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Discussion on AC servo and its application

Time:2010-11-24 12:37

   AC servo driver and inverter can be said to be a pair of brothers, are AC motor driver, according to the order of arrival, the inverter should be called brother, AC servo should be called brother. Inverter drives variable frequency motor, but also drives ordinary AC motor, the 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, accurate position control.


   The birth background of servo driver


   Servo comes from the English word Servo, and the feedback control system used to follow or reproduce a process accurately is called servo system, also called servo system. The servo system was originally used in the ship autopilot, gun control and command instrument, and then gradually extended to many fields, especially the automatic lathe, antenna position control, missile and spacecraft guidance, etc..


   In the 20 century 60, servo control technology has been applied in DC speed control, closed loop control through a plurality of discrete semiconductor components and circuit board for the torque and speed, by adjusting the number of adjustable resistor, capacitor, inductor, to achieve the parameters of the adjustment, more complex, dynamic response is not ideal. By 1980s, with the integrated circuit, power electronics and AC variable speed drive technology development, at the same time reference and the application of frequency conversion technology, permanent magnet AC servo drive technology has a prominent development, since the German MANNESMANN Rexroth company Indramat Department officially launched the MAC permanent magnet AC servo motor and drive system in 1978 Hannover trade fair, which marks this new generation of AC servo technology has entered the practical stage. Subsequently, the famous electrical manufacturers have launched their own AC servo motor and servo driver products.


   The basic working principle of AC servo driver:


   AC servo reference and the application of frequency conversion technology, realized by controlling the frequency conversion PWM imitate DC motor based on DC motor servo control, that is to say this link must have variable frequency AC servo motor. And as is the AC inverter, rectifier first DC, and then through the door of the control transistors (IGBT, IGCT) whose frequency can be adjusted through adjusting the carrier frequency and the PWM inverter AC electric pulse waveform similar to Yu Zheng cosine.


   The servo driver development of inverter technology, to drive the internal current loop, speed loop and position loop (inverter without the ring) of algorithm operation and control technology is more accurate than the general frequency, the main point can accurately control the position.


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


   Application fields of AC servo


   Any position, speed and torque control accuracy requirements are relatively high, can use AC servo drive. Such as machine tools, printing equipment, packaging equipment, textile equipment, laser processing equipment, robotics, electronics, pharmaceuticals, financial equipment, automated production lines. Because in the servo positioning, speed control occasions, so also known as servo motion control.

1、Metallurgy, iron and steel, continuous casting production line, copper bar continuous casting machine, marking equipment, cold rolling mill, fixed length cutting, automatic feeding, tilting etc.

2、Power cable, turbine speed and wind turbine pitch system, wire drawing machine, twisting machine, high speed braiding machine, winding machine, marking equipment etc.

3、Oil, chemical film extrusion machine, transmission belt, large air compressor, oil pumping machine etc.

4、Chemical fiber and textile spinning machine, spinning machine, weaving machine, carding machine, cross machine etc.

5、Automotive Manufacturing - engine parts production line, engine assembly line, vehicle assembly line, body welding line, testing equipment, etc.

6、Machine tool manufacturing industry, lathe, planer, milling machine, grinding machine, machining center, machine etc.

7、Casting manufacturing manipulator, tilting, mould processing center

8、Rubber manufacturing plastic calendering machine, plastic film bag sealing and cutting machine, injection molding machine, extrusion machine, molding machine, plastic coating machine, wire drawing machine etc.

9、The electronic manufacturing industry, printed circuit board (PCB) equipment, semiconductor device (lithography machine, wafer processing machine), liquid crystal display (LCD) equipment, machine assembly and surface mount (SMT) equipment (equipment, laser cutting machine, engraving machine, CNC equipment, etc.) such as mechanical hand

10、Paper - paper conveying equipment, specialty paper machinery etc.

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

12、The pharmaceutical industry - raw materials processing machinery, machinery, mechanical pieces, preparation of printing and packaging machinery etc.

13、Traffic - subway shield door, electric locomotive, ship navigation etc.

14、Logistics, handling, handling - Automatic warehouses, trucks, three-dimensional garage, transmission belt, robot, lifting equipment and handling equipment, etc.

15、Building elevator, conveyor belt, automatic revolving door, automatic window etc.

16、Medical treatment CT, X ray machine, nuclear magnetic resonance MRI and so on

17、Test equipment - automotive test equipment, torque test equipment


      Development trend of servo system


   The application of digital AC servo system is more and more widely, the user of the servo drive technology of the increasingly high demand. In general, the development trend of servo system can be summarized as follows:



   At present, more and more output devices of the servo control system adopts the new power semiconductor device switching frequency is high, the device will enter the isolation, braking and overtemperature, overvoltage, overcurrent protection and fault diagnosis function are integrated in a small module. With a control unit, as long as the software system parameters are set, they can change their properties, sensor can use the motor itself to form a closed loop control system configuration, and can be connected with external sensors such as position, speed, torque sensor, a high precision closed loop control system. The integrated height significantly reduced the volume of the whole control system.


2. Intellectualization

   At present, most of the servo internal control core uses a new high-speed microprocessor and a dedicated digital signal processor (DSP), so as to achieve a fully digital servo system. The digital servo system is the prerequisite for the realization of intelligent. Intelligent servo system in the following aspects: all the operating parameters of the system can be through interactive way to set up the software; secondly, they all have the fault self diagnosis and analysis functions; and parameter self-tuning function etc.. As we all know, parameter tuning of closed-loop control system is an important link to ensure system performance indicators, but also need to spend more time and effort work. The servo unit with self-tuning function can automatically adjust the parameters of the system through several trial runs and realize its optimization automatically.


3. Networking

   Network servo system is an inevitable trend of the development of integrated automation technology, control technology, computer technology and communication technology, fieldbus is a kind of application in the production field, in the field of equipment, between field devices and a control device between the two-way string form, multi node digital communication technology. Field bus has been widely used in servo systems, servo systems and other peripheral devices, such as human-computer interface HMI, programmable logic controller PLC and other information transmission. There are several types of Fieldbus FF; ProfiBus, WorldFIP, ControlNet/DeviveNet, CAN etc.. These communication protocols provide the possibility for real-time multi axis synchronous control, and are also integrated into some high-end servo drives, thus enabling the servo system to be distributed, open, interconnected and highly reliable.


4. Summary

   Here the word "Jane" is not a simple but streamlined, is based on the user, will give users the servo function enhancement, so fine, and will not use some functions to streamline, thereby reducing the cost of the servo system, create more benefits for customers, and by streamlining some parts, reduce the the waste of resources and environmental protection. The "Yi" refers to the servo system software programming and operation is from the user's point of view of development and design, and strive to be simple and easy to use, the user debugging only need to simply set it.