Realization of Multistage Detection Sensitivity and Dynamic Range in Capacitive Tactile Sensors

In this study, stoppers were designed and allocated in a planar four-capacitor (P4C) sensing unit for modulating capacitive tactile sensor (CTS) characteristics. The stoppers deterred the structural deformation of the CTS when applied with normal forces, realizing a three-stage operation: high detection sensitivity, wide dynamic range, and saturation. Comprehensive studies including theoretical design, numerical evaluation, demonstrator fabrication, experimental analysis, and a technical discussion were conducted. The proposed CTS achieved 0.901 pF/N sensitivity, enhanced dynamic range by 235.3%, and supported 2.1 N detection in the first, second, and third stages under normal force applications, respectively. With the CTS characteristics resulting from varying stopper locations, a relationship between the capacitive response and applied force is established to support typical P4C CTSs in arbitrary dimensions. In addition, systematic tolerance is studied to explain detection accuracy for the first time. The proposed CTS provides operation flexibility in normal force detections, and unaltered supportiveness on shear force and its angle detections, compared with typical CTSs.