Slack-based tunable damping leads to a trade-off between robustness and efficiency in legged locomotion

2023

Article

dlg

Animals run robustly in diverse terrain. This locomotion robustness is puzzling because axon conduction velocity is limited to a few ten meters per second. If reflex loops deliver sensory information with significant delays, one would expect a destabilizing effect on sensorimotor control. Hence, an alternative explanation describes a hierarchical structure of low-level adaptive mechanics and high-level sensorimotor control to help mitigate the effects of transmission delays. Motivated by the concept of an adaptive mechanism triggering an immediate response, we developed a tunable physical damper system. Our mechanism combines a tendon with adjustable slackness connected to a physical damper. The slack damper allows adjustment of damping force, onset timing, effective stroke, and energy dissipation. We characterize the slack damper mechanism mounted to a legged robot controlled in open-loop mode. The robot hops vertically and planar over varying terrains and perturbations. During forward hopping, slack-based damping improves faster perturbation recovery (up to 170%) at higher energetic cost (27%). The tunable slack mechanism auto-engages the damper during perturbations, leading to a perturbation-trigger damping, improving robustness at minimum energetic cost. With the results from the slack damper mechanism, we propose a new functional interpretation of animals' redundant muscle tendons as tunable dampers.

@article{slack2022,
  title = {Slack-based tunable damping leads to a trade-off between robustness and efficiency in legged locomotion},
  author = {Mo, An and Izzi, Fabio and G{\"o}nen, Emre Cemal and H{\"a}ufle, Daniel and Badri-Spr{\"o}witz, Alexander},
  journal = {Scientific Reports},
  volume = {13},
  pages = {3290},
  publisher = {Nature Publishing Group},
  month = feb,
  year = {2023},
  doi = {10.1038/s41598-023-30318-3},
  url = {https://arxiv.org/abs/2212.00475},
  month_numeric = {2}
}