BE1029754B1 - Method for detecting a jammed drum in a laundry care appliance and laundry care appliance - Google Patents

Abstract

The present invention relates to a method for detecting a drum blockage in a laundry care appliance (3), the laundry care appliance (3) having a rotatable drum (7) which can be driven by a motor (13) via a drive belt (17), the method Steps includes: a) determining at least one or more of the following values of the motor (13): torque-forming current, torque, phase current and/or envelope of the phase current, b) calculating a parameter set from the values determined in step a), c) checking the parameter set to a signal characteristic of drum blockage, d) adapting the control of the motor (13) if a characteristic signal has been detected. The present invention also relates to a laundry care appliance (3) which is designed and set up to carry out the method according to the invention.

Description

Description

Method for detecting a drum blockage in a laundry care device and

laundry care device

The invention relates to a method for detecting a blocked drum in a

Laundry care device and a laundry care device. The subject matter of the invention is defined in the appended claims.

Laundry care devices are used wherever laundry has to be either washed or dried. The places of use extend to both the private

domestic use as well as for industrial use.

In the state of the art, laundry care devices, e.g. as household and commercial dryers,

Domestic and commercial washing machines and machines and washer dryers are known.

Typically, a laundry care appliance includes at least one drum, which is rotatably mounted in relation to a housing surrounding the drum, a motor with a

Motor sprocket, a drive belt that mechanically connects the motor to the motor via the motor sprocket

Drum couples, and a controller that controls the motor. The motor pinion, together with the drive belt, transmits torque from the motor to the drum, which causes the

Drum is rotated in the absence of slip.

The interior of the drum typically has ribs which, during normal operation, collide with the laundry as the drum rotates and thus advantageously distribute, process and/or care for the laundry.

In operation, the controller controls at least the direction of rotation and the speed of the motor.

The motor is usually operated with three-phase or alternating current. The controller can control the motor in such a way that the drum rotates, for example, in only one direction or in alternating directions, i.e. reversing.

Belt drives generally have the problem that slip can occur because the torque that can be transmitted is limited. In the case of laundry care appliances or other belt-driven drums, the slippage is caused by a randomly occurring unfavorable laundry distribution. This can for example by wedging the

Washing can occur between rotating and stationary parts. For example, a

Wedging of laundry between the rotating drum and the surrounding housing, e.g. a so-called "balcony", which is a section in the housing in the area of the

Loading opening of a dryer is occur. A rib hitting the wedged laundry as the drum rotates becomes lodged in the laundry, which in turn often causes the drum and drive belt to stall, causing slippage between them

Drive belt and the motor pinion or motor leads. Such a drum jam can sometimes occur within less than a second.

Typically, when the drum jams, motor performance is not automatically interrupted or reduced. As a result, the motor pinion, which continues to rotate, wears through the stationary drive belt within a short time and a scuffing occurs

broken belt.

The result is a very complex repair of the device by specialist personnel and the resulting high costs and downtime of the device.

The object of the present invention is therefore to detect a drum jam in order to eliminate the disadvantages of the prior art and to reduce the frequency of belt breaks.

The object is achieved by the method described in claims 1 and in

Claim 15 described laundry care device solved. Preferred according to the invention

Configurations emerge from the dependent claims and the following

finishes.

According to a first aspect of the invention, the object is achieved by a method for

Fixed drum jam detection in a laundry care appliance. The

Laundry care appliance has a rotatable drum which can be driven by a motor via a drive belt. The method of the present invention includes the following

Steps: a) Determine at least one or more of the following values of the motor: torque-generating current, torque, phase current and/or envelope of

phase current, b) calculating a parameter set from the values determined in step a), c) checking the parameter set for a characteristic of a drum blockage

signal, d) adjusting the control of the motor when a characteristic signal has been detected.

Examples of laundry care appliances may include home and commercial dryers, household and

commercial washing machines and automatic machines and washer-dryers. The rotating drum

3 BE2021/5720 can preferably be rotatable in relation to a housing surrounding it at least in part. The drive belt can be a flat belt, toothed belt or V-belt or any other drive belt suitable for transmitting torque from the motor pinion coupled to the motor to the drum and the drum into a

to impart rotational movement. Depending on the application, the motor can be synchronous or

Asynchronous motor with, for example, two or more phases. The steps of the method preferably run in the order a), b), c), d).

It has been shown that the torque-forming current is a highly suitable size with

With the help of which a drum blockage can be determined. The torque-forming

Current can be controlled by means of a suitable known from the field of vector control

Method can be determined from the supply current of the motor. An example of such a method is a Clark and Park transformation performed in succession.

An alternative size that is just as suitable for detecting a blocked drum is this

Torque of the engine itself. The torque of the engine can, for example, with a

Torque observer are determined, which calculates the torque. Alternatively, the torque can be calculated from the torque-generating current using known methods. Another alternative suitable size for determining a

Drum blocking is the envelope of the phase current. In the event that an asynchronous machine is used for the motor, in addition to the methods described, the internal motor slip can be calculated as the difference between the stator speed and the rotor speed of the

Motor can be used as a measure of the torque.

Each of the quantities determined in step a) of the method according to the invention shows different characteristics in the case of a rotating motor in the cases of a stationary drum and a rotating drum. In the case of normal operation of a rotating, i.e. rotating, drum, the speeds of the frictionally contacting drive belt and motor sprocket vary little or not at all and slippage is minimal or non-existent. In this case, the quantities determined in step a) show, for example, fluctuations over time or non-vanishing amplitudes at characteristic frequencies in the frequency domain. In the event of a drum jam, the drum is stationary and there is slippage between the slowly rotating or completely stationary drive belt and the still rotating motor sprocket (and therefore the motor). In this case they disappear

Fluctuations over time or the amplitudes of the characteristic frequencies.

Additionally, just prior to and/or at the moment of drum jamming, there is a gradient or a

Increase in the maximum values over time in one of the values determined in step a).

comparison to the previous values.

° BE2021/5720

In the context of this invention, a signal characteristic of a drum jam can be any single parameter or any set of several parameters with which the two cases described above can be distinguished from each other. As part of this

Invention, the parameter set can include at least one or more parameters.

These parameters can be either fully or partially from those determined in step a).

values are calculated.

The calculation and checking of the parameter set in step b) and c) can, for example, with

done with the help of a control device. The control device can have, for example, a CPU, a microcontroller or microprocessor, an ASIC, PLD or FPGA, which is suitable and set up to carry out a corresponding calculation.

The control of the motor can preferably be adapted by the control device. The control device is set up, for example, to switch off the motor after detecting a characteristic signal of a blocked drum

Reduce speed and/or reverse its direction of motion or any

combination of them. The aim of the adjustment is to prevent the drive belt from chafing and to eliminate the jamming of laundry by means of a counter-movement.

The inventive method is preferably continuous or short

performed at intervals. A continuous implementation means in this

Connection that after the end of step d), the method according to the invention is immediately executed again beginning with step a). This is a close-meshed

Monitoring of the laundry care device as well as a quick response to a

Drum blocking possible and wearing through of the drive belt can be effectively prevented.

The method according to the invention has the advantage that slippage between the motor pinion or the motor and the drive belt can be quickly detected in the event of a drum blockage. This allows you to react directly by adjusting the motor movement, which prevents the drive belt from tearing. In addition, the procedure is via a

Software update can also be easily retrofitted to existing laundry care devices.

In a preferred embodiment, the method is only carried out when the motor of the laundry care appliance has reached a target speed after being switched on.

In the context of this invention, the target speed describes the speed of the drum which it has in normal operation, i.e. in operation without drum blocking. The target speed of the drum can, for. B. be 55 revolutions per minute.

° BE2021/5720

By starting the method according to the invention only after the setpoint speed has been reached, it is ensured that the values in step a) are determined exclusively at the start of normal operation and a speed of the engine that changes over time at

running up the laundry care device does not falsify the measurement.

In a preferred embodiment of the method, the values in step a) are determined during a defined measurement period and in step c) the parameter set is compared with a set of limit values and a signal characteristic of a drum blockage is determined if at least one parameter of the parameter set has a corresponding one Limit of the limit theorem falls below, where the

Limit set is calculated at least once from the parameter set.

Within the scope of this invention, the defined measurement duration can be a time duration within which the determination of the values in step a) of the method according to the invention is carried out. For example, the measurement duration can be between 0.5 and 5 s, preferably between 1 and 3 s. The measurement duration should preferably be selected in such a way that the measurement duration is as long as possible in order to be able to detect a characteristic signal. At the same time, the measurement duration should preferably be chosen so short that the further steps of the method are carried out and the drive belt is not already worn through when carrying out step a).

In the context of this invention, the limit theorem may have at least one or more

include limits. The limit values can be calculated completely or partially from the parameter set, for example. Preferably, the limit theorem at the first

Execution of the method according to the invention can be calculated from the set of parameters after the setpoint speed has been reached and do not change when the method according to the invention is executed repeatedly. However, the limit set can also be determined and updated after a fixed number of repetitions of the method from the parameter set and/or from the previously determined limit sets. For example, one or more of the limit values can be specified as a fraction or multiple of a parameter of the

Parameter set are calculated. If at least one parameter of the

Parameter set has a corresponding limit value of the set of limit values, there is a characteristic signal of a blocked drum.

This has the advantage that the method individually takes into account the motor installed in the laundry care appliance. This provides a reliable and simple method

detection of a blocked drum.

° BE2021/5720

In a preferred embodiment, in step b), the difference between the

Maximum and the minimum and/or the standard deviation of those determined in step a).

Values are calculated and form a parameter set.

The minimum and the maximum are determined in relation to all time-resolved values determined in step a) in the measurement period. The difference between maximum and minimum is then determined from these two values. As an alternative to this, the standard deviation, as is well known in the prior art, can also be calculated.

The difference between the minimum and the maximum and the standard deviation have the advantage of being two with little technical effort and minimal

computing power represent calculable values that allow a simple distinction between the cases of normal operation and the drum jam.

In a preferred embodiment, after step a), in a further step e), the values determined in step a) are low-pass filtered.

The low-pass filtering can be carried out, for example, by electrical or electronic components known in the prior art. The signals can also be filtered on the SW side. Preferably, the limit frequency can be selected in such a way that interfering high-frequency components, e.g. due to motor or mains frequencies, which are not in the

related to the mechanical movement of the drum, drive belt and/or motor can be eliminated or greatly reduced. Preferably the

Cut-off frequency in the range from 5 rad/s to 30 rad/s, preferably 7 rad/s to 20 rad/s, more preferably 9 rad/s to 15 rad/s. For example, the cut-off frequency can be 10 rad/s.

The low-pass filtering has the advantage that the values determined in step a) are significantly improved in relation to the signal-to-noise ratio. This in turn improves the

Jammed drum detection accuracy.

In a preferred embodiment, in step b) the values determined in step a) are broken down into at least one frequency or into a continuous or discrete frequency spectrum and form a parameter set.

Due to the rotation of the drum, the values determined in step a) correspond to the rotation

Correlated amplitudes can be detected in characteristic frequency ranges. These amplitudes can be caused, for example, by the laundry colliding with the ribs. By "overflying" the washing of a rib during drum rotation, i.e. a rib not colliding, further amplitudes of higher or lower

frequencies are added. In the event of a drum jam and standstill of the

drum decrease or disappear the corresponding amplitudes of the characteristic

Frequencies or frequency ranges. In this case, the set of limit values can be calculated, for example, from the set of parameters multiplied by a factor that is less than one.

The frequency decomposition has the advantage that it represents a parameter value or a parameter set that can be calculated with little technical effort and that makes a simple and error-resistant distinction between the cases of normal operation and a

Drum lock allowed.

In a preferred embodiment, in step b) the parameter set is converted by a discrete Fourier transformation, a fast Fourier transformation or a Goertzel

Algorithm calculated.

These methods are known in the prior art and have the advantage of being simple

Implementation and feasibility with minimal computational effort.

In a preferred embodiment, the parameter set includes the sum of

Amplitudes of multiple frequencies in a defined frequency interval.

Using the sum of multiple frequencies improves the detection of a characteristic signal of a jammed drum, since in this case the amplitudes of multiple frequencies contribute to the signal change, rather than just a single frequency.

In a preferred embodiment, the frequency interval includes frequencies from 0.5 Hz to 2.5 Hz.

This is a frequency range in which the collision of the ribs with the laundry during the

Drum rotation characteristic amplitudes occur. Based on the amplitudes of this

Frequency range is an advantageous determination of a drum blockage easily possible.

In a preferred embodiment, the drum or one or more ribs of

an artificial imbalance in the drum of the laundry care appliance.

An artificial imbalance can be, for example, an incompletely homogeneous weight distribution in the drum. Alternatively or additionally, an artificial imbalance can also be one or more ribs that are heavier than the remaining ribs. An artificial imbalance is evident from one or more corresponding amplitudes of one or more characteristic frequencies in the frequency spectrum determined in step a).

values recognizable. If the drum is blocked and the drum is at a standstill, the corresponding amplitudes decrease or disappear.

3 BE2021/5720

An artificial imbalance provides in the event that the drum with only a small

laundry load is loaded, the detection of a drum jam is safe and simplifies detection. In addition, the imbalance can improve the detection of a drum jam even in the case of a normal load of laundry.

In a preferred embodiment, after step a), in a further step f), the values determined in step a) are stored in a data memory, and in step b) the mean value and/or the maximum value are calculated from all or part of the stored values and are included in the parameter set, and in step c) is the

Parameter set compared with the last value determined in step a) and a signal characteristic of a drum blockage is detected when the last determined

value exceeds a parameter of the parameter set.

A drum stall can occur in less than a second. It was found that in the case of drum blockage, the values determined in step a), in particular the torque-forming current or the torque, rise steeply within a few hundred milliseconds. This suddenly temporal

Changing the values, i.e. their gradient, can be used to detect a blocked drum.

A signal characteristic of a blocked drum or the set of parameters based on the gradient can be calculated using the mean value or the maximum value of a part or all im

Memory stored values determined in the past are calculated. Preferably only one is used to calculate the mean value or the maximum value

Number k of most recently saved values used, where k is a positive integer.

This embodiment provides an easy-to-implement and reliable option

Jammed drum detection ready.

In a preferred embodiment, in step f) the values determined in step a) are continuously stored in a ring memory.

In the context of this invention, a ring memory describes a data memory known in the prior art, whose individual total of k memory locations are written cyclically, where k is an integer positive number: After all memory locations of the

ring memory have been written to for the first time, when the next one is saved

memory value started at the first memory location and the value stored there was overwritten, etc. In other words, only the last k values are stored in the ring memory, all other values were overwritten. The ring buffer can preferably

9 BE2021/5720 be dimensioned in such a way that it is an integer multiple of the drum rotation as the number k of

Contains storage locations, since the values determined in step a) fluctuate with the rhythm of the ribs. This prevents the determined values from being subject to large fluctuations.

A ring memory is an optimal variant of the invention for the purpose of the invention

data memory, since it always contains only the most recent k values determined in step a), from which the mean value and/or the maximum value is determined. Older values are not included. This ensures that the mean value and/or the maximum value are always up to date.

A microcontroller without a floating point unit can preferably be used to calculate the mean value. In this case it can be preferred that the mean value is formed over 2n values. The exponent n can preferably be dimensioned in such a way that it is an integer

Includes multiples of drum rotation, since the values determined in step a) fluctuate with the rhythm of the ribs. This prevents the values determined in step a) from becoming large

are subject to fluctuations. The averaging can be done by summation over the

Number n of the last values in the data memory and subsequent shifting by n places to the right.

The following is an example of a possible implementation of the calculation of the mean value

Algorithm are used: The values in step a) are determined with a time interval of 100 ms and stored in the ring memory. This preferably takes place only after the laundry care appliance has reached a target speed. The ring buffer can

Time windows of e.g. 2.1 s, which in this example is approximately two

corresponds to drum revolutions. The division by shift operation was not used in this example, since a floating point unit is assumed to be given.

As soon as the ring memory is completely filled with the 21 values for the first time, each

Running through step c) compares the value determined last, i.e. the current value, with the mean value of the past 21 values in the parameter set. If the last value determined is at least e.g. 60% above the mean value, the drum may be blocked. A

Increase of the last determined value to 1.2, for example 1.6 times the

The mean value can thus represent a characteristic signal of a drum blockage. The

Ring memory can preferably be used when performing step d), i.e. when adjusting the

Control of the engine, especially when reversing, are not emptied or refilled, but only stopped. This ensures that any blocking can be detected immediately when restarting.

It can be advantageous that the torque increase is not within the

Averaging window is located, especially if the window is small

span of time. If the period of time was short, the increase would strongly influence the mean value. For this reason, there is preferably a predetermined time interval between the elements in the ring memory and the current value.

Alternatively or in addition to the mean value, the maximum value of the past im

Values stored in the data memory are compared with the last determined value. In this case, an increase in the current value to 1.1, for example 1.5 times the maximum value can represent a characteristic signal of drum jamming.

Preferably, when considering the maximum value of the past values, a

Time windows of approximately one rib cycle are hidden.

Here, too, there is preferably a predetermined time interval between the elements in the ring memory and the current value.

In a preferred embodiment, the signal characteristic of a blocked drum is detected when the most recent value determined in step a) is 1.2, preferably 1.6 times the mean value determined in step b) or 1.1, preferably exceeds 1.5 times the maximum value determined in step b).

Within the scope of this invention, the most recent value determined in step a) describes the last value determined in terms of time and is therefore the most up-to-date value. With the values described here, a blocked drum can be detected most clearly.

In a preferred embodiment, the motor is controlled in step d) in such a way that the motor reverses its direction of movement, changes its speed and/or stops.

Preferably, the motor can also be controlled so that it performs any combination of reversing the direction of movement, changing the speed, e.g. increasing or

lowering, or executing a halt.

For example, by reversing the direction of movement, the direction of the over the

Drive belt on the drum transmitted torque. This can prevent laundry from getting wedged between the drum and a part of the housing, e.g. the balcony. A drum jam can thus by reversing the

Direction of movement of the motor and thus be solved by reversing the drum.

The laundry care machine can thus independently switch the machine to normal

bring operating condition. This improves the ease of use of the machine. In addition, it prevents long machine downtimes that would be caused by an operator manually removing the blocked laundry.

According to a second aspect of the invention, the object is achieved by a laundry care appliance according to claim 15. The laundry care appliance according to the invention is designed and set up to carry out the method according to one of claims 1 to 14. The

Laundry care device can preferably be a household or commercial dryer, a

household or commercial washing machine or automatic machine or a washer-dryer. Such a laundry care appliance has the advantage that repairs due to a worn drive belt are required much less frequently. This saves repair costs and reduces device downtime due to time-consuming repairs.

It is hereby clarified that one or more of the preferred ones described above

Embodiments, insofar as there are no contradictions, can be combined with one another and also represent preferred embodiments.

Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings. show:

Fig. 1 is a schematic representation of a dryer as an example

Laundry care device in a perspective view;

2 shows a schematic structure of the motor-drum structure of a laundry care appliance;

3a shows an exemplary section of a time-resolved torque-generating

current in the case of a rotating drum;

3b shows an exemplary section of a time-resolved torque-generating

current in case of drum jamming;

4a shows an exemplary section of a frequency spectrum of a torque-forming current in the case of a rotating drum;

4b shows an exemplary section of a frequency spectrum of a torque-forming current in the case of a drum blockage;

5 shows an exemplary section of an increase in the torque-generating current im

In the event of a sudden drum jam.

Figure 1 shows a household dryer 1 as an example of a laundry care device 3. Der

Household dryer 1 has an outer housing 5 and a drum 7 rotatably mounted therein. The drum is provided with a loading opening 9 arranged laterally in the housing 5

Laundry loadable. A balcony 11 is arranged in the area of the loading opening 9 . The

Balcony 11 typically includes a lint screen. A drum blockage can occur, for example, due to laundry becoming wedged between the balcony 11 and the drum 7 .

Figure 2 shows a schematic structure of the laundry care device 3. Das

Laundry care appliance 3 comprises the drum 7, which is rotatably mounted with respect to the housing 5 surrounding the drum 7, a motor 13 with a motor pinion 15, a

Drive belt 17 which mechanically couples the motor pinion 15 or the motor 13 to the drum 7, and a controller which controls the motor 13. The motor pinion 15, together with the drive belt 17, transmits torque from the motor 13 to the drum 7, causing the drum 7 to rotate.

In order to tension the drive belt 17 sufficiently during operation, the motor 13 can be on a

Motor holder 19 can be arranged. The motor mount 19 can be pivoted at least at one point 21 . A tension spring 23 applies a force to the motor mount 19, and thus also to the motor 13 and the motor pinion 15, and thereby tensions the drive belt 17.

The drum 7 has ribs 25 in its interior, which during normal operation of the

Laundry care device 3 collide with the laundry 27 during the drum rotation and the

Process and/or care for laundry so advantageously.

Figure 3a and 3b show an example of a detail of a time-resolved torque-forming current 29a of the motor 13 of the laundry care appliance 3 without low-pass filtering and a torque-forming current 29b of the motor 13 with

low pass filtering. Figure 3a shows the normal operating case of a rotating drum 7.

Figure 3b shows the case of a drum jam. The values in FIGS. 3a and 3b were determined or measured during step a) of the method according to the invention.

Fig. 3a and 3b show the significant improvement in the signal-to-noise ratio of the

Current 29 b by low-pass filtering of the current 29a.

The detection of a drum blockage by the method according to the invention takes place, for example, in the case of FIG Values of the torque-forming

Current calculated in the normal operating case, which is shown in Fig. 3a. In the present

In this case, the parameter has the difference between maximum 43 and minimum 45 of torque-forming current 29a. The difference in the non-low pass filtered torque producing current 29a in Figure 3a is approximately 0.8 A - 0.2

A = 0.6 A. The difference in the low-pass filtered torque-forming current 29b in Fig. 3a is approximately 0.62 A - 0.35 A = 0.27 A.

In step c) the parameter is set to a characteristic for a drum jam

signal checked. For this purpose, a set of limit values with a single limit value is determined from the parameter when the method according to the invention is initially carried out for the first time after the setpoint speed has been reached. For example, the limit value can be calculated from 0.3 A in the case of the non-low-pass filtered current 29a and 0.15 in the case of the low-pass filtered current 29b.

The values shown in FIG. 3b are each below the limit value with a difference between maximum and minimum of approximately 0.2 A for the non-low-pass filtered current 29a and with approximately 0.05 A for the low-pass filtered current 29b. Thus, Fig. 3b shows the case of a drum blockage. In the case of FIG. 3b, the motor control is adjusted in step d) and the drum is reversed, for example, in order to release the blockage.

4a and 4b show an exemplary section of a frequency spectrum 31 of a torque-generating current of the motor 13 of the laundry care appliance 3. FIG. 4a shows the case of a rotating drum 7. FIG. 4b shows the case of a drum blockage.

The frequency spectrum 31 of a rotating drum in Fig. 4a shows a clear one

Maximum 33. This maximum 33' is absent in Figure 4b in the case of drum jamming. The

The procedure of the method according to the invention is analogous to the description of FIGS. 3a and 3b. In the case of FIGS. 4a and 4b, the parameter and the one calculated therefrom include

Limit, for example, the sum of the amplitudes in the frequency range from 0.5 Hz to 2.5 Hz. For example, if the limit is calculated as half the parameter, im

Case of Fig. 4b in step c) detected a characteristic signal of a drum blockage.

Fig. 5 shows an exemplary section of a torque-forming stream of a

Laundry care appliance 3. A first section 35 in FIG

stream 37'.

The detection of a blocked drum by the method according to the invention takes place, for example, in the case of FIG. 5 as follows: In step a), the torque-generating current Iq is measured. In the subsequent step f), the measured values of the torque-forming

stream stored in a ring memory. In the subsequent step b), all im

The mean value and/or the maximum value are calculated from the values stored in the ring memory as parameters of the parameter set. In step c), the last value measured in step a) is compared with the parameter determined in step b). If the last measured value exceeds the maximum, e.g. by a factor of 1.5, or the mean value, e.g. by a factor of 1.6, there is a characteristic signal of a blocked drum. In step d), therefore, the

Motor control adjusted and the drum reversed, for example, to solve the blockage.

Claims (15)

patent claims 1. A method for detecting a drum blockage in a laundry care appliance (3), the laundry care appliance (3) having a rotatable drum (7) which can be driven by a motor (13) via a drive belt (17), the method comprising the steps: a) determining at least one or more of the following values of the motor (13): torque-forming current, torque, phase current and/or envelope of the phase current, b) calculating a parameter set from the values determined in step a), c) checking the parameter set for a signal indicative of drum jamming, d) adjusting the control of the motor (13) when a characteristic signal has been detected. 2. The method of claim 1, wherein the method is only carried out when the motor (13) of the laundry care appliance (3) has reached a target speed after switching on. 3. The method according to claim 1 or 2, wherein the values in step a) are determined during a defined measurement period, wherein in step c) the set of parameters is compared with a set of limit values and a signal characteristic of a drum blockage is determined if at least one parameter of the Parameter set falls below a corresponding limit value of the limit value set and the limit value set is calculated at least once from the parameter set. 4. The method according to claim 3, wherein in step b) the difference between the maximum and the minimum and/or the standard deviation of the values determined in step a) are calculated and form a parameter set. 5. The method according to claim 4, wherein after step a), in a further step e), the values determined in step a) are low-pass filtered. 6. The method according to claim 3, wherein in step b) the values determined in step a) are broken down into at least one frequency or a continuous or discrete frequency spectrum and form a parameter set. 7. The method according to claim 6, wherein in step b) the parameter set is calculated by a discrete Fourier transformation, a fast Fourier transformation or a Goertzel algorithm. 8. The method according to claim 6 or 7, wherein the parameter set comprises the sum of the amplitudes of a plurality of frequencies in a defined frequency interval. 9. The method of claim 8, wherein the frequency interval includes frequencies from 0.5 Hz to 2.5 Hz. 10. The method according to any one of claims 7 to 9, wherein the drum or one or more ribs of the drum of the laundry care appliance has an artificial imbalance. 11. The method according to claim 1 or 2, wherein after step a) in a further step f) the values determined in step a) are stored in a data memory, wherein in step b) the mean value and/or or the maximum value can be calculated and included in the parameter set, wherein in step c) the parameter set is compared with the last value determined in step a) and a signal characteristic of a blocked drum is detected if the last determined value exceeds a parameter of the parameter set . 12. The method according to claim 10 or 11, wherein in step f) the values determined in step a) are continuously stored in a ring memory. 13. The method according to claim 10 to 12, wherein the signal characteristic of a blocked drum is detected when the most recent value determined in step a) is 1.2 times, preferably 1.6 times the mean value determined in step b) or the 1.1 times, preferably 1.5 times, the maximum value determined in step b). 14. The method according to any one of the preceding claims, wherein in step d) the motor (13) is controlled such that the motor (13) reverses its direction of movement, changes its speed and / or stops. 15. laundry care appliance (3), wherein the laundry care appliance (3) is designed and set up to carry out the method according to any one of the preceding claims.