1. Control motor

In the automatic control system, the rotating motors used as measurement and comparison components, amplification components, execution and calculation components are collectively referred to as control motors.

1. Classification of control motors

Control motors are divided into DC control motors and AC control motors. DC control motors include tachogenerators, motor amplifiers and servo motors; AC control motors include servo motors, tachogenerators, stepping motors, resolvers and synchros.

2. Application of control motor

1) Automatic control and automatic adjustment systems in the production process and scientific experiments.

2) Remote control and telemetry system.

3) Synchronous servo system.

4) Automatic monitoring system during production.

5) Automatic instruments and automatic recording devices.

6) Analog computing device.

According to different purposes and functions, control motors are divided into two categories: signal components and power components. Those used to convert signals are signal components, such as rotary transformers that convert angular displacement into electrical signals, self-aligning transformers, and tachogenerators that convert speed into voltage signals.

Anything that converts electrical signals into power belongs to power components, such as motor amplifiers that amplify smaller electrical signals and control higher power, indicating auto-aligners and servo motors that convert electrical energy into mechanical energy.

2. Stepping motor

A stepper motor is a control motor that converts an input pulse signal into a mechanical angle or linear displacement. Every time a pulse signal is input, the stepper motor rotates through a fixed angular displacement or moves a linear displacement. Because the motion is intermittent, it is also called a pulse motor.

There are many types of stepper motors, and their structures and working principles are different. According to its different structure, it can be divided into reactive type and excitation type, and the excitation type is divided into power supply excitation type and permanent excitation type. According to the number of power supply phases, there are single-phase, two-phase and three-phase stepping motors.

Because the stepping motor can be used for rotary motion, linear motion and plane motion, it is widely used in CNC machine tools, automatic recording instruments, etc.

3. Servo motor

In automatic control systems, servo motors are used as actuators. Convert the input electrical signal into angular displacement or angular velocity on the shaft. According to the different power supply, it can be divided into DC servo motor and AC servo motor.

1. DC servo motor

DC servo motors are generally miniature DC motors. Its structure is similar to that of ordinary DC motors, and its excitation method is separately excited or permanent magnet. There are two control methods, field control and armature control. The magnetic circuit of a DC servo motor is generally not saturated, and there is no need to consider the influence of the nonlinearity of the magnetization curve and the armature reaction

2. AC servo motor

The basic structure and working principle of AC servo motors are basically the same as those of general two-phase asynchronous motors, but they also have their own characteristics.

The requirements for AC servo motors are:

1) Good controllability

When the signal voltage is zero, the motor can stop automatically, requiring no self-rotation phenomenon;

2) Stable operation

When the control signal changes, the motor can run stably in a wide speed range;

3) Quick response

It is required to be sensitive to the signal, to start quickly when receiving the control signal, and to automatically brake and stop quickly after losing the signal.

The stator structure of the AC servo motor is similar to that of the general asynchronous motor. There are two stator windings, the excitation winding and the control winding, which differ in space by 90 0 ^electrical degrees. The excitation winding is connected to the power supply, and the control winding is connected to the control circuit. The rotor structure has two types: squirrel cage type and non-magnetic cup type. The squirrel-cage type is similar to the rotor of a general cage-type asynchronous motor. This type of motor has the advantages of small excitation current, small size, and high mechanical strength, and is widely used in low-power automatic control systems.

In occasions with high requirements for fast response performance, non-magnetic hollow cup rotors are mostly used. Because of its small inertia and small friction torque, it responds sensitively during work, changes the steering quickly, has no noise, and has a large speed range, so it is widely used. in the automatic control system.