Replaceable Bit-based Gripper for Picking Cluttered Food Items

TL;DR

The paper tackles automated bento-box packaging by introducing a modular, belt-based gripper that uses food-specific bits to enable reliable grasping of challenging items and weight-controlled dropping. A passive belt-changing mechanism with magnetic docking supports rapid tool swaps, expanding the range of handleable foods without active actuation. Experimental results show weight-based dropping accuracies exceeding 80% for spaghetti and 95% for ikura, and the ability to release very small portions including a single spaghetti strand or a few ikura balls, along with 100% belt-change success in ~40 seconds. A packaging demonstration achieves 91.25% overall accuracy, illustrating practical potential for scalable, high-throughput automated bento box preparation. The hardware-centric approach promises robust, adaptable handling across diverse foods while maintaining precise portion control and fast tool switching, with future work aimed at speeding up operation and ensuring hygienic deployment.

Abstract

The food packaging industry goes through changes in food items and their weights quite rapidly. These items range from easy-to-pick, single-piece food items to flexible, long and cluttered ones. We propose a replaceable bit-based gripper system to tackle the challenge of weight-based handling of cluttered food items. The gripper features specialized food attachments(bits) that enhance its grasping capabilities, and a belt replacement system allows switching between different food items during packaging operations. It offers a wide range of control options, enabling it to grasp and drop specific weights of granular, cluttered, and entangled foods. We specifically designed bits for two flexible food items that differ in shape: ikura(salmon roe) and spaghetti. They represent the challenging categories of sticky, granular food and long, sticky, cluttered food, respectively. The gripper successfully picked up both spaghetti and ikura and demonstrated weight-specific dropping of these items with an accuracy over 80% and 95% respectively. The gripper system also exhibited quick switching between different bits, leading to the handling of a large range of food items.

Figures (8)

• Figure 1: Using food specific bits to pick up food (a) Spaghetti being picked up. (b) Ikura pick up. (c) Strawberry pick up. (d) Standard Japanese lunch box.
• Figure 2: (a).Gripper design (i) Two different parts of the gripper setup: Actuation unit and the Belt assembly unit. (ii) Components of the belt assembly unit. (b).Working of the gripper (i) Gripper approaches the food pile with bits pointitng towards the food for easier entry. (ii) The motors turn the belt and the bits move upwards, interacting and picking up the challenging food item. (iii) The bits ensure that the food is securely grasped and remains in place as the gripper moves away.
• Figure 3: Working of the belt assembly changer mechanism. (a) CAD of three parts of the belt assembly changing setup. (b) Image of the actual setup. (c) Docking process i.e. removing the belt assembly from the gripper and placing it at the docking station. (d) Undocking process i.e transferring the belt assembly from the docking station to the robotic arm gripper setup.
• Figure 4: Bit parameters for spaghetti(a)Individual bit inspired from a spaghetti spoon. (b)Bits positioned at 45° w.r.t the belt. (c)Bits arrangement from the top view of the gripper. (d)Bit density(low): Individual plates displaying 6mm distance between each bit. Gripper width is 30mm. (e)Bit parameters for ikura. (f)Distance of 25mm between each ikura bit.
• Figure 5: Setup for weight-based drop experiment: Salmon roe(Ikura) and spaghetti(not in image) being picked up and dropped according to required weight. Nextage open arm and a digital weighing scale being employed.