Monitoring system for a movable component connected to a stationary component

Abstract

A monitoring system (12) for a moving part (3), such as a rotating part, supported by a fixed part (2). The monitoring system (12) includes: a sound sensor (10) located in a movable part (3) and including two terminals (17); a first amplifier (18) located in the movable part (3) and having two input terminals and two output terminals; a contactless communication unit (14) provided with a first transceiver device (15) located in the movable part (3) and a second transceiver device (16) facing the first transceiver device (15) and located in a fixed part (2); a first connecting line (19) connecting the sensor (10) to the first amplifier (18) and having two electrical leads, each of which connects a terminal (17) of the sound sensor (10) to a corresponding input terminal of the first amplifier (18); and a second connecting line (20) connecting the first amplifier (18) to the first transceiver device (15) and having two electrical leads, each of which connects an output terminal of the first amplifier (18) to the first transceiver device (15).

Description

[Technical Field]

[0001] The present invention relates to a monitoring system for a movable component (e.g., a rotating component) connected to a fixed component.

[0002] The present invention can be advantageously applied to monitoring systems that use sound signals to support the rotating spindle of (at least) a grinding wheel in a machine tool, the following discussion of which will be explicitly referenced without loss of generality. [Previous Technology]

[0003] For example, as described in patent applications Nos. EP0690979A1, EP1870198A1 and EP3134980A1, it is known that the rotary spindle (hub) of a machine tool (especially a grinding machine) supports (at least) a grinding wheel and is provided with a balancing head housed in an axial cavity. The balancing head includes at least one balancing mass eccentric relative to the rotation axis, the position of which is adjustable and controlled by an electric motor.

[0004] Typically, the balancing head also includes a vibration sensor (i.e., a microphone) for detecting ultrasonic emissions caused by contact between the grinding wheel and the workpiece or between the grinding wheel and the dressing tool (dresser). The electrical signal generated by the vibration sensor is used (in a known manner) to control the machining cycle.

[0005] The microphone is part of the monitoring system, where the electrical signals provided by the microphone are processed to provide information about the correctness of the machining process. The machine tool's control unit can then act on the process based on this information. [Summary of the Invention]

[0006] The object of the present invention is to provide a monitoring system for a movable part connected to a fixed part, which allows for accurate and stable detection of the effects of an ongoing action, such as workpiece machining or grinding wheel dressing, and is preferably easy to install even in a confined space.

[0007] The present invention provides a monitoring system for a movable component connected to a fixed component, as defined in the appended claims.

[0008] The claims describe embodiments of the present invention and form part of this specification.

Implementation Method

[0013] In Figure 1, reference numeral 1 represents a machine tool (particularly a grinding machine) as a whole, showing only some of its components.

[0014] Typically, a machine tool includes a fixed part or fixed component and a movable part or movable component that are interconnected. In a grinding machine, the movable component typically rotates relative to the fixed component.

[0015] The machine tool 1 shown in Figure 1 includes a frame 2 (i.e., a fixed part) that supports a spindle 3 that rotates about a rotation axis 4 in a rotatable manner (by means of bearings arranged therebetween).

[0016] The spindle 3 supports the grinding wheel 5 via a corresponding grinding wheel hub, which is detachably fixed to the spindle 3 by a known (but not shown) device including, for example, a tapered coupling. The spindle 3 and the grinding wheel hub define the rotating part of the machine tool 1, also referred to as the rotor. The spindle 3 has an axial opening 6 at its center for accommodating a balancing head 7. The balancing head 7 of a known type includes two balancing masses 8 eccentric relative to the axis of rotation 4 and a corresponding motor 9 for adjusting the angular position of the balancing masses 8. The rotating part also includes (at least) a sound sensor 10 or a vibration sensor. In FIG. 1, the sound sensor 10 is integrated into the balancing head 7, but it may also be not integrated into the balancing head 7 and configured in different areas of the rotating part, as shown in FIG. 2, for example.

[0017] The function of the balancing head 7 is to balance the grinding wheel 5. This operation is generally performed when changing the grinding wheel 5, and when it is necessary due to wear of the grinding wheel 5.

[0018] The balancing head 7 includes a control device 11, which controls the operation of the balancing head 7.

[0019] The balancing head 7 described and shown in the attached drawings may not exist and the rotating part may only include sound sensor 10 or more sound sensors.

[0020] The sound sensor 10 and the balancing head 7 (if provided) are part of a monitoring system 12, which is connected to a processing unit 40 configured in a fixed position (i.e., supported by the frame 2 of the machine tool 1). The monitoring system 12 is configured to provide signals to the processing unit 40, mounted on the frame 2 (i.e., in the fixed part of the machine tool 1), relating to the vibrations experienced by the spindle 3 (i.e., the rotating part of the machine tool 1) at the grinding wheel 5, as experienced by the machine tool 1.

[0021] Figures 2-6 show the monitoring system 12, in which the sound sensor 10 is different from the embodiment of Figure 1 and is not integrated into the balance head 7.

[0022] The dashed box in the figure represents the physical division between the rotating part and the stationary part of the machine tool; the configuration of individual components of the monitoring system 12 may be different from that shown in the figure.

[0023] As shown in Figure 2, the monitoring system 12 includes a non-contact communication unit 14, which is equipped with a first transceiver device 15 located in the spindle 3 (i.e., the rotating part of the machine tool 1) and a second transceiver device 16 facing the transceiver device 15 and positioned in the frame 2 (i.e., in the fixed part of the machine tool 1). The two transceiver devices 15 and 16 are adapted to communicate with each other in a non-contact and known manner so as to send information from the transceiver device 15 to the transceiver device 16 and vice versa. The fixed part includes an interface unit 13, which distributes power to the components of the monitoring system 12 and transmits signals leaving or entering the processing unit 40.

[0024] The communication unit 14 is used by the interface unit 13 in one direction to send control signals (e.g., start / stop readings of the acoustic sensor 10 or control motor 9 of the balancing mass 8 of the balancing head 7) from the processing unit 40 and / or from the control unit (not shown) of the machine tool, and in the opposite direction to transmit diagnostic signals (generated in the balancing head 7) to the interface unit 13 and / or signals related to vibrations experienced by the spindle.

[0025] As shown in FIG2, the sound sensor 10 includes two terminals 17, between which a variable voltage (i.e. analog signal) is generated, which depends on the intensity and frequency of the vibration detected by the vibration sensor 10 itself.

[0026] The monitoring system 12 includes an amplifier 18, which is placed inside the rotor (i.e., in the rotating part of the machine tool 1) and includes two input terminals and two output terminals.

[0027] The monitoring system 12 includes a first connection line 19 that connects the sound sensor 10 to the amplifier 18 and includes two independent (i.e. electrically insulated) electrical leads, each of which connects the terminal 17 of the vibration sensor 10 to the corresponding input terminal of the amplifier 18.

[0028] The monitoring system 12 includes a second connection line 20 that connects the amplifier 18 to the transceiver device 15 and includes two separate (i.e. electrically insulated) electrical leads, each of which connects the output terminal of the amplifier 18 to the transceiver device 15.

[0029] Specifically, the amplifier 18 is positioned close to the sound sensor 10.

[0030] In the embodiment shown in FIG1, the sound sensor 10 is integrated into the balance head 7, and the amplifier 18 may be located in the control device 11 of the balance head 7 or integrated into the sound sensor 10. The connecting wire 20 is integrated into the multiply cable 21, preferably coiled, which extends along the axial opening 6 and includes one or more power lines (i.e., lines that transmit power for operating the balance head 7) in addition to the connecting wire 20.

[0031] In the embodiment shown in FIG. 2, the communication unit 14 transmits analog signals non-contactly via inductive coupling. According to different embodiments (not shown), the communication unit 14 transmits analog signals non-contactly via optical coupling (e.g., according to one of the alternatives described in US Patent No. 5688160A). The transceiver device 15 receives voltage and current varying according to vibrations detected by the acoustic sensor 10 and transmits (induces) the corresponding voltage and current via inductive coupling to the transceiver device 16. Thus, an electronic-type analog signal leaves the transceiver device 16. Preferably, the monitoring system 12 includes an amplifier 22 located in the rack 2 (i.e., in the fixed portion of the machine tool 1) and including two input terminals connected to the transceiver device 16 and two output terminals connected to the interface unit 13, which, as previously described, is configured to process the signal generated by the acoustic sensor 10.

[0032] The monitoring system 12 includes a power supply circuit 23, a first power supply device 24 located in the rotor (i.e., in the rotating part of the machine tool 1) and supplying power to the amplifier 18, and a second power supply device 25 located in the frame 2 (i.e., in the fixed part of the machine tool 1) and supplying power to the amplifier 22 and the power supply device 24, and receiving power from the interface unit 13. Due to the presence of amplifiers 18 and 22 (which must be supplied with power), signal conditioning is improved and more powerful than in the case of a direct connection between the sound sensor 10 and the transceiver device 15. In addition, the power supply circuit 23 includes an air-coupled transformer 26 with a first coil 27 located in the rotor (i.e., in the rotating part of the machine tool 1) and supplying power to the power supply device 24, and a second coil 28 located in the frame 2 (i.e., in the fixed part of the machine tool 1) and receiving power from the power supply device 25. In the embodiment shown in Figure 2, the power supply device 24 is directly connected to the coil 27 of the air coupling transformer 26; that is, the power supply device 24 receives power directly from the coil 27 of the air coupling transformer 26 without a medium.

[0033] Figure 2 also shows an additional power supply circuit 29, which is completely separate and independent from the power supply circuit 23 of the monitoring system 12, and supplies power to the balancing head 7. This power supply circuit 29 is present when the balancing head 7 is present. The power supply circuit 29 includes, for example, a power supply device 30 located in the rotor (i.e., in the rotating part of the machine tool 1) and supplying power to the balancing head 7, and a power supply device 31 located in the frame 2 (i.e., the fixed part of the machine tool 1), supplying power to the power supply device 30 via an air coupling transformer 32 and receiving power from the interface unit 13.

[0034] In the embodiments shown in Figures 2-5, the balancing head 7 is powered by a power supply circuit 29, which supplies power only to the balancing head 7 and is independent of the power supply circuit 23 of the monitoring system 12. In the embodiment shown in Figure 6, only the power supply circuit 23 is provided, and it is shared by the entire monitoring system 12, including the balancing head 7. In other words, the power supply circuit 23 also supplies power to the balancing head 7.

[0035] In the alternative embodiment shown in FIG. 3, the monitoring system 12 includes another amplifier 33 located in the rotor (i.e., in the rotating part of the machine tool 1), connected in series with the amplifier 18 along the connecting line 20, and including two input terminals connected to the two output terminals of the amplifier 18 and two output terminals connected to the transceiver device 15. In particular, the amplifier 18 is configured near the vibration sensor 10 (i.e., at the beginning of the connecting line 20 with reference to the layout shown in the figures), while the amplifier 33 is configured near the transceiver device 15 (i.e., to the end of the connecting line 20 with reference to the layout shown in the figures).

[0036] In the embodiment shown in FIG3, amplifier 33 is also powered by power supply device 24, which powers amplifier 18.

[0037] In the alternative embodiment shown in FIG. 4, the monitoring system 12 includes a third power supply 34 directly connected to the coil 27 of the air-coupled transformer 26; in other words, the power supply 4 receives power directly from the coil 27 of the air-coupled transformer 26 without a medium. Furthermore, the monitoring system 12 includes a coupling device 35 that receives power from the power supply 34 and feeds it to the connection line 20 at a frequency band different from the analog signal generated by the sound sensor 10, and a decoupling device 36 that obtains power from the connection line 20 and supplies power to the power supply 24 (therefore it indirectly receives power from the coil 27 of the air-coupled transformer 26). For example, the coupling device 35 and the decoupling device 36 use reactive elements to achieve frequency band separation and transmit continuous or alternating power with a frequency higher or lower than the analog signal generated by the sound sensor 10, typically having a frequency between 1 kHz and 1 MHz.

[0038] In the embodiment shown in Figures 2-4, communication unit 14 transmits analog signals (which will be digitized in processing unit 40) between two transceiver devices 15 and 16. In the embodiment shown in Figures 5-7, communication unit 14 transmits digital signals between two transceiver devices 15 and 16. Monitoring system 12 actually includes an analog-to-digital converter 37 located in the rotor (i.e., in the rotating part of machine tool 1) and configured to receive analog signals from amplifier 18 (if provided, together with amplifier 33) and convert the analog signals into digital signals.

[0039] In addition, the monitoring system 12 preferably includes a processing device 38 located in the rotor (i.e., in the rotating part of the machine tool 1) and configured to receive digital signals from the analog-to-digital converter 37, process the digital signals and obtain the processed digital signals, and provide the processed digital signals to the transceiver device 15.

[0040] More specifically, the processing device 38 performs time-domain and frequency-domain processing on the digital signal leaving the analog-to-digital converter 37. Preferably, this processing is based on Fourier transform calculations.

[0041] More specifically, this process is performed by using the Fast Fourier Transform (FFT).

[0042] For example, signal processing may include the following steps: - Selecting the frequency band of the signal and setting the gain; - Sampling the signal at a frequency higher than 2 MHz; - Calculating the FFT function; - Zeroing in the frequency domain; - Demodulating the signal spectrum to perform checks related to clearance (i.e., the distance between the grinding wheel and the workpiece or dressing tool) and checks related to collision (i.e., contact between the grinding wheel and the workpiece or dressing tool or other components of the machine tool), demodulating the two types of checks independently; - Performing time-domain processing of the signal for each of the two independent types of checks; - Triggering the automatic execution of parameterization of the frequency band and signal gain, and triggering the zeroing of background noise.

[0043] Optionally, the background noise can also be zeroed based on its average or maximum value.

[0044] Processing the rough signal inside the rotor, i.e. the signal generated by the acoustic sensor 10, allows the complete signal processing (e.g., including the steps described above) to be performed as close as possible to the signal source (i.e., the acoustic sensor 10) and significantly shortens the propagation path of the rough signal.

[0045] In known solutions, the analog signal generated by the sensor is transmitted to an external processor, which converts the analog signal into a digital signal and then processes it. The processor is typically placed in a machine cabinet or laboratory controller and can perform processing operations without adhering to strict limitations. However, due to the potentially long propagation path of the analog signal, the signal-to-noise ratio often deteriorates, and the signal quality reaching the processor is significantly worsened.

[0046] According to known solutions, the signal generated by the sensor is digitized near the sensor and then transmitted to an external processor for complete processing. However, the bandwidth required to transmit the digital signal is too large for contactless communication systems in industrial applications. This problem has been overcome in known solutions by obtaining the digital signal through quantization with poor dynamics (e.g., 8 bits) and performing only minimal digitization processing before transmission. In this way, the bandwidth of the signal to be transmitted is limited, but the poor digitization processing performed before signal transmission inevitably leads to low-performance signal processing in the external processor.

[0047] The monitoring system 12 according to the invention allows for the conversion, and especially complete processing, of the signal generated by the acoustic sensor 10 adjacent to such a sensor by simultaneously meeting the requirements of such applications, i.e., highly miniaturized, very low power consumption and low bandwidth transmission of detailed information related to process monitoring.

[0048] This is achieved by combining a processing device with lower computing power with a highly optimized software algorithm. In fact, the hardware of the processing device is designed to have lower computing power than that typically used in such applications in order to reduce overall size and power consumption, while the software is designed to perform all the operations required for monitoring but with fewer resources.

[0049] According to a preferred embodiment of the present invention, in order to obtain processed digital signals inside the rotor and to transmit the processed digital signals via a contactless communication unit 14, a monitoring system 12, and more specifically, an analog-to-digital converter 37 and a processing device 38, a method comprising the following steps is implemented: - Increasing the analog-to-digital acquisition dynamics by using a SAR (Successive Approximation Register) converter with higher resolution than known solutions. - Performing high-frequency acquisition of a coarse fundamental frequency signal generated by an acoustic sensor 10, the frequency being higher than 2 MHz. - Performing random processing on a single measurement, the random processing being highly parameterizable to maintain high efficiency as the monitored process changes. More specifically, the digital random processing technique used guarantees stability and convergence. - Implementing an automatic parameter setting mode that allows automatic parameterization of the process based on observations of the monitored process. The parameters of the process produce acoustic emissions detected and monitored by the acoustic sensor, which are not prior known because they depend on many operating and environmental conditions. The implemented automatic parameter setting mode is defined based on one or more learning phases and subsequent processing of the acquired results. The processing result, i.e., the processed digital signal, is packetized to transmit high-priority and low-priority information in real time over the same communication channel. As mentioned earlier, digital processing technology generates a large amount of data, thus requiring a large bandwidth for signal transmission. The packetization of the processed digital signal is performed according to an optimized communication protocol that allows the hierarchical structure of information to be defined based on the latency of the information used. This enables the transmission of the processed digital signal via a contactless communication channel, as provided in the monitoring system according to the invention.

[0050] Preferably, the above method further includes a step of performing specific processing based on the same coarse signal to perform multiple simultaneous measurements without requiring the addition of dedicated hardware. Machine tool applications using acoustic sensors typically perform at least two types of measurements: machine operation-related measurements with high sensitivity and narrow bandwidth to track the machine process with maximum accuracy, and monitoring measurements with lower sensitivity and wider bandwidth to identify anomalies promptly, even outside the typical process bandwidth.

[0051] The combination of hardware and software designed as described above allows for complete processing of the signal generated by the acoustic sensor 10 inside the rotor. This means that the signal processing not only has good quality and a good signal-to-noise ratio, but also has the risk of information loss because it has not been partially processed beforehand.

[0052] In the embodiment of FIG5, transceiver device 15, analog-to-digital converter 37 and processing device 38 receive power from power supply device 34, while transceiver device 16 receives power from power supply device 25.

[0053] The only difference between the embodiment shown in FIG5 and the embodiment shown in FIG6 is that in the embodiment shown in FIG5, the power supply circuit 29 supplying power to the balance head 7 is separate and independent from the power supply circuit 23, while in the embodiment shown in FIG6, only the power supply circuit 23 is provided and is shared by the entire monitoring system 12 including the balance head 7 (in other words, the power supply circuit 23 also supplies power to the balance head 7).

[0054] According to different embodiments not shown in the figures, the analog-to-digital converter 37 and the processing unit 38 are configured in the frame 2 (i.e., in the fixed part of the machine tool 1). The conversion of analog signals to digital signals and its processing are not performed in the rotating parts of the machine tool, but in the fixed part of the machine tool. This solution can be applied to alternative embodiments of the monitoring system 12 shown in Figures 5, 6, and 7.

[0055] In the embodiment shown in FIG. 7, the monitoring system 12 includes two acoustic sensors 10, two amplifiers 18 separated and independent of each other, and two connecting lines 19, each connecting line connecting one of the acoustic sensors 10 to the amplifier 18 and including two independent electrical leads. Furthermore, the monitoring system 12 includes a single communication unit 14 (shared between the two acoustic sensors 10) and a multiplexer 39 having two inputs connected to the two amplifiers 18 and a single output of a transceiver device 15 connected to the single communication unit 14. The multiplexer 39 is an input selector that receives several analog input signals and alternately sends them to the single output. The multiplexer 39 allows for multiple sensors located in different regions of the rotor and selects the signal from the most effective sensor for monitoring purposes based on the operation performed through the machine tool.

[0056] Obviously, when a single communication unit 14 transmits a digital signal (as shown in FIG. 7) and when a single communication unit 14 transmits an analog signal, i.e., when the monitoring system 12 does not include an analog-to-digital converter 37, there may be two (or more) sound sensors 10 and thus a multiplexer 39. Furthermore, when a power supply 34 is provided to each power supply device 24 using coupling device 35 and decoupling device 36, and when each power supply device 24 is directly connected to the winding 27 of the air coupling transformer 26, there may be two (or more) vibration sensors 10 and thus a multiplexer 39 (as shown in FIG. 7).

[0057] According to one possible embodiment, the processing device 38 controls the multiplexer 39 to control which sound sensor 10 must provide a signal to the transceiver device 15 of the individual communication unit 14, i.e., which sound sensor 10 must be read. The multiplexer 39 can be statically configured, or alternatively, dynamically configured, i.e., connecting each input to the output in a cyclical and alternating manner at a defined switching frequency. The multiplexer 39 can be controlled by the processing device 38 when it is configured in the rotor (as shown in FIG. 7) and when it is configured in the stationary part of the machine tool.

[0058] In the embodiment shown in FIG7, two sound sensors 10 are provided and connected to the multiplexer 39 (via a corresponding amplifier 18). According to other embodiments not shown in the figure, three or more sound sensors 10 are provided and connected to the multiplexer 39 (via a corresponding amplifier 18); all of these sensors or some of these sensors cannot be sound sensors.

[0059] So far, the presence of multiple acoustic sensors and multiplexers has been shown and described with reference to monitoring system 12, wherein signal processing occurs in the stationary or rotating parts of the machine tool. As described above, multiple sensors and multiplexers may also be present in alternative embodiments of monitoring system 12 shown in Figures 2-4, wherein signal processing occurs in processing unit 40. In these cases, processing unit 40 controls the multiplexers.

[0060] Conventionally, the processing unit 40 uses the readings of the acoustic sensor 10 only during workpiece machining or during grinding wheel maintenance or dressing to detect ultrasonic emissions caused by contact between the grinding wheel and the workpiece or between the grinding wheel and the dressing tool (dresser). Therefore, the readings of the vibration sensor 10 are conventionally (in a known manner) used only to check machining or maintenance cycles.

[0061] Due to accidental collisions between the spindle 3 and the workpiece and / or between the spindle 3 and other components of the machine tool 1 (and due to errors in control), the processing unit 40 may also use readings from the acoustic sensor 10 to detect any vibration peaks (i.e., peaks of acoustic emission) during the movement of the spindle 3 back and forth to the workpiece and / or during the assembly and disassembly of the workpiece. In other words, the acoustic sensor 10 (i.e., the monitoring system 12 includes the acoustic sensor 10) is used by the processing unit 40 as a “sentinel” for any unwanted collisions with the spindle 3 when the spindle 3 shifts or the workpiece approaches the spindle 3. Obviously, when a signal provided by the acoustic sensor 10 indicates a (possible) collision, the processing unit 40 immediately sends it to the machine tool’s control unit, stopping the ongoing motion if necessary. This type of event may also be recorded by the processing unit 40 and / or the machine tool’s control unit to allow for the reconstruction of all negative events that the spindle 3 has experienced in the future.

[0062] In the above embodiment, a vibration sensor 10 is used, while in other embodiments (not shown), different types of sensors (e.g., temperature sensor, pressure sensor, acceleration sensor, etc.) are used.

[0063] In the above embodiment, the movable part is the spindle 3 of the machine tool 1, while according to other embodiments (not shown), the movable part is a part with different functions in the machine tool 1 or other types of machines.

[0064] The embodiments described herein may be combined with each other without departing from the scope of protection of the present invention.

[0065] The above-mentioned monitoring system 12 provides several advantages.

[0066] First, the aforementioned monitoring system 12 allows for an improved signal-to-noise ratio by enhancing the accuracy, sensitivity, and stability of the readings of the acoustic sensor 10. This result is particularly due to the presence of a transmission line suitable for providing differential signals. The transmission line defines a signal path. Throughout the transmission line, the signal path is fully differential, meaning that the inputs and outputs of each component constituting part of the transmission line are differential, and the operations performed by each component are differential.

[0067] The transmission line starts from the acoustic sensor 10, includes a first connecting line 19, an amplifier 18, and a second connecting line 20, and ends at the transceiver device 15 of the communication unit 14. Throughout its path, the signal is always fully differential and has high quality and strong disturbance rejection capability.

[0068] According to a preferred embodiment, the transmission line of the differential signal runs from the acoustic sensor 10 through the communication unit 14 (also configured to maintain a fully differential signal path), amplifier 22, interface unit 13, and corresponding electrical leads to the processing unit 40. In other words, according to the preferred embodiment, there is also a contactless communication unit 14, and the amplifier 22 includes two input terminals connected to the second transmission device 16 and two output terminals connected to the interface unit 13, the interface unit (13) itself and any electrical leads connecting the latter to the processing unit 40 forming part of the transmission line providing the differential signal.

[0069] In the embodiment shown in Figures 4-7, a single connection line 20 allows the electrical power and signal of the vibration sensor 10 to be transmitted to the sound sensor 10. This allows for a significant reduction in the number of electrical leads required for the system, offering a clear advantage in miniaturization.

[0070] In the embodiment shown in FIG7, the more inputs the multiplexer has, the more advantages are achieved.

[0071] In the embodiment shown in Figures 5-7, the analog signal generated by the sound sensor 10 is digitized in the rotor, so the communication unit 14 transmits the digital signal in a non-contact manner. This digital signal is different from the analog signal and is not affected by noise or attenuation.

[0072] In the embodiment shown in Figures 5-7, the signal generated by the sound sensor 10 has been processed in the movable part (or, according to an alternative embodiment not shown, in the fixed part) due to the presence of the processing device 38, which can significantly improve the signal-to-noise ratio.

[0073] In addition to the advantages mentioned above, performing complete or most of the signal processing inside the rotor provides even more significant advantages.

[0074] First, because the monitoring system, more specifically the rotor, is more powerful and has greater autonomy, that is, it autonomously performs more complex operations, significantly reducing the workload of the control device. Therefore, the system can be improved by increasing, for example, the number and / or types of monitoring processes, such as adding more sensors and / or performing more types of checks.

[0075] Furthermore, performing complete or most of the signal processing inside the rotor allows for the possibility of self-configuring the monitoring system based on the processed signals and the possibility of implementing self-diagnostic functions in the monitoring system, such as measuring temperature, voltage or other system parameters, and checking the reliability of communication channels.

[0076] The processing of the signal generated by the sound sensor 10 can occur in a movable part (or, according to an alternative embodiment not shown, in a fixed part), even in a monitoring system that does not include a transmission line suitable for providing differential signals.

[0077] Similarly, a multiplexer can also be used in a monitoring system that includes multiple sensors (and a balance head, if present) but does not include a transmission line suitable for providing differential signals. [Simplified Explanation of the Diagram]

[0009] The present invention is described with reference to the accompanying drawings, which illustrate non-limiting examples of embodiments, wherein:

[0010] -[Figure 1] schematically shows a machine tool with a rotating spindle that supports a grinding wheel and is equipped with a balancing head;

[0011] -[Figure 2] schematically illustrates the monitoring system according to the present invention; and

[0012] -[Figures 3-7] are a series of schematic diagrams of alternative embodiments of the monitoring system of Figure 2.

Claims

1. A monitoring system (12) for connecting to a movable part (3) of a fixed component (2), the monitoring system being connected to a processing unit (40), and comprising: - A sound sensor (10), located in the movable part (3) and including two electrical terminals (17); - A first amplifier (18), located in the movable part (3); - A contactless communication unit (14), provided with a first transceiver device (15), located in the movable part (3), and a second transceiver device (16), facing the first transceiver device (15) and located in the fixed part (2); - A first connecting line (19) connecting the sound sensor (10) to the first amplifier (18); and - A second connecting line (20) connecting the first amplifier (18) to the first transceiver device (15); The monitoring system (12) is characterized in that it includes a transmission line adapted to provide differential signals, the transmission line including: - The first amplifier (18), including two electrical input terminals and two electrical output terminals; - The first connection line (19) includes two electrical leads, each of which connects the electrical terminal (17) of the acoustic sensor (10) to a corresponding electrical input terminal of the first amplifier (18); and - the second connection line (20) includes two electrical leads, each of which connects the electrical output terminal of the first amplifier (18) to the first transceiver device (15); wherein the transmission line defines a signal path that is fully differential in the transmission line.

2. The monitoring system (12) according to claim 1 or claim 2 includes a second amplifier (33) placed in the movable part (3) and connected in series with the first amplifier (18) along the second connecting line (20), and includes two electrical input terminals connected to the two electrical output terminals of the first amplifier (18) and two electrical output terminals connected to the first transceiver device (15).

3. The monitoring system (12) according to claim 1 includes a third amplifier (22) placed in the fixed component (2) and including two electrical input terminals connected to the second transceiver device (16) and two electrical output terminals connectable to an interface unit (13) configured to distribute power supply and transmit signals leaving or entering the processing unit (40).

4. The monitoring system (12) according to claim 1, and including an analog-to-digital converter (37) placed in the movable part (3) or the fixed part (2) and configured to receive an analog signal and convert the analog signal into a digital signal.

5. The monitoring system (12) according to claim 4 includes a processing device (38) placed in the movable part (3) or the fixed part (2) and configured to receive the digital signal from the analog-to-digital converter (37), process the digital signal, and obtain and output the processed digital signal.

6. The monitoring system (12) according to request item 1, wherein, The transmission line is adapted to provide a differential signal, starting from the acoustic sensor (10) and ending at the processing unit (40) connected to the monitoring system (12).

7. The monitoring system (12) according to claim 1, and including a power supply circuit (23) having: - a first power supply device (24) placed in the movable part (3) and supplying power to the first amplifier (18); and - an air coupling transformer (26) including a first coil (27) placed in the movable part (3) and supplying power to the first power supply device (24), and a second coil (28) placed in the fixed part (2) and receiving power.

8. The monitoring system (12) according to claim 7, and including a second power supply device (25) placed in the fixed component (2) to supply power to the second coil (28) and to supply power to the third amplifier (22) placed in the fixed component (2) or to the second transceiver device (16).

9. The monitoring system (12) according to claim 7, and comprising: - A third power supply device (34) directly coupled to the first coil (27); - A coupling device (35) receiving power from the third power supply device (34) and feeding power to the second connection line (20), the power being in a frequency band different from the frequency band of the analog signal generated by the sound sensor (10); and - A decoupling device (36) which obtains power from the second connection line (20) and supplies power to the first amplifier (18).

10. The monitoring system (12) according to claim 1, comprising: The balancing head is housed in the movable part (3).

11. The monitoring system (12) according to claim 9, includes a balancing head, wherein, The third power supply unit (34) is also connected to the balance head (7) to provide power to the balance head (7).

12. The monitoring system (12) according to claim 1, and comprising: - Two separate and independent acoustic sensors (10); - Two first amplifiers (18); - Two first connection lines (19), each of which connects the acoustic sensor (10) to the first amplifier (18) and includes two electrical leads; - a single communication unit (14); and - a multiplexer (39) having two electrical input terminals connected to the two first amplifiers (18) and a single electrical output terminal connected to the first transceiver device (15) of the single communication unit (14).

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