On Alternative Uses of Structural Compliance for the Development of Adaptive Robot Grippers and Hands

Abstract

Adaptive robot hands are typically created by introducing structural compliance either in their joints (e.g., implementation of flexures joints) or in their finger-pads. In this paper, we present a series of alternative uses of structural compliance for the development of simple, adaptive, compliant and/or under-actuated robot grippers and hands that can efficiently and robustly execute a variety of grasping and dexterous, in-hand manipulation tasks. The proposed designs utilize only one actuator per finger to control multiple degrees of freedom and they retain the superior grasping capabilities of the adaptive grasping mechanisms even under significant object pose or other environmental uncertainties. More specifically, in this work, we introduce, discuss, and evaluate: (a) a design of pre-shaped, compliant robot fingers that adapts/conforms to the object geometry, (b) a hyper-adaptive finger-pad design that maximizes the area of the contact patches between the hand and the object, maximizing also grasp stability, and (c) a design that executes compliance adjustable manipulation tasks that can be predetermined by tuning the in-series compliance of the tendon routing system and by appropriately selecting the imposed tendon loads. The grippers are experimentally tested and their efficiency is validated using three different types of tests: (i) grasping tests that involve different everyday objects, (ii) grasp quality tests that estimate the contact area between the grippers and the objects grasped, and (iii) dexterous, in-hand manipulation experiments to evaluate the manipulation capabilities of the Compliance Adjustable Manipulation (CAM) hand. The devices employ mechanical adaptability to facilitate and simplify the efficient execution of robust grasping and dexterous, in-hand manipulation tasks.

Design and Implementation of a Multi-Function Gripper for Grasping General Objects

“…For certain objects to be grasped, the grasping mode and grasp contact points should be carefully selected. It is also possible to increase the grasping stability by adding an appropriate compliant structure to the fingertip because the compliance increases the ability of a gripper to conform to the shape of the object being grasped, and also increases the area of the contact patches, increasing the grasp wrench space [37]. From Figures 21 and 22, it can be found that the static equilibrium might be difficult to achieve by using only two grasping forces, especially in the case that the two fingertips are not parallel to each other.…”

Improving Robotic Manipulation Without Sacrificing Grasping Efficiency: A Multi-Modal, Adaptive Gripper With Reconfigurable Finger Bases

“…A locking mechanism is created using a solenoid valve that allows the fingers to be locked perpendicularly to the base thereby converting the gripper to act as a parallel jaw gripper. This allows the gripper to exert higher grasping forces owing to the lack of post-contact reconfiguration in parallel jaw grippers [26]. When this mechanism is not activated, the finger has a bigger aperture for caging objects more easily, like adaptive grippers [25].…”

Interdigitated Sensor Based on a Silicone Foam for Subtle Robotic Manipulation

“…The sensor concept is illustrated in Figure , with panel (a) showing the IDE with compressible foam on one side, and panel (b) showing a double configuration with foam on both sides of the electrode. In panels (c) and (d), the sensor is mounted on a rigid gripping mechanism developed by Chang et al., [ 1 ] and shows how the soft sensors conform around the target object (here a kiwi fruit), thus providing information on the applied normal force without damaging the fruit. The compliance of the sensor ensures that the closing motion of the gripper only creates a gradual increase of the grabbing pressure on the target object.…”