Improving the Accuracy of Road Surface Distinction Based on Reflection Intensity Variations Using Ultrasonic Sensor

Fall cases in the daily lives of elderly people are increasing owing to the progressing aging society problem. The falls of elderly people usually have correlations with poor physical conditions and judgment and cause severe consequences. To prevent elderly people from falling, a movement support system was developed in our previous research. The system employs a reflection intensity value obtained by an ultrasonic sensor to identify the type of road surface and sounds an alert when the road surface is dangerous and may cause the user to slip or fall. However, the conventional method does not solve the problem of low detection rate on rough road surfaces without considering the variation in the reflection intensity due to the change in the shape of the road surface. In this paper, the variation in the reflection intensity is measured by investigations at multiple types of locations. The variation in the reflection intensity is introduced as a parameter to improve the road surface identification accuracy. The effectiveness of the proposed method in this paper is verified by experiments on four types of road surfaces. The necessary number of reflection intensity samples for road surface identification is also discussed.