The AC servo driver and the inverter can be said to be a pair of brothers, all of which are AC motor drives. According to the order of the world, the inverter should be called a brother, and the AC servo should be called a younger brother. The inverter drives the variable frequency motor and also drives the ordinary AC motor. The main function is to adjust the speed of the motor. The AC servo driver drives the AC servo motor, whose main features are precise and fast positioning and tracking for precise position control.

　　The birth background of the servo driver.

　　The servo is derived from the English word Servo. The feedback control system used to accurately follow or reproduce a process is called a servo system, also known as a servo system. The servo system was originally used in the automatic driving, gun control and commander of the ship, and was gradually extended to many fields, especially automatic lathes, antenna position control, missile and spacecraft guidance.

　　In the 1960s, servo control technology began to be applied in DC speed regulation, through a number of discrete semiconductor components and their circuit boards for closed-loop control of torque, speed etc by adjusting several adjustable resistors, capacitors, and inductance components. The matching of parameters is realized, the adjustment is complicated, and the dynamic response is not ideal. In the 1980s, with the development of integrated circuits, power electronics technology and AC variable speed drive technology, and the use of frequency conversion technology, the permanent magnet AC servo driver technology has developed significantly since the Rexroth company of MANNESMANN, Germany. The Indramat division officially launched the MAC permanent magnet AC servo motor and driver system at the Hannover Trade Fair in 1978, which indicates that this new generation of AC servo technology has entered the practical stage. Subsequently, the famous electric manufacturers in various countries successively launched their own series of AC servo motors and servo drivers.

　　The basic working principle of AC servo driver:

　　The AC servo draws on and applies the frequency conversion technology, which is realized by the variable frequency PWM method to simulate the control mode of the DC motor on the basis of the servo control of the DC motor. That is to say, the AC servo motor must have this part of the frequency conversion. Like the frequency converter, the power frequency AC power is first rectified into DC power, and then the inverters of the various types of transistors (IGBT, IGCT etc.) that can control the gate are adjusted to the frequency-adjustable AC power through the carrier frequency and PWM. The waveform is positive too. The pulsating electricity of the cosine.

　　The servo driver has developed the frequency conversion technology. The presise control techiques and algorithm are performed inside the current loop, speed loop and position loop (the inverter does not have the loop) inside the driver than the general frequency conversion. The main point is precise position control. 

　　The control part of the current AC servo uses the digital signal processor (DSP) as the control core. Its advantage is that it can implement more complicated control algorithms to complete the closed-loop control of the servo system, including closed-loop control such as torque, speed and position.

      The application field of AC servo.

　　AC servo drivers can be used in wherever the control accuracy of position, speed and torque is relatively high. Such as machine tools, printing equipment, packaging equipment, textile equipment, laser processing equipment, robots, electronics, pharmaceuticals, financial equipment, automated production lines because the servo is used in positioning and speed control, and the servo is also called motion control.

1. Metallurgy, steel-continuous casting blanking production line, copper rod upper continuous casting machine, jet marking equipment, cold continuous rolling mill, fixed length shearing, automatic feeding, converter tilting etc.

2, power, cable-turbine governor, wind turbine pitch system, wire drawing machine, twisting machine, high speed knitting machine, winding machine, printing marking equipment etc.

3, petroleum, chemical - extruder, film drive belt, large air compressor, pumping unit etc.

4, chemical fiber and textile - spinning machine, fine spinning machine, loom, carding machine, horizontal edge machine etc.

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

6, machine tool manufacturing-lathes, planers, milling machines, grinding machines, machining centers, gear making machines etc.

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

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

9. Electronics manufacturing-printed circuit board (PCB) equipment, semiconductor device equipment (lithography machines, wafer processing machines, etc.), liquid crystal display (LCD) equipment, machine-mounted and surface mount (SMT) equipment, lasers Equipment (cutting machine, engraving machine, etc.), general-purpose numerical control equipment, robots etc.

10. Paper industry—paper conveying equipment, special papermaking machinery etc.

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

12. Pharmaceutical industry - raw material processing machinery, preparation machinery, decoction machinery, printing and packaging machinery etc.

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

14. Logistics, loading and unloading, handling - automatic warehouse, truck, three-dimensional garage, transmission belt, robot, lifting equipment and handling equipment etc.

15. Construction - elevators, conveyor belts, automatic revolving doors, automatic window opening etc.

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

17. Test equipment—automobile test equipment, torque test equipment etc.

      The development trend of servo system

The application of digital AC servo system is more widely, and users have higher requirements for servo driver technology. In general, the development trend of the servo system can be summarized as follows:

1. Integration

At present, the output devices of servo control systems are increasingly using new power semiconductor devices with high switching frequency. These devices provide functions such as input isolation, energy braking, over temperature, over voltage, over current protection and fault diagnosis. All are integrated into one small module. The same control unit can change its performance by setting the system parameters through software. It can use the sensor configured by the motor itself to form a semi-closed loop adjustment system, and external external sensors such as position, velocity and torque sensors can be constructed to form high precision. Fully closed loop adjustment system. The high level of integration significantly reduces the size of the entire control system.

2. Intelligence

At present, the servo internal control core mostly adopts a new high-speed microprocessor and a dedicated digital signal processor (DSP) to realize a fully digital servo system. The digitization of the servo system is a prerequisite for its realization of intelligence. The intelligentization of the servo system is manifested in the following aspects: all operating parameters of the system can be set by software through man-machine dialogue; secondly, they all have fault self-diagnosis and analysis functions; and parameters self-tuning functions. As we all know, the parameter setting of the closed-loop regulation system is an important part of ensuring the performance index of the system, and it also requires a lot of time and effort. The servo unit with self-tuning function can automatically set the parameters of the system through several trial runs and automatically optimize it.

3. Networking

Servo system networking is an inevitable trend in the development of integrated automation technology. It is the combination of control technology, computer technology and communication technology. Fieldbus is a kind of application field, between field devices, field devices and control devices. Implement two-way, serial, multi-node digital communication technology. Fieldbus is now widely used for interactive transmission of information between servo systems, servo systems and other peripheral devices such as human machine interface HMI and programmable controller PLC. Fieldbus has the following types of FF; ProfiBus, WorldFIP, ControlNet/DeviveNet, CAN etc. These communication protocols offer the possibility of multi-axis real-time synchronous control and are also integrated into some high-end servo drivers, resulting in distributed, open, interconnected and highly reliable servo systems.

4. Simplification

The "simplification" mentioned here is not simple but streamlined. It is based on the user's situation, giving the servo function used by the user to the reinforcement, making it special and precise, and reducing some functions that are not used, thereby reducing the servo system. Cost, create more revenue for customers, and reduce resources waste by negotiating some components to benefit the environment. The term "easy" used herein refers to the software programming and operation of the servo system is developed from the user's point of view, and strives to be simple and easy so that the user can simply set up when debugging.