Dynomotion

Group: DynoMotion Message: 10366 From: Dan Date: 10/22/2014
Subject: 3rd Order Coordinated Motion
Tom,
A while back you said that g-code is run as a 2nd order move (no jerk) and rapids are a 3rd order. Can you tell me why g-code is not run as a 3rd order move?
 
I ask because the hard acceleration of not having the jerk in the calculation is forcing me to turn my acceleration way down to keep the movement smooth. Even a small amount off jerk would greatly improve the performance of my machine.
 
-Dan
Group: DynoMotion Message: 10368 From: Tom Kerekes Date: 10/22/2014
Subject: Re: 3rd Order Coordinated Motion
Hi Dan,

Sorry we haven't yet figured out how to trajectory plan 3rd order motion through complex paths while obeying all Jerk, Acceleration, Velocity, and position constraints of all the axes.  It is a very complex problem.

You should be aware that you can set different accelerations for 2nd order motion and 3rd order motion (rapids).

There is an option to apply some low pass filtering to the motion trajectory.  This can reduce Jerk spikes significantly at the expense of slight trajectory errors.  See the section on Low Pass Filter (KLP) here:

http://www.dynomotion.com/Help/KMotionCNC/TrajectoryPlanner.htm

HTH
Regards
TK


From: "'Dan' engnerdan@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Wednesday, October 22, 2014 3:24 PM
Subject: [DynoMotion] 3rd Order Coordinated Motion

 
Tom,
A while back you said that g-code is run as a 2nd order move (no jerk) and rapids are a 3rd order. Can you tell me why g-code is not run as a 3rd order move?
 
I ask because the hard acceleration of not having the jerk in the calculation is forcing me to turn my acceleration way down to keep the movement smooth. Even a small amount off jerk would greatly improve the performance of my machine.
 
-Dan