A Robust Antenna Provides Tactile Feedback in a Multi-legged Robot

Abstract

Multi-legged elongate robots hold promise for maneuvering through complex environments. Prior work has demonstrated that reliable locomotion can be achieved using open-loop body undulation and foot placement on rugose terrain. However, robust navigation through confined spaces remains challenging when body-environment contact is extensive and terrain rheology varies rapidly. To address this challenge, we develop a pair of tactile antennae for multi-legged robots that enable real-time sensing of surrounding geometry, modeling the morphology and function of biological centipede antennae. Each antenna features gradient compliance, with a stiff base and soft tip, allowing repeated deformation and elastic recovery. Robophysical experiments reveal a relationship between continuous antenna curvature and contact force, leading to a simplified mapping from antenna deformation to inferred discrete collision states. We incorporate this mapping into a controller that selects among a set of locomotor maneuvers based on the inferred collision state. Experiments in obstacle-rich and confined environments demonstrate that tactile feedback enables reliable steering and allows the robot to recover from near-stuck conditions without requiring global environmental information or real-time vision. These results highlight how mechanically tuned tactile appendages can simplify sensing and enhance autonomy in elongate multi-legged robots operating in constrained spaces.

Figures (8)

• Figure 1: Robophysical antenna model integrated on a multi-legged robot (top-down view). (A) Antenna design; The antenna enables compliant contact sensing through measured bending. (B) Top-down view of the centipede S. subspinipes showing wall-sensing of antenna. (C) Top-down view of the multi-legged robot SCUTTLE (Ground Control Robotics, Inc.). The dashed box highlights the modular antenna mounted on the anterior segment.
• Figure 2: Antenna morphology of a centipede. (A) Lateral view showing the cephalic plate, antennae, ocelli, and forcipules, with anterior direction and sagittal plane indicated (scale bar: 1 cm). (B) Anterior view highlighting the bilaterally extended antennae and their descending segment diameter from base to tip (proximal diameter 0.15 cm; distal diameter 0.02 cm). (C) Diameter based stiffness proxy along the antenna, computed from the proximal to distal diameter profile using a fourth power scaling ($\hat{K}_i \propto d^{4}$), showing a descending stiffness distribution from base to tip.
• Figure 3: Antenna contact and in-contact antenna morphologies during wall-following in S. subspinipes (top-down view). (A) Representative time sequence showing sustained antenna contact with a wall during forward travel (scale bar: 2 cm). (B) Three stereotyped in-contact antenna morphologies, defined by the direction the antenna points relative to the body: forward pointing, backward pointing, and straight. (C) Distribution of in-contact antenna morphologies across trials ($n=4$), including a transition category for brief switching between morphologies during continuous contact.
• Figure 4: Robotic antenna modes and actuation schematic. (A) Representative in-contact antenna morphologies during wall interaction, labeled by the direction the antenna points relative to the body (forward pointing and backward pointing). (B) Planar antenna sweep used for calibration and testing, parameterized by a sinusoidal base angle $\theta_\mathrm{joint}(t)=\theta_0+A\sin(2\pi f t)$.
• Figure 5: Antenna calibration and mapping from ADC to normalized bending level. Raw 12-bit ADC readings are recorded while the antenna is swept through controlled deflections at three traverse speeds ($v=5,10,15$ cm/s). Markers show the mean and error bars indicate variability across trials. A global decreasing sigmoid fit (inset) defines the mapping from averaged ADC to a normalized bending level $b\in[0,1]$ used by the controller. Fit parameters for this dataset: $k_s=18.3$, $x_0=0.305$.