Assistive Input Device for Users with Limb Impairments

Abstract

Individuals with severe limb impairments encounter substantial barriers during human‑computer interaction, while commercially available assistive input devices are often prohibitively expensive. This paper presents a low‑cost wearable assistive input device (bill‑of‑materials cost < ¥130) built around the nRF52832 Bluetooth‑Low‑Energy (BLE) system‑on‑chip and an MPU‑6050 inertial measurement unit. A real‑time‑clock‑based asynchronous event‑driven architecture reduces power consumption, and the sensor's on‑chip 5 Hz digital low‑pass filter suppresses involuntary muscle tremor at the signal source. A multi‑threaded PC‑side client maps real‑time posture data to discrete keyboard commands. A user study with three participants exhibiting distinct physiological profiles was carried out under two interaction modes. In discrete click‑trigger mode, the system achieved a peak directional‑selection throughput of 12 WPM, while continuous dwell‑hold control yielded an average throughput of 4.2 WPM. The participant with a full, unrestricted range‑of‑motion (ROM) reached a trigger accuracy of 98.2 %, whereas the participant with severely‑restricted head movement obtained only 64.0 % accuracy. Experimental results demonstrate that fixed‑cutoff on‑chip filtering carries inherent performance limitations for users with extremely limited motion range. Directions for future work include adaptive filtering algorithms and multi‑modal interaction schemes.