The effect of spine on the bounding dynamic performance of legged system

The effect of the spinal joint on the dynamic performance of a legged system in bounding gait is presented in this paper. We employ the simplified quadruped passive model to discuss the underlying mechanism of the bounding gait pattern. A comparison between the dynamic model with and without the spinal joint suggests that the model with a spinal joint is superior to the model with a rigid body in dynamic indicators including the vertical fluctuation of the centre of mass (CoM), leg forces and energy consumption. The effects of different initial included angles of the spinal joint and different initial vertical positions of the CoM on the dynamics of bounding are also analysed. We found that a low level of the energy consumption and leg forces can be obtained with the proper initial included angle and initial vertical position of the CoM, and there exists an optimal situation for each horizontal running velocity that the lowest energy consumption and the lowest leg forces could be obtained at the same time.