Method for identifying the progress of work on a handheld machine tool

Abstract

The invention relates to a method for identifying a work progress of a handheld power tool (100), the handheld power tool (100) comprising an electric motor (180), the method comprising the following method steps: S1 providing at least one template waveform (240), wherein the template waveform (240) can be assigned to the work progress of the handheld power tool; S2 determining a signal of an operating variable (200) of the electric motor (180); S3 comparing the signal of the operating variable (200) with the template waveform (240) and determining a consistency evaluation from the comparison; S4 identifying the work progress at least partially based on the consistency evaluation determined in method step S3. A handheld power tool, in particular an impact driver, is also disclosed, which has an electric motor and a control unit, wherein the control unit is designed to carry out the method according to the invention.

Description

Technical Field

[0001] The invention relates to a method for detecting a working progress of a hand-held power tool and a hand-held power tool which is designed to carry out the method. Background Art

[0002] A rotary impact driver for tightening threaded elements, such as nuts and screws, is known from the prior art, such as EP 3 381 615 A1. Such a rotary impact driver comprises, for example, a structure in which an impact force in a rotational direction is transmitted to the threaded element by the rotary impact force of a hammer. A rotary impact driver having such a structure comprises a motor, a hammer driven by the motor, an anvil struck by the hammer, and a tool. In such a rotary impact driver, a motor installed in a housing is driven, wherein the hammer is driven by the motor, and the anvil is struck by the rotating hammer and outputs the impact force to the tool, wherein two different operating states can be distinguished, namely "non-impact operation" and "impact operation".

[0003] EP 2 599 589 B1 also discloses a rotary impact driver having a motor, a hammer and a rotation speed detection unit, wherein the hammer is driven by the motor.

[0004] When using a rotary impact driver, it is desirable to draw conclusions from the machine about the progress of the work in order to trigger a desired reaction or routine of the tool determined accordingly, such as switching off the motor, changing the motor speed or triggering a feedback to the user.

[0005] In order to provide such intelligent tool functions, in particular, knowledge of the currently active operating state is required. The recognition of the operating state is carried out in the prior art, for example, by monitoring operating variables of the electric motor, such as the rotational speed and the motor current. In this case, the operating variables are evaluated to determine whether certain limit values ​​and / or threshold values ​​have been reached. Corresponding evaluation methods work with absolute threshold values ​​and / or signal gradients.

[0006] The disadvantage here is that fixed limit values ​​and / or threshold values ​​are in practice only optimal for one application. As soon as the application changes, the corresponding current value or speed value or its temporal course changes, and the impact detection based on the set limit values ​​and / or threshold values ​​or their temporal course is no longer effective.

[0007] Thus, it can be seen that, for example, an automatic shut-off function based on the detection of an impact operation shuts down reliably in different speed ranges when using self-tapping screws in some applications, but does not shut down in other applications when using self-tapping screws.

[0008] In other methods for determining the operating mode in the case of rotary impact drivers, additional sensors, such as acceleration sensors, are used in order to derive the currently active operating mode from the vibration state of the tool.

[0009] Disadvantages of this method are the additional cost outlay for the sensors and the impairment of the robustness of the handheld power tool, since the number of installed components and electrical connections is greater than for handheld power tools without these sensor systems.

[0010] Furthermore, the simple information about whether the impact mechanism is working is not sufficient to draw reasonable conclusions about the progress of the work. For example, when screwing in a certain woodworking screw, the rotary impact mechanism is activated very early, and the screw has not yet been completely screwed into the material, but the required torque has exceeded the release torque of the rotary impact mechanism. A reaction based purely on the operating state of the rotary impact mechanism (impact operation and non-impact operation) is not sufficient for the correct function of the automation system of the tool, such as shutdown.

[0011] In principle, even with other handheld power tools, such as impact drills, there are problems with drawing conclusions about the progress of work, so that the present invention is not limited to rotary impact drivers. Summary of the invention

[0012] The object of the present invention is to provide a method for identifying the progress of work or describing the situation of an application which is improved compared to the prior art and which at least partially eliminates the above-mentioned disadvantages or provides at least one alternative to the prior art. Another object is to provide a corresponding handheld power tool.

[0013] These objects are achieved by means of the corresponding subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the corresponding dependent claims.

[0014] According to the present invention, a method for identifying the progress of work of a handheld power tool is disclosed, wherein the handheld power tool has an electric motor. The method comprises the steps of:

[0015] S1 provides at least one model waveform (Modellsignalform), wherein the model waveform can be assigned to the working progress of the hand-held power tool;

[0016] S2 obtains the signal of the operating parameter of the electric motor;

[0017] S3 compares the signal of the operating parameter with the sample waveform and obtains a consistency evaluation from the comparison;

[0018] S4 identifies the progress of the work at least partially based on the consistency evaluation determined in method step S3.

[0019] In this way, simple and reliable monitoring and control for detecting the progress of the work can be carried out, wherein in principle various operating variables can be considered as operating variables recorded by suitable measured value transmitters. It is particularly advantageous here that no additional sensors are required for this purpose, since, for example, various sensors for speed monitoring, preferably Hall sensors, are already integrated into the electric motor.

[0020] In a preferred embodiment, the model waveform is a model waveform that is typical for a state and is typical for a certain working progress of the handheld power tool, for example the contact of a screw head against a fastening plate or the free rotation of a loose screw.

[0021] Approaches for detecting the progress of work by means of operating variables from among the measured variables in the tool, such as the rotational speed of an electric motor, have proven to be particularly advantageous, since this method allows the progress of work to be detected particularly reliably and largely independently of the general operating state of the tool or its application.

[0022] In this case, in particular additional sensor units, such as acceleration sensor units, for checking measured variables within the tool are substantially omitted, so that the method according to the invention is essentially used only for detecting the progress of the work.

[0023] Preferably, the model waveform is an oscillation curve about a mean value, in particular an oscillation curve substantially in the form of a trigonometric function. The model waveform preferably represents an ideal impact operation of the hammer on the anvil of the rotary impact mechanism, wherein the ideal impact operation is preferably an impact without further rotation of the tool spindle of the handheld power tool.

[0024] Advantageously, the operating variable is the rotational speed of the electric motor or an operating variable that is correlated with the rotational speed. A fixed transmission ratio of the electric motor to the impact mechanism results, for example, in a direct relationship between the motor rotational speed and the impact frequency. Another conceivable operating variable that is correlated with the rotational speed is the motor current. As operating variables of the electric motor, the motor voltage, the Hall signal of the motor, the battery current or the battery voltage are also conceivable, wherein the acceleration of the electric motor, the acceleration of the tool holder or the acoustic signal of the impact mechanism of the handheld power tool are also conceivable operating variables.

[0025] Preferably, the determination of the consistency evaluation in method step S3 includes a comparison of the consistency between the signal of the operating variable and the template waveform with at least one consistency threshold value.

[0026] In an alternative embodiment of the invention, step S3 includes comparing the signal of the operating variable with a template waveform and determining the deviation from the comparison.

[0027] In a preferred embodiment, the consistency threshold value can be determined by a user of the handheld power tool, in another embodiment, the consistency threshold value is predefined by the factory.

[0028] In a particularly preferred embodiment, the consistency threshold can be selected by the user based on factory-defined pre-selections of the application of the handheld power tool. This can occur, for example, via a user interface / such as an HMI (Human-Machine Interface), such as a mobile device, especially a smartphone and / or a tablet computer.

[0029] In particular, in method step S1, the template waveform is variably determined, in particular by the user. In this case, the template waveform is assigned to the work progress to be identified, so that the user can predetermine the work progress to be identified. In this context, limit values ​​and / or threshold values ​​for the existing correspondence and existing deviations of the signal of the operating variable from the template waveform can also constitute adjustable variables for the application case of identifying the work progress.

[0030] Advantageously, the method further comprises a method step S5, in which a routine of the handheld power tool is triggered at least partially based on the work progress detected in method step S4. In principle, it should be pointed out here that method step S5 can be performed after S4.

[0031] In a preferred embodiment, at least one or more reactions or routines from the following reaction groups or routine groups are executed in method step S5: change of the rotation speed of the electric motor; reversal of the rotation direction of the electric motor; and / or visual, auditory and tactile feedback to the user.

[0032] Advantageously, the template waveform is predefined in method step S1 , in particular factory-defined. In principle, it is conceivable that the template waveform is stored or stored in the device and alternatively and / or additionally provided to the handheld power tool, in particular from an external data device.

[0033] In another embodiment, in method step S2, the signal of the operating variable is recorded as the time curve of the measured value of the operating variable, or as the measured value of a variable of the operating variable associated with the time curve of the electric motor, such as acceleration, in particular high-order jerk, power, energy, rotation angle of the electric motor, rotation angle of the tool receiving part or frequency.

[0034] In the last-mentioned embodiment, it can be ensured that a constant periodicity of the signal to be investigated is obtained, which is independent of the motor speed.

[0035] Alternatively, the signal of the operating variable is recorded in method step S2 as a time curve of the measured value of the operating variable, wherein in step S2a following method step S2 the time curve of the measured value of the operating variable is converted into a curve of a variable of the measured value of the operating variable with respect to the electric motor which is associated with the time curve based on the fixed transmission ratio of the transmission. The same advantages are thus obtained as in the case of direct receipt of the signal of the operating variable over time.

[0036] The method according to the invention makes it possible to detect the progress of work independently of at least one desired rotational speed of the electric motor, at least one starting characteristic of the electric motor and / or at least one charge state of an energy supply of the handheld power tool, in particular a battery.

[0037] The signal of the operating variable is to be understood here as a sequence of measured values ​​in time. Alternatively and / or additionally, the signal of the operating variable can also be a spectrum. Alternatively and / or additionally, the signal of the operating variable can also be supplemented by processing, for example, smoothing, filtering, adaptation, etc.

[0038] In a further embodiment, the signal of the operating variable is stored as a sequence of measured values ​​in a memory, in particular a memory of the handheld power tool, preferably a ring memory.

[0039] In a particularly advantageous embodiment, in method step S3, the signal of the operating variable is compared by means of one of the following comparison methods: the comparison method comprises at least one frequency-based comparison method and / or at least one comparative comparison method, wherein the comparison method compares the signal of the operating variable with a template waveform to see whether at least one predetermined threshold value is met. The predetermined threshold value can be predetermined by the factory or can be set by the user.

[0040] In this case, it can be determined at least partially by means of a frequency-based comparison method, in particular a bandpass filter and / or a frequency analysis, whether a work progress to be identified has been recognized in the signal of the operating variable.

[0041] In one specific embodiment, the frequency-based comparison method comprises at least a bandpass filter and / or a frequency analysis, wherein the predefined threshold value is at least 90%, in particular 95%, and in particular exactly 98% of the predefined limit value.

[0042] In a bandpass filter, for example, the recorded signal of the operating variable is filtered through a passband whose pass range corresponds to the template waveform. In the presence of a decisive work progress to be identified, in particular an ideal impact without further rotation of the impacted element, a corresponding amplitude value will occur in the resulting signal. The predetermined threshold value of the bandpass filter can thus be at least 90%, in particular 95%, completely, in particular 98% of the corresponding amplitude in the work progress to be identified, in particular an ideal impact without further rotation of the impacted element. The predetermined limit value can here be the corresponding amplitude value in the resulting signal of the ideal work progress to be identified, in particular an ideal impact without further rotation of the impacted element.

[0043] By means of known frequency-based frequency analysis comparison methods, a previously determined template waveform can be searched for in the recorded signal of the operating variable, for example, the frequency spectrum of the work progress to be identified, in particular the ideal impact without further rotation of the impacted element. The corresponding amplitude of the work progress to be identified, in particular the ideal impact without further rotation of the impacted element, will appear in the recorded signal of the operating variable. The predetermined threshold value of the frequency analysis can be at least 90%, in particular 95%, completely, in particular 98% of the corresponding amplitude in the work progress to be identified, in particular the ideal impact without further rotation of the impacted element. The predetermined limit value can be the corresponding amplitude in the recorded signal of the ideal work progress to be identified, in particular the ideal impact without further rotation of the impacted element. A suitable segmentation of the recorded signal of the operating variable may be necessary in this case.

[0044] In one embodiment, the comparative comparison method includes at least one parameter evaluation And / or cross-correlation, wherein the threshold value is predefined as a signal of the operating variable that corresponds to the template waveform by at least 40%.

[0045] The measured signal of the operating variable can be compared with the model waveform by means of a comparative comparison method. The measured signal of the operating variable is determined in such a way that it has a finite signal length substantially equal to the model waveform. The comparison of the model waveform with the measured signal of the operating variable can be output as a finite length, in particular discrete or continuous signal. Depending on the degree of consistency of the comparison or the deviation of the comparison, a result can be outputted: whether there is a work progress to be identified, in particular whether there is an ideal impact without further rotation of the impacted element. When the measured signal of the operating variable is at least 40% consistent with the model waveform, there is a work progress to be identified, in particular an ideal impact without further rotation of the impacted element. It is also conceivable that the comparison method can output the degree of identity as a comparison result by means of the comparison of the measured signal of the operating variable with the model waveform. Here, at least 60% identity can be used as a criterion for the presence of a work progress to be identified, in particular an ideal impact without further rotation of the impacted element. The starting point here is that the lower limit of the consistency is 40% and the upper limit of the consistency is 90%. Accordingly, the upper boundary of the deviation is 60% and the lower boundary of the deviation is 10%.

[0046] In the parameter evaluation, a comparison can be made in a simple manner between a previously determined model waveform and the signal of the operating variable. For this purpose, evaluation parameters of the model waveform are identified in order to adapt the model waveform to the measured signal of the operating variable. By means of a comparison between the previously determined evaluation parameters of the model waveform and limit values, a conclusion can be drawn as to the presence of an ideal impact to be detected, in particular without further rotation of the impacted element. A further evaluation of the comparison result can then be carried out: whether a predetermined threshold value has been reached. The evaluation is either a quality determination of the evaluation parameters or a consistency between the determined model waveform and the detected signal of the operating variable.

[0047] In another embodiment, method step S3 includes a step S3a of determining the quality of the identification of the model waveform in the signal of the operating variable, wherein in method step S4 it is determined at least partially based on the quality determination whether there is a work progress to be identified. The quality of the adaptation of the evaluation parameter can be determined as a measure of the quality determination.

[0048] In method step S4 , it can be determined at least partially with the aid of a quality determination, in particular a quality measure, whether a work progress to be identified has been recognized in the signal of the operating variable.

[0049] In addition or as an alternative to the quality determination, method step S3 may include the identification of a model waveform and the determination of the consistency of the signal of the operating variable. The consistency of the evaluation parameter of the model waveform and the measured signal of the operating variable may be, for example, 70%, in particular 60%, and in particular 50%. In method step S4, it is determined at least partially based on the consistency determination whether there is a work progress to be identified. The determination of whether there is a work progress to be identified can be carried out at a predefined threshold value of at least 40% consistency between the measured signal of the operating variable and the model waveform.

[0050] In the cross correlation, a comparison between a previously determined model waveform and a measured signal of an operating variable can be performed. In the cross correlation, a previously determined model waveform can be correlated with a measured signal of an operating variable. In the correlation of the model waveform with the measured signal of the operating variable, the degree of consistency of the two signals can be determined. The degree of consistency can be, for example, 40%, in particular 50%, or even 60%.

[0051] In method step S4 of the method according to the invention, it can be determined at least partially based on the cross-correlation of the template waveform with the measured signal of the operating variable whether there is a work progress to be identified. The determination can be made at least partially based on a predetermined threshold value of at least 40% agreement between the measured signal of the operating variable and the template waveform.

[0052] In one method step, the work progress to be identified is identified based on less than ten impacts of the impact mechanism of the handheld power tool, in particular based on less than ten impact oscillation cycles of the electric motor, preferably based on less than six impacts of the impact mechanism of the handheld power tool, in particular based on less than six impact oscillation cycles of the electric motor, and most preferably based on less than four impacts of the impact mechanism of the handheld power tool, in particular based on less than four impact oscillation cycles of the electric motor. Here, the impact of the impact mechanism is understood to be an axially, radially, tangentially and / or circumferentially directed impact of the impact mechanism striker, in particular a hammer, on the impact mechanism body, in particular anvil. The impact oscillation cycle of the electric motor is associated with an operating variable of the electric motor. The impact oscillation cycle of the electric motor can be determined based on operating variable fluctuations in the signal of the operating variable.

[0053] The progress of the work can be recognized, for example, by the fact that the further rotation angle of the tool holder decreases when the impact mechanism strikes. The further rotation angle can be the rotation angle by which the tool holder is rotated with each impact of the impact mechanism. The further rotation angle decreases as the work progresses, which can also be reflected by a decreasing cycle duration.

[0054] A handheld power tool forms another subject of the present invention, which has an electric motor, a measured value recorder of operating parameters of the electric motor and a control unit, wherein the handheld power tool is advantageously an impact screwdriver, in particular a rotary impact screwdriver, and the work progress to be identified is an impact without further rotation of the tool receiving part of the handheld power tool. In this case, the electric motor sets the input spindle in rotation, wherein the output spindle is connected to the tool receiving part. The anvil is connected to the output spindle in a rotationally fixed manner, and the hammer is connected to the input spindle in such a way that it performs intermittent movement along the axial direction of the input spindle and intermittent rotational movement around the input spindle based on the rotational movement of the input spindle, wherein the hammer intermittently strikes the anvil in this way and thereby outputs the impact momentum and angular momentum to the anvil and thereby to the output spindle. The first sensor transmits a first signal, for example, for determining the rotation angle of the motor to the control unit. In addition, the second sensor transmits a second signal for determining the motor speed to the control unit. The control unit is advantageously designed to perform the aforementioned method.

[0055] Advantageously, the handheld power tool has a memory unit in which a plurality of values ​​can be stored.

[0056] In another embodiment, the handheld power tool is a battery-operated handheld power tool, in particular a battery-operated rotary impact screwdriver. In this way, flexible and power-network-independent use of the handheld power tool can be ensured.

[0057] Advantageously, the handheld power tool is an impact driver, in particular a rotary impact driver, and the work progress to be detected is an impact of the rotary impact mechanism without further rotation of the impacted element or the tool receiver.

[0058] The detection of the impact of the impact mechanism of the handheld power tool, in particular the impact oscillation period of the electric motor, can be realized, for example, by using a fast fitting algorithm, by means of which the impact detection can be evaluated in less than 100 milliseconds, in particular less than 60 milliseconds, and in particular less than 40 milliseconds. The method according to the invention mentioned here makes it possible to detect the progress of the work for basically all the above-mentioned application cases and the tightening of loose or tight fastening elements in the fastening carrier.

[0059] The invention largely eliminates complex signal processing methods such as filtering, signal looping, system models (static and adaptive) and signal tracking.

[0060] Furthermore, the invention allows for a faster recognition of the impact operation or the progress of the work, thereby evoked a faster reaction of the tool. This applies in particular to the number of impacts that have passed after the use of the impact mechanism until the recognition and in certain operating situations, such as the start-up phase of the drive motor. In this case, it is also not necessary to limit the effectiveness of the tool, for example by reducing the maximum drive speed. Furthermore, the algorithm function is also independent of other influencing factors, such as the desired speed and the battery charge state.

[0061] In principle, no additional sensor means (eg, acceleration sensor) is required, but these evaluation methods can also be used for signals of other sensor means. In addition, in other motor designs, for example, without rotational speed detection, the methods can also be used in other signals.

[0062] In a preferred embodiment, the handheld power tool is a battery screwdriver, an electric drill, an impact drill or an electric hammer, wherein drill bits, drill crowns or different bit attachments can be used as tools. The handheld power tool according to the invention is in particular designed as an impact driver tool, wherein a higher peak torque is generated by the pulsed release of motor energy for screwing in or screwing out screws or nuts. In this context, the transmission of electrical energy is understood to mean in particular that the handheld power tool transmits energy via a battery and / or a power cord on the main body.

[0063] In addition, according to the selected embodiment, the screwdriver tool can be flexibly configured in the direction of rotation. In this way, the method mentioned can be used for both screwing in a screw or nut and also for screwing it out.

[0064] In the context of the present invention, “ascertaining” is to be understood in particular as measuring or recording, wherein “recording” is to be understood in the sense of measuring and storing, and furthermore, “ascertaining” is to include any signal processing of the measured signal.

[0065] Furthermore, "determining" is also to be understood as identifying or detecting, wherein an unambiguous assignment is to be achieved. "Recognition" is to be understood as the recognition of a partial agreement with a template, which can be achieved, for example, by fitting the signal to a template, Fourier analysis or the like. "Partial agreement" is to be understood as a fit with an error less than a predefined threshold value, in particular less than 30%, completely in particular less than 20%.

[0066] Further features, application possibilities and advantages of the present invention are apparent from the following description of the exemplary embodiments of the present invention shown in the drawings. It should be noted that the features described or shown in the drawings may form the subject matter of the present invention alone or in any combination, and have only the described features independently of their overview in the claims or the reference relationship of the claims or their representation and display in the description and drawings and should not be considered as any form of restriction of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The present invention will be explained in detail below based on preferred embodiments. The accompanying drawings are schematic and show:

[0068] Figure 1 A schematic diagram of an electric handheld power tool is shown.

[0069] FIG. 2( a ) shows the working progress of an exemplary application and the corresponding signals of operating parameters.

[0070] FIG2(b) shows the consistency of the signal shown in FIG2(a) of the operating parameter with the sample signal.

[0071] FIG. 3 shows a schematic diagram of two different graphs of a signal of an operating variable.

[0072] Figure 4 A flow chart of the method according to the present invention is shown.

[0073] FIG. 5 shows an overview of the signals of the operating parameters and the output signal of the bandpass filter, based on a sample signal.

[0074] FIG. 6 shows an overview of the output of the signal and frequency analysis of the operating parameters, based on a sample signal.

[0075] FIG. 7 shows an overview of the signals of the operating variables and the sample signals used for parameter evaluation.

[0076] FIG. 8 shows an overview of the signals of the operating parameters and the sample signals used for the cross-correlation.

[0077] FIG9(a) shows the signals of the operating parameters.

[0078] FIG9(b) shows the amplitude function of the first frequency contained in the signal of FIG9(a).

[0079] FIG9(c) shows the amplitude function of the second frequency contained in the signal of FIG9(a). DETAILED DESCRIPTION

[0080] Figure 1 A handheld power tool 100 according to the invention is shown, which has a housing 105 with a handle 115. According to the embodiment shown, the handheld power tool 100 can be mechanically and electrically connected to a battery pack 190 for power supply independent of a power supply network. Figure 1 In the embodiment, the handheld power tool 100 is exemplarily configured as a battery-operated impact driver. However, it should be noted that the present invention is not limited to battery-operated impact drivers, but can be applied in principle to any handheld power tool 100 that needs to identify the progress of work, such as an impact drill.

[0081] An electric motor 180 and a transmission 170, which are supplied with current by a battery pack 190, are arranged in the housing 105. The electric motor 180 is connected to the input spindle via the transmission 170. Furthermore, a control unit 370 is arranged in the housing 105 in the region of the battery pack 190, which acts on the electric motor 180 and the transmission 170 in order to control and / or regulate the electric motor 180 and the transmission 170, for example, by means of a set motor speed n, a selected angular momentum, a desired transmission gear x or the like.

[0082] The electric motor 180 can be actuated, i.e. started and switched off, for example, by means of a manual switch 195 and can be any type of motor, for example an electronically commutated motor or a DC motor. In principle, the electric motor 180 can be electronically controlled or regulated in such a way that reverse operation can be achieved and a desired motor speed n and a desired angular momentum can be preset. The mode of operation and the design of suitable electric motors are sufficiently known from the prior art, so that they are not described in detail here for the sake of brevity of the description.

[0083] The tool receiver 140 is rotatably supported via the input spindle and the output spindle in the housing 105. The tool receiver 140 is used to receive a tool and can be directly molded onto the output spindle or connected to the output spindle in the form of a plug-in assembly.

[0084] The control unit 370 is connected to a power source and is designed such that the control unit can electronically control the electric motor 180 in a controlled or regulated manner by means of different current signals. The different current signals are used for different angular momentums of the electric motor 180, wherein the current signals are transmitted to the electric motor 180 via control lines. The power source can be designed, for example, as a battery or, as in the illustrated embodiment, as a battery pack 190 or as a mains connection.

[0085] Furthermore, operating elements (not shown in detail) may be provided for setting different operating modes and / or directions of rotation of electric motor 180 .

[0086] According to one aspect of the invention, a method is provided by means of which it is possible to determine, for example, Figure 1 The handheld power tool 100 is shown as it progresses in use, for example during a screwing-in or screwing-out process. The method is essentially based on studying the waveform and determining the degree of consistency of the waveform, which can correspond, for example, to an evaluation of the further rotation of an element driven by the handheld power tool 100, for example a screw.

[0087] 2 shows in this context exemplary signals of operating variables 200 of the electric motor 180 of a rotary impact driver, as would occur in the case of intended use of a rotary impact driver or in a similar manner. Although the following embodiments relate to a rotary impact driver, they are also applicable within the scope of the invention to other handheld power tools 100, such as a hammer drill.

[0088] In the embodiment of FIG. 2 , time is plotted on the abscissa x as a reference variable. However, in alternative embodiments, time-related variables may also be used as reference variables, such as the rotation angle of the tool receiving part 140, the rotation angle of the electric motor 180, acceleration, jerk (Ruck), in particular higher-order jerk, power or energy. In the figure, the motor speed n acting at each moment is plotted on the ordinate f(x). Instead of the motor speed, other operating variables related to the motor speed may also be selected. In alternative embodiments of the present invention, f(x) represents, for example, a signal of the motor current.

[0089] The motor speed and the motor current are operating variables which are usually detected in the portable power tool 100 and which are detected by the control unit 370 without any additional effort. The signal of the operating variable 200 of the electric motor 180 is determined in Figure 4 In the method step S2, Figure 4 A schematic flow chart of the method according to the invention is shown. In a preferred embodiment of the invention, a user of the handheld power tool 100 can select the operating variables based on which the method according to the invention is to be carried out.

[0090] FIG2(a) shows the use of a loose fastening element, such as a screw 900, in a fastening carrier 902, such as a wooden board. FIG2(a) shows that the signal includes a first region 310, which is characterized by a monotonically increasing motor speed and a relatively constant motor speed region (also referred to as a plateau). In FIG2(a), the intersection of the abscissa x and the ordinate f(x) corresponds to the start of the rotary impact screwdriver during the screwing process.

[0091] In the first region 310, the screw 900 encounters relatively little resistance in the fastening carrier 902, and the torque required for screwing in is lower than the breakaway torque of the rotary impact mechanism. Thus, the motor speed in the first region 310 corresponds to the operating state of the screwdriver without impact.

[0092] As can be seen in FIG. 2 (a), the head of the screw 900 does not rest against the fastening carrier 902 in the region 322, which means that the screw 900 driven by the rotary impact driver rotates further with each impact. This additional rotation angle decreases during the further operation, which is reflected in the figure by the reduced cycle duration. In addition, the further screwing in is also reflected by the average reduced rotation speed.

[0093] Then, if the head of screw 900 reaches base plate 902, a higher torque and thus more impact energy are required for further screwing in. However, since handheld power tool 100 does not provide more impact energy, screw 900 is not rotated further or is only rotated further by a much smaller rotation angle.

[0094] The rotary impact operation performed in the second region 322 and the third region 324 is characterized by an oscillating profile of the signal of the operating variable 200, wherein the waveform of the oscillation can be, for example, a trigonometric function or another form of oscillation. In the present case, the oscillation has a profile that can be called a modified trigonometric function. In the impact screwing operation, the characteristic waveform of the signal of the operating variable 200 is formed by the opening and idling of the impact mechanism striker and the system chain between the impact mechanism and the electric motor 180, in particular the transmission 170.

[0095] That is, the qualitative waveform of the impact operation is known in principle based on the inherent characteristics of the rotary impact driver. Figure 4 In the method according to the invention, based on this knowledge, at least one state-typical model waveform 240 is provided in step S1, wherein the state-typical model waveform 240 is assigned to a work progress, which is, for example, until the head of the screw 900 comes to rest on the fastening carrier 902. In other words, the state-typical model waveform 240 contains features that are typical for the work progress, such as the presence of an oscillation curve, an oscillation frequency or an oscillation amplitude or individual signal sequences in continuous, quasi-continuous or discrete form.

[0096] In other applications, the work progress to be detected is characterized by a waveform other than vibration, for example by a discontinuity or rate of increase in the function f(x). In these cases, instead of vibration, a typical model waveform in terms of the state is characterized by these parameters.

[0097] In a preferred embodiment of the method of the present invention, in method step S1, a state-typical model waveform 240 is determined by the user. The state-typical model waveform 240 can also be stored or stored in the device. In an alternative embodiment, the state-typical model waveform can be provided to the handheld power tool 100 instead and / or in addition, for example, from an external data device.

[0098] In method step S3 of the method according to the invention, the signal of the operating variable 200 of the electric motor 180 is compared with the state-typical model waveform 240. "Comparison" is to be interpreted broadly and in the sense of signal analysis in the context of the present application, so that the result of the comparison can also be, in particular, that the signal of the operating variable 200 of the electric motor 180 partially or gradually matches the state-typical model waveform 240, wherein the degree of consistency of the two signals can be determined by different mathematical methods, which will be mentioned later.

[0099] Furthermore, in step S3, the comparison determines a consistency evaluation of the signal of the operating variable 200 of the electric motor 180 with the state-typical template waveform 240 and thus draws conclusions about the consistency of the two signals. The execution and sensitivity of the consistency evaluation are factory- or user-adjustable parameters for detecting the progress of the work.

[0100] Figure 2(b) shows a curve of the function q(x) of the consistency evaluation 201 corresponding to the signal of the operating parameter 200 of Figure 2(a), which shows the value of the consistency between the signal of the operating parameter 200 of the electric motor 180 and the typical sample waveform 240 in terms of the state at each point on the horizontal axis x.

[0101] In the present example of screwing in a screw 900, the evaluation is considered to determine the extent of further rotation during the impact. The model waveform 240, which is typical in terms of the state, which is predefined in step S1, corresponds in this example to an ideal impact without further rotation, i.e. a state in which the head of the screw 900 rests on the surface of the fastening carrier 902, as shown in area 324 of FIG. 2(a). Accordingly, a high consistency of the two signals is obtained in area 324, which is reflected by the constant high value of the function q(x) of the consistency evaluation 201. In area 310, where there is a large rotation angle of the screw 900 with each impact, only a small consistency value is achieved. The less the screw 900 is further rotated during the impact, the higher the consistency, which can be seen from the following: the function q(x) of the consistency evaluation 201 already shows a continuously increasing consistency value in the case of using an impact mechanism in area 322, which is characterized by the fact that the rotation angle of the screw 200 with each impact is continuously reduced due to the increased screw-in resistance.

[0102] In method step S4 of the method according to the invention, the progress of the work is identified at least in part based on the consistency evaluation 201 determined in method step S3. As can be seen in FIG. 2 , the consistency evaluation 201 of the signal is very suitable for distinguishing impacts based on its more or less step-like characteristics, wherein this step change is caused by a more or less step-like change in the further rotation angle of the screw 900 at the end of the exemplary work process. The identification of the progress of the work can be carried out at least in part here, for example, based on a comparison of the consistency evaluation 201 with a threshold value, which is represented by a dashed line 202 in FIG. 2( b). In the example of FIG. 2( b), the intersection point SP of the function q(x) of the consistency evaluation 201 and the line 202 is assigned to the progress of the work: the head of the screw 900 is in contact with the surface of the fastening carrier 902.

[0103] The criterion for determining the progress of work derived therefrom is also adjustable here so that the function can be used for different application situations. It should be pointed out here that the function is not limited to the screw-in situation, but can also include the application in the screw-out situation.

[0104] According to the invention, the further rotation of the element driven by the rotary impact driver can be evaluated by differentiating the waveform to confirm the progress of work in the application. According to a preferred embodiment of the invention, in method step S5, a suitable reaction or routine of the tool related to the application is implemented at least partially based on the progress of the work, such as shutting down the machine, changing the rotation speed of the electric motor 180 and / or providing visual, acoustic and / or tactile feedback to the user of the handheld power tool 100.

[0105] In practical applications, it can be provided that method steps S2 and S3 are repeatedly performed during operation of the handheld power tool 100 in order to monitor the progress of the work of the application being performed. For this purpose, in method step S2, the ascertained signal of the operating variable 200 can be segmented so that method steps S2 and S3 are performed on signal segments that preferably have a constant, determined length.

[0106] For this purpose, the signal of the operating variable 200 can be stored as a sequence of measured values ​​in a memory, preferably a ring-shaped memory. In this embodiment, the handheld power tool 100 comprises a memory, preferably a ring-shaped memory.

[0107] As already mentioned in conjunction with FIG. 2 , in a preferred embodiment of the invention, in method step S2, the signal of operating variable 200 is ascertained as a time profile of a measured value of the operating variable or as a measured value of a variable of the operating variable associated with the time profile with respect to electric motor 180. The measured values ​​can be discrete, approximately continuous or continuous.

[0108] One embodiment provides that, in method step S2, the signal of the operating parameter 200 is recorded as the time curve of the measured value of the operating parameter and, in method step S2a following method step S2, the time curve of the measured value of the operating parameter is converted into the curve of a variable of the measured value of the operating parameter associated with the time curve with respect to the electric motor 180, such as the rotation angle of the tool receiving part 140, the motor rotation angle, acceleration, jerk, in particular higher-order jerk, power or energy.

[0109] The advantages of this embodiment are described below with reference to FIG3. Similar to FIG2, Figure 3a The signal f(x) of the operating variable 200 is shown with respect to the abscissa x, where the abscissa is currently the time t. As in FIG2 , the operating variable may be the motor speed or a variable associated with the motor speed.

[0110] The image contains two signal curves of the operating variable 200, which can each be assigned to a work progress, for example, to a rotary impact screwing mode in the case of a rotary impact screwdriver. In both cases, the signal includes a wavelength of an oscillation curve that is ideally assumed to be sinusoidal, wherein the signal with a shorter wavelength T1 has a curve with a higher impact frequency, and the signal with a longer wavelength T2 has a curve with a lower impact frequency.

[0111] Both signals can be generated with the same handheld power tool 100 at different motor speeds and depend in particular on the rotational speed requested by the user via an operating switch of the handheld power tool 100 .

[0112] If, for example, the parameter “wavelength” is used to define a state-typical model waveform 240, then in the present case at least two different wavelengths T1 and T2 must be stored as possible parts of the state-typical model waveform so that a comparison of the signal of the operating variable 200 with the state-typical model waveform 240 leads to “identical” results in both cases. Since the motor speed generally changes over time and to a large extent, this has the consequence that the wavelength to be sought also changes and therefore the method for identifying the impulse frequency must be adapted accordingly.

[0113] With a large number of possible wavelengths, the complexity of such methods and programming increases correspondingly rapidly.

[0114] Thus, in a preferred embodiment, the time values ​​of the abscissa are converted into values ​​associated with the time values, such as acceleration values, higher-order jerk values, power values, energy values, frequency values, values ​​of the rotation angle of the tool receiving part 140 or values ​​of the rotation angle of the electric motor 180. This is possible because the fixed transmission ratio of the electric motor 180 to the impact mechanism and to the tool receiving part 140 results in a direct, known relationship between the motor speed and the impact frequency. By normalization, a periodically constant oscillating signal is achieved that is independent of the motor speed, which is Figure 3b , which is shown by two signals resulting from the transformation of the signals belonging to T1 and T2 , wherein the two signals now have the same wavelength P1 = P2 .

[0115] Accordingly, in an embodiment of the present invention, a sample waveform 240 which is typical in terms of the state and which is applicable to all rotational speeds is determined by a single parameter of the wavelength with respect to a time-related variable, such as the rotation angle of the tool receiving part 140, the motor rotation angle, acceleration, jerk, in particular high-order jerk, power or energy.

[0116] In a preferred embodiment, in method step S3, the comparison of the signal of the operating variable 200 is performed by a comparison method, wherein the comparison method includes at least one frequency-based comparison method and / or a comparative comparison method. The comparison method compares the signal of the operating variable 200 with a sample waveform 240 that is typical in terms of the state: whether at least one predetermined threshold value is met. The comparison method compares the measured signal of the operating variable 200 with at least one predetermined threshold value. The frequency-based comparison method includes at least a bandpass filter and / or a frequency analysis. The comparative comparison method includes at least a parameter evaluation and / or a cross correlation. The frequency-based comparison method and the comparative comparison method are described in detail below.

[0117] In an embodiment with the aid of a bandpass filter, the input signal, which is likewise transformed into a time-dependent variable as described, is filtered through one or more passbands, the passbands of which correspond to one or more state-typical model waveforms. The passbands are obtained from the state-typical model waveform 240. It is also conceivable that the passbands correspond to a frequency determined in conjunction with the state-typical model waveform 240. When the work progress to be identified is reached, the amplitude of the frequency exceeds a previously determined limit value, if the amplitude of the frequency exceeds the limit value, then the comparison in method step S3 leads to the conclusion that the signal of the operating variable 200 is identical to the state-typical model waveform 240, so that the work progress to be identified has been reached. In this embodiment, the determination of the amplitude limit value can be understood as the determination of a consistency evaluation of the state-typical model waveform 240 and the signal of the operating variable 200, based on which it is determined in method step S4 whether there is a work progress to be identified.

[0118] The following embodiment is to be explained with reference to FIG. 9 , in which a frequency analysis is used as a frequency-based comparison method. In this case, a signal of the operating variable 200 , as shown in FIG. 9 ( a ) and corresponding, for example, to the time course of the rotational speed of the electric motor 180 , is transformed from the time domain into the frequency domain with corresponding weighting of the frequencies based on the frequency analysis, for example, based on a Fast Fourier Transformation (FFT). Here, the term “time domain” is to be understood as both “the time course of the operating variable” and “the course of the operating variable as a time-dependent variable” according to the above embodiment.

[0119] This form of frequency analysis is well known as a mathematical tool for signal analysis in many technical fields and is used in particular to approximate the measured signal as a series expansion of weighted periodic harmonic functions of different wavelengths. Figure 9(b) and 9(c) By way of example, the weighting factors κ1(x) and κ2(x) of the function curves 203 and 204 as a function of time indicate whether and to what extent corresponding frequencies or frequency bands exist in the signal under investigation, i.e., the course of the operating variable 200, which are not plotted here for the sake of clarity.

[0120] That is, in the method according to the invention, it is possible to determine by means of frequency analysis whether a frequency associated with a state-typical model waveform 240 is present in the signal of the operating variable 200 and at what amplitude it is present. In addition, however, it is also possible to define a frequency whose absence is a measure of the presence of the work progress to be detected. As mentioned in connection with the bandpass filter, an amplitude limit value can be determined, which is a measure of the degree of correspondence between the signal of the operating variable 200 and the state-typical model waveform 240.

[0121] In the example of FIG. 9( b ), in the signal of the operating variable 200 , for example at time t2 (point SP2), the amplitude κ1(x) of the first frequency which should not normally be present in the first sample waveform 240 which is typical for the state falls below the corresponding boundary value 203(a), which is a necessary but not sufficient criterion for the presence of the work progress to be identified in this example. In the signal of the operating variable 200 , at time t3 (point SP3), the amplitude κ2(x) of the second frequency which can normally be found in the second sample waveform 240 which is typical for the state exceeds the corresponding boundary value 204(a). In a corresponding embodiment of the present invention, the simultaneous presence of the amplitude functions κ1(x), κ2(x) falling below or exceeding the boundary values ​​203(a), 204(a) respectively is a decisive criterion for the evaluation of the consistency of the signal of the operating variable 200 with the sample waveform 240 which is typical for the state. Accordingly, in this case, it is determined in method step S4 that the work progress to be identified has been reached.

[0122] In alternative embodiments of the present invention, only one of these criteria or a combination of one or two of these criteria with other criteria (eg, achieving a desired rotational speed of electric motor 180 ) is used.

[0123] In one embodiment, a comparative comparison method is used, in which the signal of the operating variable 200 is compared with a state-typical model waveform 240 to find out whether the measured signal of the operating variable 200 is at least 50% consistent with the state-typical model waveform 240 and thus whether a predetermined threshold value is reached. It is also conceivable to compare the signal of the operating variable 200 with the state-typical model waveform 240 to determine the consistency of the two signals with each other.

[0124] In some embodiments of the method according to the invention, parameter evaluation is used as a comparative comparison method, in which the measured signal of the operating variable 200 is compared with a state-typical model waveform 240, wherein the parameters evaluated for the state-typical model waveform 240 are identified. The degree of consistency between the measured signal of the operating variable 200 and the state-typical model waveform 240 can be determined with the aid of the evaluation parameters: whether the work progress to be identified has been achieved. The parameter evaluation is based on an adjustment calculation (Ausgleichungsrechnung), which is a mathematical optimization method known to those skilled in the art. This mathematical optimization method makes it possible to adapt the state-typical model waveform 240 to a series of measurement data of the signal of the operating variable 200 with the aid of the evaluation parameters. Based on the degree of consistency between the state-typical model waveform 240 parameterized with the aid of the evaluation parameters and the limit values, it can be determined whether the work progress has been achieved.

[0125] By means of an adjustment calculation using a comparative method of parameter evaluation, it is also possible to determine the degree of consistency between the evaluation parameters of the state-typical template waveform 240 and the measured signal of the operating variable 200 .

[0126] In order to determine whether the state-typical model waveform 240 is sufficiently consistent or sufficiently good with the measured signal of the operating variable 200 with the evaluation parameter, a consistency determination is performed in method step S3a following method step S3. If 70% consistency is determined between the state-typical model waveform 240 and the measured signal of the operating variable, it can be determined whether the work progress to be identified has been recognized based on the signal of the operating variable and whether the work progress to be identified has been achieved.

[0127] In another embodiment, in order to determine whether the state-typical model waveform 240 and the signal of the operating variable 200 are sufficiently consistent, a quality determination of the evaluation parameter is performed in method step S3b following method step S3. In the quality determination, a quality value between 0 and 1 is determined, wherein a low value represents a high degree of confidence in the value of the identified parameter and thus represents a high degree of consistency between the state-typical model waveform 240 and the signal of the operating variable 200. In a preferred embodiment, in method step S4, the determination of whether there is a work progress to be identified is at least partially based on the condition that the quality value is in the range of 50%.

[0128] In an embodiment of the method according to the invention, in method step S3, a cross-correlation method is used as a comparative comparison method. Like the mathematical methods mentioned above, the cross-correlation method is also sufficiently known to the person skilled in the art. In the cross-correlation method, a sample waveform 240 which is typical for the state is correlated with the measured signal of the operating variable 200.

[0129] Analogously to the parameter evaluation method described above, the result of the cross-correlation is a signal sequence having a signal length which is the sum of the length of the signal of the operating variable 200 and the state-typical model waveform 240, which indicates the similarity of the time-shifted input signals. The maximum of the output sequence represents the time of maximum agreement of the two signals (i.e. the signal of the operating variable 200 and the state-typical model waveform 240) and is thus also a measure of the correlation itself, which in this embodiment is used in method step S4 as a criterion for reaching the work progress to be identified. In the execution of the method according to the invention, a significant difference from the parameter evaluation is that any state-typical model waveform can be used for the cross-correlation, whereas in the parameter evaluation the state-typical model waveform 240 must be representable by a parameterizable mathematical function.

[0130] 5 shows a measured signal of an operating variable 200 for the case in which a bandpass filter is used as a frequency-based comparison method. The abscissa x is the time t or a variable that is correlated with time. Figure 5a Measured signals of operating variables, input signals of a bandpass filter, are shown, wherein in a first range 310 the handheld power tool 100 is operated in a screw-driving operating mode. In a second range 320 the handheld power tool 100 is operated in a rotary impact operating mode. Figure 5b The output signal is presented after the input signal has been pass-band filtered.

[0131] FIG. 6 shows a measured signal of an operating variable 200 for the case where a frequency analysis is used as a frequency-based comparison method. Figure 6a A and b show a first region 310, in which the handheld power tool 100 is operated in a screw-driving mode. Figure 6a The horizontal axis x is time t or a parameter related to time. Figure 6b In FIG. 1 , the signal of the operating variable 200 is shown in a transformed form, wherein the transformation from time to frequency can be performed, for example, by means of a fast Fourier transformation. Figure 6b For example, the frequency f is plotted on the abscissa x' of , so that the amplitude of the signal of the operating variable 200 is shown. Figure 6c d show a second region 320 in which the handheld power tool 100 is in a rotary impact operation. Figure 6c A measured signal of operating variable 200 over time is shown during a rotary impact operation. Figure 6d The transformed signal of operating variable 200 is shown, wherein the signal of operating variable 200 is plotted over frequency f as abscissa x′. Figure 6d Characteristic amplitudes of the rotary impact operation are shown.

[0132] Figure 7a A typical case of a comparison between the signal of the operating variable 200 and the state-typical model waveform 240 by means of a comparative comparison method of parameter evaluation in the first region 310 described in FIG2 is shown. While the state-typical model waveform 240 has an essentially trigonometric course, the signal of the operating variable 200 has a course that differs greatly from this. Independent of the choice of the comparison method described above, in this case the comparison between the state-typical model waveform 240 and the signal of the operating variable 200 carried out in method step S3 yields the result that the degree of agreement between the two signals is so low that no work progress to be identified in method step S4 can be determined.

[0133] and Figure 7b 2 shows the situation where there is a work progress to be identified, so that the typical template waveform 240 and the signal of the operating variable 200 have a high degree of consistency in terms of the state, although deviations can be determined at individual measuring points. It can be determined by a comparative comparison method of parameter evaluation whether the work progress to be identified has been achieved.

[0134] FIG. 8 shows a typical sample waveform 240 for the state (see FIG. Figure 8b and e) with the measured signal of the operating variable 200 (see Figure 8a and 8d), for the following cases: using cross-correlation as a contrastive comparison method. Figure 8a –f plots time or a time-related parameter on the horizontal axis x. Figure 8a -c shows the first region 310 corresponding to the screwing operation. Figure 8d -f shows a third area 324 corresponding to the work progress to be identified. As described above, the measured signal ( Figure 8a and Figure 8d ) and the typical sample waveform in terms of state ( Figure 8b and 8e). Figure 8c The corresponding correlation results are shown in and 8f. Figure 8c The correlation result during the first region 310 is shown in FIG. , where it can be seen that there is a small coincidence of the two signals. Figure 8c In the example of , it is determined in method step S4 that the work progress to be identified has not been reached. Figure 8f The correlation during the third region 324 is shown in FIG. Figure 8f As can be seen in FIG. 1 , there is a high degree of consistency, so that in method step S4 it is determined that the work progress to be identified has been reached.

[0135] The invention is not limited to the exemplary embodiments described and shown, but rather also encompasses all developments conceivable by a person skilled in the art within the scope of the inventive concept defined by the claims.

[0136] Other embodiments are conceivable that may include further variations and combinations of features besides those described and shown.

Claims

1. A method for identifying a working progress of a handheld power tool (100), the handheld power tool (100) comprising an electric motor (180), the method comprising the following method steps: S1 provides at least one sample waveform (240), wherein: The template waveform (240) can be assigned to the work progress of the handheld power tool, the template waveform (240) being an oscillating curve; S2 obtains a signal of an operating parameter (200) of the electric motor (180); S3 comparing the signal of the operating parameter (200) with the template waveform (240) and obtaining a consistency evaluation from the comparison; S4 identifies the work progress at least partially based on the consistency evaluation determined in method step S3; The handheld power tool (100) is an impact driver and the work progress to be detected is an impact without further rotation of the tool holder.

2. The method according to claim 1, characterized in that The template waveform (240) is an oscillating curve substantially in the form of a trigonometric function.

3. The method according to claim 1 or 2, characterized in that: The operating variable is the rotational speed of the electric motor (180) or an operating variable correlated with the rotational speed.

4. The method according to claim 1 or 2, characterized in that: The determination of the consistency evaluation in method step S3 includes a comparison of the consistency between the signal of the operating variable (200) and the template waveform (240) with at least one consistency threshold value.

5. The method according to claim 4, characterized in that The consistency threshold value may be determined by a user of the handheld power tool and / or may be predefined at the factory.

6. The method according to claim 5, characterized in that The consistency threshold value can be selected by a user based on factory-defined preselections of an application scenario of the handheld power tool.

7. The method according to claim 1 or 2, characterized in that: The template waveform (240) in method step S1 is variably provided; The template waveform (240) can be variably predefined by a user.

8. The method according to claim 1 or 2, characterized in that: The method further comprises a method step S5, in which a routine of the handheld power tool (100) is triggered at least partially based on the work progress detected in method step S4.

9. The method according to claim 8, characterized in that The reaction of the handheld power tool (100) in method step S5 includes at least one of the following routine groups: changing the rotation speed of the electric motor (180); reversing the rotation direction of the electric motor (180); providing visual, acoustic and haptic feedback to the user.

10. The method according to claim 1 or 2, characterized in that: In method step S1, the template waveform (240) is predefined; The template waveform is determined by the factory.

11. The method according to claim 1 or 2, characterized in that: In method step S2, the signal of the operating variable (200) is recorded as a time profile of a measured value of the operating variable or as a measured value of a variable of the operating variable associated with the time profile with respect to the electric motor (180).

12. The method according to claim 1 or 2, characterized in that: In method step S2, the signal of the operating variable (200) is recorded as a time curve of a measured value of the operating variable, and, in method step S2a following method step S2, the time curve of the measured value of the operating variable is converted into a curve of a variable of the measured value of the operating variable with respect to the electric motor (180) which is associated with the time curve.

13. The method according to claim 1 or 2, characterized in that: In method step S3, the signal of the operating variable (200) is compared by means of one of the following comparison methods: the comparison method comprises at least one frequency-based comparison method and / or at least one comparative comparison method.

14. The method according to claim 13, characterized in that The frequency-based comparison method comprises at least a bandpass filter and / or a frequency analysis, wherein the threshold value is at least 90% of a predefined limit value.

15. The method according to claim 13, characterized in that The comparative comparison method comprises at least parameter evaluation and / or cross correlation, wherein the threshold value is that the signal of the operating parameter (200) is at least 40% consistent with the template waveform (240).

16. The method according to claim 1 or 2, characterized in that: The work progress is detected based on less than ten impacts of a striking mechanism of the handheld power tool (100).

17. The method according to claim 1 or 2, characterized in that: The handheld power tool (100) is a rotary impact driver.

18. The method according to claim 14, characterized in that The threshold value is at least 95% of the predefined limit value.

19. The method according to claim 14, characterized in that The threshold value is at least 98% of the predefined limit value.

20. The method according to claim 16, characterized in that The work progress is identified based on less than ten impulse oscillation cycles of the electric motor (180).

21. The method according to claim 16, characterized in that The work progress is detected based on less than six impacts of the impact mechanism of the handheld power tool (100).

22. The method according to claim 16, characterized in that The work progress is identified based on less than six impulse oscillation cycles of the electric motor (180).

23. The method according to claim 16, characterized in that The work progress is detected based on less than four impacts of a striking mechanism of the handheld power tool (100).

24. The method according to claim 16, characterized in that The work progress is identified based on less than four impulse oscillation cycles of the electric motor (180).

25. A handheld power tool (100) comprising an electric motor (180), a measured value recorder for operating variables of the electric motor (180), and a control unit (370), characterized in that: The control unit (370) is configured to perform the method according to any one of claims 1 to 24.

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