Firgelli L12 Linear Actuator documentation

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Firgelli L12 Linear Actuator documentation

Postby kirkpthompson » Sat Feb 19, 2011 8:53 pm

Hi All. I am looking for documentation for the L12 to start work on a LeJOS class for it and am not finding what I need. I have an email into Xander Soldaat (mightor@gmail) since he wrote a C library for it but I can't read RobotC. Does anyone have any URLs to wiring/interface/etc. docs? The Firgelli site has some specs for different models but couldn't find which model the NXT version implements.

Thnx.
-K
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Postby kirkpthompson » Tue Feb 22, 2011 1:46 pm

I am working on a class that supports the Firgelli L12 Linear Actuators for NXT. I will post it when I get things working.

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Re: Firgelli L12 Linear Actuator documentation

Postby kirkpthompson » Sun Mar 13, 2011 5:54 am

It's now in the snaphot: lejos.nxt.addon.LinearActuator.

-K
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Re: Firgelli L12 Linear Actuator documentation

Postby kirkpthompson » Sun Mar 20, 2011 9:29 am

Here is a little project I created that tests and demonstrates the LinearActuator and PIDController classes to keep an actuator-controlled lever mechanism level. A HiTechnic accelerometer is used as the tilt sensor.

http://www.youtube.com/watch?v=qGxGO5YicE4

-K
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Re: Firgelli L12 Linear Actuator documentation

Postby gloomyandy » Sun Mar 20, 2011 10:57 am

Hi Kirk,
Nice demo. Interesting how much slop the design has. Is that purely from the Lego parts or does the actuator have any slop as well?

Andy
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Re: Firgelli L12 Linear Actuator documentation

Postby kirkpthompson » Sun Mar 20, 2011 10:07 pm

Hi Andy. Interesting question so I took some measurements.

Actuator play/lash=~.63 mm (used a dial caliper)
Tan, "Non-friction" pegs and cross axles used for all fulcrums and connect points in the lever mechanism.

As oriented in the video (straight up, level), Measurements at end of levers to a common baseline (unit in vise on my desk. Desk surface=baseline):

With actuator in the drive train:
bottom lever vertical movement at the end =7.5 mm, top lever=250 mm, lever1:lever2 ratio=33.3333

With actuator replaced with a beam the drive train:
bottom lever vertical movement at the end =4.0 mm, top lever=130 mm, lever1:lever2 ratio=32.5 (should be the same as other but close enough given measuring tolerance)

Difference between the two: 52%. So, it appears just that small amount of play in the actuator contributes to 52% of the total play of the lever mechanism. Well, probably not that much because even friction pegs (used in the beam that replaced the actuator for second set of measurements) have some play. Overall, the compound lever mechanism greatly amplifies motion and slop/play/lash (and force needed to move it I assume).

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