Photoelectric Encoder in Motor Control Application！

Photoelectric encoder in Motor Control
    

Position detection of the motor in motor control is very important, especially the need for motor control applications depending on the exact state of motion of the rotor position, such as position servo system. Motor control system position detection usually are: components, optoelectronic components, magnetic components, electromagnetic induction components such as micro-motor solver. The position detection sensor is connected to the non-load side or coaxial motor, or directly on a specific part of the motor. Wherein the photovoltaic element of high measurement accuracy, can accurately reflect the mechanical position of the rotor of the motor, to accurately reflect the mechanical position of the motor is indirectly connected to the mechanical load, so as to achieve the purpose of the precise control of the position of the motor. In this article I will focus on the internal structure of high-precision optical encoder, the method works with location detection.

    A photoelectric encoder description:

Optical encoder pattern is read by optical encoder disk or encoded information on the position information to indicate photoelectric encoder connected to the motor rotor. Photoelectric encoder can be divided into absolute optical encoder with incremental photoelectric encoder photoelectric encoder according to the working principle, I do the following presentation on the structure and working principle of the two photoelectric encoder.

(A), the absolute optical encoder

Absolute optical encoder as shown, he is to represent the absolute position information by reading binary coded information encoded on the disc.

Encoder disk is a disk in accordance with a certain code in the form of steel. FIG. 1 is a binary code disc, a blank part of the figure is transparent, with "0" to represent; blacked out portion is opaque, with "1" to represent. The ring is usually composed of coding called code channels, each channel represents a binary code, in which the outermost is the lowest position, the innermost side is highest. If the encoder disk has four yards Road, inside-out by the code channels are represented as binary 20,4 23,22,21 and 16-bit binary binary number can be formed, so the disc will be divided into 16 sectors each sector corresponds to a 4-bit binary number, such as 0000, 0001, ..., 1111.

Formed on the code wheel according to code channel configuration corresponding photoelectric sensor includes a light source, a lens, encoder, photodiodes and drive electronics. When the code wheel to a certain angle, the sector opaque code channel corresponding to the photodiode is turned on, the output of the low level "0", the code channel corresponding to the light shielding photodiode is not conducting, the output high. " 1 ", and thus the formation consistent encoding high and low level output to obtain a position of the sector pin.

(B), incremental optical encoders

Incremental photoelectric encoder varies with position encoder outputs a series of pulses and pulse counter for up / down counting according to the position change of direction in order to achieve the position detection purposes. It is composed of a light source, a lens, the main grating encoder, in view of the disc, the photosensitive element and the electronic circuit components.

Incremental optical encoder is a rotary drive works in uniform radial slit main grating is rotated by the rotary shaft encoder, in the above code wheel has a main grating parallel to the mirror to the disk, the disk Kam there are two 90o phase shifted from each other slit, respectively, and a photodiode receiver through the main grating encoder signals come. At work, in view of the steering wheel does not move, the main grating encoder rotating with the rotor, the light source is directed through the lens parallel to the main grating encoder, by the main grating disc and identification code received by the photodiode to the late phase of an approximately sinusoidal signal 90o, then the logic circuit formed by the turn signal and counting pulses. In order to obtain an absolute position angle in incremental photoelectric encoder zero pulse, that every revolution the main grating, output a zero pulse of the position angle is cleared. Use incremental photoelectric encoder can detect the position and speed of the motor.

Second, the optical encoder measurement methods:

Photoelectric encoder in motor control can be used to change the speed and direction of change of the magnetic field and the mechanical position measurement of the rotor position and mechanical position of the magnetic field and the rotor. Here I would photoelectric encoder application methods in these areas to do some introduction.

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