Capacitive tactile sensor with asymmetric electrodes for angle-detection-error alleviation

•Identified three mechanisms for shear force angle detection errors (ADEs),.•Proposed and realized fan-shaped electrodes for capacitive tactile sensor to suppress ADEs,.•Compared the ADEs with fan- and (conventional) square-shaped electrodes, and showed universal solution for electrode designs.

A capacitive tactile sensing unit with an asymmetric electrode arrangement to support tolerable angle detection errors (ADEs) in processes and operations was proposed and demonstrated in this study. Each capacitor in the sensing unit contains one fan-shaped electrode on top and one square-shaped electrode at the bottom with an intentional shift on the xy-plane, which alleviated the rotational misalignment and suppressed shear force ADE from more than 2.5° to less than 0.4°. The suppression of the ADE was realized by enlarging the sector angle of the fan-shaped electrode to 100°, which provided 5° clockwise and 5° counterclockwise coverages for electrode alignment. Complete theoretical derivation of the relationships among the capacitors, design, simulation, and measurement was conducted in this research. Experimental results proved that this fan-shaped electrode design showed identical functionalities and sensitivities to those of the square-shaped electrode design for capacitive tactile sensing applications.