling between the radial levitation forces in the x and y directions. However, in reality, due to the presence of harmonics in the air gap magnetic field and other reasons, there is a certain coupling between the levitation forces in these two degrees of freedom. When only the levitation current i is applied to the winding... sx At this time, a radial levitation force will also be generated in the y direction, and its amplitude will vary with i. sxIncreases as it increases.

[0153] The topology of the alternating pole magnetic levitation permanent magnet synchronous motor makes this problem difficult to solve by optimizing the winding structure. However, it can be addressed by using suitable control methods to adjust the levitation force / current F for two different degrees of levitation. x and i sy F y and i sx Decouple them from each other.

[0154] (5) Research on control strategies for suspension systems.

[0155] To achieve complete decoupling between the suspension system and the torque system, this invention proposes a decoupling control based on a sliding mode disturbance observer. The torque inverter terminal voltage v... m Treated as a disturbance term, along with other factors affecting the floating current i s The controlled disturbance factors are treated together as system disturbances. A sliding mode disturbance observer is designed to monitor the disturbances in real time and compensate for them to the floating current given signal i. * s middle.

[0156] To suppress the inherent chattering problem of sliding mode, the levitation current sliding mode observer employs and improves the Super-twisting Algorithm (STW) to enhance the accuracy and response speed of disturbance observation. In the displacement / levitation force loop, couplings between different levitation degrees of freedom and other displacement disturbances are treated as system disturbances. A sliding mode active disturbance rejection controller is designed for observation, compensation is performed at the given levitation force, and the nonlinear characteristic function in the nonlinear state error feedback law is improved using the sliding mode variable structure approach rate.

[0157] The control structure block diagram of the levitation system of the alternating pole magnetic levitation permanent magnet synchronous motor is as follows: Figure 5 In the diagram, x * y * This indicates the desired position of the motor rotor in the x and y axes, used to define the target position of the suspension system; This represents the reference levitation force calculated by the sliding mode active disturbance rejection controller in the x and y directions. yes Compensated levitation force; The reference current is the current signal obtained by converting the levitation force control signal through a proportional coefficient F / i. They are respectively The compensated current signal; i sx i sy This refers to the actual floating current generated by the motor in the x-axis and y-axis directions; The estimated floating currents are located in the x-axis and y-axis directions; This is the output of the sliding mode perturbation observer; Using the floating voltage as a reference, these two signals are the adjustment results of the floating current obtained after calculation by the PID controller; v sx v sy This is the actual floating voltage.

[0158] 1) Design of torque-voltage decoupling strategy for suspension system.

[0159] The levitation control system of the alternating pole magnetic levitation permanent magnet synchronous motor has a dual closed-loop structure consisting of a current loop and a displacement / levitation force loop. The levitation current i s It contains the torque inverter terminal voltage v m The coupling terms and other unknown disturbances can be considered as bounded noise in engineering. A sliding mode disturbance observer is designed to observe the disturbance quantities. In this way, the torque-voltage coupling quantities, which originally needed to be measured online, can be obtained through the observer, and their impact can be compensated for in the i-th... sx * i sy * In this process, the decoupling of the levitation current control from the torque system is achieved.

[0160] Based on the analysis of the levitation motion model, the voltage relationship at the levitation inverter terminal (7) is rewritten as equation (35):

[0161]

[0162] In the formula, v sx v sy The floating voltages in the x and y directions are v and v, respectively. mx v my These are the torque voltages in the x and y directions, respectively.

[0163] The voltage v at the torque inverter terminal m Considered as a known disturbance of the system, and together with other disturbances affecting the levitation current, it is considered as the total disturbance of the levitation current control loop, denoted as d. i With the suspending current i x For example, taking the floating current and disturbance as state variables, the floating inverter terminal voltage v s As a system input, equation (35) can be written in the following form:

[0164]

[0165] In the formula, f i Let be the rate of change of the disturbance.

[0166] Taking the floating current and disturbance as the objects of observation, let u0 be the designed sliding mode control law, g be the observation gain, and the superscript "^" indicate that the quantity is an observed value. The designed current sliding mode observer can be expressed as:

[0167]

[0168] Assume the following observation errors: Floating current observation error and disturbance observation error:

[0169]

[0170] In the formula, e ix For the observation error of the levitation current, e di This represents the observation error caused by the disturbance.

[0171] Combining equations (36) and (37), the error of the current sliding mode observer can be obtained:

[0172]

[0173] The linear sliding surface is designed as follows:

[0174]

[0175] Sliding mode observers are robust and easy to implement, but they suffer from chattering. The integrator in the high-order sliding mode of the superspiral algorithm can smooth discontinuous signals, improve the dynamic performance of the system, and effectively suppress chattering. Therefore, in order to suppress chattering in the sliding mode system and improve observation accuracy, the sliding mode convergence law based on the superspiral algorithm is used to make the state trajectory converge to the sliding mode surface. The general form of the sliding mode convergence law of the superspiral algorithm is shown in equation (41):

[0176]

[0177] To further suppress system chattering, the approach rate is improved by introducing a power function of the system switching surface, so that the approach rate of the sliding surface motion point adaptively increases or decreases with the distance of the system state variable from the sliding switching surface. The improved sliding mode approach law of the superspiral algorithm is shown in equation (42):

[0178]

[0179] In the formula, k1 and k2 are the superspiral sliding mode gains, and k1 and k2 > 0; s is the sliding surface, v is the state variable, ρ1 and ρ2 are external disturbances, and t is time; λ > 0 is the exponential gain; 0 < α < 1 / 2.

[0180] The perturbation observation error e di Treating it as a disturbance term, the control law for the sliding mode disturbance observer based on the improved superspiral algorithm is:

[0181]

[0182] The block diagram of the levitation current sliding mode perturbation observer based on the improved superhelical algorithm is shown below. Figure 6 In the picture For a given levitation current

[0183] flow, To observe the levitation current, e is This refers to the floating current error.

[0184] 2) Design of decoupling strategy for two degrees of freedom of suspension system.

[0185] Alternating pole magnetic levitation permanent magnet synchronous motor is a complex nonlinear system, with levitation forces F in the x and y directions. x F y There are actual couplings between the components, and it is difficult to establish an accurate mathematical model. The wide speed range of the motor and the numerous positional disturbances affecting levitation performance make traditional control methods ineffective. Active disturbance rejection technology (ADRT) treats the known and unknown coupling factors of the system as a "total disturbance," observes them using a disturbance observer, and compensates the given quantity in real time based on the system's input and output information and the observed disturbance information, achieving robust decoupling control. Furthermore, addressing the challenges of numerous adjustable parameters and difficult tuning in ADRT, the advantages of sliding mode variable structure control technology are combined. In the displacement / levitation force control stage of the levitation control system, sliding mode control is introduced into the design of the disturbance observer and ADRT controller, allowing for smooth transitions in the controller's adjustable parameters during switching, reducing system errors, and improving the system's internal disturbance rejection capability.

[0186] a. Design of the displacement loop transition link

[0187] To avoid the conflict between overshoot and speed in the control system, a "transition process" needs to be designed based on the control objective. The actual behavior of the system then tracks this transition process to ultimately achieve the control objective. In the motor's suspension control system, to achieve better control performance, the inner current loop has a fast response speed, while the outer displacement / force loop output is relatively smooth and gradual. Based on this principle, a transition process is designed for the outer loop control.

[0188] Let the given signal for rotor displacement be x. * For the rotor displacement tracking signal x1(t) and the approximate differential of the rotor displacement x2(t), the following differential equation holds:

[0189]

[0190] As t→∞, x1(t)→0, x2(t)→0, and the function f satisfies |f(x1(t),(x2(t))|≤r.

[0191] Equation (44) can be written in discrete form as follows:

[0192]

[0193] In the formula, h is the integration step size, and the function f is the nonlinear comprehensive control function fal(·), which has the following specific form:

[0194]

[0195] In the formula, α is the nonlinear factor and δ is the filtering factor.

[0196] The discrete form of the rotor position tracking differentiator in the motor suspension control system is as follows:

[0197]

[0198] The filtering factor δ of TD can also be taken as the step size h. r is the speed factor. Adjusting the value of r can adjust the speed of the transition process. The larger the value of r, the faster the tracking speed, but an excessively large value of r will cause system oscillation.

[0199] b. Design of sliding mode disturbance observer for displacement / levitation force ring

[0200] The alternating pole magnetic levitation permanent magnet synchronous motor is designed with an alternating pole structure. Theoretically, the motor is decoupled in the two degrees of freedom of levitation in the x and y axes. However, in actual operation, due to the presence of magnetomotive force harmonics, there is coupling between the levitation forces in the x and y axes, which is difficult to model accurately. This coupling effect, along with other disturbances affecting rotor levitation force control, is considered as a system disturbance in levitation force control, denoted as d in the x and y axes respectively. x d y The mathematical model of levitation force (Equation (27)) is rewritten in the following form:

[0201]

[0202] The design method of the extended state observer takes the displacement / levitation force in the x-direction as an example. The variable x is the displacement of the motor rotor in the positive x-axis direction. Let the state variables of the sliding mode disturbance observer be:

[0203]

[0204] Substituting into equation (48), we have:

[0205]

[0206] Let u1 be the control law to be designed, and the sliding mode disturbance observer is designed as follows:

[0207]

[0208] From equations (49) and (51), the error of the sliding mode perturbation observer can be obtained:

[0209]

[0210] In the formula, g1 is the observation error of rotor displacement disturbance.

[0211] Design the sliding surface:

[0212] s = c1e1 + e2 = 0 (53)

[0213] The constant c1 should be chosen to satisfy Hurwitz stability and have c1>0.

[0214] To eliminate chattering and improve the robustness and stability of the system, a sliding mode reaching law based on the superspiral algorithm is designed as shown in equation (54), where k 21 >0, k 22 >0.

[0215]

[0216] The designed sliding mode disturbance observer, such as Figure 7 As shown.

[0217] c. Design of Sliding Mode Active Disturbance Rejection Controller

[0218] The coupling of the rotor in the x and y degrees of freedom of suspension and other disturbances in the suspension control system are regarded as system disturbances. Active disturbance rejection control technology is adopted for the second-order system of the displacement / force control loop, combined with the sliding mode nonlinear state error feedback control law, to achieve decoupled control of rotor suspension. The output of the sliding mode disturbance observer in 2) is written as [z... x1 z x2 z x3 ] T Let the intermediate quantity e x1 =x1-z x1 e x2 =x2-z x2 Design the sliding surface s = c2e x1 +e x2 Where c2>0; The sliding mode feedback control law u of the active disturbance rejection controller is designed using sliding mode technology. f 0(t) is as follows:

[0219]

[0220] In the formula, k3>0, λ1>0,

[0221] The disturbance compensation is as follows:

[0222]

[0223] The designed sliding mode active disturbance rejection controller is as follows:

[0224]

[0225] In the formula, b1 is the system parameter and f0 represents the disturbance.

[0226] (6) Research on torque system control strategy.

[0227] The alternating pole magnetic levitation permanent magnet synchronous motor designed in this invention has good decoupling performance. The torque system is decoupled from the levitation current and is minimally affected by rotor displacement eccentricity. Classical control methods can meet the torque performance requirements. However, when the motor is subjected to strong external disturbances, the levitation current and rotor displacement exceeding a certain range can significantly impact the stable operation of the torque system. Therefore, a control method with better disturbance rejection and stronger robustness is considered. This method treats internal disturbances unknown in the precise mathematical model of the motor ("precise model" refers to the derived torque mathematical model, and "unknown internal disturbances" refer to complex nonlinear factors or uncertainties that cannot be reflected in the precise model) and external disturbances caused by the external environment and operating conditions as disturbances affecting the stable operation of the motor torque system. A sliding mode-active disturbance rejection composite control method is used to observe and compensate for disturbances in real time, achieving high-performance, robust torque system control. The control principle block diagram is shown below. Figure 8 As shown in the figure. ω r * ω is the given speed of the motor. r This refers to the actual rotational speed. Let i be the torque reference current in the d- and q-axis coordinate system. md i mq The actual measured d-axis and q-axis torque currents, The torque voltage reference voltage is shown in the d- and q-axis coordinate system. Let θ be the torque reference voltage in the α and β coordinate system. e The rotor electrical angle, where ω is the electrical angular velocity.

[0228] 1) Transition process design

[0229] To extract the signal more accurately, a nonlinear tracking differentiator is used to manage the transient process. Let the given speed of the motor be ω. r * The tracking signal ω for a given rotational speed is obtained through a nonlinear tracking differentiator. v1 and differential signal ω v2 The design of the fastest tracking differentiator for the motor speed is as follows:

[0230]

[0231] In the formula, h is the integration step size.

[0232] The specific expression for the fastest synthesis function fhan(·) of a discrete system is as follows:

[0233]

[0234] In the formula, r is the speed factor, which determines the tracking speed; the transition interval is defined as d = rh, the saturation interval is defined as d0 = hd, a represents the adjustment amount, a0 represents the adjustment factor, and y represents the intermediate variable.

[0235] 2) Design of Extended State Observer

[0236] The state equation of the speed loop of the motor torque system can be written as:

[0237]

[0238] The motor speed is affected by known and unknown disturbances such as changes in load torque, changes in operating conditions, and changes in motor parameters due to external environmental influences. Let w in equation (60) be the unknown external disturbance of the speed loop, and the first two terms on the right side of the equation be the known disturbances, denoted as f(ω1). The sum of the two is regarded as the total disturbance quantity f(t, ω1, w) of the speed loop control system, and is used as the extended state quantity of the state observer, denoted as z. ω Then the state equation of the speed loop after state expansion can be written as:

[0239]

[0240] In the formula, g ω It is the total derivative of the extended state variables, for the actual system g ω Bounded; The system control gain is determined by the motor structure.

[0241] Considering the limited range of the total system disturbance, a high-gain state observer is designed. This simplifies the structure, reduces the number of parameters requiring tuning, and, due to the lower system order, avoids situations where the gain is significantly higher than that of a nonlinear observer. Let the extended state observer output... The second-order rotational speed ESO (Extended State Observer) is designed as follows:

[0242]

[0243] Where, β 01 β 02 This is the gain coefficient.

[0244] 3) Design of Sliding Mode Active Disturbance Rejection Controller

[0245] The speed of the rotational speed ring is given by ω. * r The tracking signal is ω v1If the ESO outputs z1, then the error between the given speed and the speed feedback is:

[0246] e ω =ω v1 -z1(63)

[0247] Let the sliding mode control surface s = e ω , Selecting parameter k4, and according to equation (61), using the sliding mode control design method, the SM-NLSEF (sliding mode active disturbance rejection controller) of the speed loop is designed as follows:

[0248]

[0249] in, This is the control law for the speed loop (outer loop);

[0250] Since the SM-NLSEF (Sliding Mode Active Disturbance Rejection Controller) cannot cancel out disturbances and uncertainties in the system, an extended state observer (ESO) is used to calculate the reference torque current of the SM-NLSEF. Compensation is performed, and the compensated current command i q * (Inner loop) is used to counteract disturbances and uncertainties in the system and improve the steady-state and dynamic performance of the system;

[0251]

[0252] The designed speed sliding mode active disturbance rejection control can stabilize the system, with the error converging to the sliding surface within a finite time. Furthermore, it requires fewer parameters and has a simple structure. Its control principle diagram is shown below. Figure 9 The target speed signal is converted into a smooth speed reference signal by a first-order tracking differentiator (TD), which facilitates controller processing. Figure 9 middle, Represents ω v1 The derivative with respect to time; ω is the actual motor speed, representing the actual operating speed of the motor, measured in real time by sensors or estimators and fed back to the control system for closed-loop regulation; e ω For speed error; Representing the reference torque current, this is the reference current signal calculated by the sliding mode active disturbance rejection controller, used to control the motor's output torque to achieve the desired dynamic performance; q Z1 is the actual q-axis current of the motor (the current component used to generate torque); Z2 are state variables, which are state feedback variables inside the sliding mode active disturbance rejection controller, representing the internal dynamics of the controller, used to improve control performance and suppress disturbances.

[0253] Based on the above ideas, and using the topology-control cooperative decoupling concept, the designed alternating pole levitation parallel single winding magnetic levitation permanent magnet synchronous motor can achieve full coupling variable decoupling between the torque system and the levitation system, while also having the application advantages of high power density and high torque output.

[0254] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for decoupling the torque system and suspension system of a single-winding magnetically levitated permanent magnet synchronous motor, characterized in that: The motor adopts a suspended parallel single winding structure to decouple the torque system from the suspended current; The permanent magnets employ an alternating pole design to decouple the levitation system from the rotor position angle; In the current loop of the levitation system, the voltage at the torque inverter terminal is regarded as a disturbance term, which, together with other disturbance factors affecting the levitation current control, constitutes the system disturbance. A sliding mode disturbance observer is designed to observe the disturbance in real time and compensate the levitation current, thereby decoupling the levitation current control from the torque system. In the displacement / levitation force loop of the suspension system, the coupling between different levitation degrees of freedom and other displacement disturbances are all regarded as system disturbances. A sliding mode active disturbance rejection controller is designed to observe and compensate for the levitation force, thereby achieving control decoupling between different levitation degrees of freedom. The unknown internal disturbances in the mathematical model of the torque control system, as well as the external disturbances caused by the external environment and operating conditions, are regarded as disturbances affecting the stable operation of the motor torque system. The sliding mode-active disturbance rejection composite control method is used to observe and compensate for the disturbances in real time, so as to achieve high-performance and robust torque system control. The motor adopts a floating parallel single-winding structure to decouple the torque system from the floating current. Specifically, each phase torque winding is connected in series, and the torque inverter only provides three-phase torque current i. mA i mB i mC The floating inverter provides the floating current i s and Where i s Including three-phase floating current i sA i sB i sC The i sA i sB i sC Injected from the midpoint of each phase torque winding, the Connect to the torque inverter and inject torque windings.

2. The method for decoupling the torque system and the suspension system according to claim 1, characterized in that, The permanent magnet adopts an alternating pole design, specifically: the permanent magnet adopts a surface insertion type, and the number of permanent magnet pole pairs is ≥4; the magnetization direction of the permanent magnet is arranged with the same polarity along the rotor surface, and the rotor core part adjacent to the permanent magnet is magnetized with the opposite polarity.

3. The method for decoupling the torque system and the suspension system according to claim 1, characterized in that, In the sliding mode disturbance observer, the designed linear sliding surface s is: Among them, e ix For the observation error of the levitation current, i sx This represents the actual floating current generated by the motor in the x-axis direction. This represents the estimated floating current in the x-axis direction.

4. The method for decoupling the torque system and the suspension system according to claim 3, characterized in that, In the sliding mode perturbation observer, the sliding mode reaching law of the improved superspiral algorithm is: Where k1 and k2 are the superspiral sliding mode gains, v is the state variable, ρ1 and ρ2 are the external disturbances, t is time, λ is the exponential gain, and α is a constant.

5. The method for decoupling the torque system and the suspension system according to claim 4, characterized in that, The perturbation observation error e di Treating it as a disturbance term, the control law for the sliding mode disturbance observer based on the improved superspiral algorithm is: u0 is the designed sliding mode control law.

6. The method for decoupling the torque system and the suspension system according to claim 1, characterized in that, The sliding mode active disturbance rejection controller is: Where, the sliding surface s = c2e x1 +e x2 intermediate quantity e x1 =x1-z x1 e x2 =x2-z x2 , z x1 z x2 z x3 The output of the sliding mode disturbance observer for the displacement / levitation force loop is given by k3, λ1, and c2, which are constants greater than 0. f0 (t) represents the feedback control law of the sliding mode active disturbance rejection controller. For disturbance compensation, b1 is the system parameter, f0 represents the disturbance, and x1 is the displacement of the motor rotor in the positive x-axis direction.

7. The method for decoupling the torque system and the suspension system according to claim 6, characterized in that, The feedback control law of the sliding mode active disturbance rejection controller satisfies: Among them, intermediate quantity x represents the displacement of the motor rotor in the positive x-axis direction, and the coefficient k ecc Related to the characteristics of the air gap magnetic field and the air gap permeability, m is the rotor mass.

8. The method for decoupling the torque system and the suspension system according to claim 1, characterized in that, The aforementioned sliding mode-active disturbance rejection composite control method specifically involves: setting the sliding mode control surface s = e ω By selecting parameter k4 and employing the sliding mode control design method, a sliding mode active disturbance rejection controller for the speed loop is designed: Among them, e ω For speed error, For the control law of the speed loop, Let z1 be the first derivative of the state variable z1.

9. The method for decoupling the torque system and the suspension system according to claim 8, characterized in that, The reference torque current calculated by the sliding mode active disturbance rejection controller of the speed loop is compensated using an extended state observer. The compensated current command i q * for: Where b2 is the system control gain, and z2 is the state variable. The tracking signal ω represents a given rotational speed. v1 The derivative with respect to time.

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