The state machine's viability was first demonstrated using a text-only interface. This experiment was performed to integrate the visual system with the state machine. An appropriate DRFSM was generated by observing the part and generating the feature information. A mechanical part was put on a black velvet background on top of the coordinate measuring machine table to simplify the vision algorithms. The camera was placed on a stationary tripod at the base of the table so that the part was always in view.
Once the first level of the DRFSM was created, the experiment proceeded as follows: First, an image was captured from the camera. Next, the appropriate image processing takes place to find the position of the part, the number of features observed (and the recursive string), and the location of the probe. A program using this information produces a state signal that is appropriate for the scene. The signal is read by the state machine and the next state is produced and reported. Each closed feature is treated as a recursive problem, as the probe enters a closed region, a new level of the DRFSM is generated with a new transition vector. This new level then drives the inspection for the current closed region.
The specific dynamic recursive DEDS automaton generated for the test was a
state machine (shown in figure 4.)
Where the set of states
{Initial,EOF,Error,A,B,C,D}and the set of transitional events
{1,2,3,4,5,6,7,8,9,eof}. The state transitions were controlled by
the input signals supplied by intermediate vision programs. There are four stable states A,B,C, and D
that describe the state of the probe and part in the scene. The three other
states, Initial, Error, and EOF specify the actual state of the system in
special cases.
In one sequence, the probe was introduced into the scene and moved in a legal way (accepted by stable states in the machine) towards the part until contact was made. Next, the probe backed off and again approached until the probe and part overlapped. The automaton was forced into an error state by approaching from the other side of the part much too fast. The probe was not seen until it was too close to the object body. Because a transition from state A to C is invalid, an error state is reached. The part used was a simple one with only one hole, that is, it is represented by : C(C()).
In another sequence, the part was more complex. The representation was recovered to be the following string : C(C(),C(C()),C()). The probe was introduced into the scene and moved legally towards the part. Next, the probe backed off and again approached until the probe and the part overlapped. The automaton was forced into an error state by the sudden disappearance of the probe after it was very close to the part. Because a transition from state C to state A is invalid, an error state is reported. Each image was displayed on a terminal window as it was captured along with the corresponding state of the automaton. The same state representations are displayed for different layers in the DRFSM (i.e., for different features.)