How to deal with the zero-crossing problem of absolute encoder

How to deal with the zero-crossing problem of absolute encoder? The zero-crossing problem of absolute encoders has always been a difficult problem in the industrial control industry. In order to avoid the zero point, many manufacturers have thought of many ways. It is more common to determine the running direction of the machine, first rotate the encoder shaft to a place far away from the zero point, and then install the encoder on the machine. The output of the encoder is only a pulse, and this position is actually determined according to requirements. In this way, a position sensor can be installed to make the moving part reach a certain position, and the controller can set this position to be the zero position, and the subsequent positions can be controlled.

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In many cases, this operation is not easy. Since the machine has been installed on the machine when it leaves the factory, the installer may have to climb or drill holes to ensure that the installation is good and does not affect other parts of the machine. In short, this is a very painful thing, which increases the complexity of the operation. When debugging the absolute encoder, we sorted out the zero-crossing data and found out some specific data rules. Adopt absolute value encoder, the data range is 0~16383. By collecting zero-crossing data when the machine is running, some messy data is obtained.

The red part is the zero-crossing data. It can be seen that the zero-crossing data is disordered, but when the data is not zero-crossing, the difference is basically stable. According to this characteristic, when programming, two adjacent data are usually used to judge the difference. If the difference is small (for example, less than 20), take the average of the two numbers as the result. If the difference is large, discard these two numbers and move on to the next set of data.

Through such processing, useful data is reserved for zero-crossing data, and obviously wrong data is lost, so as to avoid judging the wrong position at the zero-crossing stage, thereby making it possible to use the zero-crossing phase of the encoder. Servo motor encoder zero adjustment is a bit cumbersome. If you need to find the zero point and align the magnetic pole, it is best to let the motor manufacturer or professional do it.