On AC servo and its application

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Talking about AC servo and its application

AC servo driver and frequency converter can be said to be a pair of brothers, both of which are drivers of AC motor. According to the order of appearance, frequency converter should be called brother, and AC servo should be called brother. The frequency converter drives the variable frequency motor and also drives the ordinary AC motor. Its main function is to adjust the speed of the motor. AC servo driver drives AC servo motor. Its main feature is accurate and fast positioning and tracking, and accurate position control

the birth background of servo driver

servo comes from the English word servo. The feedback control system used to accurately follow or reproduce a process is called servo system, also known as servo system. Servo system was initially used in ship autopilot, artillery control and command instrument, and then gradually extended to many fields, especially automatic lathes, antenna position control, missiles and feifraunhofer Engineering Center, which has the manufacturing capacity of parts in the production range and the guidance of processing equipment ships

in the 1960s, servo control technology began to be applied in DC speed regulation. Closed loop control of torque and speed was carried out through several discrete semiconductor components and their circuit boards, and parameter matching was achieved by adjusting several adjustable resistance, capacitance and inductance components. The adjustment was relatively complex, and the dynamic response was not ideal. By the 1980s, with the development of integrated circuit, power electronics technology and AC variable speed drive technology - ---- Dr. Chen 1, Packaging Research Institute of Hunan University of technology, and the reference and application of frequency conversion technology, permanent magnet AC servo drive technology had a prominent development, Since the indramat branch of Rexroth company of Mannesmann in Germany officially launched MAC permanent magnet AC servo motor and drive system at the Hannover trade fair in 1978, this marks that this new generation of AC servo technology has entered the practical stage. Subsequently, famous electrical manufacturers in various countries successively launched their own series of AC servo motors and servo drivers

basic working principle of AC servo driver:

AC servo draws on and applies the technology of frequency conversion. Based on the servo control of DC motor, it simulates the control mode of DC motor by frequency conversion PWM, that is to say, AC servo motor must have the link of frequency conversion. Like the frequency converter, it first rectifies the power frequency alternating current into direct current, and then inverts it into frequency adjustable alternating current through various transistors (IGBT, IGCT, etc.) that can control the gate through carrier frequency and PWM adjustment. The waveform is similar to sine and cosine pulsating electricity

the servo driver has developed the frequency conversion technology. The current loop, speed loop and position loop inside the driver (the frequency converter does not have this loop) have carried out more accurate control technology and algorithm calculation than the general frequency conversion. The main point is that it can carry out accurate position control

now the control part of AC servo adopts digital signal processor (DSP) as the control core. Its advantage is that it can realize relatively complex control algorithm to complete the closed-loop control of servo system, including torque, speed and position

working principle of AC servo

application field of AC servo

AC servo drive can be used in all occasions that require high control accuracy of position, speed and torque. Such as machine tools, printing equipment, packaging equipment, textile equipment, laser processing equipment, robots, electronics, pharmaceuticals, financial machinery, automated production lines, etc. Because servo is mostly used in positioning and speed control occasions, servo is also known as motion control

1, metallurgy, steel continuous casting and drawing production line, copper rod up drawing caster, spray marking equipment, tandem cold mill, fixed length shearing, automatic feeding, converter tilting, etc.

2, power, cable hydraulic turbine governor, wind turbine pitch system, wire drawing machine, counter winch, high-speed braiding machine, coiler Printing marking equipment, etc.

3. Petroleum and chemical industry - extruders, film transmission belts, large air compressors, oil pumping machines, etc.

4. Chemical fiber and textile - spinning machines, worsted machines, looms, carding machines, transverse machines, etc.

5. Automobile manufacturing - engine parts production lines, engine assembly lines, vehicle assembly lines, body welding lines, testing equipment, etc.

6. Machine tool manufacturing - lathes, planers, milling machines Grinder, machining center, gear making machine, etc.

7, casting manufacturing - manipulator, converter tilting, mold processing center, etc.

8, rubber and plastic manufacturing - plastic calender, plastic film bag sealing and cutting machine, injection molding machine, extruder, molding machine, plastic coating compound machine, news wire drawing machine, etc.

9, electronic manufacturing - printed circuit board (PCB) equipment, semiconductor device equipment (lithography machine, wafer processing machine, etc.) Liquid crystal display (LCD) equipment, machine coupling and surface mount (SMT) equipment, laser equipment (cutting machine, engraving machine, etc.), general numerical control equipment, manipulator, etc.

10, papermaking industry - paper conveying equipment, special paper papermaking machinery, etc.

11, food manufacturing industry - raw material processing equipment, filling machinery, sealing machine, other food packaging and printing equipment, etc.

12, pharmaceutical industry - raw material processing machinery, preparation machinery Beverage machinery, printing and packaging machinery, etc.

13, transportation - subway screen doors, electric locomotives, ship navigation, etc.

14, logistics, loading and unloading, handling - Automatic warehouses, handling vehicles, three-dimensional garages, transmission belts, robots, lifting equipment and handling equipment, etc.

15, construction - elevators, conveyor belts, automatic revolving doors, automatic windows, etc.

16, medical treatment - CT, X-ray machines, nuclear magnetic resonance MRI, etc.

17 Test equipment - automobile test equipment, torque test equipment and other

servo system development trend

Digital AC servo system is more and more widely used, and users have higher and higher requirements for servo drive technology. In general, the development trend of servo system can be summarized as the following aspects:

1 Integration

at present, the output devices of servo control systems increasingly use new power semiconductor devices with high switching frequency, which integrate the functions of input isolation, energy braking, over temperature, over voltage, over-current protection and fault diagnosis into a small module. As long as the system parameters of the same control unit are set through software, its performance can be changed. It can not only use the sensors configured by the motor itself to form a semi closed-loop regulation system, but also connect external sensors such as position, speed, torque sensors, etc., to form a high-precision full closed-loop regulation system. The high integration significantly reduces the volume of the whole control system

2. Intelligent

at present, the internal control core of servo mostly adopts new high-speed microprocessor and special digital signal processor (DSP), so as to realize a completely digital servo system. The digitalization of servo system is the precondition of its intellectualization. The intelligence of servo system is shown in the following aspects: all operating parameters of the system can be set by software through man-machine dialogue; Secondly, they all have the function of fault self diagnosis and analysis; And the function of parameter self-tuning. As we all know, the parameter setting of the closed-loop regulation system is an important part of the performance indicators of the certification system of Baojiao ordnance and environmental protection stocks (Pengqi technology, Wanze shares, BaoTi shares, Western materials, etc.), and it is also a work that requires more time and energy. The servo unit with self-tuning function can automatically set the parameters of the system and realize its optimization through several trial runs

3. Networking

the networking of servo system is the inevitable trend of the development of integrated automation technology, and it is the product of the combination of control technology, computer technology and communication technology. Fieldbus is a kind of digital communication technology that is applied to the production site to realize bidirectional, serial and multi node between field devices, field devices and control devices. Fieldbus has been widely used in the interactive transmission of information between servo systems, servo systems and other peripheral devices, such as HMI, PLC and so on. Fieldbus has the following types of FF; PROFIBUS, WorldFIP, controlnet/devivenet, can, etc. These communication protocols provide the possibility of multi axis real-time synchronous control, and are also integrated by some high-end servo drivers, so that the servo system achieves distribution, openness, interconnection and high reliability

3. Simplification

the "simplification" mentioned here is not simplicity but simplification. It is to strengthen the servo function used by the user according to the user's situation, make it specialized and refined, and simplify some functions that are not used, so as to reduce the cost of the servo system and create more benefits for customers. By simplifying some components, it reduces the waste of resources, which is conducive to environmental protection. The "easy" mentioned here refers to that the software programming and operation of the servo system are developed and designed from the perspective of users, striving to be simple and easy, so that users can debug easily. (end)

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