Design and Analysis of a Robust, Low-cost, Highly Articulated manipulator enabled by jamming of granular media

Abstract

Abstract-Hyper-redundant manipulators can be fragile, expensive, and limited in their flexibility due to the distributed and bulky actuators that are typically used to achieve the precision and degrees of freedom (DOFs) required. Here, a manipulator is proposed that is robust, high-force, low-cost, and highly articulated without employing traditional actuators mounted at the manipulator joints. Rather, local tunable stiffness is coupled with off-board spooler motors and tension cables to achieve complex manipulator configurations. Tunable stiffness is achieved by reversible jamming of granular media, which-by applying a vacuum to enclosed grainscauses the grains to transition between solid-like states and liquid-like ones. Experimental studies were conducted to identify grains with high strength-to-weight performance. A prototype of the manipulator is presented with performance analysis, with emphasis on speed, strength, and articulation. This novel design for a manipulator-and use of jamming for robotic applications in general-could greatly benefit applications such as human-safe robotics and systems in which robots need to exhibit high flexibility to conform to their environments. [6], and to create a variable stiffness endoscopic tube [7]. The combination of these projects highlights the primary benefits of utilizing jamming for robotics:it allows robots to be more human-safe, inexpensive, and robust compared to most technologies that have traditionally been used for such applications.The goal of this paper is to further the use and understanding of jamming for engineering applications. Specifically, we present the design and analysis of a robotic manipulator composed of 1) serial modules that can transition between rigid and flexible states via jamming and 2) tension cables running along the length of the manipulator and whose lengths are controlled by spooler motors. We previously demonstrated this robotic architecture of coupling locally tunable stiffness with global actuation as a thrust toward soft robotics [8] [9]. One of the main benefits of this type of system is that by eliminating the need for distributed-and often rigid and bulky-actuators throughout the robot, the system can be more robust and flexible, enabling it to conform to its environment better. In addition, the cost of the robot can be drastically reduced.In this paper we also begin to explore how grain properties affect the performance of jammed systems. Specifically, we seek to maximize the strength-to-weight ratio of jammed systems. This is an important figure of merit for manipulators, where the robot must be able to support its own weight in addition to any payloads.Because granular systems inherently lack mechanical structure in their unjammed states, their flexibility and high DOFs can be beneficial for hyper-redundant robotic systems such as a manipulator. Most approaches in hyper-redundant robotics have involved employing distributed and rigid pneumatic or electromagnetic actuators. Much of the effort in this area has been in dev...

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