WO2015036198A2

WO2015036198A2 - Determining the position of an electric motor by evaluating the direction of movement

Info

Publication number: WO2015036198A2
Application number: PCT/EP2014/067318
Authority: WO
Inventors: Eman Mehrjerdian; Christian Kugler; Khaled Sharaf
Original assignee: Zf Lenksysteme Gmbh
Priority date: 2013-09-10
Filing date: 2014-08-13
Publication date: 2015-03-19
Also published as: DE102013109885A1; WO2015036198A3

Abstract

The invention relates to a method for determining the position of a rotor of an electric machine, comprising the following steps: the possible potential positions of the rotor (23) are determined, a target position (24 ) is determined, a commutation for reaching the target position (25) is applied and the rotational direction of the rotor (26) is determined.

Description

Position determination of an electric motor by evaluation of the direction of movement

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a method for determining the position of a rotor of an electric machine, a steering system for a vehicle with a

Control unit, a computer program and a computer program product.

BACKGROUND OF THE INVENTION

In the prior art Hall sensors for determining the position of a rotor of an electric machine are known.

SUMMARY OF THE INVENTION

The current position of rotors / rotors of electric machines can be determined by means of Hall sensors. There are embodiments in which there is no clear correlation between the results of the Hall sensors and the position of the rotor / rotor. In this case, the starting position is determined and stored in a non-volatile memory, whereby an always accurate position determination can be made due to the known starting position of the rotor. However, if, for example, a battery change takes place, the starting position stored in the memory can be deleted. In this case, no definite position determination may be possible anymore. It is therefore an object to provide a method for re-determining the exact position after clearing the starting position of the rotor.

As a first embodiment of the invention, there is provided a method of determining the position of a rotor of an electric machine comprising the steps of: determining the potentially possible positions of the rotor, determining a target position, applying a commutation to reach the target position, and determining the direction of rotation of the rotor. By means of a method according to the invention, an accurate determination of the position of the rotor can be carried out without the arrangement of further sensors even if the sensor values and motor poles are not unambiguously assigned.

As a second embodiment of the invention, a steering system for a vehicle is provided with a control unit, wherein the control unit a

Storage means having a computer program stored thereon, wherein the computer program for carrying out a method according to one of claims 1 to 5 is configured. As a third embodiment of the invention, a computer program for

Implementation of a method according to one of claims 1 to 5 provided.

As a fourth embodiment of the invention, a computer program product is provided, comprising program code means, which on a

computer-readable data carrier are carried out to perform the method according to one of claims 1 to 5, when the program code means on a

Computer are running.

Exemplary embodiments are set forth in the dependent claims

described. According to an exemplary embodiment of the invention, there is provided a method further comprising the step of: determining the position based on the direction of rotation. In a further embodiment according to the invention, a method for

Provided, further comprising the steps: n-times specification target position, n-times corresponding commutation and n-times determining the direction of rotation.

By repeated use of the method, a higher security can be achieved in determining the actual position of the rotor.

According to another embodiment of the present invention there is provided a method wherein n = 2, 3, 4, 5, 6, 7, 8 or any natural value and / or being the same by the commutations

Rotation directions or different directions of rotation are generated and / or wherein the different directions of rotation in each case have alternating directions.

By applying commutations that lead to different directions of rotation, it can be ensured that the measurement result is not falsified by an external force.

According to an exemplary embodiment of the invention, a method is provided wherein an equal waiting time or different waiting times are inserted between individual PWMs.

By inserting waiting times, the mechanical inertia of the

Electric motor accounted for. This ensures that the effects of applied commutations can be determined.

As an idea of the invention can be considered to provide a method that without detecting the detection of the actual position of a Rotor of an electric machine allows, especially if the assignment of Hall sensor values and motor poles is not unique.

Of course, the individual features can also be combined with each other, which can also be partially beneficial effects that go beyond the sum of the individual effects.

BRIEF DESCRIPTION OF THE DRAWINGS Further details and advantages of the invention will become apparent from the reference to FIGS

Drawings illustrated embodiments clearly. Show it

1 a magnetic motor ring and a first magnetic sensor ring, FIG. 2 a magnetic motor ring and a second magnetic sensor ring, FIG.

3 Hall sensor values of three Hall sensors in a magnetic sensor ring according to FIG. 1, FIG. 4 Hall sensor values of three Hall sensors in a magnetic sensor ring according to FIG. 2, FIG.

Fig. 5 Hall sensor values of three Hall sensors in a magnetic sensor ring of FIG. 2 with the representation of the potential positions of the possible rotor

Electric machine

6 shows an increase of the PWM control (for example based on 0%, over 2%, 4% and 6% up to 8%), FIG. 7 Hall sensor values and associated motor poles and a schematic procedure according to the invention, 8 is an illustration of an alternative method according to the invention,

9 shows a representation of a further alternative method according to the invention, FIG. 10 shows a representation of a further alternative method according to the invention,

11 shows a method according to the invention as a flow chart.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fig. 1 shows a magnetic motor ring 1, which is a part of the rotor of the drive motor, and a magnetic sensor ring 5, which is also arranged on the drive motor and synchronously runs with the magnetic motor ring 1. Based on the magnetic sensor ring 5, a position of the rotor of the drive motor can be uniquely determined by the arrangement of Hall sensors 2, 3, 4.

Fig. 2 shows the magnetic motor ring 1 of the drive motor and another synchronously co-rotating magnetic sensor ring 6, wherein the magnetic sensor ring 6 in comparison to the magnetic sensor ring 5 of Figure 1 has a double resolution.

3 shows a tabular list of the Hall sensor values and the respective associated motor poles according to the situation of FIG. 1. It can be stated that, starting from a Hall sensor value, the associated motor pole can be unambiguously determined. For example, starting from the

Hall sensor value "5" determined that at the corresponding position, a north pole N of the rotor / rotor is present.

4 shows a further tabulation of the Hall sensor values and the respective associated motor poles according to the situation of FIG. 2. From a given Hall sensor value "5", the absolute rotor position can no longer be used be determined, since it is actually possible that at the position in question both a north pole N and a south pole S may be present.

FIG. 5 shows the possible effects if a wrong position 8 is assumed. Starting situation is that a position between the

Hall sensor values 2 and 6 to be approached. This could in principle be position 10 or position 11. In the (false) assumption that the position 8 is the actual position of the rotor, a commutation would be made, which would lead from the correct position 9 to a movement to the left (with respect to drawing plane), which would be opposite to the actual direction of rotation of the electric motor and therefore never should. In this case, the electric motor is switched off immediately by the control unit and an error message is generated. If the correct position 9 had been selected as the assumed position, a movement to the right (with regard to the plane of the drawing) would actually have resulted, ie in the direction of the actual direction of rotation. The task is therefore, in an electric motor with ambiguous assignment of Hall sensor values and

Rotor position to provide a method that allows initialization and avoids that the rotor is moved counter to the actual direction of rotation. The problem should be solved in particular without an extension of the sensors. (Thus, for example, no arrangement of an additional Hall sensor is required.)

FIG. 6 shows a slow or stepwise increase of the pulse width modulation in order to overcome external forces slowly. By a successive increase in the PWM can be largely prevented that the rotor by an external

Force is turned in the wrong direction, which would result in a wrong initialization.

Fig. 7 shows an inventive method to determine the correct position of the rotor can. For this purpose, first the two possible positions 1, 2 of the rotor, which are possible on the basis of the present Hall sensor values, are determined. It is set a desired value 16, which lies between these two positions 1, 2. Will now a corresponding commutation applied to approach this setpoint 16, so there is a direction of movement 21 to the right (with respect to the plane), if the first position 14, the actual starting position of the rotor

Electric machine was. If the actual starting position was position 15, a movement 22 to the left (with regard to the plane of the drawing) results from the applied commutation. It follows that based on this

Depending on the actual position of the rotor results in a different direction of rotation, which can be used to determine the actual rotor position.

There is basically the possibility that external forces act on the rotor of the electric machine and therefore falsify a measurement result obtained by a method mentioned above. For example, the electric motor could be a servomotor of a steering assistance of a vehicle. If, for example, the relevant steering wheel is held in place, an external force acts and a force acts

Commutation of the electric machine will not lead to a corresponding movement of the rotor.

FIG. 8 shows a particular embodiment of a method in which PWM phases 17, 18 alternately lead to the generation of Hall sensor values 19, 20. By the

PWM phases 17, 18 are to be generated pulsating Hall sensor values 19, 20.

If alternating Hall sensor values 19, 20 result, it can be assumed that no (relevant) external forces act and therefore the measurement result is correct. The PWM phases 17, 18 are formed as rising and falling stairs, respectively, to form a successively increasing force. This can be used to overcome existing external forces gradually, without resulting in an initial "overreacting".

FIG. 9 shows a further variant of a method according to the invention in which a larger force (higher PWM) is used to start from the outset

To overcome forces (for example, the steering wheel is held). Was started in the process of FIG. 8 with a PWM of 0%, 1%, 2%, 3%, so can Alternatively, according to the method of Fig. 9 with a PWM of 5%, 6%, 7%, 8%, 9% to be started.

FIG. 10 shows a further variant in the case of between individual PWM phases

Waiting times / breaks are inserted. During the waiting / pause the electric motor can continue to turn. As soon as a new PWM is output, the current Hall sensor value is saved (Start_Hall_Pattern). After changing a Hall sensor value, the new Hall sensor value is compared with the current value before the output. This allows the motor to follow its own motion through the test PWM.

11 shows a method according to the invention as a flow chart.

It should be noted that the term "comprise" further elements or

Does not preclude procedural steps, just as the term "a" and "an" does not preclude several elements and steps.

The reference numerals used are for convenience of reference only and are not to be considered as limiting, the scope of the invention being indicated by the claims.

LIST OF REFERENCE SIGNS

1 pole arrangement rotor

2 first Hall sensor

3 second Hall sensor

4 third Hall sensor

5 magnetic sensor ring

6 magnetic sensor ring

7 direction of rotation

8 assumed, wrong, position

9 correct position

10 wrong commutation

11 correct commutation

12 force pointing in the right direction

13 force pointing in the wrong direction

14 first position

15 second position

16 Default / Target

17 rising stairs PWM

18 falling stairs PWM

19 high Hall sensor value

20 low Hall sensor value

21 first direction of movement

22 second direction of movement

23 Determining the potentially possible positions of the rotor

24 Determining a Target Position

25 Creating a commutation to reach the target position

26 Determining the direction of rotation of the rotor

27 Determining the actual position based on the direction of rotation

Claims

A method of determining the position of a rotor of an electric machine, comprising the steps of:

determining the potentially possible positions of the rotor (23),

determine a target position (24),

Creating a commutation to reach the target position (25) and

determine the direction of rotation of the rotor (26).

2. The method of claim 1, further comprising the step of:

determine the position based on the direction of rotation (27).

3. The method according to any one of claims 1 or 2, further comprising the steps n-times default target position,

n times corresponding commutation and

Determining the direction of rotation n times.

4. The method of claim 3, wherein n = 2, 3, 4, 5, 6, 7, 8 or any natural value and / or being the same by the commutations

5. The method according to any one of the preceding claims, wherein between individual PWMs a same waiting time or different waiting times are inserted.

6. A steering system for a vehicle with a control unit, wherein the control unit has a storage means with a computer program stored thereon, wherein the computer program for carrying out a method according to one of claims 1 to 5 is configured.

7. Computer program for carrying out a method according to one of claims 1 to 5.

A computer program product comprising program code means stored on a computer readable medium for carrying out the method of any one of claims 1 to 5 when said program code means are executed on a computer.