Hsin-Yi Hung | Searcharxiv

arXiv2026

Creating a biologically more accurate spider robot to study active vibration sensing

Orb-weaving spiders detect prey on a web using vibration sensors at leg joints. They often dynamically crouch their legs during prey sensing, likely an active sensing strategy. However, how leg crouching enhances sensing is poorly understood, because measuring system vibrations in behaving animals is difficult. We use robophysical modeling to study this problem. Our previous spider robot had only four legs, simplified leg morphology, and a shallow crouching range of motion. Here, we developed a new spider robot, with eight legs, each with four joints that better approximated spider leg morphology. Leg exoskeletons were 3-D printed and joint stiffness was tuned using integrated silicone molding with variable materials and geometry. Tendon-driven actuation allowed a motor in the body to crouch all eight legs deeply as spiders do, while accelerometers at leg joints record leg vibrations. Experiments showed that our new spider robot reproduced key vibration features observed in the previous robot while improving biological accuracy. Our new robot provides a biologically more accurate robophysical model for studying how leg behaviors modulate vibration sensing on a web.

cs.RO↗

arXiv2025

Why orb-weaving spiders use leg crouching behavior in vibration sensing of prey on a web: A physical mechanism from robophysical modeling

Orb-weaving spiders primarily sense leg vibrations to detect and locate prey caught on their wheel-shaped webs. Biological experiments and computational modeling elucidated the physics of how these spiders use long-timescale web-building behaviors, which occur before prey capture, to modulate vibration sensing of prey by controlling web geometry, materials, and tension distribution. By contrast, the physics of how spiders use short-timescale leg behaviors to modulate vibration sensing on a web during prey capture is less known. This is in part due to challenges in biological experiments (e.g., having little control over spider behavior, difficulty measuring the whole spider-web-prey system vibrations) and theoretical/computation modeling (e.g., close-form equations intractable for a complex web, high computation cost for simulating vibrations with behaving animals). Here, we use robophysical modeling as a complementary approach to address these challenges and study how dynamic leg crouching behavior common in orb-weaving spiders contributes to vibration sensing of prey on a web. We created a robophysical model consisting of a spider robot that can dynamically crouch its legs and sense its leg vibrations and a prey robot that can shake both on a horizontal physical wheel-shaped web. We discovered a physical mechanism that can allow the spider to use leg crouching to detect prey presence and distance. Our work demonstrated that robophysical modeling is a useful approach for discovering physical mechanisms of how spiders use short-time scale leg behaviors to enhance vibration sensing of objects on a web and providing new biological hypotheses.

physics.bio-ph↗