Ultrasonic-assisted cutting force control system and ultrasonic-assisted cutting system

Abstract

The invention provides an ultrasonic-assisted cutting force control system and an ultrasonic-assisted cutting system, and relates to the technical field of ultrasonic machining. The ultrasonic-assisted cutting force control system comprises an amplitude measuring circuit and a control circuit. Wherein the amplitude measuring circuit is electrically connected with an ultrasonic transduction element in the ultrasonic transducer and is used for acquiring an electric signal on the surface of the ultrasonic transduction element; and the control circuit is used for calculating the actual ultrasonic amplitude of the ultrasonic transduction element according to the electric signal and controlling the cutting force based on the actual ultrasonic amplitude. By means of real-time online detection and control over the ultrasonic amplitude, online accurate regulation and control over the cutting force are achieved, and the precision and reliability of cutting force control are guaranteed. Meanwhile, in the ultrasonic amplitude detection process, an external sensor does not need to be additionally introduced, the driving voltage of the transducer is not affected, the cost can be effectively reduced, and the machining efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic machining, and particularly relates to an ultrasonic-assisted cutting force control system and an ultrasonic-assisted cutting system. Background Art

[0002] Due to its excellent properties such as light weight, high temperature resistance, and corrosion resistance, fiber composite materials have been widely used in a variety of extreme service environments. However, the high hardness and high wear resistance of fiber composite materials result in excessive cutting force during traditional machining processes, seriously reducing the machining quality. Ultrasonic machining technology can effectively improve the machining quality of fiber composite materials by applying ultrasonic vibrations with different amplitudes and frequencies to the tool end face.

[0003] The ultrasonic vibration changes the contact mode between the tool and the workpiece, changes the cutting force, and thus changes the machining quality. The ultrasonic amplitude has an important influence on the cutting force. Accurately detecting the ultrasonic amplitude is the prerequisite and the key to improving the machining quality. However, existing ultrasonic amplitude detection methods (such as laser detection methods) are all carried out when the ultrasonic transducer is operating without load. During actual machining, the tool tip contacts the workpiece, and the existing methods cannot measure the ultrasonic amplitude of the ultrasonic transducer. Importantly, the amplitudes of the ultrasonic transducer when operating without load and when contacting the workpiece are different, and the amplitude of the ultrasonic transducer also changes during different machining processes.

[0004] Since the existing ultrasonic amplitude detection methods cannot achieve on-line measurement of the ultrasonic amplitude, and the ultrasonic amplitude data measured based on no-load operation cannot accurately reflect the actual amplitude during the machining process, the existing ultrasonic amplitude detection methods cannot achieve accurate measurement of the ultrasonic amplitude, seriously affecting the machining quality of the material. Therefore, how to achieve accurate detection of the ultrasonic amplitude and then accurately control the ultrasonic-assisted cutting force to ensure the machining quality is an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides an ultrasonic-assisted cutting force control system and an ultrasonic-assisted cutting system to solve the defect of inaccurate ultrasonic amplitude detection in the prior art, achieve accurate detection of the ultrasonic amplitude, and then achieve accurate control of the cutting force.

[0006] The present invention provides an ultrasonic-assisted cutting force control system, including: An amplitude measurement circuit, electrically connected to the ultrasonic transducer element in the ultrasonic transducer, for collecting the electrical signal on the surface of the ultrasonic transducer element; A control circuit, for calculating the actual ultrasonic amplitude of the ultrasonic transducer element according to the electrical signal and controlling the cutting force based on the actual ultrasonic amplitude.

[0007] According to the ultrasonic-assisted cutting force control system provided by the present invention, the amplitude measurement circuit is used to accumulate the charges on the surface of the ultrasonic transducer element and output the accumulated charges in the form of voltage.

[0008] According to the ultrasonic-assisted cutting force control system provided by the present invention, the amplitude measurement circuit includes an integration amplifier circuit. The input end of the integration amplifier circuit is electrically connected to the surface of the ultrasonic transducer element, and the output end of the integration amplifier circuit is electrically connected to the control circuit.

[0009] According to the ultrasonic-assisted cutting force control system provided by the present invention, the ultrasonic transducer element is a piezoelectric ceramic.

[0010] According to the ultrasonic-assisted cutting force control system provided by the present invention, the amplitude measurement circuit and the control circuit are integrated together.

[0011] According to the ultrasonic-assisted cutting force control system provided by the present invention, the control circuit is used to calculate the actual amplitude of the ultrasonic transducer element according to the electrical signal and the amplitude calculation model; the amplitude calculation model is used to describe the functional relationship between the charges on the surface of the ultrasonic transducer element and the amplitude of the ultrasonic transducer element.

[0012] According to the ultrasonic-assisted cutting force control system provided by the present invention, it further includes: a digital-to-analog conversion circuit, an analog-to-digital conversion circuit, and a drive circuit; The digital-to-analog conversion circuit is used to convert the control signal of the control circuit into an analog signal; the analog signal is used to control the operation of the drive circuit; the drive circuit is used to drive the operation of the ultrasonic transducer element; The analog-to-digital conversion circuit is used to convert the voltage signal output by the amplitude measurement circuit into a digital signal; the control circuit calculates the ultrasonic amplitude based on the digital signal.

[0013] According to the ultrasonic-assisted cutting force control system provided by the present invention, it further includes: a signal processing circuit, which is used to perform signal conditioning on the output signal of the analog-to-digital conversion circuit, and the conditioned signal is input to the control circuit.

[0014] According to the ultrasonic-assisted cutting force control system provided by the present invention, it further includes: an isolation circuit, which is arranged between the control circuit and the digital-to-analog conversion circuit, and between the signal processing circuit and the analog-to-digital conversion circuit.

[0015] The present invention also provides an ultrasonic-assisted cutting system, which includes an ultrasonic-assisted cutting device and any one of the above ultrasonic-assisted cutting force control systems; The ultrasonic-assisted cutting device is used to perform ultrasonic cutting on the workpiece material, and includes an ultrasonic transducer. The ultrasonic transducer includes an ultrasonic transducer element, and the ultrasonic transducer element is provided with electrodes. The input end of the amplitude measurement circuit in the ultrasonic-assisted cutting force control system is electrically connected to the electrode. The ultrasonic-assisted cutting force control system is used to calculate the actual ultrasonic amplitude of the ultrasonic transducer element according to the electrical signal collected by the amplitude measurement circuit, and control the cutting force based on the actual ultrasonic amplitude.

[0016] The ultrasonic-assisted cutting force control system and the ultrasonic-assisted cutting system provided by the present invention collect the electrical signal generated on the surface of the ultrasonic transducer element through the amplitude measurement circuit electrically connected to the surface of the ultrasonic transducer element, and determine the ultrasonic amplitude of the ultrasonic transducer element based on the relationship between the electrical signal on the surface of the ultrasonic transducer element and the ultrasonic amplitude of the ultrasonic transducer element. This method can realize the on-line measurement of the ultrasonic amplitude during the cutting process. Compared with the prior art in which the ultrasonic amplitude can only be measured when the ultrasonic transducer is running without load and used as the actual ultrasonic amplitude during the cutting process to control the cutting force, the ultrasonic amplitude measured by the present invention is the actual ultrasonic amplitude during the cutting process, which is more accurate. Based on this, compared with the prior art, the control of the cutting force by the present invention is also more accurate. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic diagram of ultrasonic machining provided by an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of the amplitude measurement circuit provided by an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the structure of the ultrasonic-assisted cutting control system provided by an embodiment of the present invention.

[0021] Reference Signs: 1: Workpiece Material; 2: Chip; 3: Tool; 4: Ultrasonic Transducer Element; 5: Amplitude Measurement Circuit; 6: Analog-to-Digital Conversion Circuit; 7: Isolation Circuit; 8: Signal Processing Circuit; 9: Communication Circuit; 10: Operating Console; 11: Control Circuit; 12: Digital-to-Analog Conversion Circuit; 13: Driving Circuit. Detailed Embodiments

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] The following will introduce Figures 1 - 3 the ultrasonic-assisted cutting force control system and the ultrasonic-assisted cutting system of the present invention in conjunction with

[0024] Figure 1 is a schematic diagram of ultrasonic machining provided by an embodiment of the present invention. As Figure 1 shown, with the assistance of ultrasonic vibration, the work material 1 is cut by the cutting tool 3, and the cutting part becomes the chip 2. During the machining process, since the cutting tool 3 is in contact with the work material 1 and running, the existing ultrasonic amplitude detection methods (such as the laser detection method) will have many interference factors (such as the work material 1 and the chip 2) during measurement, and these interference factors will seriously affect the detection of the ultrasonic amplitude and make the detection impossible to carry out.

[0025] Based on this, to achieve the on-line measurement of the ultrasonic amplitude, an embodiment of the present invention provides an ultrasonic-assisted cutting force control system. The cutting force control system includes: a control circuit 11 and an amplitude measurement circuit 5.

[0026] Among them, the amplitude measurement circuit 5 is electrically connected to the surface of the ultrasonic transducer element 4 in the ultrasonic transducer and is used to collect the electrical signal generated on the surface of the ultrasonic transducer element 4. The control circuit 11 is used to calculate the actual amplitude of the ultrasonic transducer element 4 according to the electrical signal and output a closed-loop control of the ultrasonic amplitude of the ultrasonic transducer element 4 based on the actual amplitude to achieve precise control of the cutting force.

[0027] Since the cutting force control system provided by the embodiment of the invention calculates the ultrasonic amplitude based on the electrical signal on the surface of the ultrasonic transducer element, only a measurement circuit for collecting the electrical signal needs to be electrically connected to the surface of the ultrasonic transducer element. This measurement method can realize the on-line measurement of the ultrasonic amplitude, that is, the measurement of the ultrasonic amplitude of the ultrasonic transducer element during the machining process (under the condition of load).

[0028] In some embodiments of the present invention, the amplitude measurement circuit 5 and the control circuit 11 are integrated on the same PCB circuit board.

[0029] In the embodiment of the present invention, the ultrasonic transducer element 4 is a part of the ultrasonic transducer, and the ultrasonic transducer element 4 is a piezoelectric ceramic.

[0030] Under the combined action of the driving voltage and the material characteristics of the ultrasonic transducer element, charge Q accumulates on the surface area of the ultrasonic transducer element. Figure 2 FIG. 2 is a schematic structural diagram of the amplitude measurement circuit provided by an embodiment of the present invention. In some embodiments of the present invention, as Figure 2 shown, the amplitude measurement circuit 5 may be an integrating amplifier circuit, which is used to collect the charge on the surface of the ultrasonic transducer element 4 and accumulate the charge, and output the accumulated charge in the form of a voltage.

[0031] Specifically, referring to Figure 2 , the first input terminal of the integrating amplifier circuit is grounded, and the second input terminal is in contact connection with the surface of the ultrasonic transducer element 4. After the charge on the surface of the ultrasonic transducer element 4 is cumulatively amplified by the integrating amplifier circuit, it is output in the form of a voltage from the output terminal of the integrating amplifier circuit.

[0032] It should be noted that, as Figure 2 shown, the potentials at points A and B of the integrating amplifier circuit are approximately equal, that is, the voltage difference across the PZT is still (U Driving -0) V, and it is not changed due to the introduction of the integrating amplifier circuit. That is, the introduction of the above-mentioned integrating amplifier circuit does not affect the driving voltage of the ultrasonic transducer element 4. That is to say, the amplitude measurement circuit 5 designed in the embodiment of the present invention can extract the electrical signal characterizing the ultrasonic amplitude without affecting the driving voltage.

[0033] The present invention also provides an ultrasonic-assisted cutting system, which includes an ultrasonic-assisted cutting device and the ultrasonic-assisted cutting force control system described above. Among them, the ultrasonic-assisted cutting device is used for ultrasonic cutting of the material to be processed, and an ultrasonic transducer is provided in the ultrasonic-assisted cutting device. The ultrasonic transducer includes an ultrasonic transducer element 4, and a first electrode is provided on the surface of the ultrasonic transducer element 4. The input terminal of the amplitude measurement circuit 5 in the cutting force control system is electrically connected to the first electrode on the surface of the ultrasonic transducer element 4. The first electrode transmits the charge on the surface of the ultrasonic transducer element 4 to the amplitude measurement circuit 5, and the amplitude measurement circuit 5 accumulates the charge and outputs the accumulated charge in the form of a voltage. The control circuit 11 in the cutting force control system calculates the actual amplitude of the ultrasonic transducer element 4 based on the voltage signal output by the amplitude measurement circuit 5, and controls the cutting force based on the actual amplitude.

[0034] It should be noted that the present invention creatively discovers and applies the functional relationship between the electric charge generated on the surface of the ultrasonic transducer element and the ultrasonic amplitude of the ultrasonic transducer element. Based on the above functional relationship, the present invention calculates the actual ultrasonic amplitude of the ultrasonic transducer element during the processing according to the electrical signal encoded by the ultrasonic transducer element 4, realizes the online measurement of the ultrasonic amplitude of the ultrasonic transducer element, and based on this measured value, the closed-loop control of the ultrasonic amplitude of the ultrasonic transducer element can be realized, and further the accurate control of the cutting force can be realized.

[0035] The following introduces the functional relationship between the electric charge on the surface of the ultrasonic transducer element and the ultrasonic amplitude of the ultrasonic transducer element.

[0036] The piezoelectric ceramic material satisfies the following piezoelectric equation (1) (2) Substitute formula (2) into formula (1), and combine with Gauss's theorem , to obtain: (3) In formula (3), T 3 is the load force on the end face, which can be expressed as (Hooke's law), and further obtain the linear correspondence between the amplitude and the electric charge : (4) (5) (6) In formulas (5) and (6), is the output voltage of the amplitude measurement circuit. The control circuit can calculate the ultrasonic amplitude of the ultrasonic transducer element according to formula (6) and the output voltage value of the amplitude measurement circuit, or calculate the electric charge on the surface of the ultrasonic transducer element according to formula (5) and the output voltage value of the amplitude measurement circuit , and then calculate the ultrasonic amplitude of the ultrasonic transducer element based on formula (4).

[0037] It should be noted that in the embodiment of the present invention, the amplitude measurement circuit 5 and the control circuit 11 and other circuits are integrated together to jointly form a cutting force control system. Specifically, the amplitude measurement circuit 5, the control circuit 11, the drive circuit 13, the analog-to-digital conversion circuit 6, the digital-to-analog conversion circuit 12, the isolation circuit 7, the signal processing circuit 8 and other circuits are integrated on the same circuit board.

[0038] In the embodiment of the present invention, the amplitude measurement circuit 5 is integrated into the cutting force control system, and is directly electrically connected to the first electrode on the surface of the ultrasonic transducer element 4 through a wire. The charge on the surface of the ultrasonic transducer element 4 reaches the amplitude measurement circuit 5 through the first electrode, without any other auxiliary components or auxiliary sensors being filled, and thus there is no need to provide an installation space or installation structure for any other auxiliary components or auxiliary sensors, or to change any structural design of the existing ultrasonic-assisted cutting system for any other auxiliary components or auxiliary sensors. While saving costs, it is friendly to space requirements.

[0039] In some embodiments of the present invention, specifically, the ultrasonic-assisted cutting force control system further includes: a digital-to-analog conversion circuit 12, an analog-to-digital conversion circuit 6, and a drive circuit 13.

[0040] Among them, the digital-to-analog conversion circuit 12 is used to convert the control signal of the control circuit 11 into an analog signal; this analog signal is used to control the operation of the subsequent drive circuit 13. A second electrode is also provided on the surface of the ultrasonic transducer element in the ultrasonic-assisted cutting device, and the drive circuit 13 loads the drive signal onto the ultrasonic transducer element 4 through the second electrode to drive the operation of the ultrasonic transducer element.

[0041] The analog-to-digital conversion circuit 6 is used to convert the voltage signal output by the amplitude measurement circuit 5 into a digital signal, and this digital signal is subsequently fed back to the control circuit 11, and the control circuit 11 calculates the ultrasonic amplitude based on this digital signal.

[0042] In some embodiments of the present invention, the ultrasonic-assisted cutting force control system further includes: a signal processing circuit 8, which is used to perform signal conditioning on the output signal of the analog-to-digital conversion circuit 6, mainly performing preprocessing operations such as signal amplification, attenuation, and filtering, and the conditioned signal is output to the control circuit 11.

[0043] In some embodiments of the present invention, the ultrasonic-assisted cutting force control system further includes: an isolation circuit 7, the purpose of which is to separate the control circuit and the power circuit to play a protective role. As Figure 3 shown, the isolation circuit 7 is provided between the control circuit 11 and the digital-to-analog conversion circuit 12, and between the signal processing circuit 8 and the analog-to-digital conversion circuit 6.

[0044] See Figure 3 , and the ultrasonic-assisted cutting control system provided by the embodiment of the present invention will be described in detail below in combination with a specific control process.

[0045] In the embodiment of the present invention, without adding an external sensor and without affecting the driving voltage of the ultrasonic device, an electrical signal representing the amplitude is directly extracted from the surface of the ultrasonic transducer element 4 (piezoelectric ceramic), and the feedback and control of the ultrasonic amplitude are completed.

[0046] The operation console 10 is for users to operate. Users input control instructions through the operation console 10, and the system status is also displayed and output through the operation console 10. The control instructions input by the operation console 10 are transmitted to the control circuit 11 through the communication circuit 9. After receiving the control instructions from the operation console 10, the control circuit 11 receives the signal representing the amplitude of the ultrasonic transducer, and calculates the drive signal through the cutting force control algorithm. This drive signal passes through the high-precision digital-to-analog conversion circuit 12, which converts the digital signal output by the control circuit 11 into an analog signal for controlling the drive circuit 13. The drive circuit 13 receives the instructions from the control circuit 11 and outputs a drive voltage, which is applied to the ultrasonic transducer element 4 to control the operation of the ultrasonic transducer element 4.

[0047] The amplitude measurement circuit 5 (integrating amplifier circuit) accumulates the charges on the surface of the ultrasonic transducer element 4 and outputs the accumulated charges in the form of a voltage. Without affecting the drive voltage, it extracts the electrical signal representing the amplitude. After receiving the above electrical signal representing the amplitude, the high-precision analog-to-digital conversion circuit 12 converts it into a digital signal. The signal processing circuit 8 receives the digital signal from the high-precision analog-to-digital conversion circuit 6 and performs signal preprocessing, including signal scaling, filtering, etc. The preprocessed signal is transmitted to the control circuit 11, and the control circuit 11 inputs the received signal into the amplitude calculation model and performs closed-loop control of the amplitude based on the calculated ultrasonic amplitude (i.e., the actual ultrasonic amplitude), thereby realizing the control of the cutting force.

[0048] The present invention has the following advantages: (1) Realize on-line real-time feedback and control of ultrasonic amplitude Existing ultrasonic amplitude detection technologies are difficult to detect ultrasonic amplitude in real time when the ultrasonic transducer is working. For example, optical detection is a common technology for detecting the amplitude of ultrasonic transducers, but during the measurement process, the ultrasonic transducer cannot perform material processing.

[0049] (2) Realize accurate detection of ultrasonic amplitude Many existing studies have established the corresponding relationship between ultrasonic amplitude and ultrasonic cutting force. However, in the use of the model, the accuracy of the ultrasonic amplitude data is defaulted. But the actual working conditions are unstable, and the ultrasonic amplitude also needs to be detected and controlled in real time on-line. This solution meets this requirement.

[0050] (3) Adopt piezoelectric self-sensing technology to improve the amplitude control accuracy Adopt self-sensing technology to directly extract the electrical signal representing the amplitude from the surface of the ultrasonic transducer element (piezoelectric ceramic). Since no additional sensor is added, the signal transmission loop is shorter and the signal delay time is shorter.

[0051] (4) Low cost and small volume Adopting self-sensing technology, it does not require an external sensor and does not need to transform the machine tool structure, reducing the equipment usage cost and having the advantage of small volume at the same time.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrasonic assisted cutting force control system, characterized in that: include: an amplitude measurement circuit, electrically connected to the ultrasonic transducer element in the ultrasonic transducer, and used for collecting electrical signals on the surface of the ultrasonic transducer element; The control circuit is used to calculate the actual ultrasonic amplitude of the ultrasonic transducer element according to the electrical signal, and control the cutting force based on the actual ultrasonic amplitude.

2. The ultrasonic assisted cutting force control system according to claim 1, characterized in that: The amplitude measurement circuit is used to accumulate the charges on the surface of the ultrasonic transducer element and output the accumulated charges in the form of voltage.

3. The ultrasonic assisted cutting force control system according to claim 1 or 2, characterized in that: The amplitude measurement circuit comprises an integral amplifier circuit, an input end of the integral amplifier circuit is electrically connected to the surface of the ultrasonic transducer element, and an output end of the integral amplifier circuit is electrically connected to the control circuit.

4. The ultrasonic assisted cutting force control system according to claim 1, characterized in that: The ultrasonic transducer element is piezoelectric ceramic.

5. The ultrasonic assisted cutting force control system according to claim 1, characterized in that: The amplitude measurement circuit is integrated with the control circuit.

6. The ultrasonic assisted cutting force control system according to claim 1, characterized in that: The control circuit is used to calculate the actual amplitude of the ultrasonic transducer element according to the electrical signal and the amplitude calculation model; the amplitude calculation model is used to describe the functional relationship between the surface charge of the ultrasonic transducer element and the amplitude of the ultrasonic transducer element.

7. The ultrasonic assisted cutting force control system according to claim 2, characterized in that: Also includes: Digital-to-analog conversion circuit, analog-to-digital conversion circuit and driving circuit; The digital-to-analog conversion circuit is used to convert the control signal of the control circuit into an analog signal; the analog signal is used to control the operation of the drive circuit; the drive circuit is used to drive the ultrasonic transducer element to operate; The analog-to-digital conversion circuit is used to convert the voltage signal output by the amplitude measurement circuit into a digital signal; and the control circuit calculates the ultrasonic amplitude based on the digital signal.

8. The ultrasonic-assisted cutting force control system according to claim 7, characterized in that: Also includes: The signal processing circuit is used to perform signal conditioning on the output signal of the analog-to-digital conversion circuit, and the conditioned signal is input into the control circuit.

9. The ultrasonic assisted cutting force control system according to claim 8, characterized in that: Also includes: The isolation circuit is arranged between the control circuit and the digital-to-analog conversion circuit, and between the signal processing circuit and the analog-to-digital conversion circuit.

10. An ultrasonic assisted cutting system, characterized in that: It comprises an ultrasonic assisted cutting device and an ultrasonic assisted cutting force control system according to any one of claims 1 to 9; The ultrasonic assisted cutting device is used for ultrasonic cutting of the processed material, and comprises an ultrasonic transducer, wherein the ultrasonic transducer comprises an ultrasonic transducer element, and the ultrasonic transducer element is provided with an electrode; The input end of the amplitude measurement circuit in the ultrasonic assisted cutting force control system is electrically connected to the electrode. The ultrasonic assisted cutting force control system is used to calculate the actual ultrasonic amplitude of the ultrasonic transducer element according to the electrical signal collected by the amplitude measurement circuit, and control the cutting force based on the actual ultrasonic amplitude.

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