Balance Belt: Vibrotactile Balance Feedback (2020)

In my Ph.D. thesis at the Shared Reality Lab of McGill University, I investigated vibrotactile feedback systems for balance feedback, specifically a belt for novel feedback mappings, and shoes (described on their own page). The belt combines four state-of-the-art voicecoil actuators and an orientation sensor, forming a test-bed for embedded or external synthesis of novel trunk-tilt feedback.

When I began working on this problem, means for embedded synthesis and wide-band tactile actuators (tactors) were scarce. Through three iterations of haptic belts, I worked towards a modular vibrotactile prototyping system for wearables, BRIX5, described on its own page.

First Prototype

In the first prototype, the main goal was to demonstrate a four-channel embedded synthesis in a self-contained belt system. For each actuator, we build a synthesis unit out of an Arduino Pro Micro running Mozzi, combined with a D-class amplifier board. A central BRIX2 controller measured trunk tilt and computed synthesis parameters, relayed to the tactor controllers through a shared serial bus. Everything was placed in fabric pouches, later replaced by 3d-printed belt-attachements for better coupling.

Second Prototype

Though functional, the first prototype was not without issues. A major issue was that programming five microcontrollers for each update cycle becomes tedious quickly. The second generation, based on a dual Teensy audio adaptor on a custom PCB with BNO055 motion/orientation sensor, allowed for rapid development cycles, and also supported connecting external signal sources through audio adapters.

Third Prototype

The second iteration worked well, but the DIY-interconnects were too fragile and time-consuming to make. We designed the BRIX5 toolkit around JST SH/Qwiic cables for a uniform interconnect, and based the third belt prototype on its modules.