DE102017125956A1 - Method for operating an electric drive, preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner - Google Patents

Abstract

The invention relates to a method for operating an electric drive (A), preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner,
the electric drive (A)
A voltage source (Q),
• an electric motor (M) and
A control unit (S),
the method with at least the steps:
Operating (100) of the electric motor (M) by the control unit (S) at a predetermined speed by means of a pulse width modulated voltage (Uq) of the voltage source (Q) with a predetermined duty cycle,
Detecting (200) the voltage (Uq) of the voltage source (Q),
Determining (300) the effective voltage (Ueff) applied to the electric motor (M) by multiplying the duty cycle by the voltage (Uq) of the voltage source (Q),
Determining (400) the induced voltage (Ui) of the electric motor (M), and
• Determining (500) a load indicator of the electric motor (M) by subtracting the induced voltage (Ui) of the electric motor (M) from the effective voltage applied to the electric motor (M) (Ueff).

Description

The invention relates to a method for operating an electric drive, preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, according to claim 1 and a household appliance, preferably a vacuum cleaner and / or a vacuum cleaner, according to claim 12.

In the field of household appliances vacuum cleaners are known, which serve the cleaning of surfaces.

A vacuum cleaner is a cleaning device that is equipped with a blower that generates a vacuum. On the suction side of the vacuum cleaner, a suction opening is provided which can be guided by the user in a targeted manner over the surfaces to be cleaned. The air taken in by the blower usually flows through several filters; which components such as dust, usually house dust, as well as smaller dirt particles can filter out of the air stream. The air leaves the vacuum cleaner far cleaner as it has flowed into it. In order to improve the cleaning effect of the surfaces to be cleaned, the suction opening usually has a rotatable brush, which can stir up the components of the surface to be cleaned in the air flow. The blower has an electric blower motor and the brush has an electric brush motor.

A disadvantage of known vacuum cleaners is that an operator input is required by the user to set a mode of operation of the blower and brush. This can be perceived as annoying. Also, this can be forgotten so that the vacuum cleaner is most likely operated with a non-optimal cleaning setting.

A further disadvantage is that it depends on the choice of operating mode by the user, whether or how much an optimal cleaning setting for the surface to be cleaned is actually found. This can very easily lead to incorrect settings, especially with changing and especially with frequently changing types of surfaces to be cleaned.

The invention thus provides the problem of providing a method for operating an electric drive, preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, so that the electric drive automatically to different load conditions, in particular to different surfaces to be cleaned, can be set with a maximum possible operating point. This should be done better and / or easier, preferably with less or even completely without sensors than previously known. Preferably, this should be as energy efficient as possible, i. with the lowest possible input power of the electric fan motor and / or the electric brush motor, done.

According to the invention, this problem is solved by a method having the features of patent claim 1 and by a control unit having the features of patent claim 12 and a domestic appliance having the features of patent claim 13. Advantageous embodiments and further developments of the invention will become apparent from the following subclaims.

• • Betreiben des Elektromotors seitens der Steuerungseinheit mit einer vorbestimmten Drehzahl mittels einer pulsweitenmodulierten Spannung der Spannungsquelle mit einem vorbestimmten Tastgrad,
• • Erfassen der Spannung der Spannungsquelle,
• • Bestimmen der effektiv am Elektromotor anliegenden Spannung durch Multiplizieren des Tastgrads mit der Spannung der Spannungsquelle,
• • Bestimmen der induzierten Spannung des Elektromotors, und
• • Bestimmen eines Lastindikators des Elektromotors durch Subtrahieren der induzierten Spannung des Elektromotors von der effektiv am Elektromotor anliegenden Spannung.

The invention thus relates to a method for operating an electric drive, preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, wherein the electric drive comprises a voltage source, an electric motor and a control unit. The method has at least the steps:

• Operating the electric motor on the part of the control unit at a predetermined speed by means of a pulse-width-modulated voltage of the voltage source with a predetermined duty cycle,
• Detecting the voltage of the voltage source,
• Determining the effective voltage applied to the electric motor by multiplying the duty cycle by the voltage of the voltage source,
• • Determining the induced voltage of the electric motor, and
• • determining a load indicator of the electric motor by subtracting the induced voltage of the electric motor from the effective voltage applied to the electric motor.

The voltage source is preferably a DC voltage source. The voltage source can be a power supply network. Preferably, however, the voltage source is a battery or a rechargeable battery. The duty factor, also called the modulation rate, indicates the ratio of the pulse duration to the period duration for a periodic sequence of pulses, as here the voltage pulses.

The invention is based on the finding that in this way a load indicator of an electric motor can be determined in order to be able to make a statement about the external load currently applied to the electric motor. As a result, different load conditions can be distinguished from each other. Additional sensors can be dispensed with.

The knowledge of the present invention determined current load of the electric motor can be used to the power of the electric motor control or regulate. Thus, the power of the electric motor of the applied load can be optimally adapted. If the method according to the invention is applied to an electric motor or to a plurality of electric motors of a blower or a brush of a vacuum cleaner or a vacuum cleaner, the optimum speed or the optimum performance of the floor brush and / or the optimum speed or the optimum performance of the blower can be achieved according to the invention become.

This can on the one hand have the advantage that the electric motor can be operated energy-efficiently. This can keep the consumption of electrical energy as low as possible while maintaining adequate power at the same time as the applied load. As a result, e.g. In the application of the method according to the invention to an electric drive of a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, a good dust absorption with low energy consumption can be achieved. If a battery or accumulator-powered device is used, the term can be extended. In other words, an optimal ratio of dust pickup to input power can be achieved.

It is also advantageous that its life can be extended by a load-dependent operation of the electric motor, since unnecessarily powerful operating conditions can be avoided. This can also have a positive effect on the life of the accumulator in the case of an accumulator-operated device. In other words, a conservation of the electric motor and, if necessary, of the accumulator can be achieved by the lowest possible input power of the electric motor.

It is also advantageous in the application of the method according to the invention to an accumulator-operated device that limit values of the electrical power can be maintained in the case of future regulation for accumulator-operated devices, since the applied load is determined according to the invention and the maximum electric power available for this purpose, which is the accumulator may be taken, can be specified.

It is also advantageous that detection of overloading of the electric motor can take place via the specific load of the electric motor. In this case, the electric motor can be operated with a lower and permissible power or, if necessary, be switched off in order to avoid damaging the electric motor.

In general, it can also be said that the drives in vacuum cleaners or in vacuuming robots can generally only be controlled with considerable effort, since both the load and the input parameters, in particular the motor voltage, vary greatly during operation. The ultimate negative pressure and the indirect volumetric flow depend on several external factors, which are difficult to combine. An essential approach to simple control and in particular suction power control of vacuum cleaner drives according to the invention is the knowledge of the speed of the motor and its output torque, which is proportional to the current. The use of PMDC motors (English: permanently magnet direct current electric motor) with their electrical characteristics opens up simplified sensing and thus control possibilities compared to normal RSM machines (series-wound motors).

• • Bestimmen des Drehmoments und bzw. oder des Stroms des Elektromotors durch Multiplizieren des Lastindikators mit einem vorbestimmten Faktor.

According to one aspect of the invention, the method has at least the further step:

• • Determining the torque and / or the current of the electric motor by multiplying the load indicator by a predetermined factor.

This aspect of the present invention is based on the finding that the load indicator of the electric motor is both proportional to the torque and proportional to the current of the electric motor. Thus, the load indicator can be converted by multiplication into the torque or current of the electric motor, e.g. directly to regulate. Likewise, the findings described above can also be applied to the specific torque or current.

• • Unterbrechen der pulsweitenmodulierten Spannung der Spannungsquelle am Elektromotor,
• • zu einem ersten Messzeitpunkt, während dem ein Strom durch den Freilauf fließt, Erfassen der Spannung der Spannungsquelle,
• • zu einem zweiten Messzeitpunkt, während dem kein Strom mehr durch den Freilauf fließt, Erfassen einer überlagerten Spannung des Elektromotors, und
• • Bestimmen der induzierten Spannung des Elektromotors durch Subtrahieren der überlagerten Spannung des Elektromotors von der Spannung der Spannungsquelle.

According to a further aspect of the invention, the electric drive further comprises a freewheel which is arranged parallel to the electric motor. Furthermore, determining the induced voltage of the electric motor comprises at least the steps:

• Interrupting the pulse width modulated voltage of the voltage source at the electric motor,
• At a first measuring time during which a current flows through the freewheel, detecting the voltage of the voltage source,
• At a second measuring time during which no current flows through the freewheel, detecting a superimposed voltage of the electric motor, and
• • Determining the induced voltage of the electric motor by subtracting the superimposed voltage of the electric motor from the voltage of the voltage source.

In this way, according to the invention, the induced voltage of the electric motor can be determined without this having to be measured by additional measures. For this purpose, the actual pulse width modulated operation of the electric motor can be interrupted for such a short time, for example every 100 ms for about 0.5 ms, that this is imperceptible to the user. During this brief interruption of operation, initially, as long as a current flows through the freewheel, the voltage of the voltage source is detected. After the decay of the current then a superimposed voltage of the electric motor is detected. Subsequently, the normal operation of the electric motor can be resumed.

From these two voltages, the induced voltage of the electric motor can be determined by subtracting. This can, as described above, be used to determine the load indicator. Alternatively or additionally, the specific induced voltage of the electric motor can also be used for other purposes.

The freewheel can be designed as a passive freewheel by means of a diode. This freewheel can be realized very easily and inexpensively, but has a non-negligible power loss due to the voltage drop in the forward direction.

Preferably, therefore, the freewheel may alternatively be described as an active freewheel, e.g. be carried out by means of a correspondingly controlled MOSFET (metal oxide semiconductor field effect transistor). Here, although the realization is complicated, among other things, since a control at the appropriate times is required, but the power loss compared to a diode freewheel is significantly reduced.

• • Bestimmen der Drehzahl des Elektromotors durch Multiplizieren der induzierten Spannung des Elektromotors mit einem vorbestimmten Faktor.

According to a further aspect of the invention, the method has at least the further step:

• • Determining the speed of the electric motor by multiplying the induced voltage of the electric motor with a predetermined factor.

This aspect of the present invention is based on the finding that the induced voltage of the electric motor is proportional to the rotational speed of the electric motor. Thus, the rotational speed of the electric motor can be obtained from its induced voltage. The speed can e.g. be used for a speed control of the electric motor, without the need for a separate speed sensor must be used.

• • für den Fall, dass der Elektromotor ausgebildet ist, ein Gebläse oder eine Bürste eines Staubsaugers oder eines Staubsaugroboters anzutreiben, Vergleichen des Lastindikators und bzw. oder des Drehmoments und bzw. oder des Stroms des Elektromotors mit wenigstens einem Referenzwert und bzw. oder mit wenigstens einem Schwellenwert, welcher einer Art eines Untergrunds entspricht, und
• • Betreiben des Elektromotors seitens der Steuerungseinheit in Abhängigkeit der erkannten Art des Untergrunds.

According to a further aspect of the invention, the method comprises at least the further steps:

• In the event that the electric motor is designed to drive a blower or a brush of a vacuum cleaner or a vacuum cleaner, comparing the load indicator and or or the torque and / or the current of the electric motor with at least one reference value and / or at least a threshold corresponding to a type of underground, and
• • Operation of the electric motor by the control unit as a function of the detected type of subsurface.

In this way, the load indicator determined according to the invention or the torque obtained therefrom and / or the current of the electric motor obtained therefrom can be used for the application of the method according to the invention to a blower or to a brush of a vacuum cleaner or a vacuum cleaner to recognize the underground to be cleaned. This can be done by providing data to the control unit of the electric motor which correspond to different substrates, so that the present underground can be selected from the deposited undergrounds and thus recognized by comparison. For this purpose, the data can be specified as reference values or as threshold values.

In this way, it can be achieved according to the invention that a vacuum cleaner or a vacuum cleaner robot can identify the substrate to be cleaned and adjust itself automatically with respect to the performance of its fan and / or its brush on the ground. This can thus be done sensorless.

This aspect of the present invention is based on the finding that on hard floors, the brush contributes relatively little to the suction, the suction power of the blower, however, already. On carpet it is rather the other way round. Therefore, in this way an optimal cleaning effect can be achieved while maintaining the highest possible energy efficiency. In the case of a battery or accumulator-operated device, the running time can thereby be extended. Even a conservation of the substrate to be cleaned by an adapted and thus not unnecessarily strong blower power or brush activity can be achieved.

According to another aspect of the invention, in the event that the electric motor is designed to drive a brush of a vacuum cleaner or a vacuum cleaner, a Reference value and or or a threshold predetermined so that it can be distinguished by comparing between the absence and the presence of the brush. In other words, the absence of the brush, the electric motor is quasi idle in this state, lead to such a low load of the electric motor, that this load state of the electric motor can be distinguished from the other load conditions of the electric motor and thereby recognized. In this case, preferably, the electric motor of the brush off to avoid damage to the electric motor itself, the vacuum cleaner or the vacuum cleaner robot and the substrate. Furthermore, this electrical energy can be saved, which would not contribute to the cleaning result due to lack of existing brush.

According to a further aspect of the invention, the operation of the electric motor by the control unit is speed-controlled. As a result, a speed-controlled operation of the electric motor can be achieved, as already described above. This can be done without additional speed sensor.

According to a further aspect of the invention takes place in the event that a comparatively high carpet is detected as a substrate (such as a previously defined torque upper limit) and the electric motor is designed to drive a brush of a vacuum cleaner or a vacuum cleaner, the operation of the electric motor on the part the control unit with a comparatively low speed. This aspect of the invention is based on the finding that a comparatively high carpet can be strained by the brush of a vacuum cleaner or a vacuum cleaner. Therefore, if such a carpet is recognized according to the invention, the performance of the brush of the vacuum cleaner or the vacuum cleaner robot to protect the carpet can be set lower than in any other ground.

According to a further aspect of the invention, the determination of the induced voltage of the electric motor and / or the detection of the superposed voltage of the electric motor via a voltage divider, which is arranged in series with the electric motor and parallel to the control unit. As a result, the detection of the respective voltage can be implemented simply and reliably within the drive.

According to a further aspect of the invention, the voltage of the voltage source is detected at the first measurement time and / or at the second measurement time by means of a detection over a predetermined measurement period with subsequent averaging. As a result, fluctuations of the measurement signal as well as measurement noise can be compensated for and thus reduced. This can increase the quality of the measurement and thus the reliability of the conclusions based on it.

According to a further aspect of the invention, the electric motor is an electric motor of a blower or an electric motor of a brush of a vacuum cleaner or a vacuum cleaner. In this way, the features and advantages described above can be used in such devices, which can be advantageous in particular in the case of battery or accumulator operated devices in terms of energy efficiency. The present invention also relates to a control unit for operating an electric drive, preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, wherein the control unit is designed to carry out a method as described above.

The present invention also relates to a household appliance, preferably a vacuum cleaner and / or a vacuum cleaner, preferably accumulator-operated, with at least one electric drive, at least one voltage source, at least one electric motor and at least one control unit, wherein the control unit is formed, a method as described above perform. In this way, the properties and advantages of the method according to the invention described above can be used with such devices, which may be advantageous in terms of energy efficiency, in particular in the case of battery-operated or accumulator-operated devices.

The present invention also includes the recognition that, due to the inventively speed or load controlled operation of the electric motor, which takes into account the effectively applied voltage of the electric motor, when using a battery as a voltage source, a higher number of battery cells can be used as previously known, since the Operation of the electric motor is independent of the voltage of the voltage source. Thus, the running time of the device, which has the electric motor operated according to the invention, be increased by the higher number of battery cells.

The present invention further includes the knowledge that a decreasing voltage of the voltage source, for example due to a weakening battery or a weakening accumulator, can be compensated by adjusting the duty cycle of the pulse width modulated voltage again. Thus, the operation of the electric drive can be continued unabated in this case. For the same reasons It is also possible to use different types of batteries and accumulators from different manufacturers with possibly different voltages. It is also possible to offer an accumulator with a larger number of cells, which lead to a higher voltage, with longer maturities. This too can be compensated by the pulse width modulated voltage.

• 1 ein Schaltbild eines elektrischen Antriebs;
• 2 ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens zum Betrieb des elektrischen Antriebs der 1;
• 3 ein Messdiagramm eines Betriebs des elektrischen Antriebs der 1; und
• 4 ein Messdiagramm von verschiedenen Proportionalitäten des elektrischen Antriebs der 1.

An embodiment of the invention is shown purely schematically in the drawings and will be described in more detail below. It shows

• 1 a circuit diagram of an electric drive;
• 2 a flow diagram of a method according to the invention for operating the electric drive of 1 ;
• 3 a measurement diagram of an electric drive operation of the 1 ; and
• 4 a measurement diagram of different proportions of the electric drive of 1 ,

1 shows a circuit diagram of an electric drive A , The electric drive A has a voltage source Q in the form of a rechargeable battery Q on which a tension U _q or a battery voltage U _q with 24V. It is an electric motor M present, parallel to a diode D ₁ which is arranged by a diode current I _D1 can be flowed through. The electric motor M and the diode D ₁ are together in series to the accumulator Q connected. The passive diode freewheel shown here and described below is merely to be understood as an example, the function may alternatively be ensured by an active freewheel, such as by a correspondingly controlled MOSFET.

Next in series is also a control unit S with a voltage divider, which by a first ohmic resistance R1 and by a second ohmic resistance R2 is formed. About the voltage divider can be a first voltage U ₁ , which over the first ohmic resistance R ₁ falls, be detected. The control unit S is as a microcontroller S executed. This closes the circuit to the accumulator Q out.

According to the present embodiment, the electric drive A used in a vacuum cleaner for driving the floor brush. On the basis of this embodiment, various advantages of the method according to the invention will be considered in more detail.

2 shows a flowchart of a method according to the invention for operating the electric drive of 1 ,

In a first step 100 becomes the electric motor M on the part of the control unit S at a predetermined speed by means of a pulse width modulated battery voltage U _q operated with a predetermined duty cycle, see in the diagram of 3 left before a first measurement time T ₁ , In this time will be in a second step 200 the accumulator voltage U _q detected. Furthermore, in this time in a third step 300 which is effective on the electric motor M voltage applied U _eff by multiplying the duty cycle by the accumulator voltage U _q certainly.

Subsequently, in a fourth step 400 determining the induced voltage U _i of the electric motor M , This is done in a first step 410 the pulse width modulated accumulator voltage U _q on the electric motor M interrupted. During immediately after interrupting the battery voltage U _q through the diode current I _D1 the diode D ₁ is still maintained, takes place at the first measurement time T ₁ in a second sub-step 420 a detection of the battery voltage U _q , please refer 3 , Is the diode current I _D1 the diode D ₁ subsided, so takes place at a second measurement time T ₂ in a third step 430 a detection of a superimposed voltage U _k of the electric motor M , see also 3 , Subsequently, the pulse width modulated battery voltage U _q on the electric motor M abut again, so that the operation of the electric motor M as before can be resumed. Regardless, this is done in a fourth sub-step 440 determining the induced voltage U _i of the electric motor M by subtracting the superimposed voltage U _k of the electric motor M from the accumulator voltage U _q , so now the induced voltage U _i of the electric motor M is available.

In a fifth step 500 then takes place a determination of a load indicator of the electric motor M by subtracting the induced voltage U _i of the electric motor M from the effective on the electric motor M applied voltage U _eff , Subsequently, in a first sixth step 600a the torque and or or the current of the electric motor M by multiplying the load indicator by a predetermined factor. Parallel will be in a second sixth step 600b the speed of the electric motor M by multiplying the induced voltage U _i of the electric motor M determined with a predetermined factor.

Subsequently, in a seventh step 700 a comparison of the load indicator and or or the torque and or or the current of the electric motor M with at least one reference value and / or with at least one threshold value which corresponds to a type of underground. In an eighth step 800 then takes place an operation of the electric motor M on the part of the control unit S depending on the detected type of underground.

Based on this, the performance of the floor brush can now be regulated. In addition to the detection of the ground, the presence or absence of the floor brush can be detected. Furthermore, the speed of the electric motor M determined sensorless and used eg for a speed control.

These respective proportionalities, which are the predetermined factors for determining the torque or the current or the rotational speed of the electric motor M can be used are exemplary of 4 refer to.

LIST OF REFERENCE NUMBERS

A

electric drive

D ₁

diode

I _D1

diode current

M

electric motor

Q

Voltage source; accumulator

R ₁

first ohmic resistance

R ₂

second ohmic resistance

S

Control unit; microcontroller

t

Time

T ₁

first measuring time or measuring period

T ₂

second measuring time or measuring period

U ₁

electrical voltage across first ohmic resistance R ₁

U _eff

effective voltage of the electric motor M

U _i

induced voltage of the electric motor M

U _k

superimposed voltage of the electric motor M

U _q

Voltage of the voltage source Q ; Source voltage; accumulator

V

measuring signal

100

Operating the electric motor M with pulse width modulated voltage U _q

200

Detecting the voltage U _q the voltage source Q

300

Determine the effective on the electric motor M applied voltage U _eff

400

Determine the induced voltage U _i of the electric motor M

410

Interrupting the pulse width modulated voltage U _q on the electric motor M

420

Detecting the voltage U _q at a first measuring time T ₁

430

Detecting a superimposed voltage U _k of the electric motor M at a second time of measurement T ₂

440

Determine the induced voltage U _i of the electric motor M by subtracting

500

Determining a load indicator of the electric motor M by subtracting

600a

Determining the torque and / or the current of the electric motor M

600b

Determining the speed of the electric motor M by multiplying

700

Compare the load indicator and / or the torque and / or the current of the electric motor M

800

Operating the electric motor M depending on the detected type of underground

Claims (13)

Method for operating an electric drive (A), preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, the electric drive (A) having a voltage source (Q), an electric motor (M) and a control unit (S), the method comprising at least the steps of: operating (100) the electric motor (M) by the control unit (S) at a predetermined speed by means of a pulse width modulated voltage (U _q ) of the voltage source (Q) at a predetermined duty cycle, detecting (200) the voltage (U _q ) of the voltage source (Q), determining (300) the effective voltage (U _eff ) applied to the electric motor (M) by multiplying the duty cycle by the voltage (U _q ) of the voltage source (Q), determining (400) the induced voltage Voltage (U _i ) of the electric motor (M); and determining (500) a load indicator of the electric motor (M) by subtracting the induced voltage (U _i ) of the electric motor (M) from that at the electric motor r (M) applied voltage (Ueff). Method according to Claim 1 with at least the further step of: determining (600a) the torque and / or the current of the electric motor (M) by multiplying the load indicator by a predetermined factor. Method according to Claim 1 or 2 wherein the electric drive (A) further comprises a freewheel (D ₁ ) which is arranged parallel to the electric motor (M), wherein the determining (400) of the induced voltage (U _i ) of the electric motor (M) comprises at least the steps: Interrupting (410) the pulse-width-modulated voltage (U _q ) of the voltage source (Q) at the electric motor (M) at a first measurement time (T ₁ ) during which a current (I _D1 ) flows through the freewheel (D ₁ ), detecting ( 420) of the voltage (U _q ) of the voltage source (Q), at a second measuring time (T ₂ ), during which no current (I _D1 ) flows through the freewheel (D ₁ ), detecting (430) a superimposed voltage (U _k ) of the electric motor (M), and determining (440) the induced voltage (U _i ) of the electric motor (M) by subtracting the superimposed voltage (U _k ) of the electric motor (M) from the voltage (U _q ) of the voltage source (Q ). Method according to Claim 3 with at least the further step of: determining (600b) the rotational speed of the electric motor (M) by multiplying the induced voltage (U _i ) of the electric motor (M) by a predetermined factor. Method according to one of the preceding claims, with at least the further steps: in the event that the electric motor (M) is adapted to drive a blower or a brush of a vacuum cleaner or a vacuum cleaner, comparing (700) the load indicator and / or the torque and / or the current of the electric motor (M) with at least one reference value and / or with at least one threshold, which corresponds to a type of underground, and Operating (800) the electric motor (M) by the control unit (S) as a function of the detected type of underground. Method according to Claim 5 characterized in that, in the case where the electric motor (M) is adapted to drive a brush of a vacuum cleaner or a vacuum cleaner, a reference value and / or a threshold is predetermined so that by comparing (700) between the absence and the Presence of the brush can be distinguished. Method according to Claim 5 or 6 , characterized in that the operation (800) of the electric motor (M) by the control unit (S) is speed-controlled. Method according to Claim 5 to 7 characterized in that, in the case where a comparatively high carpet is recognized as a substrate and the electric motor (M) is adapted to drive a brush of a vacuum cleaner or a vacuum cleaner, the operation (800) of the electric motor (M) by the control unit ( S) takes place at a relatively low speed. Method according to one of the preceding claims, characterized in that the determination (400) of the induced voltage (U _i ) of the electric motor (M) and / or the detection (430) of the superimposed voltage (U _k ) of the electric motor (M) via a Voltage divider (R ₁ , R ₂ ) takes place, which is arranged in series with the electric motor (M) and parallel to the control unit (S). Method according to one of Claims 3 to 9 , characterized in that the detection (430; 440) of the voltage (U _q ) of the voltage source (Q) at the first measuring time (T ₁ ) and / or at the second measuring time (T ₂ ) by means of detecting (430; 440) over a predetermined measuring period (T ₁ ; T ₂ ) followed by averaging. Method according to one of the preceding claims, characterized in that the electric motor (M) is an electric motor (M) of a blower or an electric motor (M) of a brush of a vacuum cleaner or a vacuum cleaner. Control unit (S) for operating an electric drive (A), preferably a blower and / or a brush of a vacuum cleaner or a vacuum cleaner, wherein the control unit (S) is formed, a method according to one of Claims 1 to 11 perform. Domestic appliance, preferably vacuum cleaner and / or vacuum cleaner, preferably accumulator-operated, with at least one electric drive (A), at least one voltage source (Q), at least one electric motor (M) and at least one control unit (S) Claim 12 ,

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