https://forge.codesys.com/forge/talk/Engineering/thread/236dbc5c6c/2020-02-27T13:48:11.705000ZRecent posts to unexpected drive position (fActPosition) after SMC3_ReinitDrive2020-02-27T13:48:11.705000Z2020-02-27T13:48:11.705000Zalejhohttps://forge.codesys.com/u/alejho/https://forge.codesys.com57a640d0ce276376bd4848dfe028a47cb9301a3f

<div class="markdown_content"><p>We found something that I hope will be useful for someone else.</p> <p>The "wrong" <strong>fActPosition isn't calculated according to the encoder master's position, but it always has a variation of 216°</strong>.</p> <p>This value is not causal, but it's due to the fact that <strong>the increments per output turn of the axis (in our application 65536*10 is equal to 360°) is NOT a power of two</strong>.</p> <p><strong>For our application 216°=393216 increments that is exactly the number of increments "missing" from 655360 to reach the first power of two (2^20)</strong>.<br/> (It isn't easy to imagine...but try to draw a trivial example for a 4bit encoder where you get 360° every 3 increments and it will be clear)</p> <p>This is not a problem when the machine is running (it just count the increments managing the overflow I suppose)...but <strong>when you reinit the drive after a drive encoder's overflow (32bit) you get an error in fActPosition of 216° equal to 393216 increments (216°)</strong> </p> <p><strong>Now the question is...what's the best pratice to manage this problem?</strong></p> <p>I was thinking about counting the number of overflow and triggering an MC_Home after a reinit (to set fActPosition := fActPosition * 216 * numberOfOverflows)</p></div>

2020-02-27T13:48:11.649000Z2020-02-27T13:48:11.649000Zalejhohttps://forge.codesys.com/u/alejho/https://forge.codesys.comfb1e63b0a279daca6b1a5fb7ec47d687519f1db1

<div class="markdown_content"><p>I have a slave drive attached to a master with <strong>MC_Phasing</strong>.<br/> When I call <strong>SMC3_ReinitDrive</strong> is <strong>fActPosition is set to the variation of the Master position while the drive is re-initializing</strong>.</p> <p>This is quite strange because it happens also if the drive's position coming from the fieldbus is constant (the axis is not moving).<br/> I expect fActPosition not changing before and after SMC3_ReinitDrive...since the axis is not moving!</p> <p>In attachment a picture of a trace what is happening...<br/> <strong>Does anyone know what can cause such a strange behaviour?</strong></p> <p>Thank you for any kind of help!</p> <p><img alt="IMG: codesys_forum.png" rel="nofollow" src="https://forum.codesys.com//download/file.php?id=5163"/></p></div>