Monitoring device and method of slip form paver for monitoring concrete compaction

Abstract

The invention relates to a monitoring device (8) of a slipform paver for monitoring the compaction of concrete placed in a slipform of the slipform paver by at least one concrete compaction device (7) having a hydraulic motor (19) for driving an imbalance of the generated vibrations. Furthermore, the invention relates to a method for monitoring the compaction of concrete placed in a slipform of a slipform paver by means of at least one concrete compaction device having a hydraulic motor for driving a vibration-generating imbalance. The monitoring device (8) according to the invention and the method according to the invention are 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, 25.4) arranged in the hydraulic fluid system (11), which generates a pressure signal dependent on the pressure in the hydraulic fluid, and a conclusion of compaction of the concrete placed in the slip form is obtained based on analysis of the pressure signal.

Description

Technical Field

[0001] The invention relates to a monitoring device for a slipform paver, the monitoring device being used to monitor the compaction of concrete placed in a slipform of the slipform paver by at least one concrete compacting device, wherein the concrete compacting device has an unbalanced hydraulic motor for driving a vibration-generating unbalance. Furthermore, the invention relates to a method for monitoring the compaction of concrete placed in a slipform of a slipform paver by at least one concrete compacting device, wherein the at least one concrete compacting device has an unbalanced hydraulic motor for driving a vibration-generating unbalance. Background Art

[0002] Known slipform pavers are equipped with slipforms, also referred to as concrete molds. For example, a slipform pavers is described in EP 1 103 659 B1. With slipform forming, structures of different shapes, such as safety barriers, curbs or entire concrete roads, can be produced. Concrete is poured continuously into the slipform, which moves over the substrate at a constant speed. There must always be a certain amount of concrete in the slipform so that sufficient pressure is applied to the concrete by its own weight. The concrete must be compacted in the slipform and / or in front of the slipform. Concrete compacting devices are used to compact the concrete, which are arranged on or in the slipform. These concrete compacting devices are also referred to as external vibrators or internal vibrators. Slipform pavers are usually equipped with several bottle-shaped or bar-shaped internal vibrators, which are suspended in and / or in front of the slipform and immersed in the concrete during operation.

[0003] When operating a slipform paver, the problem arises that technical defects in the concrete vibrators can lead to the concrete in the slipform not being compacted sufficiently. Particularly when operating internal vibrators that are completely immersed in the concrete, it can be difficult for the slipform paver operator to identify technical defects in individual vibrators. Since subsequent compaction is not possible, sections can be produced in which the concrete does not meet the requirements in certain places. Due to their lack of strength, these concrete sections have to be dismantled and rebuilt, which involves huge costs.

[0004] Known electric concrete vibrators have an asynchronous motor that drives an eccentric flywheel mass (unbalanced) that causes the concrete vibrator to vibrate. The compaction performance of the vibrator depends on the frequency of the vibrations, which in turn 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 use in a slipform paving machine, at least one concrete compacting device of which has an asynchronous motor for driving an eccentric flywheel mass (imbalance) that generates vibrations. The functional principle of the known monitoring device is based on the recognition that during operation of the concrete compacting device, the eccentric flywheel mass (imbalance) is driven by the asynchronous motor, and the rotor shaft can deform elastically due to the imbalance during operation of the asynchronous motor. If the rotor shaft bends, 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 the evaluation of the stator current of the asynchronous motor in order to be able to infer changes in the compaction of the concrete placed in the slipform of the slipform paving machine.

[0006] In addition to electric concrete vibrators, hydraulic concrete vibrators are also known, which have a hydraulic motor to drive an eccentric flywheel mass (unbalanced). Due to the different operating principles of the drive of the eccentric flywheel mass, the monitoring device known from DE 10 201 9 125590 A1 is neither intended nor suitable for such concrete vibrators.

[0007] Typically, the upper and lower operating limits of hydraulic concrete vibrators can be set, for example, between 8000 rpm and 12000 rpm. When using hydraulic vibrators, 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 caused by the nominal volume flow and the nominal pressure, and due to these losses (leaking oil), the achievable rotational speed of the hydraulic vibrator decreases with increasing wear. However, before pouring the concrete, the wear conditions and therefore the achievable rotational speed are unknown in practice. Therefore, the rotational speed required to achieve compaction cannot be guaranteed.

[0008] US 6 055 486 A describes an internal vibrator with a hydraulic drive having a rotational speed control. In order to identify the operating state of the hydraulic vibrator, a device for recording the vibrations of the vibrator is proposed. An acceleration sensor for recording the vibrations is proposed, which is arranged in the vibrator. However, a 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 more than 100° C. In addition, due to the limited installation space, the arrangement of the sensor inside the vibrator is in principle very difficult. In addition, the power supply lines for the power supply of the sensor and the signal lines for recording the signals must be routed back and forth over a long distance to the vibrator immersed in the concrete, which means considerable effort and makes the entire system very prone to failure. Summary of the invention

[0009] The invention is based on the object of creating a monitoring device for a slipform paver having at least one concrete compacting device with an unbalanced hydraulic motor for driving a vibration-generating device, which makes it possible to reliably monitor the compaction of concrete placed in the slipform during operation of the slipform paver under harsh environmental conditions. Another object of the invention is to provide a method allowing to reliably monitor the compaction of concrete placed in a slipform having a concrete compacting device with an unbalanced hydraulic motor for driving a vibration-generating device. An object of the invention is also to provide a slipform paver having such a monitoring device. The invention is also based on the object of being able to use conventional hydraulic concrete vibrators that are not equipped with sensors for monitoring the operating state or do not need to be equipped with such sensors.

[0010] According to the invention, these objects are achieved by the features of the independent claims. The dependent claims relate to advantageous embodiments of the invention.

[0011] The monitoring device according to the invention and the method according to the invention are based on the following knowledge obtained from experiments. Hydraulically driven concrete compacting devices generate oscillations at the rotational frequency of the hydraulic motor due to imbalance. The oscillations are transmitted to the hydraulic fluid (hydraulic oil) used to drive the hydraulic motor, which flows through the connecting line between the hydraulic motor and the concrete vibrator. The velocity changes caused by the oscillations lead to changes in the local acceleration, which cause the occurrence of additional inertial forces in an unstable flow, which leads to corresponding changes in the pressure. These pressure fluctuations in the hydraulic fluid and the resulting changes in density propagate at the speed of sound as longitudinal waves in the fluid and can be recorded with a suitable sensor system.

[0012] The monitoring device according to the invention and the method according to the invention are characterized in that the pressure in the hydraulic fluid is measured at at least one point in the hydraulic fluid system using at least one pressure sensor arranged in the hydraulic fluid system, which pressure sensor generates a pressure signal related to the pressure in the hydraulic fluid, and based on the analysis of the pressure signal, the compaction of the concrete placed in the slipform of the slipform laying machine by means of at least one concrete compacting device is inferred. Thus, it can be determined whether the compaction of the concrete by means of the at least one concrete compacting device is sufficient. Furthermore, it can be determined whether the concrete compacting device is operated with sufficient power (unbalance). Furthermore, it can be determined whether the hydraulic motor of the concrete compacting device is operated with a sufficient rotational speed. This will 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 invention has an evaluation device for evaluating (analyzing) a pressure signal of at least one pressure sensor, the evaluation device being configured to draw conclusions about the compaction of the concrete based on the 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 invention and the method according to the invention have the decisive advantage that the monitoring of the concrete compaction does not utilize components (especially sensitive sensors) in the vicinity of the concrete compacting device, which would be exposed to harsh environmental conditions during operation of the slipform paver. Therefore, there is no risk of failure of such components, which would make the monitoring unreliable. Suitable sensors for recording pressure fluctuations can be arranged in a non-hazardous environment outside the concrete compacting device. In addition, longer supply lines can also be omitted, which would imply considerable expenses and make the entire system very susceptible to failures.

[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 a discrete time Fourier transform (DFT), in particular a discrete time fast Fourier transform (FFT). The signal processing methods required for this are prior art.

[0016] One embodiment provides that the evaluation device is configured to determine, preferably continuously, from the amplitude spectrum of the pressure signal at least one spectral component attributable to an imbalance, and to determine the frequency of at least one spectral component and compare it with at least one predetermined limit value, generating a control signal if the predetermined limit value is exceeded and / or undershot, which 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 the value is below the limit, it can be concluded that the compaction of the concrete is not correct because the rotation speed of the hydraulic motor is too low, which is why the vibration is insufficient. The frequency of at least one spectral component in the amplitude spectrum can also be used to draw conclusions about the wear state of the concrete compacting device. In principle, it is sufficient if the characteristic parameter is determined from the corresponding peak in the amplitude spectrum and then compared with a reference parameter characteristic for a specific operating state of the concrete compacting device.

[0017] In this context, preferably continuous determination of at least one spectral component attributable to an imbalance is understood to mean that the spectral component is determined at at least two consecutive points in time in order to be able to monitor the concrete compacting device during at least part of the operating time or to be able to make a comparison between a previous 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 threshold values ​​for harmonic amplitudes for analyzing the pressure signal of the hydraulic motor. Thus, small amplitudes that are within the noise range and do not 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 an inadequate compaction of the concrete during operation of the slipform paver using an acoustic and / or optical and / or tactile signal, if the output unit receives the control signal, because the determined frequency is below a predetermined limit value. The monitoring device can also be designed to indicate an appropriate compaction of the concrete during operation of the slipform paver using an acoustic and / or visual and / or tactile signal, if the output unit does not receive the control signal, because the determined frequency is above a predetermined limit value. If there are a plurality of concrete compacting 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 compacting device is not used for proper compaction.

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

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

[0022] A further embodiment of the slipform paver according to the invention provides that 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 based on an analysis of the pressure signal generated by the at least one pressure sensor.

[0023] The evaluation device of the monitoring device can be configured such that a flow control valve arranged in the hydraulic fluid system is actuated in dependence on a pressure signal related to the pressure in the hydraulic fluid so that the concrete compacting device is operated at a predetermined rotational speed, the flow control valve being used to set the volume flow of the hydraulic fluid flowing into the hydraulic motor of at least one concrete compacting device. In this case, the flow control valve is actuated such that the pressure signal related 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 invention can form a separate component with which 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 THE DRAWINGS

[0025] Hereinafter, exemplary embodiments of the present invention are explained in more detail with reference to the accompanying drawings.

[0026] In the attached picture:

[0027] Figure 1 shows a side view of a slipform paver having a monitoring device for monitoring the compaction of concrete;

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

[0029] Figure 3 shows the frequency spectrum of the pressure signal of the concrete compaction device over a period of time;

[0030] Figure 4 shows the amplitude spectrum of the pressure signal of the concrete compacting device;

[0031] Figure 5 shows another frequency spectrum of a pressure signal of a concrete compacting device determined during the test, showing the variation over time; and

[0032] Figure 6 Another amplitude spectrum determined during the testing is shown. DETAILED DESCRIPTION

[0033] Figure 1 A side view of an exemplary embodiment of a slipform paving machine without a conveyor device, which is described in detail in EP 1 103 659 B1, is shown. Since such slipform paving machines belong to the prior art, only the parts of the construction machine which are of great value for the present invention are described here.

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

[0035] The traveling gear 4A, 4B and the lifting columns 5A, 5B are part of the drive unit of the slipform paving machine for performing translational and / or rotational movements on site. The drive unit also preferably comprises a hydraulic drive (not shown) for the traveling gear 4A, 4B and an internal combustion engine (not shown). The construction machine can move forward and backward using the traveling gear 4A, 4B. By raising and lowering the traveling gear 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 are arranged in the slipform, which are immersed in the concrete when the slipform paver is in operation. Figure 1 In FIG. 1 , one of the concrete compacting devices 7 is schematically indicated by a dashed line.

[0037] The concrete compacting device 7 is a hydraulic concrete compacting device, such as a conventional hydraulic internal vibrator. A plurality of concrete compacting devices (eg 9 concrete compacting devices) can be arranged on the slipform paver, wherein the concrete compacting devices are connected in parallel.

[0038] The slipform paver according to the invention has a monitoring device 8 for monitoring the compaction of the concrete (only in Figure 1The 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's 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 compacting devices 7 connected in parallel, wherein in the exemplary embodiment there are four concrete compacting devices 7, however Figure 2 Only one of the concrete compacting devices 7 is shown in the figure. 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 conveying 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, which are assigned to the individual concrete compacting devices 7 for load-independent control of the volume flow of the hydraulic fluid (hydraulic oil) flowing to the individual concrete compacting devices 7. The inlet of the flow control valve 17 is connected to the central pressure line 14, wherein the individual pressure lines 14.1, 14.2, 14.3, 14.4 are attached to the outlet of the flow control valve 17. The return lines 16 . 1 , 16 . 2 , 16 . 3 , 16 . 4 of the concrete compacting devices 7 are connected to the central return line 16 .

[0040] The hydraulically operated concrete compacting device 7 has in each case a bottle-shaped or rod-shaped housing 18, in which a hydraulic motor 19 is arranged. The hydraulic motor 19 drives an unbalanced shaft 21 arranged between bearings 22 via a coupling 20. If the unbalanced shaft 21 rotates, its unbalance generates vibrations which are transmitted to the concrete, thereby compacting the concrete. The concrete compacting device 7 is fastened to a bracket 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 insufficient. Therefore, the rotational speed of the hydraulic motor should be at least between a predetermined higher rotational speed or a lower rotational speed, or have a predetermined rotational speed, which is why the hydraulic motor should be operated at 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 invention is capable of monitoring the rotation speed of the hydraulic motor 19 of one or more concrete compacting devices 7. Furthermore, the monitoring device 8 according to the invention is also capable of controlling the rotation speed of the hydraulic motor 19 of the concrete compacting device 7.

[0043] The structure and mode of operation 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 compacting devices 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 arranged only on or in the pressure line, the known slipform paving machine 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 current signal I(t) (for example 4 to 20 mA). This pressure signal can be tapped off 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 compacting devices 7 are arranged in or on the pressure lines 14.1, 14.2, 14.3, 14.4 of the respective concrete compacting devices 7 downstream of the valve block 13. However, the pressure sensors can also be arranged on the return lines 16.1, 16.2, 16.3, 16.4 of the concrete compacting devices 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 sensor via signal lines S1, S2, S3, S4 to receive the measurement signal of the pressure sensor, and the monitoring device 8 has an input unit 8A and an output unit 8B, so that the operator can input instructions and information can be output. For example, the input unit 8A can include a keyboard, a joystick or other user interface, and the output unit 8B can include a screen and / or a signal lamp. The input unit 8A and the output unit 8B can also be touch-sensitive screens (touch screens), which are arranged 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-to-digital converter 27 (ADC) which receives the analog measurement signal. The analog-to-digital converter 27 converts the analog measurement signal into a digital signal. Since the measurement signal which has passed through the low-pass filter is sampled by the analog-to-digital converter 27, aliasing effects may occur, which can be prevented by the low-pass filter 33, the filter characteristics of which can be adapted to the occurring interference and useful signals. The minimum sampling frequency is determined according to the Nyquist-Shannon sampling theorem:

[0048] fabtast>2fmax(Equation 1)

[0049] For the present exemplary embodiment, the sampling frequency is 10 kHz. In addition, 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 signals of the pressure sensors 25.1, 25.2, 25.3, 25.4 and thereby suppress noise in the low-frequency range. The measurement signals of the pressure sensors 25.1, 25.2, 25.3, 25.4 can be filtered and converted by the evaluation device 26 simultaneously or sequentially in this way.

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

[0051] It should be understood that the evaluation device 26 can be a single control device (controller) with all the functions described, or can include multiple controllers, wherein the functions described are distributed between the controllers. Different operations, steps or algorithms as described in this regard can be directly embodied in hardware, in a computer program product, such as a software module executed by a processor, or in a combination of the two. The computer program product may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable storage medium, or any other form of computer-readable medium known in the art. An exemplary computer-readable medium can be connected to a processor so that the processor can read information from a memory / storage medium and write information to a memory / storage medium. Alternatively, the medium can be integrated into a processor. The processor and the medium can be located in an application-specific integrated circuit (ASIC). The ASIC can be located in a user terminal device. Alternatively, the processor and the medium can be located in a user terminal device as discrete components. The term "processor" as used herein can refer at least to a general-purpose or special-purpose processing device and / or logic as understood by those skilled in the art, including but not limited to a microprocessor, a microcontroller, a state machine, etc. A processor may also be implemented as a combination of computing devices, eg, 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 carry out 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 to 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 to the frequency domain is performed using a discrete time fast Fourier transform (FFT / DFT). The algorithms required for this purpose are known to those skilled in the art. Corresponding software can be implemented for this purpose.

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

[0056] fk=Nk·n (Equation 2)

[0057] At the current number of pistons N k 9 and the pump rotation speed n is 2039 rpm (converted to about 33.98 r / s), which results in the piston frequency f of the hydraulic pump k is 305.85 Hz. This result is consistent with the position of straight line III.

[0058] Figure 4 A single amplitude spectrum calculated from the pressure value measured about 6 seconds after the start of the measurement is shown. The frequency of 307.6 Hz of the peak marked III again corresponds to the piston frequency fk of the hydraulic pump 15, and the frequency of the peak marked IV corresponds to the first harmonic of the piston frequency 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 compacting device 7. Figure 4 In the amplitude spectrum of the concrete vibrator, this frequency is 102.5 Hz. It is taken into account that the peak corresponding to the rotation speed of the concrete vibrator is not always the peak with the highest amplitude. For example, the peak of the piston frequency fk of the hydraulic pump 15 can have a larger amplitude than the peak corresponding to the rotation speed of the concrete vibrator. A data processing program runs on the hardware of the evaluation device 26, which contains an algorithm for filtering out the peak whose frequency corresponds to the rotation speed of the vibrator from the respective amplitude spectrum by means of corresponding filtering techniques.

[0060] The discrete-time fast Fourier transform (FFT / DFT) requires a finite number of measured values. Since the measured signal is recorded continuously, a time window is cut out of the measured signal. If the window width is not a multiple of the duration of the signal period, a jump occurs between the first and last sampled value, since the signal is periodically continuous. The jump produces additional frequencies in the spectrum that are not present in the signal. This effect is called the leakage effect (Meyer, Martin: Analoge und digitale Signale, Systeme und Filter, 8th edition, Wiesbaden: Springer Vieweg 20179). In order to avoid this effect, the signal is weighted with a window function in this exemplary embodiment. Due to the leakage effect, the frequency that appears in the signal is not a sharp current peak in the amplitude spectrum, but a main lobe is created at this frequency, which is surrounded by multiple side lobes. For oscillations with high amplitudes, the sidelobe response can be higher than the response of the main lobe of the adjacent oscillation, causing it to disappear into the noise. By changing the window function, the shape of the main lobe and the side lobes can be changed so that the maximum possible number of relevant frequencies can be reliably detected.

[0061] When analyzing a pressure signal, various window functions can be used that affect the spectrum differently. For this reason, a window function whose properties are appropriate for the desired spectrum should be selected. 11 A Hamming window with a window width of measurement points is used Figure 3 and Figure 4 The measurement results shown in . 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 given by the sampling frequency f abtast and the window width N. At a current sampling frequency of 10 kHz and 2 11 With a window width of , this results in a frequency resolution of approximately 4.88 Hz.

[0062] Δf=f abtast / N (Equation 3)

[0063] In a further test, two hydraulic lines were fixed firmly to the concrete vibrator, which was pre-tensioned to a pressure of 15 bar using a hand pump. Subsequently, the rotation speed of the vibrator was slowly increased. Figure 5 The spectrum over the course of time is shown, in which the increase in the shaker rotation speed and other harmonic oscillations can be identified. Figure 6 The amplitude of the pressure change over frequency is shown. It can be seen that the amplitude also increases with increasing frequency. This is due to the fact that acceleration increases with increasing rotation speed.

[0064] On the slipform paver, a monitoring device 8 with a plurality of pressure sensors 25.1, 25.2, 25.3, 25.4 can be provided for monitoring a plurality of hydraulic concrete compacting devices 7 in order to determine the rotational speed of each individual concrete compacting device, as described above, or a plurality of monitoring devices with only one pressure sensor can be provided for monitoring only one concrete compacting device. The rotational speed of the hydraulic motor can be determined simultaneously or continuously based on the measurement signal of the pressure sensor attached to the monitoring device. The recorded rotational speed of the hydraulic motor of the individual concrete compacting devices can be sent cyclically via the CAN interface. The CAN message can be visualized on the 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 may also have a plurality of digital outputs for activating a signal light 32 arranged on the output unit 8B, wherein the signal light may be assigned to each concrete compacting device. An exemplary embodiment is that if the rotation speed of the hydraulic motor of the concrete compacting device is below a defined threshold value for a certain period of time, the red signal light assigned to the concrete compacting device is turned on.

[0066] In the present exemplary embodiment, the monitoring device 8 also serves as a control device, which generates control signals for actuating flow control valves 17.1, 17.2, 17.3, 17.4 for setting the volume flow of hydraulic fluid for driving the concrete compacting device 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 pressure signal P(t) is generated by the respective pressure sensor 25.1, 25.2, 25.3, 25.4, such that the associated concrete compacting device 7 is operated at a predetermined rotational speed. If the rotational speed of the hydraulic motor 19 of the hydraulic concrete compacting device 7 decreases, for example due to oil loss, the evaluation device 26 generates a control signal which causes the volume flow of the hydraulic fluid to the hydraulic motor of the concrete compacting device to increase. 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 during the service life of the concrete compacting device.

Claims

1. A monitoring device for a slipform paver, the monitoring device being used to monitor the compaction of concrete placed in a slipform of the slipform paver by at least one hydraulic concrete compacting device (7), wherein the concrete compacting device (7) has an unbalanced hydraulic motor (19) for driving a vibration-generating hydraulic motor, the hydraulic motor being operated by means of a hydraulic fluid provided in a hydraulic fluid system (11); It is 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 conclusions about the compaction of concrete placed in the slipform of the slipform paver based on an analysis of the pressure signal.

2. The monitoring device according to claim 1, characterized in that: The evaluation device (26) is configured to determine an amplitude spectrum of the pressure signal in order to analyze the pressure signal.

3. The monitoring device according to claim 2, characterized in that: The evaluation device (26) is configured to sample the pressure signal, wherein an amplitude spectrum of the pressure signal is determined by a discrete time Fourier transformation (DFT), in particular a discrete time fast Fourier transformation (FFT), 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 an imbalance from the amplitude spectrum of the pressure signal, to determine the frequency of the at least one spectral component and to compare it with at least one predetermined limit value and to generate a control signal if the at least one limit value is exceeded and / or undershot.

5. The monitoring device according to one of claims 2 to 4, characterized in that The evaluation device (26) is configured to predetermine a threshold value for the amplitude of the harmonics for evaluating the pressure signal.

6. The monitoring device according to claim 4 or 5, characterized in that: The monitoring device (8) has an output unit (8B) which receives a control signal and is designed to indicate, by means of acoustic and / or optical and / or tactile signals, improper compaction of concrete during operation of the slipform paver if the output unit (8B) receives a control signal, or to indicate, by means of acoustic and / or optical and / or tactile signals, proper compaction of concrete during operation of the slipform paver if the output unit (8A) does not receive a control signal.

7. A slipform paver comprising at least one hydraulic concrete compacting device (7) having an unbalanced hydraulic motor (19) for driving a vibration-generating hydraulic motor, the hydraulic motor (19) being operated by means of a hydraulic fluid provided in a hydraulic fluid system (11), and a monitoring device (8) according to any one of claims 1 to 6.

8. The slipform paver according to claim 7, characterized in that: 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), the pressure line (14) leading to a hydraulic motor (19) of the concrete compacting device (7), the return line (16) leading from the hydraulic motor (19), and the at least one pressure sensor (25.1, 25.2, 25.3, 25.4) being arranged in or on the pressure line (14) and / or the return line (16).

9. The slipform paver according to claim 7 or 8, 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) based on an analysis of a pressure signal generated by at least one pressure sensor (25.1, 25.2, 25.3, 25.4).

10. The slipform paver according to claim 9, characterized in that: The evaluation device (26) of the monitoring device (8) is configured such that a flow control valve (17.1, 17.2, 17.3, 17.4) is arranged in the hydraulic fluid system (11) to set the volume flow of hydraulic fluid flowing into the hydraulic motor (19) of at least one concrete compacting device (7), the flow control valve being actuated in accordance with a pressure signal related to the pressure in the hydraulic fluid so that the concrete compacting device (7) is operated at a predetermined rotational speed.

11. A method for monitoring the compaction of concrete placed in a slipform of a slipform paver by at least one hydraulic concrete compacting device having an unbalanced hydraulic motor for driving a vibration-generating hydraulic motor, the hydraulic motor being operated with a hydraulic fluid provided in a hydraulic fluid system, characterized in that The pressure in the hydraulic fluid is measured using at least one pressure sensor arranged in the hydraulic fluid system, the pressure sensor generating a pressure signal which is related to the pressure in the hydraulic fluid, wherein conclusions are drawn about the compaction of concrete placed in a slipform of the slipform laying machine based on an analysis of the pressure signal.

12. The method according to claim 11, characterized in that The pressure signal is analyzed by determining an amplitude spectrum of the pressure signal by means of a discrete time Fourier transformation (DFT), in particular a discrete time fast Fourier transformation (FFT).

13. The method according to claim 11 or 12, characterized in that: At least one spectral component attributable to the imbalance is determined from the amplitude spectrum of the pressure signal, and the frequency of the at least one spectral component is determined and compared with at least one predetermined limit value, and a control signal is generated if the predetermined limit value is exceeded and / or fallen below, and if the control signal is generated, an acoustic and / or optical and / or tactile signal is used to indicate improper compaction of the concrete during operation of the slipform paver, or if no control signal is generated, an acoustic and / or optical and / or tactile signal is used to indicate proper compaction of the concrete during operation of the slipform paver.

14. The method according to any one of claims 11 to 13, characterized in that The rotational speed of the hydraulic motor of the at least one concrete compacting device is controlled based on an analysis of the pressure signal generated by the at least one pressure sensor.

15. The method according to claim 14, characterized in that A flow control valve is provided in the hydraulic fluid system for setting a volume flow of hydraulic fluid flowing into a hydraulic motor of at least one concrete compacting device, the flow control valve being actuated according to a pressure signal related to the pressure in the hydraulic fluid so that the concrete compacting device operates at a predetermined rotational speed.

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