Update 5/21/2013

Hello Internet!

It’s happened again… we have failed to keep posting updates in a timely manner. Many apologies. I’ll try to catch us up a bit:

On the control side, there was a huge amount of progress in April. The system is a huge challenge to control. Keep in mind that in the testing below, we are moving at roughly the maximum speed allowed by our electric lab pumps. When running off the real HPU, the leg can move about twice the speed.

On the mechanical front, final leg design and FEA is in progress. Many of the shortcomings of the prototype leg are being addressed, including:

The Protoleg has bushing alignment issues.  We got around this through a tedious and sketchy hand-reaming process on every joint axis on Protoleg.  The process accounted for a significant portion of the time necessary to assemble the leg.  In the revised leg design, the joint bushings will be mounted inside spherical bearings to soak up misalignment.  This will make for much more even wear of the bushings and hopefully a longer-lived robot.

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Also changing in the legs is the means of attachment to the piston.  On Protoleg,the piston attachment pin spans the entire width of the leg.  On the revised design, tabs have been added to allow for a much shorter pin.  Shorter pins means easier alignment during assembly and less pin flex during operation.

The revised leg design is also about 20% wider than Protoleg. This increases the strength of the leg significantly for the same amount of weight. The new leg design is undergoing FEA and detail design right now, but here are some preliminary renderings of the new yaw and thigh members.

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All of our electronics for the entire robot are also in fabrication right now. The designs on the Protoleg have performed admirably and the simple potting-and-hardwire system has proven very robust.

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We’re pushing forward on all fronts. It’s taken much more time than we anticipated to get all the designs finalized, but we are almost ready to begin construction in earnest. More detailed reviews of all designs will be posted as they are finalized, but hopefully this post provides a good overview of things we’ve been working on.

Thanks!

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5 thoughts on “Update 5/21/2013

  1. Richard says:

    I imagine sitting there watching the leg move, thinking, “What could go wrong?”

  2. W says:

    I know that you’ve calculated/measured out the no go zone around the robot leg but I can’t help but feel that it’s extremely small, especially if something were to break off and/or go flying…

  3. One idea for the potting: why not use a spare PCB as spacer for the pins? Just put it on top after you’ve filled in the potting compound.

  4. Derek says:

    @W – I can assure you that the red area is not the no-go zone but the ‘leg absolutely will go’ zone and in fact the leg comes significantly farther forward as it comes up from the floor. :)

  5. Dennis G Dahl says:

    Is the beam the leg fastened to checked to see if it is strong enough?
    If it is a support beam for the roof it would not be good if it lost integrity.

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