Shinji Kotani

A Robotic Travel Aid for the Blind

We have been developing Robotic Travel Aid(RoTA) “HARUNOBU” to guide the visually impaired in the sidewalk or campus. RoTA is a motor wheel chair equipped with vision system, sonar, differential GPS system, dead reckoning system and a portable GIS. We estimate the performance of RoTA in two viewpoints, the viewpoint of guidance and the viewpoint of safety. RoTA is superior to the guide dog in the navigation function, and is inferior to the guide dog in the mobility. It can show the route from the current location to the destination but can not walk up and down stairs. RoTA is superior to the portable navigation system in the orientation, obstacle avoidance and physical support to keep balance of walking, but is inferior in portability.

Development of the robotic travel aid “HITOMI”

Abstract The Robotic Travel Aid (RoTA) is a motorized wheelchair equipped with vision, sonar, and tactile sensors, in addition to a map database system. The visually impaired can get orientation, mobility and obstacle information from RoTA, and can inquire about their present location, landmarks and the future part of the route. The concept is implemented on a RoTA called “HITOMI”. It can guide the impaired to avoid vehicles along a road with lane marks or along a sidewalk marked with Braille.

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.

HITOMI: Design and Development of a Robotic Travel Aid

A Robotic Travel Aid (RoTA) is a motorized wheelchair equipped with vision, sonar, and tactile sensors and a map database system. A RoTA can provide a visually impaired user assistance with orientation and obstacle avoidance, as well as information about their present location, landmarks, and the route being followed. In this paper we describe HITOMI, an implementation of the RoTA concept that can guide a visually impaired user along a road with lane marks or along a sidewalk while avoiding obstacles.

A mobile robot strategy applied to Harunobu-4

A mobile robot strategy called stereo-typed motion by sign pattern, drawn from a study of lower animals is applied to the mobile robot Harunobu. A stereotyped motion is specified by a fixed action pattern which always appears when the robot encounters a certain situation. The motion classified into two groups; vision-based motion and sensor-based motion. The former consists of moving-along, moving-toward, turning-corner and avoiding-obstacle. A sign pattern is specified by a part of an object that initiates and guides the stereotyped motion. The latter consists of run-over-stop motion and several collision-avoiding motions initiated by bumper switches or ultrasonic sensors. To deal with error status in vision-based motion such as no-passage-found or sign-pattern-missing, several error recovery motions are specified.<<ETX>>

Finding pedestrians by estimating temporal-frequency and spatial-period of the moving objects

A new method of finding pedestrians in a time sequence of visual images has been proposed, and its great practical applicability has been demonstrated. Walkers exhibit periodic motion in a quite different way from other moving objects. This periodicity, or in other words rhyth of walking, is the result of the walking action and can be observed in two kinds of periodic intensity change of the pedestrians image. So, pedestrians can be found if we look for these periodicities which are quite unique to them. To realize this idea, we estimate the temporal-frequency and the spatial-period of the moving objects. The temporal-frequency is the oscillation of intensity against time. The spatial-period represents the fluctuation of intensity along the trajectory of the object, and is referred to as the stride of walking. A pedestrian detection method using these two oscillations has the following advantages. (1) This method is independent of the absolute intensity or contrast of the objects. (2) Clothes, hairstyle, shape of body, illumination and the distance from the camera do not affect the reliability of detection. Finally, the algorithm is simple enough for real time operation. The detailed algorithm is presented here and its validity and practical applicability are examined in an experiment on asphalt paved road.

Color impression factor: an image understanding method for outdoor mobile robots

The color vision in the outdoor environment has two problems. The first is the hue shift of the object under the changes of the season, weather, the hour and the view position. The second is the hue shift of the object between in the sunny place and in the shaded place. We propose the color impression factor to memory the hue of the object. The color impression factor is defined as R-B. It is the function of the sunlight condition (sunny/shaded) and the hour. We show this factor is useful to discriminate objects from the shadows in the asphalt paved road-yellow tactile blocks from the asphalt paved road.

Danger estimation of vehicles at intersection

This paper deals with dynamic vision, vehicle avoidance, navigation, and applications to guide dog robot and vehicle intelligent control system. Danger estimation of vehicles at the intersection is proposed in this paper. Traffic rules of vehicles and the locomotion strategy of robot is formulated, and finally a danger matrix is defined for each vehicle represented by its location and its moving direction. This method is implemented on an image processing system. The location, velocity, and the moving direction of a vehicle are measured by computer vision and its danger coefficient is evaluated. About 90% of vehicles at a T shape intersection have been successfully voted in danger judgment.

Image processing and motion control of a lane mark drawing robot

The authors propose a method for detecting and following a half-faded lane mark on an asphalt road using image processing. It ensures reliable detection and high speed following in the actual outdoor environment. The method is based on a template matching between a lane mark model and a detected lane mark. The authors built a testbed robot, which aims to repaint a half-faded lane mark semi-automatically. The details of this testbed robot and experimental results of a half-faded lane mark detection and following are described. Experimental results (trajectories of this robot) for a actual half-faded lane mark show the availability of this method.

Danger estimation of the Robotic Travel Aid (RoTA) at intersection

We have been developing Robotic Travel Aid (RoTA) system since 1991 which guides the blind on a road or a sidewalk. One of the most difficult problems for RoTA is how to cross the intersection without a traffic accident. So, danger estimation for vehicles at the intersection is proposed in this paper. This method is implemented on an image processing system. The location, velocity, and the moving direction of a vehicle are measured by computer vision and its danger coefficient is evaluated. About 90% of vehicles in a T-shaped intersection have been correctly interpreted in danger judgments in real world scenes.