Utilize a digital method to determine the rotation direction in incremental photoelectric encoder

摘要

The principles of incremental photoelectric encoders are: When a encoder disk rotates, ©it will produce the pulse signalproportional to the angle; © it will also produce the sensing signal of identifying the rotation direction.The way that the existing incremental photoelectric encoders determine the rotation direction is: one encoder disk has 3 code channels: 'A', 'B' and 'Z'. On both 'A' and 'B' code channels, there are a number of evenly distributed grid holes, and they have the same cycle, but with one quarter cycle difference in phase between channel 'A' and 'B'. When disk rotates clockwise, signal phase from 'A' channel is a quarter cycle ahead of that from 'B'; Similarly, when disk rotates counterclockwise, 'B' signal phase will be a quarter cycle ahead of 'A'. Based on the above phenomena, a circuit can identify the rotation direction, which is known as 'Kam-Phase Method'. The mechanism of the new direction recognition method is: When the encoder disk rotates , it continuously generatesthree kinds of state binary information sequentially. These three states are defined as state 1, state 2, state 3 . While rotatingclockwise, the state changes in the order of state 1, state 2, state 3, state 1......; While rotating counterclockwise, the statechanges in the sequence of state 1, state 3, state 2, state 1.......The new theory differentiate the digitized state changingsequence between the clockwise and counter clockwise to determine the rotation direction.This method is called as 'DigitalMethod'.The advantages of applying the digital method for the rotation direction determination in incremental photoelectricencoder are: the code channel structure is simpler and there is no accumulative errors and so on.