Incremental Encoder Convert to Degree

[feisaladam]

I have an application using an incremental encoder and then I convert it to degree (0-360) using calculation program. For a while, the calculation is correct, but after several movement from the machine, the degree calculation is not the same anymore. Have you all experience something like this before and how you resolve this

 

[parky]

You say an incremental encoder these are normally single phase so keep counting where absolute are actual position 2 phase, need more information how are you determining the fwd/rev, or is it circular motion, how are you reading the pulses high speed input, counter card or interrupts it will depend on what you are doing.

 

[feisaladam]

It's a circular motion and i just use an increment instruction to read the high speed pulses

 

[Steve Bailey]

I convert it to degree (0-360)

If your result is getting worse over time, perhaps you should be converting to a range of zero to 359 degrees.

 

[feisaladam]

Yes, it's getting worse overtime the machine cycle. I haven't thought that before, thanks I will try that

 

[drbitboy]

You say these are "high-speed pulses?"

Is it possible the pulses are coming in too fast for the PLC? The PLC is a discrete device, and there need to be at least two PLC scan cycles (one to see the "1" and one to see the "0", and preferably more, per rising edge of the encoder signal, to ensure the PLC detects every edge.

 

[feisaladam]

Yes I use high-speed pulses
Previously I use rising edge and falling edge pulses when I use 2000 pls/rev encoder, but the increment not very stable so I changed it to 10000 pls/rev and I change the method (from rising/falling edge increment) to the automatic increment from buffer address my module and apparently using this address is more suitable for highspeed application

 

[drbitboy]

Some PLCs have high-speed counters (HSC) available on certain inputs. An HSC counts pulses independently of, and is capable of handling a higher pulse frequency than, the scan cycle. In the scan cycle the code can use the HSC accumulator value, with some tap dancing at rollover (typically from +32767 to -32768 or +2147483647 to -2147483648, or the unsigned equivalents).

 

[feisaladam]

If your result is getting worse over time, perhaps you should be converting to a range of zero to 359 degrees.

Thank you for your advice, I try this method to calculation but the result is worse than before