To enhance robotic grasping capabilities, we are developing new contactless fingertip sensors to measure distance in close proximity and simultaneously detect the type of material and the interior structure. These sensors are referred to as pre-touch dual-modal and dual-mechanism (PDM$^2$) sensors, and they operate using both pulse-echo ultrasound (US) and optoacoustic (OA) modalities. We present the design of a PDM$^2$ sensor that utilizes a pulsed laser beam and a customized ultrasound transceiver with a wide acoustic bandwidth for ranging and sensing. Both US and OA signals are collected simultaneously, triggered by the same laser pulse. To validate our design, we have fabricated a prototype of the PDM$^2$ sensor and integrated it into an object scanning system. We have also developed algorithms to enable the sensor, including time-of-flight (ToF) auto estimation, ranging rectification, sensor and system calibration, distance ranging, material/structure detection, and object contour detection and reconstruction. The experimental results demonstrate that the new PDM$^2$ sensor and its algorithms effectively enable the object scanning system to achieve satisfactory ranging and contour reconstruction performances, along with satisfying material/structure detection capabilities. In conclusion, the PDM$^2$ sensor offers a practical and powerful solution to improve grasping of unknown objects with the robotic gripper by providing advanced perception capabilities.

翻译：为提升机器人抓取能力，我们正在开发新型非接触式指尖传感器，用于在近距离范围内测量距离，并同时检测材料类型与内部结构。此类传感器称为预触双模态双机制（PDM$^2$）传感器，其工作模式包括脉冲回波超声（US）与光声（OA）两种模态。本文提出一种PDM$^2$传感器的设计方案，该传感器采用脉冲激光束与定制化宽声学带宽超声收发器实现测距与感知。US与OA信号由同一激光脉冲触发同步采集。为验证设计，我们制作了PDM$^2$传感器原型并将其集成到物体扫描系统中，同时开发了包括飞行时间（ToF）自动估计、测距校正、传感器与系统标定、距离测量、材料/结构检测以及物体轮廓检测与重建在内的算法。实验结果表明，新型PDM$^2$传感器及其算法能够有效驱动物体扫描系统，实现令人满意的测距与轮廓重建性能，并具备良好的材料/结构检测能力。结论表明，PDM$^2$传感器通过提供先进的感知能力，为提升机器人夹爪对未知物体的抓取提供了实用且强大的解决方案。