The servo motor encoder is a sensor mounted on the servo motor for measuring the magnetic pole position and the servo motor rotation angle and the rotational speed. The servo motor encoder can be divided into a photoelectric encoder and a magnetoelectric encoder, depending on the physical medium. In addition, the rotary transformer is also regarded as a special servo encoder. The photoelectric encoder is basically used in the market. However, as a rising star, the magnetoelectric encoder has the characteristics of reliability, low price, anti-pollution, etc. trend.
The basic function of the servo encoder is the same as that of the ordinary encoder. For example, the absolute type has A, A, B, B, Z, Z and other signals. In addition, the servo encoder has a common code. Different places, that is, the servo motor is mostly a synchronous motor. When the synchronous motor starts, it needs to know the magnetic pole position of the rotor, so that the servo motor can be started with a large torque. This requires several additional signals to detect the current position of the rotor. Incremental type has UVW and other signals. Just because of these signals for detecting the rotor position, the servo encoder is a bit complicated, so that most people can't understand it, and some manufacturers deliberately cover some signals. The related information is not complete, which adds to the mysterious color of the servo motor encoder.
Since the two phases of A and B are 90 degrees out of phase, the encoder can be obtained by comparing the A phase before or the B phase to determine the forward and reverse rotation of the encoder, and the zero reference pulse can be used to obtain the zero reference position of the encoder.
The material of the encoder code disc is glass, metal and plastic. The glass code disc is deposited on the glass with very thin engraved lines. The thermal stability is good and the precision is high. The metal code disc is directly passed through and the line is not cut, and it is not easy to be broken. However, due to the certain thickness of the metal, the accuracy is limited, and its thermal stability is one order of magnitude worse than that of the glass. The plastic code disk is economical, and its cost is low, but the accuracy, thermal stability and life are both poor. .
The encoder manufacturer uses the principle of the clock gear mechanism. When the center code wheel rotates, another set of code wheels (or sets of gears, multiple sets of code disks) is driven by the gear, and the number of turns is added on the basis of the single-turn coding. Encoding to expand the measuring range of the encoder, such an absolute encoder is called a multi-turn absolute encoder, which is also determined by mechanical position determination, and each position code is unique and does not need to be memorized.