A Semi-Enclosed Flux-Focusing Hall-Based Tactile Sensor

Hall-effect-based magnetic tactile sensors are attractive for compliant force-sensing systems, but their force sensitivity is often limited by the local magnetic-flux-density distribution around the permanent magnet. In this work, a semi-enclosed American Iron and Steel Institute (AISI) 430 flux-focusing layer was introduced around the magnet to form a low-reluctance return path and increase the useful axial magnetic flux density in the sensing region. An external normal force applied to the curved rigid contact is transmitted to the silicone elastomer. Its deformation can change the magnet–Hall geometry and redistribute the local magnetic flux at the Hall sensing plane. The resulting axial magnetic-flux-density variation is detected by the KTH5701-based sensing system. This passive magnetic-circuit design improved the sensitivity from 0.063 to 0.119 mT/N over 0–10 N, corresponding to an 88.9% increase over the reference configuration, without changing the Hall readout principle. Among the tested elastomers, the formulation carrying the supplier-labeled hardness grade of 5° provided a balanced response, with a hysteresis gap of 0.0019 mT and a sensitivity retention of 96.9% after 100 cycles. Repeated loading from 0 to 1.0 N further confirmed a monotonic and repeatable low-force response. The magnet–Hall sensing unit was integrated into a 4 × 4 array to demonstrate qualitative spatial contact-pattern measurement. Under the tested conditions, these results support local magnetic-return-path regulation as a structural route for improving force sensitivity, while the selected elastomer formulation is associated with the accompanying hysteresis and repeatability trade-off.