21 February 2016

2.77 PUPS #3: Machine Design Specification

PUPS #3: Machine Design Specification

 Error Apportionment for Strategy 1: Robot Motion is X-Axis.
This seems like a useful tool to think about how errors accumulate, but the choice of values seems really arbitrary. Here, the structure of the aircraft (which we can't change or control) dominates the error, with the robot moving past the most compliant point between each tack fastener

Error Apportionment for Strategy 2: Stationary Robot with built-in X-axis
In this case, the bearings and general alignment and initial clamping would dominate the error, the robot would be placed and clamped near the tack fastener by the larger "momma" robot for maximum stiffness, and the structure of all 3 axes would all be controllable.


  1. I like the project idea - really different and useful application.

    Somehow exploiting gravity to help the robot stick to the rail is a clever strategy. Did you design your planar constraint model with this in mind? In any case, having a passive or pseudo-passive method of anchoring the robot is probably better than relying on an active clamp, if you can get something reliable and robust.

    Could you possibly design in some compliance so that the screw can be somewhat off from the hole? Since screws have some taper, you might be able to get away with being off center (within reason). Just a thought.


  2. There are some noticeable gaps in the bolt pattern looking at some of your Photos,
    how can the robot account for this? Another FR?
    I think you can fill table in a bit more, but given time constraints I totally get it. One
    FR that I think would be useful to note is speed. How fast should it scale. Vague
    numbers are fine, but I think that also might prove to be a serious design constraint.
    However, I can also see it not being critical enough and have other things prioritized
    first, but its worth thinking about nonetheless.
    For mechanical stiffness you can think about the stiffness and requirements of your
    constraint mechanism right? How stiff should that be, and how stiff should the
    alignment between both sides be? What z-axis [normal to the fuselage panel]
    tolerances are affordable and what stiffness is needed in that direction?
    I’m really looking forward to seeing how this develops as it looks like it is gonna be
    super cool. I really like the whole concept and the way of leveraging the physical
    structure you need to scale. Grasping the bolt heads is a cool idea. I wonder though
    how irregularity in the aligned shape of the bolt head will affect it. i.e. they are a
    hexagonal and so you might get flat, angled or a corner when the gripper wheels roll
    over it… I think the way you described it when we talked, with serious elastic
    averaging going on, it should work though. Great that you have the PUP 2 as a basic
    prototype already!

    -Zack Bright