Rotating electrical machine whose input or output is direct current energy. Its analog speed regulation system generally consists of two closed loops, namely speed closed loop and current closed loop. In order to make them coordinate with each other and play a role, two regulators are set in the system to adjust the speed and current respectively. The structure of two feedback closed loops adopts a nested structure of one loop and one loop, that is, the so-called double closed loop speed regulation system. It has the advantages of fast dynamic response and strong anti-interference ability, so it is widely used. Usually, PI or PID circuits consist of analog operational amplifiers. Signal conditioning is mainly to filter and amplify the feedback signal. Considering the mathematical model of DC motor and the dynamic transfer function relationship of analog speed regulation system, it is very troublesome to change the circuit parameters frequently to obtain the expected dynamic performance index in the debugging process of analog speed regulation system because the parameters of motor or the mechanical characteristics of load are quite different from the theoretical values. If the voltage stabilizing circuit is composed of programmable analog devices, the system parameters such as gain, bandwidth and even circuit structure can be modified by software, which is very convenient to debug.
DC servo motors are divided into brush motors and brushless motors. Brushed motor has the advantages of low cost, simple structure, large starting torque, wide speed range, easy control and maintenance, but it is convenient to maintain (replacing carbon brush), which will produce electromagnetic interference and require the environment. Therefore, it can be used in common industrial and civil occasions which are sensitive to cost. Brushless motor has the advantages of small volume, light weight, large output, fast response, high speed, small inertia, smooth rotation and stable torque. It is easy to realize intelligence, and its electronic commutation mode is flexible, which can be square wave commutation or sine wave commutation. The motor has the advantages of maintenance-free, no carbon brush loss, high efficiency, low working temperature, low noise, small electromagnetic radiation and long service life, and can be used in various environments.
DC servo motor can be used in spark machine, manipulator, precision machine tool and so on. At the same time, it can be equipped with a gearbox, which makes the mechanical equipment bring reliable accuracy and high torque.
2. AC servo motor:
A rotating electric machine whose input or output is AC electric energy. AC motors are divided into stator windings and rotor conductors. Rotor conductors are shaped like silicon steel sheets used between squirrel cage conductors, and some AC motors also have windings. The rotor of AC servo motor is made of high impedance metal alloy. There are two groups of coils on the stator, namely excitation coil and torque coil. The excitation coil excites the rotor at a fixed frequency, and the torque coil is responsible for providing the rotating torque. Both groups of coils work under the drive of the driver. The self-contained encoder is called rotary encoder, and its accuracy is: fractional degree (the number of pulses emitted by one rotation).
Ac servo motor is also a brushless motor, which is divided into synchronous motor and asynchronous motor. At present, synchronous motor is generally used in motion control, which has a large power range and can achieve great power. The inertia is large, the maximum speed is low, and it decreases rapidly with the increase of power. Therefore, it is suitable for low-speed stable operation.
There are three main operation modes of synchronous motor, namely, as generator, motor and compensator. Running as a generator is the main operation mode of synchronous motor, and running as a motor is another important operation mode of synchronous motor. The power factor of synchronous motor can be adjusted, and when speed regulation is not needed, the operation efficiency can be improved by applying large synchronous motor. In recent years, small synchronous motors have been widely used in variable frequency speed regulation systems. Synchronous motors can also be connected to the power grid as synchronous compensators. At this time, in the absence of any mechanical load, the motor delivers the required inductive or capacitive reactive power to the power grid by adjusting the excitation current in the rotor, thus improving the power factor of the power grid or adjusting the voltage of the power grid.
The ratio between the speed of asynchronous motor under load and the frequency of the connected power grid is not constant. Asynchronous motors include induction motors, doubly-fed asynchronous motors and AC commutator motors. Induction motor is the most widely used, which can be generally called asynchronous motor, and will not cause misunderstanding or confusion. The stator winding of ordinary asynchronous motor is connected to AC power grid, and the rotor winding does not need to be connected to other power sources. Therefore, it has the advantages of simple structure, convenient manufacture, use and maintenance, reliable work, small mass and low cost. Asynchronous motor has high operating efficiency and good working characteristics, and can run at a constant speed from no-load to full load, which can meet the transmission requirements of most industrial and agricultural production machinery. Asynchronous motors can also easily generate various protection types to meet the needs of different environmental conditions. When asynchronous motor is running, reactive excitation power must be absorbed from the power grid, which makes the power factor of the power grid worse. Therefore, synchronous motors are often used to drive high-power and low-speed mechanical equipment such as ball mills and compressors. Because the speed of asynchronous motor has a certain slip relationship with its rotating magnetic field speed, the speed regulation performance is poor (except AC commutator motor). For transportation machinery, rolling mills, large machine tools, printing and dyeing and papermaking machinery that require wide and smooth speed regulation, it is more economical and convenient to use DC motor. However, with the development of high-power electronic devices and AC speed regulation system, the speed regulation performance and economy of asynchronous motor suitable for wide speed regulation have been equivalent to that of DC motor.
Up to now, high-performance electric servo systems mostly use permanent magnet synchronous AC servo motors, and control drivers mostly use all-digital position servo systems with fast and accurate positioning. Typical manufacturers are Siemens, kollmorgen, Panasonic and An Chuan.
Since 1980s, with the development of integrated circuit, power electronics technology and AC variable speed drive technology, the permanent magnet AC servo drive technology has made outstanding progress, and famous electrical manufacturers in various countries have successively introduced their own AC servo motors and servo drive series products, which are constantly improved and updated. Ac servo system has become the main development direction of contemporary high-performance servo system, which makes the original DC servo face the crisis of being eliminated. After the 1990s, all commercial AC servo systems in the world are driven by sine wave motor servo with full digital control. The development of AC servo drive device in transmission field is changing with each passing day. Compared with DC servo motor, permanent magnet AC servo motor has the following main advantages:
(1) has no brush and commutator, so it works reliably and has low maintenance requirements.
⑵ The stator winding is convenient for heat dissipation.
(3) Inertia is small, which is easy to improve the rapidity of the system.
(4) Adapt to high-speed and high-torque working conditions.
5] Smaller size and lighter weight under the same power.