From: W. Trevor King Date: Fri, 19 Nov 2010 13:33:06 +0000 (-0500) Subject: Add stepper backlash post. X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=8babe4b7dc5d3512ee6f1db9bcc48be02a14ff6a;p=blog.git Add stepper backlash post. --- diff --git a/posts/MultiMode/stepper/backlash.mdwn b/posts/MultiMode/stepper/backlash.mdwn new file mode 100644 index 0000000..69dbc77 --- /dev/null +++ b/posts/MultiMode/stepper/backlash.mdwn @@ -0,0 +1,37 @@ +There is a good deal of drive-train [backlash][] in the stepper +mechanism. + +Detection procedure +=================== + +1. Step towards surface until there is plenty of surface contact. +2. Step away until you leave the surface. +3. Repeat until you have too much data :p. + +[[!img step_backlash.png + alt="Data from 17 counterclockwise approach-retreat cycles" + title="Data from 17 counterclockwise approach-retreat cycles"]] + +Conclusions +=========== + +About 47 steps of backlash. Since we never touch the stepper while any +critcal surface interactions are going on, simply replace *step back 1 +step* with *step back 60 steps, then forward 59*. + +Supporting evidence +=================== + +Noise on reversal +----------------- + +When we reversing the stepper (by any means), the movement is “clearly +audible” for “a bit” and then becomes “almost silent”. + +To give a rough idea, I usually have keep my finger on the drive-shaft +to tell if the motor is moving in “almost silent” mode, but can hear +the motor from around 5 ft away in “clearly audible” mode. “A bit” is +about 0.5 s when controlling the motor using the manual Up/Down +switch. + +[backlash]: http://en.wikipedia.org/wiki/Backlash_%28engineering%29 diff --git a/posts/MultiMode/stepper/backlash/step_backlash.png b/posts/MultiMode/stepper/backlash/step_backlash.png new file mode 100644 index 0000000..28dd30f Binary files /dev/null and b/posts/MultiMode/stepper/backlash/step_backlash.png differ