[Import] principle of incremental rotary encoder [Mouse principle]

Principle of incremental rotary encoder

The incremental rotary encoder converts the sequence and Phase Relationships of its angle data disk through two photosensitive receiver tubes, and obtains the increase (positive direction) or decrease (negative direction) of the angle data disk displacement ). After joining a digital circuit, especially a single-chip microcomputer, the incremental rotary encoder is cheaper and easier than the absolute rotary encoder in angle measurement and angular velocity measurement.

The following figure shows the internal working principle of the incremental rotary encoder)

Two points A and B correspond to two photosensitive tubes. The distance between two points A and B is S2, And the grating distance between angle block is S0 and s1. When the angle block rotates at a certain speed, we can see that the S0: S1: S2 ratio in the output waveform is the same as the S0: S1: S2 ratio in the actual figure, similarly, when the disk rotates at a constant speed at another speed, the S0: S1: S2 ratio in the output waveform chart is still the same as the S0: S1: S2 ratio in the actual figure. If the angle code disk performs a variable speed movement and regards it as a combination of multiple motion cycles (defined below), then S0: S1 in the waveform is output in each motion cycle: the S2 ratio is the same as the S0: S1: S2 ratio in the actual graph.

The output waveform shows that the time sequence of each motion cycle is
Clockwise Movement: a B clockwise movement: A B
1 1 1 1
0 1 1 0
0 0 0 0
1 0 0 1

We save the current output values of A and B, and compare them with the output values of A and B to easily obtain the direction of motion of the Angle Block. If S0 is equal to S1, that is, the angle between S0 and S 1 radian is the same, and S2 is equal to 1/2 of S0, so we can get that the angle of motion displacement of the code disk is 0 radian of the angle of S 1/2, divided by the time of the Offset, we can see the moving displacement angular velocity of the code disk from this angle.

When S0 is equal to S1, and S2 is equal to 1/2 of S0, 1/4 motion cycles can get the motion direction position and displacement angle. If S0 is not equal to S1, S2 is not equal to 1/2 of S0, it takes one motion cycle to get the direction position and displacement angle of the motion.

This is also the principle of common mouse.

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