DE102012110049A1 - Method for determining position of positioning device that is driven by brushless direct-current motor, involves triggering control unit in order to exit standby mode such that signals of position sensors are determined - Google Patents

Abstract

The method involves determining a rotation position of an electromotor i.e. brushless direct-current (DC) motor, in a predetermined angular range by signals of position sensors i.e. hall sensors. Current signals are stored in a non volatile memory before a control unit goes into a standby mode. One of the sensors is supplied with energy at the standby mode such that the signal of the corresponding sensor is monitored. The control unit is triggered to exit the standby mode such that the signals of all sensors are determined when the monitored signal is changed from the corresponding state. Independent claims are also included for the following: (1) a control unit for determination of a position of a positioning device (2) a brushless DC motor.

Description

FIELD OF THE INVENTION

The invention relates to a method and a control unit for determining the position of a control device, as well as a brushless DC motor with such a control unit.

BACKGROUND OF THE INVENTION

Brushless DC motors have position sensors for commutation control. As position sensors, for example, Hall sensors are used, which cooperate with the rotor magnet or a separate position detecting magnet to detect the rotational position of the motor. The rotary position detection is necessary to control the stator windings, or commutation. An example of a motor controller for a brushless DC motor is shown in FIG US 2011/0316459 A1 described.

In the following description, reference will be made, in essence, to a three-phase permanent magnet motor using three Hall sensors for position detection. However, the invention is not limited thereto, and in particular more or fewer Hall sensors and other position sensors can be used.

An example of a brushless DC motor in which the invention can be used is in 1a shown schematically. The in 1a schematically shown in sectional view electric motor 1 is a DC motor, with a stator 2 and a rotor 3 , The stator 2 carries stator windings 5 on a variety of pole teeth 4 , The rotor 3 includes a variety of rotor magnets 7 standing on a rotor yoke 8th are applied, and is rotatable with a shaft 6 connected. Between rotor 3 and stator 2 is formed a working gap. One will understand that 1a merely by way of example shows one of many different electric motors in which the method and actuator of this invention may be used.

In the exemplary electric motor is at a front end of a circuit board 9 arranged in 1b is shown schematically. The circuit board 9 can the control electronics for the electric motor 1 wear. On the circuit board 9 In the example shown, three Hall sensors H1, H2, H3 or other magnetic sensors are applied, which serve as position sensors for detecting the rotational position of the electric motor 1 serve. Both the in 1b shown arrangement of the position sensors as well as the use of Hall sensors are merely exemplary and are not intended to limit the invention.

1a shows a conventional electric motor 1 in which the method and the adjusting device of the invention can be used. However, the method and actuator may also be used in conjunction with a variety of other electric motor configurations, whether those already known today or those yet to be developed.

2 shows the waveform of three Hall sensors for detecting the rotational position of the engine, wherein the three Hall sensors are assigned to the three phases U, V, W of the DC motor.

The outputs of the Hall sensors are logic high, "1", or logic low, "0" depending on their relative position to the position sensing magnet. The output signal of each sensor can thus assume the digital value 1 or 0. The output signals of the Hall sensors can be combined into a pattern or pattern at any time, whereby there are eight possible combinations. In practice, the pattern [0,0,0], ie 0, and the pattern [1,1,1], ie 7, basically do not occur. Such patterns are therefore treated as errors. The remaining six Hall patterns are repeated in succession: Via a clockwise electrical turn (CW), the Hall pattern of the three sensors [HU, HV, HW] develops as follows:
[0,0,1], [0,1,1], [0,1,0], [1,1,0], [1,0,0], [1,0,1], [0 , 0,1], [0,1,1], ... etc.

In the embodiment shown, each change of the Hall pattern by one increment, or depending on the direction of rotation by a decrement, corresponds to a change of 60 ° electrically, the electrical angle in turn being dependent on the mechanical angle and the number of pole pairs. As a result, the rotational position of the motor can be determined with sufficient accuracy for the commutation.

3 shows an example of a drive circuit of a brushless DC motor, which can be used in the invention. In the embodiment, the three phases of the brushless DC motor are in star connection 34 switched, with the stator windings or phase windings 5 are connected to the connection points U, V, W. About the star connection 34 are the stator windings 5 with a bridge circuit 30 connected to an upper bridge branch 31 and a lower bridge branch 32 having. Each bridge branch contains three phase connections for the three phases U, V, W of the stator, the phase connections of the upper bridge branch 31 UH, VH and WH and the phase terminals of the lower bridge branch 32 labeled UL, VL and WL. The Phase connections and thus the phase windings U, V, W are via switches 33 , for example MOSFETs, energized, the switches 33 be driven so that they each form a current path between the input voltage Uin and ground GND, for example, a current path from WH to VL, "WH-VL", a current path from WH to UL, "WH-UL", etc., wherein the bridge circuit 30 is connected to the ground terminal GND via a resistor Rs. As a result, the phase terminals U, V, W for the commutation of the DC motor can be alternately energized, it being possible to operate the motor in both directions.

Brushless DC motors are used as actuators, for example in the automotive sector for seat height and tilt adjustment and flap valve, just to name a few examples. When the motors operate an actuator, it is important to precisely detect, control, and reconstruct the actuator adjustment path when the engine is restarted. In the prior art, it is bekamt to refer to the engine for this purpose initially on a mechanical end stop on a normalization cycle, with the thus learned rotational position of the engine and the associated position of the actuator should not be lost.

In applications in the automotive sector, but also in many other areas, high demands are placed on the quiescent current operation beyond. That is, electrical loads, including DC motors and their controller, must be able to go into standby mode as long as they are not needed. In this standby mode, they may only have a minimum residual charge, so they can not permanently determine their position, for example. This requirement is in practice, for example, solved by calculating the position of the DC motors through the evaluation of the Hall sensors and stored during the preparation of the standby operation in a non-volatile memory. When the engine is then reactivated and a new actuation of the actuator is to be performed, the controller may retrieve the last displacement and associated rotational position of the engine from memory. An example of such a system is in DE 197 02 931 C1 described.

In this solution, however, there is a problem that external influences on the motor shaft, such as shocks or vibrations, may cause an actual position change of the actuator while the engine is in standby mode. These position changes are not recognized by the engine control and are lost. As a result, the position accuracy of the adjusting device can no longer be guaranteed.

It is an object of the invention to provide a method and a control unit for determining the position of a control device and an associated DC motor, with which the position errors described above can be excluded as possible over the entire life of the engine and its control unit.

SUMMARY OF THE INVENTION

This object is achieved by a method according to claim 1, a control unit according to claim 7 and a brushless DC motor according to claim 8.

The invention provides a method for determining the position of an actuating device, which is driven by an electric motor, in particular a brushless DC motor having a control unit and at least two position sensors. The position sensors give depending on the rotational position of the electric motor 1 in each case a signal, wherein the signals of all position sensors, the rotational position of the electric motor 1 uniquely determine within a specified angular range. The current signals are stored in non-volatile memory before the control unit enters standby mode. During standby, one of the position sensors is energized and the signal from this position sensor is monitored. The control unit is woken up to leave standby mode and to detect the signals of all position sensors if the signal of this monitored position sensor changes state.

A defined initial position of the adjusting device can be determined in order to determine a quasi-absolute position of the adjusting device starting from the initial position or a previous position by evaluating the signals of all position sensors incrementally.

In one embodiment, the current quasi-absolute position of the actuator is stored before the control unit goes into standby mode, and in the case of a position change in standby mode, the quasi-absolute position is determined by the before starting the standby mode stored quasi-absolute position is changed by one or more increments in the positive or negative direction of rotation, this change depending on the comparison of the current signals of the position sensors from the signals stored before the start of standby mode and in dependence on the number of edge changes of the monitored Sensors happens.

In one embodiment, the signal output from the position sensors is a logical one high or low signal, "1" or "0", wherein the signals of the position sensors can be combined into a pattern of 1 and 0 signals to determine the rotational position of the electric motor. It can, for. B. first, a pattern can be determined, which corresponds to a defined initial position of the actuator, and during operation of the electric motor 1 a displacement of the adjusting device based on the initial position or a previous position and thus a quasi-absolute position is determined by evaluating changes in the pattern. From this, the current position of the actuator can be derived and stored together with the current pattern when the electric motor 1 stops. When restarting the electric motor then the current position of the actuator is known, and the engine can resume its operation controlled.

Before the control unit goes into standby mode, in one embodiment the current position of the actuator and the current pattern are stored in a non-volatile memory. In this embodiment, when the control unit returns to standby mode, the current pattern is determined and compared with the stored pattern to determine if there is a deviation in the pattern produced by the Hall sensors. If so, then this is an indication that the adjusting device and thus the electric motor have moved during the standby mode, for example, by a vibration of the actuator from the outside. The position of the actuator must then be corrected.

How to relate to 2 can detect, a rotation angle change of the electric motor 1 be reconstructed one or two increments clockwise or counterclockwise from the Hall pattern, because with such a small deviation, the change can still be clearly assigned to the stored pattern. This can be illustrated by the following example:
For example, if the electric motor stops at the pattern [0,1,0] and goes into standby mode, this pattern [0,1,0] and the associated current position of the actuator in a non-volatile memory, such as an EEPROM, filed. If the motor shaft rotates clockwise or counterclockwise by one or two increments during standby mode, this can be reconstructed when the motor restarts. For example, if the motor resumes operation and the current reverb pattern is at [1,0,0] although the transition to standby mode has occurred at a Hall pattern of [0,1,0], then the control unit will detect that the motor has rotated two increments clockwise. The position of the actuator associated with the current Hall pattern can then be corrected as the stored position of the actuator plus two increments (clockwise). As a result, minor external influences on the adjusting device, for. B. by vibration, and the current Hall pattern can always be assigned to the correct position of the position direction.

In the example shown, however, if the deviation of the Hall pattern from the stored pattern is more than two increments, it can no longer be uniquely determined whether this was caused by a clockwise or counterclockwise rotation of the electric motor. Furthermore, in the above example, it is also possible that the motor has rotated more than 360 ° electrically clockwise or counterclockwise, for example by 8, 14 or 20 increments, etc. For from the stored and the current Hall Pattern alone, the current electrical angle and thus the current position of the actuator can not be derived.

The invention therefore provides to energize one of the position sensors during standby operation and to monitor the output signal of this position sensor. Typically, the power requirement of such a monitored sensor is about 3 mA, ideally less than 2 mA. The control unit is woken up to the. Leave standby mode when the output of the monitored position sensor changes state. The invention can therefore, even if the control unit of the electric motor is in standby mode, detect movement of the adjusting device and correct accordingly.

In a practical embodiment, the method according to the invention operates on the basis of three position sensors whose output signals relate to the patterns [0,0,1]; [0,1,1]; [0,1,0]; [1,1,0]; [1,0,0]; and [1,0,1] are summarized to the rotational position of the electric motor 1 in increments of 60 ° (electrical). The position of the actuator is corrected after evaluation of this pattern if necessary.

In one embodiment of the invention, the control unit is woken up when the output signal of the monitored position sensor has an edge change. The control unit is initialized as soon as it leaves standby mode and determines the current pattern of the position sensors and compares this with the stored pattern. This happens within a period of time that is shorter than the maximum time it takes the electric motor to rotate by another increment by external action. In practice, in the event that the electric motor is hit by a blow or Vibration is set in rotation, the initial rotational speed be low enough to detect the edges of the sensor signal in a steady state, even if the control unit must first be awakened and initialized by a first edge. In a practical example, the time required for this purpose may be on the order of about 2 ms, wherein it is not to be expected that a rotation of the electric motor by more than 60 ° has taken place electrically in this period.

The correction of the position of the actuator is made in consideration of the change in the direction of the edge of the output signal of the monitored position sensor, because a rising or falling edge, starting from the stored pattern, the direction of the change in position of the actuator recognizes.

According to a further aspect of the invention, the control unit checks whether the wake-up signal originates from the position sensor or from another source, for example by external actuation of the setting device. Only if the wake-up signal originates from the position sensor, the change in the output signal of the monitored position sensor must be taken into account in the position correction.

The invention also provides a control unit for determining the position of an actuating device, which is driven by an electric motor. The control unit has a computer program which is set up to carry out the method described above.

The invention also provides a brushless DC motor with a control unit and three position sensors. The control unit is configured to carry out the method described above for actuating an actuating device. This can be realized, for example, by means of a computer program, by means of a sequence defined by a hardware circuit, by means of regulations stored in tabular form or in some other way.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference to an embodiment. In the figures show:

1a an example of a brushless DC motor in which the invention can be used;

1b a schematically illustrated circuit board for installation in the brushless DC motor of 1a ;

2 the output signals of three Hall sensors for detecting the rotational position of the electric motor;

3 an example of a circuit for driving a DC motor; and

4 a flow chart according to an embodiment of the method according to the invention.

DESCRIPTION OF THE EMBODIMENTS

The invention is described below with reference to the example of a brushless DC motor having a control unit and three position sensors, for. B. Hall ICs having. These sensors can be used, for example, in 2 produce output signals shown, wherein the logic high and low output signals, 1 and 0, are generated when north and south poles of a sensor magnet or rotor magnet pass by the respective Hall ICs. As described above, based on the pattern formed by the Hall IC, the rotational position of the rotor can be determined, or reconstructed, depending on which magnetic pole is opposed to which Hall IC.

The engine can be used in 3 have shown drive circuit, wherein the 1a to 3 merely an example of many possible applications of the invention.

An example of the application of the invention is in adjusting devices in the automotive sector, for example, for seat adjustment or as a flap plate. In these areas, high demands are placed on minimum current consumption in standby mode or sleep mode, wherein in standby mode, the power consumption should be, for example <125 uA. The Hall ICs are therefore suitably controlled via a pulse width modulation. For detecting the engine position, the integrated motor control unit of a brushless DC motor can be used according to the invention.

In practice, the motor, in conjunction with the actuator for which it is intended, is initially referenced to a mechanical end stop via a normalization cycle during startup. This will change the position of the actuator and the associated position of the electric motor 1 learned and saved. The method according to the invention is based on the fact that this initial position or every last approached position of the electric motor 1 and the adjusting device stored and used as a starting position for a next adjustment cycle. During operation of the electric motor 1 the control unit permanently detects the Rotational position of the electric motor 1 , derives therefrom the current position of the actuator and stores both for a next adjustment cycle.

The method according to the invention begins in a first step 10 , in which the current rotational position of the electric motor 1 and the position of the actuator during the rotation of the electric motor 1 recorded and in any case be stored when the electric motor 1 stops. The rotational position of the electric motor 1 when using three Hall sensors based on the in 2 It will be understood that the invention is not limited to the use of three position sensors and not to that with reference to FIGS 1a explained signal pattern is limited. The current position of the adjusting device is then calculated on the basis of a previously determined position as the starting position and the change of the signal pattern of the position sensors.

When the electric motor 1 stops, the control unit can be put into standby mode immediately or after a predetermined period of time or by external command, in preparation for the standby operation of the last determined rotational position of the engine and the associated position of the actuator in a non-volatile memory of Control unit, such as an EEPROM, stored, see step 12 ,

In practice, there may be different types, such as the electric motor 1 Leaves the standby mode, which as an example only the request by a user who operates the actuator, or the control by a flank of a monitored position sensor are called. The control unit may for this purpose have a wake-up input, which is coupled to, for example, an external switch and the monitored position sensor. In one embodiment, the controller may be configured to be triggered by a rising or falling edge of one of the position sensors, such as the Hall IC U (see FIG 2 ), is triggered.

In one step 14 receives the control unit of the electric motor 1 a wake-up command and checks the source of the wake-up command, ie if it comes from an external source, eg. B. triggered by actuation of a switch by a user, or by the edge of the monitored position sensor. Depending on the result of the test, the position of the actuator is reconstructed in different ways.

If the control unit detects that the wake-up command came from an external source, such as a switch, it will be in one step 20 reconstructs the position of the actuator based on the current Hall pattern as described above in relation to the prior art. If the Hall pattern corresponds to the stored pattern, no correction of the position of the actuator is necessary, and the current position corresponds to the stored position. If a deviation of the current Hall pattern from the stored Hall pattern by one or two increments is detected, it can be deduced from this that the electric motor 1 has rotated one or two increments clockwise or counterclockwise, and the stored position of the actuator is corrected accordingly and adopted as a new current position. Subsequently, in step 22 the electric motor 1 as long as driven, as the external drive signal is present. This is basically done as in relation to step 10 described. If the external signal drops away, for example because the switch is released, the motor stops and the process continues in step 10 continued.

However, if the source of the wake-up command was a rising or falling edge of the position sensor, then not only the current Hall pattern is compared with the stored Hall pattern for the determination of the position of the actuator, but this rising or falling edge is additionally used, to uniquely determine the position of the actuator. For example, became the electric motor 1 when the pattern [0,1,0] is stopped and goes into standby mode, this pattern [0,1,0] and the corresponding position have been saved. Then, the control unit is awakened by a falling edge of the Hall ICs U and the current pattern of the Hall ICs immediately after the wake-up z. B. [1,0,1], the control unit can recognize on the basis of this information that the motor has rotated by three increments counterclockwise - and not three increments in the clockwise direction, and it can correct the current position of the actuator accordingly and save this new current position; see step 24 ,

Subsequently, the control unit monitors whether further changes of the pattern occur, indicating that the electric motor 1 by external action still further rotates; see step 26 , If so, then these further changes to the pattern are detected to detect and store the current rotational position of the engine, and thus the current position of the actuator, as in step 10 of the described method. In practice, the time required to wake up the control unit from the standby mode and to detect the current Hall pattern is so small that an incremental position detection can be ensured. If the control unit no longer detects any further changes to the Hall pattern, it returns to standby mode; the procedure is in step 12 continued.

The invention makes it possible to accurately and accurately store the position of an actuator over the life of the engine, even when the actuator is moved by external force to it or to the motor shaft, and to ensure a minimum power consumption of the motor and its drive.

LIST OF REFERENCE NUMBERS

1

electric motor

2

stator

3

rotor

4

pole tooth

5

stator windings

6

wave

7

rotor magnets

8th

conclusion

9

circuit board

10, 12, 14, 20, 22, 24, 26

steps

30

bridge circuit

31

Upper bridge branch

32

lower bridge branch

33

switch

34

star connection

AND MANY MORE

Connection points of the phase windings

R _S

resistance

GND

ground connection

Uin

input voltage

UH, VH, WH

Phase connections of the upper bridge branch

UL, VL, WL

Phase connections of the lower bridge branch

H1, H2, H3

Hall sensors

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2011/0316459 A1 [0002]
• DE 19702931 C1 [0012]

Claims (9)

Method for determining the position of a control device that is controlled by an electric motor ( 1 ), which has a control unit and at least two position sensors which depend on the rotational position of the electric motor ( 1 ) each output a signal, wherein the signals of all position sensors, the rotational position of the electric motor ( 1 ) within a predetermined angular range, wherein the current signals are stored in a non-volatile memory before the control unit goes into standby mode, during standby operation energizing one of the position sensors and monitoring the signal of that position sensor and the control unit is woken up to exit standby mode and to detect the signals of all the position sensors if the signal of this monitored position sensor changes state. A method according to claim 1, characterized in that a defined initial position of the adjusting device is determined and that a quasi-absolute position of the adjusting device is determined incrementally starting from the initial position or a previous position by evaluating the signals of all position sensors. Method according to one of the preceding claims, characterized in that the current quasi-absolute position of the position direction is stored before the control unit goes into standby mode. A method according to claim 3, characterized in that in the case of a change in position in standby mode, the quasi-absolute position is determined by changing the stored before the start of the standby operation quasi-absolute position by one or more increments in the positive or negative direction of rotation This change takes place as a function of the comparison of the current signals of the position sensors with the signals stored before the beginning of the standby mode as well as in dependence on the number of edge changes of the monitored sensor. Method according to one of the preceding claims, wherein the electric motor ( 1 ) is a brushless DC motor. Method according to one of the preceding claims, wherein the control unit is woken up when the output signal of the monitored position sensor has an edge change. Control unit for determining the position of an actuating device, which is controlled by an electric motor ( 1 ), the control unit being adapted to carry out the method according to one of the preceding claims. Brushless DC motor with a control unit according to claim 7, characterized in that the DC motor has three position sensors. The brushless DC motor of claim 8, wherein the position sensors are Hall sensors.

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