In robotics, an encoder is a sensor that measures physical movement and converts it into electrical signals, such as measuring how much a motor rotates, which is converted into electrical signals, which can then be processed by a robot’s motion control system.

It is possible to group encoders in a few ways such as:

Incremental vs. Absolute which is to keep track of positions,

Rotary vs. Linear for measuring rotational or linear movement

Or the system that is used to measure the movement such as magnetic, optical, capacitive and a few more.

As an example, (see figure below) an optical encoder works by a light source emitting a tiny amount of light, which is intercepted by a rotating disc that is attached directly (or through a coupler) to a motor’s rotating shaft. The disc has regularly spaced intervals that alternately block and allow light to pass. This means, the photo sensor will receive the light with varying durations depending on motor rotation, such as its position, speed, rotation angle and acceleration. These can then be converted into electrical signals and in turn be processed by the robot’s motion control system.

The resolution of an encoder determines the fineness of signals can be measured. This needs to be compatible with the operational revolution per minute of the motor (it has to be small enough to not miss valuable information, but too small will not bring extra value).

Another important aspect of an encoder is whether it can keep track of loops measured or not. For this, different types of encoders are used, such as incremental or absolute. Absolute encoders can still tell the exact position even after a power reset.

Post By: A. Tuter

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