The basis for building systems related regulation is principle of autonomy. In relation to an object with two inputs and outputs, the concept of autonomy means the mutual independence of output coordinates y 1 And y 2 when two closed control systems operate.

Essentially, the autonomy condition consists of two invariance conditions: invariance of the first output y 1 in relation to the signal of the second regulator X p2 and invariance of the second output y2. in relation to the signal of the first regulator X p1:

In this case the signal X p1 can be considered as a disturbance for y2, and the signal X p2 - how outrage for y 1. Then the cross channels play the role of disturbance channels (Fig. 1.35). To compensate for these disturbances, dynamic devices with transfer functions are introduced into the control system R 12 (p) And R 21 (r), the signals from which are sent to the corresponding control channels or to the inputs of the regulators.

By analogy with invariant ASRs, the transfer functions of compensators R 12 (p) And R 21 (r), determined from the autonomy condition, will depend on the transfer functions of the direct and cross channels of the object and, in accordance with expressions (1.20) and (1.20,a), will be equal to:

Just as in invariant ASRs, for the construction of autonomous control systems, an important role is played by physical feasibility and technical implementation approximate autonomy.

The condition of approximate autonomy is written for real compensators, taking into account the operating frequencies of the corresponding regulators:

In chemical technology, one of the most complex multi-connected objects is the rectification process. Even in the simplest cases - when separating binary mixtures - in distillation column Several interconnected coordinates can be identified (Fig. 1.36). For example, to regulate the process in the lower part of the column, it is necessary to stabilize at least two technological parameters that characterize the material balance in the liquid phase and in one of the components. For this purpose, the liquid level in the still and the temperature under the first plate are usually selected, and the flow of heating steam and the selection of the still product are used as control input signals. However, each of the regulatory influences affects both outputs: when the heating steam flow rate changes, the intensity of evaporation of the bottom product changes, and as a result, the liquid level and steam composition change. Similarly, a change in the bottoms product selection affects not only the level in the bottoms, but also the reflux ratio, which leads to a change in the composition of the steam at the bottom of the column.

Rice. 1.35. Block diagrams of autonomous automated control systems: A– compensation of the impact from the second regulator in the first control loop; b– compensation of the impact from the first regulator in the second control loop; V - autonomous system regulation of two coordinates

Rice. 1.36. An example of a control system for an object with several inputs and outputs:

1 - distillation column; 2 – boiler; 3 – reflux condenser; 4 – reflux tank; 5 - Temperature regulator; 6,9 – level regulators; 7 – flow regulator; 8 – pressure regulator

To regulate the process in the upper part, you can select steam pressure and temperature as output coordinates, and the supply of refrigerant to the reflux condenser and reflux to reflux the column as regulating input parameters. Obviously, both input coordinates affect the pressure and temperature in the column during thermal and mass transfer processes.

Finally, considering the temperature control system simultaneously in the upper and lower parts of the column by supplying reflux and heating steam, respectively, we also obtain a system of unrelated control of an object with internal cross-links.

There are currently a variety of systems automatic regulation(SAR) or as they are also called - systems automatic control(self-propelled guns). In this article we will consider some methods of regulation and types of automatic control systems.

Direct and indirect regulation

As is known, every automatic control system consists of a regulator and an object of regulation. The regulator has a sensitive element that monitors changes in the controlled variable depending on the value of the specified control signal. In turn, the sensitive element influences the regulatory body, which in turn changes the system parameters so that the values ​​of the set and controlled quantities become the same. In the most simple regulators the impact of the sensing element on the regulatory organ occurs directly, that is, they are directly connected. Accordingly, such ACS are called direct control systems, and regulators are called regulators direct action as shown below:

In such a system, the energy required to move the valve that regulates the flow of water into the pool comes directly from the float, which will be the sensing element here.

In the ACS of indirect regulation, to organize the movement of the regulatory body, auxiliary devices are used that use for their work additional sources energy. In such a system, the sensing element will act on the control of the auxiliary device, which in turn will move the control element to the desired position, as shown below:

Here the float (sensitive organ) acts on the contact of the excitation winding of the electric motor, which rotates the valve in the desired direction. Such systems are used when the power of the sensing element is not enough to control the operating mechanism or it is necessary to have a very high sensitivity of the measuring element.

Single-circuit and multi-circuit self-propelled guns

Modern automatic control systems very often, almost always, have parallel correction devices or local feedbacks, as shown below:

ACS in which only one value is subject to regulation, and they have only one main feedback (one control loop) are called single-circuit. In such self-propelled guns, an impact applied to some point in the system can bypass the entire system and return to the original point after passing through only one bypass path:

And self-propelled guns in which, in addition to the main circuit, there are also local or main feedback connections are called multi-circuit. Conversely to single-circuit systems, in multi-circuit systems an impact applied to some point in the system can bypass the system and return to the point of application of the impact along several circuits of the system.

Systems of coupled and uncoupled automatic control

Systems in which several quantities are subject to regulation (multidimensional automatic control systems) can be divided into connected and unrelated.

Decoupled Regulatory Systems

Systems in which regulators designed to regulate different quantities that are unrelated to each other and can interact through a common control object are called unrelated control systems. Unrelated regulation systems are divided into independent and dependent.

In dependent variables, a change in one of the quantities to be controlled entails a change in the remaining quantities to be controlled. Therefore, in such devices it is impossible to consider various parameters controls separately from each other.

An example of such a system would be an airplane with an autopilot, which has a separate rudder control channel. If the aircraft deviates from its course, the autopilot will cause the rudder to deflect. The autopilot will deflect the ailerons, and the deflection of the aileron and rudder will increase the aircraft's drag, causing the elevator to deflect. Thus, it is impossible to consider separately the processes of heading, pitch and lateral roll control, even though each of them has its own control channel.

In independent systems of unrelated regulation, the opposite is true; each of the quantities subject to regulation will not depend on changes in all the others. Such management processes can be considered separately from each other.

An example is an automatic control system for the angular velocity of a hydraulic turbine, where the voltage of the generator winding and the turbine speed are regulated independently of each other.

Linked regulation systems

In such systems, regulators of different quantities have connections among themselves that interact outside the object of regulation.

For example, consider the electric autopilot EAP, a simplified diagram of which is shown below:

Its purpose is to maintain the pitch, heading and roll of the aircraft at a given level. IN in this example We will consider the functions of the autopilot related only to maintaining a given course, pitch, and roll.

The hydraulic semi-compass 12 serves as a sensitive element that monitors the deviation of the aircraft from the course. Its main part is a gyroscope, the axis of which is directed along a given course. When the plane begins to deviate from course, the axis of the gyroscope begins to influence the sliders of the rheostatic course 7 and rotation 10 sensors connected by lever 11, while maintaining its position in space. The aircraft body, together with sensors 7 and 10, in turn, shift relative to the horoscope axis; accordingly, a difference arises between the position of the gyroscope and the aircraft body, which is detected by sensors 7 and 10.

An element that will perceive the deviation of the aircraft from the course specified in space (horizontal or vertical plane) there will be a gyrovertical 14. Its main part is the same as in the previous case - a gyroscope, the axis of which is perpendicular to the horizontal plane. If the plane begins to deviate from the horizon, the pitch sensor slider 13 will begin to shift in the longitudinal axis, and when it deviates in the horizontal plane, the roll sensors 15-17 will begin to shift.

The bodies that control the aircraft are control rudders 1, height 18 and ailerons 19, and the performing elements that control the position of the rudders are the heading, pitch and roll steering machines. The operating principle of all three autopilot channels is completely similar. The steering gear of each steering wheel is connected to a potentiometric sensor. Main potentiometric sensor (see diagram below):

Connects to the corresponding feedback sensor via a bridge circuit. The bridge diagonal is connected to amplifier 6. When the aircraft deviates from the flight path, the slider of the main sensor will move and a signal will appear in the diagonal of the bridge. As a result of the appearance of the signal, the electromagnetic relay will be activated at the output of the amplifier 6, which will lead to the closure of the electromagnetic coupling circuit 4. The drum 3 of the machine, in the circuit of which the relay has activated, will engage with the shaft of the continuously rotating electric motor 5. The drum will begin to rotate and thereby wind or unwind ( depends on the direction of rotation) cables that rotate the corresponding rudder of the aircraft, and at the same time will move the brush of the feedback potentiometer (OS) 2. When the displacement value of the feedback potentiometer (OS) 2 becomes equal to the displacement value of the potentiometric sensor brush, the signal in the diagonal of this bridge will become equal to zero and the movement steering will stop. In this case, the aircraft's rudder will rotate to the position necessary to shift the aircraft to the specified course. As the mismatch is eliminated, the main sensor brush will return back to the middle position.

The output stages of the autopilot are identical, starting from amplifiers 6 and ending with the steering gears. But the entrances are a little different. The heading sensor slider is not connected rigidly to the gyro-compass, but with the help of a damper 9 and a spring 8. Because of this, we obtain not only a movement proportional to the displacement from the heading, but also an additional one, proportional to the first derivative of the deviation with respect to time. In addition, in all channels, in addition to the main sensors, additional sensors are provided that implement connected control along all three axes, that is, they coordinate the actions of all three rudders. This connection provides algebraic addition of the signals from the main and additional sensors at the input of amplifier 6.

If we consider the course control channel, then the auxiliary sensors will be roll and turn sensors, which are controlled manually by the pilot. In the roll channel there are additional rotation and rotation sensors.

The influence of control channels on each other leads to the fact that when the aircraft moves, a change in its roll will cause a change in pitch and vice versa.

It must be remembered that an automatic control system is called autonomous if it has such connections between its regulators that when one of the values ​​changes, the rest will remain unchanged, that is, a change in one value does not automatically change the rest.

When analyzing complex systems automatic control, their structural diagrams, showing the points of application of influences and possible ways propagation of signals that interact between system elements.

Structural diagrams consist of the following structural elements:

dynamic, carrying out some functional or operator connection between their input and output signals;

transformative, serving to transform the nature or structure of signals;

comparisons in which signals are subtracted or added;

branch points, at which the signal propagation path branches into several paths leading to different points in the system;

connections or lines block diagram, indicating the direction of signal propagation;

points of application of influences;

logical, performing logical operations.

We indicated above that any automatic control system, according to the very principle of its operation, always

has at least one feedback that serves to compare the actual and required value of the controlled variable. We agreed to call this kind of feedback the main one.

It should be noted, however, that modern systems automatic control, in addition to the main feedbacks, the number of which is equal to the number of controlled quantities, often have several more auxiliary or local feedbacks. Automatic control systems with one controlled variable, having only one main feedback and no local feedback, are called single-circuit. In single-loop systems, a force applied to any point can bypass the system and return to the original point, following only one bypass path (see Fig. II.8). Automatic control systems that, in addition to one main feedback, have one or more main or local feedbacks are called multi-circuit. Multi-circuit systems are characterized by the fact that in them an impact applied to any point can bypass the system and return to the original point, following several different bypass paths.

As an example of a multi-circuit (double-circuit) automatic control system with one controlled variable, we can cite a servo system in which, in addition to the main feedback, which serves to generate an error signal and is carried out using a selsyn sensor and a selsyn receiver, there is also local feedback; the latter is carried out using a tachogenerator and an RC circuit connected to it, the voltage from the output of which is subtracted from the error signal.

An example of a multi-circuit automatic control system with several controlled variables is an aircraft engine control system, in which the controlled variables can be engine speed, boost pressure, ignition timing, oil temperature, coolant temperature and other values.

The reasons for introducing local feedback into an automatic control system are very different. For example, they are used in correcting elements to convert a signal in accordance with the required control law, in amplifying elements - for linearization, lowering the noise level, lowering the output resistance, in actuating elements - to increase power.

Feedbacks covering several series-connected system elements can be introduced to give them the required dynamic properties.

Multidimensional automatic control systems, i.e. systems with several controlled quantities, are divided into

into systems of unrelated and connected regulation.

Unrelated control systems are those in which regulators designed to regulate various quantities are not connected to each other and can only interact through a common object of regulation. Systems of unrelated regulation, in turn, can be divided into dependent and independent.

Dependent systems of unrelated regulation are characterized by the fact that in them a change in one of the controlled quantities depends on a change in the others. As a result, in such systems the processes of regulation of various controlled quantities cannot be considered independently, in isolation from each other.

An example of a dependent system of unrelated control is an airplane with an autopilot that has independent rudder control channels. Suppose, for example, that an airplane deviates from its intended course. This will cause, thanks to the presence of the autopilot, a deflection of the rudder. When returning to a given course, the angular velocities of both bearing surfaces of the aircraft, and therefore those acting on them lift forces will become unequal, which will cause the aircraft to roll. The autopilot will then deflect the ailerons. As a result of rudder and aileron deflections, the aircraft's drag will increase. Therefore, it will begin to lose height, and its longitudinal axis will deviate from the horizontal. In this case, the autopilot will deflect the elevator.

Thus, in the considered example, the processes of regulation of three controlled quantities - course, lateral roll and longitudinal roll - strictly speaking, cannot be considered independent of each other, despite the presence of independent control channels.

An independent system of unrelated regulation is characterized by the fact that in it the change in each of the controlled quantities does not depend on the change in the others, due to which the processes of regulation of various quantities can be considered in isolation from each other. As an example of independent uncoupled control systems, one can often consider the speed control system of a hydraulic turbine and the voltage control system of the synchronous generator it rotates. The regulation processes in these systems are independent, due to the fact that the voltage regulation process usually proceeds many times faster than the speed regulation process.

Coupled control systems are those systems in which regulators of various controlled quantities have mutual connections with each other, interacting between them outside the object of regulation.

A system of coupled regulation is called autonomous if the connections between its constituent regulators

are such that a change in one of the regulated quantities during the regulation process does not cause changes in the remaining regulated quantities.

2. Classification of ACP. Management principles.

Control- this is a targeted impact on an object, which ensures its optimal (in a certain sense) functioning and is quantitatively assessed by the value of the quality criterion (indicator). The criteria may be technological or economic in nature (productivity technological installation, production cost, etc.).

During operation, output values ​​deviate from specified values ​​due to disturbances z V and a discrepancy appears between the current at T and given and 3 values ​​of the output quantities of the object. If available disturbances z V the object independently ensures normal functioning, i.e., it independently eliminates any discrepancies that arise y T -i 3, then it does not need management. If the object does not ensure the fulfillment of normal operating conditions, then in order to neutralize the influence of disturbances, control action x P, changing the material or heat flows of the object using an actuator. Thus, during the control process, impacts are applied to the object that compensate for disturbances and ensure the maintenance of its normal operating mode.

Regulationcalled maintaining the output values ​​of an object near the required constant or variable values ​​in order to ensure the normal mode of its operation by applying control actions to the object.

Automatic device, ensuring the maintenance of the output values ​​of the object near the required values ​​is called automatic regulator.

According to the principle of regulation ASRs are divided into those operating by deviation, by disturbance and by a combined principle.

By deviation. In systems that operate by deviation of the controlled variable from the set value (Fig. 1-2, A), indignation z causes deviation of the current value of the controlled variable at from its set value And. The automatic regulator AR compares the values u and and, when they mismatch, it generates a regulatory effect X the corresponding sign, which through the actuator (not shown in the figure) is supplied to the control object OR, and eliminates this mismatch. In deviation control systems, mismatch is necessary to form regulatory influences; this is their drawback, since the regulator’s task is precisely to prevent mismatch. However, in practice, such systems have become predominantly widespread, since the regulatory influence in them is carried out regardless of the number, type and location of the appearance of disturbing influences. Deviation control systems are closed.

Out of outrage. When regulating by disturbance (Fig. 1-2, b) regulator AR B receives information about the current value of the main disturbance z 1. When measuring it and not matching with nominal meaning and B the regulator forms the regulatory impact X, directed to the object. In systems operating on a disturbance, the control signal travels along the circuit faster than in systems built on the principle of deviation, as a result of which the disturbing influence can be eliminated even before a mismatch occurs. However, it is practically impossible to implement disturbance-based control for most chemical technology objects, since this requires taking into account the influence of all disturbances of the object ( z 1, z 2, ...) the number of which is usually large; in addition, some of them cannot be quantified. For example, measuring such disturbances as changes in the activity of the catalyst, the hydrodynamic situation in the apparatus, the conditions of heat transfer through the wall of the heat exchanger and many others encounters fundamental difficulties and is often impracticable. Usually the main disturbance is taken into account, for example, by the load of the object.

In addition, signals about the current value of the controlled variable are sent to the system control loop by disturbances at do not arrive, therefore, over time, the deviation of the controlled value from the nominal value may exceed the permissible limits. Disturbance control systems are open.

According to the combined principle. With such regulation, i.e., with the joint use of the principles of regulation by deviation and disturbance (Fig. 1-6, V), it is possible to obtain high-quality systems . In them the influence of the main disturbance z 1 is neutralized by the AR B regulator, which operates on the principle of disturbance, and the influence of other disturbances (for example, z 2 etc.) - an AR regulator that responds to the deviation of the current value of the reacted quantity from the set value.

According to the number of controlled quantities ASRs are divided into one-dimensional and multidimensional. One-dimensional systems have one adjustable variable, the latter have several adjustable quantities.

In its turn multidimensional systems can be divided into unrelated and coupled control systems. In the first of them, the regulators are not directly related to each other and act separately on the common object of regulation. Systems unrelated controls are usually used when the mutual influence of the controlled quantities of the object is small or practically absent. Otherwise, systems are used related regulation, in which regulators of various quantities of one technological object are interconnected by external connections (outside the object) in order to weaken the mutual influence of the controlled quantities. If in this case it is possible to completely eliminate the influence of the controlled quantities on one another, then such a system of coupled regulation is called autonomous.

According to the number of signal paths ASRs are divided into single-circuit and multi-circuit. Single-circuit are called systems containing one closed loop, and multi-circuit- having several closed circuits

By purpose(the nature of the change in the reference influence) ASRs are divided into automatic stabilization systems, program control systems and tracking systems.

Automatic stabilization systems are designed to maintain the controlled variable at a given value, which is set constant ( u=const). These are the most common systems.

Program control systems constructed in such a way that the specified value of the controlled variable is a function of time known in advance u=f(t). They are equipped with software sensors that form the value And in time. Such systems are used to automate batch chemical processes or processes operating in a specific cycle.

In tracking systems the set value of the controlled variable is not known in advance and is a function of an external independent technological variable u=f(y 1). These systems serve to regulate one technological quantity ( slave), which is in a certain dependence on the values ​​of another ( leading) technological value. A type of tracking systems are systems for regulating the ratio of two quantities, for example, the costs of two products. Such systems reproduce at the output a change in the driven quantity in a certain ratio with the change in the leading one. These systems seek to eliminate the mismatch between the value of the leading quantity, multiplied by a constant factor, and the value of the driven quantity.

By the nature of regulatory influences There are continuous ASR, relay and pulse.

Continuous ACPare constructed in such a way that a continuous change in the input value of the system corresponds to a continuous change in the output value of each link.

Relay (positional) ACP contain a relay link that converts a continuous input value into a discrete relay value that takes only two fixed values: the minimum and maximum possible. Relay links make it possible to create systems with very high gain factors. However, in a closed control loop, the presence of relay links leads to self-oscillations of the controlled quantity with a certain period and amplitude. Systems with position controllers are relay-based.

Pulse ASRcontain a pulse element that converts a continuous input quantity into a discrete pulse value, i.e., into a sequence of pulses with a certain period of their alternation. The period of occurrence of pulses is set forcibly. The input value is proportional to the amplitude or duration of the output pulses. The introduction of a pulse element frees the system's measuring device from the load and allows the use of a low-power, but more sensitive measuring device at the output that responds to small deviations of the controlled value, which leads to an increase in the quality of system operation.

In the pulse mode, it is possible to construct multi-channel circuits, while reducing the energy consumption for actuating the actuator.

Systems with a digital computing device in a closed control loop also operate in a pulsed mode, since the digital device produces the calculation result in the form of pulses following certain time intervals necessary for the calculations. This device is used when the deviation of the controlled variable from the set value must be calculated based on the readings of several measuring instruments or when according to the criteria best quality operation of the system, it is necessary to calculate the program for changing the controlled variable.

Connecting the installations according to an unrelated control scheme ensures the independence of the operation of both installations, i.e., changing the water flow for hot water supply within a wide range from zero (at night) to maximum has virtually no effect on the operation of the heating system.

To do this, the water flow in the supply line must be equal to the total water flow for heating - ventilation and hot water supply. Moreover, the water consumption for hot water supply should be taken according to maximum load hot water supply and the minimum water temperature in the supply line, i.e. in the mode when the DHW load is completely covered from the supply line (if the consumer does not have storage tanks installed).

Water consumption for heating, ventilation, hot water supply and total water consumption by each network subscriber does not depend on the network configuration. The calculated flow rate by the subscriber is set using a throttle diaphragm, the diameter of the hole of which is determined by the formula (clause 4.17 SP 41-101-95)

where G is the estimated water flow in the pipeline, equal to Gtotal t/hour

DN - pressure damped by the diaphragm, m

The minimum size of the aperture opening is 3 mm

Automation of the make-up system

Automated make-up devices maintain a constant or varying according to a certain law water pressure at the network make-up point.

For heating networks with relatively small pressure losses in the mains and a favorable terrain profile, the pressure at the recharge point in all modes (including the mode when the network pumps are stopped) is maintained constant. It is planned to maintain constant pressure in the return manifold in front of the network pumps using a downstream pressure regulator (make-up regulator) installed on the make-up water pipeline.

In the case when the static pressure of the heating network exceeds the pressure in the return manifold of the boiler room when the network pumps are operating, adjustment to static pressure is carried out manually. Water pressure is measured in the pressure pipes of the feed pumps with local indicating and signaling pressure gauges, which give an impulse to turn on the backup pump, and in the return manifold - with indicating, recording and signaling pressure gauges on the local switchboard. At the local switchboard, they also provide for the installation of a secondary device indicating, recording and signaling flow meter for measuring the flow rate of make-up water and a secondary device of recording and signaling oxygen meter for measuring the oxygen content in the make-up water. The resistance thermometer on the make-up line is connected to a common recording device, which simultaneously records the temperature of the supply water.

In open heating networks, when installing central storage tanks, the pressure is return pipeline are regulated automatically by two control valves, the first of which is installed on the bypass pipeline of excess network water to the storage tanks, and the second on the pipeline from the storage tanks after the transfer pumps. During hours when the hot water supply load is below the daily average, the transfer pumps are turned off and the pressure in the return pipeline is regulated by the first valve. During hours when the hot water load is higher than the daily average, the transfer pumps are automatically turned on, the first control valve is closed, and the pressure regulator switches to the control valve installed after the transfer pumps.

To provide constant flow make-up water in an open heating network at pressure pipeline For make-up pumps, a flow regulator is installed.

The water level in the deaerator make-up tank is maintained by a control valve on the chemically purified water line. If instead of a vacuum deaerator operating on sliding pressure, an atmospheric one is used, then an additional regulator is installed that maintains constant pressure in the deaerator column. The scheme provides for an emergency stop of workers: make-up and transfer pumps and automatic switching on reserve ones, as well as signaling the pressure in the return pipeline of the level in the make-up deaerator tank and the network water storage tanks and the oxygen content in the make-up water.