The Gest-Rest: A Pressure-Sensitive Chairable Input Pad for Power Wheelchair Armrests
Patrick Carrington, Amy Hurst, Shaun K. Kane · 2014 · Proceedings of the 16th International ACM SIGACCESS Conference on Computers & Accessibility (ASSETS) · doi:10.1145/2661334.2661374
Summary
This paper introduces the Gest-Rest, a pressure-sensitive input device designed to fit over a standard power wheelchair armrest, enabling users to perform touch and gesture interactions without needing to reach for or hold a separate device. The concept builds on the authors' prior work coining "chairable" technology — input devices designed to integrate with a wheelchair's form, analogous to how wearable technology fits with clothing. Power wheelchair users face unique interaction challenges: the wheelchair frame restricts range of motion, touchscreens are difficult to hold or reach, and many custom assistive solutions draw unwanted attention. Traditional switch interfaces support only binary (on/off) input, limiting expressiveness. The Gest-Rest addresses these limitations by using a 3x4 array of FlexiForce A201 Force Sensitive Resistors (FSRs) embedded in a fabric sleeve (approximately 5cm x 8cm sensing area) attached to the armrest with adhesive tape. The hardware connects to an Arduino Mega ADK board via USB to a laptop, costing approximately US in materials. The system supports 26 gestures across three categories: tap/press gestures (single, double, triple press; short, medium, long press-and-hold), directional gestures (flick, swipe, drag in four cardinal directions), and five pressure-based gestures unique to the armrest form factor (squeeze, roll, punch, lift, and rock). Because the Gest-Rest senses pressure rather than capacitive touch, users can interact with any part of their hand, arm, or body — fingers, palm, back of hand, wrist, or fist — unlike standard touchscreens that require fingertip contact.
Key findings
A formative evaluation with nine wheelchair users (seven power, two manual; all male, ages 18-47, recruited from a spinal cord injury clinic) and three clinicians (one physical therapist, two occupational therapists) tested the gesture set. All participants could perform gestures using the Gest-Rest, but with varying difficulty. Manual wheelchair users (who had full hand function) rated all gestures as easy, while power wheelchair users showed more diverse ratings reflecting their individual motor abilities. Key challenges included: uncertainty about appropriate pressure levels (all seven power wheelchair users were unsure how firmly to press), difficulty with specific directions depending on individual motor patterns (e.g., one participant struggled with gestures toward the left and up), and the gesture recognizer's sensitivity settings not matching users' pressure ranges. No power wheelchair user could squeeze the armrest, and some had difficulty with rolling their wrists. Participants suggested novel gestures including edge sliding (to toggle phone display), rhythmic tapping (for authentication), palm swiping, and drawing letter shapes. The most desired application was using the Gest-Rest as a command centre for environmental controls (lights, fans, doors), and participants also valued it as an alternative to speech input. Therapists identified the ideal user population as people with moderate spinal injuries (C3-C5), suggested placing sensors at additional body locations (elbows, shoulders), and recommended adding haptic or visual feedback to confirm gesture recognition. Participants wanted the device surface flush with the armrest and made from matching materials.
Relevance
The Gest-Rest introduces an important concept for assistive technology design: "chairable" input — devices integrated into wheelchair form rather than requiring users to adapt to external devices. This matters because power wheelchair users spend most of their waking hours in their chairs, making the wheelchair the most consistent and accessible interaction platform available to them. For accessibility practitioners, several design insights stand out. First, pressure-sensitive input offers advantages over capacitive touchscreens for users with motor impairments: it works with any body surface (not just fingertips), can detect input from users with very limited pressure, and allows resting a hand on the surface without triggering accidental input. Second, the shift from switches (binary input) to gesture-and-pressure input (continuous, multi-dimensional) dramatically increases the number of possible interactions available from a single device location — potentially replacing multiple switches. Third, individual differences in motor ability mean that no fixed gesture set or pressure threshold works for all users; customisable sensitivity and personalised gesture recognition are essential. The concept of the wheelchair as a computing platform — a "command centre" for environmental control, communication, and device interaction — reflects the lived reality that for many power wheelchair users, the chair is their primary interface with the physical world.
Tags: wheelchair accessibility · alternative input · gesture interaction · motor disability · pressure input · assistive technology · chairable technology · spinal cord injury