Lui Sha's research while affiliated with University of Illinois, Urbana-Champaign and other places

Publications (336)

Conference Paper
Full-text available
This paper presents a self-cueing real-time framework for attention prioritization in AI-enabled visual perception systems that minimizes a notion of state uncertainty. By attention prioritization we refer to inspecting some parts of the scene before others in a criticality-aware fashion. By self-cueing, we refer to not needing external cueing sens...
Conference Paper
Full-text available
Many cyber-physical systems are offloading computation-heavy programs to hardware accelerators (e.g., GPU and TPU) to reduce execution time. These applications will self-suspend between offloading data to the accelerators and obtaining the returned results. Previous efforts have shown that self-suspending tasks can cause scheduling anomalies, but n...
Preprint
Full-text available
Object detection in state-of-the-art Autonomous Vehicles (AV) framework relies heavily on deep neural networks. Typically, these networks perform object detection uniformly on the entire camera LiDAR frames. However, this uniformity jeopardizes the safety of the AV by giving the same priority to all objects in the scenes regardless of their risk of...
Article
This paper explores criticality-based real-time scheduling of neural-network-based machine inference pipelines in cyber-physical systems (CPS) to mitigate the effect of algorithmic priority inversion. We specifically focus on the perception subsystem, an important subsystem feeding other components. In current machine perception software, significa...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-2463.vid Unmanned aerial vehicles (UAVs) suffer from sensor drifts in GPS denied environments, which can cause safety issues. To avoid intolerable sensor drifts while completing the time-critical coordination task for multi-UAV systems, we propose a safety constrained bi-level control framewor...
Preprint
Full-text available
This paper proposes a novel extension of the Simplex architecture with model switching and model learning to achieve safe velocity regulation of self-driving vehicles in dynamic and unforeseen environments. To guarantee the reliability of autonomous vehicles, an $\mathcal{L}_{1}$ adaptive controller that compensates for uncertainties and disturbanc...
Preprint
Commonly used metrics for evaluation of object detection systems (precision, recall, mAP) do not give complete information about their suitability of use in safety critical tasks, like obstacle detection for collision avoidance in Autonomous Vehicles (AV). This work introduces the Risk Ranked Recall ($R^3$) metrics for object detection systems. The...
Article
Full-text available
Multicore processors provide great average-case performance. However, the use of multicore processors for safety-critical applications can lead to catastrophic consequences because of contention on shared resources. The problem has been well-studied in literature, and solutions such as partitioning of shared resources have been proposed. Strict par...
Preprint
Real-time systems have recently been shown to be vulnerable to timing inference attacks, mainly due to their predictable behavioral patterns. Existing solutions such as schedule randomization lack the ability to protect against such attacks, often limited by the system's real-time nature. This paper presents SchedGuard: a temporal protection framew...
Preprint
This article proposes a new safety concept: backup plan safety. The backup plan safety is defined as the ability to complete one of the alternative missions in the case of primary mission abortion. To incorporate this new safety concept in control problems, we formulate a feasibility maximization problem that adopts additional (virtual) input horiz...
Preprint
Full-text available
This paper proposes a novel model inference procedure to identify system matrix from a single noisy trajectory over a finite-time interval. The proposed inference procedure comprises an observation data processor, a redundant data processor and an ordinary least-square estimator, wherein the data processors mitigate the influence of observation noi...
Preprint
Road condition is an important environmental factor for autonomous vehicle control. A dramatic change of the road condition from the nominal status is a source of uncertainty that can lead to a system failure. Once the vehicle encounters an uncertain environment, such as hitting an ice patch, it is too late to reduce the speed, and the vehicle can...
Article
During the system development process, domain experts and developers often make assumptions about specifications and implementations. However, most of the assumptions being taken for granted by domain experts and developers are too tedious to be documented by them. When these unspecified assumptions are violated in an environment in which the syste...
Preprint
Unmanned aerial vehicles (UAVs) suffer from sensor drifts in GPS denied environments, which can cause safety issues. To avoid intolerable sensor drifts while completing the time-critical coordination task for multi-UAV systems, we propose a safety constrained bi-level control framework. The first level is the time-critical coordination level that a...
Article
Improving safety of patient care is an ultimate objective for medical systems. Though many medical best practice guidelines exist and are in hospital handbooks, they are often lengthy and difficult for medical professionals to remember and apply clinically. Hence, developing safe medical best practice guideline systems is an urgent need. The paper...
Preprint
Unmanned aerial vehicles (UAVs) suffer from sensor drifts in GPS denied environments, which can lead to potentially dangerous situations. To avoid intolerable sensor drifts in the presence of GPS spoofing attacks, we propose a safety constrained control framework that adapts the UAV at a path re-planning level to support resilient state estimation...
Preprint
Improving the effectiveness and safety of patient care is the ultimate objective for medical cyber-physical systems. Many medical best practice guidelines exist, but most of the existing guidelines in handbooks are difficult for medical staff to remember and apply clinically. Furthermore, although the guidelines have gone through clinical validatio...
Article
Full-text available
This paper presents a scheduling model, called decision-driven scheduling, elaborates key optimality results for a fundamental scheduling model, and evaluates new heuristics solving more general versions of the problem. In the context of applications that need control and actuation, the traditional execution model has often been either time-driven...
Preprint
Full-text available
This paper considers a resilient state estimation framework for unmanned aerial vehicles (UAVs) that integrates a Kalman filter-like state estimator and an attack detector. When an attack is detected, the state estimator uses only IMU signals as the GPS signals do not contain legitimate information. This limited sensor availability induces a sensor...
Article
Simulink is widely used for model-driven development (MDD) of cyber-physical systems. Typically, the Simulink-based development starts with Stateflow modeling, followed by simulation, validation, and code generation mapped to physical execution platforms. However, recent trends have raised the demands of rigorous verification on safety-critical app...
Article
This paper considers a resilient state estimation framework for unmanned aerial vehicles (UAVs) that integrates a Kalman filter-like state estimator and an attack detector. When an attack is detected, the state estimator uses only IMU signals as the GPS signals do not contain legitimate information. This limited sensor availability induces a sensor...
Preprint
The Unmanned aerial vehicles (UAVs) sector is fast-expanding. Protection of real-time UAV applications against malicious attacks has become an urgent problem that needs to be solved. Denial-of-service (DoS) attack aims to exhaust system resources and cause important tasks to miss deadlines. DoS attack may be one of the common problems of UAV system...
Preprint
Improving patient care safety is an ultimate objective for medical cyber-physical systems. A recent study shows that the patients' death rate can be significantly reduced by computerizing medical best practice guidelines. To facilitate the development of computerized medical best practice guidelines, statecharts are often used as a modeling tool be...
Article
As the complexity of Cyber-Physical Systems (CPS) increases, it becomes increasingly challenging to ensure CPS reliability, especially in the presence of software and/or physical failures. The Simplex architecture is shown to be an efficient tool to address software failures in such systems. When physical failures exist, however, Simplex may not fu...
Article
Paroxysmal diseases of inpatients are globally recognized as one of the top challenges in medicine. Poor clinical outcomes are primarily caused by delayed recognition, especially due to diverse clinical diagnostic criteria with complex manifestations, irregular episodes, and already overloaded clinical activities. With the proliferation of measurin...
Conference Paper
According to the U.S. Food and Drug Administration (FDA) medical device recall database, medical device recalls are at an all-time high. One of the major causes of the recalls is due to implicit assumptions of which either the medical device operating environment does not match, or the device operators are not aware of. In this paper, we present IA...
Conference Paper
Requirements management and safety analysis have been the key foundations of the successful development of life-critical systems, and the traceability of safety-related artifacts across such systems is becoming ever more important. Unless safety analysts can trace when and how requirements and design change, their analysis will become inconsistent,...
Conference Paper
Improving patient care safety is an ultimate objective for medical cyber-physical systems. A recent study shows that the patients' death rate is significantly reduced by computerizing medical best practice guidelines. Recent data also show that some morbidity and mortality in emergency care are directly caused by delayed or interrupted treatment du...
Article
Full-text available
In this paper, we present a formal model-driven design approach to establish a safety-assured implementation of multifunction vehicle bus controller (MVBC), which controls the data transmission among the devices of the vehicle. First, the generic models and safety requirements described in International Electrotechnical Commission Standard 61375 ar...
Article
Full-text available
The paper introduces a new direction in quality-of-service-aware networked sensing that designs communication protocols and scheduling policies for data delivery that are optimized specifically for decision needs. The work complements present decision monitoring and support tools and falls in the larger framework of decision-driven resource managem...
Article
Full-text available
Model-based development is a widely-used method to describe complex systems that enables the rapid prototyping. Advances in the science of distributed systems has led to the development of large scale statechart models which are distributed among multiple locations. Taking medicine for example, models of best-practice guidelines during rural ambula...
Conference Paper
Improving effectiveness and safety of patient care is an ultimate objective for medical cyber-physical systems. A recent study shows that the patients' death rate can be reduced by computerizing medical guidelines. Most existing medical guideline models are validated and/or verified based on the assumption that all necessary medical resources neede...
Article
Full-text available
The work of a hospital’s medical staff is safety critical and often occurs under severe time constraints. To provide timely and effective cognitive support to medical teams working in such contexts, guidelines in the form of best practice workflows for healthcare have been developed by medical organizations. However, the high cognitive load imposed...
Article
Full-text available
In this article, we describe a general methodology for enhancing sensing accuracy in cyber-physical systems that involve structured human interactions in noisy physical environment. We define structured human interactions as domain-specific workflow. A novel workflow-aware sensing model is proposed to jointly correct unreliable sensor data and keep...
Article
Full-text available
The ultimate objective of medical cyber-physical systems is to enhance the safety and effectiveness of patient care. To ensure safe and effective care during emergency patient transfer from rural areas to center tertiary hospitals, reliable and real-time communication is essential. Unfortunately, real-time monitoring of patients involves transmissi...
Chapter
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This chapter considers some of the problems associated with many current approaches to automation design that adopt a displacement approach, in which automated systems are considered as substituting for functions that had typically been performed by humans in system control (e.g., control theory) and human decision making (multi-attribute decision...
Article
Full-text available
In emergency patient transport from rural medical facility to center tertiary hospital, real-time monitoring of the patient in the ambulance by a physician expert at the tertiary center is crucial. While telemetry healthcare services using mobile networks may enable remote real-time monitoring of transported patients, physiologic measures and track...
Conference Paper
Full-text available
Use of telecommunication technologies for remote, continuous monitoring of patients can enhance effectiveness of emergency ambulance care during transport from rural areas to a regional center hospital. However, the communication along the various routes in rural areas may have wide bandwidth ranges from 2G to 4G; some regions may have only lower s...
Conference Paper
As modern unmanned aerial systems (UAS) continue to expand the frontiers of automation, new challenges to security and thus its safety are emerging. It is now difficult to completely secure modern UAS platforms due to their openness and increasing complexity. We present the VirtualDrone Framework, a software architecture that enables an attack-resi...
Conference Paper
Full-text available
For emergency medical cyber-physical systems, enhancing the safety and effectiveness of patient care, especially in rural areas, is essential. While the doctor to patient ratio in the United States is 30 to 10,000 in large metropolitan areas, it is only 5 to 10,000 in most rural areas; and the highest death rates are often found in the most rural c...
Conference Paper
Existing techniques used for anomaly detection do not fully utilize the intrinsic properties of embedded devices. In this paper, we propose a lightweight method for detecting anomalous executions using a distribution of system call frequencies. We use a cluster analysis to learn the legitimate execution contexts of embedded applications and then mo...
Article
Full-text available
In a medical environment such as Intensive Care Unit, there are many possible reasons to cause errors, and one important reason is the effect of human intellectual tasks. When designing an interactive healthcare system such as medical Cyber-Physical-Human Systems (CPHSystems), it is important to consider whether the system design can mitigate the e...
Conference Paper
In this paper, we present a formal model-driven engineering approach to establishing a safety-assured implementation of Multifunction vehicle bus controller (MVBC) based on the generic reference models and requirements described in the International Electrotechnical Commission (IEC) standard IEC-61375. First, the generic models described in IEC-613...
Preprint
Full-text available
Clinical guidance systems have been widely adopted to help medical staffs to avoid preventable medical errors such as delay in diagnosis, treatment or untended deviations from best practice guidelines. However, because patient condition changes rapidly and medical staffs are usually overloaded in acute care setting, how to ensure the correctness of...
Article
Full-text available
There is a great divide between rural and urban areas, particularly in medical emergency care. Although medical best practice guidelines exist in hospital handbooks, they are often lengthy and difficult to apply clinically. The challenges are exaggerated for doctors in rural areas and emergency medical technicians (EMT) during patient transport. In...
Article
Full-text available
Architects of multicore chips for avionics must define and bound intercore interference, which requires assuming a constant worst-case execution time for tasks executing on the chip. With the Single Core Equivalent technology package, engineers can treat each core as if it were a single-core chip.