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  • Wow.  How did you get so skilled in graphics, Tyler?  Was it part of an engineering education?  I wonder if I could import parts from Tinkercad into Photoshop.  And what made that awesome animation?  Fusion360?  Nice work.

    Susanne Cardwell 8 hours ago

  • Thanks! The end-effector has a metal claw, servo, and sonar sensor. Joint friction adds a bit of load, too. It was a tiny drill bit -- must have been 1/16" -- just for a pilot hole.

    Tyler Lucas 2 days ago

  • Nice work Tyler.  It looks like you've got multiple oscilloscopes in the background. Nice setup.

     What gives your newly attached piece its weight other than the plastic?  And what size drill bit did you use to drill the holes to connect it to the arm?  

    Susanne Cardwell 2 days ago

  • Although the servos have proven to be sufficient to move the whole contraption with a moderate load, I have ended up adding something like a counterweight. The end-effector is kept level with respect to the ground regardless of arm angle via mechanical connections, but this connection only works below a certain angle. If the jib arm (2nd arm; I call it the boom) is lifted too high, the end-effector can 'flip' down, putting the whole thing in a bad state. This isn't an issue during operation, as the arm is meant to stay near the ground, but it sometimes did this when the Arduino was reset, as the driving pulse delays (usually incorrectly called PWM) are not controlled. To counter this I strung a bungee between the end-effector and a point above the boom, ensuring that it came taut when the boom was near the top of its range. I like the way it behaves and how simple it was to integrate it into the model. If I get the time, I may follow this approach to give the arm servos some extra lifting power. It'd kinda be like how a work lamp keeps its position using springs.

    An image render is below. The new pieces are in red. The bungee is a continuous loop like a belt, going between the circular shivs:

    image

     

    Printing preview:

    image

     

    Finished:

    image

     

    Video of build process and before and after comparison: https://goo.gl/cN1GtE

    image

    Tyler Lucas October 19, 2017 - 12:37am