CHAPTER 2. LITERATURE REVIEW
2.1 Wearable Devices
wearable devices, emotion recognition in wearable devices, and the service design of baby boomers are elaborated in order to build the fundamental as the required to
Heppelmann, 2015). They say that monitoring comprehensively consists of the product’s condition, the external environment, the product’s operation and usage;
control personally consists of the product’s functions and user experience;
optimization is a stage that algorithms can enhance product performance and allow predictive service; autonomy is a stage that allows autonomous product operation, self-coordination of operation with other products and systems and autonomous product enhancement and personalization. Wearable device is aimed to find more valuable information in physical data with the help of sensors. As they mention, wearable devices can offer and create much more value in the digital environment.
As Park et.al (2014) review, wearables perform five basic functions or unit operations in each scenario, respectively are sense, process (analyze), transmit, apply (utilize), especially processing may occur at a remote location (see as Figure 2.1). A sensor is defined as “a device used to detect, locate, or quantify energy or matter, giving a signal for the detection of a physical or chemical property to which the device responds” (Kress-Roger, 1997). But not all sensors can be easily worn, so there are eight key attributes in an ideal wearable device. On the one hand, from the view of physics, it should be lightweight, aesthetically pleasing, invisible and shape conformable. On the other hand, from the view of function, it should be multi-functional, configurable, responsive and bandwidth. In our research, we use two
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available products – “Fitbit” and “Spire”, to design our services.
Figure 2.1 Unit Operations in Obtaining Situational Awareness (Park et.al, 2014) We collect the information about available devices in the market, and summary them in Table 2.1.
Table 2.1 The available wearable devices in the market
BRAND FITBIT APPLE SPIRE GARMIN XIAOMI
MODEL Surge vivosmart
TYPE Watch Watch Stone Wristband Wristban
OPERATION TIME 7 days 1day 7 days 7 days 30 days
WASHER-PROOF YES YES
SENSOR Heart rate YES YES YES YES *1
3-aixs accelerom eter/ gyro
YES YES YES YES YES
WIRELESS Bluetooth YES YES YES YES YES
FUNCTION Activity Tracker
YES YES YES
YES YES *2 YES
‧download additional apps from App Store.）
2.1.1 The wearable devices - “Fitbit” and “Spire”
Fitbit Surge, which is a new and popular smart sports watch, has the following features (see from www.fitbit.com/ surge):
GPS Tracking: see distance, pace and elevation climbed and review routes and split times
PurePulseTM Heart Rate: Get continuous, automatic, wrist-based heart rate and simplified heart rate zones
All-Day Activity: Track steps, distance, calories burned, floor climbed and active minutes
Multi- Sport: Record running, cycling, cross training and other workouts and view exercise summaries
Long Battery Life: Lasts longer than competing trackers with a battery life up to seven day
Notification + Music: See call and text notifications on display and control songs from your mobile playlist
Auto Sleep + Alarms: Monitor your sleep automatically and set a silent alarm
Wireless Syncing: Sync stats wirelessly and automatically computers
Spire, which is an emotion monitor, has following features (see from www.spire.io):
Track every step and every breath
Be notified when users are tense or have not taken a deep breath
Discover what makes you clam and focused
Advanced step and calorie tracking
Guided breathing exercises and meditations
These two products have satisfied the basic eight key attributes we mention
‧can offer better services for users.
2.1.2 The Sensors of Physical Data in Wearable Devices
Inertial sensors, including accelerometers, gyroscopic sensors, and magnetic sensors, have small size, for monitoring the motion associated with human activities.
Accelerometer (triaxial accelerometer is common) is used to measure motion;
gyroscopic sensor is used to measure angular velocity; magnetic sensor is used to precisely measure body movement (Yang & Hsu 2010). The possible parameters for wearable inertial sensors are shown in the Table 2.2 (Tamura, 2014). He also mentions that static and dynamic activities can be measured through accelerometry; however, normal and abnormal walking or aged-related functions should be measured through amplitude and RMS values.
Table 2.2 Possible Parameters for Wearable Inertial Sensors
VELOCITY Triaxial acceleration
NUMBER OF STEPS Triaxial acceleration
NUMBER OF STRIDES Triaxial acceleration
TIME Triaxial acceleration
AVERAGE STRIDE TIME Triaxial acceleration
CADENCE Triaxial acceleration
ROOT MEAN SQUARE (RMS) VALUES
Triaxial acceleration, triaxial gyroscopic velocity & triaxial magnetic field
REGULARITY OF STEPS Triaxial acceleration
REGULARITY OF STRIDES Triaxial acceleration
ANGLE Combined with triaxial acceleration,
triaxial angular velocity & triaxial magnetic field
Another common kind of values is heart rate, which can be got from assessing the arterial pulsatility skin vascular beds with LED technology, which is called
Photoplethysmography (PPG). According to Lemay et.al (2014), it illuminates a living tissue with a light beam, and capture a portion of the light that has propagated through the living tissue, then analyze and depict functional information on the tissue.
As we review the inertial sensors and PPG technology, these two main kinds of physical values are the fundamental of activity-based engagement measurement, we build the basic background and idea to how to design our services, but we still need to consider the features of users in our research.
2.1.3 The Sensors of Emotional Data in Wearable Devices
Spire, which is the first product of emotion recognition in the world, use the technology of respiration to fulfill its functions and its inventor – Moraveji introduces the fundamental in his paper (2011). He says the breath speed easily be influenced by different emotion, and the changes can be recorded by sensors. The most salient finding in his studies is breath regulation, which reduces breath speed, activates the parasympathetic nervous system (PNS), the so-called ‘rest-and-digest’ response, to relax the body, reducing stress and anxiety.
Philippot and Chapelle (2002) give the description about four typical emotions like following:
Joy: Breathe and exhale slowly and deeply; breathing is very regular.
Anger: Breathe and exhale quickly; slightly deeper than regular breathing amplitude. And breathing is slightly irregular with some tremors.
Fear: Breathe and exhale quickly; with a normal amplitude. And breathing is slightly irregular with some tremors.
Sadness: Breathe and exhale through the nose with a normal amplitude and pace. And there are some sighs in your expiration.”
They also point that expressive emotional components like laughter or tears tend to be associated with happiness and sadness.
As we review the fundamental of emotion measurement through wearable sensors, we intend to enrich the patterns of emotion that can be recognized in our research, and also consider the features of users to affirm the certain patterns.