Absolute Position Encoder VS Other Transducers

 

From elevators to high-end robotics—the encoder can be found in various applications of different complexity. This electromechanical device is key to flawless functioning of machinery, whether it is used to monitor conveyor movements or to control shaft motor positions in robotics.

 

Encoders read positions of the component to which they are attached and convert them into signals. Rotary devices do this for rotating elements, whereas the linear type is utilized with machine constituent moving along a straight line. In any case, the measuring instruments play the role of a mediator linking the mechanical parts of a mechanism with a controller or another monitoring and control unit.

 

In robotics, an absolute encoder is one of the most efficient transducers for communicating position data within a motion system. What makes the device stand out?

 

Measurement systems

There are two basic measurement types employed for the encoding process—absolute and incremental. A measurement system determines the method of acquiring data in a transducer. More specifically, it is the coded disc or scale type and the way those are scanned.

 

Absolute measurement

Absolute measurement involves precise tracking of rotation. It produces a digital or analog position that can be used to derive other motion information, such as velocity or acceleration. Each position correlates with a unique binary output—i.e., it is determined absolutely.

 

Another distinguishing trait of absolute measurements is reading exact positions upon motion start without referencing to a home setting.

Why absolute encoder is much in demand

1.allows determining angular displacements with pinpoint accuracy

2.retains position data despite power disruptions

3.enables improving speed control by enabling faster motion response

4.has multiple interface options, such as BiSS, Profibus, CANOpen, etc.

5.has high resolution

 

Incremental measurement

An incremental encoder defines relative positions— differences between two points in a rotation trajectory—and requires a reference point to be set.

Output type

Since the encoder measurement system can be incremental or absolute, there is a conceptual difference between produced outputs as well. Two common output types are a data word to designate an absolute position and an incremental pulse to let users know a relative position.

 

An absolute position encoder basically works the following way: for each position of the shaft, there is a corresponding unique code. For this purpose, the rotating disc of the device includes a sophisticated slotted pattern.

 

In absolute encoders, major coded wheel patterns are the binary format or Grey code. The binary format is associated with inaccuracies that occur frequently at high-velocity measurements. As a result, the Grey code is the preferred pattern for a wider speed range.