Design and analysis of a variable-stiffness robotic gripper

This paper presents the design and analysis of a novel variable-stiffness robotic gripper, the RobInLab VS gripper. The purpose is to have a gripper that is strong and reliable as rigid grippers but adaptable as soft grippers. This is achieved by designing modular fingers that combine a jamming material core with an external structure, made with rigid and flexible materials. This allows the finger to softly adapt to object shapes when the capsule is not active, but becomes rigid when air suction is applied. A three-finger gripper prototype was built using this approach. Its validity and performance are evaluated using five experimental benchmark tests implemented exclusively to measure variable-stiffness grippers. To complete the analysis, our gripper is compared with an alternative gripper built by following a relevant state-of-the-art design. Our results suggest that our solution significantly outperforms previous approaches using similar variable stiffness designs, with a significantly higher grasping force, combining a good shape adaptability with a simpler and more robust design.This paper describes research conducted at UJI Robotic Intelligence Laboratory. Support for this laboratory is provided in part by Ministerio de Ciencia e Innnovación (DPI2015-69041-R and DPI2017-89910-R), by Universitat Jaume I (UJI-B2018-74), and by Generalitat Valenciana (PROMETEO/2020/034)

Non-Destructive Robotic Assessment of Mango Ripeness via Multi-Point Soft Haptics

To match the ever increasing standards of fresh products, and the need to reduce waste, we devise an alternative to the destructive and highly variable fruit ripeness estimation by a penetrometer. We propose a fully automatic method to assess the ripeness of mango which is non-destructive, allows the user to test multiple surface areas with a single touch and is capable of dissociating between ripe and non-ripe fruits. A custom-made gripper equipped with a capacitive tactile sensor array is used to palpate the fruit. The ripeness is estimated as mango stiffness extracted through a simplified spring model. We test the framework on a set of 25 mangoes of the Keitt variety, and compare the results to penetrometer measurements. We show it is possible to correctly classify 88% of the mango without removing the skin of the fruit. The method can be a valuable substitute for non-destructive fruit ripeness testing. To the authors knowledge, this is the first robotics ripeness estimation system based on capacitive tactile sensing technologyThis work was funded by the UK Agriculture and Horticulture Development Board (CP 172), Physical Sciences Research Council (EPSRC) MOTION grant [EP/N03211X/2] and Ministerio de Econom´ıa (DPI2015- 69041-R

Design of a novel Variable-stiffness gripper Using jamming fingers

[Resumen] Este artículo aborda el diseño de una pinza de rigidez variable. Esta se utiliza para resolver un problema que surge en las tiendas en línea, en las que grandes almacenes mantienen todo el stock. En el proceso de automatización de la tarea de escoger objetos individuales, un agarre confiable es un problema importante debido a la incertidumbre de la forma y posición de los objetos. Para abordar este problema, se ha diseñado una nueva pinza de rigidez variable capaz de agarrar diferentes tipos de objetos mediante el uso y la adaptación de la tecnología del Universal Gripper en una pinza paralela de 2 dedos. Para probar la pinza, se han manipulado cinco objetos diferentes, y se compararon con otro diseño de pinza simple basado en el Festo R FinGripper. Los experimentos muestran que esta pinza, con accionamiento de rigidez variable, mejora las capacidades de agarre de una pinza sin la capacidad de rigidez variable.[Abstract] This paper addresses the design of a variable-stiffness gripper to solve a problem that arises in online retail stores, in which huge warehouses keep all the stock. In the process of automating the task of picking individual objects, reliable grasping is a major issue due to the uncertainty of the objects shape and position. To address this problem, we have designed a novel variable-stiffness gripper capable of grasping different types of objects by using and adapting the technology of the universal gripper in a 2-finger parallel gripper. To test the gripper five different objects have been lifted and manipulated with it and compared with another simple gripper design based on Festo R FinGripper. Our experiments show that this gripper, with variable-stiffness actuation, improves the grasping capabilities of a gripper without the variable-stiffness ability.Ministerio de Economía y Competitividad; DPI2015-69041-

A gripper for delicate edible manipulation

The general manipulation of delicate edible products requires of specific grippers able to firmly grasp these kind of products without damaging them. To address this problem we follow a soft and variable-stiffness approach. In this paper we design and construct successive gripper prototypes which fingers are composed of rigid and soft parts. The stiffness of the soft parts can be modified using the jamming principle. The gripper properties are experimentally evaluated using a subset of NIST benchmarks. This allows to obtain comparable and standardised results, used to improve the initial gripper design. In addition a new benchmark, the edible grasping benchmark, is proposed and used to measure the performance of the grippers while grasping fruits and vegetables. The final gripper prototype overcomes the problems observed in fruit and vegetable picking systems. It has been demonstrated in the experimental tests that the gripper has sufficient payload and adaptability to grasp several edibles without damage