A monolithic mechanosensitive 3D-printed jaw with piezoresistive sensing for grasp force estimation

Abstract Through this work we introduce the design, development and implementation of a mechanosensitive 3D-printed jaw for a uniaxial gripper system, with an integrated sensor printed monolithically with the jaw. For many mechanical systems, accurately incorporating effects of transmission issues like stiction, dead-zone, backlash into their model presents a complex challenge. Inaccurate modeling can lead to overshoot or premature arrest in systems like screw-driven grippers. To address this, we developed a 3D-printed compliant jaw incorporating a parallelogram mechanism to maintain object orientation during grasp, while permitting a controlled deformation. Although introducing compliance improves the tolerance for force-control, the use of easily deformable bodies also necessitates reliable force estimation during operation, motivating the integration of a sensor element within the mechanism itself. The directional compliance of the jaws provides a natural means of force transduction and was leveraged by printing one blade of the mechanism with a conductive piezoresistive filament, enabling the jaw to directly estimate the grasp force. The study thus focuses only on verifying the jaw’s real-time force estimation performance against a reference force sensor. A linear model was selected for its ease of implementation, low computational costs and calibration simplicity. Six 20-cycle tests were conducted at varying force set-points, with the first five cycles of each test used for real-time calibration of the gauge factor. The jaw achieved reliable sensing within a 15–30N range, with a mean estimation error of approximately 2.6N (∼11.96% of measured peak force), demonstrating the feasibility of integrating a conductive structural element into robotic gripper jaws for practical robotic grasping.