The Internet of Medical Things (IoMT) designates the interconnection of communication-enabled medical-grade devices and their integration to wider-scale health networks in order to improve patients’ health. However, because of the critical nature of health-related systems, the IoMT still faces numerous challenges, more particularly in terms of reliability, safety, and security. In this paper, we present a comprehensive literature review of recent contributions focused on improving the IoMT through the use of formal methodologies provided by the cyber-physical systems community. We describe the practical application of the democratization of medical devices for both patients and health-care providers. We also identify unexplored research directions and potential trends to solve uncharted research problems.

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Internet of Medical Things: A Review of Recent Contributions Dealing With Cyber-Physical Systems in Medicine

Safety and security have traditionally been distinct problems in engineering and computer science. The introduction of computing elements to create cyber-physical systems (CPSs) has opened up a vast new range of potential problems that do not always show up on the radar of traditional engineers. Security, in contrast, is traditionally viewed as a data or communications security problem to be handled by computer scientists and/or computer engineers. Advances in CPSs and the Internet-of-Things (IoT) requires us to take a unified view of safety and security. This paper defines a safety/security threat model for CPSs and IoT systems and surveys emerging techniques which improve the safety and security of CPSs and IoT systems.

Safety and Security in Cyber-Physical Systems and Internet-of-Things Systems

The benefits associated with structural control include the mitigation of undesired structural responses and reduction in the probability of damage to structural components during seismic events. Structural control systems in current use depend on extensive wired communication systems to connect sensors and actuators with a centralized controller. While wired architectures are appropriate when control systems are small, the cost and installation complexity of tethered systems increases as the control system grows large (i.e., defined by hundreds of nodes). Alternatively, wireless sensors are proposed for use in large-scale structural control systems to keep costs low and to improve system scalability. Wireless sensors are capable of collecting state data from sensors, communicating data between themselves, calculating control actions, and commanding actuators in a control system. However, bandwidth and range limitations of the wireless communication channel render traditional centralized control solutions impractical for the wireless setting. While computational abilities embedded with each wireless sensor permit fully decentralized control architectures to be implemented, strategic utilization of the wireless channel can improve the performance of the wireless control system. Toward this end, this paper presents a partially decentralized linear quadratic regulation control scheme that employs redundant state estimation as a means of minimizing the need for the communication of state data between sensors. The method is validated using numerical simulations of a seismically excited six-story building model with ideal actuators. Additional experimental validation is conducted using a full-scale physical realization of the six-story building. A wireless sensor network commanding magnetorheological dampers is shown to be effective in controlling a multistory structure using the partially decentralized control architecture proposed.

Strategic Network Utilization in a Wireless Structural Control System for Seismically Excited Structures

Structural control technologies have attracted great interest from the earthquake engineering community over the last few decades as an effective method of reducing undesired structural responses. Traditional structural control systems employ large quantities of cables to connect structural sensors, actuators, and controllers into one integrated system. To reduce the high-costs associated with labor-intensive installations, wireless communication can serve as an alternative real-time communication link between the nodes of a control system. A prototype wireless structural sensing and control system has been physically implemented and its performance verified in large-scale shake table tests. This paper introduces the design of this prototype system and investigates the feasibility of employing decentralized and partially decentralized control strategies to mitigate the challenge of communication latencies associated with wireless sensor networks. Closed-loop feedback control algorithms are embedded within the wireless sensor prototypes allowing them to serve as controllers in the control system. To validate the embedment of control algorithms, a 3-story half-scale steel structure is employed with magnetorheological (MR) dampers installed on each floor. Both numerical simulation and experimental results show that decentralized control solutions can be very effective in attaining the optimal performance of the wireless control system.

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Decentralized civil structural control using real-time wireless sensing and embedded computing

Lost data recovery for structural health monitoring based on convolutional neural networks

The introduction of wireless telemetry into the design of monitoring and control systems has been shown to reduce
system costs while simplifying installations. To date, wireless nodes proposed for sensing and actuation in cyberphysical
systems have been designed using microcontrollers with one computational pipeline (i.e., single-core
microcontrollers). While concurrent code execution can be implemented on single-core microcontrollers,
concurrency is emulated by splitting the pipeline’s resources to support multiple threads of code execution. For
many applications, this approach to multi-threading is acceptable in terms of speed and function. However, some
applications such as feedback controls demand deterministic timing of code execution and maximum computational
throughput. For these applications, the adoption of multi-core processor architectures represents one effective
solution. Multi-core microcontrollers have multiple computational pipelines that can execute embedded code in
parallel and can be interrupted independent of one another. In this study, a new wireless platform named Martlet is
introduced with a dual-core microcontroller adopted in its design. The dual-core microcontroller design allows
Martlet to dedicate one core to standard wireless sensor operations while the other core is reserved for embedded
data processing and real-time feedback control law execution. Another distinct feature of Martlet is a standardized
hardware interface that allows specialized daughter boards (termed wing boards) to be interfaced to the Martlet
baseboard. This extensibility opens opportunity to encapsulate specialized sensing and actuation functions in a wing
board without altering the design of Martlet. In addition to describing the design of Martlet, a few example wings
are detailed, along with experiments showing the Martlet’s ability to monitor and control physical systems such as
wind turbines and buildings.

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Development of an extensible dual-core wireless sensing node for cyber-physical systems

In recent years, substantial research has been conducted to advance structural control as a direct means of mitigating the 
dynamic response of civil structures. In parallel to these efforts, the structural engineering field is currently exploring 
low-cost wireless sensors for use in structural monitoring systems. To reduce the labor and costs associated with 
installing extensive lengths of coaxial wires in today's structural control systems, wireless sensors are being considered 
as building blocks of future systems. In the proposed system, wireless sensors are designed to perform three major tasks 
in the control system; wireless sensors are responsible for the collection of structural response data, calculation of 
control forces, and issuing commands to actuators. In this study, a wireless sensor is designed to fulfill these tasks 
explicitly. However, the demands of the control system, namely the need to respond in real-time, push the limits of 
current wireless sensor technology. The wireless channel can introduce delay in the communication of data between 
wireless sensors; in some rare instances, outright data loss can be experienced. Such issues are considered an intricate 
part of this feasibility study. A prototype Wireless Structural Sensing and Control (WiSSCon) system is presented 
herein. To validate the performance of this prototype system, shaking table experiments are carried out on a half-scale 
three story steel structure in which a magnetorheological (MR) damper is installed for real-time control. In comparison 
to a cable-based control system installed in the same structure, the performance of the WiSSCon system is shown to be 
effective and reliable.

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Wireless feedback structural control with embedded computing

Advances in wireless communication and embedded computing technologies can have significant impacts in structural sensing, monitoring and control. Prior research efforts have demonstrated the benefits of low-cost wireless sensing systems for structural monitoring. This paper discusses the possibilities of extending the functionalities of wireless sensors for structural control applications. By incorporating a computational core module and an actuation signal generation module, wireless sensors can be extended to compute and issue appropriate control commands for structural actuation and real-time control applications. This paper discusses laboratory tests to assess the viability of utilizing wireless sensing and actuation for decentralized structural control. A six-story scaled structure installed with semi-active magnetorheological (MR) dampers is employed in the experiment. Wireless sensors and controllers are employed to compute and apply feedback control forces in real time. Different centralized and decentralized feedback control architectures are investigated. Furthermore decentralized control strategies and information processing issues related to wireless sensing and control are discussed.

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Decentralized Control Strategies with Wireless Sens ing and Actuation

Structural sensing, monitoring and control can benefit from wireless communication and embedded computing technologies in terms of installation cost and time. Our prior research has developed low-cost wireless sensing systems for structural monitoring. By incorporating an actuation signal generation module, the functionalities of wireless sensors can be extended to support structural actuation and real-time control applications. This paper discusses the laboratory experiments that are designed to assess the viability of decentralized wireless structural control using a six-story scaled structure. Commanded by wireless sensors and controllers, semi-active magnetorheological (MR) dampers are installed between neighboring floors for applying real-time feedback control forces. Multiple centralized and decentralized feedback control architectures, in combination with different sampling frequencies, are investigated. Decentralized control strategies and information processing issues related to wireless sensing and control are discussed.

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Wireless Sensing and Structural Control Strategies

This paper describes a set of preliminary laboratory experiments to demonstrate the different centralized/decentralized wireless sensing and control architectures. The results have demonstrated the viability and potential of wireless sensing and control devices for large scale decentralized structural control applications. Other robust and dynamic control strategies utilizing wireless sensing network are currently being investigated.

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Andrew Swartz

Papers

Development of an extensible dual-core wireless sensing node for cyber-physical systems

Wireless feedback structural control with embedded computing

Decentralized Control Strategies with Wireless Sens ing and Actuation

Wireless Sensing and Structural Control Strategies

Wireless sensing and vibration control of civil structures