Muhammad Umair Khan

Quantification of Phobia Treatment through Heart-Rate Monitoring in VR Environment Premise VR has been used for treatment of phobias like claustrophobia (fear of tight spaces), nyctophobia (fear of darkness), acrophobia (fear of heights) etc. in several researches. But there has never been a quantifiable measure of effectiveness of such treatments. In most cases, the subjects are taken through a questionnaire about how they feel after a certain number of training sessions. This method doesn’t provide a measure of degree of improvement. It has been well established that a person’s heart-rate increases in times of stress and fear. The more stress or fear a person experiences during these situations, the higher his/her heart-rate gets. Thus, the effectiveness of a treatment can be quantified through subject’s heart rate. Methodology The treatment platform consists of two parts; the virtual reality environment and the heart rate reading and analysis. VR Environment: Three sets of VR environments have been developed, one for each phobia listed above. The environments are set in the form of a game which force the user to go through varying levels of difficulty. Heart Rate Reading: To integrate real time heart rate measurement into our VR environment, a MAX30102 pulse sensor is used. This sensor works on the principle of photoplethysmography (PPG) using red and IR wavelengths. The sensor transfers an analog pulse signal to microcontroller through I2C bus. The sensor can be used on finger tips, wrist and earlobe, but the clearest signal with least amount of noise is acquired from earlobe. In order to measure heart rate, the raw pulse signal has to be processed. Different combinations of Low-Pass, Band-Pass, Peak Isolators and FFT were tested and the one with least average error and standard deviation was selected (i.e. Low-Pass filter + Nuttall Windowed FFT). Data Transmission to VR: In case of HTC Vive, an open USB port is available on the headset which can be used to provide power and UART interface to arduino. This port is connected to USB port of arduino and heart-rate data serially sent over to PC. In case, a different headset is used, the arduino has to be provided with an external power source (e.g. LiPo Battery) and the data to be sent over UART through a Bluetooth module (e.g. HC-05). In either case, baud rate has to be set accordingly. A baud rate of 115200bps or above (depending on PC’s chipset) can be achieved on the native serial port. Whereas, Bluetooth modules like HC-05 and HC06 etc. do not work properly beyond 9600bps.