AC servo drives (servo drives), also known as “servo controllers” and “servo amplifiers”, are a controller used to control servo motors. Part of it is mainly used in high-precision positioning systems.” So what’s the difference between an AC servo drive and an inverter? First of all, we must first understand the role of AC servo drivesWorking Principle of AC Servo Drive At present, the mainstream servo drives all use digital signal processor (DSP) as the control core, which can realize more complex control algorithm, realize digitization, networking and intelligence. Power devices generally use a drive circuit designed with an intelligent power module (IPM) as the core.
The IPM integrates the drive circuit and has fault detection and protection circuits such as overvoltage, overcurrent, overheating, and undervoltage. Start-up circuit to reduce the impact of the start-up process on the drive. The power drive unit first rectifies the input three-phase power supply or city power through a three-phase full-bridge rectifier circuit to obtain the corresponding DC power supply.
After the three-phase electricity or the mains is rectified, the three-phase permanent magnet synchronous AC servo motor is driven by the three-phase sinusoidal PWM voltage inverter by frequency conversion. The whole process of the power drive unit can be simply said to be the process of AC-DC-AC. The main topology circuit of the rectifier unit (AC-DC) is a three-phase full-bridge uncontrollable rectifier circuit. AC servo drives are an important part of modern motion control and are widely used in automation equipment such as industrial robots and CNC machining centers.
In particular, the servo drive used to control the AC permanent magnet synchronous motor has become a research hotspot at home and abroad. The three closed-loop control algorithms of current, speed and position based on vector control are widely used in the design of current AC servo drives. Whether the speed closed-loop design in the algorithm is reasonable or not plays a key role in the performance of the entire servo control system, especially the speed control performance. In the speed closed loop of the AC servo drive, the real-time speed measurement accuracy of the motor rotor is very important to improve the dynamic and static characteristics of the speed loop speed control.
In order to find a balance between measurement accuracy and system cost, incremental photoelectric encoders are generally used as speed sensors, and the corresponding common speed measurement method is M/T speed measurement method.
Although the M/T speed measurement method has a certain measurement accuracy and a wide measurement range, this method has its inherent defects.
1) At least one complete encoder pulse must be detected during the speed measurement cycle, which limits the minimum measurable speed;
2) The timing switches of the two control systems used for speed measurement are difficult to keep strictly synchronized, and the speed measurement accuracy cannot be guaranteed in the measurement occasions where the speed changes greatly.
Therefore, it is difficult to improve the speed following and control performance of the servo drive with the traditional speed loop design scheme using this speed measurement method.
In industrial applications, the speed control and torque control are not very demanding for general use of frequency converters, and in the occasions with strict position control requirements, the intelligent use of AC servo drives is used to achieve, and the response speed of the servo is much greater than Frequency conversion, some occasions that require high speed accuracy and response are also controlled by AC servo drives. That is to say, almost all occasions that can be controlled by frequency conversion can be replaced by AC servo drives.
AC servo drives and inverters can be said to be a pair of brothers, both of which are drives of AC motors. According to the order of appearance, the inverter should be called the elder brother, and the AC servo drive should be called the younger brother. The frequency converter drives the frequency conversion 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, and its main feature is precise and fast positioning and tracking, and precise position control.
As one of the supporting technologies of modern industrial automation and motion control, AC servo drives are widely used in machine tools, printing equipment, packaging equipment, textile equipment, rubber and plastics due to their precise high-speed control, wide speed regulation range, high dynamic characteristics and high efficiency. Equipment, electronic semiconductors, wind power/solar energy and other new energy, as well as robots, automated production lines and other fields. However, the AC servo drive has developed frequency conversion technology, and the AC servo drive has learned from and applied the frequency conversion technology. Based on the servo control of the DC motor, it is realized by imitating the control method of the DC motor through the frequency conversion PWM method, that is to say, the AC servo motor is realized. There must be this part of frequency conversion. Like the inverter, the power frequency alternating current is first rectified into direct current, and then converted into alternating current with adjustable frequency through the carrier frequency and PWM adjustment through various transistors (IGBT, IGCT, etc.) that can control the gate. Cosine of pulsating electricity.
Are AC Servo Drives Replacing Inverters? , there are two key factors in whether it can be replaced in the end, one is price and the other is power. If one day in the future, the servo brother “condescends” in price, will the inverter brother become more and more “lonely”? If the inverter brother makes technological breakthroughs, will it appear that there will no longer be a brother and a brother, and will become a real A family? The development of technology is as fast as a flash, always beyond our imagination, looking forward to a future with rapid technological progress.
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