A voice-controlled mechanical arm for immobilized patients

This work describes a system developed on a PDP 11/45 computer which recognizes spoken commands and controls a Scheinmann MIT mechanical arm to serve the needs of an immobilized patient. The speech recognition is discrete word with template matching, using as features zero crossing rate, average absolute magnitude, and frequency and normalized error as derived from the two pole linear predictive analysis. Commands are made up of words from a 16-word vocabulary obeying a specified, syntax. Upon recognition of a command the arm performs the corresponding pre-programmed task. A recognition time of two seconds is attained (including the one second sampling interval), plus an additional one second to verify the word. With the command syntax a recognition rate of 88% is attained, as compared with only 56% when each word is matched against every word in the vocabulary.