Design and Analysis of a Multimodal Grasper Having Shape Conformity and Within-Hand Manipulation With Adjustable Contact Forces

Abstract

This paper presents the design, analysis, and testing of a novel multimodal grasper having the capabilities of shape conformation, within-hand manipulation, and a built-in compact mechanism to vary the forces at the contact surface. The proposed grasper has two important qualities: versatility and less complexity. The former refers to the ability to grasp a range of objects having different geometrical shape, size, and payload and perform in-hand manipulations such as rolling and sliding, and the latter refers to the uncomplicated design, and ease of planning and control strategies. Increasing the number of functions performed by the grasper to adapt to a variety of tasks in structured and unstructured environments without increasing the mechanical complexity is the main interest of this research. The proposed grasper consists of two hybrid jaws having a rigid inner structure encompassed by a flexible, active gripping surface. The flexibility of the active surface has been exploited to achieve shape conformation, and the same has been utilized with a compact mechanism, introduced in the jaws, to vary the contact forces while grasping and manipulating an object. Simple and scalable structure, compactness, low cost, and simple control scheme are the main features of the proposed design. Detailed kinematic and static analysis are presented to show the capability of the grasper to adjust and estimate the contact forces without using a force sensor. Experiments are conducted on the fabricated prototype to validate the different modes of operation and to evaluate the advantages of the proposed concept.

Vision-Based In-Hand Manipulation for Variously Shaped and Sized Objects by a Robotic Gripper With Active Surfaces

“…The results of manipulation under this condition represent to the capabilities just using active surfaces (especially belts) alone. Comparing the performance of the proposed method with this baseline is equivalent to comparison with the works in [5], [21], [22], [28]- [31]. The proposed method differs in considering all challenging situations represented in Section III: when the object is easy to drop and is difficult to rotate.…”

“…Because of the adaptability of the underactuated design, IHM can be repeatedly achieved without a priori knowledge about the object. Govindan et al [31] also created a unique hand with belts on two fingers that can be deflected to a large extent. Because the deflection passively varies according to the object shape, the hand fully envelopes and stably grasps the object.…”

“…The vertical blue arrows represent the friction forces, and the arced blue arrow is the moment from them. In the strategy on the right, the belts are deflected or deformed as in [31], [32]. The tension from the deflected belts or the force from the expanded contact region due to deformation (the vertical blue arrows) can produce the rotation (the arced blue arrow) in the direction drawn in the figure.…”

“…Circle 360° [ 8]- [11], [18]- [20] [27]- [29], [31], [32] Square 360° [ 8], [10], [11], [15]- [17] [19], [20], [24]- [26], [28] Rectangle (4:3) 90° [20], [ 3) Details of the tested samples…”

Adaptive Underactuated Finger With Active Rolling Surface

“…Going beyond industrial end-effectors [10]- [13], researchers have proposed innovative end-effector designs that have the capability to maintain a stable grasp and, at the same time, manipulate objects in-hand. In [14], a gripper is made of multiple fingers with tension-controllable conveyor belts stretched along with each one. These active surfaces provide tangential forces that allow in-hand manipulation of objects with a variety of shapes by a rotational movement.…”