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\title{23.  Assembly}
\subtitle{ Mechanics of Manipulation}
\author{Matt Mason}
\institution{Carnegie Mellon}
\email{matt.mason@cs.cmu.edu \\
http://www.cs.cmu.edu/\symbol{"7E}mason}
\slideCaption{Lecture 23. \hfill Mechanics of Manipulation }

\begin{document}

\maketitle

%=======================================================================
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% SLIDE 2
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\begin{slide}[R]{Lecture 23.  Assembly.}
\vspace{-0.5in}
\includegraphics[height=3.0in]{TOC23}
\end{slide}

%=======================================================================
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% SLIDE 3
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%

\begin{slide}[R]{Outline.}

\begin{itemize}
\item Role of assembly
\item Assembly sequence planning
\item Jamming and wedging
\item Compliance
\end{itemize}

\end{slide}

%=======================================================================
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% SLIDE 4
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\begin{slide}{Role of assembly in manufacturing}
\begin{minipage}[t]{.4\linewidth}
\begin{itemize}
\item Most assembly still manual?
\item Assembly automation has a big impact.
\item Example:  SONY Smart cell
\item High volume production uses more
specialized machinery.  
\item Low volume production is usually manual.
\end{itemize}
\end{minipage}
\hfill
\begin{minipage}[t]{.6\linewidth}
\begin{figure}[h!]
\begin{center}
\movie{1.0\linewidth}{.67\linewidth}%
{SmartAssy.mov}
\end{center}
\end{figure}
\end{minipage}
\end{slide}

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% SLIDE 5
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\begin{slide}[R]{Role of assembly, more generally}
\begin{trivlist}
\item
Assembly is an application of manipulation.  It is also a fundamental
manipulation technique.  

\item
Consider Smart cell again:
\begin{enumerate}
\item Part is oriented in APOS machine.  (By assembling it with pallet nests!)
\item Part is grasped by SCARA gripper.  (Another assembly.)
\item Part is placed in product.  (Assembly again.)
\item Part is released.  (\emph{Not} assembly!  Disassembly.)
\end{enumerate}

\item
Even placing an object on a table is an assembly.  If assembly is
defined to be bringing one shape into a desired configuration relative
to another shape, then it is obvious that assembly pervades
manipulation. 
\end{trivlist}
\end{slide}

%=======================================================================
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% SLIDE 6
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\begin{slide}{Issues in assembly}
\begin{itemize}
\item
\emph{Assembly sequence.}  What order to put things together?
\item
\emph{Local constraint analysis.}  What motions to join two objects?
\item
\emph{Path planning and grasp planning.}  Finding a free path.
\item
\emph{Gripper and fixture design.}   Being able to apply the desired
forces without interfering with the assembly. 
\item
\emph{Stable subassembly.}   Partial assemblies must be stable.
\item
\emph{Assemblability.}  Even if path exists, parts might be virtually
impossible to assemble, due to jamming. 
\item
\emph{Tolerances.}  All issues must also addres variations in shape.

\item
\emph{Design for assembly.}  Product design must be integrated with
automation design. 

\end{itemize}
\end{slide}


%=======================================================================
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% SLIDE 7
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\begin{slide}[R]{Assembly sequence}
\begin{minipage}[t]{.6\linewidth}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=1\linewidth]{assseq.eps}
\end{center}
\end{figure}
\end{minipage}
\hfill
\begin{minipage}[t]{.35\linewidth}
\begin{trivlist}
\item Assume \emph{two-handed} assembly.
\item Look at all possible partitions of the parts.
\item Result is an \emph{and/or} tree.
\item Every subtree with one and-arc per node is a possible assembly.
\end{trivlist}
\end{minipage}
\end{slide}

%=======================================================================
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% SLIDE 8
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%
\begin{slide}[R]{Local constraint analysis}
To decide if an assembly motion exists,
\begin{enumerate}
\item Reverse time, consider disassembly problem.
\item Look at contact constraints, identify all motion freedoms.
\item First order form closure often is sufficient.
\end{enumerate}
Remember the refrigerator problem?
\end{slide}

%=======================================================================
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% SLIDE 9
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%
\begin{slide}[R]{Jamming and wedging}
One of the earliest papers on the mechanics of manipulation was by
Simunovic, in 1974, studying assembly of peg in hole.  This was part
of a larger project studying manufacturing issues at the Draper Labs,
supervised by Nevins and Whitney. 
\begin{itemize}
\item Study of several assemblies showed that just a few operations
      dominate manufacturing.  Assembly, joining, etc. 
\item Also, just a few directions of motion dominate all assemblies.
      Mostly vertical. 
\item Simunovic defined jamming and wedging: 
\begin{itemize}
\item[] \emph{Jamming.} An assembly force in equilibrium with the
contact forces. 
\item[] \emph{Wedging.}  A configuration such that \emph{every}
possibly force is in equilibrium with the contact forces.  I.e. force
closure. 
\end{itemize}
\end{itemize}
\end{slide}

%=========
%
% Slide 10

\begin{slide}[R]{Jamming and wedging}

\begin{figure}[h!]
\begin{center}
\includegraphics[width = .5\linewidth]{jwpeg}
\end{center}
\end{figure}
\begin{trivlist}
\item Simunovic's analysis of wedging anticipated Nguyen's approach to
      planar force closure. 
\item Simunovic's analysis of jamming anticipated the moment labeling
      method.  Jamming may occur if the applied force makes positive
      moment at $P$. 
\end{trivlist}
\end{slide}

%==========
%
% Slide 11

\begin{slide}[R]{Analysis of wedging}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=\linewidth]{wpeg}
\end{center}
\end{figure}
\end{slide}

%==========
%
% Slide 12

\begin{slide}[R]{Analysis of jamming}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=1\linewidth]{jpeg}
\end{center}
\end{figure}
\end{slide}

%==========
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% Slide 13

\begin{slide}[R]{Compliance}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=.75\linewidth]{RCC}
\end{center}
\end{figure}
\begin{itemize}
\item Active force control is an option.
\item Remote Center Compliance is a passive mechanism.
\item Compliance Center:  behaves like decoupled translational and rotational springs.
\item Put compliance center at tip of peg or at lip of hole.
\end{itemize}
\end{slide}


%=======================================================================
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% SLIDE last
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\begin{slide}[R]{Next:  Newtonian dynamics.}
\vspace{-0.5in}
\includegraphics[height=3.0in]{TOC24}
\end{slide}
\end{document}



\end{document}