Dynamic human movements are achieved by appropriate constraints on the degrees of freedom of the complex and flexible human body. The anatomy trains (ATs) theory explains such constraints with whole-body muscular connections called ATs. This paper proposes the design of a quasi-passive dynamic walker with whole-body viscoelastic connections inspired by the ATs theory and investigates the contributions of these long-distance connections to the achievement of gait. We designed a biped robot with a trunk and head, whose passive joints were supported by rubber fiber bands. The robot, named “PEARL III,” is equipped with an antagonistic pair of McKibben pneumatic actuators for each leg at the human hamstring and rectus femoris positions. The most important feature of this robot is that fabric wires mechanically connect its rubber bands and actuators on the back side from the head to the foot, modeled after one of the human ATs, the superficial back lines (SBLs). In an experiment, PEARL III achieved 2D quasi-passive dynamic walking on an inclined plane by contracting and relaxing its actuators using periodic feedforward control. This result suggests that in both the robot and human cases, when a controller contracts the SBL only in the stance phase during passive dynamic walking, the SBL can achieve whole-body posture control and weight support. In addition, the SBL appears to achieve this function depending on their mode of attachment to bones and the presence or absence of antagonistic muscles (or ATs). In the future, by introducing various ATs into robots while recognizing the importance of the appropriate attachment of ATs and the presence of their antagonistic muscles (or ATs), we can expect similar effects in various 3D movements.

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