Abstract
The spine plays important roles in the quadruped locomotion. To investigate the effects of the spine on the quadruped trotting motion, firstly, a sagittal passive model is proposed which contains four massless springy legs and two passive spinal joints. To generate the trotting gait of the model, the multibody hybrid dynamics model is established based on the defined events. The combination of optimization tools is used to find the suitable solution space in which the model can maintain a periodic motion. It reveals that the quadruped trotting motion results from the coordinated features of the spine and the legs. By comparing the model with the rigid body, it is proven that the spinal joints can reduce the effect of the ground reaction forces on the body in a special velocity range. Then, a hybrid controller whose objective is to maintain the kinematic coordination between the spinal joints is applied and it replaces the passive spinal joints, and the results prove that it can make the model achieve a stable periodic motion. Finally, the prototype of the quadruped robot with two spinal joints based on the model is established and its trotting motion is achieved successfully. The experiment results also indicate the compliant effect of the spine on the motion performance. Consequently, the effects of the spine at trotting gait are helpful to guide the development of the quadruped robots.
Highlights
A general finding reveals that when the humans or mammals run, the legs act as springs and experience a compression and extension process to improve the energy efficiency and the compliance of the interaction with the ground [2]
Many studies found out that the spine plays an important role in the quadruped motion [9, 10]. erefore, some researchers added the spine element into the models to investigate the effects of the spine on the motion performance
We establish a planar passive model with two spinal joints to investigate the effects of the spine on the Journal of Robotics dynamic performances of quadruped trotting motion. e Poincare Mapping and combined optimization method are used to search for the suitable parameters and generate the periodic trotting gait
Summary
A general finding reveals that when the humans or mammals run, the legs act as springs and experience a compression and extension process to improve the energy efficiency and the compliance of the interaction with the ground [2]. To analyze the intuitive motion mechanism of quadruped motion at different gaits, the planar model including a rigid body and four massless springy legs was established based on the SLIP model [8]. This model basically represents the dynamic modes of the quadruped motion, it does not take the spine into account. We establish a planar passive model with two spinal joints to investigate the effects of the spine on the Journal of Robotics dynamic performances of quadruped trotting motion. Some experiments for the trotting motion show the effect of the two spinal joints on the ground reaction forces
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