Passive trunk mechanism for controlling walking behavior of semi-passive walker

Although passive and semi-passive walkers provide energy-efficient locomotion, walking behavior such as a walking cycle cannot be controlled because it depends on a fixed mechanical property such as the center of mass or the foot shape. In this paper, referring to the upper body of a human, we propose a trunk mechanism that has redundant and viscoelastic joints and changes their viscoelasticity with relatively low energy consumption. By using physical and simulation models, we observe the relationship between the viscoelasticity of the trunk joints and the walking cycle. Results of the physical experiment and the simulation show that there are correlations between the joint viscoelasticity and the walking cycle, and thus, the proposed trunk mechanism is considered a suitable mechanism that controls the walking behavior of a semi-passive walker.