SU769489A1 - Variable-structure pneumatic regulator - Google Patents

Description

The invention relates to automation and can be applied in automatic control systems of technological processes in chemistry, petrochemistry, oil refining and other industries.

Known pneumatic regulator with a variable structure containing connected to the input channels of the regulator "Parameter" and "Tasks" is proportional. block and the block forming the switching function [1].

The closest in technical essence ικ invention is a pneumatic regulator with a variable structure [2], containing a proportional unit consisting of series-connected membrane comparison elements and a relay, whose nozzles are connected through variable chokes to a constant multiplication element, the output of which is connected to an output amplifier power, and a block for generating a switching function, consisting of sequentially connected first comparison element, OR element, and second element compared oia, the other input. which is connected to. the output of the preliminary link. The output of the second comparison element is connected> to another input of the membrane relay of the proportional unit.

The purpose of the invention is to improve the accuracy of the controller.

This goal is achieved by the fact that the pulse generator and the valve are installed in the switching function forming unit. The output of the pulse generator is connected to the control chamber of the valve, the flow chamber of which is connected to the ικ-output of the OR element, and the nozzle of this valve is connected to the input of the pre-opening unit.

In FIG. 1 shows a schematic diagram of the proposed controller; in FIG. 2 - curve changes the error of the error (a), the output signal of the OR element 9 (b) and the output signal of the valve 10 (g).

The controller contains a proportional unit, consisting of a comparison element 1, relay 2, variable chokes 3, 4, a multiplication element by a constant coefficient 5, a power amplifier 6, a setter 7; block-function formation-switching (BFFP), consisting of a comparison element 8, an OR element 9, a valve 10 and a pre-link, including a comparison element 11, a variable choke 12, a comparison element 13, a pulse generator 30, which consists of a comparison element 14, variable choke 15 and capacitance 16.

The regulator is assembled on the elements of industrial pneumatic automation USEPPA.

The regulator operates as follows.

Signals proportional to the given D ₃ and current P „values (of an adjustable value, as well as the reference pressure P _o .

The output of the comparison element 1 produces a signal

Rvykh., = Рз-Р „+ Р ₀ This signal, passing through the relay 2 and depending on the regulation state (S) through the variable choke 3 or 4, enters the negative chamber of element 5.

At the output of this element, the regulatory effect of the type

_The P s = Pout. ₅ = 4 ”(P _n -L,) p _o , (1) (/ <1 for S> 0 where Ψ = <„ _s (D ₂ for S <0;

A * out - the output signal of the regulator,

Ψ - gain of the regulator (Κι, Κ ₂ ),

S - switching function

FR _p -R ₃ !

S - sign Тпр --- БФФП works as follows.

Rvykh., And Rvykh., = P _n - Pz + Po simultaneously arrive at the inputs of the OR element 9, at the output of which the error error module with delay is determined due to the small values of p _p,

7 _pr —— the pre-link does not provide clear and reliable switching. To eliminate this drawback, the signal (P _n - -P ₃₎ using the pulse signal generator and the valve is formed as a (D _n - Ps) * (see Figure 2, g, Pout _{1 °...)} · When hopping allowed urovDR _P —P _{3 of the} signal, the value 7 _PR - & --- gets its limit values (1 or 0).

Then the quantized signal according to the level (Р „—Р ₃ ) * is fed to the inputs of the pre-link, which always ensures accurate and reliable switching of the gain of the regulator.

The duration of the cycles is set by selecting the conductivity of the pneumatic resistance 15 depending on the inertia of the control object.

Estimate the performance of the device. Due to the lack of capacitance in the pre-blocking unit, the signal changes in the plus camera of the comparison element and behind the throttled one are in relation

(2) ³⁰ where T _p is the “discharge” time constant;

G _DNF time constant of "differentiation", numerically equal to the time constant of the link "choke - camera".

QR ~ ^{1 00} On the other hand, 1discharge time tp = 3-4 Tp or tp = 3-4 Gd.zf. (3)

Rvykh., -; Р _П - Рз + To · 40 ✓

This signal through the valve 10 enters the inputs of the comparison element 41 of the preliminary link, where the signal is processed p p _ p p - T ^{and p 3} I P__P; _L_ P * EXIT. l - ¹ pr “'P * 3 ¹ o ·

The output _{DV's. n of the} element of comparison of the link (the anticipation on the element of comparison ^{50 is} compared with the signal P _YO x., where the sign of the switching function is determined

The area of normal modes of the pre-link is estimated by the relation (Dynamic characteristics of controllers built on USEPPA, A. I. Birman, A. A. Tagaevskaya, L. O. Khvilevitsky, in the book “Systems and Devices. Pneumatic Automation.” Edited by A. A Tal, Nauka, 1969, pp. 288-1291).

Leaf ^ gr <1.2. (4)

Taking into account formulas (3), (4), we have? P <3-4L? = 3.6- = 4.812l7 = 0.574-0.767, (5) cr>. gr d Pπ Pz /

D out. Sign T _Ave.

Next, P _ΒΒΙΧ . ₁₃ enters the control chamber of relay 2 and>, depending on .S, it turns on a variable choke 3 or 4. When the input signal P _p changes from the given d: P - PI, the value of P ₃ depends on 7 _P p —— ϊ-τ; - - ^v dt should switch. However, when controlling inertial objects, where 7 is the period of change of the input signal.

For clear recognition. moment of transition through the extremum with an error in the comparison element. 0.5% and an input signal amplitude of not more than 10% is required, 60 so that the pulse repetition period of 7 _{G of the} generator is at least 0.05 of the period of change of the input signal, i.e. 7 _G > 0.05 7..

Since, for physical reasons, 65, the discharge time should be longer or ω769489 is measurable with the period of pulse repetition, then> 0.05 T. (6)

Conditions (5) and (6) are not contradictory and, therefore, the goal is achieved.

This operation of the BFFP provides a clear and reliable switching of the controller parameters and thereby improves the quality of regulation of inertial objects with delay.

Laboratory tests of the regulator showed its performance.

Claims (2)

Comparison element 14, variable throttle 15 and capacity M. The regulator is assembled on industrial elements (pneumatic automation USEPA. The regulator works as follows. Signals proportional to a given P- and current RP value (adjustable value, as well as about-pore pressure Po. At the output of the element. Comparison 1, a signal is received - p - p pip out - 3 p i 0 This signal passes through the cut of relay 2 and, depending on the control status (5), through variable choke 3 or 4 nocTyinaeT in the minus chamber of element 5. At the output of this element is processed regulating effect of the type of Pts. ROUT., - (Pn,) - P ",. (at Lr5.0; FIRED - output signal of the generator, - the gain of the regulator (s / Cr), S - function „dPn-Ps / S signTnp .. BFPP works in the following Way. Explicit., and P out. 8 RP - RZ + simultaneously arrive at the inputs of the element OR 9, at the output of which the error error module p pip out. , h t 0. The signal through valve 10 is fed to the inputs of the comparison element i // of the preemptive link, where the 4fi signal is processed. -A + / NI-RZ -L, P - t OYX. 1 f P; The output signal of the Expression. Of the comparison element of the 1drug link on the comparison element 13 is compared with the signal PBHX.J, where the sign of the switching function djPn-P, 5 I out is determined. T dt Then P out ,, enters the control chamber of relay 2 and depending on degree 5 includes a variable choke 3 or 4. When the input signal changes, I „from the given p p / RZ value depending on Tpr--, - there must be a switch. However, when -regulating inertial objects with a delay due to the smallness of the values of j p p the pre-link does not provide a clear and reliable switching. To eliminate this drawback, a signal (P ,, - -RZ) with the help of a pulse signal generator and a valve is formed in the form (Yap-Yaz) (see Fig. 2, d, Expression, "). With a jump-like change in the allowed levels of the Y-Y signal, the value Y pr - f gets its limiting values (1 or 0). Then, the quantized level signal (Pn-RE) pushes the pins of the pitch link, which always ensures accurate and reliable switching of the controller gain factors. The duration of the cycles is determined by choosing the conductivity of the pneumatic resistance 15 IB depending on the inertia of the control object. Evaluate the performance of the device. Due to the lack of capacitance in the preprocessing unit, the rate of change of signals in the positive chamber of the reference element and behind the choked one is in relation to Tf dff (2) where Gr is a constant "discharge time"; the time of differentiation is numerically equal (the CONSTANT time of the link "throttle is the camera. On the other hand, the time is" discharge p 3-4Gy or ,,; f. (3) The region of normal modes of the link of the anticipation is estimated by built on USEPA, A.I. Birman, A.A. Tagaevok, L.O. Khvilevitsky, in the book "Systems and devices of pneumatic automation. Edited by A.A. Tal," Science, 1969, p. 288 -1291) .1,2. (4) Taking into account formula (3), (4) we have pz ,, 812l ,, 767, (5) where T is the period of change of the input signal. For a clear recognition, The transition point through the extremum with an element error of 0.5% and an input signal amplitude of no more than 10% requires that the pulse period T of the generator be at least 0.05 times the input signal change period, i.e., 05T. Since, for physical reasons, the discharge should be greater or commensurate with the period of following the impulses, then 05. The conditions (5) and (6) are not 1 contradiction and, therefore, the goal is achieved. This operation of the BFPT provides a clear and reliable: switching the parameters of the controller and thereby improves the quality of regulation of inertial objects with delay. Laboratory tests of the regulator had his performance. The invention includes a variable structure pneumatic controller containing a rotary unit consisting of a series-connected comparison membrane element and a relay nozzle (which is connected via variable chokes to a constant multiplication element, the output of which is connected With an output power amplifier and -the switching function forming unit consisting of the first comparison element connected in series, the OR element and the second comparison element, the other input of which is connected to the output A second pre-level link, the output of the second Comparison element, is connected to another input of the membrane relay of the proportional unit, which is such that, in order to improve the accuracy of the regulator, the pulse generator and the valve are installed in the switching function. The output of the generator of pulse signals is connected to the control chamber of the valve, (the flow chamber of which is connected to the output of the OR element, and the salt of this valve is connected to the input of the preliminary link. Sources of information (Taken into account during the examination: 1. Author's certificate of the USSR No. 582494; G 05 V 11/58, 1976. 2. Shigin EK, et al. Pneumatic proportional-integral regulator with variable structure. Pneumatic automation, M., "Science, 1972, p. 122 (prototyl). P L, g f ff / f plgshpppp ( to ABOUT 2