Tsutomu Tanzawa

The ultrasonic range finder for outdoor mobile robots

Ultrasonic rangefinders have already been used successfully for indoor mobile robots. However, in an outdoor environment, the sensor should be robust against noise from vehicle engines and other sound sources. The robust sensor has already been proposed, but it requires a high-performance processor. In this paper the authors propose a new ultrasonic ranging sensor which is simple and low-cost. This sonar is robust in noisy environments. A RTZ (return to zero) signal having a certain time duration modulated with a 40 KHz carrier is transmitted from a transducer, then cross-correlation is calculated between the transmitted wave form and the demodulated received wave form. If objects are present the calculated cross-correlation has relatively large value. The authors can measure the range from the sensor to the objects by the time interval between the starting time of the transmitted signal and the time which has the peak value. The experimental results show the robustness of this sensor against the impulse noises. Furthermore, the authors propose that several sonar sensors can work at the same time without mutual interference, when the different time duration signals are used as the transmitting signals.

Mixing remote locations using shared screen as virtual stage

This paper introduces a visual communication system that integrates images displayed on a shared screen and people in front of the screen using depth information obtained from a stereo camera. Conventional video conferencing systems convey PC screen contents and video of local and remote participants in different channels, making interactions among them difficult. The proposed system maps persons in the foreground onto the screen preserving relative position and size. A series of preliminary experiments is conducted to compare the performance of the proposed system against conventional systems.

Floor estimation by a wearable travel aid for visually impaired

During a disaster, it may be difficult for the visually impaired to use infrastructure or to obtain care workers support. To support the independence of the visually impaired, we have developed a wearable travel aid that assists in safe travel, including navigating stairs, without special infrastructure. Because safe navigation requires accurate position estimation, our system fuses data from different sensors to estimate a pedestrians position. In this paper, we propose a floor estimation method based on fuzzy inference with a laser range finder (LRF). When walking on a floor, an image processing system and a LRF are used together to estimate the position, but when walking on stairs, a second LRF is used to estimate the floor and detect obstacles. The experimental results show that our floor estimation is also useful for position estimation.

Proficiency evaluation of three Japanese Input Methods using an eye-controlled communication device for users with disabilities

This paper describes proficiency evaluations of three Japanese Input Methods using a portable eye-controlled communication device for users with disabilities such as Cerebral Palsy or ALS (Amyotrophic Lateral Sclerosis). We proposed three Japanese Input Methods and implemented them. Our quantitative evaluation, subjective evaluation by questionnaire and physiologic evaluation with NIRS (Near Infra-Red Spectroscopic) show the effectiveness of the “Roman letters” input method and the “modified beeper” input method. The results of proficiency evaluation show the effectiveness of the “Roman letters” input method.

Indoor localization using infrared global vision system and LRF for twin brushes floor polishing robots

We have been developing floor polishing robots, which have two rotary brush polishers. These omnidirectional mobile robots require no driving for locomotion and steering because the friction between the floor and rotating brushes is used as the driving force. The localization for these robots cannot be used dead reckoning because water and washing liquid make wheels slip. This paper proposed the localization using the infrared global vision system and a laser range finder (LRF) without touching the floor. In the infrared global vision system, assuming the model that the infrared LED is a point light source, we calculated the center of a LED from a gray scale image. From the experimental result that the processing time was approximately 40(ms) and the accuracy was approximately 16(mm), a high-speed and accurate localization was achieved. And the method using a LRF was also achieved a high speed and precise localization by the comparison with the infrared global vision system. Furthermore, we proposed the method of the precise localization and the obstacle avoidance in all of a room by using these two methods at the same time.

Position estimation of goldfish using image processing for scooping goldfish robot

We research and develop it aiming at the realization of a scooping goldfish robot copied from the method that a human being takes. This paper describes estimation method of the 3D position of a goldfish in a water tank. What is important and basic in distinguishing a timing to scoop a goldfish is to estimate the 3D position.