
Why Assemble a Model Aircraft Engine?
The real test of our RISC
approach is whether it can handle the full assembly of a mechanical
device. We have chosen first to assemble a mid-sized model-aircraft
engine. We chose it because (i) it is a good size for RobotWorld's
workspace, (ii) it has modest complexity, with about two dozen parts
(iii) in spite of this, it has some very challenging subproblems. The
cylinder/piston fit is essentially zero tolerance. These engines have
no piston rings, so they rely on the tightness of this fit for their
compression. Pistons and cylinders are finished to an extremely smooth
finish by honing, and then hand matched to get suitable fit. There are
non-vertical insertion steps, near but not perfectly cylindrical
parts, and non-rigid subassemblies.
Our goal is to make the assembly program parametric so that it can
assemble several other sizes of engine that have roughly the same
makeup. We will structure the program into subroutines that can be
re-used for other assemblies. We have already acquired a number of
these from previous assembly demos. We are seeking other good test
problems, and we hope to attempt several other realistic assemblies in
the future. It should be easier to do this as our assembly routine
library grows. We expect to run into unforseen problems, and these
should lead us to expand our vocabulary of simple sensors and
actuators.
Eric Paulos /
paulos@robotics.eecs.berkeley.edu /
15 June 1994