Haptic Representation Project

Project Overview

This project aims to produce textural concepts using tribological (friction) data acquired by an artificial finger. The long term goal is to have an artificial hand explore an environment to learn and classify different textures encountered. Before this goal can be realised the textural concept generation and aquisition techniques are being developed on an artificial finger using artificial textures specifically made to examine textural features.

This webpage gives a brief overview of the current progress toward generation of artificial texture concepts.

Experimental Overview

The current equipment simulates the action of rubbing a surface with a finger. Active movement over the surfaces is replicated using a vinyl record player as the basis for the equipment. The needle has been replaced by an artififical finger, this is held still whilst artificial textures are moved underneath. Data is recorded from a microphone using a standard PC sound card for further offline analysis.

Our Finger

The finger is made out of poly-carbonate plastic using a rapid prototyping machine. A microphone was recessed into the back of the finger to record vibrations when in contact with surfaces, because the finger is recessed ambient noise levels picked up are reduced. To boost the signal to noise ratio a pre-amplifier was positioned as close to the microphone as possible, and this results in very strong signals from direct contacts with the finger.

Initial tests proved that the bare plastic material does not have enough friction or deformation when in contact with surfaces to adequatly record tribological data. Latex skin was added to the outside of the finger to improve the quality of recordings.

Artificial Textures

We have created a number of discs to explore surface texture using the finger. Each disc has a quantifiable shape and size, we use a collection of these discs to look at specific textural features such as height and frequency. The table linked below shows every

disc currently in use in this experiment, listing height, type and illustrating the texture with repsect to the finger. There are type main types listed, the pulse discs are simply looking at frequency of texture, whilst the square discs are based on a 2 by 2 pattern and look at height and shape.

Audio Samples

These files are samples of textures recorded by the finger and converted into audio files for download. The wav files are direct conversion from raw sound card recordings to audio files, they are as lossless as possible. The MP3 files are considerably smaller for slow download connections, but lose data below 200Hz.

Weight applied	Zero	One	Two	Three
Flat Disc	MP3 WAV			MP3 WAV
Square Pulse Disc	MP3 WAV			MP3 WAV
Chequered Pulse Disc	MP3 WAV	MP3 WAV	MP3 WAV	MP3 WAV

For more information or any comments about the haptic representation project please email to james.edwardsATbrl.ac.uk