Roll Motion Control by Stretch Reflex in a Continuously Jumping Musculoskeletal Biped Robot

Human's spinal reflexes response rapidly to the change of states of muscles, therefore, they are supposed to play an important role for dynamic motion. In order to realize three dimensional stable jumping, rapid control system is indispensable. In this paper, we investigate contribution of the stretch reflex for stabilizing roll motion of continuous jumping by constructing a musculoskeletal biped robot. By conducting numerical simulation and robot experiments, we show that the stretch reflex in the Soleus muscle effectively stabilizes the roll motion of the robot. Through investigation, we confirmed that roll motion was partially stabilized by implementation of the stretch reflex in the soleus muscle. This study may lead to understanding the role of spinal reflexes in human jumping and to realization of robust jumping of bipedal robots.