WO2017148625A1

WO2017148625A1 - Method and device for rotor position diagnosis in an electric-motor drive

Info

Publication number: WO2017148625A1
Application number: PCT/EP2017/051532
Authority: WO
Inventors: Walter Hirning; Vitali Haag
Original assignee: Robert Bosch Automotive Steering Gmbh
Priority date: 2016-02-29
Filing date: 2017-01-25
Publication date: 2017-09-08
Also published as: DE102016103518B4; DE102016103518A1

Abstract

The invention relates to a method and to a device for rotor position diagnosis in an electric-motor drive, which drive has a sensor unit (S) arranged on the rotor or on a shaft connected to the rotor for determining the rotor position, which sensor unit has a plurality of magnetoresistive sensor elements (TMR), which are interconnected to each other in order to form at least two measuring bridge circuits, which serve as full bridges (VB, VB') and provide at least two measurement signals (cos, sin), which are phase-shifted with respect to each other, for signal processing. In order to detect errors occurring in the measurement signals, two half bridge signals (cosP, cosN), which are provided by the half bridges (HB1, HB2) of the same full bridge (VB), are combined with each other and evaluated in the signal processing.

Description

Method and device for rotor position diagnosis in an electric motor drive

The invention relates to a method for rotor position diagnosis in an electric motor drive according to the preamble of claim 1 and an apparatus for performing the method according to the preamble of the independent claim.

For measurement and control, in particular for electronic commutation, electric motor drives, the knowledge of the absolute angular position of the rotor, the rotor position, is required. The rotor position can by means of suitable sensors, such as. B. absolute or incremental resolution encoders are detected.

From DE 102 50 319 A1 a method and a device for detecting the rotor position of an electrical machine are known. As described there with reference to Figures 6 and 7, a sensor unit is used which has a plurality of magnetoresistive sensor elements, which are connected to form two Wheatstone bridges. Each bridge supplies sinusoidal measurement signals, with the measurement signals of one bridge being 90 degrees out of phase with the measurement signals of the other bridge. Therefore, one bridge is called a sine bridge and the other bridge a cosine bridge. As sensor elements in particular AMR (Anisotropic Magneto Resistance) or GMR (Giant Magneto Resistance) elements are used. It is known in the field of sensor technology, even more advanced magneto-resistive sensor elements, such as TMR sensors (Tunnel Magneto-Resistance) use. The measurement signals generated by the sensor unit thus represent sine and cosine signals, which are usually differentiated. Thus, a method and a device for rotor position determination in an electric motor drive are known, wherein for determining the rotor position, one on the rotor or on an associated Shaft-mounted sensor unit is provided which has a plurality of magnetoresistive sensor elements (eg GMR), which are interconnected to form at least two full-bridge measuring bridge circuits, the full bridges provide at least two mutually phase-shifted measurement signals (cos, sin) for signal processing. In the case of two full bridges or four half bridges, four measurement signals are generated, which are usually subjected to differentiation. This means that a single signal (cos # 1) is formed by signal processing from two half-bridge signals (eg cos1 and cos2) (eg cos # = cos1 - cos2, see also Fig. 1) By differentiation, eg with the aid of operations Amplifiers, high amplitudes can be achieved which are well suited for subsequent analog-to-digital conversion and / or processing in an application-specific integrated circuit (ASIC); However, only a rotor position determination and simple radius diagnosis is possible. A rotor position diagnosis, which also allows a clear and timely error detection, is not feasible.

The invention is based on the object to provide a method and apparatus for rotor position diagnosis, which allows a clear and timely error detection.

The object is achieved by a method having the features of claim 1 and by a device having the features of the independent claim.

The invention is based on the recognition that through the differentiation a clear and timely fault diagnosis, e.g. is made difficult or even impossible by means of radius diagnosis, which is explained with reference to the attached FIGS.

1 shows a conventional arrangement of two measuring bridge circuits designed as full bridges VB and VB ', each full bridge having four magnetoresistive sensor elements TMR, here in the form of four TMRs each. Sensor elements. In addition, FIG. 1 shows the course of the generated sensor signals via the rotation of a magnet, that is to say the angle-dependent signal characteristics. The two half bridges H1 and H2 of the first (upper) full bridge VB supply two cosine half-bridge signals cos1 and cos2. The two half bridges of the second (lower) full bridge VB 'provide two sine half-bridge signals sin' and sin2 '. Starting from the sensor system (area I), a normalized cosine signal cos # is generated by the usual differentiation or signal processing for signal processing (area II) for the first full bridge VB and a normalized sine signal sin # for the second full bridge VB '. generated.

The invention is based on the finding that in each case two half-bridge signals are lost and this in turn makes it more difficult to identify errors clearly and in good time via a radius diagnosis. Because in traditional systems, certain errors can only be detected using additional hardware (HW) patterns and / or software (SW) patterns. The HW patterns are obtained e.g. by shorting a half-bridge signal to ground (GND) or to the supply voltage by means of transistors. The SW patterns are obtained, for example, in the case of RPS (Rotor Position Sensor) by e.g. an engine torque reduction according to a specific comparison logic with subsequent RPS signal evaluation.

The radius diagnosis will now be explained with reference to FIG. 2: If the sine signal is plotted against the cosine signal (see sin # and cos # in FIG. 1), the result is a signal circle K (dashed representation) due to the rotation of the magnet. with the radius R, which is calculated by the following circular formula:

R = Vsin ² + cos ² . The radius can also be determined, for example, in the context of the application of the so-called Cordic algorithm. Ideally, the radius R should be constant and move in a circular orbit concentric with the zero point. However, since the analog signals change slightly due to the sensors, the system and environmental conditions (temperature, humidity, aging ...), the radius R is not always on the ideal circular path (dashed line), but deviates slightly from it. Therefore, in practice, tolerance limits are set, namely, a lower limit LL for the inner limit circle and an upper limit HL for the outer limit circle. The radius R should always be within this tolerance range (band).

With the present invention, based on the above-explained realization, a method for rotor position diagnosis in an electromotive drive is now provided, which can be realized effectively and inexpensively. In particular, a rotor position diagnosis is made possible without relying on the help of HW pattern and / or SW pattern. Furthermore, an apparatus for carrying out the method is proposed. The invention can be used in all areas of electric motor drives, but especially in electric motor driven steering systems for vehicles, i. in so-called electric power steering systems.

The invention is defined by a method having the features of claim 1 and by a device having the features of the independent claim.

Accordingly, a method and a device for rotor position diagnosis in an electromotive drive are further developed or supplemented such that for the detection of errors occurring in the measurement signals those two half-bridge signals supplied by the two half bridges of the same full bridge (sine bridge or cosine bridge) be combined and evaluated in the signal processing. In particular, the two half-bridge signals are combined by summation into a sum signal, preferably one of the following formulas, to determine an offset value:

(+ Cosp cosN

(VI) I For the cosine bridge: cosOFF = X * γ where: cosOFF is the offset value; cosP is the positive half-bridge signal; cosN is the negative half-bridge signal; and X and Y are weighting factors;

, _, (sinP + sinN)

For the sine bridge: sinOFF = X *

Y

where: sinOFF is the offset value; sinP is the positive half-bridge signal; sinN is the negative half-bridge signal; and X and Y are weighting factors.

Preferably, the offset values cosOFF and sinOFF are calculated for both bridges, whereby a complex error detection can then be carried out, which makes it possible to calculate the displacements both with respect to the cos component and the sin component, e.g. in the circle, to recognize immediately.

These and other advantageous embodiments will become apparent from the dependent claims.

Accordingly, TMR sensor elements or AMR sensor elements are preferably used as magnetoresistive sensor elements. In particular, exactly two measuring bridge circuits serving as full bridges are formed, which supply at least two measuring signals (cos, sin) phase-shifted by 90 degrees to one another as full-bridge signals for the signal processing.

The device according to the invention has the sensor unit S and a signal processing unit connected thereto, which processes the sensor signals according to the method.

The invention and the resulting advantages will be described in detail below with reference to an embodiment with reference to the accompanying figures. The figures show the following schematic representations: Fig. 1 illustrates the known structure of a sensor unit with two full bridges and the sensor signals generated therefrom;

Fig. 2 illustrates meaning and purpose of a radius diagnosis;

Fig. 3 illustrates the problem of an occurring offset error; and

Fig. 4 illustrates the combination of

Half-bridge signals for determining an offset value.

Starting from the figures 1 and 2, which have already been described above and explain the knowledge according to the invention that the differentiation usually carried out a clear and timely error detection, e.g. By means of radius diagnosis, difficult, this deficit will now be explained further with reference to FIG.

3, in addition to the ideal circle K already described (see also FIG. 2), a shifted signal circle K ^{* is} drawn, which can result in the following error case:

The behavior shown in Fig. 3 may e.g. occur when a half-bridge signal changes in offset, e.g. may occur due to a shunt after the supply voltage or coming from the measuring or sensor element itself. Points A and B, where the vertex intersects the upper limit HL of the tolerance band.

By the invention, the respective half-bridge signals, e.g. of the

Half bridges HB1 and HB2 of the upper full bridge VB (in this case the cosine bridge in FIG. 1), compared or calculated with one another:

(Cosp cosN +)

cosOFF = X *

Where cosOFF is the offset value. And Cos is the positive Half bridge signal; cosN is the negative half-bridge signal. The values X and Y can be variable and, for example, each have the value "1".

If an offset error (see Fig. 3) should occur, this can be detected earlier. No HW patterns or SW patterns need to be detected and evaluated, as would be the case if only differentiated signals were available alone.

Figure 4 illustrates the advantageous methodology of the invention:

On the left in the figure, the course of the two half-bridge signals cosP (= cos +) and cosN (= cos-) is shown by way of example. The dashed line indicates that an error OFF occurs in the form of offset drift. The combination (here summation) of the two half-bridge signals cosP and cosN and possibly weighting (X and Y) immediately calculates the current offset value cosOFF. In the second illustration of FIG. 4, this is illustrated by the dashed line, wherein it can be seen that the error OFF is constant over the entire angular range of 0-360 degrees. In the third representation, which is drawn as a circular representation, the error in the standard circle certainly makes itself noticeable as a shift in the cos component. An error in the sin component could also be detected quickly by means of a corresponding summation of the other half-bridge signals sinP and sinN (sinOFF = sinP + sinN), whereby also possibly weighting factors can be taken into account.

With the aid of the invention proposed here, the hitherto customary radius diagnosis can be extended by an offset diagnosis as described above. As a result, specific error cases, as set out above, can then be recognized immediately and reliably. The invention can be used in diagnosis and control units for any type of electric drives, in which a sensor, such as TRM sensor, sine and cosine signals as measurement signals for the position and movement of the rotor determined. A preferred one Field of application of the invention is the automotive sector and in particular the control of electric drives in power steering systems (electric steering).

Claims

claims

1 . Method for rotor position diagnosis in an electromotive drive which has a sensor unit (S) arranged on the rotor or on a shaft connected to it for determining the rotor position, which has a plurality of magnetoresistive sensor elements (TMR) which are interconnected to form at least two full bridges ( VB, VB ') serving measuring bridge circuits which provide at least two mutually phase-shifted measuring signals (cos, sin) for signal processing,

characterized in that

for detecting errors occurring in the measuring signals two

Half-bridge signals (cosP, cosN), which are supplied by the half-bridges (HB1, HB2) of the same full bridge (VB), are combined and evaluated in the signal processing.

2. The method according to claim 1, characterized in that as

Magnetoresistive sensor elements TMR sensor elements (TMR) or AMR sensor elements or GMR sensor elements can be used.

3. The method according to claim 1 or 2, characterized in that exactly two full bridges (VB, VB ') serving measuring bridge circuits are formed which provide at least two by 90 degrees mutually phase-shifted measurement signals (cos, sin) as full bridge signals for the signal processing.

4. The method according to any one of the preceding claims, characterized

characterized in that the two half-bridge signals (cosP, cosN) are combined by summation into a sum signal (cosP + cosN).

5. The method according to any one of the preceding claims, characterized characterized in that the two half-bridge signals (cosP, cosN) are combined using the following formula to determine an offset value (cosOFF):

(Cosp cosN +)

cosOFF = X *

Y

where X and Y are weighting factors.

6. The method according to any one of claims 1 -4, characterized in that the two half-bridge signals (sinP, sinN) are combined using the following formula to determine an offset value (sinOFF):

, (SINP + sense)

sinOFF = X *

Y

where X and Y are weighting factors.

7. The method according to any one of claims 3-5, characterized in that respect to the two phase-shifted by 90 degrees to each other

Measuring signals (cos, sin) the two half-bridge signals (cosP, cosN, sinP, sinN) are combined with each other, so as to determine the two corresponding offset values (cosOFF, sinOFF).

A method according to claim 7, characterized in that a first set of two half-bridge signals (cosP, cosN) are combined using the following formula to determine a first offset value (cosOFF):

(Cosp cosN +)

cosOFF = X *

Y

and in that a second set of two half-bridge signals (sinP, sinN) are combined using the following formula to determine a second offset value (sinOFF):

, , (sinP + sinN)

sinOFF = X * where X, X 'and Y, Y' are weighting factors, and in particular X and X 'are the same and Y and Y are the same.

9. Device for rotor position diagnosis in an electromotive drive, wherein the device has a sensor unit (S) arranged on the rotor or on a shaft connected thereto, which has a plurality of magnetoresistive sensor elements (TMR) which are interconnected by at least two full bridges ( VB, VB ')

To form measuring bridge circuits which provide at least two mutually phase-shifted measuring signals (cos, sin) for signal processing, the device having a signal processing unit connected to the sensor unit (S),

characterized in that

for detecting errors occurring in the measuring signals the

Signal processing unit two half-bridge signals (cosP, cosN), which provide the half-bridges (HB1, HB2) of the same full bridge (VB) combined and evaluated.

10. Apparatus according to claim 9, characterized in that the

Sensor unit (S) as magnetoresistive sensor elements, GMR, AMR or TMR sensor elements (TMR).

11. Method according to claim 9 or 10, characterized in that exactly two measuring bridge circuits serving as full bridges (VB, VB ') are formed which comprise at least two measuring signals (cos, sin) phase-shifted by 90 degrees to each other as full-bridge signals for the

Deliver signal processing unit.

12. The method according to any one of claims 9-11, characterized in that the signal processing unit combines the two half-bridge signals (cosP, cosN) by summation to a sum signal (cosP + cosN).

13. Device according to one of claims 9-12, characterized in that the signal processing unit combines the two half-bridge signals (cosP, cosN) using the following formula to determine an offset value (cosOFF):

(Cosp cosN +)

cosOFF = X *

Y

where X and Y are weighting factors.

14. Device according to one of claims 9-12, characterized in that the signal processing unit combines the two half-bridge signals (sinP, sinN) using the following formula to determine an offset value (sinOFF):

, (SINP + sense)

sinOFF = X *

Y

where X and Y are weighting factors.

15. Electromotive drive, in particular for a power steering system, with a device according to one of claims 9-14.