Author(s)

R. H. Luchsinger & M. Bräker

Abstract

Inspired by pressure driven locomotion in nature, a novel pneumatic actuator concept is presented. Based on the principle of Tensairity, the actuator consists of a conical inflated hull and a compression and a tension element that are tightly connected to the hull. The flexible compression and tension elements are stabilized by internal air pressure. Acting against gravity, a first proof of concept demonstrator weighing only 300 g is able to lift a weight of 25 N a distance of almost 70 cm with an internal air pressure of only 20 kPa. The efficiency of the actuator is studied and optimized. Possible applications of the new actuator concept are seen in locomotion, particularly in interactions with humans or fragile objects. Keywords: pneumatic actuator, Tensairity, efficiency. 1 Introduction Pressure induced stability is a common concept in nature. As an example, the green tissue of plants is stabilized by the cellular pressure. These plants start to wilt under shortage of water, which results in a reduced cellular pressure. Next to maintaining structural integrity, pressure is also used in nature for locomotion. One interesting example is the leg of the spider. It was shown by different groups that spiders stretch their legs by pumping blood from inside their body into the cavity of the long thin leg by varying the blood pressure by up to a factor of ten [1-4]. Maximal pressure values of 60 kPa have been observed. Some species can stretch their legs at speed rates that enable the spider to jump [3]. Inspired by this mechanism, the first pressure driven actuators were built [5]. A different approach to using pressure for actuators is inspired by the functionality of muscles. The so called McKibben artificial muscles are made of a tube like membrane that is reinforced by helically winded fibres [6]. Increasing

Keywords

pneumatic actuator, Tensairity, efficiency