This research has been conducted to develop a prevention module of collision and balance lost in electric wheelchairs. Ultrasonic sensors were used for detecting obstacles. Giro and acceleration sensors were used for measuring the tilt angle of wheel chair frame. Kalman filters were employed for filtering high-frequency noise of acceleration sensor and removing zero drift of the Giro sensor. The presence and location of obstacles were detected, and their information was sent to the user smartphone. When the tilt angle of the wheelchair frame exceeded a certain value, a warning signal was set to operate. Raspberry Pi camera module was used to transfer rear view image data to the smartphone to help the driver acknowledge obstacles in the rear side. A DSP processor with high computing performance was necessary to realize a real-time processing of the sensor and image data. Our research showed that a prevention module of collision and balance lost connected to a smartphone can be realized at a considerable low price.

For the safety and cost reduction in the navigation, the automatic and intelligent system has been developed for the vessel, and the most important factor in the system is to decide the collision risk exactly. In this paper, we propose an advanced collision risk decision system for collision avoidance of the system. The conventional researches using DCPA and TCPA for calculating the collision risk have a problem to produce a same collision risk regardless of bearings for the ships, if they are located in the same distance from own ship. To solve this problem, in addition to DCPA and TCPA, we introduce the factor of VCD(variation of compass degree) and constant, CR which derived from COLREG'72(International Regulation for Preventing Collision at Sea, 1972) for evaluating the collision risk including even the burden of own ship navigator due to the encountering angle of each vessels. We decided the collision risk legally by the rule considering the relative situation of vessels. And therefore, the proposed system has two advantages, of which one is to produce more detail collision risk and another is to reflect the real underway situation in conformity with the rule.