In this paper, with the goal of quantifying the qualitative image outputs of a Vision-based Tactile Sensor (VTS), we present the design, fabrication, and characterization of a novel Quantitative Surface Tactile Sensor (called QS-TS). QS-TS directly estimates the sensor's gel layer deformation in real-time enabling safe and autonomous tactile manipulation and servoing of delicate objects using robotic manipulators. The core of the proposed sensor is the utilization of miniature 1.5 mm x 1.5 mm synthetic square markers with inner binary patterns and a broad black border, called ArUco Markers. Each ArUco marker can provide real-time camera pose estimation that, in our design, is used as a quantitative measure for obtaining deformation of the QS-TS gel layer. Moreover, thanks to the use of ArUco markers, we propose a unique fabrication procedure that mitigates various challenges associated with the fabrication of the existing marker-based VTSs and offers an intuitive and less-arduous method for the construction of the VTS. Remarkably, the proposed fabrication facilitates the integration and adherence of markers with the gel layer to robustly and reliably obtain a quantitative measure of deformation in real-time regardless of the orientation of ArUco Markers. The performance and efficacy of the proposed QS-TS in estimating the deformation of the sensor's gel layer were experimentally evaluated and verified. Results demonstrate the phenomenal performance of the QS-TS in estimating the deformation of the gel layer with a relative error of <5%.

翻译：本文旨在量化基于视觉的触觉传感器（VTS）的定性图像输出，我们提出了一种新型定量表面触觉传感器（简称QS-TS）的设计、制造与表征。QS-TS能够直接实时估算传感器凝胶层的形变，从而利用机器人操作器实现对易损物体的安全自主触觉操作与伺服控制。该传感器的核心在于采用微型1.5 mm × 1.5 mm合成方形标记（具有内部二进制图案和宽黑色边框），即ArUco标记。每个ArUco标记可提供实时相机位姿估计，在我们的设计中，该估计被用作获取QS-TS凝胶层形变的定量度量。此外，得益于ArUco标记的使用，我们提出了一种独特的制造工艺，该工艺缓解了现有基于标记的VTS制造中的多种挑战，并提供了一种直观且省力的VTS构建方法。值得注意的是，所提出的制造方法促进了标记与凝胶层的集成与粘附，从而无论ArUco标记的方向如何，都能稳健可靠地实时获取形变的定量度量。通过实验评估并验证了所提出的QS-TS在估算传感器凝胶层形变方面的性能与有效性。结果表明，QS-TS在估算凝胶层形变方面表现卓越，相对误差小于5%。