Design and Workspace Characterisation of Malleable Robots

TL;DR

This paper introduces a 2-DOF malleable robot with variable stiffness links, enabling adaptable workspaces without increasing joint count, and provides a mathematical framework for workspace analysis and characterization.

Contribution

The paper presents the design, prototyping, and workspace characterization of a novel 2-DOF malleable robot with variable topology and reconfigurable workspaces.

Findings

The robot can achieve an infinite number of workspaces through reconfiguration.

A general workspace equation based on distance geometry is derived.

Experimental motion tracking demonstrates workspace versatility.

Abstract

For the majority of tasks performed by traditional serial robot arms, such as bin picking or pick and place, only two or three degrees of freedom (DOF) are required for motion; however, by augmenting the number of degrees of freedom, further dexterity of robot arms for multiple tasks can be achieved. Instead of increasing the number of joints of a robot to improve flexibility and adaptation, which increases control complexity, weight, and cost of the overall system, malleable robots utilise a variable stiffness link between joints allowing the relative positioning of the revolute pairs at each end of the link to vary, thus enabling a low DOF serial robot to adapt across tasks by varying its workspace. In this paper, we present the design and prototyping of a 2-DOF malleable robot, calculate the general equation of its workspace using a parameterisation based on distance geometry---suitable for robot arms of variable topology, and characterise the workspace categories that the end effector of the robot can trace via reconfiguration. Through the design and construction of the malleable robot we explore design considerations, and demonstrate the viability of the overall concept. By using motion tracking on the physical robot, we show examples of the infinite number of workspaces that the introduced 2-DOF malleable robot can achieve.