A Detachable FBG-Based Contact Force Sensor for Capturing Gripper-Vegetable Interactions

Vertical farming, a sustainable key for urban agriculture, has garnered attention for its land use optimization and enhanced food production capabilities. The adoption of automation in vertical farming is a pivotal response to labor shortages, addressing the need for increased efficiency, particularly in labor-intensive tasks like harvesting. Although soft robotic grippers offer a significant promise for delicately handling fragile objects, the absence of sensors has hindered their full potential to execute precise and secure grasping. To address this challenge, we present a new solution: a detachable Fiber Bragg Grating-based flexible contact force sensor to capture gripper-vegetable interactions. The sensing module was 3D printed using soft material, and the FBG fiber was attached to the module using epoxy. From evaluation tests, this lightweight sensor demonstrated a wide measurement range of up to 9.87 N, with a high sensitivity of 141.7 pm/N, good repeatability, and a hysteresis of 7.96%. Compared to commercial load cells, our sensor achieves a small measurement RMSE of 0.41 N and a percentage error of 4.15%. The sensor was integrated into two robotic 3D-printed soft grippers to enable real-time monitoring of dynamic contact force during vegetable harvesting in vertical farming scenarios. By reflecting contact status, this sensor provides a promising glimpse into the future of agricultural automation, enhancing operational efficiency and strengthening situation awareness and decision-making capabilities in vertical farms. Beyond agriculture, the versatility of this sensor extends to application in areas such as warehousing, logistics, and the food and beverage industry.