TWI775204B - Modal Detection System - Google Patents

Abstract

A mode detection system is suitable for being applied to a machine tool, and includes a sensing unit, a multiplexing unit, a control unit, and a processing unit. The sensing unit includes a reference sensor and a complex sequence sensor. The multiplexing unit switches and outputs a sensing output of one of the sequence sensors. The control unit receives the sensing output of the reference sensor and the one of the series of sensors and outputs it as a transmission signal. The processing unit receives the transmission signal and performs modal analysis according to the sensed vibration information. Therefore, since the output of each sequence sensor will be transmitted with the same reference sensor, it is convenient for the processing unit to use the sensing output of the reference sensor as the reference of the time axis for subsequent follow-up Data analysis and processing.

Description

Modal Detection System

The present invention relates to a detection system, in particular to a modal detection system.

Generally, during the machining process of the machine tool, because the vibration frequency is close to the natural frequency of the structure, a resonance effect will occur, which will increase the response of the machine tool and become unstable, and affect the machining accuracy. Therefore, through modal analysis, understanding the modal frequency, modal mode shape, modal damping ratio, etc. of the structural parts will help to improve the machining performance of the machine tool.

Traditionally, a modal analysis of a machine tool requires a known and accurate force. At present, the main method is to use an impact hammer to strike the structural parts of the machine tool, or use a vibration exciter to excite the structural parts of the machine tool, and then set up a sensor (usually an experimental accelerometer) at the appropriate position of the machine tool. Measurement, and modal analysis based on the measurement results.

However, when you want to measure the whole machine mode of the machine tool, you need to perform multi-point measurement, but because the experimental-level accelerometer is expensive, if you set multiple experimental-level accelerometers at the same time If a single experimental-grade accelerometer is used for multiple measurements, it will consume too much time and cost, and there are situations where individual measurement data are scattered and it is difficult to carry out unified analysis.

Therefore, the purpose of the present invention is to provide a modal detection system which is convenient for data integration analysis.

Therefore, the modal detection system of the present invention is suitable for being applied to a machine tool, and includes a sensing unit, a multiplexing unit, a control unit, and a processing unit.

The sensing unit includes a reference sensor and a plurality of sequence sensors suitable for being disposed on the machine tool and used for sensing the vibration of the machine tool.

The multiplexing unit is signal-connected to the sequence sensors, receives a switching signal, and switches and outputs a sensing output of one of the sequence sensors.

The control unit is signal-connected to the reference sensor and the multiplexing unit, outputs the switching signal, receives the sensing output of the reference sensor and one of the series of sensors, and outputs it as a transmission signal.

The processing unit is signal-connected to the control unit, receives the transmission signal, and performs modal analysis according to the sensed vibration information.

The effect of the present invention is: by setting the reference sensor and the sequence sensing, and setting the multiplexing unit to switch and select the outputs of the sequence sensors, the The output of each sequence sensor will be transmitted with the same reference sensor, so it is convenient for the processing unit to use the sensing output of the reference sensor as a reference for subsequent data unified analysis and processing .

2: Sensing unit

21: Reference sensor

GND: ground port

VDD: Power port

SDA: data port

SCL: clock port

AD0: address port

22: Sequence sensor

3: Multiplexing unit

31: Select the multiplexing module

Vcc: Power port

S0~S3: Control port

SIG: Signal port

EN: Enable port

C0, C1, C15: Channel ports

32: Signal multiplexing module

33: Data Multiplexer

34: Clock Multiplexer

4: Control unit

41: Control module

5V, 3V: Power port

PB6,PB7: Transmission port

PB10,PB11: Signal port

PD1~PD4: Control port

42: Transmission module

RXD, TXD: transmission port

5: Processing unit

6: Hammer

7: Data Capture Unit

8: Power

9: Tool machine

91~92: Waveform

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a schematic diagram of an embodiment of the modal detection system of the present invention; FIG. 2 is an embodiment of the present invention. Schematic diagram of part of the circuit; FIG. 3 is a waveform diagram of the force signal of a hammer and a transmission signal aligned in the time domain of the embodiment; and FIG. 4 is a comparison diagram of the frequency response function of the embodiment and an experimental accelerometer.

Referring to FIG. 1 and FIG. 2 , an embodiment of the modal detection system of the present invention is suitable for use in a machine tool 9 and includes a sensing unit 2 , a multiplexing unit 3 , a control unit 4 , and a processing unit Unit 5. Wherein, this embodiment preferably further includes a hammer 6 and a data acquisition unit 7 for signally connecting the hammer 6 and the processing unit 5 .

The sensing unit 2 includes a reference sensor 21 and sixteen sequence sensors 22 (shown in FIG. 1 ), which are suitable for being disposed on the machine tool 9 and used for sensing the vibration of the machine tool 9 . only 2 are drawn for illustration). The number of the sequence sensors 22 may vary according to the actual measurement requirements and the number of channels of the multiplexing unit 3 , but is not limited thereto. The reference sensor 21 is preferably set at a place with obvious vibration, for example, at a high place of the machine tool 9, a beam, or a place close to the workpiece (not shown), and the sequence sensors 22 are Arbitrarily set where there is a measurement requirement.

Wherein, the reference sensor 21 and the sequence sensors 22 are preferably micro-electromechanical systems (Microelectromechanical Systems, abbreviated as MEMS) sensors, and preferably use six-axis microcomputer electrical sensors. In this embodiment, the reference sensor 21 and the sequence sensors 22 are both implemented using InvenSense's GY-521, which is an inertial sensor (IMU) integrating a three-axis accelerometer and a three-axis gyroscope. , the chip it carries is MPU6050, the highest sampling frequency of MPU6050 is 1kHz, and the measurable bandwidth is 0 to 500Hz. Since the frequency bandwidth and measurement range of the low-frequency vibration of the machine tool 9 are usually within 1kHz, therefore, Its measurement bandwidth is generally sufficient for the lower frequency modal frequency of the machine tool 9 . The reference sensor 21 and each sequence sensor 22 have a ground terminal GND, a power port VDD, a data port SDA, a clock port SCL and an address port AD0.

Wherein, the output lines of the reference sensor 21 and the sequence sensors 22 are I ² C communication bus bars. Therefore, in order to connect the outputs of the reference sensor 21 and the selected serial sensor 22 to the same I ² C communication bus, the reference sensor 21 and the selected serial sensor 22 can be connected to the same I 2 C communication bus. The address port AD0 of the reference sensor 22 needs to be set to a logic high level and a logic low level. In this embodiment, the address port AD0 of the reference sensor 21 is set to a logic low level ( GND), the selected address port AD0 of the sequence sensor 22 is set to a logic high potential (3V), but the potentials of the two can be interchanged, not limited to this.

It is worth mentioning that, in order to avoid mutual interference of noise between the sensing unit 2 and the subsequent multiplexing unit 3 and the control unit 4, it is preferable to set another independent power supply 8 to provide the power supply of the sensing unit 2, In order to achieve power supply stability and anti-interference effect. In addition, it is preferable to use a double-shielded network line (for example, use a Cat6 network line) as the transmission signal line between the sensing unit 2, the multiplexing unit 3, and the control unit 4 to reduce noise interference during information transmission. , and can lengthen the transmission distance. For example, the present embodiment can lengthen the distance between the sensing unit 2 and the control unit 4 to 6 meters and still operate normally. In this way, it will be suitable for large-scale machine vibration monitoring. .

The multiplexing unit 3 is signal-connected to the sequence sensors 22 , receives a switching signal and switches and outputs the sensing output of one of the sequence sensors 22 . The multiplexing unit 3 includes a selection multiplexing module 31 and a signal multiplexing module 32 that signally connect the control unit 4 and the sequence sensors 22 .

The selection multiplexing module 31 switches to select one of the sequence sensors 22 according to the switching signal. The signal multiplexing module 32 switches and outputs the sensing output of one of the series of sensors 22 according to the switching signal. The signal multiplexing module 32 has a data multiplexer 33 and a clock multiplexer 34 .

In this embodiment, the selection multiplexer 31 , the data multiplexer 33 and the clock multiplexer 34 are all implemented using CD74HC4067 high-speed CMOS 16-channel multiplexer/demultiplexer, and all have a power supply Port Vcc, a ground port GND, four control ports S0~S3 for receiving the switching signal, a signal port SIG connected to the control unit 4, an enable port EN, and sixteen channel ports C0~C15 (for For the sake of clarity, only C0, C1 . . . C15 are marked in the figure for illustration). The enable ports EN are all grounded and enabled.

The channel ports C0-C15 of the selection multiplexing module 31 are respectively connected to the address ports AD0 by signals, and the selection multiplexing module 31 switches on the corresponding switching signals according to the switching signals received by the control ports S0-S3 One of the channel ports C0-C15 and the signal port SIG, so that the voltage (3V) provided by the control unit 4 is output from the signal port SIG through the corresponding one of the channel ports C0-C15 to the corresponding sequence sensing The address port AD0 of the sensor 22 is used to select the output of the sequence sensor 22 .

The channel ports C0-C15 of the data multiplexer 33 are respectively connected to the data ports SDA by signals, and the data multiplexer 33 switches and conducts the corresponding one of the channel ports S0-S3 according to the switching signal received by the control ports S0-S3 The channel ports C0-C15 and the signal port SIG enable the corresponding measurement data output (Serial Data, abbreviated as SDA) of the serial sensor 22 to be output from the data port SDA through one of the corresponding channel ports C0- C15 , the signal port SIG is output to the control unit 4 .

The channel ports C0-C15 of the clock multiplexer 34 are respectively connected with signals For the clock ports SCL, the clock multiplexer 34 switches on the corresponding one of the channel ports C0-C15 and the signal port SIG according to the switching signals received by the control ports S0-S3, so that the corresponding one of the channel ports C0-C15 is turned on. A clock output (Serial Clock, abbreviated as SCL) of the serial sensor 22 can be output to the control unit 4 through the clock port SCL, one of the corresponding channel ports C0-C15, and the signal port SIG.

Wherein, the selection multiplexer module 31 , the data multiplexer 33 , and the clock multiplexer 34 are all selected according to the number of the sequence sensors 22 to select one out of sixteen multiplexers/demultiplexers The switch signal is also used as the control data of 4 pins, but in fact, the number of the sequence sensors 22 and the number of pins corresponding to the switch signal can also be changed according to the requirements, and this is not the case. limit.

The control unit 4 includes a control module 41 and a transmission module 42 electrically connected between the control module 41 and the processing unit 5 .

The control module 41 is signal-connected to the reference sensor 21 and the multiplexing unit 3 , receives the control of the processing unit 5 to output the switching signal, and receives the sense of the reference sensor 21 and one of the series of sensors 22 . Measure the output and output it as a transmission signal. In this embodiment, the control module 41 is implemented by using the STM32F407 microcontroller developed by STMicroelectronics, which can receive the input of the I ² C standard, and convert it to RS after being temporarily stored in the internal memory. -232 specification output. The control module 41 has a plurality of power ports 5V and 3V, a plurality of ground ports GND, a data port SDA connected to the reference sensor 21 and a signal port SIG of the data multiplexer 33 and a signal port for receiving measurement data output PB10, a signal port PB11 connected to the clock port SCL of the reference sensor 21 and the signal port SIG of the clock multiplexer 34 and receiving the clock output, four control ports PD1-PD4 outputting the switching signal, and 2. The transmission ports PB6 and PB7 are connected to the transmission module 42 and used to transmit the transmission signal. Since those with ordinary knowledge in the technical field to which the invention pertains can know the relevant setting details from the public information of the STM32F407 microcontroller, they will not be described here.

The transmission module 42 is used for converting the data transmission format. In this embodiment, the transmission module 42 is implemented by using PL2303, and the data of the RS-232 standard output by the control module 41 is converted into the data of the USB standard and output to the processing unit 5. The transmission module 42 has a power port 5V, a ground port GND, and two transmission ports RXD and TXD connected to the control module 41 and used for receiving the transmission signal. Since those with ordinary knowledge in the technical field to which the invention pertains can know the relevant setting details from the public information of PL2303, no further description is given here.

The hammer 6 is used to excite the structural parts of the machine tool 9 and output relevant force signals.

The data capture unit 7 is used for capturing the force signal of the impact hammer 6 and converting it into a digital form for output to the processing unit 5 . In this embodiment, the data capture unit 7 is implemented using a data capture card of NI.

The processing unit 5 is signally connected to the control unit 4 and the data acquisition unit 7 . In this embodiment, the processing unit 5 is a personal computer (PC), and the transmission mode is The group 42 receives the transmission signal in the USB specification, and uses the sensing output of the reference sensor 21 as a reference, and the sensing output of the sequence sensors 22 is based on the output of the reference sensor 21 in the time domain. The time axis is aligned and arranged, and Operation Modal Analysis (OMA) can be performed according to the sensed vibration information (amplitude, frequency). The processing unit 5 can align and integrate the time domain information of the force signal of the impact hammer 6 with the time domain information of the transmission signal, and then perform an Experimental Modal Analysis (abbreviated as Experimental Modal Analysis) according to the integrated time domain information. EMA), for example, to operate a Frequency Response Function (FRF for short).

In practical application, the table movement method disclosed in the "Modal Detection System" of the Republic of China Invention Patent Certificate No. I638251 can be used to simulate the real processing state to generate automatic vibration, and the measurement and operation modal analysis can be carried out with this embodiment. , or use the impact hammer 6 to provide excitation, and perform measurement and experimental modal analysis in conjunction with the rest of the structure of this embodiment.

The processing unit 5 controls the control module 41 to switch the multiplexing unit 3 to select the corresponding sequence sensor 22 via the transmission module 42 , and reads the sequence through the multiplexing unit 3 and the control unit 4 The data output of the sensor 22 is then aligned and arranged in the time domain according to the time axis of the output of the reference sensor 21. In this way, not only can the modal analysis be performed to obtain the model modal parameters such as modal frequency, modal mode shape, modal damping ratio, etc., and due to the output of each of the sequence sensors 22 The same reference sensor 21 on the time axis can be used as a reference for alignment and comparison, thus facilitating data comparison and analysis in subsequent data processing. Among them, when the table motion method is used for measurement and analysis, since the excitation force of the equipment movement is close to white noise, the random subspace identification method can be used for modal parameter calculation.

Referring to FIG. 1 and FIG. 3 , the horizontal axis of FIG. 3 is the signal (point) sequence (or called dimensionless time) measured according to time, which can be regarded as equivalent to the time axis. When the impact hammer 6 is used together to provide excitation, the processing unit 5 can align and integrate the time domain information of the force signal of the impact hammer 6 with the time domain information of the transmission signal (ie, the force signal is integrated on the time axis). Align with the peaks of X, Y, and Z axes) to conduct experimental modal analysis, and then obtain the frequency response function of the structure and the modal parameters of the system. For example, in this embodiment, the hammer 6 mainly strikes the X axis, so the maximum value of the force signal is aligned with the maximum value of the X axis of the reference sensor 21, and the signals of the Y and Z axes are Align the signals on the X-axis, and then take the data in an interval before and after the time point of the maximum value of the signal in the X-axis direction (for example, the overall time interval in Figure 3) to perform Fourier transformation to convert it into the frequency response function of Figure 4 . Since those with ordinary knowledge in the art can infer the extended details according to the above description, no further description will be given.

Referring to FIG. 1 , FIG. 2 and FIG. 4 , the vertical axis of FIG. 4 is the transfer function (Inertance, the unit is g/N, g is the acceleration of gravity (9.81 m/s ² ), and N is Newton). Through the above description, the effect of this embodiment is as follows:

1. By setting the reference sensor 21 and the sequence sensors 22, and The multiplexing unit 3 is configured to switch and select the outputs of the sequence sensors 22. Since the output of each sequence sensor 22 is transmitted with the same reference sensor 21, it is convenient for the processing unit 5 to transmit. Using the sensing output of the reference sensor 21 as a reference on the time axis, the subsequent data integration analysis processing is performed. Moreover, by setting the multiplexing unit 3 for switching, not only multi-point sensing can be performed, but also the control unit 4 and the processing unit 5 can be combined to achieve the effect of automatic control.

2. By implementing the reference sensor 21 and the sequence sensors 22 by using a microcomputer sensor, the present embodiment can simultaneously perform multi-point measurement compared with the use of expensive experimental-grade accelerometers in the prior art and reduce costs. As can be seen from FIG. 4, the waveform 91 is the frequency response function measured by using the experimental grade accelerometer, and the waveform 92 is the frequency response function measured using the present embodiment, and the waveforms of the two are in the frequency width of the machine tool low frequency vibration 10Hz~ At 300 Hz, the error is only 1.09%, which shows that this embodiment can take into account both the measurement accuracy and the cost.

3. By arranging the impact hammer 6 and the data acquisition unit 7, the present embodiment can also provide the force signal of the impact hammer 6, and the experimental modal analysis can be performed in combination with the force signal, so as to provide the analysis of the frequency response function Compared with the conventional use of the impact hammer 6 and the experimental accelerometer for experimental modal analysis, the frequency response error analyzed by the microcomputer electrical sensor in this embodiment is within 3%, which can be seen in this embodiment. At the same time, the measurement accuracy and cost are taken into account.

To sum up, the modal detection system of the present invention can indeed achieve the present invention the goal of.

However, the above are only examples of the present invention, and should not limit the scope of the present invention. Any simple equivalent changes and modifications made according to the scope of the application for patent of the present invention and the content of the patent specification are still within the scope of the present invention. within the scope of the invention patent.

2: Sensing unit

21: Reference sensor

GND: ground port

VDD: Power port

SDA: data port

SCL: clock port

AD0: address port

22: Sequence sensor

3: Multiplexing unit

31: Select the multiplexing module

Vcc: Power port

S0~S3: Control port

SIG: Signal port

EN: Enable port

C0, C1, C15: Channel ports

32: Signal multiplexing module

33: Data Multiplexer

34: Clock Multiplexer

4: Control unit

41: Control module

5V, 3V: Power port

PB6,PB7: Transmission port

PB10,PB11: Signal port

PD1~PD4: Control port

42: Transmission module

RXD, TXD: transmission port

5: Processing unit

8: Power

Claims (9)

A modal detection system suitable for application to a machine tool, comprising: a sensing unit, comprising a reference sensor and a plurality of sequence sensors suitable for being disposed on the machine tool and used for sensing the vibration of the machine tool; a multiplexing unit, the signal is connected to the sequence sensors, receives a switching signal and switches and outputs the sensing output of one of the sequence sensors; a control unit, which is signal-connected to the reference sensor and the multiplexing unit, outputs the switching signal, receives the sensing output of the reference sensor and one of the series of sensors, and outputs it as a transmission signal; and A processing unit, connected to the control unit by signal, receives the transmission signal, and performs modal analysis according to the sensed vibration information. The modal detection system of claim 1, wherein the reference sensor and the sequence sensors are microcomputer sensors. The modality detection system of claim 1, wherein the processing unit uses the sensing output of the reference sensor as a reference in the time domain, and aligns the sensing outputs of the sequence sensors in the time domain. The modal detection system of claim 1, wherein the multiplexing unit comprises a selection multiplexing module and a signal multiplexing module that signally connect the control unit and the sequence sensors, the selection multiplexing module The multiplexing module switches and selects one of the serial sensors according to the switching signal, and the signal multiplexing module switches and outputs the sensing output of the one of the serial sensors according to the switching signal. The mode detection system of claim 4, wherein each sequence sensor has a data port and a clock port, the signal multiplexing module has a data multiplexer and a clock multiplexer, the data Both the multiplexer and the clock multiplexer have a plurality of channel ports, at least one control port for signal connection to the control unit, and a signal port for signal connection to the control unit, the channel ports of the data multiplexer respectively signal Connecting the data ports, the data multiplexer switches on the corresponding one of the channel ports and the signal port according to the switching signal received by the at least one control port, and the channel ports of the clock multiplexer are respectively A signal is connected to the clock ports, and the clock multiplexer switches on the corresponding one of the channel ports and the signal port according to the switching signal received by the at least one control port. The mode detection system of claim 1, wherein the output lines of the reference sensor and the sequence sensors are I²C communication bus bars. The modal detection system according to claim 1, further comprising an impact hammer and a data acquisition unit for signally connecting the impact hammer and the processing unit, the data acquisition unit is used to acquire the force signal of the impact hammer And converted into digital form and output to the processing unit. The modal detection system according to claim 7, wherein the processing unit aligns and integrates the time domain information of the force signal of the impact hammer and the time domain information of the transmission signal, and then calculates according to the integrated time domain information frequency response function. The modal detection system according to claim 1, wherein the sensing unit, the multiplexing unit, and the control unit are connected by a double-shielded network line.

Images