CN1391339A - Control method of brushless DC motor for simulteneously reaching optimal efficieney and maximal torque - Google Patents

Abstract

A control method of brushless DC motor for reaching optimal efficiency and maximal torque simultaneously features that the optimal current wagveform is found out according to specially designed target function, real size, copper loss limit and drive voltage limit, and the current with optimal waveform is input to the motor by control system.

Description

Can reach the control method of brushless DC motor of optimum efficiency and breakdown torque simultaneously

The present invention relates to motor control method, particularly relevant for a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously.Utilize specially designed target function type, and the actual design size of the DC Brushless Motor that drives at desire, and specific restrictive condition: copper loss restriction and driving voltage restriction, find out best current waveform; Import this best current waveform, can make this motor bring into play its maximum function, the highest running efficiency, promptly under the least power loss, can produce maximum moment.If be applied to motor vehicle, not only on efficient, can improve, and torque also can significantly promote, for the performance of motor vehicle when starting or the climbing, just can not be restricted yet, and then can promote its endurance.

General DC Brushless Motor all is that the hypothesis air gap flux density is distributed as sine wave, and is input with sinusoidal current waveform; Or suppose that air gap flux density is distributed as trapezoidal or square-wave form, and import with square-wave current waveform.Yet in fact, the motor air-gap magnetic flux distribution must be looked stator, rotor shapes, arrangement mode and magnetic flux material behavior and difference is arranged, be not pure sine wave, square wave or trapezoidal wave, therefore reluctantly with these waveform input currents, not only can't bring into play the function of motor, and on efficient, also can't promote with minimum current output maximum moment.

For example, electric motor car now promptly has aforesaid defective to exist.The development of the motor vehicle of present stage, limited maximum be energy content of battery density deficiency, cause vehicle endurance deficiency, limited the application of electric motor car greatly, therefore, how to improve the efficient of electric vehicle motor, also be the research of present stage, the emphasis of development.Now be described as follows:

General motor all is the situation of running at high rotating speed, low torque, therefore in the application of vehicle, need add reducing gear, on the one hand with speed drop to suitable road speed, torque can be improved on the one hand, but the efficient of reducing gear is not high, makes the whole efficiency of electric motor car lower.

In order to improve the index of car load efficient, thereby motor directly is installed on the wheel, can saves the energy loss of reducing gear like this; Therefore this direct drive-type wheel motor must be designed to high torsion, slow-revving performance, is just promoted the performance of vehicle when starting and climbing.

The above each example (example that comprises motor vehicle), all because the waveform failed is not to import at the actual characteristic of employed DC Brushless Motor, so that can not reach the anticipation effect, and there is no any way at present, can seek its best waveform that is suitable at employed DC Brushless Motor; Therefore, not only can't bring into play the function of motor, and on efficient, also can't promote with minimum current output maximum moment.

The present invention ties up to provides a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously, main system is via the analysis of the structure of the motor that a desire is driven and size etc., reach and to control this motor to change input motor current waveform for the mode of its optimum and optimum waveform, enable to promote the torque of motor, and and then can make it meet the starting and the required strength of climbing.

If be applied to motor vehicle, then the direct-drive type wheel motor can improve the efficient of motor vehicle, particularly when its following time of condition that operates in the slow-speed of revolution, high torque (HT), can make it meet the starting and the required strength of climbing.

The present invention is directed to DC Brushless Motor (outstanding spindle is to the magnetic flow direct current brushless motor), design the optimization current waveform, make motor output torque under restrictive condition can reach maximum.It at first derives moment equation with energy method, and according to the characteristic of motor equation is revised; Then utilize the magnetic circuit model analysis, derive the relational expression of moment and input current; According to different driving frameworks, propose three kinds of different restrictive conditions again, be target function to the maximum with moment, the current waveform of calculating optimumization; Can produce maximum moment and efficient after simulate the waveform that confirms under the copper loss restriction, be optimal results under three kinds of different situations.

One,, general dynamo-electric magnetic system is analyzed based on energy method; At first consider single exciting field system, utilize the convenience of conservative system on integration, can try to achieve the moment equation of representing with magnetic flux chain and position, utilize the notion of energy altogether again, the moment representation is converted to electric current and position function, so can obtain the direct relation formula between moment and electric current, be generalized to the compound field system again and contain the dynamo-electric magnetic system of permanent magnet, obtain moment equation.

Two, after the moment equation of general Mechatronic Systems obtained, at this second section, we were placed on research focus in the DC Brushless Motor system, characteristic at DC Brushless Motor, analyze its moment equation, make one of the remaining positive moment of equation, significantly simplify analytic process; Then to analyze air-gap flux and come factored moment, utilize the equivalent magnetic circuit model, magnetic flux be analogized to electric current, and derive air-gap flux by the circuit analytic technique.

Three, utilize second section derivation result, we are at this 3rd section specification with one group of actual DC brushless motor, and substitution magnetic flux computing formula utilizes the Matah package software to calculate air-gap flux and differential thereof, then carries out the calculating of current optimization.Optimized target is to make moment reach maximum, cooperates the different driving framework of motor, proposes three kinds of different restrictive conditions respectively, and substitution optimization formula is calculated, and respectively relatively under three kinds of frameworks in the performance performance of each rotating speed.Prove simply more at last, calculate the result's of gained optimized really current waveform.

Four, optimized result is three groups of different current waveforms, corresponding different motor performance, and we propose the drive controlling framework in this 4th section, three groups of current waveforms are described, how to realize out desirable current waveform.By the principle and the characteristic of analysis-driven circuit, to propose several feasible current control modes, propose the calcspar of whole driving control system again, and the implementation of each unit is described.

Main purpose of the present invention provides a kind ofly can use the minimum current root-mean-square value, but can reach maximum moment output, improves the control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of moyor.

Secondary objective of the present invention provides a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously, it can make and directly is installed on the wheel and save the DC Brushless Motor of reducing gear energy loss, not only on efficient, can improve, and torque also can significantly promote, can not be restricted for the performance of motor vehicle when starting or climb, and then promote the endurance of motor vehicle.

Above-mentioned purpose of the present invention is realized by following scheme:

A kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously, it may further comprise the steps at least:

1a. provide a kind of optimum current waveform of DC Brushless Motor: utilize specially designed target function type, and, add the specific limited condition, try to achieve the current waveform of this motor the best at the actual design size of controlled DC Brushless Motor;

1b. import this best current waveform with a controller and the driving electronics with plural number position signal processing capacity to controlled motor by driving control system.

Wherein, described target function is:

f＝f(I _a，I _b，I _c) $=N(I_a\frac{{\mathrm{d\φ}}_a}{\mathrm{d\φ}}+\frac{{\mathrm{d\φ}}_b}{\mathrm{d\φ}}+\frac{{\mathrm{d\φ}}_c}{\mathrm{d\φ}})$

Wherein

I _a, I _b, I _cBeing phase current to be determined, all is the function of rotor relative angle θ; Φ _a, Φ _b, Φ _cAir-gap flux function for three-phase.

This best current waveform system is directly proportional with the motor air-gap change in magnetic flux density.

Described actual design size at selected DC Brushless Motor is found out best current waveform, be to make motor running can reach minimum current under the maximum moment: this electric current changes with motor stator and rotor relative position, is one to be varied to the directly proportional waveform with air gap flux density; This current waveform is relevant with initial motors designs dimensional parameters, imports this specific currents waveform, can make motor bring into play its maximum function, the highest running efficiency, promptly under the least power loss, can produce maximum moment.

It adds specific restrictive condition is the copper loss restriction.

Its restrictive condition can further increase: the driving voltage restriction.

Described driving control system, its controller is after accepting the throttle order, cooperate the electric current of back coupling and the rotor relative angular position numerical value that position sensor is read, and find the numerical value of optimum waveform in the numerical tabular of in aforementioned controller, depositing in this rotor relative angular position, send into motor driver after multiplying each other with the yield value of throttle order, and enter in the correct coiling of motor, finish the driving of optimum waveform.

This control method can be applicable on the object that use motors such as electric motor car or electric automobile drive.

This motor is installed in the appropriate position that can directly drive wheel.

DC Brushless Motor directly is installed in wheel, and seeks out its suitableeest waveform as input at this motor.

Use the control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of the present invention, can break through conventional art, start out a kind of brand-new control mode at the substantive defect that can't take into account aspect lifting efficient and the increasing torque two; And when it is applied to motor vehicle, really can meet required strength of its starting and when climbing, and then promote the endurance of motor vehicle.

Description of drawings:

Stator and rotor and the magnetic flux schematic diagram thereof of Fig. 1 the present invention in an electrical cycle;

The equivalent magnetic circuit figure of Fig. 2 the present invention first figure;

Fig. 3 the present invention is through the equivalent magnetic circuit figure after simplifying;

The magnetic circuit model that Fig. 4 the present invention streamlines any further;

The specification of Fig. 5 motor used herein and specification table thereof;

Fig. 6 copper loss restriction of the present invention is the three-phase current waveform down;

Fig. 7 three-phase Y connection of the present invention, the current waveform that three-phase is independent and copper loss limits compare;

Fig. 8 three-phase Y connection of the present invention, the moment waveform that three-phase is independent and copper loss limits compare;

The comparison of Fig. 9 electric current of the present invention and magnetic flux differential;

Figure 10 driving control system calcspar of the present invention;

Figure 11 location sensing of the present invention and reflecting piece figure;

Figure 12 optimum waveform of the present invention and approximate waveform figure.

Followingly further describe according to the method for accompanying drawing and preferred embodiment and the characteristic on the effect.

Embodiment:

The present invention system provides a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously, and it designs the optimization current waveform at the axial magnetic flux DC Brushless Motor, makes motor output torque under restrictive condition can reach maximum.

At first, 1, derive moment equation and equation is revised according to the characteristic of motor with energy method; 2, then utilize the magnetic circuit model analysis, derive the relational expression of moment and input current; 3, again according to different driving frameworks, propose three kinds of different restrictive conditions, be target function to the maximum with moment, the current waveform of calculating optimumization; 4, after simulation confirms that the waveform under the copper loss restriction can produce maximum moment and efficient, be optimal results under three kinds of different situations.After omitting the l point, describe as follows to the 2-4 point:

In order to calculate the foundation of best three-phase separate current waveform

(1) equivalent motor magnetic circuit model:

Motor stator tooth and rotor number of poles ratio are 3: 2, and we can be considered as one group with 3 teeth, 2 utmost points, shown in 1 figure, represent an electrical cycle for one group, because the parameter tool periodically, so only need consider that one-period gets final product.

Stator tooth A and A ' are one group, and its sense of current is for producing identical moment, and B and B ' and C and C ' are also together; Boundary B L and BL ' can be considered overlapping, and the magnetic flux that flows out from BL flows into from BL ' immediately.

As shown in Figure 2, be the equivalent magnetic circuit figure of Fig. 1, wherein R _mThe interior magnetic resistance of=permanent magnet

R _MlLeakage field resistance between=magnet

R _s=stator yoke iron magnetic resistance

R _Gal, R _Gar=rotor flux is through the air-gap reluctance of A phase

R _Gbl, R _Gbr=rotor flux is through the air-gap reluctance of B phase

R _Gcl, R _Gcr=rotor flux is through the air-gap reluctance of C phase

φ _rThe equivalent sources of magnetic flux of=magnet

φ _m=air-gap flux

The material of stator tooth is a silicon steel sheet, and its magnetic capacity is much larger than the magnetic capacity of air, so the magnetic resistance of stator yoke iron can ignore, and magnetic circuit can be simplified as shown in Figure 3.

Because the facility of calculating, we change magnetic resistance into magnetic conductance in Fig. 3, and air-gap permeance is divided into left and right sides two parts, and two magnet about correspondence respectively, expression magnetic flux enter or the air-gap permeance when leaving stator tooth.

Utilize the solution of circuit, can solve air-gap flux φ _mAnd before separating the magnetic circuit equation, we need obtain the size of each magnetic conductance earlier, and the substitution equation is found the solution again.(2) calculate the three-phase air-gap flux: utilize above-mentioned magnetic conductance of trying to achieve, we can further find the solution simultaneous magnetic circuit equation, to find out the three-phase air-gap flux.At first Fig. 3 is streamlined any further the form of calculating into as shown in Figure 4 suitable magnetic circuit.

As shown in Figure 4, wherein four groups three-phase magnetic conductance by and be unified into four magnetic conductance p _Gx

P _Gx=P _Gax+ P _Gbx+ P _Gcx(formula 01)

And F ₁, F ₂, F ₃And F ₄Be the magnetomotive force of four nodes, make F ₄Be zero point, utilize the nodal method of analysis in the circuitry, we can get following three equations: enter F 1. ₁The clean magnetic flux of point is zero ${\mathrm{\&phi;}}_r+(F_2-F_1)({2P}_{\mathrm{ml}}+\frac{P_{\mathrm{gl}}{P}_{\mathrm{gr}}}{P_{\mathrm{gl}}+P_{\mathrm{gr}}})+(F_3-F_1)P_m=0$ (formula 02) 2. enters F ₂The clean magnetic flux of point is zero ${\mathrm{\&phi;}}_r+{\mathrm{<figure-callout\; id="2P"\; label="F"\; filenames="A01118683.600191.png"\; state="\{\{state\}\}">F</figure-callout>}}_2{P}_m+(F_2-F_1)(2P_{\mathrm{ml}}+\frac{P_{\mathrm{gl}}{P}_{\mathrm{gr}}}{P_{\mathrm{gl}}+P_{\mathrm{gr}}})=0$ (formula 03) 3. enters F ₃The clean magnetic flux of point is zero ${\mathrm{\&phi;}}_r+(F_3-F_1)P_m+F_3({2P}_{\mathrm{ml}}+\frac{P_{\mathrm{gl}}{P}_{\mathrm{gr}}}{P_{\mathrm{gl}}+P_{\mathrm{gr}}})=0$ (formula 04) three equations can solve F ₁, F ₂, F ₃Three unknown numbers, substitution equation again ${\mathrm{\&phi;}}_m=(F_1-F_2)\frac{P_{\mathrm{gl}}{P}_{\mathrm{gr}}}{P_{\mathrm{gl}}+P_{\mathrm{gr}}}$ (formula 05) just can be in the hope of total air-gap flux.And the three-phase air-gap flux can be tried to achieve with the mode of shunting: ${\mathrm{\&phi;}}_a=\frac{P_{\mathrm{ga}}}{P_{\mathrm{ga}}+P_{\mathrm{gb}}+P_{\mathrm{gc}}}{\mathrm{\&phi;}}_m$ (formula 06) ${\mathrm{\&phi;}}_b=\frac{P_{\mathrm{gb}}}{P_{\mathrm{ga}}+P_{\mathrm{gb}}+P_{\mathrm{gc}}}{\mathrm{\&phi;}}_m$ (formula 07) ${\mathrm{\&phi;}}_c=\frac{P_{\mathrm{gc}}}{P_{\mathrm{ga}}+P_{\mathrm{gb}}+P_{\mathrm{gc}}}{\mathrm{\&phi;}}_m$ (formula 08) (3) calculating optimum current waveform: (3.1) target function $f=f(I_a,I_b,I_c)=N(I_a\frac{{\mathrm{d\&phi;}}_a}{\mathrm{d\&phi;}}+I_b\frac{{\mathrm{d\&phi;}}_b}{\mathrm{d\&phi;}}+I_c\frac{{\mathrm{d\&phi;}}_c}{\mathrm{d\&phi;}})$ (formula 09)

Wherein: I _a, I _b, I _cBeing phase current to be determined, all is the function of rotor relative angle θ.φ _aφ _bφ _cAir-gap flux function for three-phase.

(3.2) restrictive condition

A. copper loss restriction

Excessive in order to prevent stator copper coiling electric current, and limit total copper loss (being gross calorific power).

To the relation of positive moment and electric current, as follows: $T_{\mathrm{fld}}=\mathrm{NI}\frac{{\mathrm{d\&phi;}}_m}{\mathrm{d\&phi;}}$ (formula 10)

Obviously, exist Bigger position feeds the moment of electric current gained, than The moment that less position feeds the electric current gained is big.

Reach the driving framework via other twos breeds of horses of often using relatively, that is: (1) three-phase Y connection winding, the square wave drive electric current, and for limiting its maximum current; (2) three-phase independent winding, the square wave drive electric current, and for limiting its maximum current.

But the current waveform of two kinds of framework gained thus, obtain the maximum moment under these restrictive conditions, the electric current of input all is the square-wave waveform under the maximum current, but such result does not also meet: the notion of " at the big big electric current of ground square tube of magnetic flux differential, at the little little electric current of ground square tube of magnetic flux differential "; In order to meet this notion, must remove the condition of maximum current limit.

The restriction of maximum current is excessive in order to prevent electric current, produce excessive heat and motor is burnt, if do not limit size of current, but limit total copper loss (gross calorific power) and so just can realize above-mentioned notion, feed big electric current in the big place of magnetic flux differential, and the heat that fecund is given birth to leaves when can utilize electric current less, and can not cause damage to motor.

Restriction interior total copper loss of one-period must not surpass the maximum current I that can pass through with copper cash _MaxThe total amount of heat that in one-period, produces, restrictive condition is as follows: ${\&Integral;}_0^{2\mathrm{\&pi;}}{I}_a^2\mathrm{d\&theta;}\&le;{\&Integral;}_0^{2\mathrm{\&pi;}}{I}_{\max }^2\mathrm{d\&theta;}$ (formula 11) ${\&Integral;}_0^{2\mathrm{\&pi;}}{I}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="A01118683.600201.png,A01118683.600241.png"\; state="\{\{state\}\}">b</figure-callout>}}^2\mathrm{d\&theta;}\&le;{\&Integral;}_0^{2\mathrm{\&pi;}}{I}_{\max }^2\mathrm{d\&theta;}$ (formula 12) ${\&Integral;}_0^{2\mathrm{\&pi;}}{I}_c^2\mathrm{d\&theta;}\&le;{\&Integral;}_0^{2\mathrm{\&pi;}}{I}_{\max }^2\mathrm{d\&theta;}$ (formula 13)

Promptly limit total copper loss in one-period, must not surpass the maximum current flow I that copper cash can pass through with unit are _MaxTotal heat consumption.

B. driving voltage restriction

Motor can produce the back electromotive force that is directly proportional with rotating speed, and the pressure drop that the voltage of back electromotive force adds on reaching the standard grade must not surpass battery supplied voltage in the running, and its equation is: ${\mathrm{\&omega;}}_e\frac{\mathrm{d\&lambda;}}{\mathrm{d\&theta;}}+R_i<V_{\mathrm{cc}}$ (formula 14)

Wherein:

ω _e--be electrical rotate-speed

λ---be the magnetic flux chain of single-phase winding

Ri---is single-phase winding resistance

V _Cc-----be that power supply is supplied voltage

(3.3) utilize " optimization instruction among the commercial software MATLAB '

" Constr " obtains under restrictive condition " 3.2a: copper loss restriction " and " 3.2b: driving voltage limits ", moment function when maximum, its three-phase separate current I _a, I _b, I _c, respectively be which kind of function.

(4) result of calculation:

Under the design size of " directly the flat brush DC axial magnetic flux of three-phase drive wheel motor " (consult Fig. 5 subordinate list shown in),, obtain three-phase optimum current waveform as shown in Figure 6 via the calculating of above-mentioned (3.3) mode.

The moment that optimum waveform produced and other square waves input waveform compare, and its gained moment is maximum, are the different input of expression waveforms as Fig. 7, and Fig. 8 is the moment sizes that are illustrated under the different input waveforms.

(5) the auxiliary theoretical proof of optimum waveform:

As shown in Figure 9, be the waveform of comparison electric current and magnetic flux differential, current waveform is identical with the magnetic flux differentiated waveform as can be seen from Figure, and both only differ from a constant.In fact, as long as utilize the notion of simple section's west inequality (Cauchy Inequality), just can understand why the current waveform identical with the magnetic flux differentiated waveform can obtain maximum moment.

Section's west inequality can be represented by following formula, for ab two ordered series of numbers

(a1 ²+ a2 ²...) (b1 ²+ b2 ²+ ...) 〉=(a1 * b1+a2 * b2+......) ²(formula 15)

The product of two ordered series of numbers quadratic sums more than or equal to its sum of products square, and when two ordered series of numbers proportional, just $\frac{a1}{b1}=\frac{a2}{b2}=\frac{a3}{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="A01118683.600211.png"\; state="\{\{state\}\}">b</figure-callout>}3}$ When (formula 16), (a1 * b1+a2 * b2+......) ²Have maximum.

According to equation (formula 10), the moment equation that aligns of DC Brushless Motor is: $T=\mathrm{NI}\frac{{\mathrm{d\&phi;}}_m}{\mathrm{d\&theta;}}$ (formula 17)

The generation of moment is that immediate current multiply by magnetic flux differential and umber of turn, if will calculate the average moment of one-period, the mode of available integration is tried to achieve: $T_{\mathrm{avg}}=\frac{N{\&Integral;}_0^{2\mathrm{\&pi;}}I\frac{{\mathrm{d\&phi;}}_m}{\mathrm{d\&theta;}}\mathrm{d\&theta;}}{2\mathrm{\&pi;}}$ (formula 18)

But actual when calculating, average moment is to get with (or the time point N) addition of limited location point: $T_{\mathrm{avg}}=\frac{\stackrel{n}{\&Sum;}\mathrm{Ni}\frac{\mathrm{d\&phi;}}{\mathrm{d\&theta;}}}{n}=\frac{N\{i\left(1\right)\frac{\mathrm{d\&phi;}}{\mathrm{d\&theta;}}\left(1\right)+i\left(2\right)\frac{\mathrm{d\&phi;}}{\mathrm{d\&theta;}}\left(2\right)+\&hellip;\&hellip;\}}{n}$ (formula 19)

Contrast equation (formula 15) and (formula 17), electric current corresponds to ordered series of numbers a, and the magnetic flux differential corresponds to ordered series of numbers b, when electric current and magnetic flux differential are proportional, can obtain the moment of maximum.

Equation (formula 15) does not have special restrictive condition, all can use for any ordered series of numbers, therefore for the DC Brushless Motor of arbitrary dimension, as long as its moment can equation (formula 10) or (formula 17) expression, all can be via calculating the magnetic flux differential, obtain the optimum drive current waveform, make motor output maximum moment.

The present invention ties up in providing a kind of DC Brushless Motor optimum current waveform of (referring to direct three-phase drive DC Brushless Motor especially), and with a controller with functions such as digital signals processing (the digital signals processor TMS320F240 of Texas Instruments for example, yet be not to be defined to use this kind controller, such as can reach any controller of similar effect and purpose, all can use) and driving electronics realized.Optimum waveform account form and optimum waveform are as above-mentioned, as for how realizing explanation now as back:

About the drive controlling framework

A. as shown in figure 10, be the calcspar of driving control system.Controller cooperates electric current, the position of feedbacking after accepting the throttle order, export suitable signal to control switch, flows into the size of current of DC Brushless Motor with control.Wherein, the numerical value (as described above) that has stored the motor optimum waveform in the controller (F240 is its model) is when throttle (variable resistor) order input, maximum wave numerics can be multiplied by the magnitude of voltage of input command, and this magnitude of voltage is exactly the yield value that electric current amplifies or dwindles.

Because optimum waveform is the function of stator rotor relative position, must know the relative position of rotor and stator this moment in addition, so that be multiplied by the precision waveform value.B. position sensor

Stator, rotor relative position measure, employed position sensor is the reflection type optical breaker in this specific embodiment, it utilizes white easily reverberation, the easy light absorbing characteristic of black, chequered with black and white reverberation is affixed on the determinand, relend by the number that absorbs light quantity, output high potential or electronegative potential just can be represented the position.

Reflecting piece is divided inside and outside two circles, and as shown in figure 11, inner ring is 8 pairs of chequered with black and white bar codes, and the outer ring is 720 pairs of chequered with black and white bar codes, inner ring secret note representation wave numerics be on the occasion of, informal voucher representation wave numerics is negative value.Peripheral bar code is then read detailed rotor relative angular position, and find the numerical value of optimum waveform in the numerical tabular of in aforementioned controller (TMS320F240 digital signals processor), depositing in this rotor relative angular position, send into motor driver after multiplying each other with yield value (throttle order), and enter in the correct coiling of motor, finish the driving of optimum waveform.C. whether the electric current back coupling is identical with the optimum current size waveforms in order to check the size of current that enters the motor coiling, otherwise will utilize the control circuit in the controller (TMS320F240) to be revised.D. protective circuit is in order to limit driver current or abrupt voltage wave size, avoids burning out electronic component and the protective device that designs.

Therefore:

1. with regard to motor, the current waveform (as Fig. 6) of copper loss restrictive condition gained is the optimum under the various conditions, at motor operated following in rated speed, its efficient that shows all is best, and the more important thing is its output torque, compared with the square wave drive waveform under traditional three-phase Y connection, exceed about 25% (being increased to 7.789Kg-m) from 6.21Kg-m, when the present invention is applied to motor vehicle, can solve the problem of motor vehicle starting torque deficiency really.

2. except the The numerical results analysis, also can prove the electric current that the copper loss restriction calculates down with simple mathematical, its waveform can become a ratio with the magnetic flux differentiated waveform, and the moment that is produced is the limit of this motor output torque, force to feed bigger electric current unless ignore motor life, otherwise can't increase moment output by the change of drive current.

3. as if the input current waveform that will realize calculating, just must carry out Current Control, because motor is an inductive load, voltage signal can't directly become the electric current input command, therefore needs to use current mode PWM (pulse-width modulation) to control.Use the controller (or controller of other tool similar functions) of F240, cooperate reflective Photo Interrupter, can realize independently current waveform result of three-phase Y connection and three-phase.And to realize the irregular current waveform that copper loss limits, and needing accurate position sensor, cost is higher; If be reluctant to use accurate sensor to do location sensing, then current waveform can be simplified slightly, come the irregular wave of approximate optimization with a trapezoidal wave.As shown in figure 12, solid line is the current waveform after optimization is calculated, and dotted line then is an approximate trapezoidal wave; Realize approximate waveform, only need sense eight state transition points can reach.

4. if consider the making of driver, then three-phase Y connection is preferable selection, and it only needs six power crystal can finish drive controlling, is economic way; Three-phase is independent then to need three independently full-bridge circuits, and totally ten two crystal drive; In the realization of copper loss restriction current waveform, except 12 power crystal of needs, the current capacity of crystal also will increase, its bigger immediate current of could loading.Therefore in the application of reality, must on motor performance and cost, do one and accept or reject.

The above only is of the present invention one more feasible embodiment, and the variation that utilizes the above-mentioned method of the present invention, shape, step to do such as all should be contained in the interest field of this case.

Claims (10)

1, a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously is characterized in that, may further comprise the steps at least:

1a. provide a kind of optimum current waveform of DC Brushless Motor: utilize specially designed target function type, and, add the specific limited condition, try to achieve the current waveform of this motor the best at the actual design size of controlled DC Brushless Motor;

1b. import this best current waveform with a controller and the driving electronics with plural number position signal processing capacity to controlled motor by driving control system.

2, by the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that described target function is:

f＝f(I _a，I _b，I _c) $=N(I_a\frac{{\mathrm{d\&phi;}}_a}{\mathrm{d\&phi;}}+\frac{{\mathrm{d\&phi;}}_b}{\mathrm{d\&phi;}}+\frac{{\mathrm{d\&phi;}}_c}{\mathrm{d\&phi;}})$

Wherein

I _a, I _b, I _cBeing phase current to be determined, all is the function of rotor relative angle θ;

Φ _a, Φ _b, Φ _cAir-gap flux function for three-phase.

By the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that 3, this best current waveform system is directly proportional with the motor air-gap change in magnetic flux density.

4, by the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that, described actual design size at selected DC Brushless Motor is found out best current waveform, be to make motor running can reach minimum current under the maximum moment: this electric current changes with motor stator and rotor relative position, is one to be varied to the directly proportional waveform with air gap flux density; This current waveform is relevant with initial motors designs dimensional parameters, imports this specific currents waveform, can make motor bring into play its maximum function, the highest running efficiency, promptly under the least power loss, can produce maximum moment.

By the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that 5, it adds specific restrictive condition is the copper loss restriction.

6, by the described a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that its restrictive condition further increases: the driving voltage restriction.

7, by the described a kind of control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 1, it is characterized in that, described driving control system, its controller is after accepting the throttle order, cooperate the electric current of back coupling and the rotor relative angular position numerical value that position sensor is read, and find the numerical value of optimum waveform in the numerical tabular of in aforementioned controller, depositing in this rotor relative angular position, send into motor driver after multiplying each other with the yield value of throttle order, and enter in the correct coiling of motor, finish the driving of optimum waveform.

8, by claim 1,2, the 3 or 4 described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously, it is characterized in that, can be applicable on the object that use motors such as electric motor car or electric automobile drive.

9, by the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 8, it is characterized in that, this motor is installed in the appropriate position that can directly drive wheel.

10, by the described control method of brushless DC motor that can reach optimum efficiency and breakdown torque simultaneously of claim 8, it is characterized in that, DC Brushless Motor directly is installed in wheel, and seeks out its suitableeest waveform as input at this motor.

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