Monitoring device for slip form paver and slip form paver

Abstract

The utility model relates to a monitoring device (8) for a slip-form paver and the slip-form paver, the monitoring device is used for monitoring compaction of at least one concrete compaction device (7) on concrete placed in a slip form of the slip-form paver, and the concrete compaction device is provided with an unbalanced hydraulic motor (19) for driving generated vibration. The monitoring device (8) is characterized in that the pressure in the hydraulic fluid system (11) is measured by at least one pressure sensor (25.1, 25.2, 25.3 and 25.4) arranged in the hydraulic fluid system (11), the pressure sensor (25.1, 25.2, 25.3 and 25.4) generates pressure signals related to the pressure in the hydraulic fluid, and the conclusion of compaction of concrete placed in the slip form is obtained based on analysis of the pressure signals.

Description

Technical Field

[0001] This utility model relates to a monitoring device for a slipform paver, which monitors the compaction of concrete placed in the slipform of the slipform paver by at least one concrete compaction device, wherein the concrete compaction device has an unbalanced hydraulic motor for driving to generate vibration. Background Technology

[0002] Known slipform pavers are equipped with slipforms, also known as concrete molds. For example, a slipform paver is described in EP 1 103 659 B1. Using slipform forming, structures of various shapes can be produced, such as safety barriers, curbs, or entire concrete roads. Concrete is continuously poured into the slipform, which moves above the base at a constant speed. A certain amount of concrete must always be present in the slipform so that sufficient pressure is applied to the concrete by its own weight. The concrete must be compacted in and / or in front of the slipform. Concrete compaction devices are used to compact the concrete; these devices are located on or in the slipform. These concrete compaction devices are also called external vibrators or internal vibrators. Slipform pavers are typically equipped with several bottle-shaped or strip-shaped internal vibrators that are suspended in and / or in front of the slipform and are submerged in the concrete during operation.

[0003] When operating a slipform paver, technical defects in the concrete vibrator can lead to insufficient compaction of the concrete within the slipform. This is particularly problematic when operating an internal vibrator fully submerged in the concrete, where it can be difficult for the slipform paver operator to identify defects in individual vibrators. Since subsequent compaction is impossible, it's possible to produce sections of concrete that do not meet requirements. Due to their lack of strength, these sections must be removed and rebuilt, incurring significant costs.

[0004] An electric concrete vibrator is known to have an asynchronous motor that drives an eccentric flywheel (unbalanced) to vibrate the concrete. The compaction performance of the vibrator depends on the vibration frequency, which is determined by the rotational speed of the asynchronous motor.

[0005] DE 10 201 9 125 590 A1 describes a monitoring device for monitoring the compaction of concrete, which is intended for a slipform paver, at least one concrete compaction device of which has an asynchronous motor for driving an eccentric flywheel mass (unbalance) which generates vibrations. The functional principle of the known monitoring device is based on the recognition that during the operation of the concrete compaction device, by means of which the eccentric flywheel mass (unbalance) is driven by the asynchronous motor, the rotor shaft can be elastically deformed as a result of the unbalance during the operation of the asynchronous motor. If the rotor shaft is bent, the width of the air gap between the stator and the rotor changes, which can be detected in the amplitude spectrum of the stator current. With the known monitoring device, the monitoring of the compaction of the concrete is based on an evaluation of the stator current of the asynchronous motor in order to be able to infer a change in the compaction of the concrete placed in the slipform of the slipform paver.

[0006] In addition to electric concrete vibrators, hydraulic concrete vibrators are also known, which have a hydraulic motor to drive an eccentric flywheel mass (unbalance). Due to the different operating principle of the drive of the eccentric flywheel mass, the monitoring device known from DE 10 201 9 125 590 A1 is neither intended nor suitable for such a concrete vibrator.

[0007] In general, the upper operating limit and the lower operating limit of a hydraulic concrete vibrator can be set, for example, between 8000 rpm and 12000 rpm. When using a hydraulic vibrator, the problem that arises in practice is that, in order to achieve the desired compaction of the concrete, the vibrator must be operated at a predetermined rotational speed (for example at a rotational speed of 10,500 rpm). However, due to volume losses (leaking oil), the actual rotational speed of the hydraulic motor never reaches the nominal rotational speed resulting from the nominal volume flow and the nominal pressure, and due to these losses (oil leakage), the achievable rotational speed of the hydraulic vibrator decreases with increasing wear. However, the wear condition and thus the achievable rotational speed are not known in practice before the concrete is poured. Therefore, it cannot be guaranteed that the rotational speed required for the compaction is achieved.

[0008] US 6 055 486 A describes a hydraulic drive internal vibrator with rotational speed control. In order to identify the operating state of the hydraulic vibrator, a device is proposed which records the vibrations of the vibrator. An acceleration sensor is proposed for recording the vibrations, which is arranged in the vibrator. However, the disadvantage is that the acceleration sensor is exposed to harsh environmental conditions. Such a sensor installed in a hydraulic concrete vibrator is not only exposed to vibrations, but also to extremely high temperatures of over 100°C. Furthermore, due to the limited installation space, the arrangement of the sensor within the vibrator is very difficult in principle. In addition, the power supply line for the power supply of the sensor and the signal line for recording the signal must be routed back and forth over a long distance to the vibrator which is immersed in the concrete, which means considerable effort and makes the entire system very susceptible to faults. Utility model content

[0009] The utility model is based on the following objects: to create a monitoring device for a slipform paver with at least one concrete compaction device, which has a hydraulic motor for driving an unbalance which generates vibrations, which makes it possible to reliably monitor the compaction of the concrete placed in the slipform during operation of the slipform paver in harsh environmental conditions. A further object of the utility model is to provide a method which allows reliable monitoring of the compaction of the concrete placed in the slipform with a concrete compaction device, which has a hydraulic motor for driving an unbalance which generates vibrations. It is also an object of the utility model to provide a slipform paver with such a monitoring device. The utility model is also based on the object of being able to use conventional hydraulic concrete vibrators which are not equipped with sensors for monitoring the operating state or do not need to be equipped with such sensors.

[0010] According to the utility model, these objects are achieved by the following features.

[0011] The monitoring device according to the utility model and the method according to the utility model are based on the following knowledge gained from experiments. A hydraulic drive concrete compaction device generates oscillations at the rotational frequency of the hydraulic motor due to the unbalance. This oscillation is transmitted to the hydraulic fluid (hydraulic oil) for driving the hydraulic motor, which flows through the connection lines of the hydraulic motor and the concrete vibrator. The speed changes caused by the oscillations result in a change in the local acceleration, which causes the occurrence of additional inertial forces in the unstable flow, which leads to a corresponding change in the pressure. These pressure fluctuations in the hydraulic fluid and the resulting changes in the density propagate as longitudinal waves in the fluid at the speed of sound and can be recorded with a suitable sensor system.

[0012] The monitoring device according to the utility model and the method according to the utility model are characterized in that a pressure in the hydraulic fluid is measured at at least one point of the hydraulic fluid system using at least one pressure sensor arranged in the hydraulic fluid system, the pressure sensor generates a pressure signal which is related to the pressure in the hydraulic fluid, and based on an analysis of the pressure signal, it is inferred that the compaction of the concrete placed in the slipform of the slipform paver using the at least one concrete compactor is sufficient. It is thus possible to determine whether the compaction of the concrete using the at least one concrete compactor is sufficient. Furthermore, it is possible to determine whether the concrete compactor is operated with sufficient power (imbalance). Furthermore, it is possible to determine whether the hydraulic motor of the concrete compactor is operated with sufficient rotational speed. This would not be the case if the rotational speed of the hydraulic motor is not within predetermined limit values or does not correspond to a predetermined rotational speed.

[0013] The monitoring device according to the utility model has an evaluation device for evaluating (analyzing) the pressure signal of the at least one pressure sensor, which is configured to draw a conclusion about the compaction of the concrete based on an analysis of the pressure signal. The evaluation device is preferably configured to determine an amplitude spectrum of the pressure signal in order to analyze or evaluate the pressure signal.

[0014] The monitoring device according to the utility model and the method according to the utility model have the decisive advantage that the monitoring of the compaction of the concrete is not carried out using components (in particular sensitive sensors) in the vicinity of the concrete compactor, which would be exposed to harsh environmental conditions during the operation of the slipform paver. There is thus no risk of failure of such components, which would make the monitoring unreliable. Suitable sensors for recording pressure fluctuations can be provided in a non-hazardous environment outside the concrete compactor. Furthermore, it is also possible to omit longer supply lines, which would mean considerable expense and make the entire system very susceptible to failure.

[0015] The evaluation device is preferably a digital signal processing device which is configured to sample the pressure signal, wherein the amplitude spectrum of the pressure signal is preferably determined by means of a discrete-time Fourier transform, in particular a discrete-time fast Fourier transform. The signal processing methods required for this are state of the art.

[0016] One embodiment provides that the evaluation device is configured to determine at least one spectral component attributable to the imbalance, preferably continuously, from the amplitude spectrum of the pressure signal, and to determine the frequency of the at least one spectral component and to compare it to at least one predetermined limit value, and to generate a control signal if the predetermined limit value is exceeded and / or undershot, which control signal is characteristic of the compaction of the concrete placed in the slipform of the slipform paver or indicates a change in the compaction of the concrete placed in the slipform of the slipform paver. The limit value can be determined empirically and stored in a memory of the monitoring device. If this value is undershot, it can be concluded that the compaction of the concrete is incorrect, because the rotational speed of the hydraulic motor is too low, which is why the vibration is insufficient. The frequency of the at least one spectral component in the amplitude spectrum can also be used to draw conclusions about the state of wear of the concrete compaction device. In principle, it is sufficient if the characteristic parameter is determined from the respective peak in the amplitude spectrum and is compared to a reference parameter characteristic for a specific operating state of the concrete compaction device.

[0017] At this point, the preferred continuous determination of the at least one spectral component attributable to the imbalance is understood to mean that the spectral component is determined at at least two successive points in time, so that it is possible to monitor the concrete compaction device over at least part of the operating time or to make a comparison between a preceding point in time and a subsequent point in time, so that a change in state can be identified. However, in principle, only one measurement is possible.

[0018] The evaluation device can be configured to predetermine a threshold value suitable for the harmonic amplitudes for the analysis of the pressure signal of the hydraulic motor. Thus, small amplitudes that lie in the noise range and cannot provide reliable information are filtered out.

[0019] In one embodiment, the monitoring device has an output unit which receives the control signal and is designed to indicate, if the output unit receives the control signal, an inadequate compaction of the concrete during the operation of the slipform paver using an acoustic and / or optical and / or haptic signal, because the determined frequency is below the predetermined limit value. The monitoring device can also be designed to indicate, if the output unit does not receive the control signal, a proper compaction of the concrete during the operation of the slipform paver using an acoustic and / or optical and / or haptic signal, because the determined frequency is above the predetermined limit value. If there are a plurality of concrete compaction devices on the slipform paver, the monitoring device can preferably monitor them individually. If the monitoring device indicates an inadequate compaction with a signal, it can also indicate which concrete compaction device is not used for a proper compaction.

[0020] The slipform paver according to the invention has at least one hydraulic concrete compaction device and such a monitoring device, the hydraulic concrete compaction device having a hydraulic motor for driving an imbalance which generates vibrations, which hydraulic motor is operated with hydraulic fluid provided in a hydraulic fluid system.

[0021] According to one embodiment of the slipform paver according to the utility model, the hydraulic fluid system comprises a pressure line leading to the hydraulic motor of the at least one concrete compacting device and a return line leading away from the hydraulic motor, and at least one pressure sensor is arranged in the pressure line and / or the return line or on the pressure line and / or the return line.

[0022] According to a further embodiment of the slipform paver according to the utility model, the evaluation device of the monitoring device is configured to control the rotational speed of the hydraulic motor of the at least one concrete compacting device on the basis of an analysis of the pressure signals generated by the at least one pressure sensor.

[0023] The evaluation device of the monitoring device can be configured in such a way that a flow control valve arranged in the hydraulic fluid system is actuated in accordance with the pressure signal relating to the pressure in the hydraulic fluid, so that the concrete compacting device is operated at a predetermined rotational speed, the flow control valve serving to set the volume flow of hydraulic fluid flowing into the hydraulic motor of the at least one concrete compacting device. In this case, the flow control valve is actuated in such a way that the pressure signal relating to the pressure in the hydraulic fluid measured by the pressure sensor corresponds to a predetermined value or is within predetermined limit values.

[0024] The control signal can also be fed to a central control unit of the slipform paver in order to intervene in the machine control system. The intervention in the machine control system can involve stopping the slipform paver. The monitoring device according to the utility model can form a separate component with which a conventional slipform paver can be retrofitted. However, the monitoring device can also be part of the slipform paver, wherein the device for monitoring the pressure signal can be part of the central control unit of the slipform paver. BRIEF DESCRIPTION OF DRAWINGS

[0025] In the following, exemplary embodiments of the utility model are explained in more detail with reference to the drawings.

[0026] In the drawings:

[0027] Figure 1 A side view of a slipform paver with a monitoring device for monitoring the compaction of concrete is shown;

[0028] Figure 2 A schematic diagram of a monitoring device for monitoring the compaction of concrete and a hydraulic fluid system for providing hydraulic fluid to drive a plurality of concrete compacting devices is shown;

[0029] Figure 3 A frequency spectrum of a pressure signal of a concrete compacting device over a period of time is shown;

[0030] Figure 4 An amplitude spectrum of a pressure signal of a concrete compacting device is shown;

[0031] Figure 5 a further frequency spectrum of the pressure signal of the concrete compacting device determined during the test is shown, showing the change over time; and

[0032] Figure 6 a further amplitude spectrum is shown, determined during the test. DETAILED DESCRIPTION

[0033] Figure 1 a side view of an exemplary embodiment of a slipform paver without a delivery device is shown, which is described in detail in EP 1 103 659 B1. Since such a slipform paver is state of the art, only the components of the construction machine which are of great value for the present utility model are described here.

[0034] The slipform paver 1 has a machine frame 2, which is supported by a chassis 3. The chassis 3 has two front steerable walking mechanisms 4A and two rear steerable walking mechanisms 4B, which are fastened to front lifting columns 5A and rear lifting columns 5B. The working direction (travel direction) of the slipform paver is marked with an arrow A.

[0035] The walking mechanisms 4A, 4B and the lifting columns 5A, 5B are part of a drive unit of the slipform paver for performing translational and / or rotational movements on site. The drive unit also preferably comprises hydraulic drives (not shown) for the walking mechanisms 4A, 4B and an internal combustion engine (not shown). The construction machine can be moved forwards and backwards using the walking mechanisms 4A, 4B. By raising and lowering the walking mechanisms 4A, 4B via the lifting columns 5A, 5B, the height and the inclination of the machine frame 2 relative to the floor can be adjusted.

[0036] The slipform paver has a slipform 6 for forming concrete, which can be raised or lowered together with the machine frame 2. In order to compact the concrete, a plurality of concrete compacting devices is provided in the slipform, which are immersed in the concrete when the slipform paver is in operation. In Figure 1 In the middle, one of the concrete compacting devices 7 is shown schematically in dashed lines.

[0037] The concrete compacting devices 7 are hydraulic concrete compacting devices, for example conventional hydraulic internal vibrators. A plurality of concrete compacting devices (for example 9 concrete compacting devices) can be provided on the slipform paver, wherein the concrete compacting devices are connected in parallel.

[0038] The slipform paver according to the utility model has a monitoring device 8 (only in Figure 1A monitoring device 8 is shown schematically (see Fig. 2). The monitoring device 8 has an input unit 8A and an output unit 8B, which are arranged on an operating console or control panel 9, which is located on a driver platform 10 in the field of vision of the operator.

[0039] Figure 2 A schematic diagram of an exemplary embodiment of a monitoring device 8 for monitoring the compaction of concrete and a hydraulic fluid system 11 for providing hydraulic fluid to drive a plurality of concrete compaction devices 7 connected in parallel is shown, wherein in the present exemplary embodiment there are four concrete compaction devices 7, however Figure 2 In Fig. 2 only one of the concrete compaction devices 7 is shown. The hydraulic fluid system 11 comprises a hydraulic fluid source 12 (e.g. a tank), a central pressure line 14 leading from the hydraulic fluid source 12 to a valve block 13, in which a hydraulic pump 15 for delivering hydraulic fluid is provided, and a central return line 16 leading from the valve block 13 to the tank 12. In the valve block 13 there are hydraulic flow control valves 17.1, 17.2, 17.3, 17.4 assigned to the individual concrete compaction devices 7 for load-independent control of the volume flow of hydraulic fluid (hydraulic oil) to the individual concrete compaction devices 7. The inlet of the flow control valves 17 is connected to the central pressure line 14, wherein individual pressure lines 14.1, 14.2, 14.3, 14.4 are attached to the outlet of the flow control valves 17. The return lines 16.1, 16.2, 16.3, 16.4 of the concrete compaction devices 7 are connected to the central return line 16.

[0040] In each case, the hydraulically operated concrete compaction device 7 has a bottle- or rod-shaped housing 18, in which a hydraulic motor 19 is arranged. The hydraulic motor 19 drives, via a coupling 20, an unbalanced shaft 21 arranged between bearings 22. If the unbalanced shaft 21 rotates, its unbalance generates vibrations, which are transmitted to the concrete, thereby compacting the concrete. The concrete compaction device 7 is fastened to a stand 23 with a damping element 24, so that the concrete vibrator can vibrate.

[0041] For optimal compaction of the concrete, a certain rotational speed of the unbalanced shaft 21 is targeted. If the rotational speed is too low, the unbalance will be too small, so that the compaction of the concrete is not sufficient. Therefore, the rotational speed of the hydraulic motor should be at least between a predetermined higher rotational speed or lower rotational speed, or have a predetermined rotational speed, which is the reason why the hydraulic motor should be operated with a predetermined volume flow. For example, the hydraulic motor 19 achieves a rotational speed of 10,500 rpm at a volume flow of 16 liters / minute and a supply pressure of 90 bar.

[0042] The monitoring device 8 according to the utility model can monitor the rotational speed of the hydraulic motor 19 of one or more concrete compactors 7. Furthermore, the monitoring device 8 according to the utility model can also control the rotational speed of the hydraulic motor 19 of the concrete compactor 7.

[0043] The structure and the operating mode of the monitoring device 8 are described in detail below.

[0044] The monitoring device 8 has pressure sensors 25.1, 25.2, 25.3, 25.4 assigned to the individual concrete compactors 7 for measuring the pressure in the hydraulic fluid system 11, which are each arranged at a point in the hydraulic fluid system at which particularly strong pressure fluctuations in the hydraulic fluid caused by the imbalance of the hydraulic motor 19 can be measured. Since the pressure sensors can be provided only on or in the pressure lines, the known slipform paver can be easily retrofitted with the monitoring device. The pressure sensors 25.1, 25.2, 25.3, 25.4 can be, for example, pressure transducers with strain gauges, or capacitive or piezoelectric pressure transducers. The pressure sensors convert the mechanical variable of the pressure P(t) into a proportional electrical current signal I(t) (for example 4 to 20 mA). The pressure signal can be tapped as a voltage U via a resistor R.

[0045] For the present exemplary embodiment, the pressure sensors 25.1, 25.2, 25.3, 25.4 assigned to the individual concrete compactors 7 are arranged in or on the pressure lines 14.1, 14.2, 14.3, 14.4 of the respective concrete compactor 7 downstream of the valve block 13. However, the pressure sensors can also be provided on the return lines 16.1, 16.2, 16.3, 16.4 of the concrete compactors 7.

[0046] In addition, the monitoring device 8 has an evaluation unit 26 for analyzing the pressure signal P(t) of each pressure sensor 25.1, 25.2, 25.3, 25, which is connected to the pressure sensors via signal lines S1, S2, S3, S4 in order to receive the measurement signals of the pressure sensors, and the monitoring device 8 has an input unit 8A and an output unit 8B, so that an operator can input instructions and information can be output. For example, the input unit 8A can comprise a keyboard, a joystick or other user interface, and the output unit 8B can comprise a screen and / or a signal light. The input unit 8A and the output unit 8B can also be a touch-sensitive screen (touch screen), which is provided in the control panel 10.

[0047] The evaluation device 26 for analyzing the pressure signal P(t) comprises at least one low-pass filter 33 (anti-aliasing filter) and an analog-digital converter 27 (ADC) which receives the analog measurement signal. The analog-digital converter 27 converts the analog measurement signal into a digital signal. Since the measurement signal passing through the low-pass filter is sampled by the analog-digital converter 27, an aliasing effect can occur, which can be prevented by the low-pass filter 33, the filter characteristic of which can be adapted to the disturbing and useful signal. The minimum sampling frequency is determined according to the Nyquist-Shannon sampling theorem:

[0048] f abtast > 2 fmax (equation 1)

[0049] For the present exemplary embodiment, the sampling frequency is 10 kHz. Furthermore, the evaluation device 26 comprises at least one high-pass filter 31, for example with a cut-off frequency of 10 Hz, in order to filter the measurement signal of the pressure sensor 25.1, 25.2, 25.3, 25.4, so that noise in the low-frequency range is suppressed. The measurement signal of the pressure sensor 25.1, 25.2, 25.3, 25.4 can be filtered and converted by the evaluation device 26 in this way simultaneously or sequentially.

[0050] The evaluation device 26 for analyzing the pressure signal also comprises or can cooperate with a processor 28 and a computer-readable medium 29 and a database 30.

[0051] It is to be understood that the evaluation device 26 can be a single control device (controller) with all the described functions, or can comprise a plurality of controllers, wherein the described functions are distributed among the controllers. Different operations, steps or algorithms as described in this respect can be embodied directly in hardware, in a computer program product, e.g. a software module executed by a processor, or a combination of both. The computer program product can reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, registers, a hard disk, a removable storage medium, or any other form of computer-readable medium known in the art. The exemplary computer-readable medium can be connected to the processor, so that the processor can read information from, and write information to, the memory / storage medium. Alternatively, the medium can be integrated into the processor. The processor and the medium can be located in an application-specific integrated circuit (ASIC). The ASIC can be located in the user terminal device. Alternatively, the processor and the medium can be located as discrete components in the user terminal device. The term "processor" as used herein can refer, at least, to a processing device and / or logic of general purpose or special purpose as understood by those skilled in the art, including but not limited to microprocessors, microcontrollers, state machines, etc. The processor can also be implemented as a combination of computing devices, e.g. a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or other such configurations.

[0052] The evaluation device 26 for analyzing the pressure signal is configured to perform the method steps described below.

[0053] The evaluation device 26 initially transforms the digital pressure signal p(t) of each pressure sensor 25.1, 25.2, 25.3, 25.4 from the time domain into the frequency domain in order to be able to analyze the frequency spectrum. The amplitude spectrum is of particular interest for monitoring the pressure signal.

[0054] The transformation from the time domain into the frequency domain is performed using a discrete-time fast Fourier transform. The algorithms required for this purpose are known to the person skilled in the art. A corresponding software can be implemented for this purpose.

[0055] Figure 3 The amplitude spectrum of the pressure signal over the measurement time is shown, which was determined in a test during regular internal vibrator operation. The frequency in kHz is plotted on the abscissa, while the measurement time in s is plotted on the ordinate. The pressure in mbar is represented by different levels. During the measurement, the rotational speed of the hydraulic motor 19 of the internal vibrator was increased and again reduced using a regulating device provided for this purpose. In the measurement result, this progression can be recognized as the curve marked I. The first harmonics of the individual base frequencies (marked II) can also be seen. The piston frequency f of the hydraulic pump is 2.5 kHz. Figure 3 The amplitude spectrum of the pressure signal over the measurement time is shown, which was determined in a test during regular internal vibrator operation. The frequency in kHz is plotted on the abscissa, while the measurement time in s is plotted on the ordinate. The pressure in mbar is represented by different levels. During the measurement, the rotational speed of the hydraulic motor 19 of the internal vibrator was increased and again reduced using a regulating device provided for this purpose. In the measurement result, this progression can be recognized as the curve marked I. The first harmonics of the individual base frequencies (marked II) can also be seen. The piston frequency f of the hydraulic pump is 2.5 kHz.k can be found in the straight line marked III. The straight line marked IV contains the first harmonic of the piston frequency f k of the hydraulic pump, which can be calculated using equation 2 as follows:

[0056] fk = Nk · n (Equation 2)

[0057] In the case of a current number of pistons N k of 9 and a pump rotational speed n of 2039 rpm (converted to approximately 33.98 r / s), this results in a piston frequency f k of the hydraulic pump of 305.85 Hz. This result coincides with the position of the straight line III.

[0058] Figure 4 shows the single amplitude spectrum calculated from the measured pressure values after approximately 6 seconds from the start of the measurement. The frequency of 307.6 Hz of the peak marked III again corresponds to the piston frequency f fk of the hydraulic pump 15, and the frequency of the peak marked IV corresponds to the first harmonic of the piston frequency f fk of the hydraulic pump 15.

[0059] The evaluation device 26 of the monitoring device 8 is configured to filter out the peak I attributable to the imbalance from the amplitude spectrum and to determine the frequency of this peak, which corresponds to the rotational speed of the hydraulic motor 19 of the concrete compaction device 7. In the amplitude spectrum of Figure 4 , this frequency is 102.5 Hz. It is considered that the peak corresponding to the rotational speed of the concrete vibrator is not always the peak with the highest amplitude. For example, the peak of the piston frequency f fk of the hydraulic pump 15 can have a greater amplitude than the peak corresponding to the rotational speed of the concrete vibrator. The data processing program runs on the hardware of the evaluation device 26, which program contains an algorithm for filtering out the peak whose frequency corresponds to the rotational speed of the vibrator from the respective amplitude spectrum by means of a corresponding filtering technique.

[0060] Discrete-time Fast Fourier Transform (DFT) requires a finite number of measurements. Since the measured signal is recorded continuously, a time window is cut from it. If the window width is not a multiple of the signal period duration, a jump occurs between the first and last sample values ​​due to the periodic continuity of the signal. This jump creates additional frequencies in the spectrum that are not present in the signal. This effect is called leakage (Meyer, Martin: Analoge unddigitale Signale, Systeme und Filter, 8th edition, Wiesbaden: Springer Vieweg 20179). To avoid this effect, in this exemplary embodiment, the signal is weighted with a window function. Due to the leakage effect, the frequencies appearing in the signal are not sharp current peaks in the amplitude spectrum, but rather a main lobe is created at those frequencies, surrounded by multiple side lobes. For oscillations with high amplitudes, the side lobe responses can be higher than the main lobe responses of adjacent oscillations, causing them to vanish into the noise. By changing the window function, the shapes of the main and side lobes can be altered, allowing for the reliable detection of the maximum possible number of relevant frequencies.

[0061] When analyzing pressure signals, various window functions that affect the spectrum differently can be used. For this reason, a window function whose properties are suitable for the desired spectrum should be selected. (The last sentence appears to be incomplete and possibly refers to a different window function.) 11 Hamming windows with a window width of 10000 measurement points are used for Figure 3 and Figure 4 The measurement results are shown in the figure. However, other window functions and widths can also be used. It should be noted that, according to Equation 3, the resolution Δf in the frequency domain is taken as the sampling frequency f. abtast It is affected as a function of the window width N. At the current sampling frequency of 10 kHz and 2 11 With a window width of approximately 4.88 Hz, this results in a frequency resolution of approximately 4.88 Hz.

[0062] Δf = f abtast / N (Equation 3)

[0063] In further testing, two hydraulic lines were securely attached to the concrete vibrator, which was pre-tensioned to 15 bar using a manual pump. The vibrator's rotational speed was then slowly increased. Figure 5 The spectrum over time is shown, in which the increase in the oscillator's rotational speed and other harmonic oscillations can be identified. Figure 6 The diagram shows the magnitude of pressure change at different frequencies. It can be seen that the magnitude also increases with increasing frequency. This is because acceleration increases with increasing rotational speed.

[0064] On a slipform paver, it is possible to provide a monitoring device 8 with multiple pressure sensors 25.1, 25.2, 25.3, 25.4 for monitoring multiple hydraulic concrete compactors 7 in order to determine the rotational speed of each individual concrete compactor, as described above, or it is possible to provide multiple monitoring devices with only one pressure sensor for monitoring only one concrete compactor. The rotational speed of the hydraulic motor can be determined simultaneously or consecutively from the measurement signals of the pressure sensors attached to the monitoring devices. The recorded rotational speeds of the hydraulic motors of the individual concrete compactors can be cyclically transmitted via a CAN interface. The CAN messages can be visualized on an output unit 8B. For example, the rotational speed of the hydraulic motor can be displayed on the output unit 8B.

[0065] The monitoring device 8 can also have multiple digital outputs for activating signal lights 32 provided on the output unit 8B, wherein a signal light can be assigned to each concrete compactor. One exemplary embodiment is that a red signal light assigned to a concrete compactor is switched on if the rotational speed of the hydraulic motor of the concrete compactor is below a defined threshold value for a certain period of time.

[0066] In the present exemplary embodiment, the monitoring device 8 also serves as a control device, which generates control signals for actuating the flow control valves 17.1, 17.2, 17.3, 17.4 for setting the volume flow of hydraulic fluid for driving the concrete compactors 7. The control signals are transmitted from the evaluation unit 26 to the flow control valves 17.1, 17.2, 17.3, 17.4 via control lines R1, R2, R3, R4. The evaluation device 26 is configured to control the flow control valves such that the flow control valves are actuated in dependence on a pressure signal P(t) related to the pressure in the hydraulic fluid, which is generated by the respective pressure sensor 25.1, 25.2, 25.3, 25.4, such that the associated concrete compactor 7 is operated at a predetermined rotational speed. If the rotational speed of the hydraulic motor 19 of the hydraulic concrete compactor 7 decreases, for example due to oil loss, the evaluation device 26 generates a control signal which increases the volume flow of hydraulic fluid to the hydraulic motor of the concrete compactor. The volume flow is thus controlled in such a way that the rotational speed of the hydraulic motor corresponds to a predetermined value, wherein the control deviation should be minimal. This ensures optimal compaction of the concrete over the service life of the concrete compactor.

Claims

1. Monitoring device for a slipform paver, the monitoring device being used to monitor the compaction of concrete placed in a slipform of a slipform paver by at least one hydraulic concrete compactor (7), wherein the concrete compactor (7) has a hydraulic motor (19) for driving an unbalance which generates vibrations, the hydraulic motor being operated with hydraulic fluid provided in a hydraulic fluid system (11); characterized in that the monitoring device (8) has at least one pressure sensor (25.1, 25.2, 25.3, 25.4) to be arranged in the hydraulic fluid system, which generates a pressure signal related to the pressure in the hydraulic fluid, and the monitoring device (8) has an evaluation device (26) for evaluating the pressure measured by the at least one pressure sensor, the evaluation device (26) being configured to draw a conclusion on the compaction of concrete placed in a slipform of the slipform paver based on an analysis of the pressure signal.

2. The monitoring device of claim 1, wherein, The evaluation device (26) is configured to determine an amplitude spectrum of the pressure signal for analyzing the pressure signal.

3. The monitoring device of claim 2, wherein, The evaluation device (26) is configured to sample the pressure signal, wherein the amplitude spectrum of the pressure signal is determined by a discrete-time Fourier transform of the pressure signal.

4. The monitoring device according to claim 2 or 3, characterized in that The evaluation device (26) is configured to determine at least one spectral component attributable to the unbalance from the amplitude spectrum of the pressure signal and to determine the frequency of the at least one spectral component and to compare it to at least one predetermined limit value, a control signal being generated if the at least one limit value is exceeded and / or undershot.

5. The monitoring device according to claim 2 or 3, characterized in that The evaluation device (26) is configured to predetermine a threshold value for the amplitude of a harmonic for evaluating the pressure signal.

6. The monitoring device of claim 4, wherein, The monitoring device (8) has an output unit (8B) which receives the control signal and which is designed to indicate by an acoustic and / or optical and / or haptic signal an inadequate compaction of the concrete during the operation of the slipform paver if the output unit (8B) receives a control signal or to indicate by an acoustic and / or optical and / or haptic signal a proper compaction of the concrete during the operation of the slipform paver if the output unit (8B) does not receive a control signal.

7. The monitoring device of claim 3, wherein, The evaluation device (26) is configured to determine the amplitude spectrum of the pressure signal by a discrete-time fast Fourier transform of the pressure signal.

8. Slipform paver comprising at least one hydraulic concrete compactor (7) having a hydraulic motor (19) for driving an unbalance which generates vibrations, the hydraulic motor (19) being operated with hydraulic fluid provided in a hydraulic fluid system (11), and a monitoring device (8) according to any one of claims 1 to 7.

9. The slipform paver of claim 8, wherein, The hydraulic fluid system (11) comprises a pressure line (14) leading to a hydraulic motor (19) of the concrete compacting device (7) and a return line (16) leading from the hydraulic motor (19) and the at least one pressure sensor (25.1, 25.2, 25.3, 25.4) is arranged in and / or on the pressure line (14) and / or the return line (16).

10. The slipform paver of claim 8 or 9, characterized in that The evaluation device (26) of the monitoring device (8) is configured to control the rotational speed of the hydraulic motor of the at least one concrete compacting device (7) on the basis of an analysis of the pressure signal generated by the at least one pressure sensor (25.1, 25.2, 25.3, 25.4).

11. The slipform paver of claim 10, wherein, The evaluation device (26) of the monitoring device (8) is configured in such a way that a flow control valve (17.1, 17.2, 17.3, 17.4) is provided in the hydraulic fluid system (11) to set the volume flow of hydraulic fluid flowing into the hydraulic motor (19) of the at least one concrete compacting device (7), which flow control valve is actuated in dependence on the pressure signal relating to the pressure in the hydraulic fluid in such a way that the concrete compacting device (7) is operated at a predetermined rotational speed.

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