tacTiles: Low-Cost, Room-Scale Tactile Sensing (2010)

As my Master’s thesis (in computer science, Ambient Intelligence Group, Bielefeld University), I developed 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 occlusions and privacy implications. The system outputs its reading through a USB-Video-Stream (UVC) like a webcam, allowing analysis with a computer vision toolchain.

The sensor grid is based on conductive paper, laser-cut to form a force sensing resistor (FSR) matrix (illustrated below), making it very cheap to reproduce materials-wise. An array of modules, based on a custom AVR 8-Bit microcontroller board, are read out by an AVR32 master controller, based on myrmex). The modules can be arranged flexibly around areas of interest.

Smart environment with example module placements

Smart environment with example module placements

Smart environment with example module placements

Topics

  • Human Computer Interaction
  • Physical Computing
  • Smart Environments
  • Sensor R&D / Evaluation

Methods

  • PCB design and assembly
  • CAD, Lasercutting
  • Arduino, AVR-C
  • Processing (Visualization)
  • G-Code (for Linear Table)

Paper-FSR Construction

Conductive Art Paper

Paper FSR Principle (all layers from paper)

Cut to squares...

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

...layed out in Lines...

...and layers.

tacTiles V1 Top View

tactiles V1 Bottom View

User standing on two V1

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.

We also evaluated sensor characteristics and using a single sided design, similar to commercial FSRs.

Evaluation force response and durability with linear table and strain gauge.

Second Prototype: Fully Modular Tiles

Top

Bottom

Top Detail

Bottom Detail

Strain relief for solder joints

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.

Publications

  • Diplomarbeit Informatik (equivalent Master’s thesis in Computer Science): “Development and Application of Tactile Surfaces for Smart Environments”, 2009, Bielefeld University
  • HAID'09: Anlauff J., Hermann T., Großhauser T., Cooperstock J. R. (2009) Modular tacTiles for Sonic Interactions with Smart Environments. In: Proceedings of the 4th International Conference on Haptic and Audio Design / Lecture Notes on Computer Science, Volume 5763. Altinoy E., Jekosch U., Brewster S. (Eds); , 2. Berlin, Heidelberg: Springer. (Poster, Media)
  • 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). (Paper, Media)