View source for RepRec orienter

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'''It provides the 3 rotative DOFs.''' <br>
The "orienter" (also called "wrist") is the part in the motion stage / kinematic chain <br>
that is tasked with imparting the orientation (3 rotative degrees of freedom) <br>
on everything further downstream the kinematic chain. <nr>
 
'''Downstream the kinematic chain:'''
* [[RepRec poser to tool interface]] (the orientier is the downstream patt of the poser thus poser)
* [[RepRec tool to poser interface]]
* [[RepRec end-effector]]</small> 
* end-effector to picked part interface
'''Upstream the kinematic chain:'''
* [[RepRec positioner]]
* The motion system of the [[RepRec cawler]] <small>(possibly indirected to a dedicated [[RepRec unit carrier unit]])</small>

It is desirable to have the orienter/wrist <br>
being agnostic to the choice of the [[RepRec positioner]]

== Crossing rotation axes ==

If the three rotation axes are not crossing through a single common point then the delineation to the [[RepRec positioner]] <br>
is not as good and the [[RepRec positioner]] needs to compensate for motions caused by the rotations with some math. <br>
The centers of the pick-n-placed of different sizes will be off even if there is a common rotation center any way <br>
so it's nit that severe for the pick-n-place application case. <br>

== Motion threading as especially hard problem for the section through the orienter/wrist ==

Since one likely wants at least one actuated DOF <br>
for the [[RepRec end-effector]] there is a need for <br>
– '''[[RepRec through joint motion threading]] <br>
– (= rotative [[RepRec action transmission]])''' <br>
which makes the already hard problem even harder.

Motors on the end-effectors are a non option for [[RepRec]] systems.
* macroscale: bad motor mass, nanoscale: crippling motor volume 
* macroscale: messy cable wiring; nanoscale: bending nanowires changes electrical properties & one gets ballistic electron transport & chemical is physical just like mechanical is

== Inspiring sources ==

⭐ Goniometer stages but stacked. <br>
<small>(Side-note: These are positioning stages not measurement devices despite the name.)</small> <br>
These seem especially suitable as <br>
– they provide very high stiffness and <br>
– they allow for high angles with accordingly adapted designs (unlike e.g. very stiff Steward platforms) <br>
– slightly easier mechanics in gearing (unlike the conical gear differential wrist below) <br>

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⭐ 90° differential gearbox inspired robot wrist like in this robot: <br>
CC-BY-3.0 paper: https://iopscience.iop.org/article/10.1088/1757-899X/294/1/012079/pdf <br>

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⭐ Fanuc robot wrist: <br>
2021-04-19 –– 0.5mm pencil lead insertion M-1iA/0.5A (6 axes) <br>
https://www.youtube.com/watch?v=QjVjQOvG33E <br>
Due to the [[RepRec no small parts design restriction]] the design would likely need to be modified quite a bit … <br>
Basically [[RepRec axle onion]] where at every turn the outermost tubular axle ends in driving all of the downstream kinematics. <br>

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The last points to a class of [[RepRec nested axles]] based [[RepRec orienter]]s

== Related ==

* [[RepRec nested axles]]
* [[RepRec inspiration sources]]
* '''Up: [[RepRec system topology]]'''
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{{Category:RepRec}}
<small>Page started (off wiki): 2018-10-28 Thursday.</small> <br>