EP4003657A1

EP4003657A1 - Method for detecting work progress of a handheld power tool

Info

Publication number: EP4003657A1
Application number: EP20739931.2A
Authority: EP
Inventors: Simon Erbele; Wolfgang Herberger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-07-30
Filing date: 2020-07-08
Publication date: 2022-06-01
Also published as: CN114502327A; KR20220041852A; WO2021018539A1; JP2022542896A; US20220258315A1; DE102019211303A1

Abstract

The invention relates to a method for detecting work progress of a handheld power tool, the handheld power tool having an electric motor, and the method comprising the steps of: S1 providing at least one model signal form, the model signal form being assignable to the work progress of the handheld power tool; S2 determining a signal of an operating parameter of the electric motor; S3 comparing the signal of the operating parameter with the model signal form and determining a conformity evaluation from the comparison; S4 recognizing the work progress to at least some extent using the conformity evaluation determined in method step S3. Further disclosed is a handheld power tool, more specifically an impact driver, comprising an electric motor and a control unit, the control unit being designed to carry out a method according to the invention.

Description

description

title

Method for recognizing the work progress of a hand tool machine

The invention relates to a method for recognizing the work progress of a handheld power tool, and a handheld power tool set up to carry out the method.

State of the art

From the prior art, see for example EP 3 381 615 A1, rotary impact wrenches for tightening screw elements, such as threaded nuts and screws, are known. An impact wrench of this type includes, for example, a structure in which an impact force in a rotating direction is transmitted to a screw element by a rotation force of a hammer. The impact wrench, which has this structure, includes a motor, a hammer to be driven by the motor, an am boss which is hit by the hammer, and a tool. In the impact wrench, the motor built into a housing is driven, the hammer being driven by the motor, the anvil in turn being struck by the rotating hammer and an impact force being applied to the tool, with two different operating states, namely "no impact operation" and " Schlagbetrieb "can be distinguished. EP 2 599 589 B1 also discloses an impact wrench with a motor, with a hammer and a rotational speed detection unit, where the hammer is driven by the motor.

When using impact wrenches, it is desirable to be able to make statements about the progress of work within the machine in order to trigger certain desired reactions or routines of the device, for example switching off the motor, changing the motor speed, or triggering a message to the User.

For the provision of such intelligent tool functions, among other things, knowledge of the current operating status is required. An identification of the same is carried out in the prior art, for example, by monitoring the operating variables of the electric motor, such as speed and electric motor current. The operating parameters are examined to determine whether certain limit values and / or threshold values 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 value can practically only be perfectly set for one application. As soon as the application changes, the associated current or speed values or their temporal progressions also change, and impact detection based on the set limit value and / or threshold value or their temporal progression no longer works.

It can happen, for example, that an automatic shutdown based on the detection of the impact operation reliably shuts off in different speed ranges in individual applications when using self-tapping screws, but in other applications there is no shutdown when using self-tapping screws.

In other methods for determining the operating modes of rotary impact wrenches, additional sensors, such as acceleration sensors, are set to infer the current operating mode from vibration states of the tool.

Disadvantages of these methods are additional costs for the sensors as well as losses in the robustness of the hand tool, since the number of built-in components and electrical connections increases compared to hand machine tools without these sensors.

Furthermore, simple information about whether the striking mechanism is working or not is often not sufficient to be able to make accurate statements about the progress of the work. For example, when screwing in certain wood screws, the rotary hammer mechanism starts very early, while the screw is not yet fully screwed into the material, but the required torque has already exceeded the so-called release torque of the rotary hammer mechanism. A reaction purely on the basis of the operating state (impact operation and no impact operation) of the rotary hammer mechanism is therefore not sufficient for a correct automatic system function of the tool, such as switching off, for example.

In principle, there is the problem of having to make statements about the progress of work, even with other hand-held power tools such as impact drills, so that the invention is not limited to impact wrenches.

Disclosure of the invention

The object of the invention is to provide a method for recognizing the work progress or the status of an application which is improved over the prior art, which at least partially eliminates the above-mentioned disadvantages, or at least to provide an alternative to the prior art. Another task is to specify a corresponding hand tool machine.

These objects are achieved by means of the respective subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent subclaims. According to the invention, a method for recognizing a work progress of a handheld power tool is disclosed, the handheld power tool having an electric motor. The process comprises the following steps:

51 providing at least one model signal form, wherein the model signal form can be assigned to the work progress of the handheld power tool;

52 determining a signal of an operating variable of the electric motor;

53 comparing the signal of the operating variable with the model signal shape and determining a correspondence rating from the comparison;

54 Recognition of the progress of the work, at least in part, on the basis of the conformity assessment determined in method step S3.

In this way, simple and reliable monitoring and control for recognizing the progress of work can take place, with various operating variables generally being considered as operating variables which are recorded via a suitable transducer. It is particularly advantageous that no additional sensor is necessary in this regard, since various sensors, such as, for example, for speed monitoring, are preferred

Hall sensors, already built into electric motors.

In a preferred embodiment, the model signal form is a state-typical model signal form, which is state-typical for a certain work progress of the handheld power tool, for example the resting of a screw head on a mounting base or the free rotation of a loosened screw.

The approach for recognizing the progress of work using operating variables in the tool-internal measured variables, such as the speed of the electric motor, proves to be particularly advantageous because this method enables the work progress is particularly reliable and largely independent of the general operating condition of the tool or its application.

In this case, there is essentially no need for, in particular additional, sensor units for detecting the tool-internal measured variables, such as an acceleration sensor unit, so that essentially only the method according to the invention is used to detect the progress of work.

The model signal shape is preferably an oscillation curve around an average value, in particular an essentially trigonometric oscillation curve. The model signal form preferably represents an ideal striking operation of the hammer on the anvil of the rotary percussion mechanism, the ideal percussion operation preferably being an impact without further turning the tool spindle of the handheld power tool.

The operating variable is advantageously a speed of the electric motor or an operating variable that correlates with the speed. The rigid transmission ratio of the electric motor to the hammer mechanism results, for example, in a direct dependence of the motor speed on the hammer frequency. Another conceivable operating variable that correlates with the speed is the motor current. A motor voltage, a Hall signal from the motor, a battery current or a battery voltage are also conceivable as the operating variable of the electric motor, with an acceleration of the electric motor, an acceleration of a tool holder or a sound signal from a hammer mechanism of the hand power tool also being conceivable as the operating variable.

The determination of the correspondence assessment in method step S3 preferably comprises a comparison of the correspondence between the signal of the operating variable and the model signal shape with at least one threshold value of the correspondence.

In an alternative embodiment of the invention, step S3 comprises comparing the signal of the operating variable with the model signal shape and determining a deviation from the comparison. In a preferred embodiment, the threshold value of the agreement can be determined by a user of the hand-held power tool; in further embodiments, the threshold value of the agreement is predefined at the factory.

In a particularly preferred embodiment, the threshold value of the agreement can be selected by a user on the basis of a factory-predefined preselection of use cases of the handheld power tool. This can be done, for example, via a user interface, for example an HMI (human-machine interface), for example a mobile device, in particular a smartphone and / or a tablet.

In particular, in method step S1, the model signal shape can be defined variably, in particular by a user. The model signal shape is assigned to the work progress to be recognized, so that the user can specify the work progress to be recognized. In this context, a limit and / or threshold value for an existing correspondence or an existing error from the signal of the operating variable to the model signal shape can also represent an adjustable variable for applications for recognizing the progress of work.

The method advantageously further comprises a method step S5 of triggering a routine of the handheld power tool, at least partially on the basis of the work progress recognized in method step S4. Basically, it should be noted that method step S5 can follow S4.

In a preferred embodiment, at least one or more of the reactions or routines of the group comprising changing a speed of the electric motor, reversing a direction of rotation of the electric motor and / or an optical, acoustic and haptic feedback to a user is carried out in method step S5 carried out.

The model signal shape is advantageously predefined in method step S1, in particular set at the factory. In principle, it is conceivable that the model signal shape is stored or stored inside the device, alternatively and / or additionally loaned the handheld power tool is provided, in particular is provided by an ex ternal data device.

In a further embodiment, the signal of the operating variable is recorded in method step S2 as a time curve of measured values of the operating variable, or recorded as measured values of the operating variable as a variable of the electric motor that correlates with the time curve, for example an acceleration, a jolt, in particular a higher order, a power , an energy, an angle of rotation of the electric motor, an angle of rotation of the tool holder or a frequency.

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

Alternatively, the signal of the operating variable is recorded in method step S2 as a time course of measured values of the operating variable, with a transformation of the time course of the measured values of the operating variable into a curve of the measured values of the transmission in a step S2a following the method step S2 Operating variable takes place as a variable of the electric motor that correlates with the course of time. This again results in the same advantages as with the direct recording of the signal of the operating variable over time.

The method according to the invention thus enables the progress of work to be recognized independently of at least one setpoint speed of the electric motor, at least one start-up characteristic of the electric motor and / or at least one charging state of a power supply, in particular a battery, of the handheld power tool.

The signal of the company size should be understood here as a time sequence of measured values. Alternatively and / or in addition, the signal of the operating variable can also be a frequency spectrum. As an alternative and / or in addition, the signal of the operating variable can also be post-processed, such as, for example, smoothed, filtered, fitted and the like. In a further embodiment, the signal of the operating variable is stored as a sequence of measured values in a memory, preferably a ring memory, in particular the handheld power tool.

In a particularly advantageous embodiment, in method step S3 the signal of the operating variable is compared by means of one of the comparison methods comprising at least one frequency-based comparison method and / or a comparative comparison method, the comparison method comparing the signal of the operating variable with the model signal form to determine whether at least one predetermined threshold value is met becomes. The preset threshold value can be preset at the factory or can be set by a user.

The decision can be made at least partially by means of the frequency-based comparison method, in particular a bandpass filtering and / or a frequency analysis, as to whether a work progress to be recognized has been identified in the signal of the operating variable.

In one embodiment, the frequency-based comparison method comprises at least the bandpass filtering and / or the frequency analysis, the predefined threshold value being at least 90%, in particular 95%, especially 98%, of a predefined limit value.

In the bandpass filtering, for example, the recorded signal of the operating size is filtered via a bandpass whose pass band matches the model signal form. A corresponding amplitude in the resulting signal is to be expected when the relevant work progress to be recognized is present, in particular in the ideal stroke without further turning of the hit element. The predefined threshold value of the bandpass filtering can therefore be at least 90%, in particular 95%, in particular 98%, of the corresponding amplitude in the work progress to be recognized, in particular the ideal stroke without further turning the hit element. The pre-given limit value can be the corresponding amplitude in the resulting signal of an ideal work progress to be recognized, in particular an ideal stroke without further turning of the struck element. Using the known frequency-based comparison method of frequency analysis, the previously determined model signal shape, for example a frequency spectrum of the work progress to be recognized, in particular an ideal stroke without further turning the hit element, can be searched for in the recorded signals of the operating size. In the recorded signals of the operating variable, a corresponding amplitude of the work progress to be recognized, in particular of the ideal stroke without further turning of the hit element, is to be expected. The predetermined threshold value of the frequency analysis can be at least 90%, in particular 95%, in particular 98%, of the corresponding amplitude in the work progress to be recognized, in particular the ideal stroke without further turning the hit element. The predetermined limit value can be the corresponding amplitude in the recorded signals of an ideal work progress to be recognized, in particular the ideal stroke without further turning of the hit element. Appropriate segmentation of the recorded signal of the farm size may be necessary.

In one embodiment, the comparative comparison method comprises at least one parameter estimation and / or a cross-correlation, the predefined threshold value being at least 40% of a match between the signal of the operating variable and the model signal shape.

The measured signal of the operating variable can be compared with the model signal shape by means of the comparative comparison method. The measured signal of the operating variable is determined in such a way that it has essentially the same finite signal length as that of the model signal shape. The comparison of the model signal shape with the measured signal of the operating variable can be output as a, in particular discrete or continuous, signal of a finite length. Depending on a degree of agreement or a deviation of the comparison, a result can be output as to whether the work progress to be recognized, in particular the ideal stroke without further turning the hit element, is present. If the measured signal of the operating variable agrees at least 40% with the model signal form, the work progress to be recognized, in particular the ideal field, can be performed without Continue turning the struck element. It is also conceivable that the comparative method can output a degree of comparison with one another as the result of the comparison by comparing the measured signal of the operating variable with the model signal shape. The comparison of at least 60% to one another can be a criterion for the existence of the work progress to be recognized, in particular the ideal stroke without further turning of the hit element. It can be assumed that the lower limit for agreement is 40% and the upper limit for agreement is 90%. Accordingly, the upper limit for the deviation is 60% and the lower limit for the deviation is 10%.

In the parameter estimation, a comparison between the previously established model signal shape and the signal of the operating variable can be made. For this purpose, estimated parameters of the model signal shape can be identified in order to match the model signal shape to the measured signal of the operating variables. By means of a comparison between the estimated parameters of the previously established model signal shape and a limit value, a result can be determined on the existence of the work progress to be recognized, in particular the ideal stroke without further turning the hit element. A further evaluation of the result of the comparison can then follow whether the predefined threshold value has been reached. This evaluation can either be a determination of the quality of the estimated parameters or the correspondence between the defined model signal shape and the recorded signal of the operating variable.

In a further embodiment, method step S3 contains a step S3a of a quality determination of the identification of the model signal shape in the signal of the operating variable, whereby in method step S4 the decision as to whether the work progress to be recognized is present is made at least in part on the basis of the quality determination. A goodness of fit of the estimated parameters can be determined as a measure of the quality determination.

In method step S4, by means of the quality determination, in particular the measure of the quality, the decision can be made as to whether the work progress to be recognized was identified in the signal of the operating variable. In addition or as an alternative to the quality determination, method step S3a can include a determination of agreement between the identification of the model signal shape and the signal of the operating variable. The correspondence of the estimated parameters of the model signal shape with the measured signal of the operating variable can be, for example, 70%, in particular 60%, in particular 50%. In method step S4, the decision is made as to whether the work progress to be recognized is present, at least in part based on the Compliance determination. The decision as to whether the work progress is to be recognized can be made at the predetermined threshold value of at least 40% agreement between the measured signal of the operating variable and the model signal shape.

In the case of a cross-correlation, a comparison can be made between the previously established model signal shape and the measured signal of the operating variable. With the cross-correlation, the previously defined model signal shape can be correlated with the measured signal of the operating variable. When the model signal shape is correlated with the measured signal of the operating variable, a degree of correspondence between the two signals can be determined. The degree of agreement can be, for example, 40%, in particular 50%, very particularly 60%.

In method step S4 of the method according to the invention, the decision as to whether the work progress to be recognized is present can be made at least partially on the basis of the cross-correlation of the model signal shape with the measured signal of the operating variable. The decision can be made at least partially on the basis of the predetermined threshold value of at least 40% correspondence between the measured signal of the operating variable and the model signal shape.

In one process step, the work progress to be recognized is based on less than ten blows of an impact mechanism of the hand tool machine, in particular less than ten impact oscillation periods of the electric motor, preferably less than six impacts of an impact mechanism of the hand tool machine, in particular less than six impact oscillation periods of the electric motor preferably fewer than four strokes of a striking mechanism, especially special less than four shock oscillation periods of the electric motor, identified. Here, an impact of the impact mechanism is to be understood as an axial, radial, tangentia ler and / or circumferential impact of an impact mechanism hammer, in particular a hammer, on a striking mechanism body, in particular an anvil. The impact oscillation period of the electric motor is correlated with the operating size of the electric motor. An impact oscillation period of the electric motor can be determined on the basis of operating variable fluctuations in the signal of the operating variable.

The progress of work can be identified, for example, by the fact that a further angle of rotation of the tool holder is reduced when the hammer mechanism hits. The further angle of rotation can be that angle of rotation of the tool recording that is rotated per impact of the hammer mechanism. The further angle of rotation can thus decrease as the work progresses, which can additionally be reflected by a decreasing period duration.

Another subject matter of the invention is a handheld power tool, comprising an electric motor, a measured value pick-up for an operating variable of the electric motor, and a control unit, wherein the handheld power tool is advantageously an impact wrench, in particular a rotary impact wrench, and the work progress to be recognized is an impact without further turning a tool holder of the handheld power tool is. Since the electric motor sets an input spindle in rotation, an output spindle from being connected to the tool holder. An anvil is non-rotatably connected to the output spindle and a hammer is connected to the input spindle in such a way that it executes an intermittent movement in the axial direction of the input spindle as well as an intermittent rotational movement around the input spindle as a result of the rotational movement of the input spindle, the hammer in this way strikes the anvil intermittently and thus emits an impact and a rotary impulse to the anvil and thus to the output spindle. A first sensor transmits a first signal to the control unit, for example to determine an engine rotation angle. Furthermore, a second sensor can transmit a second signal to the control unit to determine an engine speed. The control unit is partly designed to perform a method described above.

The handheld power tool advantageously has a memory unit in which various values can be stored.

In a further embodiment, the handheld power tool is a battery-powered handheld power tool, in particular a battery-powered rotary impact wrench. In this way, flexible and network-independent use of the handheld power tool is guaranteed.

The handheld power tool is advantageously an impact wrench, in particular a rotary impact wrench, and the work progress to be recognized is an impact of the rotary hammer mechanism without further turning the hammered element or the tool holder.

The identification of the impacts of the impact mechanism of the handheld power tool, in particular the impact oscillation periods of the electric motor, can be achieved, for example, by using a fast-fitting algorithm, by means of which an evaluation of the impact detection within less than 100ms, in particular less than 60ms , in particular less than 40ms, can be made possible. Here, the inventive method mentioned enables the progress of work to be recognized essentially for all of the above-mentioned applications and a screw connection for loose and fixed fastening elements in the fastening carrier.

The present invention largely eliminates the need for complex methods of signal processing such as filters, signal loopbacks, system models (static and adaptive) and signal tracking.

In addition, these methods allow an even faster identification of the impact operation or the work progress, which can cause an even faster reaction of the tool. This applies in particular to the number of past blows from the onset of the hammer mechanism to identification and also in special operating situations such as the start-up phase of the Drive motor. No restrictions on the functionality of the tool, such as a reduction in the maximum drive speed, have to be made. Furthermore, the functioning of the algorithm is also independent of other influencing variables such as target speed and battery charge status.

In principle, no additional sensors (e.g. acceleration sensors) are necessary, but these evaluation methods can also be applied to signals from other sensors. In addition, this method can also be used for other signals in other motor concepts which, for example, manage without speed detection.

In a preferred embodiment, the handheld power tool is a cordless screwdriver, a drill, a percussion drill or a hammer drill, it being possible to use a drill, a drill bit or various bit attachments as the tool. The hand power tool according to the invention is designed in particular as an impact wrench tool, with a higher peak torque for a screwing in or unscrewing a screw or a screw nut being generated by the pulsed release of the engine energy. In this context, the transfer of electrical energy is to be understood in particular as meaning that the handheld power tool transfers energy to the body via a battery and / or via a power cable connection.

In addition, depending on the selected embodiment, the screwing tool can be designed to be flexible in the direction of rotation. In this way, the proposed method can be used both for screwing in and for unscrewing a screw or a screw nut.

In the context of the present invention, “determine” should in particular include measuring or recording, with “recording” being understood in the sense of measuring and storing, and “determining” should also include possible signal processing of a measured signal. Furthermore, “decide” should also be understood as recognizing or detecting, with an unambiguous assignment being achieved. “Identify” is to be understood as recognizing a partial match with a pattern, which can be made possible, for example, by fitting a signal to the pattern, a Fourier analysis or the like. The “partial agreement” should be understood to mean that the fitting has an error that is less than a predefined threshold, in particular less than 30%, in particular less than 20%.

Further features, possible applications and advantages of the invention result from the following description of the embodiment of the invention, which is shown in the drawing. It should be noted that the features described or shown in the figures, individually or in any combination, form the subject matter of the invention, regardless of their summary in the claims or their reference, and regardless of their formulation or representation in the description or . in the drawing has only a descriptive character and is not intended to restrict the invention in any way.

drawings

The invention is explained in more detail below with reference to preferred Ausführungsbeispie len. The drawings are schematic and show:

Fig. 1 is a schematic representation of an electrical craft

machine tool;

2 (a) shows a work progress of an example application and an associated signal of an operating variable;

FIG. 2 (b) shows a correspondence of the signal shown in FIG. 2 (a)

Farm size with a model signal; 3 is a schematic representation of two different recordings of the signal of the operating variable;

4 shows a flow chart of a method according to the invention; and

5 shows a joint illustration of a signal of an operating quantity and an output signal of a bandpass filtering based on a model signal;

6 shows a joint illustration of a signal of an operating variable and an output of a frequency analysis based on a model signal;

7 shows a joint illustration of a signal for an operating variable and a model signal for parameter estimation;

8 shows a joint illustration of a signal of an operating variable and a model signal for the cross-correlation;

Fig. 9 (a) shows a signal of an operational quantity;

Fig. 9 (b) shows an amplitude function of a first frequency contained in the signal of Fig. 9 (a).

FIG. 9 (c) shows an amplitude function of a second, in the signal of FIG.

9 (a) included frequency.

FIG. 1 shows a handheld power tool 100 according to the invention, which has a housing 105 with a handle 115. According to the illustrated embodiment, the handheld power tool 100 can be mechanically and electrically connected to a battery pack 190 for mains-independent power supply. In Fig. 1, the hand power tool 100 is exemplified as a cordless rotary impact screwdriver. It should be noted, however, that the present invention is not limited to cordless impact wrenches, but in principle for handheld power tools 100 in which the detection of a work progress Step is necessary, such as impact drills, can be used.

An electric motor 180, which is supplied with power by the battery pack 190, and a transmission 170 are arranged in the housing 105. The electric motor 180 is connected to an input spindle via the transmission 170. Furthermore, a control unit 370 is arranged within the housing 105 in the area of the battery pack 190, which is used 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 gear x or the like acts on this.

The electric motor 180 can be operated, for example, via a manual switch 195, i. H. can be switched on and off and can be any type of motor, for example an electronically commutated motor or a direct current motor. In principle, the electric motor 180 can be electronically controlled or regulated in such a way that both a reversing operation and specifications with regard to the desired motor speed n and the desired angular momentum can be implemented. The mode of operation and the structure of a suitable electric motor are sufficiently known from the prior art, so that a detailed description is dispensed with 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 molded directly onto the output spindle or connected to it in the form of an attachment.

The control unit 370 is connected to a power source and is designed in such a way that it can electronically control or regulate the electric motor 180 by means of various power signals. The various current signals ensure different rotational impulses of the electric motor 180, the current signals being passed to the electric motor 180 via a control line. The power source can be designed as a battery or, as in the illustrated embodiment, as a battery pack 190 or as a mains connection. Furthermore, operating elements not shown in detail can be provided in order 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 is provided by means of which work progress, for example of the handheld power tool 100 shown in FIG. 1, can be determined during an application, for example a screwing in or unscrewing process. The method is essentially based on an examination of signal shapes and a determination of a degree of correspondence between these signal shapes, which can correspond, for example, to an evaluation of further turning of an element driven by the handheld power tool 100, such as a screw.

In this regard, FIG. 2 shows an exemplary signal of an operating variable 200 of an electric motor 180 of a rotary impact wrench, as it occurs in this way or in a similar form when a rotary impact wrench is used as intended. While the following explanations relate to a rotary impact wrench, they also apply accordingly within the scope of the invention to other handheld power tools 100 such as, for example, impact drills.

In the present example of FIG. 2, the time is plotted as a reference variable on the abscissa x. In an alternative embodiment, however, a time-correlated variable is plotted as a reference variable, such as the angle of rotation of the tool holder 140, the angle of rotation of the electric motor 180, an acceleration, a jolt, in particular a higher order, a power, or an energy. The engine speed n present at any point in time is plotted on the ordinate f (x) in the figure. Instead of the engine speed, another operating variable that correlates with the engine speed can be selected. In alternative embodiments of the invention, f (x) represents a signal of the motor current, for example.

Motor speed and motor current are operating variables that are usually used in hand tool machines 100 by a control unit without additional effort 370 can be recorded. The determination of the signal of an operating variable 200 of the electric motor 180 is identified in FIG. 4, which shows a schematic flow diagram of a method according to the invention, as method step S2. In preferred embodiments of the invention, a user of the hand machine tool 100 can select based on which operating variable the inventive method is to be carried out.

In Fig. 2 (a), an application of a loose fastening element, for example a screw 900, in a fastening support 902, for example a wooden board, is shown. It can be seen in Figure 2 (a) that the signal includes a first range 310, which is characterized by a monotonous increase in the engine speed ge, as well as a range of comparatively constant engine speed, which can also be referred to as a plateau. The intersection between abscissa x and ordinate f (x) in Figure 2 (a) corresponds to the start of the impact wrench during the screwing process.

In the first area 310, the screw 900 encounters a relatively low resistance in the mounting bracket 902, and the torque required for screwing in is below the disengagement torque of the rotary hammer mechanism.

The course of the engine speed in the first range 310 thus corresponds to the operating state of screwing without impact.

As can be seen from FIG. 2 (a), the head of the screw 900 in the area 322 does not rest on the fastening support 902, which means that the screw 900 driven by the impact wrench is rotated further with each impact. This additional angle of rotation can become smaller as the work progresses, which is reflected in the figure by a decreasing period duration. In addition, a further screwing in is also indicated by a mean speed decrease.

If the head of the screw 900 then reaches the pad 902, an even higher torque and thus more impact energy is required for further screwing in. However, since the handheld power tool 100 no longer supplies impact energy, the screw 900 no longer rotates or only rotates further by a significantly smaller angle of rotation. The rotary percussion operation carried out in the second 322 and third area 324 is characterized by an oscillating profile of the signal of the operating variable 200, wherein the form of the oscillation can be, for example, trigonometric or oscillating in some other way. In the present case, the oscillation has a course that can be described as a modified trigonometric function. This characteristic form of the signal of company size 200 in impact wrench operation is created by the pulling up 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 qualitative signal form of the impact operation is known in principle due to the inherent properties of the impact wrench. In the method according to the invention in FIG. 4, based on this knowledge, at least one state-typical model signal shape 240 is provided in a step S1, the state-typical model signal shape 240 being assigned to a work progress, for example when the head of the screw 900 rests on the fastening support 902 . In other words, the model signal shape 240 typical for the state contains features typical for the work progress, such as the presence of an oscillation curve, oscillation frequencies or amplitudes, or individual signal sequences in continuous, quasi-continuous or discrete form.

In other applications, the work progress to be detected can be characterized by signal forms other than oscillations, for example by 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 vibrations.

In a preferred embodiment of the inventive method, the state-typical model signal shape 240 can be determined by a user in method step S1. The state-typical model signal form 240 can also be stored or stored inside the device. In an alternative embodiment, the state-typical model signal form can alternatively and / or can also be provided to handheld power tool 100, for example from an external data device.

In a 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 signal form 240. In the context of the present invention, the “compare” feature is to be interpreted broadly and in the sense of a signal analysis, so that a result of the comparison can in particular also be a partial or gradual correspondence of the signal of the operating variable 200 of the electric motor 180 with the state-typical model signal form 240 , the degree of correspondence between the two signals can be determined using various mathematical methods that will be mentioned later.

In step S3, a correspondence evaluation of the signal of the operating variable 200 of the electric motor 180 with the state-typical model signal shape 240 is determined from the comparison and a statement is thus made about the agreement of the two signals. The implementation and sensitivity of the conformity assessment are parameters that can be set in the factory or by the user for recognizing the progress of work.

FIG. 2 (b) shows a curve of a function q (x) of a correspondence evaluation 201 corresponding to the signal of the company variable 200 of FIG. 2 (a), which at every point on the abscissa x shows a value of the agreement between the signal of the company variable 200 of the electric motor 180 and the model signal shape 240 typical for the state.

In the present example of screwing in the screw 900, this evaluation is used to determine the amount of further rotation in the event of a blow. The state-typical model signal form 240 predetermined in step S1 corresponds in the example to an ideal impact without further turning, i.e. the state in which the head of the screw 900 rests on the surface of the mounting bracket 902, as shown in area 324 of FIG. 2 (a). Accordingly, there is a high degree of correspondence between the two signals in area 324, which is indicated by a consistently high value of the function q (x) of the over- sentiment rating 201 is reflected. In contrast, in the area 310, in which the impact is always associated with high angles of rotation of the screw 900, only small correspondence values are achieved. The less the screw 900 continues to turn during impact, the higher this correspondence, which can be seen from the fact that the function q (x) of the correspondence evaluation 201 is already at the start of the striking mechanism in the area 322, which is continuously decreasing with each impact The angle of rotation of the screw 200 is characterized due to the increasing screw-in resistance, reproduces continuously increasing match values.

In a method step S4 of the method according to the invention, the progress of the work is now at least partially recognized on the basis of the conformity assessment 201 determined in method step S3. As can be seen in the example in FIG. 2, the correspondence evaluation 201 of the signals for striking the distinction is well suited for this because of its more or less erratic form, this erratic change being caused by the likewise more or less erratic change in the further rotation angle of the screw 900 when the exemplary work process. The progress of work can be recognized, for example, at least partially on the basis of a comparison of the conformity assessment 201 with a threshold value, which is identified in FIG. 2 (b) by a dashed line 202. In the present example of FIG. 2 (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 work of resting the head of the screw 900 on the surface of the mounting bracket 902.

The criterion derived from this, on the basis of which the work progress is determined, can be set in order to make the function usable for a wide variety of applications. It should be noted that the function is not limited to screwing-in cases, but also includes use in unscrewing applications.

According to the invention, by differentiating between signal forms, an evaluation of the further rotation of an element driven by an impact wrench to determine the work progress of an application can be made. men will be. According to a preferred embodiment of the invention, in a method step S5, an application-related, suitable reaction or routine of the tool is carried out at least partially on the basis of the work progress, for example switching off the machine, changing the speed of the electric motor 180, and / or an optical, acoustic, and / or haptic feedback to the user of handheld power tool 100.

In practical applications, it can be provided that the method steps S2 and S3 are carried out repeatedly during the operation of a handheld power tool 100 in order to monitor the work progress of the application carried out. For this purpose, the determined signal of the operating variable 200 can be segmented in method step S2, so that method steps S2 and S3 are carried out on signal segments, preferably always of the same, fixed length.

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 memory. In this embodiment, the handheld power tool 100 includes the memory, preferably the ring memory.

As already mentioned in connection with FIG. 2, in preferred embodiments of the invention, in method step S2, the signal of the operating variable 200 is determined as the time curve of measured values of the operating variable, or as measured values of the operating variable as a variable of the electric motor 180 that correlates with the time curve the measured values can be discrete, quasi-continuous or continuous.

One embodiment provides that the signal of the farm variable 200 is recorded in method step S2 as a time curve of measured values of the farm variable and in a method step S2a following method step S2 a transformation of the time curve of the measured values of the farm variable into a curve of the measured values of the farm variable takes place as a variable of the electric motor 180 that correlates with the course of time, such as the angle of rotation of the tool holder 140, the angle of rotation of the motor, an acceleration, a jolt, in particular a higher order, a power, or an energy. The advantages of this embodiment are described below with reference to FIG. Similar to FIG. 2, FIG. 3a shows signals f (x) of an operating variable 200 over an abscissa x, in this case over time t. As in FIG. 2, the operating variable can be an engine speed or a parameter that correlates with the engine speed.

The figure contains two signal curves of the operating variable 200, which can each be assigned to a work progress, in the case of an impact screwdriver, for example, the impact screwdriving mode. In both cases, the signal comprises a wavelength of an idealized sinusoidal waveform, the signal with a shorter wavelength, T1 with a higher beat frequency, and the signal with a longer wavelength, T2, with a profile with a lower beat frequency.

Both signals can be generated with the same handheld power tool 100 at different engine speeds and are, among other things, dependent on the rotational speed the user requests from the handheld power tool 100 via the operating switch.

If, for example, the parameter “wavelength” is to be used to define the typical state model signal shape 240, in the present case at least two different wavelengths T1 and T2 would have to be stored as possible parts of the typical state model signal shape so that the comparison of the signal of the operating variable 200 with the state-typical model signal form 240 leads to the result “agreement” in both cases. Since the motor speed can change over time in general and to a large extent, this means that the searched wavelength also varies and the methods for recognizing this beat frequency would have to be adjusted accordingly.

With a large number of possible wavelengths, the complexity of the procedure and the programming would increase correspondingly quickly. In the preferred embodiment, the time values on the abscissa are therefore transformed into values that correlate with the time values, such as acceleration values, higher-order jerk values, power values, energy values, frequency values, angle of rotation values of the tool holder 140 or angle of rotation values of the electric motor 180. This is possible because through the rigid transmission ratio of the electric motor 180 to the hammer mechanism and to the tool recording 140 results in a direct, known dependence of the motor speed on the impact frequency. Through this normalization, an oscillation signal of constant periodicity independent of the engine speed is achieved, which is shown in FIG. 3b by the two signals from the transformation of the signals belonging to T1 and T2, both signals now having the same wavelength P1 = P2.

Correspondingly, in this embodiment of the invention, the state-specific model signal form 240 valid for all speeds by a single parameter of the wavelength via the time-correlating variable, such as the angle of rotation of the tool holder 140, the engine angle of rotation, an acceleration, an Jerk, especially a higher order, a power, or an energy.

In a preferred embodiment, the comparison of the signal of the operating variable 200 takes place in method step S3 using a comparison method, the comparison method comprising 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 the state-typical model signal form 240, as to whether at least a 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 comprises at least the bandpass filtering and / or the frequency analysis. The comparative comparison method comprises at least the parameter estimation and / or the cross-correlation. The frequency-based and the comparative comparison method are described in more detail below.

In embodiments with bandpass filtering, if necessary, as described, the input signal transformed to a variable that correlates with time Signal filtered through one or more bandpass filters whose passbands match one or more state-typical model signal shapes.

The pass band results from the state-typical model signal form 240. It is also conceivable that the pass band corresponds to a frequency established in connection with the state-typical model signal form 240. In the event that amplitudes of this frequency exceed a previously defined limit value, as is the case when the work progress to be recognized is reached, the comparison in method step S3 then leads to the result that the signal of the operating variable 200 is the same as the state-typical model signal shape 240, and that the work progress that can be recognized has been achieved. In this embodiment, the definition of an amplitude limit value can be interpreted as determining the correspondence evaluation of the typical model signal shape 240 with the signal of the operating variable 200, on the basis of which it is decided in method step S4 whether the work progress to be recognized is present or not.

The embodiment is to be explained with reference to FIG. 9, in which frequency analysis is used as a frequency-based comparison method. In this case, the signal of the operational variable 200, which is shown in Figure 9 (a) and, for example, corresponds to the course of the speed of the electric motor 180 over time, is based on the frequency analysis, for example the fast Fourier transformation (Fast Fourier Transformation, FFT), transformed from a time domain into the frequency domain with appropriate weighting of the frequencies. In this context, the term “time range” is to be understood according to the above statements both as “course of the company size over time” and as “course of the company size as a variable that correlates with time”.

Frequency analysis in this form is well known as a mathematical tool for signal analysis from many areas of technology and is used, among other things, to approximate measured signals as series developments of weighted periodic harmonic functions of different wavelengths. In FIGS. 9 (b) and 9 (c), for example, weighting factors KI (X) and K ₂ (x) indicate, as function curves 203 and 204 over time, whether and how strong the corresponding frequencies or frequency bands are are not specified at this point for the sake of clarity, in the signal under investigation, that is, the course of the operating variable 200, are present.

In relation to the method according to the invention, the frequency analysis can therefore be used to determine whether and with what amplitude the frequency assigned to the state-typical model signal shape 240 is present in the signal of the operating variable 200. In addition, however, frequencies can also be defined, the non-existence of which is a measure of the existence of the recognizable work progress. As mentioned in connection with the bandpass filtering, a limit value of the amplitude can be established, which is a measure of the degree of correspondence between the signal of the operating variable 200 and the model signal shape 240 typical for the state.

In the example in FIG. 9 (b), for example, at time t2 (point SP2), the amplitude KI (X) of a first frequency, which is typically not found in the state-typical model signal form 240, in the signal of the operating variable 200 falls below an associated limit value 203 (a), which in the example is a necessary but not sufficient criterion for the existence of the work progress to be recognized. At time tz (point SP3), the amplitude K2 (x) of a second frequency typically found in the state-typical model signal form 240 in the signal of the operating variable 200 exceeds an associated limit value 204 (a). In the associated embodiment of the invention, the common presence of the falling below or exceeding the limit values 203 (a), 204 (a) by the

Amplitude functions KI (X) or K ₂ (x) the decisive criterion for the correspondence evaluation of the signal of the farm size 200 with the state-specific model signal form 240. Correspondingly, in this case in method step S4 it is determined that the work progress to be recognized has been achieved.

In alternative embodiments of the invention, only one of these criteria is used, or combinations of one or both of the criteria with other criteria, such as, for example, reaching a setpoint speed of the electric motor 180.

In embodiments in which the comparative comparison method is used, the signal of the operating variable 200 with the state-typical mo- dellsignalform 240 compared to find out whether the measured signal of the operational variable 200 has at least a 50% agreement with the state-typical model signal shape 240 and thus the predetermined threshold is reached. It is also conceivable that the signal of the operating variable 200 is compared with the state-typical model signal form 240 in order to determine whether the two signals match one another.

In embodiments of the method according to the invention in which the parameter estimation is used as a comparative comparison method, the measured signal of the operating variables 200 is compared with the state-typical model signal shape 240, estimated parameters being identified for the state-typical model signal shape 240. With the aid of the estimated parameters, it is possible to determine a degree of correspondence between the measured signal of the operating variables 200 and the state-typical model signal form 240, as to whether the work progress to be recognized has been achieved. The parameter estimation is based on the compensation calculation, which is a mathematical optimization method known to those skilled in the art. With the aid of the estimated parameters, the mathematical optimization method enables the model signal form 240, which is typical for the state, to be matched to a series of measurement data of the signal of the operational variable 200. The decision as to whether the work progress to be recognized has been achieved can be made as a function of a degree of correspondence between the state-typical model signal shape 240 parameterized by means of the estimated parameters and a limit value.

With the aid of the compensation calculation of the comparative parameter estimation method, a degree of agreement between the estimated parameters of the state-typical model signal shape 240 and the measured signal of the operating variable 200 can be determined.

In order to decide whether there is a sufficient correspondence or a sufficient quality of the state-typical model signal shape 240 with the estimated parameters for the measured signal of the operating variable 200, a method step S3a following method step S3a is carried out in method step S3a. If the correspondence between the state-typical model signal form 240 and the measured signal of the operating variable of 70% is telt, the decision can be made as to whether the work progress to be recognized has been identified using the signal of the company size and whether the work progress to be recognized has been achieved.

In order to decide whether there is sufficient correspondence between the state-specific model signal shape 240 and the signal of the operating variable 200, a quality determination for the estimated parameters is carried out in a further embodiment in a method step S3b following method step S3. When determining the quality, values for a quality between 0 and 1 are determined, whereby the following applies that a lower value means a higher confidence in the value of the identified parameter and thus represents a higher correspondence between the state-typical model signal form 240 with the signal of the operational variable 200 . The decision as to whether the work progress to be recognized is present is made in the preferred embodiment in method step S4 at least partially on the basis of the condition that the value of the quality is in a range of 50%.

In one embodiment of the inventive method, the method of cross-correlation is used as the comparative comparison method in method step S3. Like the mathematical methods described above, the method of cross-correlation is known per se to the person skilled in the art.

In the cross-correlation method, the state-typical model signal form 240 is correlated with the measured signal of the operating variable 200.

Compared to the parameter estimation method presented above, the result of the cross-correlation is again a signal sequence with an added signal length from a length of the signal of the operating variable 200 and the model signal shape 240 typical for the state, which represents the similarity of the time-shifted input signals. The maximum of this output sequence represents the point in time at which the two signals, i.e. the signal of the operating variable 200 and the state-typical model signal form 240, are the most closely matched, and is therefore also a measure of the correlation itself, which in this embodiment is used as a decision criterion in method step S4 is used to achieve the work progress to be recognized. In the implementation in the method according to the invention, there is an essential difference to the pa- rameterestimation that any state-typical model signal shapes can be used for the cross-correlation, while in the parameter estimation the state-typical model signal shape 240 must be able to be represented by parametrizable mathematical functions.

FIG. 5 shows the measured signal of the operating variable 200 for the case that bandpass filtering is used as the frequency-based comparison method. Here, the time or a variable correlating with time is plotted as the abscissa x. FIG. 5a shows the measured signal of the operating variable, an input signal of the bandpass filtering, the hand-held power tool 100 being operated in screwdriving mode in the first area 310. In the second area 320, the handheld power tool 100 is operated in rotary impact mode. FIG. 5b shows the output signal after the bandpass filter has filtered the input signal.

FIG. 6 shows the measured signal of the operating variable 200 for the case that the frequency analysis is used as the frequency-based comparison method. In Figure 6 a and b, the first area 310 is shown in which the hand-held power tool 100 is in the screwing mode. Time t or a quantity correlated with time is plotted on the abscissa x in FIG. 6a. In FIG. 6b, the signal of the operating variable 200 is shown transformed, it being possible, for example, to transform time into a frequency by means of a Fast Fourier Transformation. For example, the frequency f is plotted on the abscissa x ‘in FIG. 6b, so that the amplitudes of the signal of the operating variable 200 are shown. In FIGS. 6c and d, the second area 320 is shown, in which the handheld power tool 100 is in rotary impact mode. FIG. 6c shows the measured signal of operational variable 200 plotted over time in rotary impact operation. FIG. 6d shows the transformed signal of operational variable 200, the signal of operational variable 200 being plotted against frequency f as abscissa x ‘. Figure 6d shows characteristic amplitudes for the rotary impact operation.

FIG. 7a shows a typical case of a comparison using the comparative comparison method of parameter estimation between the signal of an operating variable 200 and a state-typical model signal form 240 in the First area 310 described in FIG. 2. While the state-typical model signal shape 240 has an essentially trigonometric profile, the signal of the operating variable 200 has a profile that deviates greatly therefrom. Regardless of the selection of one of the comparison methods described above, in this case the comparison carried out in method step S3 between the state-typical model signal shape 240 and the signal of the operating variable 200 has the result that the degree of correspondence between the two signals is so low that in method step S4 the work progress to be recognized is not determined.

In Figure 7b, however, the case is shown in which the work progress to be recognized is present and therefore the state-typical model signal form 240 and the signal of the operating variable 200 have a high degree of correspondence overall, even if deviations can be determined at individual measurement points. In the comparative comparison method of parameter estimation, the decision as to whether the work progress to be recognized has been achieved can be made.

FIG. 8 shows the comparison of the state-typical model signal shape 240, see FIGS. 8b and e, with the measured signal of the operating variable 200, see FIGS. 8a and 8d, for the case that the cross-correlation is used as the comparative comparison method. In FIGS. 8a-f, the time or a quantity correlating with time is plotted on the abscissa x. In FIGS. 8 a - c, the first area 310, corresponding to the screwdriving operation, is shown. The third area 324, corresponding to the work progress to be recognized, is shown in FIGS. 8d-f. As described above, the measured signal of the operating variable, FIGS. 8a and 8d, is correlated with the state-typical model signal form, FIGS. 8b and 8e. Respective results of the correlations are shown in FIGS. 8c and 8f. The result of the correlation during the first area 310 is shown in FIG. 8c, whereby it can be seen that there is little agreement between the two signals. In the example in FIG. 8c, it is therefore decided in method step S4 that the work progress to be recognized has not been achieved. The result of the correlation during the third area 324 is shown in FIG. 8f. It can be seen in Figure 8f that a high There is agreement so that it is decided in method step S4 that the work progress to be recognized has been achieved.

The invention is not restricted to the exemplary embodiment described and shown. Rather, it also includes all technical developments within the scope of the invention defined by the claims.

In addition to the described and illustrated embodiments, further embodiments are conceivable, which can include further modifications and combinations of features.

Claims

Expectations

1. A method for recognizing a work progress of a hand tool machine (100), the hand machine tool (100) comprising an electric motor (180), the method comprising the method steps

51 providing at least one model signal shape (240), the model signal shape (240) being able to be assigned to the work progress of the handheld power tool;

52 determining a signal of an operating variable (200) of the electric motor (180);

53 comparing the signal of the operating variable (200) with the model signal form (240) and determining a correspondence rating from the comparison;

54 Recognition of the work progress, at least in part, on the basis of the conformity assessment determined in method step S3.

2. The method according to claim 1, characterized in that the model signal form (240) is an oscillation curve, in particular an essentially trigonometric oscillation curve.

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

4. The method according to any one of the preceding claims, characterized in that the determination of the correspondence evaluation in method step S3 comprises a comparison of the correspondence between the signal of the operating variable (200) and the model signal shape (240) with at least one threshold value of correspondence.

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

6. The method according to claim 5, characterized in that the threshold value of the agreement can be selected by a user on the basis of a factory-predefined pre-selection of applications of the hand-held power tool.

7. The method according to any one of the preceding claims, characterized in that the model signal shape (240) in method step S1 is variable, in particular variably predeterminable by a user, can be provided.

8. The method according to any one of the preceding claims, characterized in that the method further comprises a method step S5 of triggering a routine of the handheld power tool (100) at least partially on the basis of the work progress recognized in method step S4.

9. The method according to claim 8, characterized in that the reaction of the hand machine tool (100) in method step S5 at least one of the routines of the group comprising changing a speed of the electric motor (180), reversing a direction of rotation of the electric motor (180) and a optical, acoustic and haptic feedback to a user.

10. The method according to any one of the preceding claims, characterized in that the model signal shape (240) is predefined in method step S1, in particular set at the factory.

11. The method according to any one of the preceding claims, characterized in that the signal of the operating variable (200) is recorded in method step S2 as a time curve of measured values of the operating variable, or as measured values of the operating variable via a variable of the electric motor (180) that is correlated with the time curve ).

12. The method according to any one of the preceding claims, characterized in that the signal of the operating variable (200) in method step S2 as The time course of measured values of the operating variable is recorded and in a method step S2a a transformation of the time course of the measured values of the operating variable into a course of the measured values of the operating variable over a variable of the electric motor (180) correlated with the time course ensues.

13. The method according to any one of the preceding claims, characterized

net that in method step S3 the signal of the operating variable (200) is compared by means of one of the comparison methods comprising at least one frequency-based comparison method and / or a comparative comparison method.

14. The method according to claim 13, characterized in that the frequency

based comparison method comprises at least the bandpass filtering and / or the frequency analysis, the threshold value being at least 90%, in particular special 95%, in particular 98%, of a predetermined limit value.

15. The method according to claim 13, characterized in that the compare

The corresponding comparison method comprises at least the parameter estimation and / or the cross-correlation, the threshold value being at least 40% of a match between the signal of the operating variable (200) and the model signal form (240).

16. The method according to any one of the preceding claims, characterized in that the work progress based on less than ten strikes of a hammer mechanism of the hand power tool (100), in particular less than ten impact oscillation periods of the electric motor (180), preferably less than six blows of a hammer mechanism Handheld power tool (100), in particular less than six impact oscillation periods of the electric motor (180), very preferably less than four impacts of an impact mechanism of the handheld power tool (100), in particular less than four impact oscillation periods of the electric motor (180), is identified.

17. The method according to any one of the preceding claims, characterized

net that the hand machine tool (100) is an impact screwdriver, in particular a rotary impact screwdriver, and a work progress that can be recognized is an impact without further turning a tool holder.

18. Hand machine tool (100), comprising an electric motor (180), a

Measured value sensor of an operating variable of the electric motor (180), and a control unit (370), characterized in that the control unit (370) is set up to carry out the method according to one of Claims 1 to 17.