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Dokumentenidentifikation EP0991179 24.10.2002
EP-Veröffentlichungsnummer 0991179
Titel VERFAHREN ZUM ABLEITEN DER POL-POSITION VON PERMANENTMAGNETISCHEN BÜRSTENLOSEN MOTOREN
Anmelder Kabushiki Kaisha Yaskawa Denki, Kitakyushu, Fukuoka, JP
Erfinder OGURO, Ryuichi, Kitakyushu-shi, Fukuoka 806-0004, JP;
KAMEI, Takeshi, Kitakyushu-shi, Fukuoka 806-0004, JP
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 69808088
Vertragsstaaten DE, GB
Sprache des Dokument EN
EP-Anmeldetag 16.06.1998
EP-Aktenzeichen 989246442
WO-Anmeldetag 16.06.1998
PCT-Aktenzeichen PCT/JP98/02649
WO-Veröffentlichungsnummer 0098058444
WO-Veröffentlichungsdatum 23.12.1998
EP-Offenlegungsdatum 05.04.2000
EP date of grant 18.09.2002
Veröffentlichungstag im Patentblatt 24.10.2002
IPC-Hauptklasse H02P 6/20
IPC-Nebenklasse H02P 6/18   

Beschreibung[en]
TECHNICAL FIELD

The present invention relates to a method of detecting the initial magnetic pole position of a permanent magnet type brushless motor and more particularly to a method of detecting the magnetic pole position of a rotor when a sensorless brushless motor is started.

BACKGROUND ART

In conventional brushless motors, use has been made of a method of detecting a magnetic pole position with omission of a magnetic-pole-position detecting sensor which is constituted of a resolver or a Hall-effect device.

When the rotation of a rotor is allowed at the time of starting in reference to a method of the sort mentioned above for detecting a magnetic pole position, it is possible to utilize a technique, as disclosed in Japanese Patent Publication No. 3-239186A, for determining a rotor position (the magnetic pole position) by switching between a synchronous operation mode wherein steady operation is performed and a rotor-position detecting mode wherein the magnetic pole position is detected, rotating the rotor by supplying such a gate pulse as to generate a rotating magnetic field in each three-phase armature coil at the time of starting a brushless motor and then causing a position detecting circuit to detect the voltage induced in the armature coil.

When the rotation of the rotor is not allowed at the time of starting, that is, when the magnetic pole position is estimated with the motor unoperated, there is a technique, as proposed in IEEJ IAS Vol. 116-D, No. 7, pp. 736- 742 (1996) for determining the magnetic pole position with the motor unoperated by supplying intermittent pulse-like voltage commands sequentially in a given direction to the extent that the motor is unrotated, and estimating a position angle from a difference of response, which varies in an anti-sinusoidal wavelike manner, of each of the phase currents iαu and iβu, iαv and iβv, iαw and iβw, etc., which are converted into the static coordinates.

However, there still exist the following problems in the aforesaid prior art. The technique disclosed in Japanese Patent Publication No. 3-239186 is not applicable to a motor which makes it a condition that its rotor is at a standstill before the operation of the motor because the motor has to be started by rotating the rotor in order to determine the rotor position.

In the case of the technique made known by the IEEJ IAS Vol. 116-D, No. 7, electrical parameters such as the inductance of the brushless motor, resistance values or the like are needed to obtain the difference of the current response by deriving each of the phase currents iαu, iαv, iαw or the like from a three-phase voltage equation. Consequently, the degree of difference of the current response is unclear in case these parameters remain unknown and since the voltage command is not a stepwise alternating command, overcurrent may flow, depending on the form of the voltage command, or the rotor may be rotated; thus, there arise problems in view of its practical use.

'Sensorless operation of brushless DC motor drives', IEEE IECON 1993, pp. 739 - 744 discloses the speed and position sensorless control of PM brushless DC motors, whereby a technique is proposed for determining the magnetic pole position with the motor unoperated by supplying intermittent pulse-like voltage commands sequentially in a given direction to the extent that the motor is unrotated, and estimating a position angle from a difference of response, which varies in an anti-sinusoidal wavelike manner, of each of the phase currents, which are converted into the static coordinates.

It is therefore an object of the present invention to provide a method of estimating the initial magnetic pole position of a permanent magnet type brushless motor adapted so that even though electrical parameters are not accurately acquired, the initial magnetic pole position of a rotor in the brushless motor can be estimated quickly without allowing overcurrent to flow and without rotating the rotor, namely, without operating the motor.

DISCLOSURE OF THE INVENTION

In order to accomplish the object above, there is provided a method of estimating a magnetic pole position of a permanent magnet type brushless motor comprising the steps of:

  • setting a given γ axis and a given δ axis in an advanced from the γ axis by an electrical angle of 90°;
  • forming a closed-loop electric current control system in the γ axis direction while forming an open-loop electric current control system in the δ axis direction;
  • calculating an interference current generating in the δ axis direction when a current command in the γ axis direction is given as a stepwise alternating current command;
  • advancing finely the γ axis by an angle of Δ&thetas; when a sign of a product of an integral value of the interference current and a value of the current command in the γ axis direction is positive;
  • delaying finely the γ axis by an angle of Δ&thetas; when the sign is negative; and
  • making thereby the γ axis accord with either a d axis as a true magnetic axis or with a -d axis advanced by 180° from the true magnetic axis.

In the method, a characteristic equation with respect to the response of the interference current iδ in the δ axis direction under a condition of which the velocity of the permanent magnet type motor is zero is expressed by the following equation (1):

Here,
  • iγ: current in the γ axis direction;
  • iδ : current in the δ axis direction;
  • vγ : voltage in the γ axis direction;
  • vδ : voltage in the δ axis direction;
  • Lq : q axis inductance;
  • Ld : d axis inductance;
  • Rs : stator resistance; and
  • &thetas;e : electrical angular error between the γ axis and the d axis.
In this case, with the formation of an open-loop current system in the q axis direction and the formation of a proportionally-controlled closed-loop current control system, the γ axis-current command value comes to iγRef, vδ = 0, vγ = Kγ (iγRef - iγ), whereby the state of which the speed the permanent magnet type motor is zero is expressed by the following equation (2):
Moreover, the response of iδ subjected to the Laplace transform is expressed by the following equation (3): iδ(S) = KλaγδS / (S2 + [Kγaγγ + Rs(aγγ + aδδ)]S + (Kγ + Rs)Rs(aγγaδδ - a2γδ)) iγ Ref(S) Here, Iδ(S) represents a Laplace expression of iδ, and IγRef(S) represents the Laplace expression of iγ. Furthermore, aγγ, aδδ and aγδ are indicated by the following equation (4): αγγ = Lq + (Ld - Lq)sin2 &thetas;e / (LdLq) αδδ = Ld + (Ld - Lq)sin2 &thetas;e / (LdLq) αγδ = (Lq - Ld)sin 2&thetas;e / (LdLq)

Furthermore, the integration ∫ iδdt of the interference current iδ in the δ axis direction in the case of giving the current command in the γ axis direction as a stepwise alternating current command is expressed by the following equation (5) on condition that aγγ = 1/Ld, aδδ = 1/Lq and Kγ is sufficiently large:

The product fγ of the integral value of the interference value and the γ axis-current command value is expressed by the following equation (6):

In view of the fact that the aforesaid results, fγ and the axis electrical angular error &thetas;e between the γ axis and the d axis constitute a fγ-&thetas;e characteristic which varies in a substantially sine wave form taking the fγ on the x axis and the &thetas;e on the y axis. In this relationship, when the γ axis is so adjusted to be advanced by only Δ&thetas;e if fγ ≥ 0, and to be delayed by only Δ&thetas;e if fγ < 0, the designated y axis finally and gradually converges on the d axis (equivalent to &thetas;e = 0) or -d axis (equivalent to &thetas;e = 180°) to ensure that the magnetic pole position can be estimated.

BRIEF DESCRIPTION OF THE DRAWINGS

  • Fig. 1 is a conceptual block diagram of a method of estimating the initial magnetic pole position of a permanent magnet type brushless motor according to one embodiment of the present invention;
  • Fig. 2 is a flowchart showing the method of detecting the initial magnetic pole position of the brushless motor shown in Fig. 1;
  • Fig. 3 is a waveform chart of the γ axis-current command shown in Fig. 1;
  • Fig. 4 is a diagram showing the relation between the γ and d axes shown in Fig. 1;
  • Fig. 5 is a &thetas;e - fγ characteristic curve shown in Fig. 2;
  • Fig. 6 is a diagram showing the corrected waveform of an estimated magnetic axis &thetas;γ shown in Fig. 2; and
  • Fig. 7 is a diagram showing another-phase corrected waveform of the estimated magnetic axis &thetas;γ shown in Fig. 6.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will be described below with reference to the drawings.

Fig. 1 is a conceptual block diagram of a method of estimating the initial magnetic pole position of a permanent magnet type brushless motor according to one embodiment of the invention. Fig. 2 is a flowchart showing the method of detecting the initial magnetic pole position of the brushless motor shown Fig. 1. Fig. 3 is a waveform chart of the γ axis-current command shown in Fig. 1. Fig. 4 is a diagram showing the relation between the γ and d axes shown in Fig. 1. Fig. 5 is a &thetas;e - fγ characteristic curve shown in Fig. 2. Fig. 6 is a diagram showing the corrected waveform of an estimated magnetic axis &thetas;γ shown in Fig. 2. Fig. 7 is a diagram showing another-phase corrected waveform of the estimated magnetic axis &thetas;γ shown in Fig. 6.

In Fig. 1, a stepwise y axis-current command iγRef as shown in Fig. 3 is outputted from a γ axis-current generating circuit 1. A axis-current iγ is obtained by inputting currents iu' iv for driving a brushless motor 8 into an inverter section 5 via a current sensor or the like and converting the currents in a three-to-two phase conversion section 6. The iγRef and iγ are inputted to a γ axis-current control section 2 to generate a voltage command vγ*.

On the other hand, a δ axis-directed voltage command vδ* is also generated from a δ axis-current control section 3. However, vδ* becomes zero because a δ axis-directed control system has an open loop gain of zero. Subsequently, in a &thetas;γ generating circuit 7 (see Fig. 4), a correction angle &thetas;e is determined from the γ axis-current command iγRef and a δ axis-current iδ to update a γ axis angle &thetas;γ. Accordingly, voltage command magnitude V* and an output phase &thetas;v are provided from a vector control section 4 to the inverter section 5, however, since vδ* is zero, through V* = |vδ*|, &thetas;v = &thetas;γ.

Next, the operation will be described.

Referring to a flowchart of Fig. 2, at least currents in two phases out of the three-phase current of the permanent magnet type brushless motor 8, in this case, currents iu(K), iv(K) which are respectively a u-phase and a v-phase current (or any other combination of phase currents) at the time of (K&peseta;Ts) seconds (Ts: current loop sampling time) are first inputted (S101).

Subsequently, two-to-three phase conversion is carried out in accordance with a position &thetas;γ (K) (see Fig. 4) of the γ axis away from an α phase to obtain iγ(K), iδ(K) (S102). Then S103 is caused to. branch off according to the γ axis-current command iγRef(K) of the stepwise alternating current shown in Fig. 3 (S103).

In an executing routine when iγRef(K) is not zero then, "Sign [iγRef(K)]&peseta; ∫ iδdt" is calculated on the basis of the decision made at S103 before being stored in fγ(t) (S104). At S105, S106 and S107 that follow, &thetas;γ is changed by Δ&thetas;e according to the sign of fγ(t) as shown in Fig. 4, whereby adjustment is made so as to let the γ axis accord with a d axis as a true magnetic axis.

First, a decision is made on whether fγ(t) ≥ 0 or not and if fγ(t) ≥ 0 is the then decided (S105: Yes), the change quantity Δ&thetas;e of &thetas;γ becomes positive (S106). If fγ(t) > 0 is the result decided (S105: No), the change quantity Δ&thetas;e becomes negative (S107).

The operation of making the γ axis accord with the d axis is thus carried out and a current command iγRef(K+1) for (K+1)Ts seconds is prepared by means of timer interruption. Then stepwise iγRef(K+1) is given as shown in Fig. 3 (S108).

In the case of an executing routine when iγRef (K) = 0 branching off at the preceding step S103, a decision is made on whether iγRef (K-1) = 0 or not (S109) by changing the process flow according to the preceding γ axis-current command iγRef (K-1). If iγRef (K-1) = 0 is the then decided (S109: Yes), &thetas;γ (K+1) = &thetas;γ (K) is left as it is (S110). If iγRef (K-1) is decided to be not 0 then (S109: No), the γ axis position &thetas;γ is updated (S111) according to the Δ&thetas;e determined in the executing routines at and after the preceding S104. In other words, &thetas;γ is to be updated only once in the branch routines S109 - S111 according to the Δ&thetas;e. determined at S104 - S107.

Subsequently, the integral term of iδ is reset for the branch routines at forthcoming S104 - S107.

Figs. 6 and 7 show the results of tests actually made for adjusting &thetas;γ through the aforesaid method of estimating the magnetic pole positions under the conditions that the initial magnetic pole positions are estimated when the γ axis and the d axis are initially shifted from each other by an electrical angle of 90°, and the test results reflect the fact that the d axis or -d axis was estimated at a speed of as high as about 0.1 second.

Thus, it has become possible to obtain the initial magnetic pole position quickly by only estimating the position according to the positive and negative signs of the product of the integral value of the interference current iδ and the γ axis-current according to this embodiment of the present invention. In the method, the use of integration for operations results in reducing tendency to be affected by the noise of current sensors. Further, stable estimated adjustment can be made since not the magnitude but only the positive or negative sign of the current polarity is necessary for making a decision, and since the inductance requires only a difference between Lq and Ld but is not affected by the size of the difference. Still further, since the current command iγRef is given alternately, the average torque is to be zero, the magnetic pole can be estimated while the motor is stopped with the rotor unrotated.

As set forth above, in order to estimate a magnetic pole position of a permanent magnet type brushless motor, the following steps are conducted. A given γ axis and a given δ axis in an advanced from the axis by an electrical angle of 90° are set. A closed-loop electric current control system in the γ axis direction is formed while forming an open-loop electric current control system in the δ axis direction. It is calculated an interference current generating in the δ axis direction when a current command in the γ axis direction is given as a stepwise alternating current command. The γ axis is finely advanced by an angle of Δ&thetas; when a sign of a product of an integral value of the interference current and a value of the current command in the γ axis direction is positive. Alternatively, the γ axis is finely delayed by an angle of Δ&thetas; when the sign is negative. Thereby, the γ axis is made accord with either a d axis as a true magnetic axis or with a -d axis advanced by 180° from the true magnetic axis. Therefore, even if electrical parameters such as inductance, resistance or the like are not accurately acquired, it is possible to estimate quickly the initial magnetic pole position of a rotor with the motor unoperated, that is, with the rotor unrotated.


Anspruch[de]
  1. Verfahren zum Schätzen der Magnetpolposition eines bürstenlosen Motors des Permanentmagnettyps, das die folgenden Schritte umfasst:
    • Einstellen einer bestimmten γ-Achse und einer bestimmten δ-Achse, die um einen elektrischen Winkel von 90° gegenüber der γ-Achse vorgerückt ist,
    • Bilden eines geschlossenen elektrischen Stromregelkreises in der Richtung der γ-Achse und Bilden eines offenen elektrischen Stromsteuerkreises in der Richtung der δ-Achse,
    • Berechnen eines in der Richtung der δ-Achse erzeugten Interferenzstroms, wenn ein Strombefehl in der Richtung der γ-Achse als schrittweise alternierender Strombefehl ausgegeben wird,
    • Feines Vorrücken der γ-Achse um einen Winkel von Δ&thetas;, wenn das Vorzeichen des Produkts aus einem Integralwert des Interferenzstroms und einem Wert des Strombefehls in der Richtung der γ-Achse positiv ist,
    • Feines Verzögern der γ-Achse um einen Winkel von Δ&thetas;, wenn das Vorzeichen negativ ist, und
    • wodurch die γ-Achse mit entweder einer d-Achse als wahrer magnetischer Achse oder mit einer um 180° gegenüber der wahren magnetischen Achse vorgerückten -d-Achse ausgerichtet wird.
Anspruch[en]
  1. A method of estimating a magnetic pole position of a permanent magnet type brushless motor comprising the steps of:
    • setting a given γ axis and a given δ axis in an advanced from the γ axis by an electrical angle of 90°;
    • forming a closed-loop electric current control system in the γ axis direction while forming an open-loop electric current control system in the δ axis direction;
    • calculating an interference current generating in the δ axis direction when a current command in the γ axis direction is given as a stepwise alternating current command;
    • advancing finely the γ axis by an angle of Δ&thetas; when a sign of a product of an integral value of the interference current and a value of the current command in the γ axis direction is positive;
    • delaying finely the γ axis by an angle of Δ&thetas; when the sign is negative; and
    • making thereby the γ axis accord with either a d axis as a true magnetic axis or with a -d axis advanced by 180° from the true magnetic axis.
Anspruch[fr]
  1. Procédé d'estimation d'une position de pôle magnétique d'un moteur sans balai du type à aimant permanent, comprenant les étapes de :
    • établissement d'un axe γ donné et d'un axe δ donné qui est avancé par rapport à l'axe γ d'un angle électrique de 90° ;
    • formation d'un système de commande de courant électrique en boucle fermée suivant la direction d'axe γ tout en formant un système de commande de courant électrique en boucle ouverte suivant la direction d'axe δ ;
    • calcul d'un courant d'interférence qui est généré suivant la direction d'axe δ lorsqu'une commande de courant suivant la direction d'axe γ est réalisée en tant que commande de courant alternatif par pas ;
    • avancement fin de l'axe γ d'un angle de Δ&thetas; lorsqu'un signe d'un produit d'une valeur d'intégrale du courant d'interférence et d'une valeur de la commande de courant suivant la direction d'axe y est positif ;
    • retardement fin de l'axe γ d'un angle de Δ&thetas; lorsque le signe est négatif ; et
    • réalisation ainsi de l'accord de l'axe γ avec soit un axe d en tant qu'axe magnétique vrai, soit un axe -d qui est avancé de 180° par rapport à l'axe magnétique vrai.






IPC
A Täglicher Lebensbedarf
B Arbeitsverfahren; Transportieren
C Chemie; Hüttenwesen
D Textilien; Papier
E Bauwesen; Erdbohren; Bergbau
F Maschinenbau; Beleuchtung; Heizung; Waffen; Sprengen
G Physik
H Elektrotechnik

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