On Wed, 22 Mar 2017, Sebastian Kuzminsky wrote:

> Date: Wed, 22 Mar 2017 13:03:06 -0600
> From: Sebastian Kuzminsky <s...@highlab.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <emc-users@lists.sourceforge.net>
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] Different acceleration profiles - something that
>     would remove the discontinuity in the first derivative of the acceleration
>      ?
> 
> On 03/22/2017 12:50 PM, Nicklas Karlsson wrote:
>>> Hello,
>>>
>>> I want to ask if anybody has worked on different acceleration profiles
>>> for linuxcnc ? I am looking for something that would remove the
>>> discontinuity in the first derivative of the acceleration ?
>>>
>>> BR
>>> Max.
>>
>> I guess to start with the DC motor model for example here 
>> https://www.electrical4u.com/torque-equation-of-dc-motor/ would be a good 
>> idea. Driving this with a limited voltage and current would probably be a 
>> good model for the limitations.
>
> I think Max is asking about changes to the LinuxCNC trajectory planner
> that implement variable (non-constant) acceleration, aka "limited jerk".
>
> Currently when you start from a stand-still, command a move, and come to
> rest at the end of the move, LinuxCNC implements a trapezoidal velocity
> profile.  This starts with a constant-acceleration phase until it
> reaches the maximum speed for the move, then enters a constant-velocity,
> zero-acceleration "cruise phase", and finishes with a
> constant-deceleration phase back to zero velocity.  Each phase
> transition has an instant of infinite jerk, when acceleration goes from
> one constant value to another in a single motion cycle.
>
> I think Yishin Li (https://github.com/yishinli) has done some work in
> the area of jerk-limited trajectory planning, but AFAIK it has not shown
> up as a pull request to our repo yet.
>
>
> -- 
> Sebastian Kuzminsky

I think micges (Michael Geszkiewicz) also had an at least partially working
Limited jerk profile TP, not sure if this was pre-CAB or not.

>
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Peter Wallace
Mesa Electronics

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