Three-stage control method for full dynamic process of suspension force of bearingless permanent magnet motor

Abstract

The application discloses a three-stage control method for a full dynamic process of suspension force of a bearingless permanent magnet motor, and respectively provides suspension force control methods under conditions of sudden increase and sudden decrease of radial load forces in x and y directions; in the process of sudden change of the load force, linear increase or linear decrease of the suspension force is controlled according to the fastest change rate that can be provided by an inverter; through reasonable design of suspension force switching time, the system can re-enter a steady state after the suspension force is changed in only three stages in the dynamic process; in the whole dynamic process, only one overshoot exists in the speed, and the displacement has no overshoot and can converge, the dynamic time and the suspension force switching times in the dynamic process are reduced, and the problems that the suspension force switching times are too many in the existing direct suspension force control algorithm, the rotor speed and the rotor displacement cannot change at the fastest speed, and thus the dynamic trajectories of the two cannot be optimal are solved.

Description

Technical Field

[0001] This invention relates to the field of bearingless permanent magnet motor control technology, and mainly to a three-stage control method for the full dynamic process of levitation force of a bearingless permanent magnet motor. Background Technology

[0002] Bearingless permanent magnet motors are high-performance permanent magnet synchronous motors that utilize magnetic levitation technology. They not only possess the superior performance characteristics of permanent magnet synchronous motors, such as high efficiency, high energy density, and high power factor, but also the advantages of magnetic bearing motors, including no mechanical contact, no wear, no lubrication or maintenance, and long service life. They have broad application prospects in many specialized fields, including aerospace, flywheel energy storage, artificial heart pumps, hazardous liquid and gas transport, and pollution-free semiconductors.

[0003] The control of bearingless motors is divided into torque control and levitation force control. To improve the dynamic characteristics of levitation force control, patent CN112865662A proposes a levitation force control method for bearingless permanent magnet motors, operating within the range of 0 to t. c During a specific time period, controlling the levitation force ensures that the motor's radial velocity exhibits the optimal dynamic curve under sudden load changes. This is achieved within the time frame t. c ~t c During the +4Δt time period, the levitation force is controlled to ensure that the radial velocity of the motor is at its optimal dynamic curve under constant load, while compensating for the 0~t time interval. c The displacement of the motor due to a sudden change in load during a time period t causes the motor to... c The dynamic process ends at +4Δt. This invention can reduce the dynamic time during sudden changes in motor load to some extent.

[0004] However, the radial displacement of the motor can be obtained by double integral of the motor acceleration. The above-mentioned direct suspension force control method uses the motor radial velocity as an intermediate variable and divides the motor speed into two time periods to obtain the optimal dynamic curve. Its suspension force curve goes through 5 stages, which is different from the theoretical suspension force curve of 3 stages (rise-rise or fall-rise). It is not the optimal given suspension force curve during the process of sudden change in load force. The limitation of this method is that the optimal dynamic curves of the two time periods combined are not the optimal dynamic curve for the entire dynamic process. c If the speed is 0 at the same time as the radial acceleration is 0, the radial speed of the motor cannot change at the fastest rate during the dynamic process. Therefore, it cannot guarantee that the dynamic trajectory of the rotor displacement and rotor displacement acceleration is optimal during the sudden change of load force. Summary of the Invention

[0005] Purpose of the invention: In view of the problems existing in the background technology, the present invention provides a three-stage control method for the full dynamic process of levitation force of a bearingless permanent magnet motor, which solves the problem that the direct levitation force control algorithm in the prior art has too many levitation force switching times, and the rotor speed and rotor displacement cannot change at the fastest speed, so that the dynamic trajectory of the two cannot reach the optimal.

[0006] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A three-stage control method for the full dynamic process of levitation force of a bearingless permanent magnet motor is disclosed. The bearingless permanent magnet motor control structure includes a torque winding control inverter, a levitation winding control inverter, and the bearingless permanent magnet motor. The torque winding control inverter includes a DC power supply U1, with a filter capacitor C1 and three torque bridge arms connected in parallel across its terminals. Each torque bridge arm includes two series-connected switching transistors. The midpoints of the three torque bridge arms are respectively connected to the three-phase torque windings A, B, and C of the bearingless permanent magnet motor. The levitation winding control inverter includes a DC power supply U2. A filter capacitor C2 and three suspension bridge arms are connected in parallel across the two ends of the DC power supply U2; each suspension bridge arm includes two series-connected switching transistors; the midpoints of the three suspension bridge arms are respectively connected to the three-phase suspension 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 installed on the stator of the bearingless permanent magnet motor; the suspension force control method includes four cases: (1) sudden increase of radial load force in the x-direction; (2) sudden increase of radial load force in the y-direction; (3) sudden decrease of radial load force in the x-direction; and (4) sudden decrease of radial load force in the y-direction; specifically,

[0008] (1) Sudden increase of radial load force in the x-direction;

[0009] Step 11: When controlling the levitation force to rise in the x-direction, set the d-axis voltage of the levitation winding to a constant maximum value. U dc To control the bus voltage of the inverter via the floating winding, the d-axis current of the floating winding is... The rate of change of L continued to rise, among which L dF The d-axis inductance of the levitation winding is given by the levitation force in the x-direction. The rate of change of K continued to rise, among which K F Let be the levitation force coefficient, and let the rotor displacement acceleration in the x-direction be... The rate of change of ... Then the rotor displacement acceleration in the x direction is as follows: The rate of change continued to decrease;

[0010] Step 12: Measure the displacement X of the motor rotor in the x-direction using an eddy current sensor in the x-direction; set the displacement measurement error Δx>0; when -X>Δx, the bearingless permanent magnet motor experiences a sudden increase in radial load force in the x-direction, and record this moment as moment 0;

[0011] Step 13: Differentiate the displacement X in the x-direction to obtain the velocity of the motor rotor in the x-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the x-direction. After time 0, when At this moment, the levitation force of the motor in the x-direction is equal to the radial load force in the x-direction; this moment is recorded as t. a ;

[0012] Step 14: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the x-direction is controlled to increase, and the rotor displacement acceleration in the x-direction continues to increase with a rate of change of k; at t b ~t c During the time period, the levitation force in the x-direction decreases, and the rotor displacement acceleration in the x-direction continuously decreases at a rate of change of -k; at t c ~t d During the time period, the levitation force in the x-direction is increased, and the rotor displacement acceleration in the x-direction continues to increase with the rate of change of k.

[0013] Step 15, from 0 to t b During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0014]

[0015] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0016]

[0017] In t b ~t c During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + 2kt b -kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0018]

[0019] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0020]

[0021] In t c ~t d During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - 2kt c +2kt b -kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0022]

[0023] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0024]

[0025] Step 16, t d At time t, the dynamic process ends; the motor rotor's acceleration, velocity, and displacement in the x-direction are all 0, from which the relevant time t can be calculated. b t c t d ;Specifically,

[0026]

[0027] After simplification, we get:

[0028]

[0029] Solving the above equation will yield the relevant time t. b t c t d ;

[0030] (2) Sudden increase of radial load force in the y direction;

[0031] Step 21: When controlling the radial levitation force in the y-direction to rise, set the q-axis voltage of the levitation winding to a constant maximum value. The q-axis current of the levitation winding is as follows: The rate of change of L continued to rise, among which L qF The q-axis inductance of the levitation winding has a levitation force in the y-direction. The rate of change of K continued to rise, among which K F Let be the levitation force coefficient, and let be the rotor displacement acceleration in the y-direction. The rate of change of ... Then the rotor displacement acceleration in the y direction is as follows: The rate of change continued to decrease;

[0032] Step 22: Use an eddy current sensor in the y direction to measure the displacement Y of the motor in the y direction, set the displacement measurement error Δy and Δy>0; when -Y>Δy, the bearingless permanent magnet motor experiences a sudden increase in radial load force in the y direction, and record this moment as moment 0;

[0033] Step 23: Differentiate the displacement Y in the y-direction to obtain the velocity of the motor rotor in the y-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the y-direction. After time 0, when At this moment, the levitation force of the motor in the y-direction is equal to the radial load force in the y-direction; this moment is recorded as t. a ;

[0034] Step 24: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the y-direction is controlled to increase, and the rotor displacement acceleration in the y-direction continues to increase with a rate of change of k; at t b ~t c During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k; at t c ~t d During the time period, the levitation force in the y-direction is increased, and the rotor displacement acceleration in the y-direction continues to increase with the rate of change of k.

[0035] Step 25, from 0 to t b During the time interval, the rotor displacement acceleration in the y direction is a = kt - kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0036]

[0037] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0038]

[0039] In t b ~t c During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + 2kt b-kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0040]

[0041] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0042]

[0043] In t c ~t d During the time interval, the rotor displacement acceleration in the y direction is: a = kt - 2kt c +2kt b -kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration:

[0044]

[0045] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0046]

[0047] Step 26, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the y-direction are all zero. From this, the relevant time t can be calculated. b t c t d ;Specifically,

[0048]

[0049] Further simplification of the process:

[0050]

[0051] Solving the above equation will yield the relevant time t. b t c t d ;

[0052] (3) The radial load force in the x-direction suddenly decreases;

[0053] Step 31: When controlling the levitation force to rise in the x-direction, set the d-axis voltage of the levitation winding to a constant maximum value. The d-axis current of the levitation winding is as follows: The rate of change continues to rise, and the suspension force in the x-direction... The rate of change of K continued to rise, among which K F The levitation force coefficient is denoted by ; the rotor displacement acceleration in the x-direction is denoted by . The rate of change of ... Then the rotor displacement acceleration in the x direction is as follows: The rate of change continued to decrease;

[0054] Step 32: Use an eddy current sensor in the x direction to measure the displacement X of the motor rotor in the x direction, and set the displacement measurement error Δx>0; when X>Δx, the radial load force of the bearingless permanent magnet motor in the x direction suddenly decreases, and record this moment as the 0 moment;

[0055] Step 33: Differentiate the displacement X in the x-direction to obtain the velocity of the motor rotor in the x-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the x-direction. After time 0, when At this moment, the levitation force of the motor in the x-direction is equal to the radial load force in the x-direction; this moment is recorded as t. a ;

[0056] Step S4: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the x-direction decreases, and the rotor displacement acceleration in the x-direction continuously decreases at a rate of change of -k; at t b ~t c During the time period, the levitation force in the x-direction is controlled to increase, and the rotor displacement acceleration in the x-direction continues to increase with a rate of change of k; at t c ~t d During the time period, the suspension force in the x-direction is controlled to decrease, and the rotor displacement acceleration in the x-direction continues to decrease at a rate of change of -k.

[0057] Step 35, in the range of 0 to t b During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0058]

[0059] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0060]

[0061] In t b ~tc During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - 2kt b +kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0062]

[0063] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0064]

[0065] In t c ~t d During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + 2kt c -2kt b +kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0066]

[0067] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0068]

[0069] Step 36, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the x-direction are all zero. From this, the relevant time t can be calculated. b t c t d as follows

[0070]

[0071] After simplification, we get:

[0072]

[0073] Solving the above equation will yield the relevant time t. b t c t d ;

[0074] (4) Sudden decrease in radial load force in the y direction

[0075] Step 41: When controlling the levitation force to rise in the y-direction, set the q-axis voltage of the levitation winding to a constant maximum value. The q-axis current of the levitation winding is as follows: The rate of change continues to rise, and the levitation force in the y-direction... The rate of change of K continued to rise, among which KF Let be the levitation force coefficient, and let be the rotor displacement acceleration in the y-direction. The rate of change of ... Then the rotor displacement acceleration in the y direction is as follows: The rate of change continued to decrease;

[0076] Step 42: Use an eddy current sensor in the y direction to measure the displacement Y of the motor rotor in the y direction, and set the displacement measurement error Δy>0; when Y>Δy, the radial load force of the bearingless permanent magnet motor in the y direction suddenly decreases, and record this moment as the 0 moment;

[0077] Step S3: Differentiate the displacement Y in the y-direction to obtain the velocity of the motor rotor in the y-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the y-direction. After time 0, when At this moment, the levitation force of the motor in the y-direction is equal to the radial load force in the y-direction; this moment is recorded as t. a ;

[0078] Step S4: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k; at t b ~t c During the time period, the levitation force in the y-direction is controlled to increase, and the rotor displacement acceleration in the y-direction continues to increase with a rate of change of k; at t c ~t d During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k.

[0079] Step 45, in the range of 0 to t b During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0080]

[0081] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0082]

[0083] In t b ~t c During the time interval, the rotor displacement acceleration in the y direction is: a = kt - 2kt b +kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0084]

[0085] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0086]

[0087] In t c ~t d During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + 2kt c -2kt b +kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0088]

[0089] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0090]

[0091] Step 46, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the y-direction are all zero. From this, the relevant time t can be calculated. b t c t d , specifically:

[0092]

[0093] Simplified, we get:

[0094]

[0095] Solving the cubic equation in three variables yields the relevant time t. b t c t d .

[0096] Beneficial effects:

[0097] The levitation force control method for bearingless permanent magnet motors provided by this invention, compared with the prior art, can achieve convergence of motor acceleration, speed and displacement by controlling the three stages of levitation force change during the load force change process, namely lifting or lowering. This makes the dynamic trajectory of rotor displacement and rotor acceleration optimal during the dynamic process, and solves the problem that the existing direct levitation force control algorithm has too many levitation force switching times, and the rotor speed and rotor displacement cannot change at the fastest speed, so the dynamic trajectory of the two cannot reach the optimal level. Attached Figure Description

[0098] Figure 1 A circuit diagram of a bearingless permanent magnet motor and its control inverter provided by the present invention;

[0099] Figure 2 The control flowchart of the levitation force control method for the bearingless permanent magnet motor provided by the present invention under the condition of sudden radial load force increase in the x direction;

[0100] Figure 3 The control flowchart of the levitation force control method for the bearingless permanent magnet motor provided by the present invention under the condition of sudden increase of radial load force in the y direction;

[0101] Figure 4 The control flowchart of the levitation force control method for the bearingless permanent magnet motor provided by the present invention under the condition of sudden reduction of radial load force in the x direction;

[0102] Figure 5 The control flowchart of the levitation force control method for the bearingless permanent magnet motor provided by the present invention under the condition of sudden reduction of radial load force in the y direction;

[0103] Figure 6 The waveform of the load force suddenly increased in the x-direction under the bearingless permanent magnet motor levitation force control method proposed in patent CN112865662A;

[0104] Figure 7 This is the waveform of a sudden increase in load force in the x-direction under the bearingless permanent magnet motor levitation force control method proposed in this invention.

[0105] Figure 8 This is a general principle block diagram of a bearingless permanent magnet motor levitation force control method proposed in this invention. Detailed Implementation

[0106] The present invention will be further described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0107] This invention provides a three-stage control method for the full dynamic process of levitation force of a bearingless permanent magnet motor, and the control structure of the bearingless permanent magnet motor used is as follows: Figure 1 The diagram shows a torque winding control inverter, a levitation winding control inverter, and a bearingless permanent magnet motor. The torque winding control inverter includes a DC power supply U1, with a filter capacitor C1 and three torque bridge arms connected in parallel across its terminals. Each torque bridge arm includes two series-connected switching transistors, Q1Q2, Q3Q4, and Q5Q6, respectively. The midpoints of the three torque bridge arms are connected to the three-phase torque windings A, B, and C of the bearingless permanent magnet motor. The levitation winding control inverter includes a DC power supply U2, with a filter capacitor C2 and three levitation bridge arms connected in parallel across its terminals. Each levitation bridge arm includes two series-connected switching transistors, Q7Q8, Q9 ... 10 and Q 11 Q 12 The midpoints of the three suspension bridge arms are respectively connected to the three-phase suspension 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 installed on the stator of the bearingless permanent magnet motor.

[0108] The suspension force control method used in this invention includes four cases: (1) sudden increase of radial load force in the x direction; (2) sudden increase of radial load force in the y direction; (3) sudden decrease of radial load force in the x direction; and (4) sudden decrease of radial load force in the y direction, as described above. Figure 2-5 As shown.

[0109] Specifically,

[0110] (1) Sudden increase of radial load force in the x-direction;

[0111] Step 11: When controlling the levitation force to rise in the x-direction, set the d-axis voltage of the levitation winding to a constant maximum value. U dc To control the bus voltage of the inverter via the floating winding, the d-axis current of the floating winding is... The rate of change of L continued to rise, among which L dF The d-axis inductance of the levitation winding is given by the levitation force in the x-direction. The rate of change of K continued to rise, among which K F Let be the levitation force coefficient, and let the rotor displacement acceleration in the x-direction be... The rate of change of ... Then the rotor displacement acceleration in the x direction is as follows: The rate of change continued to decrease;

[0112] Step 12: Measure the displacement X of the motor rotor in the x-direction using an eddy current sensor in the x-direction; set the displacement measurement error Δx>0; when -X>Δx, the bearingless permanent magnet motor experiences a sudden increase in radial load force in the x-direction, and record this moment as moment 0;

[0113] Step 13: Differentiate the displacement X in the x-direction to obtain the velocity of the motor rotor in the x-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the x-direction. After time 0, when At this moment, the levitation force of the motor in the x-direction is equal to the radial load force in the x-direction; this moment is recorded as t. a ;

[0114] Step 14: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the x-direction is controlled to increase, and the rotor displacement acceleration in the x-direction continues to increase with a rate of change of k; at t b ~t c During the time period, the levitation force in the x-direction decreases, and the rotor displacement acceleration in the x-direction continuously decreases at a rate of change of -k; at t c ~t d During the time period, the levitation force in the x-direction is increased, and the rotor displacement acceleration in the x-direction continues to increase with the rate of change of k.

[0115] Step 15, from 0 to t b During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0116]

[0117] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0118]

[0119] In t b ~t c During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + 2kt b -kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0120]

[0121] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0122]

[0123] In t c ~t d During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - 2kt c +2kt b -kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0124]

[0125] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0126]

[0127] Step 16, t d At time t, the dynamic process ends; the motor rotor's acceleration, velocity, and displacement in the x-direction are all 0, from which the relevant time t can be calculated. b t c t d ;Specifically,

[0128]

[0129] After simplification, we get:

[0130]

[0131] Solving the above equation will yield the relevant time t. b t c t d ;

[0132] (2) Sudden increase of radial load force in the y direction;

[0133] Step 21: When controlling the radial levitation force in the y-direction to rise, set the q-axis voltage of the levitation winding to a constant maximum value. The q-axis current of the levitation winding is as follows: The rate of change of L continued to rise, among which L qF The q-axis inductance of the levitation winding has a levitation force in the y-direction. The rate of change of K continued to rise, among which K F Let be the levitation force coefficient, and let be the rotor displacement acceleration in the y-direction. The rate of change of ... Then the rotor displacement acceleration in the y direction is as follows: The rate of change continued to decrease;

[0134] Step 22: Use an eddy current sensor in the y direction to measure the displacement Y of the motor in the y direction, set the displacement measurement error Δy and Δy>0; when -Y>Δy, the bearingless permanent magnet motor experiences a sudden increase in radial load force in the y direction, and record this moment as moment 0;

[0135] Step 23: Differentiate the displacement Y in the y-direction to obtain the velocity of the motor rotor in the y-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the y-direction. After time 0, when At this moment, the levitation force of the motor in the y-direction is equal to the radial load force in the y-direction; this moment is recorded as t. a ;

[0136] Step 24: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the y-direction is controlled to increase, and the rotor displacement acceleration in the y-direction continues to increase with a rate of change of k; at t b ~t c During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k; at t c ~t d During the time period, the levitation force in the y-direction is increased, and the rotor displacement acceleration in the y-direction continues to increase with the rate of change of k.

[0137] Step 25, from 0 to t b During the time interval, the rotor displacement acceleration in the y direction is a = kt - kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0138]

[0139] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0140]

[0141] In t b ~t c During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + 2kt b-kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0142]

[0143] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0144]

[0145] In t c ~t d During the time interval, the rotor displacement acceleration in the y direction is: a = kt - 2kt c +2kt b -kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration:

[0146]

[0147] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0148]

[0149] Step 26, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the y-direction are all zero. From this, the relevant time t can be calculated. b t c t d ;Specifically,

[0150]

[0151] Further simplification of the process:

[0152]

[0153] Solving the above equation will yield the relevant time t. b t c t d ;

[0154] (3) The radial load force in the x-direction suddenly decreases;

[0155] Step 31: When controlling the levitation force to rise in the x-direction, set the d-axis voltage of the levitation winding to a constant maximum value. The d-axis current of the levitation winding is as follows: The rate of change continues to rise, and the suspension force in the x-direction... The rate of change of K continued to rise, among which K F The levitation force coefficient is denoted by ; the rotor displacement acceleration in the x-direction is denoted by . The rate of change of ... Then the rotor displacement acceleration in the x direction is as follows: The rate of change continued to decrease;

[0156] Step 32: Use an eddy current sensor in the x direction to measure the displacement X of the motor rotor in the x direction, and set the displacement measurement error Δx>0; when X>Δx, the radial load force of the bearingless permanent magnet motor in the x direction suddenly decreases, and record this moment as the 0 moment;

[0157] Step 33: Differentiate the displacement X in the x-direction to obtain the velocity of the motor rotor in the x-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the x-direction. After time 0, when At this moment, the levitation force of the motor in the x-direction is equal to the radial load force in the x-direction; this moment is recorded as t. a ;

[0158] Step S4: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the x-direction decreases, and the rotor displacement acceleration in the x-direction continuously decreases at a rate of change of -k; at t b ~t c During the time period, the levitation force in the x-direction is controlled to increase, and the rotor displacement acceleration in the x-direction continues to increase with a rate of change of k; at t c ~t d During the time period, the suspension force in the x-direction is controlled to decrease, and the rotor displacement acceleration in the x-direction continues to decrease at a rate of change of -k.

[0159] Step 35, in the range of 0 to t b During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0160]

[0161] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0162]

[0163] In t b ~tc During the time interval, the rotor displacement acceleration in the x-direction is: a = kt - 2kt b +kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0164]

[0165] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0166]

[0167] In t c ~t d During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + 2kt c -2kt b +kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration:

[0168]

[0169] Continuing to integrate, the expression for the rotor displacement in the x-direction is obtained as follows:

[0170]

[0171] Step 36, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the x-direction are all zero. From this, the relevant time t can be calculated. b t c t d as follows

[0172]

[0173] After simplification, we get:

[0174]

[0175] Solving the above equation will yield the relevant time t. b t c t d ;

[0176] (4) Sudden decrease in radial load force in the y direction

[0177] Step 41: When controlling the levitation force to rise in the y-direction, set the q-axis voltage of the levitation winding to a constant maximum value. The q-axis current of the levitation winding is as follows: The rate of change continues to rise, and the levitation force in the y-direction... The rate of change of K continued to rise, among which KF Let be the levitation force coefficient, and let be the rotor displacement acceleration in the y-direction. The rate of change of ... Then the rotor displacement acceleration in the y direction is as follows: The rate of change continued to decrease;

[0178] Step 42: Use an eddy current sensor in the y direction to measure the displacement Y of the motor rotor in the y direction, and set the displacement measurement error Δy>0; when Y>Δy, the radial load force of the bearingless permanent magnet motor in the y direction suddenly decreases, and record this moment as the 0 moment;

[0179] Step S3: Differentiate the displacement Y in the y-direction to obtain the velocity of the motor rotor in the y-direction. right Differentiate to obtain the displacement acceleration of the motor rotor in the y-direction. After time 0, when At this moment, the levitation force of the motor in the y-direction is equal to the radial load force in the y-direction; this moment is recorded as t. a ;

[0180] Step S4: Set time t b =k1t a ,t c =k2t a ,t d =k3t a Where k3>k2>k1>1; in 0~t b During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k; at t b ~t c During the time period, the levitation force in the y-direction is controlled to increase, and the rotor displacement acceleration in the y-direction continues to increase with a rate of change of k; at t c ~t d During the time period, the levitation force in the y-direction is controlled to decrease, and the rotor displacement acceleration in the y-direction continues to decrease at a rate of change of -k.

[0181] Step 45, in the range of 0 to t b During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0182]

[0183] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0184]

[0185] In t b ~t c During the time interval, the rotor displacement acceleration in the y direction is: a = kt - 2kt b +kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0186]

[0187] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0188]

[0189] In t c ~t d During the time interval, the rotor displacement acceleration in the y direction is: a = -kt + 2kt c -2kt b +kt a The expression for the rotor displacement velocity in the y-direction during this time period is obtained by integration.

[0190]

[0191] Continuing to integrate, the expression for the rotor displacement in the y-direction is obtained as follows:

[0192]

[0193] Step 46, at t d At time t, the dynamic process ends, and the motor's acceleration, velocity, and displacement in the y-direction are all zero. From this, the relevant time t can be calculated. b t c t d , specifically:

[0194]

[0195] Simplified, we get:

[0196]

[0197] Solving the cubic equation in three variables yields the relevant time t. b t c t d .

[0198] The following example, using a sudden increase in radial load force in the x-direction, compares the levitation force control method proposed in existing patent CN112865662A with the control method provided by this invention. Figure 6The waveform diagram shown is for the levitation force control of the bearingless permanent magnet motor used in CN112865662A. Although its displacement curve does not have multiple adjustment processes, its levitation force undergoes five stages of change, which means that the radial speed of the motor cannot change the fastest during the dynamic process. This results in the displacement speed and displacement curve not being optimal, and the system dynamic recovery time being relatively long.

[0199] like Figure 7 The figure shown is a waveform diagram of the suspension force control method provided by the present invention under the condition of sudden increase of radial load force in the x direction, during the dynamic process from 0 to t. d The expression for displacement acceleration over a time period is as follows:

[0200]

[0201] In 0~t d Time period, displacement velocity The expression is as follows:

[0202]

[0203] In 0~t d The expression for the displacement X over a time period is as follows:

[0204]

[0205] In t d The dynamic process ends at time t, therefore the motor acceleration, velocity, and displacement are all 0 at that moment. The correlation time t can then be calculated. b t c t d .

[0206] As can be seen from the waveform diagram, the suspension force control method of the present invention enables the motor to converge its suspension force, speed and displacement by controlling the corresponding radial suspension force curve through three stages, namely, lifting or lowering, when the radial load force changes abruptly. This method requires fewer adjustments and has a shorter convergence time.

[0207] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1.A three-stage control method for full dynamic process of suspension force of a bearingless permanent magnet motor, the control structure of the bearingless permanent magnet motor comprises a torque winding control inverter, a suspension winding control inverter and a bearingless permanent magnet motor; the torque winding control inverter comprises a DC power supply U1, and a filter capacitor C1 and three torque bridge arms are connected in parallel across the DC power supply U1; each torque bridge arm comprises two series-connected switching tubes; the middle points of the three torque bridge arms are connected to three-phase torque windings A, B and C of the bearingless permanent magnet motor; the suspension winding control inverter comprises a DC power supply U2, and a filter capacitor C2 and three suspension bridge arms are connected in parallel across the DC power supply U2; each suspension bridge arm comprises two series-connected switching tubes; the middle points of the three suspension bridge arms are connected to three-phase suspension 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 installed on the stator of the bearingless permanent magnet motor; characterized in that the suspension force control method comprises: (1) x-direction radial load force sudden increase; (2) y-direction radial load force sudden increase; (3) x-direction radial load force sudden decrease; and (4) y-direction radial load force sudden decrease; in particular, (1) x-direction radial load force sudden increase; Step 11, when the x-direction levitation force is controlled to increase, the d-axis voltage of the levitation winding is set to be constant at the maximum value where U dc is the bus voltage of the inverter controlled by the levitation winding, the d-axis current of the levitation winding continuously increases at a rate of , where L dF is the d-axis inductance of the levitation winding, the x-direction levitation force continuously increases at a rate of , where K F is the levitation force coefficient, and the acceleration of the rotor displacement in the x-direction continuously increases at a rate of , where m is the mass of the rotor; when the x-direction levitation force is controlled to decrease, the d-axis voltage of the levitation winding is set to be constant at the minimum value , the acceleration of the rotor displacement in the x-direction continuously decreases at a rate of . Step 12: the displacement X of the motor rotor in the x direction is measured by the x-direction eddy current sensor; a displacement measurement error Δx > 0 is set; when -X > Δx, the bearingless permanent magnet motor has x-direction radial load force sudden increase, and the time when this occurs is recorded as 0 time; Step 13, derive the displacement X in x direction, get the speed of motor rotor in x direction deriving the displacement X in x direction, get the acceleration of motor rotor in x direction deriving the displacement X in x direction, get the acceleration of motor rotor in x direction After time 0, when the suspension force in x direction of motor equals the radial load in x direction, record this time as t a ; Step 14, set time t b = klt a c = k2t a d = k3t a where k3>k2>k1>1; in the time period of 0~t b , the x-direction levitation force is controlled to rise, and the rotor displacement acceleration in the x-direction continuously rises at a rate of k; in the time period of t b ~t c , the x-direction levitation force is controlled to fall, and the rotor displacement acceleration in the x-direction continuously falls at a rate of -k; in the time period of t c ~t d , the x-direction levitation force is controlled to rise, and the rotor displacement acceleration in the x-direction continuously rises at a rate of k.​​ Step 15, at 0 ~ t b The rotor displacement acceleration in the x direction in this time period is a = kt - kt a The rotor displacement velocity expression in the x direction in this time period is obtained by integration the rotor displacement expression in the x direction is obtained by continuing integration At t b ~t c The rotor displacement acceleration in the x direction in this time period is a = -kt + 2kt b -kt a The rotor displacement velocity expression in the x direction in this time period is obtained by integration the rotor displacement expression in the x direction is obtained by continuing integration In the time period t c ~t d , the rotor displacement acceleration in the x direction is a = kt - 2kt c + 2kt b - kt a , and the rotor displacement velocity expression in the x direction in this time period is obtained by integration the rotor displacement expression in the x direction is obtained by continuing integration Step 16, t d At this moment, the dynamic process ends; the motor rotor is 0 in the x direction acceleration, speed and displacement, thus the relevant time t can be obtained b t c t d ; specifically, After simplification, we obtain Solving the above equation gives the relevant time t b t c t d ; (2) y-direction radial load force sudden increase; Step 21, when the y-direction radial levitation force is controlled to increase, the q-axis voltage of the levitation winding is set to be constant at the maximum value Then the q-axis current of the levitation winding continuously increases at a rate of , where L qF is the q-axis inductance of the levitation winding, the y-direction levitation force continuously increases at a rate of , where K F is the levitation force coefficient, and the rotor displacement acceleration in the y-direction continuously increases at a rate of , where m is the rotor mass; when the y-direction levitation force is controlled to decrease, the q-axis voltage of the levitation winding is set to be constant at the minimum value Then the rotor displacement acceleration in the y-direction continuously decreases at a rate of . Step 22: the displacement Y of the motor in the y direction is measured by the y-direction eddy current sensor; a displacement measurement error Δy > 0 is set; when -Y > Δy, the bearingless permanent magnet motor has y-direction radial load force sudden increase, and the time when this occurs is recorded as 0 time; Step 23, derivative of displacement Y in y direction, get the motor rotor y direction speed derivative of derivative, get the motor rotor y direction displacement acceleration 0 time, after When the motor y direction suspension force is equal to the y direction radial load, record this time as t a ; Step 24, set time t b = klt a , t c = k2t a , t d = k3t a where k3> k2> klt 1; in the time period 0 ~ t b , the y direction suspension force is controlled to rise, and the rotor displacement acceleration in the y direction continuously rises at a change rate of k; in the time period t b ~ t c , the y direction suspension force is controlled to fall, and the rotor displacement acceleration in the y direction continuously falls at a change rate of -k; in the time period t c ~ t d , the y direction suspension force is controlled to rise, and the rotor displacement acceleration in the y direction continuously rises at a change rate of k; Step 25, at 0 ~ t b The rotor displacement acceleration in the y direction is a = kt - kt a The rotor displacement velocity expression in the y direction is obtained by integration in this time period the rotor displacement expression in the y direction is obtained by continuing integration In the time period t b ~t c , the rotor displacement acceleration in the y direction is a = -kt + 2kt b -kt a , and the rotor displacement velocity expression in the y direction in this time period is obtained by integration the rotor displacement expression in the y direction is obtained by continuing integration In the time period t c ~t d The rotor displacement acceleration in the y direction in the time period is a = kt - 2kt c + 2kt b - kt a The rotor displacement velocity expression in the y direction in the time period is obtained by integration. the rotor displacement expression in the y direction is obtained by continuing integration Step 26, at time t d , the dynamic process ends, the motor y-direction acceleration, speed and displacement are all 0, thus the related time t b t c t d ; specifically, After further simplification, we obtain Solving the above equation gives the relevant time t b t c t d ; (3) x-direction radial load force sudden decrease; Step 31, when the x-direction levitation force is controlled to increase, the d-axis voltage of the levitation winding is set to be constant at the maximum value Then the d-axis current of the levitation winding continuously increases at the rate of , and the x-direction levitation force continuously increases at the rate of , where K F is the levitation force coefficient; the rotor displacement acceleration in the x-direction continuously increases at the rate of , where m is the rotor mass; when the x-direction levitation force is controlled to decrease, the d-axis voltage of the levitation winding is set to be constant at the minimum value Then the rotor displacement acceleration in the x-direction continuously decreases at the rate of . Step 32: the displacement X of the motor rotor in the x direction is measured by the x-direction eddy current sensor; a displacement measurement error Δx > 0 is set; when X > Δx, the bearingless permanent magnet motor has x-direction radial load force sudden decrease, and the time when this occurs is recorded as 0 time; Step 33, derivative of displacement X in x direction, get the speed of motor rotor in x direction derivative of derivative, get the acceleration of displacement of motor rotor in x direction 0, after , the suspension force of motor in x direction is equal to the radial load force in x direction, record this time as t a ; Step S4, setting time t b = klt a c = k2t a d = k3t a where k3> k2> klt 1; in the time period 0 ~ t b , the x-direction suspension force is controlled to decrease, and the x-direction rotor displacement acceleration continuously decreases at a change rate of -k; in the time period t b ~ t c , the x-direction suspension force is controlled to increase, and the x-direction rotor displacement acceleration continuously increases at a change rate of k; in the time period t c ~ t d , the x-direction suspension force is controlled to decrease, and the x-direction rotor displacement acceleration continuously decreases at a change rate of -k;​​ Step 35, in the range of 0 to t b During the time interval, the rotor displacement acceleration in the x-direction is: a = -kt + kt a The expression for the rotor displacement velocity in the x-direction during this time period is obtained by integration: the rotor displacement expression in the x direction is obtained by continuing integration In the time period t b ~t c , the rotor displacement acceleration in the x direction is a = kt - 2kt b + kt a , and the rotor displacement velocity expression in the x direction in this time period is obtained by integration the rotor displacement expression in the x direction is obtained by continuing integration In the time period t c ~t d , the rotor displacement acceleration in the x direction is a = -kt + 2kt c - 2kt b + kt a , and the rotor displacement velocity expression in the x direction in this time period is obtained by integration the rotor displacement expression in the x direction is obtained by continuing integration Step 36, at time t d , the dynamic process ends, the motor x-direction acceleration, speed and displacement are all 0, thus the related time t b t c t d is obtained as follows After simplification, we obtain Solving the above equation gives the relevant time t b t c t d ; (4) y-direction radial load force sudden decrease Step 41, when the y direction levitation force is controlled to increase, the q axis voltage of the levitation winding is set to be constant at the maximum value Then the q axis current of the levitation winding continuously increases at the rate of , and the y direction levitation force continuously increases at the rate of , wherein K F is the levitation force coefficient; the rotor displacement acceleration in the y direction continuously increases at the rate of , wherein m is the rotor mass; when the y direction levitation force is controlled to decrease, the q axis voltage of the levitation winding is set to be constant at the minimum value Then the rotor displacement acceleration in the y direction continuously decreases at the rate of ; Step 42: the displacement Y of the motor rotor in the y direction is measured by the y-direction eddy current sensor; a displacement measurement error Δy > 0 is set; when Y > Δy, the bearingless permanent magnet motor has y-direction radial load force sudden decrease, and the time when this occurs is recorded as 0 time; Step S3, derivation is conducted on the displacement Y in the y direction to obtain the speed of the motor rotor in the y direction derivation is conducted on the displacement Y in the y direction to obtain the speed of the motor rotor in the y direction derivation is conducted on the displacement Y in the y direction to obtain the speed of the motor rotor in the y direction After time point 0, when , the suspension force of the motor in the y direction is equal to the radial load force in the y direction, and the time point is recorded as t a ; Step S4, setting time t b = klt a , t c = k2t a , t d = k3t a where k3> k2> klt 1; in the time period 0 ~ t b , the y-direction levitation force is controlled to decrease, and the rotor displacement acceleration in the y-direction continuously decreases at a change rate of -k; in the time period t b ~ t c , the y-direction levitation force is controlled to increase, and the rotor displacement acceleration in the y-direction continuously increases at a change rate of k; in the time period t c ~ t d , the y-direction levitation force is controlled to decrease, and the rotor displacement acceleration in the y-direction continuously decreases at a change rate of -k; Step 45, rotor displacement acceleration in y direction within time period 0~t is: a=-kt+kt b Rotor displacement velocity in y direction within time period 0~t is: v=kt-kt a The expression of rotor displacement velocity in y direction within time period 0~t is obtained by integration: the rotor displacement expression in the y direction is obtained by continuing integration In the time period t b ~t c , the rotor displacement acceleration in the y direction is a = kt-2kt b + kt a , and the rotor displacement velocity expression in the y direction in this time period is obtained by integration the rotor displacement expression in the y direction is obtained by continuing integration In the time period t c ~t d , the rotor displacement acceleration in the y direction is a = -kt + 2kt c - 2kt b + kt a , and the rotor displacement velocity expression in the y direction in this time period is obtained by integration Continuing the integration, the rotor displacement in the y direction is given by Step 46, at time t d , the dynamic process ends, the motor y-direction acceleration, speed and displacement are all 0, thus the related time t b t c t d can be solved, specifically: Simplifying, we get Solving the cubic equation gives the correlation time t b t c t d .

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