The head mouse — Head gaze estimation "In-the-Wild" with low-cost inertial sensors for BMI use

We present a wearable head-tracking device using inexpensive inertial sensors as an alternative head movement tracking system. This can be used as indicator of human movement intentions for Brain-Machine Interface (BMI) applications. Our system is capable of tracking head movements at high rates (100 Hz) and achieves R² = 0.99 with a 2.5° RMSE against a ground-truth motion tracking system. The system tracks head movements over periods in the order of tens of minutes with little drift. The accuracy and precision of our system, together with its low response latency of ≈ 20 ms make it an unconventional but effective system for human-computer interfacing: the "head mouse" controls the mouse cursor on a display based on head orientation alone, so that it matches the centre of a straight-onward looking user. Our head mouse is suitable for amputees and spinal chord injury patients who have lost control of their upper extremities. We show that naive test subjects are capable to write text using our system and an on-screen keyboard at a rate of 4.65 words/minute, compared to able bodied users using a physical computer mouse which reached 7.85 words/minute. Crucially we measure the natural head movements of able bodied computer users, and show that our approach falls within the range of natural head movement parameters.