Takao Ohuchi

Transfer movement control of mobile robot using two circular arcs

This report describes a method of controlling a robot vehicle to move smoothly on a visually natural path. In this method, discrete points which the robot passes, and directions toward which it moves, are provided on an arbitrary coordinate system given in a movement environment. The continuous curve required for the robot vehicle to move is represented by a total curvature function obtained by accumulating curvatures of curves. Using the function, an algorithm is obtained for generating the robot moving path from interpolation of two circular arcs containing both the lengths and curvatures of the two circular arcs. The position at which the robot is passing and the direction toward which it is moving are measured based on the principle of the triangle survey for three reference patterns set in the movement environment. This is possible by measuring the directions from the current position to the patterns with an ITV camera. This method produces a directional error caused by the roughness of the step angle (0.9) of the stepping motor driving the ITV camera. This paper proposes a method of compensating the directional error by taking into account the number of pixels in pictures taken per step. This system has the averaged position measurement error of 0.8 percent against the coordinate system including the reference patterns. From the result, it is proved that a comparatively simple method enables the moving path of a robot to be controlled accurately.

Recognition of three- vowel sequences on the basis of perceptual phoneme boundary lines defined by a flexible model

The authors are attempting to clarify the emphasizing mechanism of phoneme perception in co-articulation. Psychoacoustic experiments were made on the symmetrical and asymmetrical three-vowel sequences, and the effect of the preceding or succeeding vowels on the central vowel is examined. Based on the examined effect, a model is proposed wherein the perceptual phoneme boundary lines of the central vowel are set, considering the three-vowel sequence as a unit. Using this model, the perceptual phoneme boundary line of the central vowel of the three-vowel sequence can be defined by adjusting the 50 percent phoneme boundary line in the perceptual phoneme distribution of the steady vowel on F1-F2 logarithmic plane, according to the positions of the formant frequencies of the preceding and succeeding vowels. A model is presented here which defines the phoneme boundary lines of the central vowel in the three-vowel sequence with co-articulation, by adjusting the 50 percent perceptual phoneme boundary lines of the steady vowel. It is then applied to the real spoken vowels, and its effectiveness is evaluated. Then an automatic recognition system for the three-vowel sequence is proposed, which is based on the trajectory of the three-vowel formant frequency and the perceptual phoneme boundary lines set by the flexible model. A recognition experiment is conducted for the three-vowel sequences using the system, and the usefulness of the system is demonstrated.

Auditory compensation effects in symmetrical three-vowel sequences and a model of perceptual phoneme boundary

To recognize the continuous speech by phonemes, the coarticulation must be analyzed. This paper presents a result of psy-choacoustic experiment for symmetrical three-vowel sequences, which are generated by the terminal-analog-type speech synthesizer, indicating the auditory compensation effects in coarticulation on the phoneme perception. Using each of five Japanese vowels as a reference vowel V0, the symmetrical three-vowel sequences, /V0-VV0/ are formed. The distribution of the perceptual phoneme for the middle vowel is examined first. By comparing the results with the perceptual phoneme distribution for five stationary vowels, the shift of the perceptual phoneme distribution due to the auditory compensation effect is investigated. A model is proposed for the boundary shift in the perceptual phoneme distribution. In the model, the 50-percent phoneme boundary of the perceptual phoneme distribution for five stationary vowels is approximated by straight lines on the F1 - F2 logarithmic plane. The straight lines are contracted in the direction of (F1, F2) point of the reference vowel along the F1 and F2 axis. The proposed model is applied to the perceptual phoneme distributions of the middle vowels in the symmetrical three-vowel sequences, and its usefulness is demonstrated.