A slipform paver monitoring device for monitoring compaction of concrete and a method for monitoring compaction of concrete during operation of a slipform paver

Abstract

The invention relates to a monitoring device 8 for a slipform paver for monitoring the compaction of concrete placed in a slipform of a slipform paver, comprising at least one concrete compaction device 7, which includes a hydraulic motor 19 for driving a vibration-generating eccentric. Furthermore, the invention relates to a method for monitoring the compaction of concrete placed in a slipform of a slipform paver, comprising at least one concrete compaction device, which includes a hydraulic motor for driving a vibration-generating eccentric. The monitoring device 8 and the method according to the invention are characterized in that at least one pressure sensor 25.1, 25.2, 25.3, 25.1 is arranged in the hydraulic fluid system 11.4, which generates a pressure signal correlating with the pressure in the hydraulic fluid, the pressure in the hydraulic fluid system 11 is measured and, based on an analysis of the pressure signal, conclusions are drawn about the compaction of the concrete placed in the slipform.

Description

[0001] The invention relates to a monitoring device for a slipform paver for monitoring the compaction of concrete introduced into a slipform of a slipform paver by at least one concrete compaction device. The concrete compaction device has a hydraulic motor for driving an imbalance that generates vibrations. Furthermore, the invention relates to a method for monitoring the compaction of concrete introduced into a slipform of a slipform paver, using at least one concrete compaction device that has a hydraulic motor for driving an imbalance that generates vibrations.

[0002] Common slipform pavers feature a slipform, also known as a concrete trough. A slipform paver, for example, is described in EP 1 103 659 B1. With the slipform, structures of various shapes, such as safety barriers, curbs, or entire roadways, can be produced from concrete. The concrete is continuously poured into the slipform, which moves over the subsoil at a constant speed. A certain amount of concrete must always be present in the slipform to ensure that its own weight exerts sufficient pressure on the concrete. The concrete must be compacted in and / or in front of the slipform. Concrete compaction devices, which are mounted on or in the slipform, are used to compact the concrete. These concrete compaction devices are also known as external or internal vibrators.Slipform pavers often have several bottle- or rod-shaped internal vibrators that are hung in and / or in front of the slipform and immerse themselves 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 sufficiently compacted. Especially when operating internal vibrators that are completely submerged in the concrete, technical defects in individual vibrators are difficult for the slipform paver's operators to detect. Since subsequent compaction is not possible, components can be produced in which the concrete does not meet requirements in some places. Due to their lack of strength, these concrete components must be demolished and recast, which entails enormous costs.

[0004] Electric concrete vibrators are known that feature an asynchronous motor that drives an eccentric flywheel (unbalanced mass) 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 speed of the asynchronous motor.

[0005] DE 10 2019 125 590 A1 describes a monitoring device for monitoring concrete compaction, which is intended for a slipform paver whose at least one concrete compaction device has an asynchronous motor for driving the vibration-generating eccentric flywheel (unbalance). The operating principle of the known monitoring device is based on the finding that during operation of a concrete compaction device in which the eccentric flywheel (unbalance) is driven by an asynchronous motor, the rotor shaft can deform elastically due to the unbalance during operation of the asynchronous motor. When the rotor shaft bends, the width of the air gap between the stator and rotor changes, which can be detected in the amplitude spectrum of the stator current.The monitoring of the compaction of the concrete in the known monitoring device is based on the evaluation of the stator current of the asynchronous motor in order to be able to determine 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 feature a hydraulic motor to drive the eccentric flywheel (unbalance). The monitoring device described in DE 10 2019 125 590 A1 is neither intended nor suitable for such concrete vibrators due to the different operating principles of the eccentric flywheel drives.

[0007] The upper and lower operating limits of a hydraulic concrete vibrator can generally be set, for example, between 8,000 and 12,000 rpm. When using hydraulic vibrators, the problem in practice is that the vibrator must be operated at a predetermined speed, for example, a speed of 10,500 rpm, in order to achieve the desired compaction of the concrete. However, due to volumetric losses (leakage oil), the actual speed of the hydraulic motor never reaches the nominal speed resulting from the nominal volume flow and nominal pressure, and the achievable speed of a hydraulic vibrator decreases with increasing wear as a result of these losses (leakage oil). In practice, however, the state of wear and thus the achievable speed are not known before concreting. Therefore, it cannot be guaranteed that the speed required for compaction will be achieved.

[0008] US Pat. No. 6,055,486 A describes a hydraulically driven internal vibrator with speed control. To detect the operating state of the hydraulic vibrator, a device is proposed that records the vibrator's vibrations. Acceleration sensors, which are to be installed in the vibrator, are proposed for detecting the vibrations. A disadvantage, however, is that the acceleration sensors are exposed to harsh environmental conditions. Such sensors, which are installed in hydraulic concrete vibrators, are exposed not only to vibrations but also to extremely high temperatures of over 100°C. Furthermore, locating a sensor inside the vibrator is fundamentally very difficult due to the limited space.Furthermore, supply lines for the power supply of the sensors and signal lines for the recorded signals must be routed over long distances to and from the vibrators immersed in the concrete, which involves considerable effort and makes the entire system very susceptible to failure.

[0009] The invention is based on the object of creating a monitoring device for a slipform paver with at least one concrete compaction device having a hydraulic motor for driving a vibration-generating imbalance, which enables reliable monitoring of the compaction of the concrete poured into the slipform during operation of the slipform paver under harsh environmental conditions. A further object of the invention is to provide a method that allows reliable monitoring of the compaction of the concrete poured into the slipform with a concrete compaction device having a hydraulic motor for driving a vibration-generating imbalance. Another object of the invention is to provide a slipform paver with such a monitoring device.The invention is also based on the object of enabling the use of conventional hydraulic concrete vibrators that are not equipped with sensors for monitoring the operating state or do not have to be equipped with them.

[0010] These objects are achieved according to the invention with the features of the independent patent claims. The dependent claims relate to advantageous embodiments of the invention.

[0011] The monitoring device and method according to the invention are based on the following experimental findings. Due to imbalance, a hydraulically driven concrete compaction device generates a vibration at the rotational frequency of the hydraulic motor. This vibration is transmitted to the hydraulic fluid (hydraulic oil) driving the hydraulic motor, which flows through the hydraulic motor and the connecting lines of the concrete vibrator. The change in speed caused by the vibration results in a change in local acceleration, which, in unsteady flows, causes the occurrence of additional mass forces that lead to a corresponding change in pressure. These pressure fluctuations in the hydraulic fluid and the resulting density changes propagate at the speed of sound as longitudinal waves in the fluid and can be detected with suitable sensors.

[0012] The monitoring device 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 generates a pressure signal correlating with the pressure in the hydraulic fluid. Based on an analysis of the pressure signal, a conclusion is drawn about the compaction of the concrete poured into the slipform of the slipform paver with the at least one concrete compaction device. Consequently, it can be determined whether the compaction of the concrete with the at least one concrete compaction device is sufficient. Furthermore, it can be determined whether the concrete compaction device is operating with sufficient power (imbalance).Furthermore, it can be determined whether the hydraulic motor of the concrete compaction device is operating at a sufficient speed. This would not be the case if the speed of the hydraulic motor were not within specified limits or did not correspond to a specified speed.

[0013] The monitoring device according to the invention has an evaluation device for evaluating (analyzing) the pressure signal from the at least one pressure sensor, which is configured such that the compaction of the concrete is determined based on an analysis of the pressure signal. The evaluation device is preferably configured such that the amplitude spectrum of the pressure signal is determined for the analysis or evaluation of the pressure signal.

[0014] The monitoring device and method according to the invention have the crucial advantage that monitoring of the concrete compaction is not carried out using components, especially sensitive sensors, in the vicinity of the concrete compaction device, which would be exposed to the harsh environmental conditions during operation of the slipform paver. Therefore, there is no risk of such components failing, which would render monitoring unreliable. Suitable sensors for detecting pressure fluctuations can be provided in a non-critical environment outside the concrete compaction device. Furthermore, longer supply lines can be eliminated, which would entail considerable expense and make the entire system highly susceptible to failure.

[0015] The evaluation device is preferably a digital signal processing device configured to sample the pressure signal, with the amplitude spectrum of the pressure signal preferably being 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 state-of-the-art.

[0016] One embodiment provides that the evaluation device is configured such that at least one spectral component attributable to the imbalance is determined from the amplitude spectrum of the pressure signal, preferably continuously, and the frequency of the at least one spectral component is determined and compared with at least one predetermined limit value. If the predetermined limit value is exceeded and / or undershot, a control signal is generated that is characteristic of the compaction of the concrete poured into the slipform of the slipform paver or that signals a change in the compaction of the concrete poured into the slipform of the slipform paver. The limit value can be determined empirically and stored in a memory of the monitoring device.If the limit value is exceeded, it can be concluded that the concrete is not being compacted properly because the speed of the hydraulic motor is too low, resulting in insufficient vibration. The frequency of at least one spectral component in the amplitude spectrum can also be used to determine the wear condition of the concrete compaction device. It is generally sufficient to determine a characteristic parameter from the corresponding peak in the amplitude spectrum, which is then compared with a reference parameter characteristic of a specific operating condition of the concrete compaction device.

[0017] In this context, a preferably continuous determination of at least one spectral component attributable to the imbalance is understood to mean a determination of the spectral component at at least two consecutive points in time in order to be able to monitor the concrete compaction device over at least part of its operating period or to make a comparison between a previous point in time and a subsequent point in time so that a change in the condition can be detected. In principle, however, only a single measurement is also possible.

[0018] The evaluation device can be configured to specify a threshold value for the amplitudes of the harmonics for analyzing the pressure signal of the hydraulic motor. Consequently, small amplitudes that are in the noise range and cannot provide reliable information are masked out.

[0019] In one embodiment, the monitoring device has an output unit receiving the control signal, which is designed such that an acoustic and / or optical and / or tactile signal indicates improper compaction of the concrete during operation of the slipform paver if the output unit receives the control signal because the determined frequency is below a predetermined limit. The monitoring device can also be designed such that an acoustic and / or optical and / or tactile signal indicates proper compaction of the concrete during operation of the slipform paver if the output unit does not receive the control signal because the determined frequency is above a predetermined limit. If several concrete compaction devices are present on the slipform paver, the monitoring device can preferably monitor these individually.If the monitoring device indicates improper compaction with a signal, an indication can also be given of which of the concrete compaction devices is not compacting properly.

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

[0021] An embodiment of the slipform paver according to the invention provides that the hydraulic fluid system comprises a pressure line leading to the hydraulic motor of the at least one concrete compaction device and a return line leading from the hydraulic motor, and the 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 such that the speed of the hydraulic motor of the at least one concrete compaction device is controlled on the basis of an analysis of the pressure signal generated by the at least one pressure sensor.

[0023] The evaluation unit of the monitoring device can be configured such that a flow control valve provided in the hydraulic fluid system is controlled to adjust the volume flow of the hydraulic fluid flowing into the hydraulic motor of the at least one concrete compaction device as a function of the pressure signal correlating with the pressure in the hydraulic fluid, such that the concrete compaction device is operated at a predetermined speed. This is the case if the flow control valve is controlled such that the pressure signal correlating with the pressure in the hydraulic fluid, which is measured by the pressure sensor, corresponds to a predetermined value or lies within predetermined limits.

[0024] The control signal can also be fed to the slipform paver's central control unit 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 assembly with which a conventional slipform paver can be retrofitted. However, the monitoring device can also be part of the slipform paver, whereby the device for monitoring the pressure signal can be part of the slipform paver's central control unit.

[0025] In the following, an embodiment of the invention is explained in more detail with reference to the drawings.

[0026] They show: Fig. 1 shows a side view of a slipform paver with a monitoring device for monitoring the compaction of concrete, Fig. 2 shows a monitoring device for monitoring the compaction of concrete together with a hydraulic fluid system for providing hydraulic fluid to drive several concrete compaction devices in a schematic representation, Fig. 3 shows the frequency spectrum of the pressure signal of a concrete compaction device shown over the time course, Fig. 4 shows the amplitude spectrum of the pressure signal of a concrete compaction device, Fig. 5 shows a further frequency spectrum of the pressure signal of a concrete compaction device determined in tests shown over the time course and Fig. 6 shows a further amplitude spectrum determined in tests.

[0027] Fig. 1shows an embodiment of a slipform paver in a side view without a conveyor system, which is described in detail in EP 1 103 659 B1. Since slipform pavers as such are state of the art, only the components of the construction machine essential to the invention are described here.

[0028] The slipform paver 1 has a machine frame 2 supported by a chassis 3. The chassis 3 has two front and two rear steerable tracks 4A, 4B, which are attached to front and rear lifting columns 5A, 5B. The working direction (direction of travel) of the slipform paver is indicated by an arrow A.

[0029] The undercarriages 4A, 4B and the lifting columns 5A, 5B are part of a drive system of the slipform paver for performing translational and / or rotational movements on the ground. The drive system also includes not shown, preferably hydraulic drives for the undercarriages 4A, 4B, as well as a combustion engine (not shown). The construction machine can be moved forward and backward using the undercarriages 4A, 4B. By raising and lowering the undercarriages 4A, 4B via the lifting columns 5A, 5B, the height and inclination of the machine frame 2 relative to the ground can be adjusted.

[0030] The slipform paver has a slipform 6 for forming concrete, which can be raised or lowered together with the machine frame 2. To compact the concrete, several concrete compaction devices are provided in the slipform, which are immersed in the concrete during operation of the slipform paver. Fig. 1one of the concrete compaction devices 7 is shown schematically in dashed lines.

[0031] The concrete compaction device 7 is a hydraulic concrete compaction device, for example, a conventional hydraulic internal vibrator. Several concrete compaction devices, for example, nine concrete compaction devices, can be provided on the slipform paver, with the concrete compaction devices connected in parallel.

[0032] The slipform paver according to the invention has a Fig. 1 A monitoring device 8, shown only schematically, for monitoring the compaction of the concrete. The monitoring device 8 has an input unit 8A and an output unit 8B, which are provided on a control panel or control panel 9 located at the driver's cab 10 within the field of vision of the operating personnel.

[0033] Fig. 2shows a schematic representation of an embodiment of a monitoring device 8 for monitoring the compaction of the concrete together with a hydraulic fluid system 11 for providing hydraulic fluid for driving several parallel-connected concrete compaction devices 7, in the present embodiment four concrete compaction devices, of which, however, in Fig. 2only one concrete compaction device 7 is shown. The hydraulic fluid system 11 comprises a hydraulic fluid source 12, for example 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 is provided for conveying the hydraulic fluid, 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 the hydraulic fluid (hydraulic oil) flowing to the respective concrete compaction device 7. The inlets of the flow control valves 17 are connected to the central pressure line 14, with the individual pressure lines 14.1, 14.2, 14.3, 14.4 of the concrete compaction devices 7 being connected to the outlets 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.

[0034] The hydraulically operated concrete compaction devices 7 each have a bottle- 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. When the unbalanced shaft 21 rotates, its imbalance generates vibrations that are transmitted to the concrete, compacting the concrete. The concrete compaction device 7 is attached to a bracket 23, which has a damping element 24, allowing the concrete vibrator to vibrate.

[0035] For optimal concrete compaction, a specific speed of the unbalanced shaft 21 is desired. A speed that is too low results in insufficient imbalance, resulting in insufficient concrete compaction. Consequently, the speed of the hydraulic motor should be at least between a specified upper or lower speed or have a specified speed, which is why the hydraulic motor should be operated with a specified flow rate. For example, the hydraulic motor 19 achieves a speed of 10,500 rpm at a flow rate of 16 liters / min and a supply pressure of 90 bar.

[0036] The monitoring device 8 according to the invention allows the monitoring of the speed of the hydraulic motor 19 of one or more concrete compaction devices 7. Furthermore, the monitoring device 8 according to the invention also allows the control of the speed of the hydraulic motor 19 of a concrete compaction device 7.

[0037] The structure and functioning of the monitoring device 8 are described in detail below.

[0038] The monitoring device 8 has pressure sensors 25.1, 25.2, 25.3, 25.4 assigned to the individual concrete compaction devices 7 for measuring the pressure in the hydraulic fluid system 11. Each of these sensors is located at a point in the hydraulic fluid system where particularly strong pressure fluctuations in the hydraulic fluid, attributable to the imbalance of the hydraulic motor 19, can be measured. Since a pressure sensor can be easily provided on or in the pressure line, the known slipform pavers can be easily retrofitted with the monitoring device. The pressure sensor 25.1, 25.2, 25.3, 25.4 can, for example, be a pressure sensor with strain gauges or a capacitive or piezoelectric pressure sensor. The pressure sensor converts the mechanical quantity pressure P(t) into a proportional electrical current signal I(t) of, for example, 4 to 20 mA. This pressure signal can be tapped as voltage U via a resistor R.

[0039] In the present embodiment, the pressure sensors 25.1, 25.2, 25.3, 25.4 assigned to the individual concrete compaction devices 7 are arranged in or on the pressure line 14.1, 14.2, 14.3, 14.4 of the respective concrete compaction device 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 compaction devices 7.

[0040] In addition, the monitoring device 8 has an evaluation device 26 for analyzing the pressure signal P(t) of each pressure sensor 25.1, 25.2, 25.3, 25.4, which is connected to the pressure sensors via signal lines S1, S2, S3, S4 to receive the measurement signals from the pressure sensors. It also has an input unit 8A and an output unit 8B so that the human operator can enter instructions and output information. The input unit 8A can, for example, comprise a keyboard, a joystick, or other user interface, and the output unit 8B can comprise a screen and / or signal lamps. The input and output units 8A, 8B can also be a touchscreen provided in a control panel 10.

[0041] 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 (analog-to-digital converter)), which receives the analog measurement signals. The analog-to-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-to-digital converter 27, aliasing effects can occur, which can be suppressed by the low-pass filter 33, whose filter characteristics must be adapted to the occurring interference and the desired signal. The minimum sampling frequency is determined by the Nyquist-Shannon sampling theorem. f abtast > 2 f max In the present embodiment, the sampling frequency is 10 kHz. Furthermore, the evaluation device 26 comprises at least one high-pass filter 31, for example, with a cutoff frequency of 10 Hz, to filter the measurement signals from the pressure sensors 25.1, 25.2, 25.3, 25.4 so that noise in the low-frequency range is suppressed. In this way, the measurement signals from the pressure sensors 25.1, 25.2, 25.3, 25.4 can be filtered and converted simultaneously or sequentially by the evaluation device 26.

[0042] 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.

[0043] It is understood that the evaluation device 26 may be a single control device (controller) with all of the described functions or may comprise multiple controllers, wherein the described functionality is distributed among the controllers. Different operations, steps, or algorithms as described in this context may be embodied directly in hardware, in a computer program product, for example, in a software module executed by the processor, or in a combination of both. The computer program product may be located in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable storage device, or any other form of computer-readable medium known in the art.An exemplary computer-readable medium may be coupled to the processor such that the processor can read information from the memory / storage medium and write information to the memory / storage medium. Alternatively, the medium may be integrated with the processor. The processor and the medium may be located within an application-specific integrated circuit (ASIC). The ASIC may be located within a user terminal. Alternatively, the processor and the medium may be located within a user terminal as discrete components. The term "processor," as used herein, may refer to at least general-purpose or special-purpose processing devices and / or logic as understood by those skilled in the art, including, but not limited to, a microprocessor, a microcontroller, a state machine, or the like. A processor may also be implemented as a combination of computing devices, e.g.,as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0044] The evaluation device 26 for analyzing the pressure signal is configured such that the method steps described below are carried out.

[0045] The evaluation device 26 first 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 analyze the frequency spectrum. The amplitude spectrum is of particular interest for monitoring the pressure signal.

[0046] 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 are familiar to those skilled in the art. Appropriate software can be implemented for this purpose.

[0047] Fig. 3 shows the amplitude spectra of the pressure signal over the measurement time, which were determined in tests during operation of a conventional internal vibrator. The frequency is plotted on the abscissa in kHz and the measurement time in s on the ordinate. The pressure in mbar is represented by different gradations. During the measurement, the speed of the hydraulic motor 19 of the internal vibrator was increased and then decreased again using a dedicated adjustment device. This curve can be seen in the measurement result. Fig. 3marked I. The first harmonics of the individual fundamental frequencies are also visible (marked II). The straight line marked III represents the piston frequency fk of the hydraulic pump. The straight line marked IV contains the first harmonic of the piston frequency fk of the hydraulic pump, which can be calculated using Equation 2 as follows: ƒk = Nk ⋅ n

[0048] With the number of pistons N k of 9 and a pump speed n of 2039 rpm (equivalent to approx. 33.98 rpm), the piston frequency f k of the hydraulic pump is 305.85 Hz. This result corresponds to the position of straight line III.

[0049] In Fig. 4A single amplitude spectrum is visible, calculated from the pressure measurements starting approximately 6 seconds after the start of the measurement. The frequency of 307.6 Hz of the peak marked III again corresponds to the piston frequency fk of hydraulic pump 15, and the frequency of the peak marked IV corresponds to the first harmonic of the piston frequency fk of hydraulic pump 15.

[0050] The evaluation device 26 of the monitoring device 8 is configured such that the peak I attributable to the imbalance is filtered out of the amplitude spectrum and the frequency of this peak is determined, which corresponds to the speed of the hydraulic motor 19 of the concrete compaction device 7. In the amplitude spectrum of Fig. 4 This frequency is 102.5 Hz. It should be noted that the peak corresponding to the speed of the concrete vibrator is not always the peak with the highest amplitude. For example, the peak of the piston frequency fkof the hydraulic pump 15 have a greater amplitude than the peak corresponding to the speed of the concrete vibrator. A data processing program runs on the hardware of the evaluation device 26. This program contains an algorithm that uses appropriate filtering techniques to filter out the peak whose frequency corresponds to the speed of the vibrator from the individual amplitude spectra.

[0051] The discrete-time fast Fourier transform (FFT / DFT) requires a finite number of measurement values. Since the measurement signal is continuously acquired, a time window is cut from the measurement signal. If the window width is not a multiple of the signal period, a jump occurs between the first and last sample value, as the signal continues periodically. This jump creates additional frequencies in the frequency spectrum that are not present in the signal. This effect is known as the leakage effect (Meyer, Martin: Analog and Digital Signals, Systems and Filters, 8th ed., Wiesbaden: Springer Vieweg 20179). To avoid this effect, the signal is weighted with a window function in the present embodiment.Due to the leakage effect, the frequencies present in the signal are not sharp current peaks in the amplitude spectrum, but rather a main lobe is formed at that frequency, surrounded by several side lobes. For a high-amplitude oscillation, the side lobe response can be higher than that of the main lobe of a neighboring oscillation, causing it to disappear into the noise. By varying the window function, the shape of the main lobe and the side lobes can be changed, allowing the largest possible number of relevant frequencies to be reliably detected.

[0052] When analyzing the pressure signal, various window functions can be used, each of which influences the frequency spectrum differently. Therefore, a window function should be selected whose properties are adapted to the desired spectrum. For the present measurement results from Fig. 3 and Fig. 4The Hamming window was used with a window width of 2 11< measurement points. However, other window functions and widths can also be used. It should be noted that the resolution Δf in the frequency domain is influenced by the sampling frequency f sample and the window width N according to Equation 3. With a sampling frequency of 10 kHz and a window width of 2 11<, this results in a frequency resolution of approximately 4.88 Hz. Δ f = f abtast / N

[0053] In further tests, two hydraulic lines were firmly fixed to a concrete vibrator and pre-tensioned to a pressure of 15 bar using a hand pump. The speed of the vibrator was then slowly increased. Figure 5 The frequency spectrum is shown over time, where the increase in the vibrator speed and other harmonic oscillations can be seen. Figure 6The amplitude of the pressure change is plotted against frequency. It is clear that as the frequency increases, the amplitude also increases. This is because as the speed increases, the acceleration also increases.

[0054] On a slipform paver, a monitoring device 8 with multiple pressure sensors 25.1, 25.2, 25.3, 25.4 can be provided for monitoring multiple hydraulic concrete compaction devices 7 in order to determine the speed of each individual concrete compaction device, as described above, or multiple monitoring devices with only one pressure sensor can be provided for monitoring only one of the concrete compaction devices. The speed of the hydraulic motor can be determined from the measurement signal of the pressure sensors connected to the monitoring device simultaneously or sequentially. The recorded speeds of the hydraulic motors of the individual concrete compaction devices can be transmitted cyclically via a CAN interface. The CAN messages can be visualized on the output unit 8B. For example, the speeds of the hydraulic motors can be displayed on the output unit 8B.

[0055] The monitoring device 8 can also have a plurality of digital outputs for controlling signal lamps 32 provided on the output unit 8B, wherein each concrete compaction device can be assigned a signal lamp. One exemplary embodiment is that a red signal lamp assigned to a concrete compaction device is switched on when the speed of the hydraulic motor of this concrete compaction device falls below a defined threshold value for a specific period of time.

[0056] In the present embodiment, the monitoring device 8 also functions as a control device that generates control signals for controlling the flow control valves 17.1, 17.2, 17.3, 17.4 for adjusting the volume flow of the hydraulic fluid for driving the concrete compaction devices 7. The control signals are transmitted from the evaluation device 26 via control lines R1, R2, R3, R4 to the flow control valves 17.1, 17.2, 17.3, 17.4. The evaluation device 26 is configured to control the flow control valves in such a way that the flow control valves are controlled as a function of the pressure signal P(t) correlated with 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 respective concrete compaction device 7 is operated at a predetermined speed.If the speed of the hydraulic motor 19 of a concrete compaction device 7 decreases, for example due to an oil leak, the evaluation device 26 generates a control signal that causes an increase in the volume flow of the hydraulic fluid flowing to the hydraulic motor of the concrete compaction device. Consequently, the volume flow is regulated such that the speed of the hydraulic motor corresponds to a predetermined value, with the control deviation being minimal. This ensures optimal compaction of the concrete over the service life of the concrete compaction device.

Claims

1. Monitoring device for a slipform paver for monitoring the compaction of concrete introduced into a slipform of the slipform paver by at least one hydraulic concrete compaction device (7), wherein the concrete compaction device (7) has a hydraulic motor (19) for driving a vibration-generating imbalance, which is operated with a hydraulic fluid provided in a hydraulic fluid system (11), characterized in thatthe 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 correlating with the pressure in the hydraulic fluid, and an evaluation device (26) for evaluating the pressure measured by the at least one pressure sensor, which is configured such that, on the basis of an analysis of the pressure signal, conclusions are drawn about the compaction of the concrete introduced into the slipform of the slipform paver.

2. Monitoring device according to claim 1, characterized in that the evaluation device (26) is configured such that the amplitude spectrum of the pressure signal is determined for the analysis of the pressure signal.

3. Monitoring device according to claim 2, characterized in thatthe evaluation device (26) is configured such that the pressure signal is sampled, wherein the amplitude spectrum of the pressure signal is determined by a time-discrete Fourier transformation (DFT), in particular a time-discrete fast Fourier transformation (FFT), of the pressure signal.

4. Monitoring device according to claim 2 or 3, characterized in that the evaluation device (26) is configured such that at least one spectral component which is 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, wherein a control signal is generated if the at least one limit value is exceeded and / or undershot.

5. Monitoring device according to one of claims 2 to 4, characterized in thatthe evaluation device (26) is configured such that a threshold value for the amplitudes of the harmonics is specified for the evaluation of the pressure signal.

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

7. Slipform paver with at least one hydraulic concrete compaction device (7) having a hydraulic motor (19) for driving a vibration-generating imbalance, which is operated with a hydraulic fluid provided in a hydraulic fluid system (11), and with a monitoring device (8) according to one of claims 1 to 6.

8. Slipform paver according to claim 7, characterized in that the hydraulic fluid system (11) comprises a pressure line (14) leading to the hydraulic motor (19) of the concrete compaction 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 or on the pressure line (14) and / or the return line (16).

9. Slipform paver according to claim 7 or 8, characterized in thatthe evaluation device (26) of the monitoring device (8) is configured such that the speed of the hydraulic motor of the at least one concrete compaction device (7) is controlled 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).

10. 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) provided in the hydraulic fluid system (11) for adjusting the volume flow of the hydraulic fluid flowing into the hydraulic motor (19) of the at least one concrete compaction device (7) is controlled as a function of the pressure signal correlating with the pressure in the hydraulic fluid such that the concrete compaction device (7) is operated at a predetermined speed.

11. A method for monitoring the compaction of concrete placed in a slipform of a slipform paver with at least one hydraulic concrete compaction device having a hydraulic motor for driving a vibration-generating imbalance, which is operated with a hydraulic fluid provided in a hydraulic fluid system, characterized in that with at least one pressure sensor arranged in the hydraulic fluid system, which generates a pressure signal correlating with the pressure in the hydraulic fluid, the pressure in the hydraulic fluid is measured, wherein on the basis of an analysis of the pressure signal, conclusions are drawn as to the compaction of the concrete introduced into the slipform of the slipform paver.

12. Method according to claim 11, characterized in thatTo analyze the pressure signal, the amplitude spectrum of the pressure signal is determined by a discrete-time Fourier transform (DFT), in particular a discrete-time fast Fourier transform (FFT).

13. Method according to claim 11 or 12, characterized in thatat least one spectral component which is 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, wherein if the predetermined limit value is exceeded and / or undershot, a control signal is generated and an acoustic and / or optical and / or tactile signal is used to indicate improper compaction of the concrete during operation of the slipform paver if the control signal is generated, or an acoustic and / or optical and / or tactile signal is used to indicate proper compaction of the concrete during operation of the slipform paver if the control signal is not generated.

14. Method according to one of claims 11 to 13, characterized in thatthe speed of the hydraulic motor of the at least one concrete compaction device is controlled on the basis of an analysis of the pressure signal generated by the at least one pressure sensor.

15. Method according to claim 14, characterized in that a flow control valve provided in the hydraulic fluid system for adjusting the volume flow of the hydraulic fluid flowing into the hydraulic motor of the at least one concrete compaction device is controlled as a function of the pressure signal correlating with the pressure in the hydraulic fluid in such a way that the concrete compaction device is operated at a predetermined speed.

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