Absolute Encoder

An encoder that gives a unique reading for every angle, so it knows its position even after a power cycle.

An encoder is a sensor that measures how far a motor or joint has rotated. An absolute encoder assigns a unique code to every position, so it can report the current angle the instant it's powered on; an incremental encoder only counts pulses, so after losing power it has to be re-homed before it knows where it is. For robots, an absolute encoder means the joints don't need to be driven to a hard limit to find zero at startup, and it's now standard in humanoid and robot-arm joint modules. Common implementations include magnetic encoders and optical encoders; multi-turn absolute encoders can also remember how many full rotations have occurred. Many joints place one encoder at the motor and another at the output, a setup called a dual encoder.

ExampleWhen a humanoid robot powers on, the absolute encoders in its joints report each joint's angle directly, with no need to first move to a fixed pose to home.

Also called

Absolute-Type Encoder

Related

Rotary Encoder · Incremental Encoder · Magnetic Encoder · Optical Encoder · Dual Encoder · Joint Actuator Module

Sources

Rotary encoder - Wikipedia