Design of search balls with wide field of view for searching inside of rubble

"Search balls" are small sensor units for searching inside of rubble. A search ball is not equipped with locomotion mechanisms but contains some sensors for searching disaster victims and a radio transceiver. Many balls are thrown into rubble and fall down while repeating collision; they are scattered inside the rubble. The sensor information from the balls is transmitted on radio out of the rubble and monitored at safe area by rescuers. Thus search balls allow rapid and wide-area search inside rubble. Two types of search balls with wide field of view are developed: one type has three fixed wireless cameras, and the other has two wireless cameras rotated by a motor. Both types have infrared LEDs for illumination, a radio receiver for communication with monitoring computers, batteries and electronic circuit; these components are packed into sphere impact-resistant outer shells. Impact-resistance of the balls is tested by drop experiment on wooden floors. It is experimentally checked using a model of rubble that the monitoring computer can send commands to the ball inside this rubble and the ball can transmit the video signal of its cameras out. We also check if humans can be found in the camera images sent from the ball in darkness.