Partha Roop

Partha Roop
University of Auckland · Department of Electrical & Computer Engineering

PhD, UNSW, Sydeny, 2001

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201
Publications
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Publications

Publications (201)
Chapter
Cyber‐physical (CP) attacks, originate in cyber space but damage physical infrastructure, and are a significant recent research focus. Such attacks have affected many CP systems such as smart grids, intelligent transportation systems and medical devices. In this chapter we consider techniques for the detection and mitigation of CP attacks on medica...
Article
Background and objective: Gastrointestinal (GI) motility disorders can be significantly detrimental to the quality of life. Pacing, or long pulse gastric electrical stimulation, is a potential treatment option for treating GI motility disorders by modulating the slow wave activity. Open-loop pacing of the GI tract is the current standard for modul...
Preprint
Biophysical signals such as Electrocardiogram (ECG) and Photoplethysmogram (PPG) are key to the sensing of vital parameters for wellbeing. Coincidentally, ECG and PPG are signals, which provide a "different window" into the same phenomena, namely the cardiac cycle. While they are used separately, there are no studies regarding the exact correction...
Article
Objective Ventilatory pacing by electrical stimulation of the phrenic nerve has many advantages compared to mechanical ventilation. However, commercially available respiratory pacing devices operate in an open-loop fashion, which require manual adjustment of stimulation parameters for a given patient. Here, we report the model development of a clos...
Preprint
Cyber-Physical Systems (CPSs) such as those found within autonomous vehicles are increasingly adopting Artificial Neural Network (ANN)-based controllers. To ensure the safety of these controllers, there is a spate of recent activity to formally verify the ANN-based designs. There are two challenges with these approaches: (1) The verification of suc...
Article
Full-text available
Hybrid systems are a subset of Cyber-Physical Systems, where a physical process (the plant) is controlled by a discrete controller. The controller induces mode switches, which are modelled as guard conditions leading to sudden discontinuities. Correctly capturing sudden discontinuities during simulation is the primary challenge to maintain fidelity...
Article
Full-text available
The COVID-19 pandemic has posed significant challenges globally. Countries have adopted different strategies with varying degrees of success. Epidemiologists are studying the impact of government actions using scenario analysis. However, the interactions between the government policy and the disease dynamics are not formally captured. We, for the f...
Preprint
Artificial Neural Networks (ANNs) are increasingly being used within safety-critical Cyber-Physical Systems (CPSs). They are often co-located with traditional embedded software, and may perform advisory or control-based roles. It is important to validate both the timing and functional correctness of these systems. However, most approaches in the li...
Article
Artificial Neural Networks (ANNs) are increasingly being used within safety-critical Cyber-Physical Systems (CPSs). It is important to validate both the timing and functional correctness of these systems. However, most approaches in the literature consider guaranteeing only the functionality of ANN based controllers. This issue stems largely from t...
Article
Full-text available
Cyber–physical Systems (CPS) involve a network of discrete controllers that control physical processes, e.g., pacemakers controlling the heart rhythm. The intuitive and formal Hybrid Automata (HA) based modelling approach for CPS is gaining momentum. HA combines the model of the plant along with its discrete controller resulting in a piece-wise con...
Preprint
Full-text available
COVID-19 pandemic has posed significant challenges globally. Countries have adopted different strategies with varying degrees of success. Epidemiologists are studying the impact of government actions using scenario analysis. However, the interactions between the government policy and the disease dynamics are not formally captured. We, for the first...
Article
Full-text available
Rear-end collision avoidance relies on mathematical models to calculate the safety distance. Vehicle deceleration is a key parameter for the accuracy of the models. Current models, however, assume a constant deceleration during braking, which is unrealistic. This assumption results in large over-approximation / under-approximation. In this paper, w...
Article
Particle Hopping Models (PHM) are discrete models employed to mimic vehicular traffic, protein transport mechanisms, granular flows and other extended dynamic systems. Despite their simplistic exclusion principle, PHM correctly reproduce many macroscopic phenomena. Currently, positions of simulated entities in a PHM are updated at distinct moments...
Article
Full-text available
Understanding the slow wave propagation patterns of Interstitial Cells of Cajal (ICC) is essential when designing Gastric Electrical Stimulators (GESs) to treat motility disorders. A GES with the ability to both sense and pace, working in closed-loop with the ICC, will enable efficient modulation of Gastrointestinal (GI) dysrhythmias. However, exis...
Article
Full-text available
Co-simulation--based validation of hardware controllers adjoined with plant models, with continuous dynamics, is an important step in model-based design of controllers for Cyber-physical Systems (CPS). Co-simulation suffers from many problems, such as timing delays, skew, race conditions, and so on, making it unsuitable for checking timing properti...
Article
Full-text available
Abstract—Objective: Cardiovascular Implantable Electronic Devices (CIEDs) are used extensively for treating life-threatening conditions such as bradycardia, atrioventricular block and heart failure. The complicated heterogeneous physical dynamics of patients provide distinct challenges to device development and validation. We address this problem b...
Conference Paper
Cyber-Physical Systems are highly safety critical, especially since they have to provide both functional and timing guarantees. Increasingly, Cyber-Physical Systems such as autonomous vehicles are relying on Artificial Neural Networks in their decision making and this has obvious safety implications. While many formal approaches have been recently...
Conference Paper
In recent years we have seen numerous proof-of-concept attacks on implantable medical devices such as pacemakers. Attackers aim to breach the strict operational constraints that these devices operate within, with the end-goal of compromising patient safety and health. Most efforts to prevent these kinds of attacks are informal, and focus on applica...
Conference Paper
Full-text available
Simulink/Stateflow® is the de-facto tool for design of Cyber-physical Systems (CPS). CPS include hybrid systems, where a discrete controller guides a continuous plant. Hybrid systems are characterised by their continuous time dynamics with sudden discontinuities, caused by level/zero crossings. Stateflow can graphically capture hybrid phenomenon, m...
Article
Cyber-Physical Systems (CPSs) are implemented in many industrial and embedded control applications. Where these systems are safety-critical, correct and safe behaviour is of paramount importance. Malicious attacks on such CPSs can have far-reaching repercussions. For instance, if elements of a power grid behave erratically, physical damage and loss...
Chapter
The intuitionistic theory of the real interval [0, 1], known as Skolem-Gödel-Dummet logic (SGD), generates a well-known Heyting algebra intermediate between intuitionistic and classical logic. Originally of purely mathematical interest, it has recently received attention in Computer Science, notably for its potential applications in concurrency the...
Article
Full-text available
Organ level simulation of bioelectric behavior in the body benefits from flexible and efficient models of cellular membrane potential. These computational organ and cell models can be used to study the impact of pharmaceutical drugs, test hypotheses, assess risk and for closed-loop validation of medical devices. To move closer to the real-time requ...
Article
Full-text available
Objective: Evaluating and testing cardiac electrical devices in a closed-physiologic-loop can help design safety, but this is rarely practical or comprehensive. Furthermore, in-silico closed-loop testing with biophysical computer models cannot meet the requirements of time-critical cardiac device systems, while simplified models meeting time-criti...
Article
Full-text available
Objective: Efficient and accurate organ models are crucial for closed-loop validation of implantable medical devices. This paper investigates bio-electric slow wave modeling of the stomach, so that Gastric Electrical Stimulator (GES) can be validated and verified prior to implantation. In particular, we consider high-fidelity, scalable, and efficie...
Article
The emerging Die-stacking technology enables DRAM to be used as a cache to break the “Memory Wall” problem. Recent studies have proposed to use DRAM as a victim cache in both CPU and GPU memory hierarchies to improve performance. DRAM caches are large in size and, hence, when realized as a victim cache, non-inclusive design is preferred. This non-i...
Article
Die-stacking technology enables the use of a high density DRAM as a cache. Major processor vendors have recently started using these stacked DRAM modules as the last level cache of their products. These stacked DRAM modules provide high bandwidth with relatively low latency compared to the off-package DRAM modules. Recent studies on DRAM caches pro...
Preprint
Full-text available
Cyber-physical systems involve a network of discrete controllers that control physical processes. Examples range from autonomous cars to implantable medical devices, which are highly safety critical. Hybrid Automata (HA) based formal approach is gaining momentum for the specification and validation of CPS. HA combines the model of the plant along w...
Article
User data is touted as new oil in our times of digital economy. Colluding apps can pose a threat to leak private information in Android. In this paper, a technique is proposed to address the threat emanating from multiple colluding Android applications (apps). Android framework is not made to protect the data that is going outside an app. In such a...
Chapter
Full-text available
Synchronous Programming (SP) is a universal computational principle that provides deterministic concurrency. The same input sequence with the same timing always results in the same externally observable output sequence, even if the internal behaviour generates uncertainty in the scheduling of concurrent memory accesses. Consequently, SP languages h...
Article
Microscopic traffic simulations capture the trajectories of individual drivers as responses to stimuli from their surroundings (i.e. other vehicles or road conditions). Mathematically, these models are usually designed with differential equations or as sets of integer-based rules. Since both approaches have disadvantages, we propose an in-between a...
Conference Paper
Microscopic traffic models replicate the behaviour of individual drivers and their interactions with each other. As such, the accuracy of simulation predictions is closely tied to a realistic reproduction of actual human driving behaviour. Despite being a well-researched subject, there is not much literature about the differences between drivers; i...
Article
Full-text available
Car-following is the activity of safely driving behind a leading vehicle. Traditional mathematical car-following models capture vehicle dynamics without considering human factors, such as driver distraction and the reaction delay. Consequently, the resultant model produces overly safe driving traces during simulation, which are unrealistic. Some re...
Conference Paper
IEC61499 is an emerging standard for the design of automation systems. While many compilers and associated tools for IEC61499 have been developed, systematic techniques for modelling the continuous dynamics of the physical processes are lacking. Current practices involve using co-simulation, where plants are modelled in a tool such as Simulink and...
Article
Full-text available
Models of the cardiac conduction system are usually at two extremes: (1) high fidelity models with excellent precision but lacking a real-time response for emulation (hardware in the loop simulation); or (2) models amenable for emulation, but that do not exhibit appropriate dynamic response, which is necessary for arrhythmia susceptibility. We intr...
Article
Full-text available
Hybrid systems combine discrete controllers with adjoining physical processes. While many approaches exist for simulating hybrid systems, there are few approaches for their emulation, especially when the actual physical plant is not available. This paper develops the first formal framework for emulation along with a new compiler that enables large-...
Article
Synchronous languages are ideal for designing safety-critical systems. Static Worst-Case Reaction Time (WCRT) analysis is an essential component in the design flow that ensures the real-time requirements are met. There are a few approaches for WCRT analysis, and the most versatile of all is explicit path enumeration. However, as synchronous program...
Article
Many implantable medical devices, such as pacemakers, have been recalled due to failure of their embedded software. This motivates rethinking their design and certification processes. We propose, for the first time, an additional layer of safety by formalising the problem of run-time enforcement of implantable pacemakers. While recent work has form...
Conference Paper
Synchronous programming is a paradigm of choice for the design of safety-critical reactive systems. Runtime enforcement is a technique to ensure that the output of a black-box system satisfies some desired properties. This paper deals with the problem of runtime enforcement in the context of synchronous programs. We propose a framework where an enf...
Article
Full-text available
Automation systems used in smart grids, transportation, and medical electronics are cyber-physical in nature. Automation standards, such as IEC-61499, while well suited to the design of discrete controllers, are not ideally suited to model the dynamics of the plant. Such modelling is essential for emulation-based validation of the controllers in th...
Conference Paper
Full-text available
Virtual heart models have been proposed to enhance the safety of implantable cardiac devices through closed loop validation. To communicate with a virtual heart, devices have been driven by cardiac signals at specific sites. As a result, only the action potentials of these sites are sensed. However, the real device implanted in the heart will sense...
Article
Full-text available
Objective: A flexible, efficient and verifiable pacemaker cell model is essential to the design of real-time virtual hearts that can be used for closed-loop validation of cardiac devices. A new parametric model of pacemaker action potential is developed to address this need. Methods: The action potential phases are modeled using hybrid automaton...
Conference Paper
Sensitive (private) information can escape from one app to another using one of the multiple communication methods provided by Android for inter-app communication. This leakage can be malicious. In such a scenario, individual benign app, in collusion with other conspiring apps, if present, can leak the private information. In this work in progress,...
Article
Full-text available
Virtual heart models have been proposed to enhance the safety of implantable cardiac devices through closed loop validation. To communicate with a virtual heart, devices have been driven by cardiac signals at specific sites. As a result, only the action potentials of these sites are sensed. However, the real device implanted in the heart will sense...
Article
Full-text available
Synchronous programming is a paradigm of choice for the design of safety-critical reactive systems. Runtime enforcement is a technique to ensure that the output of a black-box system satisfies some desired properties. This paper deals with the problem of runtime enforcement in the context of synchronous programs. We propose a framework where an enf...
Conference Paper
Full-text available
To estimate the efficiency of ITS or other traffic flow improvement activities, microsimulations of solitary intersections or real-world topologies are the preferred tool in transport engineering. Both approaches have major drawbacks: the former neglects system-wide network effects and the latter impedes transferring the results to other environmen...
Conference Paper
The synchronous paradigm is widely used for the design of safety critical systems. Such systems, especially in the medical devices domain, must meet strict timing requirements while also ensuring long battery life. As a consequence, they are subject to very strict constraint both regarding their WCRT (Worst-Case Reaction Time) and their WCEC (Worst...
Article
The IEC 61499 standard enables the model-based design of complex industrial automation systems where a model of the controlled physical processes called a plant is co-developed with the controller. However, the existing design flow does not address functional safety issues which include limiting risk to acceptable levels. Standards like IEC 61508 p...
Conference Paper
Full-text available
Cyber-physical systems (CPSs) are embedded systems that are tightly integrated with their physical environment. The correctness of a CPS depends on the output of its computations and on the timeliness of completing the computations. This paper proposes the ForeC language for the deterministic parallel programming of CPS applications on multi-core e...
Conference Paper
Semantics for synchronous programming languages are well known. They capture the execution behaviour of reactive systems using precise formal operational or denotational models for verification and unambiguous semantics-preserving compilation. As synchronous programs are highly time critical, there is an imminent need for the development of an exec...
Conference Paper
Virtual heart models have been proposed for closed loop validation of safety-critical embedded medical devices, such as pacemakers. These models must react in real-time to off-the-shelf medical devices. Real-time performance can be obtained by implementing models in computer hardware, and methods of compiling classes of Hybrid Automata (HA) onto FP...
Article
Full-text available
The heart is a vital organ that relies on the orchestrated propagation of electrical stimuli to coordinate each heartbeat. Abnormalities in the heart’s electrical behaviour can be managed with a cardiac pacemaker. Recently, the closed-loop testing of pacemakers with an emulation (real-time simulation) of the heart has been proposed. This enables de...
Article
IEC 61499 enables component-oriented descriptions of complex industrial processes facilitating model-driven engineering. One aspect that is lacking, however, is the ability to directly express Statecharts-like hierarchy and concurrency within basic function blocks (BFBs). Such features can significantly enhance function blocks and help create more...