Viscous damping in legged locomotion


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


P33-10  Sat Jan 2  Viscous damping in legged locomotion Mo, A*; Izzi, F; Haeufle, DFB; Badri-Spröwitz, A; MPI for Intelligent Systems, Stuttgart; MPI for Intelligent Systems, Stuttgart; University of Tübingen; MPI for Intelligent Systems, Stuttgart mo@is.mpg.de http://dlg.is.mpg.de/person/mo

Damping likely plays an essential role in legged animal locomotion but remains an insufficiently understood mechanism. Intrinsic damping in muscle can regulate joint torque, stabilize movements, and reject perturbations. Recently, legged robots started exploring model-based, virtual damping. However, this control mechanism requires high-frequency force control loops, precision sensing, and high-power actuators. Legged animals are, in comparison, ‘handicapped’ due to inherent sensorimotor noise, nerve conduction delay of their ‘wetware’, and lower ‘computational power’. Alternatively, physical damping in robots can simulate intrinsic damping in muscle to achieve instantaneous action, sensor-free response, and adaptive force output (Mo et al, 2020). It is so far unexplored how physical damping can be deployed for locomotion tasks. Here we utilize a robot leg drop experiment to capture core aspects of legged locomotion: negotiating ground contact in the presence of uncertainties, with physical damping mounted in-parallel to a tendon-like structure (a spring). We also studied the energy dissipation from viscous and Coulomb damping in a numerical leg model, under equivalent conditions. These simulation results indicate that adjustable and viscous damping is indeed a desirable characteristic. The hardware experiments showed that adjusting the damper’s setting did not substantially alter the effectively dissipated energy per drop, unlike in the numerical model. Still importantly, effective viscous damping was achieved under various initial conditions, and fully characterized with the help of the sensorized robot leg drop setup. This effective damping has the potential to increase robustness in locomotion without the need for computation or sensing.

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