AC servo motor has the advantages of high efficiency, high precision and high reliability, so it is widely used in various occasions that require high-precision control and speed regulation, such as CNC machine tools, robots, power electronic equipment, etc. At the same time, with the continuous development of technology, the application field of AC servo motor is also expanding.
According to the structural form, AC servo motors can be divided into two basic types: cage motors and hollow cup motors. Cage motors are a common AC servo motor with a solid iron core rotor structure, high moment of inertia and low rotational resistance. Hollow cup motors are a special type of AC servo motor with a hollow cup rotor structure, low moment of inertia and high rotational resistance. The rotor of this motor is not solid, but hollow, so it can have a higher speed and a smaller volume.
Ac servo motors can also be divided into two basic types: ordinary servo motors and high-efficiency servo motors according to their uses. Ordinary servo motors are mainly used in general transmission systems, with short response time and high precision, and are suitable for most industrial control and automation equipment. High-efficiency servo motors are mainly used in high-efficiency transmission systems. They have high speed and large power and are suitable for transmission systems that require high efficiency, high precision and high reliability. High-efficiency servo motors usually use permanent magnet excitation or electronic excitation to improve efficiency and precision.
In terms of control methods, AC servo motors are also different from general motors. AC servo motors can convert electrical signals into angular displacement or angular velocity of the shaft, thereby achieving smooth control and precise adjustment. Its control methods mainly include amplitude control, phase control and amplitude-phase control. Amplitude control is to change the speed and torque of the motor by changing the amplitude of the control voltage; phase control is to change the speed of the motor by changing the phase of the control voltage; amplitude-phase control is to change the amplitude and phase of the control voltage at the same time to achieve a more precise control effect.
DC servo motor is an actuator widely used in various automation control systems. It has two main parts: stator and rotor. The stator is usually stacked with silicon steel sheets and equipped with a three-phase winding. When the DC power supply is connected to the winding, a fixed magnetic field will be generated. The rotor is made of magnetic material, and is usually equipped with cage windings or squirrel cage windings. When the stator magnetic field interacts with the rotor winding, the rotor begins to rotate.
The DC servo motor has a series of advantages. First, it has the advantages of high precision, fast response, stability and reliability, and can achieve high-precision position control, speed control and torque control, providing accurate, stable and reliable driving methods for various mechanical equipment. Secondly, it has good speed regulation performance, which can be achieved by changing the armature voltage or excitation current, with a wide speed regulation range and high smoothness. In addition, the DC servo motor also has the characteristics of high precision and fast response speed, can operate smoothly in a wide speed range, and has a high torque-to-inertia ratio, which can quickly accelerate the load. At the same time, it has high efficiency, which can be close to 90% when lightly loaded, and has high output power, which can meet the needs of various high-precision control systems. Finally, the maintenance of DC servo motors is relatively cheap, and DC motors are more energy-saving and environmentally friendly than AC.
DC servo motors can be divided into two types according to the different brushes: brushed motors and brushless motors. The brushes of the brushed motor are in contact with the commutator, and the armature current is commutated by the commutator. It has the advantages of low cost and simple structure, but the wear of the brushes will produce particles, which is not suitable for dust-free and explosive environments. The brushless motor realizes the commutation of the armature current through the electronic commutation circuit, which has the advantages of high efficiency, small size, light weight, etc., and is suitable for occasions with high requirements for precision and control performance.
The control methods of DC servo motors mainly include open-loop control and closed-loop control. Open-loop control is to control the speed and position by adjusting the armature voltage or excitation current. It has the advantages of simplicity and ease, but the control accuracy is relatively low. Closed-loop control is to feedback the actual speed or position signal of the motor, compare it with the command signal, and adjust it according to the error. It has the advantages of high control accuracy and fast response speed, but it needs to add feedback links and regulators.
AC servo motors and DC servo motors are two different types of motors, which have obvious differences in many aspects.
Working principle: The working principle of AC servo motors is based on the principle of electromagnetic induction. The winding on the stator generates a rotating magnetic field to drive the rotation of the rotor. The DC servo motor is based on the principle of electromagnetic drive, and the rotor is rotated by the combination of brushes and commutators.
Structural form: AC servo motors usually use stator cores and windings, and the rotor uses a permanent magnet structure. DC servo motors usually use armatures and magnetic poles.
Speed regulation performance: AC servo motors can achieve motor speed regulation by changing the frequency and amplitude of the power supply, with a wide speed regulation range and fast response speed. DC servo motors achieve motor speed regulation by changing the armature voltage or current, with a relatively narrow speed regulation range and slow response speed.
Reliability: AC servo motors have high reliability because of their simple structure and easy maintenance. DC servo motors are prone to wear and failure due to the friction between brushes and commutators, and require regular maintenance and replacement.
Efficiency: AC servo motors usually have high efficiency because of their high energy conversion efficiency. DC servo motors have large energy losses and relatively low efficiency due to the friction between brushes and commutators.
Cost: The cost of AC servo motors is relatively low because of their simple structure and low manufacturing cost. The manufacturing cost of DC servo motors is relatively high because their structure is relatively complex.