Head-Guided Wheelchair Control System
John B. Hinkel · 2010 · Proceedings of the 12th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS 2010) · doi:10.1145/1878803.1878888
Summary
This student research paper presents a system that allows individuals without hand use to control a motorized wheelchair through simple head movements. The author identifies that existing alternative wheelchair control methods — such as sip-and-puff devices, tongue-touch keypads, and switch scanners — have significant drawbacks including invasiveness, cost, and the potential to inhibit speech. The system consists of three components: a headset with an accelerometer mounted on an adjustable headband, a joystick control module that mechanically interfaces with the wheelchair's existing joystick, and a custom program that translates head movements into servomotor commands. The joystick control module uses an X-Y table design — two perpendicular plates mounted on ball-bearing miniature drawer slides, each controlled by a servomotor. Tilting the head forward/backward moves the bottom plate (Y-axis), moving the wheelchair forward/backward. Tilting left/right moves the top plate (X-axis), steering left/right. Diagonal head tilts combine both axes for diagonal movement.
Key findings
The system successfully met most of its design criteria. The program can distinguish voluntary directional head movements from involuntary ones, activating servomotors only for intentional control inputs. A critical safety feature is the emergency stop function: when the user's head tilts beyond a set point (indicating the user may have fallen unconscious), the accelerometer triggers the servomotors to return to neutral position, stopping all wheelchair motion immediately. Users can customize sensitivity through track bars that adjust servo velocity and acceleration, and a checkbox allows disabling wheelchair control for freedom of head movement when not navigating. The module is designed to attach over the wheelchair's existing joystick without permanent modifications, making installation and removal straightforward. The prototype is heavier than originally planned and not yet as compact as desired due to custom fabrication limitations — professional manufacturing with lighter materials would reduce size and weight. The system costs less than or is comparable to existing commercial alternatives. Personal experience by the author confirmed the system is very easy to learn and control.
Relevance
This project addresses a real and ongoing need for affordable, non-invasive wheelchair control alternatives for people with quadriplegia, stroke, cerebral palsy, amputations, and mild Parkinson's. The key design principle — interfacing mechanically with the existing joystick rather than replacing the wheelchair's electronic control system — is notable because it makes the system compatible with any joystick-controlled wheelchair without voiding warranties or requiring specialized installation. For accessibility practitioners and rehabilitation engineers, the emergency stop feature represents an essential safety consideration that is sometimes overlooked in alternative control systems. While commercial head-controlled wheelchair systems have advanced considerably since 2010, the emphasis on non-invasiveness (no surgical implants, no oral devices), ease of installation, affordability, and the ability to toggle control on and off remain important design principles for assistive mobility technology.
Tags: power wheelchair · head tracking · motor impairment · alternative input · assistive technology · quadriplegia