DE102009040332A1 - Rotor's rotation variable e.g. rotation angle, determining method for drive control of synchronous electric motor, involves determining angular variable i.e. difference between characteristics of induction and determined induction - Google Patents

Abstract

The method involves determining induction from a rotor magnetic field in which repletion characteristics of a core of a magnetic coil is used. The determined induction is compared with characteristics of the induction. An angular variable i.e. difference between the characteristics of the induction and the determined induction, is determined based on the comparison. Main induction is produced by a magnetic field to be produced. The rotor magnetic field measurement is determined and evaluated by weighting factors of the repletion characteristics. An independent claim is also included for a device for determining a rotation variable of a rotor, such as rotor angle or rotor angle change in a drive control for a motor.

Description

The This invention relates to a method and apparatus for Determining (or detecting) a rotor angle (angular position or Lage) and / or a rotor angle change over a Magnetic field measurement. In general, a variable to be assigned to the rotor is detected or determined with the location or one of its derivatives correlated (related) to time.

For variable speed Electric drives are nowadays mostly frequency converters and Servo inverter used. They serve to the electric motor with to supply exactly the power required for the drive task is. The inverters consist of the power electronic part and the control part intended for the control of the power components, the regulation, the monitoring and the communication with a superimposed one Controls responsible is.

For the business of synchronous machines is the return of the Rotor position required to allow current or voltage to match the rotor magnetic field can be specified. For this purpose, angle sensors are used, for. B. resolver or optical encoder. The givers must be grown separately and restrict the mechanical expression the engines. Today's returns are relatively expensive. Here the magnetic field of the rotor for the return is considered. Is to the measurement of the magnetic field necessary.

Therefore the invention is based on the object, cost-effective drives to realize with synchronous machines and converters, which are characterized by a high efficiency, low power consumption and low volume and Distinguish weight.

These Task is with the method for determining a rotation amount, in particular the rotor angle position, the generic type by the features of claim 1, 10 or 16 solved.

The "angle measurement" (rotation, in particular a rotor angle as angular position or position and / or a rotor angle change) over a measurement of the magnetic field of the rotor by the use of the saturation behavior of the magnet coil core. It is evaluated by a magnetic field sensor, where the saturation is obsolete the core is known exactly. The field to be measured becomes the Main induction generated. By determining an induction and comparing the measured induction with the known course of induction the turning size becomes the rotor angle or rotor angle change determined or determined. From the comparison, especially subtraction, between the known course of the induction and the measured Course of induction results in the measurement result.

advantageous Design features of the invention as claimed (claim 1, 10 or 16) will become apparent from the dependent claims.

The inventive method solve the above Task by combinations of the saturation dependences of the permeability, the hysteresis losses and the harmonics, in dependence from induction.

to Magnetic field measurement here becomes the saturation behavior of the magnet coil core dependent on from the permeability, exploited the losses and distortion, because the saturation dependence for different Ranges of induction is different.

to Measurement in the lower and middle range of the induction is suitable primarily the saturation dependency the permeability. In the upper part of the context is no longer so clear and pronounced.

at high inductions a remagnetization loss consideration is suitable for the superimposed Alternating field. Take the losses with the induction of the main field especially at high inductions too.

With increasing saturation increases the distortion of induction. That means with sinusoidal time course the field strength contains the time course of induction shares with multiple frequency of field strength.

The resolution and accuracy of the method according to the invention is dependent on Manufacturing variations. To further improve the accuracy is a compensation of the main field of the magnetic field to be measured performed. The current is controlled in the control coil so that it compensates the main field and has an accurate image of the current to be measured.

• – hohe Messgenauigkeit bei geringem Aufwand;
• – Robustheit gegen hohe Temperaturen (keine elektronischen Bauteile im Motor);
• – Robustheit gegen Verschmutzung (kein optisches System).

Advantages of the method are:

• - high measuring accuracy with little effort;
• - robustness against high temperatures (no electronic components in the engine);
• - Robustness against contamination (no optical system).

The Invention will be described below with reference to the drawings of embodiments explained in more detail. there demonstrate:

1 Block diagram for current measurement,

2 Block diagram for current measurement with compensation method,

3 Saturation dependence of reversible permeability and specific losses,

4 Saturation dependence of the harmonics,

5 Diagram the course of the induction as a function of the angle of rotation,

6 Embodiment for a synchronous motor with permanent magnets and angle measurement on the rotor magnetic field view.

• – Auswertung der Sättigungsabhängigkeit der Oberschwingungen (Funktionsgruppe 1);
• – Auswertung der Sättigungsabhängigkeit der Permeabilität (Funktionsgruppe 2);
• – Auswertung der Sättigungsabhängigkeit der Hystereseverluste (Funktionsgruppe 3);
• – Auswertung der Sättigungsabhängigkeit der Oberschwingungen mit der Hauptfeldkompensation (zeigt 2).

1 is a schematic diagram in a schematic representation of a feedback device for determining the rotor angle position, which consists of a parallel combination for the magnetic field detection of the following parts:

• - evaluation of the saturation dependence of the harmonics (function group 1);
• - evaluation of the saturation dependence of the permeability (function group 2);
• - Evaluation of the saturation dependence of the hysteresis losses (function group 3);
• - Evaluation of the saturation dependence of the harmonics with the main field compensation (shows 2 ).

• – Mit zunehmender Sättigung nimmt die Permeabilität des Kernmaterials ab.
• – Das bedeutet, dass auch die Induktivität einer Spule auf dem Kern mit zunehmender Sättigung abnimmt.
• – Die Sättigung wird durch Messung der Induktivität einer Messwicklung auf dem Kern bestimmt.
• – Eine Strombestimmung erfolgt über eine Kennlinie, die den Zusammenhang zwischen Induktivität der Messspule und dem zu messenden Strom beschreibt.

For the evaluation of the saturation dependence of the permeability, functional group 2 in 1 , the magnetic field sensor uses the saturation behavior of the core, which is magnetized by the magnetic field to be measured

• - With increasing saturation, the permeability of the core material decreases.
• - This means that the inductance of a coil on the core decreases with increasing saturation.
• - The saturation is determined by measuring the inductance of a measuring winding on the core.
• - A current is determined by a characteristic curve that describes the relationship between the inductance of the measuring coil and the current to be measured.

requirement However, that is the saturation behavior the core is at least substantially known.

The inductance of the measuring coil is proportional to the reversible permeability of the ferromagnetic core for a small superimposed magnetic field. 3 shows that the reversible permeability decreases from 1800 for small inductions to 1000 for higher inductions, but then shows only slight changes.

In the application for Magnetic field sensors become the main induction through the to be measured Field generated. The superimposed Alternating field is generated by a sensor coil fed by the transmitter and evaluated.

The saturation dependence the permeability is primarily suitable for measurement in the lower and middle range the induction. In the upper part of the context is no longer so clear and pronounced.

The evaluation of the saturation dependency of the hysteresis losses takes place after the function group 3 in the 1 , For the superimposed alternating field, the induction of the main field increases. 3 shows that this dependence is especially pronounced at high inductions. Thus, loss analysis is particularly suitable for high inductions or currents.

For the evaluation of the saturation dependence of the harmonics (function group 1 according to 1 ) As saturation increases, the distortion of induction increases. 4 shows that with sinusoidal time course of the field strength of the time course of the induction contains portions with multiple frequency of the field strength. Particularly pronounced are the low-frequency components with two and three times the frequency.

Clear It can be seen how the constant field strength of a fundamental vibration Inductions for the double and triple frequency increase. The inductions reflect itself as induced voltage in the sensor winding again.

In order to further improve the measurement accuracy, regardless of manufacturing variations, the main field is compensated by the magnetic field to be measured, cf. 2 , The compensation is done by using a control coil which is controlled so that the current in the control coil is an accurate image of the field to be measured. To measure the control difference, the second harmonic is used. With exact compensation, it has the amplitude zero. The polarity of the induction to be measured can be determined from the phase relation to the fundamental oscillation. 2 shows this basic structure of the current measurement with the transmitter.

On This is a field measurement with high accuracy at low Effort possible, without that manufacturing variations affect the result. Only the Compensation controller must be for the respective nuclear material are compared once.

From the induction of the magnetic field, the angle of rotation of the rotor is determined. This is the Induk tion measured at least 2 places. The induction B generally has the following dependence on the rotor angle β: B (β) = B 1 cos (β - β 1 ) + B 2 cos (2β - β 2 ) + B 3 cos (3β - β 3 ) + B 4 cos (4β - β4) + ...

Upon rotation of the rotor by the angle φ, the rotor induction results in dependence on the stator angle α B (α) = B 1 cos (α - φ - β1) + + B 2 cos (2α - 2φ - β 2 ) + B 3 cos (3α - 3φ - β 3 ) + + B 4 cos (4α - 4φ - β 4 ) + ...

If the induction is measured at two points α ₁ and α ₂ , the angle φ can be determined from the two inductions B (α ₁ ) and B (α ₂ ).

This can be z. B. from the measured inductions, the ratios B (α ₁ ) / B (α ₂ ) and B (α ₂ ) / B (α ₁ ) are determined. The ratio whose amount is smaller than 1 (one) is searched in a characteristic. In general, two associated angles result from the characteristic curve. By comparing the sign of the measured induction, the characteristic associated with the inductions is selected. Thus, the angle is uniquely determined.

An example shows how the induction curve of the magnetic field is marked with the following data for the induction
B1 = 1T
B2 = 0.2T
B3 = 0.1T
B4 = 0.03 T
beta 1 = 0 °
beta 2 = 0 °
beta 3 = 0 °
beta 4 = 0 °

The induction is measured at the following locations:
α ₁ = 0 °
α ₂ = 70 °

The diagram of 5 shows the course of the induction as a function of the angle of rotation. In addition, the induction ratios B (α ₁ ) / B (α ₂ ) and B (α ₂ ) / B (α ₁ ) are found in the diagram for the value range from -1 to + 1, respectively.

An example a) with the measured inductions -0.1 T and -0.8 T results B (α 1 ) = -0.8 T, B (α 2 ) = -0.1T The inductions result in the induction ratios B (α 1 ) / B (α 2 ) = 8; B (α 2 ) / B (α 1 ) = 0.125.

So the curve (See 5 ) to B (α ₂ ) / B (α ₁ ).

Since induction B (α ₁ ) is negative, only the mean curve between 120 ° and 215 ° is valid.

This results in the angle φ for B (a 2 ) / B (α 1 ) = 0.125 to φ = 154 ° Thus, the inductions measured at two points lead to a uniquely determined angle of rotation.

Now the angle φ should be measured for Inductions are determined.

In example b), the measured inductions are 0.4 T and 1.2 T. Therefore, this results B (α 1 ) = 0.4 T, B (α 2 ) = 1.2T The inductions result in the induction ratios B (α 1 ) / B (α 2 ) = 0.33; B (a 2 ) / B (α 1 ) = 3.1.

So the curve (see 5 ) to B (α ₁ ) / B (α ₂ ).

Since induction B (α ₂ ) is positive, only the left curve is between 35 ° and 120 °. This results in the angle φ for B (α 1 ) / B (α 2 ) = 0.33 to φ = 54 °.

Consequently to lead the inductions measured at two locations to a clearly determined angle of rotation.

1

Saturation-dependent harmonic behavior

2

Saturation-dependent inductance curve

3

Saturation-dependent loss history

4

block for weighting factors

5

selection block

6

Association Saturation-dependent harmonic behavior with a compensation coil or with a measuring winding and a Compensation winding.

Claims (18)

Method for determining a rotary variable of the rotor, in particular as a rotor angle or rotor angle change, in a drive control for a motor with permanent magnets that are relative to a sensor with a sensor coil are movable, comprising the following steps - determining an induction of a rotor magnetic field by a known saturation behavior of a core of the magnetic coil is utilized; Comparing a measured induction with the known course of the induction; Determining the angle size from the comparison, in particular a difference, between the known course of the induction and the measured induction. Method for determining a rotor angle after Claim 1, wherein a main induction by the magnetic field to be measured is produced. Method for determining a rotor angle after Claims 1 to 2, characterized in that the rotor magnetic field measurement via weighting factors the saturation behavior determined and evaluated. Method for determining a rotor angle after Claims 1 to 3, wherein the rotor magnetic field measurement is carried out by Evaluation of - saturation behavior the permeability, - saturation behavior the hysteresis losses, - saturation behavior the harmonics. Method for determining a rotor angle after Claims 1 to 4, wherein the rotor magnetic field measurement in the lower and middle range of induction by evaluation of the saturation behavior the permeability he follows. Method for determining a rotor angle after Claims 1 to 5, wherein the rotor magnetic field measurement in the higher region induction by evaluating the saturation dependence of hysteresis losses he follows. The method of claim 1 to 6, wherein the rotor magnetic field measurement in all areas of induction by evaluation of the saturation dependence of harmonics takes place. The method of claim 7, wherein the rotor magnetic field measurement based on a main field compensation of the magnetic field to be measured by evaluation of the saturation dependence the harmonics takes place. The method of claim 2, wherein the induction as induced voltage in the sensor windings. An apparatus for determining a rotor angle or a rotor angle change in a drive controller for a permanent magnet machine, which permanent magnet is movable relative to a sensor; wherein the device comprises a sensor coil in the sensor, which measures the rotor magnetic field for specific regions of the induction, and an evaluation circuit is provided, for evaluating a saturation behavior of the permeability, hysteresis losses and harmonics via a function block ( 4 ) with weighting factors and a function block ( 5 ) for selecting the determination of the rotor angle or the change of the angle. Apparatus according to claim 10, wherein the device having a plurality of magnetic field sensors to the rotor magnetic field through the use of saturation behavior of the core to measure and evaluate. Apparatus according to claim 10, wherein the spool core additionally with a control coil, which is the main field of the magnetic field to be measured compensated, in order to reduce manufacturing spreads or even eliminated. Apparatus according to claim 10, wherein a rotor angle and a rotor angle change in the drive control for the machine is determined by permanent magnets. Device according to claim 10, characterized in that that the current in the control coil or in additional windings so controllable is that it compensates the main field of the magnetic field to be measured and represents an exact image of the induction to be measured. Apparatus according to claim 10, and 12 to 14, wherein used in a control difference measurement, the second harmonic is, which has a zero amplitude with accurate compensation. Method for detecting a rotor to be assigned Turning size in one Drive control for a permanent magnet machine, this magnet being relative to a sensor is moved with arranged therein sensor coil, the Procedure with the following steps - Determining a course a first induction from a magnetic field of the rotor, under use a saturation behavior a core of the sensor coil; - Compare a history a second induction with the first induction, in each case Course; - To capture the rotor to be assigned rotary size from the comparison between the course of the first induction and the course of the second induction. The method of claim 16, wherein the first induction is known, and the second induction is measured. The method of claim 16, wherein the Ver is equal to a difference.