The Study On Collaborative Optimization For Networked Cyber-physical Systems

In recent years,with the rapid development of embedded system technology,computing technology and network technology,the application system should not only meet the basic functional demand,but also lay more emphasis on the(rational/appropriate)allocation of physical resources in the whole system,and the optimization of overall performance.The traditional embedded system aims at the design and analysis of the computation unit,but the CPS(Cyber-Physcial System)pays more attention to the interaction among computation,communication and physical systems and the(rational/appropriate)allocation of physical resources along with scheduling optimization.Thus,the whole system is able to have more rapid response rate,better execution precision and higher efficiency with reliability.CPS processes computation and communication transmission according to the operation pattern and requirement of the physical system,which organically integrates computation,control and communication and makes them deeply interact with each other.CPS realizes the information interaction function with high reliability and efficiency between the physical and the information systems.The CPS has an extremely wide application field,including automated manufacturing process,digital medical treatment,automotive electronics,aerospace,smart power grids,intelligent transportation system and etc.It is not only changing traditional system design(philosophy/concept),but also will advance the improvement of human life and productivity in the future.Facing the typical industrial application CPS system,this thesis adapts collaborative optimization as the main theme,and conducts the research based on the model-based optimization control.The research includes the three aspects of CPS real-time network analysis,typical CPS collaborative optimization control and CPS collaborative optimization method under network delay respectively.As a result,this research proposes a series of new CPS-oriented system design methods.The main contents of this thesis are as follows:1.This thesis presents a real-time analysis method based on the theory of network calculus for the AFDX(Avionic Full Duplex Switched Ethernet)based networked CPS.The AFDX is recognized as one of the appropriate solutions allowing bridging this gap.As a real-time network,the AFDX is sensitive to data transmission delay.Hence,real-time assessment represents an important issue in the design of such networked CPS.This method is based on SP-FIFO(Fix Priority-First-In-First-Out)scheduling policy,and a worst-case upper bound on deterministic delay is given.Moreover,the delay distribution is modeled and a probabilistic delay upper bound is computed using the stochastic network calculus.Experiments are carried out for both deterministic and probabilistic cases and the results conform the validity of the approaches developed in the present work.2.This thesis presents a control scheme for thermal management in smart buildings(CPS typical applications)based on predictive power admission control with ideal networked CPS model(weak coupling between cyber and physical parts).This approach combines model predictive control with budget-schedulability analysis in order to reduce peak power consumption as well as ensure thermal comfort.First,the power budget with a given thermal comfort constraint is optimized through budget-schedulability analysis which amounts to solving a constrained linear programming problem.Second,the effective peak power demand is reduced by means of the optimal scheduling and cooperative operation of multiple thermal appliances.The performance of the proposed control scheme is assessed by simulation based on the thermal dynamics of a real eight-room office building located at Danish Technical University.3.This thesis presents a scheme aimed at mitigating the influence of random data transmission delays in networked thermal appliances control systems in smart buildings(strong coupling between cyber and physical parts)using a networked CPS model with delays.The effect of this type of delays is first analyzed,and this thesis proposes to utilize loose timing synchronization and add blank gaps between the consecutive appliance operations to avoid the possible violation of the given power budget.A cooperative control of thermal appliances operation is developed using the networked Model Predictive Control(MPC)-based controller with delays.This thesis shows that the schedulability of such a control scheme can be assessed online.The performance of the proposed control scheme is assessed by a simulation study based on the thermal dynamics of an eight-room office building.The results show that the proposed solution can achieve an efficient power peaks shaving in the presence of random network delays.