阅读说明：本技术 一种无轴承永磁电机的悬浮力控制方法 (Suspension force control method of bearingless permanent magnet motor ) 是由 王宇 张艺 郝雯娟 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种无轴承永磁电机的悬浮力控制方法,分别考虑x、y方向径向负载力突加和突减情况下的悬浮力控制方法,在负载力突变的过程中,以实现悬浮力、位移速度、位移的动态轨迹最优为目标,按照逆变器所能提供的最快变化率来控制悬浮力的线性增加或者线性减小,并且合理设计悬浮力的线性增加和悬浮力的线性减小的区域和组合,使得动态过程中位移速度只存在一次超调、位移无超调即可收敛,使得调节次数最小,减小了动态时间,解决了现有直接悬浮力控制算法不能保证负载力突变的过程中转子位移和转子位移加速度两者的动态轨迹最优的问题。(The invention discloses a suspension force control method of a bearingless permanent magnet motor, which respectively considers suspension force control methods under the conditions of sudden increase and sudden decrease of radial load forces in x and y directions, and in the process of sudden change of the load force, the linear increase or linear decrease of the suspension force is controlled according to the fastest change rate which can be provided by an inverter, and the regions and combinations of the linear increase of the suspension force and the linear decrease of the suspension force are reasonably designed, so that the displacement speed in the dynamic process can be converged only by once overshoot and the displacement can not be overshot, the adjustment times are minimized, the dynamic time is reduced, and the problem that the dynamic trajectory of the rotor displacement and the rotor displacement acceleration in the process of sudden change of the load force cannot be ensured by the existing direct suspension force control algorithm is solved.)

1. A suspension force control method of a bearingless permanent magnet motor is disclosed, wherein the bearingless permanent magnet motor structure comprises a torque winding control inverter, a suspension winding control inverter and a bearingless permanent magnet motor; the torque winding control inverter comprises a direct current voltage source U₁Said DC voltage source U₁The two ends are connected with a filter capacitor C1 in parallel; the switching tubes Q1 and Q2 are sequentially connected in series with a direct-current voltage source U₁Two ends forming a first bridge arm; the switching tubes Q3, Q4, Q5 and Q6 sequentially form a second bridge arm and a third bridge arm in the same method; the middle points of three bridge arms of the torque winding control inverter are respectively connected with a three-phase torque winding A, B, C of the bearingless permanent magnet motor; the suspension winding control inverter comprises a direct current voltage source U₂Said DC voltage source U₂The two ends are connected with a filter capacitor C2 in parallel; the switching tubes Q7 and Q8 are sequentially connected in series with a direct-current voltage source U₂Two ends of the bridge form a fourth bridge arm; the switching tubes Q9, Q10, Q11 and Q12 sequentially form a fifth bridge arm and a sixth bridge arm in the same method; three bridge arm midpoints of the suspension winding control inverter are respectively permanently connected with the bearingless inverterThree-phase torque windings a, b and c of the magneto are connected; an x-direction eddy current sensor and a y-direction eddy current sensor are arranged on a stator of the bearingless permanent magnet motor; the suspension force control method is characterized by comprising the following four conditions:

(1) sudden application of radial load force in x direction

Step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when-X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the d-axis voltage of the levitation winding constant to the maximum valueWherein U is_dcFor the suspension winding to control the bus voltage of the inverter, the d-axis current of the suspension winding is controlled byIs continuously increasing, wherein L_dFFor suspending the d-axis inductance of the winding, the suspension force in the x direction isThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairDerivation is carried out to obtain the x direction of the motor rotorAcceleration of the displacement in the direction ofAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the d-axis voltage of the suspension winding to be constant at a maximum value in a time periodThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the suspension winding to be constant at the minimum value in a time periodD-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) kt-kt_aThe expression of the rotor displacement speed in the x direction in the time period is obtained by integration as

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) — kt +2kt during the time period_b-kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(2) the radial load force in the y direction is suddenly added;

step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when-Y is larger than delta Y, the radial load force in the Y direction of the bearingless permanent magnet motor is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the q-axis voltage of the levitation winding constant to the maximum valueThen the q-axis current of the levitation windingIs continuously increasing, wherein L_qFFor suspending the q-axis inductance of the winding, the suspension force in the y direction is as followsThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y direction; after time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the y direction is as follows: (t) kt-kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) — kt +2kt during the time period_b-kt_aThe time period is obtained by integrationThe rotor displacement speed in the y direction is expressed as:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(3) a sudden decrease in radial load force in the x direction;

step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly reduced, and the moment is recorded as 0 moment;

step S2, starting from time 0, setting the d-axis voltage of the levitation winding to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairObtaining the displacement acceleration of the motor rotor in the x direction by derivationAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the d-axis voltage of the suspension winding to be constant to a minimum value in a time periodThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the levitation winding to be constant at a maximum value during a time periodD-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) ═ kt + kt_aThe time is obtained by integrationThe expression of the displacement speed of the rotor in the x direction in the section is

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the minimum valueD of the levitation windingShaft current toIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(4) sudden decrease of radial load force in y direction

Step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when Y is larger than delta Y, the radial load force of the permanent magnet motor without the bearing in the Y direction is reduced suddenly, and the moment is recorded as 0 moment;

step S2, starting from time 0, setting the q-axis voltage of the levitation winding to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y directionAfter time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodQ-axis current of the levitation windingTo be provided withThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the y direction is as follows: (t) ═ kt + kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the y-direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the y direction in the time period through integration as follows:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionThe rate of change of (c) is continuously increased and the rotor displacement in the y direction is acceleratedTo degree inThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_cAt time +4 Δ t, the dynamic process ends.

Technical Field

The invention relates to the technical field of bearing-free permanent magnet motor control, and mainly relates to a suspension force control method of a bearing-free permanent magnet motor.

Background

The bearingless motor is characterized in that a winding generating radial force in a magnetic bearing is arranged on a motor stator according to the similarity of the principle of generating electromagnetic force by the magnetic bearing and the motor, and the independent control of the torque and the radial suspension force of the motor is realized through decoupling control. The bearingless motor has all the advantages of a magnetic suspension magnetic bearing, needs maintenance-free and long-life operation, and is a typical application occasion of the bearingless motor due to the fact that the bearingless motor is sterile, pollution-free and transmission of toxic and harmful liquid or gas.

The control of the bearingless motor is divided into torque control and levitation force control. In order to improve the dynamic performance of suspension force control, patent CN200810155789.2 proposes a direct suspension force control method for a permanent magnet type bearingless motor, which controls the amplitude and direction of the space vector of the stator flux linkage of the suspension winding by properly selecting the switching state of the inverter while keeping the synthetic air gap flux linkage of the torque winding constant, controls the magnitude and direction of the suspension force of the bearingless permanent magnet synchronous motor, adopts closed-loop control on the suspension force, and further decouples the torque control winding and the suspension force winding.

However, the above-mentioned direct levitation force control method only realizes that the actual levitation force can be quickly and accurately tracked to the given levitation force. In the process of sudden change of the load force, the given suspension force ground track is determined by a displacement ring controller, the displacement ring controller adopts a linear PID controller based on incomplete differentiation, the given suspension force ground track cannot be guaranteed to be optimal in the process of sudden change of the load force, and therefore the dynamic tracks of rotor displacement and rotor displacement acceleration cannot be guaranteed to be optimal in the process of sudden change of the load force.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a suspension force control method of a bearingless permanent magnet motor, which solves the problems that a given suspension force track is influenced by a linear controller and the dynamic tracks of rotor displacement and rotor displacement acceleration cannot realize optimal ground in the conventional direct suspension force control method.

The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:

the suspension force control method of the bearingless permanent magnet motor comprises a torque winding control inverter, a suspension winding control inverter and a bearingless permanent magnet motorA magneto; the torque winding control inverter comprises a direct current voltage source U₁Said DC voltage source U₁The two ends are connected with a filter capacitor C1 in parallel; the switching tubes Q1 and Q2 are sequentially connected in series with a direct-current voltage source U₁Two ends forming a first bridge arm; the switching tubes Q3, Q4, Q5 and Q6 sequentially form a second bridge arm and a third bridge arm in the same method; the middle points of three bridge arms of the torque winding control inverter are respectively connected with a three-phase torque winding A, B, C of the bearingless permanent magnet motor; the suspension winding control inverter comprises a direct current voltage source U₂Said DC voltage source U₂The two ends are connected with a filter capacitor C2 in parallel; the switching tubes Q7 and Q8 are sequentially connected in series with a direct-current voltage source U₂Two ends of the bridge form a fourth bridge arm; the switching tubes Q9, Q10, Q11 and Q12 sequentially form a fifth bridge arm and a sixth bridge arm in the same method; the middle points of three bridge arms of the suspension winding control inverter are respectively connected with three-phase torque windings a, b and c of the bearingless permanent magnet motor; an x-direction eddy current sensor and a y-direction eddy current sensor are arranged on a stator of the bearingless permanent magnet motor; the suspension force control method is divided into the following four cases:

(1) sudden application of radial load force in x direction

Step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when-X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the d-axis voltage of the levitation winding constant to the maximum valueWherein U is_dcFor the suspension winding to control the bus voltage of the inverter, the d-axis current of the suspension winding is controlled byIs continuously increasing, wherein L_dFFor suspending the d-axis inductance of the winding, the suspension force in the x direction isThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairObtaining the displacement acceleration of the motor rotor in the x direction by derivationAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the d-axis voltage of the suspension winding to be constant at a maximum value in a time periodThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the suspension winding to be constant at the minimum value in a time periodD-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) kt-kt_aThe expression of the rotor displacement speed in the x direction in the time period is obtained by integration as

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) — kt +2kt during the time period_b-kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(2) the radial load force in the y direction is suddenly added;

step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when-Y is larger than delta Y, the radial load force in the Y direction of the bearingless permanent magnet motor is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the q-axis voltage of the levitation winding constant to the maximum valueThen the q-axis current of the levitation windingIs continuously increasing, wherein L_qFFor suspending the q-axis inductance of the winding, the suspension force in the y direction is as followsThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y direction; after time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the y direction is as follows: (t) kt-kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cRotation in the x direction during a time periodSub-displacement acceleration of f (t) ═ -kt +2kt_b-kt_aAnd obtaining the expression of the rotor displacement speed in the y direction in the time period through integration as follows:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(3) a sudden decrease in radial load force in the x direction;

step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly reduced, and the moment is recorded as 0 moment;

step S2, starting from time 0, sets the levitation windingConstant d-axis voltage ofThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairObtaining the displacement acceleration of the motor rotor in the x direction by derivationAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the d-axis voltage of the suspension winding to be constant to a minimum value in a time periodThen is suspendedD-axis current of windingIs continuously reduced, the levitation force in the x-directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the levitation winding to be constant at a maximum value during a time periodD-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) ═ kt + kt_aThe expression of the rotor displacement speed in the x direction in the time period is obtained by integration as

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

(4) sudden decrease of radial load force in y direction

Step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when Y is larger than delta Y, the radial load force of the permanent magnet motor without the bearing in the Y direction is reduced suddenly, and the moment is recorded as 0 moment;

step S2, starting from time 0, setting the q-axis voltage of the levitation winding to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y directionAfter time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the y direction is as follows: (t) ═ kt + kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the y-direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the y direction in the time period through integration as follows:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingOf (2) aThe transformation ratio is continuously reduced, and the suspension force in the y direction is reducedIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_cAt time +4 Δ t, the dynamic process ends.

Has the advantages that:

the suspension force control method of the bearingless permanent magnet motor aims at realizing the optimal dynamic tracks of the suspension force, the displacement speed and the displacement in the process of sudden change of the load force, controls the linear increase or the linear decrease of the suspension force according to the fastest change rate which can be provided by an inverter, and reasonably designs the region and the combination of the linear increase of the suspension force and the linear decrease of the suspension force, so that the displacement speed can be converged only by one-time overshoot and the displacement can not be overshot in the dynamic process, the regulation frequency is minimized, the dynamic time is reduced, and the problem that the optimal dynamic tracks of the rotor displacement and the rotor displacement acceleration in the process of sudden change of the load force can not be ensured by the conventional direct suspension force control algorithm is solved.

Drawings

Fig. 1 is a circuit diagram of a bearingless permanent magnet motor and inverter provided by the present invention;

fig. 2 is a control flow chart of the suspension force control method of a bearingless permanent magnet motor provided by the invention under the condition of sudden addition of radial load force in the x direction;

fig. 3 is a control flowchart of the suspension force control method of a bearingless permanent magnet motor provided by the invention under the condition that the radial load force in the y direction is suddenly added;

fig. 4 is a control flowchart of the suspension force control method of a bearingless permanent magnet motor provided by the invention under the condition of abrupt decrease of the radial load force in the x direction;

fig. 5 is a control flowchart of the suspension force control method of a bearingless permanent magnet motor provided by the invention under the condition that the radial load force in the y direction is suddenly reduced;

fig. 6 is a waveform of a case where a load force in an x direction is suddenly added in a direct levitation force control method of a permanent magnet type bearingless motor proposed in patent CN 200810155789.2;

fig. 7 is a waveform of a sudden load force in the x direction under the suspension force control method of a bearingless permanent magnet motor according to the present invention;

fig. 8 is a generalized implementation step of a suspension force control method of a bearingless permanent magnet motor according to the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings.

A suspension force control method of a bearingless permanent magnet motor adopts a bearingless permanent magnet motor structure as shown in figure 1, and comprises a torque winding control inverter, a suspension winding control inverter and a bearingless permanent magnet motor. The torque winding controlled inverter comprises a DC voltage source U₁D.C. voltage source U₁And a filter capacitor C1 is connected in parallel at two ends. The switching tubes Q1 and Q2 are sequentially connected in series with a direct-current voltage source U₁Two ends form a first bridge arm. Switching tubes Q3, Q4, Q5 and Q6 form a second arm and a third arm in this order in the same manner. The midpoints of three bridge arms of the torque winding control inverter are respectively connected with a three-phase torque winding A, B, C of the bearingless permanent magnet motor. The suspension winding control inverter comprises a DC voltage source U₂D.C. voltage source U₂The two ends are connected with a filter capacitor C2 in parallel; the switching tubes Q7 and Q8 are sequentially connected in series with a direct-current voltage source U₂Two ends of the bridge form a fourth bridge arm; switching tubes Q9, Q10, Q11, and Q12 form a fifth arm and a sixth arm in this order in the same manner. The middle points of three bridge arms of the suspension winding control inverter are respectively connected with three-phase torque windings a, b and c of the bearingless permanent magnet motor. The stator of the bearingless permanent magnet motor is provided with an x-direction eddy current sensor and a y-direction eddy current sensor.

The suspension force control method provided by the invention sequentially aims at the situation that the radial load force in the x direction is suddenly increased, the radial load force in the y direction is suddenly increased, the radial load force in the x direction is suddenly reduced and the radial load force in the y direction is suddenly reduced.

As shown in fig. 2, under the condition that the radial load force in the x direction is suddenly applied, the specific steps include:

step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when-X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the d-axis voltage of the levitation winding constant to the maximum valueWherein U is_dcFor the suspension winding to control the bus voltage of the inverter, the d-axis current of the suspension winding is controlled byIs continuously increasing, wherein L_dFFor suspending the d-axis inductance of the winding, the suspension force in the x direction isThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairObtaining the displacement acceleration of the motor rotor in the x direction by derivationAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bWithin a time period, setD-axis voltage of the levitation winding is constant to a maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the suspension winding to be constant at the minimum value in a time periodD-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) kt-kt_aThe expression of the rotor displacement speed in the x direction in the time period is obtained by integration as

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) — kt +2kt during the time period_b-kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+4 Δ t timeAnd the dynamic process ends.

As shown in fig. 3, under the condition that the radial load force in the y direction is suddenly applied, the specific steps include:

step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when-Y is larger than delta Y, the radial load force in the Y direction of the bearingless permanent magnet motor is suddenly added, and the moment is recorded as 0 moment;

step S2, starting from 0, setting the q-axis voltage of the levitation winding constant to the maximum valueThen the q-axis current of the levitation windingIs continuously increasing, wherein L_qFFor suspending the q-axis inductance of the winding, the suspension force in the y direction is as followsThe rate of change of (a) is continuously rising, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionWherein m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y direction; after time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S6, at 0-t_bWithin a time period, y-directionThe acceleration of the rotor displacement is: (t) kt-kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) — kt +2kt during the time period_b-kt_aAnd obtaining the expression of the rotor displacement speed in the y direction in the time period through integration as follows:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising rate of change of (c), rotor displacement in the y-directionAcceleration ofThe rate of change of (c) continuously increases;

at t_cAt time +4 Δ t, the dynamic process ends.

As shown in fig. 4, under the condition that the radial load force in the x direction is suddenly reduced, the specific steps include:

step S1, measuring and obtaining the displacement X of the motor rotor in the X direction by using an X-direction eddy current sensor, and presetting a displacement error value in the X direction to be delta X, wherein the delta X is larger than 0; when X is larger than delta X, the radial load force of the permanent magnet motor without the bearing in the X direction is suddenly reduced, and the moment is recorded as 0 moment;

step S2, starting from time 0, setting the d-axis voltage of the levitation winding to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in x directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement X in the X direction to obtain the speed of the motor rotor in the X directionTo pairObtaining the displacement acceleration of the motor rotor in the x direction by derivationAfter time 0, whenThe suspension force of the motor in the x direction is equal to the radial load force in the x direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the d-axis voltage of the suspension winding to be constant to a minimum value in a time periodThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the d-axis voltage of the levitation winding to be constant at a maximum value during a time periodD-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the x direction is as follows: (t) ═ kt + kt_aThe expression of the rotor displacement speed in the x direction in the time period is obtained by integration as

The expression of the rotor displacement in the x direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the x direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the x direction in the time period through integration as follows:

the integral solution to the x-direction rotor displacement is expressed as

At t_cAt the moment, the value of the rotor displacement in the x direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the d-axis voltage of the levitation winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the d-axis voltage of the suspension winding is set to be constant to the maximum valueThen the d-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the x directionContinuously rising, acceleration of the rotor displacement in the x-directionThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the d-axis voltage of the suspension winding is set to be constant at the minimum valueThen the d-axis current of the levitation windingIs continuously reduced, the levitation force in the x-directionIs continuously reduced, the rotor displacement acceleration in the x direction is increasedThe rate of change of (c) continuously decreases;

at t_cAt the moment of +4 delta t, the dynamic process is ended;

as shown in fig. 5, in the case of the sudden decrease of the radial load force in the y direction, the specific steps are as follows:

step S1, measuring and obtaining the Y-direction displacement Y of the motor rotor by using a Y-direction eddy current sensor, and presetting a Y-direction displacement error value delta Y, wherein the delta Y is larger than 0; when Y is larger than delta Y, the radial load force of the permanent magnet motor without the bearing in the Y direction is reduced suddenly, and the moment is recorded as 0 moment;

step S2, starting from time 0, setting the q-axis voltage of the levitation winding to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, wherein K_FAs coefficient of levitation force, acceleration of rotor displacement in y-directionIs continuously reduced, where m is the rotor mass;

step S3, derivation is carried out on the displacement Y in the Y direction to obtain the speed of the motor rotor in the Y directionTo pairDerivation is carried out to obtain the displacement acceleration of the motor rotor in the y directionAfter time 0, whenThe suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the moment is recorded as t_a；

Step S4, setting timeAt t_a～t_bSetting the q-axis voltage of the levitation winding to be constant at a minimum value during a time periodThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

step S5, setting timeAt t_b～t_cSetting the q-axis voltage of the levitation winding to be constant at a maximum value during a time periodThen hangQ-axis current of the floating windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

step S6, at 0-t_bIn the time period, the displacement acceleration of the rotor in the y direction is as follows: (t) ═ kt + kt_aThe expression of the rotor displacement speed in the y direction in the time period is obtained through integration

The expression of the rotor displacement in the y direction obtained by continuous integration is

At t_b～t_cThe rotor displacement acceleration in the y-direction is f (t) -kt-2 kt during the time period_b+kt_aAnd obtaining the expression of the rotor displacement speed in the y direction in the time period through integration as follows:

the integral is used for solving the rotor displacement expression in the y direction as

At t_cAt the moment, the value of the rotor displacement in the y direction is

Step S7, setting time periodAt t_c～t_cWithin the time period of + delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_c+Δt～t_cWithin the time period of +3 delta t, the q-axis voltage of the levitation winding is set to be constant at the maximum valueThen the q-axis current of the levitation windingThe rate of change of (2) continuously increases, the levitation force in the y-directionContinuously rising, acceleration of rotor displacement in the y-directionThe rate of change of (c) continuously increases;

at t_c+3Δt～t_cWithin the time period of +4 delta t, the q-axis voltage of the levitation winding is set to be constant at the minimum valueThen the q-axis current of the levitation windingWith a continuously decreasing rate of change, the levitation force in the y-directionIs continuously reduced, the rotor displacement acceleration in the y-direction andthe rate of change of (c) continuously decreases;

at t_cAt time +4 Δ t, the dynamic process ends.

In the prior art, patent CN200810155789.2 proposes a method for controlling direct levitation force of a permanent magnet type bearingless motor, and the following lateral comparison is performed by taking the case of sudden load force in the x direction as an example, so as to further illustrate the advantages of the present invention.

Fig. 6 shows a waveform diagram of the prior art in which direct levitation force control is adopted, which only increases the response speed of actual levitation force tracking for a given levitation force, but the actual levitation force is determined by a linear controller, so that multiple adjustment processes exist for the actual levitation force and displacement acceleration, and the displacement speed and displacement. The time shown by the arrow in fig. 6 is the zero crossing point of the displacement acceleration and the displacement velocity, but because the actual suspension force is not specially applied according to the steps of the present invention, the integral value of the displacement velocity at this time is not zero, and therefore the displacement cannot return to the zero position at this time, the system will continue to adjust, and such an adjustment process needs to pass through multiple times, the displacement acceleration, the displacement velocity and the displacement can be converged at the same time, so that the displacement velocity and the displacement are all at the zero crossing points for multiple times, and the system dynamic recovery time is long due to multiple overshooting.

FIG. 7 shows a bearingless permanent magnet bearing provided by the present inventionThe magnetic motor suspension force control method is a waveform diagram under the condition that the load force in the x direction is suddenly added. Wherein, is between 0 and t_cWithin the range, the displacement acceleration is expressed as follows:

at 0 to t_cWithin range, speed of displacementThe expression of (a) is as follows:

at 0 to t_cWithin the range, the displacement X is expressed as follows:

at t_cAt the moment of time, the time of day,

area in the corresponding graph

At t_c～t_cIn the +2 Δ t range, the displacement acceleration is expressed as follows:

the above formula can be equivalent to:

velocity of displacementThe expression is as follows:

the expression for the displacement X is as follows:

according to the above formula, at t_c～t_cIn the +2 Δ t period, the variation amount of X is:

the area corresponding to S2 in fig. 7 is S2 ═ k Δ t³

From step S7, the displacement acceleration curve is obtained at t_c～t_cWithin +2 Δ t and at t_c+2Δt～t_cWithin +4 Δ t with respect to t_c+2 Δ t centrosymmetry, the displacement velocity curve t_c～t_cWithin +2 Δ t and at t_c+2Δt～t_cWithin +4 Δ t with respect to t_c+2 Δ t is axisymmetric, i.e., S2 ═ S3. At t_c～t_cIn the +4 Δ t period, the amount of change in X is S1+ S2 ═ 2k Δ t³。

Due to the fact thatThen it can be obtained:

the verification proves that the suspension force control method can ensure that the displacement speed is increased under the condition that the radial load force in the x direction is suddenly increasedOnly one-time overshoot exists, and the displacement does not exceed the overshoot, so that the suspension force and the displacement speed can be ensuredThe displacement three are all converged, the adjusting times are few, and the convergence time is short.

Without loss of generality, the suspension force control idea provided by the suspension force control method of the bearingless permanent magnet motor can also be applied to other types of bearingless motors, including bearingless asynchronous motors, bearingless switched reluctance motors, bearingless alternating pole motors, bearingless sheet motors and the like.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.