Method for determining the compaction of a soil base during the operation of a vibrating plate, and vibrating plate for soil compaction

Abstract

The invention relates to a method for determining the compaction of a subsoil during the operation of a vibratory plate compactor, wherein, to derive a statement about the compaction state and / or a change in the compaction state of the subsoil, recourse is made to the instantaneous drive power curve of an electric drive system and / or to the extent of required control interventions of a motor control system. The invention further relates to a vibratory plate compactor designed for carrying out this method.

Description

[0001] The invention relates to a method for determining the compaction of a soil subsoil during the operation of a vibratory plate compactor and to a vibratory plate compactor for soil compaction.

[0002] Various types of soil compaction machines are known in the art for compacting subsoil, such as rollers, vibratory rammers, or vibratory plates. These soil compaction machines have in common that they are guided over the soil surface by means of a soil contact device to compact the subsoil. In doing so, they compact the soil surface statically, through their own weight (as is particularly the case with rollers), and / or dynamically by applying vibrations to the soil contact device via one or more vibration excitation devices. In the latter case, these vibrations can, in particular, have an amplitude that is at least partially vertical or exhibit a vertically oriented vibration component.The vibration excitation devices can in particular be so-called unbalance exciters, which typically have an unbalance mass rotating around an axis of rotation and thereby generate a vibrational movement during rotational operation.

[0003] Vibratory plate compactors typically have a ground contact plate that does not roll on the ground but moves across it in a hopping or jumping motion due to the vibrations generated by the vibration excitation device. Such machines can be hand-operated or remotely controlled, for example. In addition to vibratory plate compactors with a single vibratory exciter, those with multiple vibratory exciters are also known. The use of multiple vibratory exciters makes it possible to generate a resulting vibration that essentially travels along one spatial direction, or a so-called directional vibrator. Vibratory plate compactors with such a directional vibrator can, for example, generate forward motion by tilting the axis of vibration relative to the vertical.Furthermore, it is possible to design the oscillation axis of the vibration excitation device, which is configured as a directional oscillator, to be adjustable, so that these vibratory plates can be switched by an operator from forward travel to stationary vibration to reverse travel. Such vibratory plates are also referred to as reversible vibratory plates.

[0004] In light of steadily increasing restrictions on permissible emission levels from construction machinery in general, and vibratory plate compactors in particular, these machines are increasingly being electrified or equipped with an electrically driven drive train. One such vibratory plate compactor is disclosed, for example, in EP2540912A2 of the applicant.

[0005] When performing soil compaction work using surface-acting compaction equipment, knowledge of the progress of the compaction process and / or the compaction state of the subsoil is helpful in determining, for example, whether uniform and / or sufficient compaction of an area of ​​the subsoil has been achieved and / or whether over-compaction has already occurred. Ideally, this information should be obtained directly during the ongoing compaction operation of the soil compaction machine.Due to the stamping movement behavior of vibratory plates during compaction, which can also change significantly during operation depending on the compaction state of the subsoil, the detection and monitoring of the soil compaction state during the operation of a vibratory plate using conventional methods, such as the acceleration sensors established especially for rollers, is often not yet satisfactory or requires a comparatively high level of equipment, since special acceleration sensors adapted to the comparatively high acceleration loads in the operation of a vibratory plate must be used.

[0006] Starting from this, the object of the invention is to provide a cost-effective and reliable way to make conclusions about the current compaction state and / or a change in the current compaction state of the subsoil during the operation of a vibratory plate.

[0007] The problem is solved using a method and a vibrating plate according to the independent claims. Preferred embodiments are specified in the dependent claims.

[0008] In a first aspect, the invention relates to a method for determining the compaction of a soil subsoil during the operation of a vibratory plate compactor.

[0009] The vibratory plate includes a ground contact plate. This plate can, for example, be essentially a plate-like device with a substantially rectangular contour. The edge regions of the vibratory plate, directed forward and / or backward in the working direction, can be curved upwards in the vertical direction. The ground contact plate can have a bottom and a top surface, the bottom surface being the contact surface with the ground and the top surface a mounting surface for other elements of the vibratory plate. A vibration excitation device can be arranged on the ground contact plate. This device can be directly connected to the ground contact plate, in particular such that the vibration excitation device is undamped and connected to the ground contact plate, especially on its mounting side, or is directly flanged to it.The vibration excitation device can comprise one or more unbalance exciters. Each unbalance exciter(s) can have an unbalance mass rotatable about an axis of rotation, in particular horizontally and / or transversely to a forward direction of the vibrating plate. The unbalance mass can comprise several unbalance mass elements that are adjustable relative to one another, for example, to vary the vibration amplitude of the vibration excitation device. Furthermore, the vibration excitation device can be designed such that the phase relationship of several unbalance exciters relative to one another is variable or adjustable. Additionally or alternatively, the angular position of a resulting overall vibration motion from two or more unbalance exciters relative to a vertically extending reference line can be varied.

[0010] The vibratory plate, in particular the vibratory plate used for the method according to the invention, can have an electric drive system for driving the vibration excitation device, in particular for driving a rotational movement of the unbalance mass(s) of the unbalance exciter about their axes of rotation. Part of the electric drive system can be an electric motor that drives the vibration excitation device and, in particular, the rotational operation of the unbalance masses about their respective axes of rotation. The electric drive system can also include several electric motors. In particular, it can be provided that one electric motor is provided for each unbalance exciter to drive it. It is advantageous if the electric motor(s) each directly drive a shaft of the unbalance exciter(s) with one or more unbalance masses.The electric motor(s) could be, for example, an induction motor, a brushless DC motor (BLDC motor), or something similar. Basically, however, virtually all types of electric motors are suitable.

[0011] The vibratory plate compactor may include a motor control unit designed to control the speed and / or phase of the electric motor(s) and / or the vibratory exciter(s). The motor control unit may be connected via a signal transmission line to an operating device, allowing the operator of the vibratory plate compactor to issue commands such as activation / deactivation, direction of movement, and / or speed of movement.

[0012] An electrical power source can also be part of the electric drive system. This could, for example, be a connection of the vibratory plate compactor to an external electrical power supply, or additionally or alternatively, one or more electrical energy storage devices carried by the vibratory plate compactor, in particular one or more rechargeable and / or replaceable batteries. One or more electrically transmitting connecting lines, such as power cables, can be provided between the electrical power source and the electric motor and may be included in the electric drive system.

[0013] The electrical drive system may also include other supplementary or alternative components. In particular, especially as part of power electronics, one or more conversion devices, especially power converters, may be included in the electrical drive system. These may be designed to convert the frequency and / or amplitude of a voltage and / or current supplied by the electrical energy source. Additionally or alternatively, the electrical drive system may also include one or more mains disconnect switches, one or more fuses, other switches, etc.

[0014] Particularly starting from a vibratory plate as described above, the method according to the invention provides in step a) for determining the instantaneous drive power curve, in particular the instantaneous drive power curve, of the electric drive system. Instantaneous drive power in this sense refers in particular to the product of, for example, a voltage and a current per unit of time, whereby the assumed time interval for determining the instantaneous drive power can approach zero or be comparatively short. The instantaneous drive power curve thus refers in particular to the recording of temporal changes in the instantaneous drive power over time, in particular within a consideration time interval, as described in more detail below. During operation of the vibratory plate, the drive energy required for the operation of the electric motor per unit of time is...The required instantaneous drive power to maintain a relatively constant speed of the electric motor, and thus, for example, the speed of the excitation shaft of an unbalanced exciter, is not constant. This can be caused, in particular, by the fact that the unbalanced mass or other vibration-generating component of the vibration excitation system must be driven periodically and alternately, especially at least partially in the vertical direction upwards and downwards. It is understood that the energy requirement, and therefore the instantaneous drive power required by the electric motor to maintain the speed, is greater for moving one or more unbalanced masses vertically upwards than for the opposite movement vertically downwards.Therefore, the energy drawn by the electric motor(s) from the electrical power source via the electric drive train varies per unit of time, specifically depending in particular on the current rotational position, direction of rotation, and / or rotational speed of the one or more unbalanced masses of the one or more excitation shafts. In other words, the instantaneous drive power in the electric drive system fluctuates periodically, among other things, due to the existing and driven unbalanced masses.

[0015] In the case of vibratory plates, the soil compaction can also affect the movement of the vibration excitation device and the current power requirement for maintaining a specified rotational speed. This is because, for example, the counter-impulses generated by the undamped impact of the contact plate on the subsoil are also transmitted to the vibration excitation device, particularly to the one or more unbalanced masses of the exciter(s). This effect is more pronounced the stiffer or more compacted the subsoil is. Therefore, the current compaction level, or any changes therein, also affects the instantaneous drive power required for operating the electric drive system.

[0016] The essential point here is that the determination of the instantaneous drive power curve now takes place within the electrical drive system or within the electrically energy-transmitting area of ​​the vibratory plate, i.e., in particular in the area between the electrical power source and the electric motor, including the electrical power source and the electric motor. "In the area" can mean that this is done at one or more points, especially at specific locations, using one or more sensors, particularly as described in more detail below.

[0017] Starting from this, the inventive method can, in step b), now include determining the distribution of frequency components in the determined curve of the instantaneous drive power of the electric drive system. In other words, step b) can include decomposing the time-dependent curve of the instantaneous drive power into its frequency components, or, alternatively, breaking down the time-based curve of the instantaneous drive power into frequency components. The term "frequency components" can, for example, qualitatively mean that a signal is detected at a specific frequency. In this case, the frequency components represent the group of frequencies at which the presence of signals is determined. The term "frequency components" can also, additionally or alternatively, quantitatively mean that the strength or...The extent of a signal at one or more frequencies is detected. In this case, the frequency components are therefore not only compared to each other based on their mere presence, but also relative to each other with respect to their current signal strength. Regardless of this, determining a distribution of frequency components can equally mean determining a frequency spectrum, particularly a continuous one, especially over a defined frequency range, and / or defined regions of such a frequency spectrum. Therefore, whenever a distribution of frequency components is referred to below, this also specifically means considering the distribution of signals within a frequency spectrum, particularly over a defined frequency range.

[0018] Based on step b), step c) may involve deriving a statement about the compaction state and / or changes in the compaction state of the subsoil from the determined distribution of frequency components. This step is based on the fact that the instantaneous energy output for compacting the subsoil, and thus the instantaneous drive power required for operating the vibration excitation device, changes depending on the current compaction state of the subsoil. Specifically, the instantaneous drive power curve can be relatively uniform over successive vibration cycles of the vibration excitation device in a comparatively soft or poorly compacted subsoil.If the compaction of the subsoil and thus its stiffness increases, the energy transfer into the subsoil can decrease, resulting in increasingly chaotic movement of the vibratory plate. This can affect the instantaneous drive power of the electric drive system insofar as harmonic frequency components may increasingly appear in the current frequency distribution. The occurrence of these harmonic frequency components, in particular, can be determined using steps a) and b) and can serve as a basis for deriving a statement about the compaction state and / or a change in the compaction state of the subsoil. Specifically, the occurrence and / or distribution of harmonic frequency components, or...The level of harmonic frequency components can therefore be used as an indicator of a compaction state and / or a change in compaction state during the operation of a vibratory plate compactor. This makes it possible to derive information about the compaction state and / or a change in compaction state of the subsoil from operating parameters of the vibratory plate compactor's electric drive system itself, without relying on, for example, special acceleration sensors. This makes the method not only comparatively cost-effective but also relatively robust compared to conventional methods for determining the compaction state and / or a change in compaction state of the subsoil.

[0019] Regarding the specific determination of the instantaneous drive power curve in step a), several possibilities exist, as this curve does not necessarily have to be identical across the entire electric drive system. While it is generally possible to determine the curve in virtually any area of ​​the electric drive system where electrical energy is transmitted from the electrical power source (including the source itself) to the electric motor (including the source itself), there are, for example, preferred areas due to manufacturing-related factors.

[0020] In step a), for example, it may be necessary to determine the instantaneous power consumption of the electric motor, particularly within the electric motor itself. In this case, the instantaneous drive power is measured by measuring the instantaneous power consumption or the energy consumption of the electric motor over time within the electric motor itself.

[0021] Additionally or alternatively, for step a), determining the instantaneous drive power of the electrical drive system may also include determining the instantaneous conversion power of a power electronics unit, specifically, for example, one or more converters, in particular a power converter, especially an inverter. In this case, the instantaneous drive power is determined, for example, within the power electronics unit itself, specifically by determining the electrical energy consumed by the inverter and / or the electrical energy output by the inverter over time. It may be sufficient, for example, to measure only one phase of a three-phase alternating current and / or the input power (e.g., direct current from a battery).

[0022] Additionally or alternatively, for step a) it may also be provided that the determination of the course of the instantaneous drive power of the electrical drive system is carried out by determining an instantaneous drive power in a region of the electrical drive system between the electrical energy source, in particular the electrical energy storage device, and a power electronics, in particular a power converter, most especially a converter.

[0023] As a further supplement or alternative, it may be provided that in step a) determining the instantaneous drive power curve of the electric drive system includes determining the output power delivered from an electrical energy storage device to, or in the direction of, the electric motor. This means, for example, that the output of electrical energy from the electrical energy storage device is determined over time. In this way, the determination in step a) is achieved within the electrical energy storage device itself.

[0024] The electric motor, the power converter, and / or the electrical energy storage system can be designed as separate modules. These modules can already include one or more sensors that can acquire measurements enabling the determination of the instantaneous drive power. Ideally, this eliminates the need for additional sensors specifically designed for determining instantaneous drive power, unlike conventional vibratory plates. Furthermore, these modules can already be connected to a control unit, such as a machine control unit, via one or more communication links. Ideally, this also eliminates the need for additional signal transmission links compared to conventional vibratory plates, or at least reduces them to a minimum.

[0025] It is advantageous if the determination in step a) takes place within a defined time interval. A defined time interval refers, in particular, to a time interval specified, for example, by a control unit. This can simplify the subsequent steps b) and c) and / or increase the informative value of the determination in step a) for deriving information about the compression state in step c). Ideally, the length of the defined time interval should correspond to at least an integer multiple of the period of one excitation wave revolution. The sampling rate should, in particular, correspond to at least five times, and especially at least ten times, a given excitation frequency. The excitation frequency, or...The vibration generated by the vibration excitation device for soil compaction can, for example, be in the range of 30 Hz to 140 Hz and refers to the actual vibration frequency of the vibration excitation device, in particular the unbalanced exciter(s) of the vibration excitation device, which is determined by the motor speed of the electric motor. The defined time interval can thus be, for example, at least in the range of approximately 0.02 s to approximately 0.1 s, specifically at least 0.04 s, for an excitation frequency of 50 Hz, and in the range of approximately 0.01 s to 0.07 s, specifically at least 0.0143 s, for an excitation frequency of 140 Hz. Extending the defined time interval is possible and increases the accuracy, particularly of the frequency scale, but also increases the data volume.This illustrates that, within the scope of the method according to the invention, a comparatively high-frequency and thus almost real-time determination of the instantaneous drive power curve is preferred.

[0026] It is possible for the measurement in step a) to take place within a defined time interval with a constant duration. This means that the duration of the measurement interval is constant regardless of the operating conditions of the vibratory plate compactor. Alternatively, it is possible for the measurement in step a) to take place within a defined time interval that can be dynamically varied. This could mean, in particular, that the time interval is shortened with increasing excitation frequency and, conversely, lengthened with decreasing excitation frequency. A dynamic adjustment of the time interval, especially depending on the current excitation frequency of the vibration excitation device, can be performed automatically by a control unit of the vibratory plate compactor during operation.By dynamically adjusting the defined time interval, the measurement interval of step a) can be adapted to one or more changing operating and / or environmental conditions during the operation of the vibratory plate.

[0027] Ideally, the measurements taken in step a), as well as the subsequent steps b) and c), should be performed continuously and repetitively during the compaction operation of the vibratory plate compactor. By running steps a) to c) in a continuous loop, information on the compaction state of the subsoil and / or changes in its compaction state is made available to the vibratory plate compactor operator throughout the entire compaction operation. It is possible for a measurement according to step a) to immediately follow a previous measurement according to step a). Alternatively, a time window can be defined between two consecutive measurements according to step a), during which no measurement according to step a) is taken.

[0028] Information on the compaction state can, for example, be the specification of an estimated degree of compaction, such as a percentage of a maximum degree of compaction. Additionally or alternatively, this can involve an estimated soil stiffness or an estimated relative compaction, or it can be determined whether a further increase or even a decrease in the current compaction of the subsoil will occur if the compaction process continues.

[0029] Information regarding changes in the compaction state can include, for example, whether the current estimated compaction state is increasing, decreasing, or remaining constant compared to a previously estimated compaction state. This information on changes in the compaction state can thus be used to determine the current, and especially the relative, progress of compaction.

[0030] For the specific measurement in step a), it may be provided that the voltage and current profiles in the electrical drive system are recorded using at least one current-power sensor device, for example, with one or more suitable voltage and current sensors. It may also be provided that these measurements are performed over time. The sensor(s) and / or a control unit of the vibratory plate compactor may include a suitable time module for this purpose. Thus, in addition to the time component, measurement parameters relating solely to operating parameters of the electrical drive system form the basis for steps b) and c) and therefore for the resulting derivation of information on the compaction state and / or changes in the compaction state of the subsoil. The measurement can be performed, in particular, at the output of a power electronics unit, especially at the output of an inverter or converter.

[0031] Ideally, power data, in particular voltage and / or current and / or time data, acquired by the power sensor device are transmitted to a control unit, in particular the vibratory plate compactor, for carrying out steps b) and c). This transmission can be wireless and / or wired. It is also possible for the control unit to be carried along with the rest of the vibratory plate compactor during compaction operation. Alternatively, the vibratory plate compactor can be provided with a machine module, comprising in particular the ground contact plate, the electric drive system, and the vibration excitation device, and a display module, which is, in particular, separately operable from the machine module.In this case, it may be provided that the measurement data, particularly as mentioned above, are transmitted from the machine module to the display module, which, for example, can be carried independently of the machine module by the operator of the vibratory plate compactor. The display module could be, for example, a remote control and / or a smart device, such as a tablet or a smartphone. The control unit for carrying out steps b) and c) can be part of the machine module and / or the display module.

[0032] The determination of the frequency components in step b) is ideally carried out using a Fourier transform analysis, for example an FFT analysis ("fast Fourier transform"). "fast Fourier transform" ) ,which can be performed by a control unit. The control unit can include a computer program suitable for performing this calculation. Additionally or alternatively, a discrete Fourier transform and / or a wavelet transform can also be used, performed by a suitably designed control unit.

[0033] There are various possibilities for deriving a statement about the compaction state and / or a change in the compaction state of the subsoil from the determined distribution of frequency components in step c). The derivation need not include a quantitative statement, but can also be purely qualitative, in particular a statement as to whether compaction is currently increasing or not.

[0034] For example, step c) can include evaluating the relative distribution of frequency components, particularly within one and / or more defined frequency ranges. As mentioned above, with increasing floor stiffness, the frequency components in the comparatively high-frequency range increase, or, for example, the frequency component corresponding to the current excitation frequency decreases. The comparatively high-frequency range is therefore above the current excitation frequency of the vibration excitation device and can be, in particular, in the range of 180 Hz to 270 Hz.

[0035] Additionally or alternatively, step c) can also include, at least as a supplement, the inclusion of an absolute instantaneous drive power from the electric motor and / or a power output from the electrical energy source, in particular one or more electrical energy storage devices. The absolute instantaneous drive power can be the consumption power and / or conversion power and / or output power as described above. Including an absolute instantaneous drive power can facilitate the derivation, in particular, of a quantitative statement regarding the soil compaction state and / or changes in the soil compaction state.

[0036] As a further supplement or alternative, step c) also allows for the evaluation of one or more ratios of frequency components, particularly predefined frequency components relative to each other. This can be done, for example, by including the current excitation frequency on the one hand and one or more integer multiples of the excitation frequency on the other. For instance, if the ratio of the frequency components "excitation frequency" to "one or more integer multiples of the excitation frequency" decreases, this indicates that the compaction of the subsoil is increasing, and vice versa.

[0037] It is also possible, as a supplement or alternative, to evaluate the absolute level of one or more frequency components in step c). For example, particularly with regard to a defined excitation frequency, a limit value can be defined in advance for one or more frequency components, at which point sufficient compaction of the subsoil is assumed. Such a limit value can also be set for one or more ratios of two or more frequency components.

[0038] In principle, to derive a statement about the compaction state and / or a change in the compaction state of the subsoil in step c), in addition to the instantaneous drive power determined in step a) and the frequency component distribution determined in the instantaneous drive power curve of the electric drive system in step b), further measured values ​​relating to operating parameters of the vibratory plate compactor can be included, such as acceleration measurements at the ground contact plate and / or at a superstructure connected to the ground contact plate via a vibration damping device, distance measurements between the ground contact plate and the superstructure, and / or torque measurements at one or more mechanically loaded elements of the vibration excitation device. However, it is particularly preferred if, in step c), only the frequency component distribution determined in steps a) and b) is used.In this way, the overall system can be kept relatively simple, while at the same time a sufficiently accurate statement can be made about the compaction state and / or a change in the compaction state of the subsoil for the operation of the vibratory plate.

[0039] It is particularly preferred if the derivation of a statement in step c) is based on the occurrence and / or extent of one or more harmonic frequency components determined in step b) relative to a given excitation frequency of the vibration excitation device. Here, one or more threshold values ​​can be defined, above which the presence of an occurring harmonic frequency is assumed.

[0040] Additionally or alternatively, the derivation of a statement in step c) can be based on a ratio of at least two harmonic frequency components determined in step b) relative to a given excitation frequency of the vibration excitation device and / or on a ratio of a frequency component of a given excitation frequency relative to one or more harmonic frequency components.

[0041] Step c) is particularly successful, for example, by comparing the determined distribution of frequency components with one or more predefined reference distributions. In this case, it may be possible to compare a currently determined distribution of frequency components, in particular a currently determined frequency spectrum, with a library comprising several reference distributions, especially reference frequency spectra, for example, using mathematical similarity analyses or comparable calculations, particularly those performed by a control unit of the vibratory plate compactor. The reference distributions can, for example, be determined in advance under defined test conditions and stored in a memory device of the vibratory plate compactor, in particular the control unit, for comparison purposes.Additionally or alternatively, machine learning methods can be used to identify and / or utilize characteristic features of the frequency spectra, for example, so that explicit comparison criteria do not necessarily have to be formulated.

[0042] Alternatively, or as a supplement to the standard procedure, reference distributions can also be recorded during operation of the vibratory plate compactor and stored in the compactor's control unit. This allows, for example, the definition of a target compaction value on-site at a reference point, and then the compaction of an area extending beyond the reference point until this value is reached. This method makes it relatively easy to achieve uniform compaction of the subsoil over a relatively large surface area.It is also possible, additionally or alternatively, to define a test interval, for example triggered by the push of a button, within which an initial measurement is taken over a first time interval and then, ideally when repeatedly driving over the same area, it is determined and displayed whether a change in floor stiffness, in particular a higher or lower one, is currently detected.

[0043] It is understood that the control unit for performing this comparison operation may include a suitable computer program. It may therefore be provided that a currently determined distribution of frequency components is compared, similar to a fingerprint comparison, with a multitude of available reference distributions, for example, those stored in the control unit, and that the compaction state underlying the reference distribution with the highest similarity to the currently determined reference distribution is assumed to be the compaction state of the currently compacted subsoil.

[0044] It is possible for the comparison to be performed based on a specification of one or more soil parameters. In this case, the library containing multiple reference distributions can thus comprise two or more subcatalogs of reference distributions, whereby the subcatalogs can be assigned to one or more specific soil parameters and / or ranges of soil parameters. Such a soil parameter could, for example, be a characteristic of the current subsoil material, such as a distinction between cohesive and non-cohesive soil, and / or a soil type, such as clay, sand, gravel, earth, etc., and / or a soil moisture content, such as dry or moist, etc.

[0045] It may be possible that steps a) to c) are preceded by the input and / or definition of one or more soil parameters, particularly manually by an operator. It is then possible that a subcatalog of reference distributions is selected from the multitude of available subcatalogs, particularly by a control unit of the vibratory plate compactor. However, it is also possible that the control unit itself makes such a selection, particularly, for example, based on existing similarities in compaction progress, etc.

[0046] Operating a vibratory plate compactor can involve adjusting the force direction vector of a vibration amplitude from the vibration excitation device, for example, when switching from forward to stationary or reverse operation. This adjustment of the force direction vector can be relative to the rest of the vibratory plate compactor and, in particular, relative to the ground surface. Changing the force direction vector can influence the frequency distribution. Therefore, it is advantageous if step c) includes the consideration of a force direction vector from the vibration excitation device and / or a change in the force direction vector of the vibration excitation device. This consideration can be achieved, for example, by accessing sub-catalogs assigned to specific positions of the force direction vector.

[0047] The method according to the invention can also include displaying the information derived in step c) regarding the compaction state and / or a change in the compaction state of the subsoil from the determined distribution of frequency components. The display can, in particular, include displaying the information by means of a visually perceptible indicator on a display device. It can be provided that the display device alone indicates whether the degree of compaction or the compaction of the subsoil is currently increasing, stagnating, or decreasing. It can further be provided that, when an increase and / or decrease in the degree of compaction of the subsoil is displayed, a further differentiation is made between a comparatively rapid and a comparatively slow increase and / or decrease.Additionally or alternatively, specifically estimated numerical values ​​that correlate at least approximately with a current soil stiffness or similar information can also be displayed.

[0048] In addition to or as an alternative to the inventive method described above, the problem can also be solved by a method for determining the compaction of a subsoil during the operation of a vibratory plate compactor. This method can be based on determining the extent of control interventions by the motor control system to maintain a predetermined speed of the electric motor. Regarding possible embodiments of the vibratory plate compactor itself, particularly for carrying out the present method, reference is made to the preceding information. Here, too, the vibratory plate compactor can comprise a ground contact plate and a vibration excitation device arranged on the ground contact plate, which is driven by an electric drive system with an electric motor.The electric motor's current speed can be controlled by a motor controller, specifically in such a way that the actual speed is continuously adjusted to a target speed. This can be achieved through control interventions by the motor controller. It is understood that one or more suitable sensors, such as speed and / or position sensors, may be provided to measure the actual speed, and / or that the actual speed is calculated, for example, from a machine model.

[0049] This procedure can be designed so that, in step a), the extent of control interventions by the motor control system to maintain a predetermined target motor speed is determined, and in step b), a statement about the compaction state and / or changes in the compaction state of the subsoil is derived from the determined extent of control interventions by the motor control system to maintain the predetermined target motor speed. In this case, deviations in the speed control by the motor control system can thus be used as a measured variable. As the subsoil becomes stiffer, the control effort increases in order to ensure a constant speed despite the increasing shock forces acting on the excitation system.Therefore, in this case, the extent to which the motor control has to intervene to keep the speed of the electric motor constant serves as a measure for deriving a statement about the compaction state and / or the change in compaction state of the subsoil during the operation of the vibratory plate.

[0050] This alternative training can be combined with one or more of the characteristics mentioned in the previous procedure.

[0051] Another aspect of the invention relates to a vibratory plate compactor for soil compaction. The vibratory plate compactor can be designed, in particular, to carry out the method described above according to the invention, including one or more aspects of preferred embodiments.

[0052] Regarding possible design features and further developments of the vibratory plate itself, reference is made to the possible device features of the vibratory plate already described for the method according to the invention.

[0053] The vibratory plate compactor can therefore include a ground contact plate, in particular as described above. The ground contact plate ensures physical contact between the vibratory plate compactor and the surface of the subsoil to be compacted. The vibratory plate compactor can have a superstructure connected to the ground contact plate, in particular via vibration damping elements. This superstructure can be designed as a support frame and, for example, mount one or more components of the electric drive system described in more detail below. The vibratory plate compactor can additionally or alternatively include a guide bar and / or a guide handle, in particular articulated to the superstructure, by means of which an operator can manually guide the vibratory plate compactor during operation.Alternatively or additionally, the vibratory plate may include a machine module and a display and / or operating module that can be handled separately from the machine module, and in this way it may also be remotely controllable.

[0054] A further component of the vibratory plate compactor is a vibration excitation device, which is arranged, in particular, directly on the ground contact plate. The vibration excitation device can be the component of the vibratory plate compactor that directly generates the vibrations intended for compacting the subsoil. The vibration excitation device can, in particular, comprise one or more unbalanced exciters. Each unbalanced exciter can have an excitation shaft rotatable about an axis of rotation, on which an unbalanced mass is mounted eccentrically with respect to the axis of rotation, so that centrifugal forces acting about the respective axis of rotation can be generated during rotation. Such an unbalanced exciter can also be referred to as a rotary exciter.When two or more such unbalance exciters are combined and operated simultaneously on a common base contact plate, essentially linear vibrations acting along a force direction vector can be generated as the resultant vibration of the entire vibration excitation device in a manner known per se. This is also referred to as a directional oscillator. The unbalance mass of one or more of the unbalance exciters can include one or more unbalance mass elements that are adjustable relative to each other in order to generate different resultant vibration amplitudes at the same rotational speed of the excitation shaft. The rotational speed of the excitation shaft corresponds in particular to the excitation frequency mentioned above.

[0055] Finally, part of the vibratory plate can be an electric drive system with an electric motor to drive the vibration excitation device and an electrical energy source to supply the electric motor with electrical drive energy.

[0056] The electric motor can be directly connected to the excitation shaft, thus acting as a direct drive. Additionally or alternatively, the electric motor, together with the vibration excitation device, can also be arranged directly on or attached to the base contact plate, particularly on its upper surface. The electric motor can, for example, be a BLDC electric motor.

[0057] The electrical energy source can be a connection to an external energy source or, in particular, one or more electrical energy storage devices, especially one or more accumulators. It is therefore preferred if the electrical energy source is an electrical energy storage device, in particular one mounted on a superstructure that is vibration-damped relative to the base contact plate.

[0058] The electric drive system may also include other elements, such as a conversion device, as described above and specifically referenced here, and / or other components. The conversion device may be designed to convert the frequency and / or amplitude of a voltage and / or current supplied by the electrical energy source and may, for example, be a power converter or inverter.

[0059] The vibratory plate and, in particular, the electric drive system can be designed such that the instantaneous drive power is measured in an area of ​​the electric drive system, in particular in an area that lies between the forming device and the electrical energy source, and / or in an area that lies between the forming device and the electric motor.

[0060] The vibratory plate according to the invention may include a device for determining the instantaneous drive power profile of the electric drive system. With the aid of this device, it is thus possible to determine the current instantaneous drive power and its change over a defined period. For this purpose, this device may comprise a sensor assembly including one or more suitable sensors, in particular at least one device for determining current power and / or a current sensor and / or a voltage sensor.

[0061] Part of the vibratory plate compactor can be a control unit for determining the distribution of frequency components from the measured instantaneous drive power curve and for deriving information about the compaction state and / or changes in the compaction state of the subsoil from the measured distribution of frequency components. The control unit can, in particular, be configured to perform at least steps b) and c) of the method according to the invention. The control unit can, in particular, be a computer device comprising one or more computer programs suitable for performing one or more of the steps described above.

[0062] The device for determining the current drive power of the electric drive system of the vibratory plate can be a current sensor device, in particular comprising at least one voltage sensor and at least one current sensor.

[0063] Ideally, the control unit includes a storage device in which one or more predefined reference distributions, in particular reference frequency spectra, are stored. These can, for example, be subdivided and grouped into various sub-catalogs, particularly those specifically assigned to one or more soil and / or operating parameters. The control unit can include a comparison module configured to compare a currently determined distribution of frequency components or a currently determined frequency spectrum with one or more of the predefined reference distributions and / or reference frequency spectra, particularly in the manner described above for the method according to the invention.

[0064] It is possible for the vibratory plate compactor to have a display device designed to indicate the compaction state and / or changes in the compaction state of the subsoil based on the determined distribution of frequency components. The display device may be permanently attached to the rest of the vibratory plate compactor. Alternatively or additionally, it is also possible for the vibratory plate compactor to have a machine module and a display module that can be operated separately from the machine module. The display module could, for example, be a smart device, in particular a smartphone or a tablet. The display module and the machine module may each have a communication device that enables data transmission, particularly wireless transmission, between these two modules.

[0065] The vibratory plate may also have a motor control unit designed to control and, in particular, regulate a motor speed, especially to adapt and maintain an actual speed of the electric motor to a target speed corresponding to the specified excitation frequency.

[0066] The vibratory plate may include an operating device through which an operator can input operating commands to change a force direction vector of the vibration excitation device and / or a predetermined excitation frequency and / or one or more other operating parameters of the vibratory plate. These commands are transmitted to the control unit and / or the motor control unit. The control unit, which may be configured in particular to carry out steps b) and c) of the method according to the invention, and the motor control unit may be configured as a single, combined control unit.

[0067] The invention relates additionally or alternatively to a vibratory plate comprising a ground contact plate, a vibration excitation device arranged on the ground contact plate, an electric drive system with an electric motor for driving the vibration excitation device and an electrical energy source for supplying the electric motor with electrical drive energy, a device for determining the extent of control interventions of the motor control to maintain a predetermined target motor speed and a control unit for deriving a statement about a compaction state and / or a change in the compaction state of the subsoil from the determined control effort.It is preferred if the vibratory plate is designed to carry out the above-described method, in which in step a) the extent of control interventions of the motor control to maintain a predetermined target motor speed is determined, and in which in step b) a statement about a compaction state and / or a change in the compaction state of the subsoil is derived from the determined extent of control interventions of the motor control to maintain the predetermined target motor speed.

[0068] This vibratory plate compactor can be combined with one or more features of the vibratory plate compactor described above.

[0069] The invention is explained in more detail below with reference to the embodiments shown in the figures. The figures schematically show: Fig. 1 a side view of a vibratory plate compactor; Fig. 2 a functional view of a vibratory plate compactor; Fig. 3 an example of the instantaneous drive power curve of an electric drive system of a vibratory plate compactor; Figs. 4 to 8 examples of different frequency component distributions starting from a comparatively soft subsoil ( Fig. 3 ) rising to a comparatively stiff subsoil ( Fig. 8); Fig. 9 a schematic representation of deriving a statement about a compaction state and / or a change in the compaction state of the subsoil from a determined distribution of frequency components; and Fig. 10 a graphical representation of the extent of control interventions of the motor control to maintain a predetermined target motor speed at different compaction states of a subsoil; Fig. 11 a flowchart of a method for determining the compaction of a subsoil during the operation of a vibratory plate compactor; and Fig. 12 a flowchart of an alternative method for determining the compaction of a subsoil during the operation of a vibratory plate compactor.

[0070] Identical or similarly functioning components are designated with the same reference numerals in the figures. Repeating components are not necessarily designated separately in each figure.

[0071] Figure 1Figure 1 shows a vibratory plate compactor 1 in a side view. The vibratory plate compactor 1 can have a base plate 2 on which it rests on a ground surface 3. The vibratory plate compactor 1 can have a superstructure 4 connected to the base plate 2 via damping elements, which can serve as a support frame for one or more further components of the vibratory plate compactor 1. The vibratory plate compactor 1 can also have an electric drive system 5 with an electric motor 6 and an electrical power source 7, as well as a vibration excitation device 9. Part of the electric drive system 5 can be a conversion device 8, in particular a power converter. The electrical power source 7 can be a connection point to an external electrical power source or one or more energy storage devices for electrical energy.

[0072] The vibratory plate 1 can further comprise a vibration excitation device 9. This device can include one or more unbalance exciters 10 and 10'. The one or more unbalance exciters 10 and / or 10' can be directly connected to the ground contact plate 2. The unbalance exciter(s) 10 and / or 10' can each have one in the Fig. 1 have an excitation shaft (not shown in detail) on which an unbalanced mass is arranged, and rotate around a rotation axis of the excitation shaft during operation of the vibrating plate, thereby generating the vibrations desired for compaction operation and transmitting them to the ground contact plate 2.

[0073] If the vibratory plate has two or more vibratory exciters 10, 10', the rotation of these vibratory exciters 10, 10' can be coordinated such that the resulting total vibration transmitted to the ground contact plate 2 has a force direction vector 12. For example, the rotation direction of the two vibratory exciters 10, 10' can be opposite to each other, or one vibratory exciter 10 can rotate clockwise and the other counterclockwise. The force direction vector 12 can be fixed and, for example, inclined forward with respect to a vertical in the forward direction A, so that the vibratory plate 1 moves automatically in the working direction A during compaction. The vibratory plate 1 then moves forward, as shown by the force direction vector 12 specified for forward movement 11, and moves under its own power in the forward direction A during compaction.The vibration excitation device 9 can also be designed such that the force direction vector 12 can be changed within an adjustment range 14, for example by corresponding operating instructions from an operator. The vibratory plate 1 is then designed as a so-called reversible vibratory plate 1, as with the adjustment range 13 specified for reversibility in the . Fig. 1 indicated, and can optionally move in or against the forward direction A on its own initiative, or vibrate in place in the operating mode of so-called stationary vibration.

[0074] The vibratory plate 1 can also have a hand-held guide device 15. This can be, for example, a guide bar or a guide drawbar. This can be articulated to the superstructure 4.

[0075] The vibratory plate 1 can further comprise an operating device 16, via which an operator of the vibratory plate can make operating inputs for the operation of the vibratory plate 1. This can, for example, be arranged on the hand guide device 15.

[0076] Alternatively or additionally, the vibratory plate compactor 1 may also include a machine module 17, for example as described above, and a display and / or control module 18. The display and / or control module 18 may be designed as an operating device 16. The display and / or control module 18 may, for example, be a remote control, a smartphone, and / or a tablet. Both the machine module 17 and the display and / or control module 18 may each have a communication device 19 through which data can be exchanged between the two modules 17 and 18, in particular wirelessly. This data may include, for example, operating instructions entered by an operator via the display and / or control module 18 and / or evaluation results determined by a control unit 20 of the vibratory plate compactor 1, in particular of the machine module 17, as explained in more detail below.

[0077] The vibratory plate 1 can include a display device 21, for example for indicating a compaction state and / or a change in a compaction state. This can be arranged on the superstructure 4 or the hand-held guide device 15.

[0078] Fig. 2Figure 1 illustrates further details of the possible construction of a vibratory plate compactor 1. The electric drive system 5 comprises a transmission line 26, via which electrical drive power or electrical energy per unit of time is transmitted from the electrical energy source 7, optionally via a converter 8, to the electric motor 6. The vibratory plate compactor 1 can, for example, in addition to the components already mentioned above, have a current sensor device 22. This device can have one or more individual sensors, in particular at least one voltage sensor 23 and at least one current sensor 24. These individual sensors and / or the current sensor device 22 can each be connected to the control unit 20 via a signal transmission link 25.The power sensor 22 and / or the at least one voltage sensor 23 and / or the at least one current sensor 24 can be arranged in the area of ​​the electric drive system 5, in particular including the electrical power source 7 and the electric motor 6. Several of these sensors can also be present simultaneously and arranged at several locations within this area. This area is defined in the . Fig. 2 Illustrated as measuring range 27.

[0079] Furthermore, a motor control unit 28 may be provided, which controls and regulates the operation of the electric motor 6, in particular based on operating instructions from an operator of the vibratory plate 1. The motor control unit 28 can be in communication with the electric motor 6 via a control line 29. In particular, the motor control unit 28 can be configured to maintain a motor output speed specified for driving the vibration excitation device 9 as constant as possible during operation of the vibratory plate 1. For this purpose, the motor control unit 28 can be configured to control the current energy consumption or the instantaneous drive motor power or instantaneous drive power currently made available to the electric motor 6 via the transmission line. The motor control unit 28 can be part of the control unit 20 and vice versa.

[0080] The control unit 20 receives the measured values ​​acquired by the power sensor device 22 during the operation of the vibratory plate 1. The control unit 20 can include a device 34 for determining the drive power profile of the electric drive system 5. This device can include a timer 30, a calculation module 31, a storage device 32, and a comparison module 33.

[0081] The timing element 30 can establish a temporal relationship between the sensor data received from the power sensor device 22, so that the control unit 20 can monitor the instantaneous drive power of the electric drive system 5, or at least parts thereof. The timing element 30 can also be part of the power sensor device 22 itself.

[0082] The calculation module 31 can be configured to determine the distribution of frequency components in the determined curve of the instantaneous drive power of the electric drive system 5. For this purpose, the calculation module 31 can, for example, be configured to perform an FFT operation.

[0083] The storage device 20 can be configured for the storage, in particular on a rolling basis, of sensor data received by the control unit 20 from the power sensor device 22 and / or time data from the timer 30, in particular data of instantaneous drive powers. Additionally or alternatively, the storage device 20 can also be configured for storing one or more reference distributions, in particular reference frequency spectra, especially as part of a library comprising a large number of different reference distributions, in particular reference frequency spectra. The comparison module 33 can be configured for comparing frequency components and / or frequency spectra currently determined by the calculation module 31 with the reference distributions, in particular reference spectra, and especially at least one subgroup thereof.

[0084] The control unit 20 can be designed as a computer device with, for example, suitable computer programs and / or hardware components for providing the timer 30, the calculation module 31, the storage device 32 and / or the comparison module 33.

[0085] Fig. 3 Figure 36 shows an exemplary curve 36 of a drive power P in the electric drive system 5 determined by a current power sensor device 22 as a function of time t. Based on this, a time interval 35 can be used for further evaluation.

[0086] The curve 36 of the drive power P within the respective time interval 35 can be used by the calculation module 31 to determine a distribution of frequency components 37 or to determine a frequency spectrum, for example using an FFT calculation operation. Figures 4 to 8show, by way of example, such a distribution of frequency components 37 or frequency spectra in a defined frequency range 38 in the determined course of the instantaneous drive power of the electric drive system 5.

[0087] Fig. 4 This corresponds to a distribution of frequency components 37 or a frequency spectrum for a comparatively soft subsoil. The frequency spectrum has an amplitude AP [%] or a frequency component FA1 at approximately 60 Hz, which in the present embodiment corresponds to the excitation frequency or the rotational speed of the excitation shaft, of almost 100% (The frequency component FA2 can be neglected, for example, if its amplitude is not yet above a threshold value 39).

[0088] About the Figures 5, 6 and 7 The stiffness of the subsoil continues to increase until... Fig. 8A near-maximum achievable degree of compaction or a near-maximum soil stiffness achievable with vibratory plate 1 is reached. Figures 4 to 8 This illustrates that, on the one hand, an increasing number of amplitudes FA3 to FA8, particularly as integer multiples of the excitation frequency FA1, appear in the respective frequency spectra, and on the other hand, the distribution of the individual frequency components FA1 to FA8 becomes increasingly and more evenly distributed across the various amplitudes FA1 to FA8. In particular, the frequency component FA1 of the excitation frequency also decreases.

[0089] The in the Figures 4 to 8The illustrated changes in the respective distribution of frequency components and / or in the respective frequency spectra demonstrate how a statement about the compaction state and / or a change in the compaction state of the subsoil can be derived from the determined distribution of frequency components. In particular, the proportion of the harmonic frequency components FA2, FA3, FA4 determined relative to the excitation frequency FA1 increases.

[0090] This can be achieved even more precisely if the evaluation is not only based on individually determined distributions of frequency components and / or frequency spectra, but is also carried out, for example, by comparison with one or more distributions of frequency components and / or frequency spectra determined earlier in time.

[0091] Alternatively or additionally, it is also possible to use one or more reference distributions and / or reference spectra for which information regarding the compaction state of the subsoil is known, such as a degree of compaction and / or soil stiffness. This is the case, for example, in the Fig. 9 illustrated in more detail.

[0092] For example, the storage device 32 may contain a library 41 with several reference distributions and / or reference spectra 40. This library may also include sub-catalogs 42 relating to one or more specific soil and / or operating parameters 43, such as different soil types 43.1, 43.2, or 43.3. Additionally or alternatively, further soil and / or operating parameters 43 may also be considered, such as different soil moisture levels, different excitation frequencies, etc. In the present embodiment, the selection of soil type 43.1 was made, for example, by a corresponding input from an operator. The reference distributions and / or reference spectra 40.1, 40.2, 40.3, 40.3, and 40.3 that are included in the relevant sub-catalog 42 for this soil type 43.1 are...5 can now be compared by, for example, the comparison module 33 of the control unit 20 with a currently determined distribution 37 of frequency ranges and / or a currently determined frequency spectrum 37, for example by means of suitable mathematical comparison algorithms that determine from the subcatalog 42 for the selected soil type, for example soil type 43.1, the distribution of frequency components and / or the frequency spectrum that shows the highest similarity to the distribution 37 of frequency ranges and / or to the determined frequency spectrum 37. Subsequently, the known statement about the compaction state of the most similar reference distribution and / or the most similar reference spectrum can then be taken as a statement about the compaction state of the currently compacted subsoil and, for example, displayed via the display device 21.

[0093] Fig. 10Figure 1 shows a graphical representation of the extent of control interventions by the motor control unit 28 to maintain a predetermined target motor speed or a predetermined excitation frequency at various compaction states I - III of a subsoil. Compaction state I can, for example, be the Fig. 4 (soft subsoil), compaction state II of the Fig. 6 (medium-stiff subsoil) and compaction state III of the Fig. 8 (stiff ground surface). The Y-axis shows the extent of a control intervention as a percentage relative to a setpoint, in this case, a setpoint speed of 45. It is understood that in normal operation of the vibratory plate compactor, the extent of the required control interventions is smooth and not abrupt, as in the Fig, 10The extent of the required control interventions per defined time interval 35 increases in the present embodiment with increasing compaction of the subsoil. This altered control behavior for maintaining the target speed 45 can be used, in addition to or as an alternative to using a determined distribution of frequency components and / or a determined frequency spectrum, to derive a statement about the compaction state and / or a change in the compaction state of the subsoil during the ongoing operation of the vibratory plate compactor.

[0094] An evaluation can be carried out, for example, based on the absolute and / or relative range in, for example, Δ% of the extent of the control interventions compared to the target speed 45 within the defined time interval 35.

[0095] The extent of the control interventions can be recorded directly via the motor control 28 and transmitted, for example, to the control unit 20.

[0096] Furthermore, there are also the additional or alternative possibilities of using reference amounts and / or reference trends, so that at this point, the description for the following applies analogously. Fig. 9 Reference is made to this.

[0097] In particular, building on the preceding information, illustrates Fig. 11 in a flowchart a flow diagram of a procedure for determining the compaction of a subsoil during the operation of a vibratory plate, in particular a vibratory plate 1, as described above.

[0098] In step a), the procedure 46 initially provides for the determination 47 of a curve 36 of an instantaneous drive power of the electric drive system 5, for example, as described above, in particular with regard to the Figures 1 to 3 .

[0099] In step b), a determination 48 of a distribution 37 of frequency components FA or of a frequency spectrum in the determined course 36 of the instantaneous drive power of the electric drive system 5 can then be carried out, for example as described above.

[0100] In step c), a statement about a compaction state and / or a change in the compaction state of the subsoil 3 can finally be derived from the determined distribution of frequency components FA and / or the determined frequency spectrum, in particular as described above by way of example.

[0101] It may be provided that the inclusion of a force direction vector of the vibration excitation device takes place in step 49.

[0102] Furthermore, in step 51, the statement derived in step 49 can be displayed.

[0103] Fig. 12 Finally, the essential steps of an alternative method for determining the compaction of a subsoil during the operation of a vibratory plate compactor, in particular a vibratory plate compactor 1, as described above, are illustrated. This method can also be used in conjunction with or in combination with method 46.

[0104] In procedure 52, in one step a) a determination 53 of the extent of control interventions of the motor control to maintain a specified target motor speed is carried out, for example as described above.

[0105] Subsequently, in step b), a statement is derived here as well about a compaction state and / or a change in the compaction state of the subsoil, but here from the determined extent of control interventions of the engine control to maintain the specified target engine speed.

[0106] Steps 50 and / or 51 can also be applied to procedure 52. REFERENCE MARK LIST

[0107] 1 Vibratory plate 2 Ground contact plate 3 Ground surface 4 Superstructure 5 Electric drive system 6 Electric motor 7 Electric power source 8 Conversion device 9 Vibration excitation device 10 Unbalance exciter 11 Forward rotation 12 Force direction vector 13 Reversibility 14 Adjustment range 15 Hand guide device 16 Operating device 17 Machine module 18 Display and / or operating module 19 Communication link 20 Control unit 21 Display device 22 Power sensor device 23 Voltage sensor 24 Current sensor 25 Signal transmission links 26 Transmission line 27 Measuring range 28 Motor control 29 Control line 30 Timer 31 Calculation module (FFT module) 32 Storage device 33 Comparison module 34 Device for determining the drive power curve of the electric drive system35 Time interval 36 Curve 37 Distribution of frequency components / frequency spectrum 38 Frequency range 39 Threshold 40 Reference distribution / reference spectrum 41 Library 42 Subcatalog 43 Operating / soil parameters 44 Comparison 45 Target speed 46 Method for determining compression 47 Determining a curve 48 Determining a distribution of frequency components 49 Deriving a statement 50 Including a force direction vector 51 Display 52 Method for determining compression 53 Determining an extent 54 Deriving a statement A Forward direction A Amplitude T Time P Power f Frequency FAFrequency components I-IIICompression states

Claims

1. Method (46) for determining the compaction of a subsoil (3) during the operation of a vibratory plate compactor (1), the vibratory plate compactor (1) comprising a ground contact plate (2) and a vibration excitation device arranged on the ground contact plate (2) and driven by an electric drive system (5) with an electric motor (6), the method (46) comprising a) determining (47) a profile (36) of an instantaneous drive power of the electric drive system (5); b) determining (48) a distribution (37) of frequency components (FA) in the determined profile (36) of the instantaneous drive power of the electric drive system (5); c) deriving (49) a statement about a compaction state and / or a change in the compaction state of the subsoil (3) from the determined distribution (37) of frequency components.

2. Method (46) according to claim 1, characterized by thatIn step a) the determination (48) of the curve (37) of an instantaneous drive power of the electric drive system (5) includes at least a determination of - an instantaneous consumption power of the electric motor (6) or - an instantaneous conversion power of a converter device (8) or - an instantaneous output power delivered from an energy storage device for electrical energy to the electric motor (6).

3. Method (46) according to any one of the preceding claims, characterized by that the determination (48) in step a) takes place within a defined time interval (35), wherein the length of the defined time interval (35) corresponds in particular to at least an integer multiple of a given excitation frequency.

4. Method (46) according to any one of the preceding claims, characterized by thatin step a) the course of a voltage and a current in the electrical drive system (5) is recorded using at least one current power sensor device (22), and that current power data recorded using the current power sensor device (22) are transmitted to a control unit (20) for the execution of steps b) and c).

5. Method (46) according to any one of the preceding claims, characterized by that The derivation (49) of a statement in step c) includes at least one of the following steps: - evaluating a relative distribution of frequency components (FA); - supplementary inclusion of an absolute instantaneous drive power; - evaluating one or more ratios of frequency components (FA) to each other; - evaluating an absolute level of one or more frequency components (FA).

6. Method (46) according to any one of the preceding claims, characterized by thatthe derivation (49) of a statement in step c) is carried out exclusively via the distribution of frequency components (FA) determined in steps a) and b).

7. Method (46) according to any one of the preceding claims, characterized by that the derivation (49) of a statement in step c) on the basis of - the occurrence and / or extent of the occurrence of one or more harmonic frequency components (FA) determined in step b) compared to a given excitation frequency of the vibration excitation device (9) or - the ratio of at least two harmonic frequency components (FA) determined in step b) compared to a given excitation frequency of the vibration excitation device (9).

8. Method (46) according to any one of the preceding claims, characterized by thatIn step c) a comparison (44) of the determined distribution of frequency components (FA) against one or more predefined reference distributions (40) is carried out, in particular depending on a specification of one or more soil parameters (43).

9. Method (46) according to any one of the preceding claims, characterized by that In step c) the inclusion (50) of a force direction vector (12) of the vibration excitation device (9) takes place.

10. Method (52) for determining the compaction of a subsoil (3) during the operation of a vibratory plate compactor (1), the vibratory plate compactor (1) comprising a ground contact plate (2) and a vibration excitation device (9) arranged on the ground contact plate (2) and driven by an electric drive system (5) with an electric motor (6) controllable by a motor control unit (28), in particular supplementing an implementation of the method (46) according to one of claims 1 to 9, the method (52) comprising a) determining (53) the extent of control interventions by the motor control unit (28) to maintain a predetermined target motor speed (45); b) deriving (54) a statement about a compaction state and / or a change in the compaction state of the subsoil (3) from a determined extent of control interventions by the motor control unit (28) to maintain the predetermined target motor speed (54).

11. Vibrating plate (1) for soil compaction, in particular for carrying out a method (46) according to any one of claims 1 to 9, comprising: - a ground contact plate (2); - a vibration excitation device (9) arranged on the ground contact plate (2); - an electric drive system (5) with an electric motor (6) for driving the vibration excitation device (9) and an electrical energy source for supplying the electric motor (6) with electrical drive energy; - a device (34) for determining a profile of an instantaneous drive power of the electric drive system (5); - a control unit (20) for determining a distribution of frequency components (FA) from the determined profile (36) of the instantaneous drive power and for deriving (49) a statement about a compaction state and / or a change in the compaction state of the subsoil (3) from the determined distribution of frequency components (FA).

12. Vibrating plate (1) according to claim 11, characterized by that the electric drive system (5) comprises a forming device (8), and the measurement of the instantaneous drive power takes place in a region of the electric drive system (5) that lies between the forming device and the electric motor (6).

13. Vibrating plate (1) according to one of claims 11 or 12, characterized by that The device (34) for determining the current drive power profile of the electric drive system (5) is a current power sensor device (22).

14. Vibrating plate (1) according to one of claims 11 to 13, characterized by thatthe control unit (20) comprises a storage device (32) in which one or more predefined reference distributions (40) are stored, and the control unit (20) comprises a comparison module (33) that is designed to compare a currently determined distribution of frequency components (FA) with one or more of the predefined reference distributions (40).

15. Vibrating plate (1) for soil compaction, in particular according to one of claims 11 to 14, in particular for carrying out a method (52) according to claim 10, comprising: - a ground contact plate (2); - a vibration excitation device (9) arranged on the ground contact plate (2); - an electric drive system (5) with an electric motor (6) for driving the vibration excitation device (9) and an electrical energy source for supplying the electric motor (6) with electrical drive energy; - a device for determining the extent of control interventions of the motor control (28) for maintaining a predetermined target motor speed (45); - a control unit (20) for deriving a statement about a compaction state and / or a change in the compaction state of the subsoil (3) from the determined extent of control interventions.

16. Vibrating plate (1) according to one of claims 11 to 15, characterized by thatit has at least one of the following features: - the vibratory plate (1) has a display device (21) which is designed to indicate a compaction state and / or a change in the compaction state of the subsoil (3) from the determined distribution of frequency components (FA) and / or the determined control effort; - the electrical energy source (7) is an electrical energy storage device, in particular mounted on a vibration-damped superstructure (4) relative to the ground contact plate (2); - the electric motor (6) is arranged directly on the ground contact plate (2) together with the vibration excitation device (9).

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