Abstract

New mobile applications need to estimate user activities by using sensor data provided by smart wearable devices and deliver context-aware solutions to users living in smart environments. We propose a novel hybrid data fusion method to estimate three types of daily user activities (being in a meeting, walking, and driving with a motorized vehicle) using the accelerometer and gyroscope data acquired from a smart watch using a mobile phone. The approach is based on the matrix time series method for feature fusion, and the modified Better-than-the-Best Fusion (BB-Fus) method with a stochastic gradient descent algorithm for construction of optimal decision trees for classification. For the estimation of user activities, we adopted a statistical pattern recognition approach and used the k-Nearest Neighbor (kNN) and Support Vector Machine (SVM) classifiers. We acquired and used our own dataset of 354 min of data from 20 subjects for this study. We report a classification performance of 98.32 % for SVM and 97.42 % for kNN.

Highlights

  • Today, mobiles devices such as smartphones and tablet computers have powerful processors, high memory capacities and other sophisticated features, which allow for the development of intelligent context-aware services for smart environments such as smart homes, smart cities, and smart mobility [49]

  • Better-than-the-Best Fusion (BB-Fus) method with a stochastic gradient descent algorithm for construction of optimal decision trees for classification; 3) a new dataset of the accelerometer and gyroscope signals acquired from a smartphone of users performing three types of daily user activities; 4) classification of the fused accelerometer and gyroscope data using K-NN and Support Vector Machine (SVM) classifiers

  • Classification was performed for a combination of two activities and lastly for all three activities using the k-Nearest Neighbor (k-NN) and SVM classifiers

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Summary

Introduction

Mobiles devices such as smartphones and tablet computers have powerful processors, high memory capacities and other sophisticated features, which allow for the development of intelligent context-aware services for smart environments such as smart homes, smart cities, and smart mobility [49]. Correct determination of user activity enables high-level reasoning over the domain of activities and services in order to create contextual rules such as “unmute my phone when the meeting ends and I start walking”, “forward all the incoming calls if I am driving”, “ring my phone loudly if I am walking”, etc. Such rules can be utilized by contextual reasoning engines to provide support for upper-level applications that provide smart context-aware services to its users. Better-than-the-Best Fusion (BB-Fus) method with a stochastic gradient descent algorithm for construction of optimal decision trees for classification; 3) a new dataset of the accelerometer and gyroscope signals acquired from a smartphone of users performing three types of daily user activities (being in a meeting, walking, and driving with a motorized vehicle); 4) classification of the fused accelerometer and gyroscope data using K-NN and SVM classifiers

Related works
Outline of the methodology
Raw data filtering
Feature extraction
Data fusion
Classification
Evaluation of accuracy
Implementation of mobile app
User activities
Data acquisition
Measurement quality
Feature fusion
Results obtained using accelerometer data only
Results obtained using gyroscope data only
Results obtained using fused accelerometer and gyroscope data
Evaluation of results
Conclusions
Full Text
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