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Kinematics

A project log for Cable Robot

Using low cost parts to construct a cable robot with incredible capabilities.

TomTom 07/18/2019 at 02:222 Comments

One of the key components of the cable robot is understanding the forward and inverse kinematics. Lucky for us there a great resource out there that already exists. For this robot I used emc2 which I use to control my CNC Mill and CNC router.  That can be found at the following location -> EMC2 (now linuxcnc). Typically that software is used to control mills and lathes that are orthogonal in nature, XYZ style setups. However if you dig into it you find out that it supports different kinematics such as a cable robot. The real beauty resides in this file called tripodkins.c. If you want to make your head hurt a little you can try to derive it out, kind of fun.

Discussions

Tom wrote 08/05/2019 at 03:26 point

 I remember that when I drive the robot all the way to the top that it will start going down even if I continue to press the up arrow. Basically it does not know that it cannot work above the plane so it tries to do it, and it actually continues to work. I think what you mention here solves that.

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Daren Schwenke wrote 07/19/2019 at 04:57 point

tripodkins.c assumes you are above z=0, aka linear accutators.  Starting out below z=0, aka cables, can be problematic.  I took the easy way out and just hard coded a version of tripodkins to always be inverted.  https://github.com/machinekit/machinekit/blob/master/src/emc/kinematics/itripodkins.c

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