DE102011105502A1 - Method for adjusting a phase offset between a rotor position sensor and the rotor position of an electrically commutated motor - Google Patents

Abstract

The invention relates to a method for adjusting a phase offset between a rotor position sensor and a rotor position of an electrically commutated motor, in which the rotor position sensor measures a position of the rotor of the electrically commutated motor, which is compared with an expected position, based on the difference between the measured and expected position a phase offset is formed which is used to control the electrically commutated motor. In order to be able to correct a phase offset without great technical effort and in a time-optimized manner, the position of the rotor is measured with an absolute rotor position sensor, which is related to a motor parameter that characterizes the expected position of the rotor.

Description

The invention relates to a method for adjusting a phase offset between a rotor position sensor and a rotor position of an electrically commutated motor, wherein the rotor position sensor measures a position of the rotor of the electrically commutated motor, which is compared with an expected position, wherein the difference between measured and expected Position a phase offset is formed, which is used to control the electrically commutated motor.

In modern motor vehicles, especially passenger cars, increasingly automated clutches are used. The use of such clutches has the advantage of improved ride comfort and leads to the further advantage that can be driven more often in gears with long translation. The couplings used in this case are used in hydraulic clutch systems in which an electro-hydraulic actuator which is driven by an electrically commutated motor is connected via a hydraulic line to the clutch.

In order to improve the driving comfort in the vehicle, the position measured by a rotor position sensor must be matched with the actual position assumed by the rotor of the electric motor. For this purpose, a method is known in which the electric motor is externally driven by a second electric motor. At the same time, the phase voltage at the three phases of the electric motor and the rotor position of the electric motor are detected. The rotor position is detected by means of three mutually offset Hall sensors. The flanks supplied by the Hall sensors are matched with the phase voltage signals of the three different phases of the electric motor. It is assumed that the phase voltages have an approximately sinusoidal shape. If it is determined that the maximum of each oscillation of the phase voltage is not formed exactly between two edges of two Hall sensors, the Hall sensors are adjusted by hand, so that the condition is met and the phase offset thus occurred is reliably corrected at the end of the tape. However, such a mechanical adjustment requires a lot of time during commissioning and requires a mechanical Vorhaltes.

The invention is therefore based on the object of specifying a method in which the phase offset between a rotor position sensor and the rotor position of an electrically commutated motor can be corrected time-optimized both during commissioning and during operation of the electric motor.

According to the invention the object is achieved in that the position of the rotor is measured with an absolute value rotor position sensor, which is set in relation to a motor parameter that characterizes the expected position of the rotor. This has the advantage that the offset which occurs in the assembly of the motor with the rotor position sensor can be automatically corrected during operation by the use of such an absolute value rotor position sensor. Such an automatic balance between the position of the rotor delivered by the absolute-value rotor position sensor and the expected rotor position can thus be reliably carried out both during operation and during the commissioning of the electric motor. A mechanical advantage for the band end adjustment is thus eliminated. In addition, time is saved in the production. During adjustment, the full moment of the electric motor can be used at any time.

Advantageously, the electrically commutated motor is energized accordingly for setting a fixed predetermined, expected position and then determined by the rotor actually occupied position by the absolute value rotor position sensor, wherein a difference between the fixed position and the rotor actually occupied and the Absolute value rotor position sensor detected position is formed, which represents the phase offset. This allows adaptive determination of the ideal electric motor drive to achieve the optimum motor torque of the electric motor. The basis for the adaptation is a very precise knowledge of the rotor position, which is ensured by the use of the absolute value rotor position sensor. Through this purely software measure can be dispensed with a mechanical adjustment by hand.

In one refinement, the phase offset is determined for a plurality of predefined positions of the electrically commutated motor, wherein a phase offset mean value, which is used to drive the electrically commutated motor, is determined from the phase offsets determined for the several predetermined positions. The determination of a phase offset mean value is particularly suitable for those electric motors which have several pairs of rotor magnets. Thus, the tolerances of the phases and the rotor magnets in the electrically commutated motor are included in the determination of the phase offset, whereby all influence on the phase offset are taken into account.

In a development, the phase offset and / or the phase offset mean value during operation of the electrically commutated motor are subtracted from the position measured by the absolute value rotor position sensor. With this simple software measure, the adjustment of the phase offset can be performed without further great effort during operation of the electric motor.

In one variant, the electrically commutated motor is operated without load. The fact that the electrically commutated motor delivers no torque, it is ensured that at the time of determining the actual position taken by the rotor by the absolute value rotor position sensor no distortions occur.

Advantageously, the electrically commutated motor is used in an electrohydraulic clutch system in which an electrohydraulic actuator, in particular a hydrostatic clutch actuator, adjusts a clutch into its position via a hydraulic line. When using the motor in such an electro-hydraulic clutch system, the load freedom can be set very easily, since it is always given when the motor-driven piston is in its movement at a pressure equalization opening (sniffer bore).

In another embodiment, during operation of the electrically commutated motor, a phase voltage is measured on a current-free guided phase of the electrically commutated motor and the zero crossing of the phase voltage is compared with the position measured by the absolute value rotor position sensor, wherein the phase voltage is assigned to the measured position of the rotor which is compared with the position expected at the zero crossing of the phase voltage, wherein the phase offset is formed from the expected position and the measured position. This method has the advantage that it can be carried out, as it were, on a rotating engine.

In one variant, the electrically commutated motor is subjected to a block commutation. Since the block commutation represents the usual control possibility of an electrically commutated motor, the adjustment method is executable at any time during operation of the electric motor.

Advantageously, the three phases of the electrically commutated motor are each driven with a pulse width modulated signal. The control by means of a pulse width modulated signal allows accurate adjustment of the phase relationships with each other, so that, for example, a block commutation can be performed safely.

In one embodiment, the phase offset is determined during the deactivated PWM signal.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

It shows:

1 : Schematic representation of an electrohydraulic coupling system.

2 : Example of the energization of an electric motor, which has a pole pair.

3 : Representation of a phase diagram in block commutation of an electrically commutated motor.

Identical features are identified by the same reference numerals.

In 1 an electro-hydraulic clutch system is shown, as it is used in motor vehicles today. This coupling system has an electro-hydraulic actuator 1 on which an actuator housing 2 includes, in which a piston 3 is movably arranged. The piston 3 This is done by an electrically commutated electric motor 4 powered by a control unit 5 is controlled. Via a hydraulic line 6 is the electrohydraulic actuator 1 with a clutch 7 connected, due to the movement of the piston 3 in the electrohydraulic actuator 1 is adjusted in their position. The electrohydraulic actuator 1 and the clutch 7 are arranged spatially separated in the vehicle.

The control unit 5 controls the electric motor 4 by means of a block commutation. That means the electric motor 4 , which has three phases U, V, W, is so controlled that always one phase U, V, W is de-energized, while the other phases U, V, W are energized.

In 2 is a schematic diagram to see in which in a spatial coordinate system, the three phases U, V, W are given. The given example assumes that the electric motor 4 is formed only with a pole pair. With a fixed commutation, phase U is supplied with 100% PWM signal (PWM-modulated signal), while phases V and W are only activated with 50% PWM signal. In this control, a rotor field vector adjusts the position of the rotor in that of the electric motor 4 generated electromagnetic field indicates how it is from the 2 is apparent. The arrow U1 characterizes the vector which adjusts itself at the controlled phase U, while the arrow W1 or the arrow V1 represent the vectors of the phases V and W. The vectors U1, V1 and W1 thereby determine the orientation of the electromagnetic field, which builds up in the electrically commutated motor. From this resulting field results in a current I_Res, which flows through the phase U and affects the orientation of the rotor.

First, it will be described how a phase adjustment via a defined energization of the phases U, V, W of the initially stationary electric motor 4 he follows. In a first step, it is determined which position the rotor of the electric motor 4 should take. Subsequently, the phases U, V, W are connected in accordance with 2 described boundary conditions to achieve the expected position. After that, wait until the rotor of the electric motor 4 has come to rest again. Now, the position is read out by means of an absolute value rotor position sensor which determines the rotor position. The difference of the position read from the absolute value rotor position sensor and the expected position minus 90 ° / pole pair number gives the phase offset Δα. Δα = (αSensor - αcommand) - (90 ° / pole pair)

This phase offset is then always subtracted during operation from the value which the absolute value rotor position sensor measures.

Condition for this procedure is that the electric motor 4 is operated without load, which means that the electric motor 4 at the time of determining the phase offset does not apply torque. This is especially the case with an electrohydraulic actuator 1 as he is in 1 shown is particularly easy to adjust. As always when the piston 3 at the sniff hole 8th of the actuator housing 2 is passed, the load-free state is present.

To the tolerances of the phases U, W, V and the rotor magnets of the electrically commutated motor 4 to consider with, the predetermined angular position, z. B. in 90 ° steps electrically, for 360 ° steps mechanically, first in the positive direction of rotation of the electric motor 4 and then in the negative direction of rotation of the electric motor 4 be performed. It must be ensured that the number of steps <180 ° is electrically selected. The phase offset angles determined in each step are then averaged and fed to the controller 5 For further control of the electric motor 4 entered during operation of the coupling system.

In addition to the just explained phase adjustment over a defined energization of the phases U, V, W of the electric motor 4 There is also the possibility of phasing in a rotating electric motor 4 perform. During operation of the electric motor 4 in which it is driven with a block commutation, in which always one phase is current-free, the phase voltage is measured at the current-free phase. In 3 is the energization of the phases U, V, W shown in a block commutation. In the upper part of the 3 the electrical angle φ of the rotor is shown between 0 and 360 °. Including the phases U, V, W, which are controlled by means of a PWM signal, and the amplitudes of the respective phase voltage during the individual drive phases are shown. It can be seen how the current flows from one phase to the other. Thus, in the angle φ between 0 and 60 °, the current flows from the phase V to the phase W. The phase U is thereby de-energized. At the subsequent angle of 60 to 120 °, the current flows from the phase U to the phase W, the phase V remains de-energized.

In the lower part of the 3 is a section of the angular range 240 to 300 ° shown electrically. It can be seen from this that the phase U is not subject to current supply. The phase V is at half the generator voltage of the electric motor 4 applied during the phase W with a full generator voltage of the electric motor 4 is fed. Again 3 can be seen, the phase V and W are driven by the PWM signal in area A, while in area B, the PWM signal is turned off.

In the present case, the phase voltage is measured on the phase which is current-free according to 3 this is the phase V. The measurement takes place at the moment when the PWM signal is switched on, that is to say in the region A. At the point where the zero crossing of the phase voltage lies, this is determined by the position which the absolute value rotor position sensor measures. adjusted. Thus, via the phase voltage information about the position of the rotor of the electric motor 4 produced. In order to determine whether a phase offset is present, the actually determined position is compared with an expected value of the rotor position, as can be seen from the following table. de-energized phase (energization direction of the energized phases) Angle electrical (example) U (V => W) 30 ° V (U => W) 90 ° W (U => V) 150 ° U (W => V) 210 ° V (W => U) 270 ° W (V => U) 330 °

At the time when a phase voltage zero crossing is detected, the absolute value rotor position sensor should indicate the expected position of the rotor. In the table, therefore, the de-energized phase is shown, wherein in the brackets the Bestromungsrichtung the energized phases is shown. If, in the actual measurement with the absolute-value rotor position sensor, it is determined that the rotor has an angular position of 29 °, according to the table an angular position of 30 ° in the case of de-energized phase U and in the direction of current flow from phase V to phase W at the zero crossing of the phase voltage is expected, so a phase offset of 1 ° is electrically present. This phase offset is also software-based in the control unit 5 further processed and in the control of the electric motor 4 of the electrohydraulic actuator 1 recycled. In the previous considerations it is assumed that the position of the rotor is always an angle.

The described method allows an adaptive determination of the ideal motor control to achieve the optimum engine torque. This adaptation can be done at the end of the tape and / or during operation. Basis for the adaptation is u. a. a very precise knowledge of the rotor position, which is made possible by an absolute value rotor position sensor. The software-based measure can be dispensed with a mechanical adjustment during commissioning, whereby time is saved. In addition, eliminates the need for a mechanical Vorhaltes.

LIST OF REFERENCE NUMBERS

1

actuator

2

actuator housing

3

piston

4

electric motor

5

control unit

6

hydraulic line

7

clutch

8th

sniffing hole

U

phase

V

phase

W

phase

A

Area

B

Area

φ

Angle of the rotor

Δα

phase displacement

Claims (10)

A method for adjusting a phase offset between a rotor position sensor and a rotor position of an electrically commutated motor, wherein the rotor position sensor is a position of the rotor of the electrically commutated motor ( 4 ), which is compared with an expected position, wherein the difference between the measured and expected position, a phase offset is formed, which is used to control the electrically commutated motor ( 4 ), characterized in that the position of the rotor is measured with an absolute value rotor position sensor which is set in relation to a motor parameter characterizing the expected position of the rotor. Method according to Claim 1, characterized in that the electrically commutated motor ( 4 ) is energized correspondingly to set a predefined, expected position, and then the position actually assumed by the rotor is determined by the absolute value rotor position sensor, a difference between the fixed, expected position and the actual value assumed by the rotor and the absolute value Rotor position sensor detected position is formed, which represents the phase offset. A method according to claim 2, characterized in that the phase offset for a plurality of predetermined positions of the electrically commutated motor ( 4 ), wherein a phase offset average value is determined from the phase offsets determined for the plurality of predefined positions, which is used to control the electrically commutated motor ( 4 ) is being used. Method according to Claim 2 or 3, characterized in that the phase offset and / or the phase offset mean value during operation of the electrically commutated motor ( 4 ) is subtracted from the position measured by the absolute value rotor position sensor. Method according to at least one of the preceding claims, characterized in that the electrically commutated motor ( 4 ) is operated without load. Method according to Claim 5, characterized in that the electrically commutated motor ( 4 ) is used in an electro-hydraulic coupling system in which an electro-hydraulic actuator ( 1 ), in particular a hydrostatic clutch actuator, via a hydraulic line ( 6 ) a coupling ( 7 ) adjusted in their position. Method according to claim 1, characterized in that during the operation of the electrically commutated motor ( 4 ) a phase voltage at a current-free guided phase of the electrically commutated motor ( 4 ) and the zero crossing of the phase voltage is compared with the position measured by the absolute value rotor position sensor, wherein the phase voltage is assigned to the measured position of the rotor, which is compared with a zero crossing of the phase voltage of the de-energized expected position, from the expected position and the measured position of the phase offset is formed. Method according to at least one of the preceding claims, characterized in that the electrically commutated motor ( 4 ) is applied with a block commutation. Method according to claim 7 or 8, characterized in that the three phases of the electrically commutated motor ( 4 ) are controlled with a pulse width modulated signal. A method according to claim 9, characterized in that the phase offset during the deactivated pulse width modulated signal is determined.

Images