CN112415933B - Automatic air inlet adjusting auxiliary positioning device and method - Google Patents

Automatic air inlet adjusting auxiliary positioning device and method Download PDF

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Publication number
CN112415933B
CN112415933B CN202011358281.XA CN202011358281A CN112415933B CN 112415933 B CN112415933 B CN 112415933B CN 202011358281 A CN202011358281 A CN 202011358281A CN 112415933 B CN112415933 B CN 112415933B
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valve
air inlet
value
time
valve position
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CN112415933A (en
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姜家骥
江爱朋
陈云
张博
林峰
林伟伟
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Hangzhou Dianzi University
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
    • G05B19/0423—Input/output
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/20—Pc systems
    • G05B2219/24—Pc safety
    • G05B2219/24215—Scada supervisory control and data acquisition

Abstract

The invention provides an auxiliary positioning device and method for automatic intake adjustment. The intelligent microprocessor sends out control signals, and the stepping motor module receives corresponding signals to drive the device to move, so that the device is matched with a positioning algorithm. The positioning control algorithm can be optimally controlled through the opening of the automatic adjusting device, and the problem of inaccuracy caused by manual control in the prior art is solved. In addition, the rapidity of the control process can be improved by matching with a positioning algorithm, and the problem of callback caused by overshoot of the valve rod and the problem of oscillation caused by overhigh speed of the valve rod are avoided.

Description

Automatic air inlet adjusting auxiliary positioning device and method
Technical Field
The invention relates to an intelligent automatic instrument, in particular to an automatic air inlet adjusting and auxiliary positioning device and method.
Background
The valve positioner is the control core of the pneumatic control valve, is mainly used for improving the characteristics of the pneumatic control valve, increasing the control flexibility of the pneumatic control valve and improving the control speed and precision of the pneumatic control valve, and plays a decisive role in the pneumatic control valve and the whole control system. The dynamic and static characteristics of the pneumatic regulating valve are influenced by not only the static parameters such as stroke type, valve cylinder size, regulating valve installation angle and packing quality, but also dynamic parameters such as working load, air source pressure and ambient temperature. Thereby causing great influence on the control accuracy and possibly causing overshoot and oscillation phenomena. Therefore, how to develop a matching device and automatically control the air inflow makes the locator have good universality and high precision become additional importance.
At present, a throttle valve is arranged on an air pipeline of an air compressor and an intelligent valve positioner to control air inflow. However, the throttle valve has poor flow stability, and can only be used in a system with small load change or low requirement on speed control precision, and automatic control cannot be formed. In addition, foreign positioning algorithm matching devices only have devices for manually controlling the air inflow, but the effect is poor, and experience debugging is needed. Therefore, the domestic effort is increased to develop an automatic air inflow control device independently, the device rapidly occupies the global market share, and the foreign market no longer occupies the leading position in the field of the valve positioner for a long time.
Disclosure of Invention
The invention provides an auxiliary positioning device and method for automatic air inlet adjustment, aiming at the problems that the air inlet amount between an air compressor and a piezoelectric valve air inlet is insufficient in control precision and is not matched with a positioning algorithm.
An automatic air inlet adjusting and auxiliary positioning method specifically comprises the following steps:
step A1: connecting an automatic air inlet adjusting auxiliary positioning device with an air inlet port of a piezoelectric valve with an intelligent valve positioner arranged in a regulating valve, and setting the opening degree to be 45% -50%; user input of standard valve travel time tstandardMeanwhile, the intelligent microprocessor controls to enter a parameter self-setting stage to set the actual valve travel time tinit(ii) a If t isinit＞tstandardThe regulating valve is a big valve relative to a standard valve; t is tinit＜tstandardThe regulating valve is a small valve relative to the standard valve;
step A2: establishing a mathematical model of the travel time and the air inflow of the air inlet nozzle, and calculating the air inflow required to be adjusted by the adjusting valve; the method specifically comprises the following steps:
step C1: the system formed by the pipeline and the air inlet nozzle is equivalent to a convergent nozzle, the process of pneumatic flow through the air inlet nozzle is considered to be one-dimensional isentropic flow of ideal gas through the convergent nozzle, and an energy equation is established: dh + vdv ═ 0; where dh is the differential of the height at the inlet; v is the inlet flow rate in mm/s; dv is the differential of the inlet flow rate;
step C2: integrating the energy equation established in the step C1 to obtain:
Figure GDA0003236729040000021
wherein h is the height of the inlet and the unit is mm; h isa＝kRTa/(k-1)，haIs the height in the container, and the unit is mm; t isaIs the temperature in the container, and the unit is; r is the gas constant in units of J/(kg × K); k is a proportionality coefficient;
step C3: h is to beaSubstitution into
Figure GDA0003236729040000022
In the method, the following steps are obtained:
Figure GDA0003236729040000023
wherein, TcIs the inlet temperature in units of;
step C4: substituting the gas state equation P into the equation rho RT
Figure GDA0003236729040000024
In the method, the following steps are obtained:
Figure GDA0003236729040000025
wherein the pressure at the inlet is PcIn Pa; density at inlet is rhocIn units of g/cm3(ii) a Gas source pressure is PaIn Pa; air source density is rhoaIn units of g/cm3；
Step C5: for isentropic flow
Figure GDA0003236729040000026
Substitution into
Figure GDA0003236729040000027
In the method, the following steps are obtained:
Figure GDA0003236729040000031
step C6: the ideal gas has the following air inflow amount through the air inlet nozzle:
Figure GDA0003236729040000032
wherein S is the sectional area of the outlet in mm2；
Step C7: when the regulating valve is fully opened, the required amount of air intake or exhaust is the largest at the moment, and the longer the stroke time is, the more the amount of increase or decrease of the air in the cylinder is, so that the larger the pressure variation is; on the contrary, the shorter the stroke time is, the smaller the intake and exhaust quantities are, and the smaller the variation of the gas pressure in the cylinder of the regulating valve is; thus obtaining the output QmRelationship to travel time: qms＝Qmtstandard，Qmi＝Qmtinit(ii) a Wherein Q ismsAnd QmiThe air inflow required by the standard travel time and the setting travel time of the piezoelectric valve;
and step C8, adjusting the air inlet quantity required to be adjusted by the adjusting valve, wherein the air inlet quantity required to be adjusted is as follows: qm'＝|Qms-Qmi|；
Step A3: comparing a target valve value r (t) input by a user with a real-time valve value c (t), and entering a closed-loop control stage A4 of a positioning algorithm if the error is greater than the set precision; if the error is smaller than the set precision, the target position is reached;
step A4: feeding back the opening of the automatic adjusting device by the intelligent microprocessor according to the air inflow calculated in the step A2; the method specifically comprises the following steps:
step D1, define ε ═ β FSR, e1＝Sover1,e2＝Sover2The valve position error e (t) (r) (t) -c (t) divides the closed-loop control process into a coarse adjustment area, a fine adjustment area and a dead area, wherein t represents time, beta represents control precision, the default of the system leaving the factory adopts 0.5% precision, the value range of beta is 0-1, epsilon and e represent products1、e2Indicating a valve position, e (t) indicating a real-time error;
step D2: when the valve position is in the coarse adjustment area, Bang-Bang control is adopted, and the original opening degree is kept unchanged; when the valve position is in the fine adjustment area, the step D3 is carried out; when the valve position is in the dead zone, the valve position reaches the target position, and the closed-loop control algorithm is ended;
step D3: according to the required air inflow calculated in the step A2, the intelligent microprocessor sends out a corresponding adjusting signal; if the regulating valve is a big valve, increase
Figure GDA0003236729040000041
Opening degree; if the regulating valve is a small valve, then decrease
Figure GDA0003236729040000042
Opening degree; a stepping motor module in the flow regulating hand wheel receives a control signal of the intelligent microprocessor, and then the stepping motor drives the flow regulating hand wheel to rotate;
step D4: the rod core is tightly attached to the bottom of the push rod, the push rod can move along the axial direction through the flow adjusting hand wheel, the flow area between the air inlet cavity and the air outlet cavity is changed, namely the opening of the device can be adjusted, and the air inflow is automatically controlled; and the manual control of the device can be realized by manually rotating the flow adjusting hand wheel.
Further, the parameter self-tuning stage specifically includes the following processes:
step B1: determining a travel type; sending an exhaust signal to the piezoelectric valve, completely exhausting the gas in the cylinder, and recording a current valve position feedback value; sending an air inlet signal to the piezoelectric valve, and judging the change direction of the valve position feedback value after air inlet for 30-40 seconds; if the current valve position feedback value is smaller than the initial valve position feedback value, the valve position can be judged to be a positive stroke, otherwise, the valve position is a reverse stroke;
step B2: setting a valve stroke range FSR; sending an inflation instruction, recording the position as the top end position once the speed acquisition module detects that the speed of the valve rod is 0, and recording a corresponding AD value (the AD value represents a numerical value for converting an analog signal into a digital signal) Xtop(ii) a Sending an exhaust instruction, recording the position as a bottom end position once the speed acquisition module detects that the speed of the valve rod is 0, and recording a corresponding AD value Xbotton(ii) a Range of travel FSR ═ Xtop-Xbotton|；
Step B3: calculating the travel time tinit(ii) a If the type of the stroke is positive, the intelligent microprocessor is in XbottonSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t1(ii) a In this position the smart microprocessor sends out a reverse 100% PWM wave and when a valve stem speed of 0 is detected, the time is recorded as t2Time of flight tinit＝(t1+t2) 2; if the type of the journey is reverse journey, the intelligent microprocessor is in XtopSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t3(ii) a In this position the smart microprocessor sends out a reverse 100% PWM wave and when a valve stem speed of 0 is detected, the time is recorded as t4Time of flight tinit＝(t3+t4)/2；
Step B4: obtaining the AD value corresponding to the maximum overshoot of the inflation and exhaust stages; outputting 100% PWM wave to the switch type piezoelectric valve, sending an inflation instruction, adjusting the switch type piezoelectric valve to be in an inflation state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when detecting that the moving speed of the valve position reaches a maximum valueup1(ii) a And immediately sending a valve position holding instruction to the switch type piezoelectric valve, and recording the corresponding AD value S of the valve position at the moment in 10 seconds of delayup2Defining the AD value corresponding to the maximum overshoot of the inflation stage as Sover1＝|Sup1-Sup2L, |; sending an inflation instruction to the piezoelectric valve, immediately sending an exhaust instruction when the speed is detected to be equal to 0, adjusting the switch type piezoelectric valve to be in an exhaust state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when the speed of the valve position moving is detected to be maximumdown1(ii) a Immediately sending a valve position holding instruction (neither inflation nor exhaust) to the switch type piezoelectric valve, and recording the corresponding AD value S of the valve position at the time after 10 seconds of delaydown2Defining the maximum overshoot corresponding to AD value in the exhaust stage as Sover2＝|Sdown1-Sdown2|。
The automatic air inlet adjusting auxiliary positioning device comprises a main body, an air inlet nozzle, a flow adjusting hand wheel, a push rod, a rod core, a stainless steel spring, a stepping motor module, an air inlet cavity and an air outlet cavity; the push rod is arranged in the middle of the main body and divides the inner cavity of the main body into an air inlet cavity and an air outlet cavity; one end of the push rod is fixedly provided with a flow regulating hand wheel, and a stepping motor is arranged in the flow regulating hand wheel; the stepping motor drives the flow regulating hand wheel to rotate, so as to drive the push rod to move in the vertical direction; the other end of the push rod is provided with a rod core, the rod core is hollow and is used for conducting media between the air outlet cavity and the air inlet cavity, and when the push rod moves in the vertical direction, the rod core extends or shortens; the air inlet end of the air inlet cavity is provided with an air inlet nozzle; the bottom of the inner cavity of the main body is provided with a stainless steel spring at a position corresponding to the push rod.
The invention can optimally control the positioning control algorithm by automatically adjusting the opening of the device, and overcomes the inaccuracy problem caused by manual control in the prior art. In addition, the rapidity of the control process can be improved by matching with a positioning algorithm, and the problem of callback caused by overshoot of the valve rod and the problem of oscillation caused by overhigh speed of the valve rod are avoided.
Drawings
FIG. 1 is a schematic view of the internal structure of the apparatus of the present invention;
FIG. 2 is a schematic view of the flow of gas through the convergent nozzle.
FIG. 3 is a schematic of closed loop control of the regulator valve.
Detailed Description
The technical scheme of the present invention is explained in detail below with reference to the accompanying drawings:
as shown in fig. 1, an automatic air intake adjusting and positioning device comprises a main body 1, an air intake nozzle 6, a flow adjusting hand wheel 2, a push rod 3, a rod core 4, a stainless steel spring 5, a stepping motor module 9, an air intake cavity 8 and an air outlet cavity 7. The push rod 3 is arranged in the middle of the main body 1 and divides the inner cavity of the main body 1 into an air inlet cavity 8 and an air outlet cavity 7; one end (top) of the push rod 3 is fixedly provided with a flow regulating hand wheel 2, and a stepping motor 9 is arranged in the flow regulating hand wheel 2. The stepping motor 9 drives the flow regulating handwheel 2 to rotate, thereby driving the push rod 3 to move in the vertical direction; the other end (bottom end) of the push rod 3 is provided with a rod core 4, the rod core 4 is hollow and is used for conducting media between the air outlet cavity and the air inlet cavity, and when the push rod 3 moves in the vertical direction, the rod core 4 can be extended or shortened; the air inlet end of the air inlet cavity 8 is provided with an air inlet nozzle 6; the stainless steel spring 5 is arranged at the bottom of the inner cavity of the main body 1 and corresponds to the push rod, the stainless steel spring 5 is in an uncompressed state initially, and along with the extension and contraction of the rod core 4, the stainless steel spring 5 becomes a compressed state (such as the state of the stainless steel spring in fig. 1), so that the opening degree between the air outlet cavity 7 and the air inlet cavity 8 is changed, and finally the air inlet of the device gas from the air inlet nozzle 6 and the air inlet process of the main body 1 are realized. The device compares the setting travel time with the standard valve time input by a user through the parameter self-setting process of the intelligent microprocessor, and additionally establishes a mathematical model of the travel time and the air inflow at the opening of the device to determine the required size of the air inflow. The intelligent microprocessor sends out control signals, and the stepping motor module receives corresponding signals to drive the device to move, so that the device is matched with a positioning algorithm.
The automatic air inlet adjusting and auxiliary positioning method for the device specifically comprises the following steps:
step A1: the air inlet automatic adjusting auxiliary positioning device is connected with an air inlet port of a piezoelectric valve of which the adjusting valve is provided with an intelligent valve positioner, and the opening degree is set to be 45-50%. User input of standard valve travel time tstandardMeanwhile, the intelligent microprocessor controls to enter a parameter self-setting stage to set the actual valve travel time tinit. If t isinit＞tstandardThen the regulating valve is a large valve (relative to a standard valve); t is tinit＜tstandardThen the regulating valve is a small valve (as opposed to a standard valve).
The parameter self-tuning stage specifically comprises the following processes:
step B1: the type of trip is determined. Sending an exhaust signal to the piezoelectric valve, completely exhausting the gas in the cylinder, and recording a current valve position feedback value; and sending an air inlet signal to the piezoelectric valve, and judging the change direction of the valve position feedback value after air inlet for 30-40 seconds. If the current valve position feedback value is smaller than the initial valve position feedback value, the valve position can be judged to be a positive stroke, otherwise, the valve position is a reverse stroke.
Step B2: and adjusting the valve stroke range FSR. Sending an inflation instruction, once a speed acquisition moduleWhen the valve rod speed is detected to be 0, the position is recorded as the top end position, and the corresponding AD value (AD value represents the value of converting an analog signal into a digital signal) Xtop(ii) a Sending an exhaust instruction, recording the position as a bottom end position once the speed acquisition module detects that the speed of the valve rod is 0, and recording a corresponding AD value Xbotton. Range of travel FSR ═ Xtop-Xbotton|。
Step B3: calculating the travel time tinit. If the type of the stroke is positive, the intelligent microprocessor is in XbottonSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t1(ii) a In this position the smart microprocessor sends out a reverse 100% PWM wave and when a valve stem speed of 0 is detected, the time is recorded as t2Time of flight tinit＝(t1+t2)/2. If the type of the journey is reverse journey, the intelligent microprocessor is in XtopSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t3(ii) a In this position the smart microprocessor sends out a reverse 100% PWM wave and when a valve stem speed of 0 is detected, the time is recorded as t4Time of flight tinit＝(t3+t4)/2。
Step B4: and obtaining the AD value corresponding to the maximum overshoot of the inflation and exhaust stages. Outputting 100% PWM wave to the switch type piezoelectric valve, sending an inflation instruction, adjusting the switch type piezoelectric valve to be in an inflation state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when detecting that the moving speed of the valve position reaches a maximum valueup1(ii) a And immediately sending a valve position holding instruction to the switch type piezoelectric valve, and recording the corresponding AD value S of the valve position at the moment in 10 seconds of delayup2Defining the AD value corresponding to the maximum overshoot of the inflation stage as Sover1＝|Sup1-Sup2L. Sending an inflation instruction to the piezoelectric valve, immediately sending an exhaust instruction when the speed is detected to be equal to 0, adjusting the switch type piezoelectric valve to be in an exhaust state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when the speed of the valve position moving is detected to be maximumdown1(ii) a And immediately sends a valve position holding instruction (no charging) to the switch type piezoelectric valveGas is not exhausted), the time delay is 10 seconds, and the corresponding AD value S of the valve position at the time is recordeddown2Defining the maximum overshoot corresponding to AD value in the exhaust stage as Sover2＝|Sdown1-Sdown2|。
Step A2: and establishing a mathematical model of the travel time and the air inflow of the air inlet nozzle 6, and calculating the air inflow required to be adjusted by the adjusting valve.
The mathematical modeling stage specifically comprises the following process implementation:
step C1: since the gas is compressible, the system of lines and nozzles 6 is calculated as equivalent to a convergent nozzle, taking the pneumatic flow through the nozzles 6 as an ideal one-dimensional isentropic flow of gas through the convergent nozzle, as shown in fig. 2, and establishing the energy equation: dh + vdv ═ 0; where dh is the differential of the height at the inlet; v is the inlet flow rate in mm/s; dv is the differential of the inlet flow rate.
Step C2: after integrating the energy equation, the following results are obtained:
Figure GDA0003236729040000081
wherein h is the height of the inlet and the unit is mm; h isa＝kRTa/(k-1)，haIs the height in the container, and the unit is mm; t isaIs the temperature in the container, and the unit is; r is the gas constant in units of J/(kg × K); k is a scaling factor.
Step C3: h is to beaSubstitution into
Figure GDA0003236729040000091
In the method, the following steps are obtained:
Figure GDA0003236729040000092
wherein, TcThe temperature at the inlet is given in degrees Celsius.
Step C4: substituting the gas state equation P into the equation rho RT
Figure GDA0003236729040000093
In the method, the following steps are obtained:
Figure GDA0003236729040000094
wherein the pressure at the inlet is PcIn Pa; density at inlet is rhocIn units of g/cm3(ii) a Gas source pressure is PaIn Pa; air source density is rhoaIn units of g/cm3。
Step C5: for isentropic flow
Figure GDA0003236729040000095
Substitution into
Figure GDA0003236729040000096
In the method, the following steps are obtained:
Figure GDA0003236729040000097
step C6: the ideal air flow through the air inlet nozzle 6 is as follows:
Figure GDA0003236729040000098
wherein S is the sectional area of the outlet in mm2。
Step C7: when the adjustment valve is fully opened, the required amount of intake or exhaust is the largest, and the longer the stroke time is, the more the amount of increase or decrease in the gas in the cylinder is, and the larger the amount of change in the pressure is. Conversely, the shorter the stroke time, the smaller the intake and exhaust amounts, and the smaller the amount of change in the gas pressure in the regulator valve cylinder. Thus obtaining the output QmRelationship to travel time: qms＝Qmtstandard，Qmi＝Qmtinit(ii) a Wherein Q ismsAnd QmiAnd the air inflow is required for the standard stroke time and the setting stroke time of the piezoelectric valve.
And step C8, adjusting the air inlet quantity required to be adjusted by the adjusting valve, wherein the air inlet quantity required to be adjusted is as follows: qm'＝|Qms-Qmi|。
Step A3: and (4) comparing the target valve value r (t) input by the user with the real-time valve value c (t), and entering a closed-loop control stage A4 of the positioning algorithm if the error is greater than the set precision. If the error is less than the set accuracy, the target position is reached.
Step A4: the opening degree of the automatic adjusting device is fed back by the intelligent microprocessor according to the air inflow calculated in the step A2. The method specifically comprises the following steps:
step D1, define ε ═ β FSR, e1＝Sover1,e2＝Sover2The valve position error e (t) (r) (t) -c (t) divides the closed-loop control process into a coarse adjustment area, a fine adjustment area and a dead area, wherein t represents time, beta represents control precision, the default of the system leaving the factory adopts 0.5% precision, the value range of beta is 0-1, epsilon and e represent products1、e2Indicating the valve position, e (t) indicating the real time error, as shown in fig. 3.
Step D2: when the valve position is in the coarse adjustment area, Bang-Bang control is adopted, and the original opening degree is kept unchanged; when the valve position is in the fine adjustment area, the step D3 is carried out; and when the valve position is in the dead zone, the valve position reaches the target position, and the closed-loop control algorithm is ended.
Step D3: according to the required air inflow calculated in the step A2, the intelligent microprocessor sends out a corresponding adjusting signal. If the regulating valve is a big valve, increase
Figure GDA0003236729040000101
Opening degree; if the regulating valve is a small valve, then decrease
Figure GDA0003236729040000102
The opening degree. A stepping motor module 9 in the flow regulating hand wheel receives a control signal of the intelligent microprocessor, and then the stepping motor 9 drives the flow regulating hand wheel 2 to rotate.
Step D4: the rod core 4 is tightly attached to the bottom of the push rod, the push rod 3 can move axially through the flow adjusting hand wheel 2, the flow area between the air inlet cavity 8 and the air outlet cavity 7 is changed, the opening of the device can be adjusted, and the air inflow is automatically controlled.
Step D5: the flow regulating handwheel 2 is manually rotated, and the manual control of the device can be realized.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and is not intended to limit the practice of the invention to these embodiments. For those skilled in the art to which the invention pertains, several simple deductions or substitutions may be made without departing from the inventive concept, which should be construed as falling within the scope of the present invention.

Claims (3)

1. An automatic air inlet adjusting and auxiliary positioning method specifically comprises the following steps:
step A1: connecting an automatic air inlet adjusting auxiliary positioning device with an air inlet port of a piezoelectric valve with an intelligent valve positioner arranged in a regulating valve, and setting the opening degree to be 45% -50%; user input of standard valve travel time tstandardMeanwhile, the intelligent microprocessor controls to enter a parameter self-setting stage to set the actual valve travel time tinit(ii) a If t isinit＞tstandardThe regulating valve is a big valve relative to a standard valve; t is tinit＜tstandardThe regulating valve is a small valve relative to the standard valve;
step A2: establishing a mathematical model of the travel time and the air inflow of the air inlet nozzle, and calculating the air inflow required to be adjusted by the adjusting valve; the method specifically comprises the following steps:
step C1: the system formed by the pipeline and the air inlet nozzle is equivalent to a convergent nozzle, the process of pneumatic flow through the air inlet nozzle is considered to be one-dimensional isentropic flow of ideal gas through the convergent nozzle, and an energy equation is established: dh + vdv ═ 0; where dh is the differential of the height at the inlet; v is the inlet flow rate in mm/s; dv is the differential of the inlet flow rate;
step C2: integrating the energy equation established in the step C1 to obtain:
Figure FDA0003236729030000011
wherein h is the height of the inlet and the unit is mm; h isa＝kRTa/(k-1)，haIs the height in the container, and the unit is mm; t isaIs the temperature in the container, and the unit is; r is the gas constant in units of J/(kg × K); k is a proportionality coefficient;
step C3: h is to beaSubstitution into
Figure FDA0003236729030000012
In the method, the following steps are obtained:
Figure FDA0003236729030000013
wherein, TcIs the inlet temperature in units of;
step C4: substituting the gas state equation P into the equation rho RT
Figure FDA0003236729030000014
In the method, the following steps are obtained:
Figure FDA0003236729030000015
wherein the pressure at the inlet is PcIn Pa; density at inlet is rhocIn units of g/cm3(ii) a Gas source pressure is PaIn Pa; air source density is rhoaIn units of g/cm3；
Step C5: for isentropic flow
Figure FDA0003236729030000021
Substitution into
Figure FDA0003236729030000022
In the method, the following steps are obtained:
Figure FDA0003236729030000023
step C6: the ideal gas has the following air inflow amount through the air inlet nozzle:
Figure FDA0003236729030000024
wherein S is the sectional area of the outlet in mm2；
Step C7: when the regulating valve is fully opened, the required amount of air intake or exhaust is the largest at the moment, and the longer the stroke time is, the more the amount of increase or decrease of the air in the cylinder is, so that the larger the pressure variation is; conversely, the strokeThe shorter the time is, the smaller the intake and exhaust amounts are, and the smaller the variation amount of the gas pressure in the cylinder of the regulator valve is; thus obtaining the output QmRelationship to travel time: qms＝Qmtstandard，Qmi＝Qmtinit(ii) a Wherein Q ismsAnd QmiThe air inflow required by the standard travel time and the setting travel time of the piezoelectric valve;
and step C8, adjusting the air inlet quantity required to be adjusted by the adjusting valve, wherein the air inlet quantity required to be adjusted is as follows: qm'＝|Qms-Qmi|；
Step A3: comparing a target valve value r (t) input by a user with a real-time valve value c (t), and entering a closed-loop control stage A4 of a positioning algorithm if the error is greater than the set precision; if the error is smaller than the set precision, the target position is reached;
step A4: feeding back the opening of the automatic adjusting device by the intelligent microprocessor according to the air inflow calculated in the step A2; the method specifically comprises the following steps:
step D1, define ε ═ β FSR, e1＝Sover1,e2＝Sover2The valve position error e (t) (r) (t) -c (t) divides the closed-loop control process into a coarse adjustment area, a fine adjustment area and a dead area, wherein t represents time, beta represents control precision, the default of the system leaving the factory adopts 0.5% precision, the value range of beta is 0-1, epsilon and e represent products1、e2Indicating a valve position, e (t) indicating a real-time error; FSR is the range of travel, Sover1For the AD value, S, corresponding to the maximum overshoot of the inflation phaseover2The maximum overshoot corresponds to the AD value in the exhaust stage;
step D2: when the valve position is in the coarse adjustment area, Bang-Bang control is adopted, and the original opening degree is kept unchanged; when the valve position is in the fine adjustment area, the step D3 is carried out; when the valve position is in the dead zone, the valve position reaches the target position, and the closed-loop control algorithm is ended;
step D3: according to the required air inflow calculated in the step A2, the intelligent microprocessor sends out a corresponding adjusting signal; if the regulating valve is a big valve, increase
Figure FDA0003236729030000031
Opening degree; if the regulating valve is a small valve, then decrease
Figure FDA0003236729030000032
Opening degree; a stepping motor module in the flow regulating hand wheel receives a control signal of the intelligent microprocessor, and then the stepping motor drives the flow regulating hand wheel to rotate;
step D4: the rod core is tightly attached to the bottom of the push rod, the push rod can move along the axial direction through the flow adjusting hand wheel, the flow area between the air inlet cavity and the air outlet cavity is changed, namely the opening of the device can be adjusted, and the air inflow is automatically controlled; and the manual control of the device can be realized by manually rotating the flow adjusting hand wheel.
2. The automatic air intake adjustment auxiliary positioning method according to claim 1, characterized in that: the parameter self-tuning stage specifically comprises the following processes:
step B1: determining a travel type; sending an exhaust signal to the piezoelectric valve, completely exhausting the gas in the cylinder, and recording a current valve position feedback value; sending an air inlet signal to the piezoelectric valve, and judging the change direction of the valve position feedback value after air inlet for 30-40 seconds; if the current valve position feedback value is smaller than the initial valve position feedback value, the valve position can be judged to be a positive stroke, otherwise, the valve position is a reverse stroke;
step B2: setting a valve stroke range FSR; sending an inflation instruction, recording the position as the top end position once the speed acquisition module detects that the speed of the valve rod is 0, and recording the corresponding AD value Xtop(ii) a Sending an exhaust instruction, recording the position as a bottom end position once the speed acquisition module detects that the speed of the valve rod is 0, and recording a corresponding AD value Xbotton(ii) a Range of travel FSR ═ Xtop-Xbotton|；
Step B3: calculating the travel time tinit(ii) a If the type of the stroke is positive, the intelligent microprocessor is in XbottonSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t1(ii) a In this position the smart microprocessor sends out an inverse 100% PWM wave when a valve stem speed of 0 is detectedRecording the time as t2Time of flight tinit＝(t1+t2) 2; if the type of the journey is reverse journey, the intelligent microprocessor is in XtopSends out a positive 100% PWM wave, and when the valve rod speed is detected to be 0, records the time as t3(ii) a In this position the smart microprocessor sends out a reverse 100% PWM wave and when a valve stem speed of 0 is detected, the time is recorded as t4Time of flight tinit＝(t3+t4)/2；
Step B4: obtaining the AD value corresponding to the maximum overshoot of the inflation and exhaust stages; outputting 100% PWM wave to the switch type piezoelectric valve, sending an inflation instruction, adjusting the switch type piezoelectric valve to be in an inflation state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when detecting that the moving speed of the valve position reaches a maximum valueup1(ii) a And immediately sending a valve position holding instruction to the switch type piezoelectric valve, and recording the corresponding AD value S of the valve position at the moment in 10 seconds of delayup2Defining the AD value corresponding to the maximum overshoot of the inflation stage as Sover1＝|Sup1-Sup2L, |; sending an inflation instruction to the piezoelectric valve, immediately sending an exhaust instruction when the speed is detected to be equal to 0, adjusting the switch type piezoelectric valve to be in an exhaust state, acquiring a feedback valve position in real time, and recording an AD value corresponding to the valve position as S when the speed of the valve position moving is detected to be maximumdown1(ii) a And immediately sending a valve position holding instruction to the switch type piezoelectric valve, and recording the corresponding AD value S of the valve position at the moment in 10 seconds of delaydown2Defining the maximum overshoot corresponding to AD value in the exhaust stage as Sover2＝|Sdown1-Sdown2|。
3. The automatic air intake adjustment auxiliary positioning method according to claim 1, characterized in that: the automatic air inlet adjusting auxiliary positioning device comprises a main body, an air inlet nozzle, a flow adjusting hand wheel, a push rod, a rod core, a stainless steel spring, a stepping motor module, an air inlet cavity and an air outlet cavity; the push rod is arranged in the middle of the main body and divides the inner cavity of the main body into an air inlet cavity and an air outlet cavity; one end of the push rod is fixedly provided with a flow regulating hand wheel, and a stepping motor is arranged in the flow regulating hand wheel; the stepping motor drives the flow regulating hand wheel to rotate, so as to drive the push rod to move in the vertical direction; the other end of the push rod is provided with a rod core, the rod core is hollow and is used for conducting media between the air outlet cavity and the air inlet cavity, and when the push rod moves in the vertical direction, the rod core extends or shortens; the air inlet end of the air inlet cavity is provided with an air inlet nozzle; the bottom of the inner cavity of the main body is provided with a stainless steel spring at a position corresponding to the push rod.
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