Noriaki Okamoto

Safety System of a Welfare-service Mobile Equipment for Collision to Human and Its Functional Experiment

Various kinds of welfare-service mobile equipments such as a motor wheel chair and a tray-carrying cart have two points of common characteristics, considering their safety system for collision with a human. One point is that these mobile equipments move among various passengers walking along sidewalks or corridors. Therefore, the mobile equipments need intrinsical safety measures, in addition to preventive safety measures. The other point is that they move much slower than a general vehicle such as an automobile. Considering the low speed of these mobile equipments, this paper proposes the design concept that prevents a human falling or damage after collision, by absorbing completely the impact energy with an absorber-braking friction system and simultaneously by controlling the impact force from the equipment to a human. The design concept is applied to the safety system for a large-size tray-carrying cart with function of keeping dishes warm or cold in a hospital and a walfare institution. Functional experiments for the safety system were carried out with a test cart constructed similar to the tray-carrying one. It is shown by a series of impact tests with dummies that the impact force between a human and the equipment can be controlled under the human pain tolerance and the condition on human-fall is determined as a function of critical speed, impact force and friction between a dummy sole and a floor.

Control of Peak Load and Maintenance of Safety Load for Skin Tubular Beams (Construction of Safety Structures for Medical/Human-care Robot Adaptable to Contact/Collision with Flexibility)

The final goal of this study is to construct safety structures for medical and human-car robots and moving equipments. This paper proposes a concept of the smart structure applied to them that has an ideal load-deflection curve for the safety design. An experimental study on the denting and bending of aluminum skin tubular beams and ways to control the load-deflection curves with various reinforcements and triggers was carried out as the first step of the goal. Experimental results on simply supported tubes show that a simple skin model for low load design and a double skin model for high load design have each ideal structural property considering from a viewpoint of high initial rigidity, peak-load control, high buffer efficiency and configuration reversibility. One of three kinds of reinforced skin tubes that are able to construct the ideal load-deflection curve with a ring-shaped trigger is proposed to be of most practical use for cantilever models.