Introduce the reason why the encoder is installed in the motor

Absolute encoder

1. Basic classification of encoders

Four, encoders commonly used in motors

● Installation size, cable outlet method and protection. Including two aspects: positioning stop, shaft diameter, installation hole position, cable outlet method. Installation space volume; whether the protection level of the obligation situation can satisfy the request.

●Incremental encoder

When using an incremental encoder, the position is affirmed by the number of pulses calculated from the beginning of the zero mark, while the position of an absolute encoder is affirmed by the reading of the output code. In a circle, the reading of the output code of each position is unique; therefore, when the power is disconnected, the absolute encoder is not separated from the actual position. If the power is turned on again, the position reading is still valid afterwards.

Directly use the principle of photoelectric conversion to output three sets of square wave pulses a, b and z phases. The pulses of a and b have a phase difference of 90o, which can easily determine the rotation deflection; each pulse of the z phase is used for reference point positioning. Its strengths: The structure is simple, the average mechanical life can be more than tens of thousands of hours, the anti-interference ability is strong, the reliability is high, and it is suitable for long-distance transmission. Disadvantage: Absolute position information of shaft rotation cannot be output.

Sensors that directly output digital quantities. There are multiple concentric code tracks along the radial direction on the sensor's circular code disc. Each track is caused by light-transmitting and non-light-transmitting sectors. The number of sectors of adjacent code channels is doubled. Correlation, the number of code channels on the code wheel is the number of binary digits. On one side of the code wheel is the light source, and on the other side there is a photosensitive element corresponding to each code channel; when the code wheel is in a different position, each photosensitive element According to whether the light is received or not, the corresponding level signal is converted, resulting in a binary number.

●Hybrid absolute encoder. The hybrid absolute encoder outputs two sets of information: one set of information is used to detect the magnetic pole position, with absolute information function; the other set is completely the same as the output information of the incremental encoder.

● Resolution. The number of pulses output per revolution when the encoder is on duty.

2. The difference between incremental and absolute encoders

● Absolute encoder. The position, angle and number of turns are provided in angle increments, and each angle increment is assigned a unique code.

Three, the parameters that should be affirmed when selecting the encoder

The incremental encoder converts the displacement into a periodic electrical signal, and then the electrical signal is changed to count pulses. The number of pulses represents the magnitude of the displacement; in the absolute encoder, each position corresponds to a certain digital code, which represents the value It is only related to the start and stop position of the measurement, but is related to the side process of the measurement.

Encoder is a fine measurement device that combines mechanical and electronic rigorously. It encodes and converts signals or data for communication, transmission and storage of signal data. According to the different characteristics, the encoder classification situation is as follows:

● Code wheel and yardstick. The encoder that converts linear displacement into electrical signals is called a code scale, and the encoder that converts angular displacement into telecommunications is a code disc.

● Encoder output electrical interface. Rare are push-pull output type, voltage output, open collector, line drive output type. The output method should match the interface circuit of its control system.

● Incremental encoder. Provide information such as position, angle and number of turns, and define the separation rate with the number of pulses per turn.