Generally, industrial robots are designed to use both optical and magnetic encoders. So what is an encoder? Below is a detailed explanation of the types and applications of industrial robot encoders!
An industrial robot encoder is defined as a sensor that monitors position, angle, and speed, and is divided into rotary encoders and linear encoders. Rotary encoders are further divided into incremental encoders and absolute encoders (linear encoders are divided into wire sensors and non-contact linear sensors). An encoder is a device that encodes signals (such as bitstreams) or data and converts them into a form of signals that can be communicated, transmitted, and stored. Encoders convert angular displacement or linear displacement into electrical signals; the former is called a code disk, and the latter a code scale.
Industrial robot encoder classification: According to the reading method, encoders can be divided into contact type and non-contact type; according to the working principle, encoders can be divided into incremental type and absolute type.
Incremental encoders convert displacement into periodic electrical signals, which are then converted into counting pulses, with the number of pulses representing the magnitude of the displacement. Absolute encoders, on the other hand, assign a unique digital code to each position, so their readings depend only on the start and end of the measurement, and not on the intermediate steps.
Classification of industrial robot encoders
Based on the detection principle, encoders can be divided into optical and magnetic types. Based on their scale method and signal output form, inductive and capacitive encoders can be divided into incremental, absolute, and hybrid types.
1. Incremental encoder:
Incremental encoders can generate information such as position, angle, and number of revolutions. The number of marks on each revolution scale determines the number of pulses transmitted by the encoder's steering control unit for each direction. The control unit calculates the number of pulses from a reference point to determine the current position. After startup, the encoder needs to operate on the reference point to return to it and determine the encoder's actual position.
Incremental encoders directly utilize photoelectric conversion to output three sets of square wave pulses, AB and Z phases. The AB pulses have a 90-degree phase difference, facilitating the determination of rotation direction, while the Z phase outputs one pulse per rotation, used for reference point positioning. Its advantages include a simple principle and structure, an average mechanical lifespan exceeding tens of thousands of hours, strong anti-interference capability, high reliability, and suitability for long-distance transmission. Its disadvantage is the inability to output the absolute position information of the shaft rotation.
2. Absolute encoder:
It can generate information such as position, angle, and number of revolutions, and calculate the step distance of a specified type. Therefore, each step angle is assigned a unique code pattern. The number of code patterns available for each turn determines the resolution. Each code pattern can form a unique reference point, providing absolute position information. Therefore, after startup, this type of encoder can be measured without a reference point. A single-turn encoder measures the absolute position within one turn. A multi-turn encoder can not only measure the position within one turn but also provide the number of turns.
An absolute encoder is a sensor that directly outputs digital data. It has several concentric code discs radially arranged on a circular code disk. Each path consists of light-transmitting and light-blocking fan zones. The fan zones of adjacent code tracks are in a doubly related relationship. The number of code tracks on the code disk is the number of bits in its binary representation. One side of the disk is a light source, and the other side has a photosensitive element for each corresponding code track. When the disk is in different positions, each photosensitive element converts a corresponding level signal based on whether light is present, forming a binary number. A key feature of this encoder is that it does not require a counter. You can read the fixed corresponding digital code at any position on the shaft. Obviously, is it necessary to have N paths? Currently, there are 16 absolute encoder products in China.
3. Hybrid absolute encoder:
The hybrid absolute encoder outputs two sets of information: one set is used to detect the position of the magnetic poles with absolute information function; the other set is exactly the same as that of the incremental encoder.
