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Rajesh Ganesan

dblp:82/8683 · DBLP profile ↗
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16ranked-venue papers
4as first author
3since 2021 · last 2025
0000-0003-1875-548XORCID · corroborated

Domains — the database's venue-derived domains; a paper can count in several

Databases, data management, data science and information retrieval · 6 · 2 first-author · 1 since 2021Security and privacy · 4 · 1 since 2021Software engineering, systems software and programming languages · 2 · 1 since 2021Human-computer interaction and ubiquitous computing · 2 · 1 first-authorSystems, architecture and hardware · 1Applied, interdisciplinary, general and emerging computing · 1 · 1 first-author

Expertise — from the expertise taxonomy: the topics of the expert's papers under the CCF categories. A weight counts papers with recency: 1 for a paper about the topic, 0.3 when the topic is its context, halved every five years.

Network and information security
3 papers
Network security · 50% Usable security · 25% Digital forensics and information hiding · 19%
Computer architecture, parallel and distributed computing, and storage systems
1 paper
Distributed systems · 50% Parallel and multicore computing · 50%

Topics — the 8 heaviest of 9, each with the papers that count most for it

TopicWeightPapersLastEvidence papers
Network security › intrusion detection and prevention
intrusion detection
0.822019
A Two-Step Approach to Optimal Selection of Alerts for Investigation in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Understanding Tradeoffs Between Throughput, Quality, and Cost of Alert Analysis in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Usable security › security operations
security operations center
0.822019
A Two-Step Approach to Optimal Selection of Alerts for Investigation in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Understanding Tradeoffs Between Throughput, Quality, and Cost of Alert Analysis in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Digital forensics and information hiding
information hiding
0.612022
Generating Realistic Fake Equations in Order to Reduce Intellectual Property Theft · IEEE Trans. Dependable Secur. Comput. 2022
Distributed systems
distributed coordination
0.412020
Adaptive Alert Management for Balancing Optimal Performance among Distributed CSOCs using Reinforcement Learning · IEEE Trans. Parallel Distributed Syst. 2020
Parallel and multicore computing › load balancing
workload rebalancing
0.412020
Adaptive Alert Management for Balancing Optimal Performance among Distributed CSOCs using Reinforcement Learning · IEEE Trans. Parallel Distributed Syst. 2020
Network security › intrusion detection and prevention › intrusion detection › alert processing
alert prioritization
0.412019
A Two-Step Approach to Optimal Selection of Alerts for Investigation in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Network security › intrusion detection and prevention › intrusion detection › alert processing
alert triage
0.412019
Understanding Tradeoffs Between Throughput, Quality, and Cost of Alert Analysis in a CSOC · IEEE Trans. Inf. Forensics Secur. 2019
Hardware security and side channels
intellectual property protection
0.212022
Generating Realistic Fake Equations in Order to Reduce Intellectual Property Theft · IEEE Trans. Dependable Secur. Comput. 2022

Methods — techniques the papers use, named apart from their topics

fake equation engine · 0.6approximate optimization algorithm · 0.6stochastic dynamic programming · 0.4reinforcement learning · 0.4load balancing · 0.4value function hierarchy process · 0.4simulation · 0.4optimization · 0.4constraint optimization · 0.4
YearPublicationVenuePosition
2025 Predicting Sensor Fusion Performance for Situation Assessment in Countering Aerial Threats
abstract
This paper presents a methodology for predicting the fusion performance of multi-sensor systems in countering aerial threats (CAT). By integrating the ROC (Receiver Operating Characteristics) curves of individual sensors into a SOC (System Operating Characteristics) curve, we model the tradeoffs between various performance metrics, such as detection probability and false alarm rate, under different operating conditions. Our approach utilizes a grid-based method, dividing the Region of Interest (RoI) into small cells to evaluate system-level performance. This allows for the development of an objective function aimed at maximizing the RoI coverage rate, defined either as the average detection performance or as the percentage of cells where performance metrics exceed predefined thresholds. By applying optimization techniques such as mixed integer programming, we can strategically select and position sensors to enhance overall system performance while adhering to cost constraints. The proposed predictive fusion performance framework offers a comprehensive solution for improving situation assessment in aerial defense scenarios, leading to more effective and reliable detection, classification, and tracking of aerial targets.
Kuo-Chu Chang, Ali K. Raz, Michael R. Hieb, Rajesh Ganesan
FUSION4
2023 A Novel Team Formation Framework Based on Performance in a Cybersecurity Operations Center
abstract
A Cybersecurity Operations Center (CSOC) performs various tasks to protect an organization from cyber threats. Several types of personnel collaborate to function effectively as a team to analyze the threat signals, in the form of alerts, arriving from various sources. Teams are often formed ad hoc, resulting in an imbalance in their performances and thereby increasing the risk associated with the low-performing teams. The current approach taken by behavioral scientists in forming effective teams focuses on first qualitatively assessing individuals such as analysts, who are then grouped into teams based on their credentials and expertise. Our work takes a holistic view of the CSOC by first defining team requirements and then selecting individuals to form several collaborative teams that meet these requirements for every shift of operation. We present a novel team formation framework that integrates optimization, simulation, and scoring methods to form effective teams and introduce a new collaborative score metric that measures their effectiveness. Results from simulated experiments show the formation of effective teams whose collaborative scores are maximized and balanced. Our approach is also able to identify high and low performers within the first few months of implementing the framework.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam, Steve E. Hutchinson
IEEE Trans. Serv. Comput.2
2022 Generating Realistic Fake Equations in Order to Reduce Intellectual Property Theft
abstract
According to Symantec, the average gap from the time a company is compromised by a zero-day attack to the time the vulnerability is discovered is 312 days. This leaves an adversary with a lot of time to exfiltrate corporate IP. Recent work has suggested automatically generating multiple fake versions of a document to impose costs on the attacker who needs to correctly identify the original document from a set of mostly fake documents. But in the real world, documents contain many diverse components. In this article, we focus on technical documents that often contain equations. We present${\sf FEE}$(Fake Equation Engine), a framework to generate fake equations in such documents.${\sf FEE}$tries to preserve multiple aspects of a given equation when generating a fake. Moreover,${\sf FEE}$is very general and applies to diverse equational forms including polynomial equations, differential equations, transcendental equations, and more.${\sf FEE}$iteratively solves a complex, changing optimization problem inside it. We also present${\sf FEE-FAST}$, a fast approximate algorithm to solve the optimization problem within${\sf FEE}$. Using a panel of human subjects, we show that${\sf FEE}$achieves a high rate in deceiving sophisticated subjects.
Yanhai Xiong, Giridhar Ramachandran, Rajesh Ganesan, Sushil Jajodia, V. S. Subrahmanian
IEEE Trans. Dependable Secur. Comput.3
2020 Two Can Play That Game: An Adversarial Evaluation of a Cyber-Alert Inspection System
abstract
Cyber-security is an important societal concern. Cyber-attacks have increased in numbers as well as in the extent of damage caused in every attack. Large organizations operate a Cyber Security Operation Center (CSOC), which forms the first line of cyber-defense. The inspection of cyber-alerts is a critical part of CSOC operations (defender or blue team). Recent work proposed a reinforcement learning (RL) based approach for the defender’s decision-making to prevent the cyber-alert queue length from growing large and overwhelming the defender. In this article, we perform a red team (adversarial) evaluation of this approach. With the recent attacks on learning-based decision-making systems, it is even more important to test the limits of the defender’s RL approach. Toward that end, we learn several adversarial alert generation policies and the best response against them for various defender’s inspection policy. Surprisingly, we find the defender’s policies to be quite robust to the best response of the attacker. In order to explain this observation, we extend the earlier defender’s RL model to a game model with adversarial RL, and show that there exist defender policies that can be robust against any adversarial policy. We also derive a competitive baseline from the game theory model and compare it to the defender’s RL approach. However, when we go further to exploit the assumptions made in the Markov Decision Process (MDP) in the defender’s RL model, we discover an attacker policy that overwhelms the defender. We use a double oracle like approach to retrain the defender with episodes from this discovered attacker policy. This made the defender robust to the discovered attacker policy and no further harmful attacker policies were discovered. Overall, the adversarial RL and double oracle approach in RL are general techniques that are applicable to other RL usage in adversarial environments.
Ankit Shah 0002, Arunesh Sinha, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
ACM Trans. Intell. Syst. Technol.3
2020 Adaptive Alert Management for Balancing Optimal Performance among Distributed CSOCs using Reinforcement Learning
abstract
Large organizations typically have Cybersecurity Operations Centers (CSOCs) distributed at multiple locations that are independently managed, and they have their own cybersecurity analyst workforce. Under normal operating conditions, the CSOC locations are ideally staffed such that the alerts generated from the sensors in a work-shift are thoroughly investigated by the scheduled analysts in a timely manner. Unfortunately, when adverse events such as increase in alert arrival rates or alert investigation rates occur, alerts have to wait for a longer duration for analyst investigation, which poses a direct risk to organizations. Hence, our research objective is to mitigate the impact of the adverse events by dynamically and autonomously re-allocating alerts to other location(s) such that the performances of all the CSOC locations remain balanced. This is achieved through the development of a novel centralized adaptive decision support system whose task is to re-allocate alerts from the affected locations to other locations. This re-allocation decision is non-trivial because the following must be determined: (1) timing of a re-allocation decision, (2) number of alerts to be reallocated, and (3) selection of the locations to which the alerts must be distributed. The centralized decision-maker (henceforth referred to as agent) continuously monitors and controls the level of operational effectiveness-LOE (a quantified performance metric) of all the locations. The agent's decision-making framework is based on the principles of stochastic dynamic programming and is solved using reinforcement learning (RL). In the experiments, the RL approach is compared with both rule-based and load balancing strategies. By simulating real-world scenarios, learning the best decisions for the agent, and applying the decisions on sample realizations of the CSOC's daily operation, the results show that the RL agent outperforms both approaches by generating (near-) optimal decisions that maintain a balanced LOE among the CSOC locations. Furthermore, the scalability experiments highlight the practicality of adapting the method to a large number of CSOC locations.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Pierangela Samarati, Hasan Çam
IEEE Trans. Parallel Distributed Syst.2
2020 An Outsourcing Model for Alert Analysis in a Cybersecurity Operations Center
abstract
A typical Cybersecurity Operations Center (CSOC) is a service organization. It hires and trains analysts, whose task is to perform analysis of alerts that were generated while monitoring the client’s networks. Due to ever-increasing financial and infrastructure burden on a CSOC driven by the rapidly growing demand for security services, it would become prohibitively expensive to continually expand the size of a CSOC to meet the demands in the future. An alternative solution is to outsource the alert analysis process to on-demand analysts, to provide scalable CSOC service to its clients with features, such as (1) higher throughput, (2) higher quality, and (3) more economical service than the current in-house service. The current outsourcing model is not cost effective and an exact optimization model is computationally inefficient. This article presents a novel two-step sequential mixed integer programming optimization method that is used in the development of a new decision-support business model for outsourcing the alert analysis process. It is demonstrated that through this model, a CSOC can effectively deliver its alert management services with the above-mentioned features. Results indicate that the model is scalable, computationally viable, real-time implementable, and can deliver CSOC services that meet the service-level agreement (SLA) between the CSOC and its client. In addition, the article provides valuable insights into the cost of operating the new business process outsourcing model for cybersecurity services.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
ACM Trans. Web2
2019 Understanding Tradeoffs Between Throughput, Quality, and Cost of Alert Analysis in a CSOC
abstract
Intrusion detection systems (IDSs) analyze data that are collected by sensors, which monitor the network traffic. Any alert generated by the IDS is transmitted to a cybersecurity operations center (CSOC), which performs the important task of analyzing the alerts. In order to deliver a strong security against threats, an efficient CSOC requires the following characteristics: 1) all alerts must be analyzed in a timely manner; 2) there must be an ideal mix of analyst expertise levels in the organization because the quality of analysis performed depends on the mix; and 3) there must be adequate operating budget to hire the required number of analyst personnel. However, it is non-trivial for a CSOC manager to establish the parameter settings for the above characteristics for a desired CSOC efficiency, and current literature lacks a thorough analysis of the tradeoffs between them. This void is filled by this paper whose research objective is to develop an optimized tradeoff study model of the CSOC that studies and quantifies the interactions between the above characteristics, and to use the knowledge gained from the above study to provide the foundation principles to establish and operate an efficient CSOC. A constraint-optimization tradeoff study model is built to drive the decisions that optimize the above characteristics of the CSOC, which is then tested via several simulation runs of the alert arrival and service processes at the CSOC. The paper serves as the first step toward a unified tradeoff study model that integrates the throughput performance, the quality of analysis, and the cost metrics to design and establish an efficient CSOC. Results from the above optimization-simulation tests capture several valuable insights along with parameter settings of the metrics that explain how to operate an efficient CSOC, and quantifies the economic impact of scaling-up the CSOC operation.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
IEEE Trans. Inf. Forensics Secur.2
2019 A Two-Step Approach to Optimal Selection of Alerts for Investigation in a CSOC
abstract
A Cyber Security Operations Center (CSOC) is responsible for investigating all the alerts generated from the intrusion detection systems to identify suspicious activities in a timely manner. There exists a critical gap between the time needed (demand) and the time available (limited analyst resource) for alert investigation at a CSOC. Hence, alert prioritization is important, for which CSOCs employ ad-hoc filtering methods to prune and triage the alerts that are presented to the analysts for investigation. One of the major drawbacks of the ad-hoc methods is that they do not comprehensively take into consideration the organization-specific factors such as mission and asset criticality, CSOC resource availability, demand variations, and the desired CSOC performance metrics. Hence, an ad-hoc triaging (or prioritization) method is insufficient, and an intelligent method for optimal selection of alerts that considers the above-mentioned organization-specific factors must be developed, which is described as a two-step process in this paper. First, a composite risk score of each alert is determined using a quantitative value function hierarchy process, which takes into account several organization-specific factors. Second, an optimization model selects a list of alerts for investigation that optimizes the CSOC performance metrics for a given demand subject to its resource constraints. Experimental results show that the alerts that pertain to mission criticalities are handled in a timelier manner as compared to current practices at the CSOCs. The average persistence time of an alert in the CSOC system is also shown to significantly reduce with this new approach, which is a paradigm shift in providing a stronger cyber-defense system by protecting the critical constituents of an organization.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
IEEE Trans. Inf. Forensics Secur.2
2018 Adaptive reallocation of cybersecurity analysts to sensors for balancing risk between sensors
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
Serv. Oriented Comput. Appl.2
2018 VULCON: A System for Vulnerability Prioritization, Mitigation, and Management
abstract
Vulnerability remediation is a critical task in operational software and network security management. In this article, an effective vulnerability management strategy, called VULCON (VULnerability CONtrol), is developed and evaluated. The strategy is based on two fundamental performance metrics: (1) time-to-vulnerability remediation (TVR) and (2) total vulnerability exposure (TVE). VULCON takes as input real vulnerability scan reports, metadata about the discovered vulnerabilities, asset criticality, and personnel resources. VULCON uses a mixed-integer multiobjective optimization algorithm to prioritize vulnerabilities for patching, such that the above performance metrics are optimized subject to the given resource constraints. VULCON has been tested on multiple months of real scan data from a cyber-security operations center (CSOC). Results indicate an overall TVE reduction of 8.97% when VULCON optimizes a realistic security analyst workforce’s effort. Additionally, VULCON demonstrates that it can determine monthly resources required to maintain a target TVE score. As such, VULCON provides valuable operational guidance for improving vulnerability response processes in CSOCs.
Katheryn A. Farris, Ankit Shah 0002, George Cybenko, Rajesh Ganesan, Sushil Jajodia
ACM Trans. Priv. Secur.4
2018 Dynamic Optimization of the Level of Operational Effectiveness of a CSOC Under Adverse Conditions
abstract
The analysts at a cybersecurity operations center (CSOC) analyze the alerts that are generated by intrusion detection systems (IDSs). Under normal operating conditions, sufficient numbers of analysts are available to analyze the alert workload. For the purpose of this article, this means that the cybersecurity analysts in each shift can fully investigate each and every alert that is generated by the IDSs in a reasonable amount of time and perform their normal tasks in a shift. Normal tasks include analysis time, time to attend training programs, report writing time, personal break time, and time to update the signatures on new patterns in alerts as detected by the IDS. There are several disruptive factors that occur randomly and can adversely impact the normal operating condition of a CSOC, such as (1) higher alert generation rates from a few IDSs, (2) new alert patterns that decrease the throughput of the alert analysis process, and (3) analyst absenteeism. The impact of the preceding factors is that the alerts wait for a long duration before being analyzed, which impacts the level of operational effectiveness (LOE) of the CSOC. To return the CSOC to normal operating conditions, the manager of a CSOC can take several actions, such as increasing the alert analysis time spent by analysts in a shift by canceling a training program, spending some of his own time to assist the analysts in alert investigation, and calling upon the on-call analyst workforce to boost the service rate of alerts. However, additional resources are limited in quantity over a 14-day work cycle, and the CSOC manager must determine when and how much action to take in the face of uncertainty, which arises from both the intensity and the random occurrences of the disruptive factors. The preceding decision by the CSOC manager is nontrivial and is often made in an ad hoc manner using prior experiences. This work develops a reinforcement learning (RL) model for optimizing the LOE throughout the entire 14-day work cycle of a CSOC in the face of uncertainties due to disruptive events. Results indicate that the RL model is able to assist the CSOC manager with a decision support tool to make better decisions than current practices in determining when and how much resource to allocate when the LOE of a CSOC deviates from the normal operating condition.
Ankit Shah 0002, Rajesh Ganesan, Sushil Jajodia, Hasan Çam
ACM Trans. Intell. Syst. Technol.2
2017 Optimal Scheduling of Cybersecurity Analysts for Minimizing Risk
abstract
Cybersecurity threats are on the rise with evermore digitization of the information that many day-to-day systems depend upon. The demand for cybersecurity analysts outpaces supply, which calls for optimal management of the analyst resource. Therefore, a key component of the cybersecurity defense system is the optimal scheduling of its analysts. Sensor data is analyzed by automatic processing systems, and alerts are generated. A portion of these alerts is considered to be significant , which requires thorough examination by a cybersecurity analyst. Risk, in this article, is defined as the percentage of unanalyzed or not thoroughly analyzed alerts among the significant alerts by analysts. The article presents a generalized optimization model for scheduling cybersecurity analysts to minimize risk (a.k.a., maximize significant alert coverage by analysts) and maintain risk under a pre-determined upper bound. The article tests the optimization model and its scalability on a set of given sensors with varying analyst experiences, alert generation rates, system constraints, and system requirements. Results indicate that the optimization model is scalable and is capable of identifying both the right mix of analyst expertise in an organization and the sensor-to-analyst allocation in order to maintain risk below a given upper bound. Several meta-principles are presented, which are derived from the optimization model, and they further serve as guiding principles for hiring and scheduling cybersecurity analysts. The simulation studies (validation) of the optimization model outputs indicate that risk varies non-linearly with an analyst/sensor ratio, and for a given analyst/sensor ratio, the risk is independent of the number of sensors in the system.
Rajesh Ganesan, Sushil Jajodia, Hasan Çam
ACM Trans. Intell. Syst. Technol.1
2016 Dynamic Scheduling of Cybersecurity Analysts for Minimizing Risk Using Reinforcement Learning
abstract
An important component of the cyber-defense mechanism is the adequate staffing levels of its cybersecurity analyst workforce and their optimal assignment to sensors for investigating the dynamic alert traffic. The ever-increasing cybersecurity threats faced by today’s digital systems require a strong cyber-defense mechanism that is both reactive in its response to mitigate the known risk and proactive in being prepared for handling the unknown risks. In order to be proactive for handling the unknown risks, the above workforce must be scheduled dynamically so the system is adaptive to meet the day-to-day stochastic demands on its workforce (both size and expertise mix). The stochastic demands on the workforce stem from the varying alert generation and their significance rate, which causes an uncertainty for the cybersecurity analyst scheduler that is attempting to schedule analysts for work and allocate sensors to analysts. Sensor data are analyzed by automatic processing systems, and alerts are generated. A portion of these alerts is categorized to be significant , which requires thorough examination by a cybersecurity analyst. Risk, in this article, is defined as the percentage of significant alerts that are not thoroughly analyzed by analysts. In order to minimize risk, it is imperative that the cyber-defense system accurately estimates the future significant alert generation rate and dynamically schedules its workforce to meet the stochastic workload demand to analyze them. The article presents a reinforcement learning-based stochastic dynamic programming optimization model that incorporates the above estimates of future alert rates and responds by dynamically scheduling cybersecurity analysts to minimize risk (i.e., maximize significant alert coverage by analysts) and maintain the risk under a pre-determined upper bound. The article tests the dynamic optimization model and compares the results to an integer programming model that optimizes the static staffing needs based on a daily-average alert generation rate with no estimation of future alert rates (static workforce model). Results indicate that over a finite planning horizon, the learning-based optimization model, through a dynamic (on-call) workforce in addition to the static workforce, (a) is capable of balancing risk between days and reducing overall risk better than the static model, (b) is scalable and capable of identifying the quantity and the right mix of analyst expertise in an organization, and (c) is able to determine their dynamic (on-call) schedule and their sensor-to-analyst allocation in order to maintain risk below a given upper bound. Several meta-principles are presented, which are derived from the optimization model, and they further serve as guiding principles for hiring and scheduling cybersecurity analysts. Days-off scheduling was performed to determine analyst weekly work schedules that met the cybersecurity system’s workforce constraints and requirements.
Rajesh Ganesan, Sushil Jajodia, Ankit Shah 0002, Hasan Çam
ACM Trans. Intell. Syst. Technol.1
2012 Work in progress: STEM capacity building and STEM outreach in India: A report on a recent NSF sponsored GK-12 George Mason trip to India
abstract
This session reports on the experiences of seven NSF GK-12 fellows, A PI and Co-PI and external evaluator who participated in a one month trip to India in December, 2011-January, 2012. The seven fellows are a part of a GK-12 STEM capacity building program sponsored by the National Science Foundation that pairs graduate fellows with K-12 teachers to bring hands on, cutting edge, inquiry based science to the classrooms in the Northern Virginia area.
Philip Henning, Rajesh Ganesan, Donna Sterling
FIE2
2011 Work in progress - SUNRISE: Schools, university 'N' (and) resources in the sciences and engineering-a NSF/GMU GK-12 fellows project
abstract
This WIP report is a continuation of the 1st and 2nd year work presented at the previous FIE conferences in 2008 and 2009 respectively. The WIP documents 4th year development, implementation efforts, and results of SUNRISE, a unique graduate Fellowship program at George Mason University (GMU) that targets graduate students working in the grade 4–6 school environment. SUNRISE is a new GK-12 project aimed at partnering STEM (Science, Technology, Engineering, and Mathematics) graduate students (Fellows) with school teachers from three different school divisions in Northern Virginia. The innovative practice aspect of the project is the construction of a framework that provides training, exchange of information, and integration of scientific research from diverse disciplines with teaching to make science exciting for students. A feature of SUNRISE that makes this project different from other GK-12 projects in the nation is that the project is housed in the School of Information Technology and Engineering which is unique in the nation. One of the contributions of the project is that it is focused on infusing Information Technology (IT) rich STEM concepts into K-12 education, which is also another unique feature. This WIP presents a summary of the project's impact on its key participants.
Rajesh Ganesan, Donna Sterling, Philip Henning
FIE1
2007 A Multiresolution Analysis-Assisted Reinforcement Learning Approach to Run-by-Run Control
abstract
In recent years, the run-by run (RbR) control mechanism has emerged as a useful tool for keeping complex semiconductor manufacturing processes on target during repeated short production runs. Many types of RbR controllers exist in the literature of which the exponentially weighted moving average (EWMA) controller is widely used in the industry. However, EWMA controllers are known to have several limitations. For example, in the presence of multiscale disturbances and lack of accurate process models, the performance of EWMA controller deteriorates and often fails to control the process. Also, the control of complex manufacturing processes requires sensing of multiple parameters that may be spatially distributed. New control strategies that can successfully use spatially distributed sensor data are required. This paper presents a new multiresolution analysis (wavelet) assisted reinforcement learning (RL)-based control strategy that can effectively deal with both multiscale disturbances in processes and the lack of process models. The novel idea of a wavelet-aided RL-based controller represents a paradigm shift in the control of large-scale stochastic dynamic systems of which the control problem is a subset. Henceforth, we refer our new control strategy as a WRL-RbR controller. The WRL-RbR controller is tested on a multiple-input-multiple-output chemical mechanical planarization process of wafer fabrication for which the process model is available. Results show that the RL controller outperforms EWMA-based controllers for low autocorrelation. The new controller also performs quite well for strongly autocorrelated processes for which the EWMA controllers are known to fail. Convergence analysis of the new breed of the WRL-RbR controller is presented. Further enhancement of the controller to deal with model-free processes and for inputs coming from spatially distributed environments are also discussed. Note to Practitioners-This work was motivated by the need to develop an intelligent and efficient RbR process controller, especially for the control of processes with short production runs as in the case of the semiconductor manufacturing industry. A novel controller that is presented here is capable of generating optimal control actions in the presence of multiple time-frequency disturbances, and allows the use of realistic (often complex) process models without sacrificing robustness and speed of execution. Performance measures, such as reduction of variability in process output and control recipe, minimization of initial bias, and ability to control processes with high autocorrelations are shown to be superior in comparison to the commercially available exponentially weighted moving average controllers. The WRL-RbR controller is very generic, and can be easily extended to processes with drifts and sudden shifts in the mean and variance. The viability of extending the controller to distributed input parameter sensing environments, including those for which process models are not available, is also discussed
Rajesh Ganesan, Tapas K. Das, Kandethody M. Ramachandran
IEEE Trans Autom. Sci. Eng.1