3,169 research outputs found
Comparing CNN and Human Crafted Features for Human Activity Recognition
Deep learning techniques such as Convolutional
Neural Networks (CNNs) have shown good results in activity
recognition. One of the advantages of using these methods resides
in their ability to generate features automatically. This ability
greatly simplifies the task of feature extraction that usually
requires domain specific knowledge, especially when using big
data where data driven approaches can lead to anti-patterns.
Despite the advantage of this approach, very little work has
been undertaken on analyzing the quality of extracted features,
and more specifically on how model architecture and parameters
affect the ability of those features to separate activity classes
in the final feature space. This work focuses on identifying the
optimal parameters for recognition of simple activities applying
this approach on both signals from inertial and audio sensors.
The paper provides the following contributions: (i) a comparison
of automatically extracted CNN features with gold standard
Human Crafted Features (HCF) is given, (ii) a comprehensive
analysis on how architecture and model parameters affect separation
of target classes in the feature space. Results are evaluated
using publicly available datasets. In particular, we achieved a
93.38% F-Score on the UCI-HAR dataset, using 1D CNNs with
3 convolutional layers and 32 kernel size, and a 90.5% F-Score
on the DCASE 2017 development dataset, simplified for three
classes (indoor, outdoor and vehicle), using 2D CNNs with 2
convolutional layers and a 2x2 kernel size
DeepWalking: Enabling Smartphone-based Walking Speed Estimation Using Deep Learning
Walking speed estimation is an essential component of mobile apps in various
fields such as fitness, transportation, navigation, and health-care. Most
existing solutions are focused on specialized medical applications that utilize
body-worn motion sensors. These approaches do not serve effectively the general
use case of numerous apps where the user holding a smartphone tries to find his
or her walking speed solely based on smartphone sensors. However, existing
smartphone-based approaches fail to provide acceptable precision for walking
speed estimation. This leads to a question: is it possible to achieve
comparable speed estimation accuracy using a smartphone over wearable sensor
based obtrusive solutions?
We find the answer from advanced neural networks. In this paper, we present
DeepWalking, the first deep learning-based walking speed estimation scheme for
smartphone. A deep convolutional neural network (DCNN) is applied to
automatically identify and extract the most effective features from the
accelerometer and gyroscope data of smartphone and to train the network model
for accurate speed estimation. Experiments are performed with 10 participants
using a treadmill. The average root-mean-squared-error (RMSE) of estimated
walking speed is 0.16m/s which is comparable to the results obtained by
state-of-the-art approaches based on a number of body-worn sensors (i.e., RMSE
of 0.11m/s). The results indicate that a smartphone can be a strong tool for
walking speed estimation if the sensor data are effectively calibrated and
supported by advanced deep learning techniques.Comment: 6 pages, 9 figures, published in IEEE Global Communications
Conference (GLOBECOM
An Interpretable Machine Vision Approach to Human Activity Recognition using Photoplethysmograph Sensor Data
The current gold standard for human activity recognition (HAR) is based on
the use of cameras. However, the poor scalability of camera systems renders
them impractical in pursuit of the goal of wider adoption of HAR in mobile
computing contexts. Consequently, researchers instead rely on wearable sensors
and in particular inertial sensors. A particularly prevalent wearable is the
smart watch which due to its integrated inertial and optical sensing
capabilities holds great potential for realising better HAR in a non-obtrusive
way. This paper seeks to simplify the wearable approach to HAR through
determining if the wrist-mounted optical sensor alone typically found in a
smartwatch or similar device can be used as a useful source of data for
activity recognition. The approach has the potential to eliminate the need for
the inertial sensing element which would in turn reduce the cost of and
complexity of smartwatches and fitness trackers. This could potentially
commoditise the hardware requirements for HAR while retaining the functionality
of both heart rate monitoring and activity capture all from a single optical
sensor. Our approach relies on the adoption of machine vision for activity
recognition based on suitably scaled plots of the optical signals. We take this
approach so as to produce classifications that are easily explainable and
interpretable by non-technical users. More specifically, images of
photoplethysmography signal time series are used to retrain the penultimate
layer of a convolutional neural network which has initially been trained on the
ImageNet database. We then use the 2048 dimensional features from the
penultimate layer as input to a support vector machine. Results from the
experiment yielded an average classification accuracy of 92.3%. This result
outperforms that of an optical and inertial sensor combined (78%) and
illustrates the capability of HAR systems using...Comment: 26th AIAI Irish Conference on Artificial Intelligence and Cognitive
Scienc
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