Category: Industry trends

Distributed Control System (DCS) is a control system based on computer networks, which has high reliability, flexibility, and scalability. DCS is widely used for production process control in industries such as petroleum, chemical, power, metallurgy, and building materials. This article will provide a detailed introduction to the basic principles of DCS control, including its composition, working principle, characteristics, and applications.

1、 Composition of DCS
DCS mainly consists of the following parts:

Controller: The controller is the core component of DCS, responsible for real-time control of the production process. Controllers usually use high-performance microprocessors or digital signal processors, which have the characteristics of high speed, high precision, and high reliability.
I/O Module: The I/O module is the interface between DCS and field devices, responsible for converting the status signals of field devices into digital signals or converting the control signals of controllers into signals recognizable by field devices.
Communication Network: The communication network is the information transmission channel between various components of DCS, usually using communication technologies such as industrial Ethernet and fieldbus.
Human Machine Interface (HMI): The HMI is the interface through which operators interact with DCS, typically including operator stations, engineer stations, etc. The human-machine interface can display real-time data, trend curves, alarm information, etc. of the production process, and can also set and modify control parameters.
Database: The database is used to store DCS configuration information, historical data, alarm records, etc.
2、 The working principle of DCS

The working principle of DCS mainly includes the following aspects:

Data collection: DCS collects real-time status signals of on-site equipment, such as temperature, pressure, flow rate, etc., through input/output modules.
Data processing: The controller processes the collected data, such as filtering, scaling conversion, calculation, etc.
Control algorithm: The controller controls the processed data and generates control signals based on the control strategy and algorithm.
Control output: The controller outputs the generated control signal to the on-site equipment through the output/output module, achieving control over the production process.
Communication: DCS components exchange data and share information through a communication network.
Human computer interaction: Operators monitor and operate DCS through the human-machine interface.
Data storage: DCS stores real-time data, historical data, alarm records, etc. of the production process in a database for subsequent analysis and processing.
3、 Characteristics of DCS

Highly integrated: DCS integrates multiple functions such as control, communication, and human-computer interaction into one system, achieving comprehensive control and management of the production process.
High reliability: DCS adopts redundant design, fault detection and diagnosis technologies to ensure the stable operation of the system.
High flexibility: DCS can be modularized and expanded according to the needs of the production process, meeting the production requirements of different scales and complexities.
Highly Scalable: DCS can achieve system expansion by adding controllers, input/output modules, and other components.
High real-time performance: DCS adopts real-time operating system and high-speed communication technology to ensure the real-time transmission and processing of control signals.
Highly open: DCS supports multiple communication protocols and interfaces, allowing for integration and interoperability with other systems.
4、 Application of DCS

DCS is widely used in the following fields:

Petrochemical industry: DCS is used in the petrochemical industry to control production processes such as refining, fertilizers, and ethylene.
Power industry: DCS is used in the power industry to control the operation of equipment such as power plants and substations.
Metallurgical industry: DCS is used in the metallurgical industry to control the production processes of steel, non-ferrous metals, and other materials.
Building materials industry: DCS is used in the building materials industry to control the production processes of cement, glass, and other materials.
Water treatment industry: DCS is used in the water treatment industry to control the operation of equipment such as waterworks and sewage treatment plants.
Food and beverage industry: DCS is used in the food and beverage industry to control the production process, ensure product quality and safety.
5、 The development trend of DCS

With the continuous development of information technology, DCS is also constantly innovating and upgrading. The future DCS will have the following characteristics:

Higher intelligence: DCS will integrate technologies such as artificial intelligence and big data to achieve more intelligent control and management.
Stronger interconnection: DCS will realize deep integration with industrial Internet, Internet of Things and other technologies, and realize interconnection between equipment, systems and enterprises.
Better user experience: DCS will adopt a more user-friendly design, provide a more user-friendly human-computer interaction interface, and improve the work efficiency and satisfaction of operators.
Stronger security: DCS will strengthen security protection measures to prevent hacker attacks and data leaks, ensuring the safety and stability of the production process.
Lower energy consumption: DCS will adopt more energy-efficient technologies and equipment to reduce energy consumption in the production process and achieve green production.
In short, DCS, as an advanced control system, has been widely used in various fields. With the continuous development of technology, DCS will become more intelligent, interconnected, and user-friendly, providing more efficient, safe, and environmentally friendly solutions for the control and management of production processes.

What is a PLC control system? What does PLC mean? What is PLC

Since the 1960s, when the United States introduced Programmable Logic Controllers (PLCs) to replace traditional relay control devices, PLCs have experienced rapid development and have been widely used around the world. At the same time, the functions of PLC are constantly improving. With the continuous development of computer technology, signal processing technology, control technology, and network technology, as well as the increasing demand from users, PLC has added functions such as analog processing and motion control on the basis of switch processing. Today’s PLCs are no longer limited to logic control, but also play a very important role in fields such as motion control and process control.

As the preferred product for discrete control, PLC developed rapidly in the 1980s and 1990s, with an annual growth rate of 20% to 30% worldwide. With the continuous improvement of factory automation and the expansion of the PLC market capacity base, the growth rate of PLC in industrialized countries has slowed down in recent years. However, the growth of PLC is very rapid in developing countries such as China. Based on relevant information, the global sales revenue of PLCs in 2004 was around 10 billion US dollars, occupying a very important position in the field of automation.

PLC was developed based on the simulation of the original relay control principle. In the 1970s, PLC only had switch logic control and was first applied in the automotive manufacturing industry. It stores instructions for performing logical operations, sequential control, timing, counting, and arithmetic operations; And control various types of machinery or production processes through digital input and output operations. The control program developed by the user expresses the process requirements of the production process and is pre stored in the user program memory of the PLC. Execute the stored program content one by one during runtime to complete the operations required by the process flow. The CPU of the PLC has a program counter that indicates the storage address of the program step. During the program running process, the counter automatically increments by 1 for each executed step. The program executes sequentially from the starting step (step number zero) to the final step (usually the END instruction), and then returns to the starting step for cyclic calculation. The time required for a PLC to complete each cycle operation is called a scanning cycle. Different models of PLCs have a cyclic scanning period ranging from 1 microsecond to several tens of microseconds. PLC uses ladder diagram programming, which shows the advantage of being fast in solving logic. At the microsecond level, it can solve 1K logic programs in less than 1 millisecond. It treats all inputs as switch values, with 16 bits (or 32 bits) being an analog signal. Large PLCs use another CPU to perform analog calculations. Send the calculation results to the PLC controller.
A system with the same number of I/O points has a lower cost (about 40% savings) when using PLC compared to DCS. PLC does not have a dedicated operation station, and its software and hardware are universal, so maintenance costs are much lower than DCS. A PLC controller can receive thousands of I/O points (up to over 8000 I/O points). If the controlled object is mainly equipment interlocking with few circuits, PLC is more suitable. Due to the use of universal monitoring software, PLC is easier to design management information systems for enterprises.
In the past decade, with the continuous decrease in PLC prices and the expansion of user demand, more and more small and medium-sized equipment have begun to use PLC for control, and the application of PLC in China has grown rapidly. With the rapid development of the Chinese economy and the continuous improvement of basic automation level, PLC will continue to maintain a high-speed growth momentum in China in the coming period.

When a general-purpose PLC is applied to specialized equipment, it can be considered as an embedded controller, but PLC has higher reliability and better stability compared to general embedded controllers. In practical work, some users who used embedded controllers are gradually replacing them with general-purpose PLCs or customized PLCs.

What is PLC?
It is a real-time system that is different from the traditional relay based motor control system of personal computers. Whenever the design is changed, the entire system needs to be remade, which is not only time-consuming but also laborious; At the same time, due to the disadvantages of poor contact, wear, and large size of relays, they cause problems such as increased cost, low reliability, and difficulty in maintenance. In order to improve these disadvantages, DEC in the United States first published the Programmable Controller in 1969

At the beginning of its publication, the programmable logic controller (PLC) was called the Programmable Logic Controller (PLC). Its original purpose was to replace relays and perform sequential control of relay logic and other timing or counting functions. Therefore, it is also known as a sequential controller. Its structure is similar to a microcomputer, so it can also be called a microcomputer programmable controller (MCPC). It was not until 1976 that the American Electrical Machinery Manufacturers Association officially named it the Programmable Controller, abbreviated as PC. Due to the widespread use of personal computers and their frequent use in conjunction with programmable controllers, in order to distinguish between the two, programmable controllers are generally referred to as PLCs At present, there are various types of PLCs on the market, which vary depending on the manufacturer and applicable location. However, each brand can be classified into large, medium, and small sizes according to the complexity of the unit; Most factories and schools usually use small PLCs, among which the Japanese MITSUBISHI F-series and the A-series PLCs produced by Shilin Electric in China are more popular among Chinese people And this CAI will mainly introduce Mitsubishi FX2 PLC, hoping that users can have a deeper understanding of PLC and be more proficient in using PLC The basic internal structure of a programmable controller can be represented by the following diagram. Its internal units include three major parts: CPU, input module, and output module. The CPU of the PLC will obtain the signals generated by the input components through the input module, and then retrieve the control instructions originally input from the programmer from the memory one by one. After logical calculation by the computing department, the results will be driven by the output module to drive the external output components

Internal structure diagram of PLC
Program input device: responsible for providing operator input, modification, and monitoring of the functions used by the program
Central processing unit (CPU): responsible for PLC management, execution, computation, control and other functions
Program memory: responsible for storing sequential program parameters and annotations designed by users
Data memory: responsible for storing the state of input and output devices and the conversion data of sequential programs
System memory: stores the system programs required for PLC to execute sequential control
Input circuit: responsible for receiving signals from external input components
Output circuit: responsible for receiving signals from external output components
Widely used in industrial applications, such as the control of various automation equipment in semiconductor wafer factories, elevators, mechanical parking equipment, roadside traffic light change control, and automated production lines

Basic structure of PLC

PLC is essentially a computer specialized for industrial control, and its hardware structure is basically the same as that of a microcomputer
A Central Processing Unit (CPU)
The central processing unit (CPU) is the control center of the PLC. It receives and stores user programs and data entered from the programmer according to the functions assigned by the PLC system program; Check the status of power supply, memory, I/O, and alert timer, and be able to diagnose syntax errors in user programs. When the PLC is put into operation, it first receives the status and data of various input devices on site in a scanning manner, and stores them separately in the I/O mapping area. Then, it reads the user program from the user program memory one by one, interprets the commands, and executes logical or arithmetic operations according to the instructions. The results are then sent to the I/O mapping area or data register. After all user programs have been executed, the output states or data in the output registers of the I/O mapping area are finally transferred to the corresponding output devices, and this process is repeated until it stops running.
In order to further improve the reliability of PLCs, in recent years, redundant systems with dual CPUs or voting systems with three CPUs have been adopted for large PLCs. In this way, even if a CPU fails, the entire system can still operate normally.
b. Memory storage
The memory that stores system software is called system program memory.
The memory that stores application software is called user program memory.
C. Power supply
The power supply of PLC plays a very important role in the entire system. Without a good and reliable power system, it cannot function properly, so PLC manufacturers attach great importance to the design and manufacturing of power supplies. Generally, if the AC voltage fluctuates within the range of+10% (+15%), the PLC can be directly connected to the AC power grid without taking any other measures.
The working principle of PLC
One scanning technique
After the PLC is put into operation, its working process is generally divided into three stages, namely input sampling, user program execution, and output refresh. Completing the above three stages is called a scanning cycle. During the entire operation, the CPU of the PLC repeatedly executes the above three stages at a certain scanning speed.
（1） Input sampling stage
In the input sampling stage, the PLC sequentially reads in all input states and data in a scanning manner, and stores them in the corresponding units in the I/O mapping area. After the input sampling is completed, it enters the user program execution and output refresh phase. In these two stages, even if the input state and data change, the state and data of the corresponding unit in the I/O mapping area will not change. Therefore, if the input is a pulse signal, the width of the pulse signal must be greater than one scanning period to ensure that the input can be read in under any circumstances.
（2） User program execution phase
During the execution phase of the user program, the PLC always scans the user program in a top-down order (ladder diagram). When scanning each ladder diagram, always scan the control circuit composed of each contact on the left side of the ladder diagram first, and perform logical operations on the control circuit composed of contacts in the order of left to right and top to bottom. Then, based on the result of the logical operation, refresh the corresponding bit status of the logical coil in the system RAM storage area; Or refresh the status of the corresponding bit of the output coil in the I/O mapping area; Or determine whether to execute the special functional instructions specified in the ladder diagram.
That is, during the execution of the user program, only the state and data of the input point in the I/O mapping area will not change, while the state and data of other output points and software devices in the I/O mapping area or system RAM storage area may change. Moreover, the ladder diagram at the top will have an effect on any ladder diagram below that uses these coils or data; On the contrary, in the ladder diagram below, the status or data of the refreshed logic coil can only affect the program above it in the next scanning cycle.
（3） Output refresh phase
After scanning the user program, the PLC enters the output refresh phase. During this period, the CPU refreshes all output latch circuits according to the corresponding states and data in the I/O image area, and then drives the corresponding peripherals through the output circuits. At this point, it is the true output of the PLC.
The same number of ladder diagrams, with different arrangement orders, result in different execution outcomes. In addition, there are differences between the results of scanning user programs and the hard logic parallel operation of relay control devices. Of course, if the time occupied by the scanning cycle can be ignored for the entire operation, then there is no difference between the two.
Generally speaking, the scanning cycle of PLC includes self diagnosis, communication, etc., as shown in the following figure, that is, one scanning cycle is equal to the sum of all the time for self diagnosis, communication, input sampling, user program execution, output refresh, etc.

Application Fields of PLC
At present, PLC has been widely used in various industries such as steel, petroleum, chemical, power, building materials, machinery manufacturing, automobiles, textiles, transportation, environmental protection, and cultural entertainment both domestically and internationally. The usage can be roughly classified into the following categories.

Logic control of switch quantity
This is the most basic and widely used application field of PLC, which replaces traditional relay circuits to achieve logic control and sequential control. It can be used for controlling a single device, as well as for multi machine group control and automated assembly lines. Such as injection molding machines, printing machines, bookbinding machines, modular machine tools, grinding machines, packaging production lines, electroplating assembly lines, etc.

Analog control
In industrial production processes, there are many continuously changing quantities, such as temperature, pressure, flow rate, liquid level, and speed, which are all analog quantities. In order for a programmable controller to process analog signals, it is necessary to implement A/D conversion and D/A conversion between analog and digital signals. PLC manufacturers produce matching A/D and D/A conversion modules to enable programmable controllers for analog control.

Motion control
PLC can be used for controlling circular or linear motion. In terms of control mechanism configuration, in the early days, it was directly used to connect position sensors and actuators to switch I/O modules, but now specialized motion control modules are generally used. A single axis or multi axis position control module that can drive stepper motors or servo motors. Almost all major PLC manufacturers in the world have motion control functions in their products, which are widely used in various machinery, machine tools, robots, elevators, and other applications.

process control
Process control refers to closed-loop control of analog quantities such as temperature, pressure, and flow rate. As an industrial control computer, PLC can develop various control algorithm programs to achieve closed-loop control. PID regulation is a commonly used adjustment method in general closed-loop control systems. Large and medium-sized PLCs all have PID modules, and currently many small PLCs also have this functional module. PID processing generally involves running specialized PID subroutines. Process control has a wide range of applications in metallurgy, chemical engineering, heat treatment, boiler control, and other fields.

data processing
Modern PLCs have functions such as mathematical operations (including matrix operations, function operations, and logical operations), data transmission, data conversion, sorting, table lookup, and bit operations, which can complete data collection, analysis, and processing. These data can be compared with reference values stored in memory to perform certain control operations, and can also be transmitted to other intelligent devices through communication functions or printed into tables. Data processing is generally used for large-scale control systems, such as unmanned flexible manufacturing systems; It can also be used in process control systems, such as some large-scale control systems in the paper, metallurgy, and food industries.

Communication and networking
PLC communication includes communication between PLCs and communication between PLCs and other intelligent devices. With the development of computer control, factory automation networks have developed rapidly, and various PLC manufacturers attach great importance to the communication function of PLCs and have launched their own network systems. The newly produced PLCs all have communication interfaces, making communication very convenient.

Future prospects of PLC
In the 21st century, PLC will have greater development. Technically speaking, new achievements in computer technology will be more applied to the design and manufacturing of programmable controllers, resulting in the emergence of varieties with faster computing speed, larger storage capacity, and stronger intelligence; From the perspective of product scale, it will further develop towards ultra small and ultra large sizes; From the perspective of product compatibility, the variety of products will be more diverse and the specifications will be more complete. A perfect human-machine interface and complete communication equipment will better adapt to the needs of various industrial control scenarios; From the market perspective, the situation where each country produces multiple varieties of products will break with the intensification of international competition, resulting in a situation where a few brands monopolize the international market and the emergence of internationally recognized programming languages; From the perspective of network development, the networking of programmable controllers and other industrial control computers to form large-scale control systems is the direction of programmable controller technology. There are already a large number of programmable controllers applied in the current computer distributed control system (DCS). With the development of computer networks, programmable controllers, as an important component of automation control networks and international general networks, will play an increasingly important role in many fields beyond industry.

How to know if the motor is a vector motor

To determine whether a motor is a vector motor, one can start from the following aspects:
1. Motor type: Vector motor, also known as vector control motor, is a high-performance AC asynchronous motor, usually including two types: induction motor and permanent magnet synchronous motor.

2. Control method: Vector motors can achieve high-precision control of the motor’s magnetic field and current through vector control, thereby enabling the motor to operate efficiently. Generally speaking, vector motor controllers will indicate the vector control function. If the motor controller supports vector control, it means that the motor is a vector motor.

3. Performance indicators: Vector motors have the characteristics of high precision, high efficiency, and high controllability, with better dynamic performance and higher efficiency. Their rated power is usually greater than traditional induction motors, making them more suitable for high-performance motor applications.

4. Motor appearance: Compared with traditional induction motors, vector motors usually have a more compact appearance, as well as higher power density and torque density, which can better adapt to high demand industrial applications.

It is possible to preliminarily determine whether a motor is a vector motor through the above methods, but in order to accurately identify the type of motor, it is best to search for product information or consult professionals.

Advantages and disadvantages of vector motors

As a high-performance motor, vector motor has the following advantages and disadvantages:

Advantages:

1. High precision: Vector motors can achieve high-precision torque and speed control, which is of great significance in high-precision application fields.

2. High efficiency: Vector motors can achieve efficient operation through efficient control algorithms, and have broad application prospects in the field of energy conservation.

3. Fast response: Vector motors have excellent response capability and dynamic performance, and can quickly respond to changes in control signals in a short period of time.

4. High reliability: The vector motor controller has a complete protection mechanism, which can effectively reduce the motor failure rate and ensure the stability of the equipment.

5. Easy to operate: The operation of the vector motor controller is relatively simple, and advanced controller functions can be achieved by setting parameters through the controller.

Disadvantages:

1. Higher selling price: Compared to traditional induction motors, vector motors have higher costs and require higher technological investment and process support.

2. High technical requirements: The control algorithm of vector motors is relatively complex and requires higher technical and process support, making it difficult to master.

3. Poor adaptability: Vector motors have poor adaptability in some harsh environments, especially in situations with high temperatures, high humidity, and a lot of dust, and are prone to damage.

Overall, vector motors have many advantages, outstanding performance, and wide application scenarios. However, they also have certain disadvantages that need to be taken into account during the application process.

An electric motor is a device that converts electrical energy into mechanical energy. It generates torque and rotational motion through the interaction of currents in a magnetic field. Electric motors are key components widely used in various devices and machinery, such as household appliances, industrial machinery, transportation vehicles, aerospace equipment, etc. According to different principles and purposes, there are many types of motors, such as DC motors, AC motors, stepper motors, brushless motors, etc.

The working principle of a motor is based on the interaction between electromagnetic induction and current, and its basic principle can be summarized as the following steps:
1. In the motor, the power supply provides current to the stator, causing the coils inside the stator to form a magnetic field.

2. The interaction between the stator magnetic field and the coils inside the rotor generates a torque.

3. The rotor begins to rotate, and this rotational motion can be transmitted to mechanical devices such as wheels, fans, pumps, etc.

4. When the rotor rotates, current is also generated in the coils inside the rotor, which generates a magnetic field.

5. This magnetic field will interact with the magnetic field inside the stator, thereby changing the magnitude and direction of the torque.

The working principle of the motor is based on this interaction and feedback process, which continuously changes the current and magnetic field to enable the rotor to rotate continuously. The working principles of different types of motors vary, but they are all based on this fundamental principle of electromagnetic induction and interaction.

Electric motors are usually composed of power supply, stator, rotor, and transmission mechanism, where the stator and rotor are respectively wrapped in a housing and bearings.

1. Stator: The stator is a fixed part of the motor, usually composed of an iron core and coils. The coils arranged in a circular or planar shape in the stator are commonly referred to as stator coils.

2. Rotor: The rotor is the rotating part of a motor, usually composed of an iron core and coils. The rotor coil can be made of conductors such as copper, aluminum, etc., and is usually referred to as a rotor coil. The motion of a rotor can generate mechanical energy, such as a rotating shaft.

3. Bearings: Bearings support the rotor and maintain its stability during rotation.

4. Shell: The shell wraps around the stator and rotor, providing protection and fixation.

5. Transmission mechanism: In some motor applications, the transmission mechanism is used to transmit the motion of the motor to mechanical devices such as tires, fan blades, etc.

The structure of different types of motors also varies, for example, the structure of DC motors and AC motors is different. However, the basic structure of a motor includes the above-mentioned parts.

The ordinary motors, stepper motors, deceleration motors, and servo motors mentioned here refer to micro motors powered by direct current, and the ones we usually come into contact with are mostly direct current. The knowledge of motors is profound, and this article only briefly discusses various motors commonly used in making robots. Electric motor, commonly known as “motor”, refers to an electromagnetic device that converts or transfers electrical energy based on the law of electromagnetic induction. It is represented by the letter “M” (formerly “D”) in circuits. Its main function is to generate driving torque as a power source for electrical appliances or various machinery.

Ordinary DC motor
Ordinary motors are the ones we usually use, which are included in electric toys, razors, and more. Generally, there are only two pins, and connecting the positive and negative terminals of the battery to the two pins will cause the motor to rotate. Then, if the positive and negative terminals of the battery are connected in opposite directions to the two pins, the motor will also rotate in the opposite direction. This type of motor has the characteristics of high speed and low torque, and is generally not directly used in smart cars. When the DC power supply supplies power to the armature winding through the electric brush, the current flowing in the same direction can pass through the N-pole lower conductor on the surface of the armature. According to the left-hand rule, the conductor will be subjected to a counterclockwise torque. The conductor under the S pole on the surface of the armature also flows current in the same direction, and according to the left-hand rule, the conductor will also be subjected to a counterclockwise torque. In this way, the entire armature winding, i.e. the rotor, will rotate counterclockwise, and the input DC electrical energy will be converted into mechanical energy output on the rotor shaft. Composed of stator and rotor, stator: base, main magnetic pole, reversing pole, electric brush device, etc; Rotor (armature): armature core, armature winding, commutator, shaft, fan, etc. A DC motor is an electric motor that converts DC electrical energy into mechanical energy. Due to its excellent speed regulation performance, it has been widely used in electric drive. DC motors are divided into three categories based on excitation methods: permanent magnet, separate excitation, and self excitation. Among them, self excitation is further divided into parallel excitation, series excitation, and compound excitation.

Gear motor

A deceleration motor is a combination of an ordinary motor and a gearbox, which reduces the speed and increases the torque, making the ordinary motor more widely applicable. This type of integrated body is usually referred to as a gear motor or gear motor, and is usually assembled and supplied as a complete set by a professional gearbox manufacturer. Deceleration motors are widely used in industries such as steel and machinery. The advantages of using a deceleration motor are simplified design and space saving. After World War II, the rapid development of military electronic equipment promoted the development and production of micro reduction motors and DC reduction motors in countries such as the United States and the Soviet Union. With the continuous development of the deceleration motor industry, more and more industries and enterprises are using deceleration motors, and a group of enterprises have also entered the deceleration motor industry. Currently, countries such as Germany, France, the United Kingdom, the United States, China, and South Korea maintain a leading position in the global market for micro reduction motors and DC reduction motors. The Chinese micro reduction motor and DC reduction motor industry was founded in the 1950s. Starting from meeting the needs of supporting weapons and equipment, it has gone through stages of imitation, self design, research and development, and large-scale manufacturing. It has formed an industrial system with complete product development, large-scale production, key components, key materials, specialized manufacturing equipment, testing instruments, and continuously improving internationalization. Deceleration motors are usually used on smart cars, and the control of the motor is usually done using the H-bridge scheme. The L298 chip is based on this principle. The speed regulation generally adopts PWM (Pulse Width Modulation) mechanism, and the microcontroller uses a timer to control the generation of PWM waves with variable duty cycle or directly outputs different sized waveforms through hardware PWM to control the overall speed of the car.

Stepper motor

A stepper motor is an open-loop control element that converts electrical pulse signals into angular displacement or linear displacement. In non overloaded situations, the speed and stopping position of the motor depend only on the frequency and number of pulses of the pulse signal, and are not affected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, called the “step angle”, and its rotation runs step by step at a fixed angle. By controlling the number of pulses, the angular displacement can be controlled to achieve accurate positioning; At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency, thus achieving the purpose of speed regulation.

servo motor

Servo motor, also known as actuator motor, is used as an actuator in automatic control systems to convert received electrical signals into angular displacement or angular velocity output on the motor shaft. It is divided into two categories: DC and AC servo motors. Its main feature is that when the signal voltage is zero, there is no self rotation phenomenon, and the speed decreases uniformly with the increase of torque.

Servo motors mainly rely on pulses for positioning. Basically, it can be understood as follows: when a servo motor receives one pulse, it will rotate the corresponding angle of one pulse to achieve displacement. Because servo motors themselves have the function of emitting pulses, every time they rotate an angle, they will emit a corresponding number of pulses. This forms a response or closed loop with the pulses received by the servo motor. In this way, the system will know how many pulses have been sent to the servo motor and how many pulses have been received back. In this way, the rotation of the motor can be accurately controlled to achieve precise positioning, which can reach 0.001mm.

DC servo motors are divided into brushed and brushless motors. Brushed motors have low cost, simple structure, large starting torque, wide speed range, easy control, and require maintenance. However, maintenance is inconvenient (such as replacing carbon brushes) and can generate electromagnetic interference, which has environmental requirements. Therefore, it can be used in cost sensitive general industrial and civilian applications.

Application of Touch Screen _ Classification of Touch Screen
Nowadays, everyone enjoys the convenience brought by smart large screen smartphones to their lives, as they can easily get what we want with just a few clicks and touches. I don’t know when it started, but as a new type of human-computer interaction machine, touch screens have become the simplest and most convenient machine to replace other devices.

Application of touch screen

In the field of mobile technology, touch screen technology is ubiquitous. Mobile phones no longer require keyboards that take up space, but instead have larger screens, richer and more convenient entertainment and office functions. Clicking on the screen allows for multi application and multi window operations. The era of touch screens has brought more possibilities for people to realize their creativity, and more novel, colorful, and fun application software has been developed, which was not possible with previous devices. This new type of human-computer interaction mode brings a better customer experience.

In addition, in the fields of public information inquiry such as libraries and science museums, the emergence of touch screens has replaced the original keyboard and mouse, reducing the requirements for users and allowing those who do not understand computers to use them easily. The large screen also brings more impactful visual stimulation to users, making information such as graphics and text more vivid.

Classification of touch screens

Infrared technology touch screen. This type of touch screen is very suitable for harsh working environments, with a low price. It mainly relies on the infrared emitter and receiver of the touch screen for operation, and is not affected by voltage, current, static electricity, etc. It has high accuracy, good light transmittance, and easy installation. It is generally used in large equipment such as TV screens, but its service life is average.

Surface acoustic wave touch screen. Surface acoustic wave touch screens rely on several parts such as sound wave generators, reflectors, sound wave receivers, and touch screens to complete their work. This type of touch screen has a long service life, but is afraid of water and oil pollution. If it is contaminated, it needs to be actively cleaned and maintained. Because it uses the working principle of sound waves, it will not be affected by temperature, humidity, etc. The surface is scratch resistant, has good transparency, high resolution, and is widely used.

Resistive touch screen. It uses the principle of a voltage divider to determine the X and Y coordinates of the contact point. When the touch screen is under pressure, the top and bottom layers will touch each other due to compression, covered with a layer of scratch resistant plastic. This type of touch screen, due to its complete isolation from the outside world, can adapt to various harsh environments and has good stability. However, because it is a multi-layer device, there may be a loss in brightness.

Capacitive touch screen. Capacitive touch screens are composed of transparent conductive layers, sensors, protective glass, etc., and are often used in portable devices such as mobile phones.

At present, capacitive touch screens are widely used in smart large screen smartphones, which are not prone to wear and tear, have high stability, long service life, and are convenient and easy to use.

The working principle of touch screen

The working principle of touch screen

A touch screen is an input device for a computer, which is different from a keyboard that can input and a mouse that can click. It allows users to make selections by touching the screen. Computers with touch screens require limited storage space, have few moving parts, and can be packaged. Touchscreens are more intuitive to use than keyboards and mice, and the training cost is also very low.

All touch screens have three main components. Processing user selected sensor units; A controller that senses touch and locates, as well as a software device driver that transmits touch signals to the computer operating system. There are five technologies for touch screen sensors: resistive technology, capacitive technology, infrared technology, acoustic technology, or near-field imaging technology.

Resistive touch screens typically consist of a flexible top film and a layer of glass as the base layer, isolated by insulation points. The inner surface coating of each layer is a transparent metal oxide. The voltage has a difference in each layer of the diaphragm. Pressing the top film will form electrical contact signals between the various resistance layers

Capacitive touch screens are also coated with transparent metal oxides and bonded to a single-layer glass surface. It is not like a resistive touch screen, where any touch generates a signal. A capacitive touch screen requires direct touch with a finger or contact with a conductive iron pen. The capacitance of fingers, or the ability to store charges, can absorb the current from each corner of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners, thus determining the touch point.

What are the bonding technologies for industrial touch screens

What are the bonding technologies for industrial touch screens?

With the development of LCD touch technology, industrial control touch screens are increasingly being applied in the industrial field. Currently, the main industrial touch screens on the market are capacitive touch screens and resistive touch screens. So, how is the touch panel fixed on the LCD screen? This involves a concept, industrial touch screen bonding technology.
We usually divide LCD touch screens into three components, from top to bottom: glass cover, touch panel, and LCD screen. After these three parts are bonded together using bonding technology, a complete industrial touch screen is formed. Industrial touch screen bonding technology is divided into three types: full bonding technology, frame bonding technology, and 0-bonding technology.

Industrial touch screen bonding technology

1、 Full lamination technology for industrial touch screens

Full bonding technology: a bonding process in which the LCD screen and touch panel are seamlessly bonded together using water glue or optical glue. OCA glue and LOCA water-based glue are usually used.

OCA adhesive is mainly suitable for bonding small-sized LCD products, but the bonding cost is high, and after a long screen time, yellowing may occur, and bubbles are easily generated at ink level differences. The advantages lie in high production efficiency, uniform thickness, no glue overflow problem, controllable bonding area, no corrosion problem, and simple maintenance.

LOCA water-based adhesive is mainly suitable for bonding large-sized LCD products, curved surfaces, or more complex structures. The cost is lower than OCA adhesive. The advantage lies in the ability to bond curved or uneven surface materials, insensitivity to ink thickness, easy rework, and relatively low cost.

Overall, the main disadvantages of full lamination are complex process, low production yield, and high equipment investment cost.

2、 Frame pasting technology for industrial touch screens

Frame bonding technology: The most widely used bonding technology on the market, which uses double-sided tape to fix the touch panel (TP) to the four sides of the LCD screen. Due to its low cost and simple process, it is favored by small and medium-sized LCD screen manufacturers. The disadvantage is that there is an air layer between the LCD screen and the touch panel, resulting in unsatisfactory display performance.

3、 Zero paste technology for industrial touch screens

0-bonding technology: Its bonding method is between full bonding and frame bonding, mainly filling a non adhesive transparent medium with a refractive index equivalent to glass between the touch panel and the LCD screen. On the one hand, there is no gap between the TP and the LCD screen, which improves the display effect. On the other hand, because it has no stickiness, assembly and maintenance are very simple, and the overall cost is relatively low.

Advantages and disadvantages of touch screen

Advantages and disadvantages of touch screen
1、 Advantages

1. Various operations such as zooming in, moving, etc. can be achieved using software without physical buttons.
2. Multi touch (two or more points) can achieve various inputs such as zooming in and out.

3. The displayed operation object is consistent with the input object and has intuitive operability.

4. The integration of input and display can achieve miniaturization of the machine, with a relatively high degree of design freedom.

5. It will not have gaps like keyboards, switches, etc., and will not allow garbage, dust, water, etc. to enter. It is not easy to damage and is easy to maintain.

2、 Disadvantages

1. Not suitable for quick input with keyboards, mice, buttons, etc.

2. Directly touching the display can easily contaminate the image and make it difficult to read information; Easy to cause misoperation due to scratches and other factors.

3. There is no click sensation like buttons or mice, so input actions become clumsy (there are also touch screens that provide click sensation).

4. Blind people have difficulty using it, so it is necessary to use it in conjunction with sound indicators and buttons, or specify the touch location.

Advantages and disadvantages of infrared touch screens
1、 Advantages

1. The use effect on flat panel displays is very good

Infrared technology touch screens use infrared emitting and receiving tubes of the same wavelength distributed in the same plane to obtain monitoring results, so the advantages of using them on flat displays such as liquid crystal displays are astonishing.

2. Good usage characteristics

The touch force is very light and there are no special requirements for the touch body. Human fingers or any object that blocks infrared light can be used as a touch body.

3. Highly adaptable

It is not affected by current, voltage, and static electricity interference, and can effectively prevent explosion and dust. It has strong adaptability in harsh environmental conditions.

4. High stability

It will not drift or change due to changes in time, location, or environment.

5. Long service life

It is durable, scratch resistant, and has a long normal working time for touch control.

2、 Disadvantages

1. Poor performance on spherical display screens

Because infrared touch screens require the working infrared grating matrix to be on the same plane, in the use of spherical displays, when the working plane that truly senses touch is far away from the curved display screen, especially at the corners, the accuracy and sensitivity of infrared touch screens will be lower.

2. Vulnerable to strong infrared interference

Such as remote control, high-temperature objects, incandescent lamps, sunlight, etc.

3. Easy to be interfered by strong electromagnetic objects, such as transformers.

Advantages and disadvantages of capacitive touch screens
1、 Advantages

1. Novel operation

The capacitive touch screen supports multi touch, making the operation more intuitive and interesting.

2. Not easily touched by mistake

Due to the fact that capacitive touch screens need to sense the current of the human body, only the human body can operate them, and there will be no corresponding response when touched by other objects, thus basically avoiding the possibility of accidental touch.

3. High durability

Compared to resistive touch screens, capacitive touch screens have better performance in terms of dust, water, and wear resistance.

2、 Disadvantages

1. Low accuracy

Due to technical reasons, the accuracy of capacitive touch screens is still lacking compared to resistive touch screens. And it can only be inputted with fingers, making it difficult to recognize complex handwriting input on a small screen.

2. Vulnerable to environmental influences

When environmental factors such as temperature and humidity change, it can also cause instability and even drift of capacitive touch screens. For example, if a user brings their body close to the screen while using it, it may cause drift, and even operating in a crowded crowd can cause drift. This is mainly due to the working principle of capacitive touch screen technology. Although the user’s fingers are closer to the screen, there are still many electric fields near the screen that are much larger in volume than the fingers, which can affect the judgment of touch position.

3. High cost

In addition, there are still certain technical difficulties in the process of attaching the touch panel to the LCD panel for current capacitive touch screens, and the yield rate is not high, which invisibly increases the cost of capacitive touch screens.

Basic technology and classification of touch screens

Basic technology and classification of touch screens

Classification of touch screens
1： In terms of installation methods, touch screens can be divided into external, internal, and integrated types.
External touch screen refers to installing the touch detection device of the touch screen system directly in front of the display device. This type of touch screen is easy to install and very suitable for temporary use. The built-in touch screen is a touch detection device installed inside the housing of the display device, in front of the cathode ray tube. When manufacturing display devices, the touch detection device is made on the cathode ray tube, so that the display device directly has touch function, which is the integrated touch screen.

2： From the perspective of technical principles, touch screens can be divided into five basic types: vector pressure sensing technology touch screens, resistive technology touch screens, capacitive technology touch screens, infrared technology touch screens, and surface acoustic wave technology touch screens.
Among them, the vector pressure sensing technology touch screen has exited the historical stage; Infrared technology touch screens are inexpensive, but their outer frames are fragile and prone to light interference, resulting in distortion on curved surfaces; The design concept of capacitive technology touch screen is reasonable, but its image distortion problem is difficult to fundamentally solve; The positioning of resistive technology touch screens is accurate, but their price is quite high and they are susceptible to scratches and wear; Surface acoustic wave touch screen solves various defects of previous touch screens, with clear and not easily damaged, suitable for various occasions. The disadvantage is that if there are water droplets and dust on the screen surface, the touch screen will become sluggish or even not work. According to the working principle and information transmission medium of touch screens, they are divided into four types: resistive, infrared, capacitive sensing, and surface acoustic wave.

Absolute coordinate system

Touchscreen is an absolute coordinate system, characterized by the fact that the current positioning coordinates are not related to the previous positioning coordinates, and the data of each touch is directly converted to the coordinates on the screen through calibration. In any case, the coordinate system of the touch screen is stable for the output data of the same point. However, it cannot guarantee that every sampling of the same touch point is the same, that is, it cannot guarantee absolute coordinate positioning, which is the so-called drift problem.

location

All kinds of touch screens rely on sensors to work, and some touch screens are even a set of sensors themselves. Their respective positioning principles and the sensors they use determine the response speed, reliability, stability, and lifespan of the touch screen. The technical characteristics of various touch screens are shown in Table 1.