CN102198805A - Method for grade parking (anti-backward sliding) of permanent magnet motor-driven pure electric vehicle - Google Patents

Abstract

The invention discloses a scheme for controlling the grade parking of a permanent magnet motor-driven pure electric vehicle. The pure electric vehicle has an electrical system comprising a battery pack, a motor, a power converter, a motor controller and a vehicle controller and further comprising corresponding voltage, current and tilt sensors. The scheme comprises two steps of: (1) detection for the initial position of a rotor of a permanent magnet synchronous motor: a detection voltage is applied to the permanent magnet synchronous motor by the power converter, and the initial spatial position of the motor rotor in the case that the vehicle is stationary is calculated through a current feedback signal; and (2) torque self-balancing strategy based on vector control: the torque self-balancing characteristic can enable driving torque to track load torque automatically. The torque required by parking is calculated in accordance with the tilt angle of a ramp on which the vehicle is to be parked, and then, reasonable current amplitude and phase are given according to the initial position of the rotor and the torque required by grade parking in order to enable the driving torque to be equal to the load torque, therefore, stationary parking of the vehicle on the grade is realized.

Description

Slope (anti-slip back) method is stayed in the pure electric automobile ramp that magneto-electric machine drives

Technical field

The present invention relates to permagnetic synchronous motor is the pure electric automobile field of main drive motor, is specifically related to use the permagnetic synchronous motor vector control technology to prevent that vehicle from the slide slope taking place on the slope, to reach the effect of staying the slope.

Background technology

Pure electric automobile is a power with the vehicle power, by motor electric energy is converted into mechanical energy, and drive wheels is travelled.The drive motor type that can be applicable to electronlmobil at present mainly contains DC machine, induction motor, permagnetic synchronous motor, dc brushless motor and switched reluctance machines etc.Because magneto-electric machine has the advantage that efficient height, output torque are stable, power to volume ratio is big, add that China's rare earth resources reserves are abundant, so the electronlmobil that permagnetic synchronous motor drives is following important developing direction.

Automobile is on the ramp time, and the downslide component of gravity can make automobile that the trend of downslide is arranged.For common manual shelves fuel-engined vehicle, from stepping on power-transfer clutch, loosen the brake in the time of the pedal of stepping on the throttle, automobile is in the forfeiture dynamic regime, and the sloping phenomenon of slide very easily takes place, and vehicle driving safety is caused great harm; For the automatic transmission fuel-engined vehicle,, when D shelves loosen the brake, still can take place to slip sloping because outputting power is not enough if there is not intelligent power control system.

The takeoff output mechanism of battery-driven car is different fully with fuel-engined vehicle.Combustion engine does not have torque output when shutting down, and motor can be exported moment of torsion in full under the state of stationary rotor.Therefore, only need the output torque and the load torque of control power drive system to balance each other, can realize that electronlmobil is static on the ramp.

Chinese patent 2010105198203 discloses the anti-slip back control method of a kind of pure electric vehicle idling, it comprises entire car controller, electric machine controller, motor, brake pedal, hand brake device, Das Gaspedal, electrokinetic cell, wherein entire car controller all is connected with described electric machine controller, brake pedal, hand brake device, Das Gaspedal, electrokinetic cell, and electrokinetic cell is connected with described motor by described electric machine controller.This content mainly lays particular emphasis on the control policy and the implementation step of the anti-slip back function of general introduction electronlmobil, lacks concrete operation scheme.

Chinese patent 2010101568536 discloses a kind of ramp safe starting control system of electric vehicle, it introduces a kind of ramp recognition system, elder generation calculates the current gradient by entire car controller and calculates to preventing to slip the required torque in slope, send the respective torque instruction by electric machine controller then, make vehicle energy gentle start under slope condition.This scheme provides by the control motor torque and has realized staying the thinking on slope, but how to control motor after controller sends torque instruction, is not described, and lacks actual operation.

Chinese patent 200810215811.8 discloses a kind of anti-slip back scheme that is applied to hybrid vehicle, torque that its is exported by the vehicle motor of time in the slope earlier determines to prevent that vehicle from slipping the amount of required wheel torque, and reduce the moment of torsion that motor produces gradually, increase the fuel engines moment of torsion simultaneously, so that the summation of the wheel torque that driving engine and motor produce is substantially equal to the amount of described required wheel torque, thereby make vehicle reach the quiet effect of staying.In the method, when sensor indication vehicle remains static, calculate acquisition when the front motor output torque by controller.This scheme can be applied to pure electric automobile equally, but running state sensor has wherein increased the cost and the complexity of system.

Following pure electric automobile or will generally adopt permagnetic synchronous motor, its vector control mode can the accuracy control motor output torque, thereby splendid handling is provided, comprise acceleration, brake, cruise and function such as Parking.This area relate to when stationary vehicle on the ramp, chaufeur is wished vehicle when quiescence is quickened from the loosen the brake to the bend the throttle, overcome the phenomenon of slipping owing to not expecting of causing of the torque command that delay is provided to wheel.

Summary of the invention

The objective of the invention is for a kind of ramp Parking control policy of the pure electric automobile that drives at magneto-electric machine is provided.According to principle of vector control, the output torque of magneto-electric machine can be controlled respectively by the stator current and the air-gap field of decoupling zero.Because permanent magnet machine rotor has intrinsic permanent magnetic field, utilize a kind of self-balancing stability characteristic (quality) that is had between output torque and the rotor locus of living in, realize vehicle in the Parking of the gradient arbitrarily, avoided falling to slip or smooth phenomenon that concrete principle sees for details hereinafter.

Except that the mechanical system of vehicle routine, pure electric automobile among the present invention also has a cover electric system, comprise battery pack, motor, power inverter, electric machine controller, entire car controller, and correspondent voltage sensor, current sensor, obliquity sensor.The present invention does not make any changes to the mechanical system and the electric propulsion system of vehicle, and it is a kind of additional function on described electronlmobil vector controlled scheme.This scheme is divided into two steps: (1) permanent-magnetic synchronous motor rotor initial position detects: described electric machine controller sends and detects instruction, by described power inverter described permagnetic synchronous motor is applied detection voltage, the space initial position of rotor when calculating stationary vehicle according to current feedback signal by described electric machine controller again; (2) control based on the torque self-balancing of vector control mode: the angle of inclination according to vehicle ramp of living in calculates the required torque of Parking earlier, be reference with described rotor dq coordinate then, according to described rotor space initial position and required torque, calculate rational current amplitude and phase place, and impose on described motor stator winding by described power inverter.

In described torque self-balancing control, the angle of inclination in ramp is measured by described obliquity sensor and is obtained, and is converted to digital signal and is transferred to described electric machine controller again.Further, can not use described obliquity sensor to measure the ramp leaning angle, directly apply the electric current that amplitude is enough big, phase place is correct, utilize torque self-balancing principle to make vehicle stabilization on the ramp, vehicle has and slips sloping phenomenon slightly in this process.

There are speed closed loop and current closed-loop in the described permagnetic synchronous motor vector controlled scheme.Under the stationary vehicle situation, described current closed-loop works.Apply suitable current for described motor stator winding by described electric machine controller,, can make quiet reside on the ramp of vehicle and the slope does not take place to slip so that enough balancing moments to be provided.

When electronlmobil starts on the ramp, chaufeur switches to the shelves (D shelves) that travel with gear from Parking shelves (P shelves), and loosen the brake, this moment, described entire car controller sent instruction in the slope to described electric machine controller, the moment of torsion of motor output is delivered to wheel by described power drive system, and balance each other with the downslide moment of torsion, it is static that vehicle keeps.When chaufeur was stepped on brake pedal or pull-up parking brake, the described electric machine controller of described entire car controller order withdrawed from the sloping state of staying, and make vehicle keep static by mechanical braking sytem this moment, can save the expenditure of energy of described on-vehicle battery.

Description of drawings

Fig. 1 is that pure electric automobile of the present invention is stayed sloping control system pie graph.

Fig. 2 is a permagnetic synchronous motor space vector graph of a relation of the present invention.

Fig. 3 is a permagnetic synchronous motor torque self-balancing schematic diagram of the present invention.

Fig. 4 is the schematic diagram that injects the recognition methods of permanent-magnetic synchronous motor rotor initial position based on pulse voltage of the present invention.

Fig. 1 wherein:

1, battery pack; 2, voltage sensor; 3, power inverter (IGBT); 4, current sensor; 5, permasyn morot (PMSM); 6, obliquity sensor; 7, electric machine controller (DSP); 8, entire car controller (VCU)

The specific embodiment

1, stays sloping principle

Below be the computing formula of permagnetic synchronous motor output torque and vehicle load torque when static:

$\mathrm{Te}=\frac{3}{2}p({\mathrm{\ψ}}_d{i}_q-{\mathrm{\ψ}}_q{i}_d)=\frac{3}{2}p\·I_s\sin \mathrm{\θ}\·[{\mathrm{\ψ}}_{\mathrm{pm}}+(L_d-L_q)I_s\cos \mathrm{\θ}]---\left(1\right)$

T _L＝mgr·sina (2)

As Fig. 2, Te is a motor output torque in the formula (1), and p is the motor stator number of pole-pairs, ψ _d, ψ _qBe the component of magnetic linkage under rotor dq system of axes, wherein ψ _PmBe the permanent magnet magnetic linkage, direction is along the d axle; i _d, i _qBe the component of stator current under rotor dq system of axes, I _SBe the amplitude of stator current, L _d, L _qBe the component of stator inductance under the dq system of axes, θ is the angle of stator current vector and initial position of rotor.T in the formula (2) _LSliding force for stationary vehicle on the ramp time is promptly realized the load torque of the vehicle of time in the slope, and m is a complete vehicle quality, and g is the gravity acceleration constant, and r is a radius of wheel, and α is the inclination angle, ramp.

For second in the square bracket in the formula (1), it is worth generally much smaller than permanent magnetism magnetic linkage amplitude, especially for the surface-mount type magneto-electric machine L is arranged _d=L _q, second is zero, therefore on engineering usually with second omission, then formula (1) is reduced to:

$T_{\mathrm{\θ}}=\frac{3}{2}{\mathrm{p\ψ}}_{\mathrm{pm}}{I}_s\sin \mathrm{\θ}---\left(3\right)$

Consider system of vehicle transmission ratio and driving efficiency, the torque balance system that satisfies in sloping condition is:

ηT _θ＝T _L (4)

Wherein η is the power drive system parameter.If known the initial position angle θ of rotor in advance ₀(is the zero position R point with A phase axle), the then phase theta of stator current vector _iDetermine by following formula:

$\mathrm{mgr}\·\sin \mathrm{\α}=\frac{3}{2}\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_s\sin \mathrm{\θ}\⇒\mathrm{\θ}={\sin }^{-1}\frac{2\mathrm{mgr}\sin \mathrm{\α}}{3\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_s}---\left(5\right)$

θ _i＝θ ₀+θ (6)

There is current closed-loop in the permagnetic synchronous motor vector controlled scheme, applies along θ by electric machine controller _iThe current phhase instruction of position, and rational current amplitude instruction I _S,, can make quiet reside on the ramp of vehicle and the slope not take place to slip so that enough balancing moments to be provided.

2, self-balancing principle

According to shown in Figure 3, electric current I _SComponent I on the q axle _qProvide the component of torque.If driving torque is less than load torque, be that the electromagnetic torque of motor is during less than the downslide torque of vehicle, then vehicle satisfies the sloping condition of slipping, rotor can be followed the reversing of wheel and be reversed, and the phase place of stator current and amplitude are all constant, so the angle theta of stator current and rotor flux increases, motor output torque increases, thereby reach torque balance a new position, have this moment:

$T_L=T_{\mathrm{\θ}}=\frac{3}{2}\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_s\sin {\mathrm{\θ}}^{\′}=\frac{3}{2}\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_q^{\′}---\left(7\right)$

Equally, greater than load torque, then vehicle advances as if driving torque, and the angle of stator current and rotor flux reduces, and motor output torque reduces, and reaches torque balance a new position, and have this moment:

$T_L=T_{\mathrm{\θ}}=\frac{3}{2}\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_s\sin {\mathrm{\θ}}^{\′\′}=\frac{3}{2}\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}{I}_q^{\′\′}---\left(8\right)$

According to above-mentioned analysis as can be known, no matter being in, vehicle goes up a slope or descending, no matter whether driving torque balances each other with load torque, all can reach new torque balance by the self aligning of stator current and rotor-position angle, this is the torque self-balancing principle based on vector controlled.

When θ＞90 °, the torque balance principle will be false.For satisfying the self-balancing principle, the amplitude I of stator current _SMust be greater than a minimum value, it is to satisfy the required current value of torque balance that this value is when θ=90 °, is expressed as:

$I_s>\frac{2\mathrm{mgr}\sin \mathrm{\α}}{3\mathrm{p\η}{\mathrm{\ψ}}_{\mathrm{pm}}}---\left(9\right)$

For anti-locking system enters unstable region, need the enough big electric current I of design _SSo that safety allowance is left at the θ angle.Generally speaking, consider the maximum load of vehicle under maximum grade, I reasonable in design _SMake θ be not more than 45 °, then can realize safe and reliable ramp Parking.

Because if the self-equilibrium characteristic of torque among the present invention is original position of electric motor's rotator angle θ ₀Have estimation error, perhaps for realizing that the required angle theta of torque balance has calculation error, this scheme still can be carried out.By the automatic compensation of stator current and rotor-position angle, new torque balance can rebulid, and this moment, small rotation only took place for rotor and wheel, can not stay sloping process to vehicle and impact.

3, the permanent magnet machine rotor initial position detects

When strategy in the slope starts,, need to judge initial position angle of rotor θ for phase place exact current vector is provided ₀Present enforceable permanent magnet machine rotor initial position determination methods mainly contains high frequency rotational voltage injection method and momentary impulse voltage injection method.The invention discloses a kind of permagnetic synchronous motor initial position determination methods of injecting based on pulse voltage, applicable to surface-mount type and interior permanent magnet machines, experimental result shows that its precision reaches ± 10 ° of electric angles.Because above-mentioned self-balancing principle has error angle degree adaptivity, this scheme can satisfy the needs that electronlmobil is stayed the slope.

No matter surface-mount type or interior permanent magnet machines, there is difference more or less in its stator dq axle inductance value.Described initial position of rotor determination methods is according to motor stator dq axle inductance difference principle, apply the wide momentary impulse voltage vector of two groups of linearly independents to winding, obtain the transient current response, calculate the inductance parameters matrix that contains location information again, thereby calculate rotor-position.Its derivation is as follows:

The terminal voltage formula of magneto-electric machine under the static situation:

$\left[\begin{array}{cc}{v}_{\mathrm{\&alpha;}1}& v_{\mathrm{\&alpha;}2}\\ v_{\mathrm{\&beta;}1}& v_{\mathrm{\&beta;}2}\end{array}\right]=R\&CenterDot;\left[\begin{array}{cc}{i}_{\mathrm{\&alpha;}1}& i_{\mathrm{\&alpha;}2}\\ i_{\mathrm{\&beta;}1}& i_{\mathrm{\&beta;}2}\end{array}\right]+\left[\begin{array}{cc}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="20111005662561000031.png,HSA00000447154900021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">cos</figure-callout>}{2\mathrm{\&theta;}}_0& {\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\sin {2\mathrm{\&theta;}}_0\\ {\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\sin {2\mathrm{\&theta;}}_0& L_1-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">cos</figure-callout>}{2\mathrm{\&theta;}}_0\end{array}\right]\&CenterDot;\frac{d}{\mathrm{dt}}\left[\begin{array}{cc}{i}_{\mathrm{\&alpha;}1}& i_{\mathrm{\&alpha;}2}\\ i_{\mathrm{\&beta;}1}& i_{\mathrm{\&beta;}2}\end{array}\right]---\left(10\right)$

V in the formula ₁, v ₂Be the amplitude of twice pulse voltage, i ₁, i ₂Be the amplitude of corresponding twice current-responsive, subscript is illustrated in the α beta-axis component under the static α β of the stator system of axes; R is the stator phase resistance, L ₁, L ₂Average and value and mean range for stator dq axle inductance are defined as:

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="20111005662561000031.png,HSA00000447154900021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\stackrel{\mathrm{\&Delta;}}{=}\frac{L_d+{\mathrm{<figure-callout\; id="2"\; label="L\; q"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_q}{2},$ ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\stackrel{\mathrm{\&Delta;}}{=}\frac{L_d-L_q}{2}---\left(11\right)$

Calculate inductance matrix by formula (10), and four components in the definition inductance matrix:

$\left[\begin{array}{cc}{L}_{11}& L_{12}\\ L_{21}& L_{22}\end{array}\right]\stackrel{\mathrm{\&Delta;}}{=}\left[\begin{array}{cc}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="20111005662561000031.png,HSA00000447154900021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&theta;}}_0& {\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">sin</figure-callout>}{2\mathrm{\&theta;}}_0\\ {\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">sin</figure-callout>}{2\mathrm{\&theta;}}_0& L_1-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="20111005662561000031.png"\; state="\{\{state\}\}">cos</figure-callout>}{2\mathrm{\&theta;}}_0\end{array}\right]=\left[\begin{array}{cc}{V}_{\mathrm{\&alpha;}1}-{\mathrm{Ri}}_{\mathrm{\&alpha;}1}& V_{\mathrm{\&alpha;}2}-{\mathrm{Ri}}_{\mathrm{\&alpha;}2}\\ V_{\mathrm{\&beta;}1}-{\mathrm{Ri}}_{\mathrm{\&beta;}1}& V_{\mathrm{\&beta;}2}-{\mathrm{Ri}}_{\mathrm{\&beta;}2}\end{array}\right]{\left[\begin{array}{cc}\frac{{\mathrm{di}}_{\mathrm{\&alpha;}1}}{\mathrm{dt}}& \frac{{\mathrm{di}}_{\mathrm{\&alpha;}2}}{\mathrm{dt}}\\ \frac{{\mathrm{di}}_{\mathrm{\&beta;}1}}{\mathrm{dt}}& \frac{{\mathrm{di}}_{\mathrm{\&beta;}2}}{\mathrm{dt}}\end{array}\right]}^{-1}---\left(12\right)$

Then rotor-position can be expressed as:

${\mathrm{\&theta;}}_0=\frac{1}{2}{\tan }^{-1}\frac{L_{12}+L_{21}}{L_{11}-L_{22}}---\left(13\right)$

The rotor-position that formula (13) obtains has been determined the direction at rotor d axle place, but does not comprise the rotor polarity information, therefore need further apply voltage impulse to distinguish the NS utmost point.Its principle is, one of them voltage impulse works the effect of magnetizing to rotor d axle along the axial anti-phase each other voltage impulse of rotor d to apply two, and another voltage impulse plays demagnetizing effect to the d axle.Contrast the amplitude of two primary currents, can judge that the position that (13) formula calculates is in the N utmost point or the S utmost point: if the current-responsive of previous voltage impulse then is in the N utmost point, otherwise then is the S utmost point greater than the latter.

The above initial position of rotor determination methods only is the preferred description of implementing example, and every relating to is used for the electronlmobil self-balancing and stays the permanent-magnetic synchronous motor rotor initial position determination methods of sloping principle and all belong to covering scope of the present invention.

Though be the pure electric automobile strategy that drives at permagnetic synchronous motor in the slope, the electronlmobil field that this self-balancing principle need to be equally applicable to DC machine, asynchronous induction machine, brshless DC motor or the switched reluctance machines of rotor-position closed loop control to drive.Every electronlmobil that utilizes motor electromagnetic torque and vehicle load torque self-balancing principle that relates to all belongs to covering scope of the present invention in sloping scheme.

Claims (4)

1. sloping method is stayed in the pure electric automobile ramp that drives of magneto-electric machine, and its electric system comprises: battery pack, motor, power inverter, electric machine controller, entire car controller, and voltage sensor, current sensor, obliquity sensor.It is characterized in that: provide electric energy by on-vehicle battery group (1) to drive system, direct current (DC) is transformed to the required three phase sine alternating current of permagnetic synchronous motor (5) via power inverter (3); The PWM digital output end of electric machine controller (7) links to each other with power inverter (3), and switching valve IGBT is provided required drive signal; Be installed on the dc bus voltage sensor (2) be installed in the analog signal that the current sensor (4) that exchanges on the triple line measures bus voltage and motor three phase current, be that digital signal flows to electric machine controller (7) by the AD module converts again; Obliquity sensor (6) links to each other with electric machine controller (7), and the ramp obliquity information is provided; Entire car controller (8) links to each other by the CAN bus with electric machine controller (7), realizes data exchange.

2. sloping method is stayed in the pure electric automobile ramp that magneto-electric machine according to claim 1 drives, and it is characterized in that: the permanent-magnetic synchronous motor rotor initial position detects.Described electric machine controller (7) sends and detects instruction, by described power inverter (3) described permagnetic synchronous motor (5) is applied detection voltage, again according to the feedback signal of current sensor (4) space initial position by described electric machine controller (7) rotor when calculating stationary vehicle.

3. sloping method is stayed in the pure electric automobile ramp that magneto-electric machine according to claim 1 drives, and it is characterized in that: based on the torque self-balancing control of vector control mode.Obtain the inclination angle in vehicle ramp of living in by obliquity sensor (6), calculate the required torque of Parking according to the angle of inclination again, be reference with described permagnetic synchronous motor (5) rotor dq coordinate then, rotor space initial position according to claim 2 and required torque, calculate rational current amplitude and phase place, and impose on described motor stator winding by described power inverter (3).

4. stay sloping method according to the pure electric automobile ramp of claim 1 and the described magneto-electric machine driving of claim 3, it is characterized in that " torque self-balancing principle ": no matter promptly vehicle is in upward slope or descending, no matter whether driving torque balances each other with load torque, when applying the electric current that amplitude is enough, phase place is correct, described power inverter (3) gives described motor stator winding, the capital reaches new torque balance by the self aligning of stator current and rotor-position angle, makes that vehicle is quiet to be resided on the ramp.

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