A design method for a gas-assisted polishing system based on PID control

Abstract

This invention belongs to the field of substrate polishing technology and provides a design method for a PID-controlled gas-assisted polishing system, including a stirring system, a human-machine interaction control system, an ultrasonic vibration device, a liquid level monitoring device system, a pressure alarm system, and a gas pressurization system. The gas pressurization system includes a gas source, a gas flow control device, a gas sensor, and a data acquisition and processing unit. This invention enables pressurized gas to be delivered to the stirring tank through a filter. The ultrasonic vibration device emits ultrasonic waves of a preset frequency, which vibrate upon contact with the water, creating a gas-liquid coexistence state at the contact surface and generating numerous bubbles. Simultaneously, the stirrer, through a magnetic field generated by a magnetic generator, stirs the polishing liquid in the stirring tank, thereby achieving a larger gas-liquid contact area per unit time. This significantly improves the contact area between the gas and the polishing liquid, resulting in better abrasive dispersion.

Description

Technical Field

[0001] This invention belongs to the field of substrate polishing technology, specifically a design method for a PID-controlled gas-assisted polishing system. Background Technology

[0002] With the advancement of technology, the requirements for workpiece surface quality are increasingly stringent. Among existing grinding and polishing technologies, chemical mechanical polishing (CMP) has been widely adopted to obtain higher-quality workpiece surfaces. However, the effectiveness of CMP is influenced by various factors, among which the properties of the polishing slurry play a crucial role; parameters such as temperature, gas content, and pH value of the polishing slurry all significantly affect the polishing results. Currently, the main component of commonly used laboratory polishing slurries is deionized water, but its performance and effectiveness still need further improvement. In particular, the gas content in the polishing slurry is one of the key factors affecting the polishing effect. Increasing the corresponding gas content in the polishing slurry can, to a certain extent, accelerate the chemical reaction between the abrasive and the workpiece surface material, thereby maintaining a balance in the chemical-mechanical coupling effect as much as possible, which is crucial for obtaining higher-quality workpiece surfaces.

[0003] Existing polishing systems often cannot effectively control the gas content in the polishing slurry and the uniformity of abrasive distribution in the slurry, resulting in inconsistent chemical reaction rates between the abrasive and the workpiece surface during the polishing process, which in turn affects the polishing quality.

[0004] To address this, those skilled in the art have proposed a design method for a gas-assisted polishing system based on PID control. This method achieves a larger gas-liquid contact area per unit time, thereby significantly increasing the contact area between the gas and the polishing slurry. This optimizes the chemical reaction rate between the abrasive and the workpiece surface and improves the uniformity of abrasive distribution in the polishing slurry, thus solving the problems mentioned in the background art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a design method for a gas-assisted polishing system based on PID control. The aim is to overcome the shortcomings of existing technologies, significantly improve the gas content in the polishing slurry, the uniformity of abrasive particle distribution, and the reliability of the system. In the gas-assisted polishing system, the gas pressurization system pressurizes the polishing tank, pre-sets the target gas flow rate, obtains the current gas flow rate sampling value, and improves the process parameters of the fuzzy controller deviation E and deviation change rate EC.

[0006] A design method for a gas-assisted polishing system based on PID control, focusing on the three parameters K of the fuzzy rule PID controller. p K i K d Tuning and output are performed; the parameters of the fuzzy rule PID controller are calculated as follows:

[0007] The parameters of the fuzzy PID controller are calculated as follows:

[0008]

[0009] The proportional factor K of the analog controller kp K ki and K kd They are represented as follows:

[0010]

[0011] The inputs E and EC of the pseudo-controller, which determine the quantization factor and the scaling factor, are expressed as follows:

[0012]

[0013] The actual output ΔK of the analog controller p , △K i and △K d The formula is expressed as follows:

[0014]

[0015] In the above formula, e H and EC H These represent the upper limits of the error and the rate of change of error, respectively, while e L and EC L Δk represents the lower limit of the error and the rate of change of the error, respectively; pH , △k iH and △k dH These represent the upper limit of the output, Δk and Δk respectively. pL , △k iL and △k dL These represent the lower limit values ​​of the output.

[0016] The gas flow rate transfer function expression is obtained from the identification results and the transfer function identification model as follows:

[0017]

[0018] Subsequently, fuzzy PID calculation is performed using the gas flow transfer function expression. The gas sensor output is acquired and processed by the main control unit via the AD conversion module and then transmitted to the host computer. The gas flow sensor detects the gas flow in real time, and the host computer displays the gas flow rate feedback from the gas sensor. The host computer then controls the carrier gas valve of the gas flow control device to produce corresponding actions, so that the gas flow rate is injected into the mixing tank of the mixing system with high response, high precision, uniformity and stability. The pressurized gas and polishing liquid are fully contacted by the ultrasonic vibration and magnetic stirring device to increase the contact time between the pressurized gas and the polishing liquid, thereby obtaining higher gas dissolution and better abrasive dispersion.

[0019] The present invention discloses a design method for a gas-assisted polishing system, comprising a stirring system, an ultrasonic vibration system, a human-machine interaction control system, and a gas pressurization system. The gas pressurization system pressurizes the gas and injects it into the stirring tank of the stirring system through a control valve. Ultrasonic vibration and magnetic stirring devices ensure sufficient contact between the pressurized gas and the polishing liquid, thereby increasing the contact time between the pressurized gas and the polishing liquid and achieving a greater dissolution rate. The formula for calculating the change in dissolution rate is as follows:

[0020] Q=μ·K·A·Δt

[0021] Where: Q is the amount dissolved; μ is the vibration frequency; K is the stirring rate; Δt is the processing time; and A is the gas-liquid contact area per unit time.

[0022] Preferably, the magnetic stirring device is installed at the bottom of the mixing tank and consists of a speed sensor, a D / A module, a drive circuit, a magnetic generator, and a stir bar. During operation, to ensure the steady-state accuracy of the motor speed, the speed sensor directly detects the stir bar speed. Each revolution of the speed sensor generates a pulse signal, which is transmitted to the PLC via the D / A module. The PLC compares the actual stir bar speed with the set speed and adjusts the error using PID control, ultimately stabilizing the stir bar speed at the set value. The PID formula is as follows:

[0023] ΔV k =k p (E k -E k-1 )+k i E k (1.6)

[0024] Let the period of the Kth cycle be T. k Then the error for the kth iteration is: E k =T g -T k (ms). E k－1 For the error of the (K-1)th iteration ②k p For proportionality coefficient, k i For the integral coefficient, ΔV k This represents the voltage increment for the Kth time.

[0025] The stir bar stirs the polishing liquid in the stirring tank through the magnetic field generated by the magnetic generator, so as to obtain a larger gas-liquid contact area per unit time, thereby greatly increasing the gas dissolution rate.

[0026] Preferably, the stir bar stirs the polishing liquid in the stirring tank using a magnetic field generated by a magnetic generator, so as to obtain a larger gas-liquid contact area per unit time, thereby greatly increasing the gas dissolution rate.

[0027] Preferably, the mixing tank is made of one of 304 or 316 stainless steel, which has good corrosion resistance and thermal conductivity. At the same time, a gas content monitor is installed on the top of the tank to monitor the changes in the gas content inside the tank in real time. The gas delivery rate can be adjusted according to the changes in the value to maintain the gas content inside the tank in a steady state. The tank is equipped with an O-ring made of EPDM rubber, which has good heat resistance, aging resistance and chemical corrosion resistance.

[0028] Preferably, the ultrasonic vibration device includes a vibration head, an amplitude transformer, a transducer, and an ultrasonic generator, which outputs pulse signals. The generator emits ultrasonic waves of a preset frequency, which vibrate upon contact with the water. At this time, a gas-liquid coexistence state appears on the contact surface. By generating a large number of bubbles, the gas-liquid contact area is increased, thereby obtaining a higher gas dissolution rate.

[0029] Preferably, in the human-machine interaction control system, the controller is an S7-200 smart PLC, which receives and processes control signals input from the ultrasonic vibration, magnetic stirring device and human-machine interface, and records information such as the time and magnitude of various control signal inputs to obtain characteristic parameters of the ultrasonic vibration and magnetic stirring device, including occurrence time, vibration frequency, stirring rate, etc., providing a basis for analyzing the system's working status.

[0030] Preferably, the pressure alarm system includes a D / A module, a human-machine interface, a communication interface, a pressure relief valve, a buzzer, a pressure transmission sensor, and an execution relay. The host computer receives the digital pulse signal output by the pressure sensor, displays the actual gas pressure in the mixing tank, and when the logic arithmetic unit determines that the pressure in the tank exceeds the preset alarm pressure value, it controls the buzzer to sound an alarm and executes the pressure relief valve to ensure that the gas-assisted polishing system operates under safe and reliable conditions.

[0031] Preferably, the liquid level monitoring device system consists of a D / A module, a human-machine interface, a communication interface, a liquid level sensor, and an actuator. The sensor receives pulse signals of the actual liquid level height in the mixing tank, and the logic unit determines whether it matches a preset value to monitor the change in the total amount of liquid inside the tank.

[0032] Preferably, the specific technical solution of the present invention is as follows:

[0033] A design method for a PID-controlled gas-assisted polishing system includes a stirring system, a level gauge monitoring system, a pressure alarm system, an ultrasonic vibration system, a human-machine interaction control system, and a gas pressurization system.

[0034] Its operating mechanism is as follows: the gas pressurization system pressurizes the polishing tank, pre-sets the target gas flow rate, obtains the current gas flow rate sampling value, improves the process parameters of the fuzzy controller deviation E and deviation change rate EC, and adjusts the three parameters K of the fuzzy rule PID controller. p K i K d After tuning and output, fuzzy PID calculation is performed using the gas flow transfer function expression. The gas sensor output is acquired and processed by the main control unit via the AD conversion module and then transmitted to the host computer. The gas flow sensor detects the gas flow in real time, and the host computer displays the gas flow rate feedback from the gas sensor. The host computer then controls the carrier gas valve of the gas flow control device to produce corresponding actions, so that the gas flow rate is injected into the mixing tank of the mixing system with high response, high precision, uniformity and stability. The pressurized gas and polishing liquid are fully contacted by the ultrasonic vibration and magnetic stirring device to increase the contact time between the pressurized gas and the polishing liquid, thereby obtaining higher gas dissolution and better abrasive dispersion.

[0035] A design method for a PID-controlled gas-assisted polishing system includes the following steps:

[0036] Step 1: Input the preset vibration frequency and stirring rate of the ultrasonic vibration and magnetic stirring devices through the human-computer interaction control system.

[0037] Step 2: The control system and human-machine interaction control system use PID control to control the vibration frequency and stirring rate to maintain a stable gas dissolution rate in the system, thereby achieving the required gas content more quickly.

[0038] Step 3: The gas pressurization system pressurizes the polishing tank. A target gas flow rate is pre-set, and the current gas flow rate sample value is obtained. The process parameters of the fuzzy controller deviation E and deviation change rate EC are improved. The three parameters K of the fuzzy rule PID controller are also adjusted. p K i K d After tuning and outputting, PID calculation is performed to control the carrier gas valve of the gas flow control device to produce corresponding actions, so that the gas flow rate is injected into the mixing tank of the mixing system with high response, high precision, uniformity and stability.

[0039] Step 4: The ultrasonic vibration device emits ultrasonic waves of a preset frequency through the generator. When the ultrasonic waves come into contact with the water, they vibrate. At this time, a gas-liquid coexistence state appears on the contact surface, generating a large number of gas-liquid bubbles. At the same time, the stir bar stirs the polishing liquid in the stirring tank through the magnetic field generated by the magnetic generator, thereby greatly increasing the gas-liquid contact area and obtaining higher gas solubility and better abrasive dispersion.

[0040] Step 5: Store the aforementioned working characteristic signals through the human-machine interaction control system to detect the system's working status in real time and control the gas delivery rate of the pressurization system.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. This invention enables pressurized gas to be transported to the mixing tank through a filter screen. Ultrasonic waves of a preset frequency are emitted by the generator inside the ultrasonic vibration device. Upon contact with the water, the gas vibrates, creating a gas-liquid coexistence state on the contact surface and generating a large number of bubbles. At the same time, the stir bar stirs the polishing liquid in the mixing tank through the magnetic field generated by the magnetic generator, thereby obtaining a larger gas-liquid contact area per unit time. This greatly increases the contact area between the gas and the polishing liquid, increases the gas dissolution, and obtains better abrasive dispersion.

[0043] 2. This invention has strong controllability, enabling human-computer interaction and controlling the gas delivery rate, ultrasonic vibration frequency, and stirrer rotation rate of the system by monitoring the gas content, thereby maintaining the gas dissolution amount in line with actual needs. It can also record information such as the time and magnitude of various control signal inputs to obtain characteristic parameters of the ultrasonic vibration and magnetic stirring device, including occurrence time, vibration frequency, and stirring rate, providing a basis for analyzing the system's working status. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the control process of a gas-assisted polishing system according to the present invention;

[0045] Figure 2 This is a schematic diagram of the gas-assisted polishing system in this invention;

[0046] Figure 3 This is a cross-sectional view of the interior of the mixing tank in this invention;

[0047] Figure 4 This is a schematic diagram of the human-computer interaction control interface in this invention;

[0048] Figure 5 This is a diagram showing the strain results of the mixing tank during actual operation in this invention;

[0049] Figure 6 The microscopic morphology of the sapphire surface after processing in this invention is shown below:

[0050] Figure 7 The electrical wiring diagram of the gas-assisted polishing system in this invention is as follows:

[0051] Figure 8 This is a ladder diagram program for the gas-assisted polishing system in this invention.

[0052] In the picture:

[0053] 1. Human-machine interaction control system; 2. Ultrasonic vibration device; 3. Circulating pump; 4. Monitoring device; 5. Liquid inlet; 6. Stirring tank; 7. Liquid level monitoring point; 8. Air inlet; 9. Magnetic stirring device; 10. Monitoring sensor; 11. Overflow floating ball; 12. Vibration generator. Detailed Implementation

[0054] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0055] As attached Figure 1 - Appendix Figure 8 As shown:

[0056] Figure 1 The diagram shows the control process of the present invention, including a control system, a stirring tank, a pressurization system, and an ultrasonic vibration and magnetic stirring device 9. The control system sets the gas delivery rate, vibration frequency, and stirrer rotation rate through a human-machine interface. When the system starts working, the monitoring sensor 10 and the logic unit are controlled by the fuzzy PID controller system to stabilize the gas delivery rate of the pressurization system, thereby maintaining the stability of the gas content inside the stirring tank 6. At the same time, the ultrasonic vibration and magnetic stirring device 9 is controlled by the fuzzy PID controller to operate and record the characteristic information parameters of its working state, providing a basis for analyzing the change law of gas dissolution rate.

[0057] Gas-assisted polishing systems such as Figure 2 As shown, the system includes: a human-machine interface control system 1, an ultrasonic vibration device 2, a circulating pump 3, a monitoring device 4, a liquid inlet 5, a mixing tank 6, a liquid level monitoring point 7, an air inlet 8, and a magnetic stirring device 9. The human-machine interface control system 1 contains a control system that allows users to set the gas input rate, vibration frequency, and stir bar rotation speed via a touchscreen interface. The magnetic stirring device 9 is installed below the mixing tank 6 and performs the stirring action through the rotation of the magnetic stir bar. The ultrasonic vibration device 2 is vertically installed on the top of the mixing tank 6. After the generator emits vibrations at a preset frequency, a gas-liquid coexistence state is created at the contact surface between the polishing liquid and the generator, thereby greatly increasing the contact area between the gas and the polishing liquid and increasing the gas dissolution rate. The pressurization system works in conjunction with the filter to prevent backflow of liquid inside the mixing tank 6 due to the pressure difference inside and outside the air inlet 8, which could cause pressurization system malfunction.

[0058] A schematic diagram of mixing tank 6 is shown below. Figure 3As shown, the mixing tank 6 consists of a liquid inlet 5, a liquid level monitoring point 7, an air inlet 8, a monitoring sensor 10, an overflow floating ball 11, and a vibration generator 12. The mixing tank 6 has the liquid inlet 5, liquid level monitoring point 7, and air inlet 8 on its outer side. The air inlet 8 is connected to the pressurization system and has an internal filter to effectively prevent backflow of liquid inside the mixing tank 6 due to pressure difference between the inside and outside of the air inlet 8, which could cause pressurization system malfunctions. Simultaneously, the liquid level monitoring point 7 effectively monitors the liquid level inside the mixing tank 6, allowing for convenient observation of liquid level changes. The mixing tank 6 contains the monitoring sensor 10, vibration generator 12, and overflow floating ball 11. The monitoring sensor 10 monitors the pH value and gas content of the polishing fluid in the tank in real time. The vibration generator 12 emits vibrations at a preset frequency, creating a gas-liquid coexistence state at the contact surface between the polishing fluid and the generator, thereby greatly increasing the contact area between the gas and the polishing fluid and increasing the gas dissolution rate. The overflow floating ball can float vertically up and down, effectively preventing liquid overflow during normal operation of the gas-assisted polishing system.

[0059] The human-computer interaction interface and the tank simulation strain results are as follows: Figures 4-5 As shown in the human-machine interface, the operator can preset the processing time, vibration frequency, gas input speed, and stirrer speed before the gas-assisted polishing system starts operating. Then, the operator activates the gas supply and liquid level control switches to begin operation. During operation, the operator can monitor the overall system performance using the device status monitoring diagram. The tank simulation shows the strain simulation results after internal pressurization, which verifies that the selected 304 and 316 stainless steel materials meet the operational requirements.

[0060] Example 1: As Figure 1 , 4 As shown, this invention discloses a gas-assisted polishing system in which: the operator sets the vibration frequency of the ultrasonic vibration device 2 to 3000Hz, the processing time to 2h, the gas input rate to 10ml / s, and the stirring speed to 200r / s through the human-machine interaction control system 1. When the system starts working, the control system controls the monitoring sensor 10 and the logic arithmetic unit to stabilize the gas delivery rate of the pressurization system, thereby maintaining the stability of the gas content inside the stirring tank 6. At the same time, the microcontroller controls the operation of the ultrasonic vibration and magnetic stirring device 9 and records the time, magnitude, and other information of various control signal inputs through program design, obtaining the characteristic parameters corresponding to the normal operation of the ultrasonic vibration and magnetic stirring device 9, including the occurrence time, vibration frequency, and stirring rate. Through signal conversion processing, the vibration frequency of 2999Hz and the stirring rate of 199r / s are obtained, providing a basis for subsequent analysis of the working status of the gas-assisted polishing system.

[0061] Example 2: Figures 2-3As shown, the present invention discloses a gas-assisted polishing system, wherein the gas-assisted polishing system is divided into a human-machine interaction control module, an ultrasonic vibration module, a magnetic stirring module, and a pressurized gas module. The human-machine interaction control module presets the vibration frequency, processing time, gas delivery rate, and stirrer rate before system operation. Subsequently, the ultrasonic vibration module dissolves gas on the surface of the polishing liquid at a vibration frequency of 2000Hz. At the same time, the gas is pressurized by the pressurization system, filtered by the filter screen, and injected into the stirring tank 6. Then, the magnetic stirring device 9 generates a magnetic field through a magnetic field generator, which drives the magnetic stirrer to stir the polishing liquid at a stirring rate of 200r / s, thereby increasing the contact area between the gas and the polishing liquid per unit time and increasing the dissolution amount of the polishing liquid. The gas dissolution rate is 5ml / s.

[0062] Example 3: Figure 6 As shown, the gas-assisted polishing system of the present invention comprises the following steps in its assisted polishing action:

[0063] S1. Input the preset stirring rate -200r / s, vibration frequency -2000Hz, processing time -2h and gas delivery rate -10ml / s into the human-machine interaction control system;

[0064] S2. After adding the polishing slurry containing silica abrasive into the mixing tank 6, the gas dissolution and stirring actions are carried out.

[0065] S3. Detect the gas dissolution rate of the polishing slurry in step S2. When it stabilizes at 5 ml / s, the polishing slurry is transported from the pipeline to the polishing machine via circulation pump 3 to assist in polishing the sapphire substrate, obtaining a nanoscale surface finish with Ra < 1.6 nm. The surface morphology is as follows: Figure 6 As shown.

[0066] like Figure 7 As shown, Figure 7 The electrical wiring diagram of the gas-assisted polishing system in this invention is as follows: The PID-controlled gas-assisted polishing system designed in this paper consists of mechanical structure, information acquisition, and relay control. The control system comprises a core control module, a sensor information acquisition module, and a remote data transmission module. The sensor information acquisition module acquires the system equipment's operating status information, the remote data transmission module uploads and downloads various types of data, and the core control component, the S7-200 smart PLC, performs tasks such as acquiring sensor information, issuing control commands, and connecting to the remote transmission device. The control system involves various actuators, such as relays, magnetic stirrer motors, and pressure alarm buzzers. The signal input terminals include pressure, gas, and liquid level sensors. Each actuator uses a DC 24V intermediate relay for circuit protection and secondary control operations.

[0067] like Figure 8As shown, Figure 8 The ladder diagram program for the gas-assisted polishing system in this invention is as follows: The S7-200 smart PLC ladder diagram program designed in this paper includes a main program and five subroutines, namely the magnetic stirring speed regulation ladder diagram program, the pressure alarm ladder diagram program, the ultrasonic vibration speed regulation ladder diagram program, and the liquid level ladder diagram control program. Fuzzy PID control parameters are added to the system to improve the robustness, response speed, and accuracy of the system.

[0068] Furthermore, the performance of existing methods (i.e., by changing the pressure in the polishing tank, the gas content in the polishing slurry can be further controlled, and by adjusting the flow rate of the polishing slurry, a fresh polishing slurry can always be provided to the polished surface, thereby maintaining the uniformity of abrasive distribution) is compared with the design method of a PID-controlled gas-assisted polishing system provided in this embodiment. The comparison results are shown in Table 1.

[0069] Table 1 - Comparison Results of Performance Indicators

[0070] Existing methods This method Polishing fluid treatment method Changing the pressure (complex) Magnetic force generates a magnetic field (simple). Controlled reaction mode Manual adjustment No manual labor required Abrasive dispersibility (%) 78.6％ 96.8％ Reaction monitoring Monitoring only Monitor, analyze, and record Reaction rate (%) 87.7％ 98.2％ Polishing quality (%) 88.1％ 98.8％

[0071] As can be seen from Table 1, compared with existing methods, the design method of the PID-controlled gas-assisted polishing system provided in this embodiment has better effects in terms of polishing slurry treatment, reaction control, abrasive dispersion, reaction monitoring, reaction rate and polishing quality. This method can provide polishing systems with more efficient, faster reaction and better polishing quality.

[0072] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A design method for a gas-assisted polishing system based on PID control, comprising a stirring system, a human-machine interaction control system (1), an ultrasonic vibration device (2), a level gauge monitoring system, a pressure alarm system, and a gas pressurization system, characterized in that: The gas pressurization system includes a gas source, a gas flow control device, a gas sensor, and a data acquisition and processing unit. The gas pressurization system incorporates fuzzy PID control. The gas pressurization system also includes a fuzzy controller that uses gas flow deviation E and deviation change rate EC as two inputs to the fuzzy rule PID controller, and uses the three parameters K of the fuzzy rule PID controller. p K i K d Perform tuning and output; The stirring system includes a magnetic stirring device (9) and a stirring tank (6). The magnetic stirring device (9) is installed at the bottom of the stirring tank (6) and consists of a speed sensor, a D / A module, a drive circuit, a magnetic generator, and a stir bar. In operation, to ensure the steady-state accuracy of the motor speed, a speed sensor is used to directly detect the speed of the stir bar. The speed sensor generates a pulse signal for each revolution, which is transmitted to the PLC to compare the actual speed of the stir bar with the set speed. The error is adjusted by PID control, and finally the speed of the stir bar is stabilized at the set value. The PID formula is as follows: ΔV k =k p (E k -E k-1 )+k i E k (1.6) Let the period of the Kth cycle be T. k Then the error for the kth iteration is: E k =T g -T k (ms); E k－1 For the error of the (K-1)th iteration ②k p For proportionality coefficient, k i For the integral coefficient, ΔV k This represents the voltage increment for the Kth time. The ultrasonic vibration device (2) is equipped with a vibration head, an amplitude transformer, a transducer, and an ultrasonic generator, which outputs pulse signals. The ultrasonic vibration device (2) emits ultrasonic waves of a preset frequency from the generator, which vibrate upon contact with the water. At this time, a gas-liquid coexistence state appears on the contact surface; the relevant formulas are as follows: Q=μ·K·A·Δt Where: Q is the amount dissolved; μ is the vibration frequency; K is the stirring rate; Δt is the processing time; A is the gas-liquid contact area per unit time; The human-machine interaction control system (1) includes a PLC controller, an input / output module, a human-machine interface, a communication interface, a detection sensor and an actuator. The detection sensor receives the pulse signal of the actual gas content in the mixing tank (6). After the logic arithmetic unit determines whether it matches the preset value, it issues an action / non-action command to the gas pressurization system to maintain the stability of the gas dissolution rate in the mixing tank (6). The PLC controller receives and processes control signals input from the ultrasonic vibration, magnetic stirring device (9) and human-machine interface, and records the time and magnitude information of various control signal inputs to obtain the characteristic parameters of the ultrasonic vibration and magnetic stirring device (9), including occurrence time, vibration frequency and stirring rate, so as to provide a basis for analyzing the working status of the system. A design method for a PID-controlled gas-assisted polishing system includes the following steps: Step 1: Input the corresponding preset vibration frequency and stirring rate of the ultrasonic vibration and magnetic stirring device (9) through the human-computer interaction control system (1); Step 2, Control System and Human-Machine Interaction Control System (1) The vibration frequency and stirring rate are controlled by PID to maintain the stable gas dissolution rate of the system, so as to achieve the actual required gas content more quickly. Step 3: The gas pressurization system pressurizes the polishing tank. A target gas flow rate is pre-set, and the current gas flow rate sample value is obtained. The process parameters of the fuzzy controller deviation E and deviation change rate EC are improved. The three parameters K of the fuzzy rule PID controller are also adjusted. p K i K d After setting and outputting, PID calculation is performed to control the gas flow control device carrier gas valve to produce corresponding actions, so that the gas flow rate is injected into the mixing tank (6) of the mixing system with high response, high precision and uniform stability. Step 4: The ultrasonic vibration device (2) emits ultrasonic waves of a preset frequency through the generator. After contacting the water, it vibrates. At this time, a gas-liquid coexistence state appears on the contact surface, generating a large number of gas-liquid bubbles. At the same time, the stirrer stirs the polishing liquid in the stirring tank (6) through the magnetic field generated by the magnetic generator, thereby increasing the gas-liquid contact area and obtaining higher gas dissolution and better abrasive dispersion. Step 5: Store the working characteristic signals through the human-machine interaction control system (1) to detect the working status of the system in real time and control the gas delivery rate of the pressurization system.

2. The design method of a PID-controlled gas-assisted polishing system as described in claim 1, characterized in that: The gas flow rate transfer function expression is obtained from the identification results and the transfer function identification model as follows: The carrier gas valve acts as a gas flow control device. The gas flow sensor detects the gas flow in real time. The output of the gas sensor is collected and processed by the main control unit through the AD conversion module and then transmitted to the host computer. The host computer displays the gas flow rate fed back by the gas sensor and analyzes and obtains various performance parameters of the gas sensor.

3. The design method of a gas-assisted polishing system based on PID control as described in claim 1, characterized in that: The mixing tank (6) is made of one of 304 and 316 stainless steel, which has good corrosion resistance and thermal conductivity. At the same time, a gas content monitor and a pH sensor are installed on the top of the tank. The data are collected and processed by the main control unit through the AD conversion module and transmitted to the host computer to monitor the changes in gas content and pH of the polishing liquid in real time. The gas delivery rate can be adjusted according to the real-time values ​​to maintain the gas content inside the tank in a steady state. The mixing tank (6) is equipped with an O-ring inside the tank body, which is made of EPDM rubber and has good heat resistance, aging resistance and chemical corrosion resistance.

4. The design method of a gas-assisted polishing system based on PID control as described in claim 1, characterized in that: The gas pressurization system pressurizes the gas, filters it through a filter screen, and injects it into the stirring tank (6) of the stirring system. The pressurized gas and the polishing liquid are brought into full contact by ultrasonic vibration and magnetic stirring device (9) to increase the contact time between the gas and the polishing liquid, thereby obtaining a greater amount of dissolution.

5. The design method of a gas-assisted polishing system based on PID control as described in claim 1, characterized in that: The liquid level monitoring device system is installed outside the mixing tank (6) and consists of a D / A module, a human-machine interface, a communication interface, a liquid level sensor and an actuator. The liquid level monitoring sensor receives the pulse signal of the actual liquid level height in the mixing tank (6), and after the logic arithmetic unit determines whether it matches the preset value, a water level observation point is set on the outside of the tank to monitor the change in the total amount of liquid inside the tank.

6. The design method of a gas-assisted polishing system based on PID control as described in claim 1, characterized in that: The pressure alarm system is installed on the top of the mixing tank (6) cover and consists of a D / A module, human-machine interface, communication interface, pressure relief valve, buzzer, pressure transmission sensor and execution relay. The host computer receives the digital pulse signal output by the pressure sensor and displays the actual gas pressure in the mixing tank (6). When the logic arithmetic unit determines that the pressure in the tank is greater than the preset alarm pressure value, it controls the buzzer to sound an alarm and executes the pressure relief valve to ensure that the gas-assisted polishing system operates under safe and reliable conditions.

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