A Wireless Magnetoresistive Sensing System for an Intraoral Tongue-Computer Interface

Abstract

Tongue drive system (TDS) is a tongue-operated, minimally invasive, unobtrusive, and wireless assistive technology (AT) that infers users’ intentions by detecting their voluntary tongue motion and translating them into user-defined commands. Here we present the new intraoral version of the TDS (iTDS), which has been implemented in the form of a dental retainer. The iTDS system-on-a-chip (SoC) features a configurable analog front-end (AFE) that reads the magnetic field variations inside the mouth from four 3-axial magnetoresistive sensors located at four corners of the iTDS printed circuit board (PCB). A dual-band transmitter (Tx) on the same chip operates at 27 and 432 MHz in the Industrial/Scientific/Medical (ISM) band to allow users to switch in the presence of external interference. The Tx streams the digitized samples to a custom-designed TDS universal interface, built from commercial off-the-shelf (COTS) components, which delivers the iTDS data to other devices such as smartphones, personal computers (PC), and powered wheelchairs (PWC). Another key block on the iTDS SoC is the power management integrated circuit (PMIC), which provides individually regulated and duty-cycled 1.8 V supplies for sensors, AFE, Tx, and digital control blocks. The PMIC also charges a 50 mAh Li-ion battery with constant current up to 4.2 V, and recovers data and clock to update its configuration register through a 13.56 MHz inductive link. The iTDS SoC has been implemented in a 0.5-μm standard CMOS process and consumes 3.7 mW on average.

The Tongue Enables Computer and Wheelchair Control for People with Spinal Cord Injury

“…In comparison to previous studies with a similar setup for center-out tapping (table S3), the throughput of able-bodied participants using a mouse was slightly higher than reported here (18, 53), but in the same range considering the SD (3.66 ± 0.59). Keypad results (2.4 ± 0.6 b/s) were better for able-bodied participants than when they used regular video game controllers (51), and TDS throughput was considerably better than using head orientation or EMG commands (18).…”

“…The ergonomic design of the latest TDS headset can be found in (52). Moreover, an intraoral version of the TDS (iTDS) is under development, with the first prototype presented in (53). …”

Toward an Ultralow-Power Onboard Processor for Tongue Drive System

“…Similar to the previous versions, this prototype consists of four off-the-shelf three-axial magnetic sensors; a dual-band wireless transmitter, which uses OOK modulation; and the local processor. The sensors, analog front end, and transmitter have been extensively explained, in detail, in an earlier publication [10]. The local processor communicates with sensors and transmitter through a serial peripheral interface (SPI) and a 3-bit parallel interface, respectively.…”

Wireless Communication of Intraoral Devices and Its Optimal Frequency Selection

“…However, wireless communication between intraoral devices and the outside world is challenging because the transmitter, often located inside the mouth, experiences additional losses that do not exist in typical wireless communications in the air. Although wireless communication has been successfully established in several intraoral devices [8]-[12], researchers focused on the system operation without the in-depth study of the wireless communication. There were a few approaches to characterize antennas working inside the mouth [13], [14].…”

“…The iTDS is a new assistive technology (AT) that utilizes user-defined voluntary tongue gestures as commands [11], [12]. Since the iTDS operates inside the mouth and transmits magnetic sensor data to the outside, it uses wireless communication.…”