Method for pattern recognition
First Claim
1. A method for recognizing at least one defined pattern modeled by hidden Markov models in a time-variant measurement signal on which at least one disturbing signal is superposed, comprising the steps of:
- a) supplementing each of the hidden Markov models at its beginning and at its end by respectively one single identical state that serves to represent the disturbing signal and has at least the following characteristics;
in order to achieve independence of temporal position of defined pattern, said single identical state is free of transition probabilities,in order to achieve independence of disturbing signals in temporal environment of the defined pattern, said single identical state is free of emission probabilities,b) seeking and recognizing the defined pattern with a predetermined comparison method using expanded hidden Markov models in a time-variant measurement signal.
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Abstract
A special method recognizes patterns in measurement signals. Speech signals or signals emitted by character recognition apparatuses are thereby meant. For the execution of the invention, the hidden Markov models with which the patterns to be recognized are modeled are expanded by a special state that comprises no emission probability and transition probability. In this way, the temporal position of the sought pattern becomes completely irrelevant for its probability of production. Furthermore, the method offers the advantage that new and unexpected disturbances can also be absorbed without the model'"'"'s having to be trained on them. In contrast to standard methods, no training on background models need be carried out. However, this means a higher expense during the recognition of the patterns, since the individual paths of the Viterbi algorithm have to be normed to the current accumulated probabilities in the path with respect to their probabilities, in order to be able to compare them. The inventive method offers the advantage that only the time segment of the measurement signal also containing the pattern has to be analyzed. An increased probability of a hit is thereby reconciled with a lower computing expense.
6 Citations
10 Claims
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1. A method for recognizing at least one defined pattern modeled by hidden Markov models in a time-variant measurement signal on which at least one disturbing signal is superposed, comprising the steps of:
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a) supplementing each of the hidden Markov models at its beginning and at its end by respectively one single identical state that serves to represent the disturbing signal and has at least the following characteristics; in order to achieve independence of temporal position of defined pattern, said single identical state is free of transition probabilities, in order to achieve independence of disturbing signals in temporal environment of the defined pattern, said single identical state is free of emission probabilities, b) seeking and recognizing the defined pattern with a predetermined comparison method using expanded hidden Markov models in a time-variant measurement signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification