CN104617846A - Method for controlling fault tolerance of magnetic flux switching motor of hybrid excitation axial magnetic field - Google Patents

Abstract

The invention discloses a method for controlling fault tolerance of a magnetic flux switching motor of a hybrid excitation axial magnetic field, and aims at enabling a motor control system to run with fault tolerance under single-phase fault of an inverter. The method is that the fault is determined according to the current; when in normal operation, the id=0 control strategy is performed for the hybrid excitation axial magnetic field magnetic flux switching motor fault tolerance control system, and d axis current and q axis current are distributed; in case of single-phase breaking fault, the excitation current is utilized for fault tolerance control, the id is continuously kept to be 0, the q axis current and the excitation current are coordinately distributed and then the motor runs in the fault tolerance state. With the adoption of the hybrid excitation axial magnetic field magnetic flux switching motor fault tolerance control system, the motor can run in the fault tolerance state under the single phase breaking of the inverter, and therefore, the reliability of a motor driving system of an electric vehicle can be improved.

Description

A kind of composite excitation axial magnetic field flux switch motor fault tolerant control method

Technical field

The invention belongs to electric drive technology field, relate to a kind of faults-tolerant control, particularly relate to a kind of composite excitation axial magnetic field flux switch motor fault tolerant control method used for electric vehicle.

Background technology

Along with day by day increasing the weight of of energy crisis and environmental pollution, electric automobile becomes the inexorable trend of future automobile sustainable development.At present, the motor that electric automobile adopts mainly contains threephase asynchronous machine, switched reluctance machines and permagnetic synchronous motor, wherein permagnetic synchronous motor is because volume is little, power density is high, efficiency is high, power factor advantages of higher makes it have higher application advantage, but the shortcoming that magneto air-gap field is difficult to regulate also brings limitation to application.Based on above reason, mixed excitation electric machine arises at the historic moment, and it combines the advantage of permagnetic synchronous motor and electric excitation synchronous motor and overcome their respective shortcomings, power factor is high, speed-regulating range width.This motor has two kinds of excitation sources, i.e. permanent magnet excitation and electric excitation, and the two synthesis that interacts in motor gas-gap produces air-gap field.When electric magnet exciting coil passes into forward exciting current, can produce the magnetic flux identical with permanent magnet flux direction, increase air-gap field, realize increasing magnetic and run, starting for electric automobile or climb provides large torque; Otherwise, when electric magnet exciting coil passes into reverse exciting current, produce the magnetic flux contrary with permanent magnet flux direction, weaken air-gap field, greatly widened motor output-constant operation scope, met the requirement of electric automobile high-performance cruise.Composite excitation axial magnetic field magnetic flux switches (Hybrid excited axial field flux-switchingmagnet, HEAFFSM) be a kind of novel stator permanent magnetic type mixed excited magnetic pass switch motor, mixed excited magnetic pass is switched theory for it and motor in axial magnetic field combines effectively, as shown in Figure 1.HEAFFSM combines the advantage of flux switch motor and mixed excitation electric machine, has on the one hand that structure is simple, volume is little, control the advantages such as flexible; On the one hand there is the advantage such as high efficiency, high power density.In addition, be positioned at stator due to this motor permanent magnet and there is unique poly-magnetic effect, therefore can obtain higher air gap flux density with relatively less permanent magnetic material, rotor both without winding also without permanent magnet, structure is simple, and axial length is short, so be very suitable as hub motor for electric automobile.

It is severe that electric automobile runs bad border, and power inverter is the weak link the most easily broken down during axial magnetic field flux switch permanent magnet motor drives.The most easily there is single-phase open circuit fault in controller inverter bridge, at present, less for the research of axial magnetic field flux switch permanent magnet motor drive system faults-tolerant control, have no phase pertinent literature and report, due to the particularity of its application scenario, safety and reliability problem is particularly important, and faults-tolerant control becomes research emphasis, and the realization of faults-tolerant control comprises fault detect, identifies and isolation three steps.Failure inspect and indentifition system becomes failure diagnosis, is basis and the key of faults-tolerant control.Power semiconductor and the weak link the most easily broken down in electric system when controlling drive circuit thereof.Wherein Power Converter faults accounts for 82.5% of whole drive system fault.Power inverter is usually opened a way by power tube or short circuit causes, and fault rear motor service behaviour declines, even disablement.

Summary of the invention

Technical problem: the deficiency that the present invention is directed to prior art, on the basis analyzing composite excitation axial magnetic field flux switch motor, propose one and accurately can detect power of motor converter malfunction, make motor operate in fault-tolerant state, greatly improve the composite excitation axial magnetic field flux switch permanent magnet motor fault tolerant control method of electric automobile security performance under Power Converter faults state.

Technical scheme: composite excitation axial magnetic field flux switch motor fault tolerant control method of the present invention, comprises the following steps:

(1) phase current i is gathered from motor main circuit _a, i _bwith exciting current i _f, initial position detection is carried out to motor, collection signal from motor encoder, sends into controller and process, draw rotating speed n and rotor position angle θ;

(2) the phase current i will gathered _a, i _bthrough following, filtering, biased and A/D conversion, then carry out park transforms, obtain the d shaft current i of stator under two-phase rotating coordinate system _dwith q shaft current i _q;

(3) by given rotating speed n ^*deduct encoder actual measurement rotating speed n, the rotating speed deviation delta n input speed adjuster obtained, obtains torque reference value after proportional integral computing by torque reference value busbar voltage U _dc, stator d shaft voltage u _d, stator q shaft voltage u _q, actual measurement rotating speed n and given rotating speed n ^*input current distributor, according to electric current failure judgement state, when composite excitation axial magnetic field flux switch motor state is normal, enters step 4), when composite excitation axial magnetic field flux switch motor breaks down, enter step 5);

(4) i is adopted _d=0 control strategy, distributing switch is according to following current sharing scheme output current:

$\left\{\begin{array}{c}{i}_{\mathrm{dref}}=0\\ i_{\mathrm{qref}}=\frac{{2T}_{\mathrm{eref}}}{3p{\mathrm{\ψ}}_m}\end{array}\right.$

Wherein, i _dreffor d shaft current reference value, i _qreffor q shaft current reference value; ψ _mfor permanent magnet flux linkage, p is motor number of pole-pairs, T _ereffor electromagnetic torque reference value;

(5) adopt exciting current to carry out faults-tolerant control, continue to keep i _d=0, distributing switch is according to following current sharing scheme output current:

$\left\{\begin{array}{c}{i}_{\mathrm{dref}}=0\\ i_{\mathrm{qref}}=\frac{{2T}_{\mathrm{eref}}}{3p}({\mathrm{\ψ}}_m+\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{M}_f{I}_m)\\ i_{\mathrm{fref}}=\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{I}_m\end{array}\right.$

Wherein, I _mfor phase current magnitude, i _freffor exciting current reference value, M _ffor the mutual inductance between armature winding and excitation winding, N' is the excitation winding number of turn, and N is the armature winding number of turn;

(6) d shaft current reference value i distributing switch produced _drefdeduct the d shaft current i in step (2) _dobtain d shaft current deviation delta i _d, with q shaft current i _qrefdeduct the q shaft current i in step (2) _qobtain q shaft current deviation delta i _q; By d shaft current deviation delta i _dinput d shaft current adjuster carries out proportional integral computing, obtains d shaft voltage u _d, by q shaft current deviation delta i _qinput q shaft current adjuster carries out proportional integral computing, obtains q shaft voltage u _q, then to described d shaft voltage u _dwith q shaft voltage u _qafter jointly carrying out rotating orthogonal-static two phase inversion, obtain α shaft voltage u under static two phase coordinate systems _αwith β shaft voltage u _β, by described α shaft voltage u _αwith β shaft voltage u _βinput pulse width modulation module, computing exports 6 road pulse width modulating signals, drives main power inverter;

The exciting current i simultaneously will gathered in step (1) _f, through following, filtering, biased and A/D change after and exciting current reference value i _frefsend into DC excitation pulse width modulation module together, computing exports 4 road pulse width modulating signals to drive exciting power converter.

In a kind of preferred version of the inventive method, step 6) in Pulse width modulation module be space vector pulse width modulation module.

In a kind of preferred version of the inventive method, step 3) in the concrete grammar of failure judgement state be: according to the difference failure judgement state of phasing current with the actual measurement phase current collected, namely to phasing current be actual measurement phase current is i _k(k=a, b, c), then the two difference is when in continuous two sense cycle, Δ ε _kjack per line, then judge that composite excitation axial magnetic field flux switch motor has fault to occur, otherwise judge that composite excitation axial magnetic field flux switch motor state is normal.

Beneficial effect: composite excitation axial magnetic field flux switch motor control system power inverter used for electric vehicle and drive circuit thereof are as the maincenter actuator of system, it is the weak link of the fault the most easily occurred in system, Power Converter faults will destroy the poised state of drive system operation, the torque breach even brake torque that generation cannot suppress, chromic trouble runs and will bring infringement to electric automobile and personal safety, the present invention is by step 4) and step 5) composite excitation axial magnetic field flux switch motor fault-tolerant control system, can accurate detection failure state, make composite excitation axial magnetic field flux switch motor can operate in fault-tolerant state, so the present invention has the following advantages:

(1) this tolerant system accurately can detect composite excitation axial magnetic field flux switch motor Power Converter faults state;

(2) this control system can make composite excitation axial magnetic field flux switch motor operate in fault-tolerant state;

(3) this control system can improve the security performance of electric automobile under Power Converter faults state greatly.

Accompanying drawing explanation

Fig. 1 is HEAFFSM topological structure;

Fig. 2 is the normal service chart of HEAFFSM;

Fig. 3 is HEAFFSM fault-tolerant operation figure;

Fig. 4 is the logical procedure diagram of the inventive method;

Fig. 5 is the system block diagram of the inventive method;

Fig. 6 is the structured flowchart realizing the inventive method;

Fig. 7 is torque when breaking down of HEAFFSM control system;

Fig. 8 is torque after HEAFFSM control system faults-tolerant control;

Embodiment

Below in conjunction with embodiment and Figure of description, the present invention is further illustrated.

The present invention be directed to a kind of composite excitation axial magnetic field flux switch motor fault tolerant control method, this motor comprises the first stator, rotor, the second stator, permanent magnet, armature winding and single-phase central excitation winding in three-phase set, as shown in Figure 1;

First stator, the second stator lay respectively at the both sides of rotor, each stator has 6 E shape iron cores, 6 armature coils, every two armature coils are in sequential series, form threephase armature winding, armature winding in the three-phase set of the threephase armature winding on two stators the A phase of the whole motor of composition in sequential series, B phase, C phase respectively; Each stator has 6 magnet exciting coils, 6 magnet exciting coils are concentratred winding, and on the tooth in the middle of stator E-coil, above-mentioned 6 coils successively order head and the tail are connected in series, and form single-phase central excitation winding;

Be provided with a permanent magnet between every two E shape iron cores, in three-phase set, armature winding is around in two E shape iron core teeth; Permanent magnet excitation direction symmetrical on first stator, the second stator is contrary; Permanent magnet on first stator, the second stator circumferentially alternately magnetizes, and the direction of magnetization of adjacent permanent magnet is contrary.

Rotor has 10 teeth, be called 10 rotor poles, rotor pole is fan-shaped, its shape is consistent with the odontoid of stator E-coil, rotor pole is evenly arranged on the excircle of the non-magnetic annulus of rotor, the axial width of rotor pole is equal with the axial width of non-magnetic annulus, on rotor both without permanent magnet also without winding.

The present invention is by the three-phase (A of the mutual motor in series of armature winding in the three-phase set of armature winding and the second stator in the three-phase set of the first stator, B, C) armature winding, by the mutual motor excitation winding in series of excitation winding of the excitation winding of the first stator and the second stator.Three phase inverter bridge and H type circuit is utilized to control this motor.

Fig. 6 is for realizing composite excitation axial magnetic field flux switch motor fault-tolerant control system structured flowchart of the present invention, and this control system is made up of AC power, rectifier, bus capacitor, dsp controller, main power inverter, auxiliary power inverter, transducer, hybrid exciting synchronous motor, photoelectric encoder etc.

AC power is powered to whole system, and after rectifier rectification, filtering, voltage stabilizing, give main and auxiliary power inverter, and Hall voltage transducer gathers busbar voltage, sends into controller after conditioning.The output termination hybrid exciting synchronous motor of main and auxiliary power inverter, Hall current instrument transformer gathers phase current and exciting current, send into controller after conditioning, code device signal gathers rotating speed and rotor-position signal, sends into controller and calculate rotor position angle and rotating speed after process.Controller exports 10 road pwm signals and drives main, exciting power converter respectively.

Composite excitation axial magnetic field flux switch motor fault-tolerant control system of the present invention, shown in Fig. 6, specifically comprises the following steps:

(1) phase current i is gathered from motor main circuit _a, i _bwith exciting current i _f, accurate initial position detection is carried out to motor, collection signal from motor encoder, sends into controller and process, draw rotating speed n and rotor position angle θ;

(2) the phase current i will gathered _a, i _bthrough signal condition and A/D conversion, then carry out park transforms, obtain the d shaft current i of stator under two-phase rotating coordinate system _dwith q shaft current i _q;

(3) by given rotating speed n ^*deduct encoder actual measurement rotating speed n, the rotating speed deviation delta n input speed adjuster obtained, obtains torque reference value after proportional integral computing by torque reference value busbar voltage U _dc, stator d shaft voltage u _d, stator q shaft voltage u _q, actual measurement rotating speed n and given rotating speed n ^*input current distributor, according to the difference failure judgement state of giving phasing current with the phase current collected, namely to phasing current is actual measurement phase current is i _k(k=a, b, c), then the two difference is when in continuous two sense cycle, Δ ε _kjack per line, then illustrate and have fault to occur, when composite excitation axial magnetic field flux switch motor state is normal, enter step 4), when composite excitation axial magnetic field flux switch motor breaks down, enter step 5);

(4) under, surface analysis composite excitation axial magnetic field flux switch motor control system fault-tolerant operation principle, according to principle of vector control, in d-q coordinate system, draws the Mathematical Modeling of composite excitation axial magnetic field flux switch motor.

Three-phase current:

Flux linkage equations:

$\left[\begin{array}{c}{\mathrm{\ψ}}_d\\ {\mathrm{\ψ}}_q\\ {\mathrm{\ψ}}_f\end{array}\right]=\left[\begin{array}{ccc}{L}_d& 0& M_f\\ 0& L_q& 0\\ 3/2M_f& 0& L_f\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\\ i_f\end{array}\right]+\left[\begin{array}{c}{\mathrm{\ψ}}_m\\ 0\\ 0\end{array}\right]---\left(2\right)$

Voltage equation:

$\left\{\begin{array}{c}{u}_d=R_s{i}_d+\frac{{\mathrm{d\ψ}}_d}{\mathrm{dt}}-{\mathrm{\ω}}_e{\mathrm{\ψ}}_q\\ u_q=R_s{i}_q+\frac{{\mathrm{d\ψ}}_q}{\mathrm{dt}}+{\mathrm{\ω}}_e{\mathrm{\ψ}}_d\\ u_f=R_f{i}_f+\frac{{\mathrm{d\ψ}}_f}{\mathrm{dt}}\end{array}\right.---\left(3\right)$

Torque equation:

$T_e=\frac{3}{2}{\mathrm{pi}}_q[{\mathrm{\ψ}}_m+(L_d-L_q)i_d+M_f{i}_f]---\left(4\right)$

Wherein, i _a, i _b, i _cfor three phase network electric current, i _d, i _qbe respectively stator d axle and q shaft current, I _mfor phase current magnitude, i _ffor excitation winding electric current; L _d, L _qbe respectively d axle and q axle inductance, M _ffor the mutual inductance between armature and excitation winding; ω is angular frequency, ω _efor angular rate; ψ _mfor permanent magnet flux linkage, p is motor number of pole-pairs, u _d, u _qbe respectively the voltage of d axle and q axle, u _ffor excitation winding voltage; R _sfor armature winding resistance, R _ffor excitation winding resistance; ψ _d, ψ _q, ψ _fd axle, q axle and excitation winding magnetic linkage respectively, for initial angle.

Adopt i _dduring=0 control strategy, d shaft current equals 0, can obtain following current sharing scheme according to formula (4):

$\left\{\begin{array}{c}{i}_d=0\\ i_q=\frac{{2T}_e}{3p{\mathrm{\ψ}}_m}\end{array}\right.---\left(5\right)$

Wherein, i _dfor d shaft current reference value, i _qfor q shaft current reference value; ψ _mfor permanent magnet flux linkage, p is motor number of pole-pairs, T _efor electromagnetic torque reference value;

(5) before composite excitation axial magnetic field flux switch motor control system fault, total magnetomotive force is:

Wherein, TMMF is total magnetomotive force, F _a, F _b,f _cfor a, b, c phase magnetomotive force, N is the armature winding number of turn, and α is the Space Rotating factor.

Suppose that open circuit occurs composite excitation axial magnetic field flux switch motor A phase, adopt exciting current i _fcarry out faults-tolerant control, total magnetomotive force is:

$\begin{array}{c}{\mathrm{TMMF}}^{\′}={\mathrm{MMF}}_b^{\′}+{\mathrm{MFF}}_c^{\′}+{\mathrm{MMF}}_f\\ =\mathrm{\α}{F}_b^{\′}+{\mathrm{\α}}^2{F}_c^{\′}+F_f\\ =\mathrm{\α}{\mathrm{Ni}}_b^{\′}+{\mathrm{\α}}^2{\mathrm{Ni}}_c^{\′}+N^{\′}{i}_f\end{array}---\left(7\right)$

Wherein, TMMF' is the total magnetomotive force of faults-tolerant control, F ' _b, F ' _cfor b, c phase magnetomotive force during faults-tolerant control, F _ffor excitation magnetic kinetic potential; I ' _b, i' _c, i _ffor b, c phase current during faults-tolerant control, N' is the excitation winding number of turn.

In order to ensure that composite excitation axial magnetic field flux switch motor can fault-tolerant operation, making formula (7) and formula (6) real part equal respectively with imaginary part, thus can obtain:

$\left\{\begin{array}{c}(-\frac{1}{2}{F}_b^{\′}-\frac{1}{2}{F}_c^{\′}+F_f)=\frac{3}{2}{\mathrm{NI}}_m\cos \mathrm{\θ}\\ \frac{\sqrt{3}}{2}(F_b^{\′}-F_c^{\′})=\frac{3}{2}{\mathrm{NI}}_m\sin \mathrm{\θ}\end{array}\right.---\left(8\right)$

Can obtain:

$\left\{\begin{array}{c}{i}_b=\sqrt{2}{I}_m\cos (\mathrm{\θ}-7\mathrm{\π}/6)\\ i_c=\sqrt{2}{I}_m\cos (\mathrm{\θ}+7\mathrm{\π}/6)\\ i_f=\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{I}_m\end{array}\right.---\left(9\right)$

Adopt i _d=0 control strategy, convolution (4) can obtain following current sharing scheme:

$\left\{\begin{array}{c}{i}_d=0\\ i_q=\frac{{2T}_e}{3p}({\mathrm{\ψ}}_m+\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{M}_f{I}_m)\\ i_f=\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{I}_m\end{array}\right.---\left(10\right)$

(6) d shaft current reference value i distributing switch produced _drefdeduct the d shaft current i in step (2) _dobtain d shaft current deviation delta i _d, with q shaft current i _qrefdeduct the q shaft current i in step (2) _qobtain q shaft current deviation delta i _q; By d shaft current deviation delta i _dinput d shaft current adjuster carries out proportional integral computing, obtains d shaft voltage u _d, by q shaft current deviation delta i _qinput q shaft current adjuster carries out proportional integral computing, obtains q shaft voltage u _q, then to described d shaft voltage u _dwith q shaft voltage u _qafter jointly carrying out rotating orthogonal-static two phase inversion, obtain α shaft voltage u under static two phase coordinate systems _αwith β shaft voltage u _β, by described α shaft voltage u _αwith β shaft voltage u _βinput pulse width modulation module, computing exports 6 road pulse width modulating signals, drives main power inverter;

The exciting current i simultaneously will gathered in step (1) _f, with exciting current reference value i after signal condition and A/D are changed _frefsend into DC excitation pulse width modulation module together, computing exports 4 road pulse width modulating signals to drive exciting power converter.

Above-described embodiment is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention; some improvement and equivalent replacement can also be made; these improve the claims in the present invention and are equal to the technical scheme after replacing, and all fall into protection scope of the present invention.

Claims (3)

1. a composite excitation axial magnetic field flux switch motor fault tolerant control method, it is characterized in that, the method comprises the following steps:

(1) phase current i is gathered from motor main circuit _a, i _bwith exciting current i _f, initial position detection is carried out to motor, collection signal from motor encoder, sends into controller and process, draw rotating speed n and rotor position angle θ;

(2) the phase current i will gathered _a, i _bthrough following, filtering, biased and A/D conversion, then carry out park transforms, obtain the d shaft current i of stator under two-phase rotating coordinate system _dwith q shaft current i _q;

(3) by given rotating speed n ^*deduct encoder actual measurement rotating speed n, the rotating speed deviation delta n input speed adjuster obtained, obtains torque reference value after proportional integral computing by torque reference value busbar voltage U _dc, stator d shaft voltage u _d, stator q shaft voltage u _q, actual measurement rotating speed n and given rotating speed n ^*input current distributor, according to electric current failure judgement state, when composite excitation axial magnetic field flux switch motor state is normal, enters step 4), when composite excitation axial magnetic field flux switch motor breaks down, enter step 5);

(4) i is adopted _d=0 control strategy, distributing switch is according to following current sharing scheme output current:

$\left\{\begin{array}{c}{i}_{\mathrm{dref}}=0\\ i_{\mathrm{qref}}=\frac{2T_{\mathrm{eref}}}{3p{\mathrm{\ψ}}_m}\end{array}\right.$

Wherein, i _dreffor d shaft current reference value, i _qreffor q shaft current reference value; ψ _mfor permanent magnet flux linkage, p is motor number of pole-pairs, T _ereffor electromagnetic torque reference value;

(5) adopt exciting current to carry out faults-tolerant control, continue to keep i _d=0, distributing switch is according to following current sharing scheme output current:

$\left\{\begin{array}{}\\ i_{\mathrm{dref}}=0\\ i_{\mathrm{qref}}=\frac{2T_{\mathrm{eref}}}{3p}({\mathrm{\ψ}}_m+\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{M}_f{I}_m)\\ i_{\mathrm{fref}}=\frac{\sqrt{3}}{2}\frac{N}{N^{\′}}{I}_m\end{array}\right.$

Wherein, I _mfor phase current magnitude, i _freffor exciting current reference value, M _ffor the mutual inductance between armature winding and excitation winding, N' is the excitation winding number of turn, and N is the armature winding number of turn;

(6) d shaft current reference value i distributing switch produced _drefdeduct the d shaft current i in step (2) _dobtain d shaft current deviation delta i _d, with q shaft current i _qrefdeduct the q shaft current i in step (2) _qobtain q shaft current deviation delta i _q; By d shaft current deviation delta i _dinput d shaft current adjuster carries out proportional integral computing, obtains d shaft voltage u _d, by q shaft current deviation delta i _qinput q shaft current adjuster carries out proportional integral computing, obtains q shaft voltage u _q, then to described d shaft voltage u _dwith q shaft voltage u _qafter jointly carrying out rotating orthogonal-static two phase inversion, obtain α shaft voltage u under static two phase coordinate systems _αwith β shaft voltage u _β, by described α shaft voltage u _αwith β shaft voltage u _βinput pulse width modulation module, computing exports 6 road pulse width modulating signals, drives main power inverter;

The exciting current i simultaneously will gathered in step (1) _f, through following, filtering, biased and A/D change after and exciting current reference value i _frefsend into DC excitation pulse width modulation module together, computing exports 4 road pulse width modulating signals to drive exciting power converter.

2. a kind of composite excitation axial magnetic field flux switch motor fault-tolerant control system according to claim 1, is characterized in that, described step 6) in Pulse width modulation module be space vector pulse width modulation module.

3. a kind of composite excitation axial magnetic field flux switch motor fault-tolerant control system according to claim 1 and 2, it is characterized in that, described step 3) in the concrete grammar of failure judgement state be: according to the difference failure judgement state of phasing current with the actual measurement phase current collected, namely to phasing current be actual measurement phase current is i _k(k=a, b, c), then the two difference is when in continuous two sense cycle, Δ ε _kjack per line, then judge that composite excitation axial magnetic field flux switch motor has fault to occur, otherwise judge that composite excitation axial magnetic field flux switch motor state is normal.