A review of the text-to-speech synthesizer for human robot interaction for patients with Alzheimer's disease

ABSTRACT With the rapid growth of eldering process worldwide, the number of people with mild cognitive impairment (MCI) has also been largely increased. To ease the problem that not all the patients get diagnosed and treated properly in time, intelligent robot that additionally equipped with cognitive rehabilitation functions are widely researched and gradually applied to either clinics or families. Speech interaction acts as an indispensable part in human robot interaction (HRI) process, speech quality used during which directly affects the HRI efficiency and users' experience. Studies indicate that high-fidelity speeches that can be clearly and naturally expressed are more likely to be received and understood by MCI patients. Also, using voices that are either familiar or appeared to patients, along with positive expression, largely improves emotional accompany and mental consolation for them, which enhance the cognitive rehabilitation process. The real-time voice synthesizer provides sufficient technical support for the development of cognitive robots, which show significance for families, societies, and clinics. This article reviews the research status of the development of text-to-speech (TTS) synthesizers, including the state-of-arts expressive TTS and voice cloning models. In addition, this paper pays attention to the current challenges and prospects of cognitive rehabilitation robots.