Layer jamming‐based soft robotic hand with variable stiffness for compliant and effective grasping

Abstract

A novel variable stiffness soft robotic hand (SRH) consists of three pieces of layer jamming structure (LJS) is proposed. The mechanism is driven by the motor-based tendon along the surface of the pieces that connect to individual gas channel. Each LJS is optimised by adhering a thin layer of hot melt adhesive and overlapping the spring steel sheet as inner layer material. It can be switched between rigid and compliant independently. The structures of variable stiffness and tendondriven lead to various deformation poses. Then the control system of SRH and the performance analysis of the LJS are introduced. Finally, the experiments are implemented to prove the superiority of the proposed LJS and the demonstrations show that the designed robotic hand has multiple configurations to successfully grasp various objects.

A Review of Mechanisms to Vary the Stiffness of Laminar Jamming Structures and Their Applications in Robotics

“…LJSs have been applied in the development of grippers [7,18,19,[43][44][45][46]. These applications aim to develop compliant grippers that can adapt their grasping postures according to object geometry without compromising the capacity to execute pinch grasps efficiently.…”

“…However, it must be taken into account that the trapezoidal pin mechanism only has one pneumatic actuator (one pin) placed at the end of the LJS; if more actuators are placed along the beam, the stiffness could increase significantly as happens with the DLJ. Table 1 also presents a mechanism that is a combination of the vacuum pressure mechanism and the mechanical interference mechanism [44]. This mechanism reaches a stiffness ratio of 26.3 and has a stiffness range that makes it useful in robotic arms.…”

Shape memory meta-laminar jamming actuators fabricated by 4D printing

“…The structure offered a better strength-to-weight ratio and stiffness change ratio between the unjammed and jammed states as compared to particle and LJ structures. Wang et al 34 developed a tendon-driven soft robotic hand with variable stiffness using an LJ structure. The single tendon driver controlled the deformation while the LJ structure independently adjusted the stiffness of the actuator components.…”

Reprogrammable soft actuation and shape-shifting via tensile jamming

“…High bending stiffness impedes large deformations and creates an undesirable rigid interface. Although all three jamming systems have been integrated with actively actuating structures like soft inflating bodies, their applications have been primarily restricted to locking shape (37,40,45,48) or varying bending angles (42,49,50). The inability to independently tune tensile stiffness impedes current jamming systems from actively regulating the surface strains of soft systems to shift shape.…”