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Technical means of automation. Technical means of production automation The principle of information conversion

Topic 2

1. Sensors

A sensor is a device that converts the input influence of any physical quantity into a signal convenient for further use.

The sensors used are very diverse and can be classified according to various criteria (see Table 1).

Depending on the type of input (measured) quantity, there are: mechanical displacement sensors (linear and angular), pneumatic, electrical, flow meters, speed, acceleration, force, temperature, pressure sensors, etc.

Based on the type of output value into which the input value is converted, non-electrical and electrical are distinguished: direct current sensors (EMF or voltage), amplitude sensors alternating current(EMF or voltage), alternating current frequency sensors (EMF or voltage), resistance sensors (active, inductive or capacitive), etc.

Most sensors are electrical. This is due to the following advantages of electrical measurements:

Electrical quantities convenient to transmit over a distance, and the transmission is carried out with high speed;

Electrical quantities are universal in the sense that any other quantities can be converted into electrical quantities and vice versa;

They are accurately converted into a digital code and allow you to achieve high accuracy, sensitivity and speed of measurement instruments.

Based on their operating principle, sensors can be divided into two classes: generator and parametric. A separate group consists of radioactive sensors. Radioactive sensors are sensors that use phenomena such as changes in parameters under the influence of g and b rays; ionization and luminescence of certain substances under the influence of radioactive irradiation. Generator sensors directly convert the input value into electrical signal. Parametric sensors convert the input value into a change in any electrical parameter (R, L or C) of the sensor.

Based on the principle of operation, sensors can also be divided into ohmic, rheostatic, photoelectric (optoelectronic), inductive, capacitive, etc.

There are three classes of sensors:

Analog sensors, i.e. sensors that produce an analog signal proportional to the change in the input value;

Digital sensors that generate a pulse train or binary word;

Binary (binary) sensors that produce a signal of only two levels: “on/off” (0 or 1).


Figure 1 – Classification of sensors for mining machine automation systems


Requirements for sensors:


Unambiguous dependence of the output value on the input value;

Stability of characteristics over time;

High sensitivity;

Small size and weight;

Absence of reverse impact on the controlled process and on the controlled parameter;

Work under various operating conditions;

Various options installation

Parametric sensors

Parametric sensors are sensors that convert input signals into a change in some parameter. electrical circuit(R, L or C). In accordance with this, active resistance, inductive, and capacitive sensors are distinguished.

Characteristic feature of these sensors is that they are used only with an external power source.

In modern automation equipment, various parametric active resistance sensors are widely used - contact, rheostatic, potentiometric sensors.

Contact sensors. The most reliable with contact sensors Magnetically controlled sealed contacts (reed switches) are considered.

Figure 1 – Schematic diagram of a reed switch sensor

The sensor's sensing element, the reed switch, is an ampoule 1, inside of which contact springs (electrodes) 2, made of ferromagnetic material, are sealed. The glass ampoule is filled with a protective gas (argon, nitrogen, etc.). The tightness of the ampoule excludes bad influence(impact) of the environment on the contacts, increasing the reliability of their operation. The contacts of the reed switch located at the controlled point in space close under the action magnetic field, which is created by a permanent magnet (electromagnet) installed on a moving object. When the reed switch contacts are open, it active resistance equal to infinity, and when closed - almost zero.

The output signal of the sensor (U out on load R1) is equal to the voltage U p of the power source in the presence of a magnet (object) at the control point and zero in its absence.

Reed switches are available with both make and break contacts, as well as switching and polarized contacts. Some types of reed switches - KEM, MKS, MKA.

The advantages of reed switch sensors are high reliability and mean time between failures (about 10 7 operations). The disadvantage of reed sensors is a significant change in sensitivity with a slight displacement of the magnet in the direction perpendicular to the movement of the object.

Reed sensors are used, as a rule, in the automation of lifting, drainage, ventilation and conveyor installations.

Potentiometric sensors. Potentiometric sensors are a variable resistor (potentiometer) consisting of a flat (strip), cylindrical or ring frame on which a thin wire of constantan or nichrome with high resistivity. A slider moves along the frame - a sliding contact connected mechanically to the object (see Figure 2).

By moving the slider using the appropriate drive, you can change the resistance of the resistor from zero to maximum. Moreover, the resistance of the sensor can change both according to a linear law and according to other, often logarithmic, laws. Such sensors are used in cases where it is necessary to change the voltage or current in the load circuit.

Figure 2 - Potentiometric sensor

For a linear potentiometer (see Figure 2) length l the output voltage is determined by the expression:

,

where x is the movement of the brush; k=U p / l- transfer coefficient; U p – supply voltage.

Potentiometric sensors are used to measure various process parameters - pressure, level, etc., previously converted by a sensing element in motion.

The advantages of potentiometric sensors are their design simplicity, small size, and the ability to be powered by both direct and alternating current.

The disadvantage of potentiometric sensors is the presence of a sliding electrical contact, which reduces the reliability of operation.

Inductive sensors. The principle of operation of the inductive sensor is based on a change in the inductance L of the coil 1, placed on the ferromagnetic core 2, when moving x anchors 3 (see Figure 3).

Figure 3 - Inductive sensor

The sensor circuit is powered from an AC source.

The control element of the sensors is a variable reactance - a choke with a variable air gap.

The sensor works as follows. Under the influence of an object, the armature, approaching the core, causes an increase in flux linkage and, consequently, inductance of the coil. With decreasing gap d to a minimum value, the inductive reactance of the coil x L = wL = 2pfL increases to a maximum, reducing the load current RL, which is usually an electromagnetic relay. The latter, with their contacts, switch control, protection, monitoring circuits, etc.

Advantages inductive sensors– simplicity of the device and reliability of operation due to the absence of a mechanical connection between the core and the armature, usually attached to a moving object, the position of which is controlled. The functions of an anchor can be performed by an object itself that has ferromagnetic parts, for example a skip when controlling its position in the shaft.

The disadvantages of inductive sensors are the nonlinearity of the characteristics and the significant electromagnetic force of attraction of the armature to the core. To reduce forces and continuously measure displacements, solenoid-type sensors are used, or they are called differential.

Capacitive sensors. Capacitive sensors are structurally variable capacitors various designs and shapes, but always with two plates, between which there is a dielectric medium. Such sensors are used to convert mechanical linear or angular movements, as well as pressure, humidity or environmental level into a change in capacity. In this case, to control small linear movements, capacitors are used in which the air gap between the plates changes. To control angular movements, capacitors with a constant gap and variable working area of ​​the plates are used. For monitoring tank filling levels bulk materials or liquids with constant gaps and working areas of the plates - capacitors with the dielectric constant of the medium being controlled. The electrical capacity of such a capacitor is calculated by the formula

where: S - Total intersection area of ​​the plates; δ - distance between plates; ε - the dielectric constant environment between the plates; ε 0 is the dielectric constant.

Based on the shape of the plates, flat, cylindrical and other types of variable capacitors are distinguished.

Capacitive sensors only operate at frequencies above 1000Hz. Use at industrial frequency is practically impossible due to the high capacitance (Xc = = ).

Generator sensors

Generator sensors are sensors that directly transform various types energy into electrical energy. They do not require external power sources because they themselves produce emf. Generator sensors use well-known physical phenomena: the occurrence of EMF in thermocouples when heated, in photocells with a barrier layer when illuminated, the piezoelectric effect and the phenomenon of electromagnetic induction.

Induction sensors. In induction sensors, the conversion of an input non-electrical quantity into an induced emf. used to measure movement speed, linear or angular movements. E.m.f. in such sensors it is induced in coils or windings made of insulated copper wire and placed on magnetic circuits made of electrical steel.

Small-sized microgenerators that convert the angular velocity of an object into emf, the value of which is directly proportional to the rotation speed of the output shaft of the test object, are called tachogenerators of direct and alternating currents. Circuits of tachogenerators with and without an independent excitation winding are shown in Figure 4.

Figure 4 - Schemes of tachogenerators with and without an independent excitation winding

DC tachogenerators are a collector electric car with armature and field winding or permanent magnet. The latter do not require an additional power source. The principle of operation of such tachogenerators is that an emf is induced in the armature, which rotates in the magnetic flux (F) of a permanent magnet or field winding. (E), the value of which is proportional to the rotation frequency (ω) of the object:

E = cФn = cФω

To save linear dependence e.m.f. depending on the speed of rotation of the armature, it is necessary that the load resistance of the tachogenerator always remains unchanged and is many times higher than the resistance of the armature winding. The disadvantage of DC tachogenerators is the presence of a commutator and brushes, which significantly reduces its reliability. The collector provides conversion of alternating emf. armatures in direct current.

More reliable is an AC tachogenerator, in which the output intrinsically safe winding is located on the stator, and the rotor is a permanent magnet with a corresponding constant magnetic flux. Such a tachogenerator does not require a collector, but its variable emf. converted to direct current using bridge diode circuits. The principle of operation of a synchronous alternating current tachogenerator is that when the rotor is rotated by the control object, a variable emf is induced in its winding, the amplitude and frequency of which are directly proportional to the rotor rotation speed. Due to the fact that the magnetic flux of the rotor rotates at the same frequency as the rotor itself, such a tachogenerator is called synchronous. The disadvantage of a synchronous generator is that it has bearing units, which is not appropriate for mining conditions. The diagram for controlling the speed of a conveyor belt with a synchronous tachogenerator is shown in Figure 5. Figure 5 indicates: 1 - magnetic rotor of the tachogenerator, 2 - drive roller with tread, 3 - conveyor belt, 4 - stator winding of the tachogenerator.

Figure 5 - Scheme for synchronous conveyor belt speed control

tachogenerator

To measure the linear speed of movement of the working bodies of scraper conveyors, magnetic induction sensors are used, which have no moving parts at all. The moving part (armature) in this case is the steel scrapers of the conveyor, moving in the magnetic flux of a permanent magnet sensor with an intrinsically safe coil. When steel scrapers cross a magnetic flux in the coil, a variable emf is induced, directly proportional to the speed of movement and inversely proportional to the gap between the steel core of the coil and the scraper. The magnetic flux, which leads to the emf, in the coil in this case changes under the influence of steel scrapers, which, moving above the sensor, cause fluctuations in the magnetic resistance along the path of closing the magnetic flux formed by the permanent magnet. The diagram for monitoring the speed of movement of the working body of a scraper conveyor using a magnetic induction sensor is shown in Figure 6. Figure 6 indicates: 1 - scraper conveyor, 2 - steel core, 3 - steel washer, 4 - plastic washer, 5 - ring permanent magnet, 6 - sensor coil

Figure 6 - Scheme for controlling the speed of movement of the working body

scraper conveyor with magnetic induction sensor

Magnetoelastic sensors. The principle of operation of magnetoelastic sensors is based on the property of ferromagnetic materials to change the magnetic permeability m when they are deformed. This property is called magnetoelasticity, which is characterized by magnetoelastic sensitivity

Permallay (iron-nickel alloy) has the highest value S m = 200 H/m2. Some varieties of permallay, when elongated by 0.1%, increase the coefficient of magnetic permeability up to 20%. However, to obtain even such small elongations, a load of the order of 100 - 200 N/mm is required, which is very inconvenient and leads to the need to reduce the cross-section of the ferromagnetic material and requires a power source with a frequency of the order of kilohertz.

Structurally, the magnetoelastic sensor is a coil 1 with a closed magnetic circuit 2 (see Figure 7). The controlled force P, deforming the core, changes its magnetic permeability and, consequently, the inductive reactance of the coil. The load current RL, for example, a relay, is determined by the resistance of the coil.

Magnetoelastic sensors are used to monitor forces (for example, when loading skips and planting cages on fists), rock pressures, etc.

The advantages of magnetoelastic sensors are simplicity and reliability.

Disadvantages of magnetoelastic sensors - required expensive materials for magnetic cores and their special processing.

Figure 7 – Magnetoelastic sensor

Piezoelectric sensors. The piezoelectric effect is inherent in single crystals of some dielectric substances (quartz, tourmaline, Rochelle salt, etc.). The essence of the effect is that under the action of dynamic mechanical forces on the crystal, electric charges, the magnitude of which is proportional to the elastic deformation of the crystal. The dimensions and number of crystal plates are selected based on the strength and the required amount of charge. Piezoelectric sensors in most cases are used to measure dynamic processes and shock loads, vibration, etc.

Thermoelectric sensors. To measure temperatures in within wide limits 200-2500 °C thermoelectric sensors are used - thermocouples, which ensure the conversion of thermal energy into electrical emf. The principle of operation of a thermocouple is based on the phenomenon of the thermoelectric effect, which consists in the fact that when the junction and ends of thermoelectrodes are placed in an environment with different temperatures t 1 and t 2 in a circle formed by a thermocouple and a millivoltmeter, a thermo emf appears, proportional to the difference between these temperatures

Figure 8 - Thermocouple diagram

Conductors A and B of thermocouples are made of dissimilar metals and their alloys. The phenomenon of thermoelectric effect is given by a combination of such conductors A and B, copper-constantan (up to 300 ° C), copper - kopel (up to 600 ° C), chromel - kopel (up to 800 ° C), iron - kopel (up to 800 ° C) , chromel - alumel (up to 1300 ° C), platinum - platinum-rhodium (up to 1600 ° C), etc.

Thermal emf value for various types thermocouples range from tenths to tens of millivolts. For example, for a copper-constantan thermocouple it changes from 4.3 to –6.18 mB when the junction temperature changes from + 100 to – 260 o C.

Thermistor sensors. The operating principle of thermistor sensors is based on the property of the sensing element - the thermistor - to change resistance when the temperature changes. Thermistors are made of metals (copper, nickel, atin, etc.) and semiconductors (mixtures of metal oxides - copper, manganese, etc.). A metal thermistor is made of wire, for example, copper diameter approximately 0.1 mm, wound in a spiral on a mica, porcelain or quartz frame. Such a thermistor is enclosed in a protective tube with terminal clamps, which is located at the temperature control point of the object.

Semiconductor thermistors are manufactured in the form of small rods and disks with leads.

With increasing temperature, the resistance of metal thermistors increases, while for most semiconductor ones it decreases.

The advantage of semiconductor thermistors is their high thermal sensitivity (30 times more than metal ones).

The disadvantage of semiconductor thermistors is the large spread of resistance and low stability, which makes them difficult to use for measurements. Therefore, semiconductor thermistors in automation systems of mine process plants are mainly used to control the temperature values ​​of objects and their thermal protection. In this case, they are usually connected in series with an electromagnetic relay to the power source.

To measure temperature, the thermistor RK is included in a bridge circuit, which converts the resistance measurement into a voltage at the output Uout, used in the automatic control system or measuring system.

The bridge can be balanced or unbalanced.

A balanced bridge is used with the zero measurement method. In this case, the resistance R3 is changed (for example, by a special automatic device) following the change in the resistance of the thermistor Rt in such a way as to ensure equality of potential at points A and B. If the scale of the resistor R3 is graduated in degrees, then the temperature can be read by the position of its slider. The advantage of this method is high accuracy, but the disadvantage is complexity. measuring device, which is an automatic tracking system.

An unbalanced bridge produces a signal Uout, proportional to the overheating of the object. By selecting the resistances of resistors R1, R2, R3, the equilibrium of the bridge is achieved at the initial temperature value, ensuring that the condition is met

Rt / R1= R3 / R2

If the value of the controlled temperature and, accordingly, the resistance Rt changes, the balance of the bridge will be disrupted. If you connect an mV device with a scale graduated in degrees to its output, the device’s needle will show the measured temperature.

Induction flow meter

For feed control pumping unit For drainage, it is possible to use induction flow meters, for example, type IR-61M. The operating principle of an induction flow meter is based on Faraday's law (the law of electromagnetic induction).

Structural diagram induction flowmeter is shown in Figure 9. When a conducting liquid flows in a pipeline between the poles of a magnet, an emf occurs in a direction perpendicular to the direction of the liquid and in the direction of the main magnetic flux. U on the electrodes, proportional to the fluid velocity v:

where B is the magnetic induction in the gap between the magnet poles; d – internal diameter of the pipeline.

Figure 9 – Design diagram of an induction flow meter

If we express the speed v in terms of the volumetric flow rate Q, i.e.

Advantages of an induction flow meter:

They have a slight inertia of readings;

There are no parts inside the working pipeline (therefore they have minimal hydraulic losses).

Disadvantages of the flow meter:

The readings depend on the properties of the liquid being measured (viscosity, density) and the nature of the flow (laminar, turbulent);

Ultrasonic flow meters

The operating principle of ultrasonic flow meters is that

the speed of propagation of ultrasound in a moving medium of gas or liquid is equal to the geometric sum of the average speed of movement of the medium v ​​and the natural speed of sound in this medium.

The design diagram of the ultrasonic flow meter is shown in Figure 10.

Figure 10 - Design diagram of an ultrasonic flow meter

The emitter I creates ultrasonic vibrations with a frequency of 20 Hz and higher, which fall on the receiver P, which registers these vibrations (it is located at a distance l). Flow rate F is equal to

where S is the cross-sectional area of ​​the fluid flow; C – speed of sound in the medium (for liquid 1000-1500 m/s);

t1 is the duration of propagation of the sound wave in the direction of flow from the emitter I1 to the receiver P1;

t 2 – duration of propagation of the sound wave against the flow from the emitter I2 to the receiver P2;

l is the distance between the emitter I and the receiver P;

k – coefficient taking into account the distribution of speeds in the flow.

Advantages of an ultrasonic flow meter:

a) high reliability and speed;

b) the ability to measure non-conductive liquids.

Disadvantage: increased requirements for contamination of the controlled water flow.

2. Data transmission devices

Information is transferred from the automation object to the control device via communication lines (channels). Depending on the physical medium through which information is transmitted, communication channels can be divided into the following types:

– cable lines– electrical (symmetrical, coaxial, “ twisted pair", etc.), fiber-optic and combined electrical cables with fiber optic cores;

– power low-voltage and high-voltage Electricity of the net;

– infrared channels;

– radio channels.

Information transmission over communication channels can be transmitted without information compression, i.e. One information signal (analog or discrete) is transmitted over one channel, and with information compression, many information signals are transmitted over a communication channel. Information compaction is used for remote transmission of information over a considerable distance (for example, from automation equipment located on a roadway to a shearer or from a section of a mine to the surface to a dispatcher) and can be done using various types of signal coding.

Technical systems that provide transmission of information about the state of an object and control commands over a distance via communication channels can be systems remote control and measurements or telemechanical systems. In remote control and measurement systems, each signal uses its own line - a communication channel. As many signals as there are, so many communication channels are required. Therefore, with remote control and measurement, the number of controlled objects, especially over long distances, is usually limited. In telemechanical systems for transmitting many messages a large number objects use only one line, or one communication channel. Information is transmitted in encoded form, and each object “knows” its code, so the number of controlled or managed objects is practically unlimited, only the code will be more complex. Telemechanics systems are divided into discrete and analog. Discrete telecontrol systems are called telealarm systems(TS), they provide the transmission of a finite number of object states (for example, “on”, “off”). Analog television monitoring systems are called telemetering systems(TI), they provide the transmission of continuous changes in any parameters characterizing the state of the object (for example, changes in voltage, current, speed, etc.).

The elements that make up discrete signals have various qualitative characteristics: pulse amplitude, pulse polarity and duration, frequency or phase of alternating current, code in sending a series of pulses. Telemechanical systems are discussed in more detail in.

To exchange information between microprocessor controllers of various automation system devices, including control computers, they are used special means, methods and rules of interaction – interfaces. Depending on the method of data transfer, a distinction is made between parallel and serial interfaces. IN parallel interface q bits of data are transmitted over q communication lines. IN serial interface Data transmission is usually carried out over two lines: one continuously transmits clock (synchronizing) pulses from the timer, and the second carries information.

In mining machine automation systems, serial interfaces of the RS232 and RS485 standards are most often used.

The RS232 interface provides communication between two computers, a control computer and a microcontroller, or communication between two microcontrollers at speeds up to 19600 bps over a distance of up to 15m.

The RS-485 interface provides data exchange between several devices over one two-wire communication line in half-duplex mode. The RS-485 interface provides data transfer at speeds up to 10 Mbit/s. The maximum transmission range depends on the speed: at a speed of 10 Mbit/s maximum length line - 120 m, at a speed of 100 kbit/s - 1200 m. The number of devices connected to one interface line depends on the type of transceivers used in the device. One transmitter is designed to control 32 standard receivers. Receivers are available with input impedances of 1/2, 1/4, 1/8 of the standard. When using such receivers, the total number of devices can be increased accordingly: 64, 128 or 256. Data transfer between controllers is carried out according to rules called protocols. Exchange protocols in most systems operate on a master-slave principle. One device on the highway is the master and initiates the exchange by sending requests to slave devices, which differ in logical addresses. One of the popular protocols is the Modbus protocol.

2. Actuators

Execution of the decision, i.e. the implementation of the control action corresponding to the generated control signal is carried out actuators (ED). In general, an actuator is a combination of an actuator (AM) and a regulatory body (RO). The location of the actuators in the block diagram of the local ACS is shown in Figure 11.

Figure 11 - Location of actuators in the block diagram of a local automatic control system

An actuator (AM) is a device designed to convert control signals generated by the control unit (PLC) into signals convenient for influencing the final link of the ACS - the regulatory body (RO).

The actuator consists of the following basic elements:

executive motor (electric motor, piston, membrane);

clutch element (coupling, hinge);

transmission-converting element (gearbox with output lever or rod);

power amplifier (electric, pneumatic, hydraulic, combined)

In a specific MI model, a number of elements (except for the actuator motor) may be missing.

The main requirement for the IM: movement of the RO with the least possible distortion of the control laws of the generated PLC, i.e. The MI must have sufficient speed and accuracy.

Main characteristics:

a) nominal and maximum torque value

on the output shaft (rotary) or forces on the output rod;

b) the rotation time of the output shaft of the IM or the stroke of its rod;

c) the maximum value of the output shaft rotation angle or stroke

d) dead zone.

Actuators are classified according to the following criteria:

1) movement of the regulatory body (rotary and linear);

2) design (electric, hydraulic, pneumatic);

Electric – with drives electric motor and an electromagnet;

Hydraulic – with drives: piston, plunger, from a hydraulic motor;

Pneumatic – with drives: piston, plunger, membrane, diaphragm, from an air motor.

In practice, electrical MI is most widely used. Electrical MI are classified as:

electromagnetic;

electric motor

Electromagnetic MI are divided into:

IMs with drives from electromagnetic clutches are designed to transmit rotational motion (friction and sliding clutches;

IMs with a solenoid drive are 2-position devices (i.e., designed for 2-position control) that carry out translational movement of the drive elements according to the discrete principle: “on - off.”

Electric motor MI are divided into:

single-turn - the angle of rotation of the output shaft does not exceed 360 0. Example: MEO (electric single-turn mechanism). They use single-phase and three-phase (MEOK, MEOB) asynchronous motors.

multi-turn – for remote and local control of pipeline fittings (valves).

In automation systems of mining machines, electric hydraulic distributors, for example the GSD and 1RP2 types, are widely used as actuators. The 1RP2 electric hydraulic distributor is designed to control the feed speed and cutting elements of the combine as part of the URAN.1M automatic load controllers and the SAUK02.2M automation system. The 1RP2 electrohydraulic distributor is a hydraulic spool valve with a pull-type electromagnetic drive.

Regulatory body (RO) is the final element of the ACS that exercises direct control influence on the OS. RO changes the flow of material, energy, the relative position of parts of apparatus, machines or mechanisms in the direction of the normal flow of the technological process.

The main characteristic of the RO is its static characteristic, i.e. the relationship between the output parameter Y (flow, pressure, voltage) and the stroke value of the regulator in percent.

RO provide:

a) two-position regulation - the RO gate quickly moves from one extreme position to another.

b) continuous - in this case it is necessary that the throughput characteristic of the RO be strictly defined (gate, tap, butterfly valve).

Production automation tools include technical means automation (TSA) are devices and instruments that can either be automation tools themselves or be part of a hardware and software complex. Security systems in a modern enterprise include technical automation equipment. Most often, TCA is a basic element of an integrated security system.

Technical automation equipment includes devices for recording, processing and transmitting information in automated production. With their help, automated production lines are monitored, regulated and controlled.

Safety systems monitor the production process using a variety of sensors. They include pressure sensors, photo sensors, inductive sensors, capacitive sensors, laser sensors, etc.

Sensors are used to automatically extract information and convert it initially. Sensors differ in their principles of operation and in their sensitivity to the parameters they monitor. Technical safety equipment includes the widest range of sensors. It is the integrated use of sensors that makes it possible to create comprehensive security systems that control many factors.

Technical means of information also include transmitting devices that provide communication between sensors and control equipment. Upon receiving a signal from the sensors, the control equipment pauses the production process and eliminates the cause of the accident. If it is impossible to eliminate the emergency situation, technical safety equipment gives a signal about the malfunction to the operator.

The most common sensors that are included in any integrated security system are capacitive sensors.

They allow contactless detection of the presence of objects at a distance of up to 25 mm. Capacitive sensors operate according to the following principle. The sensors are equipped with two electrodes, between which conductivity is recorded. If any object is present in the control zone, this causes a change in the oscillation amplitude of the generator included in the sensor. At the same time, capacitive sensors are triggered, which prevents unwanted objects from entering the equipment.

Capacitive sensors are distinguished by their simplicity of design and high reliability, which allows them to be used in a wide variety of production areas. The only drawback is the small control area of ​​such sensors.

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Technical automation equipment (TAA) is designed to create systems that perform specified technological operations, in which humans are mainly assigned control and management functions.

Based on the type of energy used, technical automation equipment is classified into: electric, pneumatic, hydraulic And combined. Electronic automation tools are classified as a separate group, since they, using electrical energy, are designed to perform special computing and measuring functions.

By functional purpose, technical automation equipment can be divided according to standard circuit automatic control systems for actuators, amplifiers, correcting and measuring devices, converters, computing and interface devices.

Executive element - This is a device in an automatic regulation or control system that acts directly or through a matching device on a regulatory element or object of the system.

Regulating element carries out a change in the operating mode of the managed object.

Electrical actuator with mechanical output - electric motor- used as a terminal amplifier of mechanical power. The effect an object or mechanical load has on an actuator is equivalent to the action of internal, or natural, feedback. This approach is used in cases where a detailed structural analysis of the properties and dynamic features of the actuating elements is required, taking into account the action of the load. An electrical actuator with a mechanical output is an integral part of the automatic drive.

Electric drive - This is an electrical actuator that converts the control signal into a mechanical action while simultaneously amplifying it in power due to an external energy source. The drive does not have a special main feedback link and is a combination of a power amplifier, an electrical actuator, a mechanical transmission, a power source and auxiliary elements, united by certain functional connections. The output quantities of the electric drive are linear or angular speed, traction force or torque, mechanical power etc. The electric drive must have the appropriate power reserve necessary to influence the controlled object in forced mode.

Electric servomechanism is a servo drive that processes the input control signal with amplification of its power. The elements of the electrical servomechanism are covered by special feedback elements and can have internal feedback due to the load.

Mechanical transmission The electric drive or servomechanism coordinates the internal mechanical resistance of the actuator with the mechanical load - the regulatory body or control object. Mechanical transmissions include various gearboxes, crank, lever mechanisms and other kinematic elements, including transmissions with hydraulic, pneumatic and magnetic supports.

Electrical power supplies actuators, devices and servomechanisms are divided into sources with practically infinite power, with a value of their internal resistance close to zero, and sources with limited power with a value of internal resistance different from zero.

Pneumatic and hydraulic actuators are devices that use gas and liquid, respectively, under a certain pressure as an energy carrier. These systems occupy a strong place among other automation equipment due to their advantages, which, first of all, include reliability, resistance to mechanical and electromagnetic influences, a high ratio of the developed drive power to its own weight and fire and explosion safety.

The main task of the actuator is to amplify the signal arriving at its input to a power level sufficient to have the required effect on the object in accordance with the stated control goal.

An important factor when choosing an actuator is to ensure the specified system quality indicators with the available energy resources and permissible overloads.

The characteristics of the actuator must be determined from the analysis of the automated process. Such characteristics of actuators and servomechanisms are energy, static, dynamic characteristics, as well as technical, economic and operational characteristics.

A mandatory requirement for the actuator drive is to minimize engine power while ensuring the required speeds and torques. This leads to minimization of energy costs. Very important factors when choosing an actuator or servomechanism there are weight restrictions, overall dimensions and reliability.

Important components of automation systems are amplification and correction devices. Common tasks solved by correction and amplification devices of automation systems are the formation of the required static and frequency characteristics, synthesis of feedback, coordination with the load, ensuring high reliability and unification of devices.

Amplifier devices the power of the signal is amplified to the level necessary to control the actuator.

Special requirements for corrective elements of systems with variable parameters are the possibility and ease of restructuring the structure, program and parameters of corrective elements. Amplifier devices must meet certain technical conditions for specific and maximum output power.

The structure of an amplification device is, as a rule, a multistage amplifier with complex feedback connections, which are introduced to improve its static, dynamic and operational characteristics.

Amplification devices used in automation systems can be divided into two groups:

1) electrical amplifiers with electrical power sources;

2) hydraulic and pneumatic amplifiers, using liquid or gas, respectively, as the main energy carrier.

The power source or energy carrier determines the most essential features of automation amplification devices: static and dynamic characteristics, specific and maximum power, reliability, operational and technical and economic indicators.

Electrical amplifiers include electronic vacuum, ionic, semiconductor, dielectric, magnetic, magnetic-semiconductor, electric machine and electromechanical amplifiers.

Quantum amplifiers and generators constitute a special subgroup of devices used as amplifiers and converters of weak radio and other signals.

Corrective devices generate correction signals for the static and dynamic characteristics of the system.

Depending on the type of inclusion in the system, linear corrective devices are divided into three types: serial, parallel corrective elements and corrective feedback. The use of one or another type of correction devices is determined by the convenience of technical implementation and operational requirements.

It is advisable to use corrective elements of the sequential type if the signal, the value of which is functionally related to the error signal, is an unmodulated electrical signal. The synthesis of a sequential correction device in the process of designing a control system is the simplest.

Parallel type correction elements are convenient to use when forming a complex control law with the introduction of an integral and derivatives of the error signal.

Corrective feedback, covering amplifiers or actuators, is most widely used due to the simplicity of its technical implementation. In this case, the input of the feedback element receives a relatively high level signal, for example, from the output stage of an amplifier or motor. The use of corrective feedback makes it possible to reduce the influence of nonlinearities of those system devices that are covered by them; therefore, in some cases it is possible to improve the quality of the control process. Corrective feedback stabilizes the static coefficients of the covered devices in the presence of interference.

Automatic regulation and control systems use electrical, electromechanical, hydraulic and pneumatic corrective elements and devices. Electrical correction devices are most simply implemented using passive quadripoles, which consist of resistors, capacitors and inductances. Complex electrical correction devices also include separating and matching electronic elements.

Electromechanical correction devices, in addition to passive quadripoles, include tachogenerators, impellers, differentiating and integrating gyroscopes. In some cases, an electromechanical correction device can be implemented in the form of a bridge circuit, in one of the arms of which an electric motor of the actuator is connected.

Hydraulic and pneumatic correction devices can consist of special hydraulic and pneumatic filters included in the feedback loops of the main elements of the system, or in the form of flexible feedback loops for pressure (pressure difference), flow rate of working fluid, or air.

Corrective elements with tunable parameters ensure system adaptability. The implementation of such elements is carried out using relay and discrete devices, as well as computers. Such elements are usually referred to as logical corrective elements.

A computer operating in real time in a closed control loop has practically unlimited computing and logical capabilities. The main function of the control computer is to calculate optimal controls and laws that optimize the behavior of the system in accordance with one or another quality criterion during its normal operation. The high speed of the control computer allows, along with the main function, to perform a number of auxiliary tasks, for example, with the implementation of a complex linear or nonlinear digital correction filter.

In the absence of computers in systems, it is most advisable to use nonlinear correcting devices as they have the greatest functional and logical capabilities.

Regulating devices They are a combination of actuators, amplifying and correcting devices, converters, as well as computing and interface units.

Information about the parameters of the control object and about possible external influences affecting it comes to the control device from the measuring device. Measuring devices in the general case, they consist of sensitive elements that perceive changes in the parameters by which the process is regulated or controlled, as well as additional converters that often perform signal amplification functions. Together with sensitive elements, these converters are designed to convert signals of one physical nature into another, corresponding to the type of energy used in the automatic regulation or control system.

In automation converting devices or converters These are elements that do not directly perform the functions of measuring regulated parameters, amplifying signals or correcting the properties of the system as a whole and do not have a direct impact on the regulatory body or the controlled object. Converting devices in this sense are intermediate and perform auxiliary functions associated with the equivalent transformation of a quantity of one physical nature into a form more convenient for the formation of a regulatory effect or for the purpose of coordinating devices that differ in the type of energy at the output of one and the input of another device.

Computer devices for automation equipment are, as a rule, built on the basis of microprocessor-based tools.

Microprocessor- a software-controlled tool that carries out the process of processing and managing digital information, built on one or more integrated circuits.

The main technical parameters of microprocessors are the bit depth, addressable memory capacity, versatility, the number of internal registers, the presence of microprogram control, the number of interrupt levels, the type of stack memory and the number of main registers, as well as the composition of the software. Based on their word width, microprocessors are divided into microprocessors with a fixed word width and modular microprocessors with variable word width.

By microprocessor means are structurally and functionally complete products of computer and control equipment, built in the form or on the basis of microprocessor integrated circuits, which, from the point of view of requirements for testing, acceptance and delivery, are considered as a single whole and are used in the construction of more complex microprocessor tools or microprocessor systems.

Structurally, microprocessor means are made in the form of a microcircuit, single-board product, monoblock or standard complex, and products of the lower level of the structural hierarchy can be used in products of the highest level.

Microprocessor systems - These are computing or control systems built on the basis of microprocessor-based tools that can be used autonomously or integrated into a controlled object. Structurally, microprocessor systems are made in the form of a microcircuit, a single-board product, a monoblock complex or several products of the indicated types, built into the equipment of the controlled object or made autonomously.

According to the scope of application, technical means of automation can be divided into technical means of automation of work in industrial production and technical means of automation of other work, the most important component of which is work in extreme conditions where human presence is life-threatening or impossible. In the latter case, automation is carried out on the basis of special stationary and mobile robots.

Technical means of automation of chemical production: Reference. ed./V.S.Balakirev, L.A.Barsky, A.V.Bugrov, etc. - M.: Chemistry, 1991. –272 p.

The introduction of technical means into enterprises that allow automation of production processes is a basic condition for effective work. The variety of modern automation methods expands the range of their application, while the costs of mechanization, as a rule, are justified by the end result in the form of an increase in the volume of manufactured products, as well as an increase in their quality.

Organizations that follow the path of technological progress occupy leading positions in the market and provide better quality working conditions and minimize the need for raw materials. For this reason, it is no longer possible to imagine large enterprises without implementing mechanization projects - exceptions apply only to small craft industries, where automation of production does not justify itself due to the fundamental choice in favor of manual production. But even in such cases, it is possible to partially turn on automation at some stages of production.

Automation Basics

In a broad sense, automation involves the creation of such conditions in production that will allow certain tasks for the manufacture and release of products to be performed without human intervention. In this case, the operator’s role may be to solve the most critical tasks. Depending on the goals, automation technological processes and production can be complete, partial or complex. The choice of a specific model is determined by the complexity of the technical modernization of the enterprise due to automatic filling.

In plants and factories where full automation is implemented, usually mechanized and electronic systems management is transferred all the functionality to control production. This approach is most rational if operating conditions do not imply changes. In partial form, automation is being introduced at individual stages of production or during the mechanization of autonomous technical component, without requiring the creation of a complex infrastructure to manage the entire process. A comprehensive level of production automation is usually implemented in certain areas - this could be a department, workshop, line, etc. In this case, the operator controls the system itself without affecting the direct work process.

Automated control systems

To begin with, it is important to note that such systems require full control over an enterprise, factory or factory. Their functions can extend to a specific piece of equipment, conveyor, workshop or production area. In this case, process automation systems receive and process information from the serviced object and, based on this data, have a corrective effect. For example, if the operation of a production complex does not meet the parameters of technological standards, the system will use special channels to change its operating modes according to the requirements.

Automation objects and their parameters

The main task when introducing production mechanization means is to maintain the quality parameters of the facility, which will ultimately affect the characteristics of the product. Today, experts try not to delve into the essence of the technical parameters of various objects, since theoretically the implementation of control systems is possible at any component of production. If we consider in this regard the basics of automation of technological processes, then the list of mechanization objects will include the same workshops, conveyors, all kinds of devices and installations. One can only compare the degree of complexity of implementing automation, which depends on the level and scale of the project.

Regarding the parameters with which they work automatic systems, we can distinguish input and output indicators. In the first case, these are the physical characteristics of the product, as well as the properties of the object itself. In the second, these are the direct quality indicators of the finished product.

Regulating technical means

Devices that provide regulation are used in automation systems in the form of special alarms. Depending on their purpose, they can monitor and control various process parameters. In particular, automation of technological processes and production can include alarms temperature indicators, pressure, flow characteristics, etc. Technically, the devices can be implemented as scaleless devices with electrical contact elements at the output.

The operating principle of the control alarms is also different. If we consider the most common temperature devices, we can distinguish manometric, mercury, bimetallic and thermistor models. Structural design, as a rule, is determined by the principle of operation, but operating conditions also have a significant influence on it. Depending on the direction of the enterprise’s work, automation of technological processes and production can be designed taking into account specific operating conditions. For this reason, control devices are developed with a focus on use in conditions high humidity, physical pressure or the effects of chemicals.

Programmable automation systems

The quality of management and control of production processes has noticeably increased against the background of the active supply of enterprises with computing devices and microprocessors. From the point of view of industrial needs, the capabilities of programmable hardware make it possible not only to ensure effective control of technological processes, but also to automate design, as well as conduct production tests and experiments.

Computer devices that are used on modern enterprises, solve problems of regulation and control of technological processes in real time. Such production automation tools are called computing systems and operate on the principle of aggregation. Systems include unified functional blocks and modules from which they can be composed various configurations and adapt the complex to work in certain conditions.

Units and mechanisms in automation systems

The direct execution of work operations is carried out by electrical, hydraulic and pneumatic devices. According to the principle of operation, the classification involves functional and portion mechanisms. Similar technologies are usually implemented in the food industry. Automation of production in this case involves the introduction of electrical and pneumatic mechanisms, the designs of which may include electric drives and regulatory bodies.

Electric motors in automation systems

The basis of actuators is often formed by electric motors. Depending on the type of control, they can be presented in non-contact and contact versions. Units that are controlled by relay contact devices can change the direction of movement of the working parts when manipulated by the operator, but the speed of operations remains unchanged. If automation and mechanization of technological processes using non-contact devices is assumed, then semiconductor amplifiers are used - electrical or magnetic.

Panels and control panels

To install equipment that must provide control and monitoring production process At enterprises, special consoles and panels are installed. Devices for automatic control and regulation, instrumentation, protective mechanisms, as well as various elements of communication infrastructure. By design, such a shield can be a metal cabinet or a flat panel on which automation equipment is installed.

The console, in turn, is the center for remote control - it is a kind of control room or operator area. It is important to note that the automation of technological processes and production should also provide access to maintenance by personnel. It is this function that is largely determined by consoles and panels that allow you to make calculations, evaluate production indicators and generally monitor the work process.

Automation systems design

The main document that serves as a guide for the technological modernization of production for the purpose of automation is the diagram. It displays the structure, parameters and characteristics of devices, which will later act as means of automatic mechanization. In the standard version, the diagram displays the following data:

  • level (scale) of automation at a specific enterprise;
  • determining the operating parameters of the facility, which must be provided with means of control and regulation;
  • control characteristics - full, remote, operator;
  • possibility of blocking actuators and units;
  • configuration of the location of technical equipment, including on consoles and panels.

Auxiliary automation tools

Despite their secondary role, additional devices provide important monitoring and control functions. Thanks to them, the same connection between actuators and a person is ensured. In terms of equipping with auxiliary devices, production automation may include push-button stations, control relays, various switches and command panels. There are many designs and varieties of these devices, but they are all focused on ergonomic and safe control of key units on site.

The means of generating and primary processing of information include keyboard devices for applying data to cards, tapes or other information carriers by mechanical (punching) or magnetic methods; the accumulated information is transferred for subsequent processing or reproduction. Keyboard devices, punching or magnetic blocks and transmitters are used to make up production recorders for local and system purposes, which generate primary information in workshops, warehouses and other places of production.

Sensors (primary transducers) are used to automatically extract information. They are very diverse devices in terms of operating principles that sense changes in the controlled parameters of technological processes. Modern measuring technology can directly evaluate more than 300 different physical, chemical and other quantities, but this requires automation in a number of new areas human activity sometimes it's not enough. An economically feasible expansion of the range of sensors in the GPS is achieved by unifying the sensitive elements. Sensitive elements that respond to pressure, force, weight, speed, acceleration, sound, light, thermal and radioactive radiation are used in sensors to control the loading of equipment and its operating modes, the quality of processing, accounting for the release of products, monitoring their movements on conveyors, stocks and consumption of materials, workpieces, tools, etc. The output signals of all these sensors are converted into standard electrical or pneumatic signals, which are transmitted by other devices.

Devices for transmitting information include signal converters into forms of energy convenient for broadcasting, telemechanics equipment for transmitting signals via communication channels over long distances, switches for distributing signals to places where information is processed or presented. These devices connect all peripheral sources of information (keyboard devices, sensors) with the central part of the control system. Their purpose is efficient use communication channels, eliminating signal distortion and the influence of possible interference during transmission over wired and wireless lines.

Devices for logical and mathematical information processing include functional converters that change the nature, shape or combination of information signals, as well as devices for processing information according to given algorithms (including computers) in order to implement laws and control (regulation) modes.

Computers for communication with other parts of the control system are equipped with information input and output devices, as well as storage devices for temporary storage of source data, intermediate and final results calculations, etc. (see Data input. Data output, Storage device).

Devices for presenting information show the human operator the state of production processes and record its most important parameters. Such devices are signal boards, mnemonic diagrams with visual symbols on boards or control panels, secondary pointer and digital indicating and recording instruments, cathode ray tubes, alphabetic and digital typewriters.

Devices for generating control actions convert weak information signals into more powerful energy pulses of the required shape, necessary to activate protection, regulation or control actuators.

Ensuring high quality of products is associated with automation of control at all main stages of production. Subjective human assessments are replaced by objective indicators from automatic measuring stations linked to central points where the source of defects is determined and from where commands are sent to prevent deviations outside of tolerances. Of particular importance is automatic control using computers in the production of radio-technical and radio-electronic products due to their mass production and a significant number of controlled parameters. No less important are final tests of finished products for reliability (see Reliability technical devices). Automated stands for functional, strength, climatic, energy and specialized tests allow you to quickly and identically check technical and economic characteristics products (products).

Actuating devices consist of starting equipment, actuating hydraulic, pneumatic or electrical mechanisms (servomotors) and regulatory bodies that act directly on the automated process. It is important that their operation does not cause unnecessary energy losses and reduce the efficiency of the process. For example, throttling, which is usually used to regulate the flow of steam and liquids, based on an increase hydraulic resistance in pipelines, they are replaced by influencing flow-forming machines or other, more advanced methods of changing the flow speed without loss of pressure. Great importance has economical and reliable control of an AC electric drive, the use of gearless electric actuators, and contactless ballasts for controlling electric motors.

The idea of ​​constructing instruments for monitoring, regulation and control in the form of units consisting of independent blocks that perform certain functions, implemented in GSP, made it possible to various combinations using these blocks to obtain a wide range of devices for solving diverse problems using the same means. Unification of input and output signals ensures a combination of blocks with various functions and their interchangeability.

The GSP includes pneumatic, hydraulic and electrical devices and devices. The greatest versatility is electrical devices, intended for receiving, transmitting and reproducing information.

The use of a universal system of industrial pneumatic automation elements (USEPPA) made it possible to reduce the development of pneumatic devices mainly to assembling them from standard units and parts with a small number of connections. Pneumatic devices are widely used for control and regulation in many fire and explosion hazardous industries.

GSP hydraulic devices are also assembled from blocks. Hydraulic instruments and devices control equipment that requires high speeds to move control elements with significant effort and high precision, which is especially important in machine tools and automatic lines.

In order to most rationally systematize GSP facilities and to increase the efficiency of their production, as well as to simplify the design and configuration of automated control systems, GSP devices are combined into aggregate complexes during development. Aggregate complexes, thanks to the standardization of input-output parameters and block design of devices, most conveniently, reliably and economically combine various technical means into automated systems controls and allow you to assemble a variety of specialized installations from multi-purpose automation units.

Targeted aggregation of analytical equipment, testing machines, mass-dosing mechanisms with unified measuring, computing and office equipment facilitates and accelerates the creation of basic designs of this equipment and the specialization of factories for their production.