Robophysical modeling of dynamic posture modulation of vibration sensing in orb weaving spiders

Orb-weaving spiders are functionally blind and detect prey-generated web vibrations through vibration sensors at their leg joints to locate and identify prey caught in their (near) planar webs. Previous studies focused on how spiders use web geometry, silk properties, and web pre-tension to modulate vibration sensing. Spiders can also dynamically adjust their posture while sensing prey, which may be a form of active sensing (Hung, Corver, Gordus, 2022, APS March Meeting). However, whether this is true and how it works is poorly understood, due to difficulty of measuring the dynamics of the entire prey-web-spider interaction system all at once. Here, we developed a robophysical model of the system to test this hypothesis of active sensing and discover its principles. Our model consists of a vibrating prey robot and a spider robot that can adjust its posture, with torsional springs at leg joints and accelerometers to measure joint vibration. Both robots are attached to a physical web made of cords with qualitatively similar properties to real spider web threads. Load cells measure web pre-tension and a high-speed camera system measure web vibrations and robot movement. Preliminary results showed vibration attenuation through the web from the prey robot. We are currently studying the complex effects of spider robot’s dynamic posture change on vibration propagation across the web and leg joints, by systematically varying the parameters of prey robot vibration, spider robot leg posture, and web pre-tension.