Inspired by the dexterous handling ability of an elephant's trunk, we propose a pneumatic actuator that generates diverse bending and extension motions in a flexible arm. The actuator consists of two flexible tubes. Each flexible tube is restrained by a single string with variable length and tilt angle. Even if a single tube can perform only three simple types of motions (bending, extension, and helical), a variety of complex bending patterns can be created by arranging a pair of tubes in parallel and making the restraint variable. This performance takes advantage of the effect of the superposition of forces by arranging two tubes to constructively interfere with each other. This paper described six resulting pose patterns. First, the configuration and operating principle are described, and the fabrication method is explained. Next, two mathematical models and four finite element method-based analyses are introduced to predict the tip position changes in five motion patterns. All the models were validated through experiments. Finally, we experimentally demonstrated that the prototype SEMI-TRUNK can realize the action of grabbing a bottle and pouring water, verifying the effectiveness of the proposed method.

Conventional robots based on separate joints do not always perform well in complex real-world tasks, particularly those that involve the dexterous manipulation of objects. Some roboticists have thus been trying to devise continuum robots, robotic platforms characterized by infinite degrees of freedom and no fixed number of joints. Continuum robots are typically based on cables or other deformable components that can move more freely and are not restricted by fixed joint structures. Despite these advantages, many continuum robot designs proposed still cannot yet efficiently navigate complex and unstructured environments. Researchers at Sun Yat-Sen University, Dalian University of Technology and London South Bank University have recently developed a new continuum robot inspired by the trunks of elephants.

Elephant trunks may be one of the most sensitive body parts in the animal kingdom. Michael Brecht at the Bernstein Center for Computational Neuroscience in Berlin and his colleagues dissected the heads of three Asian elephants (Elephas maximus) and five African bush elephants (Loxodonta africana). All the animals had lived in zoos and died of natural causes or had been euthanised because of severe health problems. These dissections are rare because the procedure is difficult. "The head of an elephant with the trunk and everything is about 600 kilograms," Brecht says.

The Army is paying for investigations on the physics of elephant trunks -- and researchers say these versatile appendages may hold clues for designing better soft-bodied robots.