面向内窥镜连续体机器人末端集成的低温漂MEMS三维力传感芯片研制
Low-thermal-drift MEMS 3D Force-sensing Chip Integrated with a Surgical Gripper for Endoscopic Continuum Robots
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摘要: 内窥镜连续体机器人在自然腔道微创手术中应用潜力巨大, 但手术器械末端空间受限, 难以获得准确的三维操作力信息。基于此, 研制一种可与末端夹钳一体化集成的低温漂微机电系统(Micro-electro-mechanical System, MEMS)三维力传感芯片。芯片薄膜的高应变区部署压阻敏感单元, 在法向/切向载荷下利用应变分布差异引起的压阻效应进行差动输出, 实现末端三维操作力的解耦测量。通过片上集成4组惠斯通压阻全桥设计, 抵消温度引起的共模漂移并抑制灵敏度漂移。该芯片基于MEMS微加工工艺制备, 体积仅为2mm × 2mm × 0.4mm, 经微装配工艺实现刚柔耦合结构封装, 可一体化嵌入内窥镜连续体机器人末端手术夹钳。实验结果可知, 该芯片在0~4N范围内三轴方向输出具有良好线性(拟合相关系数R2 ≥ 0.999), 在25~85℃范围内归一化零点漂移约为传统单臂电桥芯片的1/7, 在25~50℃范围内灵敏度基本不随温度变化, 在内窥镜微创手术力感知中具有较高的稳定性与可靠性。Abstract: Endoscopic continuum robots hold great promise for minimally invasive surgery in natural orifices, but the confined space at the distal end of surgical instruments makes it difficult to obtain accurate three-dimensional (3D) operative force information. To address this challenge, a low-thermal-drift micro-electro-mechanical systems (MEMS) 3D force-sensing chip that can be integrally embedded in the distal gripper is developed. The chip exploits the differential strain distribution of a central membrane under normal and tangential loads, and uses the differential outputs of four high-strain piezoresistive sensing units to achieve decoupled measurement of distal 3D operative forces; by integrating four on-chip wheatstone piezoresistive full bridges that share a uniform thermal field on the same silicon die, temperature-induced common-mode drift is cancelled and sensitivity variation with temperature is suppressed. The force-sensing chip is fabricated using a MEMS micromachining process, with a compact size of only 2mm × 2mm × 0.4mm, and is assembled via a rigid-flex hybrid packaging scheme to enable integral embedding into the distal surgical gripper of an endoscopic continuum robot. Experimental results show that the tri-axial outputs exhibit good linearity (R2=0. 999) over the 0~4 N range; the normalized zero-offset drift over 25~85℃ is about one seventh that of a conventional quarter-bridge chip, and the sensitivity remains nearly constant between 25~50℃, confirming the stability and reliability of the proposed chip for force sensing in endoscopic minimally invasive surgery.
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