DE102024207087A1 - Method for operating a hand-held power tool - Google Patents

Abstract

The disclosure relates to a method for operating a hand-held power tool, the hand-held power tool comprising an electric motor, the method comprising the following process steps:
S1 During use of the hand-held power tool, determining a signal of an operating parameter of the electric motor;
S2 Monitoring a frequency of the signal of the operating quantity during application;
S3 Determining the progress of the application at least partially based on the frequency of the signal of the operating variable.

Description

The invention relates to a method for operating a hand-held power tool and a hand-held power tool configured for carrying out the method. In particular, the present invention relates to a method for detecting the progress of work in the application of a hand-held power tool.

State of the art

From the state of the art, see for example EP 3 202 537 A1 Impact wrenches are known for tightening fasteners such as nuts and bolts. An impact wrench of this type comprises, for example, a mechanism in which an impact force in a rotational direction is transferred to a fastener by the rotary impact force of a hammer. The impact wrench with this mechanism includes a motor, a hammer driven by the motor, an anvil struck by the hammer, and a tool. The impact wrench also includes a position sensor that detects the motor's position and a controller coupled to the position sensor. The controller detects an impact from the impact mechanism, calculates a drive angle of the anvil caused by the impact based on the position sensor's output, and controls the brushless DC motor based on this drive angle.

From the US 9,744,658 An electrically driven tool with an impact mechanism is also known, wherein the hammer is driven by the motor. The rotary impact wrench further comprises a method for recording and reproducing a motor parameter.

When using impact wrenches, the user must maintain a high level of concentration on the work progress in order to react appropriately to changes in certain machine characteristics, such as the engagement or disengagement of the impact mechanism. This includes stopping the electric motor and/or adjusting the speed using the hand switch. Because the user often cannot react quickly or appropriately to changes in the work process, such as a screw head making contact with the material being fastened, impact wrenches can lead to problems such as overtightening screws during tightening operations and causing screws to fall out when being unscrewed at excessive speed.

It is therefore generally desirable to further automate operations and help the customer to more easily achieve a completely finished work process and to ensure reliably reproducible, high-quality screwing and unscrewing operations. Furthermore, the user should be supported by machine-triggered reactions or routines appropriate to the work progress. Examples of such machine-triggered reactions or routines include switching off the motor, changing the motor speed, or triggering a message to the user.

The provision of such intelligent tool functions can be achieved, among other things, by identifying the current operating state. In the prior art, this identification is carried out, independently of determining work progress or the status of an application, for example, by monitoring the operating parameters of the electric motor, such as speed and electrical motor current. Here, the operating parameters are examined to determine whether certain limit values and/or thresholds are reached. Corresponding evaluation methods work with absolute threshold values and/or signal gradients.

The disadvantage here is that a fixed limit value and/or threshold can practically only be perfectly set for one specific application. As soon as the application changes, the corresponding current and/or speed values, or their time profiles, also change, and impact detection based on the set limit value and/or threshold, or their time profiles, no longer works.

Thus, it can happen that, for example, an automatic shut-off based on the detection of impact operation reliably shuts off in various speed ranges in some applications when using self-tapping screws, but fails to shut off in other applications when using self-tapping screws. For various Therefore, various settings must be adjusted on the hand-held power tool or its control system to reliably achieve the desired functionality.

Other methods for determining operating modes in rotary impact wrenches use additional sensors, such as accelerometers, to infer the current operating mode from the vibration states of the tool.

Disadvantages of these methods include additional costs for the sensors and a reduction in the robustness of the hand-held power tool, as the number of built-in components and electrical connections increases compared to hand-held power tools without these sensors.

In principle, the problem of largely automating a business also exists with other hand-held power tools such as impact drills, so the invention is not limited to impact wrenches.

It is an object of the invention to provide an improved method for operating a hand-held power tool compared to the prior art, which at least partially overcomes the aforementioned disadvantages, or at least to provide an alternative to the prior art. A further object is to provide a corresponding hand-held power tool.

Disclosure of the invention

The object of the invention is achieved by means of a method for operating a hand-held power tool according to claim 1, by means of a control unit according to claim 16, and by means of a hand-held power tool according to claim 16. Advantageous further developments, additional features and/or advantages of the invention will become apparent from the dependent claims and the following description.

• S1 Während einer Anwendung der Handwerkzeugmaschine, Ermitteln eines Signals einer Betriebsgröße des Elektromotors;
• S2 Überwachen einer Frequenz des Signals der Betriebsgröße während der Anwendung;
• S3 Bestimmen eines Arbeitsfortschrittes der Anwendung zumindest teilweise auf Grundlage der Frequenz des Signals der Betriebsgröße.

According to a first aspect, the present disclosure discloses a method for operating a hand-held power tool, the hand-held power tool comprising an electric motor, the method comprising the process steps:

• S1 During use of the hand-held power tool, determining a signal of an operating parameter of the electric motor;
• S2 Monitoring a frequency of the signal of the operating quantity during application;
• S3 Determining the progress of the application at least partially based on the frequency of the signal of the operating variable.

The method defined above allows, for example, the reliable and fully automatic detection of the end of the screwing process in impact wrench applications, when the screw head is in contact with the material being screwed or is almost flush. This is because a characteristic change in frequency, such as the speed of the electric motor, occurs towards the end of the screwing process. Monitoring the frequency and thus determining the progress of the work relies exclusively on sensors and signals already integrated into the device; no additional sensors or other hardware are required. Signals that are necessary for the operation of the machine can be easily evaluated using digital signal processing functions implemented in the control software. This is possible for a wide variety of screwing applications, such as wood screws, self-tapping sheet metal screws, and direct concrete screws.

The process step S2 may include monitoring the frequency of the operating variable signal during application to determine whether a change in frequency reaches a predetermined level of change.

The change in the frequency of the operating variable signal can be determined by the ratio of a first frequency determined at a first time during the application and a second frequency of the operating variable signal determined at a second time during the application.

The process step S2 may include monitoring the frequency of the operating parameter signal during application to determine whether a predetermined frequency is reached.

The frequency of the operating variable signal can be monitored at least partially using a filter that filters out frequencies below a predetermined frequency from the operating variable signal, in particular using a bandpass filter.

The frequency of the operating variable signal can be determined by identifying zero crossings in the filtered operating variable signal.

• S4 Ausführen einer ersten Routine der Handwerkzeugmaschine zumindest teilweise auf Basis des in Verfahrensschritt S3 bestimmten Arbeitsfortschrittes.

The procedure may include the following procedural step:

• S4 Execute a first routine of the hand-held machine tool, at least partially, based on the work progress determined in process step S3.

The first routine can include stopping the electric motor based on one or more defined and/or predefinable parameters, particularly those predefinable by a user of the hand-held power tool. Examples of such parameters include a time period, a number of revolutions of the electric motor, a number of revolutions of the tool holder, a rotation angle of the electric motor, and a number of blows from the impact mechanism of the hand-held power tool.

The first routine may involve a change, in particular a reduction and/or an increase, in the speed of the electric motor. Such a change in the speed of the electric motor can be achieved, for example, by changing the motor current, the motor voltage, the battery current, or the battery voltage, or by a combination of these measures.

The amplitude of the change in the speed of the electric motor can be defined by a user of the hand-held power tool. Alternatively or additionally, the change in the speed of the electric motor can also be specified by a target value. In this context, the term amplitude should be understood generally as the magnitude of the change and not exclusively associated with cyclical processes.

The speed of the electric motor can be changed multiple times and/or dynamically, in particular in a time-staggered manner and/or along a characteristic curve of the speed change and/or based on the work progress of the hand-held power tool.

The progress of a work can be displayed to a user of the hand-held power tool using an output device on the tool. Displaying or documenting the work progress can refer to this. Documentation can also include evaluating and/or saving work progress. This includes, for example, saving multiple screwdriving operations to memory.

The first routine and/or characteristic parameters of the first routine can be set and/or displayed by a user via application software (“App”) or a user interface (“Human-Machine Interface”, “HMI”).

The HMI can be located on the machine itself or on external devices, such as a smartphone, a tablet, or a computer.

The first routine may include visual, auditory, and/or haptic feedback to a user.

The operating parameter can be the rotational speed of the electric motor or an operating parameter that correlates with the rotational speed.

The operating parameter signal can be recorded in process step S1 as a time series of measured values of the operating parameter, or as measured values of the operating parameter as a parameter of the electric motor that correlates with the time series.

The signal of the operating variable can be recorded in process step S1 as a time series of measured values of the operating variable, and in a process step S1a following the process step, a transformation of the time series of measured values of the operating variable into a series of measured values of the operating variable as a quantity of the electric motor that correlates with the time series can take place.

• V1 Bereitstellen zumindest einer Modellsignalform, wobei die Modellsignalform dem Arbeitsfortschritt der Handwerkzeugmaschine zuordenbar ist;
• V2 Vergleichen des Signals der Betriebsgröße mit der Modellsignalform und Ermitteln einer Übereinstimmungsbewertung aus dem Vergleich;
• V3 Bestimmen des Arbeitsfortschrittes zumindest teilweise anhand der in Verfahrensschritt S3 ermittelten Übereinstimmungsbewertung.

The procedure may include the following steps:

• V1 Providing at least one model signal shape, wherein the model signal shape is assignable to the work progress of the hand-held machine tool;
• V2 Comparing the signal of the operating variable with the model signal shape and determining a conformance rating from the comparison;
• V3 Determine the progress of the work, at least partially, based on the conformity assessment determined in procedure step S3.

The progress of the work can be determined, at least in part, by means of a joint evaluation of the process steps S3 and V3.

The model signal shape in step V1 can be a vibration profile, such as a vibration profile around a mean value, in particular an essentially trigonometric vibration profile. The model signal shape can, for example, represent an ideal impact operation of a hammer on an anvil of a rotary impact mechanism of a rotary impact wrench, where the ideal impact operation is preferably an impact without further rotation of the tool spindle of the power tool. Alternatively and/or additionally, the model signal shape can represent a signal profile of the operating parameter shortly before or during contact of a screw head with a screw base, or another defined work progress.

The operating parameter determined in step S1 can be recorded using a suitable sensor. It is advantageous that no additional sensor is required for this purpose, as various sensors, such as those for speed monitoring, especially Hall sensors, are already integrated into electric motors.

The operating parameter can be the rotational speed of the electric motor or an operating parameter correlated with the rotational speed. For example, the fixed gear ratio between the electric motor and the impact mechanism results in a direct relationship between motor speed and impact frequency. The motor current, which correlates with the rotational speed, can also be selected as an operating parameter, the signal of which is determined in step S1. The operating parameter of the electric motor can also be a motor voltage, a Hall effect signal from the motor, a battery current, or a battery voltage. Similarly, the operating parameter of the electric motor can be an acceleration of the electric motor, an acceleration of a tool holder, or a sound signal from the impact mechanism of the power tool.

In process step V2, the signal of the operating parameter can be compared using a comparison procedure to determine whether at least a predetermined threshold of agreement is met.

The comparison procedure can include at least a frequency-based comparison procedure and/or a comparative comparison procedure.

In this process, at least partially, the decision can be made using the frequency-based comparison method, in particular a bandpass filter and/or a frequency analysis, as to whether a detectable work progress has been identified in the signal of the operating quantity.

The frequency-based comparison method can include at least bandpass filtering and/or frequency analysis, wherein the specified threshold is at least 90%, in particular 95%, and most especially 98%, of a specified limit value.

In bandpass filtering, for example, the recorded signal of the operating parameter is filtered via a bandpass filter whose passband matches the model signal waveform. A corresponding amplitude in the resulting signal is to be expected when the relevant work progress to be detected is present, particularly in the case of an ideal strike without further rotation of the struck element. The specified threshold value of the bandpass filter can therefore be at least 90%, particularly 95%, and most especially 98%, of the corresponding amplitude in the work progress to be detected, particularly in the case of an ideal strike without further rotation of the struck element. The specified limit value can here be the corresponding amplitude in the resulting signal of an ideal work progress to be detected, particularly in the case of an ideal strike without further rotation of the struck element.

Using the well-known frequency-based comparison method of frequency analysis, the previously defined model signal shape, for example, a frequency spectrum of the work progress to be detected, in particular an ideal strike without further rotation of the struck element, can be searched for in the recorded signals of the operating variable. A corresponding amplitude of the work progress to be detected, in particular an ideal strike without further rotation of the struck element, is to be expected in the recorded signals of the operating variable. The specified threshold value of the frequency analysis can be at least 90%, in particular 95%, and most especially 98%, of the corresponding amplitude in the work progress to be detected, in particular an ideal strike without further rotation of the struck element. The specified limit value can be the corresponding amplitude in the recorded signals of an ideal work progress to be detected, in particular an ideal strike without further rotation of the struck element. Appropriate segmentation of the recorded signal of the operating variable may be necessary.

The comparative comparison method can include at least a parameter estimation and/or a cross-correlation, where the specified threshold is at least 40% agreement between the operating variable signal and the model signal shape.

The measured signal of the operating variable can be compared with the model signal waveform using a comparative comparison method. The measured signal of the operating variable is determined such that it has essentially the same finite signal length as that of the model signal waveform. The comparison of the model signal waveform with the measured signal of the operating variable can be output as a signal of finite length, in particular discrete or continuous. Depending on the degree of agreement or deviation of the comparison, a result can be output indicating whether the work progress to be detected, in particular the ideal strike without further rotation of the struck element, is present. If the measured signal of the operating variable matches the model signal waveform by at least 40%, the work progress to be detected, in particular the ideal strike without further rotation of the struck element, can be detected. Furthermore, the comparative method can output a degree of similarity between the measured signal of the operating variable and the model signal waveform as a result of the comparison. In this context, a degree of agreement of at least 60% can be a criterion for demonstrating the progress of the work, particularly the achievement of an ideal strike without further rotation of the struck element. It can be assumed that the lower limit for agreement is 40% and the upper limit is 90%. Accordingly, the upper limit for comparison is 60% and the lower limit is 10%.

Parameter estimation allows for a simple comparison between the previously defined model signal waveform and the signal of the operating variable. For this purpose, estimated parameters of the model signal waveform can be identified to align the model signal waveform with the measured signal of the operating variable. By comparing the estimated parameters of the previously defined model signal waveform with a threshold value, a result can be determined regarding the presence of the desired work progress, in particular the ideal impact without further rotation of the impacted element. Subsequently, a further evaluation of the comparison result can be performed to determine whether the predefined threshold value has been reached. This evaluation can either assess the accuracy of the estimated parameters or the agreement between the defined model signal waveform and the measured signal of the operating variable.

Process step V2 can include step V2a of a quality assessment for identifying the model signal shape within the operational variable signal, whereby in process step V3 the progress of the work is determined at least partially based on the quality assessment. A measure of the quality assessment can be the goodness of fit of the estimated parameters.

In process step V3, at least partially, a decision can be made by means of the quality determination, in particular the measure of quality, as to whether the work progress to be recognized has been identified in the signal of the company size.

In addition to or as an alternative to the quality determination, process step V2a can include a comparative determination of the identification of the model signal shape and the signal of the operating variable. The comparison of the estimated parameters of the model signal shape to the measured signal of the operating variable can be, for example, 70%, particularly 60%, and most especially 50%. In process step V3, the decision as to whether the work progress to be detected has occurred can be made, at least partially, based on the comparative determination. The decision regarding the presence of recognizable work progress can be made at the specified threshold of at least 40% agreement between the measured signal of the operating parameter and the model signal shape.

Cross-correlation allows a comparison between the previously defined model signal shape and the measured signal of the operating variable. In cross-correlation, the previously defined model signal shape can be correlated with the measured signal of the operating variable. By correlating the model signal shape with the measured signal of the operating variable, a measure of agreement between the two signals can be determined. This measure of agreement could be, for example, 40%, more specifically 50%, and most particularly 60%.

In process step V3, the progress of the work can be determined, at least partially, by cross-correlation of the model signal shape with the measured signal of the operating variable. This determination can be based, at least partially, on a predefined threshold of at least 40% agreement between the measured signal of the operating variable and the model signal shape.

In one embodiment, the conformity threshold can be set by a user of the hand-held power tool and/or is predefined at the factory.

In another embodiment, the hand-held power tool is an impact wrench, in particular a rotary impact wrench, and the work progress is an initiation or cessation of an impact operation, in particular a rotary impact operation.

In one embodiment, the conformance threshold can be selected by a user based on a factory-predefined preselection of application cases for the hand-held power tool. This can be done, for example, via a user interface, such as a human-machine interface (HMI), such as a mobile device, in particular a smartphone and/or a tablet.

In particular, the model signal shape can be variably defined in process step S1, especially by a user. Here, the model signal shape is assigned to the work progress to be detected, so that the user can specify the work progress to be detected.

Advantageously, the model signal shape is predefined in process step S1, particularly at the factory. In principle, it is conceivable that the model signal shape is stored or stored internally on the device, or alternatively and/or additionally provided to the hand-held power tool, particularly by an external data device.

In another embodiment, the signal of the operating variable is recorded in process step S2 as a time series of measured values of the operating variable, or as measured values of the operating variable as a quantity of the electric motor correlating with the time series, for example an acceleration, a jerk, in particular of a higher order, a power, an energy, a rotation angle of the electric motor, a rotation angle of the tool holder or a frequency.

In the latter embodiment, it can be ensured that a constant periodicity of the signal to be examined results regardless of the engine speed.

If the operating variable signal is recorded in process step S2 as a time series of measured values of the operating variable, then in a subsequent step S2a, based on a fixed gear ratio of the transmission, the time series of measured values of the operating variable is transformed into a series of measured values of the operating variable as a quantity of the electric motor that correlates with the time series. This results in the same advantages as with the direct recording of the operating variable signal over time.

The method according to the invention thus enables the detection of the work progress independently of at least one target speed of the electric motor, at least one starting characteristic of the electric motor and/or at least one state of charge of a power supply, in particular a battery, of the hand-held power tool.

The operating parameter signal should be understood here as a temporal sequence of measured values. Alternatively and/or additionally, the operating parameter signal can also be a frequency spectrum. and/or additionally, the signal of the operating parameter can also be processed, such as smoothed, filtered, fitted, and the like.

In another embodiment, the signal of the operating variable is stored as a sequence of measured values in a memory, preferably a ring buffer, in particular in the hand-held power tool.

In a process step, the work progress to be detected is identified based on fewer than ten impacts from a percussion mechanism of the power tool, in particular fewer than ten impact oscillation periods of the electric motor, preferably fewer than six impacts from a percussion mechanism of the power tool, in particular fewer than six impact oscillation periods of the electric motor, and most preferably fewer than four impacts from a percussion mechanism, in particular fewer than four impact oscillation periods of the electric motor. Here, an impact from the percussion mechanism is defined as an axial, radial, tangential, and/or circumferentially directed impact of a percussion striker, in particular a hammer, on a percussion body, in particular an anvil. The impact oscillation period of the electric motor is correlated with the operating parameter of the electric motor. An impact oscillation period of the electric motor can be determined based on fluctuations in the operating parameter signal.

Another object of the invention is a hand-held power tool comprising an electric motor, a sensor for an operating parameter of the electric motor, and a control unit, wherein the hand-held power tool is advantageously an impact wrench, in particular a rotary impact wrench, and the hand-held power tool is set up to carry out the method described above.

Preferably, the discernible work progress corresponds to a blow without further rotation of a tool holder of the hand-held power tool.

The electric motor of the hand-held power tool rotates an input spindle, and an output spindle is connected to the tool holder. An anvil is fixedly connected to the output spindle, and a hammer is connected to the input spindle in such a way that, as a result of the input spindle's rotation, the hammer performs an intermittent axial movement along the input spindle as well as an intermittent rotational movement around the input spindle. In this way, the hammer intermittently strikes the anvil, thus transferring an impact and a rotational impulse to the anvil and consequently to the output spindle. A first sensor transmits a first signal, for example, to determine the motor's rotation angle, to the control unit. Furthermore, a second sensor can transmit a second signal to the control unit to determine the motor's speed.

Advantageously, the hand-held power tool has a storage unit in which various values can be stored.

In another embodiment, the hand-held power tool is a battery-powered power tool, in particular a battery-powered impact wrench. This ensures flexible and mains-independent use of the power tool.

Advantageously, the hand-held power tool is an impact wrench, in particular a rotary impact wrench, and the discernible work progress is an impact of the rotary impact mechanism without further rotation of the impacted element or the tool holder.

The identification of the impacts of the impact mechanism of the hand-held power tool, in particular the impact oscillation periods of the electric motor, can be achieved, for example, by using a fitting algorithm that enables an evaluation of the impact detection within less than 100 ms, in particular less than 60 ms, and most especially less than 40 ms. The aforementioned inventive method enables the detection of work progress for essentially all of the above-mentioned applications and of the tightening of both loose and fixed fasteners into the mounting bracket.

The present invention makes it possible to largely dispense with more complex signal processing methods such as filters, signal feedback, system models (static and adaptive) and signal tracking.

Furthermore, these methods allow for even faster identification of the impact mechanism or work progress, enabling an even faster response from the tool. This applies particularly to the number of impacts elapsed after the impact mechanism is activated until identification, and also in special operating situations such as the start-up phase of the drive motor. This also eliminates the need to restrict the tool's functionality, such as reducing the maximum drive speed. Moreover, the algorithm's operation is independent of other influencing factors such as the target speed and battery charge level.

No additional sensors (e.g., accelerometers) are generally required; however, these evaluation methods can also be applied to signals from other sensors. Furthermore, in other motor designs that, for example, do not require speed measurement, this method can also be used for other signals.

The hand-held power tool can be a cordless screwdriver, a drill, an impact wrench (in particular a rotary impact wrench), a hammer drill, or a rotary hammer, using a drill bit, a core drill bit, or various bit attachments as tools. The hand-held power tool is specifically designed as an impact wrench, where the pulsed release of motor energy generates a higher peak torque for driving or unscrewing a screw or nut. In this context, "transmission of electrical energy" refers specifically to the hand-held power tool transferring energy to the body via a battery and/or a power cable connection.

Furthermore, depending on the chosen embodiment, the screw tool can be designed to be flexible in the direction of rotation. In this way, the proposed method can be used for both tightening and loosening a screw or nut.

Within the scope of the present invention, "determine" shall in particular include measuring or recording, wherein "record" shall be understood in the sense of measuring and storing, and furthermore, "determine" shall also include possible signal processing of a measured signal.

Furthermore, "decide" should also be understood as recognizing or detecting, whereby a clear assignment should be achieved. "Identify" should be understood as recognizing a partial match with a pattern, which can be made possible, for example, by fitting a signal to the pattern, performing a Fourier analysis, or similar methods. "Partial match" should be understood as the fitting exhibiting an error that is less than a predefined threshold, in particular less than 30%, and most specifically less than 20%.

According to another aspect, the present disclosure discloses a control unit for a hand-held machine tool, wherein the control unit is configured to carry out the method defined above.

According to another aspect, the present disclosure discloses a hand-held power tool comprising an electric motor, a sensor for an operating parameter of the electric motor, and a control unit as defined above.

Brief description of the characters

• 1 eine schematische Darstellung einer elektrischen Handwerkzeugmaschine;
• 2 eine schematische Darstellung eines Verfahrens zum Betrieb einer Handwerkzeugmaschine;
• 3(a) einen Arbeitsfortschritt einer Beispielanwendung sowie ein zugeordnetes Signal einer Betriebsgröße;
• 3(b) das in 3(a) gezeigte Signal der Betriebsgröße, nachdem es mit einem Filter bearbeitet wurde;
• 3(c) einen Frequenzverlauf des in 3(b) gezeigten Signal der Betriebsgröße;
• 4(a) einen Arbeitsfortschritt einer Beispielanwendung sowie ein zugeordnetes Signal einer Betriebsgröße;
• 4(b) eine Übereinstimmung des in 4(a) gezeigten Signals der Betriebsgröße mit einem Modellsignal;
• 5 eine schematische Darstellung zweier verschiedener Aufzeichnungen von Signalen einer Betriebsgröße;
• 6(a) ein Signal einer Betriebsgröße;
• 6(b) eine Amplitudenfunktion einer ersten, in dem Signal der 10 (a) enthaltenen Frequenz.
• 6(c) eine Amplitudenfunktion einer zweiten, in dem Signal der 10(a) enthaltenen Frequenz.
• 7 eine gemeinsame Darstellung eines Signals einer Betriebsgröße und eines Ausgabesignals einer Bandpassfilterung, basierend auf einem Modellsignal;
• 8 eine gemeinsame Darstellung eines Signals einer Betriebsgröße und einer Ausgabe einer Frequenzanalyse, basierend auf einem Modellsignal;
• 9 eine gemeinsame Darstellung eines Signals einer Betriebsgröße und eines Modellsignals für die Parameterschätzung; und
• 10 eine gemeinsame Darstellung eines Signals einer Betriebsgröße und eines Modellsignals für die Kreuzkorrelation.

The invention is explained in more detail below with reference to exemplary embodiments and the accompanying schematic drawing, which is not to scale. The figures (Fig.) in the drawing are merely examples and show:

• 1 a schematic representation of an electric hand-held power tool;
• 2 a schematic representation of a method for operating a hand-held power tool;
• 3(a) a progress indicator of a sample application and an associated signal of an operational variable;
• 3(b) the in 3(a) Signal shown of the operating size after it has been processed with a filter;
• 3(c) a frequency response of the in 3(b) displayed signal of the operating size;
• 4(a) a progress indicator of a sample application and an associated signal of an operational variable;
• 4(b) a match of the in 4(a) shown signal of the operating quantity with a model signal;
• 5 a schematic representation of two different recordings of signals of an operational variable;
• 6(a) a signal of an operational variable;
• 6(b) an amplitude function of a first signal, in which the signal of 10 (a) contained frequency.
• 6(c) an amplitude function of a second, in which the signal of 10(a) contained frequency.
• 7 a combined representation of a signal of an operating parameter and an output signal of a bandpass filter, based on a model signal;
• 8 a combined representation of a signal of an operating parameter and an output of a frequency analysis, based on a model signal;
• 9 a combined representation of a signal from an operating variable and a model signal for parameter estimation; and
• 10 a joint representation of a signal of an operating variable and a model signal for cross-correlation.

Based on the 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 until 10 The following schematically describes the structure and function of a method for operating a hand-held power tool, as well as a control unit and a hand-held power tool. Corresponding reference symbols are used for corresponding features.

The 1 Figure 1 shows a hand-held power tool 100 according to the invention, which has a housing 105 with a handle 115. According to the illustrated embodiment, the hand-held power tool 100 can be mechanically and electrically connected to a battery pack 190 for mains-independent power supply. 1 The hand tool 100 is exemplified as a cordless impact wrench. However, it should be noted that the present invention is not limited to cordless impact wrenches, but can in principle be applied to hand tools 100 where the detection of work progress is necessary, such as impact drills.

The housing 105 contains an electric motor 180, powered by the battery pack 190, and a gearbox 170. The electric motor 180 is connected to an input spindle via the gearbox 170. Furthermore, a control unit 370 is located within the housing 105 in the area of the battery pack 190. This control unit acts on the electric motor 180 and the gearbox 170 for control and/or regulation, for example, by means of a set motor speed n, a selected angular momentum, a desired gearbox gear x, or the like.

The electric motor 180, for example, can be operated via a hand switch 195, i.e., switched on and off, and can be any type of motor, such as an electronically commutated motor or a DC motor. In principle, the electric motor 180 is electronically controllable in such a way that both reversing operation and specifications regarding the desired motor speed n and the desired angular momentum are possible. The operating principle and construction of a suitable electric motor are sufficiently known from the prior art, so a detailed description is omitted here for the sake of brevity.

A tool holder 140 is rotatably mounted in the housing 105 via an input spindle and an output spindle. The tool holder 140 serves to hold a tool and can be integrally formed with the output spindle or attached to it as an add-on.

The control unit 370 is connected to a power source and is designed to electronically control the electric motor 180 using various current signals. These different current signals generate different rotational impulses for the electric motor 180, which are transmitted to the motor via a control line. The power source can be, for example, a battery, a battery pack 190 (as shown in the illustrated embodiment), or a mains connection.

Furthermore, operating elements, not shown in detail, may be provided to set different operating modes and/or the direction of rotation of the electric motor 180.

According to one aspect of the invention, a method for operating a hand-held power tool 100 is provided, by means of which a work progress, for example, of the in 1 The illustrated hand-held power tool 100 can detect an issue during an application, such as a screwing or unscrewing process, and this detection can trigger corresponding machine-side reactions or routines. This allows for reliably reproducible, high-quality screwing and unscrewing processes.

Aspects of the procedure are based, among other things, on an examination of at least one signal waveform and a determination of the frequency of that waveform. In addition, a determination of the degree of correspondence between this waveform and a model waveform can be made, where the model waveform can, for example, correspond to the continued rotation of an element driven by the hand-held power tool 100, such as a screw.

2 Figure 1 schematically shows a process for operating a hand-held power tool according to an embodiment of the present disclosure. In step S1, a signal of an operating parameter 200 of the electric motor 180 is determined during use of the hand-held power tool 100.

In 3(a) An exemplary signal of an operating size 200 of the electric motor 180 of an impact wrench, as it occurs in this or a similar form during the intended use of an impact wrench, is shown. While the following explanations refer to an impact wrench, they also apply analogously within the scope of the invention to other hand-held power tools 100, such as impact drills.

In the present example, the abscissa x is the 3 Time is plotted as a reference quantity. In an alternative embodiment, however, a time-correlated quantity is plotted as a reference quantity, such as the rotation angle of the tool holder 140, the rotation angle of the electric motor 180, an acceleration, a jerk, particularly of a higher order, a power, or an energy. On the ordinate f(x) in the 3(a) The motor speed n present at any given time x is plotted as a signal of the operating parameter 200. Instead of the motor speed, another operating parameter that correlates with the motor speed can also be chosen. In alternative embodiments, f(x) represents, for example, a signal of the motor current.

Motor speed and motor current are operating parameters that are typically detected by a control unit 370 of the hand-held power tool 100 without any additional effort. Therefore, no additional sensors or similar components are required. In some embodiments, a user of the hand-held power tool 100 can select the operating parameter on which the process is to be executed.

In 3(a) Figure 1 shows an application of screwing a loose fastening element, for example a screw 900, into a fastening carrier 902, for example a wooden board. It can be seen in 3(a) , that the signal 200 comprises a first region 310, characterized by a monotonous increase in engine speed, as well as a region of comparatively constant engine speed, which can also be described as a plateau. The intersection point between abscissa x and ordinate f(x) in 3(a) This corresponds to the start of the impact wrench during the screwing process.

In the first section 310, the screw 900 encounters relatively little resistance in the mounting bracket 902, and the torque required for screwing it in is below the disengagement torque of the rotary impact mechanism. The motor speed profile in the first section 310 therefore corresponds to the operating state of screwdriving without impact.

In step S2 of the method, a frequency of the signal of operating quantity 200 is monitored during application. For this purpose, the signal of operating quantity 200 is first filtered in embodiments of the method to eliminate constant and low-frequency components. 3(b) The signal of operating size 200' is shown after passing through a low-pass filter. In alternative embodiments, the frequency signal is filtered by a band-pass filter in step S2a, so that only a specific narrow frequency range, which is traversed from low to high during application, is present. is monitored. This has the advantage of significantly simpler signal processing. In particular, the frequency of the signal of operating size 200 can now be easily determined by the intervals between the zero crossings of the in 3(b) The filtered signal shown can be determined at 200'.

3(c) This shows, as an example, the 200" curve of the frequency F(x) of the motor speed over time. In the 3(a) The motor speed in the first range 310 is represented as increasing essentially monotonically or remaining constant over time, and a frequency of the filtered motor speed signal is shown in a simplified representation in 3(c) represented as equal to or close to zero.

In the second area 322, the screw's resistance to tightening is so great that the rotary impact operation is triggered. As in 3(a) As indicated, the head of screw 900 in the second area 322 is still not in contact with the mounting bracket 902, which means that the screw 900 driven by the impact wrench is turned further with each impact. Furthermore, further tightening can also be indicated by a decreasing average rotational speed.

The rotary percussion operation performed in the second 322 (and also the third area 324) is further characterized by an oscillating course of the signal of operating quantity 200, whereby the form of the oscillation can be, for example, trigonometric or otherwise oscillating. This is shown on the basis of the filtered signal 200" in 3(c) particularly easy to understand. In the present case, the oscillation has a shape that can be described as a modified trigonometric function. This characteristic shape of the signal of operating parameter 200 in impact screw operation arises from the winding and free-running of the impact mechanism hammer and the system chain, including the gearbox 170, located between the impact mechanism and the electric motor 180.

The additional rotation angle can decrease as the work process progresses, which is in the 3(c) reflected by an increasing frequency, that is, by a rising graph 200".

As the head of the screw 900 approaches the base 902 towards the end of the second section 322, an even higher torque and thus more impact energy is required for further screwing. However, since the hand-held power tool 100 does not supply any more impact energy, the screw 900 no longer rotates, or only by a significantly smaller angle. The frequency of the operating parameter signal thus continues to increase and reaches a predetermined degree of change at a time t _G , which in the illustrated embodiment represents the transition to the third section 324, as described in 3(c) shown in embodiments by a predefined limit value F _G.

When the predefined frequency limit F_{_G} is reached, the embodiment described here recognizes in step S3 that the progress of the screw head 900 resting on the mounting bracket 902 has been achieved. The frequency limit F_{_G} can be a value determined, for example, through testing, and/or can be set by the user.

In embodiments of the method, alternatively or additionally to the above, in step S2 the frequency of the signal of operating quantity 200 is monitored during application to determine whether a ratio of a first frequency _F1, determined at a first time _t1 during application, and a second frequency _F2 of the signal of operating quantity 200, determined at a second time _t2 during application, is reached. If a certain ratio value is exceeded, it is concluded that the corresponding work progress, for example, the head of the screw 902 resting on the mounting bracket 900, has been achieved. The ratio value can be a value determined, for example, through tests, and/or set by the user.

The frequency of the signal of operating quantity 200 at a specific time can be determined in step S2 by identifying zero crossings in the filtered signal of operating quantity 200'. This can be done using 3(b) This can be easily understood. For example, if it is determined in step S2b, using the known means of signal processing, that a zero crossing of the filtered signal of operating size 200' occurs at times x ₁ and x ₂ , the frequency at this time can be determined in step S2c as twice the value of the difference between x ₂ and x ₁ .

The zero crossings can be determined in step S2b by observing that the values of the sampled time series of the filtered signal of the operating quantity 200' change sign, in which 3(b) At time x1, the signal changes from a negative to a positive sign. The zero crossing is then assumed to occur at the sample with the new sign. This depends on the signal's sampling rate. For the operating size 200, it may be useful to perform an interpolation of the filtered signal of the operating size 200' in a step S2e in order to determine the time of the zero crossing even more precisely.

Again 2 As can be seen, step S2 can also include a further step S2d, in which additional filtering, for example using a moving average, is applied to further improve the accuracy of the method. Here, the rate of change of the frequency change of the previously determined oscillation frequency is examined. The frequency of the signal of operating quantity 200 changes particularly sharply at the transition of the head support, and by considering the derivative of the frequency, i.e., the rate of change, a fixed threshold value for the rate of change can be set as a limit for determining the work progress to be achieved.

In embodiments of the method, in step S4, an application-specific first routine of the hand-held power tool 100 is executed, at least partially, based on the work progress determined in step S3. For example, to prevent the screw head of the screw 900 from penetrating the fastening carrier 902, the machine can be switched off, the speed of the electric motor 180 can be changed, and/or visual, acoustic, and/or haptic feedback can be provided to the user of the hand-held power tool 100.

In one embodiment, the first routine comprises stopping the electric motor 180 taking into account at least one defined and/or predefinable parameter, in particular one predefinable by a user of the hand-held power tool.

In relation to 3(c) It should be noted that in some applications, the first region 310 may also contain a signal component within the operating parameter 200 whose frequency range is different from zero, even if the signal shape here is more or less random and, in particular, no characteristic oscillation occurs. It is therefore possible that when determining the zero crossings in step S2b, zeros in the first region 310 may also be identified, and thus frequencies may be erroneously determined, even if these are random in nature.

To further increase the reliability of the process, it is therefore possible, as in 2 Parallel to the steps described above, a comparison of the signal of operating parameter 200 with a predefined model signal shape is performed, which corresponds to the work progress to be detected, for example, impact operation in rotary impact wrenches or the contact of the head of the screw 900 with the fastening surface 902. This takes advantage of the fact that the qualitative signal shape of the work progress to be detected is, in principle, known due to the inherent properties of the rotary impact wrench.

In step V1, based on this finding, at least one state-typical model signal waveform 240 is provided, wherein the state-typical model signal waveform 240 can be assigned to a work progress, for example, a rotary impact operation or the point at which the head of the screw 900 rests on the mounting bracket 902. In other words, the state-typical model signal waveform 240 contains features typical for the work progress, such as the presence of a vibration profile, vibration frequencies or amplitudes, or individual signal sequences in continuous, quasi-continuous, or discrete form.

In other applications, the work progress to be detected may be characterized by signal forms other than oscillations, such as discontinuities or growth rates in the function f(x). In such cases, the state-typical model signal form is characterized by these parameters instead of oscillations.

In one embodiment of the method, the state-typical model signal waveform 240 can be defined by a user in process step V1. The state-typical model signal waveform 240 can also be stored or stored internally within the device. In an alternative embodiment, the state-typical model signal waveform can alternatively and/or additionally be provided to the hand-held power tool 100, for example, from an external data device.

In process step V2 of the method, the signal of the operating parameter 200 of the electric motor 180 is compared with the state-typical model signal waveform 240. The feature "compare" is to be interpreted broadly in the context of the present invention and in the sense of a signal analysis, so that a The result of the comparison may in particular be a partial or gradual agreement between the signal of the operating parameter 200 of the electric motor 180 and the state-typical model signal form 240, whereby the degree of agreement between the two signals can be determined by various mathematical procedures, which will be mentioned later.

In step V2, a conformity assessment is also determined from the comparison between the signal of operating parameter 200 of the electric motor 180 and the state-typical model signal waveform 240, thus making a statement about the conformity of the two signals. The execution and sensitivity of the conformity assessment are factory- or user-adjustable parameters for detecting work progress.

The foregoing will now be discussed with reference to 4 explained in more detail. 4(a) This corresponds to 3(a) , and those mentioned above in connection with 3(a) The explanations given apply accordingly. 4(b) shows a curve of a function q(x) corresponding to the signal of operating quantity 200. 4(a) corresponding conformity assessment 201, which specifies at each position of the abscissa x a value of conformity between the signal of the operating parameter 200 of the electric motor 180 and the state-typical model signal shape 240.

In the present example of screwing in screw 900, this evaluation is used to determine the degree of further rotation after a blow. The state-typical model signal shape 240, predetermined in step V2, corresponds in this example to an ideal blow without further rotation, that is, the state in which the head of screw 900 rests on the surface of the fastening carrier 902, as shown in section 324 of the 4(a) As shown, a high degree of agreement between the two signals is observed in region 324, reflected by a consistently high value of the q(x) function of the agreement evaluation 201. In region 310, however, where each impact is accompanied by large rotation angles of screw 900, only small agreement values are achieved. The less screw 900 rotates with each impact, the higher this agreement, as evidenced by the fact that the q(x) function of the agreement evaluation 201 already shows continuously increasing agreement values when the impact mechanism begins in region 322, which is characterized by a continuously decreasing rotation angle of screw 200 with each impact due to the increasing screw-in resistance.

In process step V3 of the embodiment of the method described herein, the work progress is now determined at least partially based on the conformity assessment 201 determined in process step V2. As in the example of the 4 As can be seen, the conformity assessment 201 of the signals for impact discrimination is well suited for this purpose due to its more or less abrupt nature, whereby this abrupt change is caused by the similarly more or less abrupt change in the further rotation angle of screw 900 when completing the exemplary work process. The determination of the work progress can, for example, be carried out at least partially by comparing the conformity assessment 201 with a threshold value, which is in 4(b) is marked by a dashed line 202. In the present example of the 4(b) The intersection point SP of the function q(x) of the conformity assessment 201 with the line 202 is assigned to the progress of the head of the screw 900 resting on the surface of the fastening carrier 902.

The resulting criterion used to determine work progress is adjustable to make the function suitable for a wide variety of applications. It should be noted that the function is not limited to screw-in applications but also includes applications for unscrewing.

In embodiments of the method, the progress is determined at least partially by a joint evaluation of process steps S3 and V3. This means that process steps S2 and V2 are initially executed essentially in parallel. Depending on whether the progress to be detected is first determined based on the frequency change of the operating variable signal or based on the conformity assessment with the model signal shape, the other criterion can be used for verification, and the progress is then considered detected if both criteria are met. Alternatively, the progress can be considered detected if it is determined either based on the frequency change of the operating variable signal or based on the conformity assessment with the model signal shape.

According to the invention, by differentiating signal shapes, it is therefore possible to evaluate the further rotation of an element driven by an impact wrench in order to determine the progress of an application.

The following explains some technical relationships and embodiments concerning the execution of process steps V1-V3.

In practical applications, it may be necessary to repeatedly execute process steps V2 and V3 during the operation of a hand-held power tool 100 in order to monitor the progress of the application. For this purpose, process step V2 may involve segmenting the determined signal of the operating parameter 200, so that process steps V2 and V3 are carried out on signal segments, preferably always of the same, fixed length.

For this purpose, the signal of the operating parameter 200 can be stored as a sequence of measured values in a memory, preferably a ring buffer. In this embodiment, the hand-held power tool 100 includes the memory, preferably the ring buffer.

As already mentioned, in preferred embodiments of the invention, in process step S1 the signal of the operating variable 200 is determined as a time series of measured values of the operating variable, or as measured values of the operating variable as a quantity of the electric motor 180 that correlates with the time series. The measured values can be discrete, quasi-continuous or continuous.

One embodiment provides that the signal of the operating variable 200 is recorded in process step S1 as a time series of measured values of the operating variable and in a process step S1a following process step S1, a transformation of the time series of measured values of the operating variable into a series of measured values of the operating variable as a quantity of the electric motor 180 that correlates with the time series takes place, such as the rotation angle of the tool holder 140, the motor rotation angle, an acceleration, a jerk, in particular of a higher order, a power, or an energy.

The advantages of this embodiment will be explained below. 5 described. Similar to 4 shows 5a Signals f(x) of an operating parameter 200 over an abscissa x, in this case over time t. As in 4 The operating parameter can be a motor speed or a parameter correlated with the motor speed.

The figure shows two signal waveforms of operating parameter 200, each of which can be assigned to a work progress, for example, the impact wrench mode in the case of a rotary impact wrench. In both cases, the signal comprises a wavelength of an idealized oscillation waveform assumed to be sinusoidal, with the signal with the shorter wavelength, T1, exhibiting a waveform with a higher impact frequency, and the signal with the longer wavelength, T2, exhibiting a waveform with a lower impact frequency.

Both signals can be generated with the same hand tool 100 at different motor speeds and depend, among other things, on the rotational speed requested by the user via the operating switch of the hand tool 100.

If, for example, the parameter "wavelength" is to be used to define the state-typical model signal waveform 240, then in this case at least two different wavelengths T1 and T2 would have to be defined as possible components of the state-typical model signal waveform so that the comparison of the signal of the operating parameter 200 with the state-typical model signal waveform 240 leads to the result "match" in both cases. Since the motor speed can generally change significantly over time, this means that the required wavelength also varies, and therefore the methods for detecting this stroke frequency would have to be adjusted accordingly.

With a large number of possible wavelengths, the effort required for the process and programming would increase correspondingly quickly.

In this embodiment, the time values of the abscissa are therefore transformed into values correlating with the time values, such as acceleration values, higher-order jerk values, power values, energy values, frequency values, rotation angle values of the tool holder 140, or rotation angle values of the electric motor 180. This is possible because the fixed transmission ratio of the electric motor 180 to the impact mechanism and the tool holder 140 results in a direct, known dependence on the motor rotation. This results in a number corresponding to the stroke frequency. This normalization achieves a vibration signal with consistent periodicity, independent of the motor speed, which is 5b represented by the two signals resulting from the transformation of the signals belonging to T1 and T2, where both signals now have the same wavelength P1=P2.

Accordingly, in this embodiment of the invention, the state-typical model signal shape 240 can be defined validly for all rotational speeds by a single parameter of the wavelength via the time-correlated quantity, such as the rotation angle of the tool holder 140, the motor rotation angle, an acceleration, a jerk, in particular of a higher order, a power, or an energy.

In one embodiment, the signal of operating parameter 200 is compared in process step V2 with a comparison method, wherein the comparison method comprises at least a frequency-based comparison method and/or a comparative comparison method. The comparison method compares the signal of operating parameter 200 with the state-typical model signal waveform 240 to determine whether at least one predefined threshold is met. The comparison method compares the measured signal of operating parameter 200 with at least one predefined threshold. The frequency-based comparison method comprises at least bandpass filtering and/or frequency analysis. The comparative comparison method comprises at least parameter estimation and/or cross-correlation. The frequency-based and the comparative comparison methods are described in more detail below.

In embodiments with bandpass filtering, the input signal, optionally transformed to a time-correlated quantity as described, is filtered by one or more bandpass filters whose passbands correspond to one or more state-typical model signal waveforms. The passband is derived from the state-typical model signal waveform 240. It is also conceivable that the passband corresponds to a frequency defined in connection with the state-typical model signal waveform 240. In the event that amplitudes of this frequency exceed a predetermined limit, as is the case when the work progress to be detected is reached, the comparison in process step V2 then leads to the result that the signal of the operating quantity 200 corresponds to the state-typical model signal waveform 240, and that thus the work progress to be detected has been reached. In this embodiment, the determination of an amplitude limit value can be understood as the determination of the conformity assessment of the state-typical model signal shape 240 with the signal of the operating parameter 200, on the basis of which it is determined in process step V3 whether the work progress to be detected is present or not.

Based on the 6 The embodiment in which frequency analysis is used as a frequency-based comparison method will be explained. In this case, the signal of operating quantity 200, which is in 6(a) The graph, which is represented, for example, as the speed of an electric motor at 180 rpm over time, is transformed from a time domain to a frequency domain with appropriate frequency weighting based on frequency analysis, such as the Fast Fourier Transform (FFT). Here, the term "time domain" is to be understood, as explained above, both as "the behavior of the operating variable over time" and as "the behavior of the operating variable as a time-correlated quantity."

Frequency analysis in this form is well-known as a mathematical tool for signal analysis in many areas of engineering and is used, among other things, to approximate measured signals as series expansions of weighted periodic harmonic functions of different wavelengths. In the 6(b) and 6(c) For example, weighting factors κ ₁ (x) and κ ₂ (x) indicate as function curves 203 and 204 over time whether and how strongly the corresponding frequencies or frequency bands, which are not specified here for the sake of clarity, are present in the signal under investigation, i.e. the course of the operating parameter 200.

With regard to the method disclosed herein, frequency analysis can thus be used to determine whether and with what amplitude the frequency associated with the state-typical model signal waveform 240 is present in the signal of the operating parameter 200. Furthermore, frequencies can also be defined whose absence is a measure of the presence of the work progress to be detected. As mentioned in connection with bandpass filtering, a limit value for the amplitude can be set, which is a measure of the degree of correspondence between the signal of the operating parameter 200 and the state-typical model signal waveform 240.

In the example of the 6(b) At time t ₂ (point SP ₂ ), the amplitude κ ₁ (x) of a first frequency, which is not typically found in the state-typical model signal waveform 240, falls below a corresponding limit value 203(a) in the signal of operating quantity 200. In this example, this is a necessary but not sufficient criterion for the presence of the work progress to be observed. At time t ₃ (point SP ₃ ), the amplitude κ ₂ (x) of a second frequency, which is typically found in the state-typical model signal waveform 240, exceeds a corresponding limit value 204(a) in the signal of operating quantity 200.

In the corresponding embodiment of the invention, the joint occurrence of the limit values 203(a) and 204(a) being exceeded or fallen below by the amplitude functions κ ₁ (x) and κ ₂ (x), respectively, is the decisive criterion for the conformity assessment of the signal of the operating parameter 200 with the state-typical model signal shape 240. Accordingly, in this case, it is determined in process step V3 that the work progress to be detected has been achieved.

In embodiments where the comparative comparison method is used, the signal of the operating parameter 200 is compared with the state-typical model signal waveform 240 to determine whether the measured signal of the operating parameter 200 exhibits at least a 50% match with the state-typical model signal waveform 240, thus reaching the predetermined threshold. It is also conceivable that the signal of the operating parameter 200 is compared with the state-typical model signal waveform 240 to determine the similarity between the two signals.

In embodiments of the method according to the invention, where parameter estimation is used as a comparative method, the measured signal of the operating variables 200 is compared with the state-typical model signal waveform 240, whereby estimated parameters are identified for the state-typical model signal waveform 240. Using the estimated parameters, a measure of the agreement between the measured signal of the operating variables 200 and the state-typical model signal waveform 240 can be determined, indicating whether the desired progress has been achieved. The parameter estimation is based on least squares analysis, a mathematical optimization method known to those skilled in the art. This mathematical optimization method allows the state-typical model signal waveform 240 to be adapted to a series of measurement data from the signal of the operating variable 200 using the estimated parameters. Depending on a measure of agreement between the state-typical model signal waveform 240, parameterized using the estimated parameters, and a limit value, a decision can be made as to whether the desired progress has been achieved.

Using the adjustment calculation of the comparative method of parameter estimation, a measure of the agreement between the estimated parameters of the state-typical model signal form 240 and the measured signal of the operating variable 200 can also be determined.

To determine whether there is sufficient agreement or a sufficiently low comparison between the state-typical model signal waveform 240 and the estimated parameters of the measured signal of the operating variable 200, a comparison determination is carried out in the following procedure step V2a. If the comparison between the state-typical model signal waveform 240 and the measured signal of the operating variable is determined to be 70%, a decision can be made as to whether the work progress to be detected has been identified based on the signal of the operating variable and whether the work progress to be detected has been achieved.

To determine whether there is sufficient agreement between the state-typical model signal waveform 240 and the signal of the operating parameter 200, a quality assessment of the estimated parameters is performed in a further embodiment in a process step V2a following process step V2. In this quality assessment, values between 0 and 1 are determined, where a lower value signifies higher confidence in the value of the identified parameter and thus represents a higher degree of agreement between the state-typical model signal waveform 240 and the signal of the operating parameter 200. In the preferred embodiment, the decision as to whether the required progress has been made is made, at least partially, in process step V3 based on the condition that the quality value is within the range of 50%.

In one embodiment of the inventive method, the cross-correlation method is used as a comparative method in process step V2. Like the mathematical methods described above, the cross-correlation method is known to those skilled in the art. In the cross-correlation method, the state-typical model signal waveform 240 is correlated with the measured signal of the operating parameter 200.

In comparison to the parameter estimation method presented above, the result of the cross-correlation is again a signal sequence with an added signal length consisting of the length of the signal representing the operating variable 200 and the state-typical model signal waveform 240, which represents the similarity of the time-shifted input signals. The maximum of this output sequence represents the point in time of highest similarity between the two signals, i.e., the signal representing the operating variable 200 and the state-typical model signal waveform 240, and is thus also a measure of the correlation itself. In this embodiment, this measure is used in process step V3 as a decision criterion for achieving the desired progress. A key difference in the implementation of the method according to the invention compared to parameter estimation is that any state-typical model signal waveform can be used for cross-correlation, whereas in parameter estimation, the state-typical model signal waveform 240 must be representable by parameterizable mathematical functions.

7 Figure 200 shows the measured signal of the operating parameter 200 when bandpass filtering is used as the frequency-based comparison method. The abscissa x represents time or a time-correlated quantity. 7(a) The measured signal of the operating parameter is shown as the input signal for the bandpass filter, with the hand tool 100 operating in screwdriving mode in the first section 310. In the second section 320, the hand tool 100 is operating in rotary impact mode. 7(b) represents the output signal after the bandpass filter has filtered the input signal.

8 represents the measured signal of operating parameter 200 in the case where frequency analysis is used as the frequency-based comparison method. In the 8(a) and 8(b) The first area 310 is shown, where the hand-held power tool 100 is in screwdriving mode. On the abscissa x of the 8(a) The graph plots time t or a quantity correlated with time. 8(b) The signal of operating quantity 200 is shown transformed, for example, using a Fast Fourier Transform to transform from a time domain to a frequency domain. On the abscissa x' of the 8(b) For example, the frequency f is plotted so that the amplitudes of the signal with an operating quantity of 200 are shown. In the 8(c) and 8(d) The second area 320 is shown, in which the hand-held power tool 100 is in rotary impact mode. 8(c) shows the measured signal of operating parameter 200 plotted over time in rotary impact operation. 8(d) shows the transformed signal of the operating quantity 200, where the signal of the operating quantity 200 is plotted against the frequency f as abscissa x'. 8(d) shows characteristic amplitudes for rotary impact operation.

9a shows a typical case of a comparison using the comparative parameter estimation method between the signal of an operating variable 200 and a state-typical model signal waveform 240 in the in 4 The first area 310 described above. While the state-typical model signal waveform 240 exhibits an essentially trigonometric profile, the signal of the operating parameter 200 has a significantly different profile. Regardless of the choice of one of the comparison methods described above, the comparison carried out in procedure step V2 between the state-typical model signal waveform 240 and the signal of the operating parameter 200 results in the finding that the degree of similarity between the two signals is so low that the work progress to be detected is not recognized in procedure step V3.

In 9b In contrast, the case presented here is one in which the desired progress has been achieved and therefore the state-typical model signal waveform 240 and the signal of the operating parameter 200 exhibit a high degree of overall agreement, even if deviations are detectable at individual measurement points. Thus, in the comparative parameter estimation method, a decision can be made as to whether the desired progress has been achieved.

10 shows the comparison of the state-typical model signal shape 240, see 10b and 10e , with the measured signal of the operating parameter 200, see 10a and 10d , in the event that cross-correlation is used as the comparative comparison method. In the 10a - f represents time or a quantity correlated with time, plotted on the abscissa x. In the 10a - c is the first area 310, corresponding to the screw operation, shown. In the 10d - f is the third area 324, corresponding to the work progress to be detected, shown. As described above, the measured signal of the operating variable, 10a and 10d , with the state-typical model signal shape, 10b and 10e , correlated. In the 10c and 10f The respective results of the correlations are presented. 10c The result of the correlation during the first range 310 is shown, revealing a low correlation between the two signals. In the example of the 10c Therefore, in process step V3, it is decided that the required progress has not been achieved. 10f is the result of the Correlation shown during the third area 324. It is in 10f It is apparent that there is a high degree of agreement, so that in procedure step V3 it is decided that the work progress to be recognized has been achieved.

The invention is not limited to the described and illustrated embodiments. Rather, it also encompasses all further developments by skilled craftsmen within the scope of the invention defined by the claims. In addition to the described and illustrated embodiments, further embodiments are conceivable, which may include further modifications and combinations of features.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 3 202 537 A1 [0002]
• US 9 744 658 [0003]

Claims (17)

Method for operating a hand-held power tool (100), the hand-held power tool (100) comprising an electric motor (180), the method comprising the process steps: S1 During an application of the hand-held power tool (100), determining a signal of an operating parameter (200) of the electric motor (180); S2 Monitoring a frequency of the signal of the operating quantity(200) during application; S3 Determining the progress of the application at least partially based on the frequency of the signal of the operating variable (200). Procedure according to Claim 1 , wherein the procedure step S2 includes monitoring the frequency of the operating quantity (200) signal during the application to determine whether a change in frequency reaches a predetermined level of change. Procedure according to Claim 2 , wherein the change in frequency of the operating variable signal (200) is determined by a ratio of a first frequency determined at a first time during the application and a second frequency of the operating variable signal (200) determined at a second time during the application. Procedure according to one of the Claims 1 until 3 , wherein the procedure step S2 includes monitoring the frequency of the signal of the operating quantity (200) during the application to see whether a predetermined frequency limit is reached. Method according to one of the preceding claims, wherein the frequency of the signal of the operating quantity (200) is at least partially monitored using a filter that filters out frequencies below a predetermined frequency from the signal of the operating quantity (200), in particular using a bandpass filter. Procedure according to Claim 5 , wherein the frequency of the signal of the operating quantity (200) is determined by determining zero crossings in the filtered signal of the operating quantity (200). Method according to any of the foregoing claims, comprising the process step: S4 Executing a first routine of the hand-held machine tool(100) at least partially based on the work progress determined in process step S3. Procedure according to Claim 7 , wherein the first routine includes stopping the electric motor (180) taking into account one or more defined and/or predefinable parameters, in particular predefinable by a user of the hand-held power tool (100). Procedure according to one of the Claims 7 and 8 , wherein the first routine includes a change, in particular a reduction and/or an increase, of the speed of the electric motor (180). Method according to one of the preceding claims, wherein the operating parameter is a rotational speed of the electric motor (180) or an operating parameter correlated with the rotational speed. Method according to one of the preceding claims, wherein the signal of the operating variable (200) is recorded in method step S1 as a time series of measured values of the operating variable, or as measured values of the operating variable as a quantity of the electric motor (180) correlating with the time series. A method according to one of the preceding claims, wherein the signal of the operating variable (200) is recorded in the process step S1 as a time series of measured values of the operating variable and in a process step S1a following the process step a transformation of the time series of The measured values of the operating quantity are incorporated into a curve of the measured values of the operating quantity as a quantity of the electric motor correlating with the time course (180). Method according to one of the foregoing claims, comprising the following process steps: V1 Providing at least one model signal shape (240), wherein the The model signal shape (240) can be assigned to the work progress of the hand-held machine tool (100); V2 Comparing the signal of the operating parameter (200) with the Modifying the signal form (240) and determining a conformity assessment from comparison; V3 Determining work progress, at least partially, based on the information provided in Procedure step S3 determined the conformity assessment. Procedure according to Claim 13 , whereby the progress of the work is determined at least partially based on a joint evaluation of the process steps S3 and V3. Method according to one of the preceding claims, characterized in that the hand-held power tool (100) is an impact wrench, in particular a rotary impact wrench. Control unit (370) for a hand-held power tool (100), wherein the control unit (370) is used to carry out the method according to one of the Claims 1 until 15 is set up. hand-held power tool (100), comprising an electric motor (180), a sensor for an operating parameter of the electric motor (180), and a control unit (370) according to Claim 16 .