The autosampler has been written about in the xtuml.org Model Snippet of the Day. Here is a new (as in today) version of the autosampler built by a small team of engineers in a training class lab exercise. This model works and has excellent state behavior.
Tangible class behavior has been modeled in probe and spinner which behave as slave classes to the batch. probe samples batch, and spinner spins batch. The probe checks safety of the spinner and will not lower unless the spinner is ready. Likewise, the spinner checks safety of the probe and will not spin unless the probe is up.
The more abstract batch class models the higher level system behavior of sampling a collection of vials full or gas or liquid. At start, the batch is raising for safety the probe. 
Upon probe_done it is selecting sample. If more samples remain, it is spinning into position, lowering probe and then sampling (waiting for the sample interval to expire). Upon sample_complete, the batch is raising probe and then selecting sample again. When all samples are finished, it is spinning home and ready again.