Text Entry by Raising the Eyebrow with HaMCoS
Torsten Felzer, Stephan Rinderknecht · 2014 · ASSETS '14: Proceedings of the 16th International ACM SIGACCESS Conference on Computers & Accessibility · doi:10.1145/2661334.2661418
Summary
This demo paper presents HaMCoS (HAnds-free Mouse COntrol System), a system that enables text entry for people with very severe physical disabilities using tiny contractions of the brow muscle. The system targets users in a "locked-in" state, where communication with the outside world using physical abilities is nearly impossible except for control over a single facial muscle. A piezoelectric sensor attached to the user's forehead with an elastic sports headband detects intentional muscle contractions through electromechanical coupling, translating them into two types of input signals: single contractions and double contractions (two signals in quick succession). The system uses a five-state finite state machine to emulate complete two-button mouse functionality from these minimal inputs, allowing the pointer to move in four cardinal directions.
Key findings
The demo showcases four distinct text entry methods built on the same eyebrow-contraction input: (1) an on-screen keyboard operated via mouse emulation, (2) an ambiguous keyboard similar to phone keypads where multiple letters share keys and word prediction disambiguates input, (3) scanning-based text entry where options are highlighted sequentially, and (4) additional auxiliary text entry applications. All four methods achieve functional text input from a single binary muscle signal. The system demonstrates that even users with only one controllable muscle can achieve meaningful computer interaction and communication through carefully designed input translation and text prediction.
Relevance
This work addresses one of the most extreme accessibility challenges: providing computer access to people who retain control over only a single muscle. For practitioners, it demonstrates that effective assistive technology can be built from low-cost hardware (a piezoelectric sensor and headband) combined with clever software design. The approach of translating minimal binary input into full mouse and keyboard functionality through finite state machines and word prediction has broad implications for designing interfaces for users with severe motor impairments, including those with ALS, advanced muscular dystrophy, or brainstem stroke. While this is a short demo paper, it illustrates important principles for switch-access interface design.
Tags: assistive technology · text entry · switch access · motor impairments · mouse emulation · locked-in syndrome · input devices