Identification of Danger State for Grasping Delicate Tofu with Fingertips Containing Viscoelastic Fluid

In this study, we experimentally investigated the process leading to fracture in tofu grasping by deformable fingertips filled with a fluid. In our previous papers [1, 2], we developed deformable fingertips using a rubber bag filled with a viscoelastic fluid, and presented a strategy for delicate tofu grasping without any advance knowledge about fracture. However, the predication point was close to fracture, and the prediction was then still a gamble. In order to realize fracture prediction at an earlier stage, we examined the process leading to fracture when pushing tofu by the deformable fingertips. The stiffness of the fingertips can be controlled with the pressure of the fluid inside the fingertips. The pushing force and fluid pressure were examined for different levels of stiffness of the fingertips. The main findings and contributions are as follows. 1) The convergence of the ratio of the contact force to fluid pressure gives an indication of dent occurrence. This convergence could be seen when fingertip rubber bag was not filled (low stiffness). 2) It was easier for a dent to occur when the fingertip rubber bag was not filled than when it was filled (high stiffness). 3) Changes in the rate of increase of the fluid pressure as the tofu was pushed were repeatedly observed. We defined this as a phase change and present a method for detecting such changes. The phase change points were detected by comparing the fitting accuracies of different approximation models. 4) The last and second to the last phase changes before fracture were detected by detecting the first phase change (after the convergence of the rate of the contact force to fluid pressure if the fingertip bag was not completely filled). The detected points can be regarded as alert points indicating a fracture risk that is not close to the fracture point. © 2015 IEEE.IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2015; Congress Center Hamburg (CCH)Messeplatz 1Hamburg; Germany; 28 September 2015 through 2 October 2015; Category numberCFP15IRO-ART; Code 11788

New Condition for Tofu Stable Grasping with Fluid Fingertips

Tofu shows the following compression behavior. First, the behavior is non-linear; subsequently, the behavior becomes elastic/linear, followed by yielding and fracture. A linear behavior indicates that there is no fracture, but further increase of compression can cause yielding or fracture. The compression in the region of linear behavior then can be regarded as maximum. With this in mind, this paper presented a grasping condition of controlling the amount of compression so that the compression behavior can be linear. This condition is applied to the previously proposed fluid fingertip that utilizes a rubber bag filled with a viscoelastic fluid and having a rigid layer inside the fluid. In addition, this paper presents a methodology for checking whether the grasping condition is held, based on our previously developed phase change detection method of comparing the fitting accuracies of different approximation models. Additionally, this paper presents the reason behind the behavioral change of fluid pressure. Before phase change, the fluid fingertip behaves like a rigid fingertip, while after phase change, the contact pressure is transmitted to the fluid pressure and can be observed by the fluid pressure. The validity of the approach was shown through experiments

Variable-grasping-mode underactuated soft gripper with environmental contact-based operation

A novel robotic gripper with soft surfaces and underactuated joints was proposed. The soft surface was fabricated from a deformable rubber bag filled with incompressible fluid and a microgripper inside the fluid. A ratchet was installed at the underactuated joint so that the joint\u27s rotation caused by contact with an environment, such as a supporting surface, can be preserved, and the actions of scooping and enveloping an object are realized. With one actuator, the gripper realized three modes, i.e., parallel gripper, pinching, and enveloping. The range of graspable objects was wide and included soft, rigid, deformable, fragile, small (boundary length less than 30 mm), large (more than 80 mm long), thin (less than 0.5 mm), and heavy (more than 3 kg) objects.INSPEC Accession Number: 1671251

Bent sheet grasping stability for sheet manipulation

[email protected] this study, we focused on sheet manipulation with robotic hands. This manipulation involves grasping the sides of the sheet and utilizing the convex area resulting from bending the sheet. This sheet manipulation requires the development of a model of a bent sheet grasped with fingertips. We investigated the relationship between the grasping force and bending of the sheet and developed a bent sheet model. We also performed experiments on the sheet grasping stability with a focus on the resistible force, which is defined as the maximum external force at which a fingertip can maintain contact when applying an external force. The main findings and contributions are as follows. 1) After the sheet buckles, the grasping force only increases slightly even if the fingertip pressure is increased. 2) The range of the applicable grasping forces depends on the stiffness of the fingertips. Stiffer fingertips cannot provide a small grasping force but can resist large external forces. Softer fingertips can provide a small grasping force but cannot resist large external forces. 3) A grasping strategy for sheet manipulation is presented that is based on controlling the stiffness of the fingertips. © 2016 IEEE

Incompressible Liquid Based Force Sensible Silicone Retractor Attachable to Surgical Suction Instruments

This paper presents a silicone retractor, which is a continuation and extension of a previously developed system that had the same three functions as the old version: 1) retracting, 2) suction, and 3) force sensing. These features make the retractor a safe choice for use in neurosurgery. Suction is achieved by attaching the retractor to a suction pipe. The retractor has a deformation area filled with an incompressible liquid that is displaced in proportion to the extent of deformation; fiberscopes or human eyes detecting the displacement get a visual representation of the force. The new design improves on the old one in three ways—miniaturization, made possible by the incompressible-liquid-based mechanism, and measurement of force distribution by distribution of the areas deformed by force. The system was validated by conducting experiments