Xiayu Zhao, Yizhi Liu, Houtan Jebelli
Building and infrastructure envelope inspections are essential for preventing early deterioration, yet conventional practice is risky and labor-intensive. Although UAVs improve safety and coverage, most inspection remains hover-based and vision-dominant, making performance sensitive to wind and illumination and limiting reliability for defects that require physical confirmation (e.g., looseness, delamination, or moisture-softened materials). This paper presents a soft pneumatic UAV landing and perception platform integrating a multi-leg compliant contact interface with synchronized visual–tactile–spatial sensing. It enables gentle, contact-aware inspection of local surface and interface conditions on inclined and fragile building-envelope surfaces. The targeted conditions include contact stability, slip tendency, and abnormal compliance responses, which may indicate loosened, delaminated, or moisture-softened regions. A modular, bi-directionally bendable soft leg unit is assembled into configurable 4-, 6-, or 8-leg architectures to support compliant load sharing and stable contact. Soft landing mechanism simulations evaluate these compliant configurations against a rigid H-Truss baseline across surface slopes of 0°, 10°, 20°, and 30°, showing that compliant designs maintain stable contact up to 30° while the rigid baseline fails at 30° due to force imbalance. To enable contact-aware decision making, a multimodal data embedding framework fuses visual, tactile, and spatial features for contact-state inference, achieving 95.3% contact detection accuracy and 89.8% stable-contact accuracy in simulation, outperforming unimodal and partial-fusion baselines. In addition, benchtop experiments with a physical soft-leg prototype validate the predicted pneumatic bending dynamics and contact stabilization behavior, demonstrating smooth inflation–release responses consistent with simulation trends and enabling higher-fidelity contact data acquisition under surface variability. Overall, distributed pneumatic compliance combined with multimodal perception provides a practical foundation for safe, stable, and slope-robust UAV contact for next-generation contact-based infrastructure inspection.