If you want to control the motor accurately, you will need to use such a thing, because it can help you to decipher the fast rotating motor?
The photoelectric encoder applies the principle of photoelectric conversion, which can convert the mechanical geometric displacement on the output shaft into a pulse or digital quantity. This is the most widely used sensor. Since the photoelectric code disk is coaxial with the motor, when the motor rotates, the code wheel (grating plate) rotates at the same speed as the motor, reflecting the current motor speed.
It is mainly composed of a light source, a code wheel, an optical system and a circuit. Below we explain according to different types of photoelectric encoders.
figure 1
First, incremental encoder
It converts the displacement into a periodic electrical signal, which is then converted into a counting pulse. The incremental encoder rotates to output a pulse while rotating, and its position is known by the counting device. And the position is determined from the zero mark to determine the number of pulses is determined, when the power is off, the encoder can not have any movement, when the power is turned on again, the encoder output pulse process, there can be no interference and loss of pulse, otherwise The zero point of the counting device memory will be offset. The result of the error is difficult to find. If the reference point cannot be accurately located, the accuracy of the position cannot be guaranteed. So every time you have to find a reference point. However, such an encoder is not affected by power outages and interference.
figure 2
Incremental encoder can output three groups of square wave pulses A, B and Z by photoelectric conversion principle; the phase difference between A and B pulses is 90 degrees, which can judge the rotation direction of the motor, and the Z phase is output per revolution. A pulse for reference point positioning. The encoder principle is simple in structure, mechanically average, and has a life span of tens of thousands of hours. It has strong anti-interference ability and high reliability. However, the absolute position information of the shaft rotation cannot be output.
Second, the absolute encoder
Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, regardless of the intermediate process of the measurement. Its position is determined by the reading of the output code. When the power is turned off, the absolute encoder is not separated from the actual position. When the power is turned back on, the position reading is still current.
image 3
Absolute encoders can directly output large digital quantities. There are several code channels on the code wheel, and the number of code channels is binary digits. Each code channel is composed of a opaque and opaque sector, and the signal is collected by using a photoelectric sensor. A light source and a photosensitive element are respectively disposed on both sides of the code wheel, so that the photosensitive element can perform level conversion according to whether or not the optical signal is received, and output a binary number. And output different digital codes at different locations. Thereby the absolute position can be detected. But the resolution is determined by the number of bits in the binary, which means that the precision depends on the number of bits. Advantages: The absolute value of the angular coordinates can be read directly, without accumulated error, and the position information will not be lost after the power is cut off. The anti-jamming characteristics of the encoder and the reliability of the data are greatly improved.
Third, the hybrid absolute encoder
A hybrid absolute encoder that outputs two sets of information: one set of information for detecting the magnetic pole position with absolute information function and the other set with the output information of the incremental encoder.
Fourth, the rotary transformer
The rotary transformer is referred to as the cyclone. It is composed of high-performance silicon steel laminations and enameled wires with special electromagnetic design. Compared with encoders using photoelectric technology, it has heat resistance and vibration resistance. Adaptability to harsh working environments such as impact resistance, oil resistance and even corrosion resistance. A one-pole (single speed) resolve can be considered as a single-turn absolute feedback system with the widest range of applications.
Figure 4
Five, sine and cosine servo motor encoder
The high-frequency communication can be used to obtain high-precision subdivision of the servo driver, which reduces the hardware requirements. At the same time, due to the single-turn angle signal, the servo motor can be started smoothly and the starting torque is large.
In order to enable better testing of motor performance parameters, ZLG Zhiyuan Electronic MPT Motor Test System has a unique "free loading engine" technology for control response test and step response test. It can meet the needs of transient measurement of motors and drives and drive the development of the industry.
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