An encoder is a rotary sensor that converts the position and displacement of a rotating part into a series of digital pulse signals. These pulse signals are collected and processed by the control system, which then issues a series of commands to adjust and change the operating state of the equipment. If the encoder is combined with a rack and pinion or a lead screw, it can also be used to measure the position and displacement of linear motion parts.
Encoders are used in motor output signal feedback systems, measurement, and control equipment. An encoder consists of two main parts: a code disk and a receiver. The optical parameters generated by the rotation of the code disk are converted into corresponding electrical parameters. These electrical parameters are then amplified and processed by the frequency converter's preamplifier and signal processing system, outputting a signal to drive the power devices. Generally, a rotary encoder can only feed back a speed signal, which is compared with a set value and fed back to the frequency converter's execution unit to adjust the motor speed.
There are many types of encoders, the most common being absolute encoders, incremental encoders, and rotary encoders, as well as some higher-resolution communication encoders. For servo systems, to achieve very high performance and accuracy, the encoder resolution must be increased. Commonly used servo encoders have 2000-2500 lines (pulses per revolution), but the higher the line count, the more expensive the encoder. Therefore, it is essential to understand the requirements of the control system to select the most suitable encoder.
Incremental encoders are the most commonly used, but their biggest problem is that the position is lost when power is off. Therefore, to maintain the position when power is off, an absolute encoder can be used. If there is a lot of mechanical vibration, photoelectric encoders are not suitable. In this case, a rotary transformer or magnetic encoder should be used.
Why do servo motors with built-in encoders still require external encoders?
1. Using a separate servo motor is a semi-closed-loop control method. The encoder built into the servo motor provides both speed and position feedback.
2. The servo motor has a built-in encoder, but does it also require a separate encoder connected to the servo motor? This is a control method between semi-closed-loop control and full closed-loop control. The encoder built into the servo motor provides speed feedback, while a separate external encoder connected to the servo motor provides position feedback.
3. In the fully closed-loop control mode, the encoder built into the servo motor provides speed feedback, while the position feedback uses a linear encoder.
Servo Motor Encoder Introduction
A servo motor encoder is a sensor mounted on a servo motor to measure the position of the magnetic poles and the speed and angle of the servo motor. Servo motor encoders can be divided into photoelectric encoders and magnetoelectric encoders, and from different physical perspectives, they are categorized into photoelectric encoders and magnetoelectric encoders, among others. Additionally, rotary encoders are also a type of servo encoder. Basically, photoelectric encoders are used in the market, but magnetic electric encoders are used for back-end development, are reliable, inexpensive, and dirt-resistant, etc., and there is a super encoder encoder. The trend is towards servo motor encoders. The shaft of the servo motor encoder should be connected to the machine using a flexible connector. Another type of encoder has sinusoidal C and D signals, exhibiting a one-to-one sinusoidal C and D signal, meaning there is only one signal period. The COS signal exhibits the mutual orthogonality of a sinusoidal C and D signal period. For SIN, D signals are a high-magnification subdivision technique of COS, SIN. The COS signal not only allows the sine and cosine encoder to detect the resolution of the original signal period, such as 2048 lines, as in the Sputum encoder. After the 2048 subdivision, you can achieve a detection resolution of over 4 million lines. Additionally, the encoder's C and D signals can provide high total rotational absolute position information, such as 2048 absolute positions per rotation. A sine/cosine encoder with C and D signals can be considered an analog-to-digital (ADC) absolute encoder.
Relationship between servo motors and encoders
1. Servo drivers and encoders are two essential components of a servo system. The servo drive control section obtains rotor speed, rotor position, and mechanical position, and can perform the following:
A, Servo motor speed control
B. Servo motor torque control
C. Synchronous tracking of mechanical position (multiple transmission points)
D, Fixed-point parking
2. There are many types of encoders, the most commonly used being absolute encoders, incremental encoders, and rotary modulators, as well as some higher-end communication encoders. For servo systems, if you want very high performance and accuracy, you must increase the encoder's resolution. Common servo encoders have 2000-2500 lines (pulses/revolutions). The higher the number of lines, the more encoders you expect, and the higher the price. Therefore, you must understand the requirements of your control system to select the most suitable encoder.
3. For incremental encoders, the most common, but biggest, problem is the loss of the power-off position. Therefore, to maintain the power-off position, an absolute encoder can be used. If there is a large mechanical vibration, then an optical encoder is not suitable, which is where a rotary transformer is required.
