Hybrid quadruped bounding with a passive compliant spine and asymmetric segmented body

Most legged animals exploit flexible body and supporting muscles to produce power for dynamic behaviors which results in fast locomotion and additional mobility. Previous works have focused on the symmetric flexible body with massless legs associated to the body. However, body bending in animals during running happens prior to the rear side instead of the middle point of body. Therefore, a quadruped model with a passive spinal joint, asymmetric segmented body, actuated hip joints and legs is introduced. By using a numerical return map, a periodic bounding locomotion of the model is found with optimal sets of initial conditions and proper system parameters. Moreover, this paper investigates the effects of spine flexibility in segmented body on quadrupedal bounding gait. The results show that asymmetric segmented body has bigger spine oscillation, shorter stride period and smaller cost of transport, which helps the robot run more efficiently.