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Architecture

A project log for Hand Tremor Suppression Wearable Device

We propose an innovative medical wearable device to assist people who suffer from hand tremor (Parkinson's Disease, Essential Tremor etc).

bikias.thomas 09/02/2017 at 17:400 Comments

Tremor Suppression Module

Our tremor suppression module consists of a smartphone/smartwatch that connects with the Microsoft Azure, along with a custom-made device, which is designed to detect the involuntary activation of agonist muscles and activate the antagonist muscles and vice versa. Thus, by detecting the involuntary movement and producing the opposite one, we manage to reduce tremor and stabilize the hand (Fig. 3).

Tremor analysis: Tremor characteristics, amplitude and frequency, are primary quantitative clinical factors for monitoring of tremors. We implemented an algorithm for tracking the frequency and amplitude of tremor from inertial sensor measurements (3 axis gyroscope & accelerometer). The algorithm has as initial value the patient’s tremor fundamental frequency, which is normally measured during a clinical diagnostic procedure. The output adapts to the current dominant tremor frequency based on the measurements of the gyroscope. The adaptation is done after the application of a noise-reduction filter, in order to avoid fast changes in the estimated frequency.

Device Functionality: Our team is building a fully functional autonomous battery-powered wearable device which is still in the prototype stage. Its main function is to detect the involuntary tremulous movement, using data from a 3-axis gyroscope & accelerometer and deliver electrical stimulations through small electrode pads, in order to reduce tremor. For that purpose, we developed an algorithm that is able to make real time decisions and efficiently stimulate the opposite muscles of the ones activated due to tremor, achieving significantly high tremor suppression (Fig.3).

Safety: The aim of TremorFreeMe is to provide an above-identified electrical stimulation device that avoids the drawbacks of known stimulation devices and allows for simple and quick application and safe stimulation even over several days. The voltage supply is provided from a 3.7V lipo battery. The muscle stimulation is achieved under 10-25mA biphasic current pulses of 30-50μs duration. It is completely safe, even in a short circuit situation, (that can be caused by water throwing) since the 22μF capacitor cannot discharge any dangerous current and the two 30mA fuses prevent any unwanted current flow above 30mA by shutting down the whole system. The battery has been tested at its maximum discharge rate by connecting both poles. Biphasic current pulses are used to avoid any skin irritation that can happen from one way current flow.

User’s Interface: Android application for Mobile or Android Wear, that communicates and controls TremorFreeMe Device, via Bluetooth, by switching it on-off and adjusting the intensity of the pulses  (Fig.5). The app is based on background tasks, always taking into consideration low battery consumption and Internet connectivity. More specifically, while online, application sends the parameters (velocity, time in period) to azure ML to achieve the First-level Personalization. Moreover, if a similar and effective patients-model found, user will be notified and will be prompted to update his current model for better suppression results (Users’ Classification (Second-level Personalization)). In order to use the application, every user must register and submit some personal and medical information. TremorFreeMe application, automatically and locally, saves data and user’s preferences. This way, users can use the application offline and their data will be auto-synced when device can access the Internet.

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