Let’s discuss the incremental encoder. Its purpose is to provide the angle feedback of the control system, and how many angles it has rotated.

• Output signal:

Usually there are two types of output signals, one is sine wave output type and the other is square wave output type. According to the number of output channels, there are three common ones:

1. One-phase output type (A phase)

2. Two-phase output type (A-phase, B-phase)

3. Two-phase output and origin signal type (A-phase, B-phase, Z-phase)

The one-phase output type cannot judge the direction of rotation. To judge the direction of rotation, there must be at least two-phase output.

In Figure 8, the square wave output type is shown. In addition, if you want to return to the origin, you need to add a Z-phase signal in order to handle the zero return of the counter when returning to the origin.

In addition, if it is an absolute encoder, the following encodings may be used:

* Gray Code

* Binary code

* BCD code

The signal transmission of absolute position is usually carried out by serial communication.

• Resolution:

Usually, how fine the resolution is required depends on the speed control function and positioning accuracy to be achieved.

Choosing a high resolution that exceeds the requirement may increase the cost, and the receiving capacity of the upper controller may not be enough to receive such high-speed data. Specifically, the receiving bandwidth of the square wave must be very high. Therefore, the resolution of the encoder should be selected carefully.

Usually, the resolution is described in terms of the number of bits or the number of divisions. If it is a linear encoder, it is usually μm or even nm.

• Structure and installation:

The structure of rotary encoders can be roughly divided into two categories: hollow shaft type (enclosed motor type) and shaft type. Please refer to the picture.

When using the hollow shaft type, directly connect the shaft of the motor to the hollow hole, which can save axial space. In order to prevent the outer ring of the encoder from rotating, the structure adopts a plate spring to connect with the motor body. In addition to preventing the outer ring of the encoder from rotating, the plate spring can also absorb imperfect shape of the motor shaft or vibration and impact. However, if it exceeds the installation tolerance, it will cause stress to the plate spring, which may break after a long time. Therefore, pay special attention to the axial and radial tolerances when installing, and the inclination of the installation shaft should not be too large.

Another shaft type, when in use, the motor transmits the rotary motion to the encoder through the following methods:

1. Communicate by roller
2. Coupling link
3. Connect with belt
4. Communicate with gears

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