RU2302029C1 - Controller with a relay characteristic - Google Patents

Abstract

FIELD: automation, possible use in systems for controlling dynamic objects in chemical industry, power engineering, tool-making industry.

SUBSTANCE: device contains extreme point indicator, relay block, adder, switch, zero-organ and is a two-positional controller with alternating hysteresis, value of which linearly depends on auto-oscillation amplitude of controlled coordinate. Special feature of the controller is that hysteresis in it may be either positive or negative.

EFFECT: expanded functional capabilities, possible measurement of amplitude and frequency of auto-oscillations in broad range during usage of the device in control systems.

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Description

The invention relates to the field of automatic control and can be used to control dynamic objects in the chemical industry, heat engineering, instrumentation.

Regulators with a relay characteristic (relay regulators) are widely used in engineering (see, for example, Besekrsky V.A., Popov E.P. Theory of automatic control. St. Petersburg: Profession, 2003. - S.491-501, 533-542 ) Also known are regulators with relay characteristics operating on an on-off basis and having positive or negative hysteresis (see, for example, AS USSR No. 631864, No. 1418648, No. 1585778). The closest in technical essence to the claimed device is a regulator with a relay characteristic for A. with. USSR No. 631864. Publ. BI 1978, No. 40.

The prototype controller contains an extreme indicator, a zero-organ, a relay block and an adder and is a two-position relay controller with negative hysteresis, the value of which is linearly dependent on the amplitude of the self-oscillations. Its peculiarity lies in the fact that the controller switches either ahead of time (with "non-profit") with respect to the signal at the second input of the controller (the signal of the "task"), or at the moment of equality of the signals at the first and second inputs of the controller (the "variable" and "tasks"). The switching times are determined by the setting of the controller. As analysis shows, the inverse value of the complex gain of this regulator, obtained by the method of harmonic linearization, is the beam that leaves the origin in the second quadrant of the complex plane, which is able to rotate 90 degrees when changing the settings of the regulator (only in the second quadrant).

The controller equation (control law implemented in the prototype controller) has the form

u = B sign (M),

where M = (1-k) X _H + kX _e -X,

k is a constant coefficient less than one (0≤k <1),

X _E - extreme values of the adjustable coordinate, equal to its maximum or minimum,

X _N - task (specified nominal value of the adjustable coordinate X (variable)),

sign is a sign function equal to +1 or -1 depending on the sign of the function M,

In - the magnitude of the control action ("shelf" of the relay).

At k = 0, the prototype regulator turns into a regulator of the "ideal relay" type, in other cases it is a regulator with negative hysteresis.

There is also a class of on-off relay controllers with positive hysteresis, the control switching in which always occurs with a delay relative to the specified nominal value of the adjustable coordinate, and its dynamic characteristic (inverse value of the complex gain with a minus sign) is located in the third quadrant of the complex plane.

The disadvantage of the prototype controller (and relay controllers with positive hysteresis) lies in its non-universality - it cannot be reconfigured, remaining within the same design, and provide control implementation both ahead of time and with delay of switching relative to the task, which narrows the scope of its application ..

The technical result of the invention is the expansion of the functionality of the regulator, which consists in its universalization, the ability to function as a regulator with positive or negative hysteresis.

The technical result is achieved in that in a controller with a relay characteristic, comprising a relay block, a zero-organ, an adder, an extreme indicator, the outputs of which are connected to the inputs of the relay unit, and the output of the relay unit is connected to the first input of the adder, the first input of the controller is connected to the indicator input extrema and the first input of the zero-organ, and the second input of the adder is connected to the second input of the controller, an additional switch is introduced, the first information input of which is connected to the output of the adder, the second information This input is connected to the second input of the regulator, and the control input is connected to the third input of the regulator, the first output of the switch is connected to the first direct input of the zero organ, the second output of the switch is connected to the second inverse input of the zero organ, the third output of the switch is connected to the first and second direct inputs of the zero-organ.

The controller is shown in figure 1, which presents its block diagram; figure 2 illustrates an example of a specific implementation of the controller on the pneumatic elements USEPA,

The controller (figure 1) contains an indicator of extrema 1, zero-organ 2, relay block 3, adder 4, switch 5, repeaters-amplifiers 6, 7 (see figure 3), pneumatic capacity 8, relay 9, element 10 comparison, elements 11, 12 for storing maximum and minimum, relays 13, 14, 15, X - adjustable coordinate, X _H - reference signal, U - controller output, Z - discrete control signal "0" or "1" that changes the state of switch 5.

The first input of the controller (variable - X) is connected to the inputs of the extremum indicator 1 and the first input (inverse) of the zero-organ 2, and the second input of the controller X _H is connected to the first information input of the switch 5 and the second input of the adder 4, the output of which is connected to the second information the input of the switch 5, the third control input of which is connected to the third input of the controller (Z), the outputs of the extrema indicator are connected to the inputs of the relay unit 3, the output of which is connected to the first input of the adder 4, the first output of the switch is connected to the first direct input of the zero-organ 2, the second output of the switch 5 is connected to the second inverse input of the zero-organ 2, the third output of the switch 5 is connected to the first and second direct inputs of the zero-organ 2. and the output of the zero-organ 2 is connected to the output of the regulator (U) .

Such a combination of elements allows you to implement the following control law:

Where

which allows in one design to implement control laws with both negative and positive variable hysteresis, which achieves the claimed technical result.

Consider the operation of individual elements of the controller and the device as a whole.

The indicator of 1 extremes (A. S. 482757 BI 1975, No. 32) works as follows. When changing the adjustable coordinate, for example, in the direction of decreasing, at the output of element 11, the signal X _{max is} stored at X <(X _max + a), where a is the shift value that can be adjusted in storage element 11, element 10 is activated and deactivates memory element 11, having closed the upper contact of the relay 9, and the output of the memory element 12 through another contact of the relay 9 is connected to the second input of the comparison element 10. With a further decrease in the signal, the output signal of the comparison element 10 does not change. With an increase in the input signal at the output of the memory element 12, X _{min is} remembered, the comparison element 10 assumes the initial position, and the second input of the comparison element 10 is again connected to the output of the maximum memory element 11. Repeaters 6 and 7 provide galvanic isolation of the signals X _max , X _min . Pneumatic capacity 8 ensures the conservation of signals when switching relays 9.

Relay block 3 (two-pin relay) provides switching X _max , X _min on command from the output of the comparison element 10 to the input of the adder 4. The latter is made according to the circuit of the throttle adder. Its output is equal to (1-k) X _Н + kX _Э , where k = d / (d + b), d and b are the conductivities of the adders chokes, Х _Н and Х _Э are the signals acting on the inputs of the adder 4.

The switch 5 is built using three relays 13, 14, 15 and operates as follows. While the signal Z = 0, the direct output of the relay 13 and 15 passes the signal from the output of the adder 4 to the direct input of the null organ 2. At the same time, the same signal is connected to the lower chamber of the relay 14, cut off from the signal X _{Н by the} closed contact of the relay 14. As a result the claimed controller is no different from the prototype controller (with the only difference being that at its output the value of the control signal takes the value "1" and "0" when the sign of the switching function changes). It implements the control law (1) with the switching function (2). If the signal Z = 1, then relays 13, 14 and 15 are triggered. As a result, the output signal of the adder 4 is now connected via the lower contact of the relay 13 to the inverse input of the zero-organ 2, and the signal from the second input of the regulator (X _Н ) through the lower contacts of the relay 14 and relay 15 is fed to the direct inputs of the zero-organ 2. As a result, the controller (1) with the switching function (3) is implemented in the controller. Indeed, the zero-organ output is now determined by the algebraic sum of four signals

M = X _H - ((1-k) X _H + kX _E ) + X _H -X = (1 + k) X _H -kX _E -X.

The controller operates as follows at Z = 0. In this case, the upper contacts of the relays 13, 14 and 15 are open and the signal from the output of the adder 4 is switched to the direct input of the zero-organ. The lower contacts of the relays 14 and 15 are closed and the reference signal X _N does not have access to the inputs of the zero-organ 2.

When the signal X (variable) changes from zero to the side of the reference signal X _H , the indicator X of the extrema 1 stores the signal X _min = 0, which is switched through the repeater 6 and relay 3, switched by the comparison element 10, to the first input of the adder 4, at the second input of which the signal X _N acts. At the output of the null-organ 2, the signal is "1", since at its first (direct) input the signal is (1-k) X _Н , and at the second (inverse) it is X = 0 (Fig. 2). As soon as the adjustable coordinate reaches the value (1-k) X _Н , the output signal of the zero-organ 2 becomes equal to "0" (the first switching occurs). A further increase in the signal of the adjustable coordinate X to the value X = X _max > X _N does not make any changes in the controller. At the moment of occurrence of X _{max, the} output signal of adder 4 becomes equal to the value (1-k) X _Н + kX _max , which is still less than the signal X = X _max (Indeed, if, for example, k = 0.2, X _max = 0 , 7, X _H = 0.5, then after substituting the numbers in equation (2), the value M = -0.04). As soon as the variable X reaches the signal value (1-k) X _H + kX _max (for the given figures, this value is 0.54, which is greater than the value of X _N ), the zero-organ 2 again switches (U = 1) ahead of in relation to the task X _N = 0.5. After the appearance of the signal X = X _min <X _N in the controller also does not occur any changes. When the value of the input signal X reaches the value (1-k) X _H + kX _min , the switching will occur again. (Indeed, if, for example, X _min = 0.4, then switching will occur when the signal value of the variable X = 0.48 (again ahead of the signal X _N = 0.5)).

If, after the first switching of the null-organ 2 X _{max, the} signal X _N is less than, for example, 0.3 for the above signal values, the output signal of the null-organ 2 is reversed, which can be easily verified by substituting the digital values of the signals in expression (2). In this case, M = 0.16> 0, and the output signal of the zero-organ 2 again becomes equal to "1". Similar switching occurs when a signal appears X _min > X _N. Next, the cycle repeats. It is clear that the switching moments are not fixed once and for all - their position is determined by the value of the coefficient k and the extreme values of the variable X.

If the signal Z = 1, then relays 13, 14, 15 are activated, and the X _N signals are switched to the direct inputs of the zero-organ 2 through the open lower contacts of the relays 14 and 15, and the output signal of the adder 4 through the lower open contact of the relay 13 to the inverse input zero-organ 2. As a result of switching the zero-organ 2, they will be determined by the sign of the algebraic sum of the signals according to equation (3) and will always be delayed with respect to X _H. Indeed, if we put the specific numerical values of the signals the same as in the above example, then the first switching will occur with the value of the variable X = (1 + k) X _H = 0.6, and the second with the value X = (1 + k) X _H -X _min k = 0.54, that is, with a delay in relation to the reference signal X _N.

An analysis of the dynamic characteristics of such a regulator by the harmonic linearization method (we can present it if necessary at the request of an expert) shows that the hodograph of the inverse gain with a minus sign when changing the coefficient k and the control signal Z can be rotated both in the second and third quadrants of the complex plane .

The control law (1), implemented in the regulator, expands the scope of its application.

The inventive controller with a relay characteristic in comparison with the prototype allows in control systems to significantly expand the ranges of both frequency and amplitude of self-oscillations and to control these parameters.

на входе которого установлен заявляемый регулятор. Первый график фиг.3 получен при Z=0, k=0,95, B=0,5. Второй график фиг.4 получен при Z=1, k=0,15, В=1. Из чертежей видно, что при прочих равных условиях на выходе объекта можно изменять только настройкой коэффициента k и командой Z амплитуду и частоту автоколебаний в десятки раз.The possibilities of this expansion are illustrated by the results of digital modeling in the MCAD environment. Figures 3 and 4 show the processes of changing the output coordinate of an object with a transfer function

at the input of which the claimed regulator is installed. The first graph of Fig. 3 was obtained at Z = 0, k = 0.95, B = 0.5. The second graph of figure 4 was obtained at Z = 1, k = 0.15, B = 1. From the drawings it can be seen that, ceteris paribus, the output of the object can only be changed by adjusting the coefficient k and the Z command, the amplitude and frequency of self-oscillations tens of times.

Claims (1)

A controller with a relay characteristic, comprising a relay block, a zero organ, an adder, an extremum indicator, the outputs of which are connected to the inputs of the relay block, the first input of the regulator is connected to the input of the extremes indicator and the first inverse input of the zero organ, the first adder input is connected to the output of the relay block, and the second input of the adder is connected to the second input of the controller, characterized in that a switch is inserted into it, the first information input of which is connected to the output of the adder, the second information input is connected to the second the input of the regulator, and the control input - with the third input of the regulator, the first output of the switch is connected to the first direct input of the zero organ, the second output of the switch is connected to the second inverse input of the zero organ, the third output of the switch is connected to the first and second direct inputs of the zero organ .

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