8 research outputs found
An ensemble learning framework for anomaly detection in building energy consumption
During building operation, a significant amount of energy is wasted due to equipment and human-related faults. To reduce waste, today\u27s smart buildings monitor energy usage with the aim of identifying abnormal consumption behaviour and notifying the building manager to implement appropriate energy-saving procedures. To this end, this research proposes a new pattern-based anomaly classifier, the collective contextual anomaly detection using sliding window (CCAD-SW) framework. The CCAD-SW framework identifies anomalous consumption patterns using overlapping sliding windows. To enhance the anomaly detection capacity of the CCAD-SW, this research also proposes the ensemble anomaly detection (EAD) framework. The EAD is a generic framework that combines several anomaly detection classifiers using majority voting. To ensure diversity of anomaly classifiers, the EAD is implemented by combining pattern-based (e.g., CCAD-SW) and prediction-based anomaly classifiers. The research was evaluated using real-world data provided by Powersmiths, located in Brampton, Ontario, Canada. Results show that the EAD framework improved the sensitivity of the CCAD-SW by 3.6% and reduced false alarm rate by 2.7%
Indoor environment data time-series reconstruction using autoencoder neural networks
As the number of installed meters in buildings increases, there is a growing
number of data time-series that could be used to develop data-driven models to
support and optimize building operation. However, building data sets are often
characterized by errors and missing values, which are considered, by the recent
research, among the main limiting factors on the performance of the proposed
models. Motivated by the need to address the problem of missing data in
building operation, this work presents a data-driven approach to fill these
gaps. In this study, three different autoencoder neural networks are trained to
reconstruct missing short-term indoor environment data time-series in a data
set collected in an office building in Aachen, Germany. This consisted of a
four year-long monitoring campaign in and between the years 2014 and 2017, of
84 different rooms. The models are applicable for different time-series
obtained from room automation, such as indoor air temperature, relative
humidity and data streams. The results prove that the proposed methods
outperform classic numerical approaches and they result in reconstructing the
corresponding variables with average RMSEs of 0.42 {\deg}C, 1.30 % and 78.41
ppm, respectively.Comment: Accepted in Building and Environmen
Artificial Intelligence based Anomaly Detection of Energy Consumption in Buildings: A Review, Current Trends and New Perspectives
Enormous amounts of data are being produced everyday by sub-meters and smart
sensors installed in residential buildings. If leveraged properly, that data
could assist end-users, energy producers and utility companies in detecting
anomalous power consumption and understanding the causes of each anomaly.
Therefore, anomaly detection could stop a minor problem becoming overwhelming.
Moreover, it will aid in better decision-making to reduce wasted energy and
promote sustainable and energy efficient behavior. In this regard, this paper
is an in-depth review of existing anomaly detection frameworks for building
energy consumption based on artificial intelligence. Specifically, an extensive
survey is presented, in which a comprehensive taxonomy is introduced to
classify existing algorithms based on different modules and parameters adopted,
such as machine learning algorithms, feature extraction approaches, anomaly
detection levels, computing platforms and application scenarios. To the best of
the authors' knowledge, this is the first review article that discusses anomaly
detection in building energy consumption. Moving forward, important findings
along with domain-specific problems, difficulties and challenges that remain
unresolved are thoroughly discussed, including the absence of: (i) precise
definitions of anomalous power consumption, (ii) annotated datasets, (iii)
unified metrics to assess the performance of existing solutions, (iv) platforms
for reproducibility and (v) privacy-preservation. Following, insights about
current research trends are discussed to widen the applications and
effectiveness of the anomaly detection technology before deriving future
directions attracting significant attention. This article serves as a
comprehensive reference to understand the current technological progress in
anomaly detection of energy consumption based on artificial intelligence.Comment: 11 Figures, 3 Table
Real-Time Detection of Demand Manipulation Attacks on a Power Grid
An increased usage in IoT devices across the globe has posed a threat to the power grid. When an attacker has access to multiple IoT devices within the same geographical location, they can possibly disrupt the power grid by regulating a botnet of high-wattage IoT devices. Based on the time and situation of the attack, an adversary needs access to a fixed number of IoT devices to synchronously switch on/off all of them, resulting in an imbalance between the supply and demand. When the frequency of the power generators drops below a threshold value, it can lead to the generators tripping and potentially failing. Attacks such as these can cause an imbalance in the grid frequency, line failures and cascades, can disrupt a black start or increase the operating cost. The challenge lies in early detection of abnormal demand peaks in a large section of the power grid from the power operator’s side, as it only takes seconds to cause a generator failure before any action could be taken.
Anomaly detection comes handy to flag the power operator of an anomalous behavior while such an attack is taking place. However, it is difficult to detect anomalies especially when such attacks are taking place obscurely and for prolonged time periods. With this motive, we compare different anomaly detection systems in terms of detecting these anomalies collectively. We generate attack data using real-world power consumption data across multiple apartments to assess the performance of various prediction-based detection techniques as well as commercial detection applications and observe the cases when the attacks were not detected. Using static thresholds for the detection process does not reliably detect attacks when they are performed in different times of the year and also lets the attacker exploit the system to create the attack obscurely. To combat the effects of using static thresholds, we propose a novel dynamic thresholding mechanism, which improves the attack detection reaching up to 100% detection rate, when used with prediction-based anomaly score techniques
Spatiotemporal anomaly detection: streaming architecture and algorithms
Includes bibliographical references.2020 Summer.Anomaly detection is the science of identifying one or more rare or unexplainable samples or events in a dataset or data stream. The field of anomaly detection has been extensively studied by mathematicians, statisticians, economists, engineers, and computer scientists. One open research question remains the design of distributed cloud-based architectures and algorithms that can accurately identify anomalies in previously unseen, unlabeled streaming, multivariate spatiotemporal data. With streaming data, time is of the essence, and insights are perishable. Real-world streaming spatiotemporal data originate from many sources, including mobile phones, supervisory control and data acquisition enabled (SCADA) devices, the internet-of-things (IoT), distributed sensor networks, and social media. Baseline experiments are performed on four (4) non-streaming, static anomaly detection multivariate datasets using unsupervised offline traditional machine learning (TML), and unsupervised neural network techniques. Multiple architectures, including autoencoders, generative adversarial networks, convolutional networks, and recurrent networks, are adapted for experimentation. Extensive experimentation demonstrates that neural networks produce superior detection accuracy over TML techniques. These same neural network architectures can be extended to process unlabeled spatiotemporal streaming using online learning. Space and time relationships are further exploited to provide additional insights and increased anomaly detection accuracy. A novel domain-independent architecture and set of algorithms called the Spatiotemporal Anomaly Detection Environment (STADE) is formulated. STADE is based on federated learning architecture. STADE streaming algorithms are based on a geographically unique, persistently executing neural networks using online stochastic gradient descent (SGD). STADE is designed to be pluggable, meaning that alternative algorithms may be substituted or combined to form an ensemble. STADE incorporates a Stream Anomaly Detector (SAD) and a Federated Anomaly Detector (FAD). The SAD executes at multiple locations on streaming data, while the FAD executes at a single server and identifies global patterns and relationships among the site anomalies. Each STADE site streams anomaly scores to the centralized FAD server for further spatiotemporal dependency analysis and logging. The FAD is based on recent advances in DNN-based federated learning. A STADE testbed is implemented to facilitate globally distributed experimentation using low-cost, commercial cloud infrastructure provided by Microsoftâ„¢. STADE testbed sites are situated in the cloud within each continent: Africa, Asia, Australia, Europe, North America, and South America. Communication occurs over the commercial internet. Three STADE case studies are investigated. The first case study processes commercial air traffic flows, the second case study processes global earthquake measurements, and the third case study processes social media (i.e., Twitterâ„¢) feeds. These case studies confirm that STADE is a viable architecture for the near real-time identification of anomalies in streaming data originating from (possibly) computationally disadvantaged, geographically dispersed sites. Moreover, the addition of the FAD provides enhanced anomaly detection capability. Since STADE is domain-independent, these findings can be easily extended to additional application domains and use cases
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Online Anomaly Detection for Time Series. Towards Incorporating Feature Extraction, Model Uncertainty and Concept Drift Adaptation for Improving Anomaly Detection
Time series anomaly detection receives increasing research interest given
the growing number of data-rich application domains. Recent additions
to anomaly detection methods in research literature include deep learning
algorithms. The nature and performance of these algorithms in sequence
analysis enable them to learn hierarchical discriminating features
and time-series temporal nature. However, their performance is affected
by the speed at which the time series arrives, the use of a fixed threshold,
and the assumption of Gaussian distribution on the prediction error
to identify anomalous values. An exact parametric distribution is often
not directly relevant in many applications and it’s often difficult to select
an appropriate threshold that will differentiate anomalies with noise.
Thus, implementations need the Prediction Interval (PI) that quantifies the
level of uncertainty associated with the Deep Neural Network (DNN) point
forecasts, which helps in making a better-informed decision and mitigates
against false anomaly alerts. To achieve this, a new anomaly detection
method is proposed that computes the uncertainty in estimates using quantile
regression and used the quantile interval to identify anomalies. Similarly,
to handle the speed at which the data arrives, an online anomaly detection
method is proposed where a model is trained incrementally to adapt
to the concept drift that improves prediction. This is implemented using a
window-based strategy, in which a time series is broken into sliding windows
of sub-sequences as input to the model. To adapt to concept drift,
the model is updated when changes occur in the new arrival instances.
This is achieved by using anomaly likelihood which is computed using the
Q-function to define the abnormal degree of the current data point based
on the previous data points. Specifically, when concept drift occurs, the
proposed method will mark the current data point as anomalous. However,
when the abnormal behavior continues for a longer period of time,
the abnormal degree of the current data point will be low compared to the
previous data points using the likelihood. As such, the current data point is
added to the previous data to retrain the model which will allow the model
to learn the new characteristics of the data and hence adapt to the concept
changes thereby redefining the abnormal behavior. The proposed method
also incorporates feature extraction to capture structural patterns in the
time series. This is especially significant for multivariate time-series data,
for which there is a need to capture the complex temporal dependencies
that may exist between the variables. In summary, this thesis contributes
to the theory, design, and development of algorithms and models for the
detection of anomalies in both static and evolving time series data.
Several experiments were conducted, and the results obtained indicate the
significance of this research on offline and online anomaly detection in
both static and evolving time-series data. In chapter 3, the newly proposed
method (Deep Quantile Regression Anomaly Detection Method) is evaluated
and compared with six other prediction-based anomaly detection
methods that assume a normal distribution of prediction or reconstruction
error for the identification of anomalies. Results in the first part of
the experiment indicate that DQR-AD obtained relatively better precision
than all other methods which demonstrates the capability of the method
in detecting a higher number of anomalous points with low false positive
rates. Also, the results show that DQR-AD is approximately 2 – 3
times better than the DeepAnT which performs better than all the remaining
methods on all domains in the NAB dataset. In the second part of the
experiment, sMAP dataset is used with 4-dimensional features to demonstrate
the method on multivariate time-series data. Experimental result
shows DQR-AD have 10% better performance than AE on three datasets
(SMAP1, SMAP3, and SMAP5) and equal performance on the remaining
two datasets. In chapter 5, two levels of experiments were conducted
basis of false-positive rate and concept drift adaptation. In the first level
of the experiment, the result shows that online DQR-AD is 18% better
than both DQR-AD and VAE-LSTM on five NAB datasets. Similarly, results
in the second level of the experiment show that the online DQR-AD
method has better performance than five counterpart methods with a relatively
10% margin on six out of the seven NAB datasets. This result
demonstrates how concept drift adaptation strategies adopted in the proposed
online DQR-AD improve the performance of anomaly detection in
time series.Petroleum Technology Development Fund (PTDF
A DATA-DRIVEN METHODOLOGY TO ANALYZE AIR TRAFFIC MANAGEMENT SYSTEM OPERATIONS WITHIN THE TERMINAL AIRSPACE
Air Traffic Management (ATM) systems are the systems responsible for managing the operations of all aircraft within an airspace. In the past two decades, global modernization efforts have been underway to increase ATM system capacity and efficiency, while maintaining safety. Gaining a comprehensive understanding of both flight-level and airspace-level operations enables ATM system operators, planners, and decision-makers to make better-informed and more robust decisions related to the implementation of future operational concepts. The increased availability of operational data, including widely-accessible ADS-B trajectory data, and advances in modern machine learning techniques provide the basis for offline data-driven methods to be applied to analyze ATM system operations. Further, analysis of ATM system operations of arriving aircraft within the terminal airspace has the highest potential to impact safety, capacity, and efficiency levels due to the highest rate of accidents and incidents occurring during the arrival flight phases. Therefore, motivating this research is the question of how offline data-driven methods may be applied to ADS-B trajectory data to analyze ATM system operations at both the flight and airspace levels for arriving aircraft within the terminal airspace to extract novel insights relevant to ATM system operators, planners, and decision-makers.
An offline data-driven methodology to analyze ATM system operations is proposed involving the following three steps: (i) Air Traffic Flow Identification, (ii) Anomaly Detection, and (iii) Airspace-Level Analysis. The proposed methodology is implemented considering ADS-B trajectory data that was extracted, cleaned, processed, and augmented for aircraft arriving at San Francisco International Airport (KSFO) during the full year of 2019 as well as the corresponding extracted and processed ASOS weather data. The Air Traffic Flow Identification step contributes a method to more reliably identify air traffic flows for arriving aircraft trajectories through a novel implementation of the HDBSCAN clustering algorithm with a weighted Euclidean distance function. The Anomaly Detection step contributes the novel distinction between spatial and energy anomalies in ADS-B trajectory data and provides key insights into the relationship between the two types of anomalies. Spatial anomalies are detected leveraging the aforementioned air traffic flow identification method, whereas energy anomalies are detected leveraging the DBSCAN clustering algorithm. Finally, the Airspace-Level Analysis step contributes a novel method to identify operational patterns and characterize operational states of aircraft arriving within the terminal airspace during specified time intervals leveraging the UMAP dimensionality reduction technique and DBSCAN clustering algorithm. Additionally, the ability to predict, in advance, a time interval’s operational pattern using metrics derived from the ASOS weather data as input and training a gradient-boosted decision tree (XGBoost) algorithm is provided.Ph.D