What is an automatic regulator? Direct and indirect acting regulator. Block diagram of an automatic regulator
AUTOMATIC REGULATORS
Control accompanied by continuous monitoring is called regulation, and the parameter that needs to be controlled, i.e., regulated, is called the controlled variable.
Regulation, in which control is carried out by various devices without human intervention, is called automatic regulation, and a set of devices consisting of a measuring element (primary transducer), an actuator and a regulatory body is called a vehicle regulator.
The automatic control system (Fig. 1) is a collection of individual elements acting directed on each other. In the comparing device, the current value of the controlled variable X, which is received via the main feedback, is compared with its specified value X 0 .
Rice. 1 Diagram of the automatic control system
CLASSIFICATION OF AUTOMATIC REGULATORS
Regulators are divided according to the following characteristics.
1.. By mode of action : regulators of direct and indirect (indirect) action. From regulators direct action the regulatory body moves due to the energy of the object itself acting on the sensitive element. From regulators indirect action the regulatory body is moved by an additional energy source (electricity, compressed air, pressurized liquid).
2. By type of action : intermittent (discrete) and continuous regulator.
In regulators continuous action a continuous change in the regulated parameter corresponds to the continuous movement of the regulating body; there is a continuous functional connection between the input and output quantities.
In regulators intermittent action there is no continuous functional connection. Intermittent systems can be divided into two main groups: relay and pulse.
Relay system Automatic control is a system that includes at least one relay element among its main elements. By relay element is meant a system element in which a continuous change in the input value corresponds to a stepwise measurement.
a change in the output quantity that appears only for very specific values of the input quantity (electromagnetic relay).
Pulse system automatic control is a system that contains at least one pulse element. A pulse element converts a continuous input effect into a series of short-term pulses appearing at certain intervals.
3. By type of energy : electric pneumatic, hydraulic, electrohydraulic and electropneumatic.
According to the regulation law:
a) proportional regulators, or P-regulators (static);
b) integral regulators or I-regulators (automatic);
c) proportionally – integral regulators, or PI regulators (isodromic);
d) proportional-derivative regulators, or PD regulators (proportional regulators with advance);
e) proportional - integral-derivative regulators, or
PID controllers (isodromic controllers with advance);
By purpose: temperature, pressure, flow controllers, etc.
Depending on the function performed: ratio regulators, software, self-adjusting, stabilizing.
8. Direct acting temperature controller. A regulator in which the regulating element moves due to the energies of the object itself acting on the sensitive element is called a direct-acting regulator. Control systems using direct-acting regulators are called direct control systems.
Let's consider the operation of a direct-acting temperature regulator of the RPD type (Fig. 1. This regulator consists of a thermometric system and a valve.
The thermometric system of the regulator is a steam manometric thermometer, which includes a thermal cylinder 1, capillary 2 and bellows 3. The thermometric system is partially filled with a low-boiling liquid whose boiling point is below the lower limit of the controlled temperature.
When the thermal cylinder is immersed in the measured medium, the vapor pressure of the working fluid is established in the thermometric system, the value of which corresponds to the temperature of the measured medium. The pressure generated in the thermal cylinder is transmitted through the vapor of the working fluid through the capillary to the bellows. The bellows develops a force proportional to its effective area; this force is balanced by the spring force 4. If the temperature of the controlled medium is higher than the set value, then the force developed by bellows 5 is greater than the spring force 4, As a result, the bellows is compressed and with the help of the rod 5 moves the spool 6 control valve down. In this case, the flow area of the valve and the amount of heating substance passing through the valve are reduced; As a result, the temperature of the medium decreases and reaches the set value. When the temperature of the controlled medium decreases, the bellows stretches and the valve opens slightly, increasing the supply of heating substance, as a result of which the temperature rises to the set value.
Regulators that act on the regulator through an amplification device and an actuator powered by an external power source are called indirect-acting regulators.
In an indirect-acting regulator, when the controlled variable changes, the force or energy generated in the sensing element activates an auxiliary device that moves the regulating element due to the energy of an external source (electric current, liquid under pressure, compressed air).
Control systems using indirectly acting regulators are called “indirect control systems.”
In Fig. Figure 1 shows a diagram of indirect control of the liquid level in a vessel. The measuring device (float 1) is connected to a movable electrical contact using levers.2. The moving contact can close with one of the fixed contacts: B (more) and M (less). Depending on which of these contacts the moving contact closes, the electric motor 3 rotates in one direction or the other. Through a worm gearbox and a system of levers, the electric motor opens or closes the regulating body - valve 4, installed on the liquid supply line Q 1 to the tank.
If the fluid flow Q 2 from the tank increases, the water level in it will decrease and the float 1
will go down. In this case, the moving contact 2
touches the upper fixed contact B, the electrical circuit will close, the motor will turn on and rotate in the direction of opening the control valve 4,
thereby increasing the flow of water into the tank. The regulator will continue to operate until the specified liquid level is restored in the tank. I moving contact 2
will not install between fixed contacts B and M, as a result of which the motor circuit will be disconnected.
In the described indirect-acting regulator, the movement of the regulating body - the valve - is carried out by an electric actuator that uses energy from an external source.
Indirect-acting regulators are highly sensitive, develop high force and allow remote control of the regulator.
Related information.
1. Automatic regulators and regulation laws
Automatic regulator is a device that ensures in automatic control systems (ACP) the maintenance of the technological value of an object, characterizing the flow of a process in it around a given value by influencing the object.
The set value can have a constant value (in stabilization systems) or change according to a specific program (in program control systems).
The block diagram of the regulator can be presented as a combination of two elements (Fig. 1): comparison element 1 and element 2, which forms the regulation algorithm (law).
Comparison element 1 receives two signals at And at w, proportional, respectively, to the current and set values of the controlled variable. Signal at is generated by the measuring transducer, and the signal at zd – by a master controller or a software device.
Error signal
(1)
enters element 2, which generates a controller output signal sent to the actuator.
Regulators can be with direct and reverse characteristics. If with magnification at relatively at zd output value u increases, then the regulator has a direct characteristic, and if it decreases, then it has an inverse characteristic. The transition from direct to reverse characteristics and vice versa in regulators is carried out using a special switch.
Negative feedback in a closed loop ACP is formed through the use of regulators with direct or reverse characteristics.
Regulatory law is called the relationship between the change in the output value of the controller u and mismatch of the current at And at zd values of the controlled variable.
According to the laws of regulation, analogue regulators are divided into proportional, proportional-integral, proportional-derivative and proportional-integral-derivative.
2. Proportional controllers
The regulation law of the proportional controller has the form
(2)
Where
- transmission (gain) coefficient of the regulator; u 0 is the output value of the controller at the initial moment of time.
Regulator gain is a controller setting parameter. Changing , you can change the degree of influence of the regulator on the object.
WITH 
The structural diagram of the P-regulator represents a link with a high gain
(k=1000040000), covered by negative feedback by an amplifier with a coefficient k oc.
Transfer function of the P-regulator shown in Fig. 2, equal
(3)
From expression (3) it is clear that the smaller the coefficient k os (the degree of influence of negative feedback), the more the output value of the controller changes at a certain mismatch.
Dynamic characteristics of the P-regulator with a step change in the input signal and various values k p are shown in Fig. 3.
According to equation (2), the controller output signal for dependencies 1 and 2 will be equal to:
(3)
TO
The advantages of a proportional controller include its inertia-free (or speed) response. This is expressed in the fact that its output value changes simultaneously with the change in the input value. The optimal value of the regulator setting parameter, as for other regulators, is determined by the selected ACP transient process, the specified control quality parameters and is set depending on the properties of the controlled object.
The disadvantage of the P-regulator is that when operating in a closed ACP loop, the controller does not return the controlled variable to the set value, but leads to a new equilibrium position with a static control error proportional to the transmission coefficient along the “disturbing influence - controlled variable” channel and inversely proportional k p. Increase k p when working on objects with a delay leads to an unstable operating mode of the automatic control system.
3. Proportional-integral controllers
The output value of proportional-integral controllers (PI controllers) changes under the action of the sum of two components: proportional and integral.
The regulation law of PI controllers with independent settings is described by the equality:
,
(4)
Where k p – regulator transmission coefficient;
T and – integration time.
In physical sense T and is the time during which the change in the output signal of the controller under the influence of the integral component reaches a step change in its input value.
The PI controller has two settings - k p and T And.
The dynamic characteristic of the PI controller (Fig. 4) represents the sum of the proportional and integral components.
It can be seen from the figure that with increasing T u the degree of influence of the integral component decreases.
The block diagram of a PI controller with independent settings is shown in Fig. 5.
P
the transfer function of this controller is described by the equation
In industry, regulators with dependent tuning parameters (isodromic regulators) are also widely used, the dynamics equation of which has the form:
, (6)
Where k p – regulator transmission coefficient;
T from – isodrome time of the controller.
P 
about the physical meaning T from is the time during which, with a step change in the input value, the output value of the controller under the influence of the integral component changes by the same amount as under the action of the proportional component.
The dynamic characteristics of the isodromic regulator are shown in Fig. 6.
WITH 
The structural diagram of the isodromic regulator is shown in Fig. 7.
The transfer function of the given block diagram is found by the equality
Designating 
through k p , we get
PI controllers are slower compared to P controllers. At the same time, due to the absence of static error when operating in a closed ACP loop, they provide better regulation. This is due to the fact that the integral component of the regulator will act until the mismatch becomes zero.
4. Advance regulators
Leading controllers (with derivative action) include proportional-derivative and proportional-integral-derivative (PD and PID) controllers.
The control law of a PD controller with independent settings is described by the equation
, (8)
Where 
– differentiation time.
Dynamic characteristics of the PD controller described by equation (8), when an input signal is applied to its input, changing at a constant speed 
, is shown in Fig. 8.
The equation of the PD controller with dependent tuning parameters has the form
, (9)
Where T p – preliminary time.
In physical sense T n shows that compared to the proportional component of the output value of the controller u n output value u PD reaches the same values with a time advance equal to T p. This is clear from the figure shown. 9 dynamic characteristics of the controller, described by dynamics equation 9.
N
and fig. 10. The block diagram of the PD controller with dependent settings is shown.
The transfer function of a PD controller with such a block diagram is equal to
The control law of a PID controller with independent settings has the form
(11)
(12)
WITH 
The block diagram of the PID controller with dependent parameters is shown in Fig. eleven.
The transfer function of such a controller is described by the equation
Characterizing the speed of the PID controller, it should be noted that if the effects of the integral and differential components are the same, then its speed approaches the speed of the P-regulator. If the effect of the differential component is greater than the effect of the integral component, then the controller will act faster than the P-controller. In the case of a greater impact of the integral component, the speed of the PID controller will approach the speed of the PI controller.
When operating in a closed ASR loop, the introduction of a differential component into the control law causes a decrease in the rate of change of the controlled variable, a decrease in the control time and the dynamic control error, as well as the integral control error.
Dynamic equations, setting parameters, transient characteristics and their graphs for various types of regulators are given in Table. 1.
5. Regulators and controllers
When automating chemical-technological production, they use regulators And controllers.
Regulators are technical means with a rigid functional structure that ensures the implementation of the regulatory law.
Controllers are specialized computing devices that ensure the implementation of the regulation law in software. When the program changes, the controller algorithm block implements the selected control algorithm.
Regulators can be pneumatic or electric, and controllers can be electric.
In pneumatic regulators, the change in input and output signals is in the range of 20100 kPa. The controllers of the "START" system implement PI and PID control laws with independent settings. These regulators use as one of the tuning parameters the inverse of the transfer coefficient, called the proportional limit
(14)
The proportional limit shows the range over which the controller's input signal changes when its output signal changes from 0 to 100%. It characterizes the degree of negative feedback in a proportional controller. The smaller, the stronger the influence of the regulator on the object.
Electrical regulators and controllers use the following signal ranges: 0–5 mA; 0–20 mA; 4–20 mA and 0–10 V.
Electrical regulators and regulation algorithms for regulating microprocessor controllers are described by laws with dependent settings.
The presence of a certain range of the controller output signal determines its value limitation. Therefore, in the event of a significant mismatch or when setting certain values of the adjustment parameters, the output signal of the controller will take limit values.
Table 1. Equations and characteristics of analog regulators
|
Regulatory Law |
Dynamic equation |
Settings |
|
|
|
k p – transmission coefficient |
||
|
|
k p – transmission coefficient T and – integration time |
||
|
k p – transmission coefficient T d – differentiation time |
|||
|
|
k p – transmission coefficient T and – integration time T d – differentiation time |
||
|
With dependent settings |
k p – transmission coefficient T from – isodrome time |
||
|
k p – transmission coefficient T p – advance time |
|||
|
|
k p – transmission coefficient T from – isodrome time T p – advance time |
||
|
Transitional characteristika |
Step response graph | ||
Automatic regulators
An automatically operating device designed to regulate any parameter of an object is called an automatic regulator.
Automatic regulators can be of direct (direct) and indirect (indirect) action (Fig. 7).
An automatic regulator of direct (direct) action is the simplest regulator, the sensitive (primary) element of which can directly influence the regulatory (executive) organ without an amplification-converting device and an additional energy source. Such a regulator operates solely due to the energy of the regulated object itself.
An example of a direct-acting automatic regulator is a system for stabilizing the water level in a tank (Fig. 8.6). The regulated object is tank 1, the regulated parameter is the height of the water level H. The value of the regulated parameter depends on the relationship between the values of water supply Qi and its flow rate Q2. Stabilization of this parameter is achieved by a regulating body - damper 2, controlled by a sensitive element - float 5 through lever 3 and adjuster 4.
A decrease in the water level causes the float to lower, and therefore the valve 2 to open, i.e., an increase in the flow of water. As the level increases, the reverse process occurs.
An automatic regulator of indirect (indirect) action is one that includes an amplifying-converting device powered externally from an additional energy source.
The diagram of an indirect-acting regulator designed to regulate the water level in tank 1 is shown in Fig. 9.6. Damper 2, which regulates the amount of incoming water Qb, is controlled by a sensitive element - float b, not due to the energy of the water, but due to additional electrical energy attracted for the operation of the converting element - potentiometer 4 and the amplification - electric motor 3 (drive of the regulating element).
For the regulator under consideration, with the potentiometer slide connected to lever 5 in the middle position, the height of the water level is equal to the specified value R, and electric motor 3 does not work. When the water level drops, the float, lowering, moves the potentiometer slider towards the plus sign, and the electric motor slightly opens damper 2. When the level rises, the slider moves towards the minus sign, which causes the electric motor to rotate in the opposite direction, and therefore close the damper.
Depending on the method of movement of the regulating body, automatic regulators can be continuous or intermittent.
In automatic continuous control regulators, the regulating body occupies, except for the extreme ones, any intermediate position depending on the course of the process. Examples of such regulators are those shown in Fig. 8 and 9. For automatic intermittent control regulators, the regulating body occupies only two extreme positions (for two-position ones) or two extreme positions and several intermediate ones (for multi-position ones).
An example of a two-position intermittent controller is the automatic temperature controller shown in Fig. 6.6. Here the regulating body (steam control valve) can be open or closed, i.e., occupy only two extreme positions.
The nature of the process of continuous regulation is determined by the regulation law, i.e., the dependence of the output value of the automatic controller on the input value.
The regulation law is determined by the control device of the regulator. Based on this feature, automatic regulators are divided into static and astatic. Their features can be considered using the example of automatic water level regulators (see Fig. 8 and 9).
Static or proportional is a regulator that provides a regulatory effect proportional to the deviation of the controlled variable:
This effect is achieved by including static elements in the controller and using rigid feedback. In the static water level regulator shown in Fig. 8.6, the value of the controlled parameter does not remain constant, but depends on the magnitude of the disturbing influence. To maintain the level at the same height, it is necessary that the flow of water equals its flow. The flow of water depends on the opening of damper 2, i.e., on the position of float 5. The greater the flow of water, the more the damper must be slightly open and the lower at In the steady state of operation of the regulator, the float will be located, with a decrease in water flow, the position of the float will be higher. Thus, the water level in the tank depends on the amount of water flow, i.e., on the magnitude of the disturbance, and fluctuates within certain small limits relative to the average value.
The operation of a static regulator is always characterized by some constant error. Its positive features include a low tendency to fluctuations in the controlled parameter. Static regulators, being simpler in design, are used in cases where a small error in their operation does not have a significant impact on the unregulated object.
In an astatic controller, the output quantity y (control action) is proportional to the integral of the deviation of the controlled quantity:
In such a controller (see Fig. 9.6), the value of the controlled parameter does not depend on the excitation value. In the example under consideration, this is ensured by the fact that there is no rigid connection between the sensitive element - float 6 and the regulating body - damper 2. Under steady conditions and different values of water flow Q2, the damper will occupy different positions, and the float will always be the same, corresponding to the given value H of the water level in the tank.
An astatic regulator, unlike a static one, has no static regulation error. However, it is prone to oscillatory processes and is not always stable in operation.
In order for an automatic regulator to be suitable for practical use, it is necessary to ensure system stability and acceptable quality of regulation.
The stability of the automatic control system is determined by a number of indicators that reflect the nature of transient processes during regulation. Special literature provides criteria and methods for analyzing the stability of regulators.
The quality of the control process is understood as the correspondence between the specified and actual change in the controlled parameter. Typically this quality is determined by the following indicators:
1) the difference between the specified and actual values of the controlled parameter in steady state (system error); 2) overshoot (overshoot), i.e. the largest deviation of the actual value of the parameter from the specified one; 3) control time (system speed), which is taken to be equal to the duration of the transient process from its beginning until the moment when the controlled parameter acquires a value close (usually 95-97%) to the value in steady state; 4) the number of oscillations of the controlled parameter at a given time.
There are two ways to increase the stability and quality of regulation of automatic control systems: by changing the parameters of the regulated object or regulator and by changing the structural diagram of the regulator. In practice, the structural diagram of the regulator is usually changed, for which additional links are introduced. Automatic regulator devices consisting of such links are called corrective. Often they represent various kinds of additional (internal) feedback.
Of the automatic regulators with corrective devices, the most common are isodromic and derivative-action (with advance).
Thus, these controllers have the good dynamic properties of static controllers combined with the good static properties (eg no steady-state deflection) of astatic controllers.
This combination is achieved using flexible feedbacks that act only during transient processes to dampen oscillations and are absent in steady state.
The diagram of an isodromic controller with flexible feedback in the form of a cataract for automatic temperature control is shown in Fig. 10. The temperature in chamber 18 is measured by a resistance thermometer 17, connected to one of the arms of the measuring electrical bridge 15. The winding of a sensitive polarized relay 9 is connected to one of the diagonals of the bridge, and the power of the second diagonal is supplied from a constant voltage source. The stabilized temperature is set by the controller 16, which moves the slider of one of the resistances R of the electric bridge.
When the temperature in the chamber is higher than the set one, relay 9 closes contact 10, which turns on winding 8 of the reversible DC motor 7. The engine rotates roller 2 connected to valve 1 of the steam line, thereby reducing the supply of steam to the heater 19 of the chamber.
When the temperature in the chamber decreases, the direction of the current in the winding of the polarized relay changes to the opposite and the relay closes contact 11, which turns on winding 6. The engine begins to rotate in the opposite direction, and roller 2 opens valve 1, as a result of which the steam supply to heater 19 increases.
An isodromic device for improving the dynamic characteristics of the regulator is made using a cataract (hydraulic brake) 4 with a spring 5. When the roller 2 rotates, the lever 3 moves, and with it the cataract 4 with the slider 12 of the potentiometer 14. Due to this, the ratio between the resistances included in the bridge arms 15, and an additional correction signal is supplied to the relay winding 9. A rigid connection of the lever 3 with the engine 12 exists only with rapid movements of the lever in transient processes, since then the small hole of the damper 13 prevents the transition of oil from one cataract cavity to another and the rod with the cataract cylinder moves as one whole. After some time, when the transition process is over, the cataract spring 5 returns the piston and slider 12 to their original position, passing oil through the damper 13 from one cavity of the cataract cylinder to the other. Thus, at the end of the regulation process, the balance of the bridge, set by the set pointer 16, is restored again.
If the controlled object has a large capacitance (the time constant is large), the use of an isodromic controller with flexible feedback is not necessary. In this case, you can use static controllers with tight feedback (see dotted line in Fig. 10).
Regulators with influence on the derivative of the deviation carry out regulation on the deviation and its derivative, which makes it possible to take into account the nature of the change in the controlled variable. Therefore, they are also called pre-controllers.
This feature is essential when regulating fast processes. The regulation law for such regulators can be expressed by the equation
Derivative controllers suppress oscillations and increase system speed, thereby improving transient quality.
The effect of improving the quality of transient processes in regulators with advance can be seen in Fig. 11. Let us assume that the change in the controlled parameter over time is expressed by a solid curve (Fig. 11, a).
The previously discussed static proportional controller without correction devices reduces the discrepancy between the given and actual parameter values not only while it exists, but also (due to inertia) for some time after it is eliminated. Therefore, such a regulator switches to action in the opposite direction not at point B, when the mismatch is zero, but somewhat later, at section BC, exerting for some time an effect opposite to the required one.
The pre-regulator operates differently. In the section of increasing deviation of the controlled parameter from the set one, the controller’s action is forced, since at the beginning of the transition process the deviation and derivative have the same signs, and the derivative has the greatest value when Ax is close to zero. Due to this, the largest deviation of the parameter at the beginning of the transition process will decrease; first, point A will take position Ai. In section AB, due to a decrease in the deviation of the controlled parameter, the derivative changes sign. Therefore, the controller delivers an effect that is not equal to the sum, but to the difference between the signals in terms of deviation and derivative, i.e., less. If the controller without advance received a command to switch to action in the opposite direction near point B, then the controller with advance receives such a command earlier, for example, near point E, when the deviation and derivative signals are equal. Switching the controller to operate in the opposite direction before the parameter deviation stops prevents this deviation in the negative direction. The transient process can become aperiodic, as shown by the dotted line in Fig. 11, a.
Corrective devices used for additional influence of the regulator on the object, proportional to the derivative of the controlled parameter, can be different. Their inclusion in the circuit can also be carried out in different ways.
In Fig. 11c shows an elemental diagram of an automatic control system with derivative action. Here, the correcting device is a differentiating element connected in series to the main chain of action of the system links. The deviation of the controlled parameter is supplied to the input of this link, and the output is a value equal to the sum of two terms, of which the first is proportional to the deviation of the controlled parameter, and the second is the derivative of this deviation. The output parameters of the converting, actuating and regulating elements are designated by train functions of time i.
In Fig. 11d shows a schematic diagram of automatic control of the shaft rotation speed of a DC electric motor, corresponding to the element diagram in Fig. 11, c. The differentiating element (shown in dotted lines) is a circuit of resistance RiR2 and capacitance C, assembled in such a way that 
, i.e.
In the circuit, the measuring element is the tachogenerator, its voltage is proportional to the number of revolutions n of the electric motor D. This voltage is compared with the specified voltage on the setpoint potentiometer.
The output voltage U3 of the differentiating circuit is supplied to amplifier 1, the amplified voltage is applied to the excitation winding of the electromagnetic amplifier EMU, used as a regulatory element of the system.
The system works as follows. As the load 2 of electric motor D increases, the rotation speed of its shaft decreases. In this regard, the magnitude of the voltage generated by the tachogenerator decreases and, consequently, the system mismatch voltage increases. As a result of the latter circumstance, the voltage on the excitation windings of the EMU increases, which leads to an increase in the current strength / flowing through the motor armature D.
An increase in the motor current provides an increase in the torque L1vp - ki, which leads to an increase in the speed of rotation of the motor shaft.
Since the value of the derivative will be greatest at the very beginning of the transition process (when it is close to 0), the regulator will begin to act before the necessary mismatch of the controlled parameter occurs. The action of the controller at the beginning of the transition process will be forced, since the deviation of the parameter and the derivative have the same signs.
In the middle of the transient process, when the parameter deviation reaches its greatest value, the derivative becomes zero, so it helps to reduce the parameter overshoot.
At the end of the transition process, the derivative again acquires the greatest value, but with the opposite sign. This helps to reduce the duration of the transient process, which can become aperiodic.
Automatic indirect-acting regulators, designed to regulate any parameter according to a predetermined program, are equipped with software control devices instead of manual adjustment (Fig. 12).
In the case of using electrical sensitive elements and an amplifying-converting device, clock mechanism 1 can be used as software, driving a profiled cam 2 into rotational motion, acting on the reference voltage potentiometer 3 slider (Fig. 12.6). The shape of the profiled cam corresponds to the control program.
Regulation with a change in the value of the controlled variable according to a predetermined law is called program regulation.
With software control, the automatic regulator “seeks” to eliminate the mismatch between the voltage Ui at the output of the sensing element and the alternating voltage UQ of the master device. “Working out” the alternating voltage U0 specified at the input, the system carries out a corresponding change in the controlled variable (for example, temperature Ѳ) at the output.
Automatic indirect-acting controllers can be made universal, suitable for regulating various process parameters. For example, any perceiving (primary) element that introduces the necessary impact and intensity can be connected to the measuring system of such regulators. Different regulatory bodies can be connected to the output of the regulator's executive body in accordance with. type and intensity of the output impact.
excerpts from the book Automation of technological processes in woodworking, N. V. MAKOVSKY (attention! recognition errors are possible)
From: LidiaZaiceva, 11545 views
Reply(22()
Automatic regulators currently used in industry can be classified according to a number of the most characteristic features:
1. By purpose (type of controlled variable):
Regulators of one controlled variable (temperature, pressure, composition);
Universal regulators, )End.
2. By mode of action (i.e. the nature of the impact on the regulatory body):
Direct-acting regulators that do not require an external source of energy;
Indirect-acting regulators, in which the movement of the regulating body is carried out due to energy supplied from the outside.
3. By type of regulation:
Stabilizing regulators that maintain a constant value of physical quantities over time;
Software controllers that change the value of controlled quantities according to a given program;
Tracking regulators that maintain the value of the controlled quantities depending on changes in any other quantities;
Self-adjusting regulators that maintain the optimal value of the controlled quantities.
4. By duration of action:
Continuous regulators, in which, with a continuous change in the controlled variable, the regulating body moves continuously;
Regulators of intermittent (discrete) action, in which, with a continuous change in the regulated variable, the regulating body moves periodically only if the regulated variable reaches certain values or when a certain period of time passes.
5. By type of energy used:
Electrical regulators;
Hydraulic regulators;
Pneumatic regulators:
Combined regulators (electro-pneumatic and electro-hydraulic).
6. According to the regulatory law (the nature of the regulatory impact):
Positional (Pos-law);
Proportional or static (P-law);
Integral or astatic (I-law);
Proportional-integral or isodromic (PI-law);
Proportional with advance or proportional-differential (PD-law);
Isodromic with anticipation or proportional-integral-differential (PID-law).
3.1.1. Classification of regulators by purpose (type of controlled variable).
ARs are divided into regulators of temperature, pressure, level, speed, flow, etc.
3.1.2. Classification of regulators by operating principle
Based on the principle of action (the nature of the impact on the regulatory body), automatic regulators are divided into regulators of direct and indirect (indirect) action.
Answer23(
Direct acting regulators . These are regulators in which the regulating body moves only due to the energy taken by the measuring device from the controlled object.
Explanation. Such regulators are used to regulate individual parameters. They are used in cases where, due to operating conditions, there is no need for high control accuracy, and actuating the regulating body does not require much effort and the sensitive element has the necessary power for this.
Direct-acting regulators are cheap, simple in design, reliable in operation and do not require highly qualified operating personnel. Their scope of application is limited to the simplest control objects with favorable dynamic characteristics.
Example. Direct acting temperature controller.
Figure 3.1. Direct acting regulator
a) regulator design, b) functional diagram;
Automatic temperature controller (AR) (the design diagram of which is shown in Fig. 3.1, a, and its functional diagram in Fig. 3.1, b), sensing changes in the controlled variable at t (current temperature value) generates a mismatch signal 
manager of the regulatory body RO in order to change the regulatory impact x p on the object of regulation.
Explanation. The purpose of the regulator elements and the principle of its operation is as follows.
The measuring device (thermal cylinder with a low-boiling liquid) senses a change in the controlled variable at T(temperature) and converts it into a parameter y’ T(pressure in the manometric system), convenient for influencing other elements. As the temperature rises at t part of the liquid in the thermal cylinder boils away and the pressure y’ T increases to the bottom of the bellows, i.e. temperature at T converted to pressure y’ T .
The memory master sets the parameter at ass, corresponding to the required flow of the technological process. Installation at ass performed manually by operator P. In the design of the regulator, the role of a charger is played by a compressed spring, the tension of which is carried out by a set coil.
The ES comparison element (sometimes called an adder) produces an error signal 
. Structurally, the comparison element is made in the form of a lever that perceives the difference in pressure forces y’ T And y ass produced by the bellows and spring, respectively.
One of the main features of direct-acting regulators is that they cannot provide a constant value of the controlled variable in all steady-state operating modes of objects.
Example. The steam boiler (see Fig. 1.5) operates in steady state with minimal steam extraction G p min. This means that the water supply to the boiler should be minimal, i.e. The gearbox supply valve is closed as much as possible. The float, and therefore the H level of the water, should occupy a certain increased value. On the contrary, in steady state with maximum steam extraction G p max, the gearbox valve should be open as much as possible, which is possible with a lower position of the float and level. Thus, this regulator has a falling static characteristic, i.e. it works with positive regulation unevenness (type 1 characteristic, Fig. 2.10).
Explanation. Obviously, if the operating conditions of the objects require that the controlled quantities be strictly constant at all loads, such regulators cannot be used. Structurally, such regulators can reduce the amount of regulation unevenness, but it is impossible to make it equal to zero. If, in addition, the automated object does not have the property of self-leveling, then excessive reduction will lead to unstable operation of the controller.
( Indirect acting regulators .
The design of the indirect-acting regulator and its functional diagram are shown in Fig. 3.2. If the signal strength ∆у is not enough to influence the regulatory body (RO), then indirect-acting regulators are used. To move the RO, an actuator IU is used, which connects an external source of electrical energy E to the regulator.
An electromagnetic relay (magnetic starter) is used as an IM, influencing the movement of the regulating body RO.
Figure 3.2. . Indirect acting regulator
a) regulator design, b) functional diagram; ; ) End.
What is an automatic regulator? Direct and indirect acting regulator. Block diagram of an automatic regulator
Automatic regulators are classified by purpose, principle of operation, design features, type of energy used, nature of changes in regulatory influence, etc.
According to the principle of operation, they are divided into direct and indirect action regulators. Direct acting regulators do not use external energy for control processes, but use the energy of the control object itself (the controlled environment). An example of such regulators are pressure regulators. In indirect-acting automatic regulators, an external source of energy is required for its operation.
Based on the type of action, regulators are divided into continuous and discrete. Discrete regulators, in turn, are divided into relay, digital and pulse.
Based on the type of energy used, they are divided into electrical (electronic), pneumatic, hydraulic, mechanical and combined. The choice of a regulator based on the type of energy used is determined by the nature of the control object and the characteristics of the automatic system.
According to the regulation law, they are divided into two- and three-position regulators, standard regulators (integral, proportional, proportional-derivative, proportional-integral, and proportional-integral-derivative regulators - abbreviated as I, P, PD, PI and PID - regulators), regulators with variable structure, adaptive (self-tuning) and optimal controllers. Two-position regulators are widely used due to their simplicity and low cost.
According to their purpose, regulators are divided into specialized (for example, level, pressure, temperature, etc.) and universal regulators with standardized input and output signals and suitable for controlling various parameters.
Based on the type of functions they perform, regulators are divided into automatic stabilization regulators, software regulators, corrective regulators, parameter ratio regulators, and others.
Figure 5 shows the block diagram of a typical automatic controller.
Rice. 5.
In control systems, automatic regulators are used to maintain a given value of process parameters. The main elements of the regulator (Fig. 5): device 1 for measuring the controlled variable; device 2 for inputting the set value of the controlled variable (setter); device 3 for comparing the measured and set values to determine the deviation; control device 4, forming [the regulation law and controlling the impact on the actuator of the regulatory body; 5 devices for adjusting the regulator,
Industrial regulators implement the principle of deflection.
Regulators maintain a constant value of the output value within specified limits by changing the controlled value.
According to the principle of operation, regulators are divided into direct-acting regulators (direct) and indirect-acting regulators, and both the first and the second can be of intermittent or continuous action.
In a direct or direct-acting regulator, the regulating element is under the influence of the regulated parameter either directly or through a dependent parameter, and when the regulated parameter changes, it is actuated by a force arising in the sensing element of the regulator and sufficient to rearrange the regulating element without any external source of energy.
In an indirect-acting regulator (automatic regulator), the sensitive element acts on the regulating body with an external independent source of energy, which can be air, gas, liquid, etc. When the value of the controlled parameter changes, the force generated in the sensitive element of the regulator activates only the auxiliary device.
Both types of regulators consist of a regulatory body, sensitive (measuring) and control elements.
In direct-acting regulators, the sensing and control elements are integral parts of the drive of the regulating body and are inseparable from it. A direct-acting regulator has sensitive and control elements - independent devices, separated from the regulating body.
Direct-acting regulators are less sensitive than indirect-acting regulators. This is explained by the fact that the regulating body, when the value of the controlled parameter changes, begins to move only after the emergence of a force sufficient to overcome the friction forces in all moving parts.
With an indirect-acting regulator, friction forces are overcome by an external source of energy, and no significant change in the forces on the actuator is required. Therefore, regulation occurs more smoothly here.
However, regardless of the operating principle, regulators must always provide sufficiently stable control.