<p>Control systems utilizing wireless sensor and actuator networks can be severely affectedby the properties of the communication links. Radio fading and interferencemay cause communication losses and outages in situations when the radio environmentis noisy and low transmission power is desirable. This thesis proposes amethod to compensate for such unpredictable losses of data in the feedback controlloop by introducing a predictive outage compensator (POC). The POC is a filter tobe implemented at the receiver sides of networked control systems where it generatesartificial samples when data are lost. If the receiver node does not receive thedata, the POC suggests a command based on the history of past data. It is shownhow to design, tune and implement a POC. Theoretical bounds and simulationresults show that a POC can improve the closed-loop control performance undercommunication losses considerably. We provide a deterministic and a stochasticmethod to synthesize POCs. Worst-case performance bounds are given that relatethe closed-loop performance with the complexity of the compensator. We also showthat it is possible to achieve good performance with a low-order implementationbased on Hankel norm approximation. Tradeoffs between achievable performance,communication loss length, and POC order are discussed. The results are illustratedon a simulated example of a multiple-tank process. The thesis is concludedby an experimental validation of wireless control of a physical lab process. Herethe controller and the physical system are separated geographically and interfacedthrough a wireless medium. For the remote control we use a hybrid model predictivecontroller. The results reflect the difficulties in wireless control as well as theyhighlight the flexibility and possibilities one obtains by using wireless instead of awired communication medium.</p> / VR, SSF, VINNOVA via Networked Embedded Control Systems, EU Sixt Framework Program via HYCON and SOCRADES

Control systems utilizing wireless sensor and actuator networks can be severely affectedby the properties of the communication links. Radio fading and interferencemay cause communication losses and outages in situations when the radio environmentis noisy and low transmission power is desirable. This thesis proposes amethod to compensate for such unpredictable losses of data in the feedback controlloop by introducing a predictive outage compensator (POC). The POC is a filter tobe implemented at the receiver sides of networked control systems where it generatesartificial samples when data are lost. If the receiver node does not receive thedata, the POC suggests a command based on the history of past data. It is shownhow to design, tune and implement a POC. Theoretical bounds and simulationresults show that a POC can improve the closed-loop control performance undercommunication losses considerably. We provide a deterministic and a stochasticmethod to synthesize POCs. Worst-case performance bounds are given that relatethe closed-loop performance with the complexity of the compensator. We also showthat it is possible to achieve good performance with a low-order implementationbased on Hankel norm approximation. Tradeoffs between achievable performance,communication loss length, and POC order are discussed. The results are illustratedon a simulated example of a multiple-tank process. The thesis is concludedby an experimental validation of wireless control of a physical lab process. Herethe controller and the physical system are separated geographically and interfacedthrough a wireless medium. For the remote control we use a hybrid model predictivecontroller. The results reflect the difficulties in wireless control as well as theyhighlight the flexibility and possibilities one obtains by using wireless instead of awired communication medium. / VR, SSF, VINNOVA via Networked Embedded Control Systems, EU Sixt Framework Program via HYCON and SOCRADES

Business processes define workflows by structuring sets of activities according to given objectives. Process Modeling Languages (PMLs) provide graphical elements to define process models. Apart from use cases in finance and commerce, PMLs gain popularity in application domains such as Cyber-Physical Systems, the Internet of Things, ubiquitous computing, mobile devices, and scenarios happening in rural, restricted, or disaster-affected regions. Many of the domains are exposed to delayed, intermittent, or broken connectivity. Existing PMLs show limitations in considering connectivity-related issues, leading to failures and breakdowns at process runtime. This thesis addresses connectivity-related issues regarding the modeling and execution of resilient business processes taking place in unreliable communication environments. With resilient BPMN (rBPMN), an extension for the Business Process Model and Notation (BPMN) addressing environments with delayed, intermittent, or broken connectivity is introduced. rBPMN extends the BPMN metamodel by new elements for resilient process models. Domain experts may define alternatives for possibly failing message flows based on priorities or characteristics of the alternatives. Functionality offered by remote participants may be moved to other participants for local execution. This thesis illustrates approaches for the graph-based analysis of business processes regarding their resilient operation. By translating process models into directed graphs, graph algorithms allow to dynamically find the most suitable process path. Domain experts are enabled to identify non-resilient parts of a process model, allowing them to optimize the involved segments before runtime. Multi-criteria analysis approaches optimize process operation according to a chosen set of criteria. A real-world scenario of an environmental-friendly slurry application illustrates the use of rBPMN’s concepts and approaches for modeling and executing resilient processes. Technical approaches realizing rBPMN’s resilience strategies using a BPMN runtime engine and microservices are illustrated. The proof-of-concept implementations may be extended and adapted, serving as guides for other application domains.