PUB - Publikationen an der Universität Bielefeld

In the evolutionary scheme, insects are the most successful creatures, having entered nearly every ecological niche and adapted to special environments. Although their morphology and senses vary widely, they tend to have one organ in common: their antennae, an effective adaptable solution for interaction with the environment. The Fraunhofer IFF and Bielefeld University have developed and constructed an antenna-like tactile device for robotic walking based on the Carausius morosus or "walking stick" on a scale of 10:1. Above all, the antenna has to be a lightweight construction because it must not compromise the carrying capacity of the robot and, since the scanning motions of the antenna are fast, every bit of weight reduces the life of joints and motors. Furthermore, the device is more than a simple push-button. It detects the contact point along the antenna. Weight constraints eliminated the option of using many small sensors along the antenna (like hairs or whiskers). We opted for a single acceleration sensor. Imagine a bored student flipping a ruler on a table. The sound, more accurately the pitch, depends on the length of the ruler, i.e. the vibration frequency is related to the length. Using an acceleration sensor to measure the vibrations makes it possible to detect the contact point along the antenna. Adding the angles in the joints provides full 3-D information on the contact point. Nature is endowed with even more sophisticated features, which have not yet been fully implemented: The natural antenna consists of a special compound material and its shape is tapered, thus improving terminal vibrations. While insects do not employ this approach, they do have little hairs for sensing and these are distributed specifically. Moreover, "Johnston's organ" analyzes antenna vibrations. Ultimately, insect antennae were the archetype that inspired the development of this dependable and accurate obstacle detection device.