Fig. 6
Schematic and rendering of the bipedal EcoWalker-2 robot. a: Schematic of the robot with spring-tendon routing, angle definitions, and range of motion of the joints. Segment lengths: \(\mathrm{l}_\mathrm{thigh}=\mathrm{l}_\mathrm{shank}={160}\mathrm{mm}\), \(\mathrm{l}_\mathrm{heel}={32}\mathrm{mm}\), \(\mathrm{l}_\mathrm{toe}={17}\mathrm{mm}\). Pulley radii: \(\mathrm{r}_\mathrm{GAS}=\mathrm{r}_\mathrm{SOL}={13}\mathrm{mm}\). Spring stiffness values: \(\mathrm{k}_\mathrm{GAS}={1.4}\mathrm{N/mm}\), \(\mathrm{k}_\mathrm{SOL}={4.5}\mathrm{N/mm}\), \(\mathrm{k}_\mathrm{toe}={8.04}\mathrm{Nmm/deg}\). The robot’s trunk movement is constrained to translations in the sagittal plane, and all trunk rotations are locked. The four-bar guide slides freely in fore-aft direction. b: Rendering of the bipedal robot with segment name indications.
