研究室輪読 Feature Learning for Activity Recognition in Ubiquitous Computing
1. Feature Learning for Activity
Recognition in Ubiquitous Computing
Thomas Plötz, Nils Y. Hammerla, and Patrick Olivier
School of Computer Science
Newcastle University
the 12th International Joint Conference on Artificial
Intelligence 2011
Paper Reading at Jun. 9th in Matsuo Lab, Presented By Yusuke Iwasawa D1
2. Outline
1. Introduction
2. State-of-the-Art
3. Feature Learning for Activity Recognition
3.1. PCA based Feature Learning
3.2. Deep Learning for Feature Extraction
4. Experimental Evaluation
4.1. Datasets
4.2. Features Analyzed: Overview
4.3. Result
5. Conclusion
20. Outline
4. Activity Recognition (AR)
• … is a core concern of the ubiquitous computing (ubicomp) community
[Atallah and Yang, 2009]
• In general, sensors are utilized to capture aspects of movement or a
user’s behavior.
4
5. Typical Activity Recognition Chain [Bulling et. al]
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• Raw data acquisition: Sensor data
• Preprocessing: Filtering etc.
• Segmentation: Sliding Window
(Predominant Approach)
• Feature Extraction:
• Based on Frames
• Classification:
• General classifier (KNN)
※the Fig. is cited from the paper[Bulling:2014jm]
6. AR Feature Extraction
6
• Almost all previous work used heuristically selected measures
• Time Domain: Average, Standard Deviation etc.
• Frequency Domain: FFT coefficients
• Few systematic research
• one of the major shortcomings of current AR [Lukowicz et al., 2010]
※the Fig. is cited from the paper[Bulling:2014jm]
Topic of This paper
7. Contributions
1. Proposing the simple work-flow that integrate unsupervised feature
learning techniques and general activity recognition procedures
• Principal Component Analysis(PCA) and Deep Learning
2. Presenting the suitability of feature learning for ubicomp activity
recognition tasks with four public datasets
• Showing how the automatically extracted features outperform
standard features across range of AR applications
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New classes of activity analysis
• Such as behavioral analysis or skill assessment
• The task requires quantitate and in-depth analyzation of the
underlying data
11. Feature Learning
• Feature learning (Representation Learning?)を利用して自動的に
データの良い表現を学習する
• ヒューリスティックな特徴のデザインがドメインスペシフィックな専門知識を要
するのに対して、表現学習では何らかの目的関数を最適化することでデータ
からよい表現を見つけることができる
• エネルギー最小化[LeCun et al., 2006]やmainfold learning (多様体学
習)[Huo et al., 2004], deep learningなどのアプローチがあ
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12. Integration Framework of AR and Feature Learning
• Sensor Data
• 多次元時系列データ
• Frame Extraction
• Sensor Dataを前から
順番にnサンプルずつ
• Training
• 学習用のデータ
(フレーム単位)
• Test
• テスト用のデータ
(フレーム単位)
• FEX
• Trainingでパラメタを
学習、Testにも利用
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13. Design Criteria
1. Capable of extracting generally applicable representations not be
limited to specific AR tasks.
2. Must not rely on the availability of ground truth annotations of the
training data.
3. Benefits from larger datasets, but not dependent on them.
4. Provides intrinsic information.
5. Must be computationally feasible and applicable in real-time
application contexts.
(論文中より抜粋)
13
本論文ではPCAとDeep Leaningを検討し5つの基準にそって評価
まとめると、2.ラベルが必ずしもたくさん利用できるとは限らない状況で、3. なるべく
多くのデータセットから、4. 本質的で、1. いろいろなタスクに利用可能な表現を、5.
高速に学習する必要がある
14. PCA & Deep Learning for Feature Learning
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• Principal Component Analysis
• 表現学習での応用事例: [Karhunen and Joutsensalo] “Representation and
separation of signals using nonlinear PCA type learning,” Neural
Networks, vol. 7, no. 1, pp. 113–127, Jan. 1994. など
PCA
Deep Learning
• 各層をRBMにしたDeep Brief Networkを採用
• Auto Encorder[Hinton, 2007]
• 1つの入力層、1つの出力層、偶数の隠れ層
• Every layer is fully connected
• Learning the layers of the autoencoder network greedily in a bottom-
up procedure, by treating each pair of subsequent layers in the encoder
as a Restricted Boltzmann Machine (RBM)
• [Hinton et.al 2006]に従って学習
28. References
• ‘Types of samples’, http://psychology.ucdavis.edu/faculty_sites/sommerb/
sommerdemo/sampling/types.htm
• ‘楽しいAutoEncoderと学習の世界’, http://vaaaaaanquish.hatenablog.com/entry/
2013/12/03/033850
• ‘Convolution Neural Network’, http://ceromondo.blogspot.jp/2012/09/convolutional-
neural-network.html
• [Prandi:2014] C. Prandi, P. Salomoni, and S. Mirri, “mPASS: Integrating People Sensing and
Crowdsourcing to Map Urban Accessibility,” IEEE Consumer Communications and
Networking Conference (CCNC 2014): People Centric Sensing and Communications (PCSC),
2014.
• [Plötz et. al] T. Plötz, N. Y. Hammerla, and P. Olivier, “Feature learning for activity
recognition in ubiquitous computing,” IJCAI Proceedings-International Joint…, 2011.
• [Glatt et. al] R. Glatt et. al., Proposal for a Deep Learning Architecture for Activity
Recognition. International Journal of Engineering & …, 2014.
• [Zeng et. al] M. Zeng, L. T. Nguyen, B. Yu, O. J. Mengshoel, J. Zhu, and P. Wu,
“Convolutional Neural Networks for Human Activity Recognition using Mobile Sensors,”
mlt.sv.cmu.edu
• [Vollmer et. al] Christian Vollmer, et.al., “Learning Features for Activity Recognition with
Shift-Invariant Sparse Coding,” 2013.
• [Bhattacharya et. al] “Using unlabeled data in a sparse-coding framework for human activity
recognition,” 2014.
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