[introduction] without brush electric machinery to belong to change flow pattern oneself (ego direction is changed) , because this is controlled,rise more complex. The rotor position that control of BLDC electric machinery asks to understand electric machinery to undertake rectification changes direction and mechanism. To control of closed circuit speed, have two additional demands, namely to rotor speed / or electric machinery electric current and PWM signal undertake metrical, in order to control electric machinery speed and power.

BLDC electric machinery controls algorithm

Without brush electric machinery to belong to change flow pattern oneself (ego direction is changed) , because this is controlled,rise more complex. The rotor position that control of BLDC electric machinery asks to understand electric machinery to undertake rectification changes direction and mechanism. To control of closed circuit speed, have two additional demands, namely to rotor speed / or electric machinery electric current and PWM signal undertake metrical, in order to control electric machinery speed and power. BLDC electric machinery can use an edge to arrange according to using a requirement or the center arranges PWM signal. Great majority application asks rate change is operated only, form the border that uses 6 independence PWM signal. The resolution that this offerred. If apply apply the brake of requirement server fixed position, specific power consumption or dynamical contrary to reason or one’s expectation, recommend use additional the center arranges PWM signal. For inductive rotor position, BLDC electric machinery uses sensor of suddenly Er effect to offer fixed position response. This is used with respect to what caused more string and higher cost. Control leave out without sensor BLDC the need to suddenly Er sensor, use electric machinery however oppose electromotive force (electromotive force) will forecast rotor position. To resembling fan and pump without sensor control such low cost gearshift applies crucial. When using BLDC electric machinery, freezer and air conditioning compressor also need to be controlled without sensor.

Carry the insertion of time and complement for nothing: Most BLDC electric machinery does not need to complementary PWM, sky carries time to insert or carry time compensation for nothing. The BLDC application that may ask these are characteristic is drive of wave of electromotor of high-powered BLDC servo, sine only type BLDC electric machinery, without brush AC, or PC synchronous electric machinery.

Control is algorithmic

A lot of different control algorithm are offerred by in order to the control to BLDC electric machinery. Typical method is, use power transistor as linear manostat will control electric machinery voltage. When electric machinery of drive high power, this kind of method is not practical. High power electric machinery must use PWM control, ask a small controller will offer start and control a function.

Control algorithm must offer following 3 functions:

? Use at controlling the PWM voltage of electric machinery speed
? Use at entering the mechanism of rectification inverting to electric machinery
? Use the method that turns over electromotive force or suddenly Er sensor to forecast rotor position

Pulse width modulation is used at using alterable tension electric machinery winding only. Effective voltage and PWM occupy sky comparing to become direct ratio. When getting proper rectification inverting, the torque speed character of BLDC and electric machinery of the following dc are identical. Can control the speed of electric machinery and alterable torsion with alterable voltage.

The inverting of power transistor realized the torsion that the proper winding in stator can generate according to rotor position. In electric machinery of a BLDC, MCU must know the place of rotor and rectification inverting can undertake in appropriate time.

The echelon commutate inverting of BLDC electric machinery

Do not have to dc brushing electric machinery to use inverting of commutate of so called echelon is one of simple methods.

Graph 1: Of the echelon controller that is used at BLDC electric machinery simplify block diagram

In the graph 1 in, every want to control electric current through coming to electric machinery terminal, and terminal of the 3rd electric machinery always go up with power source electricity disconnect. The parts of an apparatus of 3 kinds of suddenly Er in built-in big electric machinery is used at providing digital signal, they measure rotor place inside 60 degrees sector area, provide these information on electric machinery controller. As a result of every time the electric flow on two winding is equal, and the electric current on the 3rd winding is 0, this kind of method can arise only have 6 way among them one of voltaic space vector. As the roll of electric machinery, the electric current of electric machinery terminal turns in every 60 degrees when, implementation phone switch (rectification inverting) , because vector of space of this electric current always is the is close to 30 degrees position in 90 degrees of phase shift.

Graph 2: Echelon control: Drive weaveform and the torsion that rectification is in

Because the voltaic mode of every winding is echelon, from 0 begin to flow to arrive again to positive electricity 0 flow to negaive electricity again next. This produced voltaic space vector, when undertaking the pace rises on the direction that differs in 6 as the whirl of rotor when it, it will be close to a balance to rotate. In resembling mediating such electric machinery uses refrigerator for nothing, using suddenly Er sensor is not a changeless choice. Electromotive force sensor is turned over to be able to be used in what be not the induction in couplet winding obtain same result. The and rather than of simple and easy sex that system of drive of this kind of echelon dominates circuit because of its constant common, but they encounter torsion ripple problem in rectification process.

The sine commutate inverting of BLDC electric machinery

Echelon commutate inverting still can’t be those who offer balance, essence to allow to not have brush dc machine to control. Because do not have in a three-phase,this basically is brush electric machinery (contain a lineal wave to oppose electromotive force) in the torsion that produces defines by following equation: =Kt [IRSin of runner shaft torsion (O) + ISSin (O+120) + ITSin (O+240) ]

Among them:
O is the electric angle of runner shaft
Kt is the torsion constant of electric machinery
IR, IS and IT are phasic electric current

If phasic electric current is of sine: IR=I0Sino; IS=I0Sin (+ 120o) ; IT=I0Sin (+ 240o)
Will get: =1.5I0*Kt of runner shaft torsion (an independence the constant at runner shaft angle) sine commutate inverting is not had brush electric machinery controller to try hard drive winding of 3 electric machinery, thirdly road electric current turns as electric machinery and undertake sine changes smoothly. Those who choose these electric current is relevant and phasic, such they will produce vector of smooth space of rotor electric current, direction is the direction with rotor orthogonality, have invariant. This was eliminated with turn to relevant torsion ripple and turn to pulse. For the whirl as electric machinery, the smooth sine wave modulation that generates electric machinery electricity, have to rotor position with respect to the requirement measure. Suddenly Er parts of an apparatus offerred the cursory consideration to rotor position only, still can’t achieve intent requirement. Be based on this reason, give out horn to feedback from coder or similar parts of an apparatus with respect to the requirement.

Graph 3: Of controller of wave of sine of BLDC electric machinery simplify block diagram

Because winding electric current must join generation the vector between an empty of smooth constant rotor report, and the apart of every fixed position of stator winding 120 degrees of horn, accordingly the electric current of every group must be sine and phase shift is 120 degrees. The positional information in using coder will undertake synthetic to two sine wave, two phase shift between are 120 degrees. Next, take these signal be worth with torsion, because the amplitude of this sine wave and need torsion become direct ratio. Result, command of electric current of two sine wave gets appropriate phasing, produce vector of space of rotational stator electric current in orthogonal direction thereby. Output of signal of command of sine electric current is a pair in two proper electric machinery winding the P-I controller of modulation electric current. The negative that the electric current in winding of the 3rd rotor is controlled winding electric current and, because this cannot be controlled respectively. The output of every P-I controller is sent modulator of a PWM, send output the bridge and terminal of two electric machinery next. The tension that uses terminal of the 3rd electric machinery results from the negative of the signal of before applying two group and, use at parting removed 120 degrees 3 sine voltage. Result, actual output electric current dogs undeely sine electric current commands signal, vector of space of earning electric current turns smoothly, be able to stabilize on the quantity and locate with wants way. Change direction through echelon commutate commonly, cannot achieve commutate of stable pilot sine to turn to a result. However, because its are below speed of low electric machinery efficiency is very tall, will part below speed of expensive electric machinery. Because rate rises,this is, voltaic circumfluence controller must dog a sine signal that adds frequency. In the meantime, they must overcome what improve the electric machinery that increases below amplitude and frequency as speed to oppose electromotive force. Because P-I controller has narrow gain and frequency to answer, variable to the time of voltaic control loop interference will cause the gain error in phasic lag and electric machinery electric current, rate is higher, the error is bigger. This will disturb voltaic space vector relative to the direction at rotor, cause thereby produce displacement with orthogonal direction. When producing this kind of situation, the electricity that carries certain amount can produce lesser torsion, because this needs more electric current to maintain torsion, loss of efficiency. As the addition of speed, this kind is reduced will continue. Going up somehow, phasic displacement of electric current exceeds 90 degrees. When producing this kind of situation, torsion is decreased to for 0. Pass the couple of sine, speed of this bit brought about negative torsion above, because this also cannot come true.

AC electric machinery controls algorithm

1, scalar quantity of scalar quantity control is controlled (or V/Hz is controlled) the simple method that is speed of electric machinery of instruction of a control. The stable state model of instruction electric machinery basically is used at acquiring a technology, because function of this transient state is of impossible implementation. The system does not have voltaic return. To dominate electric machinery, three-phase power source changes on amplitude and frequency only.

2, vector is controlled or directional control is in magnetic field the torsion in electromotor changes as the function of stator and rotor magnetic field, and become two magnetic field reach peak value when mutual orthogonality. In the control that is based on scalar quantity, the angle between two magnetic field changes significantly. Vector control tries to create orthogonal concern again in AC electric machinery. To control torsion, generate electricity from inside the flux of generation severally, in order to realize the response of DC machine quality. Electric machinery controls the vector control of electric machinery of an AC instruction and an alone excitation DC similar. In electric machinery of a DC, the F of Φ of magnetic field energy that arises by place of IF of excitation electric current and the armature magnetic flux that arise by place of IA of armature electric current Φ A orthogonality. These magnetic field are passed go Ou and mutual very stable. Accordingly, when armature electric current controlled in order to control torsion when, magnetic field energy still keeps insusceptible, realized swifter transient state to answer. The magnetic field of three-phase AC electric machinery is directional control (FOC) the operation that includes to imitate DC electric machinery. All and controlled variable learns to alternate through number, be changed to AC of DC and rather than. Its target is independent control torsion and magnetic flux.

Magnetic field is directional control (FOC) have two kinds of methods:

Direct FOC: The direction of rotor magnetic field (Rotor Flux Angle) it is to pass magnetic flux observation implement direct calculation gets.

Indirect FOC: The direction of rotor magnetic field (Rotor Flux Angle) it is to adopt pair of rotor speed and slippery difference (Slip) estimation or measure and obtain secondhand.

Vector control asks to know the place of rotor magnetic flux, can use terminal electric current and tension (the dynamic model that introduces AC induction electric machinery) knowledge, will calculate through algorithm. Look from the angle of implementation however, the demand to computational resource is crucial.

Can use different kind to realize vector to control algorithm. Estimation of technology of make a present of, model is mixed before can use at increasing to answer from adaptive control technology with stability.

3, the vector control of AC electric machinery: What understand vector to control algorithm deep is two important changeover: Clark commutation, park commutation and their inverse operation. Use Clark and Park commutation, bring the rotor electricity that can control rotor area. Do admissibility so the voltage that system of control of a rotor decides to should supply rotor, in order to make the torsion below dynamic change load is changed. Clark commutation: Clark maths changeover revises system of a three-phase two coordinate system:

Among them the component that Ia and Ib are orthogonal datum plane, io is not important Homoplanar part

Graph 4: Three-phase rotor electric current and the relation that rotational reference fastens

4, Park changeover: Park maths changeover changes system of two-way static state into rotational system vector

Two-phase α , β frame states through Clarke changeover has consideration, input vector roll module next, it turns here horny θ , adhere to in order to accord with the D at rotor energy, q frame. According to afore-mentioned formula, realized the changeover of angle θ .

The magnetic field of AC electric machinery is directional vector pilot is basic structure

Clarke commutation uses IA of three-phase electric current, IB and IC, among them IA and IB the electric current in photograph of fixed coordinate stator is mixed into Isd by commutation Isq, become Park commutation D, the element in Q. Its come through model of electric machinery flux Isd of calculative electric current, isq and θ of instantaneous discharge horn are used to the dynamoelectric torque of electric machinery of computational communication induction.

These deriving that value and referenced value are compared each other, update by PI controller.

The electric machinery pilot that is based on vector an inherent advantage is, can use same principle, the AC that the mathematical model that the choice fits goes to dominating all sorts of types respectively, PM-AC or BLDC electric machinery.

The vector of BLDC electric machinery is controlled

BLDC electric machinery is directional vector pilot basically chooses magnetic field. Those who used FOC without brush electric machinery to be able to achieve taller efficiency, efficiency can be achieved 95% , and be opposite electric machinery is very businesslike also when high speed.

1, the pace is controlled into electric machinery

Graph 5

The pace uses two-way drive electricity normally into electric machinery control, pace of its electric machinery is entered by will come true by ordinal switch winding. Normally this kind of pace has 3 drive order into electric machinery: ① is single-phase whole situation takes drive: In this kind of mode, its winding appends report by following order, AB/CD/BA/DC (BA expresses winding AB appending report is to turn over what direction undertakes) . This one order is called single-phase whole situation takes pattern, or wave drive mode. In any time, have one addition report only. Whole situation of ② double photograph takes drive: In this kind of mode, double photograph appends report together, accordingly, rotor always is in two extremely between. This mode is called double whole situation is entered, this one mode is the normal drive order of polar electric machinery, exportable torque. Half pace of ③ takes pattern: This kind of mode takes single-phase step and double photograph pace appends report together into union: Odd addition report, next double addition report, next odd addition report… , accordingly, electric machinery runs into increment with half pace. This one mode is called half pace takes pattern, the horn of effective step pitch of every excitation reduced its electric machinery half, the torque that its output is inferior also. 3 kinds of mode all can use above at turning over direction to turn (anticlockwise direction) , if be no good instead orderly. Normally, the pace is had into electric machinery multipolar, so that reduce step pitch role, but, the amount of winding and drive order are changeless.

2, general DC electric machinery controls algorithm

The speed of general electric machinery is controlled, use the electric machinery of 2 kinds of circuit especially:

Photo corner control
PWM behead wave is controlled

Control of photo corner of control of ① photo corner is the method with simple pilot of speed of general electric machinery. Those who carry the part nodding arc of TRIAC is fluctuant will control rate. Photo corner controls the solution that is special economy, but, efficiency is not quite tall, easily electromagnetism is disturbed (EMI) .

Graph 6: The photo corner of general electric machinery is controlled

Graph 6 watches understand mechanism of photo corner pilot, it is representative application of TRIAC speed pilot. The week photograph shift of TRIAC door pulse produced businesslike tension, produced different electric machinery rate thereby, and had used 0 fold detect circuit, built sequential reference, with defer door pulse. Control of PWM of control of wave of ② PWM behead is pilot of speed of general electric machinery, more advanced solution. In this one solution, power MOSFET, or IGBT puts through line voltage of AC of high frequency commutate, produce the tension that changes along with time for electric machinery then.

Graph 7: The PWM behead wave of general electric machinery is controlled

Limits of its switch frequency is 10-20KHz commonly, in order to eliminate noise.

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