Drop test for evaluating effect of cushioning material and servo gain on parachute landing impact using a small one-legged robot

To drop a humanoid robot with a parachute from an airplane is one of the promising ways of delivering robots to a disaster site, and this research has focused on how to absorb parachute landing shock. Two large impacts were observed in one drop test using a small one-legged robot in our previous experiment. The second peak could be reduced by the shock absorbing motion, but the first peak did not change dramatically even if the landing posture was changed. Therefore, this paper forces on how to reduce the first impact acceleration and discusses on effect of cushioning material and servo gain on the impact. It was found that the difference in the hardness of the cushioning material greatly influences the impact acceleration. There was a difference in impact acceleration more than twice between a soft cushion and a hard cushion. On the other hand, impact absorption effect by change of servo gain of robot's actuators was minor. Therefore, it is concluded that flexibility with hardware is also necessary for joints.