CN101634862B - Control method of opening of large flow throttle valve for water - Google Patents

Abstract

The invention provides a method for controlling the opening degree of a large-flow water throttle valve, which is characterized in that the position of the piston rod in the proportional servo oil cylinder is controlled by adjusting the input current of the pilot electro-hydraulic proportional flow valve, and then the piston rod drives the large flow The spool of the water throttle valve moves to finally control the opening of the large flow water throttle valve; the piston rod and the water throttle valve core are fixedly connected by threads; the closed-loop asymmetric PID control method is adopted in the control process, and the input The quantity is the given opening degree value of the large-flow water throttle valve, the feedback value is the detected actual large-flow water throttle valve opening value, the given large-flow water throttle valve opening value and the detected actual The difference e(t) of the throttle valve opening value of large flow water is input into the PID controller, and the PID controller outputs a current signal to the pilot electro-hydraulic proportional flow valve. The method has high control precision, convenient installation and operation, strong practicability and high reliability.

Description

A Control Method of Opening Degree of Large Flow Water Throttle Valve

technical field

The invention belongs to the field of electromechanical-hydraulic integrated control, specifically a method for controlling the opening degree of a large-flow water throttle valve, which is applied to an oil pressure control system mainly based on an electro-hydraulic proportional reversing valve to accurately control large-flow water. The position of the spool of the valve can be controlled to control the excess flow of the large flow water valve.

Background technique

Extrusion is one of the most important pressure processing methods. Large-scale extrusion machines are indispensable equipment in aerospace, aviation, transportation, electronic communication, shipbuilding and other industries. One of the important signs.

Extrusion speed is a process parameter that needs to be strictly controlled in the aluminum extrusion process. The extrusion speed is closely related to the composition, cross-sectional shape, extrusion ratio and other factors of the extruded profile. If the extrusion speed is too high or too low, the production efficiency will be reduced or even the extrusion work will be impossible. In addition, from the perspective of the extrusion process, the extrusion speed must be relatively stable during the extrusion process. The fluctuation of the extrusion speed will cause ripples on the surface of the product and affect the quality of the product. At present, the speed control technologies of large extruders mainly include variable frequency drive volumetric speed regulation, variable pump volumetric speed regulation, and electro-hydraulic proportional cartridge valve speed regulation, but these speed regulation methods are only suitable for oil pressure control or The domestic technology is immature.

Giant hydraulic presses require a huge amount of working fluid. Considering various factors such as economy and pollution, emulsion is used as the working fluid. Due to the large leakage and high cost of emulsion, the current transmission medium is mostly replaced by water. Therefore, the giant hydraulic presses in our country are generally still hydraulic presses. At present, the research on water hydraulic technology in foreign countries has made substantial progress. The quality control of water medium, the wear and corrosion control of components and systems, as well as new materials, new processes, and new control technologies have been fully reflected in the development of existing water hydraulic components and systems. Now, there are a few series of water hydraulic components available in the world market. As shown in Table 1.1, there are mainly five grades of pressure: 10MPa, 14MPa, 21MPa, 32MPa, and 40MPa. But generally speaking, the overall performance of existing water hydraulic components is quite different from that of oil hydraulic components, and the price is also very expensive.

Table 1.1 Market Supply Status of Water Hydraulic Control Valves

my country's water hydraulic technology research has also started. Now universities such as Huazhong University of Science and Technology and Zhejiang University have carried out research work on this technology. Both studies have their own characteristics. Huazhong University of Science and Technology focuses on the research of water hydraulic technology with seawater as the medium, and its main application field focuses on naval equipment; Zhejiang University focuses on related technologies with tap water as the medium, and its application field is civilian. But so far, water hydraulic technology has only entered the first stage of practical application, and it will be an important development direction of water hydraulic technology to realize precise digital control of water throttle valve with computer.

The original throttle valve of the 125MN extruder uses a DC motor to drive the worm gear, and after being decelerated by the reducer, the drive lever is driven by the nut screw auxiliary mechanism to control the opening of the throttle valve core and indirectly control the flow. Because the original system adopts the self-aligning machine follow-up and the transmission chain is too long, the stability of the valve is poor, and the displacement of the valve stem has drift. And the whole system is an open-loop system, the control precision is not high, and the control precision and the production efficiency of the press need to be improved urgently.

Contents of the invention

The object of the present invention is to provide a method for controlling the opening degree of a large-flow water throttle valve, which is applied to high-precision control of the valve opening degree of a large-flow water throttle valve of a large extrusion machine.

To achieve the above object, the technical solution of the present invention is:

A method for controlling the opening degree of a large-flow water throttle valve, characterized in that the position of the piston rod in the proportional servo cylinder is controlled by adjusting the input current of the pilot electro-hydraulic proportional flow valve, and the piston rod is fixedly connected with the water throttle valve spool , so that the movement of the piston rod directly drives the movement of the spool of the large-flow water throttle valve, and finally realizes the precise control of the opening degree of the large-flow water throttle valve;

In the control process, the closed-loop asymmetric PID control method is adopted. The input value is the given opening degree value of the large-flow water throttle valve, and the feedback value is the detected actual large-flow water throttle valve opening value. The difference e(t) between the opening degree of the flow water throttle valve and the detected actual large flow water throttle valve opening value is input into the PID controller, and the PID controller outputs a current signal to the pilot electro-hydraulic proportional flow valve.

The PID controller adopts asymmetric parameters, and the specific parameter tuning process is:

Suppose K _P1 , K _i1 , K _d1 and K _P2 , K _i2 , K _d2 are proportional, integral and differential constants when e(t) is positive and negative respectively; K _P1 , K _i1 , K _d1 parameter tuning method is: set The dead zone value of PID control is 0.05mm, adopt Jager-Nichols method, first set K _d1 ＝K _i1 ＝0, and adjust the proportional coefficient K separately. At this time, the controller is a proportional controller. Set the set opening value of the throttle valve to be greater than the actual opening value of the throttle valve, even if e(t)>0, then increase the system proportional coefficient K until the system starts to oscillate, and record the proportional coefficient K at this time as Km ₁ , then K _P1 , K _i1 , K _d1 parameters are calculated according to the following formula:

K _P1 = 0.6K _m1 $K_{d1}=\frac{K_{P1}\mathrm{\π}}{4{\mathrm{\ω}}_m}$ $K_{i1}=\frac{K_{P1}{\mathrm{\ω}}_m}{\mathrm{\π}}$ ; where ω _m is the oscillation frequency; (when K _d1 ＝K _i1 ＝0, the system adopts a proportional link control, K _P1 , K, Km ₁ are the proportional coefficients mentioned below, and K is the proportional coefficient KM1 is the proportional coefficient at the start of oscillation, KP1 is the proportional coefficient used in PID control after multiplying KM1 by 0.6)

K _P2 , K _i2 , K _d2 parameter tuning method is as follows: set the dead zone value of PID control to 0.05mm, adopt Jager-Nichols method, first set K _d2 =K _i2 =0, at this time the controller is a Proportional controller, by setting the set opening value of the throttle valve in the monitoring system to be smaller than the actual opening value of the throttle valve, even if e(t)<0, and then increasing the system proportional coefficient K until the system starts to oscillate, Make the system in a negative step response, then increase the proportional coefficient until the system starts to oscillate, and record the proportional coefficient at this time as Km ₂ , K _P2 , K _i2 , and K _d2 parameters are calculated according to the following formula:

K _P2 = 0.6K _m2 $K_{d2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="K\; P"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">K</figure-callout>}}_P\mathrm{\&pi;}}{4{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="2"\; label="m\; K\; i"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">m</figure-callout>}}}$ $K_i$$2_{}=\frac{{\mathrm{<figure-callout\; id="2"\; label="K\; P"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">K</figure-callout>}}_P{\mathrm{\&omega;}}_m}{\mathrm{\&pi;}};$ Where ω _m is the oscillation frequency.

The large-flow water throttle valve control system using this method includes a large-flow water throttle valve and its hydraulic drive system, a state signal detection system, a PLC control system, and a real-time monitoring system for a host computer, and uses industrial field bus technology to realize system signals. The full digital communication high.

The system adopts the operation mode of direct digital input, analog bar graph adjustment and digital display. It can realize the precise digital input of the throttle valve setting opening degree and the detected actual opening degree (digital quantity input) and the pressure before and after the valve (this signal is used to provide reference for the setting opening degree, and for the analog quantity input) combined to realize the digital precise closed-loop control of the opening degree of the throttle valve spool, and its control accuracy is 0.1mm.

In the large-flow water throttle valve control system, the displacement detection range of the throttle valve spool is 0-60mm. In view of its asymmetrical dynamic characteristics during the rising and falling process of the valve core, in order To obtain a shorter adjustment time and low overshoot, set different parameters in the control system for the opening and closing process of the throttle valve through experiments, and use asymmetric dynamic parameter adjustment for it, using Ziegler-Nichols (Jager-Nichols) method) to perform parameter setting (see the specific implementation plan for the detailed setting process), so that the throttle valve has ideal dynamic characteristics in the process of opening and closing. Its response time is 0.6s, and there is almost no overshoot. It adopts asymmetric dynamic parameter setting and adjustment to solve the problem that the dynamic characteristics of the spool will be different during the opening and closing of the throttle valve.

The control system of the large-flow water throttle valve detects the displacement value of the opening degree of the valve core through a digital high-precision magnetostrictive displacement sensor.

The high-flow water throttle valve control system is characterized in that a pressure sensor is used to simultaneously collect the pressure difference before and after the throttle valve, and the pressure difference has a certain reference effect on the throttle valve opening setting value.

The control system of the large-flow water throttle valve is characterized in that it adopts the Profibus industrial field bus technology to realize the full digital communication of system detection signals and control signals.

A precise control method for a large-flow water throttle valve, which is characterized in that the position of the piston rod in the proportional servo cylinder is precisely controlled by adjusting the input current of the pilot proportional reversing valve, and then the valve core of the large-flow water throttle valve is driven by the piston rod Movement, so as to precisely control the position of the valve spool, and finally realize the precise control of its flow.

In the large-flow water throttling valve, the liquid flow through the water inlet is divided into two paths, and one path communicates with the water outlet through the flow channel formed between the valve core and the valve cup. The other way communicates with the upper chamber of the water throttle valve through the pipeline on the valve body to balance the opening pressure of the valve core.

Sealing rings are used for direct sealing between the valve core and the valve cup, and between the valve core and the gland, which effectively solves the leakage problem of the water throttle valve. The upper end of the spool of the water throttle valve is connected with the piston rod in the proportional servo cylinder through a threaded connection, and the movement of the piston rod directly drives the movement of the spool of the water throttle valve. A magnetic telescopic displacement sensor is installed on the piston rod.

Advantage and effect of the present invention:

The present invention designs a precise control method for a large-diameter, large-flow water throttle valve. This method is applied to the control system renovation project of a 125MN extruder to control the extrusion speed. The project has been successfully passed in March 2008 Acceptance, more than one year of production and operation shows that the throttle valve overcurrent flow rate changes with the opening of the valve port in an approximately linear relationship, indicating that the flow rate changes uniformly within the entire adjustment range, the micro-adjustment performance is good, and the throttle valve spool opening The dynamic response characteristic curve is shown in Figure 5, and the abscissa in the figure is the sampling time (s). From Figure 5, it can be seen that the response time of the throttle valve spool displacement to the step signal of the pilot valve spool is about 0.6s, and there is almost no overshoot , the control accuracy is 0.1mm. It effectively solves the problems of low production efficiency and low die life of the press caused by factors such as unstable extrusion speed and poor controllability.

Description of drawings

Fig. 1 is a structural schematic diagram of a water throttle valve and its accessories;

Explanation of the labels in Figure 1:

1. Valve seat 2. Removal cylinder 3. Valve core 4. Proportional oil cylinder

5. Piston rod 6. Valve rod displacement detection device 7. First control oil port

8. The second control oil port 9. Self-pressure water

Figure 2 is a structural diagram of electrical control;

Fig. 3 is a block diagram of the position control of the spool of the large-flow water throttle valve;

Fig. 4 is a hydraulic schematic diagram of the hydraulic drive system of the large-flow water throttle valve;

Explanation of the labels in Figure 4:

10. Throttling oil pump 11. DN40 pilot electro-hydraulic proportional flow valve

12. DN80 pilot electro-hydraulic proportional flow valve 13. High-pressure water pipe 14. Pressure gauge before the valve 15. DN40 water throttle valve 16. DN40 proportional oil cylinder 17. DN80 water throttle valve

18. DN80 proportional oil cylinder 19. Pressure gauge after valve 20. Main control distributor 21. Main working cylinder

22. Movable beam

Fig. 5 is a dynamic response curve diagram of the spool of the large-flow water throttle valve during the actual application process during the opening process.

Detailed ways

Example 1:

Fig. 2 has described the structure of the control system of the large-flow water throttle valve of the present invention, which includes the large-flow water throttle valve and its hydraulic drive system, state signal detection system, PLC control system, and host computer (touch screen) real-time monitoring system.

The operator can accurately set the opening degree of the throttle valve in the form of digital quantities on the monitoring system of the host computer (touch screen), and can continuously adjust it through the analog bar graph according to the actual situation. The displacement sensor detects the actual opening degree of the throttle valve (digital input) for real-time monitoring. After comparing the set opening degree with the actual opening degree through the PLC program, a signal difference is obtained, and the signal difference is input into the PID function block, and passed through the proportional amplifier. The flow and direction of the pilot electro-hydraulic proportional valve is controlled by the electrical signal, and the direction of the oil passing through the pilot valve is determined by the direction of the signal difference, and the oil flow of the pilot valve is determined by the size of the signal difference. The size of liquid flow, in Fig. 4, when pilot valve (12) (referring to have DN40 and DN80 two water valves in Fig. The valve is studied, and the DN40 water valve will not be introduced in detail.) When the electromagnet on the right is energized, the pilot control enters the proportional oil cylinder from the second control oil port (see 8 in attached drawing 1), so that the piston rod moves upward. The upper end of the spool of the water throttle valve is connected with the piston rod in the proportional servo cylinder through a thread connection, and the movement of the piston rod directly drives the movement of the spool of the water throttle valve. Therefore, when the electromagnet on the right side of the pilot valve is energized, the water section The spool of the throttle valve moves upward, the opening of the throttle valve increases, and the flow rate of the valve increases.

In this way, precise closed-loop control is realized on the position of the throttle valve spool, and its control block diagram is shown in Fig. 3 . [The displacement sensor is used to measure the valve core opening value]

The key technology of the present invention is how to obtain the input electric signal of the pilot electro-hydraulic proportional valve. It has been mentioned above that it is obtained by the difference between the actual opening degree and the given opening degree and then passed through the PID function block and the proportional amplifier, so for the PID function block Parameter setting is the key technology of the present invention. Due to the influence of the gravity of the throttle valve spool and other follow-up parts and the friction between the spool, piston rod and fittings, the throttle valve spool will The dynamic characteristics of the throttle valve will be different, that is, the system is an asymmetric dynamic system. According to this characteristic, different parameters are set in the control system for the opening and closing process of the throttle valve through experiments.

The value of the PID controller parameters is to provide short response time t _S and low overshoot M _S , but the corresponding positive and negative step responses are different, which is in line with normal logic. The question that arises from this is how to determine the moment when a controller parameter exchange is required. dYa(t)/dt (here Ya(t) refers to the actual opening of the throttle valve) can be a reference standard. However, due to the dead time of the dYa(t) response of the device, there will be a delay in the dYa(t)/dt response. Because of this, the transformation of the controller parameter value depends on the value of the previous parameter of the control system during the delay period. In this way, the uncertainty of the operation of the control system may be increased.

The change of Ya(t) directly affects the value of e(t) (e(t) is the difference between the set opening degree and the actual opening degree). Therefore, the performance of e(t) can be regarded as an indicator of the state of the control system, and when e(t) changes, the control parameters should also change. According to this idea, when e(t) is positive or negative and the values of each parameter are different, the algorithm of PID control can be expressed by the following formula:

$\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&tau;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\frac{\mathrm{<span\; class="notranslate">\; de</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

K _p (t)=K _p1 , K _i (τ)=K _i1 , K _d (t)=K _d1 , |e(t)≥0 (1)

K _p (t)=K _p2 , K _i (τ)=K _i2 , K _d (t)=K _d2 , |e(t)<0

Among them, K _P1 , K _i1 , K _d1 and K _P2 , K _i2 , K _d2 are proportional, integral and differential constants when e(t) is positive or negative. t ₀ is the initial point of calculation timing. When the sign of e(t) changes, the three constants of proportionality, integral and differential will also change respectively. Therefore, proportional, integral, and derivative are not really constants but change with time in equation (1).

In general, for e(t) to be positive or negative, the PID controller based on the formula (1) algorithm has different effects on the equipment, that is to say, this kind of PID controller is asymmetric.

The parameter adjustment process is as follows:

1) Set the dead zone value of the PID control function block to 0.05mm according to the system accuracy requirements.

2) Adopt the Ziegler-Nichols method, first set K _d1 =K _i1 =0, at this time the system is a PID controller, which is a proportional controller, by setting the opening value of the throttle valve in the monitoring system as greater than the actual opening degree of the throttle valve, even if e(t)>0, then increase the system proportional coefficient K until the system starts to oscillate, and record the proportional coefficient K at this time as Km ₁ , K _P1 , K _i1 , and K _d1 according to The following formula is calculated:

K _P1 = 0.6K _m1 $K_{d1}=\frac{K_{P1}\mathrm{\&pi;}}{4{\mathrm{\&omega;}}_m}$ $K_{i1}=\frac{K_{P1}{\mathrm{\&omega;}}_m}{\mathrm{\&pi;}}$

In the formula, Km ₁ is the K value when the system starts to oscillate; ω _m is the oscillation frequency. Through experiments, it is obtained that Km ₁ = 15, ω _m = 4πrad/s of the system when the throttle valve is opened, and then use the ZN equation [ie K _P =0.6K _m $K_d=\frac{K_P\mathrm{\&pi;}}{4{\mathrm{\&omega;}}_m}$ $K_i=\frac{K_P{\mathrm{\&omega;}}_m}{\mathrm{\&pi;}}$ 】Find the parameters. have to:

K _P1 =9, K _i1 =36, K _d1 =0.6;

Under the adjustment of this parameter, the actual response dynamic curve of the opening degree of the throttle valve read from the host computer is shown in Figure 5. It can be seen that the dynamic simulation curve of the displacement of the throttle valve core shows that the displacement of the throttle valve core has a great influence on the pilot valve. The response time of the spool step signal is about 0.6s, because the asymmetric PID control strategy is adopted in the actual system so that the system basically has no overshoot.

Similarly, the same parameter adjustment method is adopted in the closing process of the throttle valve, that is, using the Ziegler-Nichols experimental method (Jagger-Nichols method), first setting K _d2 =K _i2 =0, and by setting the throttle in the monitoring system The set opening value of the throttle valve is set to be smaller than the actual opening value of the throttle valve, even if e(t)<0, then increase the system proportional coefficient K until the system starts to oscillate, so that the system is in a negative step response, and then increase Increase the proportional coefficient until the system starts to oscillate, and record the proportional coefficients at this time as Km ₂ , K _P2 , K _i2 , and K _d2 parameters are calculated according to the following formula:

K _P2 = 0.6K _m2 $K_{d2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="K\; P"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">K</figure-callout>}}_P\mathrm{\&pi;}}{4{\mathrm{\&omega;}}_m}$ ${\mathrm{<figure-callout\; id="2"\; label="K\; i"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">K</figure-callout>}}_i=\frac{{\mathrm{<figure-callout\; id="2"\; label="K\; P"\; filenames="H2009100440142E00011.png"\; state="\{\{state\}\}">K</figure-callout>}}_P{\mathrm{\&omega;}}_m}{\mathrm{\&pi;}};$

Through experiments, the K value when the system begins to oscillate stably when the throttle valve is closed is K _m2 = 13, ω _m = 4πrad/s, and then according to the Ziegler-Nichols equation:

K _P2 =8, K _i2 =32, K _d2 =0.8.

Claims (2)

1. the control method of an opening of large flow throttle valve for water, it is characterized in that, position by piston rod in the input current control ratio servo-cylinder of regulating guide's electro-hydraulic proportional flow valve, piston rod and water throttling valve spool are fixedly connected, thereby directly drive the valve core movement of big flow water throttling valve by the motion of piston rod, the final accurate control that realizes the opening degree of big flow water throttling valve;

Adopt the PID control method of closed loop asymmetric in the control procedure, input quantity is given opening of large flow throttle valve for water value, feedback quantity is the opening of large flow throttle valve for water value of detected reality, the poor e (t) of the given opening of large flow throttle valve for water value and the opening of large flow throttle valve for water value of detected reality is input in the PID controller, and PID controller output current signal is given guide's electro-hydraulic proportional flow valve.

2. the control method of opening of large flow throttle valve for water according to claim 1 is characterized in that, described PID controller adopts asymmetry parameter, and concrete parameter tuning process is:

If K _P1, K _I1, K _D1And K _P2, K _I2, K _D2Be e (t) ratio when getting positive and negative respectively, integration, derivative constant;

K _P1, K _I1, K _D1Parameter tuning method is: the dead band value of setting PID control is 0.05mm, but adopts Ya Ge-Ni scholar's method, at first puts K _D1=K _I1=0, independent resize ratio COEFFICIENT K, this moment, controller just was a proportional controller, by in supervisory system, given opening of large flow throttle valve for water value being made as greater than throttling valve actual aperture degree value, even e (t)＞0, increase system proportional coefficient K then until system's starting oscillation, record scale-up factor K at this moment is Km ₁, K then _P1, K _I1, K _D1Parameter is calculated as follows:

K _P1=0.6K _M1

ω in the formula _M1Be K _P1, K _I1, K _D1Oscillation frequency during parameter tuning;

K _P2, K _I2, K _D2Parameter tuning method is: the dead band value of setting PID control is 0.05mm, but adopts Ya Ge-Ni scholar's method, at first puts K _D2=K _I2=0, this moment, controller was a proportional controller, by in supervisory system, the setting opening value of throttling valve being made as less than throttling valve actual aperture degree value, even e (t)＜0, increase system proportional coefficient K then until system's starting oscillation, make system be in negative step response, record scale-up factor at this moment is Km ₂, K _P2, K _I2, K _D2Parameter is calculated as follows:

K _P2=0.6K _M2

ω in the formula _M2Be K _P2, K _I2, K _D2Oscillation frequency during parameter tuning.

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