This paper discusses the important role of mechatronics technology in changing the overall appearance of machinery manufacturing industry, and explains its application and development trend in iron and steel industry.

Keywords application of mechatronics technology

1 development of mechatronics technology

Mechatronics is the cross-integration of mechanics, microelectronics, control, computer, information processing and other disciplines. Its development and progress depend on the progress and development of related technologies. Its main development direction is digitalization, intelligence, modularization, networking, humanization, miniaturization, integration, integration and greening.

1. 1 digitization

Microcontroller and its development have laid the foundation for the digitalization of electromechanical products, such as the continuous development of CNC machine tools and robots; The rapid rise of computer network paves the way for digital design and manufacturing, such as virtual design and computer integrated manufacturing. Digitalization requires the software of mechatronics products to have high reliability, easy operation, maintainability, self-diagnosis ability and friendly man-machine interface. The realization of digitalization will be beneficial to remote operation, diagnosis and maintenance.

1.2 intelligence

In other words, mechanical and electrical products are required to have certain intelligence, so that they have the ability of logical thinking, judgment and reasoning, independent decision-making and so on. It will bring great convenience to use, operate and maintain if the man-machine conversation function is added to the NC machine tool and the intelligent I/O interface and intelligent process database are set up. With the progress and development of artificial intelligence technology such as fuzzy control, neural network, grey theory, wavelet theory, chaos and bifurcation, it has opened up a broad world for the development of mechatronics technology.

1.3 modularization

Due to the wide variety of mechatronics products and numerous manufacturers, it is a complex and promising work to research and develop mechatronics product unit modules with standard mechanical interface, power interface and environmental interface. For example, develop a power drive unit that integrates deceleration and variable frequency motors; Motor integrated control unit with vision, image processing, recognition and ranging functions. In this way, in product development and design, these standard modular units can be used to quickly develop new products.

1.4 networking

Due to the popularity of the network, various remote control and monitoring technologies based on the network are in the ascendant. The remote control terminal equipment itself is a mechatronics product. Fieldbus and LAN technology make it possible to network household appliances. Using home network to connect various household appliances into a computer-centered integrated household appliance system, people can fully enjoy the benefits brought by various high technologies at home. Therefore, mechatronics products should undoubtedly develop to the network.

1.5 Humanization

The end user of mechatronics products is people. How to endow mechatronics products with human intelligence, emotion and humanity is becoming more and more important. In addition to perfect performance, mechatronics products also require harmony with the environment in color and modeling. Using these products is still an artistic enjoyment for people. For example, the highest realm of home robots is man-machine integration.

1.6 miniaturization

Miniaturization is the necessity of the development of fine machining technology and the need to improve efficiency. Micro-electronic mechanical systems (MEMS for short) refer to micro devices or systems that can be manufactured in batches and integrate micro-mechanisms, micro-sensors, micro-actuators, signal processing and control circuits until interfaces, communication and power supply are equal. Since 1986, when Stanford University developed the first medical microprobe and 1988, when the University of California, Berkeley developed the first micromotor, great progress has been made in the research of MEMS technology, materials and micromechanics at home and abroad, and various MEMS devices and systems have been developed, such as various micro-sensors (pressure sensors, micro-accelerometers and micro-tactile sensors) and various micro-components (micro-sensors).

1.7 integration

Integration not only includes the mutual penetration and integration of various technologies and the optimization and compounding of different structures of various products, but also includes the synchronous processing of processing, assembly, testing and management in the production process. In order to realize the automation and high efficiency of multi-variety and small batch production, the system should be more flexible. First of all, the system can be decomposed into several levels, so that the system functions are dispersed and all parts can run in harmony and safety. Then, all levels are organically linked through software and hardware, so that they have the best performance and the strongest function.

1.8 band source

Refers to electromechanical integration products with their own energy sources, such as solar cells, fuel cells and large-capacity batteries. Because electric energy is not used in many occasions, it has unique benefits to bring its own power source to the moving mechatronics products. With light source is one of the development directions of mechatronics products.

1.9 Greening

The development of science and technology has brought great changes to people's lives. While being rich in materials, it also brings the consequences of decreasing resources and deteriorating ecological environment. Therefore, people call for protecting the environment, returning to nature and realizing sustainable development, and the concept of green products comes into being. Green products refer to products with low energy consumption, low material consumption, low pollution, comfort, coordination and renewable utilization. The design, manufacture, use and destruction of mechatronics products shall meet the requirements of environmental protection and human health. The greening of mechatronics products mainly means that they do not pollute the ecological environment when used, and the products can be decomposed and recycled at the end of their lives.

2 application of mechatronics technology in iron and steel enterprises

In iron and steel enterprises, electromechanical integration system is based on microprocessor, which organically combines microcomputer, industrial computer, data communication, display device, instrument and other technologies, and adopts the method of assembly and merger, which creates powerful conditions for the comprehensive integration of large-scale engineering systems and enhances the control accuracy, quality and reliability of the system. Electromechanical integration technology is mainly used in the following aspects in iron and steel enterprises:

2. 1 Intelligent control technology (integrated circuit)

Because the iron and steel industry has the characteristics of large-scale, high-speed and continuous, the traditional control technology has encountered insurmountable difficulties, so it is very necessary to adopt intelligent control technology. Intelligent control technology mainly includes expert system, fuzzy control and neural network. Intelligent control technology is widely used in product design, production, control, equipment and product quality diagnosis of iron and steel enterprises, such as blast furnace control system, electric furnace and continuous casting workshop, steel rolling system, steelmaking-continuous casting-steel rolling integrated scheduling system, cold continuous rolling and so on.

2.2 Distributed Control System (DCS)

The distributed control system uses a central computer to command multiple control-oriented field measurement and control computers and intelligent control units. The distributed control system can be two-stage, three-stage or more. Centralized monitoring, operation, management and decentralized control of production process by computer. With the development of measurement and control technology, distributed control system has more and more functions. It can not only realize the control of production process, but also realize the functions of online optimization, real-time scheduling and statistical management of production plan, and become a system integrating measurement, control and management. DCS has the characteristics of diversified control functions, simple operation, extensible system, convenient maintenance and high reliability. DCS is centralized in monitoring and decentralized in control, and the fault affected area is small. In addition, the system has interlock protection function and adopts manual operation measures of system fault control, which makes the system have high reliability. Compared with centralized control system, distributed control system has stronger functions and higher security. It is the main trend of large electromechanical integration system at present.

2.3 open control system (OCS)

Open control system is a new concept of structural system introduced with the development of computer technology. "Openness" refers to the understanding and support of standard information exchange rules. The system designed according to this standard can realize the compatibility and exchange of products from different manufacturers and share resources. The open control system interconnects all kinds of control equipment and management computer through industrial communication network, realizing the integration of control and management, management and decision-making, and interconnecting field instruments and control equipment in the control room through field bus, realizing the integration of measurement and control.

2.4 Computer Integrated Manufacturing System (CIMS)

CIMS of iron and steel enterprises integrates people with production management, production management and process control, and realizes comprehensive integrated control of the whole production process from raw materials entering the factory, production and processing to product delivery. At present, iron and steel enterprises have basically realized process automation, but this "isolated island of automation" lacks the enjoyment of information resources and the unified management of production process, which is difficult to meet the requirements of modern iron and steel production. In the future, the focus of competition among iron and steel enterprises will be multi-variety and small batch production, high quality and low price, and timely delivery. In order to improve productivity, save energy and reduce consumption, reduce personnel and existing inventory, accelerate capital turnover and realize the overall optimization of production and operation management, the key is to strengthen management, obtain necessary economic benefits and improve the competitiveness of enterprises. Some large iron and steel enterprises such as the United States and Japan have generally realized CIMS in the 1980s.

2.5 Fieldbus Technology (FBT)

Fieldbus technology is a digital, bidirectional and multi-station communication link, which connects the field instrument group and the control equipment group in the control room. Replacing the current signal transmission technology (such as 4 ~ 20 mA, DC transmission) with field bus technology can make more information transmitted in two directions between the intelligent field instrument device and the superior control system on the same communication medium. Through field bus connection, 66% or more field signal connection lines can be omitted. The introduction of fieldbus has led to the transformation of DCS, and a new generation of fieldbus instruments have been developed around the open automation system, such as intelligent transmitter, intelligent actuator, fieldbus detection instrument, fieldbus PLC (programmable logic controller) and field local control station.

2.6 AC drive technology

Transmission technology plays a vital role in iron and steel industry. With the development of power electronics and microelectronics technology, AC speed regulation technology has developed very rapidly. Due to the superiority of AC drive, DC drive will be completely replaced by AC drive in the near future. With the development of digital technology, compound vector control technology has been applied in practice, and the speed regulation performance of AC speed regulation system has reached or exceeded the level of DC speed regulation. At present, both large-capacity motors and small and medium-capacity motors can adopt synchronous motors or asynchronous motors to realize reversible smooth speed regulation. Ac drive system has been welcomed by users as soon as it appeared in steel rolling production, and its application scope has been expanding continuously.

refer to

1 Yang Zihou. Artificial Intelligence Technology and Its Application in Iron and Steel Industry [J]. Metallurgical Automation 1994(5)

Tang Lixin. Study on the Characteristics and Architecture of CIMS in Iron and Steel Industry [J]. Metallurgical Automation, 1996(4)

3 Tang Huaibin. Progress and trend of industrial control [J]. Automation and instrumentation, 1996(4)

4 kings. Intelligent control [M]. Hefei: China University of Science and Technology Press, 1996.

5 Lin Xingxin. Progress and prospect of automation in iron and steel industry [J]. Hebei Metallurgy, 1998( 1)

6 yin. Practical technology of optical, mechanical and electrical integration [M]. Beijing Chemical Industry Press 2003

7 Rui Yannian. Design of mechatronics system [M]. Beijing: Machinery Industry Press, 2004.

Power conversion principle of motor

Introduction:

The discussion on the essence of motor speed regulation is an important theoretical issue related to the development of modern AC speed regulation. With the introduction and practice of modern speed regulation theories such as vector control and direct torque control, many related documents and works have recognized that speed regulation torque control is a universal law of speed regulation, and put forward that the essence and key of speed regulation lies in electromagnetic torque control. However, this view is still lack of theoretical and practical proof, which is debatable.

According to the general principle of motor power conversion, it is proposed and proved that the essence of constant torque speed regulation lies in the shaft power control of motor, speed regulation is the response of power control, and the key is how to control shaft power through electric power.

I. Power Control and Torque Control

According to the principle of electromechanical energy conversion, all motors can be divided into two functional parts: main magnetic pole and armature. The role of the main magnetic pole is to establish the main magnetic field, and the armature interacts with the magnetic field to convert electromagnetic power into shaft power.

The main pole and armature of DC motor are not only distinct in structure, but also independent in function, which undoubtedly conforms to the above definition. An AC (asynchronous) motor usually consists of a stator and a rotor, which needs to be explained.

According to the definition of armature, the shaft power of asynchronous motor is generated by rotor, so the real armature of asynchronous motor is rotor. The problem lies in the stator. On the one hand, stator excitation generates a main magnetic field, so the stator is the main magnetic pole. On the other hand, the stator delivers electromagnetic power to the armature (rotor) through electromagnetic induction, but does not produce axial power, so the stator has some characteristics of the armature, which we call pseudo armature here. This compound function of stator is the main feature that distinguishes asynchronous motor from DC motor.

From the perspective of armature output, the relationship between motor shaft power and electromagnetic torque and mechanical speed is as follows:

PM = mω( 1)

Or ω = pm/m (2)

Formula (2) not only gives the relationship between motor speed and shaft power and electromagnetic torque, but also shows that motor speed can only be adjusted by two kinds of control of shaft power or electromagnetic torque, the former is called power control and the latter is called torque control.

1. Power control

Power control takes shaft power PM as the main control variable of speed regulation, and the acting object must be armature or pseudo armature. When the electromagnetic torque is in steady state, it depends on the load torque.

That is m = mfz (3)

Once the load torque is determined by objective working conditions, the electromagnetic torque is uniquely determined, so the electromagnetic torque is not only irrelevant to speed control, but also can not be changed at will.

The influence of electromagnetic torque on speed is manifested in the transition process of speed regulation, and the change of torque is the result of the lag of speed response. At this time, power control causes electromagnetic torque response.

Let the steady speed of the motor before speed regulation be ω 1, the shaft power be PM 1, the steady speed after speed regulation be ω 2, and the corresponding shaft power be PM2. Due to electromagnetic torque:

m = PM/ω(4)

Therefore, when the speed is adjusted, the electromagnetic torque becomes:

m = PM2/ω

Due to inertia, when t = 0, the speed regulation moment ω = ω 1, so

m = PM2/ω 1

t=0

At this time, the electromagnetic torque will be different from the original electromagnetic torque m 1 = pm 1/ω 1, and the torque balance will be destroyed, resulting in dynamic torque. Under the action of dynamic torque, the motor speed will start to transition from Ω1to Ω 2, and its changing law is as follows:

ω 1 =(ω 1-ω2)e-T/T+ω2(5)

The electromagnetic torque is m = PM2/(ω 1-ω 2) e-t/t+ω 2.

With the increase of time, the dynamic torque decreases until the electromagnetic torque is balanced with the new load torque, that is:

m = PM2/ω2 = Mfz，

The speed is stabilized at ω 2, and the motor speed regulation is over. The above speed regulation process can be illustrated by the block diagram of 1.

Figure 1 power control speed regulation process

Power control acts on the armature, and the main magnetic field or flux remains unchanged. According to the motor theory, the rated electromagnetic torque of the motor is proportional to the main magnetic flux and is limited by the maximum current carrying capacity of the armature. Therefore, the rated electromagnetic torque output capacity of the motor remains unchanged during power control speed regulation, which belongs to constant torque speed regulation.

2. Torque control

According to formula (2), the motor speed is inversely proportional to the electromagnetic torque on the premise that the shaft output power is constant. Because the electromagnetic torque is limited by the rated torque, torque control can only be realized below the rated torque, so it belongs to constant power speed regulation.

The independent control method of electromagnetic torque is mainly based on torque formula:

M = cm φ MIS (DC machine) (6)

Or m = cm φ mi2cosφ 2 (AC motor) (7)

The controlled physical quantity is the main magnetic flux φ m. Since the main magnetic flux φ m is generated at the main magnetic pole, torque control is actually magnetic field control, and the object of action is the main magnetic pole. Torque control and speed adjustment should also ensure the torque balance in steady state, namely:

M=Mfz

Because the electromagnetic torque changes when the speed is stable, the load torque is required to adapt to the change of electromagnetic torque, that is, the load is required to follow the motor.

Torque control is actually weak magnetic speed regulation, which is mainly used for speed regulation above rated speed. Since this article focuses on power control, I won't go into details.

Second, the method and performance of power control

The shaft power control of motor speed regulation can only be realized by indirectly controlling electric power. Taking asynchronous motor as an example, Figure 2 shows its equivalent three-port network.

Figure 2. Equivalent network of asynchronous motor

Among them, the armature (rotor) not only produces shaft power output, but also produces electric power response with induced voltage u2 and current i2 as parameters. Because this power is proportional to the slip ratio, it is called slip power, and its port is called Ps port for short.

If the motor rotor is cage-shaped, its winding is short-circuited and the Ps port is uncontrollable. On the contrary, it is winding, the Ps port is controllable, and the rotor can output or input electric power through the Ps port. It can be seen that there are two ways to control the speed of asynchronous motor. One is to indirectly control the shaft power of the armature through the dummy armature; The other is to directly control the armature shaft power through Ps port. The former is mainly suitable for cage asynchronous motors, while the latter is suitable for wound asynchronous motors.

1. stator pseudo-armature power control.

Figure 3. Stator power control and speed regulation of asynchronous motor

As a pseudo armature, the electromagnetic power transmitted from the stator to the armature (rotor);

Pem=P 1-△P 1 (8)

The shaft power of armature is:

PM=Pem-△P2 (9)

So pm = p1-(△ p1+△ p2) (10).

It can be seen that the shaft power of the armature can be controlled by controlling the input power of the pseudo armature P 1 or increasing its loss △P 1, which is obviously an inefficient and high-loss speed regulation method and should not be recommended.

The speed control mode of P 1 is only voltage regulation and frequency conversion, which is the so-called frequency conversion speed regulation. Due to:

p 1 = m 1u 1i 1 cosφ 1( 1 1)

Therefore, adjusting the terminal voltage U 1 for voltage supply is a necessary means to control the power supply P 1. The crux of the problem is, why not simply adjust the voltage, but must be supplemented by frequency conversion? This is because the stator not only has the function of pseudo-armature, but also acts as the main magnetic pole.

As mentioned above, the main points of power control are:

① Keep the main magnetic flux unchanged.

(2) The object of action is armor or pseudo-armor.

③ The control target is shaft power.

If the voltage is simply adjusted without changing the frequency, the function of the stator main magnetic pole will be seriously affected. According to the motor theory, as the main magnetic pole, the main magnetic flux of the stator:

φm = E/4.44 w 1kr 1f 1

=KE 1/f 1

≈KU 1/f 1 ( 12)

The result of constant frequency voltage regulation is that the main magnetic flux φ m will decrease with the decrease of U 1, forming the aforementioned torque control. More importantly, the power P 1 is not controlled at this time, but the motor loss is increased, which completely violates the purpose.

Assuming that the load is constant torque, we can know from the torque balance equation that the electromagnetic torque:

M = Mfz = constant

M = cm φ mi 1cosφ 1。

= cmφmi 2 cosφ2( 13)

Assuming that the power factor is constant, the stator and rotor currents I 1 and I2 will increase in direct proportion with the decrease of the main magnetic flux φ m, and the resulting power P 1 remains unchanged, but the stator and rotor losses are:

△p 1 = m 1I 12 r 1

△P2=m2I 222 r 1

Will increase according to the square law of current. According to the formula (10), although shaft power control can be realized, it belongs to low efficiency and low loss speed regulation.

Therefore, the power control and speed regulation of asynchronous motor stator must separate the main magnetic pole of stator from the pseudo armature. For the same stator winding, on the one hand, the magnetic field generated by the main pole is kept stable, while the electromagnetic power transmitted to the armature is controlled.

Therefore, an important principle of variable frequency speed regulation is established, that is, voltage regulation and frequency conversion to ensure the constant V/F (voltage-frequency ratio), thus ensuring the realization of the above control requirements. By the way, the vector control of modern variable frequency speed regulation actually follows this principle. The core idea of vector control is to control the magnetic field and torque respectively. It is believed that the fundamental of speed regulation lies in torque, but in fact, the magnetic field and electromagnetic power are free. Although the result is correct, it must be clarified in theory.

2. Rotor power control

For the speed regulation of wound rotor asynchronous motor, the slip power port -PS port can be used to directly control the shaft power. The method is to remove or inject slip power from Ps port. It should be pointed out that:

① The slip power mentioned should be different from the rotor loss slip power in classical electrotechnics. Therefore, the latter is called rotor loss power, which is denoted as △P2.

② Slip power can be divided into electric energy and thermal energy, which are recorded as Pes and Prs respectively. Their different properties have different effects on speed regulation.

Figure 4. Rotor power control and speed regulation of asynchronous motor

When the electric slip power Pes is introduced into the Ps port of the rotor, the rotor shaft power is:

PM=(Pem Pes)-△P2 ( 14)

In the formula, Pem is the electromagnetic power transmitted from the stator to the rotor, and the negative sign of electric slip power indicates that it is taken out from the Ps port, and the positive sign indicates that it is injected from the Ps port. Pes belongs to electricity, so it is combined with electromagnetic power. As a result, the shaft power PM changes, and the motor speed is adjusted accordingly.

Typical examples of electric slip power speed regulation are cascade speed regulation and doubly-fed speed regulation. In the former, the slip power is negative, and the flow direction is far away from the rotor, so as to realize the speed regulation below the rated speed. The electric slip power of the latter can flow in both directions and can be cut off and injected, so it can realize two kinds of speed regulation: low synchronization and super synchronization.

When thermal slip power Prs is introduced into Ps port, the shaft power of the rotor is:

PM=Pem-(△P2+Prs) ( 15)

Obviously, the introduction of thermal slip power increases the loss of armature (rotor), and the shaft power decreases with the increase of Prs. A typical example is the series resistance speed regulation of asynchronous motor rotor.

Thirdly, ideal no-load speed, efficiency and mechanical power control characteristics.

According to motor mechanics, the ideal no-load speed of motor mainly depends on the electromagnetic power of armature, because:

ω0 = Pem/M( 16)

Because the electromagnetic torque is determined by the load, the ideal no-load speed ω 0 depends on the electromagnetic power under certain load conditions.

The armature power of power control and speed regulation can be expressed as:

PM=∑Pem-∑p2 ( 17)

Corresponding speed:

PM/M=∑Pem/M-∑p2/M ( 18)

Ω=Ω0-△Ω ( 19)

Where ω 0 = ∑ PEM/m is the ideal no-load speed of power control speed regulation, so adjusting the electromagnetic power of armature can change the ideal no-load speed of motor. In other words, the ideal no-load speed of the motor depends on the electromagnetic power of the armature. △ω=∑p2/m is the speed drop of the motor. This shows that increasing armature loss will increase the speed decrease of the motor.

The efficiency of motor speed regulation is expressed as:

η=PM/(P 1-∑pi)

=PM/(Pem-△P2)

Therefore, under a certain output condition of shaft power PM, the speed regulation of electromagnetic power is efficient and energy-saving, while the speed regulation of loss power is inevitably inefficient and energy-consuming.

Formula (18) also describes the mechanical characteristics of power control and speed regulation. When the electromagnetic power ∑Pem changes continuously, if the loss power is constant, the ideal no-load speed of the motor changes continuously with ∑Pem, and its mechanical characteristics are a series of parallel curves. When the loss increases and the electromagnetic power remains unchanged, the ideal no-load speed of the motor remains unchanged, but the speed drop changes, and its mechanical characteristics are a series of intersecting curves. Figure 5 shows the qualitative curves of two speed adjustments.

Fig. 5 a. Electromagnetic power speed regulation characteristics B. Speed reduction speed regulation characteristics

To sum up, we can draw the following conclusions:

① Electromagnetic power control regulates the ideal no-load speed, and loss power control regulates the speed decrease.

② Electromagnetic power control is an efficient and energy-saving speed regulation method, and its mechanical characteristics must be a parallel curve family. Loss power control belongs to low efficiency energy consumption speed regulation, and its mechanical characteristics must be a series of intersecting curves.

Four, the classification and method of asynchronous motor speed regulation

Different from the expression of n = 60F 1/p (1-s), according to the power control theory of motor speed regulation described in this paper, the speed regulation of asynchronous motors can be divided into the following categories:

Key points of attribute/scheme control point/variable method

Verb (abbreviation of verb) conclusion

1. There are two basic principles of motor speed regulation, one is shaft power control and the other is torque control. Torque control is actually magnetic field control, which is suitable for constant power regulation.

2. The object of shaft power control is armature or pseudo-armature, which can only be realized by electric power control. Among them, the electromagnetic power adjusts the ideal no-load speed, and the loss power changes the speed drop. The former is efficient and energy-saving, while the latter is inefficient and energy-consuming, which determines their mechanical properties.

3. The speed regulation of shaft power control has the characteristics of constant torque, and the change of electromagnetic torque is caused by the lag of speed response. When the speed regulation is stable, the electromagnetic torque only depends on the load and has nothing to do with the control.

4. Both frequency conversion speed regulation and electric slip power control speed regulation belong to electromagnetic power control speed regulation, with the same performance and no essential difference.