The servo encoder is aFeedback informationThe sensor is installed at the end of the servo motorMeasurement of servo motor shaft rotation angle, rotation speed, position and other informationThen the control instructions and feedback information are compared through PLC, and if there is a difference, it is corrected to achieve high-precision operation of the equipment.

This process is similar to hanging a plaque.

The colleague in red in the above picture is equivalent to a "servo encoder", which is specially used to feed back the actual position, angle and other information to help you hang the plaque upright.

The core component of the encoder--Encoding disc (code disc), And the parts that match it, are the parts that we need to focus on, because the difference between these two parts directly determines the resolution of the encoder and affects the accuracy of the servo motor.

Due to different definitions, technologies, components, etc., there are many types of encoders, and their respective precisions are different. Therefore, before selecting, it is necessary to understand the characteristics of various encoders to determine which one is more suitable for your working conditions. (Note: The following classification does not cover all, only the commonly used servo encoder on the market to be described)

Working principle: Light weaving is a kind of use.Optical principles for measurementThe device consists of an LED light source (usually an infrared light source) and a photodetector, which are located on both sides of the encoder code wheel. The code wheel is made of plastic or glass and is spaced apart by a series of light-transmitting and light-transmitting lines or grooves. When the code wheel rotates, the LED light path is blocked by spaced lines or slots on the code wheel, resulting in two typical square wave A and B quadrature pulses, which can be used to determine the rotation and speed of the motor shaft.

Features: The accuracy of optical editing is better than that of magnetic editing, and it has the characteristics of high resolution and strong stability. However, due to the particularity of the code disc material and the distance between the code disc and the detector is too close, the interior of the optical code must ensure a dust-free environment.

Suitable for working conditions: Suitable for application scenarios with high requirements on position and speed, such as precision engraving with trajectory requirements, fast die cutting, high-speed rotation, high-precision measurement, etc. It is worth noting that the high price of light weaving is not suitable for low-cost applications.

Working principle: Magnetic weaving is a type that has only been gradually used on a large scale in recent years. It is a kind of use.magnetic field principle for measurementThe device includes a magnetic field generator and a magnetic sensitive element. It is mainly to install a magnet on the motor shaft, the magnet rotates with the motor shaft, and then install a circuit board on the rear end cover. There is a magnetic field sensing chip in the middle of the circuit board, which can measure the angle of the magnetic field and determine the motor shaft. Rotation angle, angular velocity.

Features: Compared with optical encoders, magnetic encoders have the advantage of being more durable, resistant to vibration and impact, and are very suitable for harsh environments. However, the response speed of the magnetic code is slow, and it is not competent for the position feedback of the high-speed moving load. At the same time, the magnetic interference will affect the magnetic code, so the resolution and accuracy of the magnetic code are relatively low.

Suitable for working conditions: Suitable for automotive electronics, material handling/sorting, AGV wheels, conveyor belt transmission, industrial control and other application scenarios where position and speed requirements are not so strict. At the same time, the price of magnetic weaving is relatively low and the cost performance is high.

* Incremental code wheel diagram

Working principle: Incremental encoder directly uses photoelectric conversion principle to output three groups of square wave pulses A, B and Z phases; A, B two sets of pulse phase difference of 90, which can easily determine the direction of rotation, and Z phase for each turn a pulse, used for reference point positioning.

Features: The advantage is that the principle 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. The disadvantage is that once the power is cut off, the location information will be lost. Moreover, if the power is turned on again, the original point return must be performed to restart the operation.

For example, the positioning of the printer scanner is based on the principle of incremental encoder. Every time we turn on the machine, we can hear a crackling sound. It is looking for the reference zero point before it works.

Suitable for working conditions: Suitable for CNC machine tools and mechanical accessories, robots, automatic assembly machines, automatic production lines, textile machinery, packaging machinery (fixed length), printing machinery (synchronization), woodworking machinery, plastic machines and other scenes. It can be said that the accuracy and stability are good, and the price is suitable, so it is widely used.

* Absolute code wheel diagram

Working principle: Absolute encoders are directOutput DigitalThe sensor has a number of concentric code disks along the radial direction on its circular code disk. Each track is composed of transparent and opaque sectors. The number of sectors of adjacent code tracks is double. The number of code tracks on the code disk is the number of bits of its binary number. One side of the code disk is a light source, and the other side has a photosensitive element corresponding to each code track. When the code disk is in different positions, each photosensitive element converts the corresponding level signal according to whether it is illuminated or not, forming a unique binary code from the zero square of 2 to the n-1 square of 2. The more the number of code channels, the greater the accuracy. At present, there are 17-bit and 23-bit absolute value encoders in China.

Features: The advantage is that no counter is needed, and the unique digital code corresponding to the position can be read out at any position of the rotating shaft, which is not affected by power failure and interference. In other words, even if there is a power failure, the absolute encoder can know where it is now as long as it is powered on. The disadvantage is that the structure and circuit are more complex and the technical requirements are high.

Suitable for working conditionsSuitable for special machine tools, textile machinery, irrigation machinery, paper printing, water conservancy gates, robots and mechanical arms, precision measuring equipment, elevators and other precision equipment. Absolute value encoder anti-interference characteristics, data reliability is stronger, but the price is more expensive.