Kazufumi Nishikawa

Development of a new anthropomorphic flutist robot WF-4

Since 1990, we have been developing anthropomorphic flutist robots, which are mechanically similar to human organs needed for playing the flute. The goal of this research is to clarify the flute playing mechanism from an engineering point of view and to enable the communication with humans at emotional level. The control of the air beam parameters for obtaining a good sound is very important. Such parameters are related mainly to the lips shape and its relative position respect to the flute embouchure hole. Then, the newest version of the anthropomorphic flutist robot WF-4 has been implemented by improving the design of each part of the robot (lips, lungs, neck, etc.). This new version has succeeded in the improvement of the flute sound quality and the sound conversion efficiency. We describe the mechanical features of the WF-4 and the experiments done for evaluating its musical performance.

Development of a New Human-like Talking Robot for Human Vocal Mimicry

This paper describes development of a new human-like talking robot WT-4 (Waseda Talker No. 4). WT-4 was developed to overcome the problems related to the lack of variation in the formant frequency of the sounds generated by the previous talking robot WT-3. These problems arose particularly on the first formant (F1) where frequencies of less than 500 [Hz] could not be reached. And the differences among WT-3’s vowels were not clear; which may have been caused by the sound source of the vocal cords and the lips. Therefore, the connection between the vocal cords and the vocal tract was improved, as well as the lips mechanism. As the result of these improvements, WT-4’s sounds were quite similar to a human’s, and WT-4 was able to reproduce suitable sounds using auditory feedback.

Mimicry of human speech sounds using an anthropomorphic talking robot by auditory feedback

This paper describes an autonomous control method of an anthropomorphic talking robot WT-4 (Waseda Talker No.4) to mimic continuous human speech sounds by auditory feedback. WT-4 consisted of 1-DOF lungs, 4-DOF vocal cords and articulators (the 7-DOF tongue, 5-DOF lips, 1-DOF teeth, nasal cavity and 1-DOF soft palate), and could reproduce human-like articulatory motion; the total DOF was 19. In this method, the trajectory of each robot parameter was controlled so that the acoustic parameters (pitch, sound power, formant frequencies that are resonant frequencies of the vocal tract and have the peak of the output spectrum, and the timing of the switch between voiced and voiceless sounds) generated from the robot were close to those of human speech sounds. The trajectory of each robot parameter was optimized by inputting the acoustic parameters. This method would help to clarify the human speech mechanism and to create a new speech production system.

Speech planning of an anthropomorphic talking robot for consonant sounds production

This paper describes the speech planning of the anthropomorphic talking robot WT-1R (Waseda Talker-No.1 Refined) for the production of consonant sounds. WT-1R has articulators (the tongue, lips, teeth, nasal cavity and soft palate) and vocal organs (the lungs and vocal cords), and can reproduce human vocal movement. Its total DOF (degrees of freedom) is 15. The vocal movement of WT-1R for vowels is steady. We produced Japanese vowels (/a/, /i/, /u/, /e/, /o/) using the first robot WT-1 in 2000. However, the vocal movement for consonant sounds is transient. We must control the 15-DOF talking robot coordinately in the space and time to reproduce the complicated phenomena of the consonant sounds. Therefore, because the Japanese voice generally consists of two phonemes of the first consonant sound and the last vowel, we proposed the speech planning of WT-1R by considering the phenomenon of the voice as three parts (steady consonant sound, transient consonant sound and vowel). WT-1R could produce Japanese vowels (/a/, /i/, /u/, /e/, /o/) and some consonant sounds (/s/, /h/, /m/, /p/ and /waseda/).

Development of a human-like sensory feedback mechanism for an anthropomorphic talking robot

We developed a sensor feedback mechanism for an anthropomorphic talking robot WT-5 (Waseda Talker No. 5). In human speech, sensory feedback is more important when we producing obstacle consonant sounds, such as /t/ and /d/, compared to the auditory feedback mechanism. We reproduce this mechanism by placing tactile sensors and a pressure sensor on the palate of a talking robot and reducing the error between the pressure of the human voice and the robot consonant production. In addition, we developed more efficient optimization methods than those of WT-4, using speech recognition and the pre-optimized memory of vowels. Using these mechanisms, we realized continuous mimic speaking that includes consonant sounds

Development of a new human-like talking robot having advanced vocal tract mechanisms

This paper describes the development of a new talking robot WT-2 that improved on WT-1R and has advanced vocal tract mechanisms for the reproduction of human vocal movement. WT-2 consists lungs, vocal cords, a vocal cavity and nasal cavity; the total DOF is 15. The length of the vocal tract is about 175 mm and is almost the same as that of an adult male. Compared to WT-1 or WT-1R developed previously, WT-2 could utter Japanese vowels more clearly, and produce stops, fricatives and nasal sounds by a new flexible tongue mechanism as well as decrease sound leaks from the tongue except those from the lips or nostrils.

Speech production of an advanced talking robot based on human acoustic theory

This paper describes the mechanisms and the speech production of a new advanced talking robot WT-3 (Waseda Talker-No.3) that improves on WT-2 (Waseda Talker-No.2) and is based on human acoustic theory for the reproduction of human speech. WT-3 consists of 1-DOF lungs and 3-DOF vocal cords and articulators (the 7-DOF tongue, 5-DOF lips, 1-DOF teeth, nasal cavity and 1-DOF soft palate), and can reproduce human-like articulatory motion; the total DOF is 18. The oral cavity is designed based on the MRI images of the human sagittal plane, although the cross section of the vocal tract is rectangular in shape except for the mouth. The width of the vocal tract is 30 [mm]. The average length of the vocal tract is approximately 175 [mm] and the same as that of a humans. Compared to the previous robots, WT-3 can produce vowels more clearly, and produce stops, fricatives and nasal sounds with the new flexible mechanisms that function as the human vocal tract area and the other mechanisms. WT-3 can mechanically reproduce human speech.

Mechanical design of a talking robot for natural vowels and consonant sounds

Vocal movement is not only a movement of the vocal organs, it is also a movement that produces acoustic signals received by hearing as linguistic information through hydroacoustic phenomena along with the formation of the vocal way. The purpose of this research is to study the human vocal mechanism from the engineering point of view by simulating the vocal movement with a robot, and to create the dynamic model. The authors developed an anthropomorphic talking robot WT-1 (Waseda Talker-No.1) in 1999. It simulates human vocal movement, and has articulators (a 6-DOF tongue, 4-DOF lips, 1-DOF teeth, a nasal cavity and 1-DOF soft palate) and vocal organs (1-DOF lungs and 1-DOF vocal cords); the total DOF of the robot is 14. We experimented with it on Japanese vowels. However, the voice produced was not natural. In this paper we describe an improvement of the mechanisms for the realization of natural vowels and consonant sounds.

Development of a new vocal cords based on human biological structures for talking robot

We developed a new talking robot, WT-5 (Waseda Talker No. 5), having novel vocal cords, based on human biological structures. The vocal cords were made from the thermoplastic rubber “Septon”, available from Kuraray Co. Ltd. Septon has a similar elasticity to human tissue. The vocal cord model to have a structure similar to the biological structure of the human vocal cords was made. The vocal cords were vibrated like those of a human. This made clean the robots vowels. With these new mechanisms, the robot could reproduce the human speech in a more biological view and could produce voices nearer to those of a human.

Mechanical vocal cord model mimicking human biological structure

We present a mechanical vocal cord model aiming for a talking robot, WT‐5 (Waseda Talker No. 5). Unlike a musical reed which has been used in conventional mechanical speech synthesizer, the vocal cord model is formed to mimic the human’s vocal cord in the shape and the biological structure. It is made of a thermoplastic rubber, Septonh (Kuraray Co. Ltd.) of which the elasticity like a human’s, and has 3‐DOF mechanisms which is similar to the human structure. 1‐DOF link mechanism could change the pitch by stretching the length of the vocal cords. The 2‐DOF arm mechanism is used to mimic the abduction and adduction of a human arytenoid cartilage. The vocal cord model was excited by air flow exhausted from a mechanical lung model. The vibration pattern was observed by a high‐speed camera, and the glottal volume velocity and the sound pressure were recorded by a mask‐type wire screen pneumotachograph and a microphone. It was shown that the lower and upper edges of the vocal cords could vibrate in a different ...