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State Space Modeling

We do a coarse quantization of the visual manipulation actions which allows modeling both continuous and discrete aspects of the manipulation dynamics. State transitions within the manipulation domain are asserted according to probabilistic models that determine at different instances of time whether the visual scene under inspection has changed its state within the discrete event dynamic system state space. Mapping the desired visual states to a DEDS skeleton is a straight forward procedure. We attach a DEDS automaton state to each meaningful visual state within a manipulation action. The quantization threshold depends on the application requirement. In other words, the state space can be expanded or contracted depending on the level of accuracy required in reporting and observing. A surgical operation step, performed by a robotic end effector, will obviously require an observer that reports (and possibly control the effector within a closed-loop visual system) with extreme precision. The observer for a robotic manipulator whose task is to pile up heaps of waste would, most likely, report in a crude fashion, thus needing a small number of states. The quantization threshold depends heavily on the nature of the task and the application requirements. The DEDS formulation is flexible, in the sense that it allows different precisions and/or state space models depending on the requirements.

The task of building DEDS automaton skeletons for observer agents can be performed either manually or automatically. In the manual formation case, the designer would have to draw the automaton model that best suits the task(s) under observation and depending on the application requirements and implement the code for the state machine. Automatic construction of the state machine could be done by having a learning stage [17,18] in which a mapping module would form the automaton. This is performed before the actual observation process is invoked. The idea is to supply the module with sets of possible sequences in the form of strings of a certain language that the DEDS automaton should minimally accept. The language could be either supplied by an operator, in which case, the resulting automaton performance depends on the relative skill of the operator, or through showing the module a sequence of visual actions and labeling those actions appropriately. The language strings should also be accompanied by a set of transitional conditions as event descriptions. The module would then produce the minimal DEDS automaton, complete with event and state descriptions that accepts the language.

We next discuss building the manipulation model for some simple tasks, then we proceed to develop the observer for these tasks. Formulating the models for the state transitions, the inter-state continuous dynamics and recovering uncertainty will be left for sections 4 and 5 which deal with the different uncertainty levels and event identification mechanisms.

Next: Building the Model Up: State Modeling and Previous: State Modeling and
Tue Nov 22 21:30:54 MST 1994