tacTiles - Low-Cost, Room-Scale Tactile Sensing

tacTiles second generation

My Master’s thesis in computer science at the Ambient Intelligence Group, Bielefeld University, was the development of a modular, low-cost tactile sensing system to detect user’s presence and activity in a smart environment through pressure-sensing floor tiles. With a spatial resolution of 5 cm, it could detect steps and their ground-force characteristics. The goals was to substitute or complement visual tracking, often problematic due to visual occlusion and due to privacy implications. The system outputs its reading through a USB-Video-Stream (UVC, like a webcam), allowing analysis through with a computer vision toolchain. The modules are based on a custom AVR 8-Bit microcontroller board, read out by an AVR32 master controller (based on Carsten Schürmann’s myrmex project). The sensor grid is based on conductive paper, laser-cut to form a force sensing resistor matrix, making it very cheap to reproduce materials-wise.

FSR Principle (all layers from paper)
Smart environment with example module placements
Smart environment with example module placements

Published as Diplomarbeit, and at NordiCHI’10: Anlauff, J., Großhauser, T., & Hermann, T. (2010, October). tacTiles: a low-cost modular tactile sensing system for floor interactions. In Proceedings of the 6th Nordic Conference on Human-Computer Interaction: Extending Boundaries (pp. 591-594).

Skills: Embedded programming (AVR-C), Processing for Visualization. G-Code for Linear Table. Lasercutting, PCB design and, assembly for second generation.

Paper-FSR Construction

Conductive Art Paper
Cut to squares
Layed out in Lines
and layers.

The operating principle of the sensor cells is based similar to that of a force sensing resistor, with all layers made from conductive, carbon art paper of two different resistances.

First two 8x8 Prototypes

V1 top
V1 bot
User standing on two V1
Evaluation force response and durability with linear table and strain gauge.</span>
The first prototypes were completely hand-built and connected directly to a PC. We evaluated force response and durability with a linear table and a strain gauge. Mechanical adapters were CNC-milled.

Second, fully modular Prototypes

Top
Bottom
Top Detail
Bottom Detail
The goal of the second generation was a modular setup, that could be arranged freely and reproduced more easily. We laser-cut the paper and CNC-milled the support "puzzle" pieces, and designed and manufactured a PCB for the sensor readout for each module.