A Survey on Concepts, Applications, and Challenges in Cyber-Physical Systems

2014 KSII Transactions on Internet and Information Systems  
The Cyber-Physical System (CPS) is a term describing a broad range of complex, multi-disciplinary, physically-aware next generation engineered system that integrates embedded computing technologies (cyber part) into the physical world. In order to define and understand CPS more precisely, this article presents a detailed survey of the related work, discussing the origin of CPS, the relations to other research fields, prevalent concepts, and practical applications. Further, this article
more » ... s an extensive set of technical challenges and uses specific applications to elaborate and provide insight into each specific concept. CPS is a very broad research area and therefore has diverse applications spanning different scales. Additionally, the next generation technologies are expected to play an important role on CPS research. All of CPS applications need to be designed considering the cutting-edge technologies, necessary system-level requirements, and overall impact on the real world. plays an important role in CPS operation. In this regard, actuation coordination is essential to decide which actuators must be scheduled to perform a particular action or how to manage control actions properly. Various parameters, such as actuator capabilities, real-time guarantee, task completion time, energy consumption of each actuator, and the physical system requirements must be considered during control task allocation to particular actuator [17] . Regarding actuator scheduling, an important difference of CPSs compared to most cyber systems is the reversibility or preemption of actuator operations. While in most cyber systems, roll-back operations and preemption is available (e.g. databases or bus access protocols), physical operations executed by the actuators typically cannot be reversed. If an actuation is performed based on erroneous data, it is often very challenging or impossible to roll back the activity, as for instance discussed in [18] for specific healthcare applications. Additionally, non-reversibility challenge affects real-time scheduling in the cases where several jobs are managed on a shared platform. Even hard real-time tasks may be blocked by low-priority processes if a shared actuation resource access cannot be preempted or rolled back, as for instance discussed for a satellite communication system [19] . The control aspect of the physical phenomena and the theory behind control systems are the basis for all state-of-the-art continuous time dynamical systems and thus have a crucial role in CPS design. Conventionally, control policies are completely separate from the system infrastructure and implemented after manufacturing the system prototype [20] . Such an approach is not feasible to meet the demands expected from CPSs because of their complex and dynamic nature. To meet those demands and perform complex control laws, the physical system itself and its dependency relationship with those control laws should be well defined and modeled [21] . CPSs must operate in real-time. Real-time control is traditionally implemented through different forms of control mechanisms, namely open loop control, feed-forward control, and Sensor Node
doi:10.3837/tiis.2014.12.001 fatcat:juk43gp5fbhuzekljodaqxgjse